Liquid crystal display device

The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device preferably used for a mobile information terminal (for example, PDA), a mobile phone, an in-vehicle liquid crystal display, a digital camera, a personal computer, an amusement device, a television, or the like.

Information infrastructure is advancing day by day, and devices such as mobile phones, PDAs, digital cameras, video cameras, and in-vehicle navigation systems are deeply ingrained in people's lives, and most of them use liquid crystal display devices. As the amount of information handled by the main body of these liquid crystal display devices increases, it is desired to display more information, and there is a market demand for high contrast, wide viewing angle, high brightness, multicolor, and high definition. It is increasing.

A vertically oriented mode using a vertically oriented liquid crystal layer is attracting attention as a display mode capable of achieving high contrast and a wide viewing angle. The vertically oriented liquid crystal layer is generally formed by using a vertically oriented liquid crystal and a liquid crystal material having a negative dielectric anisotropy.

For example, in Patent Document 1, an oblique electric field is generated around an opening provided in a counter electrode facing a pixel electrode via a liquid crystal layer, and a liquid crystal around the liquid crystal molecule in a vertically oriented state in the opening is generated. A liquid crystal display device in which the viewing angle characteristics are improved by tilting the molecules is disclosed.

However, in the configuration described in Patent Document 1, it is difficult to form an oblique electric field in the entire region in the pixel, and as a result, a region in which the response of the liquid crystal molecules to the voltage is delayed occurs in the pixel, and an afterimage phenomenon occurs. The problem of appearing arises.

In Patent Document 2, slit electrodes (opening patterns) are provided on both sides of the pixel electrode and the common electrode on the opposite side, and at least one of the two electrodes is opened by arranging a step in the region where the slit electrode is formed. We disclose a technology that realizes a wide viewing angle by uniformly distributing the electric field gradient in four directions using a pattern.

On the other hand, Patent Document 3 discloses a technique for stabilizing the orientation state of a liquid crystal domain having an inclined radial orientation that appears around the protrusions by regularly providing a plurality of protrusions in the pixel. .. Further, this document discloses that the display characteristics can be improved by regulating the orientation of the liquid crystal molecules by utilizing the orientation regulating force by the convex portion and the oblique electric field by the opening provided in the electrode.

On the other hand, in recent years, liquid crystal display devices capable of high-quality display both outdoors and indoors have been proposed (for example, Patent Document 4 and Patent Document 5). This liquid crystal display device is called a semi-transmissive liquid crystal display device, and has a reflection region for displaying in a reflection mode and a transmission region for displaying in a transmission mode in a pixel.

ECB mode, TN mode, etc. are used in the semitransmissive liquid crystal display device currently on the market, but in Patent Document 3 above, it is applied not only to the transmissive liquid crystal display device but also to the semitransmissive liquid crystal display device. The configuration is also disclosed. Further, in Patent Document 6, in a semi-transmissive liquid crystal display device having a vertically oriented liquid crystal layer, an insulating layer provided to make the thickness of the liquid crystal layer in the transmission region twice the thickness of the liquid crystal layer in the reflection region is provided. A technique for controlling the orientation (multiaxial orientation) of a liquid crystal by a formed recess is disclosed. A configuration is disclosed in which the concave portion is formed in a regular octagonal shape, and a protrusion (convex portion) or a slit (electrode opening) is formed at a position facing the concave portion via a liquid crystal layer (for example, FIG. 6 of Patent Document 6). See 4 and Figure 16).

Further, Patent Document 7, to the dot inversion drive to a vertical alignment type liquid crystal display device by Rukoto, suppresses roughness of the display, discloses a technique for realizing a wide viewing angle characteristics with high contrast ratio. Patent Document 7 defines the orientation direction of liquid crystal molecules by utilizing the distortion of the electric field generated at the end of an adjacent pixel electrode by performing dot inversion drive at a predetermined pixel pitch. Further, it is described that the pixel electrode pitch is preferably in the range of 20 μm or less, which is equal to or larger than the thickness of the liquid crystal layer, in order to sufficiently exert the action of the electric field. Further, it is described that by providing the opening in the center of the pixel electrode, the center of the radial orientation of the liquid crystal molecules is surely fixed to the opening, and the orientation can be further stabilized.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 6-301036</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 2002-55374</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2003-167253</text></patcit><patcit num="4"><text>Japanese Patent No. 29555277</text></patcit><patcit num="5"><text>U.S. Pat. No. 6,195,140</text></patcit><patcit num="6"><text>Japanese Patent Application Laid-Open No. 2002-350853</text></patcit><patcit num="7"><text>Japanese Unexamined Patent Publication No. 2001-125144</text></patcit>

<p> In the technique disclosed in Patent Document 3, a convex portion is provided in a pixel to form a plurality of liquid crystal domains (that is, pixel division is performed), and the orientation regulating force for liquid crystal molecules is strengthened. According to the study, in order to obtain a sufficient orientation regulating force, it is necessary to form an orientation control structure of the convex portions regularly arranged inside the pixel, which causes a problem that the manufacturing process becomes complicated. In addition, the contrast ratio is lowered due to light leakage from the periphery of the convex portion by providing the orientation restricting structure of the convex portion in the pixel, or the effective aperture ratio is increased by providing a light-shielding portion to prevent this. It may decrease. Furthermore, in particular, when an orientation control structure is provided on the opposing substrate, it is affected by the alignment margin of the substrate, so that there is a problem of roughness due to the axial misalignment of the axisymmetric alignment domain, a decrease in the effective aperture ratio, and / or a contrast ratio. The decrease is even more pronounced.</p><p> Further, in the technique disclosed in Patent Document 6, it is necessary to arrange a convex portion or an electrode opening on the side opposite to the concave portion provided for controlling multiaxial orientation, which causes the same problem as the above-mentioned prior art. To do.</p><p> On the other hand, Patent Document 7 defines the direction in which the liquid crystal molecules are inclined by utilizing the lateral electric field (in-plane component of the oblique electric field) generated between the adjacent pixel electrodes by the dot inversion drive. As can be seen from the orientation directions of the liquid crystal molecules at the four corners of the pixel electrode shown in FIG. 9 of Patent Document 7, the directions of the lateral electric fields are different from each other (almost orthogonal to each other) in the vicinity of the corners of the pixel electrode. ). As a result, there is a problem that the orientation of the liquid crystal molecules becomes discontinuous near the corners of the pixels, and dispersion (alignment defects) is likely to occur. Further, the stability of the orientation state depends on the shape of the electrode, and a sufficient orientation regulation force may not be obtained in the halftone display state where the electric field is low.</p><p> The present invention has been made in view of the above points, and an object of the present invention is a liquid crystal display device having at least one axisymmetric alignment domain in a pixel, which has a good axisymmetric orientation domain even in a halftone display state. Is formed, and it is an object of the present invention to provide a wide viewing angle liquid crystal display device having excellent display quality.</p>

<p> The liquid crystal display device of the present invention is of a vertically oriented type provided between the first substrate, the second substrate provided so as to face the first substrate, and the first substrate and the second substrate. The first substrate has a liquid crystal layer, and is connected to a plurality of scanning signal lines extending in the row direction, a plurality of data signal lines extending in the column direction, the plurality of scanning signal lines, and the plurality of data signal lines. The plurality of switching elements are provided, and the plurality of first electrodes connected to the plurality of data signal lines via the plurality of switching elements are provided, and the second substrate is formed by the plurality of the first electrodes via the liquid crystal layer. The liquid crystal having a second electrode facing the first electrode of the above, and each of the plurality of first electrodes, the second electrode, and the liquid crystal provided between the first electrode and the second electrode. A liquid crystal display device having a plurality of pixels arranged in a matrix having rows and columns including a layer and a light-shielding region in a gap between the plurality of pixels, and among the plurality of switching elements, the plurality of the plurality of pixels. The switching element connected to any one of the scanning signal lines was connected to the switching element connected to one of the first electrodes belonging to the pair of rows adjacent to the arbitrary one and the other. A first electrode having alternating switching elements and any row of the plurality of pixels being supplied with a voltage of positive polarity with the potential of the second electrode as a reference potential during a certain vertical scanning period. One pixel and a second pixel having the first electrode to which a voltage of negative polarity is supplied are alternately arranged and configured, and in each pixel, of the first electrode and the second electrode. At least one has at least one opening formed at a predetermined position and forms at least one liquid crystal domain exhibiting axially symmetric orientation when at least a predetermined voltage is applied to the liquid crystal layer, and at least one of the above. The central axis of the axially symmetric orientation of the liquid crystal domain is formed in or near the at least one opening.</p><p> In certain embodiments, the first substrate further comprises regularly arranged wall structures on the liquid crystal layer side within the light-shielding region.</p><p> In certain embodiments, any row of the plurality of pixels comprises a first pixel having the first electrode to which a positive polarity voltage is supplied with the potential of the second electrode as a reference potential during a vertical scanning period. , The second pixel having the first electrode to which a voltage of negative polarity is supplied is alternately arranged and configured.</p><p> In certain embodiments, the polarity of the voltage supplied to the first electrode of each of the plurality of pixels is inverted during each vertical scan period.</p><p> In certain embodiments, the first electrode has at least one first opening formed in a predetermined position in the pixel and the second electrode has at least one formed in a predetermined position in the pixel. It has one second opening and the central axis of the axisymmetric orientation of the at least one liquid crystal domain is within at least one of the at least one first opening and the at least one second opening. It is formed in or near it.</p><p> In certain embodiments, the at least one first opening and the at least one second opening are arranged at positions where at least a part of each other overlaps with each other via the liquid crystal layer.</p><p> In certain embodiments, the first electrode has at least one notch.</p><p> In a certain embodiment, a support having a light-shielding region in the gap between the plurality of pixels and defining the thickness of the liquid crystal layer is provided in the light-shielding region.</p><p> In certain embodiments, the first electrode comprises a transparent electrode defining a transmission region and a reflection electrode defining a reflection region, the thickness dt of the liquid crystal layer in the transmission region and the said in the reflection region. The thickness dr of the liquid crystal layer satisfies the relationship of 0.3 dt &lt;dr &lt;0.7 dt.</p><p> In certain embodiments, the first electrode comprises a transparent electrode defining a transmissive region and a reflective electrode defining a reflective region, and at least one liquid crystal domain comprises a liquid crystal domain formed in the transmissive region. The first electrode has at least one first opening, the second electrode has at least one second opening, and the at least one first opening and the second opening are the transmissive. The first electrode includes a plurality of notches arranged point-symmetrically about the opening, including an opening corresponding to the central axis of the liquid crystal domain formed in the region.</p><p> In certain embodiments, a transparent dielectric layer is selectively provided in the reflective region of the second substrate.</p><p> In certain embodiments, the transparent dielectric layer has the function of scattering light.</p><p> In a certain embodiment, the color filter layer provided on the second substrate is further provided, and the optical density of the color filter layer in the reflection region is smaller than that of the color filter layer in the transmission region.</p><p> In certain embodiments, the first substrate and / or the second substrate and the pair of polarizing plates have a pair of polarizing plates arranged so as to face each other via the first substrate and the second substrate. It further has at least one biaxially optically anisotropic medium layer between and.</p><p> In certain embodiments, it further comprises a pair of polarizing plates arranged so as to face each other via the first substrate and the second substrate, and the first substrate and / or the second substrate and the pair of polarized light. It further has at least one uniaxially optically anisotropic medium layer between the plates.</p>

