TWI887449B - Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element - Google Patents

Abstract

The present invention provides a liquid crystal alignment agent capable of obtaining a liquid crystal alignment film having high voltage holding rate, high light transmittance, rapid charge accumulation, and excellent afterimage characteristics, the liquid crystal alignment film, and a liquid crystal display element. A liquid crystal alignment agent is characterized by containing at least one polymer (P) selected from the group consisting of a polyimide precursor obtained by using a diamine component containing a diamine (1) represented by the following formula (1) and its imide product, i.e., a polyimide. R represents a monovalent organic group, and R ₁ and R ₂ represent a saturated or unsaturated monovalent hydrocarbon group having 1 to 6 carbon atoms, or an alicyclic hydrocarbon group having 3 to 6 carbon atoms. A part of the hydrogen atoms in the hydrocarbon group in R ₁ and R ₂ may be substituted.

Description

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

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

In the past, various driving methods with different electrode structures and physical properties of liquid crystal molecules used have been developed for liquid crystal display elements. For example, there are known display elements such as TN (Twisted Nematic) method, STN (Super Twisted Nematic) method, VA (Vertical Alignment) method, IPS (In-Plane Switching) method, FFS (Fringe Field Switching) method, etc.

Among them, VA type liquid crystal display elements have a wide viewing angle, fast response speed, high contrast, and do not require friction processing in production processing. Therefore, they are widely used, especially for large-scale television applications and screen applications. Among the VA type liquid crystal display elements, the PSA (Polymer Sustained Alignment) method (for example, see Patent Document 1 and Non-Patent Document 1) has become the mainstream, which is to add a photopolymerizable compound to the liquid crystal composition in advance and irradiate ultraviolet light while applying voltage to the liquid crystal cell to accelerate the response speed of the liquid crystal.

On the other hand, liquid crystal display elements generally have a liquid crystal alignment film for aligning liquid crystal molecules. As for the materials of the liquid crystal alignment film, for example, polyamic acid, polyamic acid ester, polyimide, polyamide, etc. are known. In addition to the liquid crystal alignment, the liquid crystal alignment film requires a variety of properties. For example, in the above-mentioned PSA-type liquid crystal display element, if static electricity accumulates in the liquid crystal cell, or the application of positive and negative asymmetric voltages generated by driving causes charge accumulation in the liquid crystal cell, then the accumulated charge will affect the display in the form of disordered liquid crystal alignment and afterimages, causing a significant decrease in the display quality of the liquid crystal element, and thus seeking a liquid crystal alignment film with suppressed static electricity accumulation and less afterimages. As for the liquid crystal alignment film for solving such a problem, Patent Document 2 proposes a polyimide-based liquid crystal alignment film with a pyrrole structure.

In addition, in recent years, large-screen and high-precision liquid crystal televisions have been widely used, and the liquid crystal alignment films used in such applications need to have higher reliability than before. In particular, the basic characteristics of the liquid crystal alignment film, namely the electrical characteristics, need to show a higher degree of initial characteristics. Regarding the liquid crystal alignment film that solves this problem, Patent Document 3 proposes a polyimide-based liquid crystal alignment film with a diphenylamine structure. [Prior Technical Document] [Patent Document]

[Patent Document 1] Japanese Patent Publication No. 2003-307720 [Patent Document 2] International Publication No. 2019/013339 [Patent Document 3] International Publication No. 2009/093709 [Non-Patent Document 1] K. Hanaoka, SID 04 DIGEST, P1200-1202

(The problem to be solved)

In addition to the above, in recent years, in ultra-high-definition liquid crystal display elements such as 4K and 8K, the occupancy rate of the black matrix (BM), TFT (Thin Film Transistor), etc. has increased, and the aperture ratio of the panel has decreased, so it is considered important to improve the light transmittance of the display part.

In consideration of the above, the purpose of the present invention is to provide a liquid crystal alignment agent that can obtain a liquid crystal alignment film having high voltage retention and high light transmittance and having a slow and fast accumulated charge and excellent afterimage characteristics, and to provide the liquid crystal alignment film and a liquid crystal display element using the liquid crystal alignment film. (Method for solving the problem)

The inventors of this case have made great efforts to achieve the above-mentioned subject, and as a result, have found that a liquid crystal alignment agent containing a specific component is effective in achieving the above-mentioned purpose, and thus have completed the present invention. The present invention is a liquid crystal alignment agent, which is characterized by: containing a polymer (P), the polymer (P) being at least one selected from the group consisting of a polyimide precursor obtained by using a diamine component containing a diamine (1) represented by the following formula (1) and an imide compound of the polyimide precursor, i.e., a polyimide, and a liquid crystal alignment film obtained from the liquid crystal alignment agent, and a liquid crystal display element having the liquid crystal alignment film. [Chemistry 1] R represents a monovalent organic group, and R ₁ and R ₂ represent a saturated or unsaturated monovalent hydrocarbon group having 1 to 6 carbon atoms, or an alicyclic hydrocarbon group having 3 to 6 carbon atoms. A part of the hydrogen atoms in the hydrocarbon group in R ₁ and R ₂ may be substituted. (Effects of the Invention)

According to the liquid crystal alignment agent of the present invention, a liquid crystal alignment film having high voltage retention, high light transmittance, slow and fast charge accumulation and excellent residual image characteristics can be obtained. The mechanism by which the above effects of the present invention can be obtained is not clear, but it is believed that the following is one of the reasons. That is, it is believed that the raw material of the polymer component used in the liquid crystal alignment agent of the present invention, namely the diamine, has a substituent at the adjacent position of the amino group, so that stereo hindrance occurs and the formation of charge transfer is inhibited, so a liquid crystal alignment film with high light transmittance can be obtained, and the polymer obtained from the above diamine has a conjugated structure, so a liquid crystal alignment film with slow and fast charge accumulation and excellent residual image characteristics can be obtained.

(Polymer (P)) The liquid crystal alignment agent of the present invention contains at least one polymer (P) selected from the group consisting of a polyimide precursor obtained by using a diamine component containing a diamine (1) represented by the following formula (1) and an imide compound of the polyimide precursor, i.e., a polyimide.

[Chemistry 2]

In the above formula (1), R, _R1 and _R2 are as defined above. The monovalent organic group in R is preferably a monovalent organic group having an aromatic ring structure, a monovalent chain alkyl group having 1 to 30 carbon atoms, or a monovalent alicyclic alkyl group having 3 to 30 carbon atoms. A portion of the hydrogen atoms in the chain alkyl group or alicyclic alkyl group may be substituted, and a portion of the methylene groups in the chain alkyl group or alicyclic alkyl group may be substituted with oxygen atoms, carbonyl groups or -COO-. Examples of the monovalent chain alkyl group having 1 to 30 carbon atoms include alkyl groups having 1 to 30 carbon atoms, alkenyl groups having 2 to 30 carbon atoms, alkynyl groups having 2 to 30 carbon atoms, and the like. When R is a chain alkyl group or an alicyclic alkyl group, a part of the hydrogen atoms of the alkyl group may be substituted, and the substituent may be a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), a hydroxyl group, a cyano group, an alkyl group having 1 to 9 carbon atoms, an alkoxy group having 1 to 9 carbon atoms, a fluoroalkyl group having 1 to 9 carbon atoms, etc. Among them, an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group having 1 to 6 carbon atoms is more preferred, and an alkyl group having 1 to 6 carbon atoms is particularly preferred.

The above-mentioned monovalent alicyclic hydrocarbon group having 3 to 30 carbon atoms may be composed only of an alicyclic structure, or a part thereof may contain a chain structure. Examples of the alicyclic structure include cyclopentane, cyclohexane, cycloheptane, cyclooctane, norbornane, and adamantane. The above-mentioned monovalent organic group having an aromatic ring structure may be composed only of an aromatic ring structure, or a part thereof may contain a chain structure and at least one of the above-mentioned alicyclic structures. The aromatic ring structure may be a benzene ring, or a condensed benzene ring such as a naphthalene ring or anthracene ring, or a heteroaromatic ring such as a thiophene ring, pyrrole ring, furan ring, pyridine ring, pyrimidine ring, and trioxane ring. The above-mentioned monovalent group having an aromatic ring structure may have only one aromatic ring structure or may have multiple aromatic ring structures. When there are multiple aromatic ring structures, these multiple aromatic ring structures may also be bonded by a single bond. In this case, specifically, biphenyl and terphenyl may be listed. In addition, a chain structure or an alicyclic structure may exist to link multiple aromatic ring structures. At least one of these aromatic ring structures, chain structures and alicyclic structures may also have a substituent. The substituent may include a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), a hydroxyl group, a cyano group, an alkyl group with 1 to 9 carbon atoms, an alkoxy group with 1 to 9 carbon atoms, a fluoroalkyl group with 1 to 9 carbon atoms, etc.

An ideal example of the monovalent organic group having an aromatic ring structure in R is the structure represented by the following formula (Ar). [Chemistry 3] ^Ra represents a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), a hydroxyl group, a cyano group, an alkyl group having 1 to 9 carbon atoms, an alkoxy group having 1 to 9 carbon atoms, or a fluoroalkyl group having 1 to 9 carbon atoms. m is an integer of 0 to 5. When m is 2 to 5, a plurality of Ras are each independently defined above. * represents a bonding site.

