Liquid crystal aligning agent, liquid crystal alignment film, and liquid crystal display element

Abstract

The invention relates to a liquid crystal aligning agent, a liquid crystal alignment film, and a liquid crystal display element. Provided are a liquid crystal aligning agent, a liquid crystal aligning film, and a liquid crystal display element which are capable of suppressing poor coating of an aligning film and non-uniformity of display of a liquid crystal display element due to the influence of a wiring structure or C / H, and which are capable of reducing viscosity while maintaining a resin component and a molecular weight. A liquid crystal aligning agent containing: at least one polymer selected from the group consisting of polyimide precursors and polyimides that are imides thereof; and a solvent containing a solvent A, a solvent B, and a solvent C. Solvent A: is selected from the group consisting of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, [gamma]-butyrolactone, and dimethylimidazolinone. The solvent B is dipropylene glycol dimethyl ether. Solvent C: selected from the group consisting of diethylene glycol diethyl ether and diacetone alcohol.

Description

[0001] This application is a divisional application of Chinese patent application No. 201780033835.9, filed on March 30, 2017, entitled "Liquid Crystal Alignment Agent, Liquid Crystal Alignment Film, and Liquid Crystal Display Element". Technical Field

[0002] The present invention relates to a liquid crystal alignment agent suitable for inkjet film formation and having high dimensional stability during coating, and a liquid crystal alignment film obtained from the liquid crystal alignment agent. Background Technology

[0003] As a liquid crystal alignment film, a so-called polyimide-based liquid crystal alignment film is widely used, which is obtained by coating a liquid crystal alignment agent with a solution of polyimide precursors such as polyamic acid (also known as polyamic acid) and soluble polyimide as the main components and then firing it.

[0004] Commonly known methods for forming liquid crystal alignment films include spin coating, dip coating, and flexible printing. Among these, flexible printing-based coating methods have been the most prevalent to date. However, flexible printing has several drawbacks: various resin plates are required depending on the type of liquid crystal panel; changing these plates during the manufacturing process is complex; and to ensure the stability of the film formation process, film must be deposited onto a simulated substrate, making plate fabrication a contributing factor to the increased manufacturing cost of liquid crystal display panels.

[0005] Therefore, inkjet printing has attracted attention as a method for forming liquid crystal alignment films without the use of printing plates. Inkjet printing involves dropping tiny droplets of liquid onto a substrate, where the film is formed by the wetting and spreading of the liquid. Not only does it eliminate the need for printing plates, but it also allows for the free setting of printed patterns, thus simplifying the manufacturing process of liquid crystal display elements. Furthermore, it eliminates the need for film deposition on an analog substrate, as is required in flexible printing, resulting in less waste of coating liquid. With inkjet printing, it is expected that the cost of liquid crystal panels will decrease and production efficiency will increase.

[0006] Liquid crystal alignment films formed by inkjet printing require minimal thickness uniformity within the coating surface and high film deposition precision at the coating periphery. Typically, for liquid crystal alignment films formed by inkjet printing, there is a trade-off between the uniformity of film thickness within the coating surface and the film deposition precision at the coating periphery. That is, materials with high in-plane uniformity generally have low dimensional stability at the coating periphery, and the film may protrude beyond the set dimensions. On the other hand, materials with a straight coating periphery have lower in-plane uniformity.

[0007] To improve the film formation accuracy at the periphery of the coating, a method has been proposed to confine the alignment film within a specified range using special structures (see Patent Documents 1-3). However, these methods have the difficulty of requiring the use of special structures.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2004-361623

[0011] Patent Document 2: Japanese Patent Application Publication No. 2008-145461

[0012] Patent Document 3: Japanese Patent Application Publication No. 2010-281925 Summary of the Invention

[0013] The problem the invention aims to solve

[0014] In recent years, with the increasing resolution of liquid crystal display elements, multilayer wiring TFT design has gradually become mainstream. In TFT design, contact holes (also known as C / H) are formed on the substrate to connect the lower and upper wiring layers. However, due to the wiring structure and the influence of C / H, the spreadability of the liquid crystal alignment agent can be hindered during coating. As a result, unevenness in the thickness of the alignment film, such as dot-like or stripe-like unevenness, occurs around the C / H or other areas, sometimes leading to uneven display of the liquid crystal display element.

[0015] Furthermore, for liquid crystal alignment agents used in inkjet printing, low viscosity is required to ensure stable ejection of the alignment agent from the inkjet nozzle. Correspondingly, the resin component ratio in the liquid crystal alignment agent is sometimes set to be relatively low. On the other hand, reducing the resin component ratio can easily lead to problems such as decreased shape stability and film thickness uniformity at the coating periphery, and increased coating time to obtain the target film thickness. Therefore, it is desirable to reduce viscosity while maintaining the resin component ratio. While it is possible to reduce viscosity by decreasing the molecular weight of the resin component, this carries the risk of impairing the physical properties and durability of the alignment film. Therefore, it is desirable to reduce viscosity while maintaining the molecular weight of the resin component.

[0016] In view of the above-mentioned problems, the present invention provides a liquid crystal alignment agent capable of suppressing defects in the formation of the liquid crystal alignment film and the non-uniformity of the liquid crystal display element caused by the influence of wiring structure or C / H, and capable of reducing the viscosity of the liquid crystal alignment agent while maintaining the resin component ratio and the molecular weight of the resin component, a liquid crystal alignment film using the same, and a liquid crystal display element.

[0017] Solution for solving the problem

[0018] In order to solve the above problems, the inventors conducted repeated and in-depth research, and as a result, completed this invention.

[0019] The essence of this invention is a liquid crystal alignment agent, characterized in that it comprises: at least one polymer selected from the group consisting of a polyimide precursor and a polyimide as an imide thereof; and a solvent comprising solvent A, solvent B and solvent C.

[0020] Solvent A: is selected from at least one of the following groups: N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone and dimethylimidazolinone.

[0021] Solvent B: Dipropylene glycol dimethyl ether.

[0022] Solvent C: Selected from at least one of the groups consisting of diethylene glycol diethyl ether and diacetone alcohol.

[0023] The effects of the invention

[0024] According to the present invention, it is possible to obtain a polyimide-based liquid crystal alignment agent that can suppress defects in the formation of liquid crystal alignment films and uneven representation of liquid crystal display elements caused by the influence of wiring structure or C / H, and to make the liquid crystal alignment agent have low viscosity while maintaining the resin component ratio and the molecular weight of the resin component. Therefore, it is suitable for forming films using inkjet printing, liquid crystal alignment films using the same, and liquid crystal display elements. Detailed Implementation

[0025] The liquid crystal alignment agent of the present invention comprises: at least one polymer selected from the group consisting of a polyimide precursor and a polyimide as an imide thereof (also referred to as a specific polymer); and a solvent comprising solvent A, solvent B and solvent C (also referred to as a specific solvent).

[0026] <Specific solvents>

[0027] The liquid crystal alignment agent of the present invention contains solvents A, B, and C. By containing this combination of solvents, the liquid crystal alignment agent of the present invention can suppress poor film formation caused by wiring structure or C / H, and can suppress the defect of uneven display of liquid crystal display elements. Furthermore, it can reduce the viscosity of the liquid crystal alignment agent while maintaining the content ratio and molecular weight of the resin components.

