TWI864241B - Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element - Google Patents

Abstract

Provided is a liquid crystal alignment agent suitable for the photoalignment method, which can obtain a liquid crystal display element with high liquid crystal alignment, suppressed brightness unevenness within the surface during black display, and improved contrast.

(式中，X表示下述式(g)所表示的4價的有機基，Y表示來自於滿足條件(1)及條件(2)的芳香族二胺的2價的有機基，Y₁表示來自於滿足以下的條件(1)及條件(3)的芳香族二胺(d1)的2價的有機基，R、Z係分別獨立表示氫原子或碳數1~6的烷基，式(0)及式(1)中，X可互為相同或不同)

A liquid crystal alignment agent comprises a polymer (A), wherein the polymer (A) is an imidized polymer of a polyimide precursor comprising a repeating unit of the following formula (0) and a repeating unit of the following formula (1), wherein the imidization rate of the imidized polymer is 80-95%.

(In the formula, X represents a tetravalent organic group represented by the following formula (g), Y represents a divalent organic group derived from an aromatic diamine satisfying the following conditions (1) and (2), _Y1 represents a divalent organic group derived from an aromatic diamine (d1) satisfying the following conditions (1) and (3), R and Z each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and in formula (0) and formula (1), X may be the same or different)

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 and a liquid crystal display element.

In the past, liquid crystal display devices have been widely used as display parts of personal computers, smart phones, mobile phones, TV receivers, etc. Liquid crystal display devices have, for example: a liquid crystal layer sandwiched between a device substrate and a color filter substrate, pixel electrodes and common electrodes 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 method and VA method, and transverse electric field methods such as IPS method and FFS (Fringe Field Switching) method are known.

At present, the most popular liquid crystal alignment film in industry is made by wiping the surface of a film composed of polyamide and/or polyimide obtained by imidizing the polyamide formed on an electrode substrate in one direction with a cloth made of cotton, nylon, polyester, etc. (i.e., rubbing treatment). Rubbing treatment is a simple and highly productive method that is useful in industry. However, with the high performance, high precision, and large size of liquid crystal display elements, scratches, dust, mechanical force, or static electricity on the surface of the alignment film generated by rubbing treatment have caused various problems, such as unevenness within the alignment treatment surface, which have become very clear. As an alignment treatment method that replaces the rubbing treatment, a photoalignment method is known that imparts alignment ability to liquid crystal by irradiating polarized radiation. The photoalignment method that has been proposed includes those utilizing photoisomerization reaction, those utilizing photocrosslinking reaction, and those utilizing photodecomposition reaction (see non-patent document 1, patent document 1).

The liquid crystal alignment film, which is a component of the liquid crystal display element, is used to arrange the liquid crystal uniformly. The liquid crystal alignment is one of the important characteristics. However, the liquid crystal alignment film obtained by the above-mentioned optical alignment method tends to have lower liquid crystal alignment than the liquid crystal alignment film obtained by the conventional friction treatment, and the application range of the liquid crystal display device with the liquid crystal alignment film is limited.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 9-297313

[Patent Document 2] International Publication No. 2015/050135

[Non-patent literature]

[Non-patent document 1] "Liquid crystal optical alignment film" Kidowaki, Ichimura Functional Materials, November 1997, Vol. 17, No. 11, pages 13-22

In addition, actual liquid crystal display elements will have slightly uneven twist angles within the surface of the liquid crystal display element due to manufacturing unevenness. As a result, the brightness of the liquid crystal display element when displaying black will be uneven within the surface due to such unevenness within the surface.

This invention was completed in view of the above circumstances, and one of the purposes is to provide a liquid crystal alignment agent suitable for the photoalignment method, which can obtain a liquid crystal display element with high liquid crystal alignment, suppressed brightness unevenness within the surface during black display, and improved contrast.

As a result of in-depth research, the inventors found that the above-mentioned problems can be solved by using a liquid crystal alignment agent containing specific components, thus completing the present invention. Specifically, the invention is based on the following.

In this specification, fluorine atom, chlorine atom, bromine atom, iodine atom, etc. can be cited as halogen atoms, and * represents a bond.

A liquid crystal alignment agent, characterized in that it contains a polymer (A), wherein the polymer (A) is an imidized polymer of a polyimide precursor containing a repeating unit (a0) represented by the following formula (0) and a repeating unit (a1) represented by the following formula (1), and the imidization rate of the imidized polymer is 80-95%.

(式(0)及式(1)中，X表示下述式(g)所表示的4價的有機基，Y表示來自於滿足以下的條件(1)及條件(2)的芳香族二胺(d0)的2價的有機基，Y₁表示來自於滿足以下的條件(1)及條件(3)的芳香族二胺(d1)的2價的有機基，R、Z係分別獨立表示氫原子或碳數1~6的烷基，X可互為相同或不同)。

(In formula (0) and formula (1), X represents a tetravalent organic group represented by the following formula (g), Y represents a divalent organic group derived from an aromatic diamine (d0) satisfying the following conditions (1) and (2), _Y1 represents a divalent organic group derived from an aromatic diamine (d1) satisfying the following conditions (1) and (3), R and Z each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and X may be the same or different).

(式(g)中，R₁至R₄係分別獨立表示氫原子、鹵素原子、碳數1~6的烷基、碳數2~6的烯基、碳數2~6的炔基、含有氟原子的碳數1~6的1價的有機基或苯基，R₁至R₄中的至少一個係表示上述定義中的氫原子以外之基，又，上述烷基、烯基、炔基及含有氟原子的碳數1~6的1價的有機基中所包含的-CH₂-的一部分可被-O-所取代)。

(In formula (g), _R1 to _R4 each independently represents 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; at least one of _R1 to _R4 represents a group other than a hydrogen atom as defined above; and a part of _-CH2- contained in the above-mentioned alkyl group, alkenyl group, alkynyl group, and monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom may be substituted with -O-).

Condition (1): No side chain groups with more than 6 carbon atoms.

Condition (2): The two carbon-nitrogen bond axes from the amine group are not parallel to each other.

Condition (3): The two carbon-nitrogen bond axes from the amine group are parallel to each other and have a partial structure represented by the following formula (O).

[Chemistry 3] *-Ar-Q ₂ -Ar-* (O) (in formula (O), Ar independently represents a benzene ring, a biphenyl structure or a naphthyl ring, any hydrogen atom on the ring may be substituted by a halogen atom or a monovalent organic group, Q ₂ represents -(CH ₂ ) _n - (n is an integer from 2 to 18), or represents a group in which any -CH ₂ - in the above -(CH ₂ ) _n - is substituted by any one of -O-, -C(=O)- or -OC(=O)-, and * represents a bond).

The present invention can provide a liquid crystal display element with high liquid crystal alignment, suppressed brightness unevenness within the plane during black display, and excellent contrast, and a liquid crystal alignment agent suitable for the photoalignment method that can obtain the liquid crystal display element.

[Best form of implementing the invention] <Polymer (A)>

The liquid crystal alignment agent of the present invention contains a polymer (A), which is an imidized polymer of a polyimide precursor containing a repeating unit (a0) represented by the above formula (0) and a repeating unit (a1) represented by the above formula (1), and the imidization rate of the above imidized polymer is 80-95%.

(式(0)及式(1)中，X表示下述式(g)所表示的4價的有機基，Y表示來自於滿足以下的條件(1)及條件(2)的芳香族二胺(d0)的2價的有機基，Y₁表示來自於滿足以下的條件(1)及條件(3)的芳香族二胺(d1)的2價的有機基，R、Z係分別獨立表示氫原子或碳數1~6的烷基，X可互為相同或不同)。

(In formula (0) and formula (1), X represents a tetravalent organic group represented by the following formula (g), Y represents a divalent organic group derived from an aromatic diamine (d0) satisfying the following conditions (1) and (2), _Y1 represents a divalent organic group derived from an aromatic diamine (d1) satisfying the following conditions (1) and (3), R and Z each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and X may be the same or different).

(式(g)中，R₁至R₄係分別獨立表示氫原子、鹵素原子、碳數1~6的烷基、碳數2~6的烯基、碳數2~6的炔基、含有氟原子的碳數1~6的1價的有機基或苯基，R₁至R₄中的至少一個係表示上述定義中的氫原子以外之基，又，上述烷基、 烯基、炔基及含有氟原子的碳數1~6的1價的有機基中所包含的-CH₂-的一部分可被-O-所取代，*表示鍵結鍵)。

(In formula (g), _R1 to _R4 each independently represents 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; at least one of _R1 to _R4 represents a group other than a hydrogen atom as defined above; a part of _-CH2- contained in the above-mentioned alkyl group, alkenyl group, alkynyl group, and monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom may be substituted with -O-; and * represents a bond).

