WO2021177113A1 - Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element - Google Patents

Abstract

Provided is a liquid crystal alignment agent that makes it possible to obtain a liquid crystal display element exhibiting superior liquid crystal alignment properties and improved contrast, in which in-plane variations in brightness are suppressed when displaying black.　Specifically provided is a liquid crystal alignment agent including at least one polymer (A) selected from among polyimide precursors having a repeating unit (a1) represented by formula (1) and a repeating unit (a2) represented by formula (2), and imidized polymers thereof. The details of the symbols are as defined in the description. (1) (Y₁ represents a divalent organic group expressed by formula (H).) (H) (Q₁ represents a C1-18 divalent organic group having the structure *1-NH-C(=O)-*1 or *1-NH-C(=O)-NH-*1. * represents a bond. *1 represents a bond to a carbon atom.) (2) (Therein, R₁-R₄, R and Z have the same definitions as in formula (1). Y₂ represents a divalent organic group represented by formula (O).) (O)

Description

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

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

Conventionally, liquid crystal display devices have been widely used as display units for personal computers, smartphones, mobile phones, televisions, and the like. A liquid crystal display device is usually a liquid crystal layer sandwiched between an element substrate and a color filter substrate, a pixel electrode and a common electrode that apply an electric field to the liquid crystal layer, an alignment film that controls the orientation of liquid crystal molecules in the liquid crystal layer, and pixels. It includes a thin film transistor (TFT) that switches the electrical signal supplied to the electrodes. As the driving method of the liquid crystal molecule, a vertical electric field method such as a TN method and a VA method, and a horizontal electric field method such as an IPS (In Plane Switching) method and an FFS (Fringe Field Switching) method are known.

The most widely used liquid crystal alignment film in the industry is a film formed on an electrode substrate and made of polyamic acid and / or polyimide imidized thereof in one direction with a cloth such as cotton, nylon, or polyester. It is manufactured by performing a so-called rubbing process of rubbing against. The rubbing process is a simple and highly productive industrially useful method. However, as the performance, definition, and size of the liquid crystal display element increase, the surface of the alignment film generated by the rubbing process is scratched, dusted, affected by mechanical force or static electricity, and in-plane of the alignment process. Various problems such as non-uniformity of the above have been clarified. As an orientation treatment method that replaces the rubbing treatment, a photo-alignment method that imparts a liquid crystal alignment ability by irradiating polarized radiation is known. As the photoalignment method, a method using a photoisomerization reaction, a method using a photocrosslinking reaction, a method using a photodecomposition reaction, and the like have been proposed (see Non-Patent Document 1, Patent Documents 1 and 2).

The liquid crystal alignment film, which is a constituent member of the liquid crystal display element, is a film for uniformly arranging liquid crystals, and the liquid crystal alignment is one of the important characteristics. However, the liquid crystal alignment film obtained by the above photo-alignment method tends to have a lower liquid crystal alignment than the liquid crystal alignment film obtained by the conventional rubbing treatment, and the applicable range of the liquid crystal display device provided with the liquid crystal alignment film is wide. It was limited.

Japanese Patent Application Laid-Open No. 9-297313 International Publication No. 2015/050135 Pamphlet

Further, in an actual liquid crystal display element, the twist angle slightly varies in the surface of the liquid crystal display element due to variations in manufacturing. Then, due to such in-plane variation, the brightness of the liquid crystal display element at the time of black display varies in the in-plane.
The present invention has been made in view of the above circumstances, and obtains a liquid crystal display element having high liquid crystal orientation, suppressing in-plane brightness variation during black display, and having improved contrast. One purpose is to provide a liquid crystal alignment agent capable of producing a liquid crystal alignment agent.

As a result of diligent research, the present inventor has found that the above problems can be solved by using a liquid crystal alignment agent containing a specific component, and has completed the present invention. Specifically, the following is the gist.

At least one selected from the group consisting of a polyimide precursor having a repeating unit (a1) represented by the following formula (1) and a repeating unit (a2) represented by the following formula (2) and an imidized polymer thereof. A liquid crystal alignment agent containing the polymer (A) of the seed.

(In the formula, R ₁ to R ₄ are independently hydrogen atom, halogen atom, alkyl group having 1 to 6 carbon atoms, alkenyl group having 2 to 6 carbon atoms, alkynyl group having 2 to 6 carbon atoms, and fluorine atom. Represents a monovalent organic group having 1 to 6 carbon atoms or a phenyl group containing, _{and at least one of R 1} to R ₄ represents a group other than the hydrogen atom in the above definition. R and Z are independent of each other. Represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Y ₁ represents a divalent organic group represented by the following formula (H).)

(Q ₁ represents a divalent organic group having 1 to 18 carbon atoms having * 1-NH-C (= O)-* 1 or * 1-NH-C (= O) -NH- * 1. * Represents a bond. * 1 represents a bond that bonds to a carbon atom.)

(In the formula, R ₁ to R ₄ , R and Z are synonymous with the above formula (1). Y ₂ represents a divalent organic group represented by the following formula (O).)

(Ar independently represents a benzene ring, a biphenyl structure, and a naphthalene ring, and at least one of the two Ars represents a naphthalene ring. Any hydrogen atom on the ring is a halogen atom or a monovalent organic group. _{Q 2} may be replaced with − (CH ₂ ) _n − (n is an integer of 2 to 18), or _{a part of − (CH 2} ) _n − above is −O−, −C ( = O)-or -OC (= O)-represents a group replaced by either. * Represents a bond.)
In the present specification, the "integer" in the case where it is obvious that it is an "integer" such as "n is an integer of 2 to 18" may be omitted. In any case, * represents a bond. Boc represents the tert-butoxycarbonyl group. Fmoc represents a 9-fluorenylmethyloxycarbonyl group.

According to the present invention, there is provided a liquid crystal display element having high liquid crystal orientation and excellent contrast in which variations in brightness in the plane during black display are suppressed, and a liquid crystal alignment agent capable of obtaining the same. ..

<Polymer (A)>
The liquid crystal alignment agent of the present invention is a polyimide precursor having a repeating unit (a1) represented by the following formula (1) and a repeating unit (a2) represented by the following formula (2), and an imidized polymer thereof. It contains at least one polymer (A) selected from the group consisting of. The polymer (A) may be composed of one type or two or more types. The polymer (A) is obtained because it has a hydrogen-bonding amide bond or a urea bond in the molecule by containing the repeating unit (a1) or the imidized structural unit of the repeating unit (a1). The heat resistance of the liquid crystal alignment film is increased, and the decrease in contrast due to the variation in the twist angle in the surface of the liquid crystal display element that occurs during manufacturing is suppressed. Further, by further containing the repeating unit (a2) or the imidized structural unit of the repeating unit (a2), a naphthalene skeleton having excellent heat resistance and liquid crystal orientation is contained in the molecule, so that a liquid crystal alignment film obtained can be obtained. The heat resistance and liquid crystal orientation of the liquid crystal display are increased, and a liquid crystal display element having excellent contrast can be obtained. Due to the above synergistic effect, a liquid crystal display element having high liquid crystal orientation and excellent contrast can be obtained from the liquid crystal alignment agent of the present invention.

(In the formula, R ₁ to R ₄ are independently hydrogen atom, halogen atom, alkyl group having 1 to 6 carbon atoms, alkenyl group having 2 to 6 carbon atoms, alkynyl group having 2 to 6 carbon atoms, and fluorine atom. Represents a monovalent organic group having 1 to 6 carbon atoms or a phenyl group containing, _{and at least one of R 1} to R ₄ represents a group other than the hydrogen atom in the above definition. R and Z are independent of each other. Represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Y ₁ represents a divalent organic group represented by the following formula (H).)

(Q ₁ represents a divalent organic group having 1 to 18 carbon atoms having * 1-NH-C (= O)-* 1 or * 1-NH-C (= O) -NH- * 1. * 1 represents a bond that bonds to a carbon atom.)

(In the formula, R ₁ to R ₄ , R and Z are synonymous with the above formula (1). Y ₂ represents a divalent organic group represented by the following formula (O).)

(Ar independently represents a benzene ring, a biphenyl structure, and a naphthalene ring, and at least one of the two Ars represents a naphthalene ring. Any hydrogen atom on the ring is a halogen atom or a monovalent organic group. _{Q 2} may be replaced with − (CH ₂ ) _n − (n is an integer of 2 to 18), or _{a part of − (CH 2} ) _n − above is −O−, −C ( = O)-or -OC (= O)-representing a group replaced by either.)

