JP7613465B2 - Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element - Google Patents

Description

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

A liquid crystal display element is constructed by sandwiching a liquid crystal layer between a pair of transparent substrates equipped with electrodes. In the liquid crystal display element, an organic film made of an organic material is used as a liquid crystal alignment film so that the liquid crystal is aligned in a desired state between the substrates. That is, the liquid crystal alignment film is a component of the liquid crystal display element, and is formed on the surface of the substrate that sandwiches the liquid crystal and contacts the liquid crystal, and plays a role of aligning the liquid crystal in a certain direction between the substrates. Furthermore, the liquid crystal alignment film can control the pretilt angle of the liquid crystal. Methods of lowering the pretilt angle mainly by selecting a polyimide structure (see Patent Documents 1 and 2) are known.
In recent years, with the advancement of performance of liquid crystal display elements, in addition to applications such as large-screen, high-definition liquid crystal televisions, liquid crystal display elements are being used in vehicles, such as car navigation systems, meter panels, and monitors for surveillance cameras and medical cameras. In order to meet the demand for viewing angle characteristics, a lower pretilt angle than conventional ones is now being required even for rubbed alignment films.
In particular, the viewing angle dependency of color resulting from the pretilt angle, so-called color shift, has been pointed out as a problem, and in order to solve this problem, a liquid crystal alignment film having a pretilt angle of 1 degree or less has been proposed.

Japanese Patent Application Publication No. 9-188761 Japanese Patent Application Publication No. 10-123532 International Publication No. 2019-082975

In liquid crystal display elements of the horizontal electric field type, such as the IPS driving type and the FFS driving type, positive type liquid crystals have conventionally been used. However, by using negative type liquid crystals, it is possible to reduce the transmission loss above the electrodes and improve the contrast, so liquid crystal display elements using negative type liquid crystals have recently been investigated.
However, as a result of investigations conducted by the present inventors, it was found that the use of negative type liquid crystal as the liquid crystal material results in a high incidence of display defects (line burn-in), making it impossible to obtain a liquid crystal display element with excellent display quality.
In addition, polyimide-based liquid crystal alignment agents generally use organic polar solvents with high hygroscopicity such as N-methyl-2-pyrrolidone. Therefore, when a coating film is obtained from a polyimide-based liquid crystal alignment agent containing the above organic solvent, the obtained film tends to be easily affected by the environment in which the coating is performed. In particular, when coating is performed in a high humidity environment, there is a problem that the solubility of polyimide decreases due to moisture absorption, the polyimide precipitates, and the film becomes white (hygroscopic whitening). In addition, even if a film that has become white due to moisture absorption is dried or heated, there is a problem that the original characteristics of the liquid crystal alignment film cannot be obtained, and the obtained film has a problem of surface roughness.
Furthermore, when a coating film is obtained by flexographic printing using a polyimide-based liquid crystal alignment agent, the polyimide component may precipitate on the flexographic plate, resulting in printing foreign matter, or the polyimide component may precipitate in the ejection head of an inkjet device, causing clogging of the head, leading to defects in the process.

In view of the above circumstances, the object of the present invention is to provide a liquid crystal alignment agent that can obtain a liquid crystal alignment film having a pretilt angle of 1 degree or less, and at the same time, can obtain a liquid crystal display element with a low incidence of display defects (line burn-in) even when a negative liquid crystal is used as the liquid crystal material. In addition, the object of the present invention is to provide a liquid crystal alignment agent that can suppress the hygroscopic whitening phenomenon, is less likely to cause foreign matter or clogging when obtaining a coating film, and the obtained film has little surface roughness, and furthermore, can exhibit the original properties of the liquid crystal alignment film even after drying or heating.

As a result of extensive investigations to achieve the above objective, the inventors discovered that a liquid crystal alignment agent having the following composition is optimal for achieving the above objective, and thus completed the present invention.

式中、Ｄは２価の炭素数１～２０の飽和炭化水素基、不飽和炭化水素基、芳香族炭化水素基または複素環を表し、Ｄは１つ以上の置換基を有していてもよい。Ｅは単結合、または、２価の炭素数１～２０の飽和炭化水素基、不飽和炭化水素基、芳香族炭化水素基もしくは複素環であり、Ｅは１つ以上の置換基を有していてもよい。Ｆは単結合、－Ｏ－、－ＯＣＯ－、又は－ＣＯＯ－を表す。ｍは０又は１の整数である。Ａは熱によって脱離し得る有機基を表す。両端のアミノ基を有するベンゼン環の水素原子は、１つ以上の置換基で置換されていてもよい。 Thus, the present invention is based on the above findings and has the following gist.
A liquid crystal aligning agent containing a polyimide (A) obtained by imidizing a polyimide precursor which is a reaction product of a tetracarboxylic acid derivative component and a diamine component, wherein the tetracarboxylic acid derivative component contains 1,2,3,4-butanetetracarboxylic dianhydride or a derivative thereof, and the diamine component contains at least one diamine selected from the following formulas (1a) to (1b) and a diamine represented by the following formula (2):

In the formula, D represents a divalent saturated hydrocarbon group, unsaturated hydrocarbon group, aromatic hydrocarbon group or heterocycle having 1 to 20 carbon atoms, and D may have one or more substituents. E represents a single bond, or a divalent saturated hydrocarbon group, unsaturated hydrocarbon group, aromatic hydrocarbon group or heterocycle having 1 to 20 carbon atoms, and E may have one or more substituents. F represents a single bond, -O-, -OCO-, or -COO-. m is an integer of 0 or 1. A represents an organic group that can be eliminated by heat. The hydrogen atoms of the benzene ring having amino groups at both ends may be substituted with one or more substituents.

In this specification, Boc represents a tert-butoxycarbonyl group. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

By using the liquid crystal alignment agent of the present invention, a liquid crystal alignment film having a pretilt angle of 1 degree or less can be obtained, and a liquid crystal display element having a low incidence of display defects (line burn-in) can be obtained even when a negative liquid crystal is used as the liquid crystal material. In addition, a liquid crystal alignment agent can be obtained that can suppress the moisture absorption whitening phenomenon, is less likely to cause foreign matter or clogging when obtaining a coating film, and has little surface roughness, and can exhibit the original properties of a liquid crystal alignment film even when dried or heated.

<Specific Polymer>
The polyimide (A) (hereinafter also referred to as the specific polymer) contained in the liquid crystal aligning agent of the present invention is obtained by imidizing a polyimide precursor obtained from a tetracarboxylic acid derivative component containing a specific tetracarboxylic acid dianhydride and a diamine component containing a specific diamine. The polyimide (A) may be composed of one type or two or more types. The polyimide precursor may be a polyamic acid or a derivative thereof (e.g., a polyamic acid ester).
Specific examples of the materials used and the manufacturing method will be described in detail below.

<Tetracarboxylic acid derivatives>
The tetracarboxylic acid derivative component used in the production of the specific polymer of the present invention can be not only a tetracarboxylic acid dianhydride but also its derivatives, such as a tetracarboxylic acid dihalide compound, a tetracarboxylic acid dialkyl ester, and a tetracarboxylic acid dialkyl ester dihalide. As the tetracarboxylic acid derivative component, one type of tetracarboxylic acid dianhydride or its derivative may be used alone, or two or more types may be used in combination.
The tetracarboxylic acid derivative component contains 1,2,3,4-butanetetracarboxylic dianhydride or a derivative thereof.

The preferred content of the 1,2,3,4-butanetetracarboxylic dianhydride or its derivative is 50 to 100 mol % of the total tetracarboxylic acid derivative component, more preferably 50 to 95 mol %, and even more preferably 50 to 90 mol %.

The tetracarboxylic acid derivative component used in the production of the specific polymer contained in the liquid crystal aligning agent of the present invention may be the above-mentioned 1,2,3,4-butanetetracarboxylic dianhydride or its derivative, or various tetracarboxylic acid derivative components may be used depending on the desired properties of the liquid crystal aligning agent or liquid crystal alignment film.
Preferable specific examples thereof include acyclic aliphatic tetracarboxylic dianhydrides or derivatives thereof other than those mentioned above, alicyclic tetracarboxylic dianhydrides or derivatives thereof, and aromatic tetracarboxylic dianhydrides or derivatives thereof. Here, the aromatic tetracarboxylic dianhydride is an acid dianhydride obtained by intramolecular dehydration of four carboxy groups including at least one carboxy group bonded to an aromatic ring. The acyclic aliphatic tetracarboxylic dianhydride is an acid dianhydride obtained by intramolecular dehydration of four carboxy groups bonded to a chain hydrocarbon structure. However, it is not necessary to be composed of only a chain hydrocarbon structure, and it may have an alicyclic structure or an aromatic ring structure in part. The alicyclic tetracarboxylic dianhydride is an acid dianhydride obtained by intramolecular dehydration of four carboxy groups including at least one carboxy group bonded to an alicyclic structure. However, none of these four carboxy groups are bonded to an aromatic ring. In addition, it is not necessary to be composed of only an alicyclic structure, and it may have a chain hydrocarbon structure or an aromatic ring structure in part.
As the tetracarboxylic acid derivative component, one represented by the following formula (3) is preferable. The tetracarboxylic acid dianhydride or its derivative represented by the following formula (3) may be used alone or in combination of two or more.

