CN115746874A

CN115746874A - Liquid crystal aligning agent, liquid crystal alignment film, and liquid crystal display element

Info

Publication number: CN115746874A
Application number: CN202211325804.XA
Authority: CN
Inventors: 国见奈穗
Original assignee: Nissan Chemical Corp
Current assignee: Nissan Chemical Corp
Priority date: 2014-10-28
Filing date: 2015-10-26
Publication date: 2023-03-07
Also published as: CN107111190A; KR102488715B1; KR20170077144A; JP6776897B2; WO2016068085A1; JPWO2016068085A1; TWI780023B; TW201630978A

Abstract

Provided are a liquid crystal aligning agent, a liquid crystal alignment film, and a liquid crystal display element for obtaining an alignment film suitable for photo-alignment applications, which does not generate bright spots even in the case of negative-type liquid crystals and can obtain good afterimage characteristics. A liquid crystal aligning agent comprising at least 1 polymer (A) selected from the group consisting of a polyimide precursor having the formula (1) below and an imidized polymer of the polyimide precursorA structural unit and a structural unit represented by formula (2). (X) ₁ 、X ₂ : formula (X1-1) or (X1-2); r ₁ 、R ₂ 、R ₃ 、R ₄ And R ₆ Each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R ₅ Is an alkyl group having 1 to 4 carbon atoms. n is an integer of 1 to 6. )

Description

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

The present application is filed as a divisional application entitled "liquid crystal aligning agent, liquid crystal alignment film, and liquid crystal display element" filed on 26/10/2015 with application number 201580059292.9.

Technical Field

The present invention relates to a liquid crystal aligning agent suitable for a photo-alignment process, a liquid crystal alignment film obtained from the liquid crystal aligning agent, and a liquid crystal display element using the liquid crystal alignment film.

Background

Liquid crystal display elements used in liquid crystal televisions, liquid crystal displays, and the like are generally provided with a liquid crystal alignment film for controlling the alignment state of liquid crystal in the element. As the liquid crystal alignment film, a polyimide liquid crystal alignment film obtained by applying a liquid crystal alignment agent containing a polyimide precursor such as polyamic acid (polyamic acid) or a solution of a soluble polyimide as a main component to a glass substrate or the like and firing the applied liquid crystal alignment agent is mainly used. At present, the liquid crystal alignment film is produced by rubbing the surface of a polyimide-based liquid crystal alignment film formed on an electrode substrate with a cloth such as cotton, nylon, or polyester in one direction, that is, by a so-called rubbing treatment, according to the most industrially popular method.

The photo-alignment method has an advantage that it can be industrially produced by a simple manufacturing process as an alignment treatment method of a brushless mill.

In the liquid crystal display element of the IPS (In Plane Switching) driving method or the FFS (Fringe Field Switching) driving method, by using a liquid crystal alignment film obtained by a photo-alignment method, improvement of the contrast, the viewing angle characteristics, and the like of the liquid crystal display element can be expected and the performance of the liquid crystal display element can be improved as compared with a liquid crystal alignment film obtained by a brushing method, and therefore, attention is paid to the liquid crystal alignment method as a desirable liquid crystal alignment treatment method.

However, the liquid crystal alignment film obtained by the photo-alignment method has a problem that the anisotropy of the polymer film with respect to the alignment direction is small as compared with the liquid crystal alignment film obtained by the rubbing treatment. If the anisotropy is small, sufficient liquid crystal alignment properties cannot be obtained, and there is a problem that an afterimage or the like occurs when a liquid crystal display element is produced. As a method for improving the anisotropy of a liquid crystal alignment film obtained by a photo-alignment method, there are proposed: after the light irradiation, the low molecular weight component generated by the cleavage of the main chain of the polyimide by the light irradiation is removed.

Documents of the prior art

Patent literature

Patent document 1: japanese patent laid-open publication No. 9-297313

Patent document 2: japanese patent laid-open publication No. 2011-107266

Non-patent document

Non-patent document 1: "liquid Crystal photo-alignment film", functional Material, no. 11/1997, vol.17, pages 11-22

Disclosure of Invention

Problems to be solved by the invention

In the liquid crystal display device of the IPS driving method or the FFS driving method, a positive liquid crystal is conventionally used, and a negative liquid crystal is used, whereby a transmission loss at an upper portion of an electrode can be reduced, and contrast can be improved. When a liquid crystal alignment film obtained by a photo-alignment method is used for a liquid crystal display device of an IPS drive system or an FFS drive system using a negative-type liquid crystal material, it is expected to have higher display performance than a conventional liquid crystal display device.

However, the present inventors have conducted studies and, as a result, have found that: in the case of a liquid crystal display element using a negative-type liquid crystal material, a liquid crystal alignment film obtained by a photo-alignment method has a problem that a defect (bright spot) is generated at a high occurrence rate, and the defect is generated.

The present invention addresses the problem of providing a liquid crystal aligning agent suitable for photo-alignment treatment for obtaining a liquid crystal alignment film for photo-alignment purposes, which does not produce bright spots even when a negative-type liquid crystal is used and can obtain good afterimage characteristics, a liquid crystal alignment film obtained from the liquid crystal aligning agent, and a liquid crystal display element provided with the liquid crystal aligning agent.

Means for solving the problems

The inventors of the present invention conducted extensive studies to find that: a liquid crystal aligning agent containing a polyimide-based polymer having a specific structure is effective for achieving the above object, and the present invention has been completed.

The present invention is a liquid crystal aligning agent containing at least 1 polymer (A) selected from the group consisting of a polyimide precursor having structural units represented by the following formulae (1) and (2) and an imidized polymer of the polyimide precursor.

(in the formulae (1) and (2), X ₁ And X ₂ Each independently represents at least 1 kind selected from the group consisting of structures represented by the following formulae (X1-1) and (X1-2). R ₁ 、R ₂ 、R ₃ 、R ₄ And R ₆ Each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R is ₅ Is an alkyl group having 1 to 4 carbon atoms. n is an integer of 1 to 6. )

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a liquid crystal aligning agent suitable for a photo-alignment process, which can provide a liquid crystal alignment film having high irradiation sensitivity and good afterimage characteristics while suppressing bright spots observed in a conventional photo-alignment process. By providing the liquid crystal alignment film obtained from the liquid crystal alignment agent, a highly reliable liquid crystal display element free from display defects can be provided.

Detailed Description

< specific Polymer >

As described above, the liquid crystal aligning agent of the present invention contains at least 1 polymer (also referred to as a specific polymer (a) in the present invention) selected from the group consisting of a polyimide precursor having structural units represented by the following formulae (1) and (2) and an imidized polymer of the polyimide precursor. In the present invention, the structural unit represented by the formula (1) and the structural unit represented by the following formula (2) may be present in the same polyimide precursor, and the structural unit represented by the formula (1) and the structural unit represented by the following formula (2) may be present in different polyimide precursors.

X in the above formulae (1) and (2) ₁ 、X ₂ 、R ₁ 、R ₂ Are as defined above. Among them, X is X from the viewpoint of high sensitivity and liquid crystal alignment ₁ 、X ₂ Preferably having the aforementioned formula (X1-2). From the viewpoint of easiness of imidation by heating, R ₁ 、R ₂ Preferably a hydrogen atom or a methyl or ethyl group. From the viewpoint of liquid crystal alignment, R ₃ 、R ₄ 、R ₆ Preferably a hydrogen atom. From the viewpoint of liquid crystal alignment, R ₅ Preferably methyl. In addition, n is preferably an integer of 1 to 3, and particularly preferably 2, from the viewpoint of liquid crystal alignment properties.

< production of polyimide precursor-production of Polyamic acid >

The polyamic acid, which is a polyimide precursor having the structural unit represented by the formula (1) and the structural unit represented by the formula (2), in the present invention is produced by the following method. In the present invention, the polyimide precursor having the structural unit represented by formula (1) and the polyimide precursor having the structural unit represented by formula (2) may be produced separately or by mixing both.

Further, as the diamine to be polycondensed with tetracarboxylic acid or its dianhydride, it is preferable to use 1 or more of each of the diamine having the structural unit represented by formula (1) and the diamine having the structural unit represented by formula (2) to produce a polyimide precursor having the structural unit represented by formula (1) and the structural unit represented by formula (2).

In this case, X in the above formula (1) is added ₁ Tetracarboxylic acid or dianhydride thereof and X in the formula (2) ₂ With a tetracarboxylic acid or dianhydride thereof and an acid imparting Y ₁ Diamine of (2) and imparting Y ₂ The diamine of (4) is produced by a polycondensation reaction at-20 to 150 ℃ and preferably 0 to 50 ℃ for 30 minutes to 24 hours and preferably 1 to 12 hours in the presence of a solvent.

The reaction of the diamine with the tetracarboxylic acid is usually carried out in a solvent. The solvent used in this case is not particularly limited as long as it dissolves the polyimide precursor formed. Specific examples of the solvent used in the reaction are shown below, but the solvent is not limited to these examples.

