Patent Publication Number: US-9841633-B2

Title: Liquid crystal display device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 14/789,349 filed on Jul. 1, 2015, which is a continuation of U.S. patent application Ser. No. 14/541,564 filed on Nov. 14, 2014, which is a continuation of U.S. patent application Ser. No. 14/060,300 filed on Oct. 22, 2013, which is a continuation of U.S. patent application Ser. No. 13/397,841 filed on Feb. 16, 2012, which claims priority of Japanese Patent Application JP 2011-045502 filed on Mar. 2, 2011. The entire disclosures of each of these applications are hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid crystal display device. The invention more particularly relates to a liquid crystal display device including an alignment film provided with alignment controllability by irradiation of light. 
     2. Description of the Related Art 
     Liquid crystal display devices include a TFT substrate having pixel electrodes, thin film transistors (TFTs). etc. formed in a matrix; a counter substrate opposing the TFT substrate and having black matrices and an overcoat film, etc.; and liquid crystals put between the TFT substrate and the counter substrate. Images are formed by controlling the light transmittance of the liquid crystal molecules of each pixel. 
     Since liquid crystal display devices are flat and light in weight, they are applied in various fields, for example, from large-sized display devices such as television sets to mobile phones and DSCs (Digital Still Cameras). For liquid crystal display devices, the view angle characteristic issues a problem. The view angle characteristic is a phenomenon such that the luminance or chromaticity changes from that of when the screen is viewed from the front when the screen is viewed from an oblique direction. The IPS (In Plane Switching) system which operates liquid crystal molecules by a horizontal electric field has a good view angle characteristic. 
     As a method of alignment treatment, that is, a method for giving alignment controllability to an alignment film used for liquid crystal display devices, rubbing treatment has been used in the conventional art. Rubbing treatment is performed by rubbing an alignment film with a cloth. On the other hand, there is a method called an optical alignment method which can provide alignment controllability to an alignment film in a contactless manner. Since the performance of the IPS system is better as the pre-tilt angle is smaller, the optical alignment method which in principle does not generate a pre-tilt angle is advantageous. 
     The TFT substrate and the counter substrate are bonded at their periphery with a seal material; as the seal material, UV-curable resin is often used. When the display region in which the alignment film is formed is irradiated with UV-light to cure the seal material, the UV-light deteriorates the alignment film. Conventionally, a light shielding mask has been used so that the display region is not irradiated with UV-light upon the UV-irradiation against the seal material. 
     However, even when such a mask is used, the UV-light comes around to deteriorate the alignment film at the periphery of the display region. JP-A-H10-221700 discloses a configuration in which the counter substrate is provided with a band pass filter surrounding the outer side of the display region so that it cuts off the UV-light, thereby protecting the alignment film and liquid crystals in the display region from the UV-light by the combination of the light shielding mask and the band pass filter. 
     SUMMARY OF THE INVENTION 
     In a conventional configuration in which a light shielding mask is provided to shroud the display region at the time the seal material is cured by UV-light irradiation, it is necessary to align the light shielding mask to a predetermined position upon exposure. Thus, fabrication steps for this process would be added, and it is also necessary to prepare various sizes and kinds of light shielding masks. 
     Further, in a configuration as described in JP-A-H10-221700 in which the counter substrate is provided with a band pass filter formed around the periphery of the display region, there is an overlap between the band pass filter and the seal material. The effect of the band pass filter on the curing of the seal material needs to be taken into consideration. It is also necessary matters such as the bondability between the band pass filter and the seal material, as well as the black matrix, etc, around it. Further, even when the band pass filter is formed, a light shielding mask will still be needed. 
     The present invention intends to attain a liquid crystal display device employing an alignment film obtained by optical alignment and a UV-light curable resin for a seal material, which does not require the use of a UV-light shielding mask upon UV-curing of the seal material. 
