JPWO2020158818A1 - Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element using it - Google Patents

Abstract

Provided is a liquid crystal alignment agent capable of obtaining a liquid crystal alignment film having both high DC luminance relaxation speed and suppression of flicker change. A liquid crystal alignment agent containing the following polymer (A), polymer (B) and polymer (C). Polymer (A): At least one polymer selected from the group consisting of the following (i) to (iii). (I) Consists of a diamine component containing at least one diamine selected from the group consisting of a diamine represented by the formula [1] and a diamine represented by the formula [2], and an aromatic tetracarboxylic acid dianhydride. A polyamic acid obtained by polymerizing with a tetracarboxylic acid component. (Ii) A polymerization reaction of a diamine component containing at least one diamine selected from the group consisting of a diamine represented by the formula [1] and a diamine represented by the formula [2] with a tetracarboxylic acid component. The polyamic acid ester obtained by. (Iii) A diamine component containing at least one diamine selected from the group consisting of a diamine represented by the formula [1] and a diamine represented by the formula [2] is polymerized and reacted with a tetracarboxylic acid component. A polyimide obtained by imidizing the obtained polyimide precursor. Polymer (B): Consists of a polyimide precursor obtained by polymerizing a diamine-containing diamine component represented by the formula [3] and a tetracarboxylic acid component, and a polyimide obtained from the polyimide precursor. At least one polymer selected from the group. Polymer (C): A diamine component (however, the diamine component does not contain a diamine represented by the formula [3]) and an alicyclic tetracarboxylic acid dianhydride and / or an aliphatic tetracarboxylic acid dianhydride. A polyamic acid obtained by polymerizing a tetracarboxylic acid component composed of a substance. (Equations [1] to [3] are defined in the specification.)

Description

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

A polyimide-based resin film is widely used as a liquid crystal alignment film used for a liquid crystal display element or the like. This polyimide-based liquid crystal alignment film is produced by applying a liquid crystal alignment agent containing a polymer such as polyamic acid (also referred to as polyamic acid), polyamic acid ester, or polyimide and a solvent as main components to a substrate.

In recent years, the performance of liquid crystal display elements has been improved, the area has been increased, and the power consumption of display devices has been reduced. In addition, liquid crystal display elements have been used in various environments. Problems have become prominent. For example, static electricity is likely to be accumulated in the liquid crystal cell, and the electric charge accumulated in the liquid crystal alignment film affects the display as a disorder of the liquid crystal alignment or an afterimage, and significantly deteriorates the display quality of the liquid crystal display element. Further, the magnitude of flicker changes due to the application of a positive / negative asymmetric voltage due to the accumulation of electric charges generated by the driving when the liquid crystal panel is driven for a long time.

Patent Documents 1 to 4 describe liquid crystal alignment agents containing polyamic acids obtained from low resistance materials such as 4,4'-diaminodiphenylamine (DADPA).
However, when a low resistance material is used in the production of polyamic acid, the DC luminance relaxation rate becomes high, but the change in flicker may become large. On the contrary, when a material that suppresses the change of flicker is used in the production of polyamic acid, the DC luminance relaxation rate may be slowed down. That is, in the conventional liquid crystal alignment film, there is a trade-off relationship between the rapid DC luminance relaxation speed and the suppression of the change in flicker, and there is a case where both are not combined, which has been a problem.
In addition to this, when a low resistance material is used, the transmittance of the substrate may be lowered due to coloring, which has been a problem.

Japanese Patent No. 5900328 International Publication No. 2018/062440 Japanese Patent No. 6280701 Japanese Patent No. 6314488

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a liquid crystal alignment agent capable of obtaining a liquid crystal alignment film having both high DC luminance relaxation speed and suppression of flicker change. Another object of the present invention is to provide a liquid crystal alignment agent that can obtain a liquid crystal alignment film having a high transmittance of a substrate even when a low resistance material is used.

（式［１］及び［２］中、Ａ_１は単結合、エーテル結合、エステル結合、−Ｃ＝Ｃ−、−Ｃ≡Ｃ−、炭素数２〜２０のアルキレン基、又は該アルキレン基中の−ＣＨ_２−の一部又は全部がエーテル結合、エステル結合、−Ｃ＝Ｃ−、−Ｃ≡Ｃ−、シクロヘキシレン基及びフェニレン基からなる群から選ばれる少なくとも１種の基で置き換えられた基、シクロヘキシレン基又はフェニレン基である。Ａ_２は、フッ素原子、又は炭素数１〜５のアルキル基若しくはアルコキシ基（但し、該アルキル基若しくはアルコキシ基の任意の水素原子は、フッ素原子で置換されていてもよい。）である。ａは０〜４の整数であり、ａが２以上の整数である場合、Ａ_２は同一でも異なってもよい。ｂ及びｃはそれぞれ独立して１〜２の整数である。）；
重合体（Ｂ）：下記式［３］で表されるジアミンを含有するジアミン成分と、テトラカルボン酸成分とを重合反応させることにより得られるポリイミド前駆体、及び該ポリイミド前駆体から得られるポリイミドからなる群から選ばれる少なくとも一種の重合体。

（式中、Ｘは、５員環又は６員環の含窒素芳香族複素環を構成する炭素原子に芳香族炭化水素環が結合した構造を有するか、

で示される構造を有し、＊はカルボニル基を除く構造に結合し、かつ少なくとも１つは芳香環基と結合する。）；
重合体（Ｃ）：ジアミン成分（但し、該ジアミン成分は前記式［３］で表されるジアミンを含まない。）と、脂環式テトラカルボン酸二無水物及び／又は脂肪族テトラカルボン酸二無水物からなるテトラカルボン酸成分とを重合反応させることにより得られるポリアミド酸。As a result of diligent studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems are satisfied by a specific liquid crystal alignment agent.
A liquid crystal alignment agent containing the following polymer (A), polymer (B) and polymer (C).
Polymer (A): At least one polymer selected from the group consisting of the following (i) to (iii).
(I) A diamine component containing at least one diamine selected from the group consisting of a diamine represented by the following formula [1] and a diamine represented by the following formula [2], and an aromatic tetracarboxylic acid dianhydride. A polyamic acid obtained by polymerizing with a tetracarboxylic acid component composed of.
(Ii) Polymerization reaction of a diamine component containing at least one diamine selected from the group consisting of a diamine represented by the following formula [1] and a diamine represented by the following formula [2] and a tetracarboxylic acid component. Polyamic acid ester obtained by allowing.
(Iii) Polymerization reaction of a diamine component containing at least one diamine selected from the group consisting of a diamine represented by the following formula [1] and a diamine represented by the following formula [2] and a tetracarboxylic acid component. A polyimide obtained by imidizing a polyimide precursor obtained by subjecting the mixture to imidization.

(In the formulas [1] and [2], A ₁ is a single bond, an ether bond, an ester bond, -C = C-, -C≡C-, an alkylene group having 2 to 20 carbon atoms, or a group thereof. A group in which part or all of −CH ₂ − is replaced with at least one group selected from the group consisting of an ether bond, an ester bond, −C = C−, −C≡C−, a cyclohexylene group and a phenylene group. , Cyclohexylene group or phenylene group. A ₂ is a fluorine atom, or an alkyl group or an alkoxy group having 1 to 5 carbon atoms (provided that any hydrogen atom of the alkyl group or alkoxy group is substituted with a fluorine atom. A is an integer of 0 to 4, and when a is an integer of 2 or more, A ₂ may be the same or different. B and c are independently 1 to 2, respectively. It is an integer of.);
Polymer (B): From a polyimide precursor obtained by polymerizing a diamine-containing diamine component represented by the following formula [3] with a tetracarboxylic acid component, and a polyimide obtained from the polyimide precursor. At least one type of polymer selected from the group.

(In the formula, X has a structure in which an aromatic hydrocarbon ring is bonded to a carbon atom constituting a nitrogen-containing aromatic heterocycle having a 5-membered ring or a 6-membered ring.

It has a structure represented by, * is bonded to a structure excluding a carbonyl group, and at least one is bonded to an aromatic ring group. );
Polymer (C): Diamine component (however, the diamine component does not contain the diamine represented by the above formula [3]), an alicyclic tetracarboxylic acid dianhydride and / or an aliphatic tetracarboxylic acid dianiba. A polyamic acid obtained by polymerizing a tetracarboxylic acid component composed of an anhydride.

According to the liquid crystal alignment agent of the present invention, it is possible to obtain a liquid crystal alignment film having both high DC luminance relaxation speed and suppression of flicker change. Further, according to the liquid crystal alignment agent of the present invention, a liquid crystal alignment film having a high transmittance of a substrate can be obtained even when a low resistance material is used.

