Method for manufacturing a liquid crystal alignment film, method for repairing defects in a liquid crystal alignment film, method for manufacturing a liquid crystal device, and photoalignment agent for repair.

Abstract

To provide a method for manufacturing a liquid crystal alignment film that can easily and accurately repair defects present in the liquid crystal alignment film, thereby enabling the production of a liquid crystal device with sufficiently suppressed display defects. [Solution] A liquid crystal alignment film is manufactured by a method comprising: a film formation step of applying a liquid crystal alignment agent to a substrate to form a liquid crystal alignment film; a detection step of detecting defects present in the liquid crystal alignment film; a coating step of partially applying a repair photoalignment agent to the region of the liquid crystal alignment film containing the defect if a defect is detected in the detection step; and an irradiation step of irradiating the region including the area where the repair photoalignment agent has been applied with radiation.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a liquid crystal alignment film, a method for repairing defects in a liquid crystal alignment film, a method for manufacturing a liquid crystal device, and a photoalignment agent for repair.

Background Art

[0002] For liquid crystal displays, particularly liquid crystal display panels for large TVs, viewing angle, transmittance, response time, etc. are important performance indicators. As liquid crystal display operation modes for improving the values of these performance indicators, various modes such as TN (Twisted Nematic) type, STN (Super Twisted Nematic) type, VA type, PSA (Polymer Sustained Alignment) type, IPS (In Plane Switching) type, FFS (Fringe Field Switching) type, etc. have been developed. Currently, large TVs using these liquid crystal display mode technologies are being mass-produced.

[0003] A liquid crystal alignment film for controlling the alignment of liquid crystal molecules in a liquid crystal cell is provided in a liquid crystal device. When there are defects in this liquid crystal alignment film, in the defective portion, it may become impossible to control the alignment of liquid crystal molecules in a predetermined direction. When the alignment of liquid crystal molecules cannot be controlled in a predetermined direction, there is a concern that the alignment of liquid crystal molecules is disturbed and recognized as a display defect (bright spot) by an observer of the liquid crystal device.

[0004] Therefore, various methods have been proposed to repair bright spot defects in liquid crystal displays caused by defects in the liquid crystal alignment film (see, for example, Patent Document 1 and Patent Document 2). Patent Document 1 discloses a method for correcting bright spot defects in a liquid crystal display by irradiating the alignment film of an active matrix type liquid crystal display with laser light to partially remove the alignment film. Patent Document 2 discloses a method in which, when a defective area exists in the liquid crystal alignment film formed on a substrate, the defective area is repaired by applying repair ink to the defective area of ​​the liquid crystal alignment film using a repair stamp that applies repair ink. Conventionally, in the manufacturing process of liquid crystal displays, if a defect is detected in the liquid crystal alignment film formed on a substrate, a rework is performed in which the liquid crystal alignment film is peeled off the substrate and a new liquid crystal alignment film is formed. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 8-15660 [Patent Document 2] International Publication No. 2010 / 140443 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, in a method such as the one described in Patent Document 1, in which a liquid crystal display panel is constructed and then partially removed by irradiating the liquid crystal alignment film inside the panel with laser light from outside the device, there are concerns that the laser light may not be accurately irradiated to the defective areas of the liquid crystal alignment film, or that the alignment of liquid crystal molecules may be disrupted in the areas irradiated with laser light, thus failing to adequately resolve the bright spot defects.

[0007] Furthermore, there are concerns that reworking the liquid crystal alignment film may cause significant damage to the substrate during the rework process, and that the manufacturing costs will increase due to the need to re-form the liquid crystal alignment film after rework. In addition, with the use of repair ink, there are concerns that the orientation direction of liquid crystal molecules cannot be properly controlled in the repaired area, and that bright spot defects may not be sufficiently resolved.

[0008] This invention has been made in view of the above circumstances, and one of its objectives is to provide a method for manufacturing a liquid crystal alignment film that can easily and accurately repair defects present in the liquid crystal alignment film, thereby enabling the production of a liquid crystal device in which display defects are sufficiently suppressed. [Means for solving the problem]

[0009] According to the present invention, the following methods for manufacturing a liquid crystal alignment film, a method for repairing defects in a liquid crystal alignment film, a method for manufacturing a liquid crystal device, and a photo-aligning agent for repair are provided.

[0010] [1] A method for manufacturing a liquid crystal alignment film, comprising: a film formation step of applying a liquid crystal alignment agent to a substrate to form a liquid crystal alignment film; a detection step of detecting defects present in the liquid crystal alignment film; a coating step of partially applying a repair photoalignment agent to the region of the liquid crystal alignment film containing the defects if the defects are detected in the detection step; and an irradiation step of irradiating the region including the area where the repair photoalignment agent has been applied with radiation. [2] The method for producing a liquid crystal alignment film according to [1], wherein the repair photoaligning agent contains a compound having photoalignment sites and a solvent. [3] The method for manufacturing a liquid crystal alignment film according to [2], further comprising a heat application step of applying heat to the repair photoalignment agent applied to the region containing the defect by the coating step. [4] A method for manufacturing a liquid crystal alignment film according to any one of [1] to [3], further comprising a removal step of partially removing the region of the liquid crystal alignment film containing the defect in the detection step before applying the repair photoalignment agent in the coating step when the defect is detected in the detection step. [5] A method for repairing defects in a liquid crystal alignment film, comprising: a preparation step of preparing a substrate on which a liquid crystal alignment film is formed; a detection step of detecting defects present in the liquid crystal alignment film; a coating step of partially applying a repair photoalignment agent to a region of the liquid crystal alignment film containing the defect if the defect is detected in the detection step; and an irradiation step of irradiating the region including the area on which the repair photoalignment agent is applied with radiation. [6] A method for manufacturing a liquid crystal apparatus, comprising a liquid crystal alignment film manufactured by any of [1] to [4] or a liquid crystal alignment film restored by [5]. [7] A photo-aligning agent for repairing a liquid crystal alignment film formed on a substrate, for partially forming a repair film in a region of the liquid crystal alignment film that contains defects, comprising a compound having photo-alignment sites and a solvent. [Effects of the Invention]

