TWI838335B - Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element - Google Patents

Abstract

The present invention provides a liquid crystal alignment agent that suppresses the poor film formation of the liquid crystal alignment film caused by the influence of the wiring structure or C/H, and has good shape stability and film thickness uniformity of the surrounding part of the coating, and a liquid crystal alignment film and a liquid crystal display element using the same. 　　The liquid crystal alignment agent of the present invention contains at least one polymer selected from the group consisting of polyimides of polyimide precursors and imides thereof, and a solvent containing the following 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, N-butyl-2-pyrrolidone, γ-butyrolactone, γ-valerolactone and 1,3-dimethylimidazolidinone. Solvent B: at least one selected from the group consisting of propylene glycol monobutyl ether, 2-propoxyethanol, 2-(2-propoxyethoxy)ethanol and 1-propoxy-2-propanol. Solvent C: ethyl-3-ethoxypropionate.

Description

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

The present invention relates to a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display element.

As a liquid crystal alignment film, a so-called polyimide-based liquid crystal alignment film obtained by coating and firing a liquid crystal alignment agent having a polyimide precursor such as polyamide (also called polyamic acid) as the main component or a solution of a soluble polyimide is widely used. As a film forming method of the above-mentioned liquid crystal alignment film, spin coating, dip coating, flexographic printing, etc. are generally known. However, in flexographic printing, there are various problems as follows: various resin plates are required depending on the type of liquid crystal panel; the plate exchange is complicated during the manufacturing process; in order to stabilize the film forming step, the film must be formed on a dummy substrate; the production of the plate becomes a reason for the increase in the manufacturing cost of the liquid crystal display panel, etc.

Therefore, the inkjet method has attracted attention as a film-forming method for liquid crystal alignment films without using a printing plate. The inkjet method is a method of dripping fine droplets on a substrate and forming a film by the diffusion of the liquid. Not only does it not use a printing plate, but it can also freely set the printed pattern, so the manufacturing steps of liquid crystal display elements can be simplified. In addition, since the film formation on a virtual substrate that is required in flexographic printing is no longer necessary, there is an advantage of less waste of coating liquid. The inkjet method can be expected to reduce the cost of liquid crystal panels and improve production efficiency.

The liquid crystal alignment film formed by the inkjet method requires that the unevenness of the film thickness inside the coating surface is small and the film forming accuracy at the coating periphery is high. Generally speaking, the liquid crystal alignment film formed by the inkjet method has a trade-off relationship between the uniformity of the film thickness inside the coating surface and the film forming accuracy at the coating periphery. That is, generally speaking, a material with high uniformity within the surface has low dimensional stability at the coating periphery, and the film will exceed the set size. On the other hand, for a material with a straight coating periphery, the uniformity within the coating surface will be reduced. In order to improve the film forming accuracy at the coating periphery, a method of sealing the alignment film within a specified range by a special structure has been proposed (see patent documents 1 to 3). However, such methods have the disadvantage of requiring the use of a special structure. [Prior art literature] [Patent literature]

[Patent Document 1] Japanese Patent Publication No. 2004-361623 [Patent Document 2] Japanese Patent Publication No. 2008-145461 [Patent Document 3] Japanese Patent Publication No. 2010-281925

[The problem that the invention wants to solve]

In recent years, with the high precision of liquid crystal display elements, multi-layer wiring TFT design is becoming the mainstream. In TFT design, in order to connect the wiring of the lower layer with the wiring of the upper layer, a contact hole (also called C/H) is formed on the substrate. Accompanying this, due to the influence of the wiring structure or C/H, it will be easy to hinder the diffusion of the liquid when the liquid crystal alignment agent is applied. As a result, the thickness of the alignment film is uneven around the C/H or other parts, which may make the display of the liquid crystal display element uneven.

In addition, the liquid crystal alignment agent used in the inkjet method is required to have a low viscosity in order to stably discharge the liquid crystal alignment agent from the inkjet nozzle. On the other hand, if the viscosity is reduced by reducing the resin component ratio, there is a concern that the shape stability and film thickness uniformity of the coating periphery will be reduced. Therefore, it is desired to maintain the shape stability and film thickness uniformity of the coating periphery while reducing the viscosity.

The present invention is made in view of the above-mentioned problems, and aims to provide a liquid crystal alignment agent, a liquid crystal alignment film and a liquid crystal display element using the same, which can suppress the poor film formation of the liquid crystal alignment film or the uneven display of the liquid crystal display element caused by the influence of the wiring structure or C/H, and can maintain the shape stability and film thickness uniformity of the coating peripheral part. [Means for solving the problem]

The inventors of the present invention have completed the present invention after repeated and in-depth research to solve the above problems. The gist of the present invention is described below.

1. A liquid crystal alignment agent, comprising at least one polymer selected from the group consisting of polyimide precursors and imide products thereof, and a solvent comprising the following 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, N-butyl-2-pyrrolidone, γ-butyrolactone, γ-valerolactone and 1,3-dimethylimidazolidinone, 　　Solvent B: at least one selected from the group consisting of propylene glycol monobutyl ether, 2-propoxyethanol, 2-(2-propoxyethoxy)ethanol and 1-propoxy-2-propanol, 　　Solvent C: ethyl-3-ethoxypropionate,

2. The liquid crystal alignment agent of 1., wherein the solvent A comprises at least one of N-methyl-2-pyrrolidone and γ-butyrolactone,

3. The liquid crystal alignment agent according to 1. or 2., wherein the polyimide precursor has a structure represented by the following formula (1):

_X1 is a tetravalent organic group derived from a tetracarboxylic acid derivative, _Y1 is a divalent organic group derived from a diamine, two _R1s are independently a hydrogen atom or an alkylene group having 1 to 5 carbon atoms, _A1 and _A2 are 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 alignment agent according to any one of 1. to 3., wherein the liquid crystal alignment agent contains 20 to 80% by mass of the solvent A relative to the total mass of the liquid crystal alignment agent.

5. The liquid crystal alignment agent according to any one of 1. to 3., wherein the liquid crystal alignment agent contains 1 to 30% by mass of the solvent B relative to the total mass of the liquid crystal alignment agent.

