Liquid crystal display device and its manufacturing method

[0001] The present invention relates to a liquid crystal display device having a reflective electrode and a method for manufacturing the same, and the present invention can be used as a reflective liquid crystal display device particularly in a bright surrounding environment and a backlight in a dark surrounding environment. The present invention relates to a liquid crystal display device applicable to a reflective / transmissive liquid crystal display device that can be turned on and used as a transmissive liquid crystal display device, and a method for manufacturing the same.

[0002] A liquid crystal display device has advantages that it is thinner and lighter than a CRT (Cathode Ray Tube), can be driven at a low voltage, and consumes less power, and has advantages such as a television and a notebook PC (personal). It is used in various electronic devices such as computers), desktop PCs, PDAs (Personal Digital Assistants) and mobile phones. In particular, an active matrix type liquid crystal display device provided with a TFT (Thin Film Transistor) as a switching element for each sub-pixel (hereinafter referred to as "pixel" in the present application) is comparable to a CRT due to its high driving ability. It shows excellent display characteristics, and has come to be widely used in fields where CRTs have been used in the past, such as desktop PCs and televisions.

[0003] Generally, a liquid crystal display device has a structure in which a liquid crystal is enclosed between two transparent substrates. A pixel electrode, a TFT, etc. are formed for each pixel on one of the two transparent substrates, and a color filter facing the pixel electrode and a common electrode common to each pixel are formed on the other substrate. Is formed. Hereinafter, the substrate on which the pixel electrodes and the TFT are formed is referred to as a TFT substrate, and the substrate arranged so as to face the TFT substrate is referred to as a facing substrate. In the color liquid crystal display device, one pixel (Pixel) is composed of three pixels (subpixels) of red (R), green (G), and blue (B).

[0004] The liquid crystal display device includes a transmissive liquid crystal display device that controls the amount of transmitted light for each pixel to display an image, and a reflective liquid crystal display that controls the amount of reflected light for each pixel to display an image. There is a device. A transmissive liquid crystal display device requires a dedicated light source called a backlight, whereas a reflective liquid crystal display device uses ambient light (natural light or electric lamp light) as a light source. It has the advantage of consuming even less power. Further, outdoors, the reflective liquid crystal display device may have better visibility than the transmissive liquid crystal display device. Hereinafter, the pixel electrode of the reflective liquid crystal display device is also referred to as a reflective electrode.

[0005] For example, Japanese Patent Application Laid-Open No. 8-338993 describes a reflective liquid crystal display device in which a TN (Twisted Nematic) type liquid crystal is used and the alignment film is subjected to a rubbing treatment to twist-orient the liquid crystal. Further, Japanese Patent Application Laid-Open No. 5-232465 describes a liquid crystal display device in which unevenness is provided on a reflective electrode by using a photolithography method. In this way, by providing the surface of the reflective electrode with irregularities, it is possible to avoid diffuse reflection of light and a large change in visibility depending on the position where the panel is viewed.

[0006] However, in the above method, the step of forming irregularities on the surface of the reflective electrode is complicated. Therefore, the applicant of the present application has proposed a method of forming a reflective electrode having irregularities on the surface using a positive photoresist (for example, JP-A-2002-221716 and JP-A-2002-296585). .. In this method, the photoresist is irradiated with ultraviolet rays or the like to cure only the surface layer, and then heat treatment is performed to form fine irregularities on the surface of the resist film. Then, by forming the reflective electrode on the resist film, the reflective electrode having irregularities on the surface can be easily formed.

[0007] By the way, since the reflective liquid crystal display device uses ambient light (natural light or electric lamp light) as a light source, the visibility greatly changes depending on the ambient state. That is, the visibility of the reflective liquid crystal display device is good when the surroundings are bright, but the visibility is significantly reduced when the surroundings are dark. In order to eliminate such a drawback, a reflective liquid crystal display device in which a light source (front light unit) is provided on the front surface of the panel has been proposed. However, in this type of reflective liquid crystal display device, since the light reflected by the reflecting electrode is transmitted through the front light unit, the reflected light is attenuated by the front light unit. Therefore, there is a drawback that the contrast is low and the visibility is not sufficient as compared with the reflective liquid crystal display device without the front light unit.

[0008] According to Japanese Patent Application Laid-Open No. 7-333598, by forming a reflective electrode with a metal thin film that semi-transmits light, it can be used as a reflective liquid crystal display device when the surroundings are bright, and the backlight is turned on when the surroundings are dark. A liquid crystal display device that can be used as a transmissive liquid crystal display device (hereinafter, referred to as a reflection / transmissive liquid crystal display device) has been proposed. However, in this type of reflective / transmissive liquid crystal display device, when used as a transmissive liquid crystal display device, the light absorption by the metal thin film is large, so that the light utilization efficiency is poor and a high-brightness backlight is not used. There is a drawback that good visibility cannot be obtained. In addition, an Al (aluminum) film with a thickness of about 30 nm is used as a metal thin film that semi-transmits light, but in the case of a large liquid crystal display device, an Al thin film with a uniform thickness should be formed over the entire surface of the panel. Is extremely difficult.

[0009] In Japanese Patent Application Laid-Open No. 11-281972, a transmissive region through which light is transmitted is provided by opening the central portion of the reflective electrode, and a transparent electrode such as ITO (Indium-Tin Oxide) is formed in the transmissive region. A transmissive liquid crystal display device has been proposed.

[0010] FIG. 18 is a schematic view showing an example of a TFT substrate of this type of conventional reflective / transmissive liquid crystal display device.