式中Ｘ_１は、下記式（Ｘ１－１）～（Ｘ１－２５）から選ばれる構造である。

In the formula, _X1 is a structure selected from the following formulae (X1-1) to (X1-25).

In formulae (X1-1) to (X1-4), R ₃ to R ₂₃ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom, or a phenyl group. * represents a bond. From the viewpoint of liquid crystal alignment, R ₃ to R ₂₃ are preferably a hydrogen atom, a halogen atom, a methyl group, or an ethyl group, and more preferably a hydrogen atom or a methyl group.
In formulae (X1-24) and (X1-25), j and k are integers of 0 or 1, and A ₁ and A ₂ each independently represent a single bond, -O-, -CO-, -COO-, phenylene, sulfonyl, or an amide group. A ₂ may be the same or different.

Specific examples of formula (X1-1) include the following formulas (X1-1-1) to (X1-1-6). From the viewpoint of improving the liquid crystal alignment, (X1-1-1) is particularly preferred. * is as defined above.

Preferred specific examples of the above formulae (X1-24) and (X1-25) include the following formulae (X1-26) to (X1-41), where * is as defined above.

From the viewpoint of enhancing the liquid crystal alignment property, the above _X1 is preferably the above formula (X1-1) to (X1-3), (X1-5), (X1-7) to (X1-9), (X1-10) or (X1-23), and more preferably the above formula (X1-1-1), (X1-1-2), (X1-2) to (X1-3), (X1-5), (X1-7) to (X1-9), (X1-10) or (X1-23).

（式中、Ｄは２価の炭素数１～２０の飽和炭化水素基、不飽和炭化水素基、芳香族炭化水素基または複素環を表し、Ｄは１つ以上の置換基を有していてもよい。Ｅは単結合、または、２価の炭素数１～２０の飽和炭化水素基、不飽和炭化水素基、芳香族炭化水素基もしくは複素環であり、Ｅは１つ以上の置換基を有していてもよい。Ｆは単結合、－Ｏ－、－ＯＣＯ－、又は－ＣＯＯ－を表す。ｍは０又は１の整数である。Ａは熱によって脱離し得る有機基を表す。両端のアミノ基を有するベンゼン環の水素原子は、１つ以上の置換基で置換されていてもよい。） <Specific diamine>
The diamine component used in the production of the polyimide (A) contained in the liquid crystal aligning agent of the present invention contains at least one diamine selected from the following formulas (1a) to (1b) and a diamine represented by the following formula (2). The diamines represented by the following formulas (1a) to (1b) and (2) may each be used alone or in combination of two or more.

(In the formula, D represents a divalent saturated hydrocarbon group, unsaturated hydrocarbon group, aromatic hydrocarbon group or heterocycle having 1 to 20 carbon atoms, and D may have one or more substituents. E represents a single bond, or a divalent saturated hydrocarbon group, unsaturated hydrocarbon group, aromatic hydrocarbon group or heterocycle having 1 to 20 carbon atoms, and E may have one or more substituents. F represents a single bond, -O-, -OCO-, or -COO-. m is an integer of 0 or 1. A represents an organic group that can be eliminated by heat. The hydrogen atoms of the benzene ring having amino groups at both ends may be substituted with one or more substituents.)

Examples of the substituent for D or E include a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a fluoroalkyl group having 1 to 10 carbon atoms, a fluoroalkenyl group having 2 to 10 carbon atoms, a fluoroalkoxy group having 1 to 10 carbon atoms, a carboxy group, a hydroxy group, an alkyloxycarbonyl group having 1 to 10 carbon atoms, a cyano group, and a nitro group.
The organic group that can be eliminated by heat is not particularly limited as long as it is an organic group that is decomposed and eliminated by heat, thereby converting -NHA into an amino group. Examples of the structure of the organic group that can be eliminated by heat include carbamate-based organic groups such as benzyloxycarbonyl group, 9-fluorenylmethyloxycarbonyl group, allyloxycarbonyl group, and tertiary butoxycarbonyl group (tert-butoxycarbonyl group). From the viewpoint that the efficiency of elimination by heat is good, it is eliminated at a relatively low temperature, and is discharged as a harmless gas when eliminated, the tertiary butoxycarbonyl group is particularly preferable. In this specification, the organic group is, for example, a hydrocarbon group that may have a nitrogen atom or an oxygen atom.

In the above formula (1a) or (1b), the hydrogen atom of the benzene ring having amino groups at both ends may be substituted with a substituent, specifically a halogen atom or an alkyl group having 1 to 5 carbon atoms, etc., and may be selected from various types depending on the availability of reagents, but unsubstituted ones are preferred. The substitution position of the amino group is not particularly limited, but from the viewpoint of the difficulty of synthesis and the availability of reagents, the meta or para position is preferred based on the amide bond, and the para position is particularly preferred from the viewpoint of liquid crystal alignment. Similarly, in aminobenzenes that do not have a protected amino group (i.e. -NHA), the meta or para position is preferred based on the amide bond, the meta position is preferred from the viewpoint of solubility, and the para position is preferred from the viewpoint of liquid crystal alignment.

Examples of the saturated hydrocarbon group having 1 to 20 carbon atoms for D and E in formula (1a) or (1b) above include linear alkylene groups such as _-CH2- or -( _CH2 ) _m- (where m is an integer from 2 to 20); cycloalkylene groups such as cyclobutylene, cyclopentylene, and cyclohexylene; or groups in which some of the carbon-carbon bonds in -( _CH2 ) _m- have been replaced with the above cycloalkylene groups.
Examples of the unsaturated hydrocarbon group include groups in which some of the carbon-carbon bonds of a saturated hydrocarbon group having 2 to 20 carbon atoms have been replaced with double bonds or triple bonds.
Examples of the aromatic hydrocarbon group include a benzene ring, a biphenyl structure, and a naphthalene ring.
Examples of the heterocycle include nitrogen atom-containing heterocycles such as pyrrole, imidazole, pyrazole, triazole, pyridine, pyrimidine, pyridazine, pyrazine, indole, benzimidazole, purine, quinoline, isoquinoline, naphthyridine, quinoxaline, phthalazine, triazine, carbazole, acridine, piperidine, piperazine, pyrrolidine, and hexamethyleneimine. Among these, pyridine, pyrimidine, pyrazine, piperidine, piperazine, quinoline, carbazole, and acridine are preferred.

The diamine selected from the above formulae (1a) and (1b) is preferably a diamine selected from the following formulae (1-1) to (1-4).

The content of at least one diamine selected from the above formulas (1a) to (1b) is preferably 5 to 50 mol % of the total diamine components, more preferably 10 to 50 mol %, and even more preferably 10 to 40 mol %.

In the above formula (2), the hydrogen atom of the benzene ring having amino groups at both ends may be substituted with a substituent, specifically, for example, a halogen atom or an alkyl group having 1 to 5 carbon atoms, and may be selected from various types depending on the availability of reagents, etc., but unsubstituted ones are preferred.

The diamine represented by the above formula (2) is preferably a diamine represented by the following formulas (2-1) to (2-2).

The content of the diamine of the above formula (2) is preferably 50 to 95 mol % of the total diamine components, and more preferably 50 to 90 mol %.

In addition to the above diamines, various diamines (hereinafter also referred to as other diamines) can be used as the diamine component used in the production of the polyimide (A) contained in the liquid crystal alignment agent of the present invention depending on the desired properties of the liquid crystal alignment agent.
Other diamines include diamines (4) having the structure of the following formula (iv) in the molecule; diamines represented by the following formula (O); diamines having a photoalignment group such as 4,4'-diaminoazobenzene or diaminotolane; diamines having an amide bond or urea bond such as diamines represented by the following formulas (h-1) to (h-6); 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminobenzophenone, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 1,4-bis(4-aminobenzyl)benzene, and diamines represented by the following formulas (A-1) to (A-6). diamines having at least one nitrogen atom-containing structure (hereinafter also referred to as specific nitrogen atom-containing structure) selected from the group consisting of a nitrogen atom-containing heterocycle, a secondary amino group, and a tertiary amino group; 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol; diamines having a carboxy group such as 4,4'-diamino-3,3'-dihydroxybiphenyl, 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid, 3,5-diaminobenzoic acid, and diamines represented by the following formulas (3b-1) to (3b-4): amine, 4-(2-(methylamino)ethyl)aniline, 4-(2-aminoethyl)aniline, 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; diamines having a photopolymerizable group at the end, such as 2-(2,4-diaminophenoxy)ethyl methacrylate and 2,4-diamino-N,N-diallylaniline; cholestanyloxy-3,5-diaminobenzene, cholestanyloxy-3,5-diaminobenzene, cholestanyloxy-2,4-diaminobenzene, 3,5-diaminobenzoic acid Diamines having a steroid skeleton such as cholestanyl, cholestenyl 3,5-diaminobenzoate, lanostannyl 3,5-diaminobenzoate, and 3,6-bis(4-aminobenzoyloxy)cholestane; diamines represented by the following formulas (V-1) to (V-6); diamines having a siloxane bond such as 1,3-bis(3-aminopropyl)-tetramethyldisiloxane; diamines having an oxazoline structure such as the following formulas (Ox-1) to (Ox-2); diamines having two amino groups bonded to a group represented by any of the formulas (Y-1) to (Y-167) described in WO 2018/117239. The other diamines may be used alone or in combination of two or more.

（上記式（ｉｖ）において、Ｄは熱によって脱離し得る有機基である。＊は結合手を表し、少なくとも一方は脂肪族炭化水素基に結合する。）

(In the above formula (iv), D is an organic group that can be removed by heat. * represents a bond, at least one of which is bonded to an aliphatic hydrocarbon group.)

（Ａｒは、２価のベンゼン環、ビフェニル構造、又はナフタレン環を表す。２つのＡｒは同一でも異なってもよく、前記ベンゼン環、ビフェニル構造、又はナフタレン環上の任意の水素原子は１価の有機基で置き換えられてもよい。ｐは０又は１の整数である。Ｑ_２は－（ＣＨ_２）_ｎ－（ｎは２～１８の整数である。）、又は該－（ＣＨ_２）_ｎ－の－ＣＨ_２－の少なくとも一部を－Ｏ－、－Ｃ（＝Ｏ）－又は－Ｏ－Ｃ（＝Ｏ）－のいずれかで置き換えた基を表す。）

(Ar represents a divalent benzene ring, biphenyl structure, or naphthalene ring. The two Ar's may be the same or different, and any hydrogen atom on the benzene ring, biphenyl structure, or naphthalene ring may be replaced with a monovalent organic group. p is an integer of 0 or 1. Q ₂ represents -(CH ₂ ) _n - (n is an integer of 2 to 18), or a group in which at least a portion of the -CH ₂ - in the -(CH ₂ ) _n - is replaced with any of -O-, -C(═O)-, or -O-C(═O)-.)

（式（３ｂ－１）中、Ａ^１は単結合、－ＣＨ_２－、－Ｃ_２Ｈ_４－、－Ｃ（ＣＨ_３）_２－、－ＣＦ_２－、－Ｃ（ＣＦ_３）_２－、－Ｏ－、－ＣＯ－、－ＮＨ－、－Ｎ（ＣＨ_３）－、－ＣＯＮＨ－、－ＮＨＣＯ－、－ＣＨ_２Ｏ－、－ＯＣＨ_２－、－ＣＯＯ－、－ＯＣＯ－、－ＣＯＮ（ＣＨ_３）－又は－Ｎ（ＣＨ_３）ＣＯ－を示し、ｍ１及びｍ２はそれぞれ独立して、０～４の整数であり、かつｍ１＋ｍ２は１～４の整数である。式（３ｂ－２）中、ｍ３及びｍ４はそれぞれ独立して、１～５の整数である。式（３ｂ－３）中、Ａ^２は炭素数１～５の直鎖又は分岐アルキル基を表し、ｍ５は１～５の整数である。式（３ｂ－４）中、Ａ^３及びＡ^４はそれぞれ独立して、単結合、－ＣＨ_２－、－Ｃ_２Ｈ_４－、－Ｃ（ＣＨ_３）_２－、－ＣＦ_２－、－Ｃ（ＣＦ_３）_２－、－Ｏ－、－ＣＯ－、－ＮＨ－、－Ｎ（ＣＨ_３）－、－ＣＯＮＨ－、－ＮＨＣＯ－、－ＣＨ_２Ｏ－、－ＯＣＨ_２－、－ＣＯＯ－、－ＯＣＯ－、－ＣＯＮ（ＣＨ_３）－又は－Ｎ（ＣＨ_３）－ＣＯ－を表し、ｍ６は１～４の整数である。）

(In formula (3b-1), A ¹ represents a single bond, —CH ₂ —, —C ₂ H ₄ —, —C(CH ₃ ) ₂ —, —CF ₂ —, —C(CF ₃ ) ₂ —, —O—, —CO—, —NH—, —N(CH ₃ )—, —CONH—, —NHCO—, —CH ₂ O—, —OCH ₂ —, —COO—, —OCO—, —CON(CH ₃ )— or —N(CH ₃ )CO—; m1 and m2 each independently represent an integer of 0 to 4, and m1+m2 represents an integer of 1 to 4; in formula (3b-2), m3 and m4 each independently represent an integer of 1 to 5; in formula (3b-3), A In formula (3b-4), A ³ and A ^{4 each} independently represent a single bond, —CH ₂ —, —C ₂ H ₄ —, —C(CH ₃ ) ₂ —, —CF ₂ —, —C(CF ₃ ) 2 —, _—O— , —CO—, —NH—, —N(CH 3 )—, —CONH—, —NHCO—, —CH ₂ O—, _{—OCH 2} —, —COO—, —OCO—, —CON(CH ₃ )— or —N(CH ₃ )—CO—, and m6 is an integer from 1 to 4.

（Ｘ^ｖ１～Ｘ^ｖ４、Ｘ^ｐ１～Ｘ^ｐ２は、それぞれ独立に、－（ＣＨ_２）_ａ－（ａは１～１５の整数である。）、－ＣＯＮＨ－、－ＮＨＣＯ－、－ＣＯＮ（ＣＨ_３）－、－ＮＨ－、－Ｏ－、－ＣＨ_２Ｏ－、－ＣＨ_２ＯＣＯ－、－ＣＯＯ－、又は－ＯＣＯ－を表し、Ｘ^ｖ５は－Ｏ－、－ＣＨ_２Ｏ－、－ＣＨ_２ＯＣＯ－、－ＣＯＯ－、又は－ＯＣＯ－を表す。Ｘａは、単結合、－Ｏ－、－ＮＨ－、又は－Ｏ－（ＣＨ_２）_ｍ－Ｏ－（ｍは１～６の整数を表す。）を表し、Ｒ^ｖ１～Ｒ^ｖ４、Ｒ^１ａ～Ｒ^１ｂは、それぞれ独立に、炭素数１～２０のアルキル基、炭素数１～２０のアルコキシ基又は炭素数２～２０のアルコキシアルキル基を表す。２つのｋは同一であっても異なっていてもよい。）

(X ^v1 to X ^v4 and X ^p1 to X ^p2 each independently represent -(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 represents a single bond, -O-, -NH-, or -O-(CH ₂ ) _m -O- (m is an integer of 1 to 6); R ^v1 to R ^v4 and R ^1a to R Each of ^1b independently represents an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an alkoxyalkyl group having 2 to 20 carbon atoms. Two k's may be the same or different.

In the diamine (4) having the structure of the above formula (iv) in the molecule, specific examples of the organic group that can be eliminated by heat in D of the above formula (iv) include the structures exemplified in the above A, including preferred embodiments. In addition, from the viewpoint of reducing the incidence of display defects (line burn-in), it is more preferable that the above diamine (4) is an aromatic diamine having one or two benzene rings in the molecule.

Preferred specific examples of the diamine (4) include diamines represented by the following formulas (4-1) to (4-5).

The content of diamine (4) having the structure of the above formula (iv) in the molecule is preferably 5 to 40 mol % of the total diamine components, more preferably 5 to 35 mol %, and even more preferably 5 to 30 mol %.

In the diamine represented by the above formula (O), any hydrogen atom on the benzene ring, biphenyl structure, or naphthalene ring may be replaced with a monovalent organic group. Examples of the monovalent organic group include a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a fluoroalkyl group having 1 to 10 carbon atoms, a fluoroalkenyl group having 2 to 10 carbon atoms, a fluoroalkoxy group having 1 to 10 carbon atoms, a carboxy group, a hydroxy group, an alkyloxycarbonyl group having 1 to 10 carbon atoms, a cyano group, and a nitro group.

Specific preferred examples of the divalent organic group obtained by removing two amino groups from the diamine represented by the above formula (O) include the divalent organic groups represented by the following formulas (o-1) to (o-16). * represents a bond.

（式（ｏ－１４）において、２つのｍは同一であっても異なっていてもよい。）

(In formula (o-14), the two m's may be the same or different.)

Examples of the nitrogen atom-containing heterocycle that may be contained in the diamine having the specific nitrogen atom-containing structure include the heterocycles exemplified above. Among these, pyridine, pyrimidine, pyrazine, piperidine, piperazine, quinoline, carbazole, and acridine are preferred.

