JP5151554B2 - Liquid crystal display device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a liquid crystal display device and a manufacturing method thereof, and more particularly to a liquid crystal display device characterized by an alignment film formed on a surface of a substrate and a manufacturing method thereof.

  As display devices for AV equipment and OA equipment, liquid crystal display devices are widely used because of their advantages such as thinness, light weight, and low power consumption. This liquid crystal display device includes one substrate (hereinafter referred to as a TFT substrate) in which switching elements such as TFT (Thin Film Transistor) are formed in a matrix, a color filter (CF), a black matrix (BM), and the like. A liquid crystal panel in which liquid crystal is sandwiched between the other formed substrate (hereinafter referred to as a CF substrate), a backlight unit for irradiating the liquid crystal panel with backlight light, and the like are provided.

  FIG. 10 is a plan view showing a configuration of a CF substrate or a TFT substrate constituting a conventional liquid crystal panel. In manufacturing a liquid crystal panel, an alignment material is formed on both the CF substrate and the TFT substrate in an alignment film application step to form an alignment film. Examples of the method for forming the alignment film include an alignment film printing method, an ink jet method, and the like. Both types are applied to the alignment film, then subjected to a temporary drying step and then subjected to alignment film main baking to thermally imidize, and the required alignment. I have a membrane. This alignment film is generally formed so as to cover the display area inside the seal area to which the sealing material 4 is applied (for example, refer to Patent Documents 1 and 2 below regarding the formation of the alignment film).

Japanese Patent Laid-Open No. 2003-222887 JP 2006-78930 A

  FIG. 11 shows a cross-sectional structure between an end portion and a display region of a conventional liquid crystal panel. As shown in FIG. 11, an alignment film 6 is formed on the opposing surfaces of the TFT substrate 2 and the CF substrate 3 so as to cover the display area. When a bias is applied to the liquid crystal panel, the alignment material 6 The remaining impurity ions enter the display region and are adsorbed on the surface of the alignment film 6. Further, when a bias is applied to the liquid crystal panel, the uncured component of the sealing material 4 is also exuded with time and is adsorbed to the alignment film 6 in the display region. As a result, display defects such as spots and unevenness occur in the pixels to which contaminants such as residual impurity ions and uncured components are fixed.

  Therefore, Patent Document 1 discloses a method of forming irregularities on the substrate surface between the sealing material 4 and the display area and increasing the surface area of the alignment film that is adsorbed before the contaminants reach the display area. Yes. FIG. 12 shows a cross-sectional structure between the end portion of the liquid crystal panel and the display region of Patent Document 1. As shown in FIG. 12, it is possible to increase the effect of adsorbing contaminants by increasing the surface area of the alignment film 6 with the uneven portions 10 formed on the substrate surface. Invasion cannot be sufficiently suppressed.

  In Patent Document 2, an alignment film formed in a region surrounded by a TFT substrate display region and a sealing material formation region, and a region surrounded by a CF substrate display region and a sealing material formation region. Due to the different characteristics of the alignment film formed, that is, the charging characteristics of the alignment film differing from each other on the opposite surface, a potential difference is generated between the display area and the area surrounded by the sealing material formation area, and the display area. And a method of adsorbing impurity ions in a region surrounded by a sealing material formation region. FIG. 13 shows a cross-sectional structure between the end portion of the liquid crystal panel and the display region of Patent Document 2. As shown in FIG. 13, by causing a potential difference between the alignment films 6a and 6b, an effect of adsorbing the impurity ions can be exerted on the surface of the alignment film that shows charges different from the impurity ions. On the alignment film side shown, adsorption is hindered, and impurity ions may be diffused into the pixel. As a result, there is a possibility that display defects such as spots and unevenness will eventually occur in the pixel by a long-term reliability test.

  As described above, in at least one substrate, the alignment film formed between the display region and the sealing material 4 has the same film structure as that of the alignment film in the display region. There is a problem that the uncured component of the material 4 easily penetrates into the display region and is finally adsorbed on the surface of the alignment film, thereby reducing the display quality.

  The present invention has been made in view of the above problems, and its main purpose is to suppress display defects caused by residual impurity ions and uncured components of the sealing material, and to significantly improve reliability. An object of the present invention is to provide a liquid crystal display device and a manufacturing method thereof.

In order to achieve the above object, according to the present invention, an alignment film is formed on opposite surfaces of a pair of substrates, a sealing material is formed outside a display region of at least one substrate, and a liquid crystal material is sealed between the pair of substrates. In the liquid crystal display device, the alignment film is formed in at least a first alignment film formed so as to cover the display region, and a region outside the first alignment film and inside the sealing material. The second alignment film has a porous film structure, and has higher ionic impurity adsorptivity than the first alignment film.

  For confirmation of the porous film, the first alignment film and the second alignment film are cut out and measured using an automatic gas adsorption amount measuring device (Belsorp 18 plus-T manufactured by Nippon Bell Co., Ltd.). . From the obtained adsorption / desorption isotherm, the pore distribution and pore volume can be determined by the Molecular-Probe method (MP method) when the pore size is 2 nm or less, and the Dollimore-Heal method (DH method) when the pore size is 2 nm to 200 nm. It is.