Specific examples of the alkyl groups having 1 to 6 carbon atoms in R ₁ to R ₄ are methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group and tert-butyl group. , N-pentyl group and the like. 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 butynyl group and the like, and these 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 and the like. Examples _{of the halogen atom in R 1} to R ₄ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom in _{R 1} to R _{4 include a fluoromethyl group and a trifluoromethyl group.} From the viewpoint of high photoreactivity, R ₁ to R ₄ are hydrogen atoms or methyl groups, preferably at least one of _{R 1} to R ₄ is a methyl group, and at least two of _{R 1} to R _{4 are methyl.} More preferably it is a group. More preferably, R ₁ and R ₃ are methyl groups and R ₂ and R ₄ are hydrogen atoms.
From the viewpoint of obtaining the effect of the present invention satisfactorily, _{at least one of R 1} to R ₄ represents a group other than the hydrogen atom in the above definition. With the above configuration, the photoreactivity of the polyimide film is increased, and the in-plane anisotropy of the obtained liquid crystal alignment film is increased. Therefore, the contrast due to the variation in the twist angle in the surface of the liquid crystal display element generated during manufacturing. The decrease is suppressed.

_{Q 1} in the formula (H) is, * 1-NH-C ( = O) - * 1 or * 1-NH-C (= O) -NH- * 1 a divalent 1-18 carbon atoms with Represents an organic group, among which -NH-C (= O)-, -NH-C (= O) -NH-, or * 1-NH-C (= O)-* 1 or * 1-NH-C ( = O) -A divalent organic group having 2 to 18 carbon atoms having -NH- * 1 is preferable. The definition of * 1 is the same as the definition in the above formula (H).
Specific examples of a divalent organic group having 2 to 18 carbon atoms having * 1-NH-C (= O)-* 1 or * 1-NH-C (= O) -NH- * 1 include carbon atoms. Of the 2 to 18 alkylene groups, _{a part of -CH 2-} possessed by the alkylene group is either * 1-NH-C (= O)-* 1 or * 1-NH-C (= O) -NH- * 1. some are -O - - -CH ₂ in which the divalent organic group having a carbon number that was replaced 2 ~ 18 (a1), the divalent organic group (a1) having at or, - C (= O) O A divalent organic group (a2) having 2 to 18 carbon atoms replaced with at least one group selected from the group consisting of-, -C = C-, -C≡C-, a cyclohexylene group and a phenylene group. Can be mentioned. _{Among these, from the viewpoint of obtaining the effect of the present invention satisfactorily, a part of -CH 2-} possessed by the divalent organic group (a1) or the divalent organic group (a1) is replaced with -O-. Group is preferred.

The divalent organic group represented by the above formula (H) is a divalent organic group represented by any of the following formulas (h-1) to (h-6) from the viewpoint of obtaining the effect of the present invention satisfactorily. Organic groups are preferred.

Any hydrogen atom on the ring of Ar in the above formula (O) is 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, and a fluorine atom. It may be replaced with a monovalent organic group such as a monovalent organic group having 1 to 6 carbon atoms containing. Specific examples of these monovalent organic groups include the structures exemplified in _{R 1} to R _{4 above.}
As a specific example of the divalent organic group represented by the above formula (O), the divalent organic group represented by any of the following formulas (o-1) to (o-6) from the viewpoint of enhancing the liquid crystal orientation. Organic groups are preferred.

The polymer (A) is a group consisting of a polyimide precursor having a repeating unit (a2') represented by the following formula (2') and an imidized polymer thereof from the viewpoint of obtaining the effect of the present invention satisfactorily. It may be at least one polymer selected from.

(X _{2 'represents} a tetravalent organic group, Y _2' is .R representing a divalent organic group represented by the following formula (O2), Z is as defined in the above formula (1).)

(Ar 2 _'represents a benzene ring, any hydrogen atom on the ring may be substituted with halogen atom or a monovalent organic group .Q _2' is a single bond, -O -, - C (= O)-, -OC (= O)-,-(CH ₂ ) _n- (n is 2 to 18), or _{a part of- (CH 2} ) _n- above-O-,- C (= O) - or -O-C (= O) - .Ar 2 is .m represents a group replaced by any one of a 0 ~ _{2 ',} Q _2' if there are a plurality, in each identical It may be different.)

The X 2 _', other tetravalent organic group represented by the following formula (g), the tetravalent organic group represented by any one of the following formulas (X-1) ~ (X -25), aromatic Examples thereof include a tetravalent organic group derived from a group tetracarboxylic acid dianhydride.

_{(R 1, R 2, R 3} , R 4 have the same meaning as _{R 1, R 2, R 3} , R 4 in the formula (1).)

Here, the aromatic tetracarboxylic dianhydride is an acid dianhydride obtained by intramolecular dehydration of a carboxy group bonded to an aromatic ring such as a benzene ring or a naphthalene ring. To give a specific example, a tetravalent organic group represented by any of the following formulas (Xa-1) to (Xa-2) and a table according to any of the following formulas (Xr-1) to (Xr-7). The tetravalent organic group to be used can be mentioned.

(X and y are independently single bonds, ethers, carbonyls, esters, alkanediyl groups with 1 to 10 carbon atoms, 1,4-phenylene, sulfonyl or amide groups. J and k are 0 or 1 respectively. Is.)

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

Any hydrogen atom on the ring of Ar 2 _'in the formula (O2) is 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, fluorine It may be replaced with a monovalent organic group such as a monovalent organic group having 1 to 6 carbon atoms containing an atom. Specific examples of these monovalent organic groups include the structures exemplified in _{R 1} to R _{4 above.}
The divalent organic group represented by the above formula (O2) is a divalent organic group represented by any of the following formulas (o2-1) to (o2-11) from the viewpoint of less generation of AC afterimage. Is preferable.

The polymer (A) is made from a polyimide precursor having a repeating unit (a3) represented by the following formula (3) and an imidized polymer thereof from the viewpoint of enhancing adhesion to a sealant and voltage holding characteristics. It may be at least one polymer selected from the group.

(In the formula, R and Z are synonymous with the above formula (1). X ₃ represents a tetravalent organic group, and Y ₃ represents the group "-N (D)-(D represents a carbamate protecting group). It represents a divalent organic group having 6 to 30 carbon atoms having ".)" In the molecule.)

Specific examples of X _3, include tetravalent organic groups exemplified above X _{2 '.} Effect from the viewpoint of obtaining good of the present invention, X ₃ is represented by any one tetravalent organic group represented by the above formula (g), or the formula (X-1) ~ (X -25) It is preferably a tetravalent organic group, and more preferably a tetravalent organic group represented by the above formula (g).

Group in Y ₃ "-N (D) - (. D is representative of the carbamate protecting group)" Specific examples of the divalent organic group having 6 to 30 carbon atoms having in the molecule is represented by the following formula (3 Examples thereof include a divalent organic group having a partial structure represented by 1) or a divalent organic group represented by the following formula (3-2).

In the formula, Q ₅ is a single bond,-(CH ₂ ) _n- (n is 1 to 20), or any -CH _{2- of the-(CH 2} ) _n- is -O-, -COO-. _{, -OCO -, - NQ 9 -} , - NQ 9 CO -, - CONQ 9 -, - NQ 9 -CO-NQ 10 -, - NQ 9 -COO- or a group which is replaced by -O-COO- , Q ₉ and Q ₁₀ independently represent a hydrogen atom or a monovalent organic group, respectively.
Q ₆ and _{Q 7} each independently represent _{-H, -NHD, -N (D)} 2, a group having a -NHD, a group having a -N _{(D) 2.} Q ₈ represents -NHD, _-N (D) 2, a group having a -NHD, a group having a -N _{(D) 2.} D represents a carbamate-based protecting group, and examples of the carbamate-based protecting group include a tert-butoxycarbonyl group and a 9-fluorenylmethoxycarbonyl group. Provided _that at least one of Q 5, _{Q 6} and _{Q 7} have the carbamate protecting group in the radical.

A preferable specific example of Y ₃ is a divalent organic group represented by any of the following formulas (Y3-1) to (Y3-5) from the viewpoint of having less AC afterimage.