上記式（ｎ）において、Ｒは、水素原子又は炭素数１～１０の１価の炭化水素基を表す。「＊」は、炭化水素基に結合する結合手を表す。 The secondary amino group and tertiary amino group which the diamine having the specific nitrogen atom-containing structure may have are represented, for example, by the following formula (n).

In the above formula (n), R represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. "*" represents a bond bonded to the hydrocarbon group.

Examples of the monovalent hydrocarbon group R in the above formula (n) include alkyl groups such as methyl, ethyl, and propyl; cycloalkyl groups such as cyclohexyl; and aryl groups such as phenyl and methylphenyl. R is preferably a hydrogen atom or a methyl group.

Specific examples of diamines having the above-mentioned specific nitrogen atom-containing structure include, for example, 2,6-diaminopyridine, 3,4-diaminopyridine, 2,4-diaminopyrimidine, 3,6-diaminocarbazole, N-methyl-3,6-diaminocarbazole, 1,4-bis-(4-aminophenyl)-piperazine, 3,6-diaminoacridine, N-ethyl-3,6-diaminocarbazole, N-phenyl-3,6-diaminocarbazole, diamines represented by the following formulas (Dp-1) to (Dp-8), and diamines represented by the following formulas (z-1) to (z-18).

<Polymer (B)>
The liquid crystal alignment agent of the present invention may contain a polyimide precursor (B) (hereinafter also referred to as polymer (B)) which is a reaction product of a tetracarboxylic acid derivative component and a diamine component from the viewpoint of reducing residual images derived from residual DC. The polyimide precursor (B) may be composed of one type or two or more types. Specific examples of the polyimide precursor (B) include polyamic acid or its derivatives (e.g., polyamic acid esters), and among them, polyamic acid is preferred.

Examples of the tetracarboxylic acid derivative component for obtaining the polymer (B) include acyclic aliphatic tetracarboxylic acid dianhydrides, alicyclic tetracarboxylic acid dianhydrides, aromatic tetracarboxylic acid dianhydrides, or derivatives thereof. Specific examples of the acyclic aliphatic tetracarboxylic acid dianhydrides, alicyclic tetracarboxylic acid dianhydrides, and aromatic tetracarboxylic acid dianhydrides include the tetracarboxylic acid dianhydrides or derivatives thereof exemplified in the above specific polymer. Among them, preferred tetracarboxylic acid derivative components include 1,2,3,4-butane tetracarboxylic acid dianhydride or its derivatives, tetracarboxylic acid dianhydrides having at least one partial structure selected from the group consisting of a benzene ring, a cyclobutane ring structure, a cyclopentane ring structure, and a cyclohexane ring structure, or derivatives thereof, and 1,2,3,4-butane tetracarboxylic acid dianhydride, a compound represented by the above formula (3), or derivatives thereof are more preferred. As the tetracarboxylic acid derivative component, one type of tetracarboxylic acid dianhydride or its derivative may be used alone, or two or more types may be used in combination.

The tetracarboxylic acid derivative component for obtaining polymer (B) is preferably a tetracarboxylic acid dianhydride represented by formula (3) in which X is selected from the above formulas (X1-1) to (X1-10), (X1-21), (X1-23) to (X1-25), 1,2,3,4-butanetetracarboxylic acid dianhydride, or a derivative thereof.

The proportion of the tetracarboxylic dianhydride represented by the above formula (3), 1,2,3,4-butanetetracarboxylic dianhydride or a derivative thereof used is preferably 1 to 100 mol%, more preferably 5 to 100 mol%, and even more preferably 10 to 100 mol%, relative to 1 mole of the total tetracarboxylic acid derivative components used in the synthesis of polymer (B).

Examples of diamine components for obtaining polymer (B) include the diamine components exemplified in the specific polymer above. Among them, it is preferable to include at least one diamine selected from the group consisting of a diamine having at least one group selected from the group consisting of a urea bond, an amide bond, a carboxy group, and a hydroxy group in the molecule (hereinafter also referred to as diamine (b1)), and a diamine having the specific nitrogen atom-containing structure (hereinafter also referred to as diamine (b2)). The diamine component may be a single diamine or a combination of two or more diamines.

The polymer (B) may be composed of one or more polyimide precursors. More preferred specific aspects of the polymer (B) include at least one polymer (hereinafter also referred to as a copolymer) selected from the group consisting of a diamine component containing the above diamine (b1) and the above diamine (b2) and a polyimide precursor which is a reaction product of a tetracarboxylic acid derivative component, at least one polymer (B-p1) selected from the group consisting of a diamine component containing the above diamine (b1) and a polyimide precursor which is a reaction product of a tetracarboxylic acid derivative component, and at least one polymer (B-p2) selected from the group consisting of a diamine component containing the above diamine (b2) and a polyimide precursor which is a reaction product of a tetracarboxylic acid derivative component (hereinafter also referred to as a polymer blend). The above copolymers or polymer blends may be used alone or in combination.

In the above copolymer, the amount of diamine (b1) used is preferably 30 to 100 mol %, more preferably 40 to 100 mol %, and even more preferably 50 to 100 mol %, based on the total amount of diamine components used to produce polymer (B).
In the above copolymer, the amount of diamine (b2) used is preferably 30 to 100 mol %, more preferably 40 to 100 mol %, and even more preferably 50 to 100 mol %, based on the total amount of diamine components used to produce polymer (B).
In the above polymer blend, the diamine (b1) and the diamine (b2) are preferably used in an amount of 20 to 100 mol % based on the total amount of the diamine components for producing the polymer (B-p1) and the polymer (B-p2), respectively. The diamine (b1) is more preferably used in an amount of 20 to 90 mol %, and even more preferably 20 to 80 mol %, based on the total amount of the diamine components for producing the polymer (B-p1). The diamine (b2) is more preferably used in an amount of 20 to 80 mol %, and even more preferably 30 to 80 mol %, based on the total amount of the diamine components for producing the polymer (B-p2).

Specific examples of the diamine (b1) include diamines represented by the above formulas (1a) to (1b), diamines represented by the above formulas (4-1), diamines represented by the above formulas (h-1) to (h-6), 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol, 4,4'-diamino-3,3'-dihydroxybiphenyl, 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid, 3,5-diaminobenzoic acid, and diamines represented by the above formulas (3b-1) to (3b-4).

Specific examples of the diamine (b2) include the diamines exemplified for the specific polymer. Among them, the diamines represented by the formulas (Dp-1) to (Dp-8) and the diamines represented by the formulas (z-1) to (z-18) are preferred.

The mass ratio of the content of the above polymer (B-p1) to the content of the above polymer (B-p2) is preferably 5/95 to 95/5, and more preferably 10/90 to 90/10.

From the viewpoint of minimizing afterimages caused by residual DC, the content ratio of the specific polymer to polymer (B) is preferably 10/90 to 90/10 in terms of the mass ratio of [specific polymer]/[polymer (B)], more preferably 20/80 to 90/10, and particularly preferably 20/80 to 80/20.

<Production method of specific polymer, polymer (B)>
The polyimide precursor used in the present invention can be synthesized by a known method, for example, as described in International Publication WO2013/157586.

Polyimide can be obtained by ring-closing (imidization) the polyimide precursor. The imidization ratio in this specification refers to the ratio of imide groups to the total amount of imide groups derived from tetracarboxylic dianhydride or its derivatives and carboxyl groups (or its derivatives). In polyimides, the imidization ratio does not necessarily have to be 100%, and can be adjusted arbitrarily depending on the application and purpose. The imidization ratio of polyimide (A), which is a specific polymer used in the present invention, is preferably 20 to 100%, more preferably 50 to 99%, and even more preferably 70 to 99%, from the viewpoint of reducing the occurrence rate of display defects.

Methods for imidizing a polyimide precursor include, for example, thermal imidization, in which a solution of the polyimide precursor is heated as is, or catalytic imidization, in which a catalyst is added to a solution of the polyimide precursor.

When the polyimide precursor is thermally imidized in a solution, the temperature is preferably 100 to 400°C, more preferably 120 to 250°C, and it is preferable to carry out the imidization while removing the water produced by the imidization reaction from the system.

Catalytic imidization of polyimide precursors 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°C, preferably 0 to 180°C. The amount of the basic catalyst is 0.5 to 30 molar times, preferably 2 to 20 molar times, the amount of the acid anhydride is 1 to 50 molar times, preferably 3 to 30 molar times, the amount of the amic acid group. Examples of basic catalysts include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine, etc., of which pyridine is preferred because it has a suitable basicity for promoting the reaction. Examples of acid anhydrides include acetic anhydride, trimellitic anhydride, pyromellitic anhydride, etc., of which acetic anhydride is preferred because it makes purification after the reaction easier. The imidization rate by catalytic imidization can be controlled by adjusting the amount of catalyst, reaction temperature, and reaction time.