  In the present invention, the diamine chain serving as the main chain in the second alignment film may be longer than the diamine chain serving as the main chain in the first alignment film. For the confirmation of the diamine chain, the first alignment film and the second alignment film are collected, and a gas chromatograph mass spectrometer (JMS-GCmate II manufactured by JEOL Ltd.), a liquid chromatograph mass spectrometer ( Measured using JEOL Co., Ltd. JMS-T100LC type. Thereby, structural information of the diamine chain can be obtained.

Moreover, in this invention, the imidation rate after baking of the said 2nd alignment film can be set as the structure lower than the imidation rate after baking of the said 1st alignment film. In order to confirm the imidization rate, the first alignment film and the second alignment film are collected, and a Fourier transform infrared spectrophotometer (FT / IR-610 manufactured by JASCO Corporation) is used. taking measurement. It is possible to measure the IR spectrum of the collected alignment film by the KBr tablet method and calculate the imidization ratio from the peak height ratio derived from the imide ring.

  In the present invention, the film thickness of the second alignment film may be larger than the film thickness of the first alignment film. In order to confirm the film thickness of the alignment film, the first alignment film and the second alignment film are cut out and measured using a FIB-SEM composite apparatus (SMI 3050SE, manufactured by SII). Thereby, film thickness information of the alignment film can be obtained.

Further, the present invention includes at least a coating process for applying an alignment film on the substrate surface, a temporary drying process for temporarily drying the alignment film, a baking process for firing the alignment film, a rubbing process, and a rubbing cleaning process. In the manufacturing method of the liquid crystal display device having the above, in the coating step, the alignment film is formed so as to cover at least the display region, and in the temporary drying step, the drying temperature outside the display region is locally increased. A porous alignment film is formed on the outer side of the display area, and the alignment film on the outer side of the display area is modified between the temporary drying process and the rubbing cleaning process to impart adsorptivity.

  In the present invention, plasma ashing is locally performed on the outer side of the display region between the baking step and the rubbing cleaning step, and a porous alignment film is formed on the outer side of the display region. be able to.

Further, the present invention includes at least a step of applying an alignment film on the substrate surface, a step of temporarily drying the alignment film, a step of baking the alignment film, a rubbing step, and a rubbing cleaning step in this order. In the manufacturing method of the liquid crystal display device having, in the coating step, the portion facing the outer side of the display region has a smaller number of reliefs on the surface or the area of the relief convex portion than the portion facing the inner side of the display region, or Then, using an alignment plate having a large relief height, the alignment film outside the display area is printed thickly to enhance the adsorptivity of the alignment film outside the display area.

  As described above, the alignment film formed on both the CF substrate and the TFT substrate includes the first alignment film covering at least the display region, and the second alignment film outside the first alignment film and inside the sealing material. And the second alignment film has a higher quality of adsorption of ionic impurities than the first alignment film. It is possible to provide a high-quality liquid crystal display device that can suppress the leakage of a typical sealing material component and has greatly improved reliability.

  According to the liquid crystal display device and the method of manufacturing the same of the present invention, a pollutant from the sealing material enters the display region by forming a porous alignment film in a region outside at least the alignment film covering the display region. , Can be fixed. Further, by increasing the thickness of the alignment film having a porous structure, the effective surface area for adsorbing contaminants can be increased, and the adsorption efficiency of contaminants can be improved.

  This effect makes it possible to provide a high-quality liquid crystal display device with significantly improved reliability. In addition, the effective impurity adsorption efficiency can be improved while maintaining the narrow frame structure of the liquid crystal panel. Furthermore, by using the same alignment material, the structure of the present invention can be realized in a simple process, and the amount of use and the lead time can be shortened by eliminating the trouble of changing the type.

  As shown in the prior art, when a bias is applied to the liquid crystal panel, residual impurity ions from the sealing material penetrate into the display region, and uncured components of the sealing material 4 ooze out over time. Contaminants such as impurity ions and uncured components are adsorbed to the alignment film 6 in the display region, and display defects such as spots and unevenness occur in the pixels where the contaminants are fixed.

  Here, as a principle of adsorption of contaminants and the like on the alignment film, it is considered that impurity ions are attracted to the polyamic acid (unreacted component) in the alignment film. That is, usually, polyimide is generated from polyamic acid by an alignment film baking step, but at least 10 to 15% of polyamic acid is present as a residue in the thermally imidized alignment film.

  FIG. 5A shows an example of the molecular structure of polyamic acid. The polyamic acid has a carbonyl group, and adsorbs by attracting Na and K, which are impurity ions, to the CO—OH group. In addition, contaminants other than impurity ions enter fine pores and are physically adsorbed in pores corresponding to the respective molecular weight sizes.

  Therefore, in the present invention, a porous alignment film having a film quality with higher ionic impurity adsorption than the alignment film is formed outside the alignment film formed so as to cover at least the display region. Thus, the contaminant is efficiently adsorbed outside the display area, and the contaminant is prevented from entering and fixing in the display area. Hereinafter, description will be given with reference to the drawings.

  FIG. 1 is a plan view showing a configuration of a CF substrate or a TFT substrate constituting a liquid crystal panel according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing the structure of the XX ′ portion of FIG. is there. FIG. 3 is an enlarged view of a circled portion of FIG.