Examples thereof include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ -butyrolactone, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide, and 1,3-dimethylimidazolidinone. When the polyimide precursor has high solubility in the solvent, a solvent represented by methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or a solvent represented by the following formulae [ D-1] to [ D-3] can be used.

(formula [ D-1]]In (D) ¹ Represents an alkyl group having 1 to 3 carbon atoms; formula [ D-2]In (D) ² Represents an alkyl group having 1 to 3 carbon atoms; formula [ D-3]In (D) ³ Represents an alkyl group having 1 to 4 carbon atoms).

These solvents may be used alone or in combination. Further, even in the case of a solvent which does not dissolve the polyimide precursor, the solvent may be mixed and used within a range where the produced polyimide precursor is not precipitated. Further, the solvent is preferably used after dehydration and drying because the water content in the solvent inhibits the polymerization reaction and further causes hydrolysis of the polyimide precursor to be produced.

Further, in order to obtain polyamic acid alkyl ester, the following method may be used: a method of polycondensing a tetracarboxylic acid having a carboxylic acid group dialkylesterified with a primary diamine compound or a secondary diamine compound; a method of polycondensing a tetracarboxylic acid dihalide obtained by dialkylesterifying a carboxylic acid group with a primary diamine compound or a secondary diamine compound; or a method of converting the carboxyl group of the polyamic acid into an ester.

When the diamine component and the tetracarboxylic acid component are reacted in a solvent, the following methods may be mentioned: a method in which a solution obtained by dispersing or dissolving a diamine component in a solvent is stirred, and a tetracarboxylic acid component is added as it is, or a tetracarboxylic acid component is dispersed or dissolved in a solvent and then added; conversely, a method of adding a diamine component to a solution obtained by dispersing or dissolving a tetracarboxylic acid component in a solvent; a method of alternately adding a diamine component and a tetracarboxylic acid component, and any of these methods can be used. In addition, when a plurality of diamine components or tetracarboxylic acid components are used and reacted, the reaction may be carried out in a state of being mixed in advance, or the reaction may be carried out in sequence, or low molecular weight materials obtained by the respective reactions may be mixed and reacted to produce a polymer.

The polymerization temperature in this case may be any temperature selected from-20 to 150 ℃ and preferably from-5 to 100 ℃. The reaction can be carried out at any concentration, but when the concentration is too low, it is difficult to obtain a polymer having a high molecular weight, and when the concentration is too high, the viscosity of the reaction solution becomes too high, and uniform stirring becomes difficult. Therefore, the amount is preferably 1 to 50% by mass, more preferably 5 to 30% by mass. The reaction may be carried out at a high concentration in the initial stage of the reaction, and then a solvent may be added.

In the polymerization reaction of the polyimide precursor, the ratio of the total mole number of the diamine component to the total mole number of the tetracarboxylic acid component is preferably 0.8 to 1.2, and particularly preferably 0.9 to 1.0. Similarly to the ordinary polycondensation reaction, the molecular weight of the polyimide precursor to be produced increases as the molar ratio approaches 1.0.

The polyimide of the present invention is obtained by ring-closing the polyimide precursor, and a method of ring-closing the polyamic acid or polyamic acid alkyl ester to obtain the polyimide can be used.

The closing ratio of the amic acid group (also referred to as imidization ratio) of the polyimide of the present invention is not necessarily 100%, and may be arbitrarily adjusted depending on the application and purpose, and is preferably 50 to 80%.

Examples of the method for imidizing the polyimide precursor include thermal imidization in which a solution of the polyimide precursor is directly heated, and catalytic imidization in which a catalyst is added to a solution of the polyimide precursor. The temperature at which the polyimide precursor is thermally imidized in a solution is 100 to 400 ℃, preferably 120 to 250 ℃, and it is preferable to thermally imidize the polyimide precursor while removing water generated by the imidization reaction from the system. The reaction time is preferably 30 minutes to 4 hours.

The catalytic imidization of the polyimide precursor can be carried out by adding a basic catalyst and an acid anhydride to a solution of the polyimide precursor and stirring at-20 to 250 ℃, preferably at 0 to 180 ℃. The reaction time is preferably 30 minutes to 4 hours.

The amount of the basic catalyst is 0.5 to 30 mol times, preferably 2 to 20 mol times, and the amount of the acid anhydride is 1 to 50 mol times, preferably 3 to 30 mol times, the amount of the acid amide group. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, and trioctylamine. Among them, pyridine is preferred because it has basicity suitable for the progress reaction.

Examples of the acid anhydride include acetic anhydride, trimellitic anhydride, and pyromellitic anhydride. Among these, acetic anhydride is preferred because purification is easy after completion of the reaction. The imidization rate based on the catalytic imidization can be controlled by adjusting the amount of the catalyst, the reaction temperature, and the reaction time.

When the polyimide precursor or polyimide to be produced is recovered from the reaction solution of the polyimide precursor or polyimide, the reaction solution may be put into a solvent to precipitate the polyimide. Examples of the solvent used for precipitation include methanol, ethanol, isopropanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, toluene, benzene, and water. The polymer precipitated by adding a solvent may be recovered by filtration, and then dried at normal temperature or under reduced pressure or dried by heating. Further, when the operation of re-dissolving the polymer recovered by precipitation in the solvent and re-precipitating and recovering is repeated 2 to 10 times, impurities in the polymer can be reduced. Examples of the solvent in this case include alcohols, ketones, hydrocarbons and the like, and the use of 3 or more solvents selected from these is preferable because the purification efficiency is further improved.

The specific polymer (A) of the present invention is preferably a polyamic acid alkyl ester. Preferred specific methods for producing the polyamic acid alkyl ester are shown in the following (1) to (3).

(1) Method for producing polyamic acid by esterification reaction

A method for producing a polyamic acid alkyl ester by producing a polyamic acid from a diamine component and a tetracarboxylic acid component and subjecting the carboxyl group (COOH group) thereof to a chemical reaction, i.e., an esterification reaction.

Specifically, the polyamic acid is reacted with the esterifying agent in the presence of a solvent, preferably at-20 to 150 ℃ and more preferably at 0 to 50 ℃ for 30 minutes to 24 hours, and more preferably 1 to 4 hours.

The esterification agent is preferably an esterification agent which can be easily removed after the esterification reaction, and examples thereof include N, N-dimethylformamide dimethyl acetal, N-dimethylformamide diethyl acetal, N-dimethylformamide dipropyl acetal, N-dimethylformamide dineopentylbutyl acetal, N-dimethylformamide di-tert-butyl acetal, 1-methyl-3-p-tolyltriazene, 1-ethyl-3-p-tolyltriazene, 1-propyl-3-p-tolyltriazene, and 4- (4,6-dimethoxy-1,3,5-triazin-2-yl) -4-methylmorpholine hydrochloride. The amount of the esterifying agent to be used is preferably 2 to 6 molar equivalents with respect to 1 mole of the repeating unit of the polyamic acid. Among them, 2 to 4 molar equivalents are preferable.

From the viewpoint of solubility of the polyamic acid in a solvent, examples of the solvent used in the esterification reaction include solvents used in the reaction between the diamine component and the tetracarboxylic acid component. Among them, N-dimethylformamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone or γ -butyrolactone is preferable. The solvent may be used in 1 kind or in a mixture of 2 or more kinds.

In the esterification reaction, the concentration of the polyamic acid in the solvent is preferably 1 to 30% by mass from the viewpoint that the polyamic acid is not easily precipitated. Among them, 5 to 20% by mass is preferable.

(2) Process for production by reaction of diamine component and tetracarboxylic acid diester dichloride

The reaction of the diamine component with the tetracarboxylic acid diester dichloride is specifically a method of reacting the diamine component with the tetracarboxylic acid diester dichloride in the presence of a base and a solvent, preferably at-20 to 150 ℃, more preferably at 0 to 50 ℃, preferably for 30 minutes to 24 hours, more preferably for 1 to 4 hours.

As the base, pyridine, triethylamine, 4-dimethylaminopyridine and the like can be used. Among them, pyridine is preferable in order to mildly promote the reaction. The amount of the base to be used is preferably an amount which can be easily removed after the above reaction, and is preferably 2 to 4 times by mol based on the tetracarboxylic acid diester dichloride. Among them, the molar ratio is more preferably 2 to 3 times.

The solvent used in the reaction may be a solvent used in the reaction of the diamine component and the tetracarboxylic acid component, from the viewpoint of solubility of the obtained polymer, that is, polyamic acid alkyl ester in a solvent. Among them, N-dimethylformamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone or γ -butyrolactone is preferable. These solvents may be used in a single amount of 1 kind or in a mixture of 2 or more kinds.

In the reaction, the concentration of the polyamic acid alkyl ester in the solvent is preferably 1 to 30% by mass from the viewpoint that the polyamic acid alkyl ester is difficult to precipitate. Among them, 5 to 20% by mass is preferable. In order to prevent the hydrolysis of the tetracarboxylic acid diester dichloride, the solvent used for preparing the polyamic acid alkyl ester is preferably dehydrated as much as possible. Further, the reaction is preferably carried out in a nitrogen atmosphere to prevent the mixing of outside air.