Condition (1): No side chain groups with more than 6 carbon atoms.

Condition (2): The two carbon-nitrogen bond axes from the amine group are not parallel to each other.

Condition (3): The two carbon-nitrogen bond axes from the amine group are parallel to each other and have a partial structure represented by the following formula (O).

[Chemistry 6] *-Ar-Q ₂ -Ar-* (o) (in formula (O), Ar independently represents a benzene ring, a biphenyl structure or a naphthalene ring, any hydrogen atom on the ring may be substituted by a halogen atom or a monovalent organic group, Q ₂ represents -(CH ₂ ) _n - (n is an integer from 2 to 18), or represents a group in which any -CH ₂ - in the above -(CH ₂ ) _n - is substituted by any one of -O-, -C(=O)- or -OC(=O)-, and * represents a bond).

By setting such a structure, a liquid crystal display element with high liquid crystal orientation and excellent contrast can be obtained.

Here, the so-called "two carbon-nitrogen bond axes from the amine group are parallel to each other" in the above condition (3) means that when the aromatic diamine is represented by a ball-and-stick molecular structure model (for example, the HGS molecular structure model produced by Maruzen Publishing Co., Ltd.), the two carbon-nitrogen bond axes from the amine group can be arranged in a parallel manner. In addition, the so-called "two carbon-nitrogen bond axes from the amine group are not parallel to each other" in the above condition (2) means that when the aromatic diamine is represented by a ball-and-stick molecular structure model, the two carbon-nitrogen bond axes from the amine group cannot be arranged in a parallel manner.

As a method other than the above, for example, when molecular simulation (Chem3D Ultra Version 16.0.1.4) is used to optimize the molecular structure and minimize the energy by using the default MM2 force field setting and converging the minimum (root mean square) RMS gradient to 0.010, the situation where the two carbon-nitrogen bond axes from the amine group are arranged in a parallel manner is defined as "the two carbon-nitrogen bond axes from the amine group are parallel to each other" in the above condition (3); the situation where the two carbon-nitrogen bond axes from the amine group cannot be arranged in a parallel manner is defined as "the two carbon-nitrogen bond axes from the amine group are not parallel to each other" in the above condition (2).

Specific examples of the alkyl group having 1 to 6 carbon atoms in R ₁ to R ₄ of the above formula (g) include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, etc. Specific examples of the alkenyl group having 2 to 6 carbon atoms in R ₁ to R ₄ include vinyl, propenyl, butenyl, etc., which may be linear or branched. Specific examples of the alkynyl group having 2 to 6 carbon atoms in R ₁ to R ₄ include ethynyl, 1-propynyl, 2-propynyl, etc. Specific examples of the halogen atom in R ₁ to R ₄ include fluorine atom, chlorine atom, bromine atom, iodine atom, etc. Specific examples of the monovalent organic group having 1 to 6 carbon atoms and containing fluorine atom include fluoromethyl, trifluoromethyl, etc. Furthermore, a part of -CH ₂ - contained in the above-mentioned alkyl group, alkenyl group, alkynyl group and monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom may be substituted with -O-.

In terms of efficiently obtaining the effect of the present invention, at least one of _R1 to _R4 represents a group other than the hydrogen atom in the above definition. By adopting the above configuration, the photoreactivity of the polyimide film becomes higher, and the in-plane anisotropy of the obtained liquid crystal alignment film becomes higher, so that the decrease in contrast caused by the uneven twist angle in the plane of the liquid crystal display element generated during the production can be suppressed.

The tetravalent organic group represented by the above formula (g) is preferably a tetravalent organic group represented by any one of the following formulas (g-1) to (g-5) from the viewpoint of high photoreactivity, and more preferably a tetravalent organic group represented by the following formula (g-1). * represents a bond.

Any hydrogen atom on the ring of Ar in the above formula (O) may be substituted with a monovalent organic group such as 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, or a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom. Specific examples of such monovalent organic groups include the structures exemplified in the above R ₁ to R ₄ .

(Aromatic diamine (d0))

The aromatic diamine (d0) is preferably an aromatic diamine having 4 to 40 carbon atoms from the viewpoint of efficiently obtaining the effect of the present invention. Specific examples include: an aromatic diamine having one aromatic ring in the molecule; an aromatic diamine having two aromatic rings in the molecule, wherein the two aromatic rings are _-CH2- , -C( _CH3 ) _2- , -O-, -C(=O)-, -OC(=O)-, -NR-C(=O)-, -NR- (R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a phenyl group, or a tert-butyloxycarbonyl group), an alkylene group having 2 to 20 carbon atoms, or a portion of the _-CH2- of the alkylene group is replaced by -O-, -Si( _CH3 ) ₂ -, -C(=O)-, -OC(=O)-, -NR-C(=O)-, -NR-, and the total number of carbon atoms, oxygen atoms, silicon atoms and nitrogen atoms in the main chain direction of the linking group is an odd number; an aromatic diamine having one aromatic ring and an indane structure in the molecule; an aromatic diamine having three or more aromatic rings in the molecule; an aromatic diamine having a heterocyclic structure. Examples of the aromatic ring include a benzene ring, a naphthalene ring, and an anthracene ring, preferably a benzene ring and a naphthalene ring, and more preferably a benzene ring. Furthermore, a part of the hydrogen atoms on the above aromatic ring may be substituted with a hydroxyl group, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a carboxyl group, a halogen atom, a monovalent organic group having 1 to 5 carbon atoms containing a fluorine atom, a group in which a part of the hydrogen atoms on the above alkyl group having 1 to 5 carbon atoms is substituted with a hydroxyl group, or -NH(Boc) (Boc represents tert-butyloxycarbonyl).

More specifically, the aromatic diamines, 1,3-bis(4-aminophenoxy)benzene, and bis[4-(4-aminophenoxy)phenyl]ether represented by the following formulas (d0-1) to (d0-15) can be cited.

(上述式中，R表示羥基、碳數1~5的烷基、碳數1~5的烷氧基、羧基、鹵素原子、含有氟原子的碳數1~5的1價的有機基或上述碳數1~5的烷基上的氫原子的一部分被羥基所取代之基，R’表示氫原子或碳數1~5的烷基。又，若R及R’為複數時，各R及R’可互為相同或不同。L表示-CH₂-、-C(CH₃)₂-、-O-、-C(=O)-、-O-C(=O)-O-、-NR-C(=O)-NR-、-NR-(R表示氫原子、碳數1~5的烷基、苯基或tert-丁氧基羰基)、碳數2~20的伸烷基或該伸烷基的-CH₂-的一部分被-O-、-Si(CH₃)₂-、-C(=O)-、-O-C(=O)-、-NR-C(=O)-或-NR-所取代的2價的有機基，且主鏈方向的碳原子、氧原子、矽原子及氮原子之合計數為奇數個。L’表示在上述L所定義的2價的有機基之中的-NR-以外的2價的有機基。Q、Q’、Q”表示雜環。但在Q’與苯環之間所形成的分別的鍵結相互不為平行，式(d0-10)、式 (d0-11)中，在Q”與氮原子之間所形成的分別的鍵結相互不為平行。式(d0-9)中，若n為0時，在Q”與氮原子之間所形成的分別的鍵結相互為平行，若n為1時，在Q”與氮原子之間所形成的分別的鍵結相互不為平行。又，式(d0-13)中，在鄰接於Q的氮原子及碳原子之間所形成的分別的鍵結相互不為平行。於上述式中，若Q為複數時，各Q可互為相同或不同。又，上述同一式中的n可互為相同或不同)。

(In the above formula, R represents a hydroxyl group, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a carboxyl group, a halogen atom, a monovalent organic group having 1 to 5 carbon atoms containing a fluorine atom, or a group in which a part of the hydrogen atoms on the above alkyl group having 1 to 5 carbon atoms is substituted with a hydroxyl group, and R' represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. When R and R' are plural, each R and R' may be the same or different. L represents _-CH2- , -C( _CH3 ) _2- , -O-, -C(=O)-, -OC(=O)-O-, -NR-C(=O)-NR-, -NR- (R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a phenyl group, or a tert-butyloxycarbonyl group), an alkylene group having 2 to 20 carbon atoms, or a part of _-CH2- of the alkylene group is substituted with -O-, -Si( _CH3 ) ₂ -, -C(=O)-, -OC(=O)-, -NR-C(=O)- or -NR-, and the total number of carbon atoms, oxygen atoms, silicon atoms and nitrogen atoms in the main chain direction is an odd number. L' represents a divalent organic group other than -NR- among the divalent organic groups defined by L above. Q, Q', Q" represent heterocyclic rings. However, the respective bonds formed between Q' and the benzene ring are not parallel to each other. In formula (d0-10) and formula (d0-11), between Q" and the nitrogen atom The respective bonds formed between Q" and the nitrogen atom are not parallel to each other. In formula (d0-9), if n is 0, the respective bonds formed between Q" and the nitrogen atom are parallel to each other, and if n is 1, the respective bonds formed between Q" and the nitrogen atom are not parallel to each other. Furthermore, in formula (d0-13), the respective bonds formed between the nitrogen atom and the carbon atom adjacent to Q are not parallel to each other. In the above formula, if Q is plural, each Q may be the same or different. Furthermore, n in the above same formula may be the same or different).

