JP2010072457A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce lighting failure by reliably obtaining electric conduction between a switching element and a pixel electrode. <P>SOLUTION: A contact hole 27 is formed in a portion having no color layer 25a or the like, and therefore no color layer 25a or the like is present in the periphery of the contact hole 27 and thereby, the taper angle θ, which is an angle of the wall face in the contact hole 27, can be decreased. A pixel electrode to be connected to a drain electrode 26c through the contact hole 27 has a portion bent at the same angle as the taper angle θ, however, the angle is small, which reduces the possibility of generating cracks in the angled portion. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device that can reliably connect a switching element and a pixel electrode and reduce lighting failure.

  The liquid crystal display device has a structure in which a liquid crystal layer is sandwiched between an array substrate and a counter substrate. In addition, a liquid crystal display device that performs color display includes a colored layer (color filter) on a counter substrate. On the other hand, there is a liquid crystal display device including a colored layer on an array substrate, and the liquid crystal display device is referred to as a color filter on array type (hereinafter referred to as COA type) liquid crystal display device.

  In the COA type liquid crystal display device, a contact hole is formed in the colored layer in order to electrically connect the switching element below the colored layer and the pixel electrode above the colored layer.

  Usually, the colored layer contains a pigment for coloring, and has a function as a photosensitive resist when formed by photolithography. For this reason, the colored layer contains impurities such as carboxylic acid, and if these impurities dissolve into the liquid crystal, problems such as image burn-in may occur.

  Impurities can be removed by refining the pigment until no image quality problems occur, but this increases the development time and cost of the material.

  Therefore, the colored layer is often covered with an insulating layer made of a transparent resin or the like to prevent impurities from eluting. Since the insulating layer covers the unevenness of the joints between the colored layers, it contributes to the so-called gap uniformity and also prevents adverse effects on the image quality.

  FIG. 2 is a cross-sectional view schematically showing a partial cross section of the COA type liquid crystal display device.

  The colored layer, switching element, pixel electrode, contact hole, and insulating layer are given reference numerals 26a, 24, 27, and 28, respectively, in FIG.

  The colored layer 25 a and the like are formed on the insulating substrate 20 a and are partially removed at the position of the contact hole 27. The insulating layer 28 is also partially removed at substantially the same position. Thus, the contact hole 27 is formed in the insulating layer 28, and a part of the drain electrode 26c of the switching element 26 is exposed.

  Then, the pixel electrode 24 is formed on the insulating film 28 around the contact hole 27. The pixel electrode 24 is electrically connected to the drain electrode 26 c through the contact hole 27.

As shown in FIG. 6, at the position of the contact hole 27, the colored layer 25a and the like and the insulating layer 28 are provided.
Therefore, the taper angle θ which is the angle of the wall surface of the contact hole 27 is increased. The pixel electrode 24 bends at the same angle as the taper angle θ at the position of the contact hole 27. Thus, since the pixel electrode 24 is bent at a large angle, there is a high possibility that the bent portion will crack.

  For this reason, the drain electrode 26c and the pixel electrode 24 are not electrically connected, and many lighting failures may occur.

  In addition, a photosensitive resin is often used as a material for forming the insulating layer 28, but it is a liquid (referred to as a resist solution). The resist solution becomes thicker at the location due to surface tension.

  As shown in FIG. 7, the insulating layer 28 formed of a resist solution is also thick at the contact hole 27.

  Therefore, in order to form the contact hole 27 by removing the insulating layer 28 by exposure and development, it is necessary to make a deeper hole, and there is a possibility that variations in dimensions and shape after processing become large.

  For this reason, in the pixel where the area of the portion where the drain electrode 26c is exposed is narrowed, the drain electrode 26c and the pixel electrode 24 cannot be reliably conducted, and a lighting failure may occur.

Prior art document information related to the invention of this application includes the following.
Japanese Patent Application No. 2006-007126

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a liquid crystal display device capable of reliably connecting a switching element and a pixel electrode and reducing a lighting failure. It is in.

  In order to solve the above problems, a liquid crystal display device of the present invention is provided at an intersection of an insulating substrate, a plurality of scanning lines and signal lines provided on the insulating substrate, and the scanning lines and signal lines. The switching element, the scanning line, the signal line, the insulating film covering the switching element, the pixel electrode formed on the insulating film, and the pixel electrode and the switching element so as to be electrically connected A contact hole provided in the insulating film; a counter substrate disposed opposite to the insulating substrate; and a liquid crystal layer sandwiched between the insulating substrate and the counter substrate, wherein a colored layer is provided on the insulating substrate. And the insulating film covers the colored layer, and the contact hole is formed in a portion not having the colored layer.