[0011] According to the present invention, defects present in the liquid crystal alignment film can be repaired simply and accurately, and a liquid crystal device in which display defects (bright spots) are sufficiently suppressed can be obtained. [Brief explanation of the drawing]

[0012] [Figure 1] A schematic cross-sectional diagram showing the general configuration of a liquid crystal display device. [Figure 2] Schematic plan view of the first substrate. [Figure 3] A schematic cross-sectional diagram showing the general configuration of a liquid crystal display device. [Figure 4] A flowchart illustrating the manufacturing method of a liquid crystal display device. [Figure 5] A flowchart illustrating the membrane repair process performed by the membrane repair step. [Figure 6] A schematic diagram illustrating the series of processes involved in membrane repair. [Figure 7] A flowchart showing a film repair process in another embodiment. [Modes for carrying out the invention]

[0013] Hereinafter, embodiments will be described with reference to the drawings. In the following embodiments, parts that are identical or equivalent to each other are denoted by the same reference numerals in the drawings, and the description of the parts with the same reference numerals is incorporated herein.

[0014] First, the liquid crystal device obtained by the manufacturing method of the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional schematic view showing the schematic configuration of the liquid crystal device, and FIG. 2 is a plan schematic view of the first substrate.

[0015] <Liquid Crystal Device> The liquid crystal device 10 is a thin film transistor (TFT) type liquid crystal display device, and a plurality of pixels are arranged in a matrix in the display area. As shown in FIG. 1, the liquid crystal device 10 includes a pair of substrates including a first substrate 11 and a second substrate 12, and a liquid crystal layer 13 disposed between the first substrate 11 and the second substrate 12.

[0016] The first substrate 11 is a TFT substrate on which various wirings such as pixel electrodes 15, TFTs 16 as switching elements, scan signal lines 17, and data signal lines 18 are arranged on a transparent substrate 14 made of glass, resin, or the like. The pixel electrode 15 is made of a transparent conductor such as tin oxide (SnO2) or ITO (Indium Tin Oxide), and is formed, for example, in a substantially rectangular shape (see FIG. 2). The pixel electrode 15 is, for example, in an elongated rectangular shape in the direction in which the data signal line 18 extends, as shown in FIG. 2.

[0017] The second substrate 12 is a counter substrate provided with a counter electrode 19 made of a transparent conductor on a transparent substrate 16 made of glass, resin, or the like. The counter electrode 19 is made of a transparent conductor such as ITO, and is a common electrode common to all the pixel electrodes 15. The second substrate 12 is a CF substrate including a black matrix and a color filter. The color filter has, for example, three color layers of red (R), green (G), and blue (B). Instead of the configuration in which the color filter is provided on the counter substrate, a COA (Color filter On Array) provided on the pixel substrate may be adopted. <00001

[0018] In the liquid crystal device 10 shown in Figure 1, a pair of electrodes is formed by a pixel electrode 15 provided on the first substrate 11 and a counter electrode 19 provided on the second substrate 12. However, the configuration of the liquid crystal device 10 is not limited to that shown in Figure 1. For example, as shown in Figure 3, the first substrate 11 may have a pair of electrodes, and the second substrate 12 may not have electrodes. In this case, the first substrate 11 may have a common electrode 25, an insulating layer 26, and a pixel electrode 15 laminated in this order on the surface of a transparent substrate 14, and a pair of electrodes may be formed by the pixel electrode 15 and the common electrode 25. For example, the common electrode 25 may be a surface electrode, and the pixel electrode 15 may be a comb-shaped electrode.

[0019] At least one of the first substrate 11 and the second substrate 12 has a liquid crystal alignment film formed on it that orients liquid crystal molecules near the substrate surface in a predetermined orientation with respect to the substrate surface (i.e., the electrode placement surface). In the example shown in Figure 1, the liquid crystal apparatus 10 has a first alignment film 22 formed on the electrode placement surface of the first substrate 11 and a second alignment film 23 formed on the electrode placement surface of the second substrate 12 as liquid crystal alignment films. These liquid crystal alignment films may be of the horizontal alignment type, which orients liquid crystal molecules substantially horizontally when no voltage is applied, or of the vertical alignment type, which orients liquid crystal molecules substantially vertically when no voltage is applied.

