JP7800532B2 - Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element - Google Patents

Description

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

Liquid crystal display devices are widely used as display units in personal computers, smartphones, mobile phones, televisions, and more. Liquid crystal display devices typically include a liquid crystal layer sandwiched between a display element substrate and a color filter substrate, pixel electrodes and a common electrode that apply an electric field to the liquid crystal layer, an alignment film that controls the orientation of the liquid crystal molecules in the liquid crystal layer, and thin-film transistors (TFTs) that switch the electrical signals supplied to the pixel electrodes. Known methods for driving liquid crystal molecules include vertical electric field methods such as the TN method and the VA method, and horizontal electric field methods such as the IPS (In Plane Switching) driving method and the FFS (Fringe Field Switching) driving method.

The most widely used industrially, liquid crystal alignment films are produced by rubbing the surface of a film made of polyamic acid and/or its imidized polyimide formed on an electrode substrate in one direction with a cloth made of cotton, nylon, polyester, or other material. Rubbing is a simple, highly productive, and industrially useful method. However, as liquid crystal display devices become increasingly sophisticated, their resolution, and size increase, various problems have become apparent, including scratches on the alignment film surface, dust generation, mechanical force and static electricity, and unevenness within the alignment-treated surface. As an alternative to rubbing, photoalignment, which imparts liquid crystal alignment ability by irradiating polarized radiation, has been proposed. Photoalignment methods utilizing photoisomerization, photocrosslinking, and photodecomposition have been proposed (see, for example, Non-Patent Document 1, Patent Documents 1 and 2).

Japanese Patent Application Publication No. 9-297313 Japanese Patent Application Laid-Open No. 2004-206091

"Functional Materials," November 1997, Vol. 17, No. 11, pp. 13-22

The liquid crystal alignment film used in the above-mentioned IPS drive type or FFS drive type liquid crystal display element requires a high alignment control force to suppress afterimages (hereinafter also referred to as AC afterimages) that occur due to long-term AC drive. Furthermore, when performing alignment treatment by a photo-alignment method, the amount of light irradiation is a factor that affects energy costs and production speed, so it is preferable that the alignment treatment can be performed with a small amount of light irradiation.
However, the inventors' investigations revealed that liquid crystal alignment films that can achieve liquid crystal alignment with a small amount of light irradiation in alignment treatment using a photo-alignment method have problems, such as a narrow range of light irradiation doses that can produce a liquid crystal alignment film that can suppress AC image retention, and a narrow range of light irradiation doses that can produce a liquid crystal alignment film with small variations (non-uniformity) in the twist angle of the liquid crystal within the liquid crystal alignment film surface. As a result, there is a high risk of AC image retention occurring when the liquid crystal is driven, making it difficult to produce a liquid crystal display element with excellent contrast and high display quality. There is also concern that when the liquid crystal display element is made larger, the liquid crystal alignment may be incomplete in part of the liquid crystal alignment film, causing variations in brightness within the screen when an image is displayed for a long period of time, thereby degrading the display quality.

The object of the present invention is to provide a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display element using the liquid crystal alignment film, which can efficiently produce a liquid crystal alignment film with high characteristics, such as being able to suppress image retention caused by long-term AC driving even when the range of light irradiation dose in alignment treatment using a photo-alignment method is small, and being able to reduce variation (non-uniformity) in the twist angle of the liquid crystal within the liquid crystal alignment film surface.

The present inventors have conducted extensive research and have found that the above problems can be solved by using a liquid crystal aligning agent containing a specific component, thereby completing the present invention.
Specifically, the present invention has the following aspects.

A liquid crystal aligning agent comprising at least one polymer (A) selected from the group consisting of a polyimide precursor having a repeating unit (a1) represented by the following formula (1) and a polyimide which is an imidized product of the polyimide precursor:
(In formula (1), 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 containing a fluorine atom, or a phenyl group, and at least one of R ₁ to R ₄ represents a group other than a hydrogen atom as defined above. R and Z each independently represent a hydrogen atom or a monovalent organic group. _{Y 1} represents a divalent organic group represented by the following formula (H):)
(In formula (H), R _a represents a hydroxy group, a halogen atom, or a monovalent organic group having 1 to 3 carbon atoms. a is an integer of 1 to 4. When there are multiple R _a's , they may be the same or different. * represents a bond.)

In this specification, the "integer" may be omitted when it is obvious that it is an "integer," such as in the above statement, "a is an integer from 1 to 4." In addition, * represents a bond in all cases.

According to the present invention, it is possible to provide a liquid crystal alignment agent that can efficiently obtain a liquid crystal alignment film with high characteristics, such as being able to suppress AC afterimages even when the range of light irradiation dose in alignment treatment by a photo-alignment method is small, and being able to reduce the variation (non-uniformity) in the twist angle of the liquid crystal within the liquid crystal alignment film plane, as well as the liquid crystal alignment film and a liquid crystal display element using the liquid crystal alignment film.
Although the mechanism by which the above-mentioned effects of the present invention are obtained is not entirely clear, the following is thought to be one of the reasons. The polymer (A) contained in the liquid crystal aligning agent of the present invention contains a repeating unit derived from a substituted phenylenediamine. The inclusion of such a repeating unit makes it possible to adjust the imidization rate during thermal imidization and the intermolecular interaction of the polymer, making it easier to control the glass transition temperature of the polymer during alignment treatment. Therefore, it is thought that the mobility of the polymer increases during alignment treatment, improving the anisotropy of the alignment film and thereby achieving the above-mentioned effects.

1 is a schematic cross-sectional view of an example of a lateral electric field liquid crystal display element having a liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention. 1 is a schematic cross-sectional view of another example of an in-plane switching liquid crystal display element having a liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention.

<Polymer (A)>
The liquid crystal aligning agent of the present invention contains at least one polymer (A) selected from the group consisting of polyimide precursors having a repeating unit (a1) represented by the following formula (1) and polyimides which are imidized products of the polyimide precursors. The polymer (A) may be composed of one type or two or more types:

In the above formula (1), 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 containing a fluorine atom, or a phenyl group, and at least one of R ₁ to R ₄ represents a group other than a hydrogen atom as defined above.
R and Z each independently represent a hydrogen atom or a monovalent organic group, _{and Y1} represents a divalent organic group represented by the following formula (H).

In the above formula (H), R _a represents a hydroxy group, a halogen atom, or a monovalent organic group having 1 to 3 carbon atoms, and a is an integer of 1 to 4. When there are multiple R _a's , they may be the same or different.

Examples of the halogen atom in R _a in the above formula (H) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and among these, a fluorine atom is preferred. From the viewpoint of obtaining the effects of the present invention well, a in the above formula (H) is preferably 1 to 3, and more preferably 1 or 2.

The divalent organic group represented by the above formula (H) is preferably a divalent organic group represented by the following formula (H') from the viewpoint of obtaining the effects of the present invention favorably.
(R _a and a have the same meanings as in formula (H) above.)

Specific examples of the alkyl group having 1 to 6 carbon atoms in R ₁ to R ₄ include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, etc. Specific examples of the alkenyl group having 2 to 6 carbon atoms in R ₁ to R ₄ include a vinyl group, a propenyl group, a butenyl group, 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 an ethynyl group, a 1-propynyl group, a 2-propynyl group, a 1-butynyl group, a 2-butynyl group, a 3-butynyl group, etc. Examples of the halogen atom in R ₁ to R ₄ include the halogen atoms exemplified as R _a in formula (H) above. Examples of the fluorine atom-containing monovalent organic group having 1 to 6 carbon atoms in R ₁ to R ₄ include a fluoromethyl group, a trifluoromethyl group, a pentafluoroethyl group, and a pentafluoropropyl group. From the viewpoint of high photoreactivity, it is preferable that R ₁ to R ₄ are each independently a hydrogen atom or a methyl group, and that at least one of R ₁ to R ₄ is a methyl group, and more preferable that at least two of R ₁ to R ₄ are methyl groups. Even more preferable is the case where R ₁ and R ₄ are methyl groups, and R ₂ and R ₃ are hydrogen atoms.

Examples of the monovalent organic group in formula (H) include an alkyl group, a halogenated alkyl group in which at least a portion of the hydrogen atoms on the alkyl group are substituted with halogen atoms (specific examples of halogen atoms include the halogen atoms exemplified as R _a in formula (H)), an alkoxy group, a halogenated alkoxy group in which at least a portion of the hydrogen atoms on the alkoxy group are substituted with halogen atoms, and an alkenyl group. Examples of the alkyl group having 1 to 3 carbon atoms include those having 1 to 3 carbon atoms among the structures exemplified for the alkyl groups in R ₁ to R ₄ above, and examples of the halogenated alkyl group include a fluoromethyl group, a trifluoromethyl group, a pentafluoroethyl group, and a pentafluoropropyl group. Of these, a methyl group or a methoxy group is preferred as the monovalent organic group having 1 to 3 carbon atoms.

As the divalent organic group represented by the above formula (H), a divalent organic group represented by any one of the following formulas (h-1) to (h-16) is preferred, from the viewpoint of obtaining the effects of the present invention favorably.

The monovalent organic groups for R and Z in the above formula (1) include monovalent hydrocarbon groups having 1 to 20 carbon atoms, methylene groups of the hydrocarbon groups being -O-, -S-, -CO-, -COO-, -COS-, -NR ³ -, -CO-NR ³ -, -Si(R ³ ) ₂ - (wherein R ³ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms, and when there are multiple R ^3s , each R ³ may be the same or different), -SO ₂ - or the like, a monovalent group A in which at least one hydrogen atom bonded to a carbon atom of such a monovalent hydrocarbon group or the monovalent group A is substituted with a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, or the like), a hydroxy group, an alkoxy group, a nitro group, an amino group, a mercapto group, a nitroso group, an alkylsilyl group, an alkoxysilyl group, a silanol group, a sulfino group, a phosphino group, a carboxy group, a cyano group, a sulfo group, an acyl group, or the like, a monovalent group having a heterocycle, etc. The monovalent organic group for R and Z in the above formula (1) is preferably an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, a tert-butoxycarbonyl group, or a 9-fluorenylmethoxycarbonyl group, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group.
From the viewpoint of obtaining the effects of the present invention favorably, R and Z are each independently preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom or a methyl group.

From the viewpoint of achieving the effects of the present invention effectively, the polymer (A) may be at least one polymer selected from the group consisting of polyimide precursors having the repeating unit (a1) represented by the above formula (1) and the repeating unit (a2) represented by the following formula (2), and polyimides that are imidized products of the polyimide precursors. Furthermore, the repeating unit (a2) may be composed of one type or two or more types.

In the above formula (2), R ₁ to R ₄ , R, and Z have the same meanings as in the above formula (1), and Y ₂ represents a divalent organic group represented by the following formula (O).
In the above formula (O), each Ar independently represents a benzene ring, a biphenyl structure, or a naphthalene ring. Any hydrogen atom on the ring of Ar may be replaced with a halogen atom or a monovalent organic group. _Q2 represents -( _CH2 ) _n- (n is 2 to 18) or a group in which a portion of the -( _CH2 ) _n- is replaced with -O-, -C(=O)-, or -O-C(=O)-.

In the above formula (O), examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the monovalent organic group include an alkyl group having 1 to 3 carbon atoms, an alkenyl group having 2 to 3 carbon atoms, an alkynyl group having 2 to 3 carbon atoms, and a monovalent organic group having 1 to 3 carbon atoms and containing a fluorine atom. Specific examples of these monovalent organic groups include those exemplified for R ₁ to R ₄ above.
As the divalent organic group represented by the above formula (O), a divalent organic group represented by any of the following formulae (o-1) to (o-14) is preferred from the viewpoint of improving liquid crystal alignment properties. In formula (o-10), m is preferably 2. In formula (o-14), m is more preferably 0 or 2.