（式［１］及び［２］中、Ａ_１は単結合、エーテル結合、エステル結合、−Ｃ＝Ｃ−、−Ｃ≡Ｃ−、炭素数２〜２０のアルキレン基、又は該アルキレン基中の−ＣＨ_２−の一部又は全部がエーテル結合、エステル結合、−Ｃ＝Ｃ−、−Ｃ≡Ｃ−、シクロヘキシレン基及びフェニレン基からなる群から選ばれる少なくとも１種の基で置き換えられた基、シクロヘキシレン基又はフェニレン基である。Ａ_２は、フッ素原子、又は炭素数１〜５のアルキル基若しくはアルコキシ基（但し、該アルキル基若しくはアルコキシ基の任意の水素原子は、フッ素原子で置換されていてもよい。）である。ａは０〜４の整数であり、ａが２以上の整数である場合、Ａ_２は同一でも異なってもよい。ｂ及びｃはそれぞれ独立して１〜２の整数である。）<Polymer (A)>
The polymer (A) contained in the liquid crystal alignment agent of the present invention is the following polymer.
Polymer (A): At least one polymer selected from the group consisting of the following (i) to (iii).
(I) From a diamine component containing at least one diamine selected from the group consisting of a diamine represented by the following formula [1] and a diamine represented by the formula [2], and an aromatic tetracarboxylic acid dianhydride. Polyamide acid obtained by polymerizing with the tetracarboxylic acid component.
(Ii) A diamine component containing at least one diamine selected from the group consisting of a diamine represented by the following formula [1] and a diamine represented by the formula [2] is polymerized with a tetracarboxylic acid component. The polyamic acid ester obtained by this.
(Iii) A diamine component containing at least one diamine selected from the group consisting of a diamine represented by the following formula [1] and a diamine represented by the formula [2] is polymerized and reacted with a tetracarboxylic acid component. A polyimide obtained by imidizing the polyimide precursor obtained in the above process.

(In the formulas [1] and [2], A ₁ is a single bond, an ether bond, an ester bond, -C = C-, -C≡C-, an alkylene group having 2 to 20 carbon atoms, or a group thereof. A group in which part or all of −CH ₂ − is replaced with at least one group selected from the group consisting of an ether bond, an ester bond, −C = C−, −C≡C−, a cyclohexylene group and a phenylene group. , Cyclohexylene group or phenylene group. A ₂ is a fluorine atom, or an alkyl group or an alkoxy group having 1 to 5 carbon atoms (provided that any hydrogen atom of the alkyl group or alkoxy group is substituted with a fluorine atom. A is an integer of 0 to 4, and when a is an integer of 2 or more, A ₂ may be the same or different. B and c are independently 1 to 2, respectively. It is an integer of.)

(Diamine component for producing the polymer (A))
The diamine component for producing the polymer (A) contains at least one diamine selected from the group consisting of the diamine represented by the above formula [1] and the diamine represented by the formula [2]. be.
In the above formulas [1] to [2], A ₁ is a single bond, -C = C-, -C≡C-, an alkylene group having 2 to 10 carbon atoms, or -CH _2- in the alkylene group. A group, a cyclohexylene group or a group in which part or all is replaced with at least one group selected from the group consisting of an ether bond, an ester bond, -C = C-, -C≡C-, a cyclohexylene group and a phenylene group. It is preferably a phenylene group, A ₂ is CH ₃ , a is an integer of 0 to 1, b is 1 and c is an integer of 1 to 2.

Examples of diamines represented by the formulas [1] to [2] include the following.

The amount of the diamine represented by the formulas [1] and [2] is 30 to 100 mol%, more preferably 40 to 100, based on the total amount of the diamine component for producing the polymer (A). It is mol%, more preferably 50 to 100 mol%.

Further, as the diamine component for producing the polymer (A) contained in the liquid crystal alignment agent of the present invention, any diamine other than the diamines represented by the formulas [1] and [2] (hereinafter, "others"). Also referred to as "diamine"). Specific examples of other diamines include 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4- (2- (methylamino) ethyl) aniline, 4- (2-aminoethyl) aniline, 4, 4'-diaminobenzophenone, 4,4'-diaminoazobenzene, 1- (4-aminophenyl) -1,3,3-trimethyl-1H-indan-5-amine, 1- (4-aminophenyl) -2, 3-Dihydro-1,3,3-trimethyl-1H-inden-6-amine, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,7-diaminonaphthalene, 2, 2'-bis [4- (4-aminophenoxy) phenyl] propane, 2,2'-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 2,2'-bis (4-aminophenyl) Diamines having photopolymerizable groups such as propane, 2- (2,4-diaminophenoxy) ethyl methacrylate, 2,4-diamino-N, N-diallylaniline at the ends, cholestanoloxy-3,5-diaminobenzene , Cholestenyloxy-3,5-diaminobenzene, cholestanoloxy-2,4-diaminobenzene, 3,5-diaminobenzoate cholestanyl, 3,5-diaminobenzoate cholestenyl, 3,5-diaminobenzoate lanostannyl, A diamine having a steroid skeleton such as 3,6-bis (4-aminobenzoyloxy) cholesterol, a diamine represented by the following formulas (V-1) to (V-6),

(In the above equations (V-1) to (V-6), X ^{v1 to} X ^v4 and X ^{p1 to} X ^p8 are independently − (CH _{2 ) a} − (a is an integer of 1 to 15). ), _{-CONH-, -NHCO-, -CON (CH 3} )-, _{-NH-, -O-, -CH 2} O-, -CH ₂ OCO-, -COO-, or -OCO- X ^v5 represents -O-, -CH ₂ O-, -CH ₂ OCO-, -COO-, or -OCO-. Xa is a single bond, -O-, -NH-, -O- (CH _2). ) _m -O- (m represents a represents.) an integer of ^{1~6, R v1 ~R v4, R} 1a ~R 1b are each independently an alkyl group having 1 to 20 carbon atoms, 1 to carbon atoms 20 alkoxy groups or alkoxyalkyl groups having 2 to 20 carbon atoms), diamines having a siloxane bond such as 1,3-bis (3-aminopropyl) -tetramethyldisiloxane, the following formula (5-1). Aromas such as diamines having a group such as (5-11) "-N (D)-" (D represents a protective group desorbed by heating and replaced with a hydrogen atom, preferably a t-butoxycarbonyl group). Alicyclic diamines such as group diamines, metaxylylene diamines, ethylenediamines, 1,3-propanediamines, tetramethylenediamines and hexamethylenediamines, p-cyclohexanediamines and 4,4'-methylenebis (cyclohexylamines). Diamine can be mentioned.

（Ｂｏｃはｔ−ブトキシカルボニル基を表す。）

(Boc represents a t-butoxycarbonyl group.)

The diamine component for producing the polymer (A) of the present invention includes the solubility of the polymer (A) in a solvent, the coatability of a liquid crystal alignment agent, the liquid crystal orientation when a liquid crystal alignment film is used, and the voltage retention rate. , 1 type or a mixture of 2 or more types may be used depending on the characteristics such as accumulated charge.

(Tetracarboxylic acid component for producing the polymer (A))
The tetracarboxylic acid component for producing the (i) polyamic acid of the polymer (A) consists of an aromatic tetracarboxylic dianhydride.
Here, the aromatic tetracarboxylic dianhydride is an acid dianhydride obtained by intramolecular dehydration of four carboxyl groups bonded to the same or different aromatic rings. In this case, if there is only one aromatic ring, an acid dianhydride obtained by intramolecular dehydration of the four carboxyl groups bonded to the aromatic ring is preferable. If there are two or more aromatic rings, the acid obtained by intramolecular dehydration of two carboxyl groups bonded to one aromatic ring and intramolecular dehydration of two carboxyl groups bonded to another aromatic ring. Bianhydride or a carboxyl group bonded to one of two adjacent aromatic rings and a carboxyl group bonded to the other are dehydrated intramolecularly, and a carboxyl group bonded to one of the two adjacent aromatic rings and the other Acid dianhydride obtained by intramolecular dehydration of the carboxyl group bonded to is preferable.

Examples of the aromatic tetracarboxylic dianhydride include compounds represented by the following formula (3a-1).

In the above formula, X ₁ is any of the following formulas (A-1) to (A-28). * Represents a bond.

As the tetracarboxylic acid component for producing the (ii) polyamic acid ester or (iii) polyimide of the polymer (A), any tetracarboxylic dianhydride or a derivative thereof (tetracarboxylic acid, tetracarboxylic acid dihalide) , Tetracarboxylic acid dialkyl ester, or tetracarboxylic acid dialkyl ester dihalide) can be used.
The tetracarboxylic acid component for producing the (ii) polyamic acid ester or (iii) polyimide of the polymer (A) is preferably an aromatic tetracarboxylic dianhydride, an alicyclic tetracarboxylic dianhydride, or an alicyclic tetracarboxylic dianhydride. It consists of an aliphatic tetracarboxylic dianhydride or a derivative thereof. Examples of the aromatic tetracarboxylic acid dianhydride include those described above, and the alicyclic tetracarboxylic acid dianhydride or the aliphatic tetracarboxylic acid dianhydride is an alicyclic tetracarboxylic in the polymer (C). Acid dianhydride or aliphatic tetracarboxylic acid dianhydride can be mentioned. Preferred specific examples of the aromatic tetracarboxylic acid dianhydride for producing the (ii) polyamic acid ester of the polymer (A) or the (iii) polyimide include the compound represented by the above formula (3a-1). Preferred specific examples of the alicyclic tetracarboxylic acid dianhydride or the aliphatic tetracarboxylic acid dianhydride include compounds represented by the following formula (3c-1) described later.