In addition to the repeating unit (a1), the repeating unit (a2), the repeating unit (a2'), and the repeating unit (a3), the polymer (A) is a repeating unit (a4) represented by the following formula (4). It may be at least one polymer selected from the group consisting of a polyimide precursor having the above and an imidized polymer thereof.

In the formula, X ₄ represents a tetravalent organic group and Y ₄ represents a divalent organic group. R and Z are synonymous with R and Z in the above formula (1), respectively. However, Y ₄ is represented by a divalent organic group having 6 to 30 carbon atoms or the above formula (O2) having a group "-N (D)-(D represents a carbamate-based protecting group)" in the molecule. _{If X 4} represents a structure other than the divalent organic group and X 4 is synonymous with the tetravalent organic group represented by the above formula (g), Y ₄ is the divalent represented by the above formula (H). Represents a structure other than the divalent organic group represented by the above formula (O). Specific examples of X ₄ include the structure illustrated in _{X 3.}

Examples of X _4, include tetravalent organic groups exemplified above X _{2 '.} The effect of the present invention from the viewpoint of obtaining good, X ₄ is represented by any one tetravalent organic group represented by the above formula (g), or the formula (X-1) ~ (X -25) A tetravalent organic group is preferable, and a tetravalent organic group represented by the above formula (g) is more preferable.

Specific examples of the divalent organic group Y _4, divalent organic group represented by the above formula (H), the divalent organic group represented by the formula (O), by the formula (O2) A divalent organic group represented, or a divalent organic group having 6 to 30 carbon atoms having the group "-N (D)-(D represents a carbamate-based protective group)" in the molecule, according to the following formula ( In addition to the divalent organic group represented by any of g-1) to (g-5), the divalent organic group derived from diamine described below (divalent obtained by removing two amino groups from diamine). Organic group).
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, provided with the above secondary amino group and the third amino group. In the tertiary amino group, the amino group does not bind to a carbamate-based protective group), a diamine, 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diamino. Benzyl alcohol, 4,6-diaminoresorcinol, 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid or 3,5-diaminobenzoic acid, represented by the following formulas (3b-1) to (3b-4). Diamine having a carboxy group such as a diamine compound, 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, methacrylic acid Diamines having photopolymerizable groups such as 2- (2,4-diaminophenoxy) ethyl, 2,4-diamino-N, N-diallylaniline at the ends, cholestaniloxy-3,5-diaminobenzene, cholestenyloxy -3,5-diaminobenzene, cholestanyloxy-2,4-diaminobenzene, cholestanyl 3,5-diaminobenzoate, cholestenyl 3,5-diaminobenzoate, lanostenyl 3,5-diaminobenzoate, 3,6- Diamine having a steroid skeleton such as bis (4-aminobenzoyloxy) cholesterol, diamine represented by any of the following formulas (V-1) to (V-6), 1,3-bis (3-aminopropyl) -A diamine having a siloxane bond such as tetramethyldisiloxane, a divalent organic group derived from a diamine such as a diamine having an oxazoline ring structure such as the following formulas (Ox-1) to (Ox-2), International Publication 2018 / A group represented by any of the formulas (Y-1) to (Y-167) described in No. 117239.

(In the above ^{(3b-1), A} 1 is 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 are independently 0-4, and m1 + m2 are 1-4. In equation (3b-2), m3 and m4 is independently 1 to 5. In the formula (3b-3), A ² represents a linear or branched alkyl group having 1 to 5 carbon atoms, and m5 is 1 to 5. -4) in, ^{A 3} and ^{A 4} are each independently 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- _{, -CO-N (CH 3)} - or _-N (CH 3) -CO- indicates, m6 is the 1-4).

(In the above formulas (V-1) to (V-6), X ^v1 to X ^v4 and X ^p1 to X ^p2 are independently − (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 is single bond, -O-, -NH-, -O- (CH ₂ ). _{Indicates m-} O- (m is 1 to 6), and R ^v1 to R ^v4 and R ^1a to R ^1b are independently alkyl groups having 1 to 20 carbon atoms and alkoxy groups having 1 to 20 carbon atoms, respectively. Indicates a group or an alkoxyalkyl group having 2 to 20 carbon atoms.

Examples of the nitrogen atom-containing heterocycle include pyrrole, imidazole, pyrazole, triazole, pyridine, pyrimidine, pyridazine, pyrazine, indole, benzoimidazole, purine, quinoline, isoquinoline, naphthylidine, quinoxaline, phthalazine, triazine, carbazole, aclysine, and the like. Examples thereof include piperidine, piperazine, pyrrolidine, hexamethyleneimine and the like. Of these, pyridine, pyrimidine, pyrazine, piperidine, piperazine, quinoline, carbazole or acridine are preferable.

The secondary amino group and the 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 that binds to a hydrocarbon group.
Examples of the monovalent hydrocarbon group of R in the above formula (n) include an alkyl group such as a methyl group, an ethyl group and a propyl group; a cycloalkyl group such as a cyclohexyl group; and an aryl such as a phenyl group and a methylphenyl group. Group etc. can be mentioned. R is preferably a hydrogen atom or a methyl group.

Specific examples of the amine having a nitrogen atom-containing structure include 2,6-diaminopyridine, 3,4-diaminopyridine, 2,4-diaminopyrimidine, 3,6-diaminocarbazole, and N-methyl-3,6. -Diaminocarbazole, 1,4-bis- (4-aminophenyl) -piperazin, 3,6-diaminoacridine, N-ethyl-3,6-diaminocarbazole, N-phenyl-3,6-diaminocarbazole, N, N'-bis (4-aminophenyl) -benzidine, N, N'-bis (4-aminophenyl) -N, N'-dimethylbenzidine, 4,4'-diaminodiphenylamine, N, N-bis (4-aminophenyl) Aminophenyl) -methylamine or a compound represented by any of the following formulas (z-1) to (z-28) can be mentioned.

(In the formula, Py represents a pyridine ring or a pyrimidine ring.)

From the viewpoint of obtaining the effect of the present invention satisfactorily, in the polymer (A), the total of the repeating unit (a1) and the imidized structural unit of the repeating unit (a1) is 1 to 40 mol% of all the repeating units. Is more preferable, and it is more preferably 1 to 35 mol%, further preferably 1 to 30 mol%. The total here includes the case where either the repeating unit (a1) or the imidized structural unit of the repeating unit (a1) is 0 mol%. In the following, the term "total" also includes the case where one or two or more of the constituent unit elements are 0 mol%.

From the viewpoint of obtaining the effect of the present invention satisfactorily, the total of the repeating unit (a1), the repeating unit (a2) and their imidized structural units of the polymer (A) is 5 mol% or more of all the repeating units. Is preferable, and more preferably 10 mol% or more.

From the viewpoint of obtaining the effect of the present invention satisfactorily, in the polymer (A), the total of the imidized structural units of the repeating unit (a2) and the repeating unit (a2) is 1 to 95 mol% of all the repeating units. Is preferable, and it is more preferably 1 to 90 mol%, further preferably 5 to 90 mol%.

From the viewpoint of obtaining the effect of the present invention satisfactorily, the total of the imidized structural units of the repeating unit (a3) and the repeating unit (a3) in the polymer (A) is 1 to 40 mol% of all the repeating units. It is preferably 1 to 30 mol%, more preferably 1 to 25 mol%.

<Polymer (B)>
In addition to the polymer (A), the liquid crystal alignment agent of the present invention may contain a polymer (B) that does not have both the repeating unit (a1) and the repeating unit (a2) in the same molecule. good. The polymer (B) may be composed of one type or two or more types. From the viewpoint of obtaining the effect of the present invention satisfactorily, the polymer (B) is selected from the group consisting of the repeating unit (b1) represented by the following formula (5) and the imidized structural unit of the repeating unit (b1). Examples thereof include polymers having at least one repeating unit. Further, the repeating unit constituting the polymer (B) may be composed of one type or two or more types.

(In the formula, X ₅ is a tetravalent organic group, Y ₅ is a divalent organic group, and Z has 1 to 1 to carbon atoms which may independently have a hydrogen atom and a substituent. An alkyl group of 10, an alkenyl group having 2 to 10 carbon atoms which may have a substituent, an alkynyl group having 2 to 10 carbon atoms which may have a substituent, a tert-butoxycarbonyl group, or a 9-fluorole. Represents a nylmethoxycarbonyl group. R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

The tetravalent organic group in the formula X _5, aliphatic Tetokarubon dibasic derived anhydrides tetravalent organic group, tetravalent organic group or an aromatic tetracarboxylic derived from alicyclic tetracarboxylic dianhydride tetravalent organic radical derived from a dianhydride and the like, tetravalent organic groups exemplified above X ₄ can be cited as specific examples. From the viewpoint of obtaining the effect of the present invention satisfactorily, X ₅ is represented by any of the above formulas (X-1) to (X-25), which is a tetravalent organic group represented by the above formula (g). A tetravalent organic group, a tetravalent organic group represented by any of the above formulas (Xa-1) to (Xa-2), or a table according to any of the above formulas (Xr-1) to (Xr-7). The tetravalent organic group (collectively referred to as a specific tetravalent organic group) is preferable.

Polymer (B) in view of obtaining good effects of the present invention, X ₅ is more than 5 mol% of all repeating units contained repeating units is the specific tetravalent organic group in the polymer (B) It is preferably contained, and more preferably 10 mol% or more.

Examples of the divalent organic group in the _{above formula Y 5} include the divalent organic group exemplified in the _{above Y 4.} In view afterimage from residual DC is small, diamine polymer (B) is that _{Y 5} has the above nitrogen atom-containing structure, 2,4-aminophenol, 3,5-di-aminophenol, 3,5-diamino benzyl alcohol, 2 selected from the group consisting of 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol, the divalent organic group derived from the diamine having the carboxy group, and the divalent organic group represented by the above formula (H) 2 It is preferably a polymer containing a repeating unit which is a valent organic group (collectively referred to as a specific divalent organic group).

Polymer (B) in terms afterimage from residual DC is small, it contains Y ₅ is 1 mol% or more of the total repeating units contained repeating units is the specific bivalent organic group into the polymer (B) However, it may contain 5 mol% or more.

From the viewpoint of less afterimages derived from residual DC, the content ratio of the polymer (A) and the polymer (B) is 10/90 to 90 in terms of the mass ratio of [polymer (A)] / [polymer (B)]. It may be / 10, 20/80 to 90/10, or 20/80 to 80/20.

<Method for producing polymer (A) and polymer (B)>
The polyimide precursor (polyamic acid ester, polyamic acid) which is the polymer (A) and the polymer (B) used in the present invention and the polyimide which is an imidized polymer thereof are described in, for example, International Publication WO2013 / 157586. It can be synthesized by a known method as described above.
Specifically, it is synthesized by reacting a diamine component and a tetracarboxylic acid derivative component in a solvent (polycondensation). Examples of the tetracarboxylic acid derivative component include tetracarboxylic acid dianhydride or a derivative thereof (tetracarboxylic acid dihalide, tetracarboxylic acid diester, or tetracarboxylic acid diester dihalide). When a part of the polymer (A) or (B) contains an amic acid structure, for example, a polymer having an amic acid structure (polyamic acid) by reacting a tetracarboxylic dianhydride component with a diamine component. Is obtained. The solvent is not particularly limited as long as the produced polymer dissolves.

The diamine component and the tetracarboxylic acid derivative component for obtaining the polyimide precursor of the polymer (A) are the above-mentioned formulas (1), (2), and (2'), respectively, which the polymer (A) has. Depending on the repeating unit represented by the formulas (3) and (4), the structure of the repeating unit is selected and used.
For example, when the polymer (A) has a repeating unit represented by the formula (1), the diamine component has a structure of -N (Z) -Y _1- N (Z)-(Y ₁ , 1, A diamine having (the definition of Z is the same as above) is used, and as the tetracarboxylic acid derivative component, the structure of the following formula (g) ( _{the definition of R 1} to R ₄ is the same as above). ) Is used.

The polyamic acid ester is, for example, [I] a method of reacting the polyamic acid obtained by the above method with an esterifying agent, [II] a method of reacting a tetracarboxylic acid diester with a diamine, and [III] a method of reacting a tetracarboxylic acid. It can be obtained by a known method such as a method of reacting a diester dihalide with a diamine.
Examples of the method for obtaining polyimide include thermal imidization in which a solution containing a polyimide precursor such as a polyamic acid or a polyamic acid ester obtained in the above reaction is heated as it is, or catalytic imidization in which a catalyst is added to the solution.

<Solution viscosity / molecular weight of polymer>
The polyamic acid, polyamic acid ester, and polyimide used in the present invention preferably have a solution viscosity of, for example, 10 to 1000 mPa · s when the solution is prepared at a concentration of 10 to 15% by mass, from the viewpoint of workability. , Not particularly limited. The solution viscosity (mPa · s) of the polymer is a polymer having a concentration of 10 to 15% by mass prepared by using a good solvent of the polymer (for example, γ-butyrolactone, N-methyl-2-pyrrolidone, etc.). It is a value measured at 25 ° C. with an E-type rotational viscometer for the solution.
The polystyrene-equivalent weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) of the polyamic acid, polyamic acid ester and polyimide is preferably 1,000 to 500,000, more preferably 2,000. ~ 300,000. The molecular weight distribution (Mw / Mn) represented by the ratio of Mw to the polystyrene-equivalent number average molecular weight (Mn) measured by GPC is preferably 15 or less, more preferably 10 or less. Within such a molecular weight range, good orientation and stability of the liquid crystal display element can be ensured.

<Liquid crystal alignment agent>
The liquid crystal alignment agent of the present invention contains a polymer (A) and, if necessary, a polymer (B). The liquid crystal alignment agent of the present invention may contain other polymers in addition to the polymer (A) and the polymer (B). Examples of other types of polymers include polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivatives, polyacetal, polystyrene or derivatives thereof, poly (styrene-phenylmaleimide) derivatives, poly (meth) acrylates, and the like.

The liquid crystal alignment agent is used for producing a liquid crystal alignment film, and takes the form of a coating liquid from the viewpoint of forming a uniform thin film. The liquid crystal alignment agent of the present invention is also preferably a coating liquid containing the above-mentioned polymer component and an organic solvent. At that time, the concentration of the polymer in the liquid crystal alignment agent can be appropriately changed by setting the thickness of the coating film to be formed. From the viewpoint of forming a uniform and defect-free coating film, 1% by mass or more is preferable, and from the viewpoint of storage stability of the solution, 10% by mass or less is preferable. A particularly preferable concentration of the polymer is 2 to 8% by mass.

The organic solvent contained in the liquid crystal alignment agent is not particularly limited as long as the polymer component is uniformly dissolved. Specific examples thereof include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ-butyrolactone, 1,3-dimethyl-2. -Imidazolidinone, methylethylketone, cyclohexanone, cyclopentanone, 3-methoxy-N, N-dimethylpropanamide, 3-butoxy-N, N-dimethylpropanamide (collectively referred to as "good solvent"), etc. Can be mentioned. Of these, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 3-methoxy-N, N-dimethylpropanamide, 3-butoxy-N, N-dimethylpropanamide or γ-butyrolactone are preferable. 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 amount of the solvent contained in the liquid crystal alignment agent. ..

The organic solvent contained in the liquid crystal alignment agent is a mixture of the above solvent and a solvent (also referred to as a poor solvent) that improves the coatability when the liquid crystal alignment agent is applied and the surface smoothness of the coating film. The use of a solvent is preferred. Specific examples of the poor solvent used in combination are described below, but the present invention is not limited thereto.
For example, diisopropyl ether, diisobutyl ether, diisobutylcarbinol (2,6-dimethyl-4-heptanol), ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, 1,2-butoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether. , 4-Hydroxy-4-methyl-2-pentanone, diethylene glycol methyl ethyl ether, diethylene glycol dibutyl ether, 3-ethoxybutyl acetate, 1-methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene Glycol monoacetate, ethylene glycol diacetate, propylene carbonate, ethylene carbonate, ethylene glycol monobutyl ether, ethylene glycol monoisoamyl ether, ethylene glycol monohexyl ether, propylene glycol monobutyl ether, 1- (2-butoxyethoxy) -2- Propanol, 2- (2-butoxyethoxy) -1-propanol, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monobutyl ether acetate, ethylene glycol mono Acetate, ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2- (2-ethoxyethoxy) ethyl acetate, diethylene glycol acetate, propylene glycol diacetate, n-butyl acetate, propylene acetate Glycol monoethyl ether, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, propyl 3-methoxypropionate, butyl 3-methoxypropionate, n-butyl lactate, isoamyl lactate, diethylene glycol mono Ethyl ether, diisobutyl ketone (2,6-dimethyl-4-heptanone) and the like can be mentioned.

Among them, diisobutylcarbinol, propylene glycol monobutyl ether, propylene glycol diacetate, diethylene glycol diethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monobutyl ether, ethylene. Glycol monobutyl ether acetate or diisobutyl ketone is preferred.

The content of the poor solvent is preferably 1 to 80% by mass, more preferably 10 to 80% by mass, and particularly preferably 20 to 70% by mass, based on the total amount of the solvent contained in the liquid crystal alignment agent. The type and content of the poor solvent are appropriately selected according to the coating apparatus for the liquid crystal alignment agent, coating conditions, coating environment, and the like.
Preferred solvent combinations of a good solvent and a poor solvent include N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone and ethylene glycol monobutyl ether, and N-methyl-2-. Pyrrolidone and γ-butyrolactone and propylene glycol monobutyl ether, N-ethyl-2-pyrrolidone and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone and γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone and diethylene glycol diethyl Ether, N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether and diisobutylketone, N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether and diisopropyl ether, N-methyl-2-pyrrolidone γ-Butylollactone and propylene glycol monobutyl ether and diisobutylcarbinol, N-methyl-2-pyrrolidone and γ-butyrolactone and dipropylene glycol dimethyl ether, N-methyl-2-pyrrolidone and propylene glycol monobutyl ether and dipropylene glycol dimethyl ether, etc. be able to.

The liquid crystal alignment agent of the present invention may additionally contain a component other than the polymer component and the organic solvent (hereinafter, also referred to as an additive component). Such additive components include an adhesion aid for increasing the adhesion between the liquid crystal alignment film and the substrate and the adhesion between the liquid crystal alignment film and the sealant, and a compound for increasing the strength of the liquid crystal alignment film (hereinafter, (Also referred to as a crosslinkable compound), a compound for promoting imidization, a dielectric for adjusting the dielectric constant and electrical resistance of the liquid crystal alignment film, a conductive substance, and the like.

As the crosslinkable compound, from the viewpoint of exhibiting good resistance to AC afterimage and highly improving film strength, an oxylanyl group, an oxetanyl group, a protected isocyanate group, a protected isothiocyanate group, a group containing an oxazoline ring structure, and a meldrum. It consists of a compound having at least one group selected from the group consisting of a group containing an acid structure, a cyclocarbonate group, and a group represented by the following formula (d), and a compound represented by the following formula (e). It may be at least one compound selected from the group (hereinafter, these are collectively referred to as compound (C)).

(In the formula (d), R ₂ and R ₃ are independently hydrogen atoms, alkyl groups having 1 to 3 carbon atoms, or "* -CH _2- OH". * Indicates that they are bonds. In formula (e), A represents a (m + n) valent organic group having an aromatic ring, R represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, m is 1 to 6, and n is 0. to 4 aromatic ring .A may be substituted with a monovalent group, specific examples of the monovalent group said the monovalent shown with substituents Ar 2 _'in the above formula (O2) Group is mentioned.)

Specific examples of the compound having an oxylanyl group include the compound described in paragraph [0037] of JP-A-10-338880 and the compound having a triazine ring as a skeleton described in WO2017 / 170483. Examples thereof include compounds having two or more oxylanyl groups. Of these, N, N, N', N'-tetraglycidyl-m-xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N', N'-tetra Glycidyl-4, 4'-diaminodiphenylmethane, N, N, N', N'-tetraglycidyl-p-phenylenediamine, compounds represented by any of the following formulas (r-1) to (r-3), etc. It may be a compound containing a nitrogen atom of.

Specific examples of the compound having an oxetanyl group include compounds having two or more oxetanyl groups described in paragraphs [0170] to [0175] of International Publication No. 2011/132751.
Specific examples of the compound having a protected isocyanate group include the compounds having two or more protected isocyanate groups described in paragraphs [0046] to [0047] of Japanese Patent Application Laid-Open No. 2014-224978, International Publication No. 2015/141598. Examples of the compound having three or more protected isocyanate groups described in paragraphs [0119] to [0120] of the above are compounds represented by any of the following formulas (bi-1) to (bi-3). You may.

Specific examples of the compound having a protected isothiocyanate group include compounds having two or more protected isothiocyanate groups described in Japanese Patent Application Laid-Open No. 2016-209488.
Specific examples of the compound having a group containing an oxazoline ring structure include compounds containing two or more oxazoline ring structures described in paragraph [0115] of Japanese Patent Application Laid-Open No. 2007-286597.

Specific examples of the compound having a group containing a Meldrum's acid structure include the compound having two or more Meldrum's acid structures described in International Publication No. WO2012 / 091088.
Specific examples of the compound having a cyclocarbonate group include the compounds described in WO2011 / 1555777.
_{Examples of the alkyl group having 1 to 3 carbon atoms of the groups R 2} and R ₃ represented by the above formula (d) include a methyl group, an ethyl group, a propyl group and an isopropyl group.

Specific examples of the compound having a group represented by the above formula (d) include the above formula (d) described in paragraph [0058] of International Publication No. WO2015 / 072554 and Japanese Patent Application Laid-Open No. 2016-118753. Examples thereof include compounds having two or more groups represented by, compounds described in Japanese Patent Application Laid-Open No. 2016-2000798, and compounds represented by any of the following formulas (hd-1) to (hd-8). It may be.

Examples of the (m + n) -valent organic group having an aromatic ring in A of the above formula (e) include an (m + n) -valent aromatic hydrocarbon group having 6 to 30 carbon atoms and an aromatic hydrocarbon group having 6 to 30 carbon atoms. Examples thereof include a (m + n) valent organic group bonded directly or via a linking group, and a (m + n) valent group having an aromatic heterocycle. Examples of the aromatic hydrocarbon group include benzene and naphthalene. Examples of the aromatic heterocycle include the structures exemplified by the above-mentioned nitrogen atom-containing heterocycle. Examples of the linking group include -NR- (R represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms), an alkylene group having 1 to 10 carbon atoms, or a group obtained by removing one hydrogen atom from the alkylene group. Examples thereof include a divalent or trivalent cyclohexane ring. Any hydrogen atom of the alkylene group may be substituted with an organic group such as a fluorine atom or a trifluoromethyl group. Examples of the alkyl group having 1 to 5 carbon atoms in R of the above formula (e) include specific examples of the alkyl group exemplified by _{R 1} to R _{4 in the above formula (1).}
Specific examples of the above formula (e) include compounds described in International Publication WO2010 / 074269, and compounds represented by any of the following formulas (e-1) to (e-10).

The above compound is an example of a crosslinkable compound, and is not limited thereto. For example, components other than the above disclosed in International Publication No. 2015/060357 on pages 53 [0105] to 55 [0116] can be mentioned. Moreover, you may combine two or more kinds of crosslinkable compounds.
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 with respect to 100 parts by mass of the polymer component contained in the liquid crystal aligning agent, and the crosslinking reaction proceeds. From the viewpoint of exhibiting good resistance to AC afterimages, the amount is more preferably 1 to 15 parts by mass.

Examples of the adhesion aid include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldiethoxymethylsilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, and N. -(2-Aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N -Ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropyltriethylenetriamine, N-trimethoxysilylpropyltriethylenetriamine, 10-trimethoxysilyl -1,4,7-triazadecane, 10-triethoxysilyl-1,4,7-triazadecane, 9-trimethoxysilyl-3,6-diazanonyl acetate, 9-triethoxysilyl-3,6-diaza Nonylacetate, N-benzyl-3-aminopropyltrimethoxysilane, N-benzyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane , N-bis (oxyethylene) -3-aminopropyltrimethoxysilane, N-bis (oxyethylene) -3-aminopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-) Epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p. -Styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxy Silane cups such as silane, tris- (trimethoxysilylpropyl) isocyanurate, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanoxidetriethoxysilane, etc. Ring agent can be mentioned. When a silane coupling agent is used, it should be 0.1 to 30 parts by mass with respect to 100 parts by mass of the polymer component contained in the liquid crystal alignment agent from the viewpoint of exhibiting good resistance to AC afterimages. It is preferably 0.1 to 20 parts by mass, more preferably 0.1 to 20 parts by mass.

Examples of the compound for promoting imidization include a basic site (eg: primary amino group, aliphatic heterocycle (eg, pyrrolidine skeleton), aromatic heterocycle (eg, imidazole ring, indole ring), or A compound having a guanidino group or the like (however, the crosslinkable compound and the adhesion aid are excluded), or a compound in which the basic moiety is generated during firing is preferable. More preferably, it is a compound in which the above-mentioned basic moiety is generated at the time of firing, and a preferable specific example is an amino acid in which a part or all of the basic moiety of the amino acid is protected. Specific examples of the above amino acids include glycine, alanine, cysteine, methionine, asparagine, glutamine, valine, leucine, phenylalanine, tyrosine, tryptophan, proline, hydroxyproline, arginine, histidine, lysine and ornithine. More preferred specific examples of the compound for promoting imidization include N-α- (9-fluorenylmethoxycarbonyl) -N-τ- (tert-butoxycarbonyl) -L-histidine.

<Manufacturing method of liquid crystal alignment film>
The method for producing a liquid crystal alignment film using the liquid crystal alignment agent of the present invention includes a step of applying the above liquid crystal alignment agent (step (1)) and a step of heating the applied liquid crystal alignment agent to obtain a film (step (2). )), The step (step (3)) of irradiating the film obtained in the step (2) with polarized ultraviolet rays, and the film obtained in the step (3) at 100 ° C. or higher and from the step (2). It is also characterized in that the step of firing at a high temperature (step (4)) is sequentially performed.

<Process (1)>
The substrate to which the liquid crystal alignment agent used in the present invention is applied is not particularly limited as long as it is a highly transparent substrate, and a glass substrate, a silicon nitride substrate, a plastic substrate such as an acrylic substrate or a polycarbonate substrate, or the like can also be used. At that time, it is preferable to use a substrate on which an ITO electrode or the like for driving the liquid crystal is formed, from the viewpoint of simplifying the process. Further, in the reflective liquid crystal display element, an opaque object such as a silicon wafer can be used if only one side of the substrate is used, and a material that reflects light such as aluminum can also be used for the electrode in this case.
The method for applying the liquid crystal aligning agent is not particularly limited, but industrially, a method such as screen printing, offset printing, flexographic printing, or an inkjet method is generally used. Other coating methods include a dip method, a roll coater method, a slit coater method, a spinner method, a spray method, and the like, and these may be used depending on the intended purpose.

<Process (2)>
The step (2) is a step of heating the liquid crystal alignment agent applied on the substrate to form a film. Specifically, the liquid crystal aligning agent applied on the substrate in the step (1) is evaporated by a heating means such as a hot plate, a heat circulation type oven or an IR (infrared) type oven, or is contained in a polymer. Thermal imidization of the amic acid or the amic acid ester of the above can be performed. The heating step of the liquid crystal alignment agent applied on the substrate in the step (1) can be performed at any temperature and time, and may be performed a plurality of times. The heating temperature can be, for example, 40 to 180 ° C., preferably 40 to 150 ° C., and more preferably 40 to 120 ° C. from the viewpoint of shortening the process. The heating time is not particularly limited, and examples thereof include 1 to 10 minutes or 1 to 5 minutes. When the amic acid or the amic acid ester in the polymer is thermally imidized, a step of heating in a temperature range of, for example, 190 to 250 ° C. or 200 to 240 ° C. can be performed after the above heating step. The heating time is not particularly limited, and examples thereof include a heating time of 5 to 40 minutes or 5 to 30 minutes.

<Process (3)>
The step (3) is a step of irradiating the film obtained in the step (2) with polarized ultraviolet rays. The wavelength of ultraviolet rays is preferably 200 to 400 nm, and more preferably ultraviolet rays having a wavelength of 200 to 300 nm. In order to improve the liquid crystal alignment, the substrate coated with the liquid crystal alignment film may be irradiated with ultraviolet rays while being heated at 50 to 250 ° C. The irradiation amount of the ultraviolet rays is preferably 1 ~ 10,000mJ / cm ^2, more preferably 100 ~ 5,000mJ / cm ^2. The liquid crystal alignment film thus produced can stably orient the liquid crystal molecules in a certain direction.
The higher the extinction ratio of polarized ultraviolet rays, the higher the anisotropy can be imparted, which is preferable. Specifically, the extinction ratio of linearly polarized ultraviolet rays is preferably 10: 1 or more, more preferably 20: 1 or more.

<Process (4)>
The step (4) is a step of firing the film obtained in the step (3) at 100 ° C. or higher and at a temperature higher than that of the step (2). The firing temperature is not particularly limited as long as it is 100 ° C. or higher and higher than the firing temperature in step (2), but is preferably 150 to 300 ° C., more preferably 150 to 250 ° C., and further preferably 200 to 250 ° C. preferable. The firing time is preferably 5 to 120 minutes, more preferably 5 to 60 minutes, and even more preferably 5 to 30 minutes.
If the thickness of the liquid crystal alignment film after firing is too thin, the reliability of the liquid crystal display element may decrease. Therefore, the thickness is preferably 5 to 300 nm, more preferably 10 to 200 nm.

Further, after performing any of the above steps (3) or (4), the obtained liquid crystal alignment film can be contact-treated with water or a solvent.
The solvent used for the contact treatment is not particularly limited as long as it is a solvent that dissolves the decomposition products generated from the liquid crystal alignment film by irradiation with ultraviolet rays. 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, 3-. Examples thereof include methyl methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate and cyclohexyl acetate. Of these, water, 2-propanol, 1-methoxy-2-propanol or ethyl lactate is preferable, and water, 1-methoxy-2-propanol or ethyl lactate is more preferable from the viewpoint of versatility and solvent safety. The solvent may be used alone or in combination of two or more.

Examples of the above-mentioned contact treatment, that is, treatment of water or a solvent on the liquid crystal alignment film irradiated with polarized ultraviolet rays, include immersion treatment and spray treatment (also referred to as spray treatment). The treatment time in these treatments is preferably 10 seconds to 1 hour from the viewpoint of efficiently dissolving the decomposition products generated from the liquid crystal alignment film by ultraviolet rays. Above all, it is preferable to carry out the immersion treatment for 1 to 30 minutes. The solvent used during the contact treatment may be heated at room temperature, but is preferably 10 to 80 ° C, more preferably 20 to 50 ° C. In addition, from the viewpoint of solubility of the decomposed product, ultrasonic treatment or the like may be performed as necessary.
After the contact treatment, it is preferable to rinse (also referred to as rinsing) with a low boiling point solvent such as water, methanol, ethanol, 2-propanol, acetone or methyl ethyl ketone or to calcin the liquid crystal alignment film. At that time, either one of rinsing and firing may be performed, or both may be performed. The firing temperature is preferably 150 to 300 ° C, more preferably 180 to 250 ° C, and even more preferably 200 to 230 ° C. The firing time is preferably 10 seconds to 30 minutes, more preferably 1 to 10 minutes.

<Liquid crystal alignment film>
The liquid crystal alignment film of the present invention is obtained from the above liquid crystal alignment agent.
The liquid crystal alignment film of the present invention is suitable as a liquid crystal alignment film for a transverse electric field type liquid crystal display element such as an IPS system or an FFS system, and is particularly useful as a liquid crystal alignment film for an FFS type liquid crystal display element.

<Liquid crystal display element>
The liquid crystal display element of the present invention includes the liquid crystal alignment film.
The liquid crystal display element is obtained by obtaining a substrate with a liquid crystal alignment film obtained from the liquid crystal alignment agent of the present invention, then producing a liquid crystal cell by a known method, and using the liquid crystal cell.
As an example of a method for manufacturing a liquid crystal cell, a liquid crystal display element having a passive matrix structure will be described as an example. A liquid crystal display element having an active matrix structure in which a switching element such as a TFT (Thin Film Transistor) is provided in each pixel portion constituting the image display may be used.

