JP7729325B2 - Polyimide Varnish - Google Patents

Description

The present invention relates to a polyimide varnish that can suppress whitening due to moisture absorption and is suitable as a liquid crystal alignment agent, etc.

Due to its high mechanical strength, heat resistance, and solvent resistance, polyimides are widely used as protective and insulating materials in the electrical and electronic fields. Specifically, when used as an insulating film for semiconductors, a 1-10 μm thick polyimide film is formed on a silicon substrate with processed wiring. When used as a liquid crystal alignment film, a 0.05-0.2 μm thick polyimide film is formed on a transparent substrate with transparent electrodes. Thin polyimide films are typically formed on various support substrates. To form these polyimide films, a polyimide varnish, in which polyimide is dissolved in a suitable organic solvent, is applied to the substrate by methods such as spin coating, offset printing, gravure printing, flexographic printing, or inkjet printing, followed by a heat treatment of the resulting coating.

While polyimide has excellent properties as a variety of protective and insulating materials, it suffers from the drawback of poor solubility in organic solvents. Therefore, when dissolving polyimide in an organic solvent, highly soluble organic polar solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, and hexamethylphosphoramide are commonly used. However, while these solvents offer high solubility, they also suffer from the drawback of being highly hygroscopic.

Therefore, when a film is obtained using a polyimide varnish containing these organic solvents, the obtained film tends to be easily affected by the environment in which it is applied, etc. In particular, when the application is performed in a humid environment, the solubility of the composition decreases due to moisture absorption before heat treatment, causing polyimide precipitation and the film to turn white (moisture-absorption whitening). Furthermore, even if the film that has undergone moisture-absorption whitening is dried or heated, the original polyimide properties cannot be obtained, and the obtained film has a problem of surface roughness.
Furthermore, when a film is obtained by flexographic printing using a polyimide varnish, the polyimide component may precipitate on the flexographic printing plate, resulting in printing foreign matter, or the polyimide component may precipitate in the ejection head of an inkjet device, causing clogging of the head, leading to defects in the process.

As a method for suppressing the above-mentioned whitening due to moisture absorption and precipitation of polyimide components in polyimide varnish, it has been proposed to use a high-boiling solvent such as N-vinylpyrrolidone or N-cyclohexylpyrrolidone in an amount of 50% or more of the solvent (Patent Document 1). Also proposed is a method of adding a polyol compound having 3 to 15 carbon atoms and containing a tertiary nitrogen atom and a quaternary carbon atom to the polyimide varnish (Patent Document 2).

Japanese Patent Application Publication No. 5-117587 International Publication (WO) No. 2011/129414

In view of the above circumstances, the object of the present invention is to provide a polyimide varnish suitable as a liquid crystal alignment agent, etc., which can suppress the phenomenon of whitening due to moisture absorption, has little change in viscosity and excellent storage stability, is less likely to produce foreign matter or clogging when obtaining a film, and the obtained film has little surface roughness, and is able to retain the original properties of the polyimide material even after drying or heating.

As a result of intensive research to achieve the above-mentioned objectives, the inventors of the present invention discovered that the above-mentioned whitening phenomenon could be eliminated by increasing the water solubility of the polyimide in the varnish. They discovered that the whitening phenomenon due to moisture absorption could be suppressed by adding an amine compound having a secondary or tertiary amino group and a specific cyclic group to the polyimide varnish in order to increase the water solubility of the polyimide. However, they also discovered that if the amine compound is a primary amine compound, the viscosity of the varnish would be unstable and its storage stability would be significantly reduced.

The present invention is based on the above findings and has the following gist.
A polyimide varnish characterized by containing the following component (A) and component (B):
Component (A): Polyimide (A) which is an imidized product of a polyimide precursor.
Component (B): An amine compound (B) having, in the molecule, either a secondary amino group or a tertiary amino group and either a nitrogen-containing aromatic heterocyclic group or an aromatic hydrocarbon group as a cyclic group, wherein the amino group is bonded to an acyclic aliphatic hydrocarbon group or a non-aromatic cyclic hydrocarbon group.

According to the present invention, a polyimide varnish is provided which can suppress the phenomenon of whitening due to moisture absorption, has little change in viscosity and excellent storage stability, is less likely to produce foreign matter or clog the ejection head of an inkjet device when obtaining a film, and the obtained film has little surface roughness, and is able to retain the properties of the original polyimide material even after drying or heating.
The mechanism by which the above-described effects of the present invention are obtained is not entirely clear, but the following is thought to be one of the reasons.
Although polyimides are generally known to have low solubility, in the case of partially imidized polyimides, carboxylic acids derived from the tetracarboxylic dianhydrides remain, and it is possible to improve water solubility by forming a salt between the carboxylic acid and an amine. By forming a salt between the amine and the polyimide in this way, it is possible to suppress precipitation of the polyimide when the polyimide varnish absorbs moisture.
On the other hand, polyimides have an abundance of electrophilic carbonyl groups, making them susceptible to nucleophilic attack by nucleophiles such as aliphatic amine compounds. In particular, polyimides derived from aromatic tetracarboxylic dianhydrides tend to have a planar structure and little steric hindrance, making them more susceptible to nucleophilic attack by aliphatic amines. Therefore, from the perspective of ensuring minimal viscosity change and storage stability, it is preferable to use alicyclic and aliphatic tetracarboxylic dianhydrides as raw materials for polyimides. This approach reduces the risk of aliphatic amines acting as nucleophiles and undergoing nucleophilic addition to polyimides, resulting in a polyimide varnish with minimal viscosity change and high storage stability.
Furthermore, from the viewpoint of minimizing viscosity change and ensuring storage stability, it is preferable that the basicity of the polyimide varnish is low, and by adopting such an embodiment, it is possible to reduce the decrease in the molecular weight of the polyimide and the decrease in the viscosity of the polyimide varnish.
The amine compounds of the present invention having either a secondary amino group or a tertiary amino group in the molecule are unlikely to undergo nucleophilic attack due to large steric hindrance, but salt formation between the amine and a carboxylic acid does occur, which is thought to prevent precipitation of polyimide varnish due to moisture absorption.
The polyimide varnish of the present invention is suitable for use as a protective material, an insulating material, etc., typified by a liquid crystal alignment agent.

<Polyimide (A)>
The polyimide varnish of the present invention contains the following component (A):
Component (A): Polyimide (A) which is an imidized product of a polyimide precursor.
The polyimide (A) may be used alone or in combination of two or more.
The polyimide precursor is a precursor for producing a polyimide by the imidization reaction of a polyamic acid, a polyamic acid ester, or the like, and is preferably a polyamic acid obtained by the (polycondensation) reaction of a tetracarboxylic acid component containing a tetracarboxylic acid dianhydride or a derivative thereof with a diamine component. Examples of the derivative of the tetracarboxylic acid dianhydride include tetracarboxylic acid, tetracarboxylic acid dihalide, tetracarboxylic acid diester dichloride, and tetracarboxylic acid diester.

Various tetracarboxylic acid dianhydrides or derivatives thereof can be used as the tetracarboxylic acid dianhydride or its derivative. Examples of the tetracarboxylic acid dianhydride or derivative thereof include aromatic, acyclic aliphatic, or alicyclic tetracarboxylic acid dianhydrides, or derivatives thereof. Here, aromatic tetracarboxylic acid dianhydrides are acid dianhydrides obtained by intramolecular dehydration of four carboxy groups, including at least one carboxy group bonded to an aromatic ring. Acyclic aliphatic tetracarboxylic acid dianhydrides are acid dianhydrides obtained by intramolecular dehydration of four carboxy groups bonded to a chain hydrocarbon structure. However, they do not need to be composed solely of a chain hydrocarbon structure; they may partially contain an alicyclic structure or an aromatic ring structure. Furthermore, alicyclic tetracarboxylic acid dianhydrides are acid dianhydrides obtained by intramolecular dehydration of four carboxy groups, including at least one carboxy group bonded to an alicyclic structure. However, none of these four carboxy groups are bonded to an aromatic ring. Furthermore, they do not need to be composed solely of an alicyclic structure; they may partially contain a chain hydrocarbon structure or an aromatic ring structure.

