Patent Publication Number: US-9417485-B2

Title: Liquid crystal display device

Description:
CLAIM OF PRIORITY 
     This application is a continuation of U.S. application Ser. No. 13/852,565, filed on Mar. 28, 2013, which application is a continuation of U.S. application Ser. No. 12/832,221, filed Jul. 8, 2010 and which application claims priority from Japanese application serial No. 2009-161616 filed on Jul. 8, 2009, the content of which is hereby incorporated by reference into this application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a display device and more particularly to an in-plane switching (IPS) type liquid crystal display device improved in reliability of a seal portion. 
     2. Description of the Related Art 
     A liquid crystal display device includes a TFT substrate on which pixel electrodes, thin film transistors (TFTs), and the like are formed in a matrix, a counter substrate which is disposed to face the TFT substrate and on which color filters and the like are formed at positions corresponding to the pixel electrodes of the TFT substrate, and liquid crystal interposed between the TFT substrate and the counter substrate. An image is formed by controlling the transmittance ratio of light through liquid crystal molecules for each pixel. 
     The liquid crystal display device is flat and light in weight, and therefore the application of liquid crystal display device has expanded in various fields from large display devices such as TVs to small display devices such as mobile phones or digital still cameras (DSCs). On the other hand, the liquid crystal display device has a problem of viewing angle characteristics. Viewing angle characteristics refer to a phenomenon where brightness varies or chromaticity varies between when a screen is seen from the front and when the screen is seen from a diagonal direction. The IPS type, in which the liquid crystal molecules are moved by a horizontal direction electric field, has excellent viewing angle characteristics. 
     In the IPS type, it is not necessary to form a pretilt angle for liquid crystal molecules in the vicinity of an alignment film. Therefore, an alignment axis for the alignment film can be formed not by a rubbing method but by a photo-alignment method. The photo-alignment has such an advantage that it does not cause static electricity compared to the rubbing method, for example. 
     The photo-alignment imparts anisotropy to an alignment film with the irradiation of polarized ultraviolet radiation so that liquid crystal molecules are aligned in a specific direction with respect to the alignment film. JP-A-2005-351924 describes a technique relating to the photo-alignment described above. 
     The photo-alignment is performed by irradiating an alignment film made of a polymer with ultraviolet radiation polarized in a specific direction. For example, when the polymer formed in a network is irradiated with polarized ultraviolet radiation, the polymer in a specific direction with respect to the polarized direction of ultraviolet radiation is damaged. This can form anisotropy for the alignment film for aligning liquid crystal molecules. There is no problem when only the alignment film is irradiated with polarized ultraviolet radiation for photo-alignment. However, when a portion other than the alignment film is irradiated, the irradiated portion is degraded by the ultraviolet radiation, causing problems. 
     IPS type liquid crystal display devices have been used for small liquid crystal display devices. Manufacturing small liquid crystal display devices one by one is inefficient. Therefore, a number of liquid crystal display devices are formed on a mother substrate to simultaneously manufacture a number of liquid crystal display devices. 
       FIG. 13  shows an example where  35  small liquid crystal display cells  1  are prepared on a mother substrate. A mother TFT substrate  1000  on which a number of TFT substrates  100  each having TFTs and pixel electrodes are formed, and a mother counter substrate  2000  on which a number of counter substrates  200  each having color filters and the like formed thereon are formed are aligned to each other. The mother TFT substrate  1000  and the mother counter substrate  2000  are bonded together with sealing materials  15  and a mother substrate sealing material  151 . In  FIG. 13 , each of hatched rectangles surrounded by the sealing material  15  indicates a range where an alignment film  113  is formed. 
     Small liquid crystal display devices are required to be thin. For example, the TFT substrate and the counter substrate each has a thickness of about 0.2 mm. However, such thin glass does not exist as a standard product. Moreover, such a thin glass substrate cannot undergo the process at present. Accordingly, in a state of the mother counter substrate  2000  or the mother TFT substrate  1000 , glass having a thickness of about 0.5 mm is used, and after the mother counter substrate  2000  and the mother TFT substrate  1000  are aligned to each other to form a mother substrate, the outer surface of the mother counter substrate  2000  or the mother TFT substrate  1000  is polished. 
     Polishing is often carried out with a combination of mechanical polishing and chemical polishing. In both mechanical polishing and chemical polishing, when abrasive enters the inside of the mother substrate, the liquid crystal cells  1  inside of the mother substrate become defective. Therefore, the inside of the mother substrate is protected by the mother substrate sealing material  151 . The mother substrate sealing material  151  formed at the periphery of the mother substrate is sealed with a mother-substrate end-sealing material  161 . The mother substrate shown in  FIG. 13  is separated into individual liquid crystal cells after polishing.  FIG. 14  shows the mother counter substrate  2000  constituting the mother substrate shown in  FIG. 13 , in which  35  counter substrates  200  are formed corresponding to the liquid crystal cells  1  in  FIG. 13 .  FIG. 14  shows the mother counter substrate  2000  at a stage before forming the sealing materials  15  or the mother substrate sealing material  151  thereon. In  FIG. 14 , the alignment film  113  is formed on each of the counter substrates  200 . Since the presence of the alignment film in a seal portion reduces the adhesive force of the sealing material  15 , the alignment film  113  is formed so as to avoid the seal portion and cover a display region. 