  According to the present invention, since the contact hole is formed in a portion having no colored layer, the taper angle, which is the angle of the wall surface of the contact hole, can be reduced, and thus the conduction between the switching element and the pixel electrode is ensured. Can be planned. As a result, lighting failure can be reduced.

  According to the liquid crystal display device of the present invention, since the contact hole is formed in a portion having no colored layer, the taper angle, which is the angle of the wall surface of the contact hole, can be reduced. Conduction can be reliably achieved. As a result, lighting failure can be reduced.

  Embodiments of a liquid crystal display device according to the present invention will be described below with reference to the drawings. Here, a COA type liquid crystal display device will be described as an example. In the description, the same parts are denoted by the same reference numerals.

  FIG. 1 is a perspective view showing a liquid crystal display device according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view schematically showing a cross section cut along the line AA of FIG. FIG. 3 is an enlarged plan view showing the broken line portion R of FIG. 2 as viewed from the counter substrate 11 side. FIG. 4 is an enlarged cross-sectional view showing a cross section cut along the line BB in FIG. FIG. 5 is an enlarged cross-sectional view showing a state in the middle of manufacture in a cross section cut along the line BB in FIG.

  FIG. 2 is a schematic diagram, and features in the embodiment of the present invention are mainly shown in FIGS. 3 to 5, the spacer is not shown for convenience.

  The liquid crystal display device includes an array substrate 10 having a display region 12, a counter substrate 11 disposed to face the array substrate 10 at a predetermined interval, and an unillustrated integrated circuit that drives the display region 12. A backlight unit 13 serving as a light source is disposed on the lower surface of the array substrate 10. The backlight unit 13 includes a light emitting diode (LED).

  The array substrate 10 includes a transparent insulating substrate 20a made of insulating glass or the like, a multilayer thin film 21 formed on the insulating substrate 20a, and an alignment film (not shown). On the insulating substrate 20a, a plurality of signal lines 22 shown in FIG. 3 and scanning lines (not shown) are arranged in a grid pattern with the multilayer thin film 21 interposed therebetween. Further, auxiliary capacitance lines (not shown) are arranged along each scanning line, and Indium-Tin-Oxide (hereinafter referred to as “ITO”) so as to substantially correspond to the pixel openings on the squares formed by the auxiliary capacitance lines and the signal lines 22. A pixel electrode 24 made of a transparent conductive material is disposed.

  The display area 12 is an area constituted by all the pixel electrodes 24.

  The auxiliary capacity line is for forming an electrostatic capacity (generally referred to as an auxiliary capacity) by the auxiliary capacity line and the pixel electrode 24 in order to hold the potential of the pixel electrode 24.

  A switching element 26 for controlling the pixel electrode 24 is formed in the vicinity of each intersection of the scanning line and the signal line 22.

  An organic insulating film 25 that is a part of the multilayer thin film 21 is formed on the switching element 26. At that time, first, for example, a green resist solution is applied onto the insulating substrate 20a on which the switching element 26 is formed by spinner and prebaked at about 90 ° C.

  Next, a mask pattern is disposed at a predetermined position excluding the periphery of the drain electrode 26c, and exposure with ultraviolet rays having an intensity of 150 mJ / square cm is performed. Next, development is performed for about 40 seconds using a tetramethylammonium hydride (TMAH) aqueous solution of about 0.1% by weight.

  Next, the insulating substrate 20a is washed with water and post-baked at about 200 ° C. for about 1 hour. Thus, the colored layer 25a is formed as a green colored layer, for example. Since the mask pattern is not arranged around the drain electrode 26c, the colored layer 25a is not formed around the drain electrode 26c.

  Thereafter, similarly, the colored layer 25b and the colored layer 25c are formed, for example, as a blue colored layer and a red colored layer. These colored layers are also not formed around the drain electrode 26c due to the arrangement of the mask pattern.

  On each colored layer, an insulating film 28 made of, for example, a transparent acrylic resin is formed by the same process as the colored layer process. The insulating film 28 is also formed on the drain electrode 26c.

  FIG. 5 is a diagram showing a state in which the contact hole 27 is subsequently formed in the insulating film 28. As shown in FIG. 5, the insulating film 28 around each drain electrode 26c is partially removed to contact holes. 27 is formed.

  Next, the pixel electrode 24 is formed on the insulating film 28 around each contact hole 27.

  Here, for example, ITO is deposited by sputtering, the ITO is patterned, and the pixel electrode 24 is formed.