(3) Method for producing a tetracarboxylic acid diester by reacting a diamine component with a tetracarboxylic acid diester

Specifically, the diamine component and the tetracarboxylic acid diester are reacted in the presence of a condensing agent, a base and a solvent, preferably at 0 to 150 ℃, more preferably at 0 to 100 ℃, for 30 minutes to 24 hours, more preferably for 3 to 15 hours.

As the condensing agent, triphenyl phosphite, dicyclohexylcarbodiimide, 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride, N, N ' -carbonyldiimidazole, dimethoxy-1,3,5-triazinylmethyl morpholine, O- (benzotriazol-1-yl) -N, N, N ', N ' -tetramethyluronium tetrafluoroborate, O- (benzotriazol-1-yl) -N, N, N ', N ' -tetramethyluronium hexafluorophosphate, (2,3-dihydro-2-thio-3-benzoxazolyl) diphenyl phosphonate, and the like can be used. The amount of the condensing agent to be used is preferably 2 to 3 times by mol, and particularly preferably 2 to 2.5 times by mol, based on the tetracarboxylic acid diester.

As the base, tertiary amines such as pyridine and triethylamine can be used. The amount of the base to be used is preferably an amount which can be easily removed after the polycondensation reaction, and is preferably 2 to 4 times by mol, and particularly preferably 2 to 3 times by mol, based on the diamine component.

The solvent used in the polycondensation reaction may be a solvent used in the reaction between the diamine component and the tetracarboxylic acid component, from the viewpoint of solubility of the obtained polymer, i.e., polyamic acid alkyl ester in the solvent. Particularly preferred is N, N-dimethylformamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone or γ -butyrolactone. The solvent may be used in combination of 2 or more.

In addition, in the above polycondensation reaction, the reaction proceeds efficiently by adding a lewis acid as an additive. The lewis acid is preferably a halogenated lithium such as lithium chloride or lithium bromide. The amount of the lewis acid to be used is preferably 0.1 to 10 mol per mol of the diamine component, and particularly preferably 2.0 to 3.0 mol per mol of the diamine component.

When the polyamic acid alkyl ester is recovered from the polyamic acid alkyl ester solution obtained by the methods (1) to (3), the reaction solution may be put into a solvent and precipitated. Examples of the solvent used for precipitation include water, methanol, ethanol, 2-propanol, hexane, butyl cellosolve, acetone, and toluene. The polymer to be precipitated by charging a solvent is preferably subjected to a plurality of washing operations with the solvent for the purpose of removing the additives/catalysts used. After the filtration and recovery, the product may be dried at normal temperature or under reduced pressure or dried by heating. Further, when the operation of re-dissolving the polymer recovered by precipitation in the solvent and re-precipitating and recovering is repeated 2 to 10 times, impurities in the polymer can be reduced. Examples of the solvent in this case include solvents that dissolve the polymer.

The polyamic acid alkyl ester of the present invention is preferably the method (1) or (2) among the methods (1) to (3).

< liquid Crystal alignment agent >

The liquid crystal aligning agent is a coating solution for forming a liquid crystal alignment film (also referred to as a resin coating film), and is a coating solution for forming a liquid crystal alignment film containing the specific polymer (a) and a solvent. The content of the specific polymer (a) in the liquid crystal aligning agent may be appropriately changed depending on the method of applying the liquid crystal aligning agent and the target film thickness of the liquid crystal alignment film, and is preferably 2 to 10% by mass, and particularly preferably 3 to 7% by mass. On the other hand, the content of the solvent is preferably 70 to 99.9% by mass, more preferably 90 to 98% by mass.

The solvent used in the liquid crystal aligning agent of the present invention is a solvent (also referred to as a good solvent) for dissolving the specific polymer (a), and an organic solvent is particularly preferable. Specific examples of the good solvent are listed below, but the solvent is not limited to these examples.

Examples thereof include N, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ -butyrolactone, 1,3-dimethyl-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, and 4-hydroxy-4-methyl-2-pentanone. Among them, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone or γ -butyrolactone is preferably used.

Further, when the specific polymer (A) has high solubility in a solvent, it is preferable to use solvents represented by the above-mentioned formulae [ D-1] to [ D-3 ].

The good solvent in the liquid crystal aligning agent is preferably 20 to 99% by mass, more preferably 20 to 90% by mass, and particularly preferably 30 to 80% by mass of the entire solvent.

The liquid crystal aligning agent may contain a solvent (also referred to as a poor solvent) that improves the film coatability and surface smoothness of the liquid crystal alignment film when the liquid crystal aligning agent is applied, within a range that does not impair the effects of the present invention. The poor solvent is preferably 1 to 80% by mass of the entire solvent contained in the liquid crystal aligning agent. Among them, it is preferably 10 to 80% by mass. More preferably 20 to 70 mass%.

Specific examples of the poor solvent are given below, but the poor solvent is not limited to these examples. Examples thereof include ethanol, isopropanol, 1-butanol, 2-butanol, isobutanol, t-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, isoamyl alcohol, t-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-ethyl-1-hexanol, cyclohexanol, 1-methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 1,2-ethanediol, 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 diethyl ether, diethylene glycol methyl ethyl 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 monoacetate, ethylene glycol diacetate, propylene carbonate, ethylene carbonate, 2- (methoxymethoxy) ethanol, ethylene glycol monobutyl ether, ethylene glycol monoisoamyl ether, ethylene glycol monohexyl ether, 2- (hexyloxy) ethanol, furfuryl alcohol, diethylene glycol, propylene glycol monobutyl ether, 1- (butoxyethoxy) propanol, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monoacetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2- (2-ethoxyethoxy) ethyl acetate, diethylene glycol acetate, 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, 3-methoxypropionate, methyl ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, propyl 3-methoxypropionate, butyl lactate, methyl lactate, ethyl lactate, n-butyl lactate, n-isoamyl lactate, and the solvent represented by the formula 1-D.

Of these, 1-hexanol, cyclohexanol, 1,2-ethylene glycol, 1,2-propylene glycol, propylene glycol monobutyl ether, ethylene glycol monobutyl ether, or dipropylene glycol dimethyl ether are preferably used.

The following crosslinkable compounds are preferably introduced into the liquid crystal aligning agent of the present invention: a crosslinkable compound having an epoxy group, an isocyanate group, an oxetanyl group or a cyclocarbonate group; a crosslinkable compound having at least 1 substituent selected from the group consisting of a hydroxyl group, a hydroxyalkyl group and a lower alkoxyalkyl group; or a crosslinkable compound having a polymerizable unsaturated bond. These substituents and polymerizable unsaturated bonds must be present in the crosslinkable compound in an amount of 2 or more.

Examples of the crosslinkable compound having an epoxy group or an isocyanate group include bisphenol acetone glycidyl ether, phenol novolac epoxy resin, cresol novolac epoxy resin, triglycidyl isocyanurate, tetraglycidyl aminobiphenyl, tetraglycidyl m-xylylenediamine, tetraglycidyl-2 zxft 8652-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, triglycidyl p-aminophenol, tetraglycidyl m-xylylenediamine, 2- (4- (2,3-epoxypropoxy) phenyl) -2- (4- (1,1-bis (4- (5657-epoxypropoxy) phenyl) ethyl) phenyl) -2- (3429 zxft 3282-323282-3260-epoxypropoxy) phenyl) ethyl) phenyl-2- (343282-323232-epoxypropoxy) propyl-3234-3282-phenyl-3232-3282-ethyl) phenyl-3234-3282-phenyl-ethyl-3282-phenyl-3282-propyl-epoxy-propyl-2-epoxy-propyl-2-3282.

The crosslinkable compound having an oxetanyl group is a compound having at least 2 oxetanyl groups represented by the following formula [4A ].

Specifically, examples of the crosslinkable compound include crosslinkable compounds represented by the formulae [4a ] to [4k ] described in International publication No. WO2011/132751 (2011.10.27), on pages 58 to 59.

The crosslinkable compound having a cyclocarbonate group is a crosslinkable compound having at least 2 cyclocarbonate groups represented by the following formula [5A ].

Specifically, examples of the crosslinkable compound include crosslinkable compounds represented by the formulae [5-1] to [5-42] described in International patent publication No. WO2012/014898 (published by 2012.2.2) on pages 76 to 82.

Examples of the crosslinkable compound having at least 1 substituent selected from the group consisting of a hydroxyl group and an alkoxy group include amino resins having a hydroxyl group or an alkoxy group, such as melamine resin, urea resin, guanamine resin, glycoluril-formaldehyde resin, succinamide-formaldehyde resin, ethyleneurea-formaldehyde resin, and the like. Specifically, a melamine derivative, a benzoguanamine derivative, or a glycoluril in which the hydrogen atom of the amino group is substituted with a hydroxymethyl group, an alkoxymethyl group, or both of them can be used. The melamine derivative or benzoguanamine derivative may be present in the form of a dimer or trimer. They preferably have an average of 3 or more and 6 or less hydroxymethyl groups or alkoxymethyl groups per 1 triazine ring.