     In  FIG. 14 , the alignment film  113  is formed by flexographic printing. After forming the alignment film  113 , photo-alignment is performed on the alignment film  113  using polarized ultraviolet radiation. At this time, the entire surface of the mother counter substrate  2000  is irradiated with polarized ultraviolet radiation. This is because irradiation of the alignment films with polarized ultraviolet radiation one by one increases the manufacturing cost. Accordingly, also a portion where the alignment film is not formed is irradiated with polarized ultraviolet radiation. 
       FIG. 15  is a cross-sectional structure of one counter substrate  200  at an edge portion, showing a state of irradiation of polarized ultraviolet radiation for the photo-alignment. At the edge portion of the counter substrate  200 , a light shielding film  202 , a color filter  201 , an overcoat film  203 , and the like are formed as will be described later. The light shielding film  202  has a function to improve the contrast of a screen or to enhance the appearance of the screen periphery and is also referred to as black matrix. In the specification, however, the term “light shielding film” is used. As shown in  FIG. 15 , at a portion where the alignment film  113  is not present, a hatched portion  2031  of the overcoat film  203  is directly irradiated with ultraviolet radiation. Therefore, this portion  2031  of the overcoat film is degraded, whereby the overcoat film  203  allows moisture to easily penetrate. 
       FIG. 16  is a cross-sectional view of an edge portion of the counter substrate  200 , showing a state where after performing the photo-alignment using polarized ultraviolet radiation, the sealing material  15  is formed. Since the hatched portion  2031  of the overcoat film  203  is degraded by ultraviolet radiation, moisture penetrates through this portion  2031  of the overcoat film to the surface of the light shielding film  202 . 
       FIG. 17  is a cross-sectional view of an edge portion of a liquid crystal display panel in a state where the TFT substrate  100  and the counter substrate  200  are bonded together, and liquid crystal layer  300  is sealed therebetween. In  FIG. 17 , an inorganic passivation film  106 , an organic passivation film  107 , and the alignment film  113  are formed on the TFT substrate  100 . The light shielding film  202 , the color filter  201 , the overcoat film  203 , and the alignment film  113  are formed on the counter substrate  200 . In  FIG. 17 , since the hatched portion  2031  of the overcoat film  203  of the counter substrate  200  is degraded by ultraviolet radiation in the photo-alignment, moisture easily enters this portion from the outside. 
     When moisture enters the degraded overcoat film  2031 , the moisture reaches the light shielding film  202  and alters the light shielding film  202 . Especially when moisture acts on the light shielding film  202 , the adhesive force between the light shielding film  202  and the substrates  200  is reduced, which reduces the reliability in the seal portion. Moreover, when moisture acts on the light shielding film  202 , the electrical resistance of the light shielding film  202  is reduced, an electric field in the liquid crystal layer  300  is disturbed by the influence of the light shielding film  202 , and the contrast is reduced by light leakage. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to prevent moisture entering from the outside due to an overcoat film degraded by irradiation of ultraviolet radiation in photo-alignment from affecting a light shielding film. 
     To achieve the above-described object, the invention is specifically configured as follows. 
     (1) A liquid crystal display device includes: a TFT substrate having a display region where pixels each having a TFT and a pixel electrode are formed in a matrix; a counter substrate bonded to the TFT substrate with a sealing material in a seal portion at a periphery thereof and having a display region where a light shielding film and color filters of three colors are formed, an overcoat film is formed so as to cover the color filters of three colors, and an alignment film is formed so as to cover the overcoat film; and liquid crystal sealed between the TFT substrate and the counter substrate, wherein in the counter substrate, the alignment film is subjected to an alignment treatment by photo-alignment, and the alignment film is not formed in the seal portion; and in the seal portion of the counter substrate, the light shielding film, a color filter of one color among the color filters of three colors, and the overcoat film are stacked in this order, and the sealing material is formed on the overcoat film. 
     (2) A liquid crystal display device includes: a TFT substrate having a display region where pixels each having a TFT and a pixel electrode are formed in a matrix; a counter substrate bonded to the TFT substrate with a sealing material in a seal portion at a periphery thereof and having a display region where a light shielding film and color filters of three colors are formed, an overcoat film is formed so as to cover the color filters of three colors, and an alignment film is formed so as to cover the overcoat film; and liquid crystal sealed between the TFT substrate and the counter substrate, wherein in the counter substrate, the alignment film is subjected to an alignment treatment by photo-alignment, and the alignment film is not formed in the seal portion; and in the seal portion of the counter substrate, the light shielding film and color filters of a plurality of colors among the color filters of three colors are stacked, the overcoat film is formed so as to cover the stacked color filters, and the sealing material is formed on the overcoat film. 
     (3) The liquid crystal display device according to (2), wherein one of the plurality of color filters formed in the seal portion is formed continuously with the color filter formed in the display region, and the other color filters among the plurality of color filters are discontinuous with the color filters formed in the display region. 
     (4) A liquid crystal display device includes: a TFT substrate having a display region where pixels each having a TFT and a pixel electrode are formed in a matrix; a counter substrate bonded to the TFT substrate with a sealing material in a seal portion at a periphery thereof and having a display region where a light shielding film and color filters of three colors are formed, an overcoat film is formed so as to cover the color filters of three colors, and an alignment film is formed so as to cover the overcoat film; and liquid crystal sealed between the TFT substrate and the counter substrate, wherein in the counter substrate, the alignment film is subjected to an alignment treatment by photo-alignment, and the alignment film is not formed in the seal portion; in the seal portion of the counter substrate, the light shielding film, a color filter of one color among the color filters of three colors, and the overcoat film are stacked in this order; the color filter of one color formed in the seal portion is formed discontinuously with any of the color filters of three colors formed in the display region; a step is formed on the overcoat film corresponding to an edge of the color filter of one color formed in the seal portion; and the sealing material is formed on the overcoat film. 
     (5) A liquid crystal display device includes: a TFT substrate having a display region where pixels each having a TFT and a pixel electrode are formed in a matrix; a counter substrate bonded to the TFT substrate with a sealing material in a seal portion at a periphery thereof and having a display region where a light shielding film and color filters of three colors are formed, an overcoat film is formed so as to cover the color filters of three colors, and an alignment film is formed so as to cover the overcoat film; and liquid crystal sealed between the TFT substrate and the counter substrate, wherein in the counter substrate, the alignment film is subjected to an alignment treatment by photo-alignment, and the alignment film is not formed in the seal portion; in the seal portion of the counter substrate, the light shielding film and color filters of a plurality of colors among the color filters of three colors are stacked, and the overcoat film is formed so as to cover the stacked color filters; the plurality of color filters formed in the seal portion are formed discontinuously with any of the color filters of three colors formed in the display region; a step is formed on the overcoat film corresponding to an edge of the plurality of color filters formed in the seal portion; and the sealing material is formed on the overcoat film. 
     (6) A liquid crystal display device includes: a TFT substrate having a display region where pixels each having a TFT and a pixel electrode are formed in a matrix; a counter substrate bonded to the TFT substrate with a sealing material in a seal portion at a periphery thereof and having a display region where a light shielding film and color filters of three colors are formed, an overcoat film is formed so as to cover the color filters of three colors, and an alignment film is formed so as to cover the overcoat film; and liquid crystal sealed between the TFT substrate and the counter substrate, wherein in the counter substrate, the alignment film is subjected to an alignment treatment by photo-alignment, and the alignment film is not formed in the seal portion; in the seal portion of the counter substrate, the light shielding film and the overcoat film are stacked in this order; a thickness of the overcoat film at the seal portion is greater than that of the overcoat film at the display region; and the sealing material is formed on the overcoat film. 
     (7) The liquid crystal display device according to (6), wherein a thickness of the overcoat film at the seal portion is equal to or greater than 1.5 times that of the overcoat film at the display region. 
     According to an aspect of the invention, even when an overcoat film at a seal portion is degraded by ultraviolet radiation in photo-alignment, and moisture penetrates into the degraded overcoat film, the moisture can be blocked by a color filter disposed below the overcoat film and hardly reaches the light shielding film. Therefore, it is possible to prevent the peeling of the light shielding film. Moreover, since a reduction in electrical resistance of the light shielding film can be prevented, it is possible to prevent a reduction in contrast due to light leakage of a liquid crystal layer. 
     According to another aspect of the invention, since the overcoat film is formed thicker at the seal portion than at a display region, the overcoat film can be prevented from being entirely degraded by ultraviolet radiation in photo-alignment. Therefore, it is possible to prevent moisture from reaching the light shielding film. Moreover, since the overcoat film is not thick at the display region, it is possible to prevent a reduction in brightness of a display screen. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a liquid crystal display device. 
         FIG. 2  is a cross-sectional view of a display region of the liquid crystal display device. 
         FIG. 3  is a cross-sectional view of a seal portion of a liquid crystal display device according to a first embodiment. 
         FIG. 4  is a cross-sectional view of a counter substrate in photo-alignment. 
         FIG. 5  is a cross-sectional view of a counter substrate according to the first embodiment. 
         FIG. 6  is a cross-sectional view of a counter substrate according to a second embodiment. 
         FIG. 7  is a cross-sectional view of a counter substrate according to another aspect of the second embodiment. 
         FIG. 8  is a cross-sectional view of a counter substrate according to a third embodiment. 
         FIG. 9  is a cross-sectional view of a counter substrate according to a fourth embodiment. 
         FIG. 10  is a cross-sectional view of a counter substrate according to another aspect of the fourth embodiment. 
         FIG. 11  is a cross-sectional view of a counter substrate according to a fifth embodiment. 
         FIG. 12  is a cross-sectional view of a counter substrate according to another aspect of the fifth embodiment. 
         FIG. 13  is a plan view of a mother substrate. 
         FIG. 14  is a plan view of a mother counter substrate. 
         FIG. 15  is a cross-sectional view of a counter substrate in photo-alignment in the related art. 
         FIG. 16  is a cross-sectional view of the counter substrate in a state where a sealing material is formed in the related art. 
         FIG. 17  is a cross-sectional view of an edge portion of a liquid crystal display device in the related art. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, the contents of the invention will be described in detail based on embodiments. 
     First Embodiment 
       FIG. 1  is a plan view of a small liquid crystal display device used for mobile phones or the like as an example of a product to which the invention is applied. In  FIG. 1 , a counter substrate  200  is disposed above a TFT substrate  100 . A liquid crystal layer is interposed between the TFT substrate  100  and the counter substrate  200 . The TFT substrate  100  and the counter substrate  200  are bonded together with a sealing material  15  formed in a frame portion. In  FIG. 1 , a filling port is formed in the sealing material  15 , and liquid crystal is filled through the filling port. Thereafter, the filling port is sealed with an end-sealing material  16 . 
     The TFT substrate  100  is formed larger than the counter substrate  200 . In a portion of the TFT substrate  100  extended from the counter substrate  200 , a terminal portion  150  for supplying a power supply, video signals, scanning signals, and the like to a liquid crystal display panel is formed. In the terminal portion  150 , an IC driver  50  for driving scanning lines, video signal lines, and the like is disposed. The IC driver  50  is divided into three regions. At the center of the IC driver, a video signal drive circuit  52  is disposed. A scanning signal drive circuit  51  is disposed on both sides of the center. 
     In a display region  10  of  FIG. 1 , scanning lines  30  extend in the horizontal direction and are arranged in the vertical direction. Moreover, video signal lines  40  extend in the vertical direction and are arranged in the horizontal direction. The scanning lines  30  are connected to the scanning signal drive circuit  51  of the IC driver  50  through scanning-line lead lines  31 . In  FIG. 1 , for arranging the display region  10  at the center of the liquid crystal display device, the scanning-line lead lines  31  are arranged on both sides of the display region  10 . Therefore, the scanning signal drive circuit  51  is disposed on both sides in the IC driver  50 . On the other hand, video-signal-line lead lines  41  which connect the video signal lines  40  with the IC driver are collected on the lower side of a screen. The video-signal-line lead lines  41  are connected to the video signal drive circuit  52  arranged at the central portion of the IC driver  50 . 
     An alignment film  113  is formed in a region slightly larger than the display region  10  in  FIG. 1 . Photo-alignment is performed on the alignment film  113 . The alignment film  113  is not formed at a portion where the sealing material  15  is formed. This is because the presence of the alignment film  113  reduces the adhesive force between the sealing material  15  and the substrate. 
       FIG. 2  is a cross-sectional view showing the structure of an IPS type liquid crystal display device in a display region. Various electrode structures of IPS type liquid crystal display devices have been proposed and put to practice use. The structure of  FIG. 2  has been widely used at present. Briefly speaking, a pixel electrode  110  having a comb-teeth shape is formed above a counter electrode  108  which is formed in a planar and solid manner with an inter-layer insulating film  109  interposed therebetween. Liquid crystal molecules  301  are rotated by a voltage between the pixel electrode  110  and the counter electrode  108  to control the transmittance ratio of light in a liquid crystal layer  300  for each pixel, whereby an image is formed. The structure of  FIG. 2  will be described in detail below. Although the invention is described by taking the configuration of  FIG. 2  as an example, the invention can also be applied to IPS type liquid crystal display devices other than that of  FIG. 2 . 
     In  FIG. 2 , a gate electrode  101  is formed on the TFT substrate  100  formed of glass. The gate electrode  101  is formed in the same layer as the scanning lines. The gate electrode  101  includes an AlNd alloy layer and a MoCr alloy layer stacked in this order. 
     A gate insulating film  102  is formed of SiN so as to cover the gate electrode  101 . A semiconductor layer  103  is formed of an a-Si film on the gate insulating film  102  at a position facing the gate electrode  101 . The a-Si film is formed by plasma CVD. The a-Si film forms a channel portion of a TFT. A source electrode  104  and a drain electrode  105  are formed on the a-Si film with the channel portion interposed between the source electrode and the drain electrode. A not-shown n+Si layer is formed between the a-Si film and the source electrode  104  or the drain electrode  105  for establishing ohmic contact between the semiconductor layer and the source electrode  104  or the drain electrode  105 . 
     The source electrode  104  is also used as the video signal line, and the drain electrode  105  is connected to the pixel electrode  110 . The source electrode  104  and the drain electrode  105  are formed simultaneously in the same layer. In the embodiment, the source electrode  104  or the drain electrode  105  is formed of a MoCr alloy. For reducing the electrical resistance of the source electrode  104  or the drain electrode  105 , an electrode structure having an AlNd alloy layer sandwiched between MoCr alloy layers is used. 
     An inorganic passivation film  106  is formed of SiN so as to cover the TFT. The inorganic passivation film  106  protects especially the channel portion of the TFT against impurities  401 . An organic passivation film  107  is formed on the inorganic passivation film  106 . Since the organic passivation film  107  functions to protect the TFT and planarize the surface of the TFT, the film is formed thick. The thickness thereof is from 1 μm to 4 μm. 
     The counter electrode  108  is formed on the organic passivation film  107 . The counter electrode  108  is formed by sputtering an indium tin oxide (ITO) film as a transparent conductive film over the entire display region. That is, the counter electrode  108  is formed in a planar manner. After the counter electrode  108  is formed by sputtering over the entire surface, only a through hole  111  portion for establishing electrical continuity between the pixel electrode  110  and the drain electrode  105  is formed by removing the counter electrode  108  by etching. 
     An inter-layer insulating film  109  is formed of SiN so as to cover the counter electrode  108 . After forming the inter-layer insulating film  109 , the through hole  111  is formed. Thereafter, an ITO film serving as the pixel electrode  110  is deposited so as to cover the inter-layer insulating film  109  and the through hole  111 . The deposited ITO film is patterned to form the pixel electrode  110 . The ITO film serving as the pixel electrode  110  is also deposited on the through hole  111 . In the through hole  111 , the drain electrode  105  extended from the TFT and the pixel electrode  110  are electrically conducted, so that a video signal is supplied to the pixel electrode  110 . 
     The pixel electrode is a so-called comb-teeth shaped electrode. A slit  112  shown in  FIG. 2  is formed between electrodes each having a comb-tooth shape. A fixed voltage is applied to the counter electrode  108 , and a voltage due to a video signal is applied to the pixel electrode  110 . As shown in  2 , when the voltage is applied to the pixel electrode  110 , lines of electric force are generated to rotate the liquid crystal molecules  301  in a direction of the lines of electric force, whereby the transmission of light from a backlight is controlled. The transmission of light from the backlight is controlled for each pixel, whereby an image is formed. The alignment film  113  on the TFT substrate side is formed on the pixel electrode  110  to align the liquid crystal molecules  301 . Photo-alignment using polarized ultraviolet radiation is employed as an alignment treatment for the alignment film. 
     In the example shown in  FIG. 2 , the counter electrode  108  formed in a planar manner is disposed on the organic passivation film  107 , and the comb-teeth electrode  110  is disposed on the inter-layer insulating film  109 . Contrary to this, however, the pixel electrode  110  formed in a planar manner may be disposed on the organic passivation film  107 , and the counter electrode  108  having a comb-teeth shape may be disposed on the inter-layer insulating film  109 . 
     In  FIG. 2 , the counter substrate  200  is disposed with the liquid crystal layer  300  interposed between the counter substrate  200  and the TFT substrate  100 . Color filters are formed on the inner side of the counter substrate  200 . In  FIG. 2 , a red color filter  201 R is formed. A light shielding film  202  is formed below the color filter at a region where an image is not formed. The light shielding film  202  improves the contrast of image and also functions as the light shielding film of the TFT for preventing photocurrent from flowing into the TFT. 
     An overcoat film  203  is formed so as to cover the red color filter  201 R and the light shielding film  202 . Since the surface of the red color filter  201 R and the light shielding film  202  has irregularities, the surface is planarized by the overcoat film  203 . An alignment film  113  for determining the initial alignment of liquid crystal is formed on the overcoat film  203 . The alignment film  113  is subjected to the photo-alignment treatment. 
     Since  FIG. 2  shows the IPS type liquid crystal display device, the counter electrode  108  is formed on the TFT substrate  100  side but not formed on the counter substrate  200  side. In the IPS type as described above, a conductive film is not formed on the inner side of the counter substrate  200 . Therefore, the potential of the counter substrate  200  becomes unstable. Moreover, electromagnetic noise from the outside enters the liquid crystal layer  300  to exert an influence on an image. For eliminating the problems, a surface conductive film  210  is formed on the outer surface of the counter substrate  200 . The surface conductive film  210  is formed by sputtering an ITO film as a transparent conductive film. 
       FIG. 3  is a cross-sectional view of the liquid crystal display device at an edge portion shown in  FIG. 1 . In  FIG. 3 , the inorganic passivation film  106 , the organic passivation film  107 , and the alignment film  113  are formed on the TFT substrate  100 . The other configurations of the TFT substrate  100  are not illustrated in  FIG. 3 . The light shielding film  202 , the red color filter  201 R, the overcoat film  203 , and the alignment film  113  are formed on the counter substrate  200 . The edge portion is sealed with the sealing material  15 , and the gap between the TFT substrate  100  and the counter substrate  200  is defined by spacers  350  made of glass fibers. 
     In  FIG. 3 , the alignment film  113  is subjected to the alignment treatment by photo-alignment. A feature of the invention shown in  FIG. 3  is in that the red color filter  201 R is disposed below the overcoat film  203  at the edge portion. While the red color filter  201 R is formed in  FIG. 3 , a green color filter or a blue color filter may be formed. In the counter substrate  200  of  FIG. 3 , the overcoat film  203  at a portion where the alignment film  113  is not present is degraded by ultraviolet radiation in photo-alignment, and therefore is in a state where moisture easily enters the portion. 
     Even when the overcoat film  203  is degraded by ultraviolet radiation, the red color filter  201 R is present below the overcoat film  203 . Accordingly, the moisture entering the overcoat film  203  is blocked by the red color filter  201 R and does not reach the light shielding film  202  situated below the overcoat film  203 , or it takes long time for the moisture to reach the light shielding film  202 . Accordingly, it is possible to prevent a reduction in adhesive force or a reduction in electrical resistance of the light shielding film  202  due to reaction of the light shielding film  202  with moisture. 
       FIGS. 4 and 5  illustrate the above description.  FIG. 4  shows a state where the light shielding film  202 , the red color filter  201 R, the overcoat film  203 , and the alignment film  113  are formed in this order on the counter substrate  200 . The light shielding film  202  has a thickness of about 1 μm. The red color filter  201 R has a thickness of from 1 to 2 μm. The overcoat film  203  has a thickness of 1 to 2 μm. The alignment film  113  has a thickness of about 0.1 μm. The green color filter, the blue color filter, and the like have also a thickness of from 1 to 2 μm. 
     The alignment film  113  is not formed at the edge portion. This is for preventing a reduction in adhesive force of the sealing material  15  due to the alignment film  113 . In  FIG. 4 , the alignment film  113  is irradiated with ultraviolet radiation UV for applying the alignment treatment. The alignment film  113  is subjected to the alignment treatment with ultraviolet radiation, but a hatched overcoat film  2031  at the edge portion where the alignment film  113  is not present is degraded by the ultraviolet radiation. 
     Thereafter, as shown in  FIG. 5 , the sealing material  15  is formed on the overcoat film  203  at the edge portion where the alignment film  113  is not present. In  FIG. 5 , moisture easily penetrates into the hatched portion  2031  of the overcoat film degraded by the ultraviolet radiation. However, since the red color filter  201 R is present below the hatched overcoat film  2031 , the penetrated moisture is blocked by the red color filter  201 R and does not easily reach the light shielding film  202 . Accordingly, the reliability of the seal portion can be assured. 
     In the related art, a color filter is formed only in a display region. In the invention, however, a color filter is extended up to the edge portion of the counter substrate  200 . The color filter is formed by photolithography. That is, the forming range of the color filter can be defined by an exposure mask. Accordingly, even when the color filter is formed up to the edge portion of the counter substrate, the number of processes does not increase. 
     According to the embodiment as described above, even when the overcoat film  203  is degraded by ultraviolet radiation in the photo-alignment treatment, the influence of moisture penetrating through the overcoat film  203  is blocked by the color filter. Therefore, the reliability of the seal portion is not reduced. Moreover, it is also possible to prevent a reduction in electrical resistance of the light shielding film  202  caused by reaction of moisture with the light shielding film  202 . Therefore, a reduction in contrast due to light leakage of liquid crystal can be prevented. 
     In the above embodiment, although a color filter formed in the seal portion is the red color filter  201 R, this is illustrative only. Another color filter, that is, a green color filter or a blue color filter may be formed. 
     Second Embodiment 
       FIG. 6  is a cross-sectional view of the counter substrate  200  in the vicinity of an edge portion according to a second embodiment of the invention. In  FIG. 6 , the light shielding film  202 , the red color filter  201 R, the overcoat film  203 , and the alignment film  113  are formed in this order on the counter substrate  200 . However, the red color filter  201 R and a green color filter  201 G are stacked in a seal portion where the alignment film  113  is not present. The alignment film  113  is subjected to the photo-alignment treatment. Accordingly, the overcoat film  203  at the portion where the alignment film  113  is not present is degraded by ultraviolet radiation. 
     In  FIG. 6 , two layers of color filters of the green color filter  201 G and the red color filter  201 R are formed below the overcoat film  203  degraded by ultraviolet radiation. Accordingly, even when moisture penetrates into the degraded overcoat film  203 , the penetrated moisture is blocked by the green color filter  201 G and the red color filter  201 R and does not reach the light shielding film  202 . 
     In the configuration of  FIG. 6 , since the two layers of the color filters are formed in the seal portion, a protective effect against moisture is greater than that of the configuration of the first embodiment. The respective layers have the same thicknesses as those of the first embodiment. That is, both the green color filter and the red color filter are formed to have a thickness of from 1 to 2 μm in the same manner as in the first embodiment. 
     Another effect of the configuration of  FIG. 6  is in that the entering of the alignment film  113  into the seal portion can be prevented when the alignment film  113  is applied. As shown in  FIG. 6 , since the green color filter  201 G is formed in the vicinity of the edge portion, a step is produced on the overcoat film  203 . The step functions as a stopper against the alignment film  113  flowing from the display region. 
     The alignment film  113  has fluidity when applied because it is liquid, and therefore it is hard to accurately define the applying area. Especially the presence of the alignment film  113  below the sealing material  15  reduces the adhesive force of the sealing material  15 . In the embodiment, as shown in  FIG. 6 , since the range of the alignment film  113  can be defined by forming the step with the green color filter  201 G, the reliability in the seal portion can be maintained at a high level. Since the green color filter  201 G formed at the periphery is formed by photolithography, accurate dimension can be maintained. The step has a height of about from 1 to 2 μm, which is the thickness of the green color filter. 
       FIG. 7  shows another aspect in the embodiment. A display region on the left of  FIG. 7  is similar to that described with reference to  FIG. 6 , but an edge portion is different from that of  FIG. 6 . Between the light shielding film  202  and the overcoat film  203 , three layers of color filters of the red color filter  201 R, the green color filter  201 G, and a blue color filter  201 B are formed in this order. The alignment film  113  is subjected to the photo-alignment treatment in the same manner as in the first embodiment or in  FIG. 6 . 
     In  FIG. 7 , the overcoat film  203  at a portion not covered with the alignment film  113  is degraded by ultraviolet radiation in photo-alignment in the same manner as in the first embodiment. In the embodiment, since the three layers of the color filters are present until moisture penetrating through the degraded overcoat film  203  reaches the light shielding film  202 , the reliability of the seal portion can be further improved more than that of  FIG. 6 . 
     As shown in  FIG. 7 , a step is formed with two layers of color filters of the green color filter  201 G and the blue color filter  201 B in the vicinity of the seal portion. Therefore, the forming range of the alignment film  113  can be defined by the step. In the embodiment, the step is formed with the two layers of the color filters, and the step can be formed to have a height of from 2 μm to about 4 μm. Therefore, the applying range of the alignment film can be defined more reliably. 
     In the embodiment, although the red color filter  201 R and the green color filter  201 G are sequentially stacked in  FIG. 6 , two layers of color filters are not limited to those color filters. Other color filters may be stacked, and the order of stacking may be different. Also in  FIG. 7 , although the color filters are stacked in the order of the red color filter  201 R, the green color filter  201 G, and the blue color filter  201 B, the stacking order of color filters is not limited to this but can be arbitrarily determined depending on the manufacturing conditions of color filter. 
     Third Embodiment 
       FIG. 8  is a cross-sectional view of the counter substrate  200  in the vicinity of an edge portion according to a third embodiment. In  FIG. 8 , the light shielding film  202 , the red color filter  201 R, the overcoat film  203 , and the alignment film  113  are formed in this order on the counter substrate  200 . The alignment film  113  is subjected to the photo-alignment treatment. Accordingly, the overcoat film  203  at a portion not covered with the alignment film  113  is degraded by ultraviolet radiation in photo-alignment. 
     The red color filter  201 R is disposed between the overcoat film  203  degraded by ultraviolet radiation and the light shielding film  202  to thereby block moisture penetrating through the degraded overcoat film  203  by the red color filter  201 R in the same manner as in the first embodiment. Different from the first embodiment, the red color filter  201 R is not continuously formed to the edge portion in the embodiment. Instead, a region formed by removing the red color filter, that is, a portion A in  FIG. 8  is disposed between the display region and the seal portion. 
     Due to the presence of the portion A, even when only one layer of the red color filter is formed in the seal portion, a step is formed for the alignment film  113 , and therefore the step can be used as a stopper against the spreading of the alignment film. Moreover, the portion A acts as a so-called liquid pool for the alignment film  113  and can reliably prevent the spreading of the alignment film  113  to the outside together with the step. 
     In the embodiment, although a color filter formed in the seal portion is the red color filter  201 R, this is illustrative only. Another color filter, that is, the green color filter  201 G or the blue color filter  201 B may be formed. 
     Fourth Embodiment 
       FIG. 9  is a cross-sectional view of the counter substrate  200  in the vicinity of an edge portion according to a fourth embodiment. In  FIG. 9 , the light shielding film  202 , the red color filter  201 R, the overcoat film  203 , and the alignment film  113  are formed in this order on the counter substrate  200 . However, the red color filter  201 R and the green color filter  201 G are present between the overcoat film  203  and the light shielding film  202  in the seal portion. The alignment film  113  is subjected to the photo-alignment treatment. Accordingly, the overcoat film  203  at a portion not covered with the alignment film  113  is degraded by ultraviolet radiation in photo-alignment. 
     The red color filter  201 R and the green color filter  201 G are disposed between the overcoat film  203  degraded by ultraviolet radiation and the light shielding film to thereby block moisture penetrating through the degraded overcoat film  203  in the same manner as in  FIG. 6  of the second embodiment. Different from  FIG. 6 , the red color filter  201 R is not continuously formed to the edge portion in the embodiment. Instead, a region formed by removing the red color filter  201 R, that is, the portion A in FIG.  9  is disposed between the display region and the seal portion. 
     Due to the presence of the portion A, a step formed in the vicinity of the seal portion corresponds to two layers of the red color filter  201 R and the green color filter  201 G, and the height of the step can be increased to from 2 μm to 4 μm. Accordingly, the alignment film  113  spreading to the outside can be regulated more effectively. Moreover, the portion A acts as a so-called liquid pool for the alignment film  113  and can more reliably prevent the spreading of the alignment film  113  to the outside together with the step. 
       FIG. 10  is a cross-sectional view of the counter substrate  200  in the vicinity of an edge portion according to another aspect of the fourth embodiment. The configuration of  FIG. 10  is the same as that of  FIG. 9  except that three layers of color filters of the red color filter  201 R, the green color filter  201 G, and the blue color filter  201 B are present between the overcoat film  203  and the light shielding film  202  in the seal portion. 
     In the configuration of  FIG. 10 , the red color filter  201 R, the green color filter  201 G, and the blue color filter  201 B are disposed between the overcoat film  203  degraded by ultraviolet radiation in photo-alignment and the light shielding film  202  to thereby block moisture penetrating through the degraded overcoat film  203  in the same manner as in  FIG. 7  of the second embodiment. Different from  FIG. 7 , the red color filter  201 R is not continuously formed to the edge portion in the embodiment. Instead, a region formed by removing the red color filter  201 R, that is, the portion A in  FIG. 10  is disposed between the display region and the seal portion. 
     Due to the presence of the portion A, a step formed in the vicinity of the seal portion corresponds to three layers of the red color filter  201 R, the green color filter  201 G, and the blue color filter  201 B, and therefore the alignment film  113  spreading to the outside can be regulated more effectively. Since the step corresponds to three layers, the height of the step can be increased to from 3 μm to about 6 μm. Therefore, even when the viscosity of the alignment film  113  is low, the step can sufficiently function as a stopper. Moreover, the portion A acts as a so-called liquid pool for the alignment film  113  and can more reliably prevent the spreading of the alignment film  113  to the outside together with the step. 
     In the embodiment as described above, it is possible to more reliably prevent the influence of moisture penetrating through the degraded overcoat film  203  than the case of the third embodiment. Moreover, according to the configuration of the embodiment, the outer shape of the alignment film  113  can be more reliably defined. 
     In the embodiment, although the red color filter  201 R and the green color filter  201 G are sequentially stacked in  FIG. 9 , two layers of color filters are not limited to those filters. Other color filters may be stacked, and the stacking order may also be different. In  FIG. 10 , although color filters are stacked in the order of the red color filter, the green color filter, and the blue color filter, the stacking order of color filters is not limited to this. The order can be arbitrarily determined depending on the manufacturing conditions of color filter. 
     Fifth Embodiment 
       FIG. 11  is a cross-sectional view of the counter substrate  200  in the vicinity of an edge portion according to a fifth embodiment of the invention. In  FIG. 11 , the light shielding film  202 , the red color filter  201 R, the overcoat film  203 , and the alignment film  113  are formed in this order on the counter substrate  200 . In a seal portion, however, the light shielding film  202  and the overcoat film  203  are formed on the counter substrate  200 , and the sealing material  15  is formed on the overcoat film  203 . In  FIG. 11 , a color filter is not formed in the seal portion. 
     Also in the embodiment, the alignment film  113  is subjected to the photo-alignment treatment. Accordingly, the overcoat film  203  at a portion where the alignment film  113  is not present is degraded by ultraviolet radiation in photo-alignment. Moisture penetrates from the degraded portion of the overcoat film in the same manner as in the first to fourth embodiments. 
     A feature of the embodiment is in that a thickness of the overcoat film  203  is greater at the seal portion than at a display region. In  FIG. 11 , the overcoat film  203  has a thickness of d2 at the seal portion and has a thickness of d1 at the display region. As a ratio between the thickness d1 at the display region and the thickness d2 at the seal portion of the overcoat film  203 , the thickness d2 is preferably equal to or greater than twice the thickness d1. However, the effect can be provided even when the thickness d2 is equal to or greater than 1.5 times the thickness d1. In the case where the thickness d2 is twice the thickness d1, when the thickness d1 at the display region is from 1 to 2 μm, the thickness d2 is from 2 to 4 μm. An increase in thickness of the overcoat film  203  at the display region reduces the transmittance ratio of light, which reduces the brightness of a screen. Therefore, the thickness d1 of the overcoat film  203  at the display region must be limited to from 1 to 2 μm. 
     The overcoat film  203  not covered with the alignment film  113  is degraded by ultraviolet radiation in photo-alignment. However, a region in the vicinity of the surface is mainly degraded by ultraviolet radiation, and ultraviolet radiation does not largely affect a depth portion of the film. In the embodiment, the overcoat film  203  is increased in thickness at the portion directly irradiated with ultraviolet radiation, so that the depth portion of the overcoat film  203  is not damaged by ultraviolet radiation. 
     Accordingly, even in case the surface of the overcoat film  203  is damaged by ultraviolet radiation to allow moisture to penetrate therethrough, the moisture is blocked at the depth portion of the overcoat film  203  and does not reach the light shielding film  202  because the depth portion of the overcoat film  203  is not damaged. Accordingly, it is possible to prevent such a phenomenon that moisture reacts with the light shielding film  202  to cause peeling of the light shielding film  202  or reduce the electrical resistance of the light shielding film  202 . 
     As a method for forming the light shielding film  202  having an increased thickness only at the periphery, a half exposure technique can be used. In the case of using a positive photosensitive material for the overcoat film  203  for example, since the exposed portion is dissolved in a developer, such an exposure mask that the exposure amount of the overcoat film is reduced at the seal portion is used. Therefore, the thickness of the overcoat film can be increased only at the seal portion. 
     Also in the embodiment, since a step is formed between a thin portion and a thick portion of the overcoat film  203 , the step can be used as a stopper of the alignment film  113 . The step formed in this case is from 1 μm to 2 μm. Moreover, since a recessed portion formed between the edge of the red color filter  201 R and the step portion of the overcoat film  203  can function as a liquid pool of the alignment film  113 , the recessed portion can contribute to define the outer shape of the alignment film  113  together with the step of the overcoat film  203 . 
       FIG. 12  is a modified example of the embodiment, which is a combination of the embodiment and the configuration of the first embodiment. That is, the thickness of the overcoat film  203  is greater at a seal portion than at a display region, and the red color filter  201 R is disposed below the overcoat film  203 . With this configuration, the effect of protecting the light shielding film  202  against the influence of moisture penetrating into the surface of the overcoat film  203  degraded by ultraviolet radiation can be assured more reliably. 
       FIG. 12  shows the example of the combination of the fifth embodiment and the first embodiment, but the fifth embodiment can be combined with the second to fourth embodiments. When the fifth embodiment is combined with the second to fourth embodiments, the height of the step acting as a stopper of the alignment film  113  can be increased more, making it possible to use an alignment film having a low viscosity. 
     Examples of forming methods of the alignment film  113  include, in addition to flexographic printing, an inkjet method. When an alignment film is formed by an inkjet method, the viscosity of the alignment film must be low. When the viscosity of the alignment film is low, the alignment film is likely to spread to the periphery, making it hard to accurately define the forming range of the alignment film. In such a case, when the invention described in and after the second embodiment is used, a step is formed on the overcoat film  203 , and therefore the spreading of the alignment film to the outside can be prevented. That is, since the use of the invention makes it possible to apply an alignment film having a low viscosity, the choice of forming processes of the alignment film can be widened. 
     In the above-described embodiment, although the color filter formed in the seal region is formed up to the edge of the counter substrate, the color filter may be terminated stepwise in front of the edge of the counter substrate. With this configuration, the peeling of the color filter or the like at the edge of the substrate can be prevented. Moreover, instead of forming the color filter in the entire seal region, a part of the color filter can be removed in the seal region. The removed portion may have an island shape or a narrow stripe shape parallel to a side of the substrate. With this configuration, a region where the overcoat film is in contact with the light shielding film is formed in the part of the seal region. Moreover, the presence of a step portion of the color filter in the seal portion increases the contact area of the sealing material, making it possible to enhance the adhesive strength between the sealing material and the counter substrate. Therefore, the reliability of the seal portion is improved. 
     While there have been described what are at present considered to be certain embodiments of the invention, it will be understood that various modifications may be made thereto, and it is intended that the appended claims cover all such modifications as fall within the true spirit and scope of the invention.