     The present invention intends to overcome the problems described above and provides, in a first aspect, a liquid crystal display device comprising: a TFT substrate having an alignment film; a counter substrate having an alignment film, the counter substrate being bonded to the TFT substrate by means of a seal material; and liquid crystals sealed inside the substrates and the seal material; wherein a UV-light absorption layer is formed between each black matrix, the black matrices and the UV-light absorption layer being covered by an overcoat film, the overcoat film being covered by the alignment film; the seal material is a UV-light curable resin; and the transmittance of the UV-light absorption layer to IV-light at a wavelength of 300 nm is lower than that of the overcoat film, and the transmittance of the UV-light absorption layer to UV-light at a wavelength of 340 nm is higher than that of the overcoat film. 
     The present invention provides, in a second aspect, a liquid crystal display device comprising: a TFT substrate having an alignment film; a counter substrate having an alignment film, the counter substrate being bonded to the TFT substrate by means of a seal material; and liquid crystals sealed inside the substrates and the seal material; wherein a UV-light absorption layer is formed between each black matrix and over the black matrices, and the alignment film is formed over the UV-light absorption layer; the TFT substrate is covered by a TFT circuit and an organic passivation film covering the TFT circuit, and over the organic passivation film, counter electrodes, an interlayer insulation film, and pixel electrodes are formed in that order, or in the order of the pixel electrodes, the interlayer insulation film, and the counter electrodes; the alignment film is formed over the pixel electrodes or the counter substrate; the seal material is a UV-light curable resin; and the transmittance of the UV-light absorption layer to UV-light at a wavelength of 300 nm is lower than that of the organic passivation film, and the transmittance of the UV-light absorption layer to TV-light at a wavelength of 340 nm is higher than that of the organic passivation film. 
     The present invention provides, in a third aspect, a liquid crystal display device comprising; a TFT substrate having an alignment film; a counter substrate having an alignment film, the counter substrate being bonded to the TFT substrate by means of a seal material: and liquid crystals sealed inside the substrates and the seal material: wherein a color filter is formed between each black matrix, the black matrices and the color filters being covered by an overcoat film, the overcoat film being covered by the alignment film; the TFT substrate is covered by a TFT circuit and a UV-light absorption layer covering the TFT circuit, and over the UV-light absorption layer, counter electrodes, an interlayer insulation film, and pixel electrodes are formed in that order, or in the order of the pixel electrodes, the interlayer insulation film, and the counter electrodes: the alignment film is formed over the pixel electrodes or the counter substrate; the seal material is a UV-curable resin: and the transmittance of the UV-light absorption layer to UV-light at a wavelength of 300 nm is lower than that of the overcoat film, and the transmittance of the UV-light absorption layer to UV-light at a wavelength of 340 nm is higher than that of the overcoat film. 
     The present invention provides, in a fourth aspect, a liquid crystal display device comprising: a TFT substrate having an alignment film; a counter substrate having an alignment film, the counter substrate being bonded to the TFT substrate by means of a seal material; and liquid crystals sealed inside the substrates and the seal material: wherein a UV-light absorption layer is formed between each black matrix, the black matrices and the UV-light absorption layer being covered by an overcoat film, the overcoat film being covered by the alignment film; the TFT substrate is covered by a TFT circuit and a UV-light absorption layer covering the TFT circuit, and over the UV-light absorption layer, counter electrodes, an interlayer insulation film, and pixel electrodes are formed in that order, or in the order of the pixel electrodes, the interlayer insulation film, and the counter electrodes; the alignment film is formed over the pixel electrodes or the counter substrate; the seal material is a UV-curable resin; and the transmittance of the UV-light absorption layer to UV-light at a wavelength of 300 nm is lower than that of the overcoat film and that of the organic passivation layer, and the transmittance of the UV-light absorption layer to UV-light at a wavelength of 340 nm is higher than that of the overcoat film and that of the organic passivation layer. 
