Liquid crystal display device

The present invention relates to a liquid crystal display device and a method for manufacturing the same.

As thin and lightweight display devices (so-called flat panel displays), liquid crystal display devices having liquid crystal elements, light emitting devices having self-luminous elements, field emission displays (FED), and the like have been developed in competition.

In liquid crystal display devices, it is required to increase the response speed of liquid crystal molecules. There are various display modes of the liquid crystal, and among them, the FLC (Ferroelectric Liquid Crystal) mode, the OCB (Optical Compensated Birefringence) mode, and the mode using the liquid crystal showing the blue phase can be mentioned as the liquid crystal mode capable of high-speed response.

In particular, the mode in which a liquid crystal exhibiting a blue phase does not require an alignment film and a wide viewing angle can be obtained, so that more research has been conducted toward practical use (see, for example, Patent Document 1). Patent Document 1 is a report in which a liquid crystal is subjected to a polymer stabilization treatment in order to widen the temperature range in which the blue phase appears.

<p><patcit num="1"><text>International Publication No. 2005-090520</text></patcit></p>

<p>In order to realize high contrast as a problem in a liquid crystal display device, it is necessary that the white transmittance (transmittance of light at the time of white display) is large.</p><p>Therefore, one of the purposes of the present invention is to provide a liquid crystal display device suitable for a liquid crystal display mode using a liquid crystal exhibiting a blue phase for higher contrast.</p><p>Another object of the present invention is to achieve lower power consumption in a liquid crystal display device using a liquid crystal exhibiting a blue phase.</p>

<p>A liquid crystal layer showing a blue phase between a first substrate provided with a pixel electrode layer (also referred to as a first electrode layer) and a second substrate provided with a common electrode layer (also referred to as a second electrode layer). In the liquid crystal display device sandwiching the above, the pixel electrode layer and the common electrode layer are arranged so as to project from the liquid crystal layer and adjacent ones are engaged with each other with the liquid crystal layer interposed therebetween.</p><p>The pixel electrode layer adjacent to each other via the liquid crystal layer and the common electrode layer are the distances at which the liquid crystal of the liquid crystal layer interposed between the electrode layers responds when a predetermined voltage is applied to the pixel electrode layer and the common electrode layer, respectively. .. The voltage to be applied is appropriately controlled according to the distance.</p><p>The positions of the pixel electrode layer and the common electrode layer in the liquid crystal layer can be controlled by providing structures under the pixel electrode layer and the common electrode layer, respectively.</p><p>In a liquid crystal display device in which a liquid crystal layer showing a blue phase is sandwiched between a first substrate and a second substrate, the pixel electrode layer is a surface of the first substrate on the liquid crystal layer side (the surface facing the liquid crystal layer). ) Is formed so as to cover the upper surface side surface of the rib-shaped first structure provided so as to project from the liquid crystal layer, and the common electrode layer (also referred to as the second electrode layer) is the surface of the second substrate on the liquid crystal layer side. It is formed so as to cover the upper surface side surface of the rib-shaped second structure provided so as to project from the liquid crystal layer.</p><p>In the in-plane direction, the pixel electrode layer, the common electrode layer, the rib-shaped first structure and the second structure are not flat, and have bent portions and branched comb teeth having various opening patterns (slits). It has a shape including a shape, and is formed so as not to overlap when the first substrate and the second substrate are arranged to face each other.</p><p>On the other hand, in the thickness (thickness) direction, the first structure and the second structure have a first structure so as to include a surface provided with the first structure or the second structure, respectively. When the substrate and the second substrate are arranged to face each other, the rib-shaped convex portions are held by the sealing material so as to sandwich the liquid crystal layer in between and engage with each other.</p><p>The pixel electrode layer and the common electrode layer are arranged so as to project from the liquid crystal layer so that their side surfaces are adjacent to each other, so that the formation area of the pixel electrode layer and the common electrode layer is set in the film thickness direction of the liquid crystal layer (three-dimensionally). ) Can also be expanded. Therefore, when a voltage is applied between the pixel electrode layer and the common electrode layer, a wide electric field can be formed between the pixel electrode layer and the common electrode layer.</p><p>Since the pixel electrode layer (or the pixel electrode layer and the first structure) and the common electrode layer (or the common electrode layer and the second structure) are arranged so that the side surfaces thereof are arranged side by side, the pixel electrode layer The sum of the maximum thickness (thickness) of the maximum thickness of (or the pixel electrode layer and the first structure) and the maximum thickness of the common electrode layer (or the common electrode layer and the second structure) Set so that it is larger than the maximum value of the thickness of the liquid crystal layer (also called the cell gap of the liquid crystal display device).</p><p>However, the pixel electrode layer or the common electrode layer formed on the first structure or the second structure is in contact with the opposite first substrate or the second substrate (or the pixel electrode layer or the common electrode layer). The total thickness (thickness) of the structure (first structure or second structure) and the electrode layer (pixel electrode layer or common electrode layer) is the maximum thickness of the liquid crystal layer. Set to be less than the value.</p><p>Further, when the pixel electrode layer and / and the common electrode layer are formed on the first structure or the second structure, the pixel electrode layer and / and the common electrode layer are at least a rib-shaped first structure or Although it is formed on the upper surface and the side surface of the second structure, it may be formed in a flat region other than the surface of another first structure or the second structure in the pixel. For example, in the case of a pixel electrode layer in which the voltage is controlled for each pixel, it may be formed as a continuous flat conductive film for each pixel, and in the case of a common electrode layer in which a common voltage is supplied to all pixels. It may be formed as a flat plate-shaped conductive film that is continuous in a pixel region including a plurality of pixels.</p><p>By expanding the formation region of the pixel electrode layer and the common electrode layer, the formation region of the electric field in the liquid crystal layer is also expanded, so that the liquid crystal molecules can be controlled more efficiently.</p><p>Therefore, the liquid crystal molecules in the entire liquid crystal layer including the film thickness direction can be made to respond, and the white transmittance is improved. Therefore, the contrast ratio, which is the ratio between the white transmittance and the black transmittance (the transmittance of light when displaying black), can also be increased. Further, even a liquid crystal material (liquid crystal mixture) exhibiting a highly viscous blue phase can effectively form an electric field, so that low power consumption can be achieved.</p><p>The structure can be formed of an insulator using an insulating material (organic material and an inorganic material) and a conductor using a conductive material (organic material and an inorganic material). Typically, it is preferable to use a visible light curable, ultraviolet curable or thermosetting resin. For example, acrylic resin, epoxy resin, amine resin and the like can be used. Further, it may be formed of a conductive resin or a metal material. The structure may be a laminated structure of a plurality of thin films.</p><p>As the shape of the structure, a columnar shape, a shape having a trapezoidal cross section with a flat tip of a cone, a dome shape having a round tip of a cone, or the like can be used. In the present specification, since the pixel electrode layer and the common electrode layer are formed so as to cover the surfaces (upper surface and side surfaces) of the structure, the structure is placed on the surface so that the pixel electrode layer and the common electrode layer have good coverage. A rib-like shape with few steps and having a curved surface is preferable. Further, it is preferable to use a material having translucency for visible light as the structure because the aperture ratio and the white transmittance are not lowered.</p><p>Further, since the structure may be a portion that protrudes into the liquid crystal layer from the surface of the substrate on the liquid crystal layer side, the surface on the liquid crystal layer side may be processed into an uneven shape to form a protruding structure. Therefore, the structure may be a continuous film having a plurality of protruding protrusions.</p><p>In the present specification, a substrate on which a semiconductor element (for example, a transistor), a first structure, and a pixel electrode layer are formed is referred to as an element substrate (first substrate), and the element substrate and the substrate are opposed to each other via a liquid crystal layer. The board is called a facing board (second board). A second structure and a common electrode layer are formed between the facing substrate (second substrate) and the liquid crystal layer.</p><p>A liquid crystal material showing a blue phase is used for the liquid crystal layer. The liquid crystal material refers to a mixture containing a liquid crystal used for the liquid crystal layer. Since the liquid crystal material showing the blue phase has a short response speed of 1 msec or less and is capable of high-speed response, it is possible to improve the performance of the liquid crystal display device.</p><p>A liquid crystal and a chiral agent are included as a liquid crystal material showing a blue phase. Chiral agents are used to orient the liquid crystal into a spiral structure and develop a blue phase. For example, a liquid crystal material mixed with a chiral agent of several weight% or more may be used for the liquid crystal layer.</p><p>As the liquid crystal, a thermotropic liquid crystal, a low molecular weight liquid crystal, a polymer liquid crystal, a ferroelectric liquid crystal, an antiferroelectric liquid crystal or the like is used.</p><p>As the chiral agent, a material having good compatibility with liquid crystal and having a strong twisting force is used. Also, either R-form or S-form is good, and racemates with a ratio of R-form to S-form of 50:50 are not used.</p><p>The liquid crystal material exhibits a cholesteric phase, a cholesteric blue phase, a smectic phase, a smectic blue phase, a cubic phase, a chiral nematic phase, an isotropic phase and the like, depending on the conditions.</p><p>The cholesteric blue phase and the smectic blue phase, which are blue phases, are found in liquid crystal materials having a cholesteric phase or a smectic phase having a spiral pitch of 500 nm or less and a relatively short pitch. The orientation of the liquid crystal material has a double twist structure. Since it has an order below the wavelength of visible light, it is transparent, and the orientation order changes when a voltage is applied to cause an optical modulation action. Since the blue phase is optically isotropic, it does not depend on the viewing angle and does not need to form an alignment film, so that it is possible to improve the quality of the displayed image and reduce the cost.</p><p>Further, the blue phase is difficult to develop only in a narrow temperature range, and in order to improve the temperature range widely, it is preferable to add a photocurable resin and a photopolymerization initiator to the liquid crystal material to perform a polymer stabilization treatment. The polymer stabilization treatment is performed by irradiating a liquid crystal material containing a liquid crystal, a chiral agent, a photocurable resin, and a photopolymerization initiator with light having a wavelength at which the photocurable resin and the photopolymerization initiator react. This polymer stabilization treatment may be performed by irradiating light in a state showing an isotropic phase by controlling the temperature, or by irradiating light in a state showing a blue phase.</p><p>For example, the polymer stabilization treatment is performed by controlling the temperature of the liquid crystal layer and irradiating the liquid crystal layer with light in a state where the blue phase is expressed. However, the present invention is not limited to this, and by irradiating the liquid crystal layer with light in a state where an isotropic phase within + 10 ° C, preferably within + 5 ° C, is expressed from the phase transition temperature between the blue phase and the isotropic phase. The polymer stabilization treatment may be performed. The phase transition temperature between the blue phase and the isotropic phase is the temperature at which the blue phase transitions from the blue phase to the isotropic phase when the temperature rises, or the temperature at which the phase transitions from the isotropic phase to the blue phase when the temperature drops. As an example of the polymer stabilization treatment, after heating the liquid crystal layer to an isotropic phase, the temperature is gradually lowered to undergo a phase transition to the blue phase, and light is irradiated while maintaining the temperature at which the blue phase appears. Can be done. In addition, after the liquid crystal layer is gradually heated to undergo a phase transition to an isotropic phase, the phase transition temperature between the blue phase and the isotropic phase is within +10 ° C, preferably within + 5 ° C (etc.). It is possible to irradiate light in a state in which the anisotropy is expressed). When an ultraviolet curable resin (UV curable resin) is used as the photocurable resin contained in the liquid crystal material, the liquid crystal layer may be irradiated with ultraviolet rays. Even if the blue phase is not expressed, light is irradiated within + 10 ° C, preferably within + 5 ° C (state in which the isotropic phase is expressed) from the phase transition temperature between the blue phase and the isotropic phase. If the polymer is stabilized, the response speed is as short as 1 msec or less, and high-speed response is possible.</p><p>One form of the configuration of the invention disclosed herein includes a first substrate provided with a first electrode layer and a second electrode layer sandwiching a liquid crystal layer containing a liquid crystal material exhibiting a blue phase. The second substrate, the first electrode layer and the second electrode layer project to the liquid crystal layer, and the adjacent first electrode layer and the second electrode layer mesh with each other with the liquid crystal layer interposed therebetween. It is a liquid crystal display device arranged in such a manner.</p><p>Another embodiment of the configuration of the invention disclosed herein is a first substrate provided with a first electrode layer and a second electrode layer sandwiching a liquid crystal layer containing a liquid crystal material exhibiting a blue phase. The second substrate provided with the above, the first electrode layer and the second electrode layer project to the liquid crystal layer, and the adjacent first electrode layer and the second electrode layer are spaced apart from each other with the liquid crystal layer interposed therebetween. The first electrode layer and the second electrode layer are spaced apart from each other when a predetermined voltage is applied to the first electrode layer and the second electrode layer, respectively. It is a liquid crystal display device having a distance at which the liquid crystal of the liquid crystal layer interposed between the two electrode layers responds.</p><p>Another embodiment of the configuration of the invention disclosed herein is a first substrate and a second substrate sandwiching a liquid crystal layer containing a liquid crystal material exhibiting a blue phase, and a surface of the first substrate on the liquid crystal layer side. A rib-shaped first structure protruding into the liquid crystal layer from the surface, a rib-shaped second structure protruding into the liquid crystal layer from the surface of the second substrate on the liquid crystal layer side, and a rib-shaped first structure. It has a first electrode layer covering the upper surface and side surfaces of the structure and a second electrode layer covering the upper surface and side surfaces of the rib-shaped second structure, and has a first electrode layer and a second electrode layer in the liquid crystal layer. The electrode layer is a liquid crystal display device arranged so as to mesh with each other with a liquid crystal layer interposed therebetween.</p><p>Another embodiment of the configuration of the invention disclosed herein is a first substrate and a second substrate sandwiching a liquid crystal layer containing a liquid crystal material exhibiting a blue phase, and a surface of the first substrate on the liquid crystal layer side. A rib-shaped first structure protruding into the liquid crystal layer from the surface, a rib-shaped second structure protruding into the liquid crystal layer from the surface of the second substrate on the liquid crystal layer side, and a rib-shaped first structure. It has a first electrode layer covering the upper surface and side surfaces of the structure and a second electrode layer covering the upper surface and side surfaces of the rib-shaped second structure, and has a first electrode layer and a second electrode layer in the liquid crystal layer. The first electrode layer and the second electrode layer are arranged so as to mesh with each other with a liquid crystal layer interposed therebetween, and the distance between the first electrode layer and the second electrode layer is a predetermined voltage for the first electrode layer and the second electrode layer, respectively. Is a liquid crystal display device having a distance at which the liquid crystal of the liquid crystal layer interposed between the first electrode layer and the second electrode layer responds when the above is applied.</p><p>Since it is not necessary to form an alignment film by using the liquid crystal layer showing the blue phase, the first electrode layer (pixel electrode layer) and the liquid crystal layer, and the second electrode layer (common electrode layer) and the liquid crystal layer Can be in contact with each other.</p><p>The ordinal numbers attached as the first and second numbers are used for convenience and do not indicate the process order or the stacking order. In addition, this specification does not indicate a unique name as a matter for specifying the invention.</p><p>In the present specification, the semiconductor device refers to all devices that can function by utilizing the semiconductor characteristics, and the electro-optical device, the semiconductor circuit, and the electronic device are all semiconductor devices.</p>

<p>In a liquid crystal display device in which a liquid crystal layer showing a blue phase is sandwiched between a first substrate provided with a pixel electrode layer and a second substrate provided with a common electrode layer, the pixel electrode layer and the common electrode layer are liquid crystals. Arranged so as to project from the layer and adjacent objects are engaged with each other at intervals with the liquid crystal layer interposed therebetween.</p><p>Therefore, when a voltage is applied between the pixel electrode layer and the common electrode layer, a wide electric field can be formed between the pixel electrode layer and the common electrode layer, and the liquid crystal molecules can be controlled by using the electric field.</p><p>Therefore, the liquid crystal molecules in the entire liquid crystal layer including the film thickness direction can be made to respond, the white transmittance is improved, and the contrast ratio can be increased in the liquid crystal display device using the liquid crystal layer showing the blue phase.</p><p>Further, even in the liquid crystal layer exhibiting a highly viscous blue phase, an electric field can be effectively formed, so that the power consumption of the liquid crystal display device can be reduced.</p>

<figref num="1">The figure explaining the liquid crystal display device.</figref><figref num="2">The figure explaining the liquid crystal display device.</figref><figref num="3">The figure explaining the liquid crystal display device.</figref><figref num="4">The figure explaining the liquid crystal display device.</figref><figref num="5">The figure explaining the liquid crystal display module.</figref><figref num="6">The figure explaining the liquid crystal display module.</figref><figref num="7">The figure explaining the transistor which can be applied to a liquid crystal display device.</figref><figref num="8">The figure explaining the transistor which can be applied to a liquid crystal display device, and the manufacturing method of a transistor.</figref><figref num="9">The figure explaining the electronic device.</figref><figref num="10">The figure explaining the electronic device.</figref><figref num="11">The figure explaining the liquid crystal display device.</figref><figref num="12">The figure explaining the calculation result of the electric field mode of a liquid crystal display device.</figref><figref num="13">The figure explaining the calculation result of the electric field mode of a liquid crystal display device.</figref><figref num="14">The figure explaining the calculation result of the electric field mode of a liquid crystal display device.</figref><figref num="15">The figure explaining the calculation result of the electric field mode of a liquid crystal display device.</figref><figref num="16">The figure explaining the liquid crystal display device.</figref>

The embodiment will be described in detail with reference to the drawings. However, it is not limited to the following description, and it is easily understood by those skilled in the art that a person skilled in the art can change the form and details in various ways without departing from the purpose and the scope thereof. Therefore, the interpretation is not limited to the description of the embodiments shown below. In the configuration described below, the same reference numerals are commonly used between different drawings for the same parts or parts having similar functions, and the repeated description thereof will be omitted.