The tetracarboxylic acid component for producing the polymer (A) of the present invention includes the solubility of the polymer (A) in a solvent, the coatability of a liquid crystal alignment agent, the liquid crystal orientation in the case of a liquid crystal alignment film, and the voltage. Depending on the characteristics such as retention rate and accumulated charge, one kind or two or more kinds may be mixed and used.

（式中、Ｘは、５員環又は６員環の含窒素芳香族複素環を構成する炭素原子に芳香族炭化水素環が結合した構造を有するか、

で示される構造を有し、＊はカルボニル基を除く構造に結合し、かつ少なくとも１つは芳香環基と結合する。）<Polymer (B)>
The polymer (B) contained in the liquid crystal alignment agent of the present invention is the following polymer.
Polymer (B): From a polyimide precursor obtained by polymerizing a diamine-containing diamine component represented by the following formula [3] with a tetracarboxylic acid component, and a polyimide obtained from the polyimide precursor. At least one type of polymer selected from the group.

(In the formula, X has a structure in which an aromatic hydrocarbon ring is bonded to a carbon atom constituting a nitrogen-containing aromatic heterocycle having a 5-membered ring or a 6-membered ring.

It has a structure represented by, * is bonded to a structure excluding a carbonyl group, and at least one is bonded to an aromatic ring group. )

The "aromatic ring group" means an n-valent group obtained by removing n hydrogen atoms from the aromatic ring, and specific examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, and pyrene. Examples include a ring, a perylene ring, and a terylene ring. Specific examples of the 5-membered or 6-membered nitrogen-containing aromatic heterocycle include a pyrrole ring and a pyridine ring. Specific examples of the aromatic hydrocarbon ring include a benzene ring and a naphthalene ring.

（式中、＊は結合手を表す。但し、式［３−３］において、含窒素芳香族複素環を構成する炭素原子からの結合手の少なくとも一つは芳香族炭化水素環が結合する。）The diamine represented by the formula [3] preferably has a structure represented by the following formulas [3-1] to [3-3].

(In the formula, * represents a bond. However, in the formula [3-3], at least one of the bonds from the carbon atom constituting the nitrogen-containing aromatic heterocycle is bonded to the aromatic hydrocarbon ring. )

Examples of the diamine represented by the formula [3] include the following.

The amount of the diamine represented by the formula [3] is 30 to 100 mol%, more preferably 40 to 100 mol%, and further preferably 40 to 100 mol% with respect to the total amount of the diamine component for producing the polymer (B). It is preferably 50 to 100 mol%.

As the diamine component for producing the polymer (B) contained in the liquid crystal alignment agent of the present invention, any diamine other than the diamine represented by the formula [3], for example, the other diamine can be used. ..
The diamine component for producing the polymer (B) of the present invention includes the solubility of the polymer (B) in a solvent, the coatability of a liquid crystal alignment agent, the liquid crystal orientation when a liquid crystal alignment film is used, and the voltage retention rate. , 1 type or a mixture of 2 or more types may be used depending on the characteristics such as accumulated charge.

Any tetracarboxylic dianhydride or a derivative thereof can be used as the tetracarboxylic dianhydride component for producing the polymer (B) contained in the liquid crystal alignment agent of the present invention. More preferable specific examples of the tetracarboxylic dianhydride for producing the polymer (B) are the aromatic tetracarboxylic dianhydride for producing the polymer (A) and the alicyclic tetracarboxylic acid. Examples thereof include dianhydride or aliphatic tetracarboxylic dianhydride. Preferred specific examples of the aromatic tetracarboxylic dianhydride include the compound represented by the above formula (3a-1), and the alicyclic tetracarboxylic dianhydride or the aliphatic tetracarboxylic dianhydride is preferable. Specific examples include compounds represented by the following formula (3c-1), which will be described later.
The tetracarboxylic acid component for producing the polymer (B) of the present invention includes the solubility of the polymer (B) in a solvent, the coatability of a liquid crystal alignment agent, the liquid crystal orientation in the case of a liquid crystal alignment film, and the voltage. Depending on the characteristics such as retention rate and accumulated charge, one kind or two or more kinds may be mixed and used.

<Polymer (C)>
The polymer (C) contained in the liquid crystal alignment agent of the present invention is the following polymer.
Polymer (C): A diamine component (however, the diamine component does not contain a diamine represented by the formula [3]) and an alicyclic tetracarboxylic acid dianhydride and / or an aliphatic tetracarboxylic acid dianhydride. A polyamic acid obtained by polymerizing a tetracarboxylic acid component composed of a substance.

（式中、Ｙは、

で示される構造のいずれか１つ以上を有し、＊は結合手である。）The diamine component for producing the polymer (C) does not contain the diamine represented by the formula [3].
Examples of the diamine component for producing the polymer (C) include diamines represented by the following formula [4].

(In the formula, Y is

It has one or more of the structures shown by, and * is a bond. )

（式中、Ａ_１は、ヒドロキシル基、カルボキシル基、フッ素原子、又は炭素数１〜５のアルキル基若しくはアルコキシ基（但し、該アルキル基若しくはアルコキシ基の任意の水素原子は、フッ素原子で置換されていてもよい。）であり、Ａ_１の少なくとも一つはヒドロキシル基又はカルボキシル基を表す。Ａ_２は単結合、エーテル結合、エステル結合、炭素数１〜２０のアルキレン基、炭素数１〜２０のアルキレン基の一部がウレア結合又はアミド結合で置き換えられた２価の有機基、又は該２価の有機基中の−ＣＨ_２−の一部又は全部がエーテル結合、エステル結合、シクロヘキシレン基及びフェニレン基からなる群から選ばれる少なくとも１種の基で置き換えられた基である。ａ１は１〜４の整数である。ａ２１、ａ２２は０〜４の整数である。ａ１、ａ２１又はａ２２が２以上の整数である場合、Ａ_１は同一でも異なってもよい。Ａ_２が単結合又は炭素数１〜２０のアルキレン基を表す場合、ａ２１又はａ２２のいずれかは０以外の整数である。ｂ及びｃはそれぞれ独立して１〜２の整数である。）As a more preferable specific example of Y, a divalent organic group having at least one partial structure shown above and having at least one benzene ring is preferable. More preferable specific examples of the diamine represented by the above formula [4] include the diamines of the following formulas (4-1) to (4-2).

(In the formula, A ₁ is a hydroxyl group, a carboxyl group, a fluorine atom, or an alkyl group or an alkoxy group having 1 to 5 carbon atoms (however, any hydrogen atom of the alkyl group or the alkoxy group is substituted with a fluorine atom. may be.), and at least one .A ₂ is a single bond represents a hydroxyl group or a carboxyl group of _{a 1,} an ether bond, an ester bond, an alkylene group having 1 to 20 carbon atoms, 1 to 20 carbon atoms divalent organic group partially replaced with a urea bond or an amide bond of an alkylene group, or -CH 2 in the organic groups of the divalent _- some or all of an ether bond, an ester bond, cyclohexylene And a group replaced with at least one group selected from the group consisting of phenylene groups. A1 is an integer of 1 to 4. a21, a22 is an integer of 0 to 4. a1, a21 or a22 is an integer of 0 to 4. When it is an integer of 2 or more, A ₁ may be the same or different. When A ₂ represents a single bond or an alkylene group having 1 to 20 carbon atoms, either a21 or a22 is an integer other than 0. b and c are independently integers of 1 to 2).

The diamine represented by the above formula [4] is preferably the following diamine, and particularly preferable is 1,3-bis (4-aminophenethyl) urea represented by the following formula.

The diamine component for producing the polymer (C) of the present invention includes the solubility of the polymer (C) in a solvent, the coatability of a liquid crystal alignment agent, the liquid crystal orientation when a liquid crystal alignment film is used, and the voltage retention rate. , 1 type or a mixture of 2 or more types may be used depending on the characteristics such as accumulated charge. As the diamine component for producing the polymer (C), any diamine other than the diamine represented by the formula [3] or the diamine represented by the formula [4], for example, the other diamine may be used. Can be done.

The tetracarboxylic acid component for producing the polymer (C) consists of an alicyclic tetracarboxylic dianhydride and / or an aliphatic tetracarboxylic dianhydride.

Here, the aliphatic tetracarboxylic dianhydride is an acid dianhydride obtained by intramolecular dehydration of four carboxyl groups bonded to a chain hydrocarbon structure. However, it does not have to be composed only of a chain hydrocarbon structure, and may have an alicyclic structure or an aromatic ring structure as a part thereof.
The alicyclic tetracarboxylic dianhydride is an acid dianhydride obtained by intramolecular dehydration of four carboxyl groups including at least one carboxyl group bonded to the alicyclic structure. However, none of these four carboxyl groups are bonded to the aromatic ring. Further, it does not have to be composed only of an alicyclic structure, and may have a chain hydrocarbon structure or an aromatic ring structure as a part thereof.

