Liquid crystal display device

Abstract

To realize a pixel structure capable of high response speed in a high definition liquid crystal display device of which a pixel pitch is small.SOLUTION: In a liquid crystal display device, scanning lines 11 extend in a first direction and are arranged in a second direction, video signal lines 12 extend in the second direction and are arranged in the first direction, and a pixel is formed in a region surrounded by the scanning lines 11 and the video signal lines 12. In the pixel, first portions 1121, 1122, 1125, and 1126 having at least a comb electrode, a second portion 1123 having a contact portion for receiving an electrical signal, and a pixel electrode having a third portion 1124 that connects the first portions and the second portion, are formed. The third portion protrudes to an adjacent pixel side closer than the first portion and the second portion, and a normal of a side of the adjacent pixel side of the third portion forms an angle other than 0 and 90 degrees with the first direction and the second direction.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a liquid crystal display device that has a high-definition screen and enables high-speed response. [Background technology]

[0002] Viewing angle characteristics are an issue for LCDs, but the IPS (In Plane Switching) method is widely used because it provides excellent viewing angle characteristics. Furthermore, within the IPS method, the FFS (Fringe Field Switching) method is widely used because it can relatively increase pixel transmittance. LCDs are finding wider applications in a variety of fields.

[0003] Depending on the display device, high-definition screens and high-speed response are required. Patent Document 1 describes a pixel configuration that enables high-speed response. Patent Document 2 describes an electrode and wiring structure that enables a high-definition screen in an IPS or FFS mode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6772001 [Patent Document 2] Japanese Patent Application Publication No. 2019-144315 Summary of the Invention [Problem to be solved by the invention]

[0005] Liquid crystal display devices used in VR (Virtual Reality) display devices and the like are required to have high definition and fast response. Liquid crystal controls light by rotating the liquid crystal molecules in response to an electric field. However, because liquid crystal can be considered an elastic body, even within the same pixel, it is affected by the orientation of liquid crystal molecules in the surrounding area. Therefore, the response speed of the liquid crystal molecules is affected by the orientation direction of the liquid crystal in the surrounding area.

[0006] Liquid crystal display devices create images by controlling the liquid crystal molecules of each pixel using an electric field between a pixel electrode and a common electrode. However, as resolution increases, the distance between adjacent pixel electrodes decreases, and the influence of the pixel electrodes on the liquid crystal molecules in adjacent pixels becomes significant. This phenomenon not only reduces the contrast of the image, but also affects the rotation speed of the liquid crystal molecules, i.e., the response speed of the liquid crystal.

[0007] The present invention is intended to solve the above problems and to realize a liquid crystal display device with a high-definition screen and high-speed response. [Means for solving the problem]

[0008] The present invention overcomes the above problems, and the specific means are as follows.

[0009] (1) A liquid crystal display device in which scanning lines extend in a first direction and are arranged in a second direction, video signal lines extend in the second direction and are arranged in the first direction, and pixels are formed in areas surrounded by the scanning lines and the video signal lines, wherein a pixel electrode is formed within the pixel, the pixel having a first portion having a comb-tooth electrode, a second portion having a contact portion for receiving an electrical signal, and a third portion connecting the first portion and the second portion, the third portion protruding toward an adjacent pixel beyond the first portion and the second portion, and the normal to the edge of the third portion facing the adjacent pixel forms an angle other than 0 degrees or 90 degrees with the first direction and the second direction.

[0010] (2) The liquid crystal display device according to (1), wherein the side of the third portion on the side of the adjacent pixel is curved.

[0011] (3) The liquid crystal display device described in (1), characterized in that the normal to the side of the third portion on the adjacent pixel side includes an angle of 30 degrees or more with the first direction and the second direction.