  As shown in FIGS. 1 and 2, in the alignment film application step, an alignment material is generally formed by applying an alignment material on the surfaces of the CF substrate and the TFT substrate. At this time, the alignment film 6 is formed so as to cover the display area in which the pixels are arranged in a matrix, and the area outside the alignment film 6, for example, between the display area and the seal area surrounded by the seal material 4, A porous alignment film 7 having a porous film structure with higher impurity adsorption than the alignment film 6 is formed so that impurities can be efficiently adsorbed outside the display region. The alignment film 6 only needs to be formed in a region covering at least the display region, and the porous alignment film 7 only needs to be formed outside the display region.

  Here, by enclosing the liquid crystal material 5, the liquid crystal material 5 and the surface layer portion of the sealing material 4 come into contact with each other, and residual impurity ions such as Na, K, Cl move from the surface layer portion of the sealing material 4 into the liquid crystal material 5. Begin to. The residual impurity ions move more significantly when a bias is applied to the liquid crystal panel, and are adsorbed on the alignment film surface. In addition, when a bias is applied to the liquid crystal panel, uncured components of the sealing material 4 begin to elute with time and are similarly adsorbed on the alignment film surface.

  However, in the structure of this embodiment, since the porous alignment film 7 is formed in the region outside the display region, contaminants such as residual impurity ions and uncured components are efficiently adsorbed on the porous alignment film 7. Intrusion / fixation into the display area can be prevented. As a result, it is possible to provide a high-quality liquid crystal display device with significantly improved reliability.

  FIG. 3A is a diagram schematically showing the structure of the porous alignment film 7. The porous alignment film 7 has pores 9 inside as well as the surface thereof, and serves as an ion adsorption layer 8. Function. For residual impurity ions such as Na, K, and Cl, the diameter of the pores 9 (mesopores to micropores) of about 50 nm or less is effectively adsorbed, and for the uncured component of the sealing material 4 Since the diameter of the pores 9 of 20 nm to 200 nm (mesopores to macropores) is effectively adsorbed, the diameter of the pores 9 is preferably set within this range. The diameter of the pores 9 of the porous alignment film 7 according to the present invention is preferably about 50 nm or less, and those having a wide pore distribution from mesopores to micropores are particularly effective.

  As a method for forming the porous alignment film 7, for example, there is a method of partially raising the drying temperature of the alignment film application region outside the display region in a temporary drying step in the alignment film application step. As a result, the solvent in the alignment material is rapidly blown off and the imidization is promoted to make the film sparse, and a porous film can be formed.

  As another forming method, a porous film may be formed by ashing the alignment film in the alignment film application area outside the display area by an ashing apparatus such as a plasma processing apparatus to form fine holes. Is possible.

  In addition, a substance that can be extracted later with a solvent is mixed in the alignment material, and after forming this alignment film on the alignment film application area outside the display area, the substance is extracted using the solvent to form fine pores. There is also a method of forming. In this case, it is necessary to use an extractable substance that does not dissolve the alignment material component.

  Further, there is a method in which fine filler is further mixed with the alignment material to form an alignment film application region outside the display region, and then the filler is physically removed to form fine holes.

  Referring to the flow of FIG. 4, a manufacturing method for providing a leveling process for forming a porous alignment film in the temporary drying process in the alignment film coating process, and a porous alignment film formed between the alignment film baking process and the rubbing cleaning process. A manufacturing method such as providing an ashing step, a solvent extraction step, and a filler removal step can be proposed. At this time, in order to form a more porous film, it is desirable to combine the porous alignment film forming steps.

  In order to improve the adsorption efficiency of impurities, as shown in FIG. 3B, the effective adsorption surface area is increased by increasing the alignment film thickness of the region to which a porous alignment film is provided outside the display region. It can also be made. The alignment film thickness of the display area of the present invention is set from the range of 10 nm to 200 nm for each panel type, and the porous alignment film thickness outside the display area can be made larger than the alignment film thickness of the display area. Improve the adsorption of impurities more effectively.

  For example, in the case of the alignment film printing method, the number of reliefs in the alignment film application area outside the display area can be reduced with respect to the number of reliefs on the surface of the alignment plate facing the alignment film application area inside the display area. I can do it. In this case, it is necessary to make the relief diameter (relief convex area) of the alignment film application region inside and outside the display region constant. Similarly, it can be dealt with by reducing the relief convex area or increasing the relief height. Needless to say, more effective effects can be obtained by combining the reduction in the number of reliefs, the reduction in the relief convex area, and the increase in the relief height. Further, in the case of the ink jet system, it is possible to cope with the problem by increasing the alignment material discharge amount or the number of discharges in the alignment film application region outside the display region with respect to the alignment film application region inside the display region.

  EXAMPLES Hereinafter, although this invention is demonstrated with reference to an Example, this invention is not limited to a following example, unless the summary of this invention is changed.

  First, a liquid crystal display device and a manufacturing method thereof according to a first embodiment of the present invention will be described with reference to FIG.

  In general, a liquid crystal panel has a TFT substrate on which switching elements such as TFTs are formed in a matrix, and a CF substrate on which a black matrix, a color filter, and the like are formed. The aligned alignment film is formed. And between the two substrates, a predetermined shape of polymer beads, insulating spacers such as silica beads or insulating pillars such as acrylic resin are arranged to form a predetermined gap, and the gap is sealed. An image is displayed by controlling the alignment direction of the liquid crystal with an electric field generated by an electrode formed on at least one substrate.

  Therefore, in order to manufacture a high-quality liquid crystal display device with greatly improved reliability, it is necessary to prevent contaminants from entering the display area and prevent the contaminants from fixing on the alignment film surface. Therefore, in this embodiment, a liquid crystal panel is manufactured by the following method.

  In FIG. 6, the schematic of the alignment film application | coating-alignment film baking process for manufacturing the liquid crystal panel of this invention is shown. In the alignment film coating step, printing was performed using an alignment plate to apply an alignment material to the surfaces of the TFT substrate and the CF substrate, and an alignment film was applied to the display area and the display area outside (A in FIG. 6). In the next alignment film temporary drying step, the display region is positioned outside the display region so that leveling can be performed at a temperature of about 80 to 90 ° C. and the outside of the display region at a temperature of about 120 to 150 ° C. higher than the above temperature. The hot plate drying temperature was increased locally (B in FIG. 6). As a result, while shortening the lead time of the temporary drying step, an alignment film having a controlled printability can be formed in the display area, and a porous alignment film can be formed outside the display area. In the next alignment film baking step, the display area and the alignment film outside the display area were subjected to main baking to obtain a thermal imidization to obtain the necessary alignment film (C in FIG. 6). Thereafter, in the rubbing step, the alignment film surfaces of the TFT substrate and the CF substrate were rubbed with a rayon rubbing roll. Subsequently, in the rubbing cleaning / drying process, the alignment film surface of the TFT substrate and the CF substrate and the back surface of the substrate were subjected to chemical cleaning and pure cleaning, followed by IR drying at a temperature of 185 ° C. Next, in the seal coating process, a sealing material (in the case of producing a TN mode liquid crystal display panel, Au balls are mixed as a conductive material in the sealing material) is placed on the outer periphery (auxiliary) seal at a predetermined position on the TFT substrate. And this seal | sticker was each apply | coated to the shape of a closed curve. Subsequently, in the liquid crystal dropping step, a liquid crystal material was dropped inside the main seal, and a predetermined dropping amount was dropped into a matrix inside (a large number of dots in the matrix) inside the main seal. Thereafter, in the bonding step, the TFT substrate and the CF substrate were contacted and pressed to uniformly diffuse the liquid crystal material in the pixel portion and the peripheral portion between the substrates, and the gaps between the substrates were formed uniformly with columns. Next, in order to prevent misalignment of the bonded substrate during conveyance to the UV curing step, UV temporary curing was performed at several locations on the outer periphery seal as a temporary fixing of the sealing material. Then, in the next UV curing step, the sealing material was cured by 3000 mJ UV irradiation. Furthermore, in the thermosetting process, the sealing material was completely cured by heating at a temperature of 120 ° C. Thereafter, the manufactured liquid crystal display panel was subjected to an ACF (Anisotropic Conductive Film) pasting / TCP (Tape Carrier Package) pressure welding process and a substrate pressure welding process, and a backlight light source was attached in the assembly process, thereby completing a liquid crystal display device.

  Here, a reliability test of the liquid crystal display device of this example was performed. In a driving test under a temperature of 60 ° C. and a humidity of 60%, five conventional liquid crystal display devices were compared for comparison. As a result, after 500 hours from the start of the test, the conventional liquid crystal display device had unevenness and spot-like spots on the periphery of the panel, but the liquid crystal display device of this example did not have any stains or unevenness. Further, no stains and unevenness were observed in the liquid crystal display device of this example even after the test was started 1000 hours.

  Next, a liquid crystal display device and a method for manufacturing the same according to a second embodiment of the present invention will be described with reference to FIG.

  In FIG. 7, the schematic of the alignment film application | coating-plasma ashing process for manufacturing the liquid crystal panel of a present Example is shown. As in the first embodiment, in the alignment film coating process, printing is performed using an alignment plate to apply an alignment material to the surfaces of the TFT substrate and the CF substrate, and the alignment film is formed outside the display area and the display area. (A in FIG. 7). In the next alignment film temporary drying step, leveling is performed at a temperature of 80 ° C. on both the display region and the outside of the display region (FIG. 7B), and in the subsequent alignment film baking step, main baking is performed at a temperature of 230 ° C. An alignment film was obtained (C in FIG. 7). Next, a plasma ashing process for forming a porous alignment film was performed (D in FIG. 7). Here, local ashing was performed on the alignment film outside the display region. Porous alignment film by using oxygen or a mixed gas of nitrogen and oxygen as the processing gas, irradiating the plasma locally outside the display area to be ashed by driving a remote plasma head and opening fine holes Formed. Thereafter, in the rubbing step, the alignment film surfaces of the TFT substrate and the CF substrate were rubbed with a rayon rubbing roll. Subsequently, in the rubbing cleaning / drying process, the alignment film surface of the TFT substrate and the CF substrate and the back surface of the substrate were subjected to chemical cleaning and pure cleaning, followed by IR drying at a temperature of 185 ° C. Next, in the seal coating process, a sealing material (in the case of producing a TN mode liquid crystal display panel, Au balls are mixed as a conductive material in the sealing material) is placed on the outer periphery (auxiliary) seal at a predetermined position on the TFT substrate. And this seal | sticker was each apply | coated to the shape of a closed curve. Subsequently, in the liquid crystal dropping step, a liquid crystal material was dropped inside the main seal, and a predetermined dropping amount was dropped into a matrix inside (a large number of dots in the matrix) inside the main seal. Thereafter, in the bonding step, the TFT substrate and the CF substrate were contacted and pressed to uniformly diffuse the liquid crystal material in the pixel portion and the peripheral portion between the substrates, and the gaps between the substrates were formed uniformly with columns. Next, in order to prevent misalignment of the bonded substrate during conveyance to the UV curing step, UV temporary curing was performed at several locations on the outer periphery seal as a temporary fixing of the sealing material. Then, in the next UV curing step, the sealing material was cured by 3000 mJ UV irradiation. Furthermore, in the thermosetting process, the sealing material was completely cured by heating at a temperature of 120 ° C. Thereafter, the manufactured liquid crystal display panel was subjected to an ACF sticking / TCP pressure welding process and a substrate pressure welding process, and a backlight light source was attached in the assembly process, thereby completing a liquid crystal display device. Even when the rubbing process was performed before the plasma ashing process, the formation state of the porous alignment film 7 was similarly good.