[0011] The TFT substrate is formed with a plurality of gate bus lines 71 arranged parallel to each other and a plurality of data bus lines 72 orthogonal to the gate bus line 71. A TFT 73 is formed near the intersection of the gate bus line 71 and the data bus line 72. Further, a reflective electrode 74 made of a metal film that reflects light such as Al (aluminum) is formed in a rectangular region partitioned by the gate bus line 71 and the data bus line 72. An opening 74a for transmitting light is provided in the central portion of the reflective electrode 74, and a transparent electrode 75 made of a transparent conductor such as ITO (Indium-Tin Oxide) is formed in the opening 74a. ing.

[0012] The gate bus line 71, the data bus line 72 and the TFT 73 are covered with an insulating flattening film, the reflective electrode 74 is formed on the flattening film, and the transparent electrode 75 is under the flattening film. It is formed. When Al constituting the reflective electrode 74 and ITO constituting the transparent electrode 75 come into direct contact with each other, corrosion occurs due to the battery effect. Therefore, the reflective electrode 74 and the transparent electrode 75 are electrically connected via a barrier metal such as Ti (titanium).

[0013] In the liquid crystal display device configured as described above, when displaying an image, scanning signals are sequentially supplied to a plurality of gate bus lines 71, and display signals are supplied to each data bus line 72. Then, the TFT 73 connected to the gate bus line 71 to which the scanning signal is supplied is turned on, and the display signal is written to the reflective electrode 74 and the transparent electrode 75 via the TFT 73. As a result, the orientation of the liquid crystal molecules between the reflecting electrode 74 and the transparent electrode 75 and the facing substrate changes, and as a result, the amount of reflected light or transmitted light changes. By controlling the amount of reflected light or transmitted light for each pixel, a desired image is displayed on the liquid crystal display device.

[0014] According to this reflective / transmissive liquid crystal display device, relatively good visibility is ensured both when used as a reflective liquid crystal display device and when used as a transmissive liquid crystal display device. To.

[Patent Document 1] Japanese Patent Application Laid-Open No. 8-338993 [Patent Document 2] Japanese Patent Application Laid-Open No. 5-232465 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-221716 [Patent Document 4] Japanese Patent Application Laid-Open No. 2002-296585 Japanese Patent Application Laid-Open No. 7-333598 [Patent Document 6] Japanese Patent Application Laid-Open No. 11-281972 [0016] [Problems to be Solved by the Invention] However, it is described in Japanese Patent Application Laid-Open No. 11-281972. In a reflective / transmissive liquid crystal display device, it is necessary to form a transparent electrode made of ITO and a barrier metal in addition to the reflective electrode made of Al. Therefore, the number of processes is large, which causes an increase in product cost.

[0017] Further, in the reflection / transmission type liquid crystal display device described in Japanese Patent Application Laid-Open No. 11-281972, if the transmission region is enlarged, the reflection region is reduced, and the reflection characteristic and the transmission characteristic are traded off. There is a relationship. Since the area of one pixel is small in a high-resolution liquid crystal display device, it is difficult to obtain a liquid crystal display device having good reflection characteristics and transmission characteristics.

[0018] From the above, the object of the present invention is<u style="single">Reflective / transmissive type that can be manufactured more easily than before and has good reflection and transmission characteristics.</u>The present invention provides a liquid crystal display device and a method for manufacturing the same.

[Means for Solving the Problems] The above-mentioned problem is a gate in which a scanning signal is supplied to one of the pair of substrates in a liquid crystal display device configured by enclosing a liquid crystal between the pair of substrates. The bus line, the data bus line to which the display signal is supplied, and the thin film transistor in which the gate electrode is electrically connected to the gate bus line and the drain electrode is electrically connected to the data bus line are divided for each pixel. A resin film having wrinkle-like irregularities on its surface, and a reflective electrode formed on the resin film and having irregularities that imitate the irregularities of the resin film and electrically connected to the source electrode of the thin film transistor. Equipped with<u style="single">The intersection of the gate bus line and the data bus line and the thin film transistor are arranged below the reflection electrode, and the region between the adjacent reflection electrodes is a light transmission region.</u>This is solved by a liquid crystal display device characterized by the above.

[0021] In the present invention, the resin film on which wrinkle-like irregularities are formed is divided for each pixel. As described in JP-A-2002-221716, when the surface of the resin film is cured and then heat-treated, fine wrinkle-like irregularities can be formed on the surface. According to the experiments by the inventors of the present application, when the size of the resist film is large, the wrinkle-like uneven pattern formed on the surface of the resist film is not constant, but when the size of the resist film is reduced, the size of the resist film is increased. It has been confirmed that a certain uneven pattern is formed according to the situation.

[0022] In order to obtain such an effect, it is preferable that the pixels have a size corresponding to 110 to 850 ppi. When the pixel size is large, the same effect can be obtained by providing slits in the resist film and the reflective electrode and dividing the resist film and the reflective electrode for one pixel into a plurality of regions. As a result, for example, if the size of the resist film and the reflecting electrode is determined so that the light incident on the liquid crystal panel from above is reflected in the normal direction of the panel surface to form an uneven pattern, the light utilization efficiency is improved. Visibility is improved.

[0023] In order to obtain good reflection characteristics, it is preferable that the flattening region where the average inclination angle of the surface of the reflection electrode is 5 ° or less is 50% or more. Further, when the resist film is divided into a plurality of regions by slits, the length of the short side of the divided regions must be 5 μm or more in order to form irregularities on the surface of the resist film in a uniform pattern. preferable.