     According to the present invention, the UV-light absorption layer that absorbs UV-light at a wavelength of 300 nm or less is formed in the display region. Therefore, damaging to the alignment film by the W-light can be prevented during the UV-irradiation for sealing the TFT substrate and the counter substrate having the alignment films by means of the UV-light curable seal material. Since a light shielding mask for protecting the display region against the UV-light radiated in the UV-irradiation step can be saved, the manufacturing cost of the liquid crystal display device can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional view of a liquid crystal display device according to Embodiment 1; 
         FIG. 2  is a manufacturing process of a liquid crystal display device according to the present invention; 
         FIG. 3  shows the UV-light transmission characteristic of a UV-light absorption layer relative to wavelength; 
         FIG. 4  is a table comparing the UV-light transmission characteristics of the liquid crystal display devices of Embodiment 1 and a conventional example: 
         FIG. 5  is a cross sectional view of a liquid crystal display device according to Embodiment 2; 
         FIG. 6  is a table comparing the UV-light transmission characteristics of the liquid crystal display devices of Embodiment 2 and 1 and the conventional example: 
         FIG. 7  is a cross sectional view of a liquid crystal display device according to Embodiment 3: 
         FIG. 8  is a cross sectional view of a liquid crystal display device according to Embodiment 4; 
         FIG. 9  is a cross sectional view of a display region of an IPS liquid crystal display device; 
         FIG. 10  is a plan view showing an example of a pixel electrode of the IPS liquid crystal display device; and 
         FIG. 11  is a cross sectional view of the display region and the seal portion of the IPS liquid crystal display device. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Prior to the explanation of the embodiments of the present invention, the configuration of an IPS liquid crystal display device to which the present invention is applied is described. 
       FIG. 9  is a cross sectional view showing a structure in a display region of an IPS liquid crystal display device. The structure shown in  FIG. 9  is the structure generally used at present. In brief, a comb-teeth pixel electrode  110  is formed over a counter electrode  108  formed in a solid coated form with an insulation film  109  put between them. Liquid crystal molecules  301  are rotated by the voltage between the pixel electrode  110  and the counter electrode  108 , and the light transmittance of the liquid crystal layer  300  of each pixel is controlled to thereby form an image. 
     In  FIG. 9 , a gate electrode  101  is formed over a TFT substrate  100  formed of glass. The gate electrode  101  is formed in the same layer as the scanning line. The gate electrode  101  is formed from an AlNd alloy and a MoCr alloy stacked thereover. 
     A gate insulation film  102  of SiN is formed covering the gate electrode  101 . A semiconductor layer  103  of an a-Si film formed of is formed over the gate insulation film  102  at a position opposing the gate electrode  101 . The a-Si film forms a channel portion of the TFT, and over the a-Si film, a drain electrode  104  and a source electrode  105  are formed with the channel portion put between them. An n+Si layer (not shown) is formed between the a-Si film and the drain electrode  104  or the source electrode  105 . The n+Si layer is for establishing ohmic contact between the semiconductor layer  103  and the drain electrode  104  or the source electrode  105 . 
     The drain electrode  104  also serves as a video signal line, and the source electrode  105  is connected with the pixel electrode  110 . The drain electrode  104  and the source electrode  105  are formed simultaneously in the same layer. In this embodiment, the drain electrode  104  or the source electrode  105  is formed of MoCr alloy. When it is desired to lower the electric resistance of the drain electrode  104  or the source electrode  105 , for example, an electrode structure such that an AlNd layer is put between MoCr alloys is used. 
     An inorganic passivation film  106  of SiN is formed to cover the TFT. The inorganic passivation film  106  protects, particularly, the channel portion of the TFT against impurities. An organic passivation film  107  is formed over the inorganic passivation film  106 . Since the organic passivation film  107  also has a function of planarizing the surface as well as protecting the TFT, the film is formed thick. The thickness is from 1 μm to 4 μm. 