Specifically, a transparent glass substrate is prepared, and a common electrode is provided on one substrate and a segment electrode is provided on the other substrate. These electrodes can be, for example, ITO electrodes and are patterned so as to display a desired image. Next, an insulating film is provided on each substrate so as to cover the common electrode and the segment electrode. The insulating film can be, for example, a film of _{SiO 2-} TiO _{2 formed by the sol-gel method.}
Next, a liquid crystal alignment film is formed on each substrate, the other substrate is superposed on one substrate so that the liquid crystal alignment film surfaces face each other, and the periphery is bonded with a sealant. It is preferable that a spacer is usually mixed in the sealant in order to control the substrate gap, and that the spacer for controlling the substrate gap is also sprayed on the in-plane portion where the sealant is not provided. A part of the sealing agent is provided with an opening in which the liquid crystal can be filled from the outside. Next, the liquid crystal material is injected into the space surrounded by the two substrates and the sealant through the opening provided in the sealant, and then the opening is sealed with an adhesive. For injection, a vacuum injection method may be used, or a method utilizing a capillary phenomenon in the atmosphere may be used. As the liquid crystal material, either a positive type liquid crystal material or a negative type liquid crystal material may be used. Next, the polarizing plate is installed. Specifically, a pair of polarizing plates are attached to the surfaces of the two substrates opposite to the liquid crystal layer.

By using the manufacturing method of the present invention, afterimages due to long-term AC drive generated in the IPS drive type or FFS drive type liquid crystal display element can be suppressed. Further, in the step (2), the liquid crystal alignment film can be obtained in a smaller number of steps than in the conventional case by carrying out the step (3) after heating in the temperature range of 40 to 150 ° C. The liquid crystal alignment agent of the present invention is particularly preferably used in a method for producing a liquid crystal alignment film, which comprises a step of removing an organic solvent in a temperature range of 40 to 150 ° C. in step (2) and then carrying out step (3). Can be done.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. The abbreviations of the compounds and the method for measuring each property in the following are as follows.
(solvent)
NMP: N-methyl-2-pyrrolidone BCS: butyl cellosolve,
(Diamine)
DA-1 to DA-12: Compounds represented by the following formulas (DA-1) to (DA-12),
(Tetracarboxylic dianhydride)
CA-1 to CA-2: Compounds represented by the following formulas (CA-1) to (CA-2),
(Additive)
C-1: Compound represented by the following formula (C-1) S-1: Compound represented by the following formula (S-1),
F-1: Compound represented by the following formula (F-1)

<Measurement of imidization rate>
20 mg of polyimide powder was placed in an NMR sample tube (NMR sampling tube standard, φ5 (manufactured by Kusano Kagaku Co., Ltd.)) and deuterated dimethyl sulfoxide (DMSO-d 6,0.05% TMS (tetramethylsilane) mixture) (0. 53 mL) was added and ultrasonically applied to completely dissolve. This solution was measured for proton NMR at 500 MHz with an NMR measuring machine (JNW-ECA500) (manufactured by JEOL Datum Ltd.). The imidization rate is determined by using a proton derived from a structure that does not change before and after imidization as a reference proton, and the peak integrated value of this proton and the proton peak derived from the NH group of amic acid appearing in the vicinity of 9.5 ppm to 10.0 ppm. It was calculated by the following formula using the integrated value.
Imidization rate (%) = (1-α · x / y) × 100
In the above formula, x is the integrated proton peak value derived from the NH group of amic acid, y is the integrated peak value of the reference proton, and α is one NH group proton of the amic acid in the case of polyamic acid (imidization rate is 0%). It is the number ratio of the reference protons to.

[Example of polymer synthesis]
<Synthesis example 1>
In a 200 mL four-necked flask with a stirrer and a nitrogen inlet tube, weigh 9.34 g (38.3 mmol) of DA-1 and 1.60 g (6.75 mmol) of DA-3, and add 12 mass of NMP. The mixture was added so as to be%, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this diamine solution, 9.28 g (41.4 mmol) of CA-1 was added, NMP was added to a concentration of 12% by mass, and the mixture was stirred at 40 ° C. for 24 hours to obtain a polyamic acid solution. rice field.
35 g (9.3 mmol) of the obtained polyamic acid solution was taken in a 100 mL four-necked flask equipped with a stirrer and a nitrogen introduction tube, 11.7 g of NMP was added, and the mixture was stirred for 30 minutes. To the obtained solution, 2.86 g of acetic anhydride (3 equivalents of molar polyamic acid) and 0.74 g of pyridine (equal to molar polyamic acid) were added and heated at 55 ° C. for 3 hours for chemical imidization. went. The obtained reaction solution is poured into 150 mL of methanol with stirring, the precipitated precipitate is collected by filtration, the resin powder is washed by performing the same operation twice, and then dried under reduced pressure at 60 ° C. for 12 hours. As a result, a polyimide resin powder was obtained. The imidization rate of this polyimide resin powder was 71%. 3.60 g of the obtained polyimide resin powder was placed in a 100 mL Erlenmeyer flask, NMP was added so that the solid content concentration became 12%, and the mixture was stirred and dissolved at 70 ° C. for 24 hours to obtain a polyimide solution (PI-1). ..

<Synthesis Examples 2 to 11>
Polyimide solutions (PI-2) to (PI-12) were obtained in the same manner as in Synthesis Example 1 except that the type and amount of the monomers used were changed as shown in Table 1 below. The numerical values in parentheses in Table 1 represent the compounding ratio (molar portion) of each compound to 100 mol parts of the total amount of the tetracarboxylic acid derivative used in the synthesis for the tetracarboxylic acid component, and for the diamine component, The compounding ratio (molar part) of each compound with respect to 100 mol part of the total amount of diamine used for synthesis is shown. For the organic solvent, the blending ratio (parts by mass) of each organic solvent with respect to 100 parts by mass of the total amount of the organic solvents used for preparing the polyimide solution is shown.

<Synthesis Example 13>
2.69 g (9.0 mmol) of DA-6 and 7.17 g (36.0 mmol) of DA-11 were weighed in a 200 mL four-necked flask with a stirrer and a nitrogen introduction tube, and the concentration of NMP was 12 mass. The mixture was added so as to be%, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this diamine solution, 12.2 g (41.4 mmol) of CA-2 was added, NMP was added to a concentration of 12% by mass, and the mixture was stirred at 70 ° C. for 24 hours to prepare a polyamic acid solution (PAA). -1) was obtained.

[Preparation of liquid crystal alignment agent]
<Comparative example 1>
In a sample tube containing a stirrer, the solid content ratio of the polymer is the mass ratio of the polyimide solution (PI-1) obtained in Synthesis Example 1 and the polyamic acid solution (PAA-1) obtained in Synthesis Example 13. Mix at 50:50, add NMP and BCS to dilute, and add 1 part by mass of S-1, C-1 and F-1 to 100 parts by mass of the total polymer solid content. The mixture was added so as to have 10 parts by mass and 15 parts by mass, and the mixture was stirred for 30 minutes. After stirring, the mass ratio of the polymer solid content of polyimide (PI-1) and polyamic acid (PAA-1) is 50:50, the polymer solid content concentration is 6% by mass, and the solvent composition is NMP: BCS by mass ratio. A liquid crystal aligning agent (R1) at 80:20 was obtained.

<Comparative Examples 2 to 5, Examples 1 to 14>
The same method as in Comparative Example 1 was carried out except that the polymer components used were changed as shown in Table 2 below. (14) was obtained. In Table 2, the values in parentheses indicate the mixing ratio (parts by mass) of each polymer component or additive with respect to 100 parts by mass of the total of the polymer components used in the preparation of the liquid crystal alignment agent for the polymer and the additive, respectively. show. For the organic solvent, the blending ratio (parts by mass) of each organic solvent with respect to 100 parts by mass of the total amount of the organic solvents contained in the liquid crystal alignment agent is represented.

Using the liquid crystal alignment agent obtained as described above, an FFS-driven liquid crystal cell was prepared by the procedure shown below, and its characteristics were evaluated.

[FFS drive liquid crystal cell configuration]
The liquid crystal cell for the Fringe Field Switching (FFS) mode has a FOP (Finger on Plate) electrode layer formed on the surface thereof, which is composed of a surface-shaped common electrode, an insulating layer, and a comb-shaped pixel electrode. The glass substrate of No. 1 and the second glass substrate having a columnar spacer having a height of 3.5 μm on the front surface and an ITO film for preventing antistatic formation on the back surface were made into a set. The above pixel electrode has a comb tooth shape in which a plurality of electrode elements having a width of 3 μm bent at an internal angle of 160 ° are arranged in parallel with an interval of 6 μm, and one pixel has a comb tooth shape. It has a first region and a second region with a line connecting the bent portions of the plurality of electrode elements as a boundary.
The liquid crystal alignment film formed on the first glass substrate is oriented so that the direction of equally dividing the internal angle of the pixel bending portion and the orientation direction of the liquid crystal are orthogonal to each other, and the liquid crystal alignment film formed on the second glass substrate is formed. The film is oriented so that the orientation direction of the liquid crystal on the first substrate and the orientation direction of the liquid crystal on the second substrate coincide with each other when the liquid crystal cell is produced.

[Making a liquid crystal cell]
A liquid crystal alignment agent filtered through a 1.0 μm filter was applied to the surface of each of the above sets of glass substrates by spin coating, and dried on a hot plate at 80 ° C. for 2 minutes. Then, the coating film surface is irradiated with ultraviolet rays having a wavelength of 254 nm, which is linearly polarized with an extinction ratio of 26: 1 via a polarizing plate, at 150 to 350 mJ / cm ² , and then fired in a hot air circulation oven at 230 ° C. for 30 minutes to form a film. Two substrates with a liquid crystal alignment film having a thickness of 100 nm were obtained.
Next, a sealant was printed on one of the above-mentioned set of substrates with a liquid crystal alignment film, the other substrate was bonded so that the liquid crystal alignment film surfaces faced each other, and the sealant was cured to prepare an empty cell. A liquid crystal display (MLC-3019 manufactured by Merck & Co., Inc.) was vacuum-injected into this empty cell at room temperature by a vacuum injection method, and the injection port was sealed to obtain an FFS-driven liquid crystal cell. Then, the obtained liquid crystal cell was heated at 120 ° C. for 1 hour, left overnight, and then used for each evaluation.

<Evaluation of liquid crystal orientation>
Using the liquid crystal cell before the ISO treatment, the one with the initial flow orientation was defined as "defective", and the one without the initial flow orientation was defined as "good" for evaluation.
<Evaluation of in-plane uniformity of contrast>
The twist angle of the liquid crystal display element was evaluated using OPTIPRO-micro manufactured by Shintec. The produced liquid crystal cell was placed on the measurement stage, and the standard deviation was calculated by measuring 20 points in the first pixel plane in a state where no voltage was applied. The evaluation was performed by defining a twist angle standard deviation of 0.5 or more as "poor" and a twist angle of less than 0.5 as "good".

<Evaluation result>
Table 3 shows the evaluation results of the liquid crystal display elements obtained by using the liquid crystal alignment agents (1) to (14) and (R1) to (R5) obtained in Examples 1 to 14 and Comparative Examples 1 to 5. Shown in.

The liquid crystal alignment agent of the present invention is widely used for a vertical electric field type liquid crystal display element such as a TN method or a VA method, particularly a horizontal electric field type liquid crystal display element such as an IPS method or an FFS method.

The entire specification, claims and abstract of Japanese Patent Application No. 2020-039386 filed on March 6, 2020 and Japanese Patent Application No. 2020-12301 filed on July 17, 2020. The contents are cited here and incorporated as disclosure of the specification of the present invention.

Claims (15)

1. At least one selected from the group consisting of a polyimide precursor having a repeating unit (a1) represented by the following formula (1) and a repeating unit (a2) represented by the following formula (2) and an imidized polymer thereof. A liquid crystal alignment agent containing the polymer (A) of the seed.
   

   

   (In the formula, R ₁ to R ₄ are independently hydrogen atom, halogen atom, alkyl group having 1 to 6 carbon atoms, alkenyl group having 2 to 6 carbon atoms, alkynyl group having 2 to 6 carbon atoms, and fluorine atom. Represents a monovalent organic group having 1 to 6 carbon atoms or a phenyl group containing, _{and at least one of R 1} to R ₄ represents a group other than the hydrogen atom in the above definition. R and Z are independent of each other. Represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Y ₁ represents a divalent organic group represented by the following formula (H).)
   

   

   (Q ₁ represents a divalent organic group having 1 to 18 carbon atoms having * 1-NH-C (= O)-* 1 or * 1-NH-C (= O) -NH- * 1. * Represents a bond. * 1 represents a bond that bonds to a carbon atom.)
   

   

   (In the formula, R ₁ to R ₄ , R and Z are synonymous with the above formula (1). Y ₂ represents a divalent organic group represented by the following formula (O).)
   

   

   (Ar independently represents a benzene ring, a biphenyl structure, and a naphthalene ring, and at least one of the two Ars represents a naphthalene ring. Any hydrogen atom on the ring is a halogen atom or a monovalent organic group. _{Q 2} may be replaced with − (CH ₂ ) _n − (n is an integer of 2 to 18), or a part of the above − (CH ₂ ) _n − is −O−, −C ( = O)-or -OC (= O)-represents a group replaced by either. * Represents a bond.)
2. The divalent organic group represented by the formula (H) is a divalent organic group represented by any of the following formulas (h-1) to (h-6), according to claim 1. Liquid crystal alignment agent.
   

   
3. The divalent organic group represented by the formula (O) is a divalent organic group represented by any of the following formulas (o-1) to (o-6), according to claim 1 or 2. The liquid crystal alignment agent described.
   

   
4. The polymer (A) is at least one polymer selected from the group consisting of a polyimide precursor having a repeating unit (a2') represented by the following formula (2') and an imidized polymer thereof. , The liquid crystal alignment agent according to any one of claims 1 to 3.
   

   

   (X _{2 'represents} a tetravalent organic group, Y _2' is .R representing a divalent organic group represented by the following formula (O2), Z is the formula (1) as synonymous.)
   

   

   (Ar 2 _'represents a benzene ring, any hydrogen atom on the ring may be substituted with halogen atom or a monovalent organic group .Q _2' is a single bond, -O -, - C (= O)-, -OC (= O)-,-(CH ₂ ) _n- (n is an integer of 2 to 18), or a part of- _{(CH 2} ) _{n- above-O-} , -C (= O)-or -OC (= O)-represents a group replaced. M represents an integer of 0 to 2. * represents a bond. Ar _2' , Q. _{If there are multiple 2's} , they may be the same or different.)
5. The divalent organic group represented by the formula (O2) is a divalent organic group represented by any of the following formulas (o2-1) to (o2-11), according to claim 4. Liquid crystal alignment agent.
   

   
6. Claimed that the polymer (A) is at least one polymer selected from the group consisting of a polyimide precursor having a repeating unit (a3) represented by the following formula (3) and an imidized polymer thereof. Item 2. The liquid crystal alignment agent according to any one of Items 1 to 5.
   

   

   (In the formula, R and Z are synonymous with the above formula (1). X ₃ represents a tetravalent organic group, and Y ₃ represents the group "-N (D)-(D represents a carbamate protecting group). Represents a divalent organic group having 6 to 30 carbon atoms in the molecule. R and Z are synonymous with the above formula (1).
7. The liquid crystal alignment agent according to claim 6, wherein Y ₃ has a structure represented by any of the following formulas (Y3-1) to (Y3-5).
   

   

   (In each formula, Boc represents a tert-butoxycarbonyl group and * represents a bond.)
8. The liquid crystal alignment agent according to any one of claims 1 to 7, wherein the total of the repeating unit (a1) and the imidized structural unit of the repeating unit (a1) is 1 to 40 mol% of all the repeating units.
9. The liquid crystal alignment agent according to any one of claims 1 to 8, wherein the total of the repeating unit (a1), the repeating unit (a2) and their imidized structural units is 5 mol% or more of all the repeating units.
10. A liquid crystal alignment film obtained from the liquid crystal alignment agent according to any one of claims 1 to 9.
11. A liquid crystal display element including the liquid crystal alignment film according to claim 10.
12. A method for producing a liquid crystal alignment film, which comprises the following steps (1) to (3).
    Step (1): A step of applying the liquid crystal alignment agent according to any one of claims 1 to 9 onto a substrate.
    Step (2): A step of heating the liquid crystal alignment agent applied in the step (1) to obtain a film.
    Step (3): A step of irradiating the film obtained in step (2) with polarized ultraviolet rays.
13. The method for producing a liquid crystal alignment film according to claim 12, further comprising the following step (4).
    Step (4): A step of firing the film obtained in the step (3) at a temperature of 100 ° C. or higher and higher than that of the step (2).
14. The method for producing a liquid crystal alignment film according to claim 12, wherein the step (2) is a step of obtaining a film by heating in a temperature range of 40 to 180 ° C.
15. A liquid crystal display element provided with a liquid crystal alignment film obtained by the method for producing a liquid crystal alignment film according to any one of claims 12 to 14.