[0024] Further, when the resist film and the reflective electrode are formed so as to overlap the gate bus line, the data bus line, and the thin film transistor, the region between the adjacent reflective electrodes can be made into a light transmitting region through which light is transmitted, and is reflected. / A transmissive liquid crystal display device can be realized. In this case, the liquid crystal molecules in the light transmitting region are driven by the electric field leaking laterally from the reflecting electrode.

[0025] The problem described above is that in a liquid crystal display device configured by enclosing a liquid crystal between a pair of substrates, a gate bus line to which a scanning signal is supplied and a display signal are supplied to one of the pair of substrates. The data bus line and the thin film transistor whose gate electrode is electrically connected to the gate bus line and whose drain electrode is electrically connected to the data bus line are divided into pixels, and the gate bus line, the said. It includes a resin film arranged above the data bus line and the thin film transistor, and a reflective electrode formed on the resin film and electrically connected to the source electrode of the thin film transistor.<u style="single">The intersection of the gate bus line and the data bus line and the thin film transistor are arranged below the reflection electrode, and the region between the adjacent reflection electrodes is a light transmission region.</u>This is solved by a liquid crystal display device characterized by the above.

[0026] In the present invention, a resin film and a reflective electrode divided for each pixel are formed so as to overlap the gate bus line, the data bus line, and the thin film transistor. In this case, the region between the adjacent reflecting electrodes is a light transmitting region through which light is transmitted. Therefore, as compared with the method of forming an opening in the reflecting electrode to form a light transmitting region, the area of the light transmitting region can be increased even if the area of the reflecting electrode is the same.

[0027] The above-mentioned problem is that a gate bus line to which a scanning signal is supplied, a data bus line to which a display signal is supplied, and a drain electrode are connected to the gate bus line on the first substrate. A step of forming a thin film transistor connected to the data bus line, a step of forming a photoresist film above the gate bus line, the data bus line and the thin film transistor, and a step of dividing the photoresist film into each pixel. The exposure / development step of forming an opening at a position corresponding to the source electrode of the thin film transistor and the photoresist film.<u style="single">Change the internal stress in the thickness direction of</u>A step, a step of heat-treating the photoresist film to form wrinkle-like irregularities on the surface, and a reflective electrode electrically connected to the source electrode of the thin film transistor on the photoresist film via the opening. A step of forming a reflective electrode and a step of arranging a second substrate provided with an electrode made of a transparent conductor film and the first substrate so as to face each other and encapsulating a liquid crystal between them are provided.<u style="single">Then, the intersection of the gate bus line and the data bus line and the thin film transistor are arranged below the reflection electrode, and the region between the adjacent reflection electrodes is used as a light transmission region.</u>This is solved by a method of manufacturing a liquid crystal display device, which is characterized in that.

[0028] In the present invention, the photoresist film is divided into pixels and then heat-treated to form irregularities on the surface. In this case, it has been confirmed by experiments by the inventors of the present application that a constant uneven pattern can be formed according to the size of the photoresist film. Therefore, in consideration of the state when the liquid crystal display device is actually used, the size of the resist film is determined so that the light incident on the liquid crystal panel from above is reflected in the normal direction of the panel surface to form an uneven pattern. For example, the efficiency of light utilization is improved and the visibility is improved.

[0029] The above-mentioned problem is that a gate bus line to which a scanning signal is supplied, a data bus line to which a display signal is supplied, and a drain electrode are connected to the gate bus line on the first substrate. A step of forming a thin film transistor connected to the data bus line, a step of forming a photoresist film above the gate bus line, the data bus line and the thin film transistor, and a step of forming the photoresist film on the gate bus line.<u style="single">When</u>The data bus line<u style="single">Intersection with</u>An exposure / development step of dividing each region into a reflective electrode forming region overlapping the thin film transistor and forming an opening at a position corresponding to the source electrode of the thin film transistor, and on the photoresist film via the opening. A reflective electrode forming step of forming a reflective electrode electrically connected to the source electrode of the thin film transistor, and a second substrate provided with an electrode made of a transparent conductor film and the first substrate are arranged so as to face each other. This is solved by a method for manufacturing a liquid crystal display device, which comprises a step of encapsulating a liquid crystal between the two.

[0030] In the present invention, the resist film and the reflective electrode are divided into pixels so as to overlap the gate bus line, the data bus line, and the thin film transistor. In this case, the region between the adjacent reflecting electrodes is a light transmitting region through which light is transmitted, and compared to the method of forming an opening in the reflecting electrode to form a light transmitting region, light is emitted even if the area of the reflecting electrode is the same. The area of the transmission region can be increased.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(First Embodiment) FIG. 1 is a plan view showing a liquid crystal display device according to the first embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view at the position of line II in FIG. The present embodiment shows an example in which the present invention is applied to a reflection / transmission type liquid crystal display device using a VA (vertical orientation) type liquid crystal.

[0033] As shown in FIG. 2, the liquid crystal display device of the present embodiment is enclosed between the TFT substrates 10 and the opposed substrates 30 arranged so as to face each other and the TFT substrates 10 and the opposed substrates 30. It is composed of a vertically oriented nematic liquid crystal 40. Polarizing plates (linearly polarizing plates or circular polarizing plates combining linearly polarized light + λ / 4 phase difference) 38 and 39 are arranged below the TFT substrate 10 and above the opposing substrate 30, respectively. Further, a light source (backlight: not shown) is arranged below the TFT substrate 10.