Examples of the saturated or unsaturated monovalent hydrocarbon group having 1 to 6 carbon atoms in R ₁ and R ₂ include alkyl groups having 1 to 6 carbon atoms, alkenyl groups having 2 to 6 carbon atoms, and alkynyl groups having 2 to 6 carbon atoms. Examples of the alicyclic hydrocarbon groups having 3 to 6 carbon atoms in R ₁ and R ₂ include cyclopentyl and cyclohexyl. Some of the hydrogen atoms in the hydrocarbon groups in R ₁ and R ₂ may be substituted, and examples of the substituents include fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, and hydroxyl groups. In order to efficiently obtain the effects of the present invention, it is preferred that R, R ₁ , and R ₂ are each independently an alkyl group having 1 to 5 carbon atoms. Specific examples of the alkyl group having 1 to 5 carbon atoms in R, R ₁ and R ₂ include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, t-butyl, n-pentyl, isopentyl, sec-pentyl and t-pentyl. Among them, the alkyl group having 1 to 3 carbon atoms is preferred.

Preferred specific examples of the diamine (1) represented by the above formula (1) include the following formulas (d-1) to (d-4).

The polymer (P) contained in the liquid crystal alignment agent of the present invention, especially when used in a liquid crystal alignment agent for a liquid crystal display element of a TN mode, STN mode, VA mode, PSA mode, or SC-PVA mode, is preferably at least one polymer selected from the group consisting of a polyimide precursor obtained by using a diamine component containing, in addition to the diamine represented by the above formula (1), at least one diamine (s) having a structure selected from the group consisting of the following formulas (S1), (S2), and (S3), and an imide compound of the polyimide precursor, i.e., a polyimide. [Chemistry 5]

In formula (S1), ^X1 and ^X2 each independently represent a single bond, -( _CH2 ) _a- (a is an integer of 1 to 15), -CONH-, -NHCO-, -CON( _CH3 )-, -N( _CH3 )CO-, -NH-, -O-, -COO-, -OCO-, or -(( _CH2 ) _a1 - _A1 ) _m1- (a1 is an integer of 1 to 15, _A1 represents an oxygen atom or -COO-, _m1 is 1 to 2, and when _m1 is 2, a plurality of a1s and _A1s may be the same or different.). ^G1 and ^G2 each independently represent a divalent cyclic group selected from a divalent aromatic group having 6 to 12 carbon atoms and a divalent alicyclic group having 3 to 8 carbon atoms. Any hydrogen atom on the aforementioned cyclic group may be substituted with at least one selected from the group consisting of an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, an alkyl group containing fluorine having 1 to 3 carbon atoms, an alkoxy group containing fluorine having 1 to 3 carbon atoms, and a fluorine atom. m and n are each independently an integer of 0 to 3, and the sum of m and n is 1 to 4. When m and n are plural, the plural X ¹ , X ² , G ¹ and G ² may be the same or different. ^{R 1} 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, and any hydrogen atom forming R ¹ may be substituted with a fluorine atom.

In addition, the divalent cyclic groups in ^G1 and ^G2 include cyclohexylene, phenylene, etc. Any hydrogen atom on the cyclic groups may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, an alkyl group containing fluorine having 1 to 3 carbon atoms, an alkoxy group containing fluorine having 1 to 3 carbon atoms, or a fluorine atom. m and n are each independently an integer of 0 to 3, and the total of m and n is 1 to 4. From the viewpoint of improving the orientation of the liquid crystal, the total of m and n is more preferably 2 to 4.

[Chemistry 6] In formula (S2), X ³ represents a single bond, -CONH-, -NHCO-, -CON(CH ₃ )-, -N(CH ₃ )CO-, -NH-, -O-, -CH ₂ O-, -COO- or -OCO-. R ² represents an alkyl group having 1 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms, and any hydrogen atom forming R ² may be substituted with a fluorine atom. In addition, R ² is preferably an alkyl group having 3 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms from the viewpoint of improving the liquid crystal orientation.

[Chemistry 7] In formula (S3), ^X4 represents -CONH-, -NHCO-, -O-, _-CH2O- , _-OCH2- , -COO- or -OCO-. ^R3 represents a structure having a steroid skeleton. Preferably, ^R3 has a structure containing chlestanyl, cholesteryl or lanostanyl.

The ideal specific examples of formula (S1) include the following formulas (S1-x1) to (S1-x7). [Chemistry 8]

In the above formulae (S1-x1) to (S1-x7), ^R1 is as defined above. ^Xp represents -( _CH2 ) _a- (a is an integer of 1 to 15), -CONH-, -NHCO-, -CON( _CH3 )-, -N( _CH3 )CO-, -NH-, -O-, _-CH2O- , _-CH2OCO- , -COO-, or -OCO-. _A1 represents an oxygen atom or -COO-* (except that the bonding site with "*" is bonded to ( _CH2 ) _a2 ), and _A2 represents an oxygen atom or *-COO- (except that the bonding site with "*" is bonded to ( _CH2 ) _a2 ). _a1 and _a3 are each independently an integer of 0 or 1, _a2 is an integer of 1 to 10, and Cy represents a 1,4-cyclohexylene group or a 1,4-phenylene group.

In the ideal embodiment of formula (S2), X ³ is any of -O-, -CH ₂ O-, -COO- or -OCO- and R ² is an alkyl group having 3 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms. R ² is more preferably an alkyl group having 3 to 20 carbon atoms. Any hydrogen atom forming R ² may be substituted by a fluorine atom.

The following formula (S3-x) is a preferred specific example of the above formula (S3). In formula (S3-x), X represents formula (X1), formula (X2), or _-CH2O- , Col represents formula (Col1), formula (Col2), or formula (Col3), and G represents formula (G1), formula (G2), formula (G3), or formula (G4). In the formula, Me represents a methyl group, and * represents a bonding site.

[Chemistry 9]

The ideal diamine (s) having a structure represented by any of the above formulas (S1) to (S3) is preferably a diamine having a structure represented by the above formulas (S1) to (S3) and having at least one benzene ring. An ideal example of diamine (s) is a diamine represented by the following formula (d1) or formula (d2). [Chemistry 10]

In formulae (d1) and (d2), Y represents a side chain structure represented by formulae (S1) to (S3). Furthermore, X represents a single bond, -O-, -C(CH ₃ ) ₂ -, -NH-, -CO-, -COO-, -CONH-, -(CH ₂ ) _m -, -SO ₂ -, -O-(CH ₂ ) _m -O-, -OC(CH 3 ) ₂ -, -CO-(CH ₂ ) m -, -CO-(CH ₂ ) _m -CO-, -NH-(CH ₂ ) _m -, -NH-(CH ₂ ) _m -NH-, -SO 2 -(CH ₂ ) _m -, -SO ₂ -(CH ₂ ) _m -SO ₂ -, _-CONH- (CH ₂ ) _{m -} , -CONH-(CH ₂ ) _m -NHCO-, or -COO-(CH ₂ ) _m -OCO- _. m is an integer of 1 to 8. In the above formula (d2), two Ys may be the same as or different from each other.

Preferred specific examples of the diamine represented by the above formula (d1) include the following formulas (d1-1) to (d1-18). n is an integer from 1 to 20.

[Chemistry 12]

Preferred specific examples of the diamine represented by the above formula (d2) include the following formulas (d2-1) to (d2-6).

In the above formulae (d2-1) to (d2-6), ^Xp1 to ^Xp8 are each independently synonymous with ^Xp in the above formulae (S1-x1) to (S1-x6), ^Xs1 to ^Xs4 are each independently -O-, _-CH2O- , -COO-, or -OCO-. _Xa to _Xf are single bonds, -O-, -NH-, or -O-( _CH2 ) _m -O- (m is an integer of 1 to 8), and ^R1a to ^R1h are each independently 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.

(Manufacturing of polymer (P)) The polymer (P) contained in the liquid crystal alignment agent of the present invention can be composed of one component or two or more components of a polyimide precursor and/or an imide product of the polyimide precursor, i.e., polyimide. Among them, the polyimide precursor is a polymer that can obtain polyimide by imidizing polyamic acid, polyamic acid ester, etc. The ideal specific aspects of the polymer (P) can be listed as the following two types, but the present invention is not limited to these.

At least one polymer (hereinafter also referred to as a copolymer) selected from the group consisting of a polyimide precursor obtained by using a diamine component containing the above-mentioned diamine (1) and the above-mentioned diamine (s), and an imide compound of the polyimide precursor, i.e., a polyimide. A mixture (hereinafter also referred to as a polymer blend) of at least one polymer (p-1) selected from the group consisting of a polyimide precursor obtained by using a diamine component containing the above diamine (1) and an imide compound of the polyimide precursor, i.e., a polyimide, and a mixture (hereinafter also referred to as a polymer blend) of at least one polymer (p-2) selected from the group consisting of a polyimide precursor obtained by using a diamine component containing the above diamine (s) and an imide compound of the polyimide precursor, i.e., a polyimide. The above copolymer or polymer blend may be used alone or in combination.

<Diamine component> The polyimide precursor of the above polymer (P), i.e., polyamide (P), can be obtained by polymerization reaction of a diamine component containing the above diamine (1), preferably a diamine component containing diamine (s) in addition to the above diamine (1), and a tetracarboxylic acid component. In this case, the amount of diamine (1) used is preferably 1 to 100 mol%, more preferably 1 to 99 mol%, and even more preferably 5 to 95 mol%, relative to the diamine component reacted with the tetracarboxylic acid component.

When a diamine (s) is used in addition to the above diamine (1), the amount of the diamine (s) used is preferably 1 to 99 mol %, more preferably 1 to 95 mol %, based on the diamine component to be reacted with the tetracarboxylic acid component.