[0020] If the liquid crystal device 10 is equipped with a horizontally aligned liquid crystal alignment film, the driving method of the liquid crystal device 10 is, for example, TN (Twisted Nematic), STN (Super Twisted Nematic), IPS (In-Plane Switching), or FFS (Fringe Field Switching). If the liquid crystal device 10 is equipped with a vertically aligned liquid crystal alignment film, the driving method of the liquid crystal device 10 is, for example, VA (including VA-MVA, VA-PVA, etc.) or PSA (Polymer Sustained Alignment). Furthermore, one of the first alignment film 22 and the second alignment film 23 may be a strongly anchored liquid crystal alignment film, and the other may be a weakly anchored liquid crystal alignment film.

[0021] The first alignment film 22 and the second alignment film 23 may be rubbing alignment films or photoalignment films. The rubbing alignment film is formed by applying a rubbing treatment to an organic film formed on a substrate with a liquid crystal alignment agent. The photoalignment film is formed by irradiating a photosensitive organic film formed on a substrate with a liquid crystal alignment agent with radiation to give it anisotropy (photoalignment treatment). In addition, the liquid crystal device 10 may have pixels that are oriented and divided, and each pixel may have two or more regions with different orientations.

[0022] As a liquid crystal alignment agent, a polymer composition containing a polymer and a solvent is preferably used. Examples of polymer main chains include polyamic acid, polyimide, polyorganosiloxane, polyamic acid ester, polyamide, polyenamine, and addition polymers. Examples of addition polymers include (meth)acrylic polymers, styrene polymers, maleimide polymers, styrene-maleimide polymers, (meth)acrylic-styrene-maleimide polymers, (meth)acrylic-styrene polymers, and (meth)acrylic-maleimide polymers. Note that "(meth)acrylic" is a term that encompasses "acrylic" and "methacrylic".

[0023] When forming a photoalignment film on a substrate surface, the liquid crystal alignment agent typically contains a polymer having photoalignment sites as at least a portion of its polymer components. The polymer having photoalignment sites is not particularly limited, and known polymer components for photoalignment films can be used as appropriate. Specific examples of photoalignment sites include cinnamic acid-containing groups, azobenzene-containing groups, coumarin-containing groups, chalcone-containing groups, and cyclobutane-containing structures.

[0024] The liquid crystal alignment agent for forming the first alignment film 22 and the second alignment film 23 may contain only one polymer as a polymer component, or it may contain two or more polymers. The liquid crystal alignment agent is usually a liquid composition in which the polymer component is dissolved or dispersed in one or more solvents. In addition to the polymer component, the liquid crystal alignment agent may further contain one or more additives as a solid component, such as a crosslinking agent, adhesion aid, ultraviolet absorber, or photosensitive agent.

[0025] The first substrate 11 and the second substrate 12 are arranged with a predetermined gap (cell gap) between them via spacers (for example, columnar spacers or bead spacers) so that the orientation film formation surface of the first substrate 11 and the orientation film formation surface of the second substrate 12 face each other. The opposing first substrate 11 and the second substrate 12 are bonded together at the peripheral edges of each substrate via sealing members.

[0026] A liquid crystal composition is filled in the space surrounded by the first substrate 11, the second substrate 12, and the sealing member. As a result, a liquid crystal layer 13 is formed between the first substrate 11 and the second substrate 12 in the liquid crystal device 10. The liquid crystal layer 13 may contain liquid crystals with negative dielectric anisotropy or liquid crystals with positive dielectric anisotropy. When the operating mode of the liquid crystal device 10 is horizontal mode, liquid crystals with positive dielectric anisotropy are generally used as liquid crystal molecules in the liquid crystal layer 13. When the operating mode of the liquid crystal device 10 is vertical mode, liquid crystals with negative dielectric anisotropy are generally used as liquid crystal molecules in the liquid crystal layer 13. Examples of liquid crystals include nematic liquid crystals and smectic liquid crystals, with nematic liquid crystals being preferred.

[0027] As the liquid crystal, any known liquid crystal material can be used as appropriate. The refractive index anisotropy Δn of the liquid crystal is set as appropriate so that the retardation (d·Δn), which is expressed as the product of the refractive index anisotropy (Δn) of the liquid crystal and the thickness (d) of the liquid crystal layer 13, is a desired value. The thickness of the liquid crystal layer 13 is, for example, 2 to 5 μm.

[0028] Typically, a pair of polarizing plates are arranged on the outside of the first substrate 11 and the second substrate 12. The pair of polarizing plates consists of a first polarizing plate 23 provided on the outer surface of the first substrate 11 and a second polarizing plate 24 provided on the outer surface of the second substrate 12. A terminal region (not shown) is provided on the outer edge of the first substrate 11, and the liquid crystal display device 10 is driven by connecting a driver IC or the like to the terminal region to drive the liquid crystal. In this embodiment, the case of application to a TFT type liquid crystal display device has been described, but other driving methods (for example, passive matrix method, plasma address method, etc.) may also be used.

[0029] <Manufacturing method for liquid crystal devices> Next, a method for manufacturing a liquid crystal apparatus 10 equipped with a liquid crystal alignment film will be described. The liquid crystal apparatus 10 can be manufactured by a method including the following film formation step and cell construction step. The substrate used in the film formation step differs depending on the desired operating mode of the liquid crystal apparatus 10. Film formation process: A process in which a liquid crystal alignment agent is applied to a substrate to form a liquid crystal alignment film. Cell construction process: A process of constructing a liquid crystal cell by preparing a pair of substrates on which a liquid crystal alignment film is formed on at least one substrate, and placing a liquid crystal layer between the pair of substrates which are placed opposite each other.

[0030] (film formation process) In the film formation process, first, a liquid crystal alignment agent is applied to the substrate (the surfaces of the first substrate 11 and the second substrate 12 in Figure 1), and preferably the applied surface is heated to form a coating on the substrate. When manufacturing TN, STN, or VA type liquid crystal devices, two substrates, each having a patterned transparent conductive film, are used. On the other hand, when manufacturing IPS or FFS type liquid crystal devices, a substrate with a pair of electrodes and a counter substrate without electrodes are used. The liquid crystal alignment agent is applied to the substrate surface, preferably by offset printing, flexographic printing, spin coating, roll coating, or inkjet printing.

[0031] After applying the liquid crystal alignment agent to the substrate, preheating (pre-bake) is preferably performed to prevent dripping of the applied liquid crystal alignment agent. The pre-bake temperature is, for example, 30 to 200°C, and the pre-bake time is, for example, 0.25 to 10 minutes. Subsequently, a firing (post-bake) process is performed to remove the solvent in the applied liquid crystal alignment agent. The firing temperature (post-bake temperature) at this time is, for example, 80 to 250°C, and the post-bake time is, for example, 5 to 200 minutes. The thickness of the film formed in this way is preferably 0.001 to 1 μm.

[0032] When manufacturing TN, STN, IPS, or FFS type liquid crystal devices, a process (alignment treatment) is performed to impart liquid crystal alignment ability to the coating film formed on the substrate. This imparts the alignment ability of liquid crystal molecules to the coating film, making it a liquid crystal alignment film. Preferred alignment treatments include rubbing, where the surface of the coating film formed on the substrate is rubbed with cotton or the like, or photo-alignment, where the coating film is irradiated with light to impart liquid crystal alignment ability. When manufacturing vertical alignment (VA) type liquid crystal devices, the coating film formed as described above may be used as is as the liquid crystal alignment film, or an alignment treatment may be applied to the coating film to further enhance the liquid crystal alignment ability or to perform alignment division. Liquid crystal alignment films suitable for vertical alignment type liquid crystal devices are also suitable for PSA type liquid crystal devices.

[0033] In the photo-alignment process, light irradiation can be performed by methods such as irradiating the coating film after the post-bake process; irradiating the coating film after the pre-bake process but before the post-bake process; or irradiating the coating film while it is being heated in at least one of the pre-bake or post-bake processes. As radiation to irradiate the coating film, for example, ultraviolet light and visible light including wavelengths of 150 to 800 nm can be used. Preferably, ultraviolet light including wavelengths of 200 to 400 nm is used. If the radiation is polarized, it may be linearly polarized or partially polarized. If the radiation used is linearly polarized or partially polarized, irradiation may be performed from a direction perpendicular to the substrate surface, from an oblique direction, or a combination of these. In the case of unpolarized radiation, the irradiation direction should be oblique.

[0034] Examples of light sources that can be used include low-pressure mercury lamps, high-pressure mercury lamps, deuterium lamps, metal halide lamps, argon resonance lamps, xenon lamps, and excimer lasers. The radiation dose to the substrate surface is preferably 400 to 50,000 J / m². 2 And more preferably 1,000 to 20,000 J / m 2 In addition, after light irradiation to impart orientation ability, the substrate surface may be washed with, for example, water, an organic solvent (e.g., methanol, isopropyl alcohol, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, etc.), or a mixture thereof, or the substrate may be heated.

[0035] (Cell construction process) In the cell construction process, a substrate on which a liquid crystal alignment film has been formed as described above is prepared, and a liquid crystal cell is manufactured such that a liquid crystal layer is positioned adjacent to the liquid crystal alignment film between a pair of substrates. When manufacturing a liquid crystal device, a pair of substrates on which a liquid crystal alignment film has been formed is usually used. For example, there are two methods for manufacturing a liquid crystal cell. The first method involves first placing two substrates opposite each other with a gap (cell gap) between them so that the liquid crystal alignment films face each other, bonding the periphery of the two substrates with a sealing material, and then injecting and filling the cell gap surrounded by the substrate surface and the sealing material, sealing the injection hole. The second method is called the ODF (One Drop Fill) method. In the second method, a sealing material that can be cured with ultraviolet light is applied to a predetermined position on one of the two substrates on which a liquid crystal alignment film has been formed, and then liquid crystal is dropped onto the surface of the liquid crystal alignment film. After that, the other substrate is bonded so that the liquid crystal alignment films face each other, and then the entire surface of the substrate is irradiated with ultraviolet light to cure the sealing material, thereby manufacturing a liquid crystal cell. As a sealing material, for example, an epoxy resin containing an aluminum oxide sphere as a hardening agent and spacer can be used.

[0036] In manufacturing PSA-type liquid crystal devices, a liquid crystal cell is constructed by placing a photopolymerizable compound together with liquid crystal between two substrates. After the liquid crystal cell is constructed, a voltage is applied between the conductive films of the pair of substrates in the liquid crystal cell, and the liquid crystal cell is then irradiated with light.