  The pixel electrode 24 is electrically connected to the switching element 26 through the contact hole 27.

  Here, the switching element 26 uses a thin film transistor (hereinafter referred to as “TFT”) including a gate electrode 26a, a source electrode 26b, and a drain electrode 26c. The gate electrode 26a is electrically connected to the scanning line. The source electrode 26 b is electrically connected to the signal line 22. The drain electrode 26 c is electrically connected to the pixel electrode 24 through the contact hole 27.

  A black matrix layer (hereinafter referred to as “BM layer”) 31 for shielding light is formed so as to surround the display region 12 constituted by the pixel electrodes 24. The BM layer 31 is formed using a black resin by a process similar to the process of the colored layer.

  Next, an alignment film material made of, for example, polyimide is applied on the insulating substrate 20a, and an alignment process is performed on the alignment film material, thus forming an alignment film (not shown). The array substrate 10 is a general term for the insulating substrate 20a and those formed thereon after the formation of the alignment film.

  A necessary number of spherical spacers 32 are disposed on the array substrate 10 by, for example, an inkjet method. The spherical spacer 32 is a sphere made of a resin (such as a transparent acrylic resin), and the diameter of the sphere is, for example, 3 to 6 μm. Alternatively, although not shown, a necessary number of columnar spacers are arranged on the array substrate 10.

  The counter substrate 11 has a transparent insulating substrate 20b made of insulating glass or the like, and is disposed to face the array substrate 10. The counter substrate 11 has a transparent electrode 33 made of ITO and an alignment film (not shown) on the liquid crystal layer 30 side. The transparent electrode 33 is formed by patterning ITO deposited by sputtering, for example. In addition, an alignment film material made of polyimide, for example, is applied to the entire surface of the insulating substrate 20b, and an alignment process is performed on the alignment film material, thus forming an alignment film. The counter substrate 11 is a general term for the insulating substrate 20b and the substrate formed thereon after the formation of the alignment film.

  A part of the frame region surrounding the BM layer 31 in the counter substrate 11 is left as a liquid crystal injection port (not shown), and the sealing material 29 is applied to the frame region other than the liquid crystal injection port. Thereafter, the counter substrate 11 is bonded to the array substrate 10 by the sealing material 29. The array substrate 10 and the counter substrate 11 are mounted on a single wafer type sealing jig, evacuated and further baked at a curing temperature of about 170 ° C. for about 30 minutes. The distance between the array substrate 10 and the counter substrate 11 is made uniform by the spherical spacer 32 or the like.

  The array substrate 10 and the counter substrate 11 in this state are called cells. When the cell is obtained, the inside of the cell, that is, between the array substrate 10 and the counter substrate 11 is evacuated, and, for example, a nematic liquid crystal material added with a chiral agent is injected from the liquid crystal injection port. Thereafter, the liquid crystal injection port is closed by a sealing material (not shown) such as an ultraviolet curable resin, and the sealing material is cured by ultraviolet rays.

  Thus, the liquid crystal layer 30 is sandwiched between the array substrate 10 and the counter substrate 11. The gap (thickness of the liquid crystal layer) is made uniform by the spherical spacer 32 or the like.

  A polarizing plate (not shown) is disposed on the surface of the array substrate 10 opposite to the liquid crystal layer 30 side. Similarly, a polarizing plate (not shown) is disposed on the surface of the counter substrate 11 opposite to the liquid crystal layer 30 side.

  In the liquid crystal display device according to the present embodiment, each TFT 26 is turned on / off by a scanning signal given to each scanning line, and the liquid crystal layer blocks or transmits light. In addition, the video signal given to each signal line 22 is given to the pixel electrode 24 via the TFT 26, whereby the intensity of transmitted light is in accordance with the video signal. Thus, each pixel electrode region is individually lit, and the liquid crystal display device displays an image.

  Here, the structure of the contact hole 27 and the vicinity thereof will be described with reference to FIGS.

  First, since the contact hole 27 is formed in a portion that does not have the colored layer 25a or the like, the colored layer 25a or the like does not exist around the contact hole 27. Therefore, as shown in FIG. The taper angle θ, which is the angle of the wall surface, can be reduced.

  For example, if the taper angle θ is large, there is a high possibility that the pixel electrode 24 that bends at the same angle as the taper angle θ is cracked. However, in the present embodiment, the taper angle θ can be reduced. Therefore, the possibility of cracking in the pixel electrode 24 can be reduced, and conduction between the drain electrode 26c and the pixel electrode 24 can be ensured. As a result, lighting failure can be reduced.