The diamine component used in the preparation of the polyamine (P) may contain diamines other than diamine (1) and diamine (s) (hereinafter also referred to as other diamines). Examples of other diamines are given below, but the present invention is not limited thereto.

p-phenylenediamine, m-phenylenediamine, 4-(2-(methylamino)ethyl)aniline, 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid, 3,5-diaminobenzoic acid, diamines having a carboxyl group such as the following formula (3b-1) to (3b-4), 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether; 1,2-bis(4-aminophenyl)ethane, 1,3-bis(4-aminophenyl)propane, 1,4-bis(4-aminophenyl)butane, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,2-bis(4-aminophenoxy)ethane, 1,2-bis( 4-amino-2-methylphenoxy)ethane, 1,3-bis(4-aminophenoxy)propane, 1,4-bis(4-aminophenoxy)butane, 1,5-bis(4-aminophenoxy)pentane, 1,6-bis(4-aminophenoxy)hexane, 4-(2-(4-aminophenoxy)ethoxy)-3-fluoroaniline, bis(2-(4-aminophenoxy)ethyl)ether, 4-amino-4'-(2-(4-aminophenoxy)ethoxy)biphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 2,6 -diaminonaphthalene, 2,7-diaminonaphthalene, diamines represented by the following formulas (NH-1) to (NH-6), 2,2'-bis[4-(4-aminophenoxy)phenyl]propane, 2,2'-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2'-bis(4-aminophenyl)propane, 1,3-bis(4-aminophenethyl)urea and other diamines having a urea bond, 2-(2,4-diaminophenoxy)ethyl methacrylate, 2,4-diamino-N,N-diallylaniline and other diamines having a photopolymerizable group at the end, diamines having free radical initiation function such as the following formulas (R1) to (R5), 4,4'-diaminodiphenyl ketone, 3,3'-diaminodiphenyl ketone, 9,9-bis(4-aminophenyl)propane Diamines with photosensitizing function that show sensitization effect when exposed to light, such as phenyl)fluorene, 2,6-diaminopyridine, 3,4-diaminopyridine, 2,4-diaminopyrimidine, 3,6-diaminocarbazole, N-methyl-3,6-diaminocarbazole, heterocyclic diamines such as the following formula (z-1) to (z-18), and the following formula (Dp-1) to (Dp-9), etc. Diamines having a diphenylamine skeleton, diamines having "-N(D)-" (D represents a protecting group that is detached and replaced by a hydrogen atom by heating, preferably tert-butyloxycarbonyl) such as the following formulas (5-1) to (5-10), diamines having an oxazoline structure such as the following formulas (Ox-1) to (Ox-2), and diamines described in International Publication No. 2016/125870.

[Chemistry 14]

In formula (3b-1), ^A1 represents a single bond, _-CH2- , -C2H4-, -C( _CH3 ) _2- , _-CF2- , -C(CF3) _2- , _-O- , -CO-, -NH-, -N( _CH3 ) _- , -CONH-, -NHCO-, -CH2O-, -OCH2-, -COO-, -OCO-, -CON( _{CH3 )} - or -N(CH3) _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), ^A2 represents a linear or branched alkyl group having 1 to 5 carbon atoms, and m5 represents an integer of 1 to 5. In formula (3b-4), ^A3 and ^A4 each independently represent a single bond, _-CH2- , _-C2H4- , -C(CH3) _2- , _-CF2- , -C( _{CF3 )2- ,} -O-, -CO-, -NH-, -N( _CH3 )-, -CONH-, -NHCO-, _-CH2O- , _-OCH2- , -COO-, -OCO-, -CON( _CH3 )- or -N( _CH3 )CO-, and m6 represents an integer _of 1-4.

[Chemistry 15]

[Chemistry 16]

[Chemistry 17]

[Chemistry 18] In formulas (R3) to (R5), n is an integer from 1 to 6.

[Chemistry 19] Boc is tert-butoxycarbonyl. In the present invention, the same shall apply hereinafter.

[Chemistry 20]

[Chemistry 21]

With respect to the other diamines mentioned above, from the viewpoint of being able to ideally obtain the effects of the present invention, p-phenylenediamine, 3,5-diaminobenzoic acid, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ketone, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2-(2,4-diaminophenoxy)ethyl methacrylate, 2,4-diamino-N,N-diallylaniline, diamines represented by the above formulae (R1) to (R5), diamines represented by the above formulae (z-1) to (z-18), diamines represented by the above formulae (5-1) to (5-10), and diamines represented by the above formulae (Ox-1) to (Ox-2) are preferred.

When other diamines are used in addition to the above diamine (1), the amount of the other diamine used is preferably 1 to 99 mol%, more preferably 5 to 95 mol%, relative to the total diamine components used. When other diamines are used in addition to the above diamine (1) and diamine (s), the amount of diamine (s) used is preferably 98 mol% or less, and more preferably 94 mol% or less relative to the diamine component reacting with the tetracarboxylic acid component.

The usage amount of the diamine represented by the above formula (5-1) to (5-10) is preferably 5 to 40 mol%, more preferably 10 to 40 mol%, relative to the total diamine components used in the production of polyamide (P).

In the liquid crystal display element using the PSA method or SC-PVA mode, from the viewpoint of improving the response speed, when preparing the polyamide (P), one or more of 4,4'-diaminodiphenyl ketone, 3,3'-diaminodiphenyl ketone, a diamine having a photopolymerizable group at the end, a diamine represented by any of the above formulae (R1) to (R5), and a diamine represented by the above formulae (z-1) to (z-18) can be used, and the amount used is preferably 1 to 40 mol%, more preferably 5 to 40 mol%, relative to the total diamine components used in the preparation of the polyamide (P).

<Tetracarboxylic acid component> When producing the above-mentioned polyamide (P), the tetracarboxylic acid component to be reacted with the diamine component may be not only tetracarboxylic dianhydride but also tetracarboxylic acid, tetracarboxylic acid dihalide, tetracarboxylic acid dialkyl ester, or tetracarboxylic acid dialkyl ester dihalide and other tetracarboxylic acid dianhydride derivatives.

The above-mentioned tetracarboxylic dianhydride or its derivatives may be aromatic, aliphatic or alicyclic tetracarboxylic dianhydride or their derivatives. Here, aromatic tetracarboxylic dianhydride is an acid dianhydride obtained by subjecting four carboxyl groups including at least one carboxyl group bonded to an aromatic ring to intramolecular dehydration. Aliphatic tetracarboxylic dianhydride is an acid dianhydride obtained by subjecting four carboxyl groups bonded to a chain hydrocarbon structure to intramolecular dehydration. However, it is not necessary to be composed of a chain hydrocarbon structure only, and a part of it may have an alicyclic structure or an aromatic ring structure.

In addition, alicyclic tetracarboxylic acid dianhydride is an acid dianhydride obtained by intramolecular dehydration of four carboxyl groups including at least one carboxyl group bonded to an alicyclic structure. However, none of these four carboxyl groups is bonded to an aromatic ring. In addition, it is not necessary to be composed of only an alicyclic structure, and a part of it may have a chain hydrocarbon structure or an aromatic ring structure.

Among them, the tetracarboxylic dianhydride or its derivative is preferably represented by the following formula (T) or its derivative. [Chemistry 22] However, in formula (T), X represents a structure selected from the group consisting of the following formulae (x-1) to (x-13).

[Chemistry 23]

In the above formulae (x-1) to (x-13), R ¹ to R ⁴ 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. ^{R 5} and R ⁶ each independently represent a hydrogen atom or a methyl group. j and k are integers of 0 or 1, and A ₁ and A ₂ each independently represent a single bond, an ether (-O-), a carbonyl group (-CO-), an ester (-COO-), a phenylene group, a sulfonyl group (-SO ₂ -), or an amide group (-CONH-). *1 is bonded to the bonding site of one of the anhydride groups, and *2 is bonded to the bonding site of the other anhydride group. In the above formula (x-13), two A _2s may be the same or different.

More ideal specific examples of the above formula (x-1) include the following formulas (X1-1) to (X1-6). In the formula, * represents a bonding point. [Chemistry 24]

The ideal specific examples of the above formulas (x-12) and (x-13) can be listed in the following formulas (x-14) to (x-29). * indicates the bonding point. [Chemistry 25]

[Chemistry 26]

Preferred specific examples of the tetracarboxylic dianhydride or its derivative represented by the above formula (T) include: X is selected from the above formulas (x-1) to (x-7) and (x-11) to (x-13).

The ratio of the tetracarboxylic dianhydride or its derivative represented by the above formula (T) to 1 mol of the total tetracarboxylic acid components used is preferably 1 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more. The tetracarboxylic dianhydride and its derivatives used in the production of polyamide (P) may also contain tetracarboxylic dianhydride or its derivatives other than the above formula (T).

The production of polyamine (P) is carried out by reacting the above-mentioned diamine component and tetracarboxylic acid component in a solvent (condensation polymerization). The solvent is not particularly limited as long as it can dissolve the generated polymer. Specific examples of the above-mentioned solvent include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, and 1,3-dimethyl-2-imidazolidinone. In addition, when the polymer has high solvent solubility, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or solvents represented by the following formulas [D-1] to [D-3] can be used.

[Chemistry 27] In the formula [D-1], ^D1 represents an alkyl group having 1 to 3 carbon atoms, in the formula [D-2], ^D2 represents an alkyl group having 1 to 3 carbon atoms, and in the formula [D-3], ^D3 represents an alkyl group having 1 to 4 carbon atoms.

The above solvents can be used alone or in combination. Furthermore, even if the solvent does not dissolve the polymer, it can be mixed with the above solvents within the range that the generated polymer does not precipitate. When the diamine component and the tetracarboxylic acid component are reacted in the solvent, the reaction can be carried out at any concentration, but the concentration of the diamine component and the tetracarboxylic acid component relative to the above solvent is preferably 1 to 50% by mass, and more preferably 5 to 30% by mass. The reaction can be carried out at a high concentration at the beginning of the reaction, and then the solvent can be added. During the reaction, the ratio of the total molar number of the diamine component to the total molar number of the tetracarboxylic acid component (total molar number of the diamine component/total molar number of the tetracarboxylic acid component) is preferably 0.8 to 1.2. As in the usual polycondensation reaction, the closer this molar ratio is to 1.0, the greater the molecular weight of the generated polymer.