<p> Arbitrary rows of a plurality of pixels in the liquid crystal display device of the present invention are supplied with a voltage having a positive polarity with the potential of the second electrode (for example, the counter electrode) as a reference potential in a certain vertical scanning period. Since the first pixel having the pixel electrode) and the second pixel having the first electrode to which the voltage of negative polarity is supplied are alternately arranged, the steepness between the first pixel and the second pixel is steep. A gradient electric field is generated, and this gradient electric field forms an axially symmetric orientation domain.</p><p> Further, in the liquid crystal display device of the present invention, an oblique electric field formed around an opening provided in the first electrode (for example, a pixel electrode) and / or the second electrode (for example, a counter electrode) is a central axis of axisymmetric orientation. It acts to fix the position of, and cooperates with the steep diagonal electric field formed between adjacent pixels to stabilize the orientation of the axisymmetric alignment domain. Furthermore, when forming a plurality of axisymmetric orientation domains in the pixel, if a notch is provided in the first electrode, the liquid crystal molecules will collapse due to the influence of the oblique electric field generated in the vicinity of the notch. Is defined and the axisymmetric orientation domain is further stabilized.</p><p> Further, the first opening and the second opening are fixed so that one end of the central axis of the axisymmetric orientation of the liquid crystal domain is fixed in or near the first opening and the other end is fixed in or near the second opening. By arranging the portions (pairs of openings), the central axis of the axisymmetric orientation is more stably fixed. Further, when the first opening and the second opening (a pair of openings) are arranged so as to overlap at least a part of each other via the liquid crystal layer, it is possible to suppress a decrease in the effective aperture ratio due to the openings. At this time, since one central axis is fixed and stabilized by the action of the first opening and the second opening, the action that each opening (first opening or second opening) should exert is It may be smaller than when fixing and stabilizing the central axis with one opening. That is, since the sizes of the first opening and the second opening (for example, the diameter of the circular opening) can be reduced, the decrease in the effective aperture ratio can be further suppressed. The sizes of the first opening and the second opening may be equal to or different from each other. Since the first opening and the second opening are provided to fix and stabilize the position of the central axis of the axisymmetric orientation, their size is relatively small and the decrease in the effective aperture ratio is small. In addition, it is not easily affected by misalignment when the first substrate and the second substrate are bonded together.</p><p> By providing an opening at a position corresponding to the central axis of the axisymmetrically oriented liquid crystal domain, the position of the central axis is fixed and stabilized, so that the center of the axisymmetrically oriented liquid crystal domain extends over the entire surface of the liquid crystal display panel. As a result of the axes being placed in place, the uniformity of the display is improved. For example, the graininess when observing the halftone display from an angle is reduced. Further, as a result of stabilizing the axisymmetric orientation, the effect that the response time in the halftone display can be shortened can be obtained. Further, it is possible to shorten the time for the orientation disorder (sometimes called an afterimage due to pressing) that occurs when the liquid crystal display panel is pressed to recover to the normal orientation.</p><p> Furthermore, if a wall structure is provided on the liquid crystal layer side in the light-shielding region of the first substrate, the direction in which the liquid crystal molecules are tilted when a voltage is applied (when an electric field is generated) is specified due to the tilted surface effect of the wall structure. The axially symmetric orientation domain is formed more stably. Diagonal electric field generated by applying voltages of opposite polarities to the first electrodes of adjacent pixels, orientation regulation by the slope of the wall structure provided between adjacent pixels, and distortion of the electric field by the wall structure. The effect acts to stabilize the orientation of the axisymmetric orientation domain. The orientation regulation effect of the slope of the wall structure acts regardless of the presence or absence of the electric field, and the effect of distorting the electric field is obtained by the wall structure, so that the axisymmetric orientation can be stabilized even in the halftone display state. It is possible to further shorten the time for the orientation disorder that occurs when the liquid crystal display panel is pressed to recover to the normal orientation.</p><p> Further, in the liquid crystal display device of the present invention, the switching element connected to any one scanning signal line is connected to one of the first electrodes belonging to a pair of rows adjacent to the scanning signal line. It alternately has a switching element and a switching element connected to the other. That is, switching elements (and / or pixel electrodes connected via switching elements) are arranged in a staggered pattern alternately up and down with respect to an arbitrary scanning signal line. Therefore, by performing the conventional 1-line inversion drive (1H inversion drive), as a result, the liquid crystal layers of the pixels adjacent to each other in the row direction and the column direction have opposite polarities with respect to the second electrode (opposite electrode). It is possible to apply a display signal (1H dot inversion drive).</p><p> The vertical scanning period is typically a frame period, and corresponds to each field period when the frame is divided into a plurality of fields. Hereinafter, the driving method for controlling the polarity of the voltage applied to the first electrode is referred to as "reversal drive", and the case where the opposite polarity pixels are adjacent in the row is column inversion, and the opposite polarity pixels are adjacent in the column. The case is referred to as row inversion, and the case where pixels of opposite polarity are adjacent to each other in both rows and columns is referred to as dot inversion.</p><p> When applied to a semi-transmissive liquid crystal display device, if a configuration in which a transparent dielectric layer for controlling the thickness of the liquid crystal layer is provided on the second substrate side is adopted, a step is provided on the first substrate side to provide a transmission region and reflection. Compared with the conventional semi-transmissive liquid crystal display device that divides the area, it is possible to reduce the invalid area that does not contribute to the display at the time of transmission display, and the brightness at the time of transmission display can be improved. Further, the diffuse reflection plate provided to improve the brightness of the reflection region can be formed not only on the reflection region of the first substrate but also on the transparent dielectric layer of the second substrate as a light scattering layer ( A light diffusion layer) can also be formed. In this case, it is possible to eliminate the need to form irregularities or the like on the surface of the reflective electrode.</p>

Hereinafter, the configuration of the liquid crystal display device according to the embodiment of the present invention will be specifically described with reference to the drawings.

(Transmissive Liquid Crystal Display Device) First, the configuration of the transmissive liquid crystal display device 100 according to the embodiment of the present invention will be described with reference to FIG. 1 (a) and 1 (b) are diagrams schematically showing the configuration of one pixel of the transmissive liquid crystal display device 100, FIG. 1 (a) is a plan view, and FIG. 1 (b) is a plan view. It is a cross-sectional view along the line 1B-1B'in FIG. 1 (a). FIG. 1 (a) is a plan view, and FIG. 1 (b) is a cross-sectional view taken along the line 1B-1B'in FIG. 1 (a). Further, FIG. 1 (c) is a cross-sectional view schematically showing the configuration of one pixel of another transmissive liquid crystal display device 100'.

Here, an example in which one pixel is divided into two (N = 2) is shown, but the number of divisions (= N) can be set to 3 or more according to the pixel pitch. In this case, the division area on the second substrate side is abbreviated. It is preferable that the number of openings (= n) provided in the central portion is the same as the number of pixel divisions (= N). Since the effective aperture ratio tends to decrease as the number of divisions (= N) increases, it is preferable to reduce the number of divisions (= N) when applying to a high-definition display panel. Further, the present invention can be applied even when the pixels are not divided (sometimes expressed as N = 1). The divided area may also be referred to as a "sub-pixel". One liquid crystal domain is typically formed in the sub-pixel.

The liquid crystal display device 100 shown in FIGS. 1A and 1B is composed of a transparent substrate (for example, a glass substrate) 110a, a transparent substrate 110b provided so as to face the transparent substrate 110a, and transparent substrates 110a and 110b. It has a vertically oriented liquid crystal layer 120 provided between them. A vertically aligned film (not shown) is provided on the surfaces of the substrates 110a and 110b in contact with the liquid crystal layer 120, and when no voltage is applied, the liquid crystal molecules of the liquid crystal layer 120 are substantially perpendicular to the surface of the vertically aligned film. Oriented to. The liquid crystal layer 120 contains a nematic liquid crystal material having a negative dielectric anisotropy, and further contains a chiral agent, if necessary.

The liquid crystal display device 100 has a pixel electrode 111 formed on the transparent substrate 110a and a counter electrode 131 formed on the transparent substrate 110b provided so as to face the transparent substrate 110a. A liquid crystal layer 120 provided between the counter electrode 131 and the counter electrode 131 defines a pixel. Here, both the pixel electrode 111 and the counter electrode 131 are formed of a transparent conductive layer (for example, an ITO layer). Typically, on the liquid crystal layer 120 side of the transparent substrate 110b, a color filter 130 provided corresponding to a pixel (a plurality of color filters may be collectively referred to as a color filter layer 130). A black matrix (light-shielding layer) 132 provided between adjacent color filters 130 is formed, and a counter electrode 131 is formed on these, but the color filter layer 130 is formed on the counter electrode 131 (on the liquid crystal layer 120 side). Or black matrix 132 may be formed.