6. The liquid crystal alignment agent according to any one of 1. to 3., wherein the liquid crystal alignment agent contains 5 to 30% by mass of the solvent C relative to the total mass of the liquid crystal alignment agent.

7. The liquid crystal alignment agent of any one of 1. to 6., wherein the liquid crystal alignment agent contains 50% by mass or more of the solvent A, 10% to 30% by mass of the solvent B, and 1% to 20% by mass of the solvent C, relative to the total mass of the liquid crystal alignment agent.

8. The liquid crystal alignment agent according to any one of 1. to 3., wherein the total amount of the solvent B and the solvent C is 10 to 60% by mass relative to the total mass of the liquid crystal alignment agent, and the amount of the solvent B is greater than that of the solvent C.

9. The liquid crystal alignment agent according to any one of 1. to 3., wherein the liquid crystal alignment agent contains 1 to 20% more solvent B than the liquid crystal alignment agent C by weight.

10. A liquid crystal alignment agent as described in any one of 1. to 9., which can be used for film formation by inkjet method.

11. A liquid crystal alignment film, which is obtained from the liquid crystal alignment agent as described in any one of 1. to 10.

12. A liquid crystal display element, comprising the liquid crystal alignment film as described in 11. [Effect of the invention]

According to the present invention, there are provided a liquid crystal alignment agent that can suppress the poor film formation of the liquid crystal alignment film or the uneven display of the liquid crystal display element caused by the influence of the wiring structure or C/H, and can maintain the shape stability and film thickness uniformity of the coating peripheral portion, a liquid crystal alignment film using the same, and a liquid crystal display element. [Best Mode for Implementing the Invention]

The liquid crystal alignment agent as one aspect of the present invention contains at least one polymer selected from the group consisting of polyimide precursors and imide products thereof (sometimes referred to as a specific polymer), and a solvent containing solvent A, solvent B, and solvent C (sometimes referred to as a specific solvent).

<Specific solvent> The specific solvent contained in the liquid crystal alignment agent of the present invention includes solvent A, solvent B, and solvent C. The liquid crystal alignment agent containing such a specific solvent and a specific polymer can suppress the defective film formation of the alignment film caused by the influence of the wiring structure or C/H, and can suppress the defective uneven display of the liquid crystal display element, and further, can maintain the shape stability and film thickness uniformity of the peripheral portion of the coating.

<Solvent A> Solvent A is at least one selected from the group consisting of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-butyl-2-pyrrolidone, γ-butyrolactone, γ-valerolactone and 1,3-dimethylimidazolidinone. Solvent A dissolves the polymer in the liquid crystal alignment agent. Among them, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone or γ-butyrolactone is preferred, and N-methyl-2-pyrrolidone or γ-butyrolactone is more preferred. That is, solvent A preferably contains at least one of N-methyl-2-pyrrolidone or γ-butyrolactone. From the viewpoint of solubility of the polymer in the liquid crystal alignment agent, the content of the solvent A is preferably 20-80 mass %, more preferably 30-80 mass %, and particularly preferably 50-80 mass %, relative to the total mass of the liquid crystal alignment agent.

<Solvent B> Solvent B is at least one solvent selected from the group consisting of propylene glycol monobutyl ether, 2-propoxyethanol, 2-(2-propoxyethoxy)ethanol and 1-propoxy-2-propanol. Solvent B is a solvent that helps to improve the uniformity of coating of the liquid crystal alignment agent. The amount of solvent B, relative to the total mass of the liquid crystal alignment agent, is preferably 1-30 mass %, more preferably 5-30 mass %, and particularly preferably 10-30 mass %.

<Solvent C> Solvent C is ethyl-3-ethoxypropionate. Solvent C is a solvent that helps the film-forming property and shape stability of the liquid crystal alignment agent. The amount of solvent C relative to the total mass of the liquid crystal alignment agent is preferably 5-30 mass %, more preferably 10-30 mass %, and particularly preferably 10-20 mass %.

Still, from the viewpoint of the present invention, with respect to the total mass of the liquid crystal alignment agent, the solvent A may be contained at 50 mass %, the solvent B may be contained at 10-30 mass %, and the solvent C may be contained at 10-20 mass %. Furthermore, from the viewpoint of the present invention, with respect to the total mass of the liquid crystal alignment agent, the total of the solvent B and the solvent C may be contained at 10-60 mass %, and the solvent B may be contained in a larger amount than the solvent C. Furthermore, from the viewpoint of the present invention, the solvent B may be contained in an amount of 1-20 mass % more than the solvent C.

<Specific polymer> The polyimide precursor of the specific polymer contained in the liquid crystal alignment agent preferably has a structure represented by the following formula (1).

In the formula, _X1 is a tetravalent organic group derived from a tetracarboxylic acid derivative. _Y1 is a divalent organic group derived from a diamine. _R1 is independently a hydrogen atom or an alkylene group having 1 to 5 carbon atoms. In terms of the ease of the imidization reaction during heating, _R1 is preferably a hydrogen atom, a methyl group, or an ethyl group, and more preferably a hydrogen atom or a methyl group. _A1 and _A2 are 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. In terms of the liquid crystal orientation, _A1 and _A2 are preferably a hydrogen atom or a methyl group.

The components used to make the raw materials for the polyimide precursors of specific polymers are described.

<Diamine> The diamine component used in the production of the polyimide precursor is not particularly limited, but the diamine as a raw material of the polyimide precursor represented by the above formula (1) is represented by the following formula (2):

In the above formula (2), _A1 and _A2 (including respective preferred examples) have the same definitions as _A1 and _A2 in the above formula (1). When the structure of _Y1 is exemplified, the following (Y-1) to (Y-49) and (Y-57) to (Y-170) can be cited.

In the above formula, Me represents a methyl group, and n represents an integer of 1 to 6.

Among them, the structures of _Y1 are (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), (Y- 156）、(Y-159）、(Y-160）、(Y-161）、( Y-162), (Y-168), (Y-169), (Y-170) are preferred, especially (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), (Y-156), (Y-159), (Y-160), (Y-161), (Y-162), (Y-168), (Y -169) and (Y-170) are preferred.