(Embodiment 1) A liquid crystal display device, which is a form of the configuration of the invention disclosed in the present specification, will be described with reference to FIG. FIG. 1 is a cross-sectional view of a liquid crystal display device.

In a liquid crystal display device including a liquid crystal layer showing a blue phase, a method of controlling gradation by generating an electric field substantially parallel (that is, in a horizontal direction) to the substrate and moving liquid crystal molecules in a plane parallel to the substrate. Can be used.

FIG. 16 is a liquid crystal display device in which the first substrate 200 and the second substrate 201 are arranged so as to face each other with a liquid crystal layer 208 using a liquid crystal material exhibiting a blue phase sandwiched between them. A pixel electrode layer 230 is provided between the first substrate 200 and the liquid crystal layer 208, and common electrode layers 232a and 232b are provided between the second substrate 201 and the liquid crystal layer 208. The pixel electrode layer 230 is provided so as to project into the liquid crystal layer 208 from the surface of the first substrate 200 on the liquid crystal layer 208 side, and the common electrode layers 232a and 232b project from the surface of the second substrate 201 on the liquid crystal layer 208 side. ing.

In the thickness (film thickness) direction, the pixel electrode layer 230 and the common electrode layers 232a and 232b project to the liquid crystal layer 208 showing the blue phase, and adjacent ones are engaged with each other with the liquid crystal layer 208 interposed therebetween. It is located in.

The pixel electrode layer 230 adjacent to each other via the liquid crystal layer 208 and the common electrode layers 232a and 232b are common to the pixel electrode layer 230 and the common electrode layers 232a and 232b when predetermined voltages are applied to the pixel electrode layer 230 and the common electrode layers 232a and 232b, respectively. The distance is set so that the liquid crystal of the liquid crystal layer 208 interposed between the electrode layers 232a and 232b responds. The voltage to be applied is appropriately controlled according to the distance.

Further, the positions of the pixel electrode layer 230 and the common electrode layers 232a and 232b in the liquid crystal layer 208 can be controlled by providing structures under the pixel electrode layer 230 and the common electrode layers 232a and 232b, respectively.

FIG. 1 is a liquid crystal display device in which a first substrate 200 and a second substrate 201 are arranged so as to face each other with a liquid crystal layer 208 using a liquid crystal material exhibiting a blue phase sandwiched between them. The first structure 233 and the pixel electrode layer 230 are between the first substrate 200 and the liquid crystal layer 208, and the second structures 235a and 235b are between the second substrate 201 and the liquid crystal layer 208. Common electrode layers 232a and 232b are provided. The first structure 233 is in the liquid crystal layer 208 from the surface of the first substrate 200 on the liquid crystal layer 208 side, and the second structures 235a and 235b are in the liquid crystal layer 208 from the surface of the second substrate 201 on the liquid crystal layer 208 side. It is provided so as to protrude.

The pixel electrode layer 230 is formed on the upper surface side surface of the first structure 233 provided so as to project from the surface of the first substrate 200 on the liquid crystal layer 208 side (the surface facing the liquid crystal layer 208) to the liquid crystal layer 208. The common electrode layers 232a and 232b are formed so as to cover the upper surface side surface of the second structure 235a and 235b provided so as to project from the surface of the second substrate 201 on the liquid crystal layer 208 side to the liquid crystal layer 208. The liquid crystal.

In the in-plane direction (plan view in the liquid crystal display device), the pixel electrode layer 230 and the common electrode layers 232a and 232b have a shape including a bent portion having an opening pattern and a branched comb-teeth shape, and the first substrate 200 It is formed so as not to overlap when the second substrate 201 is arranged so as to face each other.

Therefore, in the in-plane direction (plan view in the liquid crystal display device), the rib-shaped first structure 233 and the second structures 235a and 235b also have the shapes of the pixel electrode layer 230 and the common electrode layers 232a and 232b. Reflecting this, the shape includes a bent portion having an opening pattern and a branched comb-teeth shape.

In the thickness (film thickness) direction, as shown in the cross-sectional view of FIG. 1, the first structure 233 and the second structures 235a and 235b are the first structure 233 or the second structure, respectively. When the first substrate 200 and the second substrate 201 are arranged to face each other so as to include the surfaces on which the bodies 235a and 235b are provided, the rib-shaped protrusions bite each other with the liquid crystal layer 208 in between. It is held by the sealing material so that it matches.

The side surfaces of the pixel electrode layer 230 (or the pixel electrode layer 230 and the first structure 233) and the common electrode layers 232a and 232b (or the common electrode layers 232a and 232b and the second structure 235a and 235b) are lateral to each other. The maximum thickness of the pixel electrode layer 230 (or the pixel electrode layer 230 and the first structure 233) and the common electrode layers 232a, 232b (or the common electrode layers 232a, 232b and the first structure 233) are arranged in parallel with each other. Set so that the total thickness (thickness) of the maximum thickness of the structures 235a and 235b) of 2 is larger than the maximum thickness (also referred to as the cell gap of the liquid crystal display device) of the liquid crystal layer 208. ..

The maximum thickness (film thickness) of the liquid crystal layer 208 is preferably 1 μm or more and 20 μm or less.

However, the pixel electrode layer 230 or the common electrode layers 232a, 232b formed on the first structure 233 or the second structure 235a, 235b reaches the opposite first substrate 200 or the second substrate 201. The total thickness of the first structure 233 and the pixel electrode layer 230, and the total thickness (thickness) of the second structures 235a and 235b and the common electrode layers 232a and 232b are The thickness is set to be smaller than the thickness of the liquid crystal layer 208 in the formation region.

Further, when a voltage is applied to the pixel electrode layer 230, the common electrode layer 232a, and the common electrode layer 232b, which are adjacent to the pixel electrode layer 230 via the liquid crystal layer 208, and the common electrode layer 232a or the common electrode layer 232b, respectively. It is a distance at which the liquid crystal of the liquid crystal layer 208 interposed between the electrode layers responds. The shortest distance between the side surfaces of the pixel electrode layer 230 adjacent to each other via the liquid crystal layer 208 and the common electrode layer 232a or the common electrode layer 232b is 0.5 μm or more and 30 μm or less, preferably 1 μm or more and 10 μm or less. The voltage to be applied is appropriately controlled according to the above.

In the present specification, the distance between the adjacent pixel electrode layer and the common electrode layer is the shortest distance between the portion of the pixel electrode layer and the common electrode layer that protrudes from the liquid crystal layer (side surface in the cross-sectional view of FIG. 1). And. The liquid crystal can be made to respond by the electric field formed between the side surface of the adjacent pixel electrode layer and the side surface of the common electrode layer.

Therefore, the shortest distance between the side surfaces of the first structure 233 adjacent to each other via the liquid crystal layer 208 and the second structure 235a or the second structure 235b is also 0.5 μm or more and 30 μm or less, preferably 1 μm or more and 10 μm. The voltage applied to the pixel electrode layer 230, the common electrode layer 232a, and the common electrode layer 232b is appropriately controlled according to the distance.

The pixel electrode layer 230 and the common electrode layers 232a and 232b shown in FIG. 16 are examples in which a structure is not used and the shape is columnar.

The first structure 233 and the second structures 235a and 235b are dome-shaped structures having a rounded tip with a cross section close to a semicircle. When the surface of the structure has a curved surface as described above, the pixel electrode layers 230 and the common electrode layers 232a and 232b laminated on the structure can be formed in a good shape with good coverage.

Since the common electrode layers 232a and 232b and the second structures 235a and 235b have a shape having an opening pattern, a plurality of divided electrode layers or structures are shown in the cross-sectional views of FIGS. 1 and 16. It is shown as.

The pixel electrode layer 230 is formed so as to cover the upper surface and the side surface of the rib-shaped first structure 233 provided on the first substrate 200, and the rib-shaped second structure provided on the second substrate 201 is formed. By forming the common electrode layers 232a and 232b so as to cover the upper surfaces and side surfaces of the structures 235a and 235b, the formation areas of the pixel electrode layers 230 and the common electrode layers 232a and 232b are set in the film thickness direction of the liquid crystal layer 208 ( It can also be expanded (three-dimensionally). Further, by covering the rib-shaped first structure 233 or the second structures 235a and 235b, the convex portions formed on the surfaces of the pixel electrode layer 230 and the common electrode layers 232a and 232b alternately mesh with each other. , The first substrate 200 and the second substrate 201 are arranged so as to face each other. Therefore, as shown in FIG. 1, the electric field shown by the arrow 202a (the electric field substantially parallel to the first substrate 200 and the second substrate 201) is formed between the pixel electrode layer 230 and the common electrode layer 232a. An electric field shown by an arrow 202b (an electric field substantially parallel to the first substrate 200 and the second substrate 201) is applied between 230 and the common electrode layer 232b over a wide range in the film thickness direction of the liquid crystal layer. Although not shown, the electric field is also formed so as to wrap around between the pixel electrode layer 230 and the common electrode layers 232a and 232b in a circular shape.

As the shape of the pixel electrode layer, the common electrode layer, and the structure, a columnar shape, a trapezoidal shape having a cone-shaped tip having a flat cross section, a dome shape having a cone-shaped tip having a round tip, and the like can be used. When the pixel electrode layer and the common electrode layer are formed so as to cover the surface (upper surface and side surface) of the structure, the structure has a curved surface with few steps on the surface so that the coverage of the pixel electrode layer and the common electrode layer is good. A shape having the above is preferable. Further, it is preferable to use a material having translucency for visible light as the structure because the aperture ratio and the white transmittance are not lowered.

Further, since the structure may be a portion that protrudes into the liquid crystal layer from the surface of the substrate on the liquid crystal layer side, the surface on the liquid crystal layer side may be processed into an uneven shape to form a protruding structure. Therefore, the structure may be a continuous film having a plurality of protruding protrusions.

The shapes of the pixel electrode layer and the common electrode layer formed on the structure reflect the shape of the structure and are also affected by the etching processing method. FIG. 11 (A), (B), and (C) show shape examples of the structure, the pixel electrode layer formed on the structure, and the common electrode layer.

FIG. 11A shows an example in which the pixel electrode layer 240 is formed on the first structure 243 and the common electrode layers 242a and 242b are formed on the second structures 245a and 245b, respectively. The first structure 243 and the second structures 245a and 245b have a trapezoidal cross section with a cone-shaped tip that is flat, and the pixel electrode layer 240 and the common electrode layers 242a and 242b that are formed over the cone are also formed. It reflects the shape. Further, the pixel electrode layer 240 and the common electrode layers 242a and 242b are formed so as to be in contact with the first substrate 200 or the second substrate 201.

As described above, the pixel electrode layer and / and the common electrode layer are formed on at least the upper surface and the side surface of the rib-shaped first structure or the second structure, but the other first structure or the other first structure in the pixel is formed. It may be formed in a flat region other than the surface of the second structure.

FIG. 11B shows an example in which the pixel electrode layer 246 is formed on the first structure 248, and the common electrode layers 247a and 247b are formed on the second structures 249a and 249b, respectively. The first structure 248 and the second structures 249a and 249b have a conical shape with a rounded tip, and the pixel electrode layers 246 and common electrode layers 247a and 247b formed by covering them also reflect the shape. There is. In the case of a cone shape like this, the pixel electrode layer 246 and the common electrode layers 247a and 247b may be partially discontinuous near the apex of the cone (for example, an opening (hole) is formed in the film). It is possible, but there is no problem if a voltage can be applied as the pixel electrode layer 246 and the common electrode layers 247a and 247b.

In FIG. 11C, the pixel electrode layer 230 is formed on the convex portion of the first structure 260 having an uneven shape, and the common electrode layers 232a and 232b are formed on the convex portion of the second structure 265 having an uneven shape, respectively. This is an example. The first structure 260 having a concavo-convex shape and the second structure 265 having a concavo-convex shape are formed from a continuous film having an insulating layer processed to form a concavo-convex surface on the liquid crystal layer side, each having a plurality of protruding convex portions. This is an example of the structure. Therefore, the pixel electrode layer 230 and the common electrode layers 232a and 232b are formed on the protruding protrusions of the first structure 260 and the second structure 265, respectively.

The results of calculating the applied state of the electric field in the liquid crystal display device are shown in FIGS. 12 (B) and 13 (B). The calculation was performed using a Shintech LCD Master and 2s Bench.

12 (A) and 13 (A) are diagrams showing the calculated configuration of the liquid crystal display device. FIG. 12 (A) shows an example in which the electrode layer is formed only on the upper surface and the side surface of the structure, and FIG. 13 (A) shows an example in which the electrode layer forms the upper surface and the side surface of the structure as shown in FIGS. 11 (A) and 11 (B). This is an example in which a part of the structure is also formed on the substrate around the structure. As the structure (first structure 233, second structure 235a, 235b), an insulator having a dielectric constant of 4 was used, and the width of the cross section of the portion in contact with the substrate was 2.5 μm. The film thickness (height) of the first structure 233 and the second structures 235a and 235b is 3 μm. The film thickness (height) of the first structure 233 and the second structures 235a and 235b referred to here is the maximum value from the bottom surface (first substrate 200 or second substrate 201).

In FIGS. 12 (A) (B) and 13 (A) (B), the pixel electrode layer 230 is formed so as to cover the upper surface and the side surface of the first structure 233, and similarly, the common electrode layers 232a and 232b are also formed. It is formed so as to cover the upper surface and the side surface of the second structures 235a and 235b, respectively. The film thickness of the pixel electrode layers 230 and the common electrode layers 232a and 232b is 0.1 μm, and the distance between the first structure 233 and the second structures 235a and 235b is 2.5 μm when it is assumed that they are arranged in the same plane. Is. The distance from the first substrate 200 to the second substrate 201, which corresponds to the cell gap (maximum film thickness of the liquid crystal layer), is 4 μm.

For the structures of FIGS. 12 (A) and 13 (A), the calculation results calculated with the common electrode layer set to 0 V and the pixel electrode layer set to 10 V are shown in FIGS. 12 (B) and 13 (B).

In FIGS. 12 (B) and 13 (B), the solid lines show equipotential lines, and the equipotential lines spread around the pixel electrode layer or the common electrode layer that covers the periphery of the rib-shaped structure. Is formed.

Since the electric field is generated perpendicular to the isobaric line, as shown in FIGS. 12 (B) and 13 (B), the pixel electrode layer 230 provided so as to cover the surface of the first structure 233 and the second It can be confirmed that a lateral electric field is applied between the common electrode layers 232a and 232b provided so as to cover the surfaces of the structures 235a and 235b.

Therefore, when a voltage is applied between the pixel electrode layer 230 and the common electrode layers 232a and 232b, a wide electric field can be formed between the pixel electrode layer 230 and the common electrode layers 232a and 232b, and the electric field is used. Can control liquid crystal molecules.

Therefore, the liquid crystal molecules in the entire liquid crystal layer 208 including the film thickness direction can be made to respond, and the white transmittance is improved. Therefore, the contrast ratio, which is the ratio between the white transmittance and the black transmittance (the transmittance of light when displaying black), can also be increased. Further, even a liquid crystal material (liquid crystal mixture) exhibiting a highly viscous blue phase can effectively form an electric field, so that low power consumption can be achieved.

The structure (first structure, second structure) is formed of an insulator using an insulating material (organic material and an inorganic material) and a conductor using a conductive material (organic material and an inorganic material). can do. Typically, it is preferable to use a visible light curable, ultraviolet curable or thermosetting resin. For example, acrylic resin, epoxy resin, amine resin and the like can be used. Further, it may be formed of a conductive resin or a metal material. The structure may be a laminated structure of a plurality of thin films.

Further, the first structure and the second structure may have the same material and shape, and the production conditions (for example, film thickness) may be different from each other.