  For this purpose, the taper angle θ is preferably at least 60 degrees or less, and is optimal if it is 45 degrees or less.

  In addition, when the colored layer is formed, the surface of the insulating substrate 20a is generally flat although there is a step due to a portion having no colored layer. Therefore, the thickness of the insulating layer 28 formed by applying a resist solution on the surface thereof is made uniform, and is not particularly thick in a portion having no colored layer. Therefore, the size and shape variations after the contact hole 27 is formed are not increased, and the drain electrode 26c and the pixel electrode 24 can be reliably connected to each other, so that lighting failure can be reduced.

  It is not preferable that the taper angle θ is too small. For example, when the taper angle θ is less than 18 degrees, it is necessary to increase a space for arranging the contact hole 27 as the distance of the taper portion becomes longer, and the aperture ratio of the pixel is lowered. Also, the taper angle θ is less than 18 degrees because the resist solution material is such that the taper portion is easily melted, or the taper portion is easy to melt. Often has become. In this case, it is difficult to accurately form the through hole, and in some cases, a resist solution residue remains in the through hole. Therefore, the taper angle θ is preferably at least 18 degrees or more, and is optimal if it is 25 degrees or more.

  Therefore, according to the liquid crystal display device according to the present embodiment, the insulating substrate 20a, the plurality of scanning lines and signal lines 22 provided on the insulating substrate, and the switching provided at the intersection of the scanning lines and signal lines. The element 26, the insulating film 28 covering the scanning line, the signal line, and the switching element, the pixel electrode 24 formed on the insulating film, and the insulating film are provided so as to electrically connect the pixel electrode and the switching element. And the liquid crystal layer 30 sandwiched between the insulating substrate and the counter substrate, and has a colored layer 25a on the insulating substrate, The insulating film covers the colored layer, and the contact hole 27 is formed in a portion having no colored layer, so that the taper angle θ that is the angle of the wall surface of the contact hole 27 can be reduced. It can be reliably conduction in the electrode 26c and the pixel electrode 24. As a result, lighting failure can be reduced.

  The taper angle of the contact hole 27 is preferably at least 18 degrees to 60 degrees, and most preferably 25 degrees to 45 degrees.

  In the present embodiment, the insulating film 28 is made of a transparent acrylic resin, but other materials may be used.

It is a perspective view which shows the liquid crystal display device by this invention. It is an expanded sectional view which shows roughly the cross section formed by cutting along the AA line of FIG. FIG. 3 is an enlarged plan view showing a broken line portion R of FIG. 2 viewed from the counter substrate 11 side. It is an expanded sectional view which shows the cross section cut | disconnected along the BB line of FIG. It is an expanded sectional view which shows the mode in the middle of manufacture in the cross section cut | disconnected along the BB line of FIG. It is sectional drawing which shows the 2 layer structure of the colored layer 25a and the insulating layer 28 in the position of the contact hole 27 in the past. It is sectional drawing which shows the thickness of the insulating layer 28 in the position of the contact hole 27 in the past.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Array substrate 11 ... Opposite substrate 12 ... Display area 13 ... Backlight unit 20a, 20b ... Insulating substrate 21 ... Multilayer thin film 22 ... Signal line 24 ... Pixel electrode 25 ... Organic insulating film 25a, 25b, 25c ... Colored layer 26 ... Switching element (TFT)
26a ... Gate electrode 26b ... Source electrode 26c ... Drain electrode 27 ... Contact hole 28 ... Insulating film 29 ... Sealing material 30 ... Liquid crystal layer 31 ... BM layer 32 ... Spherical spacer 33 ... Transparent electrode

Claims (4)

An insulating substrate;
A plurality of scanning lines and signal lines provided on the insulating substrate;
Switching elements provided at intersections of the scanning lines and the signal lines;
An insulating film covering the scanning line, the signal line, and the switching element;
A pixel electrode formed on the insulating film;
A contact hole provided in the insulating film to electrically connect the pixel electrode and the switching element;
A counter substrate disposed opposite the insulating substrate;
A liquid crystal layer sandwiched between the insulating substrate and the counter substrate,
Having a colored layer on the insulating substrate;
The insulating film covers the colored layer;
The liquid crystal display device, wherein the contact hole is formed in a portion not having the colored layer.   The liquid crystal display device according to claim 1, wherein the insulating film is made of a transparent acrylic resin.   The liquid crystal display device according to claim 1, wherein a taper angle of the contact hole is 25 degrees to 45 degrees.   The liquid crystal display device according to claim 1, wherein a taper angle of the contact hole is 18 degrees to 60 degrees.

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