Examples of the melamine derivative or benzoguanamine derivative include commercially available methoxymethylated melamines such as MX-750 substituted with an average of 3.7 methoxymethyl groups per 1 triazine ring, MW-30 substituted with an average of 5.8 methoxymethyl groups per 1 triazine ring (see above, sanhe chemical Co., ltd.), CYMEL 300, 301, 303, 350, 370, 771, 325, 327, 703, and 712; methoxymethylated butoxymethylated melamines such as CYMEL 235, 236, 238, 212, 253, 254; butoxymethylated melamines such as CYMEL 506, 508; carboxymethoxymethylated isobutoxymethylated melamines such as CYMEL 1141; methoxymethylated ethoxymethylated benzoguanamine such as CYMEL 1123; methoxymethylated butoxymethylated benzoguanamine such as CYMEL 1123-10; butoxymethylated benzoguanamine such as CYMEL 1128; carboxymethoxymethylated ethoxymethylated benzoguanamine such as CYMEL 1125-80 (manufactured by Sanjing サイアナミド Co., ltd.). Examples of glycolurils include butoxymethylated glycolurils such as CYMEL 1170, hydroxymethylated glycolurils such as CYMEL 1172, and methoxyhydroxymethylated glycolurils 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 crosslinkable compounds of the formulae [6-1] to [6-48] described in International publication No. WO2011/132751 (2011.10.27) on pages 62 to 66 can be mentioned.

Examples of the crosslinkable compound having a polymerizable unsaturated bond include crosslinkable compounds having 3 polymerizable unsaturated groups in the molecule, such as trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, tri (meth) acryloyloxyethoxytrimethylolpropane, and glycerol polyglycidyl ether poly (meth) acrylate; a crosslinkable compound having 2 polymerizable unsaturated groups in a molecule, such as 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, 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, pentaerythritol di (meth) acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, diethylene glycol diglycidyl ether di (meth) acrylate, phthalic acid diglycidyl ester di (meth) acrylate, and hydroxypivalic acid neopentyl glycol di (meth) acrylate; and crosslinkable compounds having 1 polymerizable unsaturated group in the molecule, such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 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, and N-methylol (meth) acrylamide.

Further, a compound represented by the following formula [7A ] can also be used.

(formula [7A ]]In, E ₁ 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, E ₂ Is represented by a formula [7a ] selected from]And formula [7b]Wherein n represents an integer of 1 to 4. )

The above is an example of the crosslinkable compound, but is not limited thereto. The number of the crosslinkable compounds used in the liquid crystal aligning agent of the present invention may be 1, or 2 or more.

The content of the crosslinkable compound in the liquid crystal aligning agent of the present invention is preferably 0.1 to 150 parts by mass with respect to 100 parts by mass of the entire polymer components. Among them, in order to promote the crosslinking reaction and to exhibit the desired effect, it is preferably 0.1 to 100 parts by mass with respect to 100 parts by mass of the entire polymer components. More preferably 1 to 50 parts by mass.

The liquid crystal aligning agent of the present invention may be a compound which improves the uniformity of the film thickness and surface smoothness of the liquid crystal alignment film when the liquid crystal aligning agent is applied, within a range not impairing the effects of the present invention.

Examples of the compound for improving the uniformity of the film thickness and the surface smoothness of the liquid crystal alignment film include a fluorine-based surfactant, a silicone-based surfactant, and a nonionic surfactant.

More specifically, there may be mentioned, for example, eftop EF301, EF303, and EF352 (the above are manufactured by Tohkem products Corporation); megafac F171, F173, R-30 (see DIC Corporation, supra); fluorad FC430 and FC431 (manufactured by Sumitomo 3M Limited); asahiguard AG710, surflon S-382, SC101, SC102, SC103, SC104, SC105, SC106 (manufactured by Asahi glass Co., ltd.).

The amount of the surfactant to be used is preferably 0.01 to 2 parts by mass, more preferably 0.01 to 1 part by mass, based on 100 parts by mass of the total polymer components contained in the liquid crystal aligning agent.

Further, as a compound which promotes charge transfer in the liquid crystal alignment film to promote element charge removal, a nitrogen-containing heterocyclic amine compound represented by the formulae [ M1] to [ M156] described on pages 69 to 73 of international publication No. WO2011/132751 (2011.10.27) may be added to the liquid crystal alignment agent. The amine compound may be added directly to the liquid crystal aligning agent, preferably, the solution is added after being prepared into a solution having a concentration of 0.1 to 10% by mass, preferably 1 to 7% by mass. The solvent is not particularly limited as long as the specific polymer (a) is dissolved in the solvent.

In the liquid crystal aligning agent of the present invention, in addition to the above-mentioned poor solvent, crosslinkable compound, resin coating film, or compound for improving the film thickness uniformity and/or surface smoothness of the liquid crystal alignment film and compound for promoting the charge removal, a dielectric or conductive material for changing electric characteristics such as dielectric constant, conductivity and the like of the liquid crystal alignment film may be added within a range not impairing the effect of the present invention.

< liquid Crystal alignment film/liquid Crystal display device >

The liquid crystal alignment film is obtained by applying the liquid crystal alignment agent to a substrate, drying, and firing. The substrate to which the liquid crystal aligning agent of the present invention is applied is not particularly limited as long as it is a substrate having high transparency, and a glass substrate, a silicon nitride substrate, a plastic substrate such as an acrylic substrate or a polycarbonate substrate, or the like may be used. In this case, from the viewpoint of simplifying the process, it is preferable to use a substrate on which an ITO electrode or the like for driving liquid crystal is formed. In the case of a reflective liquid crystal display element, an opaque material such as a silicon wafer may be used as the single-sided substrate, and a material that reflects light such as aluminum may be used as the electrode in this case.

The method of applying the liquid crystal aligning agent is not particularly limited, and a method of applying the liquid crystal aligning agent by screen printing, gravure printing, flexo printing, inkjet method, or the like is generally industrially used. As other coating methods, there are a dipping method, a roll coating method, a slit coating method, a spin coating method, a spray coating method, and the like, and they can be used according to the purpose.

After the liquid crystal alignment agent is coated on the substrate, the solvent can be evaporated by a heating means such as a hot plate, a thermal cycle oven, or an IR (infrared ray) oven to form a liquid crystal alignment film. The drying and firing steps after the application of the liquid crystal aligning agent of the present invention can be performed at any temperature and for any time. In general, in order to sufficiently remove the solvent contained, there are listed: drying at 50 to 120 ℃ and preferably 60 to 100 ℃ for 1 to 10 minutes, preferably 1 to 5 minutes, and then firing at 150 to 300 ℃ and preferably 180 to 250 ℃ for 5 to 120 minutes, preferably 10 to 60 minutes. If the thickness of the liquid crystal alignment film after firing is too thin, the reliability of the liquid crystal display device may be lowered, and therefore, the thickness is preferably 5 to 300nm, more preferably 10 to 200nm.

The method for aligning the liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention may be a brush-rubbing treatment method, and is preferably a photo-alignment treatment method. Preferred examples of the photo-alignment treatment method include: a method of applying a radiation polarized in a certain direction to the surface of the liquid crystal alignment film and, in some cases, heating the liquid crystal alignment film at a temperature of preferably 150 to 250 ℃. As the radiation, ultraviolet rays or visible rays having a wavelength of 100 to 800nm can be used. Among them, ultraviolet rays having a wavelength of 100 to 400nm are preferable, and ultraviolet rays having a wavelength of 200 to 400nm are more preferable.

In order to improve the liquid crystal alignment property, the substrate coated with the liquid crystal alignment film may be irradiated with radiation while being heated at 50 to 250 ℃.

The irradiation dose of the radiation is preferably 1 to 10,000mJ/cm ² . Among them, it is preferably 100 to 5,000mJ/cm ² . The liquid crystal alignment film thus produced can stably align liquid crystal molecules in a certain direction.

Further, the liquid crystal alignment film irradiated with the polarized radiation by the above-described method may be subjected to a contact treatment using water or a solvent.

The solvent used in the contact treatment is not particularly limited as long as it dissolves a decomposition product generated from the liquid crystal alignment film by irradiation with radiation. Specific examples thereof include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, methyl lactate, diacetone alcohol, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate, and cyclohexyl acetate. Among them, water, 2-propanol, 1-methoxy-2-propanol, or ethyl lactate is preferable from the viewpoint of versatility and solvent safety. More preferably water, 1-methoxy-2-propanol or ethyl lactate. The number of the solvents may be 1, or 2 or more may be used in combination.

Examples of the contact treatment include a dipping treatment and a spraying treatment (also referred to as a spray treatment). The treatment time in these treatments is preferably 10 seconds to 1 hour from the viewpoint of efficiently dissolving the decomposition product generated from the liquid crystal alignment film by the radiation. Among them, the dipping treatment is preferably performed for 1 to 30 minutes. The solvent used in the contact treatment may be normal temperature or heated, and is preferably 10 to 80 ℃. Among them, 20 to 50 ℃ is preferable. From the viewpoint of solubility of the decomposition product, ultrasonic treatment or the like may be performed as necessary.