The method for forming the structure is not particularly limited, and depending on the material, a dry method such as a vapor deposition method, a sputtering method, or a CVD method, or spin coating, dipping, spray coating, droplet ejection method (inkjet method), nanoimprint, and various types are used. A wet method such as a printing method (screen printing, offset printing) may be used, and if necessary, a desired pattern may be processed by an etching method (dry etching or wet etching).

As a method for forming the liquid crystal layer 208, a dispenser method (dropping method) or an injection method in which the first substrate 200 and the second substrate 201 are bonded together and then the liquid crystal is injected using a capillary phenomenon or the like can be used. it can.

A liquid crystal material exhibiting a blue phase is used for the liquid crystal layer 208. Since the liquid crystal material showing the blue phase has a short response speed of 1 msec or less and is capable of high-speed response, it is possible to improve the performance of the liquid crystal display device.

For example, since high-speed response is possible, RGB light emitting diodes (LEDs) are placed in the backlight device, and the time-sharing color mixing method (field sequential method) is used to display colors by time division, and left and right images are displayed by time division. Can be suitably adopted for a three-dimensional display system using a shutter glasses system in which the LEDs are viewed alternately.

A liquid crystal and a chiral agent are included as a liquid crystal material showing a blue phase. Chiral agents are used to orient the liquid crystal into a spiral structure and develop a blue phase. For example, a liquid crystal material mixed with 5% by weight or more of a chiral agent may be used for the liquid crystal layer.

As the liquid crystal, a thermotropic liquid crystal, a low molecular weight liquid crystal, a polymer liquid crystal, a ferroelectric liquid crystal, an antiferroelectric liquid crystal or the like is used.

As the chiral agent, a material having good compatibility with liquid crystal and having a strong twisting force is used. Also, either R-form or S-form is good, and racemates with a ratio of R-form to S-form of 50:50 are not used.

The liquid crystal material exhibits a cholesteric phase, a cholesteric blue phase, a smectic phase, a smectic blue phase, a cubic phase, a chiral nematic phase, an isotropic phase and the like, depending on the conditions.

The cholesteric blue phase and the smectic blue phase, which are blue phases, are found in liquid crystal materials having a cholesteric phase or a smectic phase having a spiral pitch of 500 nm or less and a relatively short pitch. The orientation of the liquid crystal material has a double twist structure. Since it has an order below the wavelength of visible light, it is transparent, and the orientation order changes when a voltage is applied to cause an optical modulation action. Since the blue phase is optically isotropic, it does not depend on the viewing angle and does not need to form an alignment film, so that it is possible to improve the quality of the displayed image and reduce the cost.

Further, the blue phase is difficult to develop only in a narrow temperature range, and in order to improve the temperature range widely, it is preferable to add a photocurable resin and a photopolymerization initiator to the liquid crystal material to perform a polymer stabilization treatment. The polymer stabilization treatment is performed by irradiating a liquid crystal material containing a liquid crystal, a chiral agent, a photocurable resin, and a photopolymerization initiator with light having a wavelength at which the photocurable resin and the photopolymerization initiator react. This polymer stabilization treatment may be performed by irradiating light in a state showing an isotropic phase by controlling the temperature, or by irradiating light in a state showing a blue phase.

For example, the polymer stabilization treatment is performed by controlling the temperature of the liquid crystal layer and irradiating the liquid crystal layer with light in a state where the blue phase is expressed. However, the present invention is not limited to this, and by irradiating the liquid crystal layer with light in a state where an isotropic phase within + 10 ° C, preferably within + 5 ° C, is expressed from the phase transition temperature between the blue phase and the isotropic phase. The polymer stabilization treatment may be performed. The phase transition temperature between the blue phase and the isotropic phase is the temperature at which the blue phase transitions from the blue phase to the isotropic phase when the temperature rises, or the temperature at which the phase transitions from the isotropic phase to the blue phase when the temperature drops. As an example of the polymer stabilization treatment, after heating the liquid crystal layer to an isotropic phase, the temperature is gradually lowered to undergo a phase transition to the blue phase, and light is irradiated while maintaining the temperature at which the blue phase appears. Can be done. In addition, after the liquid crystal layer is gradually heated to undergo a phase transition to an isotropic phase, the phase transition temperature between the blue phase and the isotropic phase is within +10 ° C, preferably within + 5 ° C (etc.). It is possible to irradiate light in a state in which the anisotropy is expressed). When an ultraviolet curable resin (UV curable resin) is used as the photocurable resin contained in the liquid crystal material, the liquid crystal layer may be irradiated with ultraviolet rays. Even if the blue phase is not expressed, light is irradiated within + 10 ° C, preferably within + 5 ° C (state in which the isotropic phase is expressed) from the phase transition temperature between the blue phase and the isotropic phase. If the polymer is stabilized, the response speed is as short as 1 msec or less, and high-speed response is possible.

The photocurable resin may be a monofunctional monomer such as acrylate or methacrylate, a polyfunctional monomer such as diacrylate, triacrylate, dimethacrylate or trimethacrylate, or a mixture thereof. Further, it may be liquid crystal or non-liquid crystal, and both may be mixed. As the photocurable resin, a resin that cures with light having a wavelength at which the photopolymerization initiator used reacts may be selected, and an ultraviolet curable resin can be typically used.

The photopolymerization initiator may be a radical polymerization initiator that generates radicals by light irradiation, an acid generator that generates an acid, or a base generator that generates a base.

Specifically, a mixture of JC-1041XX (manufactured by Chisso Co., Ltd.) and 4-cyano-4'-pentylbiphenyl can be used as the liquid crystal material, and ZLI-4572 (manufactured by Merck Co., Ltd.) as the chiral agent. 2-Ethylhexyl acrylate, RM257 (manufactured by Merck Co., Ltd.), and trimethylolpropane triacrylate can be used as the photocurable resin, and 2,2-dimethoxy-2-phenyl as the photopolymerization initiator. Acetophenone can be used.

Further, although not shown in FIG. 1, an optical film such as a polarizing plate, a retardation plate, and an antireflection film is appropriately provided. For example, circularly polarized light using a polarizing plate and a retardation plate may be used. Further, a backlight or the like can be used as the light source.

In the present specification, when the liquid crystal display device is a transmissive liquid crystal display device (or a semi-transmissive liquid crystal display device) that displays by transmitting light from a light source, it is necessary to transmit light at least in a pixel region. is there. Therefore, all the thin films such as the first substrate, the second substrate, the other insulating film, and the conductive film existing in the pixel region through which light is transmitted are made translucent with respect to the light in the wavelength region of visible light.

The pixel electrode layer and the common electrode layer are preferably translucent, but if they have an opening pattern, a non-translucent material such as a metal film may be used depending on the shape.

The pixel electrode layer and common electrode layer are indium tin oxide (ITO), IZO (indium zinc oxide), which is a mixture of indium oxide and zinc oxide (ZnO), and indium oxide and silicon oxide (SiO).₂) Mixed conductive material, organic indium, organic tin, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, or tungsten ( W), molybdenum (Mo), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), cobalt (Co), nickel (Ni), titanium ( It can be formed from metals such as Ti), platinum (Pt), aluminum (Al), copper (Cu), silver (Ag), or alloys thereof, or metal nitrides thereof, using one or more kinds. ..

As the first substrate 200 and the second substrate 201, a glass substrate such as barium borosilicate glass or aluminoborosilicate glass, a quartz substrate, a plastic substrate, or the like can be used.

As described above, the contrast ratio can be increased in a liquid crystal display device using a liquid crystal layer exhibiting a blue phase.

Further, since a high white transmittance can be obtained at a lower voltage, it is possible to achieve low power consumption of the liquid crystal display device.

(Embodiment 2) A liquid crystal display device, which is another embodiment of the configuration of the invention disclosed in the present specification, will be described with reference to FIGS. 2 and 3. 2 and 3 are cross-sectional views of the liquid crystal display device, which is an example in which the configurations of the pixel electrode layer and the common electrode layer are different in the liquid crystal display device shown in the first embodiment. The same materials and manufacturing methods can be applied to the same materials as in the first embodiment, and detailed description of the same parts or parts having the same functions will be omitted.

In the case of the pixel electrode layer and / and the common electrode layer provided on the rib-shaped first structure or the second structure, at least the upper surface and the side surface of the rib-shaped first structure or the second structure. However, it may also be formed in a flat region other than the surface of another first structure or second structure in the pixel. The present embodiment shows an example in which a pixel electrode layer and / and a common electrode layer are formed in a pixel in a flat region other than the surface of another first structure or second structure.

2 and 3 show a liquid crystal display device in which the first substrate 200 and the second substrate 201 are arranged so as to face each other with a liquid crystal layer 208 using a liquid crystal material exhibiting a blue phase sandwiched between them. is there. The first structure 233 and the pixel electrode layer 230 are between the first substrate 200 and the liquid crystal layer 208, and the second structures 235a and 235b are between the second substrate 201 and the liquid crystal layer 208. Common electrode layers 232a and 232b are provided. The first structure 233 is in the liquid crystal layer 208 from the surface of the first substrate 200 on the liquid crystal layer 208 side, and the second structures 235a and 235b are in the liquid crystal layer 208 from the surface of the second substrate 201 on the liquid crystal layer 208 side. It is provided so as to protrude.

In FIG. 2, in the pixel, the pixel electrode layer 230 is a first structure provided so as to project from the surface of the first substrate 200 on the liquid crystal layer 208 side (the surface facing the liquid crystal layer 208) to the liquid crystal layer 208. A second surface formed by covering the upper surface side surface of the body 233 and the first substrate 200, and the common electrode layers 232a and 232b project from the surface of the second substrate 201 on the liquid crystal layer 208 side to the liquid crystal layer 208. It is formed so as to cover the upper surface side surface of the structures 235a and 235b.

As shown in FIG. 2, the pixel electrode layer 230 is not selectively formed only on the side surface and the upper surface of the first structure 233, but can also be formed as a continuous conductive film covering the region of one pixel.

Even when the pixel electrode layer 230 is provided as a continuous film in a region other than the first structure 233, it is the pixel electrode layer provided on the surface of the first structure 233 that protrudes as a convex portion in the liquid crystal layer 208. It is a part of 230 conductive film. Therefore, as shown in the cross-sectional view of FIG. 2, the pixel electrode layer 230 and the common electrode layers 232a and 232b are formed by covering the rib-shaped first structure 233 or the second structures 235a and 235b. The first substrate 200 and the second substrate 201 can be arranged to face each other so that the convex portions alternately mesh with each other.

Similarly, the common electrode layers 232a and 232b may not be selectively formed only on the side surface and the upper surface of the second structure 235a and 235b, but may be provided as a continuous flat conductive film. In the case of a common electrode layer to which a common voltage is supplied to all pixels, it can be formed as a flat plate-like continuous conductive film covering a pixel region including a plurality of pixels.

FIG. 3 shows an example in which the pixel electrode layer 230 and the common electrode layer 232 are formed into a flat plate-shaped continuous conductive film that does not include an aperture pattern in at least one pixel. Since the pixel electrode layer 230 and the common electrode layer 232 are formed so as to cover the first structure 233 or the second structures 235a and 235b even if they are flat conductive films, they are arranged to face each other on the surface. It has convex parts that mesh with each other alternately.

Further, the common electrode layer may be a flat plate-shaped continuous conductive film, and the pixel electrode layer may be selectively formed only on the side surface and the upper surface of the first structure.

Further, when a voltage is applied to the pixel electrode layer 230, the common electrode layer 232a, and the common electrode layer 232b, which are adjacent to the pixel electrode layer 230 via the liquid crystal layer 208, and the common electrode layer 232a or the common electrode layer 232b, respectively. It is a distance at which the liquid crystal of the liquid crystal layer 208 interposed between the electrode layers responds. The shortest distance between the side surfaces of the pixel electrode layer 230 adjacent to each other via the liquid crystal layer 208 and the common electrode layer 232a or the common electrode layer 232b is 0.5 μm or more and 30 μm or less, preferably 1 μm or more and 10 μm or less. The voltage to be applied is appropriately controlled according to the above.

In the present specification, the distance between the adjacent pixel electrode layer and the common electrode layer is defined as the portions of the pixel electrode layer and the common electrode layer protruding from the liquid crystal layer (side surfaces in the cross-sectional views of FIGS. 2 and 3). The shortest distance of. The liquid crystal can be made to respond by the electric field formed between the side surface of the adjacent pixel electrode layer and the side surface of the common electrode layer.

Therefore, the shortest distance between the side surfaces of the first structure 233 adjacent to each other via the liquid crystal layer 208 and the second structure 235a or the second structure 235b is also 0.5 μm or more and 30 μm or less, preferably 1 μm or more and 10 μm. The voltage applied to the pixel electrode layer 230, the common electrode layer 232a, and the common electrode layer 232b is appropriately controlled according to the distance.

As described above, in the pixel, the pixel electrode layer and / and the common electrode layer can be formed as a flat plate-shaped continuous conductive film. If a flat plate-shaped continuous conductive film is used, fine etching of the electrode layer can be omitted in the process.

In the case of the present embodiment, the film thickness and shape of the first structure 233 and the second structures 235a and 235b so that the pixel electrode layer 230 and the common electrode layers 232 (232a, 232b) do not come into contact with each other. , The thickness of the pixel electrode layer 230, the common electrode layer 232 (232a, 232b), and the liquid crystal layer 208 are controlled.

The results of calculating the applied state of the electric field in the liquid crystal display device are shown in FIGS. 14 (B) and 15 (B). The calculation was performed using a Shintech LCD Master and 2s Bench.

14 (A) and 15 (A) are diagrams showing the calculated configuration of the liquid crystal display device. In FIG. 14A, as shown in FIG. 2, the pixel electrode layer 230 is formed as a continuous flat conductive film, and the common electrode layers 232a and 232b are selectively selected only on the upper surface and the side surface of the second structures 235a and 235b. 15 (A) is an example in which the pixel electrode layer 230 and the common electrode layer 232 are formed as a flat plate-like continuous conductive film as shown in FIG. As the first structure 233 and the second structures 235a and 235b, an insulator having a dielectric constant of 4 was used, and the width of the cross section of the portion in contact with the substrate was 2.5 μm. The film thickness (height) of the first structure 233 and the second structures 235a and 235b is 3 μm. The film thickness (height) of the first structure 233 and the second structures 235a and 235b referred to here is the maximum value from the bottom surface (first substrate 200 or second substrate 201).

In FIGS. 14 (A) (B) and 15 (A) (B), the film thicknesses of the pixel electrode layer 230 and the common electrode layer 232 (232a, 232b) are 0.1 μm, assuming that they are arranged in the same plane. The distance between the first structure 233 and the second structures 235a and 235b is 2.5 μm. The distance from the first substrate 200 to the second substrate 201, which corresponds to the cell gap (maximum film thickness of the liquid crystal layer), is 4 μm.

For the structures of FIGS. 14 (A) and 15 (A), the calculation results calculated with the common electrode layer set to 0 V and the pixel electrode layer set to 10 V are shown in FIGS. 14 (B) and 15 (B).

In FIGS. 14 (B) and 15 (B), the solid lines show equipotential lines, and the equipotential lines spread around the pixel electrode layer or the common electrode layer that covers the periphery of the rib-shaped structure. Is formed.

Since the electric field is generated perpendicular to the isobaric line, as shown in FIGS. 14 (B) and 15 (B), the pixel electrode layer 230 provided so as to cover the surface of the first structure 233 and the second It can be confirmed that a lateral electric field is applied between the common electrode layers 232 (232a, 232b) provided so as to cover the surfaces of the structures 235a and 235b.

Therefore, when a voltage is applied between the pixel electrode layer 230 and the common electrode layer 232 (232a, 232b), a wide and strong electric field is formed between the pixel electrode layer 230 and the common electrode layer 232 (232a, 232b). And the electric field can be used to control the liquid crystal molecules.

Therefore, the liquid crystal molecules in the entire liquid crystal layer 208 including the film thickness direction can be made to respond, and the white transmittance is improved. Therefore, the contrast ratio, which is the ratio between the white transmittance and the black transmittance (the transmittance of light when displaying black), can also be increased. Further, even a liquid crystal material (liquid crystal mixture) exhibiting a highly viscous blue phase can effectively form an electric field, so that low power consumption can be achieved.

As described above, the contrast ratio can be increased in a liquid crystal display device using a liquid crystal layer exhibiting a blue phase.

Further, since a high white transmittance can be obtained at a lower voltage, it is possible to achieve low power consumption of the liquid crystal display device.

(Embodiment 3) An example of an active matrix type liquid crystal display device to which the invention disclosed in the present specification is applied will be described with reference to FIG.

FIG. 4A is a plan view of the liquid crystal display device and shows one pixel. FIG. 4 (B) is a cross-sectional view taken along the line X1-X2 of FIG. 4 (A).