In the liquid crystal display device 100 shown in FIG. 1 having a number of divisions (= N) of 2, a wall structure 115, which will be described later, is formed on a light-shielding region around a pixel electrode 111 on a transparent substrate 110a. Further, the pixel electrode 111 has a number of first openings 114a corresponding to the number of divisions (n = 2 in FIG. 1) at a predetermined position in the pixel. The pixel electrode 111 further has four notches 113 at predetermined positions. On the other hand, the counter electrode 131 on the transparent substrate 110b on the opposite side has a second opening 114b at a predetermined position according to the number of divisions (n = 2 in FIG. 1).

Here, the first opening 114a and the second opening 114b are arranged in a positional relationship so as to spatially overlap each other via the liquid crystal layer 120. Further, the first opening 114a and the second opening 114b (a pair of openings facing each other may be referred to as an opening 114) have the same size (diameter), and are shown in FIG. 1 (a). Overlap each other.

When a predetermined voltage is applied to the liquid crystal layer 120, two liquid crystal domains (the same number as the number of divisions N) each exhibiting axisymmetric orientation are formed, and the central axis of each axially symmetric orientation of these liquid crystal domains is the first. It is formed in or near the 1st opening 114a and the 2nd opening 114b. The pair of openings 114 act to fix the position of the central axis of the axisymmetric orientation domain and to stabilize the axisymmetric orientation. As illustrated here, when the first opening 114a and the second opening 114b are arranged so as to overlap each other via the liquid crystal layer, it is possible to suppress a decrease in the effective aperture ratio due to the pair of openings 114. Since one central axis is fixed and stabilized by the action of the first opening and the second opening, the action that the first opening 114a or the second opening 114b should exert is the central axis in one opening. The diameters of the first opening 114a and the second opening 114b can be reduced, and as a result, a decrease in the effective aperture ratio can be suppressed.

As will be described in detail later, the liquid crystal display device of the present embodiment is adjacent to each other in both columns and rows within each vertical scanning period with respect to the pixels arranged in a matrix having rows and columns. The voltage applied to the pixel electrode of the pixel to be used is applied so as to have the opposite polarity with respect to the voltage applied to the counter electrode 131 (dot inversion drive). As described above, by adopting the dot inversion drive, the orientation stabilization effect due to the oblique electric field generated between the adjacent pixels can be obtained for the four sides of the substantially rectangular pixel. Therefore, a steep diagonal electric field is formed between adjacent pixels and acts to form an axisymmetric orientation.

Further, in the liquid crystal display device of the present embodiment, the switching element connected to any one scanning signal line is connected to one of the pixel electrodes 111 belonging to a pair of rows adjacent to the scanning signal line. It has a switching element and a switching element connected to the other alternately. Therefore, by performing the conventional 1-line inversion drive (1H inversion drive), as a result, display signals having opposite polarities are applied to the liquid crystal layers of pixels adjacent to each other in the row direction and the column direction with reference to the counter electrode 131. Can be (1H dot inversion drive).

Further, in the liquid crystal display device of the present embodiment, the center of the axisymmetric orientation is fixed and stabilized in or near the opening 114 as described above. This is because the action of the oblique electric field formed by the opening 114 forms a continuous orientation (axisymmetric orientation) of the liquid crystal molecules around the opening 114, and the opening 114 The action of (at least one of the first opening 114a and the second opening 114b) suppresses / prevents the formation of discontinuous orientation at the corners as shown in FIG. 9 of Patent Document 7. To. In addition, due to the action of the opening 114, a sufficiently stable axisymmetric orientation can be obtained even in a halftone display state where the electric field is low, and the orientation disorder that occurs when the liquid crystal display panel is pressed is restored to the normal orientation. The time can be shortened.

The shapes of the first opening 114a and the second opening 114b provided at predetermined positions of the pixel electrode 111 and the counter electrode 131 are as exemplified in order to obtain the continuity of the orientation of the liquid crystal molecules in the axisymmetric alignment domain. The shape is preferably circular, but is not limited to this. Further, the shapes of the first opening 114a and the second opening 114b may be different. However, in order to exert substantially the same orientation regulating force in all directions, a polygon of a quadrangle or more is preferable, and a regular polygon is preferable.

Here, an example in which openings are provided in both the pixel electrode 111 and the counter electrode 131 is shown, but even if an opening is provided in either one, the effect of fixing the central axis of axisymmetric orientation can be obtained. Further, here, when the openings are provided in both the pixel electrode 111 and the counter electrode 131, the configuration in which the first opening 114a and the second opening 114b of the same size are arranged so as to overlap each other is illustrated. , The configuration and arrangement of the first opening 114a and the second opening 114b are not limited to this. Even if the first opening 114a and the second opening 114b do not overlap each other, the effect of fixing and stabilizing the axisymmetric orientation can be obtained. However, if one end of the central axis of the axisymmetric orientation of the liquid crystal domain is fixed by the first opening 114a and the other end is fixed by the second opening 114b, the central axis of the axisymmetric orientation is further stabilized. Can be fixed to. Further, when the first opening 114a and the second opening 114b are arranged so that at least a part of the first opening 114a and the second opening 114b overlap each other via the liquid crystal layer, it is possible to suppress a decrease in the effective aperture ratio due to the opening 114. At this time, since one central axis is fixed and stabilized by the action of the first opening and the second opening, the action that the first opening 114a or the second opening 114b should exert is one opening. It may be smaller than the case where the central axis is fixed and stabilized in, and as illustrated here, it is effective by arranging the first opening 114a and the second opening 114b of the same size so as to overlap each other. The decrease in aperture ratio can be minimized.

Further, the liquid crystal display device 100 has a light-shielding region between adjacent pixels, and has a wall structure 115 on the transparent substrate 110a in the light-shielding region. Here, the light-shielding region is shaded by, for example, a TFT, a gate signal wiring, a source signal wiring, or a black matrix formed on the transparent substrate 110b, which is formed in a peripheral region of the pixel electrode 111 on the transparent substrate 110a. This area does not contribute to the display. Therefore, the wall structure 115 formed in the light-shielding region does not adversely affect the display.

The wall structure 115 acts so as to define the direction in which the liquid crystal molecules are inclined when a voltage is applied (when an electric field is generated) due to the inclined surface effect. The orientation-regulating force due to the inclined side surface of the wall structure 115 acts even when no voltage is applied, and inclines the liquid crystal molecules. Further, the electric field formed between the pixels is distorted by the wall structure 115 existing between the adjacent pixels, and acts so as to define the direction in which the liquid crystal molecules are inclined on the wall surface of the wall structure 115.

When the wall structure 115 is provided, in addition to the steep diagonal electric field formed between the adjacent pixels and the orientation regulating force formed around the opening 114, the orientation regulating force of the wall structure 115 is increased. It acts cooperatively to form an axisymmetric orientation more stably. By also using the wall surface effect of the wall structure 115, the stability of axisymmetric orientation in the halftone display state where the orientation regulating force due to the oblique electric field is small is further improved, and it occurs when the liquid crystal display panel is pressed. The time required for the orientation disorder to recover to the normal orientation can be further shortened.

The wall structure 115 illustrated here is provided as a continuous wall so as to surround the pixels, but the present invention is not limited to this, and the wall structure 115 may be divided into a plurality of walls. Since the wall structure 115 acts to define the boundary formed in the vicinity of the extension of the pixel of the liquid crystal domain, it is preferable to have a certain length. For example, when the wall structure is composed of a plurality of walls (wall portions), the length of each wall is preferably longer than the length between adjacent walls.

Further, the notch 113 provided in the pixel electrode 111 is provided near the boundary of the axisymmetric alignment domain and defines the direction in which the liquid crystal molecules collapse due to the electric field, so that the notch 113 acts to form the axisymmetric orientation domain more stably. To do. When used in combination with the wall structure 115 as illustrated here, it is affected by the diagonal electric field formed around the opening 114 and the notch 113 and the electric field on the wall surface distorted by the wall structure 115. As a result of defining the direction in which the liquid crystal molecules are inclined, the two axisymmetric orientations are stably formed as described above. Further, here, the notch 113 is centered on an opening (here, the opening on the right side in FIG. 1) 114 corresponding to the central axis of the liquid crystal domain formed in the pixel (here, the entire transmission region). It contains four notches 113 arranged point-symmetrically.

By providing the notch 113 as described above, the direction in which the liquid crystal molecules collapse when a voltage is applied is defined, and two liquid crystal domains are formed. The reason why the notch is not provided on the left side of the pixel electrode 111 in FIG. 1 is that the notch provided on the right end of the pixel electrode (not shown) located on the left side of the illustrated pixel electrode 111 has the same effect. Therefore, the notch portion that reduces the effective aperture ratio of the pixel is omitted at the left end of the pixel electrode 111. Further, since the orientation restricting force of the wall structure 115 is also obtained here, a stable liquid crystal domain is formed as in the case where the notch is provided, even if the notch is not provided at the left end of the pixel electrode 111. In addition, the effect of improving the effective aperture ratio can be obtained.

In the liquid crystal display device 100, four notches 113 are formed, but at least one notch may be provided between adjacent liquid crystal domains. For example, here, an elongated notch is provided in the center of a pixel. A part may be provided and the others may be omitted.

The shape of the notch 113, which acts to define the direction in which the liquid crystal molecules in the axisymmetric orientation domain collapse due to the electric field, is set to exert an orientation regulating force that is substantially equal to the adjacent axisymmetric orientation, for example. A quadrangle is preferred. The notch may be omitted.

It is preferable to form the support 133 for defining the thickness (also referred to as the cell gap) of the liquid crystal layer 120 in the light-shielding region (here, the region defined by the black matrix 132) because the display quality is not deteriorated. .. The support 133 may be formed on either the transparent substrate 110a or 110b, and is not limited to the case where the support 133 is provided on the wall structure 115 provided in the light-shielding region as illustrated. When the support 133 is formed on the wall structure 115, the sum of the height of the wall structure 115 and the height of the support 133 is set to be the thickness of the liquid crystal layer 120. When the support 133 is provided in the region where the wall structure 115 is not formed, the height of the support 133 is set to be the thickness of the liquid crystal layer 120. The support 133 can be formed by, for example, a photolithography step using a photosensitive resin.