Examples of the aliphatic tetracarboxylic dianhydride or the alicyclic tetracarboxylic dianhydride include a compound represented by the following formula (3c-1).

In the above formula, X ₂ is any of the following formulas (B-1) to (B-18). * Represents a bond.

The tetracarboxylic acid component for producing the polymer (C) of the present invention includes the solubility of the polymer (C) in a solvent, the coatability of a liquid crystal alignment agent, the liquid crystal orientation in the case of a liquid crystal alignment film, and the voltage. Depending on the characteristics such as retention rate and accumulated charge, one kind or two or more kinds may be mixed and used.

<Method for producing polymers (A) to (C)>
The polyimide precursor that can be contained in the liquid crystal alignment agent of the present invention refers to a polyamic acid or a polyamic acid ester.
The reaction between the diamine component and the tetracarboxylic acid component is usually carried out in a solvent. The solvent used at that time is not particularly limited as long as it dissolves the produced polyimide precursor. Specific examples of the solvent used in the reaction are given below, but the present invention is not limited to these examples.
For example, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, N, N-dimethylformamide, N, N-dimethylacetamide, 3-methoxy-N, N-dimethylpropanamide, 3- Butoxy-N, N-dimethylpropanamide, dimethyl sulfoxide, or 1,3-dimethyl-imidazolidinone can be mentioned. When the solvent solubility of the polyimide precursor is high, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone or ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, diethylene glycol monomethyl ether, etc. Diethylene glycol monoethyl ether, propyl ether such as diethylene glycol can be used.

These solvents may be used alone or in admixture. Further, even if the solvent does not dissolve the polyimide precursor, it may be mixed with the solvent and used as long as the produced polyimide precursor does not precipitate. Further, since the water content in the solvent inhibits the polymerization reaction and further causes the produced polyimide precursor to be hydrolyzed, it is preferable to use a solvent dehydrated and dried.

When the diamine component and the tetracarboxylic acid component are reacted in a solvent, the solution in which the diamine component is dispersed or dissolved in the solvent is stirred, and the tetracarboxylic acid component is added as it is or after being dispersed or dissolved in the solvent. Examples thereof include a method of adding a diamine component to a solution in which a tetracarboxylic acid component is dispersed or dissolved in a solvent, a method of alternately adding a diamine component and a tetracarboxylic acid component to a reaction system, and the like. Any of these methods may be used. In addition, when a plurality of diamine components or tetracarboxylic acid components are used for reaction, they may be reacted in a premixed state, may be reacted individually in sequence, or may be further reacted individually as a low molecular weight compound. May be mixed and reacted to form a polymer.

The temperature at which the diamine component and the tetracarboxylic acid component are polycondensed can be selected from any temperature of -20 to 150 ° C, but is preferably in the range of −5 to 100 ° C. The reaction can be carried out at an arbitrary concentration, but if the concentration is too low, it becomes difficult to obtain a polymer having a high molecular weight, and if the concentration is too high, the viscosity of the reaction solution becomes too high and uniform stirring becomes difficult. .. Therefore, the concentration of the polymer is preferably 1 to 50% by mass, more preferably 5 to 30% by mass. The initial reaction can be carried out at a high concentration and then the solvent can be added.
In the polymerization reaction for obtaining the polyimide precursor, the ratio of the total number of moles of the tetracarboxylic acid component to the total number of moles of the diamine component is preferably 0.8 to 1.2. Similar to a normal polycondensation reaction, the closer the molar ratio is to 1.0, the larger the molecular weight of the polyimide precursor produced.

Polyimide is obtained by ring-closing a polyimide precursor. In this polyimide, the ring closure rate (also referred to as imidization rate) of the amic acid group (amide acid group) does not necessarily have to be 100%, and can be arbitrarily adjusted according to the application and purpose.
Examples of the method for imidizing the polyimide precursor include thermal imidization in which the solution of the polyimide precursor is heated as it is, and catalytic imidization in which a catalyst is added to the solution of the polyimide precursor.
The temperature at which the polyimide precursor is thermally imidized in a solution is preferably 100 to 400 ° C., more preferably 120 to 250 ° C., and a method of removing water generated by the imidization reaction from the outside of the system is preferable. .. The catalytic imidization of the polyimide precursor can be carried out by adding a basic catalyst and an acid anhydride to the solution of the polyimide precursor and stirring at −20 to 250 ° C., preferably 0 to 180 ° C.

The amount of the basic catalyst is preferably 0.5 to 30 mol times, more preferably 2 to 20 mol times the amount of the amic acid group, and the amount of the acid anhydride is preferably 1 to 50 mol times the amic acid group. , More preferably 3 to 30 mol times.
Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine and the like. Of these, pyridine is preferable because it has an appropriate basicity for advancing the reaction.
Examples of the acid anhydride include acetic anhydride, trimellitic anhydride, pyromellitic anhydride and the like. In particular, acetic anhydride is preferable because it facilitates purification after the reaction is completed. The imidization rate by catalytic imidization can be controlled by adjusting the amount of catalyst, the reaction temperature, and the reaction time.

When recovering the polyimide precursor produced from the reaction solution or the polyimide obtained from the polyimide precursor, the reaction solution may be added to a solvent for precipitation. Examples of the solvent used for precipitation include methanol, ethanol, isopropyl alcohol, acetone, hexane, butyl cellsolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, toluene, benzene, water and the like. The polymer put into a solvent and precipitated can be collected by filtration and then dried at room temperature or by heating under normal pressure or reduced pressure. Further, by repeating the operation of re-dissolving the polymer recovered by precipitation in a solvent and re-precipitating and recovering it 2 to 10 times, impurities in the polymer can be reduced. Examples of the solvent at this time include alcohols, ketones, hydrocarbons and the like. It is preferable to use three or more kinds of solvents selected from these because the efficiency of purification is further improved.

When the polyimide precursor is a polyamic acid ester in the present invention, specific methods for producing the polyimide precursor include, for example, the methods described in paragraphs [0054] to [0062] of International Publication No. WO2011-115077. Be done.
The polyimide precursor or the polyimide obtained from the polyimide precursor may have its terminal modified by a terminal modifier. By modifying the end, the effect of enhancing the adhesiveness between the sealant and the liquid crystal alignment film can be obtained.
Examples of the terminal modifier include tertiary butyloxycarbonylating agents, N-tert-butoxycarbonylimidazole, tert-butylphenyl carbonate, tert-butyl carbazate, tert-butyl chloroformate, di-tert-butyl dicarbonate. And so on. As the terminal modifier, di-tert-butyl dicarbonate is preferable.

<Liquid crystal alignment agent>
An embodiment of the present invention is a liquid crystal alignment agent containing a polymer (A), a polymer (B) and a polymer (C).

The content of the polymer (A) in the liquid crystal aligning agent is preferably 10 to 50% by mass with respect to 100% by mass of the total amount of the polymers (A) to (C) from the viewpoint of the alignment regulating force of the liquid crystal. It is more preferably 10 to 30% by mass.
The content of the polymer (B) in the liquid crystal alignment agent is preferably 10 to 70% by mass with respect to 100% by mass of the total amount of the polymers (A) to (C) from the viewpoint of mitigation characteristics of accumulated charges. It is more preferably 40 to 60% by mass.
The content of the polymer (C) in the liquid crystal aligning agent is preferably 10 to 50% by mass with respect to 100% by mass of the total amount of the polymers (A) to (C) from the viewpoint of the accumulated charge amount of DC. It is more preferably 10 to 30% by mass.

The liquid crystal alignment agent of the present invention may contain polymers other than the polymers (A) to (C). Examples of other polymers include cellulosic polymers, acrylic polymers, methacrylic polymers, polystyrene, polyamides, polysiloxanes and the like. The content of the other polymers is preferably 0.5 to 15 parts by mass, more preferably 1 to 10 parts by mass, based on 100 parts by mass of the total of the polymers (A) to (C).

The liquid crystal alignment agent usually contains an organic solvent, but the content of the organic solvent is preferably 70 to 99.9% by mass with respect to the liquid crystal alignment agent. This content can be appropriately changed depending on the application method of the liquid crystal alignment agent and the film thickness of the target liquid crystal alignment film.
The organic solvent used for the liquid crystal alignment agent is preferably a solvent (also referred to as a good solvent) that dissolves the polymers (A) to (C). For example, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ-butyrolactone, 1,3-dimethyl-imidazolidinone, methylethylketone. , Cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, 3-methoxy-N, N-dimethylpropanamide, 3-butoxy-N, N-dimethylpropanamide, and the like. Among them, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 3-methoxy-N, N-dimethylpropanamide, 3-butoxy-N, N-dimethylpropanamide or γ-butyrolactone can be used. preferable.

The good solvent in the liquid crystal alignment agent of the present invention is preferably 20 to 99% by mass, more preferably 20 to 90% by mass, and particularly preferably 30 to 80% by mass, based on the total amount of the solvent contained in the liquid crystal alignment agent. Is.

As the liquid crystal alignment agent of the present invention, a solvent (also referred to as a poor solvent) that improves the coating film property and surface smoothness of the liquid crystal alignment film when the liquid crystal alignment agent is applied can be used. Specific examples are given below.
For example, diisopropyl ether, diisobutyl ether, diisobutylcarbinol (2,6-dimethyl-4-heptanol), ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, 1,2-butoxyetane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether. , 4-Hydroxy-4-methyl-2-pentanone, diethylene glycol methyl ethyl ether, diethylene glycol dibutyl ether, 3-ethoxybutyl acetate, 1-methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene Glycol monoacetate, ethylene glycol diacetate, propylene carbonate, ethylene carbonate, ethylene glycol monobutyl ether, ethylene glycol monoisoamyl ether, ethylene glycol monohexyl ether, propylene glycol monobutyl ether, 1- (2-butoxyethoxy) -2- Propanol, 2- (2-butoxyethoxy) -1-propanol, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monobutyl ether acetate, ethylene glycol mono Acetate, ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2- (2-ethoxyethoxy) ethyl acetate, diethylene glycol acetate, propylene glycol diacetate, n-butyl acetate, propylene acetate Glycol monoethyl ether, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, propyl 3-methoxypropionate, butyl 3-methoxypropionate, n-butyl ester lactic acid, isoamyl lactic acid ester, Examples thereof include diethylene glycol monoethyl ether and diisobutyl ketone (2,6-dimethyl-4-heptanone).

Among them, the preferred solvent combinations are N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether, N-methyl-2-pyrrolidone and γ-butyrolactone and ethylene glycol monobutyl ether, and N-methyl-2-pyrrolidone and γ-. Butyrolactone and Propylene Glycol Monobutyl Ether, N-Ethyl-2-pyrrolidone and Propylene Glycol Monobutyl Ether, N-Methyl-2-pyrrolidone and γ-Butyrolactone, 4-Hydroxy-4-methyl-2-pentanone and Diethylene Glycol diethyl Ether, N- Methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether and 2,6-dimethyl-4-heptanone, N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether and diisopropyl ether, N-methyl-2 -Pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether and 2,6-dimethyl-4-heptanol, N-methyl-2-pyrrolidone, γ-butyrolactone and dipropylene glycol dimethyl ether, and the like can be mentioned. The poor solvent is preferably 1 to 80% by mass, more preferably 10 to 80% by mass, and particularly preferably 20 to 70% by mass, based on the total amount of the solvent contained in the liquid crystal alignment agent. The type and content of such a solvent are appropriately selected depending on the coating device for the liquid crystal alignment agent, coating conditions, coating environment, and the like.

The liquid crystal alignment agent of the present invention includes a dielectric for changing the electrical properties such as the dielectric constant and conductivity of the liquid crystal alignment film, a silane coupling agent for improving the adhesion between the liquid crystal alignment film and the substrate, and a liquid crystal. A crosslinkable compound for the purpose of increasing the hardness and density of the film when it is made into an alignment film, and an imidization accelerator for the purpose of efficiently advancing imidization by heating the polyimide precursor when firing the coating film. It may be contained.

Examples of the compound that improves the adhesion between the liquid crystal alignment film and the substrate include functional silane-containing compounds and epoxy group-containing compounds, and examples thereof include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and 3-. Glycydoxypropyltriethoxysilane 3-glycidoxypropyltrimethoxysilane 3-glycidoxypropylmethyldiethoxysilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, N- (2-) Aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl- 3-Aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropyltriethylenetriamine, N-trimethoxysilylpropyltriethylenetriamine, 10-trimethoxysilyl-1,4 , 7-Triazadecane, 10-triethoxysilyl-1,4,7-Triazadecane, 9-trimethoxysilyl-3,6-diazanonyl acetate, 9-triethoxysilyl-3,6-diazanonyl acetate, N -Benzyl-3-aminopropyltrimethoxysilane, N-benzyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, N-bis (Oxyethylene) -3-aminopropyltrimethoxysilane, N-bis (oxyethylene) -3-aminopropyltriethoxysilane, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol Diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, 1,3,5, 6-Tetraglycidyl-2,4-hexanediol, N, N, N', N',-tetraglycidyl-m-xylene diamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, or Examples thereof include N, N, N', N', -tetraglycidyl-4, 4'-diaminodiphenylmethane and the like.

Further, the following additives (CL-1) to (CL-15) may be added to the liquid crystal alignment agent of the present invention in order to increase the mechanical strength of the liquid crystal alignment film.

The content of the above additive is preferably 0.1 to 30 parts by mass with respect to 100 parts by mass of the polymer component contained in the liquid crystal alignment agent. More preferably, it is 0.5 to 20 parts by mass.

<Manufacturing method of liquid crystal alignment film>
The liquid crystal alignment film is obtained by applying the liquid crystal alignment agent on a substrate or the like to form a film, preferably drying, and then firing. As the substrate, a highly transparent substrate is preferable, and as the material thereof, glass, ceramics such as silicon nitride, plastics such as acrylic and polycarbonate can be used. As the substrate, it is preferable to use a substrate on which an ITO (Indium Tin Oxide) electrode for driving a liquid crystal display or the like is formed, from the viewpoint of simplifying the process. Further, in the reflective liquid crystal display element, an opaque material such as a silicon wafer can be used for the substrate on one side, and a material that reflects light such as aluminum can be used for the electrode.

Industrially, screen printing, offset printing, flexographic printing, inkjet method, etc. can be used as a method for forming a film on a substrate from a liquid crystal alignment agent, and a dip method, a roll coater method, a slit coater method, a spinner method, etc. can be used. , Spray method, etc. can also be used according to the purpose.
After forming a film of the liquid crystal alignment agent on the substrate, the film is preferably 30 to 120 ° C., more preferably 50 to 120 ° C. by a heating means such as a hot plate, a heat circulation type oven, or an IR (infrared) type oven. The solvent is preferably evaporated by drying for 1 to 10 minutes, more preferably 1 to 5 minutes.

When the imide precursor in the polymer is thermally imidized, the film obtained from the liquid crystal alignment agent is then heated to preferably 120 to 250 ° C., more preferably 150 by the same heating means as the above-mentioned drying treatment. It is fired at ~ 230 ° C. The firing treatment time varies depending on the firing temperature, but is preferably 5 minutes to 1 hour, more preferably 5 minutes to 40 minutes.
The thickness of the coating film after the firing treatment is not particularly limited, but if it is too thin, the reliability of the liquid crystal display element may decrease, and if it is too thick, the electric resistance of the obtained liquid crystal alignment film increases, so that the thickness is 5 to 300 nm. Is preferable, and 10 to 200 nm is more preferable.
After the firing treatment, the obtained coating film is oriented. Examples of the alignment treatment method include a rubbing treatment method and a photoalignment treatment method.

As a specific example of the photo-alignment treatment, the surface of the coating film is irradiated with radiation deflected in a certain direction. As the radiation, ultraviolet rays having a wavelength of 100 to 800 nm or visible light can be used. Among them, ultraviolet rays having a wavelength of 100 to 400 nm are preferable, and ultraviolet rays having a wavelength of 200 to 400 nm are more preferable. In order to improve the liquid crystal alignment, the substrate coated with the liquid crystal alignment film may be irradiated with ultraviolet rays while being heated at 50 to 250 ° C. The irradiation amount of the radiation is preferably 1 to 10,000 mJ / cm2. Of these, 100 to 5,000 mJ / cm2 is preferable. The liquid crystal alignment film thus produced can stably orient the liquid crystal molecules in a certain direction.
The higher the extinction ratio of the polarized ultraviolet rays, the higher the anisotropy can be imparted, which is preferable. Specifically, the extinction ratio of linearly polarized ultraviolet rays is preferably 10: 1 or more, more preferably 20: 1 or more.

The film subjected to the alignment treatment may be further subjected to at least one treatment selected from the group consisting of heat treatment and contact treatment with a solvent.
The heat treatment after the orientation treatment can be performed by the same heating means as the above-mentioned drying treatment and firing treatment, and is preferably performed at 180 to 250 ° C., more preferably 180 to 230 ° C. When the temperature of the heat treatment is in the above range, the contrast of the liquid crystal display element obtained by the obtained liquid crystal alignment film can be enhanced.
The heat treatment time varies depending on the heating temperature, but is preferably 5 minutes to 1 hour, more preferably 5 to 40 minutes.

The solvent used for the contact treatment with the above solvent is not particularly limited as long as it is a solvent that dissolves impurities and the like adhering to the liquid crystal alignment film.
Specific examples include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, methyl lactate, diacetone alcohol, 3-. Examples thereof include methyl methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate, cyclohexyl acetate and the like. Of these, water, 2-propanol, 1-methoxy-2-propanol or ethyl lactate are preferable from the viewpoint of versatility and solvent safety. More preferred are water, 1-methoxy-2-propanol or ethyl lactate. These solvents may be one kind or two or more kinds.