(In formula (o-14), two m's are independent of each other.)

From the viewpoint of achieving the effects of the present invention effectively, the polymer (A) may be at least one polymer selected from the group consisting of polyimide precursors having at least one repeating unit selected from the group consisting of repeating units (a1) represented by formula (1) above, or repeating units (a1) and (a2) represented by formula (2) above, and repeating units (a2') represented by formula (2') below and repeating units (a3) represented by formula (3) below, and polyimides that are imidized products of the polyimide precursors:

In the above formulas (2') and (3), X2 _' and _X3 represent tetravalent organic groups, Y2 _' represents a divalent organic group represented by the following formula (O2), and _Y3 represents a divalent organic group having 6 to 30 carbon atoms and containing the group "-N(D)- (D represents a carbamate protecting group)" in the molecule. R and Z are defined as in the above formula (1).

In the above formula (O2), m is an integer of 0 to 2, and Ar _2' represents an unsubstituted or substituted benzene ring. However, when m is 0, Ar _2' represents an unsubstituted benzene ring, and when m is 1 or 2, Ar _2' each independently represent an unsubstituted benzene ring or a benzene ring in which any hydrogen atom on the benzene ring has been replaced with a halogen atom or a monovalent organic group (e.g., an alkyl group having 1 to 3 carbon atoms, an alkenyl group having 2 to 3 carbon atoms, an alkynyl group having 2 to 3 carbon atoms, a monovalent organic group having 1 to 3 carbon atoms and containing a fluorine atom, etc.). _{Q 2'} represents a single bond or -O-. When there are multiple _{Ar 2'} and multiple Q _2' , they may be the same or different.

As the divalent organic group represented by the above formula (O2), a divalent organic group represented by any one of the following formulae (o2-1) to (o2-12) is preferred from the viewpoint of reducing the occurrence of AC afterimages.

In the above formula (3), D of _Y3 represents a carbamate protecting group, and examples of the carbamate protecting group include a tert-butoxycarbonyl group and a 9-fluorenylmethoxycarbonyl group. Specific examples of _Y3 include a divalent organic group represented by the following formula (Dx):

In the above formula (Dx), _Q5 represents a single bond, -( _CH2 ) _n- (n is 1 to 20), or a group in which _{any -CH2-} in the -( _CH2 ) _n- is replaced by -O-, -Si( _CH3 ) _2- , -COO-, -OCO-, _-NQ9- , _-NQ9 -CO-, -CO- _NQ9- , _-NQ9 -CO- _NQ10- , -NQ9-COO- or -O-COO-, and _{Q9 and Q10} each independently represent a hydrogen atom or a monovalent organic group.
_Q6 and _Q7 each independently represent -H, -NHD, -N(D) ₂ , a group having -NHD, or a group having -N(D) ₂ . However, when m=0, _Q6 has a carbamate protecting group, and when m=1, at least one of _Q5 , _Q6 , and _Q7 has a carbamate protecting group in the group. Furthermore, when _Q6 or _Q7 represents a group having -NHD or a group having -N(D) ₂ , _Q6 and _Q7 preferably have 1 to 30 carbon atoms, more preferably 1 to 8 carbon atoms.

Examples of the monovalent organic group of _Q9 and _Q10 include an alkyl group having 1 to 3 carbon atoms, an alkenyl group having 2 to 3 carbon atoms, an alkynyl group having 2 to 3 carbon atoms, and a monovalent organic group containing 1 to 3 carbon atoms and containing a fluorine atom, and specific examples include those exemplified for _R1 to _R4 above that have 1 to 3 carbon atoms.
Preferred examples of _Y3 , from the viewpoint of reducing AC afterimages, include divalent organic groups represented by any of the following formulae (Y3-1) to (Y3-9): Boc represents a tert-butoxycarbonyl group.

Examples of X2 _' and _X3 in the above formula (2') and formula (3) include a tetravalent organic group represented by the following formula (g), as well as a tetravalent organic group represented by any of the following formulae (X-1) to (X-25), a tetravalent organic group derived from an aromatic tetracarboxylic dianhydride, etc. From the viewpoint of obtaining the effects of the present invention favorably, X2 _' and _X3 are more preferably a tetravalent organic group represented by the following formula (g):
(R ₁ to R ₄ have the same meanings as R ₁ to R ₄ in the above formula (1).)

The aromatic tetracarboxylic acid dianhydrides are acid dianhydrides obtained by intramolecular dehydration of a carboxy group bonded to an aromatic ring such as a benzene ring or a naphthalene ring. Specific examples include tetravalent organic groups represented by any of the following formulas (Xa-1) to (Xa-2) and tetravalent organic groups represented by any of the following formulas (Xr-1) to (Xr-7).

(x and y each independently represent a single bond, an ether, a carbonyl, an ester, an alkanediyl group having 1 to 10 carbon atoms, 1,4-phenylene, a sulfonyl, or an amide bond; j and k each represent 0 or 1.)

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

The polymer (A) may be at least one polymer selected from the group consisting of polyimide precursors further having a repeating unit (a4) represented by the following formula (4) in addition to the repeating units (a1), (a2), (a2′), and (a3) and polyimides which are imidized products of the polyimide precursors:

In the above formula (4), _X4 represents a tetravalent organic group, and _Y4 represents a divalent organic group. R and Z are respectively synonymous with R and Z in the above formula (1). However, _Y4 has a group "-N(D)- (D represents a carbamate protecting group)" in the molecule, and represents a divalent organic group having 6 to 30 carbon atoms excluding D, and a structure other than the divalent organic group represented by the above formula (O2). Furthermore, when _X4 is synonymous with the tetravalent organic group represented by the above formula (g), _Y4 represents a structure other than the divalent organic group represented by the above formula (H) and the divalent organic group represented by the above formula (O).

Specific examples of X ₄ include the tetravalent organic groups exemplified above for X _2' . From the viewpoint of favorably achieving the effects of the present invention, X ₄ 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 more preferably a tetravalent organic group represented by the above formula (g).

Specific examples of the divalent organic group for _Y4 include the divalent organic groups exemplified in the above formula (H) and formula (O), as well as divalent organic groups derived from diamines described below (divalent organic groups obtained by removing two amino groups from a diamine).
4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane; diamines having a photoalignment group such as diamines represented by the following formulas (g-1) to (g-9); diamines having a urea bond such as diamines represented by the following formulas (u-1) to (u-3) (provided that the diamine does not have a carbamate-based protecting group in the molecule); diamines having an amide bond such as diamines represented by the following formulas (u-4) to (u-7) (provided that the diamine does not have a carbamate-based protecting group in the molecule); at least one nitrogen atom-containing structure selected from the group consisting of a nitrogen atom-containing heterocycle, a secondary amino group, and a tertiary amino group (hereinafter also referred to as a nitrogen atom-containing structure) However, in the above secondary amino group and tertiary amino group, the amino group is not bonded to a carbamate-based protecting group.) diamines having; 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol; diamines having a carboxy group such as 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid, 3,5-diaminobenzoic acid or diamine compounds represented by the following formulas (3b-1) to (3b-4); 4-(2-(methylamino)ethyl)aniline, 4-(2-aminoethyl)aniline, 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-inden-6-amine; diamines having a photopolymerizable group at the terminal, such as 2-(2,4-diaminophenoxy)ethyl methacrylate and 2,4-diamino-N,N-diallylaniline; diamines having a steroid skeleton, such as cholestanyloxy-3,5-diaminobenzene, cholestanyloxy-3,5-diaminobenzene, cholestanyloxy-2,4-diaminobenzene, cholestanyl 3,5-diaminobenzoate, cholestanyl 3,5-diaminobenzoate, lanostannyl 3,5-diaminobenzoate, and 3,6-bis(4-aminobenzoyloxy)cholestane; diamines having a siloxane bond such as 1,3-bis(3-aminopropyl)-tetramethyldisiloxane; diamines having an oxazoline ring structure such as those of the following formulae (Ox-1) and (Ox-2); divalent organic groups derived from diamines such as diamines having a radical polymerization initiator function such as 1-(4-(2,4-diaminophenoxy)ethoxy)phenyl)-2-hydroxy-2-methylpropanone, 2-(4-(2-hydroxy-2-methylpropanoyl)phenoxy)ethyl-3,5-diaminobenzoate, 4,4'-diaminobenzophenone, and 3,3'-diaminobenzophenone; and groups represented by any of formulas (Y-1) to (Y-167) described in WO2018/117239.

In the above formula (3b-1), A ¹ represents a single bond, —CH ₂ —, —C ₂ H ₄ —, —C(CH ₃ ) ₂ —, —CF ₂ —, —C(CF ₃ ) ₂ —, —O—, —CO—, —NH—, —N(CH ₃ )—, —CONH—, —NHCO—, —CH ₂ O—, —OCH ₂ —, —COO—, —OCO—, —CON(CH ₃ )— or —N(CH ₃ )CO—; m1 and m2 each independently represent an integer of 0 to 4, and the sum of m1 and m2 represents an integer of 1 to 4.
In the above formula (3b-2), m3 and m4 each independently represent an integer from 1 to 5. In the above formula (3b-3), A ² represents a linear or branched alkyl group having 1 to 5 carbon atoms, and m5 represents an integer from 1 to 5. In the above formula (3b-4), A ³ and A ⁴ each independently represent a single bond, —CH ₂ —, —C ₂ H ₄ —, —C(CH ₃ ) ₂ —, —CF ₂ —, —C(CF ₃ ) ₂ —, —O—, —CO—, —NH—, —N(CH ₃ )—, —CONH—, —NHCO—, —CH ₂ O—, —OCH ₂ —, —COO—, —OCO—, —CON(CH ₃ )—, or —N(CH ₃ )—CO—, and m6 represents an integer from 1 to 4.

In the above formulas (V-1) to (V-6), X ^v1 to X ^v4 and X ^p1 to X ^p2 each independently represent —(CH ₂ ) _a — (a is 1 to 15), —CONH—, —NHCO—, —CON(CH ₃ )—, —NH—, —O—, —CH ₂ O—, —CH ₂ OCO—, —COO—, or —OCO—; and X ^v5 represents —O—, —CH ₂ O—, —CH ₂ OCO—, —COO—, or —OCO—. _Xa represents a single bond, —O—, —NH—, —O—(CH ₂ ) _m —O— (m is 1 to 6), —C(CH ₃ ) ₂ —, —CO—, —(CH ₂ ) _m — (m is 1 to 6), —SO ₂ —, —O—C(CH ₃ ) ₂ —, —CO—(CH ₂ ) _m — (m is 1 to 6), —NH—(CH ₂ ) _m — (m is 1 to 6), —SO ₂ —(CH ₂ ) _m — (m is 1 to 6), —CONH—(CH ₂ ) _m — (m is 1 to 6), —CONH—(CH ₂ ) _m —NHCO— (m is 1 to 6), or —COO—(CH ₂ ) _m represents —OCO— (m is 1 to 6), —CONH—, —NH—(CH ₂ ) _m —NH— (m is 1 to 6), or —SO ₂ —(CH ₂ ) _m —SO ₂ — (m is 1 to 6), and R ^v1 to R ^v4 and R ^1a to R ^1b 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. Each k may be the same or different.

Examples of the nitrogen atom-containing heterocycle include pyrrole, imidazole, pyrazole, triazole, pyridine, pyrimidine, pyridazine, pyrazine, indole, benzimidazole, purine, quinoline, isoquinoline, naphthyridine, quinoxaline, phthalazine, triazine, carbazole, acridine, piperidine, piperazine, pyrrolidine, and hexamethyleneimine. Of these, pyridine, pyrimidine, pyrazine, piperidine, piperazine, quinoline, carbazole, and acridine are preferred.