<Tetracarboxylic acid derivatives> The tetracarboxylic acid derivatives used in the production of the polyimide precursor are not particularly limited, but the tetracarboxylic acid derivative component as the raw material of the polyimide precursor represented by the above formula (1) can be exemplified not only tetracarboxylic dianhydride but also tetracarboxylic acids, tetracarboxylic acid dihalides, tetracarboxylic acid dialkyl esters, and tetracarboxylic acid dialkyl ester dihalides of the tetracarboxylic acid dianhydride and its derivatives. Among them, the tetracarboxylic dianhydride or its derivative is preferably represented by the following formula (3),

In formula (3), _X1 is a tetravalent organic group having an alicyclic structure, and the structure is not particularly limited. Specific examples thereof include the following formulas (X1-1) to (X1-44).

In formula (X1-1) to (X1-4), R ₃ to R ₂₃ are independently hydrogen atoms, halogen atoms, alkyl groups with 1 to 6 carbon atoms, alkenyl groups with 2 to 6 carbon atoms, alkynyl groups with 2 to 6 carbon atoms, monovalent organic groups with 1 to 6 carbon atoms containing fluorine atoms, or phenyl groups. In terms of liquid crystal orientation, R ₃ to R ₂₃ are preferably hydrogen atoms, halogen atoms, methyl groups, or ethyl groups, and preferably hydrogen atoms or methyl groups.

As specific examples of formula (X1-1), the following formulas (X1-1-1) to (X1-1-6) can be cited. In terms of liquid crystal orientation and light sensitivity, (X1-1-1) is particularly preferred.

For the polyimide precursor or polyimide of one aspect of the present invention, the tetracarboxylic dianhydride or its derivative as the raw material preferably contains 60-100 mol% of the tetracarboxylic dianhydride or its derivative represented by the above formula (3) relative to 1 mol of the total tetracarboxylic dianhydride or its derivative. In order to obtain a liquid crystal alignment film with good liquid crystal alignment, 80-100 mol% is more preferred, and 90-100 mol% is more preferred.

＜Polyimide precursor＞ ＜Method for producing polyamic acid ester＞ 　　Polyamic acid ester, which is one of the polyimide precursors, can be produced by the method (1), (2) or (3) shown below.

(1) When produced from polyamine: Polyamine esters can be synthesized by esterifying polyamine obtained from tetracarboxylic dianhydride and diamine. Specifically, the synthesis can be carried out by reacting polyamine with an esterifying agent in the presence of an organic solvent at -20°C to 150°C, preferably at 0°C to 50°C, for 30 minutes to 24 hours, preferably 1 to 4 hours.

The esterifying agent is preferably one that can be easily removed by purification, and examples thereof include N,N-dimethylformamide dimethyl acetal, N,N-dimethylformamide diethyl acetal, N,N-dimethylformamide dipropyl acetal, N,N-dimethylformamide dineopentylbutyl acetal, N,N-dimethylformamide di-t-butyl acetal, 1-methyl-3-p-tolyltriazene, 1-ethyl-3-p-tolyltriazene, 1-propyl-3-p-tolyltriazene, 4-(4,6-dimethoxy-1,3,5-triazine-2-yl)-4-methylchloroformate, etc. The amount of the esterifying agent used is preferably 2 to 6 molar equivalents relative to 1 mole of the repeating unit of the polyamine.

The solvent used in the above reaction is preferably N,N-dimethylformamide, N-methyl-2-pyrrolidone, or γ-butyrolactone in terms of polymer solubility, and these can be used alone or in combination of two or more. The concentration of the polymer in the reaction solution is preferably 1-30 mass %, more preferably 5-20 mass %, in terms of not easily causing polymer precipitation and easily obtaining a high molecular weight product.

(2) When produced by the reaction of tetracarboxylic acid diester dichloride and diamine: Polyamic acid esters can be produced by tetracarboxylic acid diester dichloride and diamine. Specifically, tetracarboxylic acid diester dichloride and diamine can be reacted in the presence of an alkali and an organic solvent at -20°C to 150°C, preferably at 0°C to 50°C, for 30 minutes to 24 hours, preferably 1 to 4 hours, to synthesize.

The above-mentioned base can be pyridine, triethylamine, 4-dimethylamine pyridine, etc., but pyridine is preferred for stable reaction. The amount of the base used is preferably 2 to 4 times the mole of the tetracarboxylic acid diester dichloride from the viewpoint of easy removal and easy to obtain a high molecular weight body.

The solvent used in the above reaction is preferably N-methyl-2-pyrrolidone or γ-butyrolactone in terms of the solubility of the monomer and the polymer, and these can be used alone or in combination of two or more. The polymer concentration in the reaction solution is preferably 1 to 30% by mass, and more preferably 5 to 20% by mass, from the viewpoint of not easily causing the precipitation of the polymer and easily obtaining a high molecular weight body. In addition, in order to prevent the hydrolysis of the tetracarboxylic acid diester dichloride, the solvent used in the synthesis of the polyamic acid ester is preferably dehydrated as much as possible, and preferably prevents the mixing of foreign gas in a nitrogen environment.

(3) When produced by reaction of tetracarboxylic acid diester and diamine: Polyamic acid ester can be produced by polycondensation of tetracarboxylic acid diester and diamine. Specifically, tetracarboxylic acid diester and diamine can be reacted in the presence of a condensation agent, an alkali, 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.

The condensation agent may be triphenylphosphite, dicyclohexylcarbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N,N'-carbonyldiimidazole, dimethoxy-1,3,5-triazinylmethylflinium, O-(benzotriazole-1-yl)-N,N,N',N'-tetramethyluronium tetrafluoroborate, O-(benzotriazole-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate, (2,3-dihydro-2-thio-3-benzoxazolyl)phosphonic acid diphenyl ester, etc. The amount of the condensation agent added is preferably 2 to 3 times the molar amount of the tetracarboxylic acid diester.

The alkali may be a tertiary amine such as pyridine or triethylamine. The amount of the alkali used is preferably 2 to 4 times the mole of the diamine component from the viewpoint of easy removal and easy acquisition of a high molecular weight product.

In the above reaction, the reaction is efficiently carried out by adding a Lewis acid as an additive. The Lewis acid is preferably a lithium halide such as lithium chloride or lithium bromide. The amount of the Lewis acid added is preferably 0 to 1.0 times the molar amount of the diamine component.