[0028] Solvent A

[0029] Solvent A is at least one solvent selected from the group consisting of N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), γ-butyrolactone (GBL), and 1,3-dimethylimidazolinone (DMI). Solvent A dissolves the polymer in the liquid crystal alignment agent.

[0030] Preferably, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, or γ-butyrolactone are used, and more preferably N-methyl-2-pyrrolidone or γ-butyrolactone are used.

[0031] The content of solvent A relative to the total mass of the liquid crystal alignment agent is preferably 20-80% by mass, more preferably 30-80% by mass, and particularly preferably 50-80% by mass.

[0032] Solvent B

[0033] Solvent B is dipropylene glycol dimethyl ether (DME). Solvent B is a solvent that helps improve the coating uniformity and reduce the viscosity of the liquid crystal alignment agent.

[0034] The solvent B is preferably 1 to 30% by mass relative to the total mass of the liquid crystal alignment agent, more preferably 5 to 30% by mass, and particularly preferably 10 to 30% by mass.

[0035] Solvent C

[0036] Solvent C is selected from at least one of the groups consisting of diethylene glycol diethyl ether (DGDE) and diacetone alcohol (DAA). Solvent C is a solvent that contributes to the low viscosity of the liquid crystal alignment agent of the present invention.

[0037] The solvent C is preferably 5 to 30% by mass, more preferably 10 to 30% by mass, and particularly preferably 10 to 20% by mass relative to the total mass of the liquid crystal alignment agent of the present invention.

[0038] <Specific polymers>

[0039] The polyimide precursor of the specific polymer contained in the liquid crystal alignment agent of the present invention preferably has the structure shown in the following formula (1).

[0040]

[0041] In formula (1) above, X1 is a tetravalent organic group derived from a tetracarboxylic acid derivative. Y1 is a divalent organic group derived from a diamine. R1 is a hydrogen atom or an alkylene group having 1 to 5 carbon atoms. From the viewpoint of ease of imidization reaction upon heating, R1 is preferably a hydrogen atom, a methyl group, or an ethyl group, and more preferably a hydrogen atom or a methyl group.

[0042] A1 and A2 are each independently a hydrogen atom, or an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms. From the viewpoint of liquid crystal orientation, A1 and A2 are preferably hydrogen atoms or methyl groups.

[0043] The components of the raw materials used to manufacture polyimide precursors for specific polymers are described.

[0044] <Diamine>

[0045] The diamine component used in the manufacture of polyimide precursors is not particularly limited. The diamine used as a raw material for the polyimide precursor shown in formula (1) above is represented by the following formula (2).

[0046]

[0047] In the above formula (2), A1 and A2, including the preferred example, are defined the same as A1 and A2 in the above formula (1). If the structure of example Y1 is given, the following (Y-1) to (Y-170) can be listed.

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

[0066] In the above formula, Me represents methyl and n represents an integer from 1 to 6.

[0067] Among them, Y1 is preferably (Y-7), (Y-8), (Y-16), (Y-17), (Y-18), (Y-20), (Y-21), (Y-22), (Y-28), (Y-35), (Y-38), (Y-43), (Y-48), (Y-64), (Y-66), (Y- 71), (Y-72), (Y-76), (Y-77), (Y-80), (Y-81), (Y-82), (Y-83), (Y156 ), (Y-159), (Y-160), (Y-161), (Y-162) (Y-168), (Y-169), or (Y-170). Particularly preferred are (Y-7), (Y-8), (Y-16), (Y-17), (Y-18), (Y-21), (Y-22), (Y-28), (Y-38), (Y-64), (Y-66), (Y -72), (Y-76), (Y-81), (Y156), (Y-159), (Y-160), (Y-161), (Y-162) (Y-168), (Y-169), or (Y-170).

[0068] <Tetracarboxylic acid derivatives>

[0069] There are no particular limitations on the tetracarboxylic acid derivatives used in the manufacture of polyimide precursors. For the tetracarboxylic acid derivative components that serve as raw materials for the polyimide precursors shown in the above formula (1), not only tetracarboxylic acid dianhydride can be listed, but also tetracarboxylic acid, tetracarboxylic acid diacyl halide, tetracarboxylic acid dialkyl ester, and tetracarboxylic acid dialkyl ester diacyl halide can be listed as derivatives.

[0070] As a tetracarboxylic acid dianhydride or a derivative thereof, the substance shown in the following formula (3) is preferred.

[0071]

[0072] In formula (3), X1 is a tetravalent organic group with an alicyclic structure, and its structure is not particularly limited. As specific examples, the following formulas (X1-1) to (X1-44) can be listed.

[0073]

[0074] In equations (X1-1) to (X1-4), R3 to R 23 Each of these atoms is independently a hydrogen atom, a halogen atom, an alkyl group with 1 to 6 carbon atoms, an alkenyl group with 2 to 6 carbon atoms, an alkynyl group with 2 to 6 carbon atoms, a monovalent organic group containing a fluorine atom with 1 to 6 carbon atoms, or a phenyl group. From the viewpoint of liquid crystal orientation, R3~R 23 Preferably, it is a hydrogen atom, a halogen atom, a methyl group, or an ethyl group, with hydrogen atom or a methyl group being more preferred.

[0075] It should be noted that, as specific examples of formula (X1-1), the following formulas (X1-1-1) to (X1-1-6) can be listed. From the viewpoint of liquid crystal alignment and photoresponse sensitivity, (X1-1-1) is particularly preferred.

[0076]

[0077]

[0078]

[0079]

[0080]

[0081]

[0082] For the tetracarboxylic dianhydride or its derivatives used as the polyimide precursor or raw material of the present invention, it is preferable that, relative to 1 mole of all tetracarboxylic dianhydride or its derivatives, it contains 60 to 100 mol% of the tetracarboxylic dianhydride or its derivatives shown in formula (3) above. To obtain a liquid crystal alignment film with good liquid crystal alignment properties, 80 to 100 mol% is more preferred, and even more preferably 90 to 100 mol%.

[0083] <Polyimide precursor>

[0084] <Manufacturing Method of Polyamide Ester>

[0085] Polyamate, one of the polyimide precursors used in this invention, can be manufactured by the methods shown in (1), (2) or (3) below.

[0086] (1) Cases involving polyamic acid manufacturing

[0087] Polyamic esters can be synthesized by esterifying polyamic acid obtained from tetracarboxylic dianhydride and diamine. Specifically, they can be synthesized by reacting polyamic acid with an esterifying agent in the presence of an organic solvent at -20°C to 150°C, preferably 0°C to 50°C, for 30 minutes to 24 hours, preferably 1 to 4 hours.

[0088] As esterifying agents, those that can be easily removed through purification are preferred, and examples include N,N-dimethylformamide dimethyl acetal, N,N-dimethylformamide diethyl acetal, N,N-dimethylformamide dipropyl acetal, N,N-dimethylformamide dineopentylbutyl acetal, N,N-dimethylformamide ditert-butyl acetal, 1-methyl-3-p-tolyltriazine, 1-ethyl-3-p-tolyltriazine, 1-propyl-3-p-tolyltriazine, and 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride. The amount of esterifying agent used is preferably 2 to 6 molar equivalents relative to 1 mole of the repeating unit of polyamic acid.