When recovering the polyimide precursor or polyimide produced from the reaction solution of the polyimide precursor or polyimide, the reaction solution may be poured into a solvent to cause precipitation. Examples of the solvent used for precipitation include methanol, ethanol, isopropyl alcohol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, toluene, benzene, and water. The polymer precipitated by pouring into the solvent can be recovered by filtration, and then dried at room temperature or by heating under normal or reduced pressure. In addition, the polymer precipitated and recovered can be redissolved in an organic solvent and the reprecipitation and recovery operation repeated 2 to 10 times to reduce impurities in the polymer. Examples of the solvent used in this case include alcohols, ketones, and hydrocarbons. It is preferable to use three or more solvents selected from these because the efficiency of purification is further improved.

The molecular weight of the polymer used in the present invention is preferably 5,000 to 1,000,000, more preferably 10,000 to 150,000, in terms of weight average molecular weight measured by GPC (Gel Permeation Chromatography), taking into consideration the strength of the liquid crystal alignment film obtained therefrom, the workability during film formation, and the coating properties.

<Terminal Modifier>
In synthesizing the specific polymer, polymer (B) in the present invention, a terminal-modified polymer may be synthesized using a suitable terminal modifier together with the above-mentioned tetracarboxylic acid derivative component and diamine component. The terminal-modified polymer has the effect of improving the film hardness of the liquid crystal alignment film obtained by coating and improving the adhesion property between the sealant and the liquid crystal alignment film.
Examples of the terminal of the specific polymer, polymer (B) in the present invention include an amino group, a carboxy group, an acid anhydride group, an isocyanate group, or a derivative thereof. The amino group, the carboxy group, the acid anhydride group, and the isocyanate group can be obtained by a normal condensation reaction, and the derivative can be obtained by modifying the terminal, for example, using the following terminal modifier.

二炭酸ジ－ｔｅｒｔ－ブチル、二炭酸ジアリルなどの二炭酸ジエステル化合物；アクリロイルクロリド、メタクリロイルクロリド、ニコチン酸クロリドなどのクロロカルボニル化合物；アニリン、２－アミノフェノール、３－アミノフェノール、４－アミノサリチル酸、５－アミノサリチル酸、６－アミノサリチル酸、２－アミノ安息香酸、３－アミノ安息香酸、４－アミノ安息香酸、シクロヘキシルアミン、ｎ－ブチルアミン、ｎ－ペンチルアミン、ｎ－ヘキシルアミン、ｎ－ヘプチルアミン、ｎ－オクチルアミンなどのモノアミン化合物；エチルイソシアネート、フェニルイソシアネート、ナフチルイソシアネートなどのモノイソシアネート化合物などを挙げることができる。 Examples of the terminal modifier include acid monoanhydrides such as acetic anhydride, maleic anhydride, nadic anhydride, phthalic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride, 3-hydroxyphthalic anhydride, trimellitic anhydride, compounds represented by the following formulas (m-1) to (m-6), 3-(3-trimethoxysilyl)propyl)-3,4-dihydrofuran-2,5-dione, 4,5,6,7-tetrafluoroisobenzofuran-1,3-dione, and 4-ethynylphthalic anhydride;

Examples of the dicarbonate diester compounds include di-tert-butyl dicarbonate and diallyl dicarbonate; chlorocarbonyl compounds include acryloyl chloride, methacryloyl chloride and nicotinic acid chloride; monoamine compounds include aniline, 2-aminophenol, 3-aminophenol, 4-aminosalicylic acid, 5-aminosalicylic acid, 6-aminosalicylic acid, 2-aminobenzoic acid, 3-aminobenzoic acid, 4-aminobenzoic acid, cyclohexylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine and n-octylamine; and monoisocyanate compounds include ethyl isocyanate, phenyl isocyanate and naphthyl isocyanate.

The proportion of terminal modifier used is preferably 0.01 to 20 molar parts, and more preferably 0.01 to 10 molar parts, per 100 molar parts of the total diamine components used.

<Liquid crystal alignment agent>
The liquid crystal aligning agent of the present invention contains a specific polymer and, if necessary, a polymer (B). The content of the polymer component contained in the liquid crystal aligning agent of the present invention is preferably 0.1 to 30% by mass, more preferably 3 to 10% by mass. The total content of the specific polymer and the polymer (B) contained in the liquid crystal aligning agent is preferably 1 to 9% by mass, more preferably 1.5 to 9% by mass. In addition, when referring to the total, the case where one or more of the constituent unit elements are 0% by mass is also included.
The liquid crystal alignment agent of the present invention may contain other polymers in addition to the specific polymer, polymer (B). Examples of the other polymers include polyimide (B) which is an imidized product of polyimide precursor (B) (excluding polyimide (A) which is a specific polymer), polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivative, polyacetal, polystyrene or its derivative, poly(styrene-phenylmaleimide) derivative, poly(meth)acrylate, etc.

The liquid crystal alignment agent is used to prepare a liquid crystal alignment film, and takes the form of a coating liquid from the viewpoint of forming a uniform thin film. It is preferable that the liquid crystal alignment agent of the present invention is also a coating liquid containing the above-mentioned polymer component and an organic solvent.

The organic solvent contained in the liquid crystal alignment agent is not particularly limited as long as it dissolves the polymer component uniformly. Specific examples include N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethyllactamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethylsulfoxide, γ-butyrolactone, γ-valerolactone, 1,3-dimethyl-2-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, 3-methylpropanol ... Examples of the good solvent include propanamide, N-(n-propyl)-2-pyrrolidone, N-isopropyl-2-pyrrolidone, N-(n-butyl)-2-pyrrolidone, N-(tert-butyl)-2-pyrrolidone, N-(n-pentyl)-2-pyrrolidone, N-methoxypropyl-2-pyrrolidone, N-ethoxyethyl-2-pyrrolidone, N-methoxybutyl-2-pyrrolidone, and N-cyclohexyl-2-pyrrolidone (collectively referred to as "good solvent"). Among these, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, or γ-butyrolactone are preferred. The content of the good solvent is preferably 20 to 99% by mass, more preferably 20 to 90% by mass, and particularly preferably 30 to 80% by mass of the total solvent contained in the liquid crystal alignment agent.

In addition, it is preferable to use a mixed solvent containing the above-mentioned solvent and a solvent (also called a poor solvent) that improves the coatability and surface smoothness of the coating film when applying the liquid crystal alignment agent. Specific examples of organic solvents to be used in combination are listed below, but are not limited to these.

For example, diisopropyl ether, diisobutyl ether, diisobutyl carbinol (2,6-dimethyl-4-heptanol), ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, 1,2-butoxyethane, 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, Examples of the 2-(2-butoxyethoxy)-1-propanol include propylene glycol monomethyl ether acetate, propylene glycol diacetate, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monobutyl ether acetate, 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 glycol monoethyl ether acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, propyl 3-methoxypropionate, butyl 3-methoxypropionate, n-butyl lactate, isoamyl lactate, diethylene glycol monoethyl ether, and diisobutyl ketone (2,6-dimethyl-4-heptanone).

Among these, diisobutyl carbinol, propylene glycol monobutyl ether, propylene glycol diacetate, diethylene glycol diethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, or diisobutyl ketone are preferred.

Preferred solvent combinations of good and poor solvents include N-methyl-2-pyrrolidone, γ-butyrolactone and ethylene glycol monobutyl ether acetate, N-ethyl-2-pyrrolidone, ethylene glycol monobutyl ether and ethylene glycol monobutyl ether acetate, N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone and ethylene glycol monobutyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone and propylene glycol monobutyl ether, N-ethyl-2-pyrrolidone and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone and 4-hydroxy-4- Examples of the poor solvent include methyl-2-pentanone and diethylene glycol diethyl ether, N-methyl-2-pyrrolidone and γ-butyrolactone and propylene glycol monobutyl ether and 2,6-dimethyl-4-heptanone, N-methyl-2-pyrrolidone and γ-butyrolactone and propylene glycol monobutyl ether and diisopropyl ether, N-methyl-2-pyrrolidone and γ-butyrolactone and propylene glycol monobutyl ether and 2,6-dimethyl-4-heptanol, N-methyl-2-pyrrolidone and γ-butyrolactone and dipropylene glycol dimethyl ether, N-methyl-2-pyrrolidone and propylene glycol monobutyl ether and dipropylene glycol dimethyl ether, etc. The content of 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 of the total solvent contained in the liquid crystal alignment agent. The type and content of the poor solvent are appropriately selected depending on the coating device, coating conditions, coating environment, etc. of the liquid crystal alignment agent.