As shown in FIGS. 1 and 2, the TFT substrate 10 includes a glass substrate 11, a gate bus line 12a formed on the glass substrate 11, a storage capacity bus line 12b, a data bus line 17a, and a storage capacity electrode. It is composed of 17b, TFT7, reflective electrode 20a, etc. The gate bus line 12a and the storage capacity bus line 12b extend horizontally, and the data bus line 17a extends vertically. The gate bus line 12a and the storage capacity bus line 12b are covered with a gate insulating film 13, and are electrically separated from the data bus line 17a by the gate insulating film 13.

[0035] TFT 7 is formed in the vicinity of the intersection of the gate bus line 12a and the data bus line 17a. In this TFT 7, a silicon film (amorphous silicon film or polysilicon film) 14 formed on the gate insulating film 13 is used as an operating layer, and a part of the gate bus line 12a is used as a gate electrode. A channel protection film 15a made of SiN is formed on the channel region of TFT7. A drain electrode 17d and a source electrode 17s are formed on both sides of the channel protection film 15a, respectively. These drain electrodes 17d and source electrodes 17s are n that are ohmic contact layers.⁺It is electrically connected to the silicon film 14 via the type amorphous silicon film 16. Further, the drain electrode 17d is electrically connected to the data bus line 17a, and the source electrode 17s is electrically connected to the reflection electrode 20a.

[0036] Further, a storage capacity electrode 17b is formed above the storage capacity bus line 12b via a gate insulating film 13.

[0037] The TFT 7 and the storage capacitance electrode 17b are covered with a final protective film (not shown) made of SiN or the like, and a resist film 19 having fine irregularities on the surface is formed on the final protective film (not shown). A reflective electrode 20a made of Al or the like is formed on the resist film 19. The reflective electrode 20a is electrically connected to the source electrode 17s of the TFT 7 and the storage capacitance electrode 17b via the contact holes 18a and 18b formed in the final protective film and the resist film 19. Further, the surface of the reflective electrode 20a is provided with irregularities following the resist film 19.

[0038] In the present embodiment, the resist film 19 is formed only below the reflective electrode 20a. Further, the resolution of the liquid crystal display device of the present embodiment is 110 to 850 ppi, and the reflective electrode 20a is set to a size corresponding to the resolution. Further, in the present embodiment, as shown in FIG. 1, the reflection electrode 20a is formed so as to overlap the gate bus line 12a, the storage capacity bus line 12b, the data bus line 17a, and the TFT7, and the reflection electrodes are adjacent to each other. The area between 20a and 20a is a transmission region through which light is transmitted.

[0039] An alignment film 21 made of polyimide or the like is formed on the reflective electrode 20a. Normally, the surface of the alignment film 21 is not subjected to a rubbing treatment for determining the orientation direction of the liquid crystal molecules when an electric field is not applied, but a rubbing treatment may be performed.

[0040] On the other hand, the facing substrate 30 is composed of a glass substrate 31 and a color filter 32 and a common electrode 33 formed on one surface side (lower side in FIG. 2) of the glass substrate 31. There are three types of color filters 32, red (R), green (G), and blue (B), and one color filter 32 is arranged in one pixel.

A common electrode 33 is formed under the color filter 32, and an alignment film 34 made of polyimide or the like is formed under the common electrode 33. The surface of the alignment film 34 is subjected to a rubbing treatment that determines the orientation direction of the liquid crystal molecules when no electric field is applied.

[0042] The TFT substrate 10 and the opposing substrate 30 are arranged with a spacer (not shown) for maintaining a constant distance between them, and a sealant (not shown) applied to the outside of the display area. It is joined by.

[0043] In the liquid crystal display device of the present embodiment, the positions of the gate bus line 12a and the data bus line 17a are different from those of the conventional reflection / transmission type liquid crystal display device, and the conventional liquid crystal display device has reflection characteristics and transmission characteristics. A region that does not contribute to any of the above, that is, a region between adjacent reflective electrodes is used as a transmission region in the present embodiment. The liquid crystal molecules in this region are driven by an electric field leaking laterally from the reflective electrode 20a.

[0044] Further, in the present embodiment, the resist film 19 is divided for each pixel. As will be described later, the surface of the resist film 19 is provided with wrinkle-like irregularities formed by curing only the surface layer of the resist film 19 and then performing heat treatment. According to experiments by the inventors of the present application, the pattern of wrinkle-like irregularities formed on the surface of the resist film is not constant when the size of the resist film is large, but when the size of the resist film is small, the size of the resist film is adjusted. It has been confirmed that a certain uneven pattern is formed according to the above. Therefore, in consideration of the state when the liquid crystal display device is actually used, the size of the resist film is determined so that the light incident on the liquid crystal panel from above is reflected in the normal direction of the panel surface to form an uneven pattern. For example, the efficiency of light utilization is improved and the visibility is improved.

[0045] Although it is not clear why the uneven pattern becomes uniform when the size of the resist film is reduced, it can be considered as follows. That is, when the size of the resist film is large, the position where the unevenness is generated by the heat treatment is indefinite, and the unevenness may be generated independently at a plurality of positions, so that the pattern of the unevenness is not constant. However, when the size of the resist film is small, the position where the stress is concentrated is periodically generated according to the size of the resist film, so that the uneven pattern becomes constant according to the size of the resist film. In order to obtain such an effect, it is necessary that the size of the pixel electrode 20a is set to a size corresponding to a resolution of 110 to 850 ppi.