The polyamic acid ester which is a polyimide precursor can be obtained by a known method such as: [I] a method of reacting the polyamic acid obtained by the above-mentioned synthesis reaction with an esterifying agent, [II] a method of reacting a tetracarboxylic acid diester with a diamine, [III] a method of reacting a tetracarboxylic acid diester dihalide with a diamine.

[Polyimide] The polyimide contained in the liquid crystal alignment agent of the present invention is obtained by ring-closing the above-mentioned polyimide precursor. In the polyimide, the ring-closing rate of the amide group (also called the imidization rate) does not necessarily need to be 100%, and can be adjusted arbitrarily depending on the use and purpose.

Methods for obtaining polyimide by imidizing a polyimide precursor include: thermal imidization by directly heating a solution of the polyimide precursor, or catalytic imidization by adding a catalyst to the solution of the polyimide precursor. The temperature for thermal imidization of the polyimide precursor in the solution is 100 to 400°C, preferably 120 to 250°C, and preferably the water generated by the imidization reaction is discharged to the outside of the system.

The catalytic imidization of the polyimide precursor can be carried out by adding an alkaline 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 alkaline catalyst is 0.5 to 30 mole times of the amide group, preferably 2 to 20 mole times, and the amount of the acid anhydride is 1 to 50 mole times of the amide group, preferably 3 to 30 mole times. Examples of the alkaline catalyst include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine, etc. Among them, pyridine is more ideal because it has a moderate alkalinity for the reaction to proceed. Examples of acid anhydrides include acetic anhydride, trimellitic anhydride, pyromellitic anhydride, etc. Among them, acetic anhydride is more preferred because it is easier to purify after the reaction. The imidization rate of catalytic imidization can be controlled by adjusting the amount of catalyst, reaction temperature, and reaction time.

When the polyimide produced is recovered from the reaction solution of the imidization of the polyimide precursor, the reaction solution is put into a solvent and precipitated. The solvent used for precipitation can be methanol, ethanol, isopropanol, acetone, hexane, butyl cellulose, heptane, methyl ethyl ketone, methyl isobutyl ketone, toluene, benzene, water, etc. After filtering and recovering the polymer put into the solvent and precipitated, it can be dried at room temperature or heated under normal pressure or reduced pressure. In addition, the polymer that has been precipitated and recovered can be dissolved in a solvent again and the operation of re-precipitation and recovery can be repeated 2 to 10 times to reduce impurities in the polymer. Examples of solvents in this case include alcohols, ketones, etc. It is more ideal to use three or more solvents selected from these solvents because the efficiency of purification is further improved.

The weight average molecular weight (Mw) of the polyimide precursor and the polyimide measured by gel permeation chromatography (GPC) in terms of polystyrene is preferably 5,000 to 1,000,000, more preferably 10,000 to 150,000. In addition, the molecular weight distribution (Mw/Mn) represented by the ratio of Mw to the number average molecular weight (Mn) in terms of polystyrene measured by GPC is preferably 15 or less, more preferably 10 or less. By falling within this molecular weight range, good alignment of the liquid crystal display element can be ensured.

<Capping agent> When preparing the polymer (P) of the present invention, an appropriate capping agent can be used together with the above-mentioned tetracarboxylic acid component and diamine component to prepare an end-sealed polymer. The end-sealed polymer has the effect of improving the film hardness of the liquid crystal alignment film obtained by coating and improving the adhesion characteristics between the sealant and the liquid crystal alignment film. In the present invention, the terminal of the polymer (P) is, for example, an amine group, a carboxyl group, an acid anhydride group, or a derivative thereof. The amine group, carboxyl group, an acid anhydride group, or a derivative thereof can be obtained using a conventional condensation reaction or the following capping agent. The aforementioned derivative can be obtained, for example, using the following capping agent.

End-capping agents, for example, acetic anhydride, maleic anhydride, naldic anhydride, phthalic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride, 3-hydroxyphthalic anhydride, trimellitic anhydride, a compound represented by any of 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, 4-ethynylphthalic anhydride and the like;

[Chemistry 28]

Dicarbonate diester compounds such as di-tert-butyl dicarbonate and diallyl dicarbonate; chlorocarbonyl compounds such as acrylyl chloride, methacrylic chloride, and nicotine chloride; monoamine compounds such as 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; monoisocyanate compounds such as ethyl isocyanate, phenyl isocyanate, and naphthyl isocyanate, etc.

The usage ratio of the end-capping agent is preferably 0.01 to 20 mol parts, more preferably 0.01 to 10 mol parts, relative to 100 mol parts in total of the diamine components used.

(Liquid crystal alignment agent) The liquid crystal alignment agent of the present invention is preferably a liquid composition obtained by dispersing or dissolving a polymer (P) and other components used as needed in an appropriate solvent. In the liquid crystal alignment agent of the present invention, for the purpose of improving electrical properties (e.g., high voltage retention characteristics), vertical alignment, solution properties, etc., in addition to the polymer (P), other polymers (hereinafter also referred to as other polymers) may also be contained. The content ratio of other polymers is preferably 90 parts by mass or less, preferably 10 to 90 parts by mass, and more preferably 20 to 80 parts by mass relative to 100 parts by mass of the total polymers contained in the liquid crystal alignment agent.

The other polymers are not particularly limited, and may be, for example, at least one polymer (B) selected from the group consisting of a polyimide precursor obtained by using a diamine component not containing the above diamine (1) and a tetracarboxylic acid component and an imide compound of the polyimide precursor, i.e., a polyimide, a polysiloxane, a polyester, a polyamide, a polyurea, a polyorganosiloxane, a cellulose derivative, a polyacetal, a polystyrene derivative, a poly(styrene-phenylmaleimide) derivative, a poly(meth)acrylate, and the like as the main skeleton. Among them, at least one selected from the group consisting of the above polymer (B), a polyamide, a polyurea, a polyorganosiloxane, a poly(meth)acrylate, and a polyester is preferred. In addition, two or more other polymers may be used in combination.

(Polymer (B)) For the above-mentioned polymer (B), from the viewpoint of improving electrical properties, it is more preferable to use at least one polymer selected from the group consisting of a polyimide precursor obtained by using a diamine component containing the above-mentioned diamine (s) and an imide compound of the polyimide precursor. The ideal state of the diamine (s) used to obtain the above-mentioned polymer (B) is the same as the diamine (s) exemplified in the polymer (P). In addition to the above-mentioned diamine (s), the diamine component used to obtain the polymer (B) can also use other diamines exemplified in the above-mentioned polymer (P). Among other diamines, diamines having the above-mentioned free radical initiation function, diamines having a photosensitizing function that exhibits a sensitizing effect due to the above-mentioned light irradiation, and diamines having the above-mentioned group "-N(D)-" can be preferably used. The diamine (s) used to produce the polymer (B) may be used in an amount of 1 or more, preferably 5 to 90 mol%, more preferably 10 to 90 mol%, relative to the total diamine components used in the production of the polymer (B). The tetracarboxylic acid component used to produce the polymer (B) may be the compounds exemplified for the tetracarboxylic acid component used to produce the polyamide (P). Among them, the tetracarboxylic dianhydride represented by the above formula (T) or its derivative is preferred. The compound represented by the above formula (T) or its derivative used to produce the polymer (B) may be used in an amount of 1 or more, preferably 10 mol% or more, more preferably 20 mol% or more relative to the total tetracarboxylic acid components used in the production of the polymer (B).

The liquid crystal alignment agent of the present invention may further contain components other than the above-mentioned components as required. Such components include, for example, crosslinking compounds having at least one substituent selected from epoxy groups, isocyanate groups, oxycyclobutane groups, cyclocarbonate groups, blocked isocyanate groups, hydroxyl groups and alkoxy groups, at least one compound selected from the group consisting of crosslinking compounds having polymerizable unsaturated groups, functional silane compounds, metal chelate compounds, hardening accelerators, surfactants, antioxidants, sensitizers, preservatives, and compounds used to adjust the dielectric constant and resistance of the liquid crystal alignment film.

Preferred specific examples of cross-linking compounds include compounds represented by any of the following formulas (CL-1) to (CL-11).

As the compound used to adjust the dielectric constant and resistance of the liquid crystal alignment film, there can be listed monomeric amines having nitrogen-containing aromatic heterocycles such as 3-picoline amine. When using monomeric amines having nitrogen-containing aromatic heterocycles, the amount thereof is preferably 0.1 to 30 parts by weight, more preferably 0.1 to 20 parts by weight, relative to 100 parts by weight of the polymer component contained in the liquid crystal alignment agent.

Preferred specific examples of the functional silane compound 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, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-epoxypropoxypropylmethyldimethoxysilane. , 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-phenylene trimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, tris(3-trimethoxysilylpropyl)isocyanurate, 3-butylpropylmethyldimethoxysilane, 3-butylpropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, etc. When the functional silane compound is used, its usage amount 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 organic solvent contained in the liquid crystal alignment agent is not particularly limited as long as the polymer component can be uniformly dissolved. Specific examples thereof 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-dimethylpropaneamide, 3-butoxy-N,N-dimethylpropaneamide, 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, N-cyclohexyl-2-pyrrolidone (these may also be collectively referred to as "good solvents"), etc. Among them, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 3-methoxy-N,N-dimethylpropaneamide, 3-butoxy-N,N-dimethylpropaneamide or γ-butyrolactone is preferred. The content of the good solvent is preferably 20 to 99 mass % of the total solvent contained in the liquid crystal alignment agent, more preferably 20 to 90 mass %, and particularly preferably 30 to 80 mass %.

In addition, the organic solvent contained in the liquid crystal alignment agent is preferably a mixed solvent containing, in addition to the above solvents, a solvent (also called a poor solvent) that improves the coating properties and surface smoothness of the coating film when the liquid crystal alignment agent is coated. Specific examples of the poor solvent used in combination are as follows but are not limited thereto.

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, ethyl carbonate, ethylene glycol monobutyl ether (butyl celoxylate), ethylene glycol monoisopentyl ether, ethylene glycol monohexyl ether, propylene glycol monobutyl ether, 1-(2-butoxyethoxy)-2-propanediol alcohol, 2-(2-butoxyethoxy)-1-propanol, 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, diisobutyl ketone (2,6-dimethyl-4-heptanone), and the like.

Among them, 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 is preferred. The content of the bad solvent is preferably 1 to 80% by mass of the total solvent contained in the liquid crystal alignment agent, preferably 10 to 80% by mass, and even more preferably 20 to 70% by mass. The type and content of the bad solvent can be appropriately selected according to the coating device, coating conditions, coating environment, etc. of the liquid crystal alignment agent.

The ideal solvent combination of a good solvent and a poor solvent includes N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether, N-methyl-2-pyrrolidone and γ-butyrolactone and ethylene glycol monobutyl ether, N-methyl-2-pyrrolidone and γ-butyrolactone and propylene glycol monobutyl ether, N-ethyl-2-pyrrolidone and propylene glycol monobutyl ether, N-ethyl-2-pyrrolidone and 4-hydroxy-4-methyl-2-pentanone, N-ethyl-2-pyrrolidone and propylene glycol diacetate, N,N-dimethyl lactamide and diisobutyl ketone, N-methyl-2-pyrrolidone and ethyl 3-ethoxypropionate, N-ethyl-2-pyrrolidone and ethyl 3-ethoxypropionate, N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether. N-ethyl-2-pyrrolidone and dipropylene glycol dimethyl ether, N,N-dimethyl lactamide and ethylene glycol monobutyl ether, N,N-dimethyl lactamide and propylene glycol diacetate, N-ethyl-2-pyrrolidone and diethylene glycol diethyl ether, N,N-dimethyl lactamide and diethylene glycol diethyl ether, N-methyl-2-pyrrolidone and γ-butyrolactone and 4-hydroxy-4-methyl-2-pentanone and diethylene glycol diethyl ether, N-ethyl-2-pyrrolidone and N-methyl-2-pyrrolidone and 4-hydroxy-4-methyl-2-pentanone, N-ethyl-2-pyrrolidone and 4-hydroxy-4-methyl-2-pentanone and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone and 4-Hydroxy-4-methyl-2-pentanone and diisobutyl ketone, N-methyl-2-pyrrolidone and 4-hydroxy-4-methyl-2-pentanone and dipropylene glycol monomethyl ether, N-methyl-2-pyrrolidone and 4-hydroxy-4-methyl-2-pentanone and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone and 4-hydroxy-4-methyl-2-pentanone and propylene glycol diacetate, γ-butyrolactone and 4-hydroxy-4-methyl-2-pentanone and diisobutyl ketone, γ-butyrolactone and 4-hydroxy-4-methyl-2-pentanone and propylene glycol diacetate, N-methyl-2-pyrrolidone and γ-butyrolactone and propylene glycol monobutyl ether and diisobutyl ketone, 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 diisobutyl carbinol, 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, N-ethyl-2-pyrrolidone and propylene glycol monobutyl ether and dipropylene glycol monomethyl ether, N-ethyl-2-pyrrolidone and propylene glycol monobutyl ether and propylene glycol diacetate, N-ethyl-2-pyrrolidone and propylene glycol monobutyl ether and diisobutyl ketone, N-ethyl-2-pyrrolidone and γ-butyrolactone and diisobutyl ketone, N-ethyl-2-pyrrolidone and N,N-dimethyl lactamide and diisobutyl ketone, etc.

The solid component 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) can be appropriately selected in consideration of viscosity, volatility, etc., and is preferably 1 to 10% by mass. The ideal solid component concentration depends on the method used when the liquid crystal alignment agent is applied to the substrate. For example, when the spin coating method is used, the solid component concentration is preferably 1.5 to 4.5% by mass. When the printing method is used, the solid component concentration is preferably 3 to 9% by mass, so that the solution viscosity is preferably 12 to 50 mPa·s. When the inkjet method is used, the solid component concentration is set to 1 to 5% by mass, so that the solution viscosity is preferably 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-mentioned liquid crystal alignment agent. The liquid crystal alignment film of the present invention can use a horizontal alignment type or a vertical alignment type liquid crystal alignment film, among which it is particularly suitable for a vertical alignment type liquid crystal display element such as a VA mode or a PSA mode described later. The liquid crystal display element of the present invention has the above-mentioned liquid crystal alignment film. The liquid crystal display element of the present invention can be manufactured, for example, according to a method comprising the following steps (1) to (3) or steps (1) to (4).

Step (1): Apply the liquid crystal alignment agent on the substrate On one side of the substrate provided with the patterned transparent conductive film, the liquid crystal alignment agent of the present invention is applied by a suitable coating method such as roller coating, spin coating, printing, inkjet, etc. Here, the substrate is not particularly limited as long as it is a highly transparent substrate, and a glass substrate, a silicon nitride substrate, and a plastic substrate such as an acrylic substrate or a polycarbonate substrate can also be used. In addition, for a reflective liquid crystal display element with only a single-sided substrate, an opaque object such as a silicon wafer can also be used, and the electrode at this time can be made of a light-reflecting material such as aluminum.

Step (2): calcining the coating film After the liquid crystal alignment agent is applied, in order to prevent the applied alignment agent from dripping, etc., it is better to perform preliminary heating (pre-baking) first. The pre-baking temperature is preferably 30-200°C, more preferably 40-150°C, and particularly preferably 40-100°C. The pre-baking time is preferably 0.25-10 minutes, more preferably 0.5-5 minutes. And it is better to further perform a heating (post-baking) step. The post-baking temperature is preferably 80-300°C, more preferably 120-250°C. The post-baking time is preferably 5-200 minutes, more preferably 10-100 minutes. The film thickness formed in this way is ideally 5 to 300 nm, and even more ideally 10 to 200 nm.

The coating formed in step (1) above can be used directly as a liquid crystal alignment film, or the coating can be subjected to an alignment capability imparting treatment. The alignment capability imparting treatment includes rubbing the coating with a roll wound with a cloth made of fibers such as nylon, rayon, cotton, etc. in a certain direction, and irradiating the coating with polarized or non-polarized radiation.

In the photo-alignment treatment, the radiation irradiated to the coating film may be, for example, ultraviolet light and visible light having a wavelength of 150 to 800 nm. When the radiation is polarized, it may be linearly polarized or partially polarized. Furthermore, when the radiation used is linearly polarized or partially polarized, the irradiation may be performed from a direction perpendicular to the substrate surface, from an oblique direction, or a combination thereof. When irradiating with non-polarized radiation, the irradiation direction is set to an oblique direction.

Step (3); Forming a liquid crystal layer (3-1) VA type liquid crystal display element Prepare two substrates with liquid crystal alignment films formed as described above, and arrange the liquid crystal between the two substrates facing each other. Specifically, the following two methods can be listed. The first method is a method known in the past. First, the two substrates are arranged face to face with their respective liquid crystal alignment films facing each other, separated by a gap (cell gap). Then, the periphery of the two substrates is bonded together using a sealant, and the liquid crystal composition is injected into the cell gap separated by the substrate surface and the sealant. After contacting the film surface, the injection hole is sealed.

The second method is called ODF (One Drop Fill) method. A UV-curable sealant is applied to a predetermined location on one of the two substrates on which a liquid crystal alignment film has been formed, and then a liquid crystal composition is dripped at a predetermined number of locations on the surface of the liquid crystal alignment film. Afterwards, the other substrate is attached in a face-to-face manner with the liquid crystal alignment film, and the liquid crystal composition is spread and pressed on the entire surface of the substrate so that it contacts the film surface. Then, ultraviolet light is irradiated on the entire surface of the substrate to cure the sealant. When using any of the methods, it is advisable to further heat the liquid crystal composition used to a temperature at which it acquires an isotropic phase, and then slowly cool it to room temperature, so as to remove the flow alignment during liquid crystal filling.

The liquid crystal alignment agent of the present invention is also suitable for use in a liquid crystal display element (PSA type liquid crystal display element) which is formed by having a liquid crystal layer between a pair of substrates having electrodes, and a liquid crystal composition containing a polymerizable compound that can be polymerized by at least one of active energy rays and heat is arranged between the pair of substrates, and a step of polymerizing the polymerizable compound by applying a voltage between the electrodes and using at least one of irradiation with active energy rays and heating. In addition, the liquid crystal alignment agent of the present invention is also suitable for use in a liquid crystal display element (SC-PVA mode type liquid crystal display element) which is formed by having a liquid crystal layer between a pair of substrates having electrodes, and a liquid crystal alignment film containing a polymerizable group that can be polymerized by at least one of active energy rays and heat is arranged between the pair of substrates, and a step of applying a voltage between the electrodes.

(3-2) PSA type liquid crystal display element The process is carried out in the same manner as in (3-1) above, except that a liquid crystal composition containing a polymerizable compound is injected or dripped. The polymerizable compound is, for example, a polymerizable compound represented by the following formulas (M-1) to (M-7).

[Chemistry 30]

(3-3) Case of SC-PVA mode liquid crystal display element A method of manufacturing a liquid crystal display element can also be adopted in which the same process as the above (3-1) is performed and then the ultraviolet irradiation step described later is performed. According to this method, a liquid crystal display element with excellent response speed can be obtained with a small amount of light, as in the case of manufacturing the above-mentioned PSA type liquid crystal display element. The compound having a polymerizable group can be a compound having one or more polymerizable unsaturated groups such as acrylate groups and methacrylate groups in the molecule as represented by the above formulas (M-1) to (M-7), and its content is preferably 0.1 to 30 parts by mass, and more preferably 1 to 20 parts by mass relative to 100 parts by mass of all polymer components. Furthermore, the above-mentioned polymerizable group may also be possessed by a polymer used in a liquid crystal alignment agent, such as a polymer obtained by using a diamine component containing the above-mentioned diamine having a photopolymerizable group at the terminal for reaction.

Step (4): Irradiate the liquid crystal cell with ultraviolet light in a state where a voltage is applied between the conductive films of a pair of substrates obtained in (3-2) or (3-3). The voltage applied here may be, for example, a direct current or alternating current of 5 to 50 V. The irradiated light may be, for example, ultraviolet light and visible light with a wavelength of 150 to 800 nm, preferably ultraviolet light with a wavelength of 300 to 400 nm. The light source of the irradiated light may be, for example, a low-pressure mercury lamp, a high-pressure mercury lamp, a deuterium lamp, a metal halide lamp, an argon resonance lamp, a xenon lamp, an excimer laser, etc. The irradiation amount of light is preferably 1,000 to 200,000 J/m ² , more preferably 1,000 to 100,000 J/m ² .

Furthermore, by attaching a polarizing plate to the outer surface of the liquid crystal cell, a liquid crystal display element can be obtained. The polarizing plate attached to the outer surface of the liquid crystal cell can be a polarizing plate formed by sandwiching a polarizing film called "H film" that stretches polyvinyl alcohol and absorbs iodine with a cellulose acetate protective film, or a polarizing plate composed of the H film itself. [Example]

The following examples are given to illustrate the present invention in more detail, but the present invention is not limited thereto. The abbreviations of the following compounds and the methods for measuring the properties are as follows. In addition, "Me" represents a methyl group.

(Tetracarboxylic dianhydride) BODA: Bicyclo[3.3.0]octane-2,4,6,8-tetracarboxylic dianhydride CBDA: 1,2,3,4-cyclobutanetetracarboxylic dianhydride

(Diamine) [Chemical 31]

[Chemistry 32]

(Organic solvent) NMP: N-methyl-2-pyrrolidone, BCS: Butyl cyanothiocyanate THF: Tetrahydrofuran, DMF: N,N-dimethylformamide DMAc: N,N-dimethylacetamide

< ^1H -NMR measurement> Apparatus: Fourier transform superconducting nuclear magnetic resonance apparatus (FT-NMR) "AVANCE III" (manufactured by BRUKER), 500 MHz. Solvent: deuterated dimethyl sulfoxide ([ _D6 ]-DMSO). Standard substance: tetramethylsilane (TMS).

<Determination of molecular weight> Measurement apparatus: GPC (LC-20 series) manufactured by Shimadzu Corporation, column temperature: 50°C, solvent: N,N-dimethylformamide (additives: lithium bromide monohydrate (LiBr・H ₂ O) 30 mmol/L, phosphoric acid・anhydrous crystals (orthophosphoric acid) 30 mmol/L, tetrahydrofuran (THF) 10 mL/L), flow rate: 1.0 mL/min, calibration standard samples: TSK standard polyethylene oxide manufactured by Tosoh Corporation (molecular weight of approximately 900,000, 150,000, 100,000, 30,000), and polyethylene glycol manufactured by Polymer Laboratories (molecular weight of approximately 12,000, 4,000, 1,000).

<Determination of imidization ratio> 20 mg of polyimide powder was placed in an NMR sample tube (NMR standard sample tube φ5 manufactured by Kusano Scientific Co., Ltd.), 1.0 mL of deuterated dimethyl sulfoxide (DMSO-d ₆ , 0.05% tetramethylsilane (TMS) mixture) was added, and ultrasonic waves were applied to completely dissolve it. This solution was measured with a Fourier transform superconducting nuclear magnetic resonance device (FT-NMR) "AVANCE III" (manufactured by BRUKER) at 500 MHz for proton NMR.

(Chemistry) The imidization rate is calculated by using the peak accumulation value of the proton from the structure that does not change before and after imidization as the reference proton and the peak accumulation value of the proton from the NH group of the acylamidinic acid appearing around 9.5-10.0 ppm according to the following formula. In the formula, x is the peak accumulation value of the proton from the NH group of the acylamidinic acid, y is the peak accumulation value of the reference proton, and α is the ratio of the reference proton to the number of protons in the NH group of the acylamidinic acid when the polyacylamidinic acid (acylamidization rate 0%) is used. Acylamidization rate (%) = (1-α・x/y)×100

<Synthesis of Compound (DA-1)> Compound (DA-1) was synthesized by the following route. (Synthesis of Compound 1) [Chemical 33]

Methanol (45.0 g) was added to 5-fluoro-2-nitroanisole (15.0 g, 87.6 mmol), and methylamine (9.8 mol/L methanol solution, 89.4 mL, 876 mmol) was added at room temperature. After stirring for 24 hours, water (270 g) was added to allow crystals to precipitate. After filtering the crystals, the crystals were washed twice with water (45 g) and dried to obtain compound 1 (15.3 g, 84.0 mmol, yield 95.9%).

(Synthesis of Compound 2) [Chemical 34]

After adding a mixed solution of 5-fluoro-2-nitroanisole (7.89 g, 46.1 mmol) and DMAc (42.0 g) to a solution containing compound 1 (8.40 g, 46.1 mmol), DMAc (84.0 g), and potassium hydroxide (3.88 g, 69.2 mmol), the mixture was heated to 60°C and stirred for 1 hour. After the reaction was completed, water (378 g) was added to cause crystals to precipitate. After filtering the crystals, they were washed twice with water (50.0 g) and twice with methanol (50.0 g) in sequence, and dried to obtain a crude product (17.0 g). The crude product was heated and dissolved in DMF (136 g) and then cooled. The precipitated crystals were recovered by filtration to obtain compound 2 (14.3 g, 42.9 mmol, yield 93.0%).

(Synthesis of DA-1) [Chemical 35]

THF (420 g) and carbon-supported palladium (5% Pd carbon powder (water-containing product) K type, manufactured by NE CHEMCAT, 1.43 g) were added to compound 2 (14.3 g, 42.9 mmol) and nitro reduction was carried out in a hydrogen atmosphere. After the reduction was completed, the carbon-supported palladium was filtered through a filter membrane, and the obtained solution was concentrated and added with isopropanol (70 g), resulting in crystal precipitation. After cooling to 0°C, the crystals were recovered by filtration, and the filter cake was washed twice with isopropanol (30.0 g) and dried to obtain solid DA-1 (9.6 g, 35.1 mmol, yield 82.0%). In addition, from the results of ¹ H-NMR shown below, it was confirmed that the above solid was DA-1. ¹ H-NMR (500MHz, [D ₆ ]-DMSO): δ = 6.52 (d, 2H, J = 8.3Hz), 6.43 (d, 2H, J = 2.4Hz), 6.30 (dd, 2H, J = 8.3, 2.3Hz), 4.29 (s, 4H), 3.66 (s, 6H), 3.07 (s, 3H)

<Synthesis of polyamine> (Synthesis Example 1) BODA (2.50 g, 10.0 mmol), DA-1 (2.19 g, 8.0 mmol), DA-4 (1.94 g, 8.0 mmol) and DA-5 (1.58 g, 4.0 mmol) were mixed in NMP (32.8 g) and reacted at 60°C for 3 hours. Then, CBDA (1.90 g, 9.7 mmol) and NMP (7.6 g) were added and reacted at 40°C for 4 hours to obtain a polyamine solution (1). The number average molecular weight (Mn) of this polyamine was 12,100, and the weight average molecular weight (Mw) was 39,700.

(Synthesis Example 2) BODA (2.50 g, 10.0 mmol), DA-2 (1.59 g, 8.0 mmol), DA-4 (1.94 g, 8.0 mmol) and DA-5 (1.58 g, 4.0 mmol) were mixed in NMP (30.4 g) and reacted at 60°C for 3 hours. Then, CBDA (1.90 g, 9.7 mmol) and NMP (7.6 g) were added and reacted at 40°C for 4 hours to obtain a polyamine solution (2). The Mn of this polyamine is 10,700 and the Mw is 26,600.

(Synthesis Example 3) BODA (2.50 g, 10.0 mmol), DA-3 (1.71 g, 8.0 mmol), DA-4 (1.94 g, 8.0 mmol) and DA-5 (1.58 g, 4.0 mmol) were mixed in NMP (30.9 g) and reacted at 60°C for 3 hours. Then, CBDA (1.90 g, 9.7 mmol) and NMP (7.6 g) were added and reacted at 40°C for 4 hours to obtain a polyamine solution (3). The Mn of this polyamine is 10,500 and the Mw is 31,600. (Synthesis Example 4) BODA (2.50 g, 10.0 mmol), DA-6 (0.99 g, 3.0 mmol), DA-7 (1.19 g, 5.0 mmol), DA-8 (1.19 g, 6.0 mmol) and DA-9 (2.61 g, 6.0 mmol) were mixed in NMP (33.9 g) and reacted at 60°C for 3 hours. Then, CBDA (1.90 g, 9.7 mmol) and NMP (7.6 g) were added and reacted at 40°C for 4 hours to obtain a polyamine solution (4). The Mn of this polyamine is 11,400 and the Mw is 29,300.