In the present invention, from the viewpoint of ensuring minimal viscosity change and storage stability, it is preferable to use an acyclic aliphatic or alicyclic tetracarboxylic acid dianhydride or a derivative thereof as the tetracarboxylic acid derivative component. Among these, it is more preferable to include a tetracarboxylic acid dianhydride or a derivative thereof 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. Furthermore, the amount used is preferably 1 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more, based on 1 mol of the total tetracarboxylic acid derivative components used. When the tetracarboxylic acid derivative includes a tetracarboxylic acid dianhydride or a derivative thereof other than the above-mentioned tetracarboxylic acid dianhydrides and their derivatives, the upper limit is preferably 95 mol% or less, more preferably 90 mol% or less.

As the tetracarboxylic dianhydride or its derivative, it is particularly preferable to use the tetracarboxylic dianhydride or its derivative represented by the following formula (3):

In the above formula (3), X represents a structure selected from the group consisting of the following (x-1) to (x-13):

In the above formulas (x-1) to (x-13), R ¹ to R ⁴ each independently represent a hydrogen atom, a methyl group, an ethyl group, a propyl group, a chlorine atom, a fluorine atom, a monovalent organic group containing 1 to 6 carbon atoms and a fluorine atom, or a phenyl group. R ⁵ and R ⁶ each independently represent a hydrogen atom or a methyl group. j and k each independently represent an integer of 0 or 1, and A ₁ and A ₂ each independently represent a single bond, -O-, -CO-, -COO-, phenylene, a sulfonyl group, or an amide group. *1 represents a bond bonded to one acid anhydride group, and *2 represents a bond bonded to the other acid anhydride group. The two A _2s may be the same or different.
Among these, it is preferable that X is any one of the above formulae (x-1) to (x-7) and (x-11) to (x-13).

More preferred examples of the above formula (x-1) include the following formulas (x1-1) to (x1-6), where * represents a bond.

The proportion of the tetracarboxylic acid dianhydride represented by the formula (3) or a derivative thereof used is preferably 1 mol % or more, more preferably 5 mol % or more, and even more preferably 10 mol % or more, relative to 1 mol of the tetracarboxylic acid component used. When the tetracarboxylic acid derivative contains a tetracarboxylic acid dianhydride other than the tetracarboxylic acid dianhydride represented by the formula (3) or a derivative thereof, or a derivative thereof, the upper limit is preferably 95 mol % or less, more preferably 90 mol % or less.
The above tetracarboxylic dianhydrides or derivatives thereof may be used alone or in combination of two or more.

On the other hand, the diamine component for obtaining the polyamic acid is not particularly limited, and various diamines can be used.
In particular, in the present invention, when polyimide is used as a liquid crystal aligning agent for a vertical alignment mode, a diamine having at least one side chain structure selected from the group consisting of the following formulae (S1), (S2), and (S3) (hereinafter also referred to as a specific diamine) is preferably used as a diamine exhibiting high vertical alignment ability.

In the above formula (S1), ^X1 and ^X2 each independently represent a single bond, -( _CH2 ) _a- (where a is an integer of 1 to 15), -CONH-, -NHCO-, -CON( _CH3 )-, -NH-, -O-, -COO-, -OCO-, or -(( _CH2 ) _a1 - _A1 ) _m1- . Of these, a1 represents an integer of 1 to 15, _A1 represents an oxygen atom or -COO-, and _m1 is 1 or 2. From the viewpoint of availability of raw materials and ease of synthesis, _X1 and _X2 are each preferably independently a single bond, -( _CH2 ) _a- (a is an integer of 1 to 15), -O-, _-CH2O- or -COO-, and more preferably a single bond, -( _CH2 ) _a- (a is an integer of 1 to 10), -O-, _-CH2O- or -COO-.

_G1 and _G2 each independently represent a divalent cyclic group selected from a divalent aromatic group having 6 to 12 carbon atoms or a divalent alicyclic group having 3 to 8 carbon atoms. Any hydrogen atom on the cyclic group may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxy group having 1 to 3 carbon atoms, or a fluorine atom. m and n each independently represent an integer of 0 to 3, and the sum of m and n is 1 to 6, preferably 1 to 4.
Among these, examples of divalent aromatic groups having 6 to 12 carbon atoms include phenylene, biphenyl structures, naphthalene, etc. Furthermore, examples of divalent alicyclic groups having 3 to 8 carbon atoms include cyclopropylene, cyclohexylene, etc.

^R1 represents an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an alkoxyalkyl group having 2 to 20 carbon atoms. Any hydrogen atom forming ^R1 may be substituted with a fluorine atom.
When there are two or more of X ¹ , X ² , G ¹ , G ² , a1 and A ₁ , the two or more X ¹ , X ² , G ¹ , G ² , a1 and A ₁ may each independently be the same or different.

Preferred specific examples of the above formula (S1) include the following formulae (S1-x1) to (S1-x7).

In formulae (S1-x1) to (S1-x7), R ¹ represents an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an alkoxyalkyl group having 2 to 20 carbon atoms; X ^p represents -(CH ₂ ) _a - (a is an integer of 1 to 15), -CONH-, -NHCO-, -CON(CH ₃ )-, -NH-, -O-, -CH ₂ O-, -CH ₂ OCO-, -COO-, or -OCO-; A ₁ represents an oxygen atom or -COO-* (where the bond marked with "*" is bonded to (CH ₂ ) _a2 ); A ₂ represents an oxygen atom or *-COO- (where the bond marked with "*" is bonded to (CH ₂ ) _a2 ); a ₁ and a ₃ each independently represent an integer of 0 or 1; ₂ is an integer of 1 to 10, and Cy is a 1,4-cyclohexylene group or a 1,4-phenylene group.

In the above formula (S2), ^X3 represents a single bond, —CONH—, —NHCO—, —CON(CH ₃ )—, —NH—, —O—, —CH ₂ O—, —COO—, or —OCO—. Among these, —CONH—, —NHCO—, —O—, —CH ₂ O—, —COO—, or —OCO— is preferred from the viewpoint of liquid crystal alignment.
^R2 represents an alkyl group having 1 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms, and any hydrogen atom forming ^R2 may be substituted with a fluorine atom. Among them, from the viewpoint of liquid crystal alignment, an alkyl group having 3 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms is preferred.

In a preferred embodiment of formula [S2], X ³ is any of —O—, —CH ₂ O—, —COO—, and —OCO—, and R ² is preferably an alkyl group having 3 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms, and more preferably an alkyl group having 3 to 20 carbon atoms, and any hydrogen atom forming R ² may be substituted with a ^fluorine atom.

In the above formula (S3), X ⁴ represents —CONH—, —NHCO—, —O—, —CH ₂ O—, —OCH ₂ —, —COO— or —OCO—.
^R3 represents a structure having a steroid skeleton, and a specific example thereof is a structure having a skeleton represented by the following formula (st):

An example of the above formula (S3) is the following formula (S3-x).

In formula (S3-x), X represents the above formula (X1), (X2), or (X3). Col represents one selected from the group consisting of the above formulas (Col1) to (Col4), and G represents the above formula (G1) or (G2). * represents a site for bonding to another group.
More preferred structures of formula (S3) include structures represented by the following formulae (S3-1) to (S3-6).

(* indicates the bond position)

Specific examples of specific diamines include diamines of the following formulas (V-1) to (V-13).