The secondary amino group and tertiary amino group that the diamine having a nitrogen atom-containing structure may have are represented by, for example, 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 bond bonded to the hydrocarbon group. Examples of monovalent hydrocarbon groups represented by R in the above formula (n) include alkyl groups such as methyl, ethyl, and propyl; cycloalkyl groups such as cyclohexyl; and aryl groups such as phenyl and methylphenyl. R is preferably a hydrogen atom or a methyl group.

Specific examples of diamines having a nitrogen atom-containing structure include 2,6-diaminopyridine, 3,4-diaminopyridine, 2,4-diaminopyrimidine, 3,6-diaminocarbazole, N-methyl-3,6-diaminocarbazole, N-ethyl-3,6-diaminocarbazole, N-phenyl-3,6-diaminocarbazole, 1,4-bis-(4-aminophenyl)-piperazine, 3,6-diaminoacridine, compounds represented by the following formulas (Dp-1) to (Dp-8), or compounds represented by the following formulas (z-1) to (z-13).

From the viewpoint of obtaining the effects of the present invention satisfactorily, the polymer (A) preferably contains the repeating unit (a1) and the imidized structural unit of the repeating unit (a1) in a total amount of 10 to 100 mol %, more preferably 15 to 100 mol %, of all repeating units. Note that this total includes cases where either the repeating unit (a1) or the imidized structural unit of the repeating unit (a1) is 0 mol %. Hereinafter, the term "total" also includes cases where one or more of the structural unit components are 0 mol %.
When polymer (A) contains a repeating unit other than the repeating unit (a1) and the imidized structural unit of the repeating unit (a1), the total of the repeating unit (a1) and the imidized structural unit of the repeating unit (a1) preferably accounts for 10 to 95 mol% of all repeating units. Polymer (A) preferably contains the repeating unit (a1) and the imidized structural unit of the repeating unit (a1) in a total amount of 95 mol% or less, more preferably 90 mol% or less, and even more preferably 80 mol% or less of all repeating units. Furthermore, polymer (A) preferably contains the repeating unit (a1) and the imidized structural unit of the repeating unit (a1) in a total amount of 10 mol% or more, and preferably 15 mol% or more of all repeating units.

From the viewpoint of achieving the effects of the present invention favorably, the polymer (A) preferably contains the repeating unit (a2) and the imidized structural units of the repeating unit (a2) in a total amount of 5 mol % or more, more preferably 10 mol % or more, and even more preferably 20 mol % or more, of all repeating units, and preferably 90 mol % or less, and even more preferably 85 mol % or less. Furthermore, from the viewpoint of achieving the effects of the present invention favorably, the polymer (A) preferably contains the repeating unit (a2) and the imidized structural units of the repeating unit (a2) in a total amount of 10 to 90 mol % of all repeating units.

To obtain the effects of the present invention effectively, the total of repeating units (a1), repeating units (a2), and their imidized structural units is preferably 10 mol % or more, and more preferably 20 mol % or more, of all repeating units in polymer (A). When polymer (A) contains repeating units other than repeating units (a1), repeating units (a2), and their imidized structural units, the total of repeating units (a1), repeating units (a2), and their imidized structural units is preferably 95 mol % or less, and more preferably 90 mol % or less.

When polymer (A) contains at least one of repeating unit (a2') and imidized structural units of repeating unit (a2'), from the viewpoint of achieving the effects of the present invention favorably, polymer (A) preferably contains repeating unit (a2') and imidized structural units of repeating unit (a2') in a total amount of 1 to 50 mol %, more preferably 1 to 40 mol %, and even more preferably 1 to 30 mol % of all repeating units. When polymer (A) contains at least one of repeating unit (a1) and imidized structural units thereof and at least one of repeating unit (a2) and imidized structural units thereof, the total amount of repeating unit (a2') and imidized structural units of repeating unit (a2') is preferably 5 mol % or more, and even more preferably 10 mol % or more.

To achieve the desired effects of the present invention, polymer (A) preferably contains at least one of repeating unit (a1) and its imidized structural unit, at least one of repeating unit (a2) and its imidized structural unit, and at least one of repeating unit (a2') and its imidized structural unit, and the sum of repeating unit (a1), repeating unit (a2), repeating unit (a2'), and their imidized structural units is preferably 30 mol% or more, more preferably 40 mol% or more, of all repeating units. When polymer (A) contains repeating units other than repeating unit (a1), repeating unit (a2), repeating unit (a2'), and their imidized structural units, the sum of repeating unit (a1), repeating unit (a2), repeating unit (a2'), and their imidized structural units is preferably 95 mol% or less, more preferably 90 mol% or less.

When the polymer (A) contains at least one of the repeating unit (a3) and the imidized structural unit of the repeating unit (a3), from the viewpoint of favorably achieving the effects of the present invention, the polymer (A) preferably contains the repeating unit (a3) and the imidized structure of the repeating unit (a3) in total in an amount of 1 to 40 mol %, more preferably 1 to 30 mol %, and even more preferably 1 to 25 mol %, of all repeating units.
The polymer (A) may contain the repeating unit (a2'), the repeating unit (a3), and imidized structural units thereof.

When the polymer (A) contains at least one of the repeating unit (a4) and an imidized structural unit thereof, it is preferred that the polymer (A) be composed of at least one of the repeating unit (a4) and an imidized structural unit thereof, in which _Y4 is a divalent organic group having 4 or more carbon atoms and no side chain structure, in order to satisfactorily obtain the effects of the present invention.
Examples of the divalent organic group having 4 or more carbon atoms and no side chain structure include divalent organic groups derived from diamines selected from the group consisting of diamines excluding, from the other diamines, 2-(2,4-diaminophenoxy)ethyl methacrylate, 2,4-diamino-N,N-diallylaniline, the diamines having a steroid skeleton, the diamines represented by the formulas (V-1) to (V-6), 1-(4-(2,4-diaminophenoxy)ethoxy)phenyl)-2-hydroxy-2-methylpropanone, 2-(4-(2-hydroxy-2-methylpropanoyl)phenoxy)ethyl-3,5-diaminobenzoate, N-phenyl-3,6-diaminocarbazole, and the diamines represented by (z-4) and (z-6).
When the polymer (A) contains at least one of the repeating unit (a4) and the imidized structural unit of the repeating unit (a4), from the viewpoint of favorably achieving the effects of the present invention, the polymer (A) preferably contains the repeating unit (a4) and the imidized structure of the repeating unit (a4) in total in an amount of 1 to 90 mol %, more preferably 5 to 70 mol %, and even more preferably 10 to 30 mol %, of all repeating units.

<Polymer (B)>
The liquid crystal aligning agent of the present invention may contain, in addition to the polymer (A), a polymer (B) that does not have the repeating unit (a1) in the molecule. The polymer (B) may be composed of one type or two or more types. From the viewpoint of obtaining the effects of the present invention favorably, examples of the polymer (B) include polymers having at least one repeating unit selected from the group consisting of the repeating unit (b1) represented by the following formula (5) and imidized structural units of the repeating unit (b1). The repeating units constituting the polymer (B) may be composed of one type or two or more types.

In the formula (5), _X5 is a tetravalent organic group, _Y5 is a divalent organic group, and R and Z have the same meanings as R and Z in the formula (1), respectively.
Examples of the tetravalent organic group for _X5 include tetravalent organic groups derived from aliphatic tetracarboxylic dianhydrides, tetravalent organic groups derived from alicyclic tetracarboxylic dianhydrides, and tetravalent organic groups derived from aromatic tetracarboxylic dianhydrides; specific examples include the tetravalent organic groups exemplified for _X4 . From the viewpoint of achieving the effects of the present invention favorably, the aliphatic or alicyclic tetracarboxylic dianhydrides are preferably tetracarboxylic dianhydrides having at least one partial structure selected from the group consisting of a cyclobutane ring structure, a cyclopentane ring structure, and a cyclohexane ring structure, in particular from the viewpoint of enhancing liquid crystal alignment properties. More preferred _X5 is a tetravalent organic group represented by formula (g), a tetravalent organic group represented by any of formulas (X-1) to (X-25), a tetravalent organic group represented by formulas (Xa-1) to (Xa-2), or a tetravalent organic group represented by formulas (Xr-1) to (Xr-7) (collectively referred to as "specific tetravalent organic groups").

In order to satisfactorily obtain the effects of the present invention, the polymer (B) preferably contains repeating units in which _X5 is the specific tetravalent organic group in an amount of 5 mol % or more, and more preferably 10 mol % or more, of all repeating units contained in the polymer (B).

Examples of the divalent organic group for _Y5 include the divalent organic groups exemplified for _Y4 . From the viewpoint of reducing afterimages resulting from residual DC, it is preferable that the polymer (B) is a polymer in which _Y5 contains a repeating unit that is a divalent organic group derived from the diamine having a urea bond, the diamine having an amide bond, the diamine having a nitrogen atom-containing structure, 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol, the diamine having a carboxy group, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, p-phenylenediamine, and m-phenylenediamine (these are also collectively referred to as specific divalent organic groups).

From the viewpoint of increasing transmittance, the polymer (B) more preferably has two or more types of repeating units represented by the above formula (5), and includes a repeating unit having _Y5 which is a divalent organic group derived from the above diamine having a urea bond, the above diamine having an amide bond, or the above diamine having a nitrogen atom-containing structure, and a repeating unit having _Y5 which is a divalent organic group derived from another diamine.

From the viewpoint of reducing afterimages caused by residual DC, the polymer (B) may contain repeating units in which _Y5 is the specific divalent organic group in an amount of 1 mol % or more, preferably 5 mol % or more, more preferably 10 mol % or more, and even more preferably 20 mol % or more of all repeating units contained in the polymer (B).
From the viewpoint of reducing afterimages resulting from residual DC, the content ratio of the polymer (A) to the polymer (B) (mass ratio of polymer (A)/polymer (B)) is preferably 10/90 to 90/10, more preferably 20/80 to 90/10, and even more preferably 20/80 to 80/20.

<Method for producing polymer (A) and polymer (B)>
The polyimide precursors of the polymer (A) and polymer (B) of the present invention, i.e., polyamic acid ester, polyamic acid, and polyimide, which is an imidized product thereof, can be synthesized by known methods such as those described in WO2013/157586.
Specifically, the polymer is synthesized by reacting a diamine component with a tetracarboxylic acid derivative component in a solvent (condensation polymerization). Examples of the tetracarboxylic acid derivative component include tetracarboxylic acid dianhydrides or derivatives thereof (tetracarboxylic acid dihalides, tetracarboxylic acid diesters, or tetracarboxylic acid diester dihalides). When the polymer (A) or (B) contains an amic acid structure as a part thereof, for example, a polymer having an amic acid structure (polyamic acid) can be obtained by reacting the tetracarboxylic acid dianhydride component with a diamine component. The solvent is not particularly limited as long as it dissolves the resulting polymer.

The diamine component and the tetracarboxylic acid derivative component for obtaining the polyimide precursor of polymer (A) are selected and used depending on the repeating units represented by the above formulas (1), (2), (2′), (3), and (4) contained in polymer (A) so as to obtain the structure of such repeating units.
For example, when polymer (A) has a repeating unit represented by formula (1), a diamine (hereinafter also referred to as specific diamine) having a structure of -N(Z)-Y ₁ -N(Z)- (where Y ₁ and Z are defined as above) is used as the diamine component, and a tetracarboxylic acid derivative having a structure of the following formula (g) (where R ₁ to R ₄ are defined as above) is used as the tetracarboxylic acid derivative component.