The liquid crystal alignment agent of the present invention may additionally contain components other than the polymer component and the organic solvent (hereinafter also referred to as additive components). Such additive components include adhesion assistants for improving the adhesion between the liquid crystal alignment film and the substrate or between the liquid crystal alignment film and the sealant, compounds for increasing the strength of the liquid crystal alignment film (hereinafter also referred to as cross-linking compounds), dielectrics or conductive substances for adjusting the dielectric constant or electrical resistance of the liquid crystal alignment film, imidization promoters, etc.

（Ｒ_２及びＲ_３は、それぞれ独立に水素原子、炭素数１～３のアルキル基又は「＊－ＣＨ_２－ＯＨ」である。＊は結合手であることを示す。Ａは芳香環を有する（ｍ＋ｎ）価の有機基を表す。ｍは１～６の整数を表し、ｎは０～４の整数を表す。Ａの芳香環は１価の基で置換されてもよく、該１価の基の具体例としては、上記式（Ｏ）のＡｒの置換基で示した１価の有機基（但し、炭素数１～１０のアルコキシ基を除く。）が挙げられる。） From the viewpoint of exhibiting good resistance to AC afterimages (afterimages caused by a decrease in the alignment performance of a liquid crystal alignment film that occurs with long-term AC driving) and highly improving film strength, the crosslinkable compound may be a compound having at least one group selected from the group consisting of an oxiranyl group, an oxetanyl group, a protected isocyanate group, a protected isothiocyanate group, a group containing an oxazoline ring structure, a group containing a Meldrum's acid structure, a cyclocarbonate group, and a group represented by the following formula (d), or a compound selected from compounds represented by the following formula (e) (hereinafter, these may be collectively referred to as compound (C)).

( _R2 and _R3 are each independently a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or "* _-CH2 -OH". * indicates a bond. A represents an (m+n)-valent organic group having an aromatic ring. m represents an integer of 1 to 6, and n represents an integer of 0 to 4. The aromatic ring of A may be substituted with a monovalent group, and specific examples of the monovalent group include the monovalent organic groups shown as the substituents of Ar in formula (O) above (excluding alkoxy groups having 1 to 10 carbon atoms).)

Specific examples of compounds having an oxiranyl group include compounds having two or more oxiranyl groups, such as the compounds described in paragraph [0037] of JP-A-10-338880 and compounds having a triazine ring skeleton described in WO 2017/170483. Among these, compounds containing nitrogen atoms, such as N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-p-phenylenediamine, and compounds represented by the following formulas (r-1) to (r-3), may be used.

Specific examples of compounds having an oxetanyl group include compounds having two or more oxetanyl groups, such as those described in paragraphs [0170] to [0175] of WO 2011/132751.

Specific examples of the compound having a protected isocyanate group include the compound having two or more protected isocyanate groups described in paragraphs [0046] to [0047] of JP 2014-224978 A, and the compound having three or more protected isocyanate groups described in paragraphs [0119] to [0120] of WO 2015/141598 A. The compound may be any of the compounds represented by the following formulae (bi-1) to (bi-3).

Specific examples of compounds having a protected isothiocyanate group include compounds having two or more protected isothiocyanate groups, as described in JP 2016-200798 A.

Specific examples of compounds having a group containing an oxazoline ring structure include compounds containing two or more oxazoline structures, as described in paragraph [0115] of JP 2007-286597 A.

Specific examples of compounds having a group containing a Meldrum's acid structure include compounds having two or more Meldrum's acid structures, as described in International Publication No. 2012/091088.

Specific examples of compounds having a cyclocarbonate group include the compounds described in WO 2011/155577.

Examples of the alkyl group having 1 to 3 carbon atoms for R ₂ and R ₃ in the group represented by formula (d) above include a methyl group, an ethyl group, and a propyl group.

Specific examples of the compound having a group represented by the above formula (d) include compounds having two or more groups represented by the above formula (d) described in WO 2015/072554 and paragraph [0058] of JP 2016-118753 A, and compounds described in JP 2016-200798 A. Also includes compounds represented by the following formulae (hd-1) to (hd-8).

Examples of the (m+n)-valent organic group having an aromatic ring in A of the above formula (e) include an (m+n)-valent aromatic hydrocarbon group having 6 to 30 carbon atoms, an (m+n)-valent organic group to which an aromatic hydrocarbon group having 6 to 30 carbon atoms is bonded directly or via a linking group, and an (m+n)-valent group having an aromatic heterocycle. Examples of the aromatic hydrocarbon include benzene and naphthalene. Examples of the aromatic heterocycle include a pyrrole ring, an imidazole ring, a pyrazole ring, a pyridine ring, a pyrimidine ring, a quinoline ring, an isoquinoline ring, a carbazole ring, a pyridazine ring, a pyrazine ring, a benzimidazole ring, an indole ring, a quinoxaline ring, and an acridine ring. Examples of the linking group include -NR- (R represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms), an alkylene group having 1 to 10 carbon atoms, or a group obtained by removing one hydrogen atom from the above alkylene group, and a divalent or trivalent cyclohexane ring. Any hydrogen atom in the alkylene group may be substituted with a fluorine atom or an organic group such as a trifluoromethyl group. Specific examples include the compounds described in WO 2010/074269 and the compounds represented by the following formulas (e-1) to (e-10).

The above compounds are examples of crosslinkable compounds, and are not limited thereto. For example, components other than those described above are disclosed on pages 53 [0105] to 55 [0116] of WO 2015/060357. Two or more types of crosslinkable compounds may be combined.

The content of the crosslinkable compound in the liquid crystal alignment agent of the present invention is preferably 0.5 to 20 parts by mass per 100 parts by mass of the polymer component contained in the liquid crystal alignment agent, and more preferably 1 to 15 parts by mass from the viewpoint of proceeding with the crosslinking reaction and exhibiting good resistance to AC afterimages.

Examples of the adhesion aids include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldiethoxymethylsilane, 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-aminopropyltrimethoxysilane, and N-ethoxycarbonyl-3-aminopropyltrimethoxysilane. N-trimethoxysilylpropyltriethylenetriamine, 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-aminopropyltriethoxysilane Aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, N-bis(oxyethylene)-3-aminopropyltrimethoxysilane, N-bis(oxyethylene)-3-aminopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane Examples of silane coupling agents include silane coupling agents such as xysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-isocyanatepropyltriethoxysilane. When using a silane coupling agent, from the viewpoint of exhibiting good resistance to AC afterimages, it is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, relative to 100 parts by mass of the polymer component contained in the liquid crystal alignment agent.

The solid content concentration in the liquid crystal alignment agent (the ratio of the total mass of the components other than the solvent of the liquid crystal alignment agent to the total mass of the liquid crystal alignment agent) is appropriately selected in consideration of viscosity, volatility, etc., and is preferably in the range of 0.5 to 15 mass%, more preferably 1 to 10 mass%.
The particularly preferred range of solid content varies depending on the method used to apply the liquid crystal alignment agent to the substrate. For example, in the case of the spin coating method, the solid content is particularly preferably in the range of 1.5 to 4.5% by mass. In the case of the printing method, the solid content is particularly preferably in the range of 3 to 9% by mass, thereby making the solution viscosity in the range of 12 to 50 mPa·s. In the case of the inkjet method, the solid content is particularly preferably in the range of 1 to 5% by mass, thereby making the solution viscosity in the range of 3 to 15 mPa·s.

<Liquid crystal alignment film/Liquid crystal display element>
The liquid crystal alignment film of the present invention is obtained from the above liquid crystal aligning agent. The liquid crystal alignment film of the present invention can be used for horizontal alignment type or vertical alignment type (VA type) liquid crystal alignment film, and is particularly suitable for horizontal alignment type liquid crystal display elements such as IPS type or FFS type. The liquid crystal display element of the present invention is provided with the above liquid crystal alignment film. The liquid crystal display element of the present invention can be produced, for example, by a method including the following steps (1) to (3).
(1) Step of applying liquid crystal alignment agent to substrate The liquid crystal alignment agent of the present invention is applied to one side of a substrate provided with a patterned transparent conductive film by an appropriate application method such as roll coater method, spin coat method, printing method, inkjet method, etc. Here, the substrate is not particularly limited as long as it is a substrate with high transparency, and plastic substrates such as acrylic substrates and polycarbonate substrates can be used in addition to glass substrates and silicon nitride substrates. In addition, in a reflective liquid crystal display element, an opaque material such as a silicon wafer can be used for only one substrate, and in this case, a material that reflects light such as aluminum can also be used for the electrode. In addition, when manufacturing an IPS type or FFS type liquid crystal element, a substrate provided with an electrode made of a transparent conductive film or metal film patterned into a comb tooth shape and an opposing substrate without an electrode are used.
(2) Step of baking the coating film After the liquid crystal alignment agent is applied, pre-heating (pre-baking) is preferably performed first for the purpose of preventing dripping of the applied alignment agent. The pre-baking temperature is preferably 30 to 200°C, more preferably 40 to 150°C, and particularly preferably 40 to 100°C. The pre-baking time is preferably 0.25 to 10 minutes, more preferably 0.5 to 5 minutes. Then, it is preferable to further perform a heating (post-baking) step. The post-baking temperature is preferably 80 to 300°C, more preferably 120 to 250°C. The post-baking time is preferably 5 to 200 minutes, more preferably 10 to 100 minutes. The film thickness of the film thus formed is preferably 5 to 300 nm, more preferably 10 to 200 nm.