[0046] The uneven pattern formed on the resist film is also related to the film thickness of the resist film. Further, in order to efficiently reflect the light incident from the upper side of the liquid crystal display device in the normal direction of the panel, the flattening region (the region where the average inclination angle is 5 ° or less) of the reflecting electrode surface must be 50% or more. It is preferable to do so.

Hereinafter, a method for manufacturing the liquid crystal display device according to the present embodiment will be described.

[0048] FIGS. 3 to 9 are schematic cross-sectional views showing the manufacturing method of the TFT substrate of the liquid crystal display device of the present embodiment in the order of processes. First, as shown in FIG. 3A, a metal film 12 is formed on the glass substrate 11 by a sputtering method, and a resist film 41 having a predetermined pattern is formed on the metal film 12 by using a photoresist.

Next, as shown in FIG. 3B, the metal film 12 is etched using the resist film 41 as a mask to form the gate bus line 12a and the storage capacity bus line 12b. Then, the resist film 41 is removed.

Next, as shown in FIG. 4A, an amorphous silicon film 14 is formed on the entire upper surface of the glass substrate 11 by the plasma CVD method, and further on the gate insulating film 13 as an operating layer of the TFT. And the SiN (silicon nitride) film 15 serving as the channel protection film is sequentially formed.

After that, a positive photoresist film is formed on the SiN film 15. Then, the photoresist film is exposed from the back surface side of the glass substrate 11, further exposed from the front surface side of the substrate 11 through a predetermined exposure mask, and then developed to form a channel protective film above the gate bus line 12a. A resist film 42 covering the region is formed.

Next, as shown in FIG. 4B, the SiN film 15 is etched using the resist film 42 as a mask to form the channel protection film 15a. Then, the resist film 42 is removed.

Next, as shown in FIG. 5A, an ohmic contact layer is formed on the entire upper surface of the glass substrate 11.⁺A type amorphous silicon film 16 is formed. After that, by the PVD (Physical Vapor Deposition) method, n⁺A metal film 17 serving as a data bus line, a source electrode, and a drain electrode is formed on the type amorphous silicon film 16. Then, using a photoresist, a resist film 45 having a predetermined pattern is formed on the metal film 17.

Next, as shown in FIG. 5 (b), the metal film 17, n, using the resist film 45 as a mask.⁺The type amorphous silicon film 16 and the silicon film 14 are etched to determine the shape of the silicon film 14 that is the operating layer of the TFT 7, and to form the data bus line 17a, the source electrode 17s, the drain electrode 17d, and the storage capacity electrode 17b. .. At this time, the portion of the silicon film 14 that becomes the channel of TFT 7 is protected by the channel protection film 15a. Then, the resist film 45 is removed.

Next, as shown in FIG. 6A, the final protective film 18 is formed on the entire upper surface of the glass substrate 11 by, for example, SiN. Then, a resist film 46 having a contact hole forming portion opened is formed on the final protective film 18.

Next, as shown in FIG. 6B, the final protective film 18 is etched using the resist film 46 as a mask to form contact holes 18a and 18b reaching the source electrode 17s and the storage capacitance electrode 17b, respectively. .. Then, the resist film 46 is removed.

Next, as shown in FIG. 7A, a positive photoresist film 19 is formed on the entire upper surface of the glass substrate 11 and exposed and developed to expose the contact holes 18a and 18b. Along with forming a portion, the resist film 19 is divided into each pixel. Then, after post-baking at a temperature of 130 to 145 ° C, the surface layer of the resist film 19 is further irradiated with ultraviolet rays (UV) to crosslink the polymer on the surface layer. Next, when heat-baked at a temperature of 200 ° C. or higher, the thermal deformation characteristics (coefficient of thermal expansion or thermal shrinkage) of the surface layer (crosslinked portion) and the deep portion (non-crosslinked portion) of the resist film 19 are different. Therefore, as shown in FIG. 7B, fine wrinkle-like irregularities are generated on the surface of the resist film 19. In this case, as described above, in the present embodiment, the resist film 19 is divided into small pixels for each pixel, so that the uneven pattern formed on the resist film 19 is made uniform.

[0058] In the present embodiment, only the surface layer of the resist film 19 is cured by UV irradiation, but the internal stress in the thickness direction of the resist film may be changed by heat, plasma, UV or ion beam irradiation.

Next, as shown in FIG. 8A, Al is sputtered on the entire upper surface of the glass substrate 11 to form the metal film 20. On the surface of the metal film 20 on the resist film 19, fine irregularities are formed following the resist film 19. Further, the metal film 20 is electrically connected to the source electrode 17s and the storage capacitance electrode 17b via the contact holes 18a and 18b. Then, a resist film 48 for determining the shape of the reflective electrode is formed on the metal film 20 in a predetermined pattern.

Next, as shown in FIG. 8B, the metal film 20 is etched using the resist film 48 as a mask to form a reflective electrode 20a for each pixel. Then, the resist film 48 is removed as shown in FIG. Then, an alignment film (not shown) made of polyimide or the like is formed on the entire upper surface of the glass substrate 11. In this way, the reflective electrode 20a having fine irregularities on the surface is formed.

[0061] Hereinafter, a method for manufacturing the opposed substrate 30 will be described. First, a color filter 32 is formed on one surface of the glass substrate 31 (lower surface in FIG. 2) by using a red photosensitive resin, a green photosensitive resin, and a blue photosensitive resin.