[0012] (4) A liquid crystal display device as described in (1), characterized in that a metal film to which a common voltage is applied overlaps with the video signal line and extends in the second direction, and the width of the metal film in the first direction is larger than the width of the video signal line in the first direction. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a plan view of a liquid crystal display device. [Figure 2] FIG. 2 is a cross-sectional view of a display area of ​​a liquid crystal display device. [Figure 3] FIG. 10 is a plan view of a pixel according to a comparative example. [Figure 4] 4 is a cross-sectional view taken along the line AA in FIG. 3. [Figure 5] 10 is a plan view showing the alignment direction of liquid crystal molecules when no signal voltage is applied to the pixel electrode. FIG. [Figure 6] 10 is a plan view showing the action between adjacent pixel electrodes when a signal voltage is applied to the pixel electrodes. FIG. [Figure 7] 7 is a plan view showing the alignment direction of liquid crystal molecules corresponding to the electric field direction in FIG. 6. FIG. [Figure 8] 10 is a plan view showing the alignment direction of liquid crystal molecules due to the action of the comb-tooth portion of the pixel electrode and the common electrode when a signal voltage is applied to the pixel electrode. [Figure 9] 10 is a plan view showing the alignment direction of liquid crystal molecules due to the action of the connection portion of the pixel electrode and the common electrode when a signal voltage is applied to the pixel electrode. FIG. [Figure 10] FIG. 2 is a plan view of a pixel according to the first embodiment. [Figure 11]10 is a plan view showing the alignment direction of liquid crystal molecules near the connection portion of pixel electrodes when no signal voltage is applied and the influence of pixel electrodes of adjacent pixels is not included. FIG. [Figure 12] 10 is a plan view showing the alignment direction of liquid crystal molecules near the connection portion of a pixel electrode due to the action of a pixel electrode and a common electrode when a signal voltage is applied without including the influence of the pixel electrode of an adjacent pixel. FIG. [Figure 13] 11 is a plan view showing the alignment direction of liquid crystal molecules in the vicinity of the connection portion of the pixel electrode in FIG. 10 when no signal voltage is applied. [Figure 14] 11 is a plan view showing the action between pixel electrodes in the vicinity of the connection portion of the pixel electrodes in FIG. 10 when a signal voltage is applied. [Figure 15] FIG. 15 is a plan view showing the alignment direction of liquid crystal molecules corresponding to FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below with reference to examples. [Example]

[0015] Fig. 1 is a plan view of a liquid crystal display device to which the present invention is applied. In Fig. 1, a TFT substrate 100 and a counter substrate 200 are bonded with a sealant 16, and a liquid crystal layer is sandwiched between the TFT substrate 100 and the counter substrate 200. A display area 14 is formed in the area where the TFT substrate 100 and the counter substrate 200 overlap.

[0016] In the display region 14 of the TFT substrate 100, scanning lines 11 extend in the horizontal direction (x-axis direction) and are arranged in the vertical direction (y-axis direction). Video signal lines 12 extend in the vertical direction and are arranged in the horizontal direction. Areas surrounded by the scanning lines 11 and the video signal lines 12 form pixels 13. Note that pixels configured in this manner are sometimes called sub-pixels, but are referred to as pixels in this specification.

[0017] The pixels in this embodiment are very small, with a horizontal pitch px of 11 μm and a vertical pitch py of 33 μm. As the pixel pitch becomes smaller, interference between adjacent pixel electrodes becomes a problem. In liquid crystal display devices, the polarity of the potential of the pixel electrode and the common electrode is regularly reversed to prevent electrolysis of the liquid crystal. Furthermore, to more reliably prevent electrolysis of the liquid crystal, methods such as row inversion driving, column inversion driving, and dot inversion driving have been developed.

[0018] In this embodiment, a column inversion driving method is adopted, as shown in Figure 1. That is, signal voltages of opposite polarity are supplied to adjacent video signal lines. This polarity is then periodically switched. In a liquid crystal display device, liquid crystal molecules are driven by a potential difference between a pixel electrode and a common electrode. On the other hand, as shown in Figure 1, in column inversion driving, the potential difference between adjacent pixels is twice the potential difference between the pixel electrode and the common electrode.

[0019] However, since the distance between the pixel electrode and the common electrode is 70 to 100 nm, while the distance between adjacent pixels is 1 μm or more, the effect on the liquid crystal molecules is still dominated by the action between the pixel electrode and the common electrode. However, as mentioned above, when the distance between pixel electrodes becomes small, the effect between adjacent pixel electrodes cannot be ignored.

[0020] In Fig. 1, the TFT substrate 100 is formed larger than the counter substrate 200, and the portion where the TFT substrate 100 does not overlap with the counter substrate 200 forms a terminal region 15. A flexible wiring substrate 17 is connected to the terminal region 15. A driver IC that drives the liquid crystal display device is mounted on the flexible wiring substrate 17. However, the driver IC may be mounted in the terminal region 15.

[0021] Since liquid crystal does not emit light by itself, a backlight is placed behind the TFT substrate 100. The liquid crystal display panel forms images by controlling the light from the backlight for each pixel. The flexible wiring substrate 17 is folded behind the backlight, thereby reducing the overall external size of the liquid crystal display device.

[0022] Fig. 2 is a cross-sectional view of a display area where pixels exist. Fig. 2 shows a liquid crystal display device of a type called FFS (Fringe Field Switching) mode, which belongs to IPS (In Plane Switching) mode. Fig. 2 is a cross-sectional view of the main parts that form an image in a pixel, and does not show all of the configurations characteristic of Example 1, which will be described later.

[0023] 2, an underlayer film 101 is formed to cover a TFT substrate 100. The underlayer film 101 prevents impurities from the substrate 100, which is made of glass or a resin such as polyimide, from contaminating the oxide semiconductor film 102. The underlayer film 101 is often formed of a stacked film of a silicon oxide film (SiO) and a silicon nitride film (SiN).