The coating film formed in the above step (1) can be used as it is as a liquid crystal alignment film, but the coating film may be subjected to an alignment ability imparting treatment. Examples of the alignment ability imparting treatment include a rubbing treatment in which the coating film is rubbed in a certain direction with a roll wrapped with a cloth made of fibers such as nylon, rayon, or cotton, and a photoalignment treatment in which the coating film is irradiated with polarized or non-polarized radiation.

In the photo-alignment treatment, the radiation to be irradiated to the coating film may be, for example, ultraviolet light and visible light containing light with a wavelength of 150 to 800 nm. When the radiation is polarized, it may be linearly polarized or partially polarized. When the radiation used is linearly polarized or partially polarized, the radiation may be applied from a direction perpendicular to the substrate surface, from an oblique direction, or a combination of these. When applying unpolarized radiation, the radiation is applied in an oblique direction.
(3) Step of preparing a liquid crystal cell Two substrates on which a liquid crystal alignment film is formed as described above are prepared, and liquid crystal is placed between the two substrates arranged opposite each other. Specifically, the following two methods can be mentioned. In the first method, first, two substrates are arranged opposite each other with a gap (cell gap) between them so that the liquid crystal alignment films face each other. Next, the periphery of the two substrates is bonded together using a sealant, and a liquid crystal composition is injected and filled into the substrate surfaces and the cell gap partitioned by the sealant so that it comes into contact with the film surface, and then the injection hole is sealed.

The second method is a method called ODF (One Drop Fill) method. For example, a UV-curable sealant is applied to a predetermined location on one of the two substrates on which a liquid crystal alignment film is formed, and a liquid crystal composition is dropped at a predetermined number of locations on the liquid crystal alignment film surface. Thereafter, the other substrate is bonded so that the liquid crystal alignment film faces the other substrate, and the liquid crystal composition is spread over the entire surface of the substrate to contact the film surface. Next, the entire surface of the substrate is irradiated with UV light to cure the sealant. In either method, it is preferable to remove the flow alignment during liquid crystal filling by heating the substrate to a temperature at which the liquid crystal composition used has an isotropic phase and then slowly cooling to room temperature.
When the coating films are subjected to a rubbing treatment, the two substrates are disposed opposite each other so that the rubbing directions of the coating films are at a predetermined angle, for example, perpendicular or anti-parallel to each other.
The sealing agent may be, for example, an epoxy resin containing a hardener and aluminum oxide spheres as spacers. The liquid crystal may be, for example, a nematic liquid crystal or a smectic liquid crystal, of which nematic liquid crystal is preferred.

A liquid crystal display element can be obtained by attaching a polarizing plate to the outer surface of the liquid crystal cell as necessary. Examples of polarizing plates that can be attached to the outer surface of the liquid crystal cell include a polarizing film called an "H film" made by absorbing iodine while stretching and aligning polyvinyl alcohol, sandwiched between cellulose acetate protective films, and a polarizing plate made of the H film itself.

The liquid crystal display element of the present invention can be effectively applied to various devices, such as watches, portable games, word processors, notebook computers, car navigation systems, camcorders, PDAs, digital cameras, mobile phones, smartphones, various monitors, liquid crystal televisions, and information displays.

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The abbreviations for compounds and solvents are as follows.
(Organic solvent)
NMP: N-methyl-2-pyrrolidone GBL: γ-butyrolactone BCA: ethylene glycol monobutyl ether acetate

(Diamine)
DA-1 to DA-10: Compounds represented by the following structural formulas

(Tetracarboxylic acid derivatives)
CA-1 to CA-5: Compounds represented by the following structural formulas

(Additives)
AD-1: 3-glycidoxypropyltriethoxysilane AD-2: A compound represented by the following structural formula.

<Viscosity>
In the synthesis examples, the viscosity of the polymer solution was measured using an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.) with a sample amount of 1.1 mL, a cone rotor TE-1 (1°34′, R24), and a temperature of 25°C.

<Measurement of imidization rate of polyimide>
The imidization rate of the polyimide in the synthesis example was measured as follows. 30 mg of polyimide powder was placed in an NMR (nuclear magnetic resonance) sample tube (NMR sampling tube standard, φ5 (Kusano Scientific Co., Ltd.)), deuterated dimethyl sulfoxide (DMSO-d6, 0.05 mass % TMS (tetramethylsilane) mixture) (0.53 ml) was added, and the mixture was completely dissolved by applying ultrasonic waves. This solution was measured for proton NMR at 500 MHz using an NMR measurement device (JNW-ECA500) (JEOL Datum Co., Ltd.). The imidization rate was calculated by the following formula, 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 integrated value derived from the NH group of the amic acid that appears around 9.5 ppm to 10.0 ppm.
Imidization rate (%)=(1−α·x/y)×100
In the above formula, x is the integrated value of the proton peak derived from the NH group of the amic acid, y is the integrated value of the peak of the reference proton, and α is the ratio of the number of the reference protons to one NH group proton of the amic acid in the case of polyamic acid (imidization rate 0%).

[Synthesis of polymer]
(Synthesis Example 1)
In a 200 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, 8.04 g (40.2 mmol) of DA-1, 4.36 g (10.9 mmol) of DA-2, and 12.2 g (21.9 mmol) of DA-3 were weighed out, 98.4 g of NMP was added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this diamine solution under water cooling, 9.40 g (47.4 mmol) of CA-1 was added, and 37.6 g of NMP was further added, and the mixture was stirred for 2 hours at 50 ° C. under a nitrogen atmosphere. Further, 4.65 g (23.7 mmol) of CA-2 was added, and 18.6 g of NMP was further added, and the mixture was stirred for 2 hours at 23 ° C. under a nitrogen atmosphere to obtain a solution of polyamic acid (PAA-0) (viscosity: 1250 mPa s).
100 g of the above-obtained polyamic acid (PAA-0) solution was placed in a 200 mL Erlenmeyer flask containing a stirrer, and 1.24 g (5.68 mmol) of di-tert-butyl dicarbonate (hereinafter also referred to as Boc ₂ O), which is a terminal modifier, was added. After stirring at 40° C. for 15 hours, a solution of terminal-modified polyamic acid (PAA-0-1) was obtained.
100 g of the above (PAA-0-1) solution was taken into a 200 mL Erlenmeyer flask containing a stirrer, 66.7 g of NMP, 14.2 g of acetic anhydride, and 4.70 g of pyridine were added, and the mixture was stirred at room temperature for 30 minutes, and then reacted at 60° C. for 4 hours. This reaction solution was poured into 650 g of methanol, and the resulting precipitate was filtered off. This precipitate was washed with methanol and then dried under reduced pressure at a temperature of 80° C. to obtain a polyimide powder (imidization rate: 89%).
Further, 9.60 g of this polyimide powder was taken into a 100 mL Erlenmeyer flask containing a stirrer, 70.4 g of NMP was added, and the mixture was stirred at 70° C. for 24 hours to dissolve the polyimide, thereby obtaining a solution of polyimide (SPI-1).

<Synthesis Examples 2 to 4>
The diamines and tetracarboxylic acid derivatives shown in Table 1 were used and the same procedures as in Synthesis Example 1 were carried out to obtain solutions of polyimides (SPI-2) to (SPI-4) shown in Table 1. In Table 1, the numerical values shown under the compound names indicate the mass (g) of the tetracarboxylic acid derivative used in the synthesis for the tetracarboxylic acid derivative components, and the mass (g) of the diamine used in the synthesis for the diamine components. The terminal modification treatment was carried out in the same procedures as in Synthesis Example 1 for those described as Boc ₂ O.

<Synthesis Examples 5 to 11>
The diamines and tetracarboxylic acid derivatives shown in Table 2 were used and the same procedure as in Synthesis Example 1 was carried out to obtain solutions of polyamic acids (PAA-1) to (PAA-7) shown in Table 2. In Table 2, the numerical values shown under the compound names indicate the mass (g) of the tetracarboxylic acid derivative used in the synthesis for the tetracarboxylic acid derivative components, and the mass (g) of the diamine used in the synthesis for the diamine components.

[Preparation of liquid crystal alignment agent]
<Examples 1 to 6 and Comparative Examples 1 to 5>
The polyamic acid and polyimide solutions obtained in Synthesis Examples 1 to 11 were weighed out in the amounts shown in the table below, and NMP, GBL, BCA, a GBL solution containing 1 mass % of AD-1, and an NMP solution containing 10 mass % of AD-2 were weighed out in the amounts shown in the table below and added with stirring. The mixture was stirred at room temperature for 2 hours to obtain liquid crystal alignment agents (1) to (11).