The diamine component and the tetracarboxylic acid derivative component used in obtaining a polyimide precursor of polymer (A) having repeating units represented by formula (2), formula (2'), formula (3), or formula (4) contained in polymer (A) are selected and used in accordance with the diamine and the tetracarboxylic acid derivative used in obtaining a polyimide precursor having the repeating unit represented by formula (1) described above, respectively.
The diamine component and tetracarboxylic acid derivative component for obtaining the polyimide precursor of polymer (B) are each selected and used so as to obtain the repeating unit structure represented by the above formula (5) that polymer (B) has. That is, as the diamine component, a diamine having the structure -N(Z) _-Y - _N (Z)- (where Y and Z are defined as above) is used, and as the tetracarboxylic acid derivative component, a tetracarboxylic acid derivative having the structure _X (where _X is defined as above) is used.

Specific examples of the solvent used when reacting the diamine component and the tetracarboxylic acid derivative component include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and 1,3-dimethyl-2-imidazolidinone. Furthermore, if the polymer has high solvent solubility, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or solvents represented by the following formulas [D-1] to [D-3] can be used.

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

These solvents may be used alone or in combination. Furthermore, even if a solvent does not dissolve the polymer, it may be mixed with the above-mentioned solvent to the extent that the produced polymer does not precipitate.
When the diamine component and the tetracarboxylic acid derivative component are reacted in a solvent, the reaction can be carried out at any concentration, preferably 1 to 50% by mass, more preferably 5 to 30% by mass. The reaction can be carried out at a high concentration in the initial stage, and then additional solvent can be added.
In the reaction, the ratio of the total number of moles of the diamine components to the total number of moles of the tetracarboxylic acid derivative components (total number of moles of the tetracarboxylic acid derivative components/total number of moles of the diamine components) is preferably 0.8 to 1.2. As in a typical condensation polymerization reaction, the closer this molar ratio is to 1.0, the larger the molecular weights of the produced polymers (A) and (B).

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

Methods for obtaining polyimide include thermal imidization, in which a solution containing a polyimide precursor such as polyamic acid or polyamic acid ester obtained by the above reaction is heated as is, or catalytic imidization, in which a catalyst is added to the above solution.

In the polyimide in polymer (A) of the present invention, some or all of the repeating units of the polyimide precursor are ring-closed. The imidization rate of the polyimide is preferably 20 to 95%, more preferably 30 to 95%, and even more preferably 50 to 95%.

<Polymer solution viscosity and molecular weight>
The polyamic acid, polyamic acid ester, and polyimide in the polymer (A) of the present invention preferably have a solution viscosity of, for example, 10 to 1,000 mPa s when prepared into a solution having a concentration of 10 to 15% by mass from the viewpoint of workability, but are not particularly limited thereto. The solution viscosity (mPa s) of the polymer is a value measured at 25°C using an E-type rotational viscometer for a polymer solution having a concentration of 10 to 15% by mass prepared using a good solvent for the polymer (e.g., γ-butyrolactone, N-methyl-2-pyrrolidone, etc.).

The polystyrene-equivalent weight-average molecular weight (Mw) of the above polyamic acids, polyamic acid esters, and polyimides, measured by gel permeation chromatography (GPC), is preferably 1,000 to 500,000, and more preferably 2,000 to 300,000. Furthermore, the molecular weight distribution (Mw/Mn), expressed as the ratio of Mw to the polystyrene-equivalent number-average molecular weight (Mn) measured by GPC, is preferably 15 or less, and more preferably 10 or less. Having the molecular weight within this range ensures good alignment and stability of liquid crystal display elements.

<End-capping agent>
In synthesizing the polymer (A) and polymer (B) of the present invention, a suitable end-capping agent may be used together with the tetracarboxylic acid derivative component and the diamine component to form an end-capping polymer. The end-capping polymer has the effect of improving the film hardness of the liquid crystal alignment film obtained by coating and improving the adhesion properties between the sealant and the liquid crystal alignment film.
Examples of the terminals of the polymer (A) and polymer (B) in the present invention include an amino group, a carboxy group, an acid anhydride group, or a derivative thereof. The amino group, the carboxy group, the acid anhydride group, and the isocyanate group can be obtained by a conventional condensation reaction or by blocking the terminals with the following terminal blocking agents, for example, they can be obtained in the same manner using the following terminal blocking agents.

Examples of end-capping agents include acid monoanhydrides such as acetic anhydride, maleic anhydride, nadic anhydride, phthalic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride, 3-hydroxyphthalic anhydride, trimellitic anhydride, 3-(3-trimethoxysilyl)propyl)-3,4-dihydrofuran-2,5-dione, 4,5,6,7-tetrafluoroisobenzofuran-1,3-dione, and 4-ethynylphthalic anhydride; dicarbonate diester compounds such as di-tert-butyl dicarbonate and diallyl dicarbonate; chlorocarbonyl compounds such as acryloyl chloride, methacryloyl chloride, and nicotinic acid chloride; aniline, 2-aminophenol, 3-aminophenol, 4 ... monoamine compounds such as 5-aminosalicylic acid, 5-aminosalicylic acid, 6-aminosalicylic acid, 2-aminobenzoic acid, 3-aminobenzoic acid, 4-aminobenzoic acid, cyclohexylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, and n-octylamine; monoisocyanate compounds such as isocyanates having an unsaturated bond, such as ethyl isocyanate, phenyl isocyanate, naphthyl isocyanate, 2-acryloyloxyethyl isocyanate, and 2-methacryloyloxyethyl isocyanate; and isothiocyanate compounds such as ethyl isothiocyanate and allyl isothiocyanate.

The proportion of end-capping agent used is preferably 0.01 to 20 mol parts, more preferably 0.01 to 10 mol parts, per 100 mol parts of the total diamine components used.

<Liquid crystal alignment agent>
The liquid crystal aligning agent of the present invention contains a polymer (A) and, if necessary, a polymer (B). The liquid crystal aligning agent of the present invention may contain other polymers in addition to the polymer (A) and the polymer (B). Specific examples of other polymers include polysiloxanes, polyesters, polyamides, polyureas, polyurethanes, polyorganosiloxanes, cellulose derivatives, polyacetals, polystyrene derivatives, poly(styrene-maleic anhydride) copolymers, poly(isobutylene-maleic anhydride) copolymers, poly(vinyl ether-maleic anhydride) copolymers, poly(styrene-phenylmaleimide) derivatives, and polymers selected from the group consisting of poly(meth)acrylates.

Specific examples of poly(styrene-maleic anhydride) copolymers include SMA1000, 2000, and 3000 (manufactured by Cray Valley) and GSM301 (manufactured by Gifu Ceramics Manufacturing Co., Ltd.). A specific example of poly(isobutylene-maleic anhydride) copolymers is ISOBAN-600 (manufactured by Kuraray Co., Ltd.). A specific example of poly(vinyl ether-maleic anhydride) copolymers is Gantrez AN-139 (methyl vinyl ether maleic anhydride resin, manufactured by Ashland). These other polymers may be used alone or in combination. The content of these other polymers is preferably 90 parts by weight or less, more preferably 10 to 90 parts by weight, and even more preferably 20 to 80 parts by weight, per 100 parts by weight of the total polymers contained in the liquid crystal alignment agent.

Liquid crystal aligning agents are used to prepare liquid crystal alignment films, and are in the form of a coating liquid from the viewpoint of forming a uniform thin film. The liquid crystal aligning agent of the present invention is also preferably a coating liquid containing the above-mentioned polymer component and an organic solvent. In this case, the polymer concentration in the liquid crystal aligning agent can be adjusted appropriately depending on the thickness of the coating film to be formed. From the viewpoint of forming a uniform, defect-free coating film, a concentration of 1% by mass or more is preferred, and from the viewpoint of the storage stability of the solution, a concentration of 10% by mass or less is preferred. A particularly preferred polymer concentration is 2 to 8% by mass.

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

The organic solvent contained in the liquid crystal aligning agent is preferably a mixed solvent that combines the above-mentioned solvent with a solvent (also called a poor solvent) that improves the coatability and surface smoothness of the coating film when applying the liquid crystal aligning agent. The content of the poor solvent is preferably 1 to 80% by mass of the total solvent contained in the liquid crystal aligning agent, more preferably 10 to 80% by mass, and particularly preferably 20 to 70% by mass. The type and content of the poor solvent are selected appropriately depending on the application device, application conditions, application environment, etc. of the liquid crystal aligning agent.

Specific examples of the poor solvent are listed below, but the poor solvent is not limited to these.
Diisopropyl ether, diisobutyl ether, diisobutyl carbinol (2,6-dimethyl-4-heptanol), ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, 1,2-butoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, 4-hydroxy-4-methyl-2-pentanone, diethylene glycol methyl ethyl ether, diethylene glycol dibutyl ether, 3-ethoxybutyl acetate, 1-methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene glycol monoacetate, ethylene glycol diacetate, propylene carbonate, ethylene carbonate, ethylene glycol monobutyl ether, ethylene glycol monoisoamyl ether, ethylene glycol monohexyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, 1-(2-butoxyethoxy)-2-propanol, 2-(2-butoxyethoxy)- 1-propanol, propylene glycol monomethyl ether acetate, propylene glycol diacetate, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monobutyl ether acetate, diethylene glycol monopropyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2-(2-ethoxyethoxy)ethyl acetate, diethylene glycol Examples of suitable esters include glycerol acetate, propylene glycol diacetate, n-butyl acetate, propylene glycol monoethyl ether acetate, cyclohexyl acetate, 4-methyl-2-pentyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, propyl 3-methoxypropionate, butyl 3-methoxypropionate, n-butyl lactate, isoamyl lactate, diethylene glycol monoethyl ether, and diisobutyl ketone (2,6-dimethyl-4-heptanone).

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

Preferred solvent combinations of good and poor solvents include N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone and ethylene glycol monobutyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone and propylene glycol monobutyl ether, N-ethyl-2-pyrrolidone and propylene glycol monobutyl ether, N-ethyl-2-pyrrolidone and 4-hydroxy-4-methyl-2-pentanone, N-ethyl-2-pyrrolidone and propylene glycol diacetate, N,N-dimethyl lactamide and diisobutyl ketone, and N-methyl-2-pyrrolidone. N-ethyl-2-pyrrolidone and ethyl 3-ethoxypropionate, N-methyl-2-pyrrolidone and ethyl 3-ethoxypropionate, dipropylene glycol monomethyl ether, N-ethyl-2-pyrrolidone and ethyl 3-ethoxypropionate and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone and ethyl 3-ethoxypropionate and diethylene glycol monopropyl ether, N-ethyl-2-pyrrolidone and ethyl 3-ethoxypropionate and diethylene glycol monopropyl ether, N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether acetate, N-ethyl-2-pyrrolidone and dipropylene glycol dimethyl ether, N,N-dimethyl lactamide and ethylene glycol monobutyl ether, N,N-dimethyl lactamide and propylene glycol diacetate, N-ethyl-2-pyrrolidone and diethylene glycol diethyl ether, N-ethyl-2-pyrrolidone and diethylene glycol monoethyl ether and butyl cellosolve acetate, N-methyl-2-pyrrolidone and diethylene glycol monomethyl ether and butyl cellosolve acetate, N,N-dimethyl lactamide and diethylene glycol diethyl ether, N-methyl-2-pyrrolidone and gamma -butyrolactone, 4-hydroxy-4-methyl-2-pentanone, and diethylene glycol diethyl ether, N-ethyl-2-pyrrolidone, N-methyl-2-pyrrolidone, and 4-hydroxy-4-methyl-2-pentanone, N-ethyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone, and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone, and diisobutyl ketone, N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone, and dipropylene glycol monomethyl ether, N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone, and dipropylene glycol monomethyl ether N-ethyl-2-pentanone and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone and propylene glycol diacetate, N-ethyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone and dipropylene glycol dimethyl ether, γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone and diisobutyl ketone, γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone and propylene glycol diacetate, N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether and diisobutyl ketone N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether, and diisopropyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether, and diisobutylcarbinol, N-methyl-2-pyrrolidone, γ-butyrolactone, and dipropylene glycol dimethyl ether, N-methyl-2-pyrrolidone, propylene glycol monobutyl ether, and dipropylene glycol dimethyl ether, N-ethyl-2-pyrrolidone, propylene glycol monobutyl ether, and dipropylene glycol monomethyl ether, N-ethyl-2-pyrrolidone, diethylene glycol monobutyl ether, and dipropylene glycol monomethyl ether N-ethyl-2-pyrrolidone, propylene glycol monobutyl ether, and propylene glycol diacetate; N-ethyl-2-pyrrolidone, propylene glycol monobutyl ether, and diisobutyl ketone; N-ethyl-2-pyrrolidone, γ-butyrolactone, and diisobutyl ketone; N-ethyl-2-pyrrolidone, N,N-dimethyl lactamide, and diisobutyl ketone; N-methyl-2-pyrrolidone, ethylene glycol monobutyl ether, and ethylene glycol monobutyl ether acetate; butyl ether acetate and dipropylene glycol dimethyl ether, N-ethyl-2-pyrrolidone, ethylene glycol monobutyl ether acetate and propylene glycol dimethyl ether, N-methyl-2-pyrrolidone, 4-methyl-2-pentyl acetate and ethylene glycol monobutyl ether, N-ethyl-2-pyrrolidone, cyclohexyl acetate, diacetone alcohol, cyclohexanone and propylene glycol monomethyl ether, cyclopentanone and propylene glycol monomethyl ether, N-methyl-2-pyrrolidone, cyclohexanone and propylene glycol monomethyl ether, and the like.