[0024] A semiconductor film 102 that constitutes a TFT is formed on an underlayer film 101. The semiconductor film 102 is, for example, a polysilicon semiconductor film 102, which is formed by first depositing amorphous silicon by CVD and then converting this to polysilicon using an excimer laser. Hereinafter, the polysilicon semiconductor film will be simply referred to as the semiconductor film 102. Furthermore, the semiconductor film 102 is not limited to polysilicon, and may be made of an amorphous semiconductor or an oxide semiconductor.

[0025] A gate insulating film 103 is formed using a silicon oxide film (SiO) or a silicon nitride film (SiN) to cover the semiconductor film 102. Two gate electrodes 104 are formed in series on the gate insulating film 103. As shown in FIG. 3, the gate electrodes 104 are also used as the scanning lines 11. That is, the semiconductor film 102 passes under the scanning lines 11 twice via the gate insulating film 103, thereby forming two TFTs in series.

[0026] 2, an interlayer insulating film 105 is formed using a silicon oxide film (SiO) or a silicon nitride film (SiN), or both, to cover the gate electrode 104 and the gate insulating film 103. Thereafter, a through-hole 121 is formed in the interlayer insulating film 105 and the gate insulating film 103, and one end of the semiconductor film 102 is connected to the video signal line 12. In FIG. 2, the video signal line 12 also serves as the drain electrode 106. Furthermore, a through-hole 122 is formed in the interlayer insulating film 105 and the gate insulating film 103, and one end of the semiconductor film 102 is connected to the source electrode 107. The source electrode 107 extends toward the pixel electrode 112.

[0027] An organic passivation film 108 is formed of a transparent resin, for example, an acrylic resin, covering the drain electrode 106, the source electrode 107, and the interlayer insulating film 105. The organic passivation film 108 also serves as a planarization film, and is formed to a thickness of 2 μm or more in order to reduce coupling between the video signal lines 12, the scanning lines 11, etc. and the common electrodes 110 and pixel electrodes 112 formed above them.

[0028] In addition, the semiconductor film 102, gate electrode 104, drain electrode 106, and source electrode 107 that constitute the thin film transistor are described as top gates in Figure 2, but they are not limited to this top gate. They may also be bottom gates in which the gate electrode is provided between the semiconductor film 102 and the TFT substrate 100, or they may be a combination of top gates and bottom gates in which the semiconductor film 102 is sandwiched between two gate electrodes, one above the other.

[0029] 2, a common electrode 110 is formed on an organic passivation film 108 using a transparent conductive film such as ITO (Indium Tin Oxide). A capacitive insulating film 111 is formed on the common electrode 110 using SiN. The capacitive insulating film is formed thin, for example, about 70 nm, in order to increase pixel capacitance. A pixel electrode 112 is formed on the capacitive insulating film 111 using a transparent conductive film such as ITO.

[0030] A through-hole 130 is formed in the organic passivation 108 in a portion corresponding to the source electrode 107 extending from the TFT, and a through-hole 131 is formed in the capacitive insulating film 111 within the through-hole 130. This connects the pixel electrode 112 and the source electrode 107. An alignment film 113 is formed from a polyimide film to cover the pixel electrode 112 and initially align the liquid crystal. The alignment process for the alignment film 113 can be performed by rubbing or by photo-alignment using polarized ultraviolet light, but since the IPS system (including the FFS system) does not require a tilt angle, so-called photo-alignment, in which polarized ultraviolet light is used to create anisotropy in the polyimide film, is advantageous.

[0031] On the left side of FIG. 2, a common metal 109 made of a metal film is formed on the upper side of the organic passivation film 108 at a position corresponding to the video signal line 12. A common voltage is supplied to the common metal 109. The main roles of the common metal 109 are to reduce the resistance of the common electrode 110, to block backlight, and to connect common electrodes formed in stripes along the horizontal direction (x-axis direction) for each pixel row as will be described later, and also to prevent potential gradients in the common electrode 110 and brightness gradients. The common metal 109 may be made of the same material as that of the video signal line 12 or the scanning line 11. For example, MoW (molybdenum tungsten alloy) or TAT (Ti-Al-Ti laminated film) may be used.

[0032] In FIG. 2, a counter substrate 200 is disposed opposite the TFT substrate 100, sandwiching a liquid crystal layer 300 therebetween. A black matrix 202 is formed on the counter substrate 200 to cover the through-holes 130 and TFTs formed on the TFT substrate 100 side, and a red, blue, or green color filter 201 is formed in the light-transmitting region, i.e., the image-forming region. An overcoat film 203 is formed to cover the color filter 201 and the black matrix 202, and an alignment film 204 for initially aligning the liquid crystal is formed thereon. The color filter 201 is not limited to being provided on the counter substrate 200, and may be a color filter on array (COA) in which the color filter is provided on the TFT substrate 100. The method for manufacturing the alignment film 204 is the same as that described for the alignment film 113 on the TFT substrate 100 side.