In this liquid crystal display device 100, axisymmetric orientation is formed by the action of an oblique electric field formed in adjacent pixels by performing dot inversion drive, and the central axis of the two axisymmetric alignment liquid crystal domains is the pixel electrode 111. It is fixed and stabilized in or near the two pairs of openings 114 provided at the center of the counter electrode 131 in the longitudinal direction. Further, the electric field distorted on the wall surface of the wall structure 115 and the wall surface effect of the wall structure mainly define the direction in which the liquid crystal molecules in the two adjacent liquid crystal domains collapse due to the electric field, and the diagonal electric field due to the pair of notches The action defines the direction in which the liquid crystal molecules in the two adjacent liquid crystal domains collapse due to the electric field, and these act cooperatively to stabilize the axially symmetric orientation of the liquid crystal domains even in the halftone display state.

By providing the opening 114 at a position corresponding to the central axis of the axisymmetrically oriented liquid crystal domain of the pixel electrode 111 and the counter electrode 131, the position of the central axis is fixed and stabilized, so that the entire surface of the liquid crystal display panel is covered. As a result, the central axis of the axisymmetrically oriented liquid crystal domain is arranged at a fixed position, and as a result, the uniformity of display is improved. Further, as a result of stabilizing the axisymmetric orientation, the effect that the response time in the halftone display can be shortened can be obtained. Further, it is possible to reduce the afterimage caused by pressing the liquid crystal display panel (shorten the recovery time). Since the axially symmetric orientation is further stabilized by providing the wall structure 115, it is preferable to provide the wall structure especially in an application in which an afterimage due to pressing is desired to be reduced.

On the liquid crystal layer 120 side of the transparent substrate 110a, for example, an active element such as a TFT and a circuit element such as a gate wiring and a source wiring connected to the TFT (all not shown) are provided. Further, the transparent substrate 110a, the circuit elements formed on the transparent substrate 110a, the pixel electrode 111 described above, the wall structure 115, and the support 133 (the support may be formed on either the active matrix substrate or the color filter substrate). It does not matter) and the alignment film, etc. may be collectively referred to as an active matrix substrate. On the other hand, the transparent substrate 110b and the color filter layer 130, the black matrix 132, the counter electrode 131, the alignment film, and the like formed on the transparent substrate 110b may be collectively referred to as a counter substrate or a color filter substrate.

The liquid crystal display device 100'shown in FIG. 1 (c) is different from the liquid crystal display device 100 shown in FIGS. 1 (a) and 1 (b) in that it does not have a wall structure. In FIG. 1 (c), the components common to the liquid crystal display device 100 are indicated by the same reference numerals as those in FIG. 1 (b).

Similar to the liquid crystal display device 100, the liquid crystal display device 100'has a steep diagonal electric field between adjacent pixels formed by being driven by dot inversion, and an opening 114 provided in the pixel electrode 111 and the counter electrode 131. Two axially symmetric oriented domains whose central axis is fixed and stabilized in or near the opening 114 (at least one of the first opening 114a and the second opening 114b) due to the oblique electric field formed in the periphery. It is formed stably. Further, since the notch 113 provided in the pixel electrode 111 regulates the orientation direction of the liquid crystal molecules near the boundary of the liquid crystal domains, the axisymmetric orientation of the two liquid crystal domains is further stabilized.

Further, in the liquid crystal display device 100', similarly to the liquid crystal display device 100, the switching element connected to any one scanning signal line is included in the pixel electrodes 111 belonging to the pair of rows adjacent to the scanning signal line. It alternately has a switching element connected to one side and a switching element connected to the other side. Therefore, by performing the conventional 1H inversion drive, as a result, display signals having opposite polarities can be applied to the liquid crystal layers of the pixels adjacent to each other in the row direction and the column direction with reference to the counter electrode 131 (1H). Dot inversion drive).

Although omitted in the above description, the liquid crystal display devices 100 and 100' further include a pair of polarizing plates arranged so as to face each other via the transparent substrates 110a and 110b. The pair of polarizing plates are typically arranged so that their transmission axes are orthogonal to each other. Further, as will be described later, a biaxial optically anisotropic medium layer or a uniaxial optically anisotropic medium layer may be provided.

(Semi-transmissive liquid crystal display device) Next, the configuration of the semi-transmissive liquid crystal display device 200 according to the embodiment of the present invention will be described with reference to FIG.

FIG. 2 is a diagram schematically showing a configuration of one pixel of the transmissive liquid crystal display device 200 according to the embodiment of the present invention, FIG. 2 (a) is a plan view, and FIG. 2 (b) is a diagram. It is a cross-sectional view along the 2B-2B'line in 2 (a).

Here, an example in which one pixel is divided into three (N = 3, the transmission area is divided into two, and the reflection area is divided into one) is shown, but the number of divisions (= N) is at least two or more (transmission area) according to the pixel pitch. Can be set to at least 1 division, and the reflection area can be set to at least 1 division). It is preferable that the number of openings (= n) provided at the substantially center of the division region (region where the axisymmetric alignment domain is formed) on the opposite substrate (second substrate) side is also the same as the number of pixel divisions (= N). .. However, as will be described later, when the transparent dielectric layer is selectively provided on the liquid crystal layer side of the reflection region of the counter substrate, the reflection region of the counter electrode (second electrode) does not have to be provided with an opening. good. Further, as the number of divisions (= N) increases, the effective aperture ratio tends to decrease. Therefore, when applied to a high-definition display panel, it is preferable to reduce the number of divisions (= N).

The liquid crystal display device 200 includes a transparent substrate (for example, a glass substrate) 210a, a transparent substrate 210b provided so as to face the transparent substrate 210a, and a vertically oriented liquid crystal layer provided between the transparent substrates 210a and 210b. Has 220 and. A vertical alignment film (not shown) is provided on the surfaces of both substrates 210a and 210b in contact with the liquid crystal layer 220, and when no voltage is applied, the liquid crystal molecules of the liquid crystal layer 220 are directed to the surface of the vertical alignment film. It is oriented almost vertically. The liquid crystal layer 220 contains a nematic liquid crystal material having a negative dielectric anisotropy, and further contains a chiral agent, if necessary.

The liquid crystal display device 200 has a pixel electrode 211 formed on the transparent substrate 210a and a counter electrode 231 formed on the transparent substrate 210b, and a liquid crystal provided between the pixel electrode 211 and the counter electrode 231. Layer 220 defines the pixels. Circuit elements such as TFTs are formed on the transparent substrate 210a as described later. The transparent substrate 210a and the components formed on the transparent substrate 210a may be collectively referred to as an active matrix substrate 210a.

Further, typically, a color filter 230 (a plurality of color filters are collectively referred to as a color filter layer 230) provided corresponding to pixels on the liquid crystal layer 220 side of the transparent substrate 210b. A black matrix (light-shielding layer) 232 provided between adjacent color filters 230 is formed, and a counter electrode 231 is formed on these, but the color filter layer 230 is formed on the counter electrode 231 (on the liquid crystal layer 220 side). Or black matrix 232 may be formed. The transparent substrate 210b and the components formed on the transparent substrate 210b may be collectively referred to as a counter substrate (color filter substrate) substrate 210b.

The pixel electrode 211 was formed of a transparent electrode 211a formed of a transparent conductive layer (for example, an ITO layer) and a metal layer (for example, an Al layer, an alloy layer containing Al, and a laminated film containing any of these). It has a reflective electrode 211b. As a result, the pixel includes a transparent region A defined by the transparent electrode 211a and a reflective region B defined by the reflective electrode 211b. The transparent area A is displayed in the transmission mode, and the reflection area B is displayed in the reflection mode.

In the liquid crystal display device 200 shown in FIG. 2 in which the number of pixel divisions (= N) is 3 (the transmission area is divided into 2 and the reflection area is divided into 1), the wall structure described later is placed on the light-shielding area around the pixel electrode 211. 215 is formed. Further, the pixel electrode 211 has a number of first openings 214a corresponding to the number of divisions (n = 3 in FIG. 2) at a predetermined position in the pixel. The pixel electrode 211 further has four notches 213 at predetermined positions. On the other hand, the counter electrode 231 on the transparent substrate 210b on the opposite side has two second openings 114b according to the number of divisions of the transmission region.

When a predetermined voltage is applied to the liquid crystal layer, three liquid crystal domains (the same number as the number of divisions N) each exhibiting axisymmetric orientation are formed, and the central axis of each axisymmetric orientation of these liquid crystal domains is the first. It is formed in or near the opening 214a and the second opening 114b. The openings 214a and 214b provided at predetermined positions of the pixel electrode 211 and the counter electrode 231 act to fix the position of the central axis of the axisymmetric orientation and to stabilize the axisymmetric orientation. As illustrated here, when the first opening 214a and the second opening 214b are arranged so as to overlap each other via the liquid crystal layer in the transmission region, the decrease in the effective aperture ratio due to the pair of openings 214 is suppressed. be able to. Since one central axis is fixed and stabilized by the action of the first opening and the second opening, the action that the first opening 114a or the second opening 114b should exert is the central axis in one opening. The diameters of the first opening 214a and the second opening 214b can be reduced, and as a result, a decrease in the effective aperture ratio can be suppressed.

As will be described in detail later, the liquid crystal display device of the present embodiment is adjacent to each other in both columns and rows within each vertical scanning period with respect to the pixels arranged in a matrix having rows and columns. The voltage applied to the pixel electrode of the pixel to be used is applied so as to have the opposite polarity with respect to the voltage applied to the counter electrode 231 (dot inversion drive). As described above, by adopting the dot inversion drive, the orientation stabilization effect due to the oblique electric field generated between the adjacent pixels can be obtained for the four sides of the substantially rectangular pixel. Therefore, a steep diagonal electric field is formed between adjacent pixels, which acts to stabilize the axisymmetric orientation.

Further, in the liquid crystal display device of the present embodiment, the switching element connected to any one scanning signal line is connected to one of the pixel electrodes 211 belonging to the pair of rows adjacent to the scanning signal line. It has a switching element and a switching element connected to the other alternately. Therefore, by performing the conventional 1-line inversion drive (1H inversion drive), as a result, display signals having opposite polarities are applied to the liquid crystal layers of pixels adjacent to each other in the row direction and the column direction with reference to the counter electrode 231. Can be (1H dot inversion drive).