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

The crosslinkable compound may be a compound having at least one group selected from the group consisting of an oxiranyl group, an oxetanyl group, a protected isocyanate group, a protected isothiocyanate group, a group containing an oxazoline ring structure, a group containing a Meldrum's acid structure, a cyclocarbonate group, and a group represented by the following formula (d), or a compound represented by the following formula (e), from the viewpoint of exhibiting good resistance to AC image retention and significantly improving film strength.

In the above formula (d), _R2 and _R3 each independently represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or * _-CH2 -OH. In the above formula (e), A represents an (m+n)-valent organic group having an aromatic ring, R and R' each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, m is 1 to 6, and n is 0 to 4. Any hydrogen atom in the aromatic ring may be replaced with a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a fluoroalkyl group having 1 to 10 carbon atoms, a fluoroalkenyl group having 2 to 10 carbon atoms, or a fluoroalkoxy group having 1 to 10 carbon atoms.

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

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

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

Specific examples of compounds having a protected isothiocyanate group include compounds having two or more protected isothiocyanate groups described in JP 2016-200798 A.
Specific examples of compounds having a group containing an oxazoline ring structure include compounds containing two or more oxazoline ring structures described in [0115] of JP-A No. 2007-286597.

Specific examples of compounds having a group containing a Meldrum's acid structure include compounds having two or more Meldrum's acid structures described in WO2012/091088.
Specific examples of the compound having a cyclocarbonate group include the compounds described in WO2011/155577.
Examples of the alkyl group having 1 to 3 carbon atoms for R ₂ and R ₃ in the group represented by the above formula (d) include a methyl group, an ethyl group, a propyl group, and an isopropyl group.

Specific examples of compounds having a group represented by formula (d) include compounds having two or more groups represented by formula (d) described in WO 2015/072554 and [0058] of JP 2016-118753, and compounds described in JP 2016-200798, and may also be compounds represented by the following formulas (hd-1) to (hd-8).

Examples of the (m+n)-valent organic group having an aromatic ring for A in formula (e) include an (m+n)-valent aromatic hydrocarbon group having 6 to 30 carbon atoms, an (m+n)-valent organic group to which an aromatic hydrocarbon group having 6 to 30 carbon atoms is bonded directly or via a linking group, and an (m+n)-valent group having an aromatic heterocycle. Examples of the aromatic hydrocarbon group include benzene and naphthalene. Examples of the aromatic heterocycle include aromatic heterocycles such as pyridine rings, which are among the structures exemplified for the nitrogen-containing heterocycle. Examples of the linking group include alkylene groups having 1 to 10 carbon atoms, -NR- (R is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms), groups obtained by removing one hydrogen atom from the alkylene groups, and divalent or trivalent cyclohexane rings. Any hydrogen atom in the alkylene group may be substituted with an organic group such as an alkyl group having 1 to 6 carbon atoms, a fluorine atom, or a trifluoromethyl group. Examples of the alkyl group having 1 to 5 carbon atoms for R and R' in the above formula (e) include the alkyl groups exemplified as R ₁ to R ₄ in the above formula (1).

Specific examples of the above formula (e) include the compounds described in WO2010/074269 and compounds represented by any of the following formulas (e-1) to (e-10).

The above-mentioned compounds are examples of crosslinkable compounds, and the crosslinkable compounds are not limited thereto. For example, the compounds disclosed on pages 53 [0105] to 55 [0116] of WO2015/060357 may be used. Two or more crosslinkable compounds may be used in combination.
The content of the crosslinkable compound in the liquid crystal aligning 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 aligning agent, and more preferably 1 to 15 parts by mass from the viewpoint of proceeding with the crosslinking reaction and exhibiting good resistance to AC afterimages.

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

The imidization-promoting compound is preferably a compound having a basic moiety (e.g., a primary amino group, an aliphatic heterocycle (e.g., a pyrrolidine skeleton), an aromatic heterocycle (e.g., an imidazole ring, an indole ring), or a guanidino group, etc.) (excluding the crosslinkable compounds and adhesion aids described above), or a compound that generates the basic moiety upon baking. More preferred are compounds that generate the basic moiety upon baking, and specific examples include the compounds represented by the following formulas (B-1) to (B-17). The content of the imidization-promoting compound is preferably 2 moles or less, more preferably 1 mole or less, and even more preferably 0.5 moles or less, per mole of amic acid or amic acid ester moiety in polymer (A).

(D represents an organic group that is eliminated by heating, and is preferably either a tert-butoxycarbonyl group or a 9-fluorenylmethoxycarbonyl group. When there are multiple Ds, the multiple Ds may be the same or different.)

The solid content concentration in the liquid crystal aligning agent of the present invention (the ratio of the total mass of the components other than the solvent of the liquid crystal aligning agent to the total mass of the liquid crystal aligning agent) is appropriately selected in consideration of viscosity, volatility, etc., and is preferably in the range of 1 to 10 mass%.
The particularly preferred range of solid content concentration varies depending on the method used when applying the liquid crystal aligning agent to the substrate. As described in step (1) below, examples of methods for applying the liquid crystal aligning agent to the substrate include a roll coater method, a spin coater method, a printing method, and an inkjet method. When using a roll coater method, a solid content concentration in the range of 4 to 10 mass% is particularly preferred. When using a spin coater method, a solid content concentration in the range of 1.5 to 4.5 mass% is particularly preferred. When using a printing method, a solid content concentration in the range of 3 to 9 mass% is particularly preferred, thereby resulting in a solution viscosity in the range of 12 to 50 mPa·s. When using an inkjet method, a solid content concentration in the range of 1 to 5 mass% is particularly preferred, thereby resulting in a solution viscosity in the range of 3 to 15 mPa·s. The temperature when preparing the polymer composition is preferably 10 to 50°C, more preferably 20 to 30°C.

<Liquid crystal alignment film>
The liquid crystal alignment film of the present invention is obtained from the liquid crystal aligning agent. The liquid crystal alignment film of the present invention can be used for horizontal alignment type or vertical alignment type (VA type) liquid crystal alignment films, and is particularly suitable for horizontal alignment type liquid crystal display elements such as IPS drive system or FFS drive system. It is also preferably used as a liquid crystal alignment film for a photo-alignment treatment method. It can also be effectively applied to various other technical applications, such as liquid crystal alignment films other than those mentioned above (liquid crystal alignment films for retardation films, liquid crystal alignment films for scanning antennas or liquid crystal array antennas, or liquid crystal alignment films for transmissive/scattering liquid crystal dimming elements), or other applications such as protective films (e.g., protective films for color filters), spacer films, interlayer insulating films, antireflection films, wiring covering films, antistatic films, and motor insulating films (gate insulating films for flexible displays).

The liquid crystal alignment film of the present invention can be produced, for example, by a method including the following steps (1) to (3), preferably steps (1) to (4).
<Step (1): Step of applying liquid crystal alignment agent onto substrate>
The liquid crystal aligning agent of the present invention is applied to one side of a substrate having a patterned transparent conductive film by an appropriate application method, such as a roll coater method, a spin coat method, a printing method, or an inkjet method. The substrate is not particularly limited as long as it is highly transparent, and plastic substrates such as acrylic substrates and polycarbonate substrates can be used in addition to glass substrates and silicon nitride substrates. In addition, in a reflective liquid crystal display element, an opaque material such as a silicon wafer can be used for only one substrate, and in this case, a light-reflecting material such as aluminum can also be used for the electrode. Furthermore, when manufacturing an IPS or FFS drive liquid crystal display element, a substrate having an electrode made of a comb-shaped patterned transparent conductive film or metal film and an opposing substrate having no electrode are used.
Examples of a method for applying the liquid crystal aligning agent to a substrate and forming a film include screen printing, offset printing, flexographic printing, an inkjet method, and a spray method. Among these, the method for applying the agent by the inkjet method and forming a film is preferably used.

<Step (2): Step of baking the applied liquid crystal alignment agent>
Step (2) is a step of baking the liquid crystal aligning agent applied to the substrate to form a film. After applying the liquid crystal aligning agent to the substrate, the solvent can be evaporated or the polyamic acid or polyamic acid ester can be thermally imidized using a heating means such as a hot plate, a heat circulation oven, or an IR (infrared) oven. The drying and baking steps after applying the liquid crystal aligning agent of the present invention can be performed at any temperature and for any time, and may be performed multiple times. The baking temperature can be, for example, 40 to 180°C. To shorten the process, the baking can be performed at 40 to 150°C. The baking time is not particularly limited, but is 1 to 10 minutes, preferably 1 to 5 minutes. When thermally imidizing the polyamic acid or polyamic acid ester, a baking step can be performed after the baking step, for example, at a temperature range of 150 to 300°C, preferably 150 to 250°C. The baking time is not particularly limited, but is 5 to 40 minutes, preferably 5 to 30 minutes.
If the film-like substance after baking is too thin, the reliability of the liquid crystal display device may be reduced, so the thickness is preferably 5 to 300 nm, more preferably 10 to 200 nm.

<Step (3): Step of subjecting the film obtained in step (2) to alignment treatment>
Step (3) is a step of optionally performing an alignment treatment on the film obtained in step (2). That is, in horizontal alignment-type liquid crystal display devices such as IPS drive systems or FFS drive systems, the coating film is subjected to an alignment ability imparting treatment. On the other hand, in vertical alignment-type liquid crystal display devices such as VA mode or PSA mode, the formed coating film can be used as a liquid crystal alignment film as is, but the coating film may also be subjected to an alignment ability imparting treatment. Alignment treatment methods for liquid crystal alignment films include rubbing treatment and photo-alignment treatment, with photo-alignment treatment being more preferred. Photo-alignment treatment methods include irradiating the surface of the film-like material with radiation polarized in a certain direction, and optionally performing a heat treatment at a temperature preferably between 150 and 250°C to impart liquid crystal alignment (also referred to as liquid crystal alignment ability). The radiation can be ultraviolet light or visible light having a wavelength of 100 to 800 nm. Among these, ultraviolet light having a wavelength of 100 to 400 nm is preferred, and more preferably between 200 and 400 nm.

The radiation dose is preferably 1 to 10,000 mJ/cm ² , more preferably 100 to 5,000 mJ/cm ² , even more preferably 100 to 1,500 mJ/cm ² , particularly preferably 100 to 1,000 mJ/cm ² , and even more preferably 100 to 400 mJ/cm ^2. Conventionally, when a liquid crystal aligning agent is used, the light irradiation dose in the alignment treatment is 100 to 5,000 mJ/cm ² , but with the liquid crystal aligning agent of the present invention, even if the light irradiation dose in the alignment treatment is reduced, it is possible to obtain a liquid crystal alignment film in which the variation (non-uniformity) of the liquid crystal alignment property within the liquid crystal alignment film plane is suppressed.
In addition, when irradiating with radiation, in order to improve the liquid crystal alignment, the substrate having the film-like material may be irradiated while being heated at 50 to 250° C. The liquid crystal alignment film thus produced can stably align liquid crystal molecules in a certain direction.
Furthermore, the liquid crystal alignment film irradiated with polarized radiation by the above method can be contact-treated with water or a solvent, or the liquid crystal alignment film irradiated with radiation can be heat-treated.

The solvent used in the contact treatment is not particularly limited, as long as it dissolves the decomposition products produced from the film-like material by irradiation. Specific examples include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, methyl lactate, diacetone alcohol, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate, and cyclohexyl acetate. Among these, water, 2-propanol, 1-methoxy-2-propanol, or ethyl lactate are preferred from the standpoint of versatility and solvent safety. Water, 1-methoxy-2-propanol, or ethyl lactate are more preferred. The solvent may be used alone or in combination of two or more types.

<Step (4): Step of Heating the Film Aligned in Step (3) at 50 to 300° C.>
The coating film irradiated with the radiation may be subjected to a heat treatment. The temperature for such heat treatment is preferably 50 to 300° C., more preferably 120 to 250° C. The time for the heat treatment is preferably 1 to 30 minutes.

<Liquid crystal display element>
The liquid crystal display element of the present invention is equipped with the liquid crystal alignment film of the present invention and is manufactured as follows. Two substrates each having the liquid crystal alignment film formed thereon obtained as described above are prepared, and a liquid crystal is disposed between the two substrates arranged opposite each other. Specifically, the following two methods can be mentioned.
In the first method, two substrates are placed opposite each other with a gap (cell gap) between them so that their liquid crystal alignment films face each other, and then the peripheral portions of the two substrates are bonded together using a sealant. A liquid crystal composition is filled into the cell gap defined by the substrate surfaces and the sealant through an injection hole so that the liquid crystal composition comes into contact with the film surface, and the injection hole is then sealed.

The second method is called the ODF (One Drop Fill) method. For example, a UV-curable sealant is applied to a predetermined location on one of two substrates on which a liquid crystal alignment film has been formed, and a liquid crystal composition is then dropped onto several predetermined locations on the liquid crystal alignment film surface. The other substrate is then attached so that the liquid crystal alignment film faces the other substrate, and the liquid crystal composition is spread over the entire surface of the substrate and brought into contact with the film surface. Next, the entire surface of the substrate is irradiated with UV light to cure the sealant.
In any of the above methods, it is further preferable to heat the liquid crystal composition used to a temperature at which it assumes an isotropic phase, and then slowly cool it to room temperature to remove flow alignment that occurs during liquid crystal filling.

When the coating films are subjected to rubbing treatment, the two substrates are arranged opposite each other so that the rubbing directions of the coating films are at a predetermined angle, for example, perpendicular or antiparallel to each other.
The sealing agent may be, for example, an epoxy resin containing a hardener and aluminum oxide spheres as spacers. The liquid crystal may be a nematic liquid crystal or a smectic liquid crystal, with a nematic liquid crystal being preferred.
The liquid crystal composition is not particularly limited, and any liquid crystal composition containing at least one liquid crystal compound (liquid crystal molecule) and having positive or negative dielectric anisotropy can be used. Note that, hereinafter, a liquid crystal composition having positive dielectric anisotropy is also referred to as a positive liquid crystal, and a liquid crystal composition having negative dielectric anisotropy is also referred to as a negative liquid crystal.
Examples of the liquid crystal composition include a liquid crystal composition exhibiting a nematic phase, a liquid crystal composition exhibiting a smectic phase, and a liquid crystal composition exhibiting a cholesteric phase, and among these, a liquid crystal composition exhibiting a nematic phase is preferred.
The liquid crystal composition may contain a liquid crystal compound having a fluorine atom, a hydroxy group, an amino group, a fluorine atom-containing group (e.g., a trifluoromethyl group), a cyano group, an alkyl group, an alkoxy group, an alkenyl group, an isothiocyanate group, a heterocycle, a cycloalkane, a cycloalkene, a steroid skeleton, a benzene ring, or a naphthalene ring, or may contain a compound having two or more rigid moieties (mesogenic skeletons) that exhibit liquid crystallinity within the molecule (e.g., a bimesogenic compound in which two rigid biphenyl structures or terphenyl structures are linked by an alkyl group).
The liquid crystal composition may further contain additives from the viewpoint of improving the liquid crystal alignment property, such as photopolymerizable monomers such as compounds having a polymerizable group, optically active compounds (e.g., S-811 manufactured by Merck Ltd.), antioxidants, ultraviolet absorbers, dyes, antifoaming agents, polymerization initiators, or polymerization inhibitors.
Examples of the positive liquid crystal include ZLI-2293, ZLI-4792, MLC-2003, MLC-2041, MLC-3019, and MLC-7081 manufactured by Merck.
Examples of negative liquid crystals include MLC-6608, MLC-6609, MLC-6610, and MLC-7026-100 manufactured by Merck.
Furthermore, an example of a liquid crystal containing a compound having a polymerizable group is MLC-3023 manufactured by Merck.
A liquid crystal display element can be obtained by attaching a polarizing plate to the outer surface of the liquid crystal cell as needed. Examples of the polarizing plate to be attached to the outer surface of the liquid crystal cell include a polarizing film called an "H film" made by stretching and aligning polyvinyl alcohol and absorbing iodine, sandwiched between cellulose acetate protective films, and a polarizing plate made of the H film itself.

An IPS substrate, which is a comb-tooth electrode substrate used in the IPS system (mode), has a base material, a plurality of linear electrodes formed on the base material and arranged in a comb-tooth pattern, and a liquid crystal alignment film formed on the base material so as to cover the linear electrodes.
The FFS substrate, which is a comb-tooth electrode substrate used in the FFS method (mode), has a base material, a surface electrode formed on the base material, an insulating film formed on the surface electrode, a plurality of linear electrodes formed on the insulating film and arranged in a comb-tooth shape, and a liquid crystal alignment film formed on the insulating film so as to cover the linear electrodes.

FIG. 1 is a schematic cross-sectional view showing an example of an IPS mode in-plane switching liquid crystal display device having a liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention.
In the IPS LCD element 1 illustrated in Fig. 1, liquid crystal 3 is sandwiched between a comb-shaped electrode substrate 2 having a liquid crystal alignment film 2c and a counter substrate 4 having a liquid crystal alignment film 4a. The comb-shaped electrode substrate 2 has a base material 2a, a plurality of linear electrodes 2b formed on the base material 2a and arranged in a comb-like pattern, and a liquid crystal alignment film 2c formed on the base material 2a so as to cover the linear electrodes 2b. The counter substrate 4 has a base material 4b and a liquid crystal alignment film 4a formed on the base material 4b. The liquid crystal alignment film 2c is a liquid crystal alignment film of the present invention. The liquid crystal alignment film 4c is also a liquid crystal alignment film of the present invention.
In the IPS LCD element 1 shown in FIG. 1, when a voltage is applied to the linear electrodes 2b, an electric field is generated between the linear electrodes 2b as indicated by electric force lines L.

FIG. 2 is a schematic cross-sectional view showing an example of an FFS mode in-plane switching liquid crystal display device having a liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention.
In the IPS LCD element 1 illustrated in Figure 2, liquid crystal 3 is sandwiched between a comb-shaped electrode substrate 2 having a liquid crystal alignment film 2h and a counter substrate 4 having a liquid crystal alignment film 4a. The comb-shaped electrode substrate 2 has a base material 2d, a surface electrode 2e formed on the base material 2d, an insulating film 2f formed on the surface electrode 2e, a plurality of linear electrodes 2g formed on the insulating film 2f and arranged in a comb-like pattern, and a liquid crystal alignment film 2h formed on the insulating film 2f so as to cover the linear electrodes 2g. The counter substrate 4 has a base material 4b and a liquid crystal alignment film 4a formed on the base material 4b. The liquid crystal alignment film 2h is a liquid crystal alignment film of the present invention. The liquid crystal alignment film 4a is also a liquid crystal alignment film of the present invention.
In the IPS LCD element 1 shown in FIG. 2, when a voltage is applied to the surface electrodes 2e and the linear electrodes 2g, an electric field is generated between the surface electrodes 2e and the linear electrodes 2g as indicated by electric force lines L.

The present invention will be explained in more detail below with reference to the following examples, but the present invention is not limited to these examples. The abbreviations for the compounds and the methods for measuring their properties are as follows:

Boc: tert-butoxycarbonyl group Fmoc: 9-fluorenylmethyloxycarbonyl group (specific diamine)

(Other diamines)

(Tetracarboxylic acid dianhydride)

(Additives)

(solvent)
NMP: N-methyl-2-pyrrolidone BCS: Ethylene glycol monobutyl ether

(Measurement of molecular weight)
The molecular weight was measured under the following conditions using a room temperature gel permeation chromatography (GPC) apparatus (GPC-101) (manufactured by Showa Denko K.K.) and columns (KD-803, KD-805) (manufactured by Showa Denko K.K.).
Column temperature: 50°C
Eluent: N,N-dimethylformamide (additives: lithium bromide monohydrate (LiBr·H ₂ O) 30 mmol/L (liter), phosphoric acid anhydrous crystal (o-phosphoric acid) 30 mmol/L, tetrahydrofuran (THF) 10 mL/L)
Flow rate: 1.0 ml/min. Standard samples for preparing a calibration curve: TSK standard polyethylene oxide (molecular weight: approximately 900,000, 150,000, 100,000, and 30,000) (manufactured by Tosoh Corporation) and polyethylene glycol (molecular weight: approximately 12,000, 4,000, and 1,000) (manufactured by Polymer Laboratory Co., Ltd.).

(Viscosity Measurement)
Measurement was carried out at 25°C using an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.) with a sample volume of 1.1 mL and a cone rotor TE-1 (1°34', R24).

<Synthesis of Polymer>
(Synthesis Example 1)
A1 (0.811 g, 7.50 mmol), WA-1 (1.02 g, 7.50 mmol), A2 (2.20 g, 9.00 mmol), A4 (2.39 g, 6.00 mmol), B1 (6.39 g, 28.5 mmol), and NMP (93.9 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 40° C. for 20 hours to obtain a solution of polyamic acid (A-1) with a solids concentration of 12% by mass (viscosity: 401 mPa s). The number average molecular weight (Mn) of this polyamic acid was 12,939, and the weight average molecular weight (Mw) was 38,921.

(Synthesis Example 2)
WA-1 (2.04 g, 15.0 mmol), A2 (2.20 g, 9.00 mmol), A4 (2.39 g, 6.00 mmol), B1 (6.39 g, 28.5 mmol), and NMP (95.5 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 40° C. for 20 hours to obtain a solution of polyamic acid (A-2) (viscosity: 373 mPa s) with a solids concentration of 12% by mass. The Mn of this polyamic acid was 11,813 and the Mw was 37,191.

(Synthesis Example 3)
A1 (0.811 g, 7.50 mmol), WA-2 (0.946 g, 7.50 mmol), A2 (2.20 g, 9.00 mmol), A4 (2.39 g, 6.00 mmol), B1 (6.46 g, 28.8 mmol), and NMP (93.9 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 40°C for 20 hours to obtain a solution of polyamic acid (A-3) with a solids concentration of 12% by mass (viscosity: 399 mPa s). The Mn of this polyamic acid was 12,191 and the Mw was 38,811.

(Synthesis Example 4)
WA-2 (1.89 g, 15.0 mmol), A2 (2.20 g, 9.00 mmol), A4 (2.39 g, 6.00 mmol), B1 (6.46 g, 28.8 mmol), and NMP (94.9 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 40° C. for 20 hours to obtain a solution of polyamic acid (A-4) (viscosity: 369 mPa s) with a solids concentration of 12% by mass. The Mn of this polyamic acid was 11,304 and the Mw was 37,191.

(Synthesis Example 5)
A1 (0.811 g, 7.50 mmol), WA-3 (1.04 g, 7.50 mmol), A2 (2.20 g, 9.00 mmol), A4 (2.39 g, 6.00 mmol), B1 (6.39 g, 28.5 mmol), and NMP (94.1 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 40°C for 20 hours to obtain a solution of polyamic acid (A-5) with a solids concentration of 12% by mass (viscosity: 372 mPa s). The Mn of this polyamic acid was 12,492 and the Mw was 40,113.

(Synthesis Example 6)
WA-3 (2.07 g, 15.0 mmol), A2 (2.20 g, 9.00 mmol), A4 (2.39 g, 6.00 mmol), B1 (6.39 g, 28.5 mmol), and NMP (95.7 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 40° C. for 20 hours to obtain a solution of polyamic acid (A-6) (viscosity: 385 mPa s) with a solids concentration of 12% by mass. The Mn of this polyamic acid was 13,012 and the Mw was 40,200.

(Synthesis Example 7)
A1 (0.811 g, 7.50 mmol), WA-4 (1.26 g, 7.50 mmol), A2 (2.20 g, 9.00 mmol), A4 (2.39 g, 6.00 mmol), B1 (6.39 g, 28.5 mmol), and NMP (95.7 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 40°C for 20 hours to obtain a solution of polyamic acid (A-7) (viscosity: 370 mPa s) with a solids concentration of 12% by mass. The Mn of this polyamic acid was 11,028 and the Mw was 37,190.

(Synthesis Example 8)
WA-4 (2.52 g, 15.0 mmol), A2 (2.20 g, 9.00 mmol), A4 (2.39 g, 6.00 mmol), B1 (6.39 g, 28.5 mmol), and NMP (99.0 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 40° C. for 20 hours to obtain a solution of polyamic acid (A-8) (viscosity: 360 mPa s) with a solids concentration of 12% by mass. The Mn of this polyamic acid was 10,221 and the Mw was 36,821.

(Synthesis Example 9)
A1 (0.487 g, 4.50 mmol), WA-1 (0.613 g, 4.50 mmol), A2 (2.20 g, 9.00 mmol), A4 (2.39 g, 6.00 mmol), A3 (1.92 g, 6.00 mmol), B1 (6.42 g, 28.7 mmol), and NMP (102 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 40° C. for 20 hours to obtain a solution of polyamic acid (A-9) with a solids concentration of 12% by mass (viscosity: 409 mPa s). The Mn of this polyamic acid was 13,001 and the Mw was 40,012.

(Synthesis Example 10)
WA-1 (1.23 g, 9.00 mmol), A2 (2.20 g, 9.00 mmol), A4 (2.39 g, 6.00 mmol), A3 (1.92 g, 6.00 mmol), B1 (6.46 g, 28.8 mmol), and NMP (104 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 40°C for 20 hours to obtain a solution of polyamic acid (A-10) (viscosity: 415 mPa s) with a solids concentration of 12% by mass. The Mn of this polyamic acid was 12,948 and the Mw was 40,889.

(Synthesis Example 11)
A1 (0.487 g, 4.50 mmol), WA-3 (0.622 g, 4.50 mmol), A2 (2.20 g, 9.00 mmol), A4 (2.39 g, 6.00 mmol), A3 (1.92 g, 6.00 mmol), B1 (6.42 g, 28.7 mmol), and NMP (102 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 40° C. for 20 hours to obtain a solution of polyamic acid (A-11) with a solids concentration of 12% by mass (viscosity: 419 mPa s). The Mn of this polyamic acid was 12,978 and the Mw was 41,048.

(Synthesis Example 12)
WA-3 (1.24 g, 9.00 mmol), A2 (2.20 g, 9.00 mmol), A4 (2.39 g, 6.00 mmol), A3 (1.92 g, 6.00 mmol), B1 (6.42 g, 28.7 mmol), and NMP (103 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 40° C. for 20 hours to obtain a solution of polyamic acid (A-12) (viscosity: 401 mPa s) with a solids concentration of 12% by mass. The Mn of this polyamic acid was 11,992 and the Mw was 39,171.

(Synthesis Example 13)
A1 (0.487 g, 4.50 mmol), WA-4 (0.757 g, 4.50 mmol), A2 (2.20 g, 9.00 mmol), A4 (2.39 g, 6.00 mmol), A3 (1.92 g, 6.00 mmol), B1 (6.39 g, 28.5 mmol), and NMP (103 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 40° C. for 20 hours to obtain a solution of polyamic acid (A-13) with a solids concentration of 12% by mass (viscosity: 398 mPa s). The Mn of this polyamic acid was 12,091 and the Mw was 42,039.

(Synthesis Example 14)
WA-4 (1.51 g, 9.00 mmol), A2 (2.20 g, 9.00 mmol), A4 (2.39 g, 6.00 mmol), A3 (1.92 g, 6.00 mmol), B1 (6.39 g, 28.5 mmol), and NMP (103 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 40°C for 20 hours to obtain a solution of polyamic acid (A-14) (viscosity: 366 mPa s) with a solids concentration of 12% by mass. The Mn of this polyamic acid was 10,208 and the Mw was 35,029.

(Synthesis Example 15)
A6 (4.78 g, 24.0 mmol), A1 (0.649 g, 6.00 mmol), B2 (5.59 g, 28.5 mmol), and NMP (99.2 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at room temperature for 5 hours to obtain a solution of polyamic acid (A-15) (viscosity: 200 mPa s) with a solids concentration of 10% by mass. The polyamic acid had an Mn of 14,101 and an Mw of 43,911.

(Synthesis Example 16)
A5 (5.37 g, 18.0 mmol), A1 (1.30 g, 12.0 mmol), B2 (5.41 g, 27.6 mmol), and NMP (68.5 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at room temperature for 5 hours to obtain a solution of polyamic acid (A-16) (viscosity: 751 mPa s) with a solids concentration of 15% by mass. The polyamic acid had an Mn of 11,038 and an Mw of 37,102.

(Synthesis Example 17)
A5 (7.16 g, 24.0 mmol), A7 (1.19 g, 6.00 mmol), B2 (5.41 g, 27.6 mmol), and NMP (78.0 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at room temperature for 5 hours to obtain a solution of polyamic acid (A-17) (viscosity: 761 mPa s) with a solids concentration of 15% by mass. The Mn of this polyamic acid was 10,951 and the Mw was 38,322.

(Synthesis Example 18 (Comparative))
A1 (1.62 g, 15.0 mmol), A2 (2.20 g, 9.00 mmol), A4 (2.39 g, 6.00 mmol), B1 (6.39 g, 28.5 mmol), and NMP (92.4 g) were added to a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 40° C. for 20 hours to obtain a solution of polyamic acid (RA-1).

<Preparation of Liquid Crystal Alignment Agent>
Example 1
To the polyamic acid (A-1) solution (6.67 g) obtained in Synthesis Example 1, NMP (9.33 g), BCS (4.00 g), and AD-2 (0.112 g) were added, and the mixture was stirred at room temperature for 2 hours to obtain a liquid crystal aligning agent (V-1).

(Examples 2 to 14)
Except that the solution of polyamic acid used was the solution of (A-2) to (A-14), the same operation as in Example 1 was carried out to obtain liquid crystal alignment agents (V-2) to (V-14).

Example 15
To the polyamic acid (A-9) solution (5.30 g) obtained in Synthesis Example 9, the polyamic acid (A-15) solution (9.54 g) obtained in Synthesis Example 15, NMP (3.78 g), BCS (9.00 g), a 10 mass % NMP diluted solution of AD-1 (0.800 g), and a 1 mass % NMP diluted solution of AD-3 (1.59 g) were added, and the mixture was stirred at room temperature for 2 hours to obtain a liquid crystal aligning agent (V-15).

Example 16
To the polyamic acid (A-10) solution (5.30 g) obtained in Synthesis Example 10, the polyamic acid (A-15) solution (9.54 g) obtained in Synthesis Example 15, NMP (3.78 g), BCS (9.00 g), a 10 mass % NMP diluted solution of AD-1 (0.800 g), and a 1 mass % NMP diluted solution of AD-3 (1.59 g) were added, and the mixture was stirred at room temperature for 2 hours to obtain a liquid crystal aligning agent (V-16).

(Example 17)
To the polyamic acid (A-9) solution (5.30 g) obtained in Synthesis Example 9, the polyamic acid (A-16) solution (6.36 g) obtained in Synthesis Example 16, NMP (6.96 g), BCS (9.00 g), a 10 mass % NMP diluted solution of AD-1 (0.800 g), and a 1 mass % NMP diluted solution of AD-3 (1.59 g) were added, and the mixture was stirred at room temperature for 2 hours to obtain a liquid crystal aligning agent (V-17).

(Example 18)
To the polyamic acid (A-9) solution (5.30 g) obtained in Synthesis Example 9, the polyamic acid (A-17) solution (6.36 g) obtained in Synthesis Example 17, NMP (6.96 g), BCS (9.00 g), a 10 mass % NMP diluted solution of AD-1 (0.800 g), and a 1 mass % NMP diluted solution of AD-3 (1.59 g) were added, and the mixture was stirred at room temperature for 2 hours to obtain a liquid crystal aligning agent (V-18).

Example 19
To the polyamic acid (A-10) solution (5.30 g) obtained in Synthesis Example 10, the polyamic acid (A-16) solution (6.36 g) obtained in Synthesis Example 16, NMP (6.96 g), BCS (9.00 g), a 10 mass % NMP diluted solution of AD-1 (0.800 g), and a 1 mass % NMP diluted solution of AD-3 (1.59 g) were added, and the mixture was stirred at room temperature for 2 hours to obtain a liquid crystal aligning agent (V-19).

(Example 20)
To the polyamic acid (A-10) solution (5.30 g) obtained in Synthesis Example 10, the polyamic acid (A-17) solution (6.36 g) obtained in Synthesis Example 17, NMP (6.96 g), BCS (9.00 g), a 10 mass % NMP diluted solution of AD-1 (0.800 g), and a 1 mass % NMP diluted solution of AD-3 (1.59 g) were added, and the mixture was stirred at room temperature for 2 hours to obtain a liquid crystal aligning agent (V-20).

(Comparative Example 1)
NMP (9.33 g) and BCS (4.00 g) were added to the polyamic acid (RA-1) solution (6.67 g) obtained in Synthesis Example 18, and the mixture was stirred at room temperature for 2 hours to obtain a liquid crystal aligning agent (RV-1).

(Comparative Example 2)
NMP (9.33 g), BCS (4.00 g), and AD-2 (0.112 g) were added to the polyamic acid (RA-1) solution (6.67 g) obtained in Synthesis Example 18, and the mixture was stirred at room temperature for 2 hours to obtain a liquid crystal aligning agent (RV-2).

Using the liquid crystal alignment agent obtained above, an FFS drive liquid crystal cell was produced according to the following procedure, and various evaluations were carried out.
<Configuration of FFS Drive Liquid Crystal Cell>
A liquid crystal cell having the structure of an FFS mode liquid crystal display element was fabricated.
First, a substrate with electrodes was prepared. The substrate was a rectangular glass substrate measuring 30 mm x 50 mm and 0.7 mm thick. A solid-patterned ITO electrode, which constituted the counter electrode as the first layer, was formed on the substrate. A SiN (silicon nitride) film deposited by CVD (chemical vapor deposition) was formed on the first counter electrode as the second layer. The second SiN film had a thickness of 300 nm and functioned as an interlayer insulating film. A comb-shaped pixel electrode, formed by patterning an ITO film as the third layer, was placed on the second SiN film, forming two pixels, the first and second pixels. Each pixel measured 10 mm long and 5 mm wide. The first counter electrode and the third pixel electrode were electrically insulated by the action of the second SiN film.