[0033] 2, when a signal voltage is applied between pixel electrodes 112 and common electrodes 110 formed on the TFT substrate 100, electric lines of force are generated as indicated by the arrows, causing liquid crystal molecules 301 to rotate and controlling the light transmittance of the pixel. An image is formed by controlling the light transmittance for each pixel.

[0034] FIG. 3 is a plan view of a pixel according to a comparative example. FIG. 3 is not a conventional example, but is provided for comparison with Example 1, and includes novel features. In FIG. 3, scanning lines 11 extend in the horizontal direction (x-axis direction) and are arranged in the vertical direction (y-axis direction). Video signal lines 12 extend in the vertical direction and are arranged in the horizontal direction. In FIG. 3, the pixel size is, for example, 11 μm in the horizontal direction and 33 μm in the vertical direction, with the video signal lines 12 having widths of approximately 2 μm and the scanning lines 11 having widths of approximately 2 μm. In FIG. 3, the pixel electrodes 112 are located in the area surrounded by the scanning lines 11 and the video signal lines 12. However, since the horizontal pitch of the pixels is very small at 11 μm, the pixel electrodes 112 partially overlap with the signal lines 12 and the common metal 109. In FIG. 3, the alignment direction AL of the alignment film, which determines the initial alignment of the liquid crystal, is the horizontal direction, the same as the x-axis direction.

[0035] A TFT serving as a switching element is formed on the upper side in the y-axis direction in Fig. 3. The TFT in Fig. 3 corresponds to the TFT in Fig. 2. One end of the semiconductor film 102 is connected to a video signal line 12 by a through-hole 121. The video signal line 12 also serves as a drain electrode 106. The semiconductor layer 102 is bent in a U-shape and passes under the scanning line 11 twice. Since the scanning line 11 also serves as the gate electrode 104, two TFTs are formed in series at this time.

[0036] The other end of the semiconductor film 102 is connected to the source electrode 107 via a through-hole 122. The source electrode 107 extends toward the pixel electrode 112 and is connected to the pixel electrode 112 via a through-hole 130 formed in the organic passivation film 108 and a through-hole 131 formed in the capacitive insulating film 111. In Figure 3, the pixel electrode 112 is represented by various element names 1121, 1122, 1123, 1124, 1125, and 1126. Reference numeral 1121 denotes five comb teeth, 1122 denotes the backbone of the comb teeth, 1123 denotes a contact portion that connects to the source electrode 107, and 1124 denotes a portion that connects the contact portion 1123 to the comb teeth 1121 and 1122.

[0037] The parts that directly contribute to image formation are the comb teeth 1121, and in FIG. 3, five comb teeth 1121 extend horizontally (in the x-axis direction) from the spine 1122. The sides of each comb tooth 1121 extending horizontally form a predetermined angle with the x-axis direction. That is, each comb tooth 1121 is narrower at its tip than at its base. This is to prevent domains from occurring when the liquid crystal is operated. The vertical width w4 of each comb tooth 1121 at the center of the comb tooth 1121 in the x-axis direction is, for example, 1.8 μm, and the comb tooth spacing w3 is, for example, 2.5 μm. The length of each comb tooth 1121 in the x-axis direction is, for example, 8 μm. The recesses between the teeth of the comb teeth 1121 have slopes 1126 at their bases. This is to prevent domains from occurring when the liquid crystal is operated.

[0038] On the side of the spine 1122 of the comb tooth facing the adjacent pixel, a roughly triangular notch 1125 is formed at a position corresponding to the tooth 1121 of the comb tooth. This is to prevent the occurrence of domains when the liquid crystal is operated and to improve the response speed.

[0039] In FIG. 3, the common electrode 110 extends in the horizontal direction (x-axis) in a stripe pattern corresponding to the width in the y-axis direction of the region where the comb teeth 1121 of the pixel electrode 112 are formed, so as to avoid the through-holes 130 formed in the organic insulating film 108. The width in the y-axis direction of the common electrode 110 is, for example, 25 μm. The common electrode 110 is formed of a transparent conductive film such as ITO, which has lower conductivity than metal and is formed thin to increase transmittance, resulting in high resistance. This causes a brightness gradient on the screen.

[0040] To prevent this, in FIG. 3, a metal film 109 is formed so as to overlap the video signal line 12. Hereinafter, this metal will be referred to as common metal 109. The common metal 109 is formed by stacking with a common electrode 110, and is at a common potential. In FIG. 3, the width w1 of the video signal line 12 is, for example, 2 μm, while the width w2 of the common metal is 4 μm. However, in the portion where the through-hole 130 of the organic insulating film 108 is formed, the widths of the video signal line 12 and the common metal 109 are the same.