In the formula, X ^v1 to X ^v4 and X ^p1 to X ^p8 each independently represent —(CH ₂ ) _a — (a is an integer of 1 to 15), —CONH—, —NHCO—, —CON(CH ₃ )—, —NH—, —O—, —CH ₂ O—, —CH ₂ OCO—, —COO—, or —OCO—; X ^v5 represents —O—, —CH ₂ O—, —CH ₂ OCO—, —COO—, or —OCO—; and X ^v6 to X ^v7 and X ^s1 to X ^s4 each independently represent —O—, —CH ₂ O—, —OCH ₂ —, —COO—, or —OCO—. X _a to X _f each independently represent a single bond, —O—, —NH—, —O—(CH ₂ ) _m —O—, —C(CH ₃ ) ₂ —, —CO—, —COO—, —CONH—, —(CH ₂ ) _m —, —SO ₂ —, —O—C(CH ₃ ) ₂ —, —CO—(CH ₂ ) _m —, —NH—(CH ₂ ) _m —, —NH—(CH ₂ ) _m —NH—, —SO ₂ —(CH ₂ ) _m —SO ₂ —, _—CONH— (CH ₂ ) _{m —} , —CONH—(CH ₂ ) _m —NHCO—, or —COO— _{(CH 2 ) m} represents —OCO—, and R ^v1 to R ^v4 and R ^1a to R ^1h 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. m represents an integer of 1 to 8.

From the viewpoint of imparting liquid crystal alignment properties, the content of the above-mentioned specific diamine is preferably 5 to 95 mol %, more preferably 5 to 90 mol %, and particularly preferably 5 to 80 mol %, of the total diamine component.

The above specific diamines can be used alone or in combination of two or more.

<Other diamines>
The diamine for obtaining the polyamic acid may be a diamine other than the specific diamines (also referred to as "other diamines"). The other diamines may be used alone or in combination of two or more.
Specific examples of other diamines include p-phenylenediamine, 2,3,5,6-tetramethyl-p-phenylenediamine, 2,5-dimethyl-p-phenylenediamine, m-phenylenediamine, 2,4-dimethyl-m-phenylenediamine, 2,5-diaminotoluene, 2,6-diaminotoluene, 2,5-diaminophenol, 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol, 4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4 '-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4,4'-diaminobiphenyl, 3,3'-dicarboxy-4,4'-diaminobiphenyl, 3,3'-difluoro-4,4'-biphenyl, 3,3'-trifluoromethyl-4,4'-diaminobiphenyl, 3,4'-diaminobiphenyl, 3,3'-diaminobiphenyl, 2,2'-diaminobiphenyl, 2,3'-diaminobiphenyl, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane,

2,2'-diaminodiphenylmethane, 2,3'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 2,2'-diaminodiphenyl ether, 2,3'-diaminodiphenyl ether, 4,4'-sulfonyldianiline, 3,3'-sulfonyldianiline, bis(4-aminophenyl)silane, bis(3-aminophenyl)silane, dimethyl-bis(4-aminophenyl)silane, dimethyl-bis(3-aminophenyl)silane, 4,4'-thiodianiline, 3,3'-thiodianiline, 4,4'-diaminodiphenylamine, 3,3'-diaminodiphenylamine, 3,4'-diaminodiphenylamine, 2,2'-diaminodiphenylamine, 2,3'-diaminodiphenylamine, N-methyl(4,4'-diaminodiphenyl) Amine, N-methyl(3,3'-diaminodiphenyl)amine, N-methyl(3,4'-diaminodiphenyl)amine, N-methyl(2,2'-diaminodiphenyl)amine, N-methyl(2,3'-diaminodiphenyl)amine, 4,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 1,4-diaminonaphthalene, 2,2'-diaminobenzophenone, 2,3 '-diaminobenzophenone, 1,5-diaminonaphthalene, 1,6-diaminonaphthalene, 1,7-diaminonaphthalene, 1,8-diaminonaphthalene, 2,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,7-diaminonaphthalene, 2,8-diaminonaphthalene, 1,2-bis(4-aminophenyl)ethane, 1,2-bis(3-aminophenyl)ethane, 1,3-bis(4-aminophenyl)propane,

1,3-bis(3-aminophenyl)propane, 1,4-bis(4-aminophenyl)butane, 1,4-bis(3-aminophenyl)butane, bis(3,5-diethyl-4-aminophenyl)methane, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 1,4-bis(4-aminobenzyl)benzene, 1,3-bis(4-aminophenoxy)benzene, 4,4'-[1,4-phenylenebis(methylene)]dianiline, 4,4'-[1,3-phenylenebis(methylene)]dianiline, 3,4'-[1,4-phenyl 1,4-phenylenebis(methylene)]dianiline, 3,4'-[1,3-phenylenebis(methylene)]dianiline, 3,3'-[1,4-phenylenebis(methylene)]dianiline, 3,3'-[1,3-phenylenebis(methylene)]dianiline, 1,4-phenylenebis[(4-aminophenyl)methanone], 1,4-phenylenebis[(3-aminophenyl)methanone], 1,3-phenylenebis[(4-aminophenyl)methanone], 1,3-phenylenebis[(3-aminophenyl)methanone], 1,4-phenylenebis(4-aminobenzoate), 1,4-phenylenebis(3-aminobenzoate), 1,3-phenylenebis(4-aminobenzoate),

1,3-phenylene bis(3-aminobenzoate), bis(4-aminophenyl) terephthalate, bis(3-aminophenyl) terephthalate, bis(4-aminophenyl) isophthalate, bis(3-aminophenyl) isophthalate, N,N'-(1,4-phenylene)bis(4-aminobenzamide), N,N'-(1,3-phenylene)bis(4-aminobenzamide), N,N'-(1,4-phenylene)bis(3-aminobenzamide), N,N'-(1,3-phenylene)bis(3-aminobenzamide), N,N'-bis(4-aminophenyl) terephthalamide, N,N'-bis(3-aminophenyl) terephthalamide, N,N'-bis(4-aminophenyl) isophthalamide, N,N'-bis(3-aminophenyl) isophthalamide, 9,10-bis(4-aminophenyl)anthracene, 4,4'-bis( 2,2'-bis[4-(4-aminophenoxy)phenyl]diphenyl sulfone, 2,2'-bis[4-(4-aminophenoxy)phenyl]propane, 2,2'-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2'-bis(4-aminophenyl)hexafluoropropane, 2,2'-bis(3-aminophenyl)hexafluoropropane, 2,2'-bis(3-amino-4-methylphenyl)hexafluoropropane, 2 , 2'-bis(4-aminophenyl)propane, 2,2'-bis(3-aminophenyl)propane, 2,2'-bis(3-amino-4-methylphenyl)propane, 3,5-diaminobenzoic acid, 2,5-diaminobenzoic acid, 1,3-bis(4-aminophenoxy)propane, 1,3-bis(3-aminophenoxy)propane, 1,4-bis(4-aminophenoxy)butane, 1,4-bis(3-aminophenoxy)butane,

1,5-bis(4-aminophenoxy)pentane, 1,5-bis(3-aminophenoxy)pentane, 1,6-bis(4-aminophenoxy)hexane, 1,6-bis(3-aminophenoxy)hexane, 1,7-bis(4-aminophenoxy)heptane, 1,7-(3-aminophenoxy)heptane, 1,8-bis(4-aminophenoxy)octane, 1,8-bis(3-aminophenoxy)octane, 1,9-bis(4-aminophenoxy)nonane, 1,9-bis(3-aminophenoxy) 1,10-bis(4-aminophenoxy)nonane, 1,10-bis(4-aminophenoxy)decane, 1,10-bis(3-aminophenoxy)decane, 1,11-bis(4-aminophenoxy)undecane, 1,11-bis(3-aminophenoxy)undecane, 1,12-bis(4-aminophenoxy)dodecane, 1,12-bis(3-aminophenoxy)dodecane, diamines represented by the following formulas (nh-1) to (nh-8), diamines represented by the following formulas (z-1) to (z-14), diamines represented by the following formulas (R1) to (R5), diamines having a radical initiation function such as diamines represented by the following formulae (5-1) to (5-11), diamines having the group "-N(D)-" (D represents a protecting group which is eliminated by heating and replaced with a hydrogen atom, preferably a tert-butoxycarbonyl group), such as diamines represented by the following formulae (Dp-1) to (Dp-6), diamines having a photopolymerizable group at the terminal such as 2-(2,4-diaminophenoxy)ethyl methacrylate and 2,4-diamino-N,N-diallylaniline. alicyclic diamines such as bis(4-aminocyclohexyl)methane and bis(4-amino-3-methylcyclohexyl)methane; and aliphatic diamines such as 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, and 1,12-diaminododecane.
(In formulas (R3) to (R5), n is an integer of 2 to 6.)