Examples of the contact treatment include a dipping treatment and a spray treatment (also referred to as a spray treatment). The treatment time in these treatments is preferably 10 seconds to 1 hour, and in particular, an embodiment in which the immersion treatment is performed for 1 to 30 minutes can be mentioned. Further, the temperature at the time of the contact treatment may be heated at room temperature or may be heated, but is preferably 10 to 80 ° C, and examples thereof include 20 to 50 ° C. At the time of contact treatment, ultrasonic treatment or the like may be further performed, if necessary.

After the contact treatment, rinsing (also referred to as rinsing) or drying with a low boiling point solvent such as water, methanol, ethanol, 2-propanol, acetone, or methyl ethyl ketone may be performed. At that time, either rinsing or drying may be performed, or both may be performed. The drying temperature is preferably 50 to 150 ° C, and examples thereof include 80 to 120 ° C. The drying time is preferably 10 seconds to 30 minutes, preferably 1 to 10 minutes.
After the contact treatment with the solvent, the heat treatment after the orientation treatment may be performed. With such an embodiment, a liquid crystal alignment film having excellent liquid crystal alignment can be obtained.

<Liquid crystal display element>
The liquid crystal alignment film of the present invention can be applied to various drive modes such as TN method, STN method, IPS method, FFS method, VA method, MVA method, PSA method, etc. It is suitable as a liquid crystal alignment film for an electric field type liquid crystal display element, and is particularly useful for an FFS type liquid crystal display element. In the liquid crystal display element of the present invention, after obtaining a substrate with a liquid crystal alignment film obtained from the liquid crystal alignment agent, a liquid crystal cell is produced by a known method, and the liquid crystal cell is used as an element.
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 as an example. A liquid crystal display element having an active matrix structure in which a switching element such as a TFT is provided in each pixel portion constituting the image display may be used.

Specifically, a transparent glass substrate is prepared, and a common electrode is provided on one substrate and a segment electrode is provided on the other substrate. These electrodes can be, for example, ITO electrodes and are patterned so as to display a desired image. Next, an insulating film is provided on each substrate so as to cover the common electrode and the segment electrode. The insulating film can be, for example, a film made of SiO _2- TiO ₂ formed by the sol-gel method. Next, under the conditions as described above, a liquid crystal alignment film is formed on each substrate, the other substrate is superposed on one substrate so that the liquid crystal alignment film surfaces face each other, and the periphery is covered with a sealing agent. Glue with. It is usually preferable to mix a spacer in the sealant in order to control the gap between the substrates. Further, it is preferable to spray the spacer for controlling the gap between the substrates also on the in-plane portion where the sealant is not provided. It is preferable that a part of the sealing agent is provided with an opening in which the liquid crystal can be filled from the outside.

Then, the liquid crystal material is injected into the space surrounded by the two substrates and the sealant through the opening provided in the sealant. The opening is then sealed with an adhesive. Examples of the injection include a vacuum injection method and a method using a capillary phenomenon in the atmosphere, and an ODF (One Drop Fill) method may be used. As the liquid crystal material, any material having positive or negative dielectric anisotropy may be used. In the present invention, a liquid crystal having a negative dielectric anisotropy is preferable from the viewpoint of liquid crystal orientation, but it can be used properly according to the intended use.
After the liquid crystal material is injected into the liquid crystal cell, the polarizing plate is installed. Specifically, it is preferable to attach a pair of polarizing plates to the surfaces of the two substrates opposite to the liquid crystal layer.

（テトラカルボン酸二無水物）

（末端修飾剤）
二炭酸ジ−ｔｅｒｔ−ブチル（Ｂｏｃ２Ｏ）
（添加剤）

（ｓ−１）：３−グリシドキシプロピルトリエトキシシラン
（有機溶媒）
ＮＭＰ：Ｎ−メチル−２−ピロリドン、
ＧＢＬ：γ−ブチロラクトン、
ＢＣＳ：ブチルセロソルブ、Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. The abbreviations of the compounds and the measurement method of each characteristic in the following are as follows.
(Diamine)

(Tetracarboxylic dianhydride)

(Terminal modifier)
Di-tert-butyl dicarbonate (Boc2O)
(Additive)

(S-1): 3-glycidoxypropyltriethoxysilane (organic solvent)
NMP: N-methyl-2-pyrrolidone,
GBL: γ-Butyrolactone,
BCS: Butyl cellosolve,

<Measurement of imidization rate>
20 mg of polyimide powder was placed in an NMR sample tube (NMR sampling tube standard, φ5 (manufactured by Kusano Kagaku Co., Ltd.)), and deuterated dimethyl sulfoxide (DMSO-d6, 0.05% TMS (tetramethylsilane) mixture) (0. 53 ml) was added and ultrasonically applied to completely dissolve it. This solution was measured for proton NMR at 500 MHz with an NMR measuring machine (JNW-ECA500) (manufactured by JEOL Datum). The imidization rate is determined by using a proton derived from a structure that does not change before and after imidization as a reference proton, and the peak integrated value of this proton and the proton peak derived from the NH group of amic acid appearing in the vicinity of 9.5 ppm to 10.0 ppm. It was calculated by the following formula using the integrated value.
Imidization rate (%) = (1-α · x / y) × 100
In the above formula, x is the integrated proton peak value derived from the NH group of amic acid, y is the integrated peak value of the reference proton, and α is one NH group proton of the amic acid in the case of polyamic acid (imidization rate is 0%). It is the number ratio of the reference protons to.

[Synthesis of polymer]
<Synthesis example 1>
In a four-necked flask with a stirrer and a nitrogen inlet tube, 10.3 g (42.5 mmol) of DA-1, 7.8 g (14.0 mmol) of DA-3, and 4.78 g (14) of DA-4. .0 mmol) was weighed, NMP was added to a solid content concentration of 15% by mass, and the mixture was stirred and dissolved while feeding nitrogen. 10.2 g (45.5 mmol) of CA-1 was added while stirring this diamine solution, and NMP was further added so that the solid content concentration became 18% by mass. After stirring at 40 ° C. for 1 hour, 3.57 g (18.2 mmol) of CA-2 was added at room temperature, and NMP was further added so that the solid content concentration became 18% by mass. This polymerization solution was stirred for 3 hours to obtain a polyamic acid solution (PA-I).
Take 100.0 g of the above polyamic acid solution (PA-I) obtained in a 100 mL four-necked flask equipped with a stirrer and a nitrogen introduction tube, and add 4 di-tert-butyl dicarbonate (Boc2O) as a terminal modifier. After adding .06 g (18.6 mmol) and stirring at 40 ° C. for 15 hours, a terminal-modified polyamic acid solution (PAboc-I) was obtained.
Take 100.0 g of the terminal-modified polyamic acid solution (PAboc-I) obtained in a 100 mL four-necked flask equipped with a stirrer and a nitrogen introduction tube, and add NMP to a solid content concentration of 12% by mass. In addition, the mixture was stirred for 30 minutes. To the obtained polyamic acid solution, 10.54 g of acetic anhydride and 2.72 g of pyridine were added, and the mixture was stirred at room temperature for 30 minutes and then heated and stirred at 55 ° C. for 2 hours and 15 minutes for chemical imidization. The obtained reaction solution was added to methanol in an amount 3.5 times the mass of the reaction solution with stirring, the precipitated precipitate was filtered, and then washed with methanol three times. The obtained resin powder was vacuum dried at 80 ° C. for 12 hours to obtain a polyimide (SPI1-1) powder. The imidization rate of this polyimide resin powder was 75%. NMP was added to the obtained polyimide (SPI1-1) so that the solid content concentration was 15% by mass, and the mixture was stirred at 70 ° C. for 15 hours to prepare a solution of the polyimide (SPI1-1) having a solid content concentration of 15% by mass. Obtained.

<Synthesis Examples 2-6>
By using the diamine and tetracarboxylic acid derivatives shown in Table 1 below and carrying out the same procedure as in Synthesis Example 1, the solutions of polyimides (SPI1-1) to (SPI1-6) shown in Table 1 below can be used. Got In Table 1, the numerical values shown under the compound name represent the mass (g) of the tetracarboxylic acid derivative used for the synthesis for the tetracarboxylic acid component, and the diamine used for the synthesis for the diamine acid component. Represents the mass (g) of. Regarding the terminal modification treatment, those described as Boc2O were carried out in the same procedure as in Synthesis Example 1, and those described as none were not subjected to the terminal modification treatment.

<Synthesis Examples 7 to 28>
By using the diamine and tetracarboxylic acid derivatives shown in Table 2 below and carrying out the same procedure as in Synthesis Example 1, the polyamic acids shown in Table 1 below (PAA2-1 to PAA2-15, PAA3-1, respectively). A solution of ~ PAA3-7) was obtained. In Table 2, the numerical values shown under the compound name represent the mass (g) of the tetracarboxylic acid derivative used for the synthesis for the tetracarboxylic acid component, and the diamine used for the synthesis for the diamine acid component. Represents the mass (g) of.

