JP7183366B2 - liquid crystal display - Google Patents

Description

The present invention relates to a display device, and more particularly, to a liquid crystal display device that takes measures against display unevenness caused by areas where an alignment film is not formed when a screen becomes high definition.

In a liquid crystal display device, a TFT substrate on which pixels having pixel electrodes, thin film transistors (TFTs) and the like are formed in a matrix, and a counter substrate are arranged opposite to the TFT substrate, and liquid crystal is sandwiched between the TFT substrate and the counter substrate. It is configured as follows. An image is formed by controlling the light transmittance of the liquid crystal molecules for each pixel.

An organic passivation film is formed to cover the TFT, and a common electrode, a pixel electrode, and an insulating film for insulating these electrodes are formed on the organic passivation film. The organic passivation film is intended to be a flattening film and to reduce stray capacitance, so it is formed as thick as about 2 to 4 μm. Since the contact hole is formed in this thick organic passivation film, the depth and taper angle of the contact hole become large, which makes it difficult for the alignment film to enter the contact hole.

On the other hand, since the organic passivation film is formed thick, it has been proposed to impart various functions to the organic passivation film. Japanese Patent Application Laid-Open No. 2002-200002 describes a configuration in which unevenness is formed in an organic passivation film in a pixel region, and a reflective film made of metal is formed thereon to form a Lambertian reflective surface.

In Patent Document 2, by changing the thickness of the organic passivation film for each of R, G, and B pixels, the thickness of the liquid crystal layer in each pixel can be changed, and the optimum liquid crystal layer thickness can be defined for each color. Have been described.

Japanese Patent Application Laid-Open No. 2003-177396 Japanese Patent Application Laid-Open No. 2002-229062

Especially in small liquid crystal display devices, the resolution of the screen is becoming higher. Since the area of a pixel becomes smaller as the definition is increased, the proportion of the area of the contact hole for connecting the pixel electrode and the source electrode of the TFT in the pixel increases. Also, the distance between contact holes existing in different pixels is reduced.

In a liquid crystal display device, an alignment film is formed to initially align liquid crystal molecules. This alignment film material is initially liquid, and is fired after application to form an alignment film. As the contact hole becomes smaller, the alignment film is repelled, and the probability that the alignment film is not formed in the contact hole increases. If the alignment film does not enter the contact hole, the thickness of the alignment film becomes uneven around the contact hole. In other words, at the edge of the alignment film, which is caused by the alignment film not entering the contact hole, the amount of the alignment film increases by the amount of the alignment film that should enter the contact hole. The alignment film may become thick in the periphery. When the thickened region of the alignment film extends beyond the light-shielding region to reach the transmissive region, the voltage applied to the liquid crystal layer in the transmissive region may decrease, or the gap in the liquid crystal layer may become smaller than in other regions. do. Therefore, there arises a problem that the display quality is lowered (dark unevenness appears) compared to other areas.

In general, since each contact hole is shielded from light by a black matrix or the like, there is no problem if the alignment film is not formed in each contact hole. If it extends to (the area not light-shielded by the black matrix), it becomes a problem. Furthermore, there are cases in which regions where the alignment film is not formed extend over a plurality of pixels. In this case, the area where the alignment film is not formed extends to the display area, resulting in deterioration of display quality. When the liquid crystal display device has a high definition, the pixel pitch is small, so that the non-uniformity of the thickness of the alignment film and the enlargement of the area where the alignment film is not formed are likely to occur.

FIG. 4 is an example of such display unevenness. As shown in FIG. 4, island-like display unevenness 50 occurs in the display area 500 . This is because in a plurality of pixels, there is an area where the thickness of the alignment film is uneven, and display unevenness occurs in this area.

Such display unevenness can be eliminated to some extent by adjusting the shape of each contact hole, the material of the alignment film, the printing conditions, or the like. However, since the film thickness of the organic passivation film cannot be reduced, there is a limit to reducing the pore size, and the printing conditions require a large process load.

SUMMARY OF THE INVENTION An object of the present invention is to take measures against display unevenness caused by light leakage by taking measures against the phenomenon that alignment films are not formed in contact holes.