Next, ITO is sputtered onto the color filters 32 to form a transparent common electrode 33. Then, an alignment film 34 made of polyimide is formed on the common electrode 33. In this way, the opposed substrate 30 is completed.

[0063] Next, a spacer (not shown) for maintaining a constant distance between the TFT substrate 10 and the opposing substrate 30 is arranged, and the TFT substrate 10 and the opposing substrate are subjected to a vacuum injection method or a dropping injection method. The liquid crystal 40 is enclosed between the 30 and the liquid crystal 40. In this way, the reflective / transmissive liquid crystal display device as shown in FIGS. 1 and 2 is completed.

[0064] In FIG. 10, the horizontal axis represents the resolution (ppi), the vertical axis represents the transmission aperture ratio (left axis) and the effective reflection area ratio (right axis), and the conventional reflection / transmission type shown in FIG. It is a figure which shows the relationship between the resolution of the liquid crystal display device and the reflection / transmission type liquid crystal display device of this embodiment, a transmission aperture ratio and an effective reflection area ratio. However, in the conventional liquid crystal display device, the transmission aperture ratio is constant at 14% regardless of the resolution. The pixel spacing is 8 μm, the width of the data bus line is 5 μm, the width of the storage capacity bus line is 12 μm, and the width of the gate bus line is 10 μm.

As can be seen from FIG. 10, in the liquid crystal display device of the conventional example, the effective reflection area ratio is about 74% when the resolution is 125 ppi, and the effective reflection area ratio decreases as the resolution becomes higher. On the other hand, in the liquid crystal display device of the present embodiment, the transmission aperture ratio is about 14% and the effective reflection area ratio is about 85% when the resolution is 125 ppi, and the effective reflection area ratio is larger than that of the conventional example. Understand. Further, in the present embodiment, when the resolution is about 180 ppi, the transmitted aperture ratio is about 18% and the effective reflection area ratio is about 78%. A resolution of 180 ppi or higher is required to recognize small characters described in catalogs and the like. That is, from FIG. 10, it can be seen that the liquid crystal display device of the present embodiment has good reflection characteristics and transmission characteristics even at a high resolution of about 180 ppi, and has excellent visibility.

FIG. 11 shows a microscope image when the liquid crystal display device according to the present embodiment is manufactured and the reflection state and the transmission state are examined when the applied voltage is 0V and 2.3V. However, the resolution of this liquid crystal display device is equivalent to 180 ppi. Further, the cell gap is 3 μm, and after the vertical alignment films of the TFT substrate and the opposing substrate are rubbed, an n-type nematic liquid crystal is enclosed between these substrates. The design values of the photomask used in the manufacture of this liquid crystal display device are also shown in FIG. In addition, FIG. 12 shows an AFM (Atomic Force Microscope) image of the reflective electrode of this liquid crystal display device. From FIG. 11, it can be seen that good characteristics can be obtained regardless of whether the device is used as a reflective liquid crystal display device or a transmissive liquid crystal display device.

(Second Embodiment) FIG. 13 (a) is a plan view showing a reflection / transmission type liquid crystal display device according to a second embodiment of the present invention. The difference between the present embodiment and the first embodiment is that the reflective electrode is provided with a slit, and the other configurations are basically the same as those of the first embodiment. The description of the overlapping part is omitted.

[0068] In the present embodiment, as shown in FIG. 13A, the reflective electrode 51 and the resist film below the reflective electrode 51 are provided with a plurality of slits 52 parallel to the gate bus line 12a. That is, these slits 52 divide the resist film into a plurality of regions within one pixel.

[0069] As described above, the pattern of irregularities formed on the resist film is determined by the size of the resist film. By providing the slit 52 in the reflective electrode 51 and the resist film under the reflective electrode 51 as in the present embodiment, a desired uneven pattern is formed on the reflective electrode 51 even when the size of the reflective electrode 51 is large. can do. Further, the portion of the slit 52 becomes a transmission region, and the transmission aperture ratio becomes high. Slits 53 and 54 having a shape as shown in FIGS. 13 (b) and 13 (c) may be formed according to a desired uneven pattern. In order to surely form unevenness of a certain pattern on the resist film, it is preferable that the short sides of the regions divided by the slits 52, 52, 54 are all 5 μm.

[0070] In FIG. 14, the horizontal axis represents the resolution (ppi), the vertical axis represents the transmission aperture ratio (left axis) and the effective reflection area ratio (right axis), and the conventional reflection / transmission type shown in FIG. It is a figure which shows the relationship between the resolution of the liquid crystal display device and the reflection / transmission type liquid crystal display device of this embodiment, a transmission aperture ratio and an effective reflection area ratio. However, in the conventional liquid crystal display device, the transmission aperture ratio is constant at 14% regardless of the resolution. The pixel spacing is 8 μm, the width of the data bus line is 5 μm, the width of the storage capacity bus line is 12 μm, and the width of the gate bus line is 10 μm.

As can be seen from FIG. 14, in the present embodiment, even in a reflective liquid crystal display device of 125 ppi or less, unevenness can be formed in a desired pattern, so that the light utilization efficiency is higher than in the conventional case. A highly reflective / transmissive liquid crystal display device is realized.

FIG. 15 shows a microscope image when the liquid crystal display device according to the present embodiment is manufactured and the display state when the applied voltage is 0 V and 2.3 V is examined. The design values of the photomask used in the manufacture of this liquid crystal display device are also shown in FIG. From FIG. 15, it can be seen that a uniform uneven pattern is formed in each pixel.