(Boc represents a tert-butoxycarbonyl group.)

The polyamic acid can be obtained from the tetracarboxylic acid component and the diamine component by a known method. That is, the reaction between the diamine component and the tetracarboxylic acid component is usually carried out in a solvent containing the diamine component and the tetracarboxylic acid component. The solvent used in this reaction is not particularly limited as long as it dissolves the produced polyamic acid.
Specific examples of the solvent 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. When the polyamic acid has high solubility in the solvent, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or the solvents represented by the following formulas [D1] to [D3] can be used.

( ^D1 and ^D2 represent alkyl groups having 1 to 3 carbon atoms. ^D3 represents alkyl groups having 1 to 4 carbon atoms.)
These organic solvents may be used alone or in combination. Furthermore, even if a solvent does not dissolve polyamic acid, it may be mixed with the above-mentioned solvent to the extent that the produced polyamic acid does not precipitate.

The concentration of the polyamic acid in the reaction system is preferably 1 to 30% by mass, more preferably 5 to 20% by mass, from the viewpoints that precipitation of the polyamic acid is unlikely to occur and a high molecular weight product is easily obtained.
The polyamic acid obtained as described above can be precipitated and recovered by pouring the reaction solution into a poor solvent while stirring it thoroughly. Alternatively, the precipitation can be repeated several times, followed by washing with a poor solvent and drying at room temperature or by heating to obtain a purified polyamic acid powder. The poor solvent is not particularly limited, but examples thereof include water, methanol, ethanol, hexane, butyl cellosolve, acetone, and toluene.
The polyamic acid ester can be obtained, for example, by subjecting the above-mentioned polyamic acid to an esterification reaction with an esterifying agent.

The polyimide (A) contained in the polyimide varnish of the present invention is obtained by imidizing a polyimide precursor such as the above-mentioned polyamic acid, polyamic acid ester, etc. In the polyimide (A), the repeating units of the polyimide precursor are ring-closed, but the ratio of the ring-closed repeating units to all repeating units of the polyimide precursor (also referred to as the ring-closure rate or imidization rate) does not necessarily have to be 100%, but is preferably 20 to 90%, more preferably 30 to 80%, and can be adjusted as desired within this range depending on the application and purpose of the polyimide varnish.
When the polyimide varnish of the present invention is used as a liquid crystal aligning agent for forming a liquid crystal alignment film, the imidization rate is preferably 20 to 95%, more preferably 30 to 95%.

Imidization of a polyimide precursor can be achieved, for example, by stirring a polyamic acid in an organic solvent in the presence of a basic catalyst and an acid anhydride. The organic solvent can be the same as that used in the polymerization reaction described above. Examples of basic catalysts include pyridine, triethylamine, trimethylamine, tributylamine, and trioctylamine. Pyridine is preferred because it has the appropriate basicity to promote the reaction. Examples of acid anhydrides include acetic anhydride, trimellitic anhydride, and pyromellitic anhydride. Acetic anhydride is preferred because it facilitates purification after the reaction.

The temperature during the imidization reaction is -20 to 140°C, preferably 0 to 100°C, and the reaction time is 0.5 to 100 hours, preferably 1 to 80 hours. The amount of the basic catalyst is 0.5 to 30 times by mole, preferably 2 to 20 times by mole, the amount of the amic acid, and the amount of the acid anhydride is 1 to 50 times by mole, preferably 3 to 30 times by mole, the amount of the amic acid. The imidization rate of the resulting polymer can be controlled by adjusting the amount of the catalyst, temperature, and reaction time.
Since the added catalyst and the like remain in the solution after the imidization reaction of the polyamic acid, it is preferable to recover the obtained polyimide by the means described below, redissolve it in an organic solvent, and use it as a component of the liquid crystal aligning agent of the present invention.
The polyimide solution obtained as described above can be poured into a poor solvent with thorough stirring to precipitate the polymer. The precipitate is filtered, washed several times with the poor solvent, and then dried at room temperature or by heating to obtain a purified polyimide powder.

The molecular weight of the polyimide obtained as described above, taking into consideration the strength of the film obtained from the polyimide varnish obtained therefrom, workability during film formation, and coatability, is preferably a weight average molecular weight (Mw) of 2,000 to 1,000,000, and more preferably 10,000 to 150,000, as measured by GPC (Gel Permeation Chromatography). Furthermore, the number average molecular weight (Mn) is preferably 3,000 to 100,000, and more preferably 10,000 to 50,000.

<Amine Compound (B)>
The polyimide varnish of the present invention contains the following component (B):
Component (B): An amine compound (B) having, in the molecule, either a secondary amino group or a tertiary amino group and either a nitrogen-containing aromatic heterocyclic group or an aromatic hydrocarbon group as a cyclic group, wherein the amino group is bonded to an acyclic aliphatic hydrocarbon group or a non-aromatic cyclic hydrocarbon group.
The amine compound (B) may be used alone or in combination of two or more.
The amine compound (B) is preferably a compound represented by the following formula (1):

In the above formula (1), R ₁ and R ₂ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and at least one of R ₁ and R ₂ represents an alkyl group having 1 to 5 carbon atoms.
The alkyl group having 1 to 5 carbon atoms may be linear or branched, and preferred examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, and a pentyl group.
Ar represents a monovalent group having a nitrogen-containing aromatic heterocycle or an aromatic hydrocarbon group, wherein a hydrogen atom on the nitrogen-containing aromatic heterocycle or a hydrogen atom on the aromatic hydrocarbon group of Ar may be substituted with an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), a halogen-containing alkyl group, a halogen-containing alkoxy group, a carboxy group, a hydroxy group, or a nitrile group.
Preferred examples of the nitrogen-containing aromatic heterocycle include cyclic structures containing at least one partial structure selected from the group consisting of the following formulae [1a], [1b], and [1c], and more preferably cyclic structures containing 1 to 4 of the above partial structures:

(wherein _Y1 is a linear or branched alkyl group having 1 to 5 carbon atoms)

More preferred examples of the nitrogen-containing aromatic heterocycle include a pyrrole ring, an imidazole ring, an oxazole ring, a thiazole ring, a pyrazole ring, a pyridine ring, a pyrimidine ring, a quinoline ring, a pyrazoline ring, an isoquinoline ring, a carbazole ring, a purine ring, a thiadiazole ring, a pyridazine ring, a triazine ring, a triazole ring, a pyrazine ring, a benzimidazole ring, a phenanthroline ring, an indole ring, a quinoxaline ring, a benzothiazole ring, a phenothiazine ring, an oxadiazole ring, and an acridine ring.
Preferred examples of the aromatic hydrocarbon group include a benzene ring, a naphthalene ring, an azulene ring, an indene ring, a fluorene ring, an anthracene ring, a phenanthrene ring, and a phenalene ring.
X represents a divalent organic group containing an acyclic aliphatic hydrocarbon group or a non-aromatic cyclic hydrocarbon group. X is preferably a divalent acyclic aliphatic hydrocarbon group or a non-aromatic cyclic hydrocarbon group. Preferred examples of the acyclic aliphatic hydrocarbon group include a linear or branched alkylene group having 1 to 10 carbon atoms, or an unsaturated alkylene group having 1 to 10 carbon atoms. Preferred examples of the non-aromatic cyclic hydrocarbon group include alicyclic hydrocarbon groups having 3 to 20 carbon atoms, such as a cyclopropane ring, cyclobutane ring, cyclopentane ring, cyclohexane ring, cycloheptane ring, cyclooctane ring, cyclononane ring, cyclodecane ring, cycloundecane ring, cyclododecane ring, cyclotridecane ring, cyclotetradecane ring, cyclopentadecane ring, cyclohexadecane ring, cycloheptadecane ring, cyclooctadecane ring, cyclononadecane ring, cycloicosane ring, tricycloeicosane ring, bicycloheptane ring, decahydronaphthalene ring, norbornene ring, and adamantane ring.