In FIG. 4A, a plurality of source wiring layers (including the source electrode layer 405a) are arranged in a state of being parallel to each other (extending in the vertical direction in the figure) and separated from each other. The plurality of gate wiring layers (including the gate electrode layer 401) extend in a direction substantially orthogonal to the source wiring layer (left-right direction in the drawing) and are arranged so as to be separated from each other. The capacitive wiring layer 408 is arranged at a position adjacent to each of the plurality of gate wiring layers, and extends in a direction substantially parallel to the gate wiring layer, that is, a direction substantially orthogonal to the source wiring layer (left-right direction in the figure). ing. A substantially rectangular space is surrounded by the source wiring layer, the capacitance wiring layer 408, and the gate wiring layer, and the pixel electrode layer and the common electrode layer of the liquid crystal display device are arranged in this space via the liquid crystal layer 444. ing. The transistor 420 that drives the pixel electrode layer is arranged in the upper left corner of the figure. A plurality of pixel electrode layers and transistors are arranged in a matrix.

In the liquid crystal display device of FIG. 4, the first electrode layer 447 electrically connected to the transistor 420 functions as a pixel electrode layer, and the second electrode layer 448 functions as a common electrode layer. The capacitance is formed by the first electrode layer 447 and the capacitance wiring layer 408. The common electrode layer can be operated in a floating state (electrically isolated state), but it is set to a level that does not cause flicker near a fixed potential, preferably a common potential (intermediate potential of the image signal sent as data). You may.

The first electrode layer 447, which is a pixel electrode layer, and the second electrode layer 448, which is a common electrode layer, project to the liquid crystal layer 444 showing the blue phase, and adjacent ones are spaced apart from each other with the liquid crystal layer 444 interposed therebetween. They are arranged so that they mesh with each other.

The first electrode layer 447 and the second electrode layer 448 that are adjacent to each other via the liquid crystal layer 444 are first when a predetermined voltage is applied to the first electrode layer 447 and the second electrode layer 448, respectively. The distance at which the liquid crystal of the liquid crystal layer 444 interposed between the electrode layer 447 and the second electrode layer 448 responds. The voltage to be applied is appropriately controlled according to the distance.

Further, the positions of the first electrode layer 447 and the second electrode layer 448 in the liquid crystal layer 444 can be controlled by providing structures under the first electrode layer 447 and the second electrode layer 448, respectively. it can.

The first electrode layer 447 is formed on the upper surface side surface of the first structure 449 provided so as to project from the surface of the interlayer film 413 on the first substrate 441 (also referred to as the element substrate) on the liquid crystal layer 444 side to the liquid crystal layer 444. The second electrode layer 448 is formed so as to cover the upper surface side surface of the second structure 445 provided so as to project from the surface of the second substrate 442 on the liquid crystal layer 444 side to the liquid crystal layer 444.

Further, in the cross-sectional view of FIG. 4, the first structure 449 and the first electrode layer 447 and the second structure 445 and the second electrode layer 448 are provided alternately without being overlapped with each other.

In the in-plane direction, as shown in the plan view of FIG. 4 (A), the rib-shaped first structure 449 and the second structure having substantially the same shape as the first electrode layer 447 or the second electrode layer 448. The structure 445 has a shape including a bent portion having an opening pattern and a branched comb-teeth shape, and is formed so as not to overlap when the first substrate 441 and the second substrate 442 are arranged to face each other.

In the thickness (film thickness) direction, as shown in the cross-sectional view of FIG. 4 (B), the first structure 449 and the second structure 445 are the first structure 449 or the second structure, respectively. When the first substrate 441 and the second substrate 442 are arranged to face each other so as to include the surface on which the structure 445 is provided, the rib-shaped protrusions mesh with each other with the liquid crystal layer 444 in between. It is held by the sealing material.

In the present embodiment, the first electrode layer 447 and the second electrode layer 448 reflect the shape of the first structure 449 or the second structure 445 provided below, and have a similar opening pattern. This is an example of a shape including a bent portion and a branched comb-teeth shape.

The first structure 449 and the second structure 445 are dome-shaped structures having a rounded tip with a cross section close to a semicircle. When the surface of the structure has a curved surface as described above, the first electrode layer 447 and the second electrode layer 448 laminated on the structure can be formed in a good shape with good coverage.

Since the first electrode layer 447, the first structure 449, the second electrode layer 448, and the second structure 445 have an opening pattern, they are shown in the cross-sectional view of FIG. 4 (B). Is shown as a plurality of divided electrode layers or structures.

The first electrode layer 447 is formed so as to cover the upper surface and the side surface of the rib-shaped first structure 449 provided on the first substrate 441, and the rib-shaped structure provided on the second substrate 442 is formed. By forming the second electrode layer 448 so as to cover the upper surface and the side surface of the second structure 445, the formation areas of the first electrode layer 447 and the second electrode layer 448 are set in the film thickness direction of the liquid crystal layer 444. Can be expanded (three-dimensionally). Further, by covering the rib-shaped first structure 449 or the second structure 445, the protrusions formed on the surfaces of the first electrode layer 447 and the second electrode layer 448 are alternately meshed with each other. , The first substrate 441 and the second substrate 442 are arranged so as to face each other.

Therefore, when a voltage is applied to the first electrode layer 447 and the second electrode layer 448, an electric field can be widely formed between the first electrode layer 447 and the second electrode layer 448. Liquid crystal molecules can be controlled using an electric field.

As in the second embodiment, the first electrode layer 447 and / and the second electrode layer 448 may be a flat plate-shaped continuous conductive film.

Therefore, the liquid crystal molecules in the entire liquid crystal layer including the film thickness direction can be made to respond, and the white transmittance is improved. Therefore, the contrast ratio, which is the ratio between the white transmittance and the black transmittance (the transmittance of light when displaying black), can also be increased.

The first structure 449 and the second structure 445 can be formed by the same materials and methods as the first structure 233 and the second structures 235a and 235b shown in the first embodiment.

As shown in FIG. 4B, the first structure 449 on which the first electrode layer 447 is formed and the second structure 445 on which the second electrode layer 448 is formed have curvatures at the ends. The tapered shape is preferable because the filmability of the first electrode layer 447 and the second electrode layer 448 is improved. In the present embodiment, the first electrode layer 447 is in contact with the drain electrode layer 405b of the transistor 420 and is continuously formed on the first structure 449, but is in contact with the drain electrode layer 405b. An electrode layer may be formed, and a first electrode layer 447 may be formed through the electrode layer.

Further, when an interlayer film is formed by covering the transistor and a structure is formed on the interlayer film, a contact hole for connecting to the transistor may be opened in the interlayer film after the structure is formed by etching. .. Note that FIG. 4 shows an example in which a contact hole is formed in the insulating film to be the interlayer film, and then the insulating film is etched to form a structure.

The transistor 420 is an inverted staggered thin film transistor, formed on a first substrate 441 which is a substrate having an insulating surface, and has a gate electrode layer 401, a gate insulating layer 402, a semiconductor layer 403, a source electrode layer 405a, and a drain electrode layer. Includes 405b.

An insulating film 407 and an insulating film 409 that cover the transistor 420 and are in contact with the semiconductor layer 403 are provided, and an interlayer film 413 is laminated on the insulating film 409.

The method for forming the interlayer film 413 is not particularly limited, and depending on the material, spin coating, dipping, spray coating, droplet ejection method (inkjet method, screen printing, offset printing, etc.), roll coating, curtain coating, knife. A coat or the like can be used.

The first substrate 441 and the second substrate 442, which is the opposite substrate, are sandwiched between the liquid crystal layer 444 and fixed with a sealing material. As a method for forming the liquid crystal layer 444, a dispenser method (dropping method) or an injection method in which the first substrate 441 and the second substrate 442 are bonded together and then the liquid crystal is injected using a capillary phenomenon or the like can be used. it can.

A liquid crystal material exhibiting a blue phase can be used for the liquid crystal layer 444. The liquid crystal layer 444 is formed by using a liquid crystal material containing a liquid crystal, a chiral agent, a photocurable resin, and a photopolymerization initiator.

As the sealing material, it is typically preferable to use a visible light curable, ultraviolet curable or thermosetting resin. Typically, acrylic resin, epoxy resin, amine resin and the like can be used. It may also contain a light (typically ultraviolet) polymerization initiator, a thermosetting agent, a filler and a coupling agent.

After filling the gap between the first substrate 441 and the second substrate 442 with the liquid crystal material, the polymer is stabilized by irradiating with light to form the liquid crystal layer 444. The light has a wavelength at which the photocurable resin contained in the liquid crystal layer and the photopolymerization initiator react. By the polymer stabilization treatment by this light irradiation, the temperature range in which the liquid crystal layer 444 shows a blue phase can be widely improved.

The sealing material may also be cured by a light irradiation step of a polymer stabilization treatment, such as when a photocurable resin such as ultraviolet rays is used as the sealing material and a liquid crystal layer is formed by a dropping method.

In the present embodiment, the polarizing plate 443a is provided on the outside of the first substrate 441 (opposite to the liquid crystal layer 444), and the polarizing plate 443b is provided on the outside of the second substrate 442 (opposite to the liquid crystal layer 444). Further, in addition to the polarizing plate, an optical film such as a retardation plate and an antireflection film may be provided. For example, circularly polarized light using a polarizing plate and a retardation plate may be used. The liquid crystal display device can be completed by the above steps.

Further, when a plurality of liquid crystal display devices are manufactured using a large substrate (so-called multi-chamfering), the dividing step can be performed before the polymer stabilization treatment or before the polarizing plate is provided. Considering the influence of the splitting process on the liquid crystal layer (such as orientation disorder due to the force applied during the splitting step), it is preferable that the first substrate and the second substrate are bonded together and then before the polymer stabilization treatment.

Although not shown, a backlight, a side light, or the like may be used as the light source. The light source is irradiated so as to pass through from the first substrate 441 side, which is the element substrate, to the second substrate 442, which is the viewing side.

The first electrode layer 447 and the second electrode layer 448 are indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, and the like. A translucent conductive material such as indium tin oxide (hereinafter referred to as ITO), indium zinc oxide, and indium tin oxide to which silicon oxide is added can be used.

The first electrode layer 447 and the second electrode layer 448 are tungsten (W), molybdenum (Mo), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), and tantalum (Ta). ), Chromium (Cr), Cobalt (Co), Nickel (Ni), Titanium (Ti), Platinum (Pt), Aluminum (Al), Copper (Cu), Silver (Ag) and other metals, or alloys thereof, or It can be formed from the metal nitride using one or more kinds.

Further, the first electrode layer 447 and the second electrode layer 448 can be formed by using a conductive composition containing a conductive polymer (also referred to as a conductive polymer). The pixel electrode formed by using the conductive composition preferably has a sheet resistance of 10000 Ω / or less and a light transmittance of 70% or more at a wavelength of 550 nm. Further, the resistivity of the conductive polymer contained in the conductive composition is preferably 0.1 Ω · cm or less.

As the conductive polymer, a so-called π-electron conjugated conductive polymer can be used. For example, polyaniline or a derivative thereof, polypyrrole or a derivative thereof, polythiophene or a derivative thereof, or a copolymer of two or more kinds thereof can be mentioned.

An insulating film serving as a base film may be provided between the first substrate 441 and the gate electrode layer 401. The base film has a function of preventing the diffusion of impurity elements from the first substrate 441, and is made of one or more films selected from a silicon nitride film, a silicon oxide film, a silicon nitride film, or a silicon oxide film. It can be formed by a single layer or a laminated structure. The material of the gate electrode layer 401 is formed as a single layer or laminated using a metal material such as molybdenum, titanium, chromium, tantalum, tungsten, aluminum, copper, neodymium, scandium, or an alloy material containing these as main components. can do. When a light-shielding conductive film is used for the gate electrode layer 401, it is possible to prevent light from the backlight (light incident from the first substrate 441) from being incident on the semiconductor layer 403.

For example, the two-layer laminated structure of the gate electrode layer 401 includes a two-layer laminated structure in which a molybdenum layer is laminated on an aluminum layer, a two-layer structure in which a molybdenum layer is laminated on a copper layer, or a copper layer. It is preferable to have a two-layer structure in which a titanium nitride layer or a tantalum nitride layer is laminated, or a two-layer structure in which a titanium nitride layer and a molybdenum layer are laminated. As the three-layer laminated structure, it is preferable to have a laminated structure in which a tungsten layer or a tungsten nitride layer, an alloy of aluminum and silicon, an alloy of aluminum and titanium, and a titanium nitride layer or a titanium layer are laminated.

The gate insulating layer 402 can be formed by using a plasma CVD method, a sputtering method, or the like to form a silicon oxide layer, a silicon nitride layer, a silicon nitride layer, or a silicon nitride layer in a single layer or in a laminated manner. Further, as the gate insulating layer 402, it is also possible to form a silicon oxide layer by a CVD method using an organic silane gas. As an organic silane gas, ethyl silicate (TEOS: chemical formula Si (OC)₂H₅)₄), Tetramethylsilane (TMS: Chemical formula Si (CH)₃)₄), Tetramethylcyclotetrasiloxane (TMCTS), Octamethylcyclotetrasiloxane (OMCTS), Hexamethyldisilazane (HMDS), Triethoxysilane (SiH (OC))₂H₅)₃), Trisdimethylaminosilane (SiH (N (CH))₃)₂)₃) And other silicon-containing compounds can be used.

In the process of manufacturing the semiconductor layer and the wiring layer, an etching process is used to process the thin film into a desired shape. As the etching step, dry etching or wet etching can be used.

Etching equipment used for dry etching includes etching equipment using reactive ion etching (RIE method) and dry etching equipment using high-density plasma sources such as ECR (Electron Cyclotron Resonance) and ICP (Inductively Coupled Plasma). Can be used. In addition, as a dry etching device that can easily obtain uniform discharge over a wider area than an ICP etching device, the upper electrode is grounded, a high frequency power supply of 13.56 MHz is connected to the lower electrode, and 3.2 is further connected to the lower electrode. There is an ECCP (Enhanced Capacitively Coupled Plasma) mode etching device connected to a MHz low frequency power supply. This ECCP mode etching apparatus can be used, for example, when a 10th generation substrate having a size of more than 3 m is used as the substrate.

In dry etching, the etching conditions (the amount of power applied to the coil-type electrode, the amount of power applied to the electrode on the substrate side, the electrode temperature on the substrate side, etc.) are appropriately adjusted so that the etching can be performed in a desired processing shape.

In wet etching, the etching conditions (etching liquid, etching time, temperature, etc.) are appropriately adjusted according to the material so that the etching can be performed in a desired processing shape.

As the material of the source electrode layer 405a and the drain electrode layer 405b, an element selected from Al, Cr, Ta, Ti, Mo, and W, an alloy containing the above-mentioned elements as a component, or an alloy film in which the above-mentioned elements are combined is used. And so on. Further, when heat treatment is performed, it is preferable that the conductive film has heat resistance to withstand the heat treatment. For example, Al alone has problems such as poor heat resistance and easy corrosion, so it is formed in combination with a heat-resistant conductive material. Elements selected from titanium (Ti), tantalum (Ta), tungsten (W), molybdenum (Mo), chromium (Cr), neodymium (Nd), and scandium (Sc) as heat-resistant conductive materials to be combined with Al. , Or an alloy containing the above-mentioned elements as a component, an alloy film in which the above-mentioned elements are combined, or a nitride containing the above-mentioned elements as a component.

The gate insulating layer 402, the semiconductor layer 403, the source electrode layer 405a, and the drain electrode layer 405b (the films forming them) may be continuously formed without being exposed to the atmosphere. By continuously forming a film without exposing it to the atmosphere, each laminated interface can be formed without being contaminated by atmospheric components or pollutant impurity elements suspended in the atmosphere, so that variations in transistor characteristics can be reduced. it can.

The semiconductor layer 403 is a semiconductor layer in which only a part of the semiconductor layer 403 is etched and has grooves (recesses).

As the insulating film 407 and the insulating film 409 covering the transistor 420, an inorganic insulating film or an organic insulating film formed by a dry method or a wet method can be used. For example, a silicon nitride film, a silicon oxide film, a silicon nitride film, an aluminum oxide film, a tantalum oxide film, or the like obtained by using a CVD method or a sputtering method can be used. Further, organic materials such as polyimide, acrylic, benzocyclobutene, polyamide and epoxy can be used. In addition to the above organic materials, low dielectric constant materials (low-k materials), siloxane-based resins, PSG (phosphorus glass), BPSG (phosphorus glass) and the like can be used. Further, a gallium oxide film may be used as the insulating film 407.

The siloxane-based resin corresponds to a resin containing a Si-O-Si bond formed using a siloxane-based material as a starting material. As the substituent of the siloxane-based resin, an organic group (for example, an alkyl group or an aryl group) or a fluoro group may be used. Moreover, the organic group may have a fluoro group. The siloxane-based resin can be used as the insulating film 407 by forming a film by a coating method and firing it.