A method for producing a liquid crystal display device for evaluating the pretilt angle and voltage holding ratio will be described below.
[Preparation of Liquid Crystal Display Element]
First, a substrate with electrodes was prepared. The substrate was a glass substrate with a size of 30 mm x 40 mm and a thickness of 1.1 mm. An ITO electrode with a film thickness of 35 nm was formed on the substrate, and the electrode had a stripe pattern of 40 mm in length and 10 mm in width.
Next, the liquid crystal alignment agent obtained above was filtered through a filter with a pore size of 1.0 μm, and then applied to the prepared substrate with the electrode by spin coating. After drying for 2 minutes on a hot plate at 80° C., it was baked for 20 minutes in an IR oven at 230° C. to form a coating film with a thickness of 100 nm to obtain a substrate with a liquid crystal alignment film. After rubbing the liquid crystal alignment film with a rayon cloth (roller diameter: 120 mm, roller rotation speed: 1000 rpm, moving speed: 20 mm/sec, indentation length: 0.4 mm), it was washed by ultrasonic irradiation in pure water for 1 minute, water droplets were removed by air blowing, and then it was dried at 80° C. for 10 minutes to obtain a substrate with a liquid crystal alignment film. Two substrates with this liquid crystal alignment film were prepared, and 4 μm spacers were sprayed on the liquid crystal alignment film surface of one of them, and then a sealant was printed on top of it. The other substrate was attached so that the rubbing direction was reversed and the film surfaces faced each other, and then the sealant was cured to prepare an empty cell. Negative liquid crystal MLC-7026 (manufactured by Merck) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain a liquid crystal cell. The obtained liquid crystal cell was then heated at 120° C. for 1 hour, and left at 23° C. overnight before being used for each evaluation.

<Pretilt angle>
The pretilt angle in the liquid crystal display element was evaluated using an AxoScan Mueller matrix polarimeter manufactured by Optometrics Co., Ltd. The lower the pretilt angle, the better the display.

<Voltage holding ratio>
A voltage of 1 V was applied to the liquid crystal display element for 60 μsec at a temperature of 60° C., and the voltage after 500 msec was measured to evaluate the extent to which the voltage could be maintained as a voltage retention rate. The higher the voltage retention rate, the better. It is known that when the voltage retention rate, which is one of the electrical properties of a liquid crystal display element, increases, line burn-in, which is one of the display defects of a liquid crystal display element, becomes less likely to occur.

The results of the pretilt angle evaluation and voltage retention rate evaluation for the liquid crystal display elements having liquid crystal alignment films obtained using each of the liquid crystal alignment agents of Examples 1 to 6 and Comparative Examples 1 to 5 are shown in Table 5 below.

<Evaluation of whitening properties>
0.1 mL of the liquid crystal alignment agents obtained in Examples 1 to 6 and Comparative Examples 1 to 5 was dropped onto a chrome substrate and left to stand in an environment of 23° C. and 68% humidity. The edge and center of the droplet were observed with an optical microscope, and the time until a precipitate was generated was measured.
In this evaluation, the whitening phenomenon is defined as the phenomenon in which the droplets become cloudy white due to precipitation or aggregation of dissolved polyimide. The state in which the droplets are not whitened at all is evaluated as "good", the state in which only the edges of the droplets are whitened is evaluated as "good", and the state in which the entire surface of the droplets is whitened is evaluated as "bad". The longer the time for which the droplets are whitened, the better the result.

By using the liquid crystal alignment agent of the embodiment of the present invention, a liquid crystal alignment film having a pretilt angle of 1 degree or less was obtained, and a liquid crystal display element having a high voltage holding ratio (i.e., a liquid crystal display element having a low incidence of display defects (line burn-in)) was obtained even when a negative type liquid crystal was used as the liquid crystal material.
In addition, by using the liquid crystal alignment agent of the embodiment of the present invention, it is possible to suppress the phenomenon of whitening due to moisture absorption, and it is difficult for foreign matter or clogging to occur when obtaining a coating film, and the obtained film has little surface roughness. Furthermore, even when dried or heated, a liquid crystal alignment agent that can exhibit the original properties of a liquid crystal alignment film can be obtained.

Liquid crystal display elements prepared using the liquid crystal alignment agent of the present invention can be liquid crystal display elements with excellent display quality, and are suitable for use in display elements using various types, such as horizontal alignment type liquid crystal display elements of the IPS type or FFS type.

The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2020-071204, filed on April 10, 2020, are hereby incorporated by reference as the disclosure of the specification of the present invention.

Claims (16)

A liquid crystal aligning agent containing a polyimide (A) obtained by imidizing a polyimide precursor which is a reaction product of a tetracarboxylic acid derivative component and a diamine component, wherein the tetracarboxylic acid derivative component contains 1,2,3,4-butanetetracarboxylic dianhydride or a derivative thereof, and the diamine component contains at least one diamine selected from the following formulas (1a) to (1b) and a diamine represented by the following formula (2):

In the formula, D represents a divalent saturated hydrocarbon group, unsaturated hydrocarbon group, aromatic hydrocarbon group or heterocycle having 1 to 20 carbon atoms, and D may have one or more substituents. E represents a single bond, or a divalent saturated hydrocarbon group, unsaturated hydrocarbon group, aromatic hydrocarbon group or heterocycle having 1 to 20 carbon atoms, and E may have one or more substituents. F represents a single bond, -O-, -OCO-, or -COO-. m is an integer of 0 or 1. A represents an organic group that can be eliminated by heat. The hydrogen atoms of the benzene ring having amino groups at both ends may be substituted with one or more substituents. A liquid crystal alignment agent as described in claim 1, wherein the content of the diamine of formula (2) is 50 to 95 mol% relative to the diamine component. The liquid crystal alignment agent according to claim 1 or 2, wherein the content of at least one diamine selected from the formulas (1a) to (1b) is 5 to 50 mol% relative to the diamine component. A liquid crystal alignment agent according to any one of claims 1 to 3, wherein the content of 1,2,3,4-butanetetracarboxylic dianhydride or its derivative is 50 to 100 mol% relative to the tetracarboxylic acid derivative component. A liquid crystal alignment agent according to any one of claims 1 to 4, wherein the imidization rate of the polyimide (A) is 20 to 100%. The liquid crystal aligning agent according to any one of claims 1 to 5, wherein the tetracarboxylic acid derivative component further comprises at least one tetracarboxylic acid dianhydride represented by the following formula (3) or a derivative thereof:

In the formula, _X1 is a structure selected from the following structures:

(R ₃ to R ₁₇ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group containing a fluorine atom and having 1 to 6 carbon atoms, or a phenyl group. * represents a bond. The at least one diamine selected from the formulas (1a) to (1b) is at least one diamine selected from the following formulas (1-1) to (1-4): Liquid crystal aligning agent according to any one of claims 1 to 6.

(Boc represents a tert-butoxycarbonyl group.) The liquid crystal aligning agent according to any one of claims 1 to 7, wherein the diamine component further contains at least one diamine (4) having a structure represented by the following formula (iv) in the molecule:

In the above formula (iv), D is an organic group that can be removed by heat. * represents a bond, at least one of which is bonded to an aliphatic hydrocarbon. The liquid crystal aligning agent according to claim 8, wherein the diamine (4) is a diamine selected from structures represented by the following formulas (4-1) to (4-5):

Boc represents a tert-butoxycarbonyl group. The liquid crystal alignment agent according to any one of claims 1 to 9, further comprising a polyimide precursor (B) which is a reaction product of a tetracarboxylic acid derivative component and a diamine component. The liquid crystal alignment agent according to claim 10, wherein the polyimide precursor (B) is a polyamic acid. The liquid crystal alignment agent according to claim 10 or 11, wherein the diamine component for obtaining the polyimide precursor (B) contains at least one diamine selected from the group consisting of a diamine (b1) having at least one group selected from the group consisting of a urea bond, an amide bond, a carboxy group, and a hydroxy group in the molecule, and a diamine (b2) having at least one nitrogen atom-containing structure selected from the group consisting of a nitrogen atom-containing heterocycle, a secondary amino group, and a tertiary amino group. A liquid crystal alignment agent according to any one of claims 1 to 12, wherein the polyimide (A) and/or polyimide precursor (B) are terminally modified polyimide and/or polyimide precursor. The liquid crystal alignment agent according to any one of claims 1 to 13, further comprising a crosslinkable compound and/or an adhesion aid. A liquid crystal alignment film obtained from the liquid crystal alignment agent according to any one of claims 1 to 14. A liquid crystal display element comprising the liquid crystal alignment film of claim 15.