[Preparation of liquid crystal alignment agent]
<Example 1>
Using the polyimide (SPI1-1) solution obtained in Synthesis Example 1, the polyamic acid solution (PAA2-1) obtained in Synthesis Example 7, and the polyamic acid solution (PAA3-3) obtained in Synthesis Example 24. , NMP, GBL and BCS, the additive (c-1) is added so as to be 3 parts by mass with respect to 100 parts by mass of all the polymers, and the additive (s-1) is further added by all the weights. The mixture was added so as to be 1 part by mass with respect to 100 parts by mass, and the mixture was stirred at room temperature. Then, by filtering this obtained solution with a filter having a pore size of 0.5 μm, the component ratio of the polymer was (SPI1-1) :( PAA2-1) :( PAA3-3) = 30:40: 30 (. A liquid crystal aligning agent (1) having a solid content equivalent mass ratio), a solvent composition ratio of NMP: GBL: BCS = 30: 35.5: 30 (mass ratio), and a polymer solid content concentration of 4.5% by mass was obtained. (Table 3 below). No abnormality such as turbidity or precipitation was observed in this liquid crystal alignment agent, and it was confirmed that the solution was uniform.

<Examples 2-33, Comparative Examples 1-7>
Liquid crystal alignment agents (2) to (33) and (R1) to (R7) were obtained by carrying out in the same manner as in Example 1 except that the polymers shown in Table 3 below were used.

[Manufacturing of liquid crystal display element]
A liquid crystal cell having a configuration of a Fringe Field Switching (FFS) mode liquid crystal display element is manufactured.
First, a substrate with electrodes was prepared. The substrate is a glass substrate having a size of 35 mm × 40 mm and a thickness of 0.7 mm. An ITO electrode having a solid pattern, which constitutes a counter electrode as a first layer, is formed on the substrate. A SiN (silicon nitride) film formed by a CVD method is formed as a second layer on the counter electrode of the first layer. The film thickness of the SiN film of the second layer is 500 nm, and it functions as an interlayer insulating film. On the SiN film of the second layer, a comb-shaped pixel electrode formed by patterning an ITO film as a third layer is arranged to form two pixels, a first pixel and a second pixel. ing. The size of each pixel is 10 mm in length and about 5 mm in width. At this time, the counter electrode of the first layer and the pixel electrode of the third layer are electrically insulated by the action of the SiN film of the second layer.

The pixel electrode of the third layer has a comb-like shape formed by arranging a plurality of dogleg-shaped electrode elements having a bent central portion. The width of each electrode element in the lateral direction is 3 μm, and the distance between the electrode elements is 6 μm. Since the pixel electrodes forming each pixel are configured by arranging a plurality of bent dogleg-shaped electrode elements in the central portion, the shape of each pixel is not rectangular, but in the central portion like the electrode elements. It has a shape that resembles a bold "dogleg" that bends. Then, each pixel is divided into upper and lower parts with a bent portion in the center as a boundary, and has a first region on the upper side and a second region on the lower side of the bent portion.

Comparing the first region and the second region of each pixel, the forming directions of the electrode elements of the pixel electrodes constituting them are different. That is, when the rubbing direction of the liquid crystal alignment film described later is used as a reference, the electrode elements of the pixel electrodes are formed so as to form an angle (clockwise) of + 10 ° in the first region of the pixel, and the pixel is formed in the second region of the pixel. The electrode elements of the electrodes are formed so as to form an angle of −10 ° (clockwise). That is, in the first region and the second region of each pixel, the directions of the rotational movement (inplane switching) of the liquid crystal in the substrate surface induced by the voltage application between the pixel electrode and the counter electrode are mutual. It is configured to be in the opposite direction.

Next, the liquid crystal alignment agent was applied to the substrate with electrodes and a glass substrate having a columnar spacer having a height of 4 μm having an ITO film formed on the back surface, and the liquid crystal alignment agent filtered with a 1.0 μm filter was applied by spin coating. And dried on a hot plate at 80 ° C. for 2 minutes. Then, it was fired in a hot air circulation type oven at 230 ° C. for 30 minutes to obtain a substrate with a liquid crystal alignment film having a film thickness of 100 nm. After rubbing the surface of the substrate with the liquid crystal alignment film with rayon cloth (YA-20R manufactured by Yoshikawa Kako) (roller diameter: 120 mm, roller rotation speed: 1000 rpm, moving speed: 20 mm / sec, pushing length: 0.4 mm), it is pure. After washing by ultrasonic irradiation for 1 minute in water and removing water droplets by air blow, it was dried at 80 ° C. for 15 minutes to obtain a substrate with a liquid crystal alignment film. The two obtained substrates with the liquid crystal alignment film are made into a set, and the sealant is printed on the substrate with the liquid crystal injection port left on the substrate. The liquid crystal alignment film surface faces the other substrate and the rubbing direction is They were pasted together so that they were antiparallel. Then, the sealant was cured to prepare an empty cell having a cell gap of 4 μm. A liquid crystal MLC-3019 (manufactured by Merck & Co., Inc.) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain an FFS type liquid crystal display element. Then, the obtained liquid crystal display element was heated at 120 ° C. for 1 hour, left at 23 ° C. overnight, and then used for evaluation.

[Evaluation of DC accumulation amount]
For the FFS-driven liquid crystal cell created above, two polarizing plates are installed between two polarizing plates arranged so that their polarization axes are orthogonal to each other, and the pixel electrode and the counter electrode are short-circuited to have the same potential. The LED backlight was irradiated from under the polarizing plate, and the angle of the liquid crystal cell was adjusted so that the brightness of the transmitted light of the LED backlight measured on the two polarizing plates was minimized. This evaluation was performed under the temperature condition that the temperature of the liquid crystal cell was 23 ° C.
Next, the VT curve (voltage-transmittance curve) was measured while applying an AC voltage having a frequency of 30 Hz to the liquid crystal cell, and the AC voltage at which the relative transmittance was 23% or 100% was calculated as the drive voltage. A rectangular wave of 20 mV was applied to the liquid crystal cell at 23 ° C. at a frequency of 1 kHz for 30 minutes.
After that, an AC drive having a relative transmittance of 100% was applied for 45 minutes, and the change amount from the start of measurement to 45 minutes after the start of measurement was calculated as the DC accumulation amount while measuring the minimum offset voltage value every 3 minutes during that period.
Since the accumulated charge affects the display as a disorder of the liquid crystal orientation or an afterimage and significantly deteriorates the display quality of the liquid crystal element, it can be said that the smaller the amount of DC accumulated during driving, the better. In the present invention, the case where the DC accumulation amount is 150 mV or less is considered to be particularly good.

[Relaxation characteristics of accumulated charge]
For the FFS-driven liquid crystal cell created above, two polarizing plates are installed between two polarizing plates arranged so that their polarization axes are orthogonal to each other, and the pixel electrode and the counter electrode are short-circuited to have the same potential. The LED backlight was irradiated from under the polarizing plate, and the angle of the liquid crystal cell was adjusted so that the brightness of the transmitted light of the LED backlight measured on the two polarizing plates was minimized. This evaluation was performed under the temperature condition that the temperature of the liquid crystal cell was 23 ° C.
Next, the VT curve (voltage-transmittance curve) was measured while applying an AC voltage having a frequency of 30 Hz to the liquid crystal cell, and the AC voltage at which the relative transmittance was 23% or 100% was calculated as the drive voltage. A rectangular wave of 20 mV was applied to the liquid crystal cell at 23 ° C. at a frequency of 1 kHz for 30 minutes.
After that, while applying a square wave with a frequency of 30 Hz to this liquid crystal cell, the VT characteristics (voltage-transmittance characteristics) at a temperature of 23 ° C. were measured, and the AC voltage at which the relative transmittance was 23% was calculated. .. Since this AC voltage corresponds to a region where the change in luminance with respect to voltage is large, it is convenient to evaluate the stored charge through the luminance.
Next, a rectangular wave having a relative transmittance of 23% and a frequency of 30 Hz was applied for 5 minutes, and then a DC voltage of + 1.0 V was superimposed and driven for 30 minutes. After that, the DC voltage was turned off, and only a rectangular wave having a relative transmittance of 23% and a frequency of 30 Hz was applied for 30 minutes.
The faster the charge is relaxed, the faster the charge is accumulated in the liquid crystal cell when the DC voltage is superimposed. Therefore, the relaxation characteristic of the stored charge is that the relative transmittance immediately after the DC voltage is superimposed is 30% or more. It was evaluated by the time required to decrease from 23% to 23%. It can be said that the shorter this time is, the better the relaxation characteristic of the accumulated charge. Specifically, the time during which the relative transmittance decreased to 30% or less from the time when the application of the DC voltage was started until 30 minutes passed was quantified. If the relative transmittance drops to 30% or less within 10 minutes, "◎", if it exceeds 10 minutes and within 20 minutes, "○", if it exceeds 20 minutes and within 30 minutes, "△", When the relative transmittance did not decrease to 30% or less in 30 minutes, it was evaluated as "x".