Among the above three methods for producing polyamic acid esters, the production method (1) or (2) is particularly preferred in order to obtain polyamic acid esters of high molecular weight. The solution of polyamic acid ester obtained as described above is injected into a poor solvent while being fully stirred, thereby precipitating a polymer. After several precipitations and washing with a poor solvent, the purified polyamic acid ester powder is obtained by drying at room temperature or by heating. The poor solvent is not particularly limited, but water, methanol, ethanol, hexane, butyl solvent, acetone, toluene, etc. can be cited.

＜Production method of polyamide＞ 　　Polyamide, which is a precursor of polyimide, can be produced by the method shown below. Specifically, it can be synthesized by reacting tetracarboxylic dianhydride and diamine at -20°C to 150°C, preferably 0°C to 50°C, for 30 minutes to 24 hours, preferably 1 to 12 hours in the presence of an organic solvent.

The organic solvent used in the above reaction is preferably N,N-dimethylformamide, N-methyl-2-pyrrolidone, or γ-butyrolactone in terms of solubility of the monomer and the polymer, and these can be used alone or in combination of two or more. The concentration of the polymer is preferably 1 to 30% by mass, and more preferably 5 to 20% by mass, in terms of not causing precipitation of the polymer and facilitating obtaining a high molecular weight product.

The polyamine obtained in the above manner can be injected into a poor solvent while stirring the reaction solution sufficiently, thereby precipitating the polymer and recovering it. In addition, after precipitation several times and washing with a poor solvent, a purified polyamine powder can be obtained by drying at room temperature or by heating. The poor solvent is not particularly limited, but water, methanol, ethanol, hexane, butyl solvent, acetone, toluene, etc. can be mentioned.

<Production method of polyimide> Polyimide can be produced by subjecting the aforementioned polyamic acid ester or polyamic acid to imidization. When producing polyimide from polyamic acid ester, it is convenient to perform chemical imidization by adding an alkaline catalyst to the aforementioned polyamic acid ester solution or the polyamic acid solution obtained by dissolving the polyamic acid ester resin powder in an organic solvent. Chemical imidization is preferred because the imidization reaction is carried out at a relatively low temperature and the molecular weight of the polymer is not easily reduced during the imidization process.

Chemical imidization can be carried out by stirring the polyamic acid ester to be imidized in an organic solvent in the presence of an alkaline catalyst. The organic solvent may be the solvent used in the above-mentioned polymerization reaction. Examples of the alkaline catalyst include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine, etc. Among them, triethylamine is preferred because it has sufficient alkalinity to allow the reaction to proceed.

The temperature for the imidization reaction can be -20°C to 140°C, preferably 0°C to 100°C, and the reaction time is 1 to 100 hours. The amount of the alkaline catalyst is 0.5 to 30 mole times of the polyamic acid ester group, preferably 2 to 20 mole times. The imidization rate of the obtained polymer can be controlled by adjusting the amount of catalyst, temperature, and reaction time. In the solution after the imidization reaction, since the added catalyst and the like remain, it is preferred to recover the obtained imidized polymer and use it as the liquid crystal alignment agent of the present invention after redissolving it in an organic solvent.

When polyimide is produced from polyamic acid, it is convenient to perform chemical imidization by adding a catalyst to a solution of the polyamic acid obtained by the reaction of a diamine component and a tetracarboxylic dianhydride. Chemical imidization is preferred because the imidization reaction is carried out at a relatively low temperature and the molecular weight of the polymer is not easily reduced during the imidization process.

Chemical imidization can be carried out by stirring the polymer to be imidized in an organic solvent in the presence of an alkaline catalyst and an acid anhydride. As the organic solvent, the solvent used in the above-mentioned polymerization reaction can be used. As the alkaline catalyst, pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine, etc. can be cited. Among them, pyridine is preferred because it has a moderate alkalinity that enables the reaction to proceed. In addition, as the acid anhydride, acetic anhydride, trimellitic anhydride, pyromelitic dianhydride, etc. can be cited. Among them, if acetic anhydride is used, it will be easy to purify after the reaction is completed, so it is preferred.

The temperature for the imidization reaction can be -20°C to 140°C, preferably 0°C to 100°C, and the reaction time can be 1 to 100 hours. The amount of the alkaline catalyst is 0.5 to 30 mole times of the amide group, preferably 2 to 20 mole times, and the amount of the acid anhydride is 1 to 50 mole times of the amide group, preferably 3 to 30 mole times. The imidization rate of the obtained polymer can be controlled by adjusting the amount of the catalyst, the temperature, and the reaction time.

Since the added catalyst etc. remain in the solution after the imidization reaction of polyamic acid ester or polyamic acid, it is preferable to recover the obtained imidized polymer by the means described below and redissolve it in an organic solvent to use it as a liquid crystal alignment agent.

The polyimide solution obtained in the above manner is poured into a poor solvent while being fully stirred to precipitate a polymer. After precipitation is performed several times and washing is performed with a poor solvent, it is dried at room temperature or by heating to obtain a purified polyamide ester powder.

The aforementioned poor solvent is not particularly limited, but examples thereof include methanol, acetone, hexane, butyl solvent, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, benzene, and the like.

<Liquid crystal alignment agent> One aspect of the liquid crystal alignment agent of the present invention has a solution form in which a polymer containing a specific polymer is dissolved in an organic solvent containing a specific solvent. The molecular weight of the polyimide precursor and the polyimide is preferably a weight average molecular weight of 2,000~500,000, preferably 5,000~300,000, and more preferably 10,000~100,000. In addition, the number average molecular weight is preferably 1,000~250,000, preferably 2,500~150,000, and more preferably 5,000~50,000.

The concentration of the polymer of the liquid crystal alignment agent can be appropriately changed according to the thickness of the coating to be formed. In terms of forming a uniform and defect-free coating, it is preferably 1% by weight or more, and in terms of the storage stability of the solution, it is preferably 10% by weight or less.

<Other solvents> The solvent in the liquid crystal alignment agent may include solvents other than the above-mentioned specific solvents (hereinafter also referred to as other solvents). Other solvents may include solvents that dissolve polyimide precursors and polyimide (also referred to as good solvents), or solvents that improve the coating properties or surface smoothness of the liquid crystal alignment film when the liquid crystal alignment agent is applied (also referred to as poor solvents). Although specific examples of other solvents may be given below, they are not limited to these examples.