Among these, X is preferably a group represented by *1-X ₁ -X ₂ -*2 for reasons of ease of synthesis and availability of raw materials.
Here, _X1 represents a divalent group containing an acyclic aliphatic hydrocarbon group or a non-aromatic cyclic hydrocarbon group having 1 to 10 carbon atoms. _X1 is preferably a divalent acyclic aliphatic hydrocarbon group or a non-aromatic cyclic hydrocarbon group having 1 to 10 carbon atoms. Preferred examples of the acyclic aliphatic hydrocarbon group or non-aromatic cyclic hydrocarbon group of _X1 are the same as the examples of X described above.
_X2 is a single bond, —O—, —NH—, —S—, —SO ₂ —, or a divalent organic group having 1 to 19 carbon atoms. The total number of carbon atoms owned by _X1 and _X2 is 1 to 20, and preferably 1 to 10.
Note that *1 is a bond bonded to N in formula (1), and *2 is a bond bonded to Ar in formula (1).

The N to which R ₁ and R ₂ are bonded is bonded to the above-mentioned acyclic aliphatic hydrocarbon group or non-aromatic cyclic hydrocarbon group.

Preferred examples of the amine compound (B) include compounds represented by the following formulas (b-1) to (b-14).

In particular, it is preferable that the amine compound (B) be one or more compounds represented by any of the above formulas (b-1) to (b-3), due to the difficulty of production and availability of raw materials.

<Polyimide varnish>
The polyimide varnish of the present invention contains the polyimide (A) as the component (A) and the amine compound (B) as the component (B). The polyimide varnish can be obtained, for example, by dispersing or dissolving these components in an organic solvent.
The total content of polyimide (A) in the polyimide varnish is preferably 1 to 20 mass%, more preferably 1 to 15 mass%, and particularly preferably 1 to 10 mass%, from the viewpoint of ease of uniform mixing with compound (B).
The content of the amine compound (B) as component (B) in the polyimide varnish is preferably 0.1 to 40 parts by mass, more preferably 0.1 to 30 parts by mass, and particularly preferably 0.1 to 10 parts by mass, per 100 parts by mass of the polyimide (A), from the viewpoints of efficiently obtaining the effects of the present invention and enhancing the stability of the polyimide varnish.

The organic solvent that may be contained in the polyimide varnish of the present invention is one that disperses or dissolves, preferably dissolves, the polyimide (A) as the component (A) and the amine compound (B) as the component (B).
Examples of organic solvents include lactone solvents such as γ-valerolactone and γ-butyrolactone, lactam solvents such as γ-butyrolactam, N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone, amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, tetramethylurea and N,N-diethylformamide, 4-hydroxy-4-methyl-2-pentanone, diisobutyl ketone (2,6-dimethyl-4-heptanone), methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, isoamyl lactate, n-butyl acetate, and cyclohexyl acetate. , 4-methyl-2-pentyl acetate, propylene glycol monoethyl ether acetate, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, propyl 3-methoxypropionate, butyl 3-methoxypropionate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol mono-i-propyl ether, ethylene glycol mono-n-butyl ether (butyl cellosolve), ethylene glycol dimethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monobutyl ether, propylene glycol di acetate, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol monomethyl ether, isoamyl propionate, isoamyl isobutyrate, diisopropyl ether, diisopentyl ether; carbonate solvents such as ethylene carbonate and propylene carbonate, 1-hexanol, cyclohexanol, 1,2-ethanediol, diisobutylcarbinol (2,6-dimethyl-4-heptanol), cyclohexanone, cyclopentanone, and the like.

Preferred combinations when using two or more organic solvents include N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone, and ethylene glycol mono-n-butyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone, and propylene glycol monobutyl ether, N-ethyl-2-pyrrolidone and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone, and diethylene glycol diethyl ether, and N-ethyl-2-pyrrolidone and N-methyl-2-pyrrolidone 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 propylene glycol monobutyl ether, N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone, and propylene glycol diacetate, 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 diisobutyl carbinol, N-methyl-2-pyrrolidone, γ-butyrolactone, and dipropylene glycol dimethyl ether, N-methyl-2-pyrrolidone and propylene Examples of such a mixture include ethylene glycol monobutyl ether and dipropylene glycol dimethyl ether, N-methyl-2-pyrrolidone, ethylene glycol monobutyl ether, and ethylene glycol monobutyl ether acetate, γ-butyrolactone, ethylene glycol monobutyl ether acetate, and dipropylene glycol dimethyl ether, N,N-dimethylpropionamide and propylene glycol diacetate, tetramethylurea and 4-hydroxy-4-methyl-2-pentanone, cyclohexanone and propylene glycol monomethyl ether, and cyclopentanone and propylene glycol monomethyl ether.

In addition to the polyimide (A) and component (B) described above, the polyimide varnish of the present invention can contain various other components (also referred to as "other components") depending on its intended use. Examples of other components include polymers other than the polyimide (A), antioxidants (phenolic, phosphite, thioether, etc.), UV absorbers, hindered amine light stabilizers, nucleating agents, resin additives (fillers, talc, glass fibers, etc.), flame retardants, processability improvers, lubricants, etc.

<Liquid crystal alignment agent>
In the case of a liquid crystal aligning agent, which is a preferred application of the polyimide varnish of the present invention, it is preferably prepared so as to be suitable for forming a liquid crystal alignment film. The liquid crystal aligning agent of the present invention preferably contains the polyimide varnish of the present invention.
The liquid crystal aligning agent of the present invention can be obtained, for example, by dispersing or dissolving the polyimide varnish of the present invention and, if necessary, other components in an organic solvent. The liquid crystal aligning agent of the present invention may also be obtained by mixing two or more liquid crystal aligning agents. For example, the liquid crystal aligning agent may be obtained by mixing two or more liquid crystal aligning agents containing the polyimide varnish of the present invention, or by mixing a liquid crystal aligning agent containing the polyimide varnish of the present invention with a liquid crystal aligning agent containing other components. Examples of the other components include polymers other than the polyimide (A), crosslinkable compounds, functional silane compounds, surfactants, compounds having a photopolymerizable group, organic solvents, etc.

The other polymer is not particularly limited, and examples thereof include polyimide precursors such as polyamic acid and polyamic acid ester, polysiloxane, polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivatives, polyacetal, and polymers of monomers having polymerizable unsaturated bonds. As the other polymer, a polymer of a monomer having a polymerizable unsaturated bond is preferably used. Note that the other polymers may be used alone or in combination of two or more.
When other polymers are used, the proportion of the other polymers used is preferably 50% by mass or less, more preferably 0.1 to 40% by mass, and even more preferably 0.1 to 30% by mass, based on the total amount of polymers contained in the polyimide varnish.