     A counter electrode  108  is formed over the organic passivation film  107 . The counter electrode  108  is formed by sputtering ITO (Indium Tin Oxide), a transparent conductive film, over the entire display region. That is, the counter electrode  108  is formed in a planar form. After the counter electrode  108  is formed over the entire surface by sputtering, a portion of the counter electrode  108  is removed by etching to form a through hole  11  so as to establish conduction between the pixel electrode  110  and the source electrode  105 . 
     An interlayer insulation film  109  of SiN is formed covering the counter electrode  108 . After the interlayer insulation film  109  is formed, the through hole  111  is formed by etching. The through hole  111  is formed by etching the inorganic passivation film  106  using the interlayer insulation film  109  as a resist. 
     Then, ITO which will be the pixel electrode  110  covering the interlayer insulation film  109  and the through hole  111  is formed by sputtering. The pixel electrode  110  is formed by pattering the sputtered ITO. ITO as the pixel electrode  110  is deposited in the through hole  111  as well. The source electrode  105  extending from the TFT and the pixel electrode  110  are connected via the through hole  111  so that video signals are supplied to the pixel electrode  110 . 
       FIG. 10  shows an example of the pixel electrode  110 . The pixel electrode  110  is a comb-teeth electrode. Slits  112  are formed between the comb-teeth. A planar counter electrode  108  is formed below the pixel electrode  110  with an interlayer insulation film  109  not illustrated put between them. 
     When video signals are applied to the pixel electrode  110 , liquid crystal molecules  301  are rotated by the lines of electric force generated between the pixel electrode  110  and the counter electrode  108  through the slit  112 . The light transmitting the liquid crystal layer  300  is thus controlled, and thereby an image is formed. 
     Returning to  FIG. 9 , an alignment film  113  for aligning the liquid crystal molecules  301  is formed over the pixel electrode  110 . In  FIG. 9 , a counter substrate  200  is disposed with a liquid crystal layer  300  put between them. Since the device shown in  FIG. 9  is a monochromatic liquid crystal display device, a black matrix  201  and an overcoat film  202  covering it are formed at the inner side of the counter substrate  200 . 
     While the black matrix  201  is for improving the contrast, it also functions as a light shielding film for the TFT. The overcoat film  202  is formed to moderate the roughness of the surface. An alignment film  113  for determining the initial orientation of the liquid crystals is formed over the overcoat film  202 . The alignment film  113  of the counter substrate side is also processed with an alignment treatment by optical alignment in the same manner as for the alignment film  113  of the TFT substrate side. 
     Although not illustrated in  FIG. 9 , a columnar spacer made of resin is formed on the counter substrate side in order to define the gap between the TFT substrate  100  and the counter substrate  200 . Since the device of  FIG. 9  is a monochromatic liquid crystal display device, color filters are not present. In color liquid crystal display devices, color filters of colors such as red, green, blue, etc. are formed at both sides of the black matrix  201 . 
       FIG. 9  shows a configuration in which the counter electrode  108  is formed over the organic passivation film  107 , and the comb-teeth pixel electrode  110  is disposed thereover with the interlayer insulation film  109  put between them. By contrast, there is also an IPS device of a configuration in which the pixel electrode  110  is disposed over the organic passivation film  107 , and a comb-teeth counter electrode  108  is disposed thereover with the interlayer insulation film  109  put between them. The present invention can be applied to either of the types of IPS. 
       FIG. 11  is a cross sectional view of the display region and the seal portion of the IPS liquid crystal display device shown in  FIG. 9  employing optical, alignment. 
     In  FIG. 11 , the part from the gate electrode  101  to the inorganic passivation film  106  in  FIG. 9  are collectively illustrated as a TFT circuit  120 . In  FIG. 11 , the TFT circuit  120  is formed over a TFT substrate  100 , an organic passivation film  107  is formed thereover, and a common electrode  108  painted in a solid form is formed over the organic passivation film  107 . A comb-teeth pixel electrode  110  is formed over the common electrode  108  with the interlayer insulation film  109  put between them, and the pixel electrode  110  is covered by an alignment film  113 . 