Examples of the good solvent include N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, methyl ethyl ketone, cyclohexanone, cyclopentanone, 3-methoxy-N,N-dimethylpropionamide, and 4-hydroxy-4-methyl-2-pentanone.

Specific examples of the poor solvent 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, neopentyl alcohol, 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-ethanediol, 1,2-propylene glycol, 1,3-propylene glycol, 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 Ether, Diethylene Glycol Dibutyl Ether, 2-Pentanone, 3-Pentanone, 2-Hexanone, 2-Heptanone, 4-Heptanone, 3-Ethoxybutyl Acetate, 1-Methylpentyl Acetate, 2-Ethylbutyl Acetate, 2-Ethylhexyl Acetate, Ethylene Glycol Mono Acetate, ethylene glycol diacetate, propylene carbonate, ethyl carbonate, 2-(methoxymethoxy)ethanol, butyl solvent, ethylene glycol monoisoamyl ether, ethylene glycol monohexyl ether, 2-(hexyloxy)ethanol, furfuryl alcohol, diethylene glycol, propylene glycol, 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, diisoamyl ether, diethylene glycol 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-ethoxypropionate, methyl ethyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, 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.

Furthermore, as a poor solvent, if the polyimide precursor and polyimide contained in the liquid crystal alignment agent have high solubility in the solvent, the solvent represented by formula [D-1] to formula [D-3] is preferred.

In formula [D-1], ^D1 represents an alkyl group having 1 to 3 carbon atoms, in formula [D-2], ^D2 represents an alkyl group having 1 to 3 carbon atoms, and in formula [D-3], ^D3 represents an alkyl group having 1 to 4 carbon atoms.

The liquid crystal alignment agent may also include a crosslinking compound having an epoxy group, an isocyanate group, an oxycyclobutane group or a cyclic carbonate, a crosslinking compound having at least one substituent selected from the group consisting of a hydroxyl group, a hydroxyalkyl group and a low-order alkoxyalkyl group, or a crosslinking compound having a polymerizable unsaturated bond. The crosslinking compound must have two or more of these substituents or polymerizable unsaturated bonds.

Examples of the crosslinking compound having an epoxy group or an isocyanate group include bisphenol acetone glycidyl ether, phenol novolac epoxy resin, cresol novolac epoxy resin, triglycidyl triisocyanate, tetraglycidyl aminodiphenylene, tetraglycidyl-m-xylylenediamine, tetraglycidyl-1,3-bis(aminoethyl)cyclohexane, tetraphenyl glycidyl ether ethane, triphenyl glycidyl 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-cyclooxypropoxy)octafluorobiphenyl, triglyceryl-p-aminophenol, tetraglyceryl-m-xylene diamine, 2-(4-(2,3-cyclooxypropoxy)phenyl)-2-(4-(1,1-bis(4-(2,3-cyclooxypropoxy)phenyl)ethyl)phenyl)propane or 1,3-bis(4-(1-(4-(2,3-cyclooxypropoxy)phenyl)-1-(4-(1-(4-(2,3-cyclooxypropoxy)phenyl)-1-methylethyl)phenyl)ethyl)phenoxy)-2-propanol, etc.

The crosslinkable compound having an oxacyclobutane group is a compound having at least two oxacyclobutane groups represented by the following formula [4A],

Specifically, the cross-linking compounds represented by formula [4a] to formula [4k] disclosed on pages 58 to 59 of International Publication No. WO2011/132751 (published on October 27, 2011) can be cited.

The crosslinking compound having a cyclic carbonate is a crosslinking compound having at least two cyclic carbonates represented by the following formula [5A],

Specifically, the cross-linking compounds represented by formula [5-1] to formula [5-42] published on pages 76 to 82 of International Publication No. WO2012/014898 (published on February 2, 2012) can be cited.

As the crosslinking compound having at least one substituent selected from the group consisting of a hydroxyl group and an alkoxy group, for example, an amino resin having a hydroxyl group or an alkoxy group, for example, melamine resin, urea resin, guanamine resin, acetylene urea-formaldehyde resin, succinylamide-formaldehyde resin or ethylene urea-formaldehyde resin can be cited. Specifically, a melamine derivative, a benzoguanamine derivative or an acetylene urea in which the hydrogen atom of the amino group is substituted by a hydroxymethyl group or an alkoxymethyl group or both can be used. The melamine derivative or the benzoguanamine derivative can also be a dimer or a trimer. It is preferred that the average number of hydroxymethyl groups or alkoxymethyl groups per triazine ring is 3 to 6.

Examples of the above-mentioned melamine derivatives or benzoguanamine derivatives include commercially available MX-750 in which an average of 3.7 methoxymethyl groups are substituted per triazine ring, MW-30 (both manufactured by Sanwa Chemical Co., Ltd.) in which an average of 5.8 methoxymethyl groups are substituted per triazine ring, or methoxymethylated melamines such as CYMEL 300, 301, 303, 350, 370, 771, 325, 327, 703, 712, etc., methoxymethylated butoxymethylated melamines such as CYMEL 235, 236, 238, 212, 253, 254, etc., butoxymethylated melamines such as CYMEL 506, 508, etc., methoxymethylated isobutoxymethylated melamines containing a carboxyl group such as CYMEL 1141, and CYMEL methoxymethylated ethoxymethylated benzoguanamine such as CYMEL 1123, methoxymethylated butoxymethylated benzoguanamine such as CYMEL 1123-10, butoxymethylated benzoguanamine such as CYMEL 1128, and carboxyl group-containing methoxymethylated ethoxymethylated benzoguanamine such as CYMEL 1125-80 (all manufactured by Mitsui Cyanamid Co., Ltd.).

Examples of acetylene carbamides include butoxymethylated acetylene carbamides such as CYMEL 1170, hydroxymethylated acetylene carbamides such as CYMEL 1172, and methoxyhydroxymethylated acetylene carbamides such as Powder Link 1174.

Examples of the benzene or phenolic compound having a hydroxyl group or an alkoxy group include 1,3,5-tris(methoxymethyl)benzene, 1,2,4-tris(isopropoxymethyl)benzene, 1,4-bis(sec-butoxymethyl)benzene, and 2,6-dihydroxymethyl-p-tert-butylphenol.