Examples of the monomer having a polymerizable unsaturated bond include (meth)acrylic compounds (including unsaturated carboxylic acids, unsaturated carboxylic acid esters, and unsaturated polycarboxylic acid anhydrides), (meth)acrylic acid amide compounds, aromatic vinyl compounds, conjugated diene compounds, maleimide group-containing compounds, α-methylene-γ-butyrolactone compounds, vinyl compounds other than aromatic vinyl compounds, and compounds containing a maleic anhydride structure.
Examples of polymers of compounds containing a maleic anhydride structure include poly(styrene-maleic anhydride) copolymer, poly(isobutylene-maleic anhydride) copolymer, poly(vinyl ether-maleic anhydride) copolymer, etc. Specific examples of poly(styrene-maleic anhydride) copolymers include SMA1000, 2000, and 3000 (manufactured by Cray Valley) and GSM301 (manufactured by Gifu Shellac Co., Ltd.), a specific example of poly(isobutylene-maleic anhydride) copolymers includes ISOBAM-600 (manufactured by Kuraray), and a specific example of poly(vinyl ether-maleic anhydride) copolymers includes GANTREZ AN-139 (methyl vinyl ether maleic anhydride resin, manufactured by ISP Japan).

In the above polymer of the (meth)acrylic compound (hereinafter also referred to as polymer (uA)), the proportion of the (meth)acrylic compound used may be 50 mol% or more, or 60 mol% or more, relative to the total amount of monomers used in the synthesis.

Polymer (uA) can be obtained, for example, by polymerizing a monomer having a polymerizable unsaturated bond in the presence of a polymerization initiator. Examples of polymerization initiators include azo compounds such as 2,2'-azobis(isobutyronitrile) and 2,2'-azobis(2,4-dimethylvaleronitrile). The polymerization initiator is preferably used in an amount of 0.01 to 30 parts by mass per 100 parts by mass of all monomers used in the reaction. The polymerization reaction is preferably carried out in an organic solvent. Examples of organic solvents used in the reaction include alcohols, ethers, ketones, amides, esters, and hydrocarbon compounds, with diethylene glycol ethyl methyl ether and propylene glycol monomethyl ether acetate being preferred. The reaction temperature is preferably 30 to 120°C. The amount of organic solvent (a) used is preferably such that the total amount of monomers (b) used in the reaction is 0.1 to 60% by mass relative to the total amount of the reaction solution (a + b).

As the monomer for obtaining the polymer (uA), a monomer represented by the following formula (S-mA), a monomer having a carboxy group and a polymerizable unsaturated bond, a monomer having an epoxy skeleton and a polymerizable unsaturated bond, and other monomers having a polymerizable unsaturated bond may be used.
(P represents a (meth)acryloyloxy group, a styryl group, a vinyloxy group (CH ₂ ═CH—O—), a maleimide group, or an α-methylene-γ-butyrolactone structure.
X represents a single bond, -(CH ₂ ) _a - (a is an integer of 1 to 15), -CONH-, -NHCO-, -CON(CH ₃ )-, -NH-, -O-, -COO-, -OCO- or -((CH ₂ ) _a1 -A ₁ ) _m1 - (a1 is an integer of 1 to 15, A ₁ represents an oxygen atom or -COO-, and m ₁ is an integer of 1 or 2; when m ₁ is 2, multiple a1s and A _1s each independently have the same definition as above), or a group "-L-OCO-CR'═CR"-". However, when P is a (meth)acryloyloxy group, a vinyloxy group (CH ₂ ═CH—O—) or a maleimide group, X represents a single bond or a linking group bonding to P via a carbon atom.
J represents a monovalent organic group having at least one group selected from the group consisting of alicyclic hydrocarbon groups having 4 to 40 carbon atoms and aromatic hydrocarbon groups having 6 to 40 carbon atoms, provided that at least one hydrogen atom possessed by the alicyclic hydrocarbon group and aromatic hydrocarbon group is substituted with a substituent selected from the group consisting of a halogen atom, a halogen-atom-containing alkyl group, a halogen-atom-containing alkoxy group, an alkyl group having 3 to 10 carbon atoms, an alkoxy group having 3 to 10 carbon atoms, an alkenyl group having 3 to 10 carbon atoms, and a heteroatom-containing group in which a carbon-carbon bond possessed by any methylene group of the halogen-atom-containing alkyl group, halogen-atom-containing alkoxy group, alkyl group, alkoxy group, and alkenyl group is interrupted by an oxygen atom.
In addition, when J in the above formula (S-mA) is a monovalent organic group having two or more groups of at least one type selected from the group consisting of alicyclic hydrocarbon groups having 4 to 40 carbon atoms and aromatic hydrocarbon groups having 6 to 40 carbon atoms, it is sufficient that at least one of the alicyclic hydrocarbon groups or aromatic hydrocarbon groups has the above-mentioned substituent, and other alicyclic hydrocarbon groups or aromatic hydrocarbon groups that J in the above formula (S-mA) has may be unsubstituted or may have a substituent other than the above-mentioned examples.
In the group "-L-OCO-CR'=CR"-", L represents a single bond or -(B ₁ -(CH ₂ ) _b1 ) _m' - (b1 is an integer of 1 to 15. _{B 1} represents a single bond, -CONH-, -NHCO-, -CON(CH ₃ )-, -NH-, -O-, -COO- or -OCO-. m ^' is an integer of 1 to 2. When m ^' is 2, multiple b1s and B _1s each independently have the same definition as above, and at least one B ₁ represents a linking group other than a single bond). R' and R" represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.

More preferred examples of the group "-X-J" include groups represented by any of the following formulae (S1) and (S2).
(X ¹ represents a single bond, —(CH ₂ ) _a — (a is an integer of 1 to 15), —CONH—, —NHCO—, —CON(CH ₃ )—, —NH—, —O—, —COO—, —OCO—, —((CH ₂ ) _a1 -A ₁ ) _m1 — (a1 is an integer of 1 to 15, _{A 1} represents an oxygen atom or —COO—, and m ₁ is an integer of 1 or 2; when m ₁ is 2, a plurality of a1s and A _1s each independently have the same definition as above), or a group “-L-OCO-CR′═CR″-”.
^G1 represents a divalent cyclic group selected from a divalent aromatic hydrocarbon group having 6 to 12 carbon atoms and a divalent alicyclic hydrocarbon group having 4 to 8 carbon atoms. Any hydrogen atom on the cyclic group may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxy group having 1 to 3 carbon atoms, or a fluorine atom. However, m is an integer of 1 to 4. When m is 2 or greater, multiple ^X1s and ^G1s each independently have the above definition.
^R1 represents a fluorine atom, a fluorine atom-containing alkyl group having 1 to 10 carbon atoms, a fluorine atom-containing alkoxy group having 1 to 10 carbon atoms, an alkyl group having 3 to 10 carbon atoms, an alkoxy group having 3 to 10 carbon atoms, or an alkoxyalkyl group having 3 to 10 carbon atoms.
In the group "-L-OCO-CR'=CR"-", L represents a single bond or -(B ₁ -(CH ₂ ) _b1 ) _m' - (b1 is an integer of 1 to 15. _{B 1} represents a single bond, -CONH-, -NHCO-, -CON(CH ₃ )-, -NH-, -O-, -COO- or -OCO-. ^m' is an integer of 1 to 2. When ^m' is 2, multiple b1s and B _1s each independently have the above definition, and at least one B ₁ represents a linking group other than a single bond).
In the group "-L-OCO-CR'=CR"-", R' and R" each represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.
( ^X2 represents -CONH-, -NHCO-, -O-, _-CH2O- , _-OCH2- , -COO- or -OCO-. ^G2 represents a structure having a steroid skeleton. At least one hydrogen atom of the structure having a steroid skeleton is substituted with a substituent selected from the group consisting of a halogen atom, a halogen-atom-containing alkyl group, a halogen-atom-containing alkoxy group, an alkyl group having 3 to 10 carbon atoms, an alkoxy group having 3 to 10 carbon atoms, an alkenyl group having 3 to 10 carbon atoms, and a heteroatom-containing group in which a carbon-carbon bond of any methylene group of the halogen-atom-containing alkyl group, halogen-atom-containing alkoxy group, alkyl group, alkoxy group, and alkenyl group is interrupted with an oxygen atom.)