The present invention overcomes the above problems, and the main concrete means are as follows. That is, TFTs in which pixels are formed between scanning lines extending in the first direction and arranged in the second direction and video signal lines extending in the second direction and arranged in the first direction A liquid crystal display device in which liquid crystal is sandwiched between a substrate and a counter substrate, wherein an organic insulating film is formed to cover the TFT in the pixel, and a first electrode is formed on the organic insulating film. , a second electrode is formed facing each other through an inorganic insulating film, an alignment film is formed thereon, and the second electrode and the TFT are connected through a contact hole formed in the organic insulating film. and the organic insulating film is formed with a convex portion and a concave portion on a bank near the contact hole in a cross section including the contact hole in the second direction from a side near the contact hole. A liquid crystal display device characterized by

1 is a plan view of a liquid crystal display device of the present invention; FIG. 2 is a plan view showing a pixel configuration of Example 1. FIG. FIG. 3 is a sectional view corresponding to the AA section of FIG. 2; This is an example of display unevenness caused by the existence of a region where no alignment film is formed. It is a top view near a contact hole. FIG. 6 is a cross-sectional view taken along the line BB of FIG. 5; FIG. 4 is a cross-sectional view for explaining a phenomenon in which an alignment film is not formed in a contact hole; 1 is a plan view of the present invention; FIG. FIG. 9 is a cross-sectional view taken along line CC of FIG. 8; 4 is a cross-sectional view showing the operation of the present invention; FIG. 9 is another example of a CC cross-sectional view of FIG. 8. FIG. 1 is a cross-sectional view illustrating features of the present invention; FIG. 4 is a plan view showing another form of Example 1. FIG. FIG. 10 is a plan view showing still another form of Example 1; FIG. 10 is a plan view showing still another form of Example 1; FIG. 10 is a plan view showing Example 2; FIG. 17 is a cross-sectional view taken along line EE of FIG. 16; FIG. 17 is a cross-sectional view taken along line DD of FIG. 16 showing Example 2; FIG. 11 is a plan view showing a second form of Example 2; It is a perspective view which shows a cross column.

The contents of the present invention will be described in detail below using examples.

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 together by a sealing material 40, and liquid crystal is sandwiched between the TFT substrate 100 and the counter substrate 200. As shown in FIG. The TFT substrate 100 is formed to be larger than the counter substrate 200 , and the portion where the TFT substrate 100 is one sheet serves as the terminal portion 150 . The terminal portion 150 is formed with terminals for connecting an IC driver 160 for driving the liquid crystal display panel, and a flexible wiring board for supplying a power source, a video signal, a clock, and the like to the liquid crystal display panel.

In FIG. 1, scanning lines 10 extend in a first direction in a display area 500 and are arranged in a second direction. Also, the video signal lines 20 extend in the second direction and are arranged in the first direction. Pixels 30 are regions surrounded by the scanning lines 10 and the video signal lines 20 . As the definition becomes higher, the area of the pixel 30 is reduced to 78 μm or less in the extending direction of the video signal line and 26 μm or less in the extending direction of the scanning line. Pixels 30 include red pixels, green pixels, and blue pixels. A set of red, green, and blue pixels is sometimes called a pixel, but in this specification, each red, green, and blue pixel is called a pixel 30 unless otherwise specified.

FIG. 2 is a plan view of the pixel 30 on the TFT substrate 100. FIG. FIG. 2 shows a configuration in which two pixels 30 are arranged horizontally. FIG. 2 is a plan view of a pixel portion in an IPS (In Plane Switching) type liquid crystal display device. In this specification, an IPS (In Plane Switching) system will be described as an example, but the present invention is not limited to this and can be applied to other liquid crystal display devices.

In FIG. 2, the scanning lines 10 extend in the horizontal direction and are arranged in the vertical direction, and the video signal lines 20 extend in the vertical direction and are arranged in the horizontal direction. A pixel electrode 111 is formed in a region surrounded by the scanning lines 10 and the video signal lines 20 . In FIG. 2, the semiconductor layer 103 extends in a U-shape from the through-hole 140 and passes under the scanning line 10 twice. A portion where the semiconductor layer 103 passes through the scanning line 10 serves as a TFT. That is, the scanning line 10 serves as a gate electrode in this portion. The semiconductor layer 103 is connected to the contact electrode 107 through the through hole 120 , and the contact electrode 107 is connected to the pixel electrode 111 through the contact hole 130 . The pixel electrode 111 has a slit 1111 inside. In FIG. 2, the pixel electrode 111 is a plurality of linear electrodes with slits 1111, but the pixel electrode 111 may be a single linear electrode without slits.