Further, in the liquid crystal display device of the present embodiment, the center of the axisymmetric orientation is fixed and stabilized in or near the opening 214 as described above. This is because the action of the oblique electric field formed by the opening 214 forms a continuous orientation (axisymmetric orientation) of the liquid crystal molecules around the opening 214, and the opening 214 The action of (at least one of the first opening 214a and the second opening 214b) suppresses / prevents the formation of discontinuous orientation at the corners as shown in FIG. 9 of Patent Document 7. To. In addition, due to the action of the opening 214, a sufficiently stable axisymmetric orientation can be obtained even in a halftone display state in which the electric field is low, and the orientation disorder that occurs when the liquid crystal display panel is pressed is restored to the normal orientation. The time can be shortened.

Further, the liquid crystal display device 200 has a light-shielding region between adjacent pixels, and has a wall structure 215 on the transparent substrate 210a in the light-shielding region. Since the light-shielding area does not contribute to the display, the wall structure 215 formed in the light-shielding area does not adversely affect the display.

The wall structure 215 acts so as to define the direction in which the liquid crystal molecules are inclined when a voltage is applied (when an electric field is generated) due to the inclined surface effect. The orientation-regulating force due to the inclined side surface of the wall structure 215 acts even when no voltage is applied, and inclines the liquid crystal molecules. Further, the electric field formed between the pixels is distorted by the wall structure 215 existing between the adjacent pixels, and acts so as to define the direction in which the liquid crystal molecules are inclined on the wall surface of the wall structure 215.

When the wall structure 215 is provided, in addition to the steep diagonal electric field formed between the adjacent pixels and the orientation regulating force formed around the opening 214, the orientation regulating force of the wall structure 215 is increased. It acts cooperatively to form an axisymmetric orientation more stably. By also using the wall effect of the wall structure 215, the stability of axisymmetric orientation in the halftone display state where the orientation restricting force due to the oblique electric field is small is further improved, and it occurs when the liquid crystal display panel is pressed. The time required for the orientation disorder to recover to the normal orientation can be further shortened.

The wall structure 215 illustrated here is provided as a continuous wall so as to surround the pixels, but the present invention is not limited to this, and the wall structure 215 may be divided into a plurality of walls. Since the wall structure 215 acts to define the boundary formed in the vicinity of the extension of the pixel of the liquid crystal domain, it is preferable to have a certain length. For example, when the wall structure 215 is composed of a plurality of walls, the length of each wall is preferably longer than the length between adjacent walls.

Further, the notch 213 to be arranged as needed is provided near the boundary of the axisymmetric orientation domain, defines the direction in which the liquid crystal molecules collapse due to the electric field, and acts to form the axisymmetric orientation domain. Similar to the openings 214a and 214b, an oblique electric field is formed around the notch 213 by the voltage applied between the pixel electrode 211 and the counter electrode 213, and the oblique electric field and the wall structure 215 form an oblique electric field. As a result of defining the direction in which the liquid crystal molecules are inclined by the action of the electric field on the distorted wall surface, the axially symmetric orientation is formed as described above.

Further, here, the notch portion 213 is point-symmetrical about the opening (here, the opening on the right side in FIG. 2A) 214a corresponding to the central axis of the liquid crystal domain formed in the transmission region of the pixel. Includes four notches 213 arranged in. When used in combination with the wall structure 215 as illustrated here, the action of the diagonal electric field formed around the opening 214 and the notch 213 and the electric field on the wall surface distorted by the wall structure 215. As a result of defining the direction in which the liquid crystal molecules are inclined, the three axisymmetric orientations are stably formed as described above. The arrangement of the wall structure 215, the opening 214, the notch 213, and their preferred shapes are the same as in the case of the transmissive liquid crystal display device 100 described above. FIG. 2 shows an example in which two liquid crystal domains are formed in the transmission region A and one liquid crystal domain is formed in the reflection region B, but the present invention is not limited to this. It is preferable that each liquid crystal domain has a substantially square shape from the viewpoint of viewing angle characteristics and orientation stability.

If the support 233 for defining the thickness of the liquid crystal layer 220 (also referred to as the cell gap) is formed in the light-shielding region (here, the region defined by the black matrix 232), the display quality is not deteriorated. preferable. The support 233 may be formed on either the transparent substrate 210a or 210b, and is not limited to the case where the support 233 is provided on the wall structure 215 provided in the light-shielding region as illustrated. When the support 233 is formed on the wall structure 215, the sum of the height of the wall structure 215 and the height of the support 233 is set to be the thickness of the liquid crystal layer 220. When the support 233 is provided in the region where the wall structure 215 is not formed, the height of the support 233 is set to be the thickness of the liquid crystal layer 220.

In this liquid crystal display device 200, when a predetermined voltage (voltage equal to or higher than the threshold voltage) is applied to the pixel electrode 211 and the counter electrode 231, two axisymmetrically oriented liquid crystal domains are applied to the transmission region A and one axis is applied to the reflection region B. A symmetric orientation domain is formed. The direction in which the liquid crystal molecules in the three adjacent liquid crystal domains (two transmission regions and one reflection region) collapse due to the electric field distorted on the wall surface of the wall structure 215 and the wall surface effect of the wall structure is defined. The orientation-regulating force that causes the liquid crystal molecules in the three adjacent liquid crystal domains to collapse due to the electric field due to the diagonal electric field action of the four notches acts cooperatively to stabilize the axially symmetric orientation of the liquid crystal domains. Further, the central axes of the two axisymmetrically oriented liquid crystal domains formed in the transmission region A are fixed and stabilized in or near the pair of openings 214 (214a and 214b facing each other), respectively. The central axis of one axisymmetric liquid crystal domain formed in the reflection region B is stabilized by the opening 214a.

Here, an example of a preferable configuration of the transflective liquid crystal display device 200 having the wall structure 215 has been described, but the wall structure 215 is used in the same manner as the transmissive liquid crystal display device 100'shown in FIG. It may be omitted. However, since the axially symmetric orientation is further stabilized by providing the wall structure 215, it is preferable to provide the wall structure, particularly in an application in which an afterimage due to pressing is desired to be reduced, as described above.

Next, a preferable configuration peculiar to the semi-transmissive liquid crystal display device 200 capable of performing both the transmission mode display and the reflection mode display will be described.

In the transmission mode display, the light used for display passes through the liquid crystal layer 220 only once, whereas in the reflection mode display, the light used for display passes through the liquid crystal layer 220 twice. Therefore, as schematically shown in FIG. 2B, it is preferable to set the thickness dt of the liquid crystal layer 220 in the transmission region A to about twice the thickness dr of the liquid crystal layer 220 in the reflection region B. By setting in this way, the retardation given by the liquid crystal layer 220 to the light in both display modes can be made substantially equal. dt = 0.5dr is the most preferable, but if it is within the range of 0.3dt &lt;dr &lt;0.7dt, good display can be achieved in both display modes. Of course, depending on the application, dt = dr may be used.

In the liquid crystal display device 200, in order to make the thickness of the liquid crystal layer 220 of the reflection region B smaller than the thickness of the liquid crystal layer of the transmission region A, the transparent dielectric layer 234 is provided only in the reflection region B of the glass substrate 210b. There is. As illustrated, the transparent dielectric layer 234 is preferably provided on the lower side (opposite side of the liquid crystal layer) of the counter electrode 231. When such a configuration is adopted, it is not necessary to provide a step under the reflective electrode 211b by using an insulating film or the like, so that there is an advantage that the production of the active matrix substrate 210a can be simplified. Further, when the reflective electrode 211b is provided on the insulating film for providing a step for adjusting the thickness of the liquid crystal layer 220, the light used for the transmitted display is blocked by the reflective electrode covering the slope (tapered portion) of the insulating film. Or, the light reflected by the reflective electrode formed on the slope of the insulating film repeats internal reflection, so that there is a problem that it is not effectively used for the reflection display. However, when the above configuration is adopted, these The occurrence of problems can be suppressed and the efficiency of light utilization can be improved.

Furthermore, if the transparent dielectric layer 234 has a function of scattering light (diffuse reflection function), a white display close to good paper white can be realized without imparting a diffuse reflection function to the reflective electrode 211b. it can. Even if the transparent dielectric layer 234 is not imparted with a light scattering ability, it is possible to realize a white display close to paper white by imparting a concavo-convex shape to the surface of the reflective electrode 211b, but depending on the concavo-convex shape, the axis The position of the central axis of symmetrical orientation may not be stable. On the other hand, if the transparent dielectric layer 234 having a light scattering ability and the reflecting electrode 211b having a flat surface are used, the position of the central axis can be more reliably stabilized by the opening 214a formed in the reflecting electrode 211b. Benefits are obtained. Of course, by providing the opening 214b in the reflection region B of the counter electrode 231, the central axis of the axisymmetric orientation can be further stabilized. When irregularities are formed on the surface of the reflective electrode 211b in order to impart a diffuse reflection function, the irregularities are preferably continuous wavy so as not to generate interference colors, and the central axis of axisymmetric orientation is set. It is preferable to set it so that it can be stabilized.

Further, in the transmission mode, the light used for display passes through the color filter layer 230 only once, whereas in the display in the reflection mode, the light used for display passes through the color filter layer 230 twice. Therefore, if a color filter layer having the same optical density is used for the transmission region A and the reflection region B as the color filter layer 230, the color purity and / or the brightness in the reflection mode may decrease. In order to suppress the occurrence of this problem, it is preferable that the optical density of the color filter layer in the reflection region is smaller than that of the color filter layer in the transmission region. The optical density referred to here is a characteristic value that characterizes the color filter layer, and the optical density can be reduced by reducing the thickness of the color filter layer. Alternatively, the optical density can be reduced by keeping the thickness of the color filter layer as it is, for example, by lowering the concentration of the dye to be added. Forming different color layers of color filters in the transmission region A and the reflection region B in this way is extremely effective for the purpose of improving the color reproducibility of the display.