(Third Embodiment) FIG. 16 (a) is a plan view showing a reflection / transmission type liquid crystal display device according to a third embodiment of the present invention. The difference between the present embodiment and the first embodiment is that the reflective electrode is not provided with irregularities and that the reflective electrode is provided with a slit, and the other configurations are basically provided. Since it is the same as that of the first embodiment, the description of the overlapping portion will be omitted.

[0074] In the present embodiment, as shown in FIG. 16A, a slit 62 is provided in the reflective electrode 61, and the portion of the slit 62 is used as a transmission region. Slits 63 and 64 having a shape as shown in FIGS. 16 (b) and 16 (c) may be provided. However, it is preferable that the shape of the slit is common to each pixel. Further, it is preferable that the short sides of the regions divided by the slits are all 5 μm or more.

[0075] In the present embodiment, the reflection electrode 61 is formed so as to overlap the gate bus line 12a, the data bus line 17a, and the TFT 7, and the region between the reflection electrode 61 and the adjacent reflection electrode 61 is a light transmission region. It has become. Further, the reflective electrode 61 is provided with a slit 61 to form a light transmitting region. Therefore, the liquid crystal display device of the present embodiment has a higher transmission aperture ratio than the conventional one, and both the reflection characteristics and the transmission characteristics are improved.

[0076] FIG. 17 shows a microscope image when the liquid crystal display device according to the present embodiment is manufactured and the display state when the applied voltage is 0 V and 2.3 V is examined. The design values of the photomask used in the manufacture of this liquid crystal display device are also shown in FIG. From FIG. 17, it can be seen that the present embodiment can realize a reflective liquid crystal display device having a high light utilization rate and good visibility even when the resolution is 125 ppi or less.

[0077] In each of the above embodiments, the case where the present invention is applied to the vertically oriented (VA) type liquid crystal display device has been described, but the scope of application of the present invention is limited to the vertically oriented liquid crystal display device. It's not something. The present invention can also be applied to a horizontally oriented liquid crystal display device, a hybrid oriented liquid crystal display device, and the like.

(Appendix 1) In a liquid crystal display device configured by enclosing a liquid crystal between a pair of substrates, a gate bus line to which a scanning signal is supplied and a display signal are supplied to one of the pair of substrates. The data bus line and the thin film transistor in which the gate electrode is electrically connected to the gate bus line and the drain electrode is electrically connected to the data bus line, and the thin film transistor is divided into pixels and has wrinkled irregularities on the surface. A liquid crystal display characterized by comprising a resin film, irregularities formed on the resin film and imitating the irregularities of the resin film, and a reflective electrode electrically connected to the source electrode of the thin film transistor. apparatus.

(Appendix 2) The liquid crystal display device according to Appendix 1, wherein the resin film is formed of a positive photoresist.

[0080] (Appendix 3) The liquid crystal display device according to Appendix 1, wherein the reflective electrode and the resin film are divided into a plurality of regions by slits.

(Appendix 4) The gate bus line, the data bus line, and the thin film transistor are arranged below the reflection electrode, and a region between adjacent reflection electrodes is a light transmission region. The liquid crystal display device according to 1.

(Appendix 5) In a liquid crystal display device configured by enclosing a liquid crystal between a pair of substrates, a gate bus line to which a scanning signal is supplied and a display signal are supplied to one of the pair of substrates. The data bus line and the thin film transistor whose gate electrode is electrically connected to the gate bus line and whose drain electrode is electrically connected to the data bus line are divided into pixels, and the gate bus line and the data A liquid crystal characterized by comprising a resin film arranged above the bus line and the thin film transistor, and a reflective electrode formed on the resin film and electrically connected to the source electrode of the thin film transistor. Display device.

[Appendix 6] The liquid crystal display device according to Appendix 5, wherein the region between adjacent reflective electrodes is a light transmission region.

(Appendix 7) The liquid crystal display device according to Appendix 5, wherein the resin film is formed of a positive photoresist.

(Appendix 8) On the first substrate, a gate bus line to which a scanning signal is supplied, a data bus line to which a display signal is supplied, a gate electrode is connected to the gate bus line, and a drain electrode is described. The step of forming the thin film transistor connected to the data bus line, the step of forming the photoresist film above the gate bus line, the data bus line and the thin film transistor, and the step of forming the photoresist film for each pixel are divided. At the same time, an exposure / development step of forming an opening at a position corresponding to the source electrode of the thin film transistor, a step of changing the internal stress in the thickness direction of the photoresist film, and a heat treatment of the photoresist film on the surface. A step of forming wrinkle-like irregularities, a step of forming a reflective electrode on the photoresist film, and a step of forming a reflective electrode electrically connected to the source electrode of the thin film transistor via the opening, and a transparent conductor film. A method for manufacturing a liquid crystal display device, which comprises a step of arranging a second substrate provided with an electrode made of the above and the first substrate facing each other and encapsulating a liquid crystal between them.

(Supplementary note 9) The method for manufacturing a liquid crystal display device according to Supplementary note 8, wherein the reflective electrode is formed at a position overlapping the gate bus line, the data bus line, and the thin film transistor.

(Appendix 10) In the exposure / development step, a slit for further dividing the resist film for one pixel into a plurality of regions is formed, and in the reflection electrode forming step, a portion corresponding to the slit is opened. The method for manufacturing a liquid crystal display device according to Appendix 8, which comprises a light transmitting region.