In this specification, a portion connecting the semiconductor layer 103 and the video signal line 20 or the semiconductor layer 103 and the contact electrode 107 is referred to as a through hole, and a portion connecting the contact electrode 107 and the pixel electrode 112 is referred to as a contact hole 130. call. Through holes and contact holes have the same function. Since the contact hole 130 is formed in the organic passivation film, the diameter of the hole is increased.

The contact hole is a mortar-shaped recess, and the contact hole 130 in FIG. 2 means the hole at the bottom of the contact hole. In FIG. indicates the edge of the capacitive insulating film at the bottom of the contact hole. 2, reference numeral 109 denotes an opening of the common electrode 109. FIG. Although 108 and 110 are rectangular, they may be polygonal or circular.

Since a large concave portion is formed in the portion of the contact hole 130, the material for the alignment film is repelled when the material for the alignment film is applied to this portion, making it difficult for the material to enter the portion. Hereinafter, the alignment film material may be simply called an alignment film. If the alignment film is only repelled from the contact hole, it is unlikely that display unevenness will be visible. get higher Furthermore, when the repelled regions in the contact holes are connected across a plurality of contact holes, the region where the alignment film is not formed becomes large, which may cause further display unevenness. Hereinafter, the region where the alignment film is not formed is also referred to as popping of the alignment film.

FIG. 3 is a cross-sectional view corresponding to AA of FIG. The TFT in FIG. 3 is a so-called top-gate type TFT, and LTPS (Low Temperature Poly-Si) is used as the semiconductor used. In FIG. 3, a first underlayer 101 made of SiN and a second underlayer 102 made of SiO ₂ are formed on a glass substrate 100 by CVD (Chemical Vapor Deposition). The role of the first base film 101 and the second base film 102 is to prevent impurities from the glass substrate 100 from contaminating the semiconductor layer 103 .

A semiconductor layer 103 is formed on the second base film 102 . This semiconductor layer 103 is obtained by forming an a-Si film on the second base film 102 by CVD and converting it into a poly-Si film by laser annealing. This poly-Si film is patterned by photolithography.

A gate insulating film 104 is formed on the semiconductor film 103 . This gate insulating film 104 is a SiO ₂ film made of TEOS (tetraethoxysilane). This film is also formed by CVD. A gate electrode 105 is formed thereon. The scanning line 10 shown in FIG. 2 also serves as the gate electrode 105 . Since the semiconductor layer passes under the scanning line 10 twice, two gate electrodes 105 are arranged in FIG. The gate electrode 105 is made of, for example, a MoW film.

An interlayer insulating film 106 is formed of SiO ₂ to cover the gate electrode 105 . The interlayer insulating film 106 is for insulating the gate electrode 105 and the contact electrode 107 . A through hole 120 for connecting the semiconductor layer 103 to the contact electrode 107 is formed in the interlayer insulating film 106 and the gate insulating film 104 . Photolithography for forming through holes 120 in the interlayer insulating film 106 and the gate insulating film 104 is performed simultaneously.

A video signal line 20 is formed on the interlayer insulating film 106 . The video signal line 20 is connected to the semiconductor layer 103 through the through hole 140 shown in FIG. That is, two TFTs are formed between the through hole 140 and the through hole 120 shown in FIG. A contact electrode 107 is formed in the same layer as the video signal line 20 on the interlayer insulating film 106 . The contact electrode 107 connects with the pixel electrode 112 through the contact hole 130 . The video signal lines 20 and contact electrodes 107 are made of, for example, an Al alloy, MoW, or a laminate of these.

An organic passivation film 108 is formed covering the video signal line 20 and the contact electrode 107 . The organic passivation film 108 is made of photosensitive acrylic resin. The organic passivation film 108 can be formed of acrylic resin, silicone resin, epoxy resin, polyimide resin, or the like. Since the organic passivation film 108 has a role as a planarizing film, it is formed thick. The film thickness of the organic passivation film 108 is 2 to 4 μm, but it is about 3.5 μm in the present invention.

A contact hole 130 is formed in the organic passivation film 108 to establish electrical connection between the pixel electrode 111 and the contact electrode 107 . After applying a photosensitive resin, when the resin is exposed to light, only the exposed areas are dissolved in a specific developer. That is, by using a photosensitive resin, the formation of a photoresist can be omitted. After forming a contact hole 130 in the organic passivation film 108, the organic passivation film 108 is completed by baking the organic passivation film at about 230.degree.