Next, an example of the structure of an active matrix substrate preferably used in a transflective liquid crystal display device will be described with reference to FIGS. 3 and 4. FIG. 3 is a partially enlarged view of the active matrix substrate, and FIG. 4 is a cross-sectional view taken along the X-X'line in FIG. The active matrix substrate shown in FIGS. 3 and 4 has a configuration in which one liquid crystal domain is formed in the transmission region A (that is, a small number of openings 214a and notches 213). It is different from the active matrix substrate 211a shown in FIG. 2, but other configurations may be the same.

The active matrix substrate shown in FIGS. 3 and 4 has, for example, a transparent substrate 1 made of a glass substrate, and the gate signal line 2 and the source signal line 3 are provided on the transparent substrate 1 so as to be orthogonal to each other. .. A TFT 4 is provided near the intersection of these signal wirings 2 and 3, and the drain electrode 5 of the TFT 4 is connected to the pixel electrode 6.

The pixel electrode 6 has a transparent electrode 7 formed of a transparent conductive layer such as ITO and a reflective electrode 8 formed of Al or the like. The transparent electrode 7 defines a transmission region A, and the reflective electrode 8 reflects. Define area B. As described above, the notch 14 for controlling the orientation of the axisymmetric alignment domain and the first opening 214 for fixing the axial position of the axisymmetric orientation domain are provided in the predetermined region of the pixel electrode 6. Has been done. Further, in order to define the orientation state of the axisymmetric alignment domain, a wall structure (not shown) surrounding the pixel region is formed in the signal line (light-shielding region) portion of the non-display region outside the pixel.

The pixel electrode 6 is superimposed on the gate signal line of the next stage via the gate insulating film 9, and an auxiliary capacitance is formed. In addition, TFT4 has a gate insulating film 9, a semiconductor layer 12, a channel protection layer 13 and n above the gate electrode 10 branched from the gate signal line 2.⁺-It has a structure in which Si layer 11 (source / drain electrode) is laminated.

Although a configuration example of a bottom gate type TFT is shown here, the present invention is not limited to this, and a top gate type TFT can also be used.

As described above, the liquid crystal display device 200 having the configuration shown in FIG. 2 has the action of an oblique electric field formed in adjacent pixels by performing dot inversion drive and the periphery of the opening 214, similarly to the liquid crystal display device 100. Axisymmetric orientation is stably formed by the action of the oblique electric field formed in. Further, each pair of openings 214 provided at substantially the center of the pixel electrode and the counter electrode fix and stabilize the central axis of the axisymmetric alignment domain in the pixel, so that the display can be performed diagonally in the halftone display state. It is possible to obtain effects such as reducing the feeling of roughness when viewed. Further, the wall structure 215 and the notch 213 provided in the light-shielding region form a stable axisymmetric orientation domain even in the halftone display state.

Further, by configuring the transparent attractant layer 234 and / or the color filter layer 230 as described above, the brightness and color purity of the display in the transmission mode and the reflection mode can be improved.

(Orientation Stabilization Driving Method) The liquid crystal display device of the above-described embodiment is adjacent to each other in both columns and rows within each vertical scanning period with respect to the pixels arranged in a matrix having rows and columns. The voltage applied to the pixel electrode of the pixel to be used is applied so as to have the opposite polarity with respect to the voltage applied to the counter electrode (dot inversion drive). Here, the orientation stabilizing effect obtained by performing the dot inversion drive will be described in detail.

FIG. 5 schematically shows a drive circuit and a pixel arrangement of the liquid crystal display device 300 according to the embodiment of the present invention. The liquid crystal display device 300 has a display area having the same configuration as the above-mentioned liquid crystal display device 100 or 200.

The liquid crystal display device 300 is a TFT type liquid crystal display device, and has a plurality of parallel data signal lines (source signal lines) 301 extending in the column direction and a plurality of parallel scanning signal lines (gate signal lines) extending in the row direction. It has 302, which are connected to the source signal drive circuit 303 and the gate signal drive circuit 304, respectively. The liquid crystal display device 300 has at least one TFT 305 for each pixel, the gate electrode of the TFT 305 is connected to the scanning signal line 302, and the data signal line 301 is connected to the source electrode. The drain electrode of the TFT 305 is connected to the pixel electrode 306, and when a predetermined voltage (scanning signal voltage) is applied to the gate electrode, the TFT 305 is turned on and the pixel electrode 306 is electrically connected to the data signal line. , A predetermined data signal voltage is supplied to the pixel electrode 306. A predetermined common voltage is supplied to the counter electrode facing the pixel electrode 306 (not shown: typically facing a plurality of pixel electrodes). The difference between the common voltage supplied to the counter electrode and the data signal voltage supplied to the pixel electrode 306 is applied to the liquid crystal layer of each pixel.

Here, the TFT 305 connected to any one scanning signal line 302 is connected to one of the pixel electrodes 306 belonging to a pair of rows adjacent to the scanning line 302 (for example, the pixel electrode 306 belonging to the upper row). It is arranged so as to have the TFT 305 connected to the other (for example, the pixel electrode 306 belonging to the lower row) alternately. In other words, of the plurality of data signal lines 301, for example, the TFT 306 connected to the odd-th data signal line 301 is located above the scanning signal line 302 (connected to the pixel electrode 306 in the upper row). The TFT 305 connected to the even-th data signal line 301 is located below the scanning signal line 302 (connected to the pixel electrode 306 in the lower row). That is, the TFT 305 (and the pixel electrode 306) connected to a certain scanning signal line 302 are arranged alternately in the vertical direction for each data signal line 301 in a staggered pattern.

By performing the conventional one-line inversion drive for the panel configuration of the staggered arrangement as described above, the voltage supplied to the pixel electrode 306 is set in the row direction and the column direction with reference to the voltage supplied to the counter electrode. The polarity is reversed between adjacent pixels, and switching is performed frame by frame. That is, the source signal line drive circuit 303 and the gate signal line drive circuit 304 can realize dot inversion drive as a result only by performing the conventional one-line inversion drive.

In the present embodiment, the counter electrode is provided to an arbitrary first pixel formed so as to be arranged in a matrix within one frame period and a second pixel in the same row adjacent to the first pixel. The voltage of opposite polarities is applied with reference to, and the first pixel connected to the scanning line of an arbitrary nth line and n + 1 connected to the data signal line in the same column as the first pixel. A voltage of opposite polarity to each other is also applied to the third pixel connected to the scanning signal line of the line (or line n-1) with reference to the counter electrode (dot inversion drive). Further, the polarity of the voltage applied to all the pixels is inverted for each frame (frame inversion drive). For example, FIG. 6 shows an example of the polarity pattern of the voltage applied to the pixels in a certain frame period of the liquid crystal display device 300 of the present embodiment. In the next frame shown in FIG. 6, plus and minus are reversed for all pixels.

Figures 7 (a) to 7 (c) show the behavior of equipotential lines when a voltage is applied to the liquid crystal layer and the simulation results of the liquid crystal alignment director. Here, the drive voltage of the liquid crystal layer is set to 4 V, and in order to confirm the effect of drawing equipotential lines by the electric field, the case where the width of the gap between the adjacent pixel electrodes is 3 μm and the case where the width is 9 μm are compared. .. In addition, when a voltage of the same polarity is applied between adjacent pixel electrodes as in the case where a conventional line inversion drive is performed with respect to a conventional panel configuration, positive and negative are positive and negative between adjacent pixels with reference to the counter electrode. The case where the polarity is applied as the opposite polarity (this embodiment) is shown.

FIG. 7 (a) shows the driving method of the embodiment according to the present invention when a voltage of opposite polarity is applied to the adjacent pixel electrodes (gap between electrodes 3 μm), and (b) the conventional driving method between adjacent pixels. This is the simulation result when a voltage of the same polarity is applied (electrode gap 3 μm) and (c) when a voltage of the same polarity is applied between adjacent pixels by the conventional driving method (electrode gap 9 μm).

It can be seen that when a voltage of opposite polarity is applied between adjacent pixels, a steep potential gradient is generated at the boundary of the pixels and equipotential lines are drawn more effectively. For example, in the driving method of the present embodiment, equipotential lines are drawn more effectively than in the case where the adjacent pixels have the same polarity and the electrode gap is 9 μm, and the liquid crystal molecules are obliquely oriented by the electric field. I understand. Further, it can be seen that in the driving method of the present embodiment, the orientation of the liquid crystal molecules is effectively controlled by the electric field even when the electrode gap is 3 μm.

As described above, one conventional line is used for a panel having a configuration in which TFT 305s (and pixel electrodes 306) connected to an arbitrary scanning signal line 302 are arranged alternately in a vertical direction for each data signal line 301. Inversion drive is performed, and the polarity of the voltage applied to the adjacent pixels in both the row direction and the column direction is applied to the counter electrode with the opposite polarity for each frame, so that a large potential gradient is formed between the pixels. This makes it possible, and the axially symmetric orientation formed on the vertically oriented liquid crystal layer can be further stabilized by the orientation regulating force utilizing this potential gradient.

Further, the driving method suitable for stabilizing the orientation is extremely effective in reducing the flicker of the liquid crystal panel.

That is, in a general active liquid crystal panel, the positive and negative of the data signal output from the source signal drive circuit (column direction) 303 are symmetric because the characteristics of the switching element such as the TFT element provided for each pixel are not sufficient. However, the transmissivity of the liquid crystal layer is not completely symmetrical with respect to the positive and negative data voltages, and the liquid crystal panel is driven by a drive method (1 frame inversion drive) in which the positive and negative characteristics of the voltage applied to the liquid crystal layer are inverted for each frame. Flicker may be noticeable.