The insulating film 407 and the insulating film 409 may be formed by laminating a plurality of insulating films formed of these materials. For example, the structure may be such that an organic resin film is laminated on the inorganic insulating film.

Further, if a resist mask having a plurality of (typically two types) thickness regions formed by a multi-gradation mask is used, the number of resist masks can be reduced, so that the process can be simplified and the cost can be reduced. You can plan.

As described above, the contrast ratio can be increased in a liquid crystal display device using a liquid crystal layer exhibiting a blue phase.

Further, since a high white transmittance can be obtained at a lower voltage, it is possible to achieve low power consumption of the liquid crystal display device.

(Embodiment 4) The liquid crystal display device shown in any one of the first to third embodiments may be provided with a light-shielding layer (black matrix). The same materials and manufacturing methods can be applied to the same materials as those in the first to third embodiments, and detailed description of the same parts or parts having the same functions will be omitted.

The light-shielding layer may be provided on the inside (side of the liquid crystal layer) of the pair of substrates to which the liquid crystal layer is sandwiched and fixed, or may be provided on the outside of the substrate (on the side opposite to the liquid crystal layer).

When a light-shielding layer is provided inside a pair of substrates in a liquid crystal display device, the light-shielding layer may be formed on the element substrate side where the pixel electrode layer is provided, or on the opposite substrate side where the common electrode layer is provided. Good. The light-shielding layer may be provided separately, or in the case of the active matrix type liquid crystal display device as in the third embodiment, it can be formed as an interlayer film provided on the element substrate. For example, in the case of the liquid crystal display device of FIG. 4 of the third embodiment, a light-shielding layer may be used as a part of the interlayer film 413.

As the light-shielding layer, a material that reflects or absorbs light and has a light-shielding property is used. For example, a black organic resin can be used, and a pigment-based black resin, carbon black, titanium black, or the like may be mixed with a photosensitive or non-photosensitive resin material such as polyimide to form the resin material. Further, a light-shielding metal film can also be used, and for example, chromium, molybdenum, nickel, titanium, cobalt, copper, tungsten, aluminum, or the like may be used.

The method of forming the light-shielding layer is not particularly limited, and depending on the material, a dry method such as a vapor deposition method, a sputtering method, or a CVD method, or a spin coating, dip, spray coating, or droplet ejection method (inkching method, screen printing, offset). A wet method such as printing) may be used, and if necessary, a desired pattern may be processed by an etching method (dry etching or wet etching).

When the light-shielding layer is used as a part of the interlayer film 413, it is preferable to use a black organic resin.

When it is formed directly on the element substrate side as a light-shielding layer as a part of the interlayer film, there is no problem of misalignment between the light-shielding layer and the pixel region, more precise control of the formation region can be performed, and even a pixel with a fine pattern can be formed. Can be handled.

In the configuration of the liquid crystal display device in which the light-shielding layer is formed on the element substrate, the light emitted from the opposite substrate side is absorbed and blocked by the light-shielding layer when the liquid crystal layer is irradiated with light for stabilizing the polymer. Since there is no such thing, the entire liquid crystal layer can be uniformly irradiated. Therefore, it is possible to prevent the orientation disorder of the liquid crystal due to the non-uniformity of photopolymerization and the accompanying display unevenness.

The light-shielding layer may be provided in the semiconductor layer of the transistor, a place where it overlaps with the contact hole, or between pixels in the liquid crystal display device.

As described above, when the light-shielding layer is provided, the light-shielding layer can block the light incident on the semiconductor layer of the transistor, so that the fluctuation of the electrical characteristics of the transistor due to the light incident can be suppressed and stabilized. it can. Further, the light-shielding layer can prevent light leakage to adjacent pixels and hide display unevenness such as light leakage due to a liquid crystal alignment defect that tends to occur on a contact hole. Therefore, it is possible to improve the definition and reliability of the liquid crystal display device.

This embodiment can be implemented in combination with the configurations described in other embodiments as appropriate.

(Embodiment 5) In this embodiment, an example of a liquid crystal display device that performs color display is shown. A color filter can be provided in the liquid crystal display device shown in any one of the first to fourth embodiments to perform color display. The same materials and manufacturing methods can be applied to the same materials as those in the first to fourth embodiments, and detailed description of the same parts or parts having the same functions will be omitted.

The color filter may be formed from a material exhibiting red (R), green (G), and blue (B) when the liquid crystal display device is used for full-color display, and at least one is used for monocolor display other than monochrome. It may be formed from a material that exhibits color.

Specifically, the liquid crystal display device is provided with a colored layer that functions as a color filter layer. The color filter layer may be provided on the inside (side of the liquid crystal layer) of the pair of substrates to which the liquid crystal layer is sandwiched and fixed, or may be provided on the outside of the substrate (on the side opposite to the liquid crystal layer).

First, a case where a color filter layer is provided inside a pair of substrates in a liquid crystal display device will be described. The color filter layer may be formed on the element substrate side where the pixel electrode layer is provided, or may be formed on the opposite substrate side where the common electrode layer is provided. Mosquitoes color filter layer may be provided separately independently, the case of an active matrix type liquid crystal display device, such as the third embodiment, it is also possible to fabricate an interlayer film provided on the element substrate. For example, in the case of the liquid crystal display device of FIG. 4 of the third embodiment, the interlayer film 413 may be configured to use a chromatic translucent resin layer that functions as a color filter layer.

When the interlayer film is directly formed on the element substrate side as a color filter layer, there is no problem of misalignment between the color filter layer and the pixel region, more precise control of the formation region is possible, and even fine pattern pixels are supported. can do. Further, since the interlayer film and the color filter layer are also used as the same insulating layer, there are advantages such as process simplification and cost reduction.

Further, in the configuration of the liquid crystal display device in which the color filter layer is built on the element substrate, the light emitted from the opposite substrate side by the color filter layer is absorbed when the liquid crystal layer is irradiated with light for stabilizing the polymer. Since it is not applied, the entire liquid crystal layer can be uniformly irradiated. Therefore, it is possible to prevent the orientation disorder of the liquid crystal due to the non-uniformity of photopolymerization and the accompanying display unevenness.

As the chromatic translucent resin that can be used as the color filter layer, a photosensitive or non-photosensitive organic resin can be used. It is preferable to use a photosensitive organic resin layer because the number of resist masks can be reduced, which simplifies the process.

The chromatic color is a color excluding achromatic colors such as black, gray, and white, and the colored layer is formed of a material that transmits only the colored chromatic light in order to function as a color filter. As the chromatic color, red, green, blue and the like can be used. Moreover, you may use cyan, magenta, yellow (yellow) and the like. To transmit only colored chromatic light means that the light transmitted through the colored layer has a peak at the wavelength of the chromatic light.

The optimum film thickness of the color filter layer may be appropriately controlled in consideration of the relationship between the concentration of the coloring material to be contained and the light transmittance.

If the thickness of the chromatic translucent resin layer differs depending on the chromatic color, or if there is unevenness due to the light-shielding layer or transistor, light of the wavelength in the visible light region is transmitted (so-called colorless and transparent) insulation. The layers may be laminated and flattened. When the flatness is increased, the coating property of the pixel electrode layer formed on the pixel electrode layer and the like can be improved, and the gap (film thickness) of the liquid crystal layer can be made uniform, so that the visibility of the liquid crystal display device can be further improved. High image quality is possible.

When the color filter is provided on the outside of the substrate, the color filter can be provided by adhering the color filter to the substrate by an adhesive layer or the like. When the color filter is provided on the outside of the facing substrate In the process order, the color filter is provided on the outside of the facing substrate after stabilizing the blue phase polymer by light irradiation.

A backlight, a side light, or the like may be used as the light source. A color display can be performed by irradiating the light source to the visual recognition side through a color filter. As a light source, a cold cathode tube or a white diode can be used. Further, optical members such as a reflector, a diffuser, a polarizing plate, and a retardation plate may be provided.

This embodiment can be implemented in combination with the configurations described in other embodiments as appropriate.

Therefore, a color display function can be added to a liquid crystal display device having high contrast and low power consumption.

(Embodiment 6) An example of configuring a liquid crystal display module as the liquid crystal display device disclosed in the present specification is shown. In this embodiment, the configuration of the liquid crystal display module 190 is shown in FIG. 6 as an example of the liquid crystal display module that performs color display.

The liquid crystal display module 190 has a backlight unit 130, a liquid crystal display panel 120 in which liquid crystal elements are provided in a matrix, a polarizing plate 125a sandwiching the liquid crystal display panel 120, and a polarizing plate 125b. In the backlight unit 130, light emitting elements, for example, LEDs (133R, 133G, and 133B) of the three primary colors are arranged in a matrix, and a diffuser plate 134 is arranged between the liquid crystal display panel 120 and the light emitting element. It can be used as 130. Further, the FPC 4018, which is an external input terminal, is electrically connected to the terminal portion provided on the liquid crystal display panel 120.

As the liquid crystal display panel 120, the liquid crystal display device shown in any one of the first to fourth embodiments can be applied.

In this embodiment, a time-addition color mixing method (field sequential method) that displays colors by time division using a light emitting diode (LED) is adopted.

The backlight unit 130 has a backlight control circuit and a backlight 132. LEDs 133R, 133G, and 133B, which are light emitting elements 133, are arranged on the backlight 132.

In this embodiment, the backlight 132 has LEDs 133R, 133G, 133B which are light emitting elements 133 having a plurality of different emission colors. As a combination of different emission colors, for example, three types of light emitting elements of red (R), green (G), and blue (B) can be used. A full-color image can be displayed by using the three primary colors of R, G, and B.

In addition, a plurality of colors selected from the light emitting elements of R, G, and B are simultaneously illuminated and expressed (for example, yellow (Y) represented by R and G, cyan (C) represented by G and B, and blue and red. Another light emitting element that emits magenta (M), etc.) may be arranged in addition to the light emitting elements of R, G, and B.

Further, in order to enrich the color reproduction characteristics of the liquid crystal display device, a light emitting element that emits light other than the three primary colors may be added. The colors that can be expressed using the R, G, and B light emitting elements are limited to the colors shown inside the triangle drawn by the three points corresponding to the respective light emitting colors on the chromaticity diagram. Therefore, the color reproducibility of the display device can be enhanced by separately adding a light emitting element arranged outside the triangle on the chromaticity diagram.

For example, deep blue (DB) represented by a point located approximately outside from the center of the chromaticity diagram toward the point corresponding to the blue light emitting element B on the chromaticity diagram, or in the chromaticity diagram. The light emitting element that emits deep red (DR), which is represented by a point located approximately outside from the center toward the point on the chromaticity diagram corresponding to the red light emitting element R, is the R of the backlight 132. Can be used in addition to, G, and B.

In FIG. 6, three colors of light 135 are schematically shown by arrows (R, G, and B). The pulsed light of different colors sequentially emitted from the backlight unit 130 is modulated by the liquid crystal element of the liquid crystal display panel 120 that operates in synchronization with the backlight unit 130, and reaches the observer from the liquid crystal display module 190. The observer captures the light emitted sequentially as an image.

Further, the liquid crystal display device exemplified in this embodiment can display a full-color image without using a color filter. Since the color filter does not absorb the light from the backlight, the light utilization efficiency is high, and the power consumption is suppressed even when displaying a full-color image.

This embodiment can be implemented in combination with the configurations described in other embodiments as appropriate.

Therefore, a color display function can be added to a liquid crystal display device having high contrast and low power consumption.

(Embodiment 7) In this embodiment, an example of a transistor applicable to the liquid crystal display device disclosed in the present specification is shown. The structure of the transistor applicable to the liquid crystal display device disclosed in the present specification is not particularly limited, and for example, a top gate structure, a stagger type or a planar type having a bottom gate structure, or the like can be used. Further, the transistor may have a single gate structure in which one channel forming region is formed, a double gate structure in which two are formed, or a triple gate structure in which three are formed. Further, it may be a dual gate type having two gate electrode layers arranged above and below the channel region via a gate insulating layer. An example of the cross-sectional structure of the transistor is shown below in FIGS. 7 (A) to 7 (D).

The transistor 410 shown in FIG. 7 (A) is one of the thin film transistors having a bottom gate structure, and is also called an inverted staggered thin film transistor.

The transistor 410 includes a gate electrode layer 401, a gate insulating layer 402, a semiconductor layer 403, a source electrode layer 405a, and a drain electrode layer 405b on a first substrate 441 having an insulating surface. Further, an insulating film 407 that covers the transistor 410 and is laminated on the semiconductor layer 403 is provided. An insulating film 409 is further formed on the insulating film 407.

The transistor 435 shown in FIG. 7B is one of the bottom gate structures called a channel protection type (also called a channel stop type) and is also called an inverted stagger type thin film transistor.

The transistor 435 has an insulating film 427 and a source that function as a channel protective layer covering the gate electrode layer 401, the gate insulating layer 402, the semiconductor layer 403, and the channel forming region of the semiconductor layer 403 on the first substrate 441 having an insulating surface. The electrode layer 405a and the drain electrode layer 405b are included. Further, the transistor 435 is covered and an insulating film 409 is formed.

The transistor 430 shown in FIG. 7C is a bottom gate type thin film transistor, and has a gate electrode layer 401, a gate insulating layer 402, a source electrode layer 405a, and a drain electrode on a first substrate 441 which is a substrate having an insulating surface. Includes layer 405b and semiconductor layer 403. Further, an insulating film 407 that covers the transistor 430 and is in contact with the semiconductor layer 403 is provided. An insulating film 409 is further formed on the insulating film 407.

In the transistor 430, the gate insulating layer 402 is provided in contact with the first substrate 441 and the gate electrode layer 401, and the source electrode layer 405a and the drain electrode layer 405b are provided in contact with the gate insulating layer 402. A semiconductor layer 403 is provided on the gate insulating layer 402, the source electrode layer 405a, and the drain electrode layer 405b.

The transistor 440 shown in FIG. 7 (D) is one of the thin film transistors having a top gate structure. The transistor 440 includes an insulating layer 437, a semiconductor layer 403, a source electrode layer 405a, a drain electrode layer 405b, a gate insulating layer 402, and a gate electrode layer 401 on a first substrate 441 having an insulating surface, and is a source electrode layer. The wiring layer 436a and the wiring layer 436b are provided in contact with the 405a and the drain electrode layer 405b, respectively, and are electrically connected to each other.

Further, a source region and a drain region (also referred to as a semiconductor layer having a single conductive type or a buffer layer) may be provided between the semiconductor layer and the source electrode layer and the drain electrode layer. For example, a semiconductor layer showing an n-type conductive type is used as the source region and the drain region.

When a semiconductor layer is used as the source region or drain region of the transistor, it is preferable that the semiconductor layer is thinner than the film thickness of the semiconductor layer used as the channel formation region and has higher conductivity (electrical conductivity).

As the conductive film such as the source electrode layer 405a, the wiring layer 436a connected to the drain electrode layer 405b, and the wiring layer 436b, the same material as the source electrode layer 405a and the drain electrode layer 405b can be used.

As the insulating films 427 and 437, the same material as the insulating film 407 can be used, and typically an inorganic insulating film such as a silicon oxide film, a silicon nitride film, an aluminum oxide film, or an aluminum nitride film is used. Can be done.

Further, as in the third embodiment, an interlayer film 413 may be formed on the insulating film 409 as a flattening insulating film in order to reduce surface irregularities caused by transistors.

This embodiment can be implemented in combination with the configurations described in other embodiments as appropriate.

(Embodiment 8) In the above embodiments 3 to 7, an oxide semiconductor will be described as an example that can be used for the semiconductor layer of the transistor.

In the transistors 410, 430, 435, and 440 of FIGS. 7A to 7D shown in the seventh embodiment, the oxide semiconductor layer can be used as the semiconductor layer 403.

Oxide semiconductors used for the semiconductor layer 403 include In-Sn-Ga-Zn-O series, which are quaternary metal oxides, In-Ga-Zn-O series, which are ternary metal oxides, and In-. Sn-Zn-O series, In-Al-Zn-O series, Sn-Ga-Zn-O series, Al-Ga-Zn-O series, Sn-Al-Zn-O series, and binary metal oxides In-Zn-O series, Sn-Zn-O series, Al-Zn-O series, Zn-Mg-O series, Sn-Mg-O series, In-Mg-O, In-Ga-O series and , In-O system, Sn-O system, Zn-O system, etc. can be used. In addition, SiO is added to the oxide semiconductor.₂May include. Here, for example, the In-Ga-Zn-O-based oxide semiconductor is an oxide containing at least In, Ga, and Zn, and the composition ratio thereof is not particularly limited. It may also contain elements other than In, Ga and Zn.

The oxide semiconductor layer has the chemical formula InMO.₃(ZnO)_mA thin film represented by (m&gt; 0) can be used. Here, M represents one or more metal elements selected from Ga, Al, Mn and Co. For example, M includes Ga, Ga and Al, Ga and Mn, or Ga and Co.

Transistors 410, 430, 435, and 440 using the oxide semiconductor layer can reduce the current value (off current value) in the off state. Therefore, when a transistor using an oxide semiconductor layer is used, the holding time of an electric signal such as an image signal can be lengthened, and the writing interval can be set long when the power is on. Therefore, the frequency of refresh operations can be reduced, which has the effect of further suppressing power consumption.

Further, the transistors 410, 430, 435, and 440 using the oxide semiconductor layer as the semiconductor layer 403 can be driven at high speed because relatively high field effect mobility can be obtained. Therefore, by using the transistor in the pixel portion of the liquid crystal display device, it is possible to provide a high-quality image. Further, since the drive circuit unit or the pixel unit can be separately manufactured on the same substrate by using the transistor, the number of parts of the liquid crystal display device can be reduced.

This embodiment can be implemented in combination with the configurations described in other embodiments as appropriate.

(Embodiment 9) This embodiment will be described in detail with reference to FIG. 8 as a transistor including an oxide semiconductor layer and another example of the manufacturing method. The same part or the part having the same function as the above-described embodiment and the steps can be performed in the same manner as in the above-described embodiment, and the repeated description will be omitted. Further, detailed description of the same part will be omitted.

FIGS. 8 (A) to 8 (E) show an example of the cross-sectional structure of the transistor. The transistor 510 shown in FIGS. 8 (A) to 8 (E) is an inverted staggered thin film transistor having a bottom gate structure similar to the transistor 410 shown in FIG. 7 (A).

The oxide semiconductor used for the semiconductor layer of the present embodiment removes hydrogen, which is an n-type impurity, from the oxide semiconductor and purifies the oxide semiconductor so as not to contain impurities other than the main component of the oxide semiconductor as much as possible. It is an type I (intrinsic) oxide semiconductor or an oxide semiconductor that is as close as possible to type I (intrinsic). That is, it is characterized in that impurities such as hydrogen and water are removed as much as possible, instead of adding impurities to form I type, so that the purified type I (intrinsic semiconductor) or close to it can be obtained. By doing so, the Fermi level (Ef) can be brought to the same level as the true Fermi level (Ei). Therefore, the oxide semiconductor layer of the transistor 510 is a highly purified and electrically type I (intrinsic) oxide semiconductor layer.

In addition, the number of carriers in the highly purified oxide semiconductor is extremely small (close to zero), and the carrier concentration is 1 × 10.¹⁴/cm³Less than, preferably 1x10¹²/cm³Less than, more preferably 1x10¹¹/cm³Is less than.

Since the number of carriers in the oxide semiconductor is extremely small, the off-current of the transistor can be reduced. The smaller the off current, the more preferable.

Specifically, the transistor 510 provided with the oxide semiconductor layer described above sets the current value (off current value) in the off state to less than 10 zA (less than 10 zA / μm) per 1 μm of the channel width and 100 zA / at 85 ° C. It can be lowered to a level less than μm.

By using a transistor having an extremely small current value (off current value) in the off state as a transistor in the pixel portion, the refresh operation in the still image region can be performed with a small number of times of writing image data.

Further, the transistor 510 provided with the oxide semiconductor layer described above has almost no temperature dependence of the on-current, and the off-current remains very small. In addition, there is little fluctuation in transistor characteristics due to photodegradation.

Hereinafter, the process of manufacturing the transistor 510 on the substrate 505 will be described with reference to FIGS. 8A to 8E.

First, a conductive film is formed on a substrate 505 having an insulating surface, and then a gate electrode layer 511 is formed by a first photolithography step. The resist mask may be formed by an inkjet method. When the resist mask is formed by the inkjet method, the photomask is not used, so that the manufacturing cost can be reduced.

As the substrate 505 having an insulating surface, a substrate similar to the first substrate 200 shown in the first embodiment can be used. In this embodiment, a glass substrate is used as the substrate 505.

An insulating film serving as a base film may be provided between the substrate 505 and the gate electrode layer 511. The undercoat has a function of preventing the diffusion of impurity elements from the substrate 505, and has a laminated structure consisting of one or more films selected from a silicon nitride film, a silicon oxide film, a silicon nitride film, or a silicon nitride film. Can be formed.

The material of the gate electrode layer 511 is formed as a single layer or laminated using a metal material such as molybdenum, titanium, tantalum, tungsten, aluminum, copper, neodymium, scandium, or an alloy material containing these as main components. can do.

Next, the gate insulating layer 507 is formed on the gate electrode layer 511. The gate insulating layer 507 uses a plasma CVD method, a sputtering method, or the like to form a silicon oxide layer, a silicon nitride layer, a silicon oxide layer, a silicon nitride layer, an aluminum oxide layer, an aluminum nitride layer, an aluminum nitride layer, and an aluminum nitride oxide. The aluminum layer or the hafnium oxide layer can be formed as a single layer or laminated.

As the oxide semiconductor of the present embodiment, an oxide semiconductor from which impurities have been removed and which has been I-shaped or substantially I-shaped is used. Since such a highly purified oxide semiconductor is extremely sensitive to interface states and interfacial charges, the interface between the oxide semiconductor layer and the gate insulating layer is important. Therefore, the gate insulating layer in contact with the highly purified oxide semiconductor is required to have high quality.

For example, high-density plasma CVD using μ waves (for example, frequency 2.45 GHz) is preferable because it can form a high-quality insulating layer that is dense and has a high dielectric strength. This is because the high-purity oxide semiconductor and the high-quality gate insulating layer are in close contact with each other, so that the interface state can be reduced and the interface characteristics can be improved.

Of course, other film forming methods such as a sputtering method and a plasma CVD method can be applied as long as a high-quality insulating layer can be formed as the gate insulating layer. Further, the insulating layer may be an insulating layer in which the film quality of the gate insulating layer and the interface characteristics with the oxide semiconductor are modified by the heat treatment after the film formation. In any case, not only the film quality as the gate insulating layer is good, but also the interface level density with the oxide semiconductor can be reduced and a good interface can be formed.

Further, in order to prevent hydrogen, hydroxyl groups and water from being contained in the gate insulating layer 507 and the oxide semiconductor film 530 as much as possible, as a pretreatment for forming the oxide semiconductor film 530, the gate is used in the preheating chamber of the sputtering apparatus. It is preferable that the substrate 505 on which the electrode layer 511 is formed or the substrate 505 on which the gate insulating layer 507 is formed is preheated to remove impurities such as hydrogen and moisture adsorbed on the substrate 505 and exhaust them. A cryopump is preferable as the exhaust means provided in the preheating chamber. The preheating process may be omitted. Further, this preheating may be similarly performed on the substrate 505 in which the source electrode layer 515a and the drain electrode layer 515b are formed before the insulating film 516 is formed.

Next, an oxide semiconductor film 530 having a film thickness of 2 nm or more and 200 nm or less, preferably 5 nm or more and 30 nm or less is formed on the gate insulating layer 507 (see FIG. 8 (A)).

Before the oxide semiconductor film 530 is formed by the sputtering method, argon gas is introduced to perform reverse sputtering to generate plasma, and powdery substances (particles, dust) adhering to the surface of the gate insulating layer 507 are performed. It is preferable to remove (also referred to as). The reverse sputtering is a method of modifying the surface by forming plasma in the vicinity of the substrate by applying a voltage to the substrate side using an RF power supply in an argon atmosphere without applying a voltage to the target side. In addition, nitrogen, helium, oxygen and the like may be used instead of the argon atmosphere.

The oxide semiconductor used for the oxide semiconductor film 530 includes the quaternary metal oxide, the ternary metal oxide, the binary metal oxide, the In-O type, and the Sn- shown in the eighth embodiment. Oxide semiconductors such as O-based and Zn-O-based can be used. In addition, SiO is added to the oxide semiconductor.₂May include. In the present embodiment, the oxide semiconductor film 530 is formed by a sputtering method using an In-Ga-Zn-O oxide target. The cross-sectional view at this stage corresponds to FIG. 8 (A). Further, the oxide semiconductor film 530 can be formed by a sputtering method in a rare gas (typically argon) atmosphere, an oxygen atmosphere, or a mixed atmosphere of a rare gas and oxygen.

As a target for producing the oxide semiconductor film 530 by the sputtering method, for example, as a composition ratio, In₂O₃: Ga₂O₃: ZnO = 1: 1: 1 [mol ratio] (that is, In: Ga: Zn = 1: 1: 0.5 [atom ratio]) can be used. In addition, a target having a composition ratio of In: Ga: Zn = 1: 1: 1 [atom ratio] or In: Ga: Zn = 1: 1: 2 [atom ratio] may be used. The filling rate of the oxide target is 90% or more and 100% or less, preferably 95% or more and 99.9%. By using a metal oxide target having a high filling rate, the formed oxide semiconductor film becomes a dense film.

As the sputter gas used for forming the oxide semiconductor film 530, it is preferable to use a high-purity gas from which impurities such as hydrogen, water, hydroxyl groups and hydrides have been removed.

The substrate is held in a film forming chamber kept under reduced pressure, and the substrate temperature is 100 ° C or higher and 600 ° C or lower, preferably 200 ° C or higher and 400 ° C or lower. By forming a film while heating the substrate, the concentration of impurities contained in the formed oxide semiconductor film can be reduced. In addition, damage due to sputtering is reduced. Then, a sputter gas from which hydrogen and water have been removed is introduced while removing residual water in the film forming chamber, and an oxide semiconductor film 530 is formed on the substrate 505 using the above target. In order to remove the residual moisture in the film forming chamber, it is preferable to use an adsorption type vacuum pump, for example, a cryopump, an ion pump, or a titanium sublimation pump. Further, the exhaust means may be a turbo pump to which a cold trap is added. The film forming chamber exhausted by using the cryopump is, for example, hydrogen atoms and water (H).₂Since a compound containing a hydrogen atom (more preferably a compound containing a carbon atom) such as O) is exhausted, the concentration of impurities contained in the oxide semiconductor film formed in the film forming chamber can be reduced.

As an example of the film forming conditions, the conditions under which the distance between the substrate and the target is 100 mm, the pressure is 0.6 Pa, the direct current (DC) power supply is 0.5 kW, and the oxygen (oxygen flow rate ratio is 100%) atmosphere are applied. It is preferable to use a pulsed DC power supply because powdery substances (also referred to as particles and dust) generated during film formation can be reduced and the film thickness distribution becomes uniform.

Next, the oxide semiconductor film 530 is processed into an island-shaped oxide semiconductor layer by a second photolithography step. Further, the resist mask for forming the island-shaped oxide semiconductor layer may be formed by an inkjet method. When the resist mask is formed by the inkjet method, the photomask is not used, so that the manufacturing cost can be reduced.

Further, when the contact hole is formed in the gate insulating layer 507, the step can be performed at the same time as the processing of the oxide semiconductor film 530.

The etching of the oxide semiconductor film 530 here may be dry etching or wet etching, or both may be used. For example, as the etching solution used for wet etching of the oxide semiconductor film 530, a solution in which phosphoric acid, acetic acid, and nitric acid are mixed can be used. Further, ITO 07N (manufactured by Kanto Chemical Co., Inc.) may be used.

Next, the oxide semiconductor layer is subjected to the first heat treatment. The oxide semiconductor layer can be dehydrated or dehydrogenated by this first heat treatment. The temperature of the first heat treatment shall be 400 ° C or higher and 750 ° C or lower, or 400 ° C or higher and lower than the strain point of the substrate. Here, the substrate is introduced into an electric furnace, which is one of the heat treatment devices, and the oxide semiconductor layer is heat-treated at 450 ° C for 1 hour in a nitrogen atmosphere, and then oxidized without being exposed to the atmosphere. Prevents water and hydrogen from being remixed into the physical semiconductor layer, and obtains an oxide semiconductor layer 531 (see Fig. 8 (B)).

The heat treatment device is not limited to the electric furnace, and a device that heats the object to be treated by heat conduction or heat radiation from a heating element such as a resistance heating element may be used. For example, an RTA (Rapid Thermal Anneal) device such as a GRTA (Gas Rapid Thermal Anneal) device or an LRTA (Lamp Rapid Thermal Anneal) device can be used. The LRTA device is a device that heats an object to be treated by radiating light (electromagnetic waves) emitted from lamps such as halogen lamps, metal halide lamps, xenon arc lamps, carbon arc lamps, high-pressure sodium lamps, and high-pressure mercury lamps. The GRTA device is a device that performs heat treatment using high-temperature gas. As the high-temperature gas, a rare gas such as argon or an inert gas such as nitrogen that does not react with the object to be treated by heat treatment is used.

For example, as the first heat treatment, the substrate is moved into an inert gas heated to a high temperature of 650 ° C to 700 ° C, heated for several minutes, and then the substrate is moved and heated to a high temperature. GRTA may be performed out of the gas.

In the first heat treatment, it is preferable that nitrogen or a rare gas such as helium, neon, or argon does not contain water, hydrogen, or the like. Alternatively, the purity of nitrogen or a rare gas such as helium, neon, or argon to be introduced into the heat treatment apparatus is 6N (99.9999%) or more, preferably 7N (99.99999%) or more (that is, the impurity concentration is 1ppm or less, preferably 0.1ppm). The following) is preferable.

In addition, after heating the oxide semiconductor layer in the first heat treatment, high-purity oxygen gas and high-purity N are placed in the same furnace.₂O gas or ultra-dry air (dew point of -40 ° C or less, preferably -60 ° C or less) may be introduced. Oxygen gas or N₂It is preferable that the O gas does not contain water, hydrogen, or the like. Alternatively, oxygen gas or N to be introduced into the heat treatment equipment₂The purity of O gas is 6N or more, preferably 7N or more (that is, oxygen gas or N).₂The impurity concentration in the O gas is preferably 1 ppm or less, preferably 0.1 ppm or less). Oxygen gas or N₂The oxide semiconductor layer is highly purified by supplying oxygen, which is the main component material of the oxide semiconductor, which has been reduced at the same time by the removal process of impurities by dehydration or dehydrogenation treatment by the action of O gas. Dehydrogenation and electrical conversion to type I (intrinsic).

Further, the first heat treatment of the oxide semiconductor layer can also be performed on the oxide semiconductor film 530 before being processed into the island-shaped oxide semiconductor layer. In that case, after the first heat treatment, the substrate is taken out from the heating device and a photolithography step is performed.

In addition to the above, in the first heat treatment, if the oxide semiconductor layer is formed, the source electrode layer and the drain electrode layer are laminated on the oxide semiconductor layer, or the source electrode layer and the source electrode layer and the first heat treatment are performed. After forming an insulating layer on the drain electrode layer, any of these may be performed.

When a contact hole is formed in the gate insulating layer 507, the step may be performed before or after the first heat treatment of the oxide semiconductor film 530.

Further, by forming the oxide semiconductor layer in two steps and performing the heat treatment in two steps, the thickness of the base member can be increased regardless of the material such as oxide, nitride, or metal. An oxide semiconductor layer having a thick crystal region (single crystal region), that is, a crystal region oriented c-axis perpendicularly to the film surface may be formed. For example, a first oxide semiconductor film of 3 nm or more and 15 nm or less is formed, and 450 ° C or more and 850 ° C or less, preferably 550 ° C or more and 750 ° in an atmosphere of nitrogen, oxygen, rare gas, or dry air. The first heat treatment of C or less is performed to form a first oxide semiconductor film having a crystal region (including plate-like crystals) in a region including the surface. Then, a second oxide semiconductor film thicker than the first oxide semiconductor film is formed, and a second heat treatment is performed at 450 ° C or higher and 850 ° C or lower, preferably 600 ° C or higher and 700 ° C or lower. , The first oxide semiconductor film is used as a seed for crystal growth, and the crystal is grown upward to crystallize the entire second oxide semiconductor film, resulting in an oxide semiconductor layer having a thick crystal region. It may be formed.

Next, a conductive film to be a source electrode layer and a drain electrode layer (including wiring formed of the same layer) is formed on the gate insulating layer 507 and the oxide semiconductor layer 531. As the conductive film used for the source electrode layer and the drain electrode layer, the materials used for the source electrode layer 405a and the drain electrode layer 405b shown in the third embodiment can be used.

A resist mask is formed on the conductive film by the third photolithography step, and is selectively etched to form the source electrode layer 515a and the drain electrode layer 515b, and then the resist mask is removed (see FIG. 8 (C)). .).

Ultraviolet rays, KrF laser light, or ArF laser light may be used for the exposure at the time of forming the resist mask in the third photolithography step. The channel length L of the transistor formed later is determined by the distance between the lower end of the source electrode layer and the lower end of the drain electrode layer adjacent to each other on the oxide semiconductor layer 531. When exposing with a channel length of less than L = 25 nm, use Extreme Ultraviolet, which has an extremely short wavelength of several nm to several tens of nm, to perform exposure during resist mask formation in the third photolithography step. Good to do. Exposure with ultra-ultraviolet rays has a high resolution and a large depth of focus. Therefore, the channel length L of the transistor formed later can be set to 10 nm or more and 1000 nm or less, and the operating speed of the circuit can be increased.