In the above formula (S1), examples of the divalent cyclic group for ^G1 include a cyclopropylene group, a cyclohexylene group, and a phenylene group. Any hydrogen atom on these cyclic groups may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxy group having 1 to 3 carbon atoms, or a fluorine atom.

In the above formula (S2), examples of the structure having a steroid skeleton in ^G2 include structures containing a cholestanyl group, a cholesteryl group, or a lanostaniyl group.

Specific examples of the monomer having the above-mentioned carboxy group and polymerizable unsaturated bond include carboxy group-containing (meth)acrylate compounds such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, 2-hydroxyethyl (meth)acrylic acid, 2-carboxyethyl (meth)acrylate, 2-carboxypropyl (meth)acrylate, 5-carboxypentyl (meth)acrylate, 2-acryloyloxyethyl succinic acid, and 2-methacryloyloxyethyl succinic acid; vinyl group-containing aromatic carboxylic acids such as 4-vinylbenzoic acid; carboxy group-containing maleimides such as 4-maleimidobenzoic acid; and carboxy group-containing (meth)acrylamide compounds such as N-(carboxyphenyl)methacrylamide and N-(carboxyphenyl)acrylamide.

Examples of monomers having the above-mentioned epoxy backbone and polymerizable unsaturated bonds include allyl glycidyl ether, glycidyl (meth)acrylate, 2-methylglycidyl (meth)acrylate, α-ethyl glycidyl (meth)acrylate, α-n-propyl glycidyl (meth)acrylate, α-n-butyl glycidyl (meth)acrylate, 3,4-epoxybutyl (meth)acrylate, 6,7-epoxyheptyl (meth)acrylate, o-vinylbenzyl glycidyl ether, m-vinylbenzyl glycidyl ether, p-vinylbenzyl glycidyl ether, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3-ethenyl-7-oxabicyclo[4.1.0]heptane, 1,2-epoxy-5-hexene, and 1,7-octadiene monoepoxide.

Other examples of monomers having polymerizable unsaturated bonds include the following monomers:

amino group-containing (meth)acrylate compounds such as aminoethyl (meth)acrylate and aminopropyl (meth)acrylate;
(meth)acrylamide compounds containing a hydroxymethyl group or an alkoxymethyl group, such as N-hydroxymethyl(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-ethoxymethyl(meth)acrylamide, and N-butoxymethyl(meth)acrylamide;
Compounds having an oxetane skeleton, such as 3-(acryloyloxymethyl)oxetane, 3-(methacryloyloxymethyl)oxetane, 3-(acryloyloxymethyl)-2-methyloxetane, 3-(methacryloyloxymethyl)-2-methyloxetane, 3-(acryloyloxymethyl)-3-ethyloxetane, and 3-(methacryloyloxymethyl)-3-ethyloxetane;
compounds having a nitrogen-containing aromatic heterocycle, such as 2-(2-pyridylcarbonyloxy)ethyl (meth)acrylate, 2-(3-pyridylcarbonyloxy)ethyl (meth)acrylate, and 2-(4-pyridylcarbonyloxy)ethyl (meth)acrylate;
(meth)acrylic acid ester compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, tert-butyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 2-ethoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, 2-propyl-2-adamantyl (meth)acrylate, 8-methyl-8-tricyclodecyl (meth)acrylate, and 8-ethyl-8-tricyclodecyl (meth)acrylate;
(meth)acrylic acid amide compounds such as acrylamide, methacrylamide, N-methylacrylamide, N,N-dimethylacrylamide, and N,N-diethylacrylamide;
Vinyl ether compounds such as methyl vinyl ether, benzyl vinyl ether, vinyl naphthalene, and vinyl carbazole; aromatic vinyl compounds such as styrene, methylstyrene, chlorostyrene, and bromostyrene; and maleimide group-containing compounds such as maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide.

As the monomer components for obtaining polymer (uA), the total of the monomer having a carboxy group and a polymerizable unsaturated bond, the monomer having an epoxy backbone and a polymerizable unsaturated bond, and the monomer represented by formula (S-mA) is preferably 10 mol% or more, and more preferably 20 mol% or more. When other monomers having a polymerizable unsaturated bond are used in combination, the total of the monomer having a carboxy group and a polymerizable unsaturated bond and the monomer represented by formula (S-mA) is preferably 99 mol% or less, more preferably 95 mol% or less, and even more preferably 90 mol% or less.

The molecular weight of the polymer (uA) obtained as described above is preferably a weight average molecular weight (Mw) of 2,000 to 1,000,000, more preferably 10,000 to 150,000, as measured by GPC (Gel Permeation Chromatography). Furthermore, the number average molecular weight (Mn) is preferably 3,000 to 100,000, more preferably 10,000 to 50,000.

Crosslinkable compounds can be used to increase the strength of liquid crystal alignment films. Examples of such crosslinkable compounds include compounds having a hydroxyalkylamide bond or an alkoxyalkylamide bond, as described in JP 2016-118753 A and WO 2015/156314 A, compounds having at least one group selected from the group consisting of an epoxy group, an oxetane group, a hydroxy group, a hydroxyalkyl group, an isocyanate group, a cyclocarbonate, and a lower alkoxyalkyl group, as described in paragraphs [0109] to [0113] of WO 2016/047771 A, and compounds having a blocked isocyanate group.

Examples of the compounds having the epoxy group include, among others, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, 1,3,5,6-tetraglycidyl-2,4-hexanediol, bisphenol A epoxy resins such as Epicoat 828 (manufactured by Mitsubishi Chemical Corporation), bisphenol F epoxy resins such as Epicoat 807 (manufactured by Mitsubishi Chemical Corporation), and YX-8000 (manufactured by Mitsubishi Chemical Corporation). hydrogenated bisphenol A epoxy resins such as EPPN-201 (manufactured by Nippon Kayaku Co., Ltd.), biphenyl skeleton-containing epoxy resins such as YX6954BH30 (manufactured by Mitsubishi Chemical Corporation), phenol novolac epoxy resins such as EPPN-201 (manufactured by Nippon Kayaku Co., Ltd.), (o-, m-, p-)cresol novolac epoxy resins such as EOCN-102S (manufactured by Nippon Kayaku Co., Ltd.), triglycidyl isocyanurates such as TEPIC (manufactured by Nissan Chemical Industries, Ltd.), alicyclic epoxy resins such as CELLOXIDE 2021P (manufactured by Daicel Chemical Industries, Ltd.), N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, and tetrakis(glycidyloxymethyl)methane are preferred.

Blocked isocyanate compounds are commercially available, and examples that can be used include Coronate AP Stable M, Coronate 2503, 2515, 2507, 2513, 2555, and Millionate MS-50 (all manufactured by Tosoh Corporation), and Takenate B-830, B-815N, B-820NSU, B-842N, B-846N, B-870N, B-874N, and B-882N (all manufactured by Mitsui Chemicals, Inc.).

Specific examples of preferred crosslinkable compounds include compounds represented by the following formulae (CL-1) to (CL-11).
The above are examples of the crosslinkable compound, and the present invention is not limited to these. Two or more types of crosslinkable compounds may be used in combination in the liquid crystal aligning agent of the present invention.

The content of the crosslinkable compound in the liquid crystal aligning agent is preferably 0.1 to 150 parts by mass, more preferably 0.1 to 100 parts by mass, and particularly preferably 1 to 50 parts by mass, relative to 100 parts by mass of all polymer components.
The functional silane compound can be used for the purpose of improving the adhesion between the liquid crystal alignment film and the base substrate. Specific examples include the silane compounds described in paragraph [0019] of International Publication No. 2014/119682. The content of the functional silane compound is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, per 100 parts by mass of all polymer components.