The specifications of each polymer obtained in the above synthesis example are shown in Table 1 below. [Table 1] Tetracarboxylic acid components Diamine component Synthesis example 1 Polyamine solution (1) CBDA 1.90 g 9.7 mmol BODA 2.50g 10.0mmol DA-1 2.19 g 8.0 mmol DA-4 1.94 g 8.0 mmol DA-5 1.58 g 4.0 mmol - Synthesis example 2 Polyamine solution (2) CBDA 1.90 g 9.7 mmol BODA 2.50g 10.0mmol DA-2 1.59 g 8.0 mmol DA-4 1.94 g 8.0 mmol DA-5 1.58 g 4.0 mmol - Synthesis example 3 Polyamine solution (3) CBDA 1.90 g 9.7 mmol BODA 2.50g 10.0mmol DA-3 1.71 g 8.0 mmol DA-4 1.94 g 8.0 mmol DA-5 1.58 g 4.0 mmol - Synthesis example 4 Polyamine solution (4) CBDA 1.90 g 9.7 mmol BODA 2.50g 10.0mmol DA-6 0.99g 3.0mmol DA-7 1.19 g 5.0 mmol DA-8 1.19 g 6.0 mmol DA-9 2.61 g 6.0 mmol

<Preparation of liquid crystal alignment agent> (Example 1) NMP (6.0 g) and BCS (8.0 g) were added to the polyamine solution (1) (6.0 g) obtained in Synthesis Example 1, and the mixture was stirred at room temperature for 2 hours to obtain a liquid crystal alignment agent (A-1). (Example 2) NMP (6.0 g) and BCS (8.0 g) were added to the polyamine solution (1) (1.8 g) obtained in Synthesis Example 1 and the polyamine solution (4) (4.2 g) obtained in Synthesis Example 4, and the mixture was stirred at room temperature for 2 hours to obtain a liquid crystal alignment agent (A-2).

(Comparative Examples 1 and 2) The same procedure as in Example 1 was followed except that polyamine solution (2) and (3) were used instead of polyamine solution (1) to obtain liquid crystal alignment agents (B-1) and (B-2) of Comparative Examples 1 and 2. (Comparative Examples 3 and 4) The same procedure as in Example 2 was followed except that polyamine solution (2) and (3) were used instead of polyamine solution (1) to obtain liquid crystal alignment agents (B-3) and (B-4) of Comparative Examples 3 and 4.

[Table 2] Liquid crystal alignment material Polymer composition Embodiment 1 A-1 Polyamine solution (1) Comparative example 1 B-1 Polyamine solution (2) Comparative example 2 B-2 Polyamine solution (3) Embodiment 2 A-2 Polyamine solution (1)/Polyamine solution (4) Comparative example 3 B-3 Polyamine solution (2)/Polyamine solution (4) Comparative example 4 B-4 Polyamine solution (3)/Polyamine solution (4)

The obtained liquid crystal alignment agents (A-1), (A-2), (B-1) to (B-4) were not observed to be abnormal such as turbidity and precipitation, and were confirmed to be uniform solutions. The obtained liquid crystal alignment agents were used to evaluate transmittance, voltage holding ratio, residual DC voltage, and afterimage characteristics.

<Evaluation of (light) transmittance> The liquid crystal alignment agents (A-1), (A-2), (B-1) to (B-4) obtained above were spin-coated on a quartz substrate and dried on a hot plate at 70°C for 90 seconds. They were then calcined in an IR oven at 230°C for 20 minutes to form a coating with a thickness of 100nm, thereby obtaining a substrate with a liquid crystal alignment film. With the substrate with the liquid crystal alignment film as the inner side, another quartz substrate was used to sandwich the contact liquid (manufactured by Shimadzu Equipment Manufacturing Co., Ltd.) to avoid light interference. The transmittance was evaluated using UV-3600 (manufactured by Shimadzu Corporation) as a measuring device, at a temperature of 25°C and a scanning wavelength of 380 to 800nm. At this time, two quartz substrates without coating were used as a control to sandwich the contact liquid. The evaluation was based on the transmittance at a wavelength of 590nm, and its values are shown in the following Table 3.

<Preparation of liquid crystal display elements for voltage retention and residual DC voltage evaluation> Using the liquid crystal alignment agents (A-1), (A-2), (B-1) to (B-4) obtained above, liquid crystal cells were prepared according to the following procedure. The liquid crystal alignment agent was spin-coated on a glass substrate with an ITO electrode, dried on a hot plate at 70°C for 90 seconds, and then calcined in an IR oven at 230°C for 20 minutes to form a liquid crystal alignment film with a film thickness of 100nm. Prepare two substrates with liquid crystal alignment films. Coat one of the liquid crystal alignment films with a 4μm diameter bead spacer (made by Sunward Catalyst Chemicals, silk ball, SW-D1). Keep the liquid crystal injection port and print a thermosetting sealant (made by Kyoritsu Chemical Industry, XN-1500T) around it. Then, use the side of the other substrate with the liquid crystal alignment film formed as the inner side, and after bonding it to the previous substrate, harden the sealant to make a hollow cell.

Liquid crystal MLC-3023 (Merck) was injected into the empty cell by the reduced pressure injection method to make a liquid crystal cell. Then, with a DC voltage of 15V applied to the liquid crystal cell, UV that had passed through a cutoff filter with a wavelength below 325nm was irradiated from the outside of the liquid crystal cell at 10J/ ^cm2 . In addition, the UV illuminance was measured using UV-MO3A made by ORC. Afterwards, in order to inactivate the unreacted polymerizable compound remaining in the liquid crystal cell, UV (UV lamp: FLR40SUV32/A-1) was irradiated for 30 minutes using a UV-FL irradiation device made by Toshiba Lighting Co., Ltd. without applying voltage.

<Evaluation of voltage retention> The voltage retention is measured using a liquid crystal cell for voltage retention evaluation after UV irradiation. A voltage of 1V is applied for 60μsec in a hot air circulation oven at 60°C, and then the voltage is measured after 16.67msec. The voltage can be maintained and calculated as the voltage retention. The voltage retention is measured using VHR-1 manufactured by TOYO CORPORATION. The values are shown in Table 3 below. The higher the value, the better.

<Evaluation of residual DC voltage> For the liquid crystal cell for residual DC voltage evaluation produced above, a 30Hz, 7.8Vpp rectangular wave of DC 2V was applied at 25℃ for 100 hours. The DC voltage was cut off and the voltage (residual DC voltage) remaining in the liquid crystal cell after 1 hour was calculated by flicker elimination method. This value becomes an indicator of afterimages caused by DC accumulation. When the value is less than 50mV, the afterimage characteristics are excellent and it is evaluated as "good". When it is greater than 50mV, it is evaluated as "poor". The results are shown in Table 3 below.

<Preparation of liquid crystal display element for afterimage characteristic evaluation> Using the liquid crystal alignment agents (A-1), (A-2), (B-1) to (B-4) obtained above, liquid crystal cells were prepared according to the following procedure. The liquid crystal alignment agent was spin-coated on an ITO electrode substrate (length: 35mm, width: 30mm, thickness: 0.7mm) with an ITO electrode pattern of 200μm×600μm pixel size and 3μm line/space, and on an ITO surface of a glass substrate with an ITO electrode (length: 35mm, width: 30mm, thickness: 0.7mm) with a 3.2μm high photospacer patterned, dried on a hot plate at 70°C for 90 seconds, and then calcined in an IR oven at 230°C for 20 minutes to form a liquid crystal alignment film with a film thickness of 100nm. In addition, the ITO electrode substrate with the ITO electrode pattern formed was divided into four parts and the four areas were driven independently to form a checkerboard shape.

Then, on the ITO electrode substrate coated with a liquid crystal alignment film and formed with a line/space of 3μm each, a liquid crystal injection port is retained and a sealant (XN-1500T manufactured by Kyoritsu Chemical Industry Co., Ltd.) is printed around it. Then, the side of the other substrate with the liquid crystal alignment film formed is used as the inner side, and after being bonded to the previous substrate, the sealant is hardened to form a hollow cell. Liquid crystal MLC-3023 (manufactured by Merck) is injected into this hollow cell by the reduced pressure injection method to form a liquid crystal cell. Then, a DC voltage of 15V is applied to this liquid crystal cell, and UV that has passed through a cutoff filter with a wavelength below 325nm is irradiated from the outside of the liquid crystal cell at 10J/ ^cm2 . The UV irradiance was measured using UV-MO3A manufactured by ORC. Then, in order to inactivate the unreacted polymerizable compound remaining in the liquid crystal cell, UV (UV lamp: FLR40SUV32/A-1) was irradiated for 30 minutes using a UV-FL irradiation device manufactured by Toshiba Lighting Co., Ltd. without applying voltage.

<Evaluation of afterimage characteristics> Using the liquid crystal cell for afterimage characteristics evaluation prepared above, 60Hz, 20Vp-p AC voltage was applied to two diagonal areas among the four pixel areas, and it was driven at 25°C for 168 hours. After that, all four pixel areas were driven with 5Vp-p AC voltage, and the brightness difference of the pixels was observed visually. The state in which there was almost no brightness difference was defined as "good", and the state in which the brightness difference could be easily confirmed was defined as "bad" for evaluation. The results are shown in Table 3 below.