As such a flicker reduction measure, a drive method (1H inversion drive) in which the positive / negative characteristics are inverted for each horizontal scanning line and the positive / negative characteristics are inverted for each frame cycle is known. A drive method (dot inversion drive) is used in which the positive / negative properties of the voltage applied to the liquid crystal layer forming the above are inverted for each scanning signal line and for each data line, and are also inverted for each frame cycle. The effect of suppressing flicker can be reduced most by the same dot inversion drive as in the present embodiment, but in the case of dot inversion drive, the pixel electrodes on the same scanning line have positive or negative polarities. It has also been pointed out that the IC withstand voltage of the source signal line drive circuit must be set high in order for the voltage to be applied. On the other hand, in the present embodiment, there is a conventional panel having a configuration in which switching elements (and pixel electrodes) connected to an arbitrary scanning signal line are arranged alternately in a vertical direction for each data signal line in a staggered pattern. As a result, the dot inversion drive can be realized by performing the one-line inversion drive, so that a high IC withstand voltage unlike the conventional dot inversion drive is not required.

In the liquid crystal display device of the embodiment of the present invention, if a wall structure is further provided, the axisymmetric orientation can be stabilized by utilizing the orientation restricting force of the wall structure, so that a sufficient electric field can be obtained. It is possible to stabilize the axisymmetric orientation even in the case of no halftone, and it is possible to improve the display quality in the halftone. Further, it is possible to shorten the time for the orientation disorder (sometimes called an afterimage due to pressing) that occurs when the liquid crystal display panel is pressed to recover to the normal orientation.

[Operating Principle] Next, with reference to FIG. 8, the reason why the liquid crystal display device of the embodiment of the present invention having the vertically oriented liquid crystal layer has excellent wide viewing angle characteristics will be described.

FIG. 8 is a diagram for explaining the action of the orientation restricting force by the wall structure 15 and the opening 14a provided on the active matrix substrate side and the opening 14b provided on the color filter substrate side, and is shown in FIG. 6 (a). ) Schematically shows the orientation state of the liquid crystal molecules when no voltage is applied, and FIG. 8 (b) shows the orientation state of the liquid crystal molecules when the voltage is applied. The state shown in Fig. 8 (b) is the state in which the halftone is displayed.

In the liquid crystal display device shown in FIGS. 8A and 8B, an insulating film 16, a pixel electrode 6 having an opening 14a at a predetermined position, and a wall structure 15 are formed on the transparent substrate 1, and an alignment film is formed. 12 are arranged in this order. On the other transparent substrate 17, a color filter layer 18, a counter electrode 19 having an opening 14b at a predetermined position, and an alignment film 32 are formed in this order. The liquid crystal layer 20 provided between the two substrates contains liquid crystal molecules 21 having negative dielectric anisotropy.

As shown in FIG. 8A, when no voltage is applied, the liquid crystal molecules 21 are oriented substantially perpendicular to the substrate surface due to the orientation restricting force of the vertically oriented films 22 and 32.

On the other hand, when a voltage is applied, as shown in FIG. 8 (b), the liquid crystal molecule 21 having a negative dielectric anisotropy tends to have its molecular major axis perpendicular to the lines of electric force, so that the pair of openings 14a and The direction in which the liquid crystal molecules 21 collapse is defined by the oblique electric field formed around 14b, the electric field strain on the side surface (wall surface) of the wall structure 15, and the orientation restricting force. Therefore, for example, the orientation is axisymmetric with respect to the openings 14a and 14b. Within this axisymmetric orientation domain, the liquid crystal director is oriented in all directions (directions in the substrate surface), so that the viewing angle characteristics are excellent.

Here, the action of the oblique electric field formed around the openings 14a and 14b and the orientation regulating force in the wall structure 15 have been described, but even in the vicinity of the notch formed at the edge portion of the pixel electrode 6. Similarly, an oblique electric field is formed, and the direction in which the liquid crystal molecules 21 are tilted by the electric field is defined. In particular, by performing the dot inversion drive described above, the oblique electric field generated between the adjacent pixel electrodes acts to stably form the axisymmetric orientation of the liquid crystal molecules. Even if the wall structure 15 is omitted, the axisymmetric orientation is stabilized by the action of the steep diagonal electric field obtained by performing the dot inversion drive and the action of the diagonal electric field formed around the openings 14a and 14b. Can be formed.

Next, the configuration of the liquid crystal display device according to the present invention will be described.

The liquid crystal display device shown in FIG. 9 includes a backlight, a semi-transmissive liquid crystal panel 50, a pair of polarizing plates 40 and 43 provided so as to face each other via the semi-transmissive liquid crystal panel 50, and a polarizing plate 40. The optical anisotropy provided between the 1/4 wave plates 41 and 44 provided between the and 43 and the liquid crystal panel 50 and the 1/4 wave plates 41 and 44 and the liquid crystal panel 50 is negative. It has a phase difference plate 42 and 45. The liquid crystal panel 50 has a vertically oriented liquid crystal layer 20 between the transparent substrate (active matrix substrate) 1 and the transparent substrate (opposing substrate) 17. As the liquid crystal panel 50, a panel having the same configuration as the liquid crystal display device 200 shown in FIG. 2 is used here.

The display operation of the liquid crystal display device shown in FIG. 9 will be briefly described below.

Regarding the reflection mode display, the incident light from above passes through the polarizing plate 43 and becomes linearly polarized light. This linearly polarized light becomes circularly polarized light when incident on the 1/4 wave plate 44 so that the transmission axis of the polarizing plate 43 and the slow axis of the 1/4 wave plate 44 are at 45 °, and is formed on the substrate 17. It is transparent to the color filter layer (not shown). Here, a retardation plate 45 that does not give a phase difference to light incident from the normal direction is used.

When no voltage is applied, the liquid crystal molecules in the liquid crystal layer 20 are oriented substantially perpendicular to the substrate surface, so that the incident light is transmitted with a phase difference of almost 0 and is reflected by the reflective electrode formed on the lower substrate 1. To. The reflected circularly polarized light passes through the liquid crystal layer 20 again, passes through the color filter layer, passes through the retardation plate 45 having a negative optical anisotropy again with circularly polarized light, passes through the 1/4 wavelength plate 44, and first. Light cannot pass through the polarizing plate 43 and is displayed in black because it is converted into linearly polarized light in the polarization direction orthogonal to the polarization direction when it is incident on the polarizing plate 43 and reaches the polarizing plate 43.

On the other hand, when a voltage is applied, the liquid crystal molecules in the liquid crystal layer 20 are tilted from the direction perpendicular to the substrate surface to the horizontal direction, so that the incident circular polarization becomes elliptically polarized light due to the birefringence of the liquid crystal layer 20 and is formed on the lower substrate 1. It is reflected by the reflective electrode. The reflected light is further depolarized by the liquid crystal layer 20, passes through the liquid crystal layer 20 again, passes through the color filter layer, and again passes through the retardation plate 45 having a negative optical anisotropy, and 1/4. Since it is incident on the wavelength plate 44 as elliptically polarized light, when it reaches the polarizing plate 43, not all the light becomes linearly polarized light orthogonal to the polarization direction at the time of incident, and some light passes through the polarizing plate 43. In particular, by adjusting the applied voltage, the tilting direction of the liquid crystal molecules can be controlled, the amount of light that the reflected light can pass through the polarizing plate 43 is modulated, and gradation display becomes possible.

Regarding the display of the transmission mode, the upper and lower two polarizing plates 43 and the polarizing plate 40 are arranged so that their transmission axes are orthogonal to each other, and the light emitted from the light source is linearly polarized by the polarizing plate 40. This linearly polarized light becomes circularly polarized light when incident on the 1/4 wave plate 41 so that the slow axis between the transmission axis of the polarizing plate 40 and the 1/4 wave plate 41 is 45 °, and the optical anisotropy is negative. It is incident on the transmission region A of the lower substrate 1 via the retarding plate 42. Here, a retardation plate 42 that does not give a phase difference to the light incident from the normal direction is used.

When no voltage is applied, the liquid crystal molecules in the liquid crystal layer 20 are oriented substantially perpendicular to the substrate surface, so that the incident light is transmitted with a phase difference of almost 0 and is incident on the lower substrate 1 in a circularly polarized state. In a circularly polarized state, the upper optical anisotropy passes through the liquid crystal layer 20 and the upper substrate 17 and reaches the 1/4 wave plate 44 through the negative retardation plate 45. Here, by arranging the slow axes of the lower 1/4 wave plate 41 and the upper 1/4 wave plate 44 intersecting at 90 °, the polarizing plate 40 can be used from the upper 1/4 wave plate 44. It becomes linearly polarized light orthogonal to the linearly polarized light of, and is absorbed by the polarizing plate 43 and displayed in black.

On the other hand, when a voltage is applied, the liquid crystal molecules 21 in the liquid crystal layer 20 are tilted from the direction perpendicular to the substrate surface to the horizontal direction, so that the circularly polarized light incident on the liquid crystal display device becomes elliptically polarized light due to the double refraction of the liquid crystal layer 20, and is on the upper side. Since the CF substrate 16 and the retardation plate 45 and the 1/4 wavelength plate 44 on the upper side, which have negative optical anisotropy, reach the polarizing plate 43 as elliptically polarized light, the linearly polarized light is orthogonal to the polarization component at the time of incident. Instead, light is transmitted through the polarizing plate 43. In particular, by adjusting the applied voltage, the tilting direction of the liquid crystal molecules can be controlled, the amount of light that the reflected light can pass through the polarizing plate 43 is modulated, and gradation display becomes possible.

The retardation plate with negative optical anisotropy minimizes the amount of change in the phase difference when the viewing angle of the liquid crystal molecules is changed in the vertically oriented state, and suppresses black floating on the wide viewing angle side. Further, a biaxial retardation plate in which a retardation plate having a negative optical anisotropy and a 1/4 wave plate are integrated may be used.

When the normally black mode, which displays black when no voltage is applied and white when voltage is applied, is performed in the axially symmetric alignment domain as in the present invention, a pair of 1/4 wavelengths above and below the liquid crystal display device (panel). By providing the plate, it is possible to eliminate the extinction pattern caused by the polarizing plate and improve the brightness. Further, when the transmission axes of the upper and lower polarizing plates are arranged orthogonally to each other and the normal black mode is performed in the axially symmetric orientation domain, in principle, the same degree as that of a pair of polarizing plates arranged on the cross Nicol. Since black display can be realized, an extremely high contrast ratio can be realized, and a wide viewing angle characteristic guided by omnidirectional orientation can be achieved.

Regarding the relationship between the liquid crystal layer thickness dt in the transmissive region and the liquid crystal layer thickness dr in the reflective region specified in the present invention, FIG. 10 shows the dependence of the liquid crystal thickness between the voltage in the transmissive region and the reflective region-reflectance (transmittance). As shown in, it is preferable to satisfy the condition of 0.3dt &lt;dr &lt;0.7dt, and more preferably the range of 0.4dt &lt;dr &lt;0.6dt. If the liquid crystal layer thickness in the reflection region is lower than the lower limit, the reflectance is 50% or less of the maximum reflectance, and sufficient reflectance cannot be obtained. On the other hand, when the liquid crystal layer thickness dr in the reflection region is larger than the upper limit value, there is a maximum value in the voltage-reflectance characteristic that maximizes the reflectance at a drive voltage different from that at the time of transmission display, and it is optimal for transmission display. At a high white display voltage, the relative reflectance tends to decrease, and the reflectance becomes 50% or less of the maximum reflectance, so that sufficient reflectance cannot be obtained. However, in the reflection region B, the optical path length of the liquid crystal layer is twice that of the transmission region. Therefore, when the same design as the transmission region A is used, the optical birefringence anisotropy (Δn) of the liquid crystal material is determined. The cell thickness design of the panel is extremely important.

Specific characteristics of the transflective liquid crystal display device according to the embodiment of the present invention will be illustrated below.

Here, a liquid crystal display device having the configuration shown in FIG. 9 was produced. As the liquid crystal cell 50, a liquid crystal cell having the same configuration as that of the liquid crystal display device 200 shown in FIG. 2 was used.

On the pixel electrode on the TFT substrate side, an opening (first opening) with a diameter of 5 μm is formed at a predetermined position in each of the transmission region and the reflection region, and a wall is formed on a light-shielding portion such as on a signal line around the pixel. The structure was placed. Further, on the counter electrode on the facing substrate side, an opening (second opening) for fixing the axis center of the axisymmetric alignment domain having a diameter of 5 μm is arranged at each predetermined position of the transmission region portion and the reflection region portion. .. The pair of first and second openings are spatially overlapped with each other via the liquid crystal layer. Here, the width of the notch is set to 3 μm, and the gap between adjacent pixel electrodes is set to 5 μm. Further, in the color filter substrate, a transparent dielectric layer 234 having no light scattering ability is used, and a resin layer having a continuous uneven shape on the surface is formed on the lower layer of the reflective electrode 211b to display the reflection. The diffuse reflection characteristics were adjusted.

A vertical alignment film was formed by a known method using a known alignment film material. Rabin processing is not performed. As the liquid crystal material, a liquid crystal material having a negative dielectric anisotropy (Δn; 0.1, Δε; -4.5) was used. Here, the liquid crystal layer thickness dt in the transmission region was set to 4 μm, and the liquid crystal layer thickness dr in the reflection region was set to 2.2 μm (dr = 0.55 dt).

The configuration of the liquid crystal display device of this embodiment consists of a polarizing plate (observation side), a 1/4 wave plate (phase difference plate 1), and a retardation plate with negative optical anisotropy (phase difference plate 2 (NR)) in this order from the top. Plate)), liquid crystal layer (upper side; color filter substrate, lower side; active matrix substrate), retardation plate with negative optical anisotropy (polarizing plate 3 (NR plate)), 1/4 wave plate (phase difference) It has a laminated structure of plate 4) and polarizing plate (backlight side). In the upper and lower 1/4 wave plates (phase difference plate 1 and phase difference plate 4) of the liquid crystal layer, the slow axes of each are orthogonal to each other, and the phase difference between them is 140 nm. For the retardation plates with negative optical anisotropy (phase difference plate 2 and retardation plate 3), the respective retardation was set to 135 nm. In addition, the two polarizing plates (observation side and backlight side) were arranged with their transmission axes orthogonal to each other.

The display characteristics were evaluated by applying a drive signal to the liquid crystal display device (applying 4 V to the liquid crystal layer). In particular, here, as described above, the switching elements are arranged alternately in the vertical direction for each data signal line in a staggered pattern, and 1H line inversion is performed to pseudo-dot invert the liquid crystal layer. The same drive signal as above is applied, + 4V and -4V signals are applied between adjacent pixels with reference to the counter electrode within one frame, and in the next one frame, polarity inversion is driven to drive the display characteristics of the liquid crystal panel. Was evaluated.

Figure 11 shows the characteristics of the viewing angle-contrast in the transparent display. The viewing angle characteristics in the transmission display showed almost omnidirectional and symmetrical characteristics, the region of CR&gt; 10 was good at ± 80 °, and the transmission contrast was as high as 300: 1 or more in the front. In addition, compared to the case of applying a conventional drive method such as line inversion in which a drive signal of the same polarity is applied between adjacent pixels, the gap between the adjacent pixel electrodes can be narrowed, so the transmittance is about 15% compared to the conventional method. The improvement effect was confirmed.

On the other hand, the characteristics of the reflection display are evaluated by a spectrophotometer (CM2002 manufactured by Minolta), the reflectance is about 9.5% (aperture ratio 100% conversion value) based on the standard diffuser plate, and the contrast value of the reflection display is 25. It was good because it showed a high contrast as compared with the conventional liquid crystal display device.

Furthermore, in the evaluation of the graininess from the diagonal direction on the gray scale of the halftone (gradation level 2 at the time of dividing into 8 gradations), no graininess was felt at all.

In addition, the halftone response time in the liquid crystal display device when a pair of electrode openings are provided on the upper and lower substrates (time required for the change from gradation level 3 to gradation level 5 when 8 gradations are divided; msec. ) Is 35 msec, and it was confirmed that the response time was greatly improved by adopting the liquid crystal panel configuration of the present invention. Furthermore, when the panel surface was pressed with a fingertip when a voltage of 4 V was applied (displayed in white), almost no afterimage was observed at the pressing portion.

When the liquid crystal panel of the present invention is driven by the conventional 1H line inversion drive method in which the voltage applied to the adjacent pixels has the same polarity, and the gap between the adjacent pixel electrodes is 3 μm, FIG. 7 (b). However, as shown in the above, it was confirmed that the orientation of the liquid crystal molecules could not be sufficiently controlled and the dispersion occurred in the liquid crystal region. In this case, the display contrast and the response speed were not sufficient, and the display quality was significantly deteriorated.

As described above, the liquid crystal display device according to the present invention can realize a liquid crystal display device having excellent display quality with a relatively simple configuration. The present invention is suitably applied to a transmissive liquid crystal display device and a transflective (transmissive / reflective) liquid crystal display device. In particular, the transflective liquid crystal display device is suitably used as a display device for mobile devices such as mobile phones.

<figref num="1">It is a figure which shows typically the structure of one pixel of the transmissive liquid crystal display device 100 of embodiment by this invention, (a) is a plan view, (b) is 1B- in FIG. 1 (a). It is a cross-sectional view along the line 1B', and (c) is a cross-sectional view schematically showing the configuration of one pixel of another transmissive liquid crystal display device 100'of the embodiment according to the present invention.</figref><figref num="2">It is a figure which shows typically the structure of one pixel of the transflective liquid crystal display device 200 of embodiment by this invention, (a) is a plan view, (b) is 2B in FIG. 1 (a). It is a cross-sectional view along the -2B'line.</figref><figref num="3">It is a top view of the active matrix substrate 210a of a transflective liquid crystal display device 200.</figref><figref num="4">It is sectional drawing of the active matrix substrate 210a of a transflective liquid crystal display device 200.</figref><figref num="5">It is a figure which shows typically the drive circuit and the pixel arrangement of the liquid crystal display device 300 of embodiment by this invention.</figref><figref num="6">It is a figure which shows an example of the polarity pattern of the voltage applied to the pixel in a certain frame period of a liquid crystal display device 300.</figref><figref num="7">It is a figure which shows typically the behavior of equipotential lines when a voltage is applied to a liquid crystal layer, and the simulation result of a liquid crystal alignment director. (c) is the case of the conventional driving method.</figref><figref num="8">It is the schematic explaining the operation principle of the liquid crystal display device of embodiment according to this invention, (a) shows when voltage is not applied, and (b) when voltage is applied, respectively.</figref><figref num="9">It is a schematic diagram which shows an example of the structure of the liquid crystal display device of embodiment according to this invention.</figref><figref num="10">It is a graph which shows the thickness dependence of the voltage-reflectance (transmittance) of a transmission region and a reflection region in the liquid crystal display device of embodiment according to this invention.</figref><figref num="11">It is a figure which shows the visual angle-contrast ratio characteristic of the liquid crystal display device of embodiment according to this invention.</figref>

Code description

1 TFT (active matrix) substrate 2 Gate signal line 3 Source signal line 4 TFT 5 Drain electrode 6 Pixel electrode 7 Transparent electrode 8 Reflective electrode 9 Gate insulating film 10 Gate electrode 11 Source / drain electrode (n + -Si layer) 12 Semiconductor layer 13 Channel protection layer 14 Aperture structure 15 Aperture 16 Insulation film 17 Transparent substrate (opposite (CF) substrate) 18 Color filter layer 19 Opposite electrode 20 Liquid crystal layer 21 Liquid crystal molecules 22, 32 Alignment film 50 Liquid crystal panel 40, 43 Plate plate 41 , 44 1/4 wavelength version 42, 45 Thin film transistor (NR plate) with negative optical anisotropy 100, 100'Transmissive liquid crystal display 110a Active Matrix Board 110b Opposed Board (Color Filter Board) 111 Pixel Electrode 113 Notch 114 Opening 115 Wall Structure 130 Color Filter Layer 131 Facing Electrode 133 Support 200 Semi-Transmissive Liquid Crystal Display 210a Active Matrix Board 210b Facing Board ( Color filter substrate) 211 Pixel electrode 213 Notch 214 Opening 215 Wall structure 230 Color filter layer 231 Opposite electrode 232 Transparent dielectric layer (reflective part step) 233 Support 300 Liquid crystal display 301 Data signal line (source signal line) ) 302 Scan signal line (gate signal line) 303 Source signal line drive circuit 304 Gate signal line drive circuit 305 Switching element 306 Pixel electrode