The surfactant can be used to improve the uniformity of the film thickness and surface smoothness of the liquid crystal alignment film. Examples of the surfactant include fluorine-based surfactants, silicone-based surfactants, and nonionic surfactants. Specific examples of these surfactants include those described in paragraph [0117] of WO2016/047771. The amount of surfactant used is preferably 0.01 to 2 parts by mass, more preferably 0.01 to 1 part by mass, relative to 100 parts by mass of the total polymer contained in the liquid crystal alignment agent.
Examples of the compound having a photopolymerizable group include compounds having one or more polymerizable unsaturated groups, such as an acrylate group or a methacrylate group, in the molecule, such as compounds represented by any of the following formulas (M-1) to (M-7).

As the organic solvent that may be contained in the liquid crystal alignment agent, those described in the polyimide varnish can be used, and the type and content of the solvent are appropriately selected depending on the application device, application conditions, application environment, etc. of the liquid crystal alignment agent.
The solid content concentration in the liquid crystal aligning agent (the ratio of the total mass of the components other than the organic 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 1 to 10 mass%.

A particularly preferred solids concentration varies depending on the method used to apply the liquid crystal alignment agent to the substrate. For example, when using a spin coating method, a concentration of 1 to 10% by mass is particularly preferred. When using a printing method, a concentration of 3 to 9% by mass is particularly preferred, thereby achieving a solution viscosity of 12 to 50 mPa·s. When using an inkjet method, a concentration of 1 to 5% by mass is particularly preferred, thereby achieving a solution viscosity of 3 to 15 mPa·s.

The liquid crystal alignment agent can be used as a liquid crystal alignment film by applying it to a substrate, baking it, and then performing an alignment treatment such as rubbing or light irradiation. In addition, in the case of vertical alignment applications, it can be used as a liquid crystal alignment film without any alignment treatment.
The substrate used in this case is not particularly limited as long as it is a highly transparent substrate, and in addition to a glass substrate, a plastic substrate such as an acrylic substrate, a polycarbonate substrate, or a PET (polyethylene terephthalate) substrate, or even a film thereof, can be used. From the viewpoint of simplifying the process, it is preferable to use a substrate on which a metal electrode such as an ITO electrode, an IZO (indium zinc oxide) electrode, or an IGZO (indium gallium zinc oxide) electrode for driving the liquid crystal, or an organic conductive film, etc., is formed. When a reflective liquid crystal display element is to be formed, a substrate on only one side can be formed of a silicon wafer, a metal such as aluminum, or a dielectric multilayer film.

The method for applying the liquid crystal aligning agent is not particularly limited, but industrially, it is generally performed by screen printing, offset printing, flexographic printing, inkjet printing, etc. Other application methods include a dipping method, a roll coating method, a slit coating method, a spin coating method, a spraying method, etc., and these may be used depending on the purpose.
After the liquid crystal alignment agent is applied to the substrate, the solvent is evaporated at a temperature of 30 to 300°C, preferably 30 to 250°C, depending on the solvent used in the liquid crystal alignment agent, using a heating means such as a hot plate, a heat circulation oven, or an IR (infrared) oven, to form a liquid crystal alignment film.

The thickness of the liquid crystal alignment film after baking is preferably 5 to 300 nm, more preferably 10 to 200 nm, since if it is too thick, it will be disadvantageous in terms of power consumption of the liquid crystal display element, and if it is too thin, it may reduce the reliability of the liquid crystal display element.
When the liquid crystal is to be horizontally or obliquely aligned, the liquid crystal alignment film after baking is treated by rubbing or by irradiating with polarized ultraviolet light.
The ultraviolet light preferably contains light with a wavelength of 300 to 400 nm. Examples of light sources that can be used for the irradiation light include low-pressure mercury lamps, high-pressure mercury lamps, deuterium lamps, metal halide lamps, argon resonance lamps, xenon lamps, and excimer lasers. Ultraviolet light in the preferred wavelength range can be obtained by using the light source in combination with, for example, a filter or a diffraction grating. The light irradiation dose is preferably 1,000 J/ ^m² or more but less than 100,000 J/ ^m² , and more preferably 1,000 to 50,000 J/ ^m² .
The liquid crystal used in the liquid crystal display element is not particularly limited, but for example, nematic liquid crystal, smectic liquid crystal, or cholesteric liquid crystal can be used. In this case, liquid crystal having positive or negative dielectric anisotropy can be selected depending on the type of liquid crystal display element. In addition, a dichroic dye can be dissolved in the liquid crystal to form a guest-host type liquid crystal display element.
The liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention can be used as a liquid crystal alignment film for a horizontal alignment type or vertical alignment type liquid crystal display element.
As a liquid crystal alignment film for horizontal alignment type liquid crystal display elements, it is suitable as a liquid crystal alignment film for horizontal electric field type liquid crystal display elements such as IPS type and FFS type, or horizontal alignment type liquid crystal display elements such as TN mode, and is particularly useful as a liquid crystal alignment film for FFS type liquid crystal display elements.
The liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention is particularly suitable as a liquid crystal alignment film for a vertical alignment type liquid crystal display element such as a VA mode or PSA mode. Furthermore, the liquid crystal alignment film for a vertical alignment type liquid crystal display element such as a VA mode or PSA mode may be obtained by an alignment treatment including a photo-alignment treatment. The preferred embodiments of the light, light source, and light irradiation amount to be irradiated in the photo-alignment treatment are as described above.
Furthermore, the liquid crystal alignment film obtained from the liquid crystal alignment agent containing the polyimide varnish of the present invention can be used as a liquid crystal alignment film for a retardation film, a liquid crystal alignment film for a scanning antenna or a liquid crystal array antenna, or a liquid crystal alignment film for a transmissive/scattering liquid crystal dimming element, or for other applications such as a protective film for a color filter, a gate insulating film for a flexible display, or a substrate material.

Liquid crystal display elements using the liquid crystal aligning agent of the present invention can be applied to a variety of devices, such as watches, portable games, word processors, notebook computers, car navigation systems, camcorders, PDAs, digital cameras, mobile phones, smartphones, various monitors, LCD televisions, and information displays.

The present invention will be described in further detail below with reference to examples, but is not limited to these examples. The abbreviations and measurement methods for the compounds used below are as follows:
(Tetracarboxylic acid dianhydride)
BODA: Bicyclo[3.3.0]octane-2,4,6,8-tetracarboxylic dianhydride CBDA: 1,2,3,4-cyclobutanetetracarboxylic dianhydride PMDA: Pyromellitic anhydride TCA: 2,3,5-tricarboxycyclopentylacetic dianhydride TDA: 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic dianhydride 13DM-CBDA: 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride

(diamine)
PDA: p-phenylenediamine DBA: 3,5-diaminobenzoic acid 3AMPDA: 3,5-diamino-N-(pyridin-3-ylmethyl)benzamide

Vertically aligning diamine represented by the following formula DA-1
Diamines represented by the following formulae DA-2 to DA-9
(Boc represents a tert-butoxycarbonyl group.)
(Methacrylic compounds)
Methacrylic compounds represented by the following formulae MA-1 to MA-3
(Radical polymerization initiator)
AIBN: Azobisisobutyronitrile

<Solvent>
NMP: N-methyl-2-pyrrolidone, BCS: butyl cellosolve <amine compound (B)>
3AMP: 3-picolylamine, Me-3AMP: N-methyl-3-picolylamine, MBA: N-methylbenzylamine, DMBA: N,N-dimethylbenzylamine

<Molecular weight measurement>
Apparatus: room temperature gel permeation chromatography (GPC) apparatus (SSC-7200) manufactured by Senshu Scientific Co., Ltd.
Column: Shodex column (KD-803, KD-805)
Column temperature: 50°C
Eluent: N,N-dimethylformamide (additives: lithium bromide monohydrate (LiBr.H ₂ O) 30 mmol/L, