TWI881079B - Liquid crystal alignment agent for photo-alignment method, liquid crystal alignment film, and liquid crystal display element - Google Patents

Abstract

The subject of the present invention is to provide a liquid crystal alignment agent for photo-alignment method, which can obtain a liquid crystal display element with high liquid crystal alignment by photo-alignment method, suppress the deviation of brightness in the plane during black display, and improve the contrast. The solution is a liquid crystal alignment agent for photo-alignment method, which contains at least one polymer (A) selected from the group consisting of polyimide precursors and imidized polymers thereof, and the polymer (A) has at least one repeating unit (a1) selected from the group consisting of repeating units represented by the following formula (1-a) and repeating units represented by the following formula (1-i), and at least one repeating unit (a2) selected from the group consisting of repeating units represented by the following formula (2-a) and repeating units represented by the following formula (2-i), and contains 1 to 20 mol% of the above-mentioned repeating unit (a1) in all the repeating units. (In the formula, _X1 represents a tetravalent organic group represented by the following formula (B), and _X2 represents a tetravalent organic group represented by the following formula (C). R and Z each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Multiple R and Z may be the same or different. _Y1 and _Y2 each independently represent a divalent organic group represented by the following formula (O)). (In the formula, R _b1 to R _b4 each independently represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms. _{L 1} represents a single bond, -CH ₂ -, -(CH ₂ ) _n - (n is an integer of 2 to 18), or a group in which at least a part of -CH ₂ - of the aforementioned -(CH ₂ ) _n - is substituted by any one of -O-, -C(=O)-, or -OC(=O)-. R _c1 to R _c4 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, and at least one of R _c1 to R _c4 represents a group other than a hydrogen atom as defined above). (Ar represents a benzene ring, a biphenyl structure, or a naphthyl ring. Two Ars may be the same or different, and any hydrogen atom on the ring may be substituted by a monovalent organic group. _Q2 represents _-CH2- , -( _CH2 ) _n- (n is an integer of 2 to 18), or a group in which at least a part of _-CH2- in the aforementioned -( _CH2 ) _n- is substituted by any one of -O-, -C(=O)-, or -OC(=O)-. p is an integer of 0 or 1. However, when p is 0, Ar represents a biphenyl structure, and when p is 1, at least one of the two Ars represents a naphthyl ring. * represents a bonding site).

Description

Liquid crystal alignment agent for photo-alignment method, liquid crystal alignment film, and liquid crystal display element

The present invention relates to a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display element for use in a photo-alignment method.

Liquid crystal display devices have been widely used as display parts of personal computers, smart phones, mobile phones, television receivers, etc. Liquid crystal display devices, for example, have a liquid crystal layer sandwiched between a device substrate and a color filter substrate, a pixel electrode and a common electrode for applying an electric field to the liquid crystal layer, an alignment film for controlling the alignment of liquid crystal molecules in the liquid crystal layer, and a thin film transistor (TFT) for switching the electrical signal supplied to the pixel electrode. As a driving method for liquid crystal molecules, longitudinal electric field methods such as TN (Twisted Nematic) method and VA (Vertical Alignment) method, and transverse electric field methods such as IPS (In Plane Switching) method and FFS (Fringe Field Switching) method are known.

At present, the most popular liquid crystal alignment film in industry is produced by rubbing the surface of a film including polyamide and/or polyimide obtained by imidization formed on an electrode substrate in one direction with a cloth such as cotton, nylon, polyester, etc. The friction treatment is a simple and productive method that is useful in industry. However, with the high performance, high precision, and large size of liquid crystal display elements, various problems such as scratches on the surface of the alignment film caused by the friction treatment, dust generation, influence caused by mechanical force or static electricity, and non-uniformity within the alignment treatment surface have become apparent. As an alignment treatment method that replaces the friction treatment, a photoalignment method is known that imparts liquid crystal alignment ability by irradiating polarized radiation. As the photo-alignment method, there are proposed methods utilizing photoisomerization reaction, photocrosslinking reaction, photodecomposition reaction, etc. (see Non-patent Document 1, Patent Document 1).

The liquid crystal alignment film, which is a component of the liquid crystal display element, is a film used to uniformly align the liquid crystal, and the liquid crystal alignment is one of the important characteristics. However, the liquid crystal alignment film obtained by the aforementioned optical alignment method tends to have lower liquid crystal alignment than the liquid crystal alignment film obtained by the conventional rubbing treatment, and the application range of the liquid crystal display device having the liquid crystal alignment film is limited. [Prior technical literature] [Patent literature]

[Patent document 1] Japanese Patent Publication No. 9-297313 [Non-patent document]

[Non-patent document 1] "Functional Materials", November 1997, Vol. 17, No. 11, pp. 13-22

[The problem that the invention wants to solve]

In addition, in actual liquid crystal display elements, due to manufacturing deviations, etc., there is a slight deviation in the torsion angle of the liquid crystal within the surface of the liquid crystal display element. As a result, due to such in-plane deviation, the brightness of the liquid crystal display element during black display is deviated within the surface. The present invention is made in view of the above facts, and one of its purposes is to provide a liquid crystal alignment agent for the photo-alignment method of a liquid crystal display element that can obtain a high liquid crystal alignment by the photo-alignment method, suppresses the brightness deviation within the surface during black display, and improves the contrast. [Means for solving the problem]

After in-depth research, the inventors found that the above-mentioned problems can be solved by using a liquid crystal alignment agent containing specific components, and thus completed the present invention. Specifically, the gist of the invention is as follows.

A liquid crystal alignment agent for photoalignment method, characterized by containing at least one polymer (A) selected from the group consisting of polyimide precursors and imidized polymers thereof, wherein the polymer (A) has at least one repeating unit (a1) selected from the group consisting of repeating units represented by the following formula (1-a) and repeating units represented by the following formula (1-i), and at least one repeating unit (a2) selected from the group consisting of repeating units represented by the following formula (2-a) and repeating units represented by the following formula (2-i), and contains 1 to 20 mol% of the above repeating unit (a1) in all the repeating units.

(In the formula, _X1 represents a tetravalent organic group represented by the following formula (B), and _X2 represents a tetravalent organic group represented by the following formula (C). R and Z each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Multiple R and Z may be the same or different. _Y1 and _Y2 each independently represent a divalent organic group represented by the following formula (O)).

(In the formula, R _b1 to R _b4 each independently represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms. _{L 1} represents a single bond, -CH ₂ -, -(CH ₂ ) _n - (n is an integer of 2 to 18), or a group in which at least a part of -CH ₂ - of the aforementioned -(CH ₂ ) _n - is substituted by any one of -O-, -C(=O)-, or -OC(=O)-. R _c1 to R _c4 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, and at least one of R _c1 to R _c4 represents a group other than a hydrogen atom as defined above).

(Ar represents a benzene ring, a biphenyl structure, or a naphthyl ring. Two Ars may be the same or different, and any hydrogen atom on the ring may be substituted by a monovalent organic group. _Q2 represents _-CH2- , -( _CH2 ) _n- (n is an integer of 2 to 18), or a group in which at least a part of _-CH2- in the aforementioned -( _CH2 ) _n- is substituted by any one of -O-, -C(=O)-, or -OC(=O)-. p is an integer of 0 or 1. However, when p is 0, Ar represents a biphenyl structure, and when p is 1, at least one of the two Ars represents a naphthyl ring. * represents a bonding site).

Furthermore, in this specification, * indicates a bonding site regardless of the situation. Boc represents a tert-butyloxycarbonyl group. Halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms. Carbamate-based protecting groups include tert-butyloxycarbonyl and 9-fluorenylmethoxycarbonyl. [Effect of the invention]

The liquid crystal alignment agent for photo-alignment method of the present invention contains: at least one polymer (A) selected from the group consisting of polyimide precursors and imidized polymers thereof, which has the above-mentioned repeating units (a1) and the above-mentioned repeating units (a2), and contains 1 to 20 mol% of the above-mentioned repeating units (a1) based on all the repeating units. This can achieve the effect of suppressing the deviation of brightness within the plane during black display by photo-alignment method, thereby improving the contrast of the liquid crystal display element.

The liquid crystal alignment agent for photo-alignment method (hereinafter also simply referred to as liquid crystal alignment agent) of the present invention is described.

<Polymer (A)> The liquid crystal alignment agent of the present invention contains at least one polymer (A) selected from the group consisting of polyimide precursors and imidized polymers thereof, and the polymer (A) has: at least one repeating unit (a1) selected from the group consisting of repeating units represented by the following formula (1-a) and repeating units represented by the following formula (1-i), and at least one repeating unit (a2) selected from the group consisting of repeating units represented by the following formula (2-a) and repeating units represented by the following formula (2-i), and contains 1 to 20 mol% of the above repeating units (a1) of all repeating units. Furthermore, the polymer (A) may be composed of one or more than two types.

<Repeating unit (a1)> The repeating unit (a1) of the present invention is at least one repeating unit selected from the group consisting of the repeating unit represented by the following formula (1-a) and the repeating unit represented by the following formula (1-i).

(In the formula, _X1 represents a tetravalent organic group represented by the following formula (B). R and Z each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. The two R and Z may be the same or different. _Y1 represents a divalent organic group represented by the following formula (O)).

(In the formula, R _b1 to R _b4 independently represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms. _{L 1} represents a single bond, -CH ₂ -, -(CH ₂ ) _n - (n is an integer of 2 to 18), or a group in which at least a part of -CH ₂ - in the aforementioned -(CH ₂ ) _n - is substituted by any one of -O-, -C(=O)- or -OC(=O)-).

(Ar represents a benzene ring, a biphenyl structure, or a naphthyl ring. Two Ars may be the same or different. Any hydrogen atom on the ring may be substituted by a monovalent organic group. _Q2 represents _-CH2- , -( _CH2 ) _n- (n is an integer of 2 to 18), or a group in which at least a part of _-CH2- in the aforementioned -( _CH2 ) _n- is substituted by any one of -O-, -C(=O)- or -OC(=O)-. p is an integer of 0 or 1. However, when p is 0, Ar represents a biphenyl structure, and when p is 1, at least one of the two Ars represents a naphthyl ring).

Preferred examples of _L1 are single bonds, _-CH2- or -( _CH2 ) _n- (n is an integer of 2 to 18) from the viewpoint of efficiently obtaining the effects of the present invention. Preferred examples of _Rb1 to _Rb4 are hydrogen atoms from the viewpoint of efficiently obtaining the effects of the present invention.

The tetravalent organic group represented by the aforementioned formula (B) is preferably a tetravalent organic group represented by the following formulas (b-1) to (b-2) from the viewpoint of improving the liquid crystal alignment.

Preferred examples of the divalent organic group represented by the aforementioned formula (O) from the viewpoint of efficiently obtaining the effects of the present invention are the divalent organic groups represented by the following formulas (o-1) to (o-7).

<Repeating unit (a2)> The repeating unit (a2) of the present invention is at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (2-a) and a repeating unit represented by the following formula (2-i).

(In the formula, _X2 represents a tetravalent organic group represented by the following formula (C). R and Z each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. The two R and Z may be the same or different. _Y2 has the same meaning as _Y1 above, including preferred specific examples).

(In the formula, R _c1 to R _c4 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, and at least one of R _c1 to R _c4 represents a group other than a hydrogen atom as defined above).

Examples of the tetravalent organic group represented by the aforementioned formula (C) include the tetravalent organic groups represented by the following formulae (Xc-1) to (Xc-6). Among these, (Xc-1) is particularly preferred from the viewpoint of improving the liquid crystal alignment.

<Repeating unit (a3)> The aforementioned polymer (A) may also be at least one selected from the group consisting of polyimide precursors and imidized polymers thereof having at least one repeating unit (a3) selected from the group consisting of repeating units represented by the following formula (3-a) and repeating units represented by the following formula (3-i) other than repeating units (a1) and (a2).

(In the formula, X ₃ represents a tetravalent organic group, and Y ₃ represents a divalent organic group represented by the following formula (3d). R and Z have the same meanings as in the above formula (1-a)).

(Ar ₃ represents a benzene ring or a biphenyl structure, two Ar ₃ may be the same or different, and any hydrogen atom on the above ring may be substituted by a monovalent organic group. _{Q 3} represents -(CH ₂ ) _n - (n is an integer of 2 to 18), or a group in which at least a part of -CH ₂ - of the above -(CH ₂ ) _n - is substituted by any one of -O-, -C(=O)- or -OC(=O)-).

Examples of the divalent organic group represented by the aforementioned formula (3d) include divalent organic groups represented by the following formulae (3d-1) to (3d-8), but are not limited thereto.

The aforementioned polymer (A) may be at least one selected from the group consisting of polyimide precursors and imidized polymers thereof having at least one repeating unit (a4) selected from the group consisting of repeating units represented by the following formula (4-a) and repeating units represented by the following formula (4-i) in addition to the repeating units (a1) and (a2).

(In the formula, R and Z are the same as those in the above formula (1-a). _X4 represents a tetravalent organic group, and _Y4 represents a divalent organic group having 6 to 30 carbon atoms and having a group "-N(D)- (D represents a carbamate protective group)" in the molecule).

Specific examples of the divalent organic group having 6 to 30 carbon atoms and having the group "-N(D)- (D represents a carbamate-based protective group)" in the molecule of _Y4 include a divalent organic group having a partial structure represented by the following formula (4-1) or a divalent organic group represented by the following formula (4-2).

In the formula, _Q5 is a single bond, -( _CH2 ) _n- (n is an integer of 1 to 20), or any _-CH2- of -( _CH2 ) _n- substituted by -O-, -COO-, -OCO-, _-NQ9- , -NQ9-CO-, -CO- _NQ9- , _-NQ9 -CO- _NQ10- , _-NQ9 -COO-, or -O-COO-; _{Q9 and Q10} each independently represent a hydrogen atom or a monovalent organic group; _Q6 and _Q7 each independently represent -H, a group having -NHD, or a group having -N(D) ₂ . _Q8 represents a group having -NHD, or a group having -N(D) ₂ . D represents a carbamate-based protecting group. However, at least one of _Q5 , _Q6 and _Q7 has a carbamate-based protecting group in the group. Specific examples of the monovalent organic group in _Q9 and _Q10 include 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, an alkyl group having 1 to 6 carbon atoms containing a fluorine atom, the aforementioned carbamate-based protecting group, and an alkoxyalkyl group having 1 to 6 carbon atoms.

Here, _Y4 can be, for example, structures represented by the following formulas (Y4-1) to (Y4-4), but is not limited thereto.