[0089] The solvent used in the above reaction is preferably N,N-dimethylformamide, N-methyl-2-pyrrolidone, or γ-butyrolactone, based on the solubility of the polymer. One or more of these solvents may be used. The concentration of the polymer in the reaction solution is preferably 1 to 30% by mass, more preferably 5 to 20% by mass, from the viewpoint of minimizing polymer precipitation and readily obtaining a high molecular weight polymer.

[0090] (2) The case of production by reaction of tetracarboxylic acid diester diacyl chloride with diamine.

[0091] Polyamates can be manufactured from tetracarboxylic acid diester diacyl chloride and diamine. Specifically, they can be synthesized by reacting tetracarboxylic acid diester diacyl chloride with diamine in the presence of a base and an organic solvent at -20°C to 150°C, preferably 0°C to 50°C, for 30 minutes to 24 hours, preferably 1 to 4 hours.

[0092] The aforementioned base can be pyridine, triethylamine, 4-dimethylaminopyridine, etc., with pyridine being preferred for a stable reaction. From the viewpoint of achieving an easily removable amount and readily yielding a high molecular weight polymer, the amount of base used is preferably 2 to 4 moles relative to the tetracarboxylic acid diester diacyl chloride.

[0093] The solvent used in the above reaction is preferably N-methyl-2-pyrrolidone or γ-butyrolactone, based on the solubility of the monomer and polymer. One or more of these solvents can be used. The polymer concentration in the reaction solution is preferably 1-30% by mass, more preferably 5-20% by mass, from the viewpoint of minimizing polymer precipitation and readily obtaining a high molecular weight polymer. Furthermore, to prevent the hydrolysis of the tetracarboxylic acid diester diacyl chloride, the solvent used in the synthesis of the polyamic ester is preferably dehydrated as much as possible, and the introduction of external gases is preferably prevented under a nitrogen atmosphere.

[0094] (3) The case of production by reaction of tetracarboxylic acid diester with diamine.

[0095] Polyamates can be manufactured by polycondensation of a tetracarboxylic acid diester with a diamine. Specifically, they can be manufactured by reacting a tetracarboxylic acid diester with a diamine in the presence of a condensing agent, a base, and an organic solvent at 0°C to 150°C, preferably 0°C to 100°C, for 30 minutes to 24 hours, preferably 3 to 15 hours.

[0096] The aforementioned condensing agents can be triphenyl phosphite, dicyclohexylcarbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N,N'-carbonyldiimidazole, dimethoxy-1,3,5-triazinylmethylmorpholinium, O-(benzotriazol-1-yl)-N,N,N',N'-tetramethylureon tetrafluoroborate, O-(benzotriazol-1-yl)-N,N,N',N'-tetramethylureon hexafluorophosphate, diphenyl phosphonate (2,3-dihydro-2-thio-3-benzoxazolyl)phosphonate, etc. The amount of condensing agent added is preferably 2 to 3 molar times relative to the tetracarboxylic acid diester.

[0097] The aforementioned base can be a tertiary amine such as pyridine or triethylamine. From the viewpoint of being an amount that is easy to remove and that easily yields a high molecular weight polymer, the amount of base used is preferably 2 to 4 moles relative to the diamine component.

[0098] Furthermore, in the above reaction, the addition of a Lewis acid as an additive allows the reaction to proceed efficiently. Lithium halides such as lithium chloride and lithium bromide are preferred as Lewis acids. The amount of Lewis acid added is preferably 0 to 1.0 molar ratio relative to the diamine content.

[0099] Of the three methods for manufacturing polyamic acid esters described above, the method described in (1) or (2) is particularly preferred in order to obtain polyamic acid esters with high molecular weight.

[0100] The polyamic acid ester solution obtained as described above can be precipitated by injecting it into a poor solvent while stirring thoroughly. After several precipitation cycles, the polymer is washed with the poor solvent and dried at room temperature or by heating to obtain a refined polyamic acid ester powder. The poor solvent is not particularly limited, but examples include water, methanol, ethanol, hexane, butyl cellosolve, acetone, and toluene.

[0101] <Manufacturing Method of Polyamic Acid>

[0102] Polyamic acid, the polyimide precursor used in this invention, can be manufactured by the method shown below. Specifically, it can be synthesized by reacting a tetracarboxylic dianhydride with a diamine in the presence of an organic solvent at -20°C to 150°C, preferably 0°C to 50°C, for 30 minutes to 24 hours, preferably 1 to 12 hours.

[0103] The organic solvent used in the above reaction is preferably N,N-dimethylformamide, N-methyl-2-pyrrolidone, or γ-butyrolactone, based on the solubility of the monomer and polymer. One or more of these solvents may be used. The polymer concentration is preferably 1 to 30% by mass, more preferably 5 to 20% by mass, from the viewpoint of minimizing polymer precipitation and readily obtaining a high molecular weight polymer.

[0104] The polyamic acid obtained through the above-described procedure can be precipitated and recovered by injecting the reaction solution into a poor solvent while stirring thoroughly. Alternatively, after several precipitation cycles, washing with the poor solvent, and drying at room temperature or by heating, a refined polyamic acid powder can be obtained. The poor solvent is not particularly limited, but examples include water, methanol, ethanol, hexane, butyl cellosolve, acetone, and toluene.

[0105] <Manufacturing Method of Polyimide>

[0106] The polyimide used in this invention can be manufactured by imidizing the aforementioned polyamic acid ester or polyamic acid. When manufacturing polyimide from polyamic acid ester, chemical imidization by adding a basic catalyst to the aforementioned polyamic acid ester solution or a polyamic acid solution obtained by dissolving polyamic acid ester resin powder in an organic solvent is simple. Chemical imidization is preferred because the imidization reaction is carried out at a lower temperature, and the molecular weight of the polymer is less likely to decrease during the imidization process.

[0107] Chemical imidization can be carried out by stirring the polyaminate to be imidized in an organic solvent in the presence of a basic catalyst. The organic solvent can be the same as that used in the aforementioned polymerization reaction. Examples of basic catalysts include pyridine, triethylamine, trimethylamine, tributylamine, and trioctylamine. Triethylamine is preferred because it is sufficiently basic for the reaction to proceed.

[0108] The imidization reaction is carried out at a temperature of -20°C to 140°C, preferably 0°C to 100°C, for a reaction time of 1 to 100 hours. The amount of alkaline catalyst is 0.5 to 30 molar times, preferably 2 to 20 molar times, of the amide ester groups. The imidization rate of the obtained polymer can be controlled by adjusting the amount of catalyst, temperature, and reaction time. Since the solution after the imidization reaction contains residual added catalyst, it is preferable to recover the obtained imidized polymer, dissolve it again in an organic solvent, and prepare the liquid crystal alignment agent of this invention.

[0109] When manufacturing polyimides from polyamic acid, chemical imidization by adding a catalyst to a solution of the aforementioned polyamic acid obtained through the reaction of a diamine component with a tetracarboxylic acid dianhydride is simple. Chemical imidization is preferred because it is carried out at a lower temperature, and the molecular weight of the polymer is less likely to decrease during the imidization process.

[0110] Chemical imidization can be carried out by stirring the polymer to be imidized in an organic solvent in the presence of a basic catalyst and an acid anhydride. The organic solvent can be the solvent used in the aforementioned polymerization reaction. Examples of basic catalysts include pyridine, triethylamine, trimethylamine, tributylamine, and trioctylamine. Pyridine is preferred because it has moderate basicity for the reaction to proceed. Examples of acid anhydrides include acetic anhydride, trimellitic anhydride, and pyromellitic anhydride. Acetic anhydride is preferred because it facilitates purification after the reaction.