After that, ITO (Indium Tin Oxide), which will be the common electrode 109, is formed by sputtering, and then patterning is performed to remove the ITO from the contact hole 130 and its periphery. The common electrode 109 can be formed in a plane common to each pixel. After that, SiN to be the capacitor insulating film 110 is formed on the entire surface by CVD. After that, in the contact hole 130 , a through hole is formed in the capacitor insulating film 110 for conducting the contact electrode 107 and the pixel electrode 111 . After that, ITO is formed by sputtering and patterned to form the pixel electrode 111 . The planar shape of the pixel electrode 111 is as shown in FIG.

An alignment film material is applied on the pixel electrodes 111 by flexographic printing, inkjet, or the like. Although the alignment film material is liquid when applied, it may not enter the contact hole 130 due to surface tension.

After the alignment film material is applied, it is baked to form the alignment film 112 . The orientation film 112 is subjected to orientation treatment by rubbing treatment or photo-orientation treatment using ultraviolet rays. When a voltage is applied between the pixel electrode 111 and the common electrode 109, electric lines of force are generated as shown in FIG. This electric field rotates the liquid crystal molecules 301, and an image is formed by controlling the amount of light passing through the liquid crystal layer 300 for each pixel.

In FIG. 3, a counter substrate 200 is arranged with a liquid crystal layer 300 interposed therebetween. A color filter 201 is formed inside the opposing substrate 200 . The color filter 201 has red, green, and blue color filters formed for each pixel, thereby forming a color image. A black matrix 202 is formed between the color filters 201 to improve the contrast of the image. The black matrix 202 also serves as a light-shielding film for the TFTs, and prevents photocurrent from flowing through the TFTs. In addition, the black matrix covers the contact holes when viewed in plan.

An overcoat film 203 is formed to cover the color filters 201 and the black matrix 202 . The overcoat film 203 prevents the components of the color filter 202 from diffusing into the liquid crystal layer. An alignment film 112 is formed on the overcoat film 203 to determine the initial alignment of the liquid crystal. The orientation treatment of the orientation film 112 is the same as that for the orientation film 112 on the TFT substrate 100 side, using a rubbing method or a photo-orientation method.

FIG. 4 shows an example of display unevenness due to uneven thickness of the alignment film. Such display unevenness is caused by the occurrence of regions where the alignment film does not enter the contact holes. The contact hole is covered with a black matrix formed on the opposing substrate, but if the region where the film thickness of the alignment film is non-uniform extends to the region where the light is not shielded, it is visually recognized as unevenness. Further, when the regions where the alignment film is not formed are connected, the problem of light leakage becomes more serious.

5 to 7 are diagrams for explaining the reason why the alignment film is not formed in the contact hole. FIG. 5 is an enlarged plan view of the vicinity of contact hole 130 in FIG. In FIG. 5, the semiconductor layers and the like are omitted in order not to complicate the drawing. In FIG. 5, 109 indicates the opening of the common electrode. 130 indicates the opening at the bottom of the contact hole in FIG. Reference numeral 110 indicates an opening in the capacitive insulating film 110, and reference numeral 108 indicates an opening in the organic passivation film 108 at the bottom of the contact hole. The same applies to plan views of the vicinity of the contact holes that follow. Others are as explained in FIG.

FIG. 6 is a cross-sectional view taken along line BB of FIG. FIG. 6 omits an interlayer insulating film and below. Also, the alignment film is omitted in FIG. In FIG. 6, a contact hole is formed in the organic passivation film 108. A contact hole is formed in the organic passivation film 108 by photolithography. An opening is formed. In this opening, the contact electrode 107 and the pixel electrode 111 are connected. A common electrode 109 is formed on the organic passivation film 108, but the common electrode 109 is removed from the contact hole 130 and its periphery. When the contact hole 130 has such a shape, a phenomenon occurs in which the alignment film is not formed in the contact hole.

FIG. 7 is a schematic cross-sectional view for explaining this. Since the organic passivation film 108 is thick and has an overwhelming effect on the shape of the contact hole, only the organic passivation film 108 is shown in FIG. Actually, the capacitive insulating film 110, the pixel electrode 111, and the like are formed on the organic passivation film, but the cross-sectional shape can be considered to follow the organic passivation film 108 substantially. FIG. 7A shows a state in which a liquid alignment film material 112 is applied on the organic passivation film 108 after contact holes are formed in the organic passivation film 108 . In FIG. 7A, air 60 is caught in the bottom of the contact hole. This air is directed upwards, as indicated by the arrows.

FIG. 7B shows that when the alignment film material 112 is divided by the bubbles 60, the alignment film material 112 moves toward the periphery of the contact hole, which is a stable position. The arrow indicates the direction in which the alignment film material is directed. FIG. 7C is a cross-sectional view showing a region where the alignment film material 112 stably exists. As shown in FIG. 7(c), the alignment film material 112 is stably present on the bank of the outer circumference of the contact hole, and the alignment film material 112 is not formed inside the contact hole. Furthermore, the film thickness of the alignment film increases in the vicinity of the contact hole. This causes display unevenness.

FIG. 8 is a plan view showing the configuration of the present invention for dealing with this. FIG. 8 is a plan view of the vicinity of the contact hole 130, and the basic configuration is the same as that explained in FIG. 8 is different from FIG. 5 in that a concave portion is formed near the contact hole 130 in the organic passivation film 108 as indicated by the region 70 .

9 is a cross-sectional view taken along line CC of FIG. 8. FIG. In FIG. 9, a recess 70 having a depth h1 is formed on the bank of the organic passivation film 108 in the vicinity of the contact hole. This depth h1 is about 0.3 to 1 μm. The depth h1 is the difference between the top of the bank of the organic passivation film 108 and the bottom of the recess (difference in distance from the surface of the substrate or the surface of the interlayer insulating film). Such recesses 70 of the organic passivation film 108 can be formed by using half exposure. That is, the concave portion 70 can be formed by exposing several tens of percent of the exposure amount of the contact hole 130 portion. The depth of the concave portion 70 can be controlled by the exposure amount of the half exposure.

Since the concave portion 70 can be formed by half exposure, the process load does not increase. By forming such recesses 70 in the organic passivation film 108 , the common electrode 109 , capacitive insulating film 110 and pixel electrode 111 formed on the organic passivation film 108 are formed along the shape of the organic passivation film 108 . will be

FIG. 10 is a schematic cross-sectional view for explaining that the phenomenon that the alignment film 112 is not applied to the contact hole 130 can be eliminated by shaping the vicinity of the contact hole as shown in FIG. In FIG. 10A, an alignment film material 112 is applied on the organic passivation film 108 having contact holes and recesses formed therein. The presence of air bubbles 60 at the bottom of the contact hole is the same as in FIG. 7(a). The movement of the bubble 60 upward is the same as in FIG. 7(a).

FIG. 10(b) shows a state in which air bubbles have escaped from the contact hole. In FIG. 10B, a concave portion is formed around the bank of the contact hole in the organic passivation film 108, thereby forming a convex portion around the contact hole. Due to the presence of the protrusions, the periphery of the contact hole is no longer a stable place for the alignment film material. Due to the presence of the protrusions, the alignment film material 112 moves so as to be divided into either the contact hole side from the protrusions or the recess side from the protrusions.

Then, the alignment film material 112 moved to the contact hole side flows into the bottom of the contact hole, and the contact hole is also filled with the alignment film material 112 . This state is shown in FIG.

FIG. 11 is a schematic cross-sectional view when the organic passivation film 108 has different heights on both sides of the recess around the contact hole. In FIG. 11, the recess is formed in a region where the thickness of the organic passivation film 108 on the side closer to the contact hole is not thicker than the thickness of the organic passivation film 108 in other regions. As a result, the thickness of the convex portion is smaller than the thickness of the bulk portion (display area) of the organic passivation film. That is, the thickness of the convex portion of the organic passivation film 108 (height from the substrate surface) is greater than the thickness of the bulk portion of the organic passivation film (height from the substrate surface). It is thinned by h2. Even in the case of such a shape, the depth of the concave portion can be considered as the difference h1 between the top of the convex portion and the bottom point of the concave portion.

FIG. 12 is a cross-sectional view showing the detailed shape of the organic passivation film 108. As shown in FIG. If the concave portion of the organic passivation film 108 in the present invention and the resulting convex portion are too far from the contact hole, the effect is lost. 8 and 12 are diagrams showing the positions of the concave portion and the convex portion. As shown in FIG. 12, the width d2 of the recess is defined from the protrusion near the contact hole to the portion where the organic passivation film has a constant thickness. Also, the distance from the end of the contact hole of the organic passivation film 108 to the apex of the projection is defined as d1. d1 and d2 in FIG. 8 are plan views corresponding to d1 and d2 in FIG.

The value of d1 is highly effective in the range of 2 μm to 5 μm. Also, the value of d2 is highly effective in the range of 2 μm to 5 μm. Also, the depth h1 of the recess is 0.3 μm to 1 μm. Note that the distance d3 from the video signal line of the concave portion in FIG. 8 does not have as large an effect as d1 and d2, but is 1 μm or more in this embodiment.

As shown in FIG. 12, a feature of the present invention is that when the vicinity of the contact hole of the organic passivation film 108 is viewed in a cross section in the same direction as the extending direction of the video signal line, the cross-sectional shape of the organic passivation film 108 is the same as that of the contact hole. A convex portion appears first, and then a concave portion appears as the distance from the edge of . In other words, the shape of the organic passivation film 108 in FIG. 12 is such that the end of the contact hole of the organic passivation film 108 is zero, the direction in which the video signal line extends (horizontal direction in FIG. 12) is x, and the substrate Assuming that the vertical direction is y and the upper side curve of the organic passivation film 108 is represented by y=f(x), this means that the sign of the second derivative of the curve y with respect to x changes once.

In FIG. 12, the secondary derivative of f(x) is negative in the vicinity R1 of the convex portion of the organic passivation film 108, and positive in the vicinity R2 of the bottom of the concave portion. After that, as x further increases, the sign of the second derivative of f(x) becomes negative again.

A feature of the present invention is that the region where the sign of f(x) changes once is generated within 4 to 10 μm from the end of the contact hole of the organic passivation film 108 . More preferably, such a region where the sign of f(x) changes once occurs within 3 to 8 μm from the end of the contact hole of the organic passivation film 108 .

By the way, f(x) shown in FIG. 12 can often be approximated by ^ax2 + ^bx4 . That is, when the curve y on the upper side of the organic passivation film 108 is represented by ax ² +bx ⁴ , it can be said that the sign of the second derivative of the curve y with respect to x changes once.

FIG. 13 is a plan view of the vicinity of the contact hole showing another aspect of this embodiment. FIG. 13 differs from FIG. 8 in that the width of the concave portion 70 formed in the organic passivation film in the direction in which the scanning lines extend is small. The recess 70 creates a trigger for the alignment film material to flow into the contact hole. Therefore, if the width of the concave portion 70 cannot be increased due to layout reasons, the shape shown in FIG. 13 may be used. Note that the dimensions such as d1 and d2 are the same as those explained in FIG. Also, the depth of the recess may be the same as that explained in FIG. 9 or shallower than that.

In FIG. 14, three concave portions 70 each having a small width in the scanning line extending direction are formed in the scanning line extending direction. Individual recesses 70 are similar to those described in FIG. Although it may be necessary to separate the concave portions in this way due to layout requirements within the pixel, the effect of the present invention can be maintained.

FIG. 15 shows a case where the concave portion 70 formed in the organic passivation film is formed in common for a plurality of pixels. Since the recesses 70 are formed by half exposure, it may be better to form the recesses all at once from the process conditions. Even in such a configuration, the effects of the present invention can be maintained. In FIG. 15, the recess 70 is formed in common for two pixels, but it may be formed in common for three or more pixels.

In the above embodiment, two recesses 70 are formed in the organic passivation film 108 so as to sandwich the contact hole in the extending direction of the video signal line. The effects of the present invention can be obtained. Incidentally, instead of forming the concave portion in the organic passivation film, an opening (removal portion) may be provided in a part of the capacitive insulating film 110 . In this case, in order to avoid connection between the pixel electrode and the common electrode, it is necessary to remove the capacitive insulating film in a region sufficiently spaced from the edge of the opening of the common electrode.

FIG. 16 is a plan view of the vicinity of a contact hole showing Embodiment 2 of the present invention. A feature of this embodiment is that the convex portion 80 is formed in the vicinity of the contact hole 130 . That is, in Example 1, by forming a concave portion in the organic passivation film 108, a convex portion is formed on the side closer to the contact hole than the concave portion is formed as a result, and the alignment film material 112 is inserted into the contact hole 130. Makes it easy to flow. According to the present invention, the protrusions 80 are formed directly on the organic passivation film 108 near the contact holes 130 to facilitate the flow of the alignment film material 112 into the contact holes 130 .