  Here, a reliability test of the liquid crystal display device of this example was performed. In a driving test under a temperature of 60 ° C. and a humidity of 60%, five conventional liquid crystal display devices were compared for comparison. As a result, after 500 hours from the start of the test, the conventional liquid crystal display device had unevenness and spot-like spots on the periphery of the panel, but the liquid crystal display device of this example did not have any stains or unevenness. Further, no stains and unevenness were observed in the liquid crystal display device of this example even after the test was started 1000 hours.

  Next, a liquid crystal display device and a method for manufacturing the same according to a third embodiment of the present invention will be described.

  In the same manner as in the second embodiment described above, the alignment film coating to the alignment film baking were performed to obtain the alignment film necessary for the display area and the outside of the display area. In the next plasma ashing step, the surface of the substrate other than the outside of the display area was covered with a mask in order to perform a local ashing process on the alignment film outside the display area. A porous alignment film was formed by directly irradiating the entire surface of the substrate with plasma using a fixed plasma head and forming fine holes only outside the display area. Thereafter, in the rubbing step, the alignment film surfaces of the TFT substrate and the CF substrate were rubbed with a rayon rubbing roll. Subsequently, in the rubbing cleaning / drying process, the alignment film surface of the TFT substrate and the CF substrate and the back surface of the substrate were subjected to chemical cleaning and pure cleaning, followed by IR drying at a temperature of 185 ° C. Next, in the seal coating process, a sealing material (in the case of producing a TN mode liquid crystal display panel, Au balls are mixed as a conductive material in the sealing material) is placed on the outer periphery (auxiliary) seal at a predetermined position on the TFT substrate. And this seal | sticker was each apply | coated to the shape of a closed curve. Subsequently, in the liquid crystal dropping step, a liquid crystal material was dropped inside the main seal, and a predetermined dropping amount was dropped into a matrix inside (a large number of dots in the matrix) inside the main seal. Thereafter, in the bonding step, the TFT substrate and the CF substrate were contacted and pressed to uniformly diffuse the liquid crystal material in the pixel portion and the peripheral portion between the substrates, and the gaps between the substrates were formed uniformly with columns. Next, in order to prevent misalignment of the bonded substrate during conveyance to the UV curing step, UV temporary curing was performed at several locations on the outer periphery seal as a temporary fixing of the sealing material. Then, in the next UV curing step, the sealing material was cured by 3000 mJ UV irradiation. Furthermore, in the thermosetting process, the sealing material was completely cured by heating at a temperature of 120 ° C. Thereafter, the manufactured liquid crystal display panel was subjected to an ACF sticking / TCP pressure welding process and a substrate pressure welding process, and a backlight light source was attached in the assembly process, thereby completing a liquid crystal display device.

  Here, a reliability test of the liquid crystal display device of this example was performed. In a driving test under a temperature of 60 ° C. and a humidity of 60%, three conventional liquid crystal display devices were compared for comparison. As a result, after 500 hours from the start of the test, in the conventional liquid crystal display device, unevenness and spot-like spots occurred in the peripheral portion of the panel. However, in the liquid crystal display device of this example, the stain and unevenness were the same as in the second example. There was no outbreak. Further, no stains and unevenness were observed in the liquid crystal display device of this example even after the test was started 1000 hours.

  Next, a liquid crystal display device and a method for manufacturing the same according to a fourth embodiment of the present invention will be described.