After the contact treatment, it is preferable to perform rinsing (also referred to as rinsing) with a low boiling point solvent such as water, methanol, ethanol, 2-propanol, acetone, or methyl ethyl ketone, and to perform firing of the liquid crystal alignment film. In this case, either one of rinsing and firing or both may be performed. The firing temperature is preferably 150 to 300 ℃. Among them, it is preferably 180 to 250 ℃. More preferably from 200 to 230 ℃. The firing time is preferably 10 seconds to 30 minutes. Among them, 1 to 10 minutes is preferable.

The liquid crystal alignment film of the present invention is suitable as a liquid crystal alignment film for a liquid crystal display element of a transverse electric field system such as IPS system or FFS system, and is particularly useful as a liquid crystal alignment film for a liquid crystal display element of FFS system. The liquid crystal display element can be obtained by obtaining a substrate with a liquid crystal alignment film obtained from the liquid crystal alignment agent of the present invention, then fabricating a liquid crystal cell by a known method, and using the liquid crystal cell.

As an example of a method for manufacturing a liquid crystal cell, a liquid crystal display element having a passive matrix structure will be described. Note that each pixel portion constituting an image display may be a liquid crystal display element of an active matrix structure provided with a conversion element such as a TFT (Thin Film Transistor).

Specifically, a transparent glass substrate is prepared, a common electrode is provided on one substrate, and a segment electrode (segment electrode) is provided on the other substrate. These electrodes may be made, for example, as ITO electrodes, which are patterned in order to enable the desired image representation. Next, an insulating film is provided on each substrate to cover the common electrode and the segment electrode. The insulating film may be made, for example, to contain SiO formed by a sol-gel method ₂ -TiO ₂ The film of (1).

Next, liquid crystal alignment films are formed on the respective substrates, one substrate is stacked on the other substrate so that the liquid crystal alignment films face each other, and the periphery is bonded with a sealant. In order to control the substrate gap, spacers are usually mixed in the sealant in advance, and it is preferable that spacers for controlling the substrate gap are also dispersed in advance in the in-plane portion where the sealant is not provided. A part of the sealant is provided with an opening capable of being filled with liquid crystal from the outside. Next, a liquid crystal material is injected into a space surrounded by the two substrates and the sealant through an opening provided in the sealant, and then the opening is sealed with an adhesive. The injection may be performed by a vacuum injection method or a method using a capillary phenomenon in the atmosphere. The liquid crystal material may be either a positive type liquid crystal material or a negative type liquid crystal material, and is preferably a negative type liquid crystal material. Subsequently, a polarizing plate was disposed. Specifically, a pair of polarizing plates is attached to surfaces of the two substrates on the opposite side to the liquid crystal layer.

In the above-described manner, by using the liquid crystal alignment agent of the present invention, a liquid crystal alignment film can be obtained which can suppress afterimages caused by ac driving and which can achieve both adhesion between the sealant and the base substrate. In particular, the liquid crystal alignment film is useful for a photo-alignment treatment method in which the liquid crystal alignment film is irradiated with polarized radiation.

Examples

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. The abbreviations of the compounds used below and the methods for measuring the respective properties are as follows.

NMP: n-methyl-2-pyrrolidone

BCS: butyl cellosolve

DA-1:1,2-bis (4-aminophenoxy) ethane

DA-2:4- (2- (methylamino) ethyl) aniline

DA-3: p-phenylenediamine

DA-4:4- (2-aminoethyl) aniline

DA-5: refer to the following formula (DA-5)

[ viscosity ]

The viscosity of the polyamic acid ester, the polyamic acid solution, and the like was measured using an E-type viscometer TVE-22H (manufactured by Toyobo Co., ltd.) under conditions of a sample volume of 1.1mL, a cone rotor TE-1 (1 ℃ 34', R24), and a temperature of 25 ℃.

[ molecular weight ]

The molecular weight of the polyamic acid ester or the like is measured by a GPC (normal temperature gel permeation chromatography) apparatus, and the number average molecular weight (Mn) and the weight average molecular weight (Mw) are calculated as values converted from polyethylene glycol and polyethylene oxide.

GPC apparatus: shodex (GPC-101), column: shodex (series of KD803 and KD 805), column temperature: 50 ℃ and eluent: n, N-dimethylformamide (as additive, lithium bromide monohydrate (LiBr. H) ₂ O) 30mmol/L, phosphoric acid anhydrous crystals (orthophosphoric acid) 30mmol/L, tetrahydrofuran (THF) 10 ml/L), flow rate: 1.0 ml/min

Standard sample for standard curve preparation: TSK standard polyethylene oxide (weight average molecular weight (Mw) of about 900,000, 150,000, 100,000, 30,000) manufactured by Tosoh corporation and polyethylene glycol (peak molecular weight (Mp) of about 12,000, 4,000, 1,000) manufactured by Polymer Laboratories Ltd. To avoid overlapping of peaks, the following two samples were separately determined: mixing 900,000, 100,000, 12,000, 1,000 samples; and samples obtained by mixing 3 of 150,000, 30,000, and 4,000.

[ anisotropy of alignment film ]

The measurement was carried out using a liquid crystal alignment film evaluation system "LAY-SCAN LABOH" (LYS-LH 30S-1A) manufactured by MORTEX Corporation. A polyimide film having a film thickness of 100nm was irradiated with linearly polarized ultraviolet rays having a wavelength of 254nm and an extinction ratio of 10 or more through a polarizing plate, and the magnitude of anisotropy with respect to the alignment direction of the resulting alignment film was measured.

[ production of liquid Crystal cell ]

A liquid crystal cell having a structure including a Fringe Field Switching (FFS) mode liquid crystal display element was fabricated.

First, a substrate with electrodes is prepared. The substrate was a glass substrate having dimensions of 30mm × 50mm and a thickness of 0.7 mm. On the substrate, as the 1 st layer, an ITO electrode having a solid pattern for constituting a counter electrode was formed. On the counter electrode of the 1 st layer, a SiN (silicon nitride) film formed by a CVD method was formed as the 2 nd layer. The SiN film as the 2 nd layer has a film thickness of 500nm and functions as an interlayer insulating film. On the SiN film as the 2 nd layer, a comb-teeth pixel electrode formed by patterning an ITO film is disposed as the 3 rd layer, and two pixels, i.e., the 1 st pixel and the 2 nd pixel, are formed. The size of each pixel is: 10mm in length and about 5mm in width. At this time, the counter electrode of the 1 st layer and the pixel electrode of the 3 rd layer are electrically insulated by the SiN film of the 2 nd layer.

The pixel electrode of the 3 rd layer has a comb-teeth shape in which a plurality of "<" -shaped electrode elements are arranged with the central portion thereof bent. The width of each electrode element in the width direction was 3 μm, and the interval between the electrode elements was 6 μm. Since the pixel electrode forming each pixel is formed by arranging a plurality of "<" -shaped electrode elements each having a bent central portion, each pixel has a shape similar to a bold "<" shape, which is bent at the central portion in the same manner as the electrode elements, instead of a rectangular shape. Each pixel is divided vertically with a curved portion at the center as a boundary, and has a 1 st region on the upper side and a 2 nd region on the lower side of the curved portion.

When comparing the 1 st region and the 2 nd region of each pixel, the forming directions of the electrode elements constituting the pixel electrodes are different. That is, when the brushing direction of the liquid crystal alignment film described later is set as a reference, the electrode elements of the pixel electrode are formed so as to make an angle of +10 ° (clockwise) in the 1 st region of the pixel, and the electrode elements of the pixel electrode are formed so as to make an angle of-10 ° (clockwise) in the 2 nd region of the pixel. That is, the 1 st region and the 2 nd region of each pixel are configured as follows: the directions of the rotation (planar switching) of the liquid crystal in the substrate plane induced by applying a voltage between the pixel electrode and the counter electrode are opposite to each other.

Next, the liquid crystal alignment agent was filtered through a 1.0 μm filter, and then the prepared substrate with electrodes and the glass substrate having the ITO film formed on the back surface and the columnar spacer having a height of 4 μm were coated by spin coating. After drying on a hot plate at 80 ℃ for 5 minutes, the resultant was baked in a hot air circulating oven at 230 ℃ for 20 minutes to form a coating film having a thickness of 100 nm. The coated surface was irradiated with ultraviolet rays having an extinction ratio of 10 or more, linearly polarized and a wavelength of 254nm through a polarizing plate. The substrate was immersed in at least 1 solvent selected from water and organic solvents for 3 minutes, then immersed in pure water for 1 minute, and heated on a hot plate at 150 to 300 ℃ for 5 minutes to obtain a substrate with a liquid crystal alignment film. The two substrates were used as a set, a sealant was printed on the substrates, and the other substrate was bonded so that the liquid crystal alignment films face each other and the alignment direction was 0 °, and then the sealant was cured to prepare an empty cell. Liquid crystal MLC-7026-100 (manufactured by MERCK CORPORATION) was injected into the empty cell by the reduced pressure injection method, and the injection port was sealed, thereby obtaining an FFS driven liquid crystal cell. Thereafter, the resulting liquid crystal cell was heated at 110 ℃ for 1 hour, left overnight, and then used for each evaluation.