The aforementioned polymer (A) may also be at least one selected from the group consisting of polyimide precursors and imidized polymers thereof having at least one repeating unit (a5) selected from the group consisting of repeating units represented by the following formula (5-a) and repeating units represented by the following formula (5-i) in addition to the repeating units (a1) and (a2).

In formula (5-a) and formula (5-i), R and Z are synonymous with those in the aforementioned formula (1-a). _{X 5} represents a tetravalent organic group, and Y ₅ represents a divalent organic group. However, when Y ₅ represents a structure other than a divalent organic group represented by the aforementioned formula (3d), or a divalent organic group having 6 to 30 carbon atoms and having the group "-N(D)-(D represents a carbamate protective group)" in the molecule, and when X ₅ has the same meaning as a tetravalent organic group represented by the aforementioned formula (B) or a tetravalent organic group represented by the aforementioned formula (C), Y ₅ represents a structure other than a divalent organic group represented by the aforementioned formula (O).

In formula (5-a) and formula (5-i), specific examples of _Y5 include p-phenylenediamine, 2,3,5,6-tetramethyl-p-phenylenediamine, 2,5-dimethyl-p-phenylenediamine, m-phenylenediamine, 2,4-dimethyl-m-phenylenediamine, 2,5-diaminotoluene, 2,6-diaminotoluene, 4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethyl 4,4'-diaminobiphenyl, 3,3'-difluoro-4,4'-diaminobiphenyl, 3,3'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,4'-diaminobiphenyl, 3,3'-diaminobiphenyl, 2,2'-diaminobiphenyl, 2,3'-diaminobiphenyl, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane Alkane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 4,4'-diaminobenzanilide, 4,4'-diaminoazobenzene, 1,5-diaminonaphthalene, 1,6-diaminonaphthalene, 1,7-diaminonaphthalene, 2,5-diamino In addition, the divalent organic group may be a divalent organic group obtained by removing two amino groups from an aromatic diamine such as naphthalene, 2,6-diaminonaphthalene, 2,7-diaminonaphthalene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, and 1,4-bis(4-aminobenzyl)benzene, and the divalent organic group exemplified below for _Y6 may be exemplified.

The structures of the tetravalent organic groups represented by X ₃ , X ₄ and X ₅ are not particularly limited, and any structure can be independently selected. Preferred specific examples include the following formulas (X1-1) to (X1-44).

In formula (X1-1) to (X1-4), R ³ to R ²³ are independently 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. 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; more preferably a hydrogen atom or a methyl group.

Specific examples of formula (X1-1) include the following formulas (X1-1-1) to (X1-1-6). From the perspective of liquid crystal alignment and light sensitivity, (X1-1-1) to (X1-1-2) are more preferred, and (X1-1-2) is particularly preferred.

From the viewpoint of obtaining the effects of the present invention in a good manner, the polymer (A) preferably contains 1 to 20 mol % of the repeating units (a1), more preferably 1 to 15 mol %, based on the total repeating units.

From the viewpoint of obtaining the effect of the present invention well, in the polymer (A), the total of the repeating units (a1) and the repeating units (a2) is preferably 5 mol% or more, more preferably 10 mol% or more of the total repeating units.

From the viewpoint of obtaining the effect of the present invention well, the polymer (A) preferably contains 1 to 95 mol% of the repeating units (a3), more preferably 1 to 90 mol%, and even more preferably 5 to 90 mol% of the total repeating units. In this case, the total of the repeating units (a1) and the repeating units (a2) is preferably 99 mol% or less, and more preferably 95 mol% or less.

From the viewpoint of obtaining the effect of the present invention well, the polymer (A) preferably contains 1 to 40 mol % of the repeating units (a4), more preferably 1 to 30 mol %, and even more preferably 1 to 25 mol % of the total repeating units.

<Polymer (B)> The liquid crystal alignment agent of the present invention may also contain a polymer (B) having a repeating unit represented by the following formula (6) from the viewpoint of reducing residual images caused by residual DC. Furthermore, the polymer (B) does not have the above-mentioned repeating unit (a1) and repeating unit (a2) in the same molecule. In addition, the polymer (B) may be composed of one or more types, and the repeating units constituting the polymer (B) may be composed of one or more types.

(X ₆ is a tetravalent organic group, Y ₆ is a divalent organic group. R and Z have the same meanings as in formula (1-a)).

The tetravalent organic group in the above formula _X6 may be a tetravalent organic group derived from a non-cyclic aliphatic tetracarboxylic dianhydride, a tetravalent organic group derived from alicyclic tetracarboxylic dianhydride, a tetravalent organic group derived from aromatic tetracarboxylic dianhydride, etc. Specific examples of the tetravalent organic group derived from a non-cyclic aliphatic tetracarboxylic dianhydride and the tetravalent organic group derived from alicyclic tetracarboxylic dianhydride include structures selected from the following formulas (X-1) to (X-13).

(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 and having a fluorine atom, or a phenyl group. R ⁵ and R ⁶ each independently represent a hydrogen atom or a methyl group).

Among them, the above formula (x-1) is preferably selected from the group consisting of the following formulas (x1-1) to (x1-6).

In the above formulae (x1-1) to (x1-6), *1 represents a bonding site to the acid anhydride group on one side, and *2 represents a bonding site to the acid anhydride group on the other side.

Aromatic tetracarboxylic dianhydride refers to an acid dianhydride obtained by intramolecular dehydration of a carboxyl group bonded to an aromatic ring such as a benzene ring or a naphthalene ring. Specific examples include the tetravalent organic groups represented by the above formulas (X1-28) to (X1-40).

The divalent organic group in the above formula _Y6 may be a heterocyclic ring containing a nitrogen atom, a diamine having at least one structure containing a nitrogen atom selected from the group consisting of a diamino group and a tertiary amino group (hereinafter also referred to as a structure containing a nitrogen atom), 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol, 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid, 3,5-diaminobenzoic acid, or two of the following formulas (3b-1) to (3b-4): Amine compounds such as diamines having a carboxyl group, 4-(2-(methylamino)ethyl)aniline, 4-(2-aminoethyl)aniline, 4,4'-diaminodiphenylmethane, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenyl ether, 4,4'-diaminobenzanilide, 4,4'-diaminoazobenzene, 1-(4-aminophenyl)-1,3,3-trimethyl-1H-indane-5-amine, 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl-1H-indane-6- amine, diamines having urea bonds such as 1,3-bis(4-aminophenethyl)urea, diamines having photopolymerizable groups at the end such as 2-(2,4-diaminophenoxy)ethyl methacrylate, 2,4-diamino-N,N-diallylaniline, cholesteryloxy-3,5-diaminobenzene, cholesteryloxy-3,5-diaminobenzene, cholesteryloxy-2,4-diaminobenzene, 3,5-diaminobenzoic acid cholesteryl ester, 3,5-diaminobenzoic acid cholesteryl ester, 3,5-diaminobenzoic acid lanosteryl ester , a diamine having a steroid skeleton such as 3,6-bis(4-aminobenzyloxy)cholestane, a diamine represented by the following formula (V-1) to (V-8), a diamine having a siloxane bond such as 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, a divalent organic group obtained by removing two amino groups from a diamine having an oxazoline structure such as the following formula (Ox-1) to (Ox-2), a group represented by any one of the formulas (Y-1) to (Y-167) described in International Publication No. 2018/117239, etc.