  As in the first embodiment, in the alignment film coating process, printing is performed using an alignment plate to apply an alignment material to the surfaces of the TFT substrate and the CF substrate, and the alignment film is formed outside the display area and the display area. (A in FIG. 6). At this time, the printing plate is used in which the number of reliefs in the alignment film coating area outside the display area is reduced with respect to the number of reliefs on the surface of the alignment plate facing the alignment film coating area in the display area. The alignment film thickness outside the region is formed to be thicker than the film thickness of the display region. In the next alignment film temporary drying step, as in the first embodiment, the display area can be leveled at a temperature of 80 ° C., and the outside of the display area can be leveled at 120 ° C., which is higher than the 80 ° C. temperature. The hot plate drying temperature located outside the display area was locally increased to form a porous alignment film only outside the display area (B in FIG. 6). In the next alignment film baking step, the display area and the alignment film outside the display area were subjected to main baking at a temperature of 230 ° C. to obtain a required alignment film (C in FIG. 6). As a result, the area of the porous alignment film outside the display region increased from that of the first embodiment, and the effective adsorption surface area could be increased. Thereafter, in the rubbing step, the alignment film surfaces of the TFT substrate and the CF substrate were rubbed with a rayon rubbing roll. Subsequently, in the rubbing cleaning / drying process, the alignment film surface of the TFT substrate and the CF substrate and the back surface of the substrate were subjected to chemical cleaning and pure cleaning, followed by IR drying at a temperature of 185 ° C. Next, in the seal coating process, a sealing material (in the case of producing a TN mode liquid crystal display panel, Au balls are mixed as a conductive material in the sealing material) is placed on the outer periphery (auxiliary) seal at a predetermined position on the TFT substrate. And this seal | sticker was each apply | coated to the shape of a closed curve. Subsequently, in the liquid crystal dropping step, a liquid crystal material was dropped inside the main seal, and a predetermined dropping amount was dropped into a matrix inside (a large number of dots in the matrix) inside the main seal. Thereafter, in the bonding step, the TFT substrate and the CF substrate were contacted and pressed to uniformly diffuse the liquid crystal material in the pixel portion and the peripheral portion between the substrates, and the gaps between the substrates were formed uniformly with columns. Next, in order to prevent misalignment of the bonded substrate during conveyance to the UV curing step, UV temporary curing was performed at several locations on the outer periphery seal as a temporary fixing of the sealing material. Then, in the next UV curing step, the sealing material was cured by 3000 mJ UV irradiation. Furthermore, in the thermosetting process, the sealing material was completely cured by heating at a temperature of 120 ° C. Thereafter, the manufactured liquid crystal display panel was subjected to an ACF sticking / TCP pressure welding process and a substrate pressure welding process, and a backlight light source was attached in the assembly process, thereby completing a liquid crystal display device.

  Here, a reliability test of the liquid crystal display device of this example was performed. In a driving test under a temperature of 60 ° C. and a humidity of 60%, five conventional liquid crystal display devices were compared for comparison. As a result, after 500 hours from the start of the test, the conventional liquid crystal display device had unevenness and spot-like spots on the periphery of the panel. However, the liquid crystal display device of this example had spots and unevenness similar to the first example. There was no outbreak. Further, even after 1500 h after the start of the test, the liquid crystal display device of this example was in a good display state with no occurrence of spots or unevenness.

  Next, a liquid crystal display device and a method for manufacturing the same according to a fifth embodiment of the present invention will be described with reference to FIG.

  FIG. 8 is a schematic view of the alignment film coating to plasma ashing process for manufacturing the liquid crystal panel of this example. In the alignment film coating step, an alignment film was applied to the display area and the outside of the display area by an inkjet coating apparatus in order to apply an alignment material to the surfaces of the TFT substrate and the CF substrate (A in FIG. 8). At this time, the discharge condition of the alignment material is such that the amount of discharge and the number of discharges in the alignment film coating region outside the display region are increased with respect to the alignment film coating region inside the display region. The film thickness was formed so as to be larger than the film thickness of the display region. In the next alignment film temporary drying step, leveling is performed at a temperature of 80 ° C. on both the display area and the outside of the display area (B in FIG. 8), and in the subsequent alignment film baking step, main baking is performed at a temperature of 230 ° C. An alignment film was obtained (C in FIG. 8). Next, a plasma ashing process for forming a porous alignment film was performed (D in FIG. 8). Here, as in the second embodiment, a local ashing process was performed on the alignment film outside the display region. A porous alignment film was formed by using oxygen or a mixed gas of nitrogen and oxygen as a processing gas, locally irradiating plasma with a remote plasma head, and opening fine holes. As a result, the area of the porous alignment film on the outer side of the display area as compared with the second example was increased, and the effective adsorption surface area could be increased. Thereafter, in the rubbing step, the alignment film surfaces of the TFT substrate and the CF substrate were rubbed with a rayon rubbing roll. Subsequently, in the rubbing cleaning / drying process, the alignment film surface of the TFT substrate and the CF substrate and the back surface of the substrate were subjected to chemical cleaning and pure cleaning, followed by IR drying at a temperature of 185 ° C. Next, in the seal coating process, a sealing material (in the case of producing a TN mode liquid crystal display panel, Au balls are mixed as a conductive material in the sealing material) is placed on the outer periphery (auxiliary) seal at a predetermined position on the TFT substrate. And this seal | sticker was each apply | coated to the shape of a closed curve. Subsequently, in the liquid crystal dropping step, a liquid crystal material was dropped inside the main seal, and a predetermined dropping amount was dropped into a matrix inside (a large number of dots in the matrix) inside the main seal. Thereafter, in the bonding step, the TFT substrate and the CF substrate were contacted and pressed to uniformly diffuse the liquid crystal material in the pixel portion and the peripheral portion between the substrates, and the gaps between the substrates were formed uniformly with columns. Next, in order to prevent misalignment of the bonded substrate during conveyance to the UV curing step, UV temporary curing was performed at several locations on the outer periphery seal as a temporary fixing of the sealing material. Then, in the next UV curing step, the sealing material was cured by 3000 mJ UV irradiation. Furthermore, in the thermosetting process, the sealing material was completely cured by heating at a temperature of 120 ° C. Thereafter, the manufactured liquid crystal display panel was subjected to an ACF sticking / TCP pressure welding process and a substrate pressure welding process, and a backlight light source was attached in the assembly process, thereby completing a liquid crystal display device.

  Here, a reliability test of the liquid crystal display device of this example was performed. In a driving test under a temperature of 60 ° C. and a humidity of 60%, five conventional liquid crystal display devices were compared for comparison. As a result, after 500 hours from the start of the test, in the conventional liquid crystal display device, unevenness and spot-like spots occurred in the peripheral portion of the panel. However, in the liquid crystal display device of this example, the stain and unevenness were the same as in the second example. There was no outbreak. Further, even after 1500 h after the start of the test, the liquid crystal display device of this example was in a good display state with no occurrence of spots or unevenness.

  Next, a liquid crystal display device and a method for manufacturing the same according to a sixth embodiment of the present invention will be described with reference to FIGS.

  In the first to fifth embodiments described above, a liquid crystal panel is similarly formed using an alignment material prepared by polyamic acid molecules having a long diamine chain serving as the main chain of the polyamic acid as the alignment film applied to the outside of the display region. May be produced.

  For example, an alignment material prepared with polyamic acid molecules as shown in FIG. 5A is used for the alignment film in the display region, and as shown in FIG. 5B for the alignment film outside the display region. An alignment material prepared with polyamic acid molecules having a long diamine chain, which is the main chain of the polyamic acid, is used. In contrast to FIG. 5A, since the diamine chain that is the main chain of the polyamic acid has a tendency to become sparse as a polyimide molecule as m = 3 or longer as shown in FIG. Of course, even an uncured component of the sealing material having a certain molecular weight easily penetrates and the amount of adsorption increases. Furthermore, the diamine chain can be lengthened by increasing the number of benzene rings in the diamine chain of the polyamic acid. As the alignment film outside the display region, m = 3 or more is preferable for the diamine chain serving as the main chain of the polyamic acid of the present invention, and m = 3 to 9 is more particularly considering the film adhesion between the base and the alignment film. preferable. It is also possible to increase the polyamic acid content and further increase the ion adsorption amount by lowering the imidization rate of the alignment film formed outside the display region. The imidation rate of the alignment film in the display region of the present invention is 70 to 95%, which differs depending on the type of the alignment material. The imidation rate of the alignment film outside the display region is higher than the imidation rate of the alignment film in the display region. It is more preferable to make it low, especially 70% or less. As one example, a liquid crystal panel having the above-described configuration was manufactured and a reliability test was performed, which will be described.

  FIG. 9 shows a schematic diagram of alignment film coating and alignment film baking steps for manufacturing the liquid crystal panel of the present invention. As in the fifth embodiment, in the alignment film application step, an alignment film was applied to the display area and the display area outside by an inkjet coating apparatus in order to apply an alignment material to the surfaces of the TFT substrate and the CF substrate ( FIG. 9A). At this time, the alignment material shown in FIG. 5A is applied to the in-head syringe that is discharged to the alignment film application region inside the display region, and the in-head syringe that is discharged to the alignment film application region outside the display region is shown in FIG. Each of the alignment materials (diamine chain m = 3) was set, and the alignment film on the outer side of the display region was provided with a material with a sparser quality than the alignment film in the display region. Needless to say, the impurity adsorption efficiency can be further improved by forming the alignment film outside the display region to be thicker than the display region. In the next alignment film temporary drying step, leveling is performed at a temperature of 80 ° C. on both the display region and the outside of the display region (FIG. 9B), and in the subsequent alignment film baking step, main baking is performed at a temperature of 230 ° C. An alignment film was obtained (C in FIG. 9). Thereafter, in the rubbing step, the alignment film surfaces of the TFT substrate and the CF substrate were rubbed with a rayon rubbing roll. Subsequently, in the rubbing cleaning / drying process, the alignment film surface of the TFT substrate and the CF substrate and the back surface of the substrate were subjected to chemical cleaning and pure cleaning, followed by IR drying at a temperature of 185 ° C. Next, in the seal coating process, a sealing material (in the case of producing a TN mode liquid crystal display panel, Au balls are mixed as a conductive material in the sealing material) is placed on the outer periphery (auxiliary) seal at a predetermined position on the TFT substrate. And this seal | sticker was each apply | coated to the shape of a closed curve. Subsequently, in the liquid crystal dropping step, a liquid crystal material was dropped inside the main seal, and a predetermined dropping amount was dropped into a matrix inside (a large number of dots in the matrix) inside the main seal. Thereafter, in the bonding step, the TFT substrate and the CF substrate were contacted and pressed to uniformly diffuse the liquid crystal material in the pixel portion and the peripheral portion between the substrates, and the gaps between the substrates were formed uniformly with columns. Next, in order to prevent misalignment of the bonded substrate during conveyance to the UV curing step, UV temporary curing was performed at several locations on the outer periphery seal as a temporary fixing of the sealing material. Then, in the next UV curing step, the sealing material was cured by 3000 mJ UV irradiation. Furthermore, in the thermosetting process, the sealing material was completely cured by heating at a temperature of 120 ° C. Thereafter, the manufactured liquid crystal display panel was subjected to an ACF sticking / TCP pressure welding process and a substrate pressure welding process, and a backlight light source was attached in the assembly process, thereby completing a liquid crystal display device.