[0111] The imidization reaction is carried out at a temperature of -20°C to 140°C, preferably 0°C to 100°C, for a reaction time of 1 to 100 hours. The amount of alkaline catalyst is 0.5 to 30 molar times, preferably 2 to 20 molar times, of the amic acid groups, and the amount of acid anhydride is 1 to 50 molar times, preferably 3 to 30 molar times, of the amic acid groups. The imidization rate of the resulting polymer can be controlled by adjusting the amount of catalyst, temperature, and reaction time.

[0112] Since the solution after the imidization reaction of polyamic acid or polyamic ester contains added catalysts and the like, it is preferable to recover the obtained imidized polymer by the means described below, and then dissolve it again with an organic solvent to prepare the liquid crystal alignment agent of the present invention.

[0113] The polyimide solution obtained by the above operation can be injected into a poor solvent while stirring thoroughly to precipitate the polymer. After several precipitation cycles, washing with the poor solvent, and drying at room temperature or by heating, a refined polyamic acid ester powder can be obtained.

[0114] The aforementioned unsuitable solvents are not specifically limited, but can include methanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, benzene, etc.

[0115] Liquid crystal alignment agent

[0116] The liquid crystal alignment agent of the present invention has the form of a solution obtained by dissolving a polymer comprising a specific polymer in an organic solvent comprising a specific solvent. The molecular weights of the polyimide precursor and the polyimide described in the present invention, in terms of weight-average molecular weight, are preferably 2,000 to 500,000, more preferably 5,000 to 300,000, and even more preferably 10,000 to 100,000. Furthermore, the number-average molecular weight is preferably 1,000 to 250,000, more preferably 2,500 to 150,000, and even more preferably 5,000 to 50,000.

[0117] The concentration of the polymer of the liquid crystal alignment agent used in this invention can be appropriately changed by setting the desired coating thickness. From the viewpoint of forming a uniform and defect-free coating, it is preferably 1% by weight or more, and from the viewpoint of the storage stability of the solution, it is preferably 10% by weight or less.

[0118] <Other solvents>

[0119] The solvent in the liquid crystal alignment agent of the present invention may contain solvents other than solvents A, B, and C that constitute the specific solvents described above (hereinafter also referred to as other solvents). Other solvents may include solvents that dissolve the polyimide precursor and polyimide (also referred to as good solvents), and solvents that improve the coating properties and surface smoothness of the liquid crystal alignment film when the liquid crystal alignment agent is applied (also referred to as poor solvents). Specific examples of other solvents are given below, but the invention is not limited to these examples.

[0120] Examples of good solvents include N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, methyl ethyl ketone, cyclohexanone, cyclopentanone, 3-methoxy-N,N-dimethylpropionamide, or 4-hydroxy-4-methyl-2-pentanone.

[0121] Specific examples of unsuitable solvents include ethanol, isopropanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, isopentanol, tert-pentanol, 3-methyl-2-butanol, neopentanol, 1-hexanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, cyclohexanol, 1-methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 1,2-ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1, 2-Butanediol, 1,3-Butanediol, 1,4-Butanediol, 2,3-Butanediol, 1,5-Pentanediol, 2-Methyl-2,4-Pentanediol, 2-Ethyl-1,3-Hexanediol, Dipropyl ether, Dibutyl ether, Dihexyl ether, Dioxane, Ethylene glycol dimethyl ether, Ethylene glycol diethyl ether, Ethylene glycol dibutyl ether, 1,2-Butoxyethane, Diethylene glycol dimethyl ether, Diethylene glycol methyl ethyl ether, Diethylene glycol dibutyl ether, 2-Pentanone, 3-Pentanone, 2-Hexanone, 2-Heptanone, 4-Heptanone, 3-Ethoxybutylacetic acid ester, 1-Methylpentylacetic acid ester, 2-Ethylbutylacetic acid ester, 2-Ethylhexylacetic acid ester, Ethylene glycol monoacetate ... Diethylene glycol diacetate, propylene carbonate, ethylene carbonate, 2-(methoxymethoxy)ethanol, butyl cellosolve, ethylene glycol monoisopentyl ether, ethylene glycol monohexyl ether, 2-(hexyloxy)ethanol, furfuryl alcohol, diethylene glycol, propylene glycol, 1-butoxy-2-propanol, 1-(butoxyethoxy)propanol, propylene glycol monomethyl ether acetate, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monoacetate, ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, propylene glycol diacetate, diisopentyl ether, diethylene glycol... Alcohol monobutyl ether acetate, 2-(2-ethoxyethoxy)ethyl acetate, diethylene glycol acetate, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol monoethyl ether acetate, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-methoxypropionate, 3-ethoxypropionic acid, 3-methoxypropionic acid, propyl 3-methoxypropionate, butyl 3-methoxypropionate, methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, isoamyl lactate, diisobutyl ketone, ethyl carbitol, etc.

[0122] In addition, as a poor solvent, when the polyimide precursor contained in the liquid crystal alignment agent and the polyimide have high solubility in the solvent, the solvents shown in formulas [D-1] to [D-3] below are preferred.

[0123]

[0124] In formula [D-1], D 1 In formula [D-2], D represents an alkyl group having 1 to 3 carbon atoms. 2 It represents an alkyl group having 1 to 3 carbon atoms, in the formula [D-3], where D 3 Indicates an alkyl group having 1 to 4 carbon atoms.

[0125] The liquid crystal alignment agent of the present invention may comprise: a crosslinkable compound having an epoxy group, an isocyanate group, an oxobutyl group, or a cyclic carbonate group; a crosslinkable compound having at least one substituent selected from the group consisting of hydroxyl, hydroxyalkyl, and lower alkoxyalkyl groups; or a crosslinkable compound having polymerizable unsaturated bonds. These substituents and polymerizable unsaturated bonds must be present in two or more of the crosslinkable compound.

[0126] Examples of crosslinking compounds having epoxy or isocyanate groups include bisphenol acetone glycidyl ether, phenolic varnish epoxy resin, cresol phenolic varnish epoxy resin, triglycidyl isocyanurate, tetraglycidyl aminodiphenylene, tetraglycidyl m-phenylenediamine, tetraglycidyl-1,3-bis(aminoethyl)cyclohexane, tetraphenylglycidyl ether ethane, triphenylglycidyl ether ethane, bisphenol hexafluoroacetyl diglycidyl ether, 1,3-bis(1-(2,3-epoxypropoxy)-1-trifluoromethyl-2,2,2-trifluoromethyl)benzene, 4,4-bis(2,3-epoxypropoxy)octafluorobiphenyl, and triglycidyl... - p-Aminophenol, tetraglycidyl-m-phenylenediamine, 2-(4-(2,3-epoxypropoxy)phenyl)-2-(4-(1,1-bis(4-(2,3-epoxypropoxy)phenyl)ethyl)phenyl)propane or 1,3-bis(4-(1-(4-(2,3-epoxypropoxy)phenyl)-1-(4-(1-(4-(2,3-epoxypropoxy)phenyl)-1-methylethyl)phenyl)ethyl)phenoxy)-2-propanol, etc.

[0127] Crosslinkable compounds having oxetane are compounds having at least two oxetane groups as shown in [4A].

[0128]

[0129] Specifically, examples include the crosslinking compounds represented by formulas [4a] to [4k] as described on pages 58-59 of International Publication No. WO2011 / 132751 (published on October 27, 2011).

[0130] As a crosslinkable compound having cyclic carbonate groups, it is a crosslinkable compound having at least two cyclic carbonate groups as shown in the following formula [5A].

[0131]

[0132] Specifically, examples include the crosslinking compounds represented by formulas [5-1] to [5-42] as described on pages 76 to 82 of International Publication No. WO2012 / 014898 (published on February 2, 2012).

[0133] Crosslinkable compounds having at least one substituent selected from the group consisting of hydroxyl and alkoxy groups include, for example, amino resins having hydroxyl or alkoxy groups, such as melamine resins, urea resins, guanidine resins, glycourea-formaldehyde resins, succinamide-formaldehyde resins, or ethylene urea-formaldehyde resins. Specifically, melamine derivatives, benzoguanamine derivatives, or glycourea can be used, where the hydrogen atom of the amino group is replaced by hydroxymethyl or alkoxymethyl groups or both. These melamine derivatives or benzoguanamine derivatives can be dimers or trimers. Preferably, each triazine ring has an average of 3 to 6 hydroxymethyl or alkoxymethyl groups.

[0134] Examples of the aforementioned melamine derivatives or benzoguanidine derivatives include commercially available MX-750, which has an average of 3.7 methoxymethyl groups substituted on each triazine ring, and MW-30, which has an average of 5.8 methoxymethyl groups substituted on each triazine ring (as described above by Sanwa Chemical Co.). (Made by MitsuiCyanamid Co., Ltd.), Cymel 300, 301, 303, 350, 370, 771, 325, 327, 703, 712 and other methoxymethylated melamines, Cymel 235, 236, 238, 212, 253, 254 and other methoxymethylated butoxymethylated melamines, Cymel 506, 508 and other butoxymethylated melamines, Cymel 1141 and other carboxyl-containing methoxymethylated isobutoxymethylated melamines, Cymel 1123 and other methoxymethylated ethoxymethylated benzoguanamines, Cymel 1123-10 and other methoxymethylated butoxymethylated benzoguanamines, Cymel 1128 and other butoxymethylated benzoguanamines, Cymel 1125-80 and other carboxyl-containing methoxymethylated ethoxymethylated benzoguanamines (all of the above are from MitsuiCyanamid Co., Ltd.) (Manufactured by Ltd.)

[0135] In addition, examples of glycourea include butoxymethylated glycourea such as Cymel1170, hydroxymethylated glycourea such as Cymel1172, and methoxyhydroxymethylated glycourea such as Powderlink1174.

[0136] Examples of benzene or phenolic compounds having hydroxyl or alkoxy groups include 1,3,5-tris(methoxymethyl)benzene, 1,2,4-tris(isopropoxymethyl)benzene, 1,4-bis(sec-butoxymethyl)benzene, or 2,6-dihydroxymethyl-p-tert-butylphenol.

[0137] More specifically, examples include the crosslinking compounds of formulas [6-1] to [6-48] described on pages 62 to 66 of International Publication No. WO2011 / 132751 (published on October 27, 2011).

[0138] Examples of crosslinked compounds with polymerizable unsaturated bonds include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, tri(meth)acryloyloxyethoxytrimethylolpropane, or glycerol polyglycidyl ether poly(meth)acrylate, which are crosslinked compounds with three polymerizable unsaturated groups within their molecules; furthermore, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene oxide bisphenol A type di(meth)acrylate, propylene oxide bisphenol type di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, glycerol di(meth)acrylate, etc. Crosslinked compounds having two polymeric unsaturated groups in the molecule, such as methacrylates, pentaerythritol dimethacrylates, ethylene glycol diglycidyl ether dimethacrylates, diethylene glycol diglycidyl ether dimethacrylates, diglycidyl phthalate dimethacrylates, or neopentyl glycol dimethacrylate with hydroxypentanoic acid; and crosslinked compounds having one polymeric unsaturated group in the molecule, such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 2-phenoxy-2-hydroxypropyl methacrylate, 2-methacryloyloxy-2-hydroxypropyl phthalate, 3-chloro-2-hydroxypropyl methacrylate, glyceryl monomethacrylate, 2-methacryloyloxyethyl phosphate, or N-hydroxymethyl (meth)acrylamide.

[0139] Alternatively, compounds represented by the following formula [7A] may also be used.

[0140]

[0141] In formula [7A], E1 represents a group selected from the group consisting of cyclohexane ring, bicyclohexane ring, benzene ring, biphenyl ring, terphenyl ring, naphthalene ring, fluorene ring, anthracene ring, and phenanthrene ring. E2 represents a group selected from formula [7a] or formula [7b] below, where n represents an integer from 1 to 4.

[0142]

[0143] The crosslinking compound used in the liquid crystal alignment agent of the present invention can be one type or a combination of two or more types.

[0144] The content of the crosslinking compound in the liquid crystal alignment agent of the present invention is preferably 0.1 to 150 parts by mass relative to 100 parts by mass of the total polymer components. Specifically, to promote the crosslinking reaction and achieve the desired effect, the content is preferably 0.1 to 100 parts by mass, more preferably 1 to 50 parts by mass.

[0145] The liquid crystal alignment agent of the present invention may contain compounds that improve the uniformity of film thickness and surface smoothness of the liquid crystal alignment film when the liquid crystal alignment agent is coated.

[0146] Compounds that improve the uniformity of film thickness and surface smoothness of liquid crystal alignment films include fluorinated surfactants, organosilicon surfactants, and nonionic surfactants.

[0147] Specifically, examples include Ftop EF301, EF303, EF352 (and above, manufactured by Tochem Products Co., Ltd.), MegaFac F171, F173, R-30 (and above, manufactured by Dainippon Ink and Chemicals, Inc.), Fluorad FC430, FC431 (and above, manufactured by Sumitomo 3M), Asahi Guard AG710, Surflon S-382, SC101, SC102, SC103, SC104, SC105, SC106 (and above, manufactured by Asahi Glass Co., Ltd.), etc.

[0148] The amount of surfactant used is preferably 0.01 to 2 parts by mass, more preferably 0.01 to 1 part by mass, relative to 100 parts by mass of all polymer components contained in the liquid crystal alignment agent.

[0149] Furthermore, in the liquid crystal alignment agent, a nitrogen-containing heterocyclic amine of formulas [M1] to [M156], as described in pages 69-73 of International Publication No. WO2011 / 132751 (published on October 27, 2011), can be added as a compound that promotes charge movement in the liquid crystal alignment film and thus promotes charge escape from the element. This amine can be added directly to the liquid crystal alignment agent, preferably after preparing a solution with a concentration of 0.1-10% by mass, more preferably 1-7% by mass. The solvent is not particularly limited as long as it dissolves the specific polymer.

[0150] In addition to the aforementioned poor solvents, crosslinking compounds, compounds that improve the uniformity of film thickness and surface smoothness of resin coatings or liquid crystal alignment films, and compounds that promote charge escape, the liquid crystal alignment agent of the present invention may also contain silane coupling agents for improving the adhesion between the alignment film and the substrate, and imidization accelerators for efficiently performing heat-based imidization of polyimide precursors during firing coating.