[0037] For each operating mode of the liquid crystal cell, a polarizing plate is then attached to the outer surface of the liquid crystal cell as needed. Examples of polarizing plates include a polarizing plate made by sandwiching a polarizing film called an "H film," which is made by stretching and oriented polyvinyl alcohol while absorbing iodine, between cellulose acetate protective films, or a polarizing plate made of the H film itself.

[0038] Liquid crystal devices manufactured in this manner can be effectively applied to a variety of uses. Specifically, they can be used in various display devices such as watches, portable game consoles, word processors, notebook computers, car navigation systems, camcorders, PDAs, digital cameras, mobile phones, smartphones, various monitors, LCD televisions, information displays, as well as dimming films, phase difference films, and the like.

[0039] In the manufacturing process of the liquid crystal display device 10, defects may occur in the liquid crystal alignment film during the manufacturing process. Defects in the liquid crystal alignment film include the adhesion of foreign matter to the film, uneven film thickness (abnormal film thickness), cleaning marks, and scratches. Foreign matter includes shavings of the liquid crystal alignment film and residues from the rubbing cloth during the rubbing process, as well as foreign matter from the environment (dust, dirt, etc.). Abnormal film thickness of the liquid crystal alignment film includes the occurrence of pinholes, localized thinning or thickening due to poor coating of the liquid crystal alignment agent, and peeling of the film during the rubbing process. Such defects in the liquid crystal alignment film can cause abnormalities in the alignment function of the liquid crystal molecules exhibited by the film, making it impossible to position the liquid crystal molecules in the predetermined direction at the defective part of the film. In this case, the display at the defective part of the film does not match the display at the normally aligned part where the liquid crystal molecules are normally aligned, which may be perceived by the observer as a display defect (bright spot). In particular, in large liquid crystal displays, the incidence of display defects due to defects in the liquid crystal alignment film is high, and this greatly affects the display quality of the liquid crystal display device.

[0040] Therefore, in this embodiment, during the manufacturing process of the liquid crystal device 10, after the film formation process and before the cell construction process, a process (film repair process) is performed to detect defects present in the liquid crystal alignment film obtained by the film formation process and to locally repair the orientation direction of the liquid crystal alignment film in the region containing the defect.

[0041] Figure 4 is a flowchart showing the manufacturing process of the liquid crystal device 10 of this embodiment. In the manufacturing process of the liquid crystal device 10 shown in Figure 4, first, a liquid crystal alignment agent is applied to a substrate in a film formation step to form a liquid crystal alignment film on the substrate (S11). Next, in a film repair step, defects present in the liquid crystal alignment film are detected, and if a defect is detected, the liquid crystal alignment film in the area containing the defect is locally repaired (S12). After that, in a cell construction step, a liquid crystal layer is placed between two opposing substrates to construct a liquid crystal cell (S13). Note that the method including the film formation step and the film repair step corresponds to the "method for manufacturing a liquid crystal alignment film" and the "method for repairing defects in a liquid crystal alignment film" of the present invention. The film formation step corresponds to the "preparation step for preparing a substrate on which a liquid crystal alignment film has been formed" of the present invention.

[0042] If a liquid crystal cell is constructed with defects in the liquid crystal alignment film, in the liquid crystal device 10, the liquid crystal alignment film cannot properly control the alignment state of liquid crystal molecules in the region corresponding to the defective portion of the liquid crystal alignment film, which can lead to bright spot defects due to light leakage, etc. In contrast, in the manufacturing method of this embodiment, if a defect is detected in the liquid crystal alignment film before cell construction, the defective portion of the liquid crystal alignment film can be locally repaired before cell construction, thereby suppressing the occurrence of bright spots due to alignment defects. Furthermore, by locally repairing the region containing defects in the liquid crystal alignment film formed on the substrate, it is possible to reduce costs and labor compared to a process (rework) in which the defective liquid crystal alignment film is peeled off the substrate and the film is reformed.

[0043] Next, the details of the film repair process of this embodiment will be described with reference to Figures 5 and 6. Figure 5 is a flowchart showing the film repair process performed by the film repair step in the manufacturing method of the liquid crystal apparatus 10 shown in Figure 4. Figure 6 is a schematic diagram showing a series of processes of the film repair process. As shown in Figure 5, the film repair process of this embodiment includes a detection step, a removal step, a coating step, a heat application step, and an irradiation step. Although Figure 6 shows the case where the film repair process is performed on the first substrate 11, the film repair process in Figure 4 is performed on the second substrate 12 in the same manner. The arrows in Figure 6 represent the orientation direction of the liquid crystal in the liquid crystal layer 13.

[0044] In the film repair process shown in Figure 5, first, a detection step is performed to detect defects 30 present in the liquid crystal alignment film (first alignment film 22) (S21). Defects 30 can be detected by known detection methods. As an example of a specific method, a mother substrate on which a liquid crystal alignment film is formed is placed in a predetermined position in an automated optical inspection (AOI) device, and image data of the substrate surface is acquired using a CCD camera or the like introduced into the AOI device. Then, by image processing based on the acquired image data, the presence or absence of defects 30 in the liquid crystal alignment film on the mother substrate, as well as the location and size of the defects 30, are detected (see Figure 6(a)). The detected defects 30 may be compared with pre-stored known defect information using, for example, a defect detection system using deep learning, to identify the type of defect 30.

[0045] In the detection step S21, if it is determined that no defects 30 exist in the liquid crystal alignment film on the substrate, the film repair process is terminated and the process proceeds to the cell construction step shown in Figure 4. If liquid crystal alignment films are formed on both the first substrate 11 and the second substrate 12, the film repair process is terminated if no defects 30 exist in the liquid crystal alignment films on both substrates. On the other hand, if it is determined in the detection step S21 that a defect 30 exists in the liquid crystal alignment film on the substrate, the removal step S22 then removes the area of ​​the liquid crystal alignment film on the substrate containing the defect 30, designating it as a defective area 31, and partially removing the defective area 31.

[0046] The method for partially removing the liquid crystal alignment film corresponding to the defect region 31 is not particularly limited. For example, as shown in Figure 6(b), the liquid crystal alignment film in the defect region 31 can be partially removed by irradiating the defect region 31 of the liquid crystal alignment film on the substrate with laser light from a light source 41. The irradiation conditions for the laser light can be appropriately set by referring to, for example, the description in Japanese Patent Application Publication No. 8-15660. If the type of defect 30 is identified in the detection step S21, the removal step S22 may be performed to remove the liquid crystal alignment film corresponding to the defect region 31 in a manner corresponding to the identified type of defect 30.

[0047] The size of the defect area 31 is not particularly limited and can be set appropriately according to the size and shape of the defect 30. From the viewpoint of ensuring the quality of the display device 10, it is preferable to make the defect area 31 as small as possible. Specifically, it is preferable to make it a part of the defect 30, or the defect 30 and its surrounding area. For example, the defect area 31 may be the same size as the defect 30, or slightly larger than the defect 30. The shape of the defect area 31 is also not particularly limited and may be a predetermined shape (for example, circular, elliptical, rectangular), or an irregular shape set based on the shape of the defect 30.

[0048] In S21, a defect 30 is detected, and in S22, the liquid crystal alignment film in the defective region 31 is removed. Subsequently, in the coating step of S23, a repair photoalignment agent is partially applied to the defective region 31 after the liquid crystal alignment film has been locally removed. The repair photoalignment agent is a photoalignment agent for partially forming a film in the region containing defects in the liquid crystal alignment film formed on the substrate, and is a composition capable of forming an anisotropic film by photoalignment. In the present invention, a minute film is formed in the defective region 31 by applying the repair photoalignment agent to the defective region 31, and in a subsequent step, anisotropy in a desired direction (i.e., the same direction as the liquid crystal alignment direction controlled by the first alignment film 22) is imparted to this minute film by photoalignment. To accurately impart anisotropy to the film and improve the controllability of liquid crystal alignment in the defective area, the repair photoalignment agent preferably contains a compound having a photoalignment site and a solvent. Hereinafter, the compound having a photoalignment site will also be referred to as "compound (A)".

[0049] The photo-oriented sites of compound (A) are sites that can impart anisotropy to the film through photoreactions such as isomerization, dimerization, Fries rearrangement, or decomposition reactions induced by light irradiation. Specific examples of photo-oriented sites include, for example, azobenzene-containing groups with azobenzene or its derivatives as the basic skeleton, cinnamic acid structure-containing groups with cinnamic acid or its derivatives (cinnamic acid structure) as the basic skeleton, chalcone-containing groups with chalcone or its derivatives as the basic skeleton, benzophenone-containing groups with benzophenone or its derivatives as the basic skeleton, coumarin-containing groups with coumarin or its derivatives as the basic skeleton, cyclobutane-containing structures with cyclobutane or its derivatives as the basic skeleton, stilbene-containing groups with stilbene or its derivatives as the basic skeleton, and phenylbenzoate-containing groups with phenylbenzoate or its derivatives as the basic skeleton. Of these, the photo-orienting moiety of compound (A) is preferably at least one selected from the group consisting of an azobenzene-containing group, a cinnamic acid structure-containing group, a chalcone-containing group, a stilbene-containing group, a cyclobutane-containing structure, and a phenylbenzoate-containing group. Furthermore, in terms of higher sensitivity to light, the photo-orienting moiety of compound (A) is preferably a cinnamic acid structure-containing group or a cyclobutane-containing structure, with the cinnamic acid structure being particularly preferred.

[0050] Compound (A) may be a polymer or a nonpolymer. If compound (A) is a polymer, the main skeleton of compound (A) is not particularly limited, but examples include polyamic acid, polyimide, polyorganosiloxane, polyamic acid ester, polyamide, polyenamine, and addition polymers. Specific examples of addition polymers are the same as those exemplified as polymer components of the liquid crystal alignment agent used in the formation of the first alignment film 22 and the second alignment film 23. If compound (A) is a polymer, compound (A) may have photo-aligning moieties in the main chain or in the side chains. It is preferable for compound (A) as a polymer to have photo-aligning moieties in the side chains, as this makes it easier to adjust the orientation direction of the film by the photo-alignment method and effectively suppresses the occurrence of bright spot defects. If compound (A) is a polymer, the weight-average molecular weight of compound (A) is, for example, 1,000 to 500,000, preferably 5,000 to 100,000.

[0051] When compound (A) is a nonpolymer, examples of compound (A) include polymerizable compounds having photo-orienting sites. In polymerizable compounds, preferred polymerizable groups include functional groups that can polymerize between the same or different functional groups by heat or light, such as (meth)acryloyl groups, vinyl groups, vinyloxy groups, vinylphenyl groups, maleimide groups, oxyranyl groups, and oxetanyl groups. When compound (A) is a nonpolymer, the molecular weight of compound (A) is, for example, 1,000 or less, and preferably 800 or less.

[0052] From the viewpoint of accurately applying the repair photoaligning agent locally, a solvent capable of dissolving or dispersing compound (A) is preferably used as the solvent component of the repair photoaligning agent. Examples of such solvents include water, organic solvents, or mixed solvents of water and organic solvents. Specific examples of organic solvents include, for example, aprotic polar solvents, phenolic solvents, alcohols, ketones, esters, ethers, halogenated hydrocarbons, and hydrocarbons.

[0053] The photo-aligning agent for repair may further contain components other than compound (A) and the solvent. Examples of such components include crosslinking agents, adhesion aids, ultraviolet absorbers, and photosensitive agents.

[0054] The method for applying the photo-aligning agent to the defective region 31 on the substrate is not particularly limited, as long as the photo-aligning agent can be applied locally to the desired region on the substrate. Examples of methods for applying the photo-aligning agent include the stamping method, inkjet printing method, transfer method, dispenser method, spray method, and nanoimprint method. Among these, the stamping method, as shown in International Publication No. 2010 / 140443, is a method of applying liquid to a desired region by bringing a stamp 42, which has liquid supplied to its tip, into contact with the application surface from above the substrate, and moving the stamp 42 along the application surface as needed. In this embodiment, the photo-aligning agent is applied to the defective region 31 after the liquid crystal alignment film has been locally removed by supplying the photo-aligning agent to the application surface from the tip of the stamp 42 (see Figure 6(c)).

[0055] The size of the coating area 32, which is the area where the repair photoalignment agent is applied, is not particularly limited and can be set appropriately according to the size and shape of the defect area 31, the type of defect, etc. From the viewpoint of minimizing the impact on the performance of the liquid crystal alignment film other than the defect area 31, it is preferable that the coating area 32 be the area corresponding to the defect area 31, or the defect area 31 and its periphery. For example, the coating area 32 may be the same size as the defect area 31, or slightly larger than the defect area 31.

[0056] In S23, the photo-aligning agent for repair is applied to the defective region 31. In the subsequent heat application step, heat is applied to the photo-aligning agent applied to the application area 32 (S24). This heat application step removes the solvent component from the photo-aligning agent on the substrate, forming a minute repair film 33 in the region containing the defective region 31 (i.e., the application area 32) that corresponds to the size of the defective region 31. Furthermore, if compound (A) is a nonpolymer having polymerizable groups, the heat application step accelerates the curing reaction of compound (A), making it possible to form a higher-performance repair film 33.

[0057] One method of heat application in the heat application process involves first performing preheating (pre-bake) to remove the solvent in the repair photoalignment agent applied to the coating area 32, and then performing firing (post-bake) to promote further reaction of compound (A) and improve the performance of the film. Heat application to the repair photoalignment agent on the substrate may be performed locally on the coating area 32 or on the entire first substrate 11. When heat application to the coating area 32 is performed locally, for example, by irradiating it with infrared light for a short time (e.g., a few seconds to a few minutes) using spot infrared light.

[0058] Furthermore, when heat is applied to the entire substrate, the pre-bake temperature is preferably 30 to 150°C and the pre-bake time is preferably 0.05 to 15 minutes, in order not to relax the liquid crystal alignment ability applied to the parts of the liquid crystal alignment film other than the defect region 31. The post-bake temperature is preferably 80 to 180°C, more preferably 80 to 150°C. The post-bake time is preferably 1 to 100 minutes. From the viewpoint of minimizing the influence on the performance of the liquid crystal alignment film other than the defect region 31, it is preferable to locally heat the application area 32 of the repair photoalignment agent during the heat application process.

[0059] In S24, heat is applied to the photo-aligning agent for repair in the coated area 32. In the subsequent irradiation step, radiation is irradiated onto the coated area 32 of the photo-aligning agent to perform the photo-alignment process (S25). This makes it possible to control the orientation direction of the liquid crystal, which is controlled by the repair film 33 formed in the defect region 31, to be the same direction as the orientation direction of the liquid crystal, which is controlled by the first alignment film 22 (see Figure 6(d)). Radiation irradiation of the coated area 32 may be performed locally on the region including the coated area 32, or on the entire surface of the first substrate 11. From the viewpoint of minimizing the influence on the performance of the liquid crystal alignment film other than the defect region 31, it is preferable to irradiate the coated area 32 of the photo-aligning agent, or the coated area 32 and its surrounding area, locally in the irradiation step.