(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 ), A1 represents a single bond, -CH2-, -C2H4-, -C(CH3) _2- , -CF2-, -C(CF3) _2- , -O-, -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), A1 represents a single bond, -CH2-, -C2H4-, -C(CH3)2-, -C(CF3)2-, -O-, -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. ^m2 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 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 to 4).

( ^Xv1 to ^Xv4 , ^Xp1 to ^Xp2 each independently represents -( _CH2 ) _a- (a is an integer of 1 to 15), -CONH-, -NHCO-, -CON( _CH3 )-, -NH-, -O-, _-CH2O- , _-CH2OCO- , -COO-, or -OCO-, ^Xv5 represents -O-, _-CH2O- , -CH2OCO-, -COO-, or -OCO-. _Xa represents a single bond, -O-, -NH-, -O-( _{CH2 ) m} -O- (m represents an integer of 1 to 6), ^Rv1 to ^Rv4 , ^R1a to ^R1b each 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. ^Xv7 to X ^V8 independently represents -O-, _-CH2O- , -COO- or -OCO-).

Examples of the nitrogen-containing heterocyclic ring include pyrrole, imidazole, pyrazole, triazole, pyridine, pyrimidine, pyridazine, pyrazine, indole, benzimidazole, purine, quinoline, isoquinoline, The present invention can be used in combination with pyridine, pyrimidine, pyrazine, piperidine, piperazine, quinoline, carbazole, acridine, piperidine, piperazine, pyrrolidine, hexamethyleneimine, etc. Among them, pyridine, pyrimidine, pyrazine, piperidine, piperazine, quinoline, carbazole or acridine is preferred.

The diamine having a nitrogen atom-containing structure may have a diamine group and a tertiary amine group, for example, which are represented 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. "*1" represents a bonding site to the hydrocarbon group.

Examples of the monovalent alkyl group in the above formula R 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 a structure containing a nitrogen atom include 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, N,N'-bis(4-aminophenyl)benzidine, N,N'-bis(4-aminophenyl)-N,N'-dimethylbenzidine, 4,4'-diaminodiphenylamine, N,N-bis(4-aminophenyl)-methylamine, and compounds represented by the following formulas (z-1) to (z-23).

From the viewpoint of less residual image due to residual DC, the polymer (B) is preferably a polymer comprising repeating units, wherein _Y6 is a divalent organic group selected from the group consisting of a diamine having a structure containing a nitrogen atom, 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol, a diamine having a carboxyl group or a diamine having a urea bond as described above, and a divalent organic group obtained by removing two amino groups (these are also collectively referred to as specific divalent organic groups).

From the viewpoint of reducing residual DC afterimages, the polymer (B) may contain 1 mol% or more of all repeating units in the polymer (B) in which _Y6 is the aforementioned specific divalent organic group, or 5 mol% or more.

From the viewpoint of reducing residual images due to residual DC, the content ratio of polymer (A) to polymer (B) can be 10/90 to 90/10, 20/80 to 90/10, or 20/80 to 80/20, in terms of the mass ratio of [polymer (A)]/[polymer (B)].

<Production method of polyamine, polyamine ester and polyimide> The polyamine ester, polyamine and polyimide of the polyimide precursor used in the present invention can be synthesized by a known method such as described in International Publication No. 2013/157586. Specifically, it is synthesized by reacting a diamine component with a tetracarboxylic acid derivative component in a solvent (polycondensation). The above-mentioned tetracarboxylic acid derivative component can be tetracarboxylic dianhydride or its derivative (tetracarboxylic acid dihalide, tetracarboxylic acid diester, or tetracarboxylic acid diester dihalide). When a part of the polymer (A) or (B) contains an amide structure, for example, a polymer (polyamide) having an amide structure can be obtained by reacting a tetracarboxylic dianhydride component with a diamine component. The solvent is not particularly limited as long as it can dissolve the generated polymer.

The diamine component and the tetracarboxylic acid derivative component of the polyimide precursor for obtaining the polymer (A) are selected and used in accordance with the repeating units represented by the above formula (1-a), formula (2-a), and the formula (3-a), formula (4-a), and formula (5-a) contained in the polymer (A) as required, so as to obtain the structure of the repeating units. For example, when the polymer (A) has the repeating unit represented by the formula (1-a), the diamine component is a diamine having a structure of -N(Z)-Y ₁ -N(Z)- (the definitions of Y ₁ and Z are the same as above), and the tetracarboxylic acid derivative component is a tetracarboxylic acid derivative having a structure of the following formula.

(The definition of _X1 is the same as above).

The polyamic acid ester can be obtained by a known method such as [I] a method of reacting the polyamic acid obtained by the above method with an esterifying agent, [II] a method of reacting a tetracarboxylic acid diester with a diamine, or [III] a method of reacting a tetracarboxylic acid diester dihalide with a diamine.

The method of obtaining polyimide can be exemplified by thermal imidization in which a solution containing a polyimide precursor such as polyamic acid, polyamic acid ester, etc. obtained by the above reaction is directly heated, or catalytic imidization in which a catalyst is added to the above solution. In the polyimide used in the present invention, the ring closure rate of the amide group (also called the imidization rate) does not necessarily have to be 100%, and can be arbitrarily adjusted according to the use or purpose. For example, the imidization rate of the polyimide can be 20-100%, 50-99%, or 70-99% from the viewpoint of improving the solubility of the polyimide coating.

<Polymer solution viscosity/molecular weight> The polyamine, polyamine ester and polyimide used in the present invention, when used as a solution with a concentration of 10-15% by mass, preferably has a solution viscosity of 10-1000 mPa･s, for example, from the viewpoint of workability, but is not particularly limited. Furthermore, the solution viscosity (mPa･s) of the above polymer is a value measured at 25°C using an E-type rotational viscometer for a polymer solution with a concentration of 10-15% by mass prepared using a good solvent for the polymer (e.g., γ-butyrolactone, N-methyl-2-pyrrolidone, etc.).

The weight average molecular weight (Mw) of the polyamine, polyamic acid ester and polyimide measured by gel permeation chromatography (GPC) in terms of polystyrene is preferably 1,000 to 500,000, more preferably 2,000 to 300,000. 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 having such a molecular weight range, good orientation and stability of the liquid crystal display element can be ensured.

<Liquid crystal alignment agent> The liquid crystal alignment agent of the present invention contains polymer (A) and polymer (B) as required. The liquid crystal alignment agent of the present invention may contain other polymers in addition to polymer (A) and polymer (B). The types of other polymers include polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivatives, polyacetal, polystyrene or its derivatives, poly(styrene-phenylmaleimide) derivatives, poly(meth)acrylate, etc.

The liquid crystal alignment agent is used to make a liquid crystal alignment film. From the perspective of forming a uniform thin film, it takes the form of a coating liquid. The liquid crystal alignment agent of the present invention is also preferably a coating liquid containing the aforementioned polymer component and an organic solvent. At this time, the concentration of the polymer in the liquid crystal alignment agent can be appropriately changed according to the setting of the thickness of the coating to be formed. From the perspective of forming a uniform and defect-free coating, it is preferably 1% by mass or more, and from the perspective of the storage stability of the solution, it is preferably 10% by mass or less. The particularly preferred polymer concentration is 2~8% by mass.

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

Furthermore, the organic solvent contained in the liquid crystal alignment agent is preferably a mixed solvent in which a solvent (also called a poor solvent) is used in addition to the above-mentioned solvents to improve the coating property or the surface smoothness of the coating film when the liquid crystal alignment agent is coated. Specific examples of the organic solvent used in combination are as follows, but are not limited to these.

For example, there can be mentioned 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 monoisopentyl ether, ethylene glycol monohexyl ether, propylene glycol monobutyl ether, 1-(2-butoxyethoxy)-2 -propanol, 2-(2-butoxyethoxy)-1-propanol, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monobutyl ether acetate, 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 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 particularly preferred.

The preferred solvent combinations of good solvent and poor solvent include 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-methyl-2-pyrrolidone and γ-butyrolactone and 4-hydroxy-4-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 bad solvent is preferably 1-80% by mass of the total solvent contained in the liquid crystal alignment agent, more preferably 10-80% by mass, and particularly preferably 20-70% by mass. The type and content of the adverse solvent should be appropriately selected according to the coating equipment, coating conditions, coating environment, etc. of the liquid crystal alignment agent.

The liquid crystal alignment agent of the present invention may also contain additional components other than polymer components and organic solvents (hereinafter also referred to as additive components). Such additive components include adhesion promoters 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 improving the strength of the liquid crystal alignment film (hereinafter also referred to as cross-linking compounds), compounds for promoting imidization, and dielectrics or conductive substances for adjusting the dielectric constant or resistance of the liquid crystal alignment film.

The crosslinking compound may be a compound having at least one group selected from the group consisting of an oxirane group, an oxacyclobutane 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 formula (d), or a compound selected from the group represented by the following formula (e) from the viewpoint of exhibiting good resistance to AC residual image and improving film strength (hereinafter, these are also collectively referred to as compound (C)).

( _R2 and _R3 are independently hydrogen atom, alkyl group with 1 to 3 carbon atoms or "*-CH2 _- OH". 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. R represents a hydrogen atom or an alkyl group with 1 to 5 carbon atoms. The hydrogen atom on the aromatic ring of A mentioned above may be substituted by a monovalent organic group such as a halogen atom, an alkyl group with 1 to 6 carbon atoms, an alkenyl group with 2 to 6 carbon atoms, an alkynyl group with 2 to 6 carbon atoms, a monovalent organic group with 1 to 6 carbon atoms containing a fluorine atom, etc.).

Specific examples of compounds having an oxirane group include compounds described in paragraph [0037] of Japanese Patent Application Laid-Open No. 10-338880, or compounds having a triazine ring in the skeleton described in International Publication No. 2017/170483, etc. Compounds having two or more oxirane groups. Among these, compounds containing nitrogen atoms such as N,N,N',N'-tetraoxopropyl-m-xylenediamine, 1,3-bis(N,N-dioxopropylaminomethyl)cyclohexane, N,N,N',N'-tetraoxopropyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraoxopropyl-p-phenylenediamine, and compounds represented by the following formulas (r-1) to (r-3) may also be mentioned.

Specific examples of the compound having an oxacyclobutane group include compounds having two or more oxacyclobutane groups described in paragraphs [0170] to [0175] of International Publication No. 2011/132751.

Specific examples of compounds having a protected isocyanate group include compounds having two or more protected isocyanate groups described in paragraphs [0046] to [0047] of Japanese Patent Application Publication No. 2014-224978, compounds having three or more protected isocyanate groups described in paragraphs [0119] to [0120] of International Publication No. 2015/141598, and compounds represented by the following formulas (bi-1) to (bi-3).

Specific examples of the compound having a protected isothiocyanate group include compounds having two or more protected isothiocyanate groups described in Japanese Patent Application Laid-Open No. 2016-200798.

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

Specific examples of the compound having a group containing a Michaelis acid structure include compounds having two or more Michaelis acid structures described in International Publication No. 2012/091088.

Specific examples of the compound having a cyclocarbonate group include the compounds described in International Publication No. 2011/155577.

The alkyl group having 1 to 3 carbon atoms in R ₂ and R ₃ of the group represented by the above formula (d) may be methyl, ethyl, propyl or the like.

Specific examples of compounds having a group represented by the aforementioned formula (d) include compounds having two or more groups represented by the aforementioned formula (d) described in paragraph [0058] of International Publication No. 2015/072554 or Japanese Patent Publication No. 2016-118753, compounds described in Japanese Patent Publication No. 2016-200798, and compounds represented by the following formulas (hd-1) to (hd-8).

The (m+n)-valent organic group having an aromatic ring in A of the aforementioned formula (e) may 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 directly or via a linker, and an (m+n)-valent group having an aromatic heterocyclic ring. Examples of the aforementioned aromatic hydrocarbon include benzene and naphthalene. Examples of the aromatic heterocyclic ring include pyrrole ring, imidazole ring, pyrazole ring, pyridine ring, pyrimidine ring, quinoline ring, isoquinoline ring, carbazole ring, pyridazine ring, pyrazine ring, benzimidazole ring, indole ring, quinoxaline ring, acridine ring, and the like. The aforementioned linking group may be an alkylene group having 1 to 10 carbon atoms, -NR- (R represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms), a group obtained by removing a hydrogen atom from the aforementioned alkylene group, a divalent or trivalent cyclohexane ring, etc. Furthermore, any hydrogen atom of the aforementioned alkylene group may be substituted by an organic group such as a fluorine atom or a trifluoromethyl group. If specific examples of the compound represented by the aforementioned formula (e) are listed, the compounds described in International Publication No. 2010/074269 and the compounds represented by the following formulas (e-1) to (e-10) may be listed.

The above compounds are examples of crosslinking compounds, but are not limited thereto. For example, the components other than the above disclosed on pages 53 [0105] to 55 [0116] of International Publication No. 2015/060357 can be cited. In addition, two or more crosslinking compounds can be combined.

In the liquid crystal alignment agent of the present invention, the content of the crosslinking compound is preferably 0.5 to 20 parts by mass relative to 100 parts by mass of the polymer component contained in the liquid crystal alignment agent. From the perspective of crosslinking reaction and good resistance to AC residual image, it is more preferably 1 to 15 parts by mass.

The adhesion promoter may be, for example, 3-aminopropyl trimethoxysilane, 3-aminopropyl triethoxysilane, 3-aminopropyl diethoxymethyl silane, 2-aminopropyl trimethoxysilane, 2-aminopropyl triethoxysilane, N-(2-aminoethyl)-3-aminopropyl trimethoxysilane, N-(2-aminoethyl)-3-aminopropyl methyl dimethoxysilane, 3-ureidopropyl trimethoxysilane, 3-ureidopropyl triethoxysilane, N-ethoxycarbonyl-3-aminopropyl trimethoxysilane, N-ethoxy Carbonyl-3-aminopropyl triethoxysilane, N-triethoxysilylpropyl triethylenetriamine, N-trimethoxysilylpropyl triethylenetriamine, 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-aminopropyl trimethoxysilane, N-benzyl-3-aminopropyl triethoxysilane, N-phenyl-3 -aminopropyl trimethoxysilane, N-phenyl-3-aminopropyl triethoxysilane, N-bis(oxyethyl)-3-aminopropyl trimethoxysilane, N-bis(oxyethyl)-3-aminopropyl triethoxysilane, vinyl trimethoxysilane, vinyl triethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, 3-glycidoxypropyl methyl dimethoxysilane, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl methyl diethoxysilane, 3-glycidoxypropyl Silane coupling agents such as triethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, 3-butylpropylmethyldimethoxysilane, 3-butylpropyltrimethoxysilane, and 3-isocyanatepropyltriethoxysilane. When a silane coupling agent is used, from the viewpoint of exhibiting good resistance to AC residual image, the amount thereof is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, based on 100 parts by mass of the polymer component contained in the liquid crystal alignment agent.