Specific examples of the heterocyclic ring in the above Q, Q', and Q" include pyrrole, imidazole, pyrazole, triazole, pyridine, pyrimidine, pyridazine, pyrazine, indole, benzimidazole, purine, quinoline, isoquinoline, naphthyridine, quinoxaline, phthalazine, triazine, carbazole, acridine, piperidine, piperazine, pyrrolidine, hexamethyleneimine, and oxazoline. In addition, any hydrogen atom on the above heterocyclic ring 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. The heterocyclic ring may be substituted by at least one of the following: Preferred specific examples are pyrrole, pyridine, pyrimidine, pyridazine, pyrazine, benzimidazole, carbazole, piperidine, piperazine, and oxazoline. The above-mentioned "the respective bonds formed between Q' and the benzene ring are not parallel to each other", for example, when pyridine is taken as an example, it means that the bonding positions of pyridine bonded to the benzene ring are 2,4-position, 2,6-position, and 3,5-position; the above-mentioned "the respective bonds formed between Q' and the nitrogen atom are not parallel to each other", for example, when pyridine is taken as an example, it means that the bonding positions of pyridine bonded to the nitrogen atom are 2,4-position, 2,6-position, or 3,5-position. The so-called "the respective bonds formed between Q" and the nitrogen atom are parallel to each other", if pyridine is used as an example, it means that the bonding position of pyridine bonded to the nitrogen atom is 2,5-position. Moreover, the so-called "the respective bonds formed between the nitrogen atom and the carbon atom adjacent to Q are not parallel to each other", if pyridine is used as an example, it means that the bonding position of pyridine bonded to the adjacent nitrogen atom or carbon atom is 2,4-position, 2,6-position or 3,5-position.

Specific examples of more preferred aromatic diamines (d0) include 1,3-diaminobenzene, 2,4-diaminotoluene, 2,6-diaminotoluene, 2,4-diaminophenol, 3,5-diaminophenol, 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzoic acid, 3,5-diaminobenzoic acid, 3,3'-diaminodiphenyl Methane, 4,4'-diaminodiphenylmethane, bis(4-aminophenoxy)methane, 1,5-bis(4-aminophenoxy)pentane, 1,3-bis(4-aminophenethyl)urea, 4,4'-diaminodiphenyl ether, 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 4,4'-diaminobenzophenone, 1-(4-aminophenyl)-1,3,3- trimethyl-1H-indan-5-amine, 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl-1H-indan-6-amine, diamines represented by the following formulas (Dp-1) to (Dp-2), diamines represented by the following formulas (5-1) to (5-4), 1,3-bis(4-aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]ether, 2,6-diaminopyridine , 3,4-diaminopyridine, 2,4-diaminopyrimidine, 3,6-diaminocarbazole, N-methyl-3,6-diaminocarbazole, 3,6-diaminoacridine, N-ethyl-3,6-diaminocarbazole, aromatic diamines containing heterocyclic rings in the molecules of the following formulas (z-1) to (z-17), (Ox-1) to (Ox-2), or diamines represented by the following formula (Si-1). In the following formulas (5-1) to (5-4), "Boc" represents tert-butyloxycarbonyl.

(式中，Py分別獨立表示2,5-伸啶基(2,5-pyridylene)或2,5- 伸嘧啶基(2,5-pyrimidinylene))。

(wherein, Py independently represents 2,5-pyridylene or 2,5-pyrimidinylene).

From the viewpoint of improving the liquid crystal alignment, Y in the above formula (1) is preferably a divalent organic group derived from 1,3-diaminobenzene, 2,4-diaminotoluene, 2,6-diaminotoluene, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, bis(4-aminophenoxy)methane, 1,5-bis(4-aminophenoxy)pentane, 1,3-bis(4-aminophenethyl)urea, 4,4'-diaminodiphenyl ether, 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 4,4'-diaminobenzophenone or 1,3-bis(4-aminophenoxy)benzene.

(Aromatic diamine (d1))

The aromatic diamine (d1) is preferably an aromatic diamine having 4 to 40 carbon atoms from the viewpoint of efficiently obtaining the effect of the present invention. In addition, the total number of carbon atoms and oxygen atoms in the main chain direction of _Q2 in the above (d1) is preferably an even number. The preferred total number of carbon atoms and oxygen atoms in the main chain direction is 2n (n represents an integer of 1 to 9, preferably 1 to 8, and more preferably 1 to 6). As a specific example of the aromatic diamine, there can be cited an aromatic diamine in which two amine groups are bonded to the partial structure represented by the above formula (O).

From the viewpoint of improving the liquid crystal alignment, Y ₁ in the above formula (1) is preferably a divalent organic group derived from a diamine represented by the following formulas (d1-1) to (d1-14).

The above-mentioned polymer (A) may also be an imidized polymer of a polyimide precursor further having a repeating unit (a2) represented by the following formula (2) which is different from the above-mentioned repeating unit (a0) or (a1).

In the above formula (2), _X2 represents a tetravalent organic group, _Y2 represents a divalent organic group derived from an aromatic diamine having no side chain group with 6 or more carbon atoms, and R and Z are synonymous with R and Z in the above formula (0). However, when _X2 is synonymous with the tetravalent organic group represented by the above formula (g), _Y2 represents a structure other than the divalent organic group defined by Y in the above formula (0) or the divalent organic group defined by _Y1 in the above formula (1). Specific examples of _X2 include, in addition to the tetravalent organic group represented by the above formula (g), a tetravalent organic group represented by any of the following formulas (X-1) to (X-25), a tetravalent organic group derived from an aromatic tetracarboxylic dianhydride, and the like.

Here, the so-called 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 a tetravalent organic group represented by any one of the following formulas (Xa-1) to (Xa-2) and a tetravalent organic group represented by the following formulas (Xr-1) to (Xr-7).

(上述式(Xa-1)~(Xa-2)中，x及y分別獨立為單鍵、醚、羰基、酯、碳數1~10的烷二基、1,4-伸苯基、磺醯基或醯胺 基，j及k為0或1的整數，*表示鍵結鍵)。

(In the above formulas (Xa-1) to (Xa-2), x and y are independently a single bond, an ether, a carbonyl group, an ester, an alkanediyl group having 1 to 10 carbon atoms, a 1,4-phenylene group, a sulfonyl group or an amide group, j and k are integers of 0 or 1, and * represents a bond).

The tetravalent organic group represented by the above formula (Xa-1) or (Xa-2) may also be a structure represented by any of the following formulas (Xa-3) to (Xa-19).

From the viewpoint of efficiently obtaining the effect of the present invention, _X2 is preferably a tetravalent organic group represented by the above formula (g) or a tetravalent organic group represented by any one of the above formulas (X-1) to (X-25), and is more preferably a tetravalent organic group represented by the above formula (g).

Specific examples of the divalent organic group represented by _Y2 include the divalent organic group defined as Y in the above formula (0) or Y in the above formula (1): In addition to the divalent organic groups defined in ₁ , there can be cited: groups formed by removing two amino groups from diamines such as p-phenylenediamine, 4,4'-diamino-2,2'-dimethylbiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4,4'-diaminobiphenyl, 3,3'-difluoro-4,4'-diaminobiphenyl, 3,3'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, and 4,4'-diaminobenzanilide; divalent organic groups represented by the following formula (h-1); and groups represented by the following formula (h-2)~ A divalent organic group having a photo-alignment group such as (h-4); a divalent organic group represented by (h-5); a group obtained by removing two amino groups from a diamine such as 4-(2-(methylamino)ethyl)aniline, 4-(2-aminoethyl)aniline, 2,5-diaminobenzoic acid, 4,4'-diaminobiphenyl-3,3'-dicarboxylic acid, a diamine having a diphenylamine skeleton such as the following formula (Dp-5) to (Dp-6), a diamine having "-N(D)- (D represents a carbamate-based protective group, preferably a tert-butyloxycarbonyl group)" in the molecule such as the following formula (5-5) to (5-9), and a diamine represented by (z-18) to (z-23).