[0151] <Liquid Crystal Alignment Film & Liquid Crystal Display Element>

[0152] The liquid crystal alignment film of the present invention is a film obtained by coating the aforementioned liquid crystal alignment agent onto a substrate, followed by drying and firing. As for the substrate for coating the liquid crystal alignment agent of the present invention, there are no particular limitations as long as it is a highly transparent substrate; glass substrates, silicon nitride substrates, acrylic substrates, polycarbonate substrates, and other plastic substrates can also be used. In this case, using a substrate with ITO electrodes or the like for driving the liquid crystal is preferred from the viewpoint of process simplification. Furthermore, in reflective liquid crystal display elements, if the substrate is only on one side, an opaque material such as a silicon wafer can be used, and the electrodes can be made of light-reflective materials such as aluminum.

[0153] In industry, liquid crystal alignment agents are typically applied using methods such as screen printing, offset printing, flexographic printing, or inkjet printing. Other known coating methods include immersion coating, roller coating, slot coating, spin coating, or spray coating.

[0154] As described above, the liquid crystal alignment agent of the present invention can achieve low viscosity while maintaining a high ratio of polymer components and a high molecular weight of polymer, and therefore can be suitable for use in inkjet coating and film-forming methods.

[0155] After the liquid crystal alignment agent is coated onto the substrate, the solvent can be evaporated using heating methods such as a hot plate, a thermal cycling oven, or an IR (infrared) oven, thereby forming a liquid crystal alignment film. The drying and firing processes after coating the liquid crystal alignment agent can be performed at any temperature and time. Typically, to fully remove the contained solvent, conditions such as firing at 50–120°C for 1–10 minutes, followed by firing at 150–300°C for 5–120 minutes are recommended. If the thickness of the fired liquid crystal alignment film is too thin, the reliability of the liquid crystal display element may decrease; therefore, a thickness of 5–300 nm is preferred, and 10–200 nm is more preferable.

[0156] The liquid crystal alignment agent of the present invention can be aligned by brushing, photoalignment, or other methods after being coated onto a substrate and fired. However, it is not aligned for applications such as vertical alignment, and can thus be used as a liquid crystal alignment film. Alignment processes such as brushing and photoalignment can be performed using known methods and apparatus.

[0157] As an example of a method for manufacturing liquid crystal cells, a passive matrix structure liquid crystal display element will be used for explanation. It should be noted that an active matrix structure liquid crystal display element, in which switching elements such as TFTs (thin-film transistors) are provided in each pixel portion constituting the image representation, can also be used.

[0158] Specifically, a transparent glass substrate is prepared, with a standard electrode disposed on one substrate and segmented electrodes disposed on another substrate. These electrodes, for example, can be ITO electrodes, and are patterned to enable the desired image representation. Next, an insulating film is disposed on each substrate to cover the standard and segmented electrodes. The insulating film, for example, can be a SiO2-TiO2 film formed by a sol-gel method.

[0159] Next, a liquid crystal alignment film is formed on each substrate. One substrate is then overlapped with another substrate so that their liquid crystal alignment film surfaces face each other, and the perimeter is bonded with a sealant. To control the substrate spacing, spacers are typically mixed into the sealant. It is also preferable that spacers for controlling substrate spacing are dispersed in the in-situ areas where no sealant is applied. An opening is provided in a portion of the sealant to allow liquid crystal to be filled from the outside. Next, liquid crystal material is injected into the space surrounded by the two substrates and the sealant through the opening in the sealant, and then the opening is sealed with an adhesive. Injection can be performed using a vacuum injection method or a method utilizing capillary action in the atmosphere. The liquid crystal material can be either a positive liquid crystal material or a negative liquid crystal material, preferably a negative liquid crystal material. Next, polarizers are applied. Specifically, a pair of polarizers are bonded to the surfaces of the two substrates opposite to the liquid crystal layers.

[0160] Example

[0161] The invention will then be described in more detail by way of examples. However, the invention is not to be limited by these examples. The meanings of the abbreviations used below and the methods of measurement are as follows.

[0162] DA-1: 1,5-bis(4-aminophenoxy)pentane

[0163] DA-2: 4,4'-Diaminodiphenylmethane

[0164] DA-3: 4,4'-Diaminodiphenylamine

[0165] CA-1: Pyromellitic dianhydride

[0166] CA-2: 1,2,3,4-Cyclobutanetetracarboxylic dianhydride

[0167] CA-3: 3,4-Dicarboxy-1,2,3,4-Tetrahydro-1-naphthous succinic anhydride

[0168] NMP: N-methyl-2-pyrrolidone; GBL: γ-butyrolactone

[0169] DME: Dipropylene glycol dimethyl ether

[0170] DPM: Dipropylene glycol monomethyl ether

[0171] DAA: Diacetone alcohol

[0172] DEDG: Diethylene glycol diethyl ether

[0173] NEP: N-ethyl-2-pyrrolidone

[0174] <Viscosity Measurement>

[0175] The viscosity of polyamic acid, liquid crystal alignment agent, etc. was measured at 25°C using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.).

[0176] <Method for Determination of Solid Component Concentration>

[0177] The concentration of solid components in solutions such as polyamic acid solutions was determined. 1.0 g of the solution was weighed into an aluminum cup, heated at 200°C for 2 hours, and the amount of solid remaining in the cup was measured to determine the concentration of solid components in the solution.

[0178] [Manufacturing of Polyamic Acid A1]

[0179] 171.8 g of DA-1 and 1676 g of NMP were added to a 2000 ml flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred while being supplied with nitrogen to dissolve it. 113.8 g of CA-1 was added to the diamine solution while it was being stirred under water cooling, followed by the addition of NMP at a solids concentration of 12% by weight. The mixture was heated to 50°C and stirred for 20 hours under a nitrogen atmosphere to obtain a polyamic acid (A1) solution (viscosity: 90 mPa·s, solids concentration: 11.2% by weight).

[0180] [Preparation of polyamic acid solution a1]

[0181] Compared with 535.7g of polyamic acid (A1) solution, 264.3g of NMP and 200.0g of DME were added to obtain a polyamic acid solution (a1) with a solid content concentration of 6.0% by weight.

[0182] [Manufacturing of polyamic acid a2]

[0183] Compared with 535.7g of polyamic acid (A1) solution, 264.3g of NMP and 200.0g of DAA were added to obtain a polyamic acid solution (a2) with a solid content concentration of 6.0% by weight.

[0184] [Preparation of polyamic acid solution a3]

[0185] Compared with 535.7g of polyamic acid (A1) solution, 264.3g of NMP and 200.0g of DPM were added to obtain a polyamic acid solution (a3) ​​with a solid content of 6.0% by weight.

[0186] [Manufacturing of Polyamic Acid A2]

[0187] 100.8 g of DA-1 and 34.9 g of DA-5 were added to a 2000 ml flask equipped with a stirrer and a nitrogen inlet tube. 1337 g of NMP was added while stirring with nitrogen gas to dissolve the diamine solution. 92.2 g of CA-1 was added while stirring under water cooling, followed by the addition of NMP at a solid content of 12% by weight. The mixture was heated at 50 degrees Celsius and stirred for 20 hours under a nitrogen atmosphere to obtain a polyamic acid (A2) solution (viscosity: 520 mPa·s).