[Evaluation of afterimage characteristics by long-term AC drive]
An AC voltage of ± 5 V was applied to the FFS-driven liquid crystal cell created above at a frequency of 60 Hz in a constant temperature environment of 60 ° C. for 120 hours. Then, the pixel electrode of the liquid crystal cell and the counter electrode were short-circuited and left at room temperature for one day.
With respect to the liquid crystal cell subjected to the above processing, the deviation between the orientation direction of the liquid crystal in the first region of the pixel and the orientation direction of the liquid crystal in the second region in the state where no voltage was applied was calculated as an angle.
Specifically, a liquid crystal cell is installed between two polarizing plates arranged so that the polarization axes are orthogonal to each other, the backlight is turned on, and the liquid crystal cell is set so that the transmitted light intensity in the first region of the pixel is minimized. After adjusting the arrangement angle of the light crystal cell, the rotation angle required when the liquid crystal cell was rotated so that the transmitted light intensity in the second region of the pixel was the smallest was obtained.
It can be said that the smaller the value of this rotation angle, the better the afterimage characteristic due to the long-term AC drive. Specifically, "◎" when the rotation angle is 0.5 degrees or less, "○" when the rotation angle exceeds 0.5 degrees and 1.0 degrees or less, and 1.5 degrees when the rotation angle exceeds 1.0 degrees. If it is as follows, it is evaluated as "Δ", and if it further exceeds 2.0 degrees, it is evaluated as "x".

[Evaluation of optical characteristics (transparency)]
A quartz substrate having a size of 40 mm × 40 mm and a thickness of 1.0 mm was prepared. Next, the liquid crystal alignment agent was filtered through a 1.0 μm filter and then spin-coated on the quartz substrate. Then, it was dried on a hot plate at 80 ° C. for 2 minutes and then fired at 230 ° C. for 20 minutes to obtain a polyimide film having a film thickness of 100 nm on each substrate.
The transparency was evaluated by measuring the transmittance of the substrate obtained by the above method. Specifically, UV-3600 (manufactured by Shimadzu Corporation) was used as a measuring device, and the transmittance was measured under the conditions of a temperature of 25 ° C. and a scan wavelength of 300 to 800 nm. At that time, a quartz substrate on which nothing was applied to the reference (reference example) was used. In the evaluation, the average transmittance of wavelengths of 400 to 800 nm was calculated, and the higher the transmittance, the better the transparency.

Regarding the liquid crystal display elements using the liquid crystal alignment agents of Examples 1 to 3 and Comparative Examples 1 to 7, the DC storage amount, the storage charge relaxation characteristics, the afterimage characteristics by long-term AC drive, and the optical characteristics, which were carried out as described above, were exhibited. The evaluation results are shown in Table 4 below.

It can be seen that the liquid crystal display element using the liquid crystal alignment agent of the embodiment of the present invention has a high degree of compatibility with other characteristics while suppressing the amount of DC accumulation.

The liquid crystal alignment agent of the present invention is useful for forming a liquid crystal alignment film in a wide range of liquid crystal display elements such as an IPS drive system and an FFS drive system.

The entire specification, claims and abstracts of Japanese Patent Application No. 2019-014146 filed on January 30, 2019 and Japanese Patent Application No. 2019-100642 filed on May 29, 2019. The contents are cited here and incorporated as disclosure of the specification of the present invention.

Claims (14)

A liquid crystal alignment agent containing the following polymer (A), polymer (B) and polymer (C).
Polymer (A): At least one polymer selected from the group consisting of the following (i) to (iii).
(I) A diamine component containing at least one diamine selected from the group consisting of a diamine represented by the following formula [1] and a diamine represented by the following formula [2], and an aromatic tetracarboxylic acid dianhydride. A polyamic acid obtained by polymerizing with a tetracarboxylic acid component composed of.
(Ii) Polymerization reaction of a diamine component containing at least one diamine selected from the group consisting of a diamine represented by the following formula [1] and a diamine represented by the following formula [2] and a tetracarboxylic acid component. Polyamic acid ester obtained by allowing.
(Iii) Polymerization reaction of a diamine component containing at least one diamine selected from the group consisting of a diamine represented by the following formula [1] and a diamine represented by the following formula [2] and a tetracarboxylic acid component. A polyimide obtained by imidizing a polyimide precursor obtained by subjecting the mixture to imidization.

(In the formulas [1] and [2], A ₁ is a single bond, an ether bond, an ester bond, -C = C-, -C≡C-, an alkylene group having 2 to 20 carbon atoms, or a group thereof. A group in which part or all of −CH ₂ − is replaced with at least one group selected from the group consisting of an ether bond, an ester bond, −C = C−, −C≡C−, a cyclohexylene group and a phenylene group. , Cyclohexylene group or phenylene group. A ₂ is a fluorine atom, or an alkyl group or an alkoxy group having 1 to 5 carbon atoms (provided that any hydrogen atom of the alkyl group or alkoxy group is substituted with a fluorine atom. A is an integer of 0 to 4, and when a is an integer of 2 or more, A ₂ may be the same or different. B and c are independently 1 to 2, respectively. It is an integer of.);
Polymer (B): From a polyimide precursor obtained by polymerizing a diamine-containing diamine component represented by the following formula [3] with a tetracarboxylic acid component, and a polyimide obtained from the polyimide precursor. At least one type of polymer selected from the group.

(In the formula, X has a structure in which an aromatic hydrocarbon ring is bonded to a carbon atom constituting a nitrogen-containing aromatic heterocycle having a 5-membered ring or a 6-membered ring.

It has a structure represented by, * is bonded to a structure excluding a carbonyl group, and at least one is bonded to an aromatic ring group. );
Polymer (C): A diamine component (however, the diamine component does not contain a diamine represented by the above formula [3]) and an alicyclic tetracarboxylic acid dianhydride and / or an aliphatic tetracarboxylic acid dianiba. A polyamic acid obtained by polymerizing a tetracarboxylic acid component composed of an anhydride. In the above formulas [1] and [2] in the polymer (A), A ₁ is a single bond and an alkylene group having 1 to 10 carbon atoms (provided that at least one −CH ₂ − of the alkylene group is an ether group. Or it is substituted with an ester group), or it is a phenylene group, A ₂ is CH ₃ , a is an integer of 0 to 1, b is 1, and c is an integer of 1 to 2. , The liquid crystal alignment agent according to claim 1. The liquid crystal alignment agent according to claim 1 or 2, wherein the diamine represented by the formula [3] in the polymer (B) has a structure represented by the following formulas [3-1] to [3-3]. ..

(In the formula, * represents a bond. However, in the formula [3-3], at least one of the bonds from the carbon atom constituting the nitrogen-containing aromatic heterocycle is bonded to the aromatic hydrocarbon ring. ) The liquid crystal alignment agent according to any one of claims 1 to 3, wherein the diamine represented by the above formula [3] in the polymer (B) is selected from the group consisting of the following formulas.

The liquid crystal alignment agent according to any one of claims 1 to 4, wherein the diamine component in the polymer (C) contains a diamine represented by the following formula [4].

(In the formula, Y is

It has one or more of the structures shown by, and * is a bond. ) The liquid crystal alignment agent according to claim 5, wherein the diamine represented by the formula [4] is selected from the group consisting of the following formulas.

The tetracarboxylic acid component in (ii) and (iii) of the polymer (A) is an aromatic tetracarboxylic dianhydride, an alicyclic tetracarboxylic dianhydride, an aliphatic tetracarboxylic dianhydride, or these. The liquid crystal alignment agent according to any one of claims 1 to 6, which comprises a derivative of. The liquid crystal alignment agent according to any one of claims 1 to 7, wherein the aromatic tetracarboxylic dianhydride in the polymer (A) is a compound represented by the following formula (3a-1).

(In the above formula, X ₁ is any of the following formulas (A-1) to (A-28). * Represents a bond.)

Any of claims 1 to 8, wherein the alicyclic tetracarboxylic dianhydride and / or the aliphatic tetracarboxylic dianhydride in the polymer (C) is a compound represented by the following formula (3c-1). The liquid crystal alignment agent according to item 1.

(In the above formula, X ₂ is any of the following formulas (B-1) to (B-18). * Represents a bond.)

The liquid crystal orientation according to any one of claims 1 to 9, wherein the polymer (A) is contained in an amount of 10 to 50% by mass with respect to 100% by mass of the total amount of the polymers (A) to (C). Agent. The liquid crystal orientation according to any one of claims 1 to 10, wherein the polymer (B) is contained in an amount of 10 to 70% by mass with respect to 100% by mass of the total amount of the polymers (A) to (C). Agent. The liquid crystal orientation according to any one of claims 1 to 11, wherein the polymer (C) is contained in an amount of 10 to 50% by mass with respect to 100% by mass of the total amount of the polymers (A) to (C). Agent. A liquid crystal alignment film obtained from the liquid crystal alignment agent according to any one of claims 1 to 12. The liquid crystal display element having the liquid crystal alignment film according to claim 13.