     In  FIG. 11 , black matrices  201  are formed on a counter substrate  200 . An overcoat film  202  is formed to cover the black matrices  201 , and an alignment film  113  is formed over the overcoat film  202 . Further, a columnar spacer  130  is formed between the counter substrate  200  and the TFT substrate  100 . 
     In  FIG. 11 , a seal material  150  is formed at the periphery of the counter substrate  200  and the TFT substrate  100 , and a liquid crystal layer  300  is sealed in the inner side of the seal material  150 . In  FIG. 11 , the seal material  150  is formed between the interlayer insulation film  109  of the TFT substrate  100  and the overcoat film  202  of the counter substrate  200 . The alignment films  113  do not exist at the portion the seal material  150  is formed. This is because the alignment film  113  has a property of lowering the adhesion of the seal material  150 . 
     In  FIG. 11 , the alignment film  113  is optically aligned by UV-light at a wavelength of 300 nm or less and the seal material  150  is cured by UV-light at a wavelength of 340 nm or more. At the time the seal material  150  is to be cured, the optical alignment for the alignment film  113  will already be finished. If the UV-light at a wavelength of 300 nm or less is applied again to the alignment film  113  after finishing the alignment treatment, the alignment film  113  will deteriorate. 
     The degradation can be prevented by filtering the UV-light for curing the seal material  150  and use the UV-light that has been cut off the light at a wavelength of 300 nm or less, or by using a UV-light shielding mask to thereby prevent radiation of the UV-light to the alignment film  113 . However, forming the filter for UV-light increases the manufacturing cost, and the filter has to be replaced frequently because the UV-light deteriorates the filter. On the other hand, the method of using the light screening mask involves the problem as described herein earlier (refer to SUMMARY OF THE INVENTION). 
     The present invention described in the following by way of embodiments provides a configuration that can prevent UV-degradation of the alignment film without providing a filter for the UV-light light source and using a light shielding mask upon UV-curing of the seal material. 
     [Embodiment 1] 
       FIG. 1  is a cross sectional view showing the structure of a liquid crystal display device of Embodiment 1. A cross sectional view of the display region is shown on the left and a cross sectional view of the seal portion is shown on the right. 
     In  FIG. 1 , a TFT circuit  120  is formed over a TFT substrate  100 . The TFT circuit  120  collectively represents the configuration from the gate electrode  101  to the inorganic passivation film  106  in  FIG. 9 , The same applies to the following drawings. 
     The device shown in  FIG. 1  is a monochromatic liquid crystal display device. Since the configuration of  FIG. 1  is identical with that of  FIG. 11  except that a UV-light absorption layer  210 , a feature of the present invention, is formed between each black matrix  201 , detailed description for the structure is omitted. The arrow UV in  FIG. 1  represents the UV-light for curing a seal member  150 . 
       FIG. 2  is a flow of manufacturing of the liquid crystal display device of Embodiment 1. In  FIG. 2 , the manufacturing flow for the TFT substrate  100  is shown on the left. Since the manufacturing process for the TFT substrate  100  has been described with reference to  FIG. 9 , details thereof are omitted. After an alignment film  113  is coated over the TFT substrate  100  and then baked, an alignment treatment is performed on the alignment film  113  by using UV-light. A wavelength of the UV-light effective for the alignment treatment is 300 nm or less. 
     Since the manufacturing process for the counter substrate  200  shown on the right side of  FIG. 2  has been described with reference to  FIG. 9 , its details are omitted. After coating and baking the alignment film  113 , an alignment treatment is performed upon the alignment film  113  by using UV-light at a wavelength of 300 nm or less. Then, a seal material  150  is formed on the counter substrate  200  and liquid crystals are dropped into the region surrounded by the seal material  150 . 