Further, in order to reduce the number of photomasks and the number of steps used in the photolithography step, even if the etching step is performed using a resist mask formed by a multi-gradation mask which is an exposure mask in which the transmitted light has a plurality of intensities. Good. The resist mask formed by using the multi-gradation mask has a shape having a plurality of film thicknesses, and the shape can be further deformed by etching, so that it can be used in a plurality of etching steps for processing different patterns. .. Therefore, it is possible to form a resist mask corresponding to at least two or more different patterns by using one multi-tone mask. Therefore, the number of exposure masks can be reduced, and the corresponding photolithography process can also be reduced, so that the process can be simplified.

It is desired to optimize the etching conditions so that the oxide semiconductor layer 531 is not etched and divided when the conductive film is etched. However, it is difficult to obtain the condition that only the conductive film is etched and the oxide semiconductor layer 531 is not etched at all. When the conductive film is etched, only a part of the oxide semiconductor layer 531 is etched, and the groove (recess) is formed. It may be an oxide semiconductor layer having.

In the present embodiment, a Ti film is used as the conductive film, and an In-Ga-Zn-O-based oxide semiconductor is used for the oxide semiconductor layer 531. Therefore, ammonia superwater (ammonia, water, hydrogen peroxide) is used as the etchant. Water mixture) is used.

Then N₂O, N₂Alternatively, plasma treatment using a gas such as Ar may be performed to remove adsorbed water or the like adhering to the surface of the exposed oxide semiconductor layer. When plasma treatment is performed, an insulating film 516 is formed as a protective insulating film that comes into contact with a part of the oxide semiconductor layer without being exposed to the atmosphere.

The insulating film 516 has a film thickness of at least 1 nm or more, and can be formed by appropriately using a method such as a sputtering method in which impurities such as water and hydrogen are not mixed into the insulating film 516. When hydrogen is contained in the insulating film 516, the hydrogen penetrates into the oxide semiconductor layer or oxygen is extracted from the oxide semiconductor layer by hydrogen, and the back channel of the oxide semiconductor layer becomes low resistance (N type). There is a risk that parasitic channels will be formed. Therefore, it is important not to use hydrogen in the film forming method so that the insulating film 516 is a film containing as little hydrogen as possible.

In the present embodiment, a silicon oxide film having a film thickness of 200 nm is formed as the insulating film 516 by a sputtering method. The substrate temperature at the time of film formation may be room temperature or higher and 300 ° C. or lower, and in this embodiment, 100 ° C. The film formation of the silicon oxide film by the sputtering method can be performed in a rare gas (typically argon) atmosphere, an oxygen atmosphere, or a mixed atmosphere of a rare gas and oxygen. Further, a silicon oxide target or a silicon target can be used as the target. For example, using a silicon target, silicon oxide can be formed by a sputtering method in an atmosphere containing oxygen. The insulating film 516 formed in contact with the oxide semiconductor layer contains water, hydrogen ions, and OH.^-An inorganic insulating film that does not contain impurities such as, and blocks the invasion of these from the outside is used, and is typically a silicon oxide film, a silicon nitride film, an aluminum oxide film, an aluminum nitride film, or a gallium oxide film. Is used.

As in the case of film formation of the oxide semiconductor film 530, it is preferable to use an adsorption type vacuum pump (cryopump or the like) in order to remove residual moisture in the film formation chamber of the insulating film 516. It is possible to reduce the concentration of impurities contained in the insulating film 516 formed in the film forming chamber exhausted by using a cryopump. Further, as an exhaust means for removing residual moisture in the film-forming chamber of the insulating film 516, a turbo pump to which a cold trap is added may be used.

As the sputter gas used for forming the insulating film 516, it is preferable to use a high-purity gas from which impurities such as hydrogen, water, hydroxyl groups and hydrides have been removed.

Next, the second heat treatment (preferably 200 ° C. or higher and 400 ° C. or lower, for example 250 ° C. or higher and 350 ° C. or lower) is performed in an inert gas atmosphere or an oxygen gas atmosphere. For example, a second heat treatment is performed at 250 ° C. for 1 hour in a nitrogen atmosphere. When the second heat treatment is performed, a part of the oxide semiconductor layer (channel forming region) is heated in contact with the insulating film 516.

Through the above steps, the oxide semiconductor film is subjected to the first heat treatment to intentionally remove impurities such as hydrogen, water, hydroxyl groups or hydrides (also referred to as hydrides) from the oxide semiconductor layer. In addition, oxygen, which is one of the main component materials constituting the oxide semiconductor, which is simultaneously reduced by the removal process of impurities, can be supplied. Therefore, the oxide semiconductor layer is highly purified and electrically converted to type I (intrinsic).

The transistor 510 is formed by the above steps (see FIG. 8 (D)).

Further, when a silicon oxide layer containing many defects is used in the insulating film 516, impurities such as hydrogen, water, hydroxyl groups or hydrides contained in the oxide semiconductor layer are removed from the oxide insulating layer by heat treatment after the silicon oxide layer is formed. It has the effect of further reducing the impurities contained in the oxide semiconductor layer.

An insulating film 506 may be further formed on the insulating film 516. For example, an RF sputtering method is used to form a silicon nitride film. The RF sputtering method is preferable as a method for forming a protective insulating layer because it has good mass productivity. The protective insulating layer uses an inorganic insulating film that does not contain impurities such as moisture and blocks the invasion of these from the outside, and uses a silicon nitride film, an aluminum nitride film, or the like. In the present embodiment, the insulating film 506 is formed by using the silicon nitride film (see FIG. 8 (E)).

In the present embodiment, as the insulating film 506 as the protective insulating layer, the substrate 505 formed up to the insulating film 516 is heated to a temperature of 100 ° C to 400 ° C to contain high-purity nitrogen from which hydrogen and water have been removed. A sputter gas is introduced to form a silicon nitride film using a silicon semiconductor target. In this case as well, it is preferable to form the insulating film 506 while removing the residual water in the treatment chamber as in the insulating film 516.

After forming the protective insulating layer, heat treatment may be further carried out in the air at 100 ° C. or higher and 200 ° C. or lower, and 1 hour or longer and 30 hours or shorter. This heat treatment may be performed while maintaining a constant heating temperature, or the temperature may be raised from room temperature to a heating temperature of 100 ° C or more and 200 ° C or less, and the temperature may be lowered from the heating temperature to room temperature multiple times. You may go there.

Although not shown, an interlayer film 413 is formed on the insulating film 516. The post-process may be performed in the same manner as in the third embodiment.

As described above, by using the transistor including the highly purified oxide semiconductor layer produced by using the present embodiment, the current value (off current value) in the off state can be further lowered. Therefore, in the driving method, the holding time of an electric signal such as an image signal can be lengthened, and the writing interval can be set to be long. Therefore, since the frequency of the refresh operation can be reduced, the effect of suppressing the power consumption can be enhanced.

The size of the holding capacitance provided in the liquid crystal display device is set so that the electric charge can be held for a predetermined period in consideration of the leakage current of the transistor arranged in the pixel portion and the like. The size of the holding capacitance may be set in consideration of the off-current of the transistor and the like. If a transistor having a high-purity oxide semiconductor layer shown in the present embodiment is used, the holding capacity is 1/3 or less, preferably 1/5 or less of the liquid crystal capacity of each pixel. It is sufficient to provide a capacity.

Further, the transistor containing the highly purified oxide semiconductor layer can be driven at high speed because high field effect mobility can be obtained. Therefore, by using the transistor in the pixel portion of the liquid crystal display device, it is possible to provide a high-quality image. Further, since the drive circuit unit or the pixel unit can be separately manufactured on the same substrate by the transistor, the number of parts of the liquid crystal display device can be reduced.

Further, when the blue phase liquid crystal material is used, the rubbing treatment on the alignment film is not required, so that the electrostatic breakdown caused by the rubbing treatment can be prevented, and the transistor due to the influence of static electricity caused during the manufacturing process can be prevented. It is possible to reduce defects and damage of the liquid crystal display device such as fluctuations in electrical characteristics. Therefore, it is possible to improve the productivity of the liquid crystal display device.

Since the response speed of the blue phase liquid crystal material is more than an order of magnitude faster than that of the conventional liquid crystal material, the high functionality of the liquid crystal display device can be achieved by combining it with a device capable of double speed (high speed) drive such as a transistor using an oxide semiconductor layer. And high-speed response can be realized.

From the above, it is more effective to use a blue phase liquid crystal material for a liquid crystal display device having a transistor using an oxide semiconductor layer as in the present embodiment.

This embodiment can be implemented in combination with the configurations described in other embodiments as appropriate.

(Embodiment 10) In the above-described third to seventh embodiments, examples of other materials that can be used for the semiconductor layer of the transistor will be described.

The material that forms the semiconductor layer of the semiconductor element is an amorphous (also referred to as amorphous) semiconductor produced by a vapor phase growth method or a sputtering method using a semiconductor material gas typified by silane or Germanan, or the amorphous material. A amorphous semiconductor obtained by crystallizing a semiconductor using light energy or thermal energy, a microcrystalline semiconductor, or the like can be used. The semiconductor layer can be formed by a sputtering method, an LPCVD method, a plasma CVD method, or the like.

The microcrystalline semiconductor film can be formed by a high-frequency plasma CVD method having a frequency of several tens of MHz to several hundreds of MHz, or a microwave plasma CVD apparatus having a frequency of 1 GHz or more. Typically, SiH₄, Si₂H₆, SiH₂Cl₂, SiHCl₃, SiCl₄, SiF₄It can be formed by diluting silicon hydride such as hydrogen with hydrogen. Further, in addition to silicon hydride and hydrogen, it can be diluted with one or more rare gas elements selected from helium, argon, krypton, and neon to form a microcrystalline semiconductor film. At these times, the flow rate ratio of hydrogen to silicon hydride is 5 times or more and 200 times or less, preferably 50 times or more and 150 times or less, and more preferably 100 times.

Typical examples of amorphous semiconductors include hydrogenated amorphous silicon, and typical examples of crystalline semiconductors include polysilicon. Polysilicon (polycrystalline silicon) includes so-called high-temperature polysilicon that uses polysilicon formed at a process temperature of 800 ° C or higher as the main material, and polysilicon that is formed at a process temperature of 600 ° C or lower. It contains so-called low-temperature polysilicon used as a main material, and polysilicon obtained by crystallizing amorphous silicon using an element that promotes crystallization. Of course, as described above, a microcrystalline semiconductor or a semiconductor containing a crystal phase in a part of the semiconductor layer can also be used.

When a crystalline semiconductor film is used for the semiconductor layer, the method for producing the crystalline semiconductor film is various methods (laser crystallization method, thermal crystallization method, or heat using an element that promotes crystallization such as nickel. Crystallinity method, etc.) may be used. It is also possible to improve the crystallinity by irradiating a microcrystalline semiconductor with a laser to crystallize it. When no element that promotes crystallization is introduced, the hydrogen concentration of the amorphous silicon film is reduced by 1 by heating at 500 ° C for 1 hour in a nitrogen atmosphere before irradiating the amorphous silicon film with laser light. × 10²⁰atoms / cm³It is released to the following. This is because the amorphous silicon film is destroyed when the laser beam is applied to the amorphous silicon film containing a large amount of hydrogen.

The method of introducing the metal element into the amorphous semiconductor layer is not particularly limited as long as the metal element can be present on the surface of the amorphous semiconductor film or inside the amorphous semiconductor film. For example, a sputtering method, a CVD method, or the like. Plasma treatment methods (including plasma CVD methods), adsorption methods, and methods of applying a metal salt solution can be used. Of these, the method using a solution is convenient in that the concentration of the metal element can be easily adjusted. At this time, in order to improve the wettability of the surface of the amorphous semiconductor film and spread the aqueous solution over the entire surface of the amorphous semiconductor film, UV light irradiation in an oxygen atmosphere, thermal oxidation method, and hydroxyl radical are applied. It is desirable to form an oxide film by treatment with ozone water containing ozone or hydrogen peroxide.

Further, in the crystallization step of crystallizing an amorphous semiconductor film to form a crystalline semiconductor film, an element (also referred to as a catalyst element or a metal element) that promotes crystallization is added to the amorphous semiconductor film, and heat treatment (also referred to as a catalyst element or a metal element) is performed. Crystallization may be carried out at 550 ° C to 750 ° C for 3 minutes to 24 hours). Elements that promote (promote) crystallization include iron (Fe), nickel (Ni), cobalt (Co), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), and iridium (Ir). ), Platinum (Pt), copper (Cu) and gold (Au).

In order to remove or reduce the elements that promote crystallization from the crystalline semiconductor film, a semiconductor film containing an impurity element is formed in contact with the crystalline semiconductor film to function as a gettering sink. As the impurity element, an impurity element that imparts n-type, an impurity element that imparts p-type, a rare gas element, and the like can be used. For example, phosphorus (P), nitrogen (N), arsenic (As), and antimony (Sb) can be used. ), Bismuth (Bi), Boron (B), Helium (He), Neon (Ne), Argon (Ar), Kr (Krypton), Xe (Xenon). A semiconductor film containing a rare gas element is formed on a crystalline semiconductor film containing an element that promotes crystallization, and heat treatment (3 minutes to 24 hours at 550 ° C to 750 ° C) is performed. The element that promotes crystallization contained in the crystalline semiconductor film moves into the semiconductor film containing the rare gas element, and the element that promotes crystallization in the crystalline semiconductor film is removed or reduced. Then, the semiconductor film containing the rare gas element that has become the gettering sink is removed.

The crystallization of the amorphous semiconductor film may be a combination of heat treatment and crystallization by laser light irradiation, or the heat treatment or laser light irradiation may be performed independently or a plurality of times.

Further, the crystalline semiconductor film may be formed directly on the substrate by the plasma method. Further, the crystalline semiconductor film may be selectively formed on the substrate by using the plasma method.

This embodiment can be implemented in combination with the configurations described in other embodiments as appropriate.

(Embodiment 11) A transistor can be manufactured, and the transistor can be used in a pixel unit and further in a drive circuit to manufacture a liquid crystal display device having a display function. Further, a part or the whole of the drive circuit can be integrally formed on the same substrate as the pixel portion by using a transistor to form a system-on-panel.

The liquid crystal display device includes a liquid crystal element (also referred to as a liquid crystal display element) as a display element.

Further, the liquid crystal display device includes a panel in which the display element is sealed, and a module in which an IC or the like including a controller is mounted on the panel. Further, with respect to the element substrate corresponding to one form before the display element is completed in the process of manufacturing the liquid crystal display device, the element substrate is provided with means for supplying a current to the display element in each of a plurality of pixels. .. Specifically, the element substrate may be in a state in which only the pixel electrodes of the display element are formed, or after the conductive film to be the pixel electrodes is formed, the pixel electrodes are formed by etching. It may be in the previous state, and all forms apply.

The liquid crystal display device in the present specification refers to an image display device, a display device, or a light source (including a lighting device). Also, a module with a connector, such as an FPC (Flexible printed circuit) or TAB (Tape Automated Bonding) tape or TCP (Tape Carrier Package), or a module with a printed wiring board at the end of the TAB tape or TCP, or a display. All modules in which ICs (integrated circuits) are directly mounted on the elements by the COG (Chip On Glass) method shall be included in the liquid crystal display device.

The appearance and cross section of the liquid crystal display panel corresponding to one form of the liquid crystal display device will be described with reference to FIG. FIGS. 5 (A1) and 5 (A2) show a panel in which the transistors 4010 and 4011 formed on the first substrate 4001 and the liquid crystal element 4013 are sealed between the transistors 4010 and 4011 and the second substrate 4006 with a sealing material 4005. It is a top view, and FIG. 5 (B) corresponds to a cross-sectional view in MN of FIGS. 5 (A1) and 5 (A2).

A sealing material 4005 is provided so as to surround the pixel portion 4002 provided on the first substrate 4001 and the scanning line drive circuit 4004. Further, a second substrate 4006 is provided on the pixel unit 4002 and the scanning line drive circuit 4004. Therefore, the pixel portion 4002 and the scanning line drive circuit 4004 are sealed together with the liquid crystal layer 4008 by the first substrate 4001, the sealing material 4005, and the second substrate 4006.

Further, FIG. 5 (A1) is formed of a single crystal semiconductor film or a polycrystalline semiconductor film on a separately prepared substrate in a region different from the region surrounded by the sealing material 4005 on the first substrate 4001. The signal line drive circuit 4003 is mounted. Note that FIG. 5 (A2) shows an example in which a part of the signal line drive circuit is formed by a transistor provided on the first substrate 4001, and the signal line drive circuit 4003b is formed on the first substrate 4001. In addition, a signal line drive circuit 4003a formed of a single crystal semiconductor film or a polycrystalline semiconductor film is mounted on a separately prepared substrate.