  Here, a reliability test of the liquid crystal display device of this example was performed. In a driving test under a temperature of 60 ° C. and a humidity of 60%, three conventional liquid crystal display devices were compared for comparison. As a result, after 500 hours from the start of the test, the conventional liquid crystal display device had unevenness and spot-like spots on the periphery of the panel, but the liquid crystal display device of this example did not have any stains or unevenness. Further, no stains and unevenness were observed in the liquid crystal display device of this example even after the test was started 1000 hours.

  In the above description, the case where the porous alignment film 7 is formed on both the TFT substrate 2 and the CF substrate 3 is described. However, even if the porous alignment film 7 is formed only on one of the TFT substrate 2 or the CF substrate 3, Display defects due to residual impurity ions and uncured components of the sealing material 4 can be suppressed.

  The present invention is applicable to a liquid crystal display device and a manufacturing method thereof.

It is a top view which shows the structure of CF board | substrate or TFT substrate which comprises the liquid crystal panel in one embodiment of this invention. 3 is a cross section showing a structure between an end portion of the liquid crystal panel and a display region in an embodiment of the present invention. It is sectional drawing which shows typically the structure of the porous alignment film in one embodiment of this invention. It is a flowchart which shows a part of manufacturing process of the liquid crystal display device in one embodiment of this invention. It is a figure which shows the molecular structure example of a polyamic acid. It is the schematic of the alignment film application | coating-alignment film baking process in the 1st Example of this invention. It is the schematic of the alignment film application | coating-plasma ashing process in the 2nd Example of this invention. It is the schematic of the alignment film application | coating-plasma ashing process in the 5th Example of this invention. It is the schematic of the alignment film application | coating-alignment film baking process in the 6th Example of this invention. It is a top view which shows the structure of CF board | substrate or TFT substrate which comprises the conventional liquid crystal panel. It is sectional drawing which shows the structure between the edge part of the conventional liquid crystal panel-display area. It is sectional drawing which shows the structure between the edge part of the liquid crystal panel of the past (patent document 2), and a display area. It is sectional drawing which shows the structure between the edge part of a liquid crystal panel of the past (patent document 3)-a display area.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 2 TFT substrate 3 CF substrate 4 Sealing material 5 Liquid crystal material 6, 6a, 6b Alignment film 7 Porous alignment film 8 Ion adsorption layer 9 Pore 10 Uneven part

Claims (7)

In a liquid crystal display device in which an alignment film is formed on opposing surfaces of a pair of substrates, a sealing material is formed outside a display area of at least one substrate, and a liquid crystal material is sealed between the pair of substrates.
The alignment film includes a first alignment film formed so as to cover at least the display region, and a second alignment film formed in a region outside the first alignment film and inside the sealing material. And
The liquid crystal display device, wherein the second alignment film has a porous film structure and has higher ionic impurity adsorption than the first alignment film. The liquid crystal display device according to claim 1 , wherein a diamine chain serving as a main chain in the second alignment film is longer than a diamine chain serving as a main chain in the first alignment film . 3. The liquid crystal display device according to claim 1, wherein an imidization rate after firing of the second alignment film is lower than an imidization rate after firing of the first alignment film . 4. The liquid crystal display device according to claim 1, wherein a film thickness of the second alignment film is larger than a film thickness of the first alignment film . 5. A liquid crystal having at least a coating process for applying an alignment film on the substrate surface, a temporary drying process for temporarily drying the alignment film, a baking process for baking the alignment film, a rubbing process, and a rubbing cleaning process in this order. In the manufacturing method of the display device,
In the coating step, the alignment film is formed so as to cover at least the display region,
In the temporary drying step, locally raising the drying temperature outside the display area, forming a porous alignment film outside the display area,
A method for manufacturing a liquid crystal display device , wherein the alignment film outside the display region is modified to provide adsorptivity between the temporary drying step and the rubbing cleaning step . 6. The porous alignment film is formed outside the display region by performing plasma ashing locally on the outside of the display region between the baking step and the rubbing cleaning step . A method for manufacturing a liquid crystal display device. Manufacture of a liquid crystal display device having at least a step of applying an alignment film on the substrate surface, a step of temporarily drying the alignment film, a step of baking the alignment film, a rubbing step, and a rubbing cleaning step In the method
In the coating step, an orientation plate having a smaller number of reliefs on the surface or a relief convex area, or an orientation plate having a larger relief height than the portion facing the inside of the display region. A method of manufacturing a liquid crystal display device, wherein the alignment film outside the display region is printed thick to increase the adsorptivity of the alignment film outside the display region .

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