     Next, the TFT substrate  100  and the counter substrate  200  are bonded by means of the seal material  150 . As shown in  FIG. 1 , UV-light is radiated on the counter substrate side to cure the seal material  150 . A light shielding mask is not used at this process. The seal material  150  reacted and cured by UV-light at a wavelength of 340 nm or more, however, the UV-light used here includes not only UV-light at a wavelength of 340 nm or more but also UV-light at a wavelength of 300 nm or less. In the conventional configuration, when the UV-light includes UV-light at a wavelength of 300 nm or less, the alignment film is degraded if the seal material  150  is cured without using the light shielding mask. 
     In the portion where a black matrix  201  is formed, the black matrix  210  yields a light shielding effect against the UV-light. However, in the conventional embodiment, since only the overcoat film  202  is present at the portions where the black matrices  201  are not formed, the UV-light at a wavelength of 300 nm or less transmits the overcoat film  202 . In this embodiment, a UV-light absorption layer  210  is formed between a black matrix  201  and a black matrix  201  as to shield particularly the UV-light at a wavelength of 300 nm or less. Thus, degradation of the alignment film can be prevented without disposing a light shielding mask. 
       FIG. 3  is a graph showing the UV-light transmittances of the organic materials used in the present invention: that is, the overcoat film  202  (material for OC), the organic passivation film  107  (organic PAS material), and the UV-light absorption layer  210  (UV absorption layer) which are. As shown in  FIG. 3 , the transmittance of the UV-light absorption layer  210  is extremely low to UV-light at a wavelength of 300 nm or less. On the other hand, the layer has a high transmittance to UV-light at a wavelength of 340 nm or more. 
     In  FIG. 3 , the transmittance of the UV-light absorption layer  210  to the UV-light at a wavelength of 300 nm is 10%, and the transmittance of the UV-light absorption layer  210  to the UV-light at a wavelength of 340 nm is 90%. The values represent those that can be obtained when the UV-light absorption layer  210  has a thickness of 1 μm. The table in  FIG. 4  shows the result of an evaluation of the transmittances in the display region and the seal portion of the liquid crystal display device shown in  FIG. 1  to the UV-light at a wavelength of 300 nm and at a wavelength of 340 nm, for the conventional example and the present embodiment provided with the UV-light absorption layer  210 , respectively. 
       FIG. 4  shows the intensity of the IV-light that were radiated from the counter substrate  200  side, transmitted through the liquid crystal display device, and then measured at the TFT substrate  100  side. 
     In  FIG. 4 , since the configurations of the seal portions  150  of the conventional example and this embodiment are same, the UV-light transmittance is identical. On the other hand, in the display portion, since the UV-light absorption layer  210  exists in this embodiment, while the transmittance to the UV-light at a wavelength of 300 nm is 2.7% in the conventional example, it is lowered to 0.6% in this embodiment. As can be seen from  FIG. 3 , the transmittance to UV-light at a wavelength of 300 nm or less is further lowered. Therefore, according to this embodiment, since the UV-light at a wavelength of 300 nm or less that affects the alignment film  113  scarcely transmits in the display region, the damage to the alignment film  113  due to the UV-light can be inhibited. 
     However, the transmittance to the UV-light at a wavelength of 340 nm is 13.6% in the conventional example, whereas it increases to 19.9% in this embodiment. This is because the UV-light absorption layer shows higher transmittance than that of the overcoat film  202  to the wavelength at a wavelength of 340 nm or more. However, since the UV-light at a wavelength of 340 nm or more causes no damage to the alignment film  113 , practically there would be no problem. 
     The table in  FIG. 4  shows examples. The film thickness of the UV-light absorption layer  210 , etc. actually varies. The effect of the invention can be obtained even when the thickness of the UV-light absorption layer  210  and other elements varies, so long as the transmittance to the UV-light at a wavelength of 300 nm or less in the display region is 1% or lower, and the transmittance to the UV-light at a wavelength of 340 nm in the seal portion is 20% or higher. 