The method of connecting the separately formed drive circuit is not particularly limited, and a COG method, a wire bonding method, a TAB method, or the like can be used. FIG. 5 (A1) is an example of mounting the signal line drive circuit 4003 by the COG method, and FIG. 5 (A2) is an example of mounting the signal line drive circuit 4003 by the TAB method.

Further, the pixel unit 4002 provided on the first substrate 4001 and the scanning line drive circuit 4004 have a plurality of transistors. In FIG. 5 (B), the transistor 4010 included in the pixel unit 4002 and the scanning line The transistor 4011 included in the drive circuit 4004 is illustrated. An insulating layer 4020 and an interlayer film 4021 are provided on the transistors 4010 and 4011.

As the transistors 4010 and 4011, the transistor shown in any of the third to tenth embodiments can be applied.

Further, a conductive layer may be provided on the interlayer film 4021 or the insulating layer 4020 at a position overlapping the channel forming region of the semiconductor layer of the transistor 4011 for the drive circuit. The conductive layer may have the same potential as the gate electrode layer of the transistor 4011 or may be different, and may function as a second gate electrode layer. Further, the potential of the conductive layer may be GND, 0V, or a floating state.

Further, the pixel electrode layer 4030 is formed on the first structure 4037 provided so as to project into the liquid crystal layer 4008 on the first substrate 4001 and on the interlayer film 4021, and the pixel electrode layer 4030 is electrically connected to the transistor 4010. Is connected. On the second substrate 4006, a common electrode layer 4031 is formed on the second structure 4038 which is provided so as to project into the liquid crystal layer 4008. The liquid crystal element 4013 includes a pixel electrode layer 4030, a common electrode layer 4031 and a liquid crystal layer 4008. Polarizing plates 4032a and 4032b are provided on the outside of the first substrate 4001 and the second substrate 4006, respectively. Further, in the present embodiment, the pixel electrode layer 4030 as shown in FIG. 2 in the second embodiment is provided as a flat plate-shaped continuous conductive film. Of course, the configurations of the pixel electrode layer and the common electrode layer as shown in FIGS. 1, 3 and 16 can also be applied.

The pixel electrode layer 4030 is formed so as to cover the upper surface and the side surface of the rib-shaped first structure 4037 provided on the first substrate 4001, and the rib-shaped second structure provided on the second substrate 4006 is formed. By forming the common electrode layer 4031 so as to cover the upper surface and the side surface of the structure 4038, the formation area of the pixel electrode layer 4030 and the common electrode layer 4031 can be increased (three-dimensionally) in the film thickness direction of the liquid crystal layer 4008. Can be expanded. Further, the first substrate 4001 and the second substrate 4006 are arranged to face each other so that the convex portions formed on the surfaces of the pixel electrode layer 4030 and the common electrode layer 4031 alternately mesh with each other by covering the rib-shaped structure. To do.

Therefore, when a voltage is applied between the pixel electrode layer 4030 and the common electrode layer 4031, a wide electric field can be formed between the pixel electrode layer 4030 and the common electrode layer 4031. Can be controlled.

Therefore, the liquid crystal molecules in the entire liquid crystal layer including the film thickness direction can be made to respond, and the white transmittance is improved. Therefore, the contrast ratio, which is the ratio between the white transmittance and the black transmittance, can also be increased.

As the first substrate 4001 and the second substrate 4006, translucent glass, plastic, or the like can be used. As the plastic, an FRP (Fiberglass-Reinforced Plastics) plate, a PVF (polyvinyl fluoride) film, a polyester film or an acrylic resin film can be used. Further, a sheet having a structure in which aluminum foil is sandwiched between a PVF film or a polyester film can also be used.

Further, 4035 is a columnar spacer obtained by selectively etching the insulating film, and is provided to control the film thickness (cell gap) of the liquid crystal layer 4008. A spherical spacer may be used. In a liquid crystal display device using the liquid crystal layer 4008, the cell gap, which is the thickness of the liquid crystal layer, is preferably 1 μm or more and 20 μm or less. In the present specification, the thickness of the cell gap is the maximum value of the thickness (film thickness) of the liquid crystal layer.

Although FIG. 5 shows an example of a transmissive liquid crystal display device, it can also be applied to a semi-transmissive liquid crystal display device.

Further, in the liquid crystal display device of FIG. 5, an example in which a polarizing plate is provided on the outside (visual side) of the substrate is shown, but the polarizing plate may be provided on the inside of the substrate. It may be appropriately set depending on the material of the polarizing plate and the manufacturing process conditions. Further, a light-shielding layer that functions as a black matrix may be provided.

A color filter layer or a light-shielding layer may be formed as a part of the interlayer film 4021. FIG. 5 shows an example in which a light-shielding layer 4034 is provided on the second substrate 4006 side so as to cover the upper portions of the transistors 4010 and 4011. By providing the light-shielding layer 4034, the effect of improving the contrast and stabilizing the transistor can be further enhanced.

It may be covered with an insulating layer 4020 that functions as a protective film for the transistor, but is not particularly limited.

The protective film is for preventing the invasion of pollutant impurities such as organic substances, metal substances, and water vapor suspended in the atmosphere, and a dense film is preferable. The protective film is a single layer of a silicon oxide film, a silicon nitride film, a silicon nitride film, a silicon nitride film, an aluminum oxide film, an aluminum nitride film, an aluminum nitride film, or an aluminum nitride film, using a sputtering method. Alternatively, it may be formed by lamination.

When a translucent insulating layer is further formed as the flattening insulating film, a heat-resistant organic material such as polyimide, acrylic, benzocyclobutene, polyamide, or epoxy can be used. In addition to the above organic materials, low dielectric constant materials (low-k materials), siloxane-based resins, PSG (phosphorus glass), BPSG (phosphorus glass) and the like can be used. An insulating layer may be formed by laminating a plurality of insulating films formed of these materials.

The method for forming the insulating layer to be laminated is not particularly limited, and depending on the material, a sputtering method, a spin coating, a dip, a spray coating, a droplet ejection method (inkjet method, screen printing, offset printing, etc.), a roll coating, etc. A curtain coat, a knife coat, or the like can be used.

The pixel electrode layer 4030 and the common electrode layer 4031 include indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, and indium tin oxide ( Hereinafter, it is referred to as ITO.), Indium zinc oxide, indium tin oxide to which silicon oxide is added, and other conductive materials having translucency can be used.

The pixel electrode layer 4030 and the common electrode layer 4031 include tungsten (W), molybdenum (Mo), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), titanium (Ta), and chromium (Cr). ), Cobalt (Co), nickel (Ni), titanium (Ti), platinum (Pt), aluminum (Al), copper (Cu), silver (Ag) and other metals, or alloys thereof, or metal nitrides thereof. It can be formed by using one or more kinds.

Further, the pixel electrode layer 4030 and the common electrode layer 4031 can be formed by using a conductive composition containing a conductive polymer (also referred to as a conductive polymer).

Further, various signals and potentials given to the separately formed signal line drive circuit 4003 and the scanning line drive circuit 4004 or the pixel unit 4002 are supplied from the FPC 4018.

Further, since the transistor is easily destroyed by static electricity or the like, it is preferable to provide a protection circuit for protecting the drive circuit on the same substrate for the gate line or the source line. The protection circuit is preferably configured by using a non-linear element.

In FIG. 5, the connection terminal electrode 4015 is formed of the same conductive film as the pixel electrode layer 4030, and the terminal electrode 4016 is formed of the same conductive film as the source electrode layer and drain electrode layer of the transistors 4010 and 4011.

The connection terminal electrode 4015 is electrically connected to the terminal of the FPC 4018 via the anisotropic conductive film 4019.

Further, FIG. 5 shows an example in which the signal line drive circuit 4003 is separately formed and mounted on the first substrate 4001, but the present invention is not limited to this configuration. The scanning line drive circuit may be separately formed and mounted, or only a part of the signal line driving circuit or a part of the scanning line driving circuit may be separately formed and mounted.

As described above, the contrast ratio can be increased in a liquid crystal display device using a liquid crystal layer exhibiting a blue phase.

Further, since a high white transmittance can be obtained at a lower voltage, it is possible to achieve low power consumption of the liquid crystal display device.

This embodiment can be implemented in combination with the configurations described in other embodiments as appropriate.

(Embodiment 12) The liquid crystal display device disclosed in the present specification can be applied to various electronic devices (including game machines). Examples of electronic devices include television devices (also referred to as televisions or television receivers), monitors for computers, digital cameras, digital video cameras, digital photo frames, and mobile phones (also referred to as mobile phones and mobile phone devices). ), Portable game machines, mobile information terminals, sound reproduction devices, large game machines such as pachinko machines, and the like.

FIG. 9A is an electronic book (also referred to as an E-book), which can have a housing 9630, a display unit 9631, an operation key 9632, a solar cell 9633, and a charge / discharge control circuit 9634. The electronic book shown in Fig. 9 (A) has a function to display various information (still images, moving images, text images, etc.), a function to display a calendar, date or time on the display unit, and information displayed on the display unit. It can have a function of operating or editing an image, a function of controlling processing by various software (programs), and the like. In addition. FIG. 9A shows a configuration having a battery 9635 and a DCDC converter (hereinafter abbreviated as a converter) 9636 as an example of the charge / discharge control circuit 9634. By applying the liquid crystal display device shown in any one of the first to eleventh embodiments to the display unit 9631, it is possible to obtain an electronic book having high contrast, good visibility, and low power consumption.

With the configuration shown in Fig. 9 (A), when a transflective or reflective liquid crystal display device is used as the display unit 9631, it is expected to be used in relatively bright conditions, and power generation by the solar cell 9633 is expected. And the battery 9635 can be charged efficiently, which is preferable. Since the solar cell 9633 can be appropriately provided in an empty space (front surface or back surface) of the housing 9630, it is suitable because it can be configured to efficiently charge the battery 9635. As the battery 9635, if a lithium ion battery is used, there are advantages such as miniaturization.

Further, the configuration and operation of the charge / discharge control circuit 9634 shown in FIG. 9 (A) will be described by showing a block diagram in FIG. 9 (B). FIG. 9B shows the solar cell 9633, the battery 9635, the converter 9636, the converter 9637, the switches SW1 to SW3, and the display unit 9631. The battery 9635, the converter 9636, the converter 9637, and the switches SW1 to SW3 are charged and discharged. This is the part corresponding to the control circuit 9634.

First, an example of operation when power is generated by the solar cell 9633 by external light will be described. The power generated by the solar cell is boosted or stepped down by the converter 9636 so that it becomes the voltage for charging the battery 9635. Then, when the power from the solar cell 9633 is used for the operation of the display unit 9631, the switch SW1 is turned on, and the converter 9637 boosts or lowers the voltage required for the display unit 9631. Further, when the display unit 9631 is not displayed, SW1 may be turned off and SW2 may be turned on to charge the battery 9635.

Next, an example of operation when the solar cell 9633 does not generate electricity due to external light will be described. The power stored in the battery 9635 is boosted or stepped down by the converter 9637 by turning on the switch SW3. Then, the electric power from the battery 9635 is used for the operation of the display unit 9631.

Although the solar cell 9633 is shown as an example of the charging means, the battery 9635 may be charged by other means. Further, the configuration may be performed by combining other charging means.

FIG. 10A shows a notebook-type personal computer, which is composed of a main body 3001, a housing 3002, a display unit 3003, a keyboard 3004, and the like. By applying the liquid crystal display device shown in any one of the first to eleventh embodiments to the display unit 3003, it is possible to obtain a notebook-type personal computer having high contrast, good visibility, and low power consumption.

FIG. 10B shows a personal digital assistant (PDA), and the main body 3021 is provided with a display unit 3023, an external interface 3025, an operation button 3024, and the like. There is also a stylus 3022 as an accessory for operation. By applying the liquid crystal display device shown in any one of the first to eleventh embodiments to the display unit 3023, it is possible to obtain a portable information terminal (PDA) having high contrast, good visibility, and low power consumption.

FIG. 10 (C) shows an example of an electronic book. For example, the electronic book 2700 is composed of two housings, a housing 2701 and a housing 2703. The housing 2701 and the housing 2703 are integrated by a shaft portion 2711, and can be opened and closed with the shaft portion 2711 as an axis. With such a configuration, it is possible to perform an operation like a paper book.

The display unit 2705 is incorporated in the housing 2701, and the display unit 2707 is incorporated in the housing 2703. The display unit 2705 and the display unit 2707 may be configured to display a continuous screen or may be configured to display different screens. By displaying different screens, for example, the text is displayed on the right display unit (display unit 2705 in FIG. 10 (C)), and the image is displayed on the left display unit (display unit 2707 in FIG. 10 (C)). Can be displayed. By applying the liquid crystal display device shown in any one of the first to eleventh embodiments to the display unit 2705 and the display unit 2707, it is possible to obtain an electronic book 2700 having high contrast, good visibility, and low power consumption. ..

Further, FIG. 10 (C) shows an example in which the housing 2701 is provided with an operation unit and the like. For example, the housing 2701 is provided with a power supply 2721, operation keys 2723, a speaker 2725, and the like. The page can be sent by the operation key 2723. A keyboard, a pointing device, or the like may be provided on the same surface as the display unit of the housing. Further, the back surface or the side surface of the housing may be provided with an external connection terminal (earphone terminal, USB terminal, etc.), a recording medium insertion portion, or the like. Further, the electronic book 2700 may be configured to have a function as an electronic dictionary.

Further, the electronic book 2700 may be configured to be able to transmit and receive information wirelessly. It is also possible to purchase desired book data and the like from an electronic book server and download them wirelessly.

FIG. 10D shows a mobile phone, which is composed of two housings, a housing 2800 and a housing 2801. The housing 2801 is equipped with a display panel 2802, a speaker 2803, a microphone 2804, a pointing device 2806, a camera lens 2807, an external connection terminal 2808, and the like. In addition, the housing 2800 is equipped with a solar cell 2810 for charging a mobile phone, an external memory slot 2811, and the like. In addition, the antenna is built in the housing 2801. By applying the liquid crystal display device shown in any one of the first to eleventh embodiments to the display panel 2802, a mobile phone having high contrast, good visibility, and low power consumption can be obtained.

In addition, the display panel 2802 is provided with a touch panel, and in FIG. 10D, a plurality of operation keys 2805 displayed as images are shown by dotted lines. A booster circuit for boosting the voltage output by the solar cell 2810 to the voltage required for each circuit is also mounted.

The display direction of the display panel 2802 changes as appropriate according to the usage pattern. In addition, since the camera lens 2807 is provided on the same surface as the display panel 2802, videophone calls are possible. The speaker 2803 and the microphone 2804 are capable of videophone, recording, playback, etc., as well as voice calls. Further, the housing 2800 and the housing 2801 can be slid and changed from the unfolded state to the overlapping state as shown in FIG. 10 (D), and can be miniaturized to be suitable for carrying.

The external connection terminal 2808 can be connected to various cables such as an AC adapter and a USB cable, and can be charged and data communication with a personal computer or the like is possible. Further, a recording medium can be inserted into the external memory slot 2811 to support storage and movement of a larger amount of data.

Further, in addition to the above functions, an infrared communication function, a television reception function, and the like may be provided.

FIG. 10 (E) is a digital video camera, which is composed of a main body 3051, a display unit (A) 3057, an eyepiece unit 3053, an operation switch 3054, a display unit (B) 3055, a battery 3056, and the like. By applying the liquid crystal display device shown in any one of the first to eleventh embodiments to the display unit (A) 3057 and the display unit (B) 3055, a digital video having high contrast, good visibility, and low power consumption. It can be a camera.

FIG. 10 (F) shows an example of a television device. In the television device 9600, the display unit 9603 is incorporated in the housing 9601. The display unit 9603 makes it possible to display an image. Further, here, a configuration in which the housing 9601 is supported by the stand 9605 is shown. By applying the liquid crystal display device shown in any one of the first to eleventh embodiments to the display unit 9603, a television device 9600 having high contrast, good visibility, and low power consumption can be obtained.

The operation of the television device 9600 can be performed by the operation switch provided in the housing 9601 or a separate remote control operation device. Further, the remote controller operating device may be provided with a display unit for displaying information output from the remote controller operating device.

The television device 9600 is configured to include a receiver, a modem, and the like. The receiver can receive general television broadcasts, and by connecting to a wired or wireless communication network via a modem, it can be unidirectional (sender to receiver) or bidirectional (sender and receiver). It is also possible to perform information communication between (or between recipients, etc.).

This embodiment can be implemented in combination with the configurations described in other embodiments as appropriate.