(上述式中，*表示鍵結鍵)。

(In the above formula, * represents a bond).

(上述式中，Boc表示tert-丁氧基羰基)。

(In the above formula, Boc represents tert-butoxycarbonyl).

(上述式中，Py分別獨立表示2,5-伸啶基或2,5-伸嘧啶基)。

(In the above formula, Py independently represents a 2,5-pirimidinyl group or a 2,5-pyrimidinyl group).

The above polymer (A) may also be an imidized polymer of a polyimide precursor further having a repeating unit (a3) represented by the following formula (3) which is different from the above repeating units (a0), (a1), and (a2).

In the formula, _X3 represents a tetravalent organic group, _Y3 represents a divalent organic group other than the divalent organic group defined by _Y2 in the above formula (2), and R and Z are synonymous with R and Z in the above formula (0). However, when _X3 is synonymous with the tetravalent organic group represented by the above formula (g), _Y3 represents a structure other than the divalent organic group defined by Y in the above formula (0) or the divalent organic group defined by _Y1 in the above formula (1). As specific examples of _X3 , the structures exemplified by _X2 in the above formula (2) can be cited, and from the viewpoint of being able to suitably obtain the effects of the present invention, the tetravalent organic group represented by the above formula (g) is preferred.

Specific examples of the divalent organic group represented by _Y3 include diamines having a photopolymerizable group at the terminal such as N-phenyl-3,6-diaminocarbazole, 2-(2,4-diaminophenoxy)ethyl methacrylate, 2,4-diamino-N,N-diallylaniline, cholestanyloxy-3,5-diaminobenzene, cholestanyloxy-3,5-diaminobenzene, cholestanyloxy-2,4-diaminobenzene, 3,5-diaminobenzoic acid cholestanyl ester, 3,5-diaminobenzoic acid cholestanyl ester, 3,5-diaminobenzoic acid lanosteryl ester, 3,6-bis(4-aminobenzyloxy)cholestane, and diamines having a steroid skeleton such as the following formula (V- 1) to (V-6), diamines represented by the following formulas (z-24) to (z-25), diamines represented by the following formulas (5-10) to (5-13), alicyclic diamines such as bis(4-aminocyclohexyl)methane and bis(4-amino-3-methylcyclohexyl)methane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diamino A group formed by removing two amino groups from a diamine such as an aliphatic diamine such as hexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, or a group represented by any one of formulas (Y-1) to (Y-167) described in International Publication No. 2018/117239. From the viewpoint of being suitable for obtaining the effect of the present invention, _Y3 is preferably a group formed by removing two amino groups from a diamine represented by formulas (5-10) to (5-13).

(In the above formulae (V-1) to (V-6), ^Xv1 to ^Xv4 and ^Xp1 to ^Xp2 each independently represent -( _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- or -O-( _{CH2 ) m} -O- (m represents an integer of 1 to 6); ^Rv1 to ^Rv4 and ^R1a to ^R1b 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).

(上述式中，Boc表示tert-丁氧基羰基)。

(In the above formula, Boc represents tert-butoxycarbonyl).

From the perspective of obtaining the effects of the present invention, the total amount of the repeating units (a0), repeating units (a1) and the imidized repeating units in the polymer (A) is preferably 5 mol% or more, and more preferably 10 mol% or more, relative to the total repeating units.

From the perspective of obtaining the effects of the present invention, the polymer (A) preferably contains 1 to 40 mol% of the repeating units (a1) and the imidized repeating units relative to the total repeating units, more preferably 1 to 35 mol%, and even more preferably 1 to 30 mol%.

From the perspective of obtaining the effects of the present invention, the polymer (A) preferably contains 1 to 95 mol% of the repeating units (a2) and the imidized repeating units relative to the total repeating units, more preferably 1 to 90 mol%, and even more preferably 5 to 90 mol%.

From the perspective of obtaining the effects of the present invention, the polymer (A) preferably contains 1 to 40 mol% of the repeating units (a3) and the imidized repeating units relative to the total repeating units, more preferably 1 to 30 mol%, and even more preferably 1 to 25 mol%.

The polymer (A) has an imidized repeating unit of less than 95 mol%.

If the polymer (A) contains repeating units other than repeating units (a0), repeating units (a1) and the repeating units subjected to imidization, the total amount of repeating units (a0), repeating units (a1) and the repeating units subjected to imidization is preferably 95 mol% or less, more preferably 90 mol% or less.

<Polymer (B)>

The liquid crystal alignment agent of the present invention may contain, in addition to the above-mentioned polymer (A), at least one polymer (B) selected from the group consisting of a polyimide precursor and a polyimide having an imidization rate of less than 80%. From the perspective of efficiently obtaining the effect of the present invention, as the polymer (B), a polymer having a repeating unit represented by the following formula (4) can be cited.

(上述式(4)中，X₄為4價的有機基，Y₄為2價的有機基。Z係分別獨立表示氫原子、可具有取代基的碳數1~10的烷基、可具有取代基的碳數2~10的烯基、可具有取代基的碳數2~10的炔基、tert-丁氧基羰基或9-茀基甲氧基羰基，R係分別獨立表示氫原子或碳數1~4的烷基)。

(In the above formula (4), _X4 is a tetravalent organic group, and _Y4 is a divalent organic group. Z is independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms which may have a substituent, an alkenyl group having 2 to 10 carbon atoms which may have a substituent, an alkynyl group having 2 to 10 carbon atoms which may have a substituent, a tert-butoxycarbonyl group or a 9-fluorenylmethoxycarbonyl group, and R is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms).

As the tetravalent organic group in _X4 in the above formula (4), there can be mentioned a tetravalent organic group derived from aliphatic tetracarboxylic dianhydride, a tetravalent organic group derived from alicyclic tetracarboxylic dianhydride or a tetravalent organic group derived from aromatic tetracarboxylic dianhydride, and as a specific example, there can be mentioned the tetravalent organic group exemplified in the above _X2 . From the viewpoint of efficiently obtaining the effect of the present invention, _X4 is preferably a tetravalent organic group represented by the above formula (g), a tetravalent organic group represented by any one of the above formulas (X-1) to (X-25), a tetravalent organic group represented by the above formulas (Xa-1) to (Xa-2) or a tetravalent organic group represented by the above formulas (Xr-1) to (Xr-7) (these are also collectively referred to as "specific tetravalent organic groups").

Regarding polymer (B), from the viewpoint of efficiently obtaining the effect of the present invention, it is preferred that the polymer (B) contains 5 mol% or more of repeating units in which _X4 is the above-mentioned specific tetravalent organic group, and more preferably contains 10 mol% or more, based on all repeating units contained in the polymer (B).

As the divalent organic group in _Y4 of the above formula (4), there can be mentioned the divalent organic groups exemplified in Y in the above formula (0) or _Y1 to _Y3 in the above formulas (1) to (3). From the viewpoint of less residual DC afterimage, the polymer (B) is preferably a polymer containing _Y4 as the following repeating unit: ₄ is a divalent organic group selected from the group consisting of the following divalent organic groups (these groups are also collectively referred to as "specific divalent organic groups"): a divalent organic group obtained by removing two amino groups from a diamine having a nitrogen-containing structure (hereinafter also referred to as a nitrogen-containing structure) selected from the group consisting of a nitrogen-containing heterocycle, a secondary amino group and a tertiary amino group, 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol, a diamine having a carboxyl group, and a divalent organic group obtained by removing two amino groups from a diamine having a urea bond such as 1,3-bis(4-aminophenethyl)urea.

Examples of the nitrogen-containing heterocyclic ring include pyrrole, imidazole, pyrazole, triazole, pyridine, pyrimidine, pyridazine, pyrazine, indole, benzimidazole, purine, quinoline, isoquinoline, naphthyridine, quinoxaline, phthalazine, triazine, carbazole, acridine, piperidine, piperazine, pyrrolidine, hexamethyleneimine, etc. Among them, pyridine, pyrimidine, pyrazine, piperidine, piperazine, quinoline, carbazole or acridine are preferred.

The secondary amine group and the tertiary amine group that the diamine having a nitrogen-containing structure may have are represented by the following formula (n), for example.

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

As the monovalent alkyl group of R in the above formula (n), there can be mentioned alkyl groups such as methyl, ethyl, propyl, etc.; cycloalkyl groups such as cyclohexyl, etc.; aryl groups such as phenyl, methylphenyl, etc. R is preferably a hydrogen atom or a methyl group.

Specific examples of the diamine having a nitrogen-containing structure 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-diamine. Carbazole, N,N'-bis(4-aminophenyl)-benzidine, N,N'-bis(4-aminophenyl)-N,N'-dimethylbenzidine, 4,4'-diaminodiphenylamine, N,N-bis(4-aminophenyl)-methylamine, diamines represented by the above formula (Dp-1) to (Dp-6) or diamines represented by the above formula (z-1) to (z-25).

As specific examples of the above-mentioned diamine having a carboxyl group, there can be cited 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid, 3,5-diaminobenzoic acid or 4,4'-diaminobiphenyl-3,3'-dicarboxylic acid.

From the perspective of less afterimage from the residual DC, the polymer (B) may contain 1 mol% or more of "repeating units in which Y ₄ is the above-mentioned specific divalent organic group" relative to the total repeating units contained in the polymer (B), and may also contain 5 mol% or more of "repeating units in which Y ₄ is the above-mentioned specific divalent organic group".

From the perspective of less residual DC afterimage, 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)].

<Method for producing polyamine, polyamine ester and polyimide>

The polyimide precursors used in the present invention, such as polyamic acid esters, polyamic acid and polyimide polymers thereof, can be synthesized using known methods such as those described in International Publication WO2013/157586.

The polymer (A) of the present invention is obtained by imidizing the above-mentioned polyimide precursor. The repeating units of the polyimide precursor in the polymer (A) are closed rings, but the ratio of closed ring repeating units to all repeating units of the polyimide precursor (also called the closed ring rate or imidization rate) is 80-95%, preferably 82-95%, and more preferably 85-95%.

By adopting the above-mentioned structure, the obtained liquid crystal alignment film will have high liquid crystal alignment, so the above-mentioned effect of the present invention can be obtained.

<Polymer solution viscosity and molecular weight>

When the polyamine, polyamine ester and polyimide used in the present invention are made into a solution with a concentration of 10-15% by mass, it is preferred to have a solution viscosity of, for example, 10-1000 mPa‧s from the viewpoint of workability, but it is not particularly limited. The solution viscosity (mPa‧s) of the above polymer is the value obtained by measuring as follows: the polymer is prepared into a polymer solution with a concentration of 10-15% by mass using a good solvent (such as γ-butyrolactone, N-methyl-2-pyrrolidone, etc.), and the polymer solution is measured at 25°C using an E-type rotary viscometer.

The weight average molecular weight (Mw) of the polyamide, polyamide ester and polyimide measured by gel permeation chromatography (GPC) in terms of polystyrene is preferably 1,000 to 500,000, and 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 obtained by GPC measurement is preferably 15 or less, and more preferably 10 or less. By setting the molecular weight range to this, 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 a required polymer (B). In addition to polymer (A) and polymer (B), the liquid crystal alignment agent of the present invention may also contain other polymers. As other types of polymers, polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivatives, polyacetal, polystyrene or its derivatives, poly(styrene-phenylmaleimide) derivatives, poly(meth)acrylate, etc. can be cited.

Liquid crystal alignment agent is used to make liquid crystal alignment film. From the perspective of forming a uniform film, it is in the form of a coating liquid. The liquid crystal alignment agent of the present invention is preferably a coating liquid containing the above-mentioned 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 desired coating thickness. From the perspective of forming a uniform and defect-free coating, it is preferably more than 10% by mass, and from the perspective of the storage stability of the solution, it is preferably less than 10% by mass. 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 can dissolve the polymer component uniformly. Specific examples thereof include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethylsulfoxide, γ-butyrolactone, 1,3-dimethyl-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, 3-methoxy-N,N-dimethylpropaneamide, 3-butoxy-N,N-dimethylpropaneamide (also 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 are preferred. The content of the good solvent is preferably 20-99% by mass of the total solvent contained in the liquid crystal alignment agent, more preferably 20-90% by mass, and particularly preferably 30-80% by mass.

Furthermore, the organic solvent contained in the liquid crystal alignment agent is preferably a mixed solvent, which is a solvent (also called a poor solvent) that improves the coating properties or surface smoothness of the coating film when the liquid crystal alignment agent is applied in addition to the above-mentioned solvents. Specific examples of the poor solvents used are shown below, but are not limited to them.

For example, diisopropyl ether, diisobutyl ether, diisobutyl carbinol (2,6-dimethyl-4-heptanol), ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, 1,2-butoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, 4-hydroxy-4-methyl-2-pentanone, diethylene glycol methyl ethyl ether, diethylene glycol dibutyl ether, 3-ethoxybutyl acetate, 1-methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene glycol monoacetate, ethylene glycol diacetate, propylene carbonate, ethylene carbonate, ethylene glycol monobutyl ether, ethylene glycol 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, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monobutyl ether acetate, ethylene glycol monoacetate, ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2-(2-ethoxyethoxy)ethyl acetate, diethylene glycol acetate, propylene glycol diacetate, n-butyl acetate, propylene 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), etc.

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 are preferred.

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 20-80% by mass, and particularly preferably 20-70% 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.

As a preferred combination of good solvent and poor solvent, 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 can be cited. , 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, etc.

The liquid crystal alignment agent of the present invention may additionally contain 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 promoting imidization, compounds for improving the strength of the liquid crystal alignment film (hereinafter, also referred to as cross-linking compounds), dielectrics or conductive substances for adjusting the dielectric constant or resistance of the liquid crystal alignment film, etc.

As the crosslinking compound, from the viewpoint of exhibiting good resistance to AC afterimage and improving film strength, the following compounds (hereinafter collectively referred to as compounds (C)) may also be used: a compound having at least one group selected from the group consisting of an oxiranyl group, an oxadiazine 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 cyclic carbonate group, and a group represented by the following formula (d), and a compound having at least one group selected from the group consisting of compounds represented by the following formula (e).

(式(d)中，R₂及R₃分別獨立為氫原子、碳數1~3的烷基或「*-CH₂-OH」，*表示鍵結鍵。式(e)中，A表示具有芳香環的(m+n)價的有機基，R表示氫原子或碳數1~5的烷基，m表示1~6的整數，n表示0~4的整數)。

(In formula (d), R ₂ and R ₃ are independently a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or "*-CH ₂ -OH", and * represents a bond. In formula (e), A represents an (m+n)-valent organic group having an aromatic ring, R represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, m represents an integer of 1 to 6, and n represents an integer of 0 to 4).

In formula (e), the hydrogen atom on the aromatic ring of A can be replaced by a monovalent organic group such as 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, or a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom.

As specific examples of compounds having an oxirane group, compounds having two or more oxirane groups, such as compounds described in paragraph [0037] of Japanese Patent Publication No. 10-338880 or compounds having a triazine ring skeleton described in International Publication No. WO2017/170483, can be cited. Among them, compounds containing nitrogen atoms such as N,N,N',N'-tetraglycidyl-m-xylene diamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-p-phenylenediamine, and compounds represented by the following formulas (r-1) to (r-3) may also be cited.

As specific examples of compounds having an oxocyclobutane group, there can be cited compounds having two or more oxocyclobutane groups described in paragraphs [0170] to [0175] of International Publication No. 2011/132751.

Specific examples of compounds having protected isocyanate groups include compounds having two or more protected isocyanate groups described in paragraphs [0046] to [0047] of Japanese Patent 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).

As a specific example of a compound having a protected isothiocyanate group, there can be cited a compound having two or more protected isothiocyanate groups described in Japanese Patent Application Publication No. 2016-200798.

As a specific example of a compound having a base containing an oxazoline ring structure, there can be cited a compound containing two or more oxazoline ring structures described in paragraph [0115] of Japanese Patent Application Publication No. 2007-286597.

As specific examples of compounds having a base containing a Michaelis acid structure, compounds having two or more Michaelis acid structures described in International Publication No. WO2012/091088 can be cited.

As specific examples of compounds having a cyclic carbonate group, compounds described in International Publication No. WO2011/155577 can be cited.

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

As specific examples of compounds having a group represented by formula (d), there can be cited international publication No. WO2015/072554 or compounds having two or more groups represented by formula (d) described in paragraph [0058] of 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).

Examples of the (m+n)-valent organic group having an aromatic ring in A of formula (e) include an (m+n)-valent aromatic hydrocarbon group having 6 to 30 carbon atoms, an (m+n)-valent organic group in which an aromatic hydrocarbon group having 6 to 30 carbon atoms is directly bonded or bonded via a linker, and an (m+n)-valent group having an aromatic heterocyclic ring. Examples of the aromatic hydrocarbon group include benzene and naphthalene. Examples of the aromatic heterocyclic ring include a pyrrole ring, an imidazole ring, a pyrazole ring, a pyridine ring, a pyrimidine ring, a quinoline ring, an isoquinoline ring, a carbazole ring, a pyridazine ring, a pyrazine ring, a benzimidazole ring, an indole ring, a quinoxaline ring, and an acridine ring. Examples of the linking group include -NR- (R is a hydrogen atom or a methyl group), an alkylene group having 1 to 10 carbon atoms or a group formed by removing a hydrogen atom from an alkylene group, a divalent or trivalent cyclohexane ring, etc. In addition, any hydrogen atom of the alkylene group may be substituted with an organic group such as a fluorine atom or a trifluoromethyl group. As the alkylene group having 1 to 5 carbon atoms in R of formula (e), specific examples of the alkyl groups exemplified for R ₁ to R ₄ in formula (g) above can be given.

If specific examples are given, the compounds described in International Publication No. WO2010/074269 and the compounds represented by the following formulas (e-1) to (e-10) can be cited.

The above-mentioned compound is an example of a cross-linking compound, but is not limited thereto. For example, the components other than the above-mentioned disclosed in International Publication No. 2015/060357, page 53 [0105] to page 55 [0116] can be cited. In addition, the cross-linking compound can also be used in combination of two or more types.

The content of the crosslinking compound in the liquid crystal alignment agent of the present invention 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 allowing the crosslinking reaction to proceed and exhibiting good resistance to AC afterimages, it is preferably 1 to 15 parts by mass.

Examples of the adhesion aid include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldiethoxymethylsilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-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(ethylene oxide)-3-aminopropyl trimethoxysilane, N-bis(ethylene oxide)-3-aminopropyl triethoxysilane, vinyl trimethoxysilane, vinyl triethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, 3-glycidyloxypropyl methyl dimethoxysilane, 3-glycidyloxypropyl trimethoxysilane, 3-glycidyloxypropyl methyl diethoxysilane, 3-glycidyloxy Silane coupling agents include propyl triethoxysilane, p-phenylene trimethoxysilane, 3-methacryloxypropyl methyl dimethoxysilane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl methyl diethoxysilane, 3-methacryloxypropyl triethoxysilane, 3-acryloxypropyl trimethoxysilane, tris-(trimethoxysilylpropyl) isocyanurate, 3-butylene propyl methyl dimethoxysilane, 3-butylene propyl trimethoxysilane, and 3-isocyanate propyl triethoxysilane. If a silane coupling agent is used, from the perspective of exhibiting good resistance to AC afterimage, the preferred amount is 0.1 to 30 parts by mass, and 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.

As the compound for promoting imidization, 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.) (but excluding the crosslinking compound and the adhesion promoter), or a compound that can generate the above-mentioned basic site during calcination is preferred. More preferred is a compound that can generate the above-mentioned basic site during calcination. If specific examples are given, the compounds represented by the following formulas (B-1) to (B-17) can be given. The content of the compound used to promote imidization is preferably 2 mol or less, more preferably 1 mol or less, and even more preferably 0.5 mol or less, relative to 1 mol of the amide or amide ester site of the polymer (A).

(上述式中(B-1)~(B-17)中，D表示藉由加熱而脫離的有機基，較佳為tert-丁氧基羰基或9-茀基甲氧基羰基之任一者，若D為複數時，各D可互為相同或不同)。

(In the above formulas (B-1) to (B-17), D represents an organic group that is released by heating, preferably tert-butyloxycarbonyl or 9-fluorenylmethoxycarbonyl. If D is plural, each D may be the same or different).

<Method for manufacturing liquid crystal alignment film>

The method for manufacturing a liquid crystal alignment film using the liquid crystal alignment agent of the present invention is characterized by sequentially performing the following steps: a step of coating the liquid crystal alignment agent on a substrate (step (1)), a step of heating the coated liquid crystal alignment agent to obtain a film (step (2)), a step of irradiating the film obtained in step (2) with polarized ultraviolet light (step (3)), and a step of further calcining the film obtained in step (3) at a temperature of 100°C or higher and higher than that in step (2) as required (step (4)).

<Step (1)>

As a substrate for coating the liquid crystal alignment agent used in the present invention, any substrate with high transparency is not particularly limited, and a glass substrate, a silicon nitride substrate, an acrylic substrate, a plastic substrate such as a polycarbonate substrate, etc. can also be used. At this time, it is better to use a substrate that has formed an ITO electrode for driving the liquid crystal, etc., from the perspective of simplifying the process. In addition, in the case of a reflective liquid crystal display element, if it is only a single-sided substrate, an opaque object such as a silicon wafer can also be used. At this time, a material that reflects light, such as aluminum, can also be used as an electrode.

The coating method of the liquid crystal alignment agent is not particularly limited, but in industry, it is generally performed by screen printing, offset printing, flexographic printing or inkjet printing. Other coating methods include immersion, roller coating, slit coating, rotary coating or spraying, which can be used according to the purpose.

<Step (2)>

Step (2) is a step of heating the liquid crystal alignment agent applied to the substrate to form a film. Specifically, the liquid crystal alignment agent applied to the substrate in step (1) is heated by a hot plate, a heat circulation oven, or an IR (infrared) oven to evaporate the solvent, or to perform thermal imidization of the amide acid or amide ester in the polymer. The heating step of the liquid crystal alignment agent applied to the substrate in step (1) can be selected at any temperature and time, and can also be performed multiple times. The heating temperature can be, for example, 40 to 180°C. From the perspective of shortening the process, it is preferably 40 to 150°C, and more preferably 40 to 120°C. The heating time is not particularly limited, but 1 to 10 minutes or 1 to 5 minutes can be cited. If thermal imidization of amide or amide ester in the polymer is performed, after the above step, the heating step can be performed at a temperature range of, for example, 190 to 250°C or 200 to 240°C. The heating time is not particularly limited, but 5 to 40 minutes or 5 to 30 minutes can be cited.

<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 more preferably 200~300nm. In order to improve the liquid crystal alignment, the substrate coated with the liquid crystal alignment film can be heated at 50~250℃ while irradiating with ultraviolet light. In addition, the irradiation amount of the above radiation is preferably 1~10,000mJ/ ^cm2 , and more preferably 100~5,000mJ/ ^cm2 . The liquid crystal alignment film produced in this way can stably align the liquid crystal molecules in a certain direction.

The higher the extinction ratio of polarized ultraviolet light, the higher the anisotropy can be, so it is better. Specifically, the extinction ratio of ultraviolet light polarized in a straight line is preferably greater than 10:1, and more preferably greater than 20:1.

<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). It 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 will be reduced, so it is preferably 5~300nm, and more preferably 10~200nm.

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

As the solvent used in the above-mentioned contact treatment, any solvent that can dissolve the decomposition products generated from the liquid crystal alignment film due to ultraviolet irradiation is not particularly limited. As specific examples, water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propanol acetate, butyl solvent, ethyl lactate, methyl lactate, diacetone alcohol, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate or cyclohexyl acetate can be cited. Among them, from the perspective of versatility or safety of the solvent, water, 2-propanol, 1-methoxy-2-propanol or ethyl lactate are preferred. Water, 1-methoxy-2-propanol or ethyl lactate is more preferred. The solvent may be one type or a combination of two or more types.

As the above-mentioned contact treatment (i.e., a method of treating the liquid crystal alignment film irradiated with polarized ultraviolet rays with water or solvent), immersion treatment or spray treatment (also called spray treatment) can be cited. The treatment time of such treatment is preferably 10 seconds to 1 hour from the perspective of efficiently dissolving the decomposition products generated from the liquid crystal alignment film due to ultraviolet rays. Among them, it is preferred to perform the immersion treatment for 1 to 30 minutes. In addition, the solvent during the above-mentioned contact treatment can be at room temperature or heated, but it is preferably 10 to 80°C, and 20 to 50°C is more preferred. In addition, from the perspective of the solubility of the decomposition products, ultrasonic treatment can also be performed as needed.

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

<Liquid crystal alignment film>

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 is suitable as a liquid crystal alignment film for a liquid crystal display element of a lateral 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.

<Liquid crystal display element>

The liquid crystal display element of the present invention is equipped with the above-mentioned liquid crystal alignment film.

The liquid crystal display element is manufactured as follows: after manufacturing a substrate with a liquid crystal alignment film obtained from the liquid crystal alignment agent of the present invention, a liquid crystal cell is manufactured using a known method, and the liquid crystal cell is used to obtain a liquid crystal display element.

As an example of a method for manufacturing a liquid crystal cell, a liquid crystal display element with a passive matrix structure is used as an example for explanation. In addition, 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 the image display may also be used.

Specifically, a transparent glass substrate is prepared, a common electrode is set on one side of the substrate, and a segment electrode is set on the other side of the substrate. Such electrodes can be set, for example, as ITO electrodes, and are patterned to display the desired image. Next, an insulating film is set on each substrate in a manner covering the common electrode and the segment electrode. The insulating film can be set, for example, as a SiO2 _{- TiO2} film formed by a sol-gel method.

Next, a liquid crystal alignment film is formed on each substrate, and the substrate on the other side is overlapped on the substrate on one side 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, spacers are usually mixed into the sealant first. Moreover, even in the in-plane portion where the sealant is not provided, it is preferred to first spread spacers for controlling the gap between the substrates. For a part of the sealant, an opening portion that can be filled with liquid crystal from the outside is first provided. Next, through the opening portion provided in the sealant, liquid crystal material is injected into the space surrounded by the two substrates and the sealant, and then the opening portion 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 installed. Specifically, a pair of polarizing plates are attached to the surface opposite to the liquid crystal layer of the two substrates.

By using the manufacturing method of the present invention, afterimages caused by long-term AC driving in liquid crystal display elements of IPS drive mode or FFS drive mode can be suppressed. In addition, by removing the organic solvent at a temperature range of 40~150°C in step (2) and then performing step (3), a liquid crystal alignment film can be obtained with fewer steps compared to the previous technology. The liquid crystal alignment agent of the present invention is particularly preferably used in a method for manufacturing a liquid crystal alignment film comprising the following steps: in step (2), removing the organic solvent at a temperature range of 40~150°C and then performing step (3).

[Implementation example]

The following are examples to more specifically illustrate the present invention, but the present invention is not limited to them. The abbreviations of the following compounds and the measurement methods of each property are as follows.

(Solvent)

NMP: N-methyl-2-pyrrolidone

BCS: Butyl cellosolve

(Diamine)

DA-1~DA-13: Compounds represented by the following formulas (DA-1)~(DA-13) respectively

(Tetracarboxylic dianhydride)

CA-1~CA-3: Compounds (additives) represented by the following formulas (CA-1)~(CA-3) respectively

C-1: The compound represented by the following formula (C-1)

S-1: The compound represented by the following formula (S-1)

F-1: The compound represented by the following formula (F-1)

(上述式中，Boc表示tert-丁氧基羰基)。

(In the above formula, Boc represents tert-butoxycarbonyl).

(上述式中，Boc表示tert-丁氧基羰基，Fmoc表示9-茀基甲氧基羰基)。

(In the above formula, Boc represents tert-butyloxycarbonyl, and Fmoc represents 9-fluorenylmethoxycarbonyl).

<Measurement of imidization rate>

20 mg of polyimide powder was placed in an NMR sampling tube stand (Φ5, manufactured by Kusano Scientific Co., Ltd.), dimethyl sulfoxide (DMSO-d6, 0.05% TMS (tetramethylsilane) mixture) (0.53 mL) was added, and ultrasonication was applied to completely dissolve it. The 500 MHz proton NMR of the solution was measured by an NMR measuring instrument (JNW-ECA500) (manufactured by JEOL DATUM). The imidization rate is obtained 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 amide appearing around 9.5ppm~10.0ppm, and the following formula is used.

Imidization rate (%) = (1-α‧x/y) × 100

In the above formula, x is the peak accumulation value of the protons from the NH group of acylamidin; y is the peak accumulation value of the reference proton; α is the ratio of the reference proton to the number of protons of one NH group of acylamidin when the polyacylamidin (acylimidization rate is 0%).

[Polymer synthesis example] <Synthesis Example 1>

In a 100 mL eggplant-shaped flask equipped with a stirring device and a nitrogen inlet tube, 5.62 g (19.2 mmol) of DA-2, 4.18 g (10.5 mmol) of DA-10, and 2.92 g (5.24 mmol) of DA-7 were weighed, and 50.9 g of NMP was added, and the mixture was dissolved while stirring with nitrogen. 4.50 g (22.7 mmol) of CA-3 was added to the diamine solution while stirring under water cooling, and 18.0 g of NMP was further added, and the mixture was stirred at 50°C for 1 hour in a nitrogen environment. Furthermore, 2.63 g (11.7 mmol) of CA-1 was added, and NMP was added in a concentration of 20% by mass, and the mixture was stirred at 40°C for 24 hours to obtain a polyamide solution.

25.0 g of the polyamide solution was separated and placed in a 100 mL Erlenmeyer flask with a stirrer. 8.33 g of NMP, 2.96 g (3 equivalents per mole ratio to polyamide) of acetic anhydride, and 0.766 g (equivalent per mole ratio to polyamide) of pyridine were added thereto. After stirring at room temperature for 30 minutes, the mixture was reacted at 55°C for 3 hours. The reaction solution was added to 170 g of methanol, and the precipitate was filtered out. The precipitate was washed with methanol and then dried under reduced pressure at 80°C to obtain a polyimide resin powder (imidization rate: 86%). Furthermore, 4.00 g of the polyimide resin powder was separated and placed in a 500 mL Erlenmeyer flask with a stirrer, to which 29.3 g of NMP was added and stirred at 70°C for 24 hours to dissolve the powder, thereby obtaining a polyimide solution (PI-1).

<Synthesis Example 2>

In a 200 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 2.44 g (10.0 mmol) of DA-1, 2.37 g (10.0 mmol) of DA-3, 2.30 g (10.0 mmol) of DA-4, 2.98 g (10.0 mmol) of DA-6, and 3.44 g (10.0 mmol) of DA-9 were weighed, and NMP was added to a concentration of 12 mass %, and stirred while nitrogen was supplied to dissolve. 10.6 g (47.2 mmol) of CA-1 was added to the diamine solution while stirring, and NMP was added to a concentration of 12 mass %, and stirred at 40°C for 24 hours to obtain a polyamide solution.

35 g (8.7 mmol) of the obtained polyamine solution was separated and placed in a 100 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 11.7 g of NMP was added thereto and stirred for 30 minutes. 2.67 g (3 equivalents based on the molar ratio of the polyamine) of acetic anhydride and 0.69 g (equivalent based on the molar ratio of the polyamine) of pyridine were added to the obtained polyamine solution and reacted at 55° C. for 3 hours to perform chemical imidization. The obtained reaction solution was added to 150 ml of methanol while stirring, and the precipitated precipitate was filtered out. The same operation was performed twice and the resin powder was washed, and then dried under reduced pressure at 60°C for 12 hours to obtain a polyimide resin powder. The imidization rate of the polyimide resin powder was 86%. 3.60 g of the obtained polyimide resin powder was separated in a 100 ml conical flask, and NMP was added in a manner that the solid concentration became 12% by mass, and it was stirred at 70°C for 24 hours to dissolve it, and a polyimide solution (PI-2) was obtained.

<Synthesis Examples 3~5>

Except for changing the type and amount of the monomers used to those shown in Table 1 below, the rest is the same as in Synthesis Example 2 to obtain polyimide solutions (PI-3)~(PI-5).

<Synthesis Example 6>

In a 200 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 2.69 g (9.0 mmol) of DA-6 and 7.17 g (36.0 mmol) of DA-11 were weighed, and NMP was added to a concentration of 12 mass %, and the mixture was dissolved while stirring with nitrogen. 12.2 g (41.4 mmol) of CA-2 was added to the diamine solution while stirring, and NMP was added to a concentration of 12 mass %, and the mixture was stirred at 70°C for 24 hours to obtain a polyamide solution (PAA-1).

The values in parentheses in Table 1 are: For tetracarboxylic acid components, it indicates the mixing ratio (molar parts) of each compound relative to 100 mol parts of the total amount of tetracarboxylic acid derivatives used in the synthesis; for diamine components, it indicates the mixing ratio (molar parts) of each compound relative to 100 mol parts of the total amount of diamines used in the synthesis. For organic solvents, it indicates the mixing ratio (mass parts) of each organic solvent relative to 100 mass parts of the total amount of organic solvents used in the preparation of polyimide solutions.

[Preparation of liquid crystal alignment agent] <Comparison Example 1>

The polyimide solution (PI-1) obtained in Synthesis Example 1 was added to a sample tube containing a stirrer, and NMP and BCS were added to dilute it. S-1, C-1 and F-1 were added in an amount of 1 mass part, 10 mass parts and 15 mass parts relative to 100 mass parts of the polymer solid content, respectively, and stirred for 30 minutes. In this way, a liquid crystal alignment agent (R1) having a solid content concentration of 6 mass% of polyimide (PI-1) and a solvent composition of NMP:BCS=80:20 in a mass ratio was obtained.

<Implementation Examples 1~8>

Except for changing the polymer components used to those described in Table 2 below, the rest is the same as in the above-mentioned comparative example 1 to obtain liquid crystal alignment agents (1) to (8). The values in parentheses in Table 2 are: For polymers and additives, they represent the proportions (in parts by mass) of each polymer component or additive relative to 100 parts by mass of the total polymer components used in the preparation of the liquid crystal alignment agent. For organic solvents, they represent the proportions (in parts by mass) of each organic solvent relative to 100 parts by mass of the total organic solvents used in the preparation of the liquid crystal alignment agent.

Using the liquid crystal alignment agent obtained by the above operation, the FFS-driven liquid crystal cell is produced according to the procedure shown below, and the characteristics are evaluated.

[The structure of FFS-driven liquid crystal cells]

The liquid crystal cell for the Fringe Field Switching (FFS) mode is a set of a first glass substrate having a FOP (Finger on Plate) electrode layer composed of a common electrode-insulating layer-comb-shaped pixel electrode in a planar shape on the surface, and a second glass substrate having a columnar spacer with a height of 3.5μm on the surface and an ITO film on the back for preventing static charge. The pixel electrode has a plurality of comb-shaped electrodes with a width of 3μm bent at an inner angle of 160° in the center and arranged in parallel with a spacing of 6μm. One pixel has a first region and a second region with a line connecting the bent portions of the plurality of electrode elements as a boundary.

The liquid crystal alignment film formed on the first glass substrate is oriented in such a way that the direction dividing the inner angle of the pixel bending portion into equal parts is orthogonal to the liquid crystal alignment direction; the liquid crystal alignment film formed on the second glass substrate is oriented in such a way that the liquid crystal alignment direction on the first substrate when making the liquid crystal cell is consistent with the liquid crystal alignment direction on the second substrate.

[Production of Liquid Crystal Cells]

On the surfaces of the glass substrates of the above group, the liquid crystal alignment agent filtered by a 1.0μm filter was spin-coated and dried on a hot plate at 80°C for 2 minutes. Afterwards, the coated surface was irradiated with 150-350mJ/ ^cm2 of linearly polarized ultraviolet light with an extinction ratio of 26:1 and a wavelength of 254nm through a polarizing plate, and then baked in a hot air circulation oven at 230°C for 30 minutes to obtain two substrates with liquid crystal alignment films (film thickness 100nm).

Next, a sealant is printed on one side of the substrate with a liquid crystal alignment film in the above group, and the other side substrate is laminated in a manner that the liquid crystal alignment film faces each other, and the sealant is cured to produce an empty cell. Liquid crystal (MLC-3019, manufactured by MERCK) is vacuum injected into the empty cell at room temperature by the reduced pressure injection method, and the injection port is sealed to obtain an FFS-driven liquid crystal cell. Afterwards, the obtained liquid crystal cell is heated at 120°C for 1 hour (hereinafter also referred to as "ISO treatment"), left overnight, and used for each evaluation.

<Liquid crystal alignment evaluation>

Using liquid crystal cells before ISO treatment, those with initial flow alignment are defined as "bad", and those without initial flow alignment are defined as "good" for evaluation.

<Evaluation of in-plane uniformity of contrast>

The twist angle of the liquid crystal display element is evaluated using OPTIPRO-micro manufactured by SHINTEC. The manufactured liquid crystal cell is placed on the measuring table, and 20 points in the first pixel plane are measured without external voltage, and the standard deviation is calculated. The evaluation is performed by defining the case where the standard deviation of the twist angle is 0.5 or more as "bad", and the case where it is less than 0.5 as "good".

<Evaluation results>

Liquid crystal display elements were obtained using the liquid crystal alignment agents (1) to (8) and (R1) obtained in the above-mentioned Examples 1 to 8 and Comparative Example 1. The evaluation results of the liquid crystal display elements are shown in Table 3.

[Industrial Utilization]

The liquid crystal alignment agent of the present invention is widely used in liquid crystal display elements of longitudinal electric field mode such as TN mode and VA mode, and especially in lateral electric field mode such as IPS mode and FFS mode.

The entire contents of the specification, patent application scope and abstract of Japanese Patent Application No. 2020-039387 filed on March 6, 2020 and Japanese Patent Application No. 2020-123014 filed on July 17, 2020 are cited here and used as the disclosure contents of the specification of the present invention.

Claims (13)

A liquid crystal alignment agent, characterized in that it contains a polymer (A), wherein the polymer (A) is an imidized polymer of a polyimide precursor containing a repeating unit (a0) represented by the following formula (0) and a repeating unit (a1) represented by the following formula (1), wherein the imidization rate of the imidized polymer is 80-95%,

(In formula (0) and formula (1), X represents a tetravalent organic group represented by the following formula (g), Y represents a divalent organic group derived from an aromatic diamine (d0) satisfying the following conditions (1) and (2), and Y is derived from 1,3-diaminobenzene, 2,4-diaminotoluene, 2,6-diaminotoluene, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenyl methane, bis(4-aminophenoxy)methane, 1,5-bis(4-aminophenoxy)pentane, 1,3-bis(4-aminophenethyl)urea, 4,4'-diaminodiphenyl ether, 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 4,4'-diaminobenzophenone or 1,3-bis(4-aminophenoxy)benzene, _Y1 represents a divalent organic group derived from an aromatic diamine (d1) satisfying the following conditions (1) and (3), R and Z are independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and in formula (0) and formula (1), X may be the same or different)

(In formula (g), _R1 to _R4 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, and at least one of _R1 to _R4 is a group other than a hydrogen atom as defined above, and _-CH2 contained in the above-mentioned alkyl group, alkenyl group, alkynyl group, and monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom is -a part of which may be replaced by -O-, * represents a bond) Condition (1): it does not have a side chain group with more than 6 carbon atoms; Condition (2): the two carbon-nitrogen bond axes derived from the amine group are not parallel to each other; Condition (3): the two carbon-nitrogen bond axes derived from the amine group are parallel to each other, and it has a partial structure represented by the following formula (O): *-Ar-Q ₂ -Ar-* (O) (In the formula (O), Ar is independently a benzene ring, a biphenyl structure, or a naphthalene ring, and any hydrogen atom on the ring may be replaced by a halogen atom or a monovalent organic group, and Q ₂ represents -(CH ₂ ) _n - (n is an integer of 2 to 18), or represents any -CH ₂ in the aforementioned -(CH ₂ ) _n - - a group substituted by any of -O-, -C(=O)- or -OC(=O)-, and * represents a bond). The liquid crystal alignment agent of claim 1, wherein _Y1 in the aforementioned formula (1) is a divalent organic group derived from a diamine represented by the following formulas (d1-1) to (d1-14),

The liquid crystal alignment agent of claim 1, wherein the total amount of the aforementioned repeating unit (a0), repeating unit (a1) and the imidized repeating unit is 5 mol% or more relative to the total repeating unit. The liquid crystal alignment agent of claim 1, wherein the tetravalent organic group represented by the aforementioned formula (g) is a tetravalent organic group represented by any one of the following formulas (g-1) to (g-5),

(In formula (g-1) to formula (g-5), * represents a bond). The liquid crystal alignment agent of claim 1, wherein the polymer (A) is an imidized polymer of a polyimide precursor having a repeating unit (a2) represented by the following formula (2) different from the repeating unit (a0) or (a1),

(wherein, _X2 represents a tetravalent organic group, _Y2 represents a divalent organic group derived from an aromatic diamine having no side chain group with more than 6 carbon atoms, and R and Z are synonymous with R and Z in the aforementioned formula (0)). The liquid crystal alignment agent of claim 1, wherein either or both of the aromatic diamine (d0) and the aromatic diamine (d1) are aromatic diamines having 4 to 40 carbon atoms. The liquid crystal alignment agent in claim 1 is used for photo-alignment method. A liquid crystal alignment film obtained from a liquid crystal alignment agent as described in any one of claims 1 to 7. A liquid crystal display element having a liquid crystal alignment film as claimed in claim 8. A method for manufacturing a liquid crystal alignment film comprises the following steps (1) to (3): step (1): applying a liquid crystal alignment agent as described in any one of claims 1 to 7 on a substrate; step (2): heating the liquid crystal alignment agent applied in step (1) 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 10 further comprises the following step (4): step (4): calcining the film obtained in step (3) at a temperature above 100°C and higher than that in step (2). The method for manufacturing a liquid crystal alignment film as claimed in claim 10 or 11, wherein the aforementioned step (2) is a step of obtaining the film by heating at a temperature range of 40 to 180°C. A liquid crystal display element having a liquid crystal alignment film obtained by the method for manufacturing a liquid crystal alignment film as described in any one of claims 10 to 12.