[ evaluation of afterimages by Long-term AC drive ]

A liquid crystal cell having the same structure as the liquid crystal cell used for the evaluation of the afterimage was prepared.

Using this liquid crystal cell, an AC voltage of. + -.5V was applied at a frequency of 60Hz for 120 hours in a constant temperature environment of 60 ℃. Then, the pixel electrode and the counter electrode of the liquid crystal cell were short-circuited and left to stand at room temperature for one day.

After the placement, the liquid crystal cell was placed between 2 polarizing plates arranged so that the polarization axes were perpendicular, the backlight was turned on in a state where no voltage was applied, and the arrangement angle of the liquid crystal cell was adjusted so that the luminance of transmitted light was minimized. Then, the rotation angle when the liquid crystal cell is rotated from the 2 nd area darkest angle to the 1 st area darkest angle of the 1 st pixel is calculated as an angle Δ. Similarly, in the 2 nd pixel, the 2 nd area is compared with the 1 st area to calculate the same angle Δ. Then, the average value of the angle Δ values of the 1 st pixel and the 2 nd pixel is calculated as the angle Δ of the liquid crystal cell, and the liquid crystal alignment property is evaluated by the magnitude of the value. That is, the smaller the value of the angle Δ, the better the liquid crystal alignment.

[ evaluation of Bright Point of liquid Crystal cell (contrast) ]

The evaluation of the bright spots was performed on the liquid crystal cells produced in the same manner as described above (production of liquid crystal cells).

The liquid crystal cell was observed with a polarizing microscope (ECLIPSE E600 WPOL) (Nikon Co., ltd.). Specifically, a liquid crystal cell is provided in a cross prism (cross prisms), the liquid crystal cell is observed with a polarizing microscope at a magnification of 5 times, the number of confirmed bright points is counted, and a number of bright points less than 10 is referred to as "good", and a number of bright points greater than 10 is referred to as "bad".

< Synthesis example 1>

DA-1.03g (4.20 mmol), DA-2.421g (2.80 mmol) and DA-3.76g (7.00 mmol) were weighed into a 50mL four-necked flask equipped with a stirring apparatus and a nitrogen introduction tube, and NMP 33.60g was added and dissolved with stirring while feeding nitrogen. While stirring the diamine solution, 2.95g (13.16 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and 3.73g of NMP was added so that the solid content concentration became 12 mass%. Thereafter, the mixture was stirred at room temperature for 24 hours, thereby obtaining a polyamic acid solution (a). The polyamic acid solution had a viscosity of 316 mPas at a temperature of 25 ℃. Further, the molecular weight of the polyamic acid was Mn =13530, mw =29850.

Synthesis example 2

DA-1.95g (3.90 mmol), DA-2.98g (6.5 mmol) and DA-4.35g (2.60 mmol) were weighed into a 50mL four-necked flask equipped with a stirrer and a nitrogen introduction tube, and NMP 33.15g was added thereto and dissolved by stirring while feeding nitrogen. While stirring the diamine solution, 2.74g (12.22 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and 3.73g of NMP was added so that the solid content concentration became 12 mass%. Thereafter, the mixture was stirred at room temperature for 24 hours, thereby obtaining a polyamic acid solution (B). The polyamic acid solution had a viscosity of 483 mPas at a temperature of 25 ℃. The molecular weight of the polyamic acid was Mn =14260, mw =30050.

< Synthesis example 3>

1.47g (6.00 mmol) of DA-1.90g (6.00 mmol) and 0.90g (6.00 mmol) of DA-2 were weighed into a 50mL four-necked flask equipped with a stirrer and a nitrogen introduction tube, and 31.96g of NMP was added thereto, and dissolved by stirring while feeding nitrogen. While stirring the diamine solution, 2.60g (11.58 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and 3.55g of NMP was added so that the solid content concentration became 12 mass%. Thereafter, the mixture was stirred at room temperature for 24 hours, thereby obtaining a polyamic acid solution (C). The polyamic acid solution had a viscosity of 423 mPas at a temperature of 25 ℃. The molecular weight of the polyamic acid was Mn =14010, mw =29540.

< Synthesis example 4>

DA-1.59g (6.50 mmol) and DA-3.70g (6.50 mmol) were weighed into a 50mL four-necked flask equipped with a stirrer and a nitrogen introduction tube, and NMP 33.01g was added thereto and dissolved with stirring while feeding nitrogen. While stirring the diamine solution, 2.78g (12.42 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and 3.66g of NMP was added so that the solid content concentration became 12 mass%. Thereafter, the mixture was stirred at room temperature for 24 hours, thereby obtaining a polyamic acid solution (D). The polyamic acid solution had a viscosity of 360 mPas at a temperature of 25 ℃. The molecular weight of the polyamic acid was Mn =13810, mw =28400.

< Synthesis example 5>

DA-1.03g (4.20 mmol), DA-3.76g (7.00 mmol) and DA-4.38g (2.80 mmol) were weighed into a 50mL four-necked flask equipped with a stirring apparatus and a nitrogen introduction tube, and NMP 34.38g was added and dissolved with stirring while feeding nitrogen. While stirring the diamine solution, 3.04g (13.58 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride was added, and 3.82g of NMP was added so that the solid content concentration became 12 mass%. Thereafter, the mixture was stirred at room temperature for 24 hours, thereby obtaining a polyamic acid solution (E). The polyamic acid solution had a viscosity of 428 mPas at a temperature of 25 ℃. The molecular weight of the polyamic acid was Mn =14080, mw =29960.

< Synthesis example 6>

DA-2.13g (7.50 mmol) and DA-3.81g (7.50 mmol) were weighed into a 50mL four-necked flask equipped with a stirrer and a nitrogen introduction tube, and NMP 33.87g was added thereto and dissolved with stirring while feeding nitrogen. While stirring the diamine solution, 3.39g (14.85 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and 3.76g of NMP was added so that the solid content concentration became 12 mass%. Thereafter, the mixture was stirred at room temperature for 24 hours, thereby obtaining a polyamic acid solution (F). The polyamic acid solution had a viscosity of 280 mPas at a temperature of 25 ℃. Further, the molecular weight of the polyamic acid was Mn =12250, mw =26550.

< Synthesis example 7>

To a 50mL four-necked flask equipped with a stirrer and a nitrogen introduction tube, 3.36g (15.00 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was measured, and 3.73g of NMP was added and dissolved by stirring while feeding nitrogen. While the acid dianhydride solution was stirred, 1.13g (12.68 mmol) of DA-5.81g (1.50 mmol) was added, and 7.46g of NMP was added so that the solid content concentration became 10 mass%. Thereafter, stirring was performed at room temperature for 24 hours, thereby obtaining a polyamic acid solution (G). The polyamic acid solution had a viscosity of 460 mPas at a temperature of 25 ℃. Further, the molecular weight of the polyamic acid was Mn =15020, mw =33320.

< example 1>

15.00g of 12 mass% polyamic acid solution (A) was weighed into a 100ml Erlenmeyer flask, and 9.00g of NMP and 6.00g of BCS were added and mixed at 25 ℃ for 8 hours to obtain a liquid crystal aligning agent (1). The liquid crystal aligning agent was confirmed to be a uniform solution without any abnormality such as turbidity and precipitation.

< example 2>

A liquid crystal aligning agent (2) was obtained in the same manner as in example 1, except that 15.00g of 12 mass% polyamic acid solution (B) was used. The liquid crystal aligning agent was confirmed to be a uniform solution without any abnormalities such as turbidity and precipitation.

< example 3>

A liquid crystal aligning agent (3) was obtained in the same manner as in example 1, except that 15.00g of 12 mass% polyamic acid solution (C) was used. The liquid crystal aligning agent was confirmed to be a uniform solution without any abnormality such as turbidity and precipitation.

< comparative example 1>

A liquid crystal aligning agent (4) was obtained in the same manner as in example 1, except that 15.00g of a 12 mass% polyamic acid solution (D) was used. The liquid crystal aligning agent was confirmed to be a uniform solution without any abnormality such as turbidity and precipitation.

< comparative example 2>

A liquid crystal aligning agent (5) was obtained in the same manner as in example 1, except that 15.00g of 12 mass% polyamic acid solution (E) was used. The liquid crystal aligning agent was confirmed to be a uniform solution without any abnormality such as turbidity and precipitation.

< comparative example 3>

A liquid crystal aligning agent (6) was obtained in the same manner as in example 1, except that 15.00g of the 12 mass% polyamic acid solution (F) was used. The liquid crystal aligning agent was confirmed to be a uniform solution without any abnormalities such as turbidity and precipitation.

< comparative example 4>

A liquid crystal aligning agent (7) was obtained in the same manner as in example 1, except that 15.00G of 12 mass% polyamic acid solution (G) was used. The liquid crystal aligning agent was confirmed to be a uniform solution without any abnormality such as turbidity and precipitation.