     [Embodiment 2] 
       FIG. 5  is a cross sectional view showing the structure of a liquid crystal device of Embodiment 2. A cross sectional view of the display region is shown on the left and the cross sectional view of the seal portion is shown on the right. The configuration of  FIG. 5  is different from that of Embodiment 1 in  FIG. 1  in that a UV-light absorption layer  210  is formed instead of the overcoat film. In  FIG. 5 , the UV-light absorption layer  210  is formed not only in the display region but also in the seal portion instead of the overcoat film. 
     In  FIG. 5 , after the TFT substrate  100  is bonded to the counter substrate  200  by means of the seal material  150 , a UV-light is radiated from the counter substrate  200  side to cure the seal material  150  in the same manner as performed in Embodiment 1. Further, in this embodiment, a light shielding mask for preventing radiation of the UV-light to the display region is not used as with Embodiment 1. 
     The transmittance of the UV-light absorption layer  210  and the overcoat film  202  to UV-light is as shown in  FIG. 3 . The UV-light absorption layer  210  has a lower transmittance to UV-light at a wavelength of 300 nm or less and shows a higher transmittance to UV-light at a wavelength of 340 nm or more compared with the overcoat film  202 . Accordingly, even if the UV-light is radiated without using a light shielding mask, only an extremely small amount of the UV-light at a wavelength of 300 nm or less reaches the alignment film  113  in the display region. The effect of the UV-light on the alignment film present in the display region is extremely small. 
     The table shown in  FIG. 6  compares the transmittances of UV-light at a wavelength of 300 nm and UV-light at a wavelength of 340 nm in the display portion and in the seal portion of this embodiment and Embodiment 1 and the conventional example. The measuring method is similar to that taken for the measurement for  FIG. 4 , the UV-light is radiated from the counter substrate  200  side and the degree of transmittance of the UV-light are measured at the TFT substrate  100  side and compared. 
     In the seal portion  150 , different from the conventional example and Embodiment 1, the UV-light absorption layer  210  is formed instead of the overcoat film  202  in this embodiment. While the transmittance to the UV-light at a wavelength of 300 nm is as low as 2.7%, the transmittance to the UV-light at a wavelength of 340 nm is as high as 49.2%. That is, since the UV-light at a wavelength of 340 nm for curing the seal material  150  is less absorbed by the UV-light absorption layer  210 , the seal material is irradiated efficiently with the UV-light. Therefore, the seal material  150  can be cured efficiently by the UV-light in this embodiment. 
     In the display region, regarding the UV-light at a wavelength of 300 nm, since the overcoat film  202  is entirely replaced by the UV-light absorption layer  210 , the transmittance is more lowered than that of Embodiment 1, to 0.2%. Accordingly, since the UV-light at a wavelength of 300 nm is cut off more efficiently in this embodiment, damage to the alignment film  113  can be prevented more efficiently. Although the transmittance to the UV-light at a wavelength of 340 nm in the display region is as high as 49.2%, the effect caused by the UV-light at a wavelength of 340 nm on the alignment film is small, so it does not damage the alignment film  113 . 
     As described above, the seal material  150  can be cured by UV-light without damaging the alignment film  113  even when a light shielding mask is not used in this embodiment as well. 
     As shown in  FIG. 5 , in this embodiment, a columnar spacer  130  is formed on the UV-light absorption layer  210 . By using the same material as the UV-light absorption layer  210  for the columnar spacer  130 , the UV-light absorption layer  210  and the columnar spacer  130  can be formed simultaneously. 
     As an example of this process, a UV-light absorption layer of a thickness equal to the total thickness of the UV-light absorption layer  210  and the columnar spacer  130  is coated over the counter substrate  200 . Then, only the portion other than the columnar spacer  130  is removed by etching to a predetermined thickness by controlling the exposure dose in photolithography. The columnar space  130  and the UV-light absorption layer  210  can thus be formed simultaneously in the process of forming the columnar spacer  130 , resulting in a reduced manufacturing cost. 
     [Embodiment 3] 
       FIG. 7  shows a cross sectional view of a liquid crystal display device of Embodiment 3 according to the invention. Different from Embodiment 1 and Embodiment 2, the device shown in  FIG. 7  is a color liquid crystal display device. Color filters  220  are formed between each black matrix  201  in the counter substrate  220 . On the other hand, in the TFT substrate  100 , a UV light absorption layer  210  is formed instead of an organic passivation film  107 . Since other portions have the same configuration as those of Embodiment 1 in  FIG. 1 , descriptions thereof are omitted. 
     In this embodiment, a counter substrate  200  having an optically aligned alignment film  113  and a TFT substrate  100  having an optically aligned alignment film  113  are sealed at their periphery with a UV-curable seal material  150 . As shown in  FIG. 7 , UV-light for curing the seal material  150  is radiated from the TFT substrate  100  side. The relationship of the UV-light transmittances of the organic passivation film  107  and the UV-light absorption layer  210  are as shown in  FIG. 3 . That is, the UV-light absorption layer  210  efficiently cuts off the UV-light at a wavelength of 300 nm or less, and it efficiently transmits the UV-light at a wavelength of 340 nm or more, compared with the organic passivation film  107 . 
     In the configuration shown in  FIG. 7 , when UV-light is radiated from the TFT substrate  100  side, since the UV-light absorption layer  210  is formed instead of the organic passivation film  107  at the TFT substrate  100  side, UV-light at a wavelength of 300 nm or less which may damage the alignment film  113  is efficiently cut off in the display region. Although UV-light at a wavelength of 340 nm or more is more likely to transmit through the UV-light absorption layer  210  in the display region, the UV-light at a wavelength of 340 nm or more does not damage the alignment film  113 , so there is no problem. 
     On the other hand, for the seal material  150  at the seal portion, since the UV-light absorption layer  210  formed over the TFT substrate  100  has higher transmittance to the UV-light at a wavelength of 340 nm or more, the seal material  150  can be cured efficiently. While also the UV-light at a wavelength of 300 nm or less is less radiated to the seal material  150 , the UV-light within this range causes less effect on the curing of the seal material. Thus, no problem arises. 
     As described above, the seal material  150  can be cured by UV-light with no damage on the alignment film  113  due to the UV-light radiation without using a light shielding material in this embodiment as well. 
     [Embodiment 4] 
       FIG. 8  is a cross sectional view of a liquid crystal display device showing Embodiment 4 of the invention. The device shown in  FIG. 8  is also a monochromatic liquid display device as with those of Embodiment 1 and Embodiment 2. In  FIG. 8 , a UV-light absorption layer  210  is formed between each black matrix  201  as in Embodiment 1. On the other hand, a UV-light absorption layer  210  is formed instead of an organic passivation film  107  at the TFT substrate  100  side as with Embodiment 3. That is, this embodiment has a configuration such that the UV-light at a wavelength of 300 nm or less is efficiently cut off at both the counter substrate  200  side and TFT substrate  100  side, and the transmittance to the UV-light at a wavelength of 340 nm or more is high also at both sides. 
     In this embodiment, UV-light can be radiated from both the counter substrate  200  side and the TFT substrate  100  side as shown in  FIG. 8 . Since it is adapted such that the UV-light at a wavelength of 300 nm or less is efficiently cut off at both the counter substrate  200  side and the TFT substrate  100  side, the UV-light does not damage the alignment film  113 . 
     On the other hand, the UV-light at a wavelength of 340 nm or higher is transmitted efficiently, particularly in the TFT substrate  100  side. Further, also in the counter substrate  200  side, the transmittance of the seal portion  3  to the UV-light at a wavelength of 340 nm or more is maintained at a level equivalent to that of the conventional example. 
     Therefore, according to this embodiment, since the radiation dose of the UV-light at a wavelength of 340 nm or more to the seal material  150  can be increased remarkably, the seal material  150  can be cured by UV-light within a shorter time period. Further, the seal material  150  can be cured by UV-light with no damage to the alignment film  113  without using a light shielding mask as with Embodiment 1 to 3.