[0188] [Manufacturing of Polyamic Acid B1]

[0189] Add 87.7g of DA-3 to a 2000ml four-necked flask equipped with a stirrer and a nitrogen inlet tube. Add 1052.5g of solvent (solvent 1) prepared by mixing NMP and GBL in a 50% by weight ratio, and stir while supplying nitrogen to dissolve the diamine solution. While stirring the solution under water cooling, add 70.1g of CA-2 and 382.7g of solvent 1, and stir for 3 hours under a nitrogen atmosphere and water cooling.

[0190] Then, 21.8 g of DA-2 and 1,191.3 g of solvent 1 were added and stirred. After DA-2 dissolved, 33.0 g of CA-3 and 1,287.0 g of solvent 1 were added, and the mixture was stirred again under nitrogen atmosphere and water cooling for 3 hours to obtain a solution of polyamic acid (B1) with a solid content concentration of 9.8% by weight (viscosity: 65 mPa·s).

[0191] [Manufacturing of Polyamic Acid B2]

[0192] In a 2000 ml four-necked flask equipped with a stirrer and a nitrogen inlet tube, 95.6 g of DA-3 and 18.2 g of DA-4 were added, along with 967 g of NMP. The mixture was stirred while supplying nitrogen gas until dissolved. While stirring the diamine solution under water cooling, 54.8 g of CA-2 and 276 g of NMP were added. The mixture was stirred for 3 hours under a nitrogen atmosphere and water cooling. Then, 75.0 g of CA-4 and NMP were added at a solids concentration of 15% by weight. The mixture was stirred while heating at 50°C under a nitrogen atmosphere for 12 hours. This yielded a polyamic acid (B2) solution (viscosity: 302 mPa·s).

[0193] [Manufacturing of Polyamic Acid B3]

[0194] In a 2000 ml four-necked flask equipped with a stirrer and a nitrogen inlet tube, 87.7 g of DA-3 and 1052.5 g of solvent (solvent 1) prepared by mixing NMP and NEP in a 50% by weight ratio were added. The mixture was stirred while supplying nitrogen to dissolve the diamine solution. While stirring the solution under water cooling, 70.1 g of CA-2 and 382.7 g of solvent 1 were added. The mixture was stirred for 3 hours under a nitrogen atmosphere and water cooling. Then, 21.8 g of DA-2 and 1191.3 g of solvent 1 were added and stirred. After DA-2 dissolved, 33.0 g of CA-3 and 1287.0 g of solvent 1 were added, and the mixture was stirred again for 3 hours under a nitrogen atmosphere and water cooling to obtain a polyamic acid (B3) solution with a solid content of 9.8% by weight (viscosity: 65 mPa·s).

[0195] [Example 1]

[0196] Weigh 153.4 g of polyamic acid (B1) solution, add 1.3 g of NMP, 38.5 g of GBL solution containing 1.3 wt% 3-epoxypropoxypropyltriethoxysilane, 95.9 g of GBL, 53.5 g of DME, and 50.0 g of DAA to the solution, and stir at room temperature for 1 hour. Then, add 107.5 g of the above polyamic acid solution (a1), and stir for another 1 hour to obtain 500.0 g of liquid crystal alignment agent composed of a solution (C1) with solid components in a weight ratio of NMP:GBL:DME:DAA = 4.3:30:40.7:15:10.

[0197] [Example 2]

[0198] Relative to 153.4 g of polyamic acid (B1) solution, 1.3 g of NMP, 38.5 g of GBL solution containing 1.3 wt% 3-epoxypropoxypropyltriethoxysilane, 95.9 g of GBL, 53.5 g of DME, and 50.0 g of DEDG were added, and the mixture was stirred at room temperature for 1 hour. Next, 107.5 g of the aforementioned polyamic acid solution (a1) was added, and the mixture was stirred for another 1 hour to obtain 500.0 g of a liquid crystal alignment agent consisting of a solution (C2) with solid components in a weight ratio of NMP:GBL:DME:DEDG = 4.3:30:40.7:15:10.

[0199] [Example 3]

[0200] A mixture of 33.3 g of 12 wt% polyamic acid (A2) solution and 106.6 g of 15 wt% polyamic acid (B2) solution was stirred for 30 minutes. Then, 11.1 g of NMP, 20.0 g of NMP solution containing 1.0 wt% 3-epoxypropoxypropyltriethoxysilane, 204.0 g of GBL, 75.0 g of DME, and 50.0 g of DAA were added. The mixture was stirred at room temperature for 3 hours to obtain 500.0 g of a liquid crystal alignment agent composed of a solution (C7) with a polymer solid component ratio of A2 to B2 of 2:8 and a solid component ratio of NMP:GBL:DME:DAA of 4.2:30:40.8:15:10 by weight.

[0201] [Example 4]

[0202] A mixture of 33.3 g of 12 wt% polyamic acid (A2) solution and 106.6 g of 15 wt% polyamic acid (B2) solution was stirred for 30 minutes. Then, 11.1 g of NMP, 20.0 g of NMP solution containing 1.0 wt% 3-epoxypropoxypropyltriethoxysilane, 204.0 g of GBL, 75.0 g of DME, and 50.0 g of DEDG were added. The mixture was stirred at room temperature for 3 hours to obtain 500.0 g of a liquid crystal alignment agent composed of a solution (C8) with a polymer solid component ratio of A2 to B2 of 2:8 and a solid component ratio of NMP:GBL:DME:DEDG of 4.2:30:40.8:15:10 by weight.

[0203] [Example 5]

[0204] A mixture of 33.3 g of 12 wt% polyamic acid (A2) solution and 106.6 g of 15 wt% polyamic acid (B2) solution was stirred for 30 minutes. Then, 5.1 g of NMP, 20.0 g of NMP solution containing 1.0 wt% 3-epoxypropoxypropyltriethoxysilane, 6.0 g of NMP solution containing 10 wt% AD-1, 204.0 g of GBL, 75.0 g of DME, and 50.0 g of DAA were added. The mixture was stirred at room temperature for 3 hours to obtain a liquid crystal alignment agent (C9) consisting of a polymer solids ratio of A2 to B2 of 2:8, containing 3.0 wt% AD-1, and a total solids content of NMP:GBL:DME:DAA of 4.2:30:40.8:15:10 (wt%).

[0205] [Example 6]

[0206] Weigh 153.4 g of polyamic acid (B3) solution, add 1.3 g of NMP, 38.5 g of NEP solution containing 1.3 wt% 3-epoxypropoxypropyltriethoxysilane, 95.9 g of NEP, 53.5 g of DME, and 50.0 g of DAA to the solution, and stir at room temperature for 1 hour. Then add 107.5 g of a1, and stir for another 1 hour to obtain 500.0 g of liquid crystal alignment agent composed of a solution (C10) with solid components in a weight ratio of NMP:NEP:DME:DAA = 4.3:30:40.7:15:10.

[0207] [Comparative Example 1]

[0208] Weigh 153.4 g of polyamic acid (B1) solution, add 1.3 g of NMP, 38.5 g of GBL solution containing 1.3 wt% 3-epoxypropoxypropyltriethoxysilane, 145.9 g of GBL, and 53.5 g of DME to the solution, and stir at room temperature for 1 hour. Next, add 107.5 g of the above polyamic acid solution (a1), and stir for another 1 hour to obtain 500.0 g of a liquid crystal alignment agent composed of a solution (C3) with a solid component ratio of NMP:GBL:DME = 4.3:30:50.7:15 by weight.