(example 5)

The liquid crystal aligning agent (1) was filtered through a 1.0 μm filter and then spin-coated on a 30mm × 40mm ITO substrate. The resultant was dried on a hot plate at 80 ℃ for 2 minutes, and then baked in a hot air circulation oven at 230 ℃ for 14 minutes to form a coating film having a thickness of 100 nm. The film surface was irradiated with linearly polarized ultraviolet rays having an extinction ratio of 26 and a wavelength of 254nm through a polarizing plate, to obtain a liquid crystal alignment film.

The height of anisotropy with respect to the alignment direction of the obtained liquid crystal alignment film was measured. The ultraviolet ray irradiation amount is 200mJ/cm ² The anisotropy value was 3.39 and 300mJ/cm ² The anisotropy value was 4.10 and 400mJ/cm ² The anisotropy value was 3.26. Anisotropy becomesThe maximum dose of the ultraviolet ray irradiation is 300mJ/cm ² The optimum irradiation conditions for the photo-alignment treatment were set.

(example 6)

A liquid crystal alignment film was obtained in the same manner as in example 5, except that the liquid crystal alignment agent (2) was used. The magnitude of anisotropy with respect to the alignment direction of the obtained liquid crystal alignment film was measured. The ultraviolet ray irradiation amount is 50mJ/cm ² The anisotropy value was 0.05 and 100mJ/cm ² The anisotropy value was 0.61 and 200mJ/cm ² The anisotropy value was 0.06. The ultraviolet irradiation dose at which the anisotropy becomes highest was 100mJ/cm ² The irradiation conditions are set to be optimal in the photo-alignment treatment.

(example 7)

A liquid crystal alignment film was obtained in the same manner as in example 5, except that the liquid crystal alignment agent (3) was used. The magnitude of anisotropy with respect to the alignment direction of the obtained liquid crystal alignment film was measured. The ultraviolet ray irradiation amount is 50mJ/cm ² The anisotropy value was 0.10 and 100mJ/cm ² The anisotropy value was 0.92 and 200mJ/cm ² The anisotropy value was 0.15. The ultraviolet ray irradiation amount at which the anisotropy becomes the highest was 100mJ/cm ² The irradiation conditions are set to be optimal in the photo-alignment treatment.

Comparative example 5

A liquid crystal alignment film was obtained in the same manner as in example 5, except that the liquid crystal alignment agent (4) was used. The magnitude of anisotropy with respect to the alignment direction of the obtained liquid crystal alignment film was measured. The ultraviolet ray irradiation amount is 100mJ/cm ² The anisotropy value was 3.02 and 200mJ/cm ² The anisotropy value was 5.37 and 300mJ/cm ² The anisotropy value was 3.40. The ultraviolet irradiation dose at which the anisotropy became maximum was 200mJ/cm ² The irradiation conditions are set to be optimal in the photo-alignment treatment.

Comparative example 6

A liquid crystal alignment film was obtained in the same manner as in example 5, except that the liquid crystal alignment agent (5) was used. The liquid crystal alignment film obtained was measured for alignmentMagnitude of the directional anisotropy. The dose of the ultraviolet ray is 200mJ/cm ² The anisotropy value was 4.28 and 300mJ/cm ² The anisotropy value was 4.57 and 400mJ/cm ² The anisotropy value was 3.03. The ultraviolet irradiation dose at which the anisotropy became maximum was 300mJ/cm ² The irradiation conditions are set to be optimal in the photo-alignment treatment.

Comparative example 7

A liquid crystal alignment film was obtained in the same manner as in example 5, except that the liquid crystal alignment agent (6) was used. The magnitude of anisotropy with respect to the alignment direction of the obtained liquid crystal alignment film was measured. The ultraviolet ray irradiation amount is 300mJ/cm ² The anisotropy value was 0.54 and 400mJ/cm ² The anisotropy value was 0.65 and 500mJ/cm ² The anisotropy value was 0.60. The ultraviolet irradiation amount at which the anisotropy became maximum was 400mJ/cm ² The irradiation conditions are set to be optimal in the photo-alignment treatment.

Comparative example 8

A liquid crystal alignment film was obtained in the same manner as in example 5, except that the liquid crystal alignment agent (7) was used. The magnitude of anisotropy with respect to the alignment direction of the obtained liquid crystal alignment film was measured. The dose of the ultraviolet ray is 400mJ/cm ² The anisotropy value was 1.61 and 600mJ/cm ² The anisotropy value was 1.71 and 800mJ/cm ² The anisotropy value was 1.59. The ultraviolet irradiation dose at which the anisotropy became maximum was 600mJ/cm ² The optimum irradiation conditions for the photo-alignment treatment were set.

The measurement results of the magnitude of anisotropy with respect to the alignment direction of the liquid crystal alignment films obtained in examples 5 to 7 and comparative examples 5 to 8 are summarized in table 1.

[ Table 1]

(example 8)

The liquid crystal aligning agent (1) was filtered through a 1.0 μm filterThe substrate with electrodes and the glass substrate having an ITO film formed on the back surface and a columnar spacer having a height of 4 μm were prepared and coated by spin coating. The resultant was dried on a hot plate at 80 ℃ for 5 minutes, and then baked in a hot air circulating oven at 230 ℃ for 20 minutes to form a coating film having a thickness of 100 nm. The coated surface was irradiated with linearly polarized ultraviolet rays having an extinction ratio of 26 and a wavelength of 254nm of 0.3J/cm through a polarizing plate ² . Thereafter, the substrate was heated on a hot plate at 230 ℃ for 14 minutes to obtain a substrate with a liquid crystal alignment film. The 2 substrates were used as one set, a sealant was printed on the substrates, and another 1 substrate was attached so that the liquid crystal alignment films faced each other and the alignment direction became 0 °, and then the sealant was cured to prepare an empty cell. Liquid crystal MLC-7026-100 (manufactured by MERCK CORPORATION) was injected into the empty cell by a reduced pressure injection method, and the injection port was sealed, thereby obtaining an FFS-driven liquid crystal cell. Thereafter, the resulting liquid crystal cell was heated at 110 ℃ for 1 hour, then left overnight, and evaluation of afterimage by long-term ac driving was performed. The angle Δ of the liquid crystal cell after long-term ac driving was 0.04 degrees. Further, as a result of observation of the bright spots in the cell, the number of bright spots was less than 10, which was good.

(example 9)

A coating film having a film thickness of 100nm was formed in the same manner as in example 8, except that the liquid crystal aligning agent (2) was used. The coated surface was irradiated with linearly polarized ultraviolet rays having an extinction ratio of 26 and a wavelength of 254nm of 0.1J/cm through a polarizing plate ² Then, the substrate was heated on a hot plate at 230 ℃ for 14 minutes to obtain a substrate with a liquid crystal alignment film. An FFS-driven liquid crystal cell was produced in the same manner as in example 8, except that the substrate with a liquid crystal alignment film was used, and the cell obtained was subjected to an afterimage evaluation by long-term ac driving. The angle Δ of the liquid crystal cell after long-term ac driving was 0.10 degrees. Further, as a result of observation of the bright spots in the cell, the number of bright spots was less than 10, which was good.

(example 10)

An FFS driving liquid crystal cell was produced in the same manner as in example 9, except that the liquid crystal cell was immersed in 2-propanol for 3 minutes and then in pure water for 1 minute after irradiation with polarized ultraviolet light. The FFS-driven liquid crystal cell is subjected to afterimage evaluation by long-term ac driving. The angle Δ value of the liquid crystal cell after long-term ac driving was 0.08 degrees. Further, as a result of observation of the bright spots in the cell, the number of bright spots was less than 10, which was good.

(example 11)

A coating film having a film thickness of 100nm was formed in the same manner as in example 8, except that the liquid crystal aligning agent (3) was used. The coated film surface was irradiated with linearly polarized ultraviolet rays having an extinction ratio of 26 ² Thereafter, the resultant was immersed in 2-propanol for 3 minutes and then in pure water for 1 minute. Thereafter, the substrate was heated on a hot plate at 230 ℃ for 14 minutes to obtain a substrate with a liquid crystal alignment film attached thereto. An FFS-driven liquid crystal cell was produced in the same manner as in example 8, except that the substrate with a liquid crystal alignment film was used, and the resulting cell was subjected to afterimage evaluation by long-term ac driving. The angle Δ value of the liquid crystal cell after long-term ac driving was 0.08 degrees. Further, as a result of observation of the bright spots in the cell, the number of bright spots was less than 10, which was good.

Comparative example 9

A coating film having a film thickness of 100nm was formed in the same manner as in example 8, except that the above-mentioned liquid crystal aligning agent (4) was used. The coated surface was irradiated with linearly polarized ultraviolet rays having an extinction ratio of 26 and a wavelength of 254nm of 0.2J/cm through a polarizing plate ² . Thereafter, the substrate was heated on a hot plate at 230 ℃ for 14 minutes to obtain a substrate with a liquid crystal alignment film attached thereto. An FFS-driven liquid crystal cell was produced in the same manner as in example 8, except that the substrate with a liquid crystal alignment film was used, and the cell obtained was subjected to an afterimage evaluation by long-term ac driving. The angle Δ value of the liquid crystal cell after long-term ac driving was 0.15 degrees. Further, as a result of observation of the bright spots in the cell, the number of bright spots was 10 or more, which was a defect.