(Appendix 11) On the first substrate, a gate bus line to which a scanning signal is supplied, a data bus line to which a display signal is supplied, a gate electrode is connected to the gate bus line, and a drain electrode is described. The step of forming the thin film transistor connected to the data bus line, the step of forming the photoresist film above the gate bus line, the data bus line and the thin film transistor, and the step of forming the photoresist film on the gate bus line, An exposure / development step of dividing each of the data bus line and the reflection electrode forming region overlapping the thin film transistor and forming an opening at a position corresponding to the source electrode of the thin film transistor, and the opening on the photoresist film. A reflective electrode forming step of forming a reflective electrode electrically connected to the source electrode of the thin film transistor via a portion, and a second substrate provided with an electrode made of a transparent conductor film and the first substrate facing each other. A method for manufacturing a liquid crystal display device, which comprises a step of arranging them so as to be arranged and enclosing a liquid crystal between them.

[Additional Note 12] The liquid crystal display device according to Appendix 11, wherein a region between adjacent reflective electrodes is a light transmission region.

[Effect of the Invention] As described above, according to the present invention, since the resin film is divided for each pixel, the unevenness of the surface of the resin film has a constant pattern according to the size of the resin film. It becomes. As a result, the efficiency of light utilization is improved, and it is possible to manufacture a reflective liquid crystal display device having excellent reflection characteristics as compared with the conventional one.

[0091] Further, when the resin film and the reflective electrode are formed so as to overlap the gate bus line, the data bus line, and the thin film transistor, the region between the adjacent reflective electrodes can be used as the light transmission region. This makes it possible to apply it to a reflection / transmission type liquid crystal display device, and improves both reflection characteristics and transmission characteristics as compared with a conventional reflection / transmission type liquid crystal display device in which an opening is provided in a reflection electrode. be able to.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view at the position of line II in FIG.

FIG. 3 is a schematic cross-sectional view (No. 1) showing a method of manufacturing a TFT substrate of the liquid crystal display device according to the first embodiment of the present invention in process order.

FIG. 4 is a schematic cross-sectional view (No. 2) showing a method of manufacturing a TFT substrate of the liquid crystal display device according to the first embodiment of the present invention in process order.

FIG. 5 is a schematic cross-sectional view (No. 3) showing a method of manufacturing a TFT substrate of the liquid crystal display device according to the first embodiment of the present invention in process order.

FIG. 6 is a schematic cross-sectional view (No. 4) showing a method of manufacturing a TFT substrate of the liquid crystal display device according to the first embodiment of the present invention in process order.

FIG. 7 is a schematic cross-sectional view (No. 5) showing a method of manufacturing a TFT substrate of the liquid crystal display device according to the first embodiment of the present invention in process order.

FIG. 8 is a schematic cross-sectional view (No. 6) showing a method of manufacturing a TFT substrate of the liquid crystal display device according to the first embodiment of the present invention in process order.

FIG. 9 is a schematic cross-sectional view (No. 7) showing a method of manufacturing a TFT substrate of the liquid crystal display device according to the first embodiment of the present invention in process order.

FIG. 10 is a diagram showing the relationship between the resolution, the transmission aperture ratio, and the effective reflection area ratio of the conventional reflection / transmission type liquid crystal display device and the reflection / transmission type liquid crystal display device of the first embodiment. is there.

FIG. 11 is a diagram showing a microscope image when the liquid crystal display device according to the first embodiment is manufactured and the reflection state and the transmission state are examined when the applied voltage is 0V and 2.3V. ..

FIG. 12 is a diagram showing an AFM image of a reflective electrode of a liquid crystal display device according to the first embodiment.

13 (a) to 13 (c) are plan views showing a reflective / transmissive liquid crystal display device according to a second embodiment of the present invention.

FIG. 14 is a diagram showing the relationship between the resolution, the transmission aperture ratio, and the effective reflection area ratio of the conventional reflection / transmission type liquid crystal display device and the reflection / transmission type liquid crystal display device of the second embodiment. is there.

FIG. 15 is a diagram showing a microscope image when the liquid crystal display device according to the second embodiment is manufactured and the display state when the applied voltage is 0 V and 2.3 V is examined.

16 (a) to 16 (c) are plan views showing a reflective / transmissive liquid crystal display device according to a third embodiment of the present invention.

FIG. 17 is a diagram showing a microscope image when the liquid crystal display device according to the third embodiment is manufactured and the display state when the applied voltage is 0 V and 2.3 V is examined.

FIG. 18 is a schematic view showing an example of a TFT substrate of a conventional reflective / transmissive liquid crystal display device.

[Explanation of symbols] 7,73 ... TFT, 10 ... TFT substrate, 11,31 ... glass substrate, 12,17 ... metal film, 12a, 71 ... gate bus line, 12b. .. Storage Capacity Bus Line, 13 ... Gate Insulation Film, 14 ... Silicon Film, 15 ... SiN Film, 16 ... n⁺Type Amorphous Silicon Film, 17a, 72 ... Data Bus Line, 17b ... Storage Capacity Electrode, 17d ... Drain Electrode, 17s ... Source Electrode, 18 ... Final Protective Film, 18a, 18b .. Contact hole, 19,41,42,45,48 ... resist film, 20a, 51,61,74 ... reflective electrode, 21,34 ... alignment film 30 ... opposed substrate, 32. Color filter, 33 ... common electrode, 38,39 ... polarizing plate, 40 ... liquid crystal, 52,53,54,62,63,64 ... slit, 74a ... opening, 75 ... transparent electrode.