[0041] Fig. 4 is a cross-sectional view taken along the line AA in Fig. 3. In Fig. 4, a wide common metal 109 is formed corresponding to the video signal line 12, and a common electrode 110 is formed covering this. A capacitive insulating film 111 is formed covering the common electrode 110. A backbone portion 1122 of a pixel electrode 112 is formed overlapping the common metal 109, and an alignment film 123 is formed covering the pixel electrode 112 and the capacitive insulating film 111.

[0042] 3 and 4, the horizontal (x-axis) transmission region of the pixel is substantially defined by the common metal 109. Since the common metal 109 is formed in a portion close to the liquid crystal layer 300, it has an excellent light-blocking effect and can improve the contrast of the image.

[0043] FIG. 5 is a plan view of the vicinity of the contact portion 1123 and the connecting portion 1124 of the pixel electrode 112. In FIG. 5, TFTs and other components are omitted to avoid complicating the drawing. The pixel electrode 112 is indicated by the numbers 1121, 1122, 1123, 1124, 1125, 1126, and so on. This also applies to the following figures. In FIG. 5, the alignment direction AL of the alignment film, which initially aligns the liquid crystal molecules 301, is the x-axis direction. Therefore, the liquid crystal molecules 301 are also aligned in the x-axis direction. Note that this specification will be described using a positive-type liquid crystal, in which the dielectric constant of the long axis side of the liquid crystal molecules is greater than the dielectric constant of the short axis side. However, in the case of a negative-type liquid crystal, the direction of movement of the liquid crystal molecules can be considered to be 90 degrees different.

[0044] Figure 6 is a plan view of the state of Figure 5 when a voltage is applied to the pixel electrodes. When a voltage is applied to the pixel electrodes, the liquid crystal molecules move due to the electric field lines between the pixel electrodes and the common electrode, as shown in Figure 2. However, in column inversion driving, when the horizontal pixel pitch becomes small, influence between adjacent pixel electrodes occurs.

[0045] The double-headed arrows in Figure 6 indicate the direction of the electric field acting between adjacent pixel electrodes. In the comb-tooth regions 1121 and 1122 of the pixel electrode 112, the action of this electric field is angled with respect to the x-axis direction due to the action of the notches 1125, and therefore does not hinder the rotation of the liquid crystal molecules. However, in the connection region 1124, the action of this electric field is in the x-axis direction, and therefore acts to hinder the rotation of the liquid crystal molecules 301. In other words, this action makes it easier for domains to occur.

[0046] Figure 7 is a plan view showing the orientation of liquid crystal molecules 301 in a portion corresponding to Figure 6. In Figure 7, only the portion of liquid crystal molecules 301 corresponding to the double-headed arrow shown in Figure 6 is shown. The liquid crystal molecules 301 try to align in the electric field direction indicated by the double-headed arrow.

[0047] The orientation direction of the liquid crystal molecules 301 is primarily influenced by the direction of the electric field formed by the pixel electrode 112 and the common electrode 110. Fig. 8 is a detailed plan view of the tip of the comb-tooth electrode 1121, which shows the orientation direction of the liquid crystal molecules 301 due to the action of the electric field between the comb-tooth electrode 1121 and the common electrode 110 (shown in shaded form) formed below it when a voltage is applied to the pixel electrode 112. The comb-tooth electrode 1121 is shaped so that the orientation direction of the liquid crystal molecules 301 due to the electric field formed between the pixel electrode 112 and the common electrode 110 does not coincide with the orientation direction AL of the alignment film. This prevents the occurrence of domains.

[0048] The orientation of the liquid crystal molecules 301 caused by the electric field between adjacent pixel electrodes shown in Fig. 7 is consistent with, and is similar to, the orientation direction of the liquid crystal molecules 301 caused by the electric field between the pixel electrode 1121 and the common electrode 110 shown in Fig. 8 at the tip of the comb-tooth electrode 1121. Therefore, the effect of preventing the occurrence of domains is maintained in this region.

[0049] 9 shows the alignment direction of liquid crystal molecules 301 at the connection portion 1124 of the pixel electrode 112 due to the action of an electric field between the comb-tooth electrode 112 and the common metal 109 or common electrode 110 formed thereunder when a voltage is applied to the pixel electrode 112. At the connection portion 1124 of the comb-tooth electrode 112, the alignment direction of the liquid crystal molecules 301 to which an electric field is applied coincides with the alignment direction AL of the alignment film, resulting in a shape in which domains are generated.