Comparative example 10

A film was formed by the same method as in example 8 except that the above-mentioned liquid crystal aligning agent (5) was usedA coating film having a thickness of 100 nm. The coated surface was irradiated with linearly polarized ultraviolet rays having an extinction ratio of 26 and a wavelength of 254nm of 0.3J/cm through a polarizing plate ² . Thereafter, the substrate was heated on a hot plate at 230 ℃ for 14 minutes to obtain a substrate with a liquid crystal alignment film. An FFS-driven liquid crystal cell was produced in the same manner as in example 8, except that the substrate with a liquid crystal alignment film was used, and the cell obtained was subjected to an afterimage evaluation by long-term ac driving. The angle Δ of the liquid crystal cell after long-term ac driving was 0.20 degrees. Further, as a result of observation of the bright spots in the cell, the number of bright spots was 10 or more, which was a defect.

Comparative example 11

A coating film having a film thickness of 100nm was formed in the same manner as in example 8, except that the liquid crystal aligning agent (6) was used. The coated surface was irradiated with linearly polarized ultraviolet rays having an extinction ratio of 26 and a wavelength of 254nm of 0.4J/cm through a polarizing plate ² . Thereafter, the substrate was heated on a hot plate at 230 ℃ for 14 minutes to obtain a substrate with a liquid crystal alignment film. An FFS-driven liquid crystal cell was produced in the same manner as in example 8, except that the substrate with a liquid crystal alignment film was used, and the cell obtained was subjected to an afterimage evaluation by long-term ac driving. The angle Δ of the liquid crystal cell after long-term ac driving was 0.20 degrees. Further, as a result of observation of the bright spots in the cell, the number of bright spots was 10 or more, which was a defect.

Comparative example 12

A coating film having a film thickness of 100nm was formed in the same manner as in example 8, except that the above-mentioned liquid crystal aligning agent (7) was used. The coated surface was irradiated with linearly polarized ultraviolet rays having an extinction ratio of 26 and a wavelength of 254nm of 0.6J/cm through a polarizing plate ² . Thereafter, the substrate was heated on a hot plate at 230 ℃ for 14 minutes to obtain a substrate with a liquid crystal alignment film attached thereto. An FFS-driven liquid crystal cell was produced in the same manner as in example 8, except that the substrate with a liquid crystal alignment film was used, and the cell obtained was subjected to an afterimage evaluation by long-term ac driving. The angle Δ of the liquid crystal cell after long-term ac driving was 0.24 degrees. In addition, observation of bright spots in the cells was performed, and as a result, the bright spots were numerousWhen the number is 10 or more, the number is not less than 10.

[ Table 2]

	Evaluation of Bright Point	Afterimage evaluation (orientation)
			Example 8	Is good	0.04°
Example 9	Good effect	0.10°
			Example 10	Good effect	0.08°
Example 11	Is good	0.12°
			Comparative example 9	Failure to meet the requirements	0.15°
Comparative example 10	Good effect	0.20°
			Comparative example11	Good effect	0.20°
Comparative example 12	Failure to meet the requirements	0.24°

Industrial applicability

The liquid crystal alignment film obtained from the liquid crystal alignment agent of the present invention has fewer bright spots, which are factors of contrast reduction, can reduce afterimages caused by alternating current driving generated in the liquid crystal display elements of the IPS driving method and the FFS driving method, and can obtain the liquid crystal display elements of the IPS driving method and the FFS driving method which have excellent afterimage characteristics.

The liquid crystal display element having the liquid crystal alignment film of the present invention is excellent in reliability, and can be widely used for liquid crystal televisions, medium and small sized car navigation systems, smart phones, and the like, which are large in size, high in definition, and seek high display quality.

The entire contents of the specification, claims and abstract of japanese patent application No. 2014-219597 filed on 10/28/2014 are incorporated herein as the disclosure of the present invention specification.

Claims

1. A liquid crystal aligning agent for a photo-alignment method, comprising at least 1 polymer (A) selected from the group consisting of a polyimide precursor having a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2) and an imidized polymer of the polyimide precursor,

the structural unit represented by the formula (1) and the structural unit represented by the following formula (2) are present in the same polyimide precursor,

the liquid crystal aligning agent is used for forming a liquid crystal aligning film in a liquid crystal display element of which the liquid crystal is a negative liquid crystal material,

in the formulae (1) and (2), X ₁ And X ₂ Each independently has a structure represented by the following formula (X1-2); r ₁ 、R ₂ 、R ₃ 、R ₄ And R ₆ Each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; r ₅ An alkyl group having 1 to 4 carbon atoms; n is an integer of 2, and n is an integer of 2,

2. the liquid crystal aligning agent according to claim 1, wherein the content of the structural unit represented by the formula (1) is 10 to 50 mol% based on 1 mol of the total structural units of the polymer (A), and the content of the structural unit represented by the formula (2) is 20 to 90 mol% based on 1 mol of the total structural units of the polymer (A).

3. The liquid crystal aligning agent according to claim 1 or 2, wherein R in formula (1) and formula (2) ₁ And R ₂ Each independently is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ₃ 、R ₄ And R ₆ Is a hydrogen atom, R ₅ Is methyl.

4. The liquid crystal aligning agent according to claim 1 or 2, which contains the polymer (A) in an amount of 2 to 10% by mass.

5. A method for producing a liquid crystal alignment film, wherein a film obtained by applying and firing a liquid crystal alignment agent is irradiated with polarized ultraviolet rays,

the manufacturing method further comprises heating at a temperature of 150-250 ℃,

the liquid crystal aligning agent is used for a photo-alignment method, and contains at least 1 polymer (A) selected from the group consisting of a polyimide precursor and an imidized polymer of the polyimide precursor, wherein the polyimide precursor has a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2),

the liquid crystal alignment film is a liquid crystal alignment film in a liquid crystal display element in which liquid crystal is a negative-type liquid crystal material,

in the formulas (1) and (2), X ₁ And X ₂ Each independently has a structure represented by the following formula (X1-2); r ₁ 、R ₂ 、R ₃ 、R ₄ And R ₆ Each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; r ₅ An alkyl group having 1 to 4 carbon atoms; n is an integer of 2, and n is an integer of 2,

6. a method for producing a liquid crystal alignment film, wherein a film obtained by applying and firing a liquid crystal alignment agent is irradiated with polarized ultraviolet rays,

the method further comprises subjecting the liquid crystal alignment film irradiated with the polarized radiation to a contact treatment using water and/or a solvent,

in the formulae (1) and (2), X ₁ And X ₂ Each independently has a structure represented by the following formula (X1-2); r is ₁ 、R ₂ 、R ₃ 、R ₄ And R ₆ Each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; r ₅ Is an alkyl group having 1 to 4 carbon atoms; n is an integer of 2, and n is an integer of 2,

7. the method for producing a liquid crystal alignment film according to claim 5 or 6, wherein the content ratio of the structural unit represented by the formula (1) is 10 to 50 mol% based on 1 mol of the total structural units of the polymer (A), and the content ratio of the structural unit represented by the formula (2) is 20 to 90 mol% based on 1 mol of the total structural units of the polymer (A).

8. The method for producing a liquid crystal alignment film according to claim 5 or 6, wherein R is represented by formula (1) or formula (2) ₁ And R ₂ Each independently is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ₃ 、R ₄ And R ₆ Is a hydrogen atom, R ₅ Is methyl.

9. The method for producing a liquid crystal alignment film according to claim 5 or 6, wherein the polarized ultraviolet ray has a wavelength of 100 to 800 nm.

10. A liquid crystal alignment film obtained by the production method according to any one of claims 5 to 9.

11. A liquid crystal display element having a liquid crystal alignment film obtained by the production method according to any one of claims 5 to 9, wherein the liquid crystal is a negative-type liquid crystal material.

12. The liquid crystal display element according to claim 11, wherein the liquid crystal display element is of an FFS type.

13. A liquid crystal display element of FFS system having a liquid crystal alignment film formed from a liquid crystal aligning agent for photo-alignment,

the liquid crystal aligning agent contains at least 1 polymer (A) selected from the group consisting of a polyimide precursor and an imidized polymer of the polyimide precursor, wherein the polyimide precursor has a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2),

the liquid crystal is a negative type liquid crystal material,

14. the liquid crystal display element according to claim 13, wherein a content ratio of the structural unit represented by the formula (1) is 10 to 50 mol% based on 1 mol of the total structural units of the polymer (a), and a content ratio of the structural unit represented by the formula (2) is 20 to 90 mol% based on 1 mol of the total structural units of the polymer (a).

15. The liquid crystal display element according to claim 13 or 14, wherein R is represented by formula (1) or formula (2) ₁ And R ₂ Each independently is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ₃ 、R ₄ And R ₆ Is a hydrogen atom, R ₅ Is methyl.