The pixel electrode in the third layer has a comb-like shape in which multiple electrode elements, each 3 μm wide and bent at an interior angle of 160° in the center, are arranged in parallel at intervals of 6 μm, and each pixel has a first region and a second region separated by a line connecting the bent portions of the multiple electrode elements.
Next, the liquid crystal alignment agent obtained above was filtered through a filter with a pore size of 1.0 μm, and then spin-coated onto the prepared electrode-attached substrate (first glass substrate) and a glass substrate (second glass substrate) having a 4 μm-high columnar spacer and an ITO film formed on the backside. After drying for 2 minutes on a hot plate at 80 ° C, it was baked for 30 minutes in a hot air circulating oven at 230 ° C to form a coating film with a thickness of 100 nm. The coating surface was subjected to an alignment treatment by irradiating the ultraviolet light with a wavelength of 254 nm, linearly polarized with an extinction ratio of 26:1 through a polarizer, at the dose shown in each table, to obtain a substrate with a liquid crystal alignment film. The liquid crystal alignment film formed on the electrode-attached substrate was aligned so that the direction dividing the interior angle of the pixel bends was perpendicular to the alignment direction of the liquid crystal. The liquid crystal alignment film formed on the second glass substrate was aligned so that the alignment direction of the liquid crystal on the first glass substrate would coincide with the alignment direction of the liquid crystal on the second glass substrate when the liquid crystal cell was fabricated. The two substrates were combined into a pair, and a sealant (Mitsui Chemicals, Inc., XN-1500T) was printed on one substrate. The other substrate was then attached so that the alignment direction of the liquid crystal alignment film faces was 0°. The sealant was then cured to prepare an empty cell. Liquid crystal MLC-3019 (Merck) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain an FFS-driven liquid crystal cell. The resulting liquid crystal cell was then heated at 120°C for 1 hour and left overnight before being used for evaluation.

<Evaluation of in-plane contrast uniformity>
The variation in the twist angle of the liquid crystal cell was evaluated using an AxoStep manufactured by AXOMETRICS. The liquid crystal cell prepared as described above was placed on a measurement stage, and the distribution of circular retardance within the pixel plane was measured with no voltage applied, and 3σ, which is three times the standard deviation σ, was calculated. The smaller the 3σ value, the better the in-plane uniformity. As evaluation criteria, a 3σ value of less than 1.00 was rated as "excellent," a value of 1.00 to 1.15 was rated as "good," and a value of more than 1.15 was rated as "poor."
Table 3 shows the results of evaluations carried out on the liquid crystal display devices using the liquid crystal alignment agents of the above Examples and Comparative Examples.

<Evaluation of Liquid Crystal Alignment Stability>
An AC voltage of ±5 V at a frequency of 60 Hz was applied to the FFS-driven liquid crystal cell prepared above for 120 hours at a constant temperature of 60°C. The pixel electrode and counter electrode of the liquid crystal cell were then shorted and left at room temperature for one day. For the liquid crystal cell subjected to the above treatment, the deviation between the alignment direction of the liquid crystal in the first region of the pixel and the alignment direction of the liquid crystal in the second region was calculated as an angle when no voltage was applied. Specifically, the liquid crystal cell was placed between two polarizing plates arranged so that their polarization axes were perpendicular to each other. A backlight was turned on, and the alignment angle of the liquid crystal cell was adjusted to minimize the transmitted light intensity in the first region of the pixel. The rotation angle required to rotate the liquid crystal cell to minimize the transmitted light intensity in the second region of the pixel was then calculated. The smaller the rotation angle, the better the liquid crystal alignment stability. The evaluation criteria were: 0.10 or less was "excellent," 0.10 to 0.30 was "good," and 0.30 or more was "poor."
Table 3 shows the results of evaluations carried out on the liquid crystal display devices using the liquid crystal alignment agents of the above Examples and Comparative Examples.

As can be seen from Table 3 above, liquid crystal alignment films obtained from liquid crystal alignment agents using specific diamines WA-1 to WA-4 exhibited at least one of the following characteristics over a wide range of light exposure doses: high in-plane uniformity and high liquid crystal alignment stability, compared to liquid crystal alignment films obtained from liquid crystal alignment agents composed of diamine components that do not contain specific diamines.

By using the liquid crystal aligning agent of the present invention, it is possible to obtain a liquid crystal alignment film in which image retention caused by long-term AC driving is suppressed in IPS-driven and FFS-driven liquid crystal display elements. Therefore, it is expected to be used in liquid crystal display elements that require high display quality. These elements are also useful in liquid crystal displays for display purposes, dimming windows that control the transmission and blocking of light, optical shutters, etc.

The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2021-022830, filed on February 16, 2021, are hereby incorporated by reference as part of the disclosure of the specification of the present invention.

1: In-plane switching liquid crystal display element, 2: Comb electrode substrate, 2a: Base material, 2b: Linear electrode, 2c: Liquid crystal alignment film, 2d: Base material, 2e: Planar electrode, 2f: Insulating film, 2g: Linear electrode, 2h: Liquid crystal alignment film, 3: Liquid crystal, 4: Counter substrate, 4a: Liquid crystal alignment film, 4b: Base material, L: Electric field lines

Claims (20)

A liquid crystal aligning agent characterized by containing at least one polymer (A) selected from the group consisting of a polyimide precursor having a repeating unit (a1) represented by the following formula (1) and a repeating unit (a3) represented by the following formula (3) , and a polyimide which is an imidized product of the polyimide precursor:
In formula (1), 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 containing a fluorine atom, or a phenyl group, and at least one of R ₁ to R ₄ represents a group other than a hydrogen atom as defined above.
R and Z each independently represent a hydrogen atom or a monovalent organic group. _Y represents a divalent organic group represented by the following formula (H):
(In formula (H), R _a represents a hydroxy group, a halogen atom, or a monovalent organic group having 1 to 3 carbon atoms. a is an integer of 1 to 4. When there are multiple R _a's , they may be the same or different. * represents a bond.)
In formula (3), X3 _represents a tetravalent organic group, and _Y3 represents a divalent organic group having 6 to 30 carbon atoms and containing the group "-N(D)- (D represents a carbamate protecting group)" in the molecule. R and Z are defined as in formula (1) above. The liquid crystal aligning agent according to claim 1, wherein the monovalent organic group in formula (H) is an alkyl group, a halogenated alkyl group in which at least a portion of the hydrogen atoms on the alkyl group are substituted with halogen atoms, an alkoxy group, a halogenated alkoxy group in which at least a portion of the hydrogen atoms on the alkoxy group are substituted with halogen atoms, or an alkenyl group. The divalent organic group represented by the formula (H) is a divalent organic group represented by any one of the following formulas (h-1) to (h-16): A liquid crystal aligning agent according to claim 1 or 2.
(In formulas (h-1) to (h-16), * represents a bond.) The polymer (A) further comprises a repeating unit (a2) represented by the following formula (2): A polyimide precursor and a polyimide which is an imidized product of the polyimide precursor. The liquid crystal aligning agent according to any one of claims 1 to 3, wherein the polymer (A) is at least one polymer selected from the group consisting of:
(In formula (2), R ₁ to R ₄ , R, and Z have the same meanings as in formula (1). Y ₂ represents a divalent organic group represented by formula (O) below.)
(In formula (O), each Ar independently represents a benzene ring, a biphenyl structure, or a naphthalene ring. Any hydrogen atom on the ring of Ar may be replaced with a halogen atom or a monovalent organic group. _Q2 represents -( _CH2 ) _n- (n is 2 to 18) or a group in which a portion of the -( _CH2 ) _n- is replaced with -O-, -C(=O)-, or -O-C(=O)-. * represents a bond.) The divalent organic group represented by the formula (O) is a divalent organic group represented by any one of the following formulas (o-1) to (o-14):
(In formulas (o-1) to (o-14), * represents a bond. In formula (o-14), two m's are independent of each other.) The liquid crystal aligning agent according to any one of claims 1 to 5, wherein the polymer (A) is at least one polymer selected from the group consisting of polyimide precursors and polyimides which are imidized products of the polyimide precursors, further having the repeating unit (a2') represented by the following formula (2'):
(In formula (2') , X _{2 '} represents a tetravalent organic group, and Y _2' represents a divalent organic group represented by the following formula (O2). R and Z are defined as in the above formula (1).)
(In formula (O2), m is an integer of 0 to 2, and Ar _2′ represents an unsubstituted or substituted benzene ring. However, when m is 0, Ar _2′ represents an unsubstituted benzene ring, and when m is 1 or 2, each Ar _2′ independently represents either an unsubstituted benzene ring or a benzene ring in which any hydrogen atom on the benzene ring has been replaced with a halogen atom or a monovalent organic group. Q _2′ represents a single bond or —O—. * represents a bond. When there are multiple _{Ar 2′} and multiple Q _2′ , they may be the same or different.) The liquid crystal aligning agent according to claim 6, wherein the divalent organic group represented by the formula (O2) is a divalent organic group represented by any one of the following formulas (o2-1) to (o2-12):
(In formulas (o2-1) to (o2-12), * represents a bond.) The liquid crystal aligning agent according to any one of claims 1 to 7, wherein the polymer (A) contains the repeating unit (a1) and the imidized structural unit of the repeating unit (a1) in total in an amount of 10 to 95 mol% of all repeating units. The polymer (A) contains the repeating unit (a2) and the imidized structural unit of the repeating unit (a2) in a total amount of 10 to 90 mol% of all repeating units. The liquid crystal aligning agent according to any one of claims 4 to 8. The liquid crystal aligning agent according to claim 6, wherein the polymer (A) contains the repeating units (a1), (a2), (a2'), and their imidized structural units in total at 30 mol % or more of all repeating units. The liquid crystal alignment agent according to any one of claims 1 to 10, used in a liquid crystal alignment film for a photoalignment method. In the formula (3), Y ₃ The liquid crystal aligning agent according to any one of claims 1 to 11, wherein is a divalent organic group represented by any one of the following formulas (Y3-1) to (Y3-9):
In the formula (3), Y ₃ The liquid crystal aligning agent according to claim 12, wherein is a divalent organic group represented by the following formula (Y3-1):
A liquid crystal alignment film obtained from the liquid crystal aligning agent according to any one of claims 1 to 13 . A liquid crystal display device comprising the liquid crystal alignment film according to claim 14 . A method for producing a liquid crystal alignment film for a liquid crystal display element, comprising the following steps (1) to (3):
Step (1): A step of applying the liquid crystal aligning agent according to any one of claims 1 to 13 onto a substrate; Step (2): A step of baking the applied liquid crystal aligning agent; Step (3): A step of performing an alignment treatment on the film obtained in Step (2) as needed. The method for producing a liquid crystal alignment film according to claim 16 , wherein the alignment treatment is a photo-alignment treatment. The method for producing a liquid crystal alignment film according to claim 17 , wherein the radiation exposure dose in the photo-alignment treatment is 100 to 1,500 mJ/ ^cm² . The method for producing a liquid crystal alignment film according to any one of claims 16 to 18 , further comprising a step (4) of subjecting the film that has been subjected to the alignment treatment in the step (3) to a heat treatment at 50 to 300°C. 20. The method for producing a liquid crystal alignment film according to claim 16 , wherein the liquid crystal display element is an IPS driving type or an FFS driving type liquid crystal display element.