The compound used to promote the above-mentioned imidization is preferably a compound having a basic site (e.g., a primary amine group, an aliphatic heterocycle (e.g., a pyrrolidine skeleton), an aromatic heterocycle (e.g., an imidazole ring, an indole ring), or a guanidine group, etc.) (except the above-mentioned cross-linking compound and adhesion promoter), or a compound that generates the above-mentioned basic site when calcined. More preferably, it is a compound that generates the above-mentioned basic site when calcined. When enumerating preferred specific examples, amino acids having a partially or completely protected basic site can be cited. Specific examples of the above amino acids include glycine, alanine, cysteine, methionine, asparagine, glutamine, valine, leucine, phenylalanine, tyrosine, tryptophan, proline, hydroxyproline, arginine, histidine, lysine, and ornithine. More specific examples of compounds for promoting acylation include N-α-(9-fluorenylmethoxycarbonyl)-N-τ-(tert-butyloxycarbonyl)-L-histidine.

<Method for producing a liquid crystal alignment film> The method for producing a liquid crystal alignment film using the liquid crystal alignment agent of the present invention is characterized by sequentially carrying out: a step of applying the liquid crystal alignment agent (step (1)), a step of firing the applied liquid crystal alignment agent (step (2)), a step of irradiating the film obtained in step (2) with polarized ultraviolet light (step (3)), and a step of firing the film obtained in step (3) at a temperature above 100°C and higher than that in step (2) (step (4)).

<Step (1)> The substrate on which the liquid crystal alignment agent used in the present invention is applied is not particularly limited as long as it is a highly transparent substrate, and a glass substrate, a silicon nitride substrate, an acrylic substrate, a plastic substrate such as a polycarbonate substrate, etc. can also be used. In this case, it is better to use a substrate formed with an ITO electrode for driving the liquid crystal from the perspective of simplifying the process. In addition, in a reflective liquid crystal display element, as long as it is a single-sided substrate, an opaque material such as a silicon wafer can also be used, and the electrode in this case can also be made of a light-reflecting material such as aluminum.

There is no particular limitation on the method of applying the liquid crystal alignment agent. Generally speaking, it is done by screen printing, lithography, flexographic printing or inkjet printing in industry. Other methods of application include immersion, roll coater, slit coater, rotary coater or spraying, which can be used according to the purpose.

<Step (2)> Step (2) is a step of baking the liquid crystal alignment agent coated on the substrate to form a film. After the liquid crystal alignment agent is coated on the substrate, the solvent can be evaporated or the amide or amide ester in the polymer can be thermally imidized by heating means such as a heating plate, a heat cycle oven or an IR (infrared) oven. The drying and baking steps after coating the liquid crystal alignment agent of the present invention can be selected at any temperature and time, and can also be performed multiple times. The baking temperature can be, for example, 40 to 150°C. From the perspective of shortening the process, it can also be performed at 40 to 120°C. The calcining time is not particularly limited, and may be 1 to 10 minutes or 1 to 5 minutes. When the thermal imidization of the amide or amide ester in the polymer is performed, a calcining step may be performed at a temperature range of, for example, 190 to 250° C. or 200 to 240° C. after the above calcining step. The calcining time is not particularly limited, and may be 5 to 40 minutes or 5 to 30 minutes.

<Step (3)> Step (3) is a step of irradiating the film obtained in step (2) with polarized ultraviolet light. The wavelength of the ultraviolet light is preferably 200~400nm, and the ultraviolet light with a wavelength of 200~300nm is particularly preferred. In order to improve the liquid crystal alignment, the substrate coated with the liquid crystal alignment film can be heated at 50~250℃ and irradiated with ultraviolet light at the same time. In addition, the irradiation amount of the aforementioned ultraviolet light is preferably 1~10,000 mJ/ ^cm2 , and more preferably 100~5,000mJ/ ^cm2 . The liquid crystal alignment film produced in this way can align the liquid crystal molecules stably in a certain direction.

The higher the extinction ratio of the polarized ultraviolet light, the higher the anisotropy can be given, so it is better. Specifically, the extinction ratio of the linearly polarized ultraviolet light is preferably 10:1 or more, and more preferably 20:1 or more.

<Step (4)> Step (4) is a step of firing the film obtained in step (3) at a temperature of 100°C or higher and higher than that in step (2). The firing temperature is not particularly limited as long as it is 100°C or higher and higher than the firing temperature in step (2), and is preferably 150-300°C, more preferably 150-250°C, and more preferably 200-250°C. The firing time is preferably 5-120 minutes, more preferably 5-60 minutes, and more preferably 5-30 minutes.

If the thickness of the liquid crystal alignment film after firing is too thin, the reliability of the liquid crystal display element may be reduced, so it is preferably 5~300nm, and more preferably 10~200nm.

Furthermore, after performing any of the aforementioned steps (3) or (4), the obtained liquid crystal alignment film may be contact treated with water or a solvent.

The solvent used in the above-mentioned contact treatment is not particularly limited as long as it is a solvent that can dissolve the decomposition products generated by the liquid crystal alignment film by ultraviolet irradiation. Specific examples include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propanol acetate, butyl celecoxib, ethyl lactate, methyl lactate, diacetone alcohol, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate or cyclohexyl acetate. Among them, from the perspective of versatility or safety of the solvent, water, 2-propanol, 1-methoxy-2-propanol or ethyl lactate are preferred. More preferred are water, 1-methoxy-2-propanol or ethyl lactate. The solvent may be one or a combination of two or more.

The above-mentioned contact treatment, i.e., the treatment of the liquid crystal alignment film irradiated with polarized ultraviolet rays with water or a solvent, can be exemplified by immersion treatment or spray treatment (also referred to as spray treatment). The treatment time of such treatments is preferably 10 seconds to 1 hour from the viewpoint of efficiently dissolving the decomposition products generated by the liquid crystal alignment film by ultraviolet rays. Among them, it is particularly preferred to perform the immersion treatment for 1 to 30 minutes. Furthermore, the solvent used in the above-mentioned contact treatment may be at room temperature or may be heated, preferably at 10 to 80°C, and more preferably at 20 to 50°C. In addition, from the viewpoint of the solubility of the decomposition products, ultrasonic treatment may be performed as needed.

After the aforementioned contact treatment, it is preferred to perform cleaning (also called wetting) or firing of the liquid crystal alignment film with a low boiling point solvent such as water, methanol, ethanol, 2-propanol, acetone or methyl ethyl ketone. At this time, either wetting or firing can be performed, or both can be performed. The firing temperature is preferably 150~300℃. Among them, 180~250℃ is particularly preferred. 200~230℃ is more preferred. In addition, the firing time is preferably 10 seconds to 30 minutes. Among them, 1~10 minutes is particularly preferred.

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

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

Specifically, transparent glass substrates are prepared, a common electrode is set on one substrate, and a segment electrode is set on the other substrate. These electrodes can be, for example, ITO electrodes, which are patterned so that the desired image can be displayed. Then, an insulating film is set on each substrate to cover the common electrode and the segment electrode. The insulating film can be, for example, a _SiO2 - _TiO2 film formed by a sol-gel method.

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

By using the manufacturing method of the present invention, the residual image caused by long-term AC driving in the liquid crystal display element of the IPS drive method or the FFS drive method can be suppressed. In addition, in step (2), after firing at a temperature range of 40 to 150°C, by implementing step (3), a liquid crystal alignment film can be obtained with fewer steps than before. The liquid crystal alignment agent of the present invention can be particularly preferably used in a method for manufacturing a liquid crystal alignment film, which includes the step of implementing step (3) after firing at a temperature range of 40 to 150°C in step (2). [Example]

(Solvent) NMP: N-methyl-2-pyrrolidone BCS: Butyl cylosol (Diamine) DA-1~DA-9: Compounds represented by the following formula (DA-1)~(DA-9) (Tetracarboxylic dianhydride) CA-1~CA-5: Compounds represented by the following formula (CA-1)~(CA-5) (Additive) C-1: 2,2'-bis(4-hydroxy-3,5-dihydroxymethylphenyl)propane (compound represented by the following formula (C-1)) S-1: Compound represented by the following formula (S-1) F-1: Compound represented by the following formula (F-1)

(Fmoc represents 9-fluorenylmethoxycarbonyl).

<Viscosity measurement> The measurement was performed using an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.) with a sample volume of 1.1 mL, a conical rotor TE-1 (1°34’, R24), and a temperature of 25°C.

<Determination of imidization rate> Put 20 mg of polyimide powder in an NMR sample tube (NMR sample tube standard, φ5 (manufactured by Kusano Scientific Co., Ltd.)), add dimethyl sulfoxide deuteride (DMSO-d6, 0.05% TMS (tetramethylsilane) mixture) (0.53 mL), and apply ultrasound to completely dissolve it. The solution is measured by 500 MHz proton NMR using an NMR measuring instrument (JNW-ECA500) (manufactured by JEOL Datum Co., Ltd.). The imidization rate is determined by using the peak integral value of the proton derived from the unchanged structure before and after imidization as the reference proton and the peak integral value of the proton derived from the NH group of the amide appearing around 9.5ppm~10.0ppm, and is obtained by the following formula. Imidization rate (%) = (1-α･x/y) × 100 In the above formula, x is the peak integral value of protons derived from the NH group of acylamidin, y is the peak integral value of the reference proton, and α is the ratio of the number of reference protons to one NH group proton of acylamidin in the case of polyacylamidin (acymidization rate is 0%).

[Synthesis Example of Polymer] <Synthesis Example 1> In a 200 mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, weigh 4.95 g (20.3 mmol) of DA-1, 5.30 g (18.0 mmol) of DA-2, and 1.60 g (6.75 mmol) of DA-3, add NMP to a concentration of 12% by mass, and stir to dissolve while introducing nitrogen. While stirring the diamine solution, add 9.28 g (41.4 mmol) of CA-1, add NMP to a concentration of 12% by mass, and stir at 40°C for 24 hours to obtain a polyamide solution. 35 g (8.9 mmol) of the obtained polyamide solution was taken into a 100 mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, and 11.7 g of NMP was added and stirred for 30 minutes. 2.74 g of acetic anhydride (3 equivalents to the molar ratio of polyamide) and 0.71 g of pyridine (equivalent to the molar ratio of polyamide) were added to the obtained polyamide solution, and heated at 50°C for 3 hours to perform chemical imidization. The obtained reaction solution was put into 150 mL of methanol under stirring, and the precipitate was filtered. The same operation was performed twice to wash the resin powder, and then dried at 60°C for 12 hours to obtain a polyimide resin powder. The imidization rate of the polyimide resin powder was 75%. 3.60 g of the obtained polyimide resin powder was taken into a 100 mL Erlenmeyer flask, NMP was added to make the solid content concentration 12%, and the mixture was stirred at 70°C for 24 hours to dissolve the mixture, thereby obtaining a polyimide solution (PI-1).

<Synthesis Examples 2 to 10> Except that the types and amounts of the monomers used were changed as described in Table 1 below, polyimide solutions (PI-2) to (PI-10) were obtained in the same manner as in Synthesis Example 1. In addition, the values in parentheses in Table 1, for tetracarboxylic acid components, represent the blending ratio (molar parts) of each compound relative to 100 mol parts of the total amount of tetracarboxylic acid derivatives used in the synthesis, and for diamine components, represent the blending ratio (molar parts) of each compound relative to 100 mol parts of the total amount of diamines used in the synthesis. For organic solvents, they represent the blending ratio (mass parts) of each organic solvent relative to 100 mass parts of the total amount of organic solvents used to prepare the polyimide solution. <Synthesis Example 11> In a 200 mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, 3.37 g (8.0 mmol) of DA-7, 2.39 g (8.0 mmol) of DA-8, and 4.78 g (24.0 mmol) of DA-9 were weighed, and NMP was added to a concentration of 12% by mass. Nitrogen was introduced while stirring to dissolve. While stirring the diamine solution, 11.3 g (38.5 mmol) of CA-5 was added, and NMP was added to a concentration of 12% by mass. The mixture was stirred at 70°C for 24 hours to obtain a polyamide solution (PAA-1).

[Preparation of liquid crystal alignment agent] <Comparative Example 1> In a sample tube with a stirrer, add the polyimide solution (PI-1) obtained in Synthesis Example 1, NMP, and BCS, add S-1, C-1, and F-1 so that they are 1 mass part, 10 mass parts, and 15 mass parts, respectively, relative to 100 mass parts of the polymer solid component, and stir for 30 minutes. After stirring, the solid component concentration of the polyimide solution (PI-1) is 6 mass%, and the solvent composition is a liquid crystal alignment agent (R1) with a mass ratio of NMP:BCS=80:20.

<Comparative Examples 2 to 5, Examples 1 to 12> Except that the polymer components used are changed to those described in Table 2 below, the liquid crystal alignment agents (R2) to (R5), (1) to (12) are obtained in the same manner as in Comparative Example 1. In Table 2, the values in parentheses, for polymers and additives, respectively, represent the blending ratio (mass parts) of each polymer component or additive relative to 100 mass parts of the total polymer components used to prepare the liquid crystal alignment agent. For organic solvents, they represent the blending ratio (mass parts) of each organic solvent relative to 100 mass parts of the total organic solvent in the liquid crystal alignment agent.

Using the liquid crystal alignment agent obtained as described above, a FFS-driven liquid crystal cell was produced by the following procedure to evaluate its characteristics.

[Composition of FFS-driven liquid crystal cell] The liquid crystal cell for the edge field switching (Fringe Field Switching: FFS) mode is a set of a first glass substrate with a FOP (Finger on Plate) electrode layer composed of a common electrode-insulating layer-comb-shaped pixel electrode formed on the surface, and a second glass substrate with a columnar spacer with a height of 3.5μm on the surface and an ITO film for anti-static formed on the back. The above-mentioned pixel electrode has a comb shape in which a plurality of electrode elements with a width of 3μm bent at an inner angle of 160° in the center are arranged in parallel at intervals of 6μm. One pixel has a first region and a second region bounded by a line connecting the bent portions of the plurality of electrode elements. Furthermore, the liquid crystal alignment film formed on the first glass substrate is aligned in a manner such that the direction of the inner angle of the curved portion of the pixel is equally divided and is perpendicular to the alignment direction of the liquid crystal, and the liquid crystal alignment film formed on the second glass substrate is aligned in a manner such that the alignment direction of the liquid crystal on the first substrate is consistent with the alignment direction of the liquid crystal on the second substrate when manufacturing the liquid crystal cell.

[Production of Liquid Crystal Cells] Liquid crystal alignment agents filtered through a filter with an aperture of 1.0 μm were applied by spin coating on the surfaces of each of the above-mentioned glass substrates and dried on a heating plate at 80°C for 2 minutes. Afterwards, the coated surface was irradiated with 150-350 mJ/cm ² of ultraviolet light with a wavelength of 254 nm and an extinction ratio of 26:1 through a polarizing plate, and then baked in a hot air circulation oven at 230°C for 30 minutes to obtain two substrates with a liquid crystal alignment film with a film thickness of 100 nm. Next, a sealant was printed on one side of the substrate with a liquid crystal alignment film in the above set, and the other substrate was laminated with the liquid crystal alignment film surface facing each other, and the sealant (XN-1500T manufactured by Mitsui Chemicals Co., Ltd.) was cured to produce an empty cell. Liquid crystal (MLC-3019 manufactured by Merck) was vacuum injected into the empty cell at room temperature by the reduced pressure injection method, and the injection port was sealed to obtain an FFS-driven liquid crystal cell. After that, the obtained liquid crystal cell was heated at 120°C for 1 hour (hereinafter referred to as ISO treatment), left overnight, and then used in various evaluations.

<Evaluation of liquid crystal alignment> Using liquid crystal cells before ISO treatment, those with initial flow alignment are defined as "bad", and those without this are defined as "good" for evaluation. <Comparative in-plane uniformity evaluation> The twist angle of the liquid crystal display element is evaluated using OPTIPRO-micro manufactured by SHINTECH. The produced liquid crystal cell is set on the measuring table, and 20 points are measured in the first pixel plane without applying voltage, and the standard deviation is calculated. The evaluation is performed by defining the twist angle standard deviation of 0.5 or more as "bad", and the standard deviation of less than 0.5 as "good".

<Evaluation of voltage retention> The liquid crystal cell produced above was subjected to a voltage of 1V for 60 microseconds at 60°C using a device manufactured by Dongyang Technica, and the voltage retention was measured 1,000 milliseconds later. At this time, the voltage retention was defined as "good" when it was maintained at 90% or more, and "bad" when it was less than 90%.

<Evaluation Results> The evaluation results of the liquid crystal display elements obtained using the liquid crystal alignment agents (1) to (12) and (R1) to (R5) obtained in the above-mentioned Examples 1 to 12 and Comparative Examples 1 to 5 are shown in Table 3.

Claims (12)

A liquid crystal alignment agent for photo-alignment method, characterized by containing at least one polymer (A) selected from the group consisting of polyimide precursors and imidized polymers thereof, wherein the polymer (A) has at least one repeating unit (a1) selected from the group consisting of repeating units represented by the following formula (1-a) and repeating units represented by the following formula (1-i), and at least one repeating unit (a2) selected from the group consisting of repeating units represented by the following formula (2-a) and repeating units represented by the following formula (2-i), and contains 1 to 20 mol% of the above-mentioned repeating unit (a1) in all the repeating units; (wherein, _X1 represents a tetravalent organic group represented by the following formula (B), _X2 represents a tetravalent organic group represented by the following formula (C); R and Z each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; multiple R and Z may be the same or different; _Y1 and _Y2 each independently represent a divalent organic group represented by the following formula (O)); (wherein, R _b1 to R _b4 each independently represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms; L ₁ represents a single bond, -CH ₂ -, -(CH ₂ ) _n - (n is an integer of 2 to 18), or a group in which at least a part of -CH ₂ - of the aforementioned -(CH ₂ ) _n - is substituted by any one of -O-, -C(=O)-, or -OC(=O)-; R _c1 to R _c4 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, and at least one of R _c1 to R _c4 represents a group other than a hydrogen atom as defined above); (Ar represents a benzene ring, a biphenyl structure, or a naphthyl ring. Two Ars may be the same or different. Any hydrogen atom on the ring may be substituted by a monovalent organic group. However, at least one of the two Ars represents a naphthyl ring. _Q2 represents _-CH2- , -( _CH2 ) _n- (n is an integer of 2 to 18), or a group in which at least a part of _-CH2- in the aforementioned -( _CH2 ) _n- is substituted by any one of -O-, -C(=O)- or -OC(=O)-. p is 1. * represents a bonding site). The liquid crystal alignment agent for photo-alignment method of claim 1, wherein the tetravalent organic group represented by the aforementioned formula (B) is a tetravalent organic group represented by the following formulas (b-1) to (b-2); (*Indicates the bonding site). The liquid crystal alignment agent for photo-alignment method of claim 1, wherein the divalent organic group represented by the aforementioned formula (O) is a divalent organic group represented by the following formulas (o-1) to (o-6); . The liquid crystal alignment agent for photo-alignment method of claim 1, wherein the polymer (A) has at least one repeating unit (a3) selected from the group consisting of a repeating unit represented by the following formula (3-a) and a repeating unit represented by the following formula (3-i); (wherein, X ₃ represents a tetravalent organic group, Y ₃ represents a divalent organic group represented by the following formula (3d); R and Z have the same meanings as in the aforementioned formula (1-a)); (Ar ₃ represents a benzene ring or a biphenyl structure, the two Ars may be the same or different, and any hydrogen atom on the ring may be substituted by a monovalent organic group; Q ₃ represents -(CH ₂ ) _n - (n is an integer of 2 to 18), or a group in which at least a part of the -CH ₂ - of the aforementioned -(CH ₂ ) _n - is substituted by any one of -O-, -C(=O)- or -OC(=O)-; * represents a bonding site). The liquid crystal alignment agent for photo-alignment method of claim 1, wherein the polymer (A) has at least one repeating unit (a4) selected from the group consisting of a repeating unit represented by the following formula (4-a) and a repeating unit represented by the following formula (4-i); (wherein, R and Z are synonymous with the aforementioned formula (1-a); _X4 represents a tetravalent organic group, _{and Y4} represents a divalent organic group having 6 to 30 carbon atoms and having a group "-N(D)- (D represents tert-butyloxycarbonyl or 9-fluorenylmethoxycarbonyl)" in the molecule). The liquid crystal alignment agent for photo-alignment method of claim 5, wherein the aforementioned _Y4 is a structure represented by the following formula (Y4-1) to (Y4-4); (Boc represents tert-butyloxycarbonyl; * represents the bonding site). A liquid crystal alignment film is obtained by using a liquid crystal alignment agent by the photo-alignment method of any one of claims 1 to 6. A liquid crystal display element having a liquid crystal alignment film as claimed in claim 7. A method for manufacturing a liquid crystal alignment film comprises the following steps (1) to (3); Step (1): coating a liquid crystal alignment agent for photo-alignment method as described in any one of claims 1 to 6 on a substrate, Step (2): heating the coated liquid crystal alignment agent for photo-alignment method to obtain a film, Step (3): irradiating the film obtained in step (2) with polarized ultraviolet light. The method for manufacturing a liquid crystal alignment film as claimed in claim 9 further comprises the following step (4); Step (4): sintering the film obtained in step (3) at a temperature above 100°C and higher than that in step (2). In the method for manufacturing a liquid crystal alignment film of claim 9, the aforementioned step (2) is a step of obtaining the film by heating at a temperature range of 40-180°C. A liquid crystal display element comprises a liquid crystal alignment film obtained by the method for manufacturing a liquid crystal alignment film as recited in any one of claims 9 to 11.