[0209] [Comparative Example 2]

[0210] Weigh 153.4 g of polyamic acid (B1) solution, add 1.3 g of NMP, 38.5 g of GBL solution containing 1.3 wt% 3-epoxypropoxypropyltriethoxysilane, 95.9 g of GBL, 53.5 g of DME, and 50.0 g of DPM to the solution, and stir at room temperature for 1 hour. Next, add 107.5 g of the above polyamic acid solution (a1), and stir for another 1 hour to obtain 500.0 g of a liquid crystal alignment agent consisting of a solution (C4) having a solid composition ratio of NMP:GBL:DME:DPM of 4.3:30:40.7:15:10 by weight.

[0211] [Comparative Example 3]

[0212] Weigh 153.4 g of polyamic acid (B1) solution, add 1.3 g of NMP, 38.5 g of GBL solution containing 1.3 wt% 3-epoxypropoxypropyltriethoxysilane, 20.9 g of GBL, 83.5 g of DAA, and 95.0 g of DEDG to the solution, and stir at room temperature for 1 hour. Then, add 107.5 g of the above polyamic acid solution (a2), and stir for another 1 hour to obtain 500.0 g of liquid crystal alignment agent composed of a solution (C5) having a solid composition ratio of NMP:GBL:DAA:DEDG of 4.3:30:25.7:21:19 by weight.

[0213] [Comparative Example 4]

[0214] Weigh 153.4 g of polyamic acid (B1) solution, add 1.3 g of NMP, 38.5 g of GBL solution containing 1.3 wt% 3-epoxypropoxypropyltriethoxysilane, 145.9 g of GBL, and 53.5 g of DAA to the solution, and stir at room temperature for 1 hour. Then, add 107.5 g of a2, and stir for another 1 hour to obtain 500.0 g of liquid crystal alignment agent composed of a solution (C6) having a solid composition ratio of NMP:GBL:DAA of 4.3:30:50.7:15 by weight.

[0215] [Comparative Example 5]

[0216] Weigh 153.4 g of polyamic acid (B1) solution, add 1.3 g of NMP, 38.5 g of GBL solution containing 1.3 wt% 3-epoxypropoxypropyltriethoxysilane, 95.9 g of GBL, 53.5 g of DPM, and 50.0 g of DAA to the solution, and stir at room temperature for 1 hour. Then, add 107.5 g of a3, and stir for another 1 hour to obtain 500.0 g of liquid crystal alignment agent composed of a solution (C11) with solid components in the ratio of NMP:GBL:DPM:DAA = 4.3:30:40.7:15:10 (wt%).

[0217] The liquid crystal alignment agents of Examples 1-6 and Comparative Examples 1-5 were filtered through a filter with a pore size of 1 μm, and their viscosities were measured, as shown in Table 2. A lower viscosity indicates a better liquid crystal alignment agent. Furthermore, the following coating evaluation was also performed.

[0218] [Evaluation of Coating Performance Based on Inkjet Technology]

[0219] For Examples 1 and 2 and Comparative Examples 1-4 prepared above, inkjet coating was applied to TFT substrates using an inkjet coating apparatus (manufactured by ISHIIHYOKI CO.,LTD.). Coating was performed under the following conditions: nozzle spacing of 127 μm, coating speed of 250 mm / s, dispensing amount of 70 pL, and coating area of ​​36 × 36 mm. The coating film was pre-dried on a hot plate at 110°C for 1 minute, and then fired in an IR oven at 230°C for 15 minutes, resulting in a thickness of 120 nm.

[0220] [Evaluation methods for coatings]

[0221] For coatings obtained by pre-drying coated substrates at 110°C, the degree of point or stripe-like unevenness caused by contact holes or wiring is compared and evaluated on a 4-level scale. Unevenness that is clearly visible across the entire surface is designated as Lv4, unevenness that is locally visible is designated as Lv3, unevenness that is not visible to the naked eye is designated as Lv2, and unevenness that is completely invisible even with an optical microscope is designated as Lv1.

[0222] In addition, coatings are also applied to glass substrates with chromium vapor-deposited surfaces. The width of the portion at the end of the coating where there are tonal variations (uneven film thickness) is measured with vernier calipers and used as the Halo dimension for evaluation. It should be noted that the smaller the Halo dimension value, the better the coating.

[0223] These results are shown in Tables 1 and 2.

[0224] [Table 1]

[0225]

[0226] [Table 2]

[0227]

[0228] As part of the disclosure of this invention, the entire contents of the specification, claims and abstract of Japanese Patent Application No. 2016-072566, filed on March 31, 2016, are incorporated herein by reference.

Claims

1. A liquid crystal alignment agent, characterized in that, contains: at least one polymer selected from the group consisting of a polyimide precursor and a polyimide which is an imidized product thereof; and a solvent containing solvent A, solvent B, and solvent C, solvent A: at least one selected from the group consisting of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, and dimethylimidazolidinone, solvent B: dipropylene glycol dimethyl ether, solvent C: at least one selected from the group consisting of diethylene glycol diethyl ether and diacetone alcohol.

2. The liquid crystal aligning agent according to claim 1, wherein The solvent A is N-methyl-2-pyrrolidone or γ-butyrolactone.

3. The liquid crystal aligning agent according to claim 1 or 2, wherein The polyimide precursor has a structure represented by the following formula (1), X1is a tetravalent organic group derived from a tetracarboxylic acid derivative, Y1is a divalent organic group derived from a diamine, R1is a hydrogen atom or an alkylene group having 1 to 5 carbon atoms, and A1and A2are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms.

4. The liquid crystal aligning agent according to any one of claims 1 to 3, wherein The solvent A is contained at 20 to 80% by mass relative to the total mass of the liquid crystal alignment agent.

5. The liquid crystal aligning agent according to any one of claims 1 to 4, wherein The solvent B is contained at 1 to 30% by mass relative to the total mass of the liquid crystal alignment agent.

6. The liquid crystal aligning agent according to any one of claims 1 to 5, wherein The solvent C is contained at 1 to 30% by mass relative to the total mass of the liquid crystal alignment agent.

7. The liquid crystal aligning agent according to any one of claims 1 to 6, wherein The solvent A is contained at 50 to 80% by mass in total, the solvent B is contained at 10 to 30% by mass, and the solvent C is contained at 1 to 20% by mass relative to the total mass of the liquid crystal alignment agent.

8. The liquid crystal aligning agent according to any one of claims 1 to 7, wherein The solvent B and the solvent C are contained at 10 to 60% by mass in total relative to the total mass of the liquid crystal alignment agent, and the solvent B is contained more than the solvent C.

9. The liquid crystal aligning agent according to claim 8, wherein The solvent B is contained at 1 to 20% by mass more than the solvent C.

10. The liquid crystal alignment agent according to any one of claims 1 to 9, which is used for film formation by an inkjet method.

11. A liquid crystal alignment film obtained from the liquid crystal alignment agent according to any one of claims 1 to 10.

12. A liquid crystal display element provided with the liquid crystal alignment film according to claim 11.

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