[0060] For example, ultraviolet and visible light, including light with wavelengths of 150 to 800 nm, can be used as radiation to irradiate the photoaligning agent for repair on the substrate. The wavelength of the irradiation light can be appropriately set according to the type of photo-oriented site that compound (A) has, so as to be a wavelength that causes photoreactions such as photoisomerization and photodimerization reactions in compound (A) contained in the photoaligning agent. For example, if the photoaligning site of compound (A) is a cinnamic acid structure-containing group, the wavelength of the irradiation light is preferably 313 nm, and if it is a cyclobutane-containing structure, the wavelength of the irradiation light is preferably 254 nm.

[0061] When the radiation is polarized, it may be linearly polarized or partially polarized. Furthermore, when the radiation used is linearly polarized or partially polarized, the radiation irradiation should be set to coincide with the orientation direction of the liquid crystal controlled by the first alignment film 22. Specifically, the radiation irradiation of the repair film 33 may be performed from a direction perpendicular to the substrate surface, from an oblique direction, or a combination of these. The light source used is the same as described when the first alignment film 22 and the second alignment film 23 are photoalignment films. The radiation dose is preferably 100 to 50,000 J / m². 2 And more preferably, 300 to 20,000 J / m 2 The thickness of the repair film 33 formed by the film repair process is preferably the same as that of the liquid crystal alignment film (first alignment film 22, second alignment film 23), for example, 0.001 to 1 μm.

[0062] Through this series of processes, a repair film 33 can be formed in the region containing the defect 30 in the liquid crystal alignment film (first alignment film 22 in Figure 6), which can control the orientation of the liquid crystal in the liquid crystal layer 13 to a desired direction. As a result, even in the defective portion of the liquid crystal alignment film, the orientation direction of the liquid crystal can be controlled to match the orientation direction of the liquid crystal controlled by the liquid crystal alignment film. Therefore, with this method, the region containing the defect 30 in the liquid crystal alignment film can be repaired locally before cell construction, thereby avoiding the generation of bright spots due to alignment defects. Furthermore, since the region containing the defect 30 in the liquid crystal alignment film formed on the substrate is repaired locally, costs can be reduced compared to conventional rework processes.

[0063] The film repair method in this embodiment is particularly suitable for horizontal mode liquid crystal apparatus 10 because it can relatively easily and accurately impart to the repair film 33 a liquid crystal alignment capability that controls the liquid crystal in the same direction as the liquid crystal alignment direction controlled by the liquid crystal alignment films (first alignment film 22, second alignment film 23).

[0064] In the embodiments described above, the following may be implemented, for example.

[0065] The film repair process in the above embodiment has a configuration comprising a detection step, a removal step, a coating step, a heat application step, and an irradiation step, but it may also be configured to omit at least one of the removal step and the heat application step. For example, as shown in Figure 7, the film repair process may have a configuration comprising a detection step, a coating step, and an irradiation step, without performing the removal step and the heat application step. Alternatively, the film repair process may have a configuration comprising a detection step, a removal step, a coating step, and an irradiation step, without performing the heat application step, or it may have a configuration comprising a detection step, a coating step, a heat application step, and an irradiation step, without performing the removal step. [Explanation of symbols]

[0066] 10...Liquid crystal device, 11...First substrate, 12...Second substrate, 13...Liquid crystal layer, 22...First alignment layer, 23...Second alignment layer, 30...Defect, 31...Defect area, 32...Coated area, 33...Repair film, 41...Light source, 42...Stamp

Claims

1. A film formation step involves applying a liquid crystal alignment agent to a substrate to form a liquid crystal alignment film, A detection step for detecting defects present in the liquid crystal alignment film, If the defect is detected by the detection step, a coating step is performed to partially apply a repair photoalignment agent to the region of the liquid crystal alignment film containing the defect. An irradiation step of irradiating the region including the area where the repair photoalignment agent is applied with radiation, A method for manufacturing a liquid crystal alignment film, including the above.

2. The method for producing a liquid crystal alignment film according to claim 1, wherein the repair photoaligning agent contains a compound having photoalignment sites and a solvent.

3. A method for manufacturing a liquid crystal alignment film according to claim 2, further comprising a heat application step of applying heat to a repair photoalignment agent applied to the region containing the defect by the coating step.

4. A method for manufacturing a liquid crystal alignment film according to claim 1, further comprising a removal step of partially removing the region of the liquid crystal alignment film containing the defect in the detection step before applying the repair photoalignment agent in the coating step, if the defect is detected in the detection step.

5. Preparation steps for preparing a substrate on which a liquid crystal alignment film has been formed, A detection step for detecting defects present in the liquid crystal alignment film, If the defect is detected by the detection step, a coating step is performed to partially apply a repair photoalignment agent to the region of the liquid crystal alignment film containing the defect. An irradiation step of irradiating the region including the area where the repair photoalignment agent is applied with radiation, A method for repairing defects in liquid crystal alignment films, including the method described above.

6. A method for manufacturing a liquid crystal apparatus, comprising a liquid crystal alignment film manufactured according to any one of claims 1 to 4 or a liquid crystal alignment film restored according to claim 5.

7. A photo-aligning agent for repairing liquid crystal alignment films formed on a substrate, for partially forming a repair film in a region of the liquid crystal alignment film that contains defects, A photo-aligning agent for repair, comprising a compound having a photo-alignment site and a solvent.

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