In FIG. 16, the video signal line 20 extends in the vertical direction, and the common metal wiring 90 is formed so as to overlap the video signal line 20 when viewed from above. Also, a common metal wiring 90 is formed overlapping with the scanning line 10 . A common metal line 90 is used to prevent a voltage drop in the common electrode 109, which is made of ITO with high resistance. FIG. 17 is a cross-sectional view taken along line EE of FIG. 17, a first base film 101, a second base film 102, a gate insulating film 104, and an interlayer insulating film 106 are formed on a TFT substrate 100, and video signal lines 20 are arranged on the interlayer insulating film 106. In FIG. ing. An organic passivation film 108 is formed to cover the video signal line 20, and a common electrode 109 made of ITO is formed thereon. A common metal wiring 90 is formed overlapping the video signal line 20, a capacitive insulating film 110 is formed covering the common metal wiring 90, and an alignment film 112 is formed thereon.

The common metal wiring 90 has a core made of Al and is formed with a relatively large thickness of 150 nm to 500 nm. Therefore, the resistance is low, and voltage drop at the common electrode can be prevented. In some cases, the common metal wiring 90 has a core made of Al, a MoW layer with a thickness of about 10 nm as an anti-oxidation layer made of ITO as a lower layer, and a MoW layer with a thickness of about 10 nm as a barrier layer as an upper layer. The common metal wiring may be formed with the same structure as the video signal line. Further, although the common metal wiring 90 is formed above the common electrode 109 in FIG. 17, it may be formed below the common electrode 109 .

A feature of this embodiment is that the convex portion 80 is formed by forming the common metal wiring 90 from the tapered portion of the contact hole of the organic passivation film 109 to part of the bulk portion. FIG. 18 shows a cross-sectional view of this embodiment. 18 is a cross-sectional view taken along line DD of FIG. 16. FIG. In FIG. 18, a convex portion 80 is formed by a common metal wiring 90 on the bank portion of the contact hole of the organic passivation film 109 .

In FIG. 18, since the convex portion 80 is formed inside the opening of the common electrode 109 , the common metal wiring 90 for the convex portion 80 is formed directly on the organic passivation film 108 . A capacitive insulating film 110 , a pixel electrode 111 and an alignment film 112 are formed to cover the common metal wiring 109 . In FIG. 18, in the vicinity of the bank of the contact hole, first, a convex portion 80 is formed and then a concave portion is formed.

In FIG. 18, when the edge of the organic passivation film 108 in the contact hole is zero, the distance in the direction away from the contact hole is x, and the curve of the upper surface of the alignment film 112 is y=f(x), then f(x). , the sign of the second derivative changes at least once as the distance from the contact hole increases. That is, in FIG. 18, the sign of the second derivative is negative in the vicinity of the region indicated by R1, and the sign of the second derivative is positive in the region indicated by R2. The region where the sign of the second derivative changes exists within a range of 4 to 10 nm, more preferably within a range of 5 to 8 μm, from the inner edge of the contact hole.

Note that the curve f(x) on the upper side of the alignment film in FIG. 18 can be approximated by ax ² +bx ⁴ in many cases. That is, in the case of FIG. 18 as well, when the curve y on the upper side of the alignment film is represented by ax ² +bx ⁴ , it can be said that the sign of the second derivative of the curve y with respect to x changes once.

FIG. 19 is a plan view of the vicinity of the contact hole showing the second form in this embodiment. Also in FIG. 19, forming a convex portion 80 on the bank in the vicinity of the contact hole is the same as in FIG. However, in this embodiment, the method of forming the convex portion 80 is different. In this embodiment, the convex portion 80 is formed at the same time as the cross column 250 formed on the TFT substrate side.

Spacers are also required in the display area in order to maintain the distance between the TFT substrate and the opposing substrate. FIG. 20 is a perspective view showing the shape of this spacer. In FIG. 20, first rod-shaped spacers 250 extending in the same direction as the video signal lines 20 are formed on the TFT substrate side, and second rod-shaped spacers 251 extending in the same direction as the scanning lines 10 are formed on the opposite substrate side. The first spacer 250 and the second spacer 251 are brought into contact with each other in a cross shape to secure a space between the TFT substrate and the opposing substrate.

FIG. 19 describes this as a plan view. At the intersection of the scanning line 10 and the video signal line 20 in FIG. 19, the first spacer 250 is formed on the video signal line 20 when viewed from above. In addition, the second spacers 251 are formed on the scanning lines 10 in a plan view. Since the second spacers 251 are formed on the opposing substrate side, they are indicated by dotted lines in FIG.

In FIG. 19, a convex portion 80 is formed with a contact hole 130 interposed therebetween. This convex portion 80 is formed at the same time as the first spacer 250 . The height of the protrusions 80 is much lower than the height of the first spacers 250 . Since the first spacers 250 are formed by photolithography, it is possible to form the low-height projections 80 at the same time as the first spacers 250 by using the half-exposure technique.

The FF section in FIG. 19 is the same as in FIG. However, the difference is that instead of the common metal wiring forming the convex portion 80, a protrusion made of the same material as the columnar spacer, that is, an organic material is formed. Also in the case of FIG. 19, the effect is the same as that of the present embodiment described in FIGS. 16 and 18. FIG.

Also in this embodiment, two protrusions are formed so as to sandwich the contact hole in the extending direction of the video signal line, but the effect of the present invention can be obtained even if only one of the protrusions is formed.

In the above description, the case where the pixel electrode exists above the common electrode has been described. On the other hand, there is also a configuration in which a common electrode having a slit is arranged on a planar pixel electrode via a capacitive insulating film. The present invention can also be applied to an IPS liquid crystal display device having such a configuration.

Furthermore, the present invention can be applied to a liquid crystal display device having an organic passivation film and having a structure in which a contact hole is formed in the organic passivation film, other than the IPS type liquid crystal display device.

DESCRIPTION OF SYMBOLS 10... Scanning line 20... Video signal line 30... Pixel 40... Seal material 50... Display unevenness 60... Air bubble 70... Concave part 80... Convex part 90... Common metal wiring 100... TFT substrate 101 First base film 102 Second base film 103 Semiconductor layer 104 Gate insulating film 105 Gate electrode 106 Interlayer insulating film 107 Contact electrode 108 Organic passivation film 109 Common electrode , 110...Capacitor insulating film 111...Pixel electrode 112...Alignment film 120...First through hole 130...Contact hole 140...Second through hole 150...Terminal section 160...Driver IC 200...Counter substrate , 201... Color filter 202... Black matrix 203... Overcoat film 250... First cross column 251... Second cross column

Claims (4)

a glass substrate, a first scanning line, a second scanning line adjacent to the first scanning line, a video signal line intersecting the first scanning line and the second scanning line, and the image a semiconductor layer connected to a signal line and overlapping the first scanning line; a contact electrode connected to the semiconductor layer; a pixel electrode connected to the contact electrode through a contact hole; an organic passivation film; A common electrode having a first surface facing an organic passivation film, an inorganic insulating film covering a second surface of the common electrode opposite to the first surface, and a metal layer provided between the glass substrate and the inorganic insulating film. and a first alignment film in contact with the pixel electrode and the inorganic insulating film;
a counter substrate;
A liquid crystal display device comprising a liquid crystal sandwiched between the TFT substrate and the counter substrate,
both the pixel electrode and the common electrode are formed of a transparent conductive material;
the contact hole includes a hole in the organic passivation film;
The metal layer further has a linear portion formed parallel to the first scanning line and the second scanning line,
Between the contact hole and the second scanning line, the linear portion is not connected to all of the scanning line, the video signal line, the semiconductor layer, the contact electrode, the common electrode and the pixel electrode. ,
The linear portion overlaps the pixel electrode,
The linear portion forms a convex portion by raising the height of the inorganic insulating film from the glass substrate,
The alignment film is present on the bottom surface of the contact hole,
the metal layer is provided between the organic passivation film and the inorganic insulating film;
A liquid crystal display device , wherein the linear portion is formed in a tapered portion of the contact hole . The common electrode has an opening at a position overlapping the contact hole,
2. The liquid crystal display device according to claim 1, wherein said linear portion is positioned inside said opening. 2. The liquid crystal display device according to claim 1, wherein said linear portion directly contacts said organic passivation film and does not contact said common electrode. 4. The liquid crystal display device according to claim 3, wherein said linear portion does not overlap said contact electrode.

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