More specifically, the cross-linked compounds of formula [6-1] to formula [6-48] disclosed on pages 62 to 66 of International Publication No. WO2011/132751 (published on October 27, 2011) can be cited.

Examples of crosslinking compounds having polymerizable unsaturated bonds include trihydroxymethylene propane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, tri(meth)acryloyloxyethoxy trihydroxymethylene propane, or glycerol polyglycidyl ether poly(meth)acrylate, which are crosslinking compounds having three polymerizable unsaturated groups in the molecule, and ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and diethylene glycol di(meth)acrylate. meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butylene glycol 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 A crosslinking compound having two polymerizable unsaturated groups in the molecule, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, ... ester, 2-hydroxybutyl (meth)acrylate, 2-phenoxy-2-hydroxypropyl (meth)acrylate, 2-(meth)acryloyloxy-2-hydroxypropyl phthalate, 3-chloro-2-hydroxypropyl (meth)acrylate, glycerol mono(meth)acrylate, 2-(meth)acryloyloxyethyl phosphate or N-hydroxymethyl (meth)acrylamide, etc., a crosslinking compound having one polymerizable unsaturated group in the molecule.

Furthermore, the compound represented by the following formula [7A] can also be used,

In formula [7A], _E1 represents a group selected from the group consisting of a cyclohexane ring, a bicyclohexane ring, a benzene ring, a biphenyl ring, a terphenyl ring, a naphthalene ring, a fluorene ring, an anthracene ring and a phenanthrene ring. _E2 represents a group selected from the group consisting of the following formula [7a] or formula [7b], and n represents an integer of 1 to 4.

.

The crosslinking compound used in the liquid crystal alignment agent may be one type or a combination of two or more types. The content of the crosslinking compound in the liquid crystal alignment agent is preferably 0.1 to 150 parts by mass relative to 100 parts by mass of the total polymer component. Among them, in order to carry out the crosslinking reaction and show the target effect, 0.1 to 100 parts by mass is preferred, and 1 to 50 parts by mass is more preferred.

The liquid crystal alignment agent may contain a compound that improves the uniformity of the film thickness or the surface smoothness of the liquid crystal alignment film when the liquid crystal alignment agent is applied. As the compound that improves the uniformity of the film thickness or the surface smoothness of the liquid crystal alignment film, fluorine-based surfactants, silicone-based surfactants, non-ionic surfactants, etc. can be cited. Specifically, for example, F-Top EF301, EF303, EF352 (made by Tokem Products), MEGAFACE F171, F173, R-30 (made by Dainippon Ink Co., Ltd.), Fluorad FC430, FC431 (made by Sumitomo 3M Co., Ltd.), Aashi Guard AG710, Surflon S-382, SC101, SC102, SC103, SC104, SC105, SC106 (made by Asahi Glass Co., Ltd.), etc. can be cited. The amount of the surfactant used is preferably 0.01-2 parts by mass, and more preferably 0.01-1 parts by mass, relative to 100 parts by mass of all polymer components contained in the liquid crystal alignment agent.

Furthermore, a compound that promotes charge movement in the liquid crystal alignment film and charge release of the device may also be added to the liquid crystal alignment agent, such as a nitrogen-containing heterocyclic amine represented by formula [M1] to formula [M156] published on pages 69 to 73 of International Publication WO2011/132751 (published on October 27, 2011). The amine may be added directly to the liquid crystal alignment agent, but it is preferred to add the amine after preparing a solution with a concentration of 0.1 to 10% by mass, preferably 1 to 7% by mass. The solvent is not particularly limited as long as it can dissolve the specific polymer.

The liquid crystal alignment agent may contain, in addition to the above-mentioned poor solvents, cross-linking compounds, resin coatings or compounds that improve the uniformity of the film thickness or the surface smoothness of the liquid crystal alignment film and compounds that promote charge release, silane coupling agents for the purpose of improving the adhesion between the alignment film and the substrate, imidization promoters for the purpose of efficiently promoting imidization by heating the polyimide precursor when sintering the coating, etc.

<Liquid crystal alignment film/liquid crystal display element> 　　The liquid crystal alignment film as one aspect of the present invention is a film obtained by coating the above-mentioned liquid crystal alignment agent on a substrate, drying it, and firing it. The substrate on which the liquid crystal alignment agent is coated is not particularly limited as long as it is a highly transparent substrate, and a glass substrate, a silicon nitride substrate, an acrylic substrate, or a plastic substrate such as a polycarbonate substrate may be used. At this time, if a substrate such as an ITO electrode for driving the liquid crystal is used, it is preferable from the point of view of simplifying the process. In addition, in a reflective liquid crystal display element, if it is only a single-sided substrate, an opaque material such as a silicon wafer may be used, and in this case, the electrode may be made of a light-reflecting material such as aluminum.

Liquid crystal alignment agents are generally applied by screen printing, offset printing, flexographic printing or inkjet printing in industry. Other known application methods include immersion coating, roll coating, slot coating, spin coating or spraying.

After the liquid crystal alignment agent is applied on the substrate, the solvent can be evaporated by heating means such as a heating plate, a heat circulation oven or an IR (infrared) oven to form a liquid crystal alignment film. The drying and firing steps after applying the liquid crystal alignment agent can be selected at any temperature and time. Usually, in order to fully remove the contained solvent, the conditions of firing at 50~120℃ for 1~10 minutes and then firing at 150~300℃ for 5~120 minutes can be cited. The thickness of the liquid crystal alignment film after firing is preferably 5~300nm, and more preferably 10~200nm, because if it is too thin, the reliability of the liquid crystal display element will be reduced. After the liquid crystal alignment agent is coated on the substrate and fired, it can be subjected to alignment treatment such as rubbing treatment or photo-alignment treatment. Moreover, when used for vertical alignment purposes, it can be used as a liquid crystal alignment film even without alignment treatment. For alignment treatment such as rubbing treatment or photo-alignment treatment, known methods or devices can be used.

As an example of a method for manufacturing a liquid crystal cell, a liquid crystal display element having a passive matrix structure is described. In addition, a liquid crystal display element having an active matrix structure in which a switching element such as a TFT (Thin Film Transistor) is provided in each pixel portion constituting a screen display may also be used.

Specifically, transparent glass substrates are prepared, and a common electrode is set on one substrate, and a segment electrode is set on another substrate. These electrodes can be, for example, ITO electrodes, and patterned in a manner that can present a desired screen display. Next, an insulating film is set on each substrate in a manner that covers the common electrode and the segment electrode. The insulating film can be, for example, a _SiO2 - _TiO2 film formed by a sol-gel method.

Next, a liquid crystal alignment film is formed on each substrate, and the liquid crystal alignment film surfaces on one substrate are overlapped on the other substrate in a manner that they face each other, and the periphery is bonded with a sealant. In order to control the gap between the substrates, spacers are usually mixed into the sealant, and it is also preferred to scatter spacers for controlling the gap between the substrates in the surface where the sealant is not provided. A portion of the sealant can be provided with an opening that can be filled with liquid crystal from the outside. Next, liquid crystal material is injected into the space surrounded by the two substrates and the sealant through the opening provided on the sealant, and then the opening is sealed with an adhesive. The injection can be performed by a vacuum injection method or by a method utilizing a capillary phenomenon in the atmosphere. The liquid crystal material can be either a positive liquid crystal material or a negative liquid crystal material, but a negative liquid crystal material is preferred. Next, the polarizing plates are placed. Specifically, a pair of polarizing plates are attached to the surfaces of the two substrates that are opposite to the liquid crystal layers.

[Example]

Hereinafter, the present invention will be described with reference to the following embodiments, but the present invention is not limited to the embodiments.

＜Abbreviation＞ (Organic solvent) 　　NMP: N-methyl-2-pyrrolidone 　　GBL: γ-butyrolactone 　　PB: Propylene glycol monobutyl ether 　　S-1: 2-Propoxyethanol 　　S-2: 2-(2-propoxyethoxy)ethanol 　　S-3: 1-Propoxy-2-propanol 　　EEP: Ethyl-3-ethoxypropionate 　　DPM: Dipropylene glycol monomethyl ether 　　BCS: Butyl solvent 　　Acid dianhydride (A): Formula (A) 　　Acid dianhydride (B): Formula (B) 　　Acid dianhydride (C): Formula (C) 　　DA-1: Formula (DA-1) 　　DA-2: Formula (DA-2) 　　DA-3: Formula (DA-3)

<Evaluation of Printability> The printability of the prepared liquid crystal alignment agent on the substrate was evaluated. The evaluation was performed as follows. First, the prepared liquid crystal alignment agent was tested using an inkjet printer (ishiihyoki ( Co., Ltd.), IP-1212NC1180L) under the following conditions.

<Conditions> Scanning speed: 250mm/sec Leveling: 35sec, 23℃ Coating area: 65×75mm

＜Evaluation Criteria＞ The spread of liquid is measured by using a TFT substrate and comparing the speed at which the liquid flows into the C/H during the same leveling time. During the leveling time, when the C/H is coated, it is ○, and when it is not coated, it is ×.

Halo evaluation (evaluation of the width of the portion where the film thickness at the end of the coating is thinner than the center and the color tone changes) is performed by heating the respective substrates after coating the liquid crystal alignment agent at 110°C for 1 minute (pre-baking), removing the solvent, and then heating at 210°C for 10 minutes (post-baking) to form a coating with a thickness of about 90nm. The coating is observed under a microscope with a magnification of 20 times. The case where the width is less than 2.0mm is ○, and the case where it is longer is ×. The results are shown in Table 1.

<Viscosity> In the following synthesis examples, the viscosity of polyamic acid ester and polyamic acid solution was measured using E-type viscometer TV-25H (manufactured by Toki Sangyo Co., Ltd.) at a sample volume of 1.1 mL, CORD-1 (1°34’, R24) and a temperature of 25°C.

(Synthesis Example 1) In a 2000 ml flask equipped with a stirring device and a nitrogen inlet tube, 71.6 g of (DA-1) and 619.4 g of NMP were placed, and nitrogen was introduced while stirring to dissolve. The diamine solution was stirred under water cooling while 49.1 g of (A) was added, and then 265.5 g of NMP was added to make the solid concentration 12% by mass. In a nitrogen environment, the mixture was heated at 50°C while stirring for 20 hours to obtain a solution of polyamine (PAA-1). The viscosity of the polyamine (PAA-1) solution at 25°C was confirmed by an E-type viscometer and was 84.5 mPa･s.

(Synthesis Example 2) In a 2000ml flask equipped with a stirring device and a nitrogen inlet tube, put 47.8g of (DA-2), add 174.4g of NMP, and stir and dissolve while introducing nitrogen. Add 18.0g of (C) to the diamine solution while stirring under water cooling, and then add 261.6g of NMP, and stir for 2 hours at room temperature in a nitrogen environment. Furthermore, after adding 11.9g of (DA-3), add 174.4g of NMP, and stir for 30 minutes at room temperature in a nitrogen environment. Thereafter, add 41.2g of (B) and 261.6g of NMP, heat at 50°C while stirring for 20 hours to obtain a solution of polyamide (PAA-2). The viscosity of the polyamide (PAA-2) solution at 25°C was confirmed by an E-type viscometer and was 72.7 mPa･s.

(Comparative Example 1) In a 1000 mL Erlenmeyer flask, add 30.0 g of polyamine (PAA-1) solution and 144 g of polyamine (PAA-2) solution, 10.8 g of NMP, 77.2 g of GBL, 18 g of NMP solution containing 1.0 mass % of 3-glycidoxypropyltriethoxysilane, and 120 g of BCS, and stir at room temperature for 1 hour. 400.0 g of a solution (AL-1) with a solid content of NMP: GBL: BCS = 4.5:30:35.5:30 (mass %) is obtained.

(Comparative Example 2) In a 1000 mL Erlenmeyer flask, add 30.0 g of polyamine (PAA-1) solution and 144 g of polyamine (PAA-2) solution, 10.8 g of NMP, 77.2 g of GBL, 18 g of NMP solution containing 1.0 mass % of 3-glycidoxypropyltriethoxysilane, 60 g of BCS, and 60 g of DPM, and stir at room temperature for 1 hour. 400.0 g of a solution (AL-2) with a solid content of NMP: GBL: BCS: DPM = 4.5: 30: 35.5: 15: 15 (mass %) is obtained.

(Example 1) In a 1000 mL Erlenmeyer flask, add 30.0 g of polyamine (PAA-1) solution and 144 g of polyamine (PAA-2) solution, 10.8 g of NMP, 77.2 g of GBL, 18 g of NMP solution containing 1.0 mass % of 3-glycidoxypropyltriethoxysilane, 60 g of PB, and 60 g of EEP, and stir at room temperature for 1 hour. 400.0 g of a solution (AL-3) with a solid content of NMP: GBL: PB: EEP = 4.5: 30: 35.5: 15: 15 (mass %) is obtained.

(Example 2) In a 1000 mL Erlenmeyer flask, add 30.0 g of polyamine (PAA-1) solution and 144 g of polyamine (PAA-2) solution, 10.8 g of NMP, 77.2 g of GBL, 18 g of NMP solution containing 1.0 mass % of 3-glycidoxypropyltriethoxysilane, 60 g of (S-1), and 60 g of EEP, and stir at room temperature for 1 hour. 400.0 g of a solution (AL-4) with a solid content of NMP: GBL: (S-1): EEP = 4.5: 30: 35.5: 15: 15 (mass %) is obtained.

(Example 3) In a 1000 mL Erlenmeyer flask, add 30.0 g of polyamine (PAA-1) solution and 144 g of polyamine (PAA-2) solution, 10.8 g of NMP, 77.2 g of GBL, 18 g of NMP solution containing 1.0 mass % of 3-glycidoxypropyltriethoxysilane, 60 g of (S-2), and 60 g of EEP, and stir at room temperature for 1 hour. 400.0 g of a solution (AL-5) with a solid content of NMP: GBL: (S-2): EEP = 4.5: 30: 35.5: 15: 15 (mass %) is obtained.

(Example 4) In a 1000 mL Erlenmeyer flask, add 30.0 g of polyamine (PAA-1) solution and 144 g of polyamine (PAA-2) solution, 10.8 g of NMP, 77.2 g of GBL, 18 g of NMP solution containing 1.0 mass % of 3-glycidoxypropyltriethoxysilane, 60 g of (S-3), and 60 g of EEP, and stir at room temperature for 1 hour. 400.0 g of a solution (AL-6) with a solid content of NMP: GBL: (S-3): EEP = 4.5:30:35.5:15:15 (mass %) is obtained.

Moreover, after using the liquid crystal alignment agent of Examples 1 to 4, a liquid crystal alignment film can be manufactured by a known method. Furthermore, using the liquid crystal alignment agent of Examples 1 to 3, a liquid crystal alignment film can be manufactured by a known method to manufacture a liquid crystal display element.

According to the above embodiments, it is understood that a liquid crystal alignment agent, a liquid crystal alignment film and a liquid crystal display element using the same can be provided which can suppress the poor film formation of the liquid crystal alignment film or the uneven display of the liquid crystal display element caused by the influence of the wiring structure or C/H, and can maintain the shape stability and film thickness uniformity of the peripheral portion of the coating.

Claims (11)

A liquid crystal alignment agent comprises at least one polymer selected from the group consisting of a polyimide precursor having a structure represented by the following formula (1) and its imide product, and a solvent comprising the following solvent A, solvent B and solvent C; the solvent B is contained in an amount of 1 to 30% by weight relative to the total weight of the liquid crystal alignment agent.

_X1 is a tetravalent organic group derived from a tetracarboxylic acid derivative, _Y1 is a divalent organic group derived from a diamine, and is selected from the following structural formulas (Y-9) to (Y-18), (Y-37) to (Y-38), (Y-44), (Y-48), (Y-71) to (Y-77), (Y-80) to (Y-96), (Y-126), (Y-132), (Y-135) to (Y-138), (Y-156), (Y-158) to (Y-166), and (Y-168) to (Y-170),

(Me represents a methyl group, and n represents an integer of 1 to 6) two R _1s are independently a hydrogen atom or an alkylene group having 1 to 5 carbon atoms, A ₁ and A ₂ are 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, solvent A: at least one selected from the group consisting of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-butyl-2-pyrrolidone, γ-butyrolactone, γ-valerolactone, and 1,3-dimethylimidazolidinone; solvent B: at least one selected from the group consisting of propylene glycol monobutyl ether, 2-propoxyethanol, 2-(2-propoxyethoxy)ethanol, and 1-propoxy-2-propanol; solvent C: ethyl-3-ethoxypropionate. As in claim 1, the liquid crystal alignment agent, wherein the aforementioned solvent A comprises at least one of N-methyl-2-pyrrolidone or γ-butyrolactone. The liquid crystal alignment agent of claim 1, wherein _X1 in the aforementioned formula (1) is a tetravalent organic group selected from the following formulas (X1-28) to (X1-40),

The liquid crystal alignment agent of claim 1, wherein the liquid crystal alignment agent contains 20-80% by mass of the aforementioned solvent A relative to the total mass of the liquid crystal alignment agent. The liquid crystal alignment agent of claim 1, wherein the liquid crystal alignment agent contains 5-30 mass % of the aforementioned solvent C relative to the total mass of the liquid crystal alignment agent. The liquid crystal alignment agent of claim 1, wherein, relative to the total mass of the liquid crystal alignment agent, the aforementioned solvent A is contained at 50 mass %, the aforementioned solvent B is contained at 10-30 mass %, and the aforementioned solvent C is contained at 10-20 mass %. As in claim 1, the liquid crystal alignment agent, wherein the total amount of the aforementioned solvent B and the aforementioned solvent C is 10-60% by mass relative to the total mass of the liquid crystal alignment agent, and the aforementioned solvent B is contained in a larger amount than the aforementioned solvent C. The liquid crystal alignment agent of claim 1, wherein the solvent B contains 1-20% more solvent C than the solvent B. The liquid crystal alignment agent of claim 1 can be used for film formation by inkjet method. A liquid crystal alignment film obtained from a liquid crystal alignment agent as described in any one of claims 1 to 9. A liquid crystal display element having a liquid crystal alignment film as claimed in claim 10.