[Table 3] Liquid crystal alignment agent Transmittance(%) Residual DC voltage Afterimage feature 4 pixels Voltage holding rate(%) Embodiment 1 A-1 99.8 Good (14mV) good 88 Comparative example 1 B-1 99.1 Good (14mV) good 85 Comparative example 2 B-2 99.3 Good (5mV) good 83 Embodiment 2 A-2 98.3 Good (20mV) good 96 Comparative example 3 B-3 97.6 Good (24mV) good 92 Comparative example 4 B-4 97.4 Good (18mV) good 93

As shown in Table 3, the liquid crystal alignment film obtained by using the liquid crystal alignment agent (A-1) of Example 1 has a higher transmittance than the liquid crystal alignment film obtained by using the liquid crystal alignment agents (B-1) and (B-2) of the corresponding comparative examples 1 and 2. Furthermore, the liquid crystal alignment film obtained by using the liquid crystal alignment agent (A-2) of Example 2 has a higher transmittance than the liquid crystal alignment film obtained by using the liquid crystal alignment agents (B-3) and (B-4) of the corresponding comparative examples 3 and 4. Moreover, the difference of 0.5% in transmittance is a significant difference in this technical field. Furthermore, it can be seen that: if the liquid crystal alignment agent obtained in the embodiment is used, a liquid crystal alignment film having a high voltage retention rate can be obtained in the voltage retention rate evaluation. Furthermore, it can be seen that: a liquid crystal alignment film having good characteristics in the residual DC voltage evaluation and the afterimage characteristic evaluation can be obtained. [Industrial Applicability]

The liquid crystal alignment film obtained from the liquid crystal alignment agent of the present invention can be widely used in, for example, clocks, portable game consoles, word processors, notebook personal computers, navigation systems, cameras, PDAs, digital cameras, mobile phones, smart phones, various displays, LCD TVs, information displays, etc., and can be particularly widely used in ultra-high-precision liquid crystal display devices such as 4K and 8K.

In addition, the entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2020-120867 filed on July 14, 2020 are hereby cited and incorporated as the disclosure of the specification of the present invention.

Claims (17)

A liquid crystal alignment agent characterized by containing a polymer (P), wherein the polymer (P) is at least one selected from the group consisting of a polyimide precursor obtained by using a diamine component containing a diamine (1) represented by the following formula (1) and an imide thereof, i.e., a polyimide; R represents a monovalent organic group, and R ₁ and R ₂ each independently represent a saturated or unsaturated monovalent hydrocarbon group having 1 to 6 carbon atoms, or an alicyclic hydrocarbon group having 3 to 6 carbon atoms; a part of the hydrogen atoms in the hydrocarbon group in R ₁ and R ₂ may be substituted. As claimed in claim 1, the liquid crystal alignment agent, wherein, in the formula (1), R is a monovalent organic group having an aromatic ring structure, a monovalent chain hydrocarbon group having 1 to 30 carbon atoms, or a monovalent alicyclic hydrocarbon group having 3 to 30 carbon atoms, and a portion of the hydrogen atoms of the chain hydrocarbon group or the alicyclic hydrocarbon group may be substituted, and a portion of the methylene groups may be substituted with oxygen atoms, carbonyl groups or -COO-. The liquid crystal alignment agent of claim 2, wherein the monovalent organic group having an aromatic ring structure in R has a structure represented by the following formula (Ar); ^Ra represents a halogen atom, a hydroxyl group, a cyano group, an alkyl group having 1 to 9 carbon atoms, an alkoxy group having 1 to 9 carbon atoms, or a fluoroalkyl group having 1 to 9 carbon atoms; m is an integer of 0 to 5, and when m is 2 to 5, a plurality of ^Ras each independently have the above definition; * represents a bonding site. A liquid crystal alignment agent as claimed in any one of claims 1 to 3, wherein in formula (1), R, _R1 and _R2 are each independently methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, t-butyl, n-pentyl, isopentyl, sec-pentyl or t-pentyl. The liquid crystal aligner of any one of claims 1 to 3, wherein the diamine (1) is any diamine selected from the group consisting of the following formulas (d-1) to (d-4); . The liquid crystal alignment agent of any one of claims 1 to 3, wherein the polymer (P) is further obtained using a diamine component having a diamine (s) having at least one structure selected from the group consisting of the following formulae (S1), (S2) and (S3); ^X1 and ^X2 each independently represent a single bond, -( _CH2 ) _a- (a is an integer of 1 to 15), -CONH-, -NHCO-, -CON( _CH3 )-, -N( _CH3 )CO-, -NH-, -O-, -COO-, -OCO- or -(( _CH2 ) _a1 - _A1 ) _m1- , a1 is an integer of 1 to 15, _A1 represents an oxygen atom or -COO-, _m1 is an integer of 1 or 2, and when _m1 is 2, _a1 and _A1 may be the same or different; ^G1 and G2 ² each independently represents a divalent cyclic group selected from a divalent aromatic group having 6 to 12 carbon atoms and a divalent alicyclic group having 3 to 8 carbon atoms; any hydrogen atom on the cyclic group may be substituted by at least one selected from the group consisting of an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluorinated alkyl group having 1 to 3 carbon atoms, a fluorinated alkoxy group having 1 to 3 carbon atoms and a fluorine atom; m and n each independently represent an integer of 0 to 3, and the sum of m and n is 1 to 4; when m and n are plural, the plural X ¹ , X ² , G ¹ and G ² may be the same or different; R ¹ 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, and any hydrogen atom forming R ¹ may be substituted by a fluorine atom; X ³ represents a single bond, -CONH-, -NHCO-, -CON(CH ₃ )-, -N(CH ₃ )CO-, -NH-, -O-, -CH ₂ O-, -COO- or -OCO-; R ² represents an alkyl group having 1 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms, and any hydrogen atom forming R ² may be substituted with a fluorine atom; X ⁴ represents -CONH-, -NHCO-, -O-, -CH ₂ O-, -OCH ₂ -, -COO- or -OCO-; R ³ represents a structure having a steroid skeleton. The liquid crystal alignment agent of claim 6, wherein the diamine (s) is a diamine represented by the following formula (d1) or formula (d2); X represents a single bond, -O-, -C(CH ₃ ) ₂ -, -NH-, -CO-, -COO-, -CONH-, -(CH ₂ ) _m -, -SO ₂ -, -O-(CH ₂ ) _m -O-, -OC(CH 3 ) ₂ -, -CO-(CH ₂ ) _m -, -CO-(CH ₂ ) _m -CO-, -NH-(CH ₂ ) m -, -NH-( _CH2 ) _m -NH-, -SO ₂ -(CH ₂ ) _m -, -SO ₂ -(CH ₂ ) _m -SO ₂ -, -CONH-(CH ₂ ) _{m -} , -CONH-(CH2) _m -NHCO-, or a divalent organic group of -COO-(CH ₂ ) _m -OCO-; m is an integer of 1 to 8; Y represents any structure in the formulae (S1) to (S3); in the formula (d2), two Ys may be the same as or different from each other. The liquid crystal aligner of claim 7, wherein the diamine represented by formula (d1) is any diamine selected from the group consisting of the following formulas (d1-1) to (d1-18); n is an integer from 1 to 20; . The liquid crystal aligner of claim 7, wherein the diamine represented by formula (d2) is any diamine selected from the group consisting of the following formulas (d2-1) to (d2-6); ^Xp1 to ^Xp8 each independently represent -( _CH2 ) _a- (a is an integer of 1 to 15), -CONH-, -NHCO-, -CON( _CH3 )-, -N( _CH3 )CO-, -NH-, -O-, -CH2O-, _-CH2OCO- , -COO-, or -OCO-; ^Xs1 to Xs4 each independently represent -O-, _-CH2O- , -COO-, or -OCO-; Xa to ^Xf each independently represent a single bond, -O-, -NH-, or -O-( _{CH2 ) m} - ^{O- (m is an integer of 1 to 8); R1a to R1h} _{each independently} ^represent 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. The liquid crystal alignment agent of any one of claims 1 to 3, wherein the polymer (P) is obtained by a polymerization reaction of the diamine component and a tetracarboxylic acid component containing tetracarboxylic dianhydride represented by the following formula (T) or a derivative thereof; X represents any structure selected from the group consisting of the following formulae (x-1) to (x-13); R ¹ to R ⁴ 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; R ⁵ and R ⁶ each independently represent a hydrogen atom or a methyl group; j and k are integers of 0 or 1; A ₁ and A ₂ each independently represent a single bond, an ether (-O-), a carbonyl group (-CO-), an ester (-COO-), a phenylene group, a sulfonyl group (-SO ₂ -) or an amide group (-CONH-), and two A _2's may be the same or different; *1 is bonded to the bonding site of one of the anhydride groups, and *2 is bonded to the bonding site of the other anhydride group. As in claim 10, the liquid crystal alignment agent, wherein X in the formula (T) is any one of (x-1) to (x-7) and (x-11) to (x-13). The liquid crystal alignment agent of any one of claims 1 to 3, wherein the diamine (1) is contained in the total diamine components in an amount of 1 to 100 mol%. As in claim 6, the liquid crystal alignment agent, wherein the diamine (s) is contained in 1-99 mol % of all diamine components. A liquid crystal alignment agent as claimed in any one of claims 1 to 3, wherein the liquid crystal alignment agent further contains a polymer (B), wherein the polymer (B) is at least one selected from the group consisting of a polyimide precursor obtained by using a diamine component that does not contain the diamine (1) and a tetracarboxylic acid component and an acylation product of the polyimide precursor, i.e., polyimide. A liquid crystal alignment film for vertical alignment is formed using a liquid crystal alignment agent as described in any one of claims 1 to 14. A liquid crystal display element comprises a liquid crystal alignment film as claimed in claim 13. A method for manufacturing a liquid crystal display element comprises applying a liquid crystal alignment agent as described in any one of claims 1 to 14 on a pair of substrates having a conductive film to form a coating, arranging the coating face to face with a layer of liquid crystal molecules in between to form a liquid crystal cell, and illuminating the liquid crystal cell while applying a voltage between the conductive films of the pair of substrates.