[0050] The orientation of the liquid crystal molecules 301 due to the electric field between adjacent pixels, shown at the connection portion 1124 of the pixel electrodes 112 in Fig. 7, coincides with the orientation direction AL of the alignment film, similar to the orientation direction of the liquid crystal molecules due to the electric field between the connection portion 1124 of the pixel electrodes 112 and the common electrode 110 in Fig. 9, making it easier for domains to occur. In other words, at the connection portion 1124 of the pixel electrodes 112, as shown in Figs. 7 and 9, the influence of the electric field generated between the connection electrode 1124 and the common electrode 110 and the electric field generated between adjacent pixel electrodes 112 all cause domains to occur.

[0051] Incidentally, most of the connection electrode 1124 overlaps with the common metal 109, which is a light-shielding body, and does not contribute to the transmittance of the pixel. However, liquid crystal can be considered an elastic body, and the orientation of the liquid crystal in the area shielded by the common metal 109 affects the orientation of the liquid crystal in the transmissive area of ​​the pixel. In other words, if the rotation of the liquid crystal molecules in the transmissive area of ​​the pixel is in the same direction as the rotation of the liquid crystal molecules in the non-transmissive area, the liquid crystal molecules in the transmissive area can rotate quickly. On the other hand, in a configuration in which the liquid crystal molecules 301 in the non-transmissive area do not rotate even when a voltage is applied to the pixel electrode 112, the rotation speed of the liquid crystal molecules 301 in the transmissive area is affected by the non-rotating liquid crystal molecules 301, and this slows down the rotation speed of the liquid crystal molecules 301 in the transmissive area. In other words, the response speed of the liquid crystal is slowed.

[0052] FIG. 10 is a plan view of a pixel showing the features of the first embodiment, which addresses such a problem.

[0053] In Figure 10, the alignment direction of the alignment film that determines the initial alignment direction of the liquid crystal molecules 301 is AL, which is the horizontal direction (x-axis direction). Figure 10 differs from the comparative example in Figure 3 in the shape of the connection part 1124 of the pixel electrode 112 and the shape of the contact part 1123. In Figure 10, the connection part 1124 of the pixel electrode 112 is curved toward the adjacent pixel so that the area where the normal direction of the curve coincides with the initial alignment direction AL of the alignment film is minimized. It is desirable that the outside of the connection part 1124, i.e., the normal direction of the side on the adjacent pixel electrode side, include an area that is at an angle of 30 degrees or more with the horizontal direction.

[0054] The connection portion 1124 overlaps the common metal 109, the video signal line 12, and the common metal 109. Furthermore, it protrudes toward the adjacent pixel from the center line of the video signal line 12 in the x-axis direction. Furthermore, the connection portion 1124 protrudes toward the adjacent pixel from the spine portion 1122 of the comb-tooth electrode. This allows the normal to the edge of the connection portion 1124 to form a larger angle with the x-axis direction, which is the alignment direction AL of the alignment film. Therefore, when a voltage is applied to the pixel electrode 112, it is possible to prevent the occurrence of an area where the liquid crystal molecules 301 do not rotate, i.e., the occurrence of a domain. At the same time, it is possible to prevent a decrease in the operating speed of the liquid crystal due to the occurrence of a domain.

[0055] 10, a notch 1127 is provided in the lower corner of the approximately rectangular contact portion 1123 of the pixel electrode 112 in the y-axis direction to correspond to and avoid the protrusion of the pixel electrode 1124 of the adjacent pixel. The sides of this notch 1127 form an angle with both the x-axis direction and the y-axis direction, and this angle is 30 degrees or more. In addition, the lower side of the contact portion 1123 forms an angle θ with the x-axis direction (see FIG. 14).

[0056] In the pixel electrode 112 described above, the various elements may be referred to as follows: a first portion having the comb-tooth portion 1121, the spine portion 1122, the notched portion 1125, and the inclined portion 1126, a second portion having the contact portion 1123, and a third portion having the connection portion 1124. Alternatively, the first portion may be defined as a first portion including the comb-tooth electrode 1121. This is because the comb-tooth electrode 1121 is an essential requirement for operation in the first portion.

[0057] Fig. 11 is a plan view showing a state in which no voltage is applied to the pixel electrode 112 (1123, 1124). The shapes of the contact portion 1123 and the connection portion 1124 of the pixel electrode 112 are as described in Fig. 10. In Fig. 11, the alignment direction AL of the alignment film is the horizontal direction (x-axis direction), so the liquid crystal molecules 301 are aligned in the horizontal direction.

[0058] Fig. 12 is a plan view showing the orientation of liquid crystal molecules near the connection portion 1124 of the pixel electrode 112 when a voltage is applied to the pixel electrode 112. Fig. 12 shows the behavior of liquid crystal molecules 301 due to the action of an electric field between the pixel electrode 1124 and the common electrode 110 (or the common metal 109). When a voltage is applied between the pixel electrode 112 and the common electrode 110, electric field lines are generated as shown in Fig. 2, and the liquid crystal molecules 301 are oriented. If the connection portion 1124 of the pixel electrode 112 has a shape as shown in Figs. 11 and 12, the liquid crystal molecules can rotate, and the occurrence of domains is avoided.

[0059] 13 to 15 are plan views of the vicinity of the connection portion 1124 and the contact portion 1123 of the pixel electrode 112, illustrating the influence of the electric field between adjacent pixel electrodes 112. Fig. 13 is a plan view when no voltage is applied between the pixel electrodes 112. In Fig. 13, the liquid crystal molecules 301 are aligned in the horizontal direction (x-axis direction), which is the same as the alignment direction AL of the alignment film.

[0060] Fig. 14 is a plan view showing the effect when a voltage is applied to the pixel electrodes 112 (1123, 1124). In Fig. 14, the double-headed arrows are a plan view showing the electric field between adjacent pixel electrodes 112 when a signal voltage is applied to the pixel electrodes 112 (1123, 1124). In column inversion driving, the voltage between adjacent pixel electrodes 112 is twice the voltage between the pixel electrode and the common electrode.

[0061] In Figure 14, the connection portion 1124 of the pixel electrode 112 extends beyond the center line of the signal line in the x-axis direction toward the adjacent pixel so that its normal direction does not coincide with the horizontal direction (x-axis direction). It also extends beyond the backbone portion 1122 of the pixel electrode 112 toward the adjacent pixel. In Figure 14, the amount by which the connection portion 1124 extends toward the adjacent pixel is d. Here, in Figure 14, the amount of extension d indicates the distance from the backbone portion 1122 to the tip of the curve of the connection portion 1124. In other words, the pixel electrode structure in Figure 14 increases the area where the direction of the electric field formed between adjacent pixel electrodes 112 does not coincide with the horizontal direction (x-axis direction), and this electrode structure enables the liquid crystal molecules 301 to rotate in this area.

[0062] If the distance between the connection portion 1124 and the pixel electrode 112 of an adjacent pixel becomes extremely small, an irregular electric field may be generated, which may adversely affect the alignment of the liquid crystal molecules 301. Therefore, in the configurations shown in Figures 10 to 15, a chamfered notch 1127 is formed at the corner of the contact portion 1123 of the pixel electrode 112. The normal direction of the side of the chamfered notch 1127 includes an angle of 30 degrees or more with respect to the horizontal direction (x-axis direction) or the vertical direction (y-axis direction).

[0063] Another feature of the contact portion 1123 of the pixel electrode 112 in FIG. 14 is that the lower edge of the y-axis direction forms an angle θ with the x-axis direction. In FIG. 14, the common electrode 110 is not present below the contact portion 1123, so there is no fringe electric field between the common electrode 110 and the contact portion 1123. However, an electric field exists between the lower edge of the contact portion 1123 of the pixel electrode 112 and the upper edge of the common electrode 110. This electric field is weaker than the electric fields in other locations, but it has some effect when the distance between the common electrode 110 and the contact portion 1123 becomes small. In FIG. 14, the lower edge of the contact portion 1123 is formed so as to form an angle θ with the x-axis direction, so that this portion does not interfere with the rotation of the liquid crystal molecules 301.

[0064] FIG. 15 is a plan view showing the case where liquid crystal molecules 301 are aligned due to the interaction between adjacent pixel electrodes 112 when a signal voltage is applied to the pixel electrodes 112. As shown in FIG. 15, the alignment direction of the liquid crystal molecules 301 due to the electric field between adjacent pixel electrodes 112 forms an angle with the horizontal direction (x-axis direction), making it difficult for domains to occur. Furthermore, the alignment direction of the liquid crystal molecules 301 due to the interaction between adjacent pixel electrodes 112 shown in FIG. 15 is substantially the same as the alignment direction of the liquid crystal molecules 301 due to the interaction between the pixel electrode 112 and the common electrode 110 shown in FIG. 12, and both of these have the effect of making it difficult for domains to form in the liquid crystal molecules 301. Therefore, there is no effect that reduces the response speed of the liquid crystal molecules 301 in the transmissive region of the pixel.

[0065] 15, in the region along the lower side of the contact portion 1123 of the pixel electrode 112, the liquid crystal molecules 3011 are oriented at an angle to the vertical direction (y-axis direction). This region is affected by the planar interaction between the contact portion 1123 and the common electrode 110, rather than by the interaction between adjacent pixel electrodes, and therefore the effect is smaller than in other regions. However, even in this region, the absence of any interaction that hinders the rotation of the liquid crystal molecules 301 has a favorable effect on the response speed in the transmissive region.

[0066] The pixel electrode portion of the present embodiment described above is not a transmissive region of the pixel, i.e., it is not a region that directly forms an image. However, even in a non-transmissive region, if the occurrence of a region where the liquid crystal molecules 301 cannot rotate can be prevented, it is possible to prevent the formation of domains and prevent a decrease in the response speed of the transmissive region due to the elasticity of the liquid crystal.

[0067] As explained above, the present invention is particularly effective when the pixel pitch is small. In Example 1, the pixel pitch in the horizontal direction (x-axis direction) is 11 μm, but the present invention is particularly effective in a pixel structure where the pixel pitch in the horizontal direction is smaller than about 20 μm.

[0068] According to the present invention, even if the pixel pitch is reduced, it is possible to prevent a decrease in response speed due to interactions between pixel electrodes, thereby realizing a liquid crystal display device that is capable of high-resolution display and has a fast response speed. [Explanation of symbols]

[0069] 11...scanning line, 12...video signal line, 13...pixel, 14...display area, 15...terminal area, 16...sealing material, 17...flexible wiring substrate, 100...TFT substrate, 101...underlying film, 102...semiconductor film, 103...gate insulating film, 104...gate electrode, 105...interlayer insulating film, 106...drain electrode, 107...source electrode, 108...organic passivation film, 109...common metal, 110...common electrode, 111...capacitive insulating film, 112...pixel electrode, 113...alignment film, 121...through hole, 122...through hole, 130...through hole, 131...through hole, 135...through hole, 136...through hole, 200...opposing substrate, 201...color filter, 202...black matrix, 203...overcoat film, 204...alignment film, 300...liquid crystal layer, 301...liquid crystal molecules, 1121...comb-tooth electrode, 1122...backbone portion of comb-tooth electrode, 1123...contact portion of pixel electrode, 1124...connection portion, 1125...notch, 1126...inclined portion, 1127...notch in contact portion, 3011...liquid crystal molecules

Claims

1. A liquid crystal display device in which scanning lines extend in a first direction and are arranged in a second direction, video signal lines extend in the second direction and are arranged in the first direction, and pixels are formed in areas surrounded by the scanning lines and the video signal lines, a pixel electrode is formed in the pixel, the pixel electrode having a first portion having a comb-teeth electrode, a second portion having a contact portion for receiving an electric signal, and a third portion connecting the first portion and the second portion; the third portion protrudes toward an adjacent pixel side beyond the first portion and the second portion, a normal to a side of the third portion on the adjacent pixel side forms an angle other than 0 degrees and 90 degrees with the first direction and the second direction; the comb-tooth electrode has a comb-tooth portion extending along the first direction and a backbone portion extending along the second direction, a third portion located between the spine portion and the second portion, connecting the spine portion and the second portion, and protruding toward the adjacent pixel beyond the spine portion of the comb-tooth electrode.

2. 2. The liquid crystal display device according to claim 1, wherein the side of the third portion on the side of the adjacent pixel is curved.

3. 2. The liquid crystal display device according to claim 1, wherein a normal to a side of the third portion on the side of the adjacent pixel forms an angle of 30 degrees or more with the first direction and the second direction.

4. 2. The liquid crystal display device according to claim 1, wherein a metal film to which a common voltage is applied overlaps with the video signal line and extends in the second direction, and the width of the metal film in the first direction is larger than the width of the video signal line in the first direction.

5. 5. The liquid crystal display device according to claim 4, wherein the width of the light-transmitting region of the pixel in the first direction is defined by the metal film.

6. 5. The liquid crystal display device according to claim 4, wherein the width of the metal film in the first direction is smaller in a portion corresponding to the second portion of the pixel electrode than in a portion corresponding to the first portion of the pixel electrode.

7. 5. The liquid crystal display device according to claim 4, wherein the third portion of the pixel electrode overlaps with the metal film.

8. 2. The liquid crystal display device according to claim 1, wherein the third portion of the pixel electrode overlaps with the video signal line.

9. 2. The liquid crystal display device according to claim 1, wherein the side of the third portion of the pixel electrode on the adjacent pixel side protrudes toward the adjacent pixel side beyond the center of the video signal line in the first direction.

10. 2. The liquid crystal display device according to claim 1, wherein the third portion of the pixel electrode has a portion that overlaps with a common electrode and a portion that does not overlap with the common electrode, and the second portion of the pixel electrode does not overlap with the common electrode.

11. 2. The liquid crystal display device according to claim 1, wherein the second portion of the pixel electrode is substantially rectangular, and a chamfered notch is formed at the corner opposite to the side to which the third portion is connected.

12. 12. The liquid crystal display device according to claim 11, wherein the normal direction of the chamfered notch includes a side that forms an angle of 30 degrees or more with respect to the first direction.

13. 2. The liquid crystal display device according to claim 1, wherein the second portion of the pixel electrode is substantially rectangular, and the side of the second portion facing the first portion of the pixel electrode has an angle other than 0 degrees with the first direction.

14. 2. The liquid crystal display device according to claim 1, wherein the pitch of the pixels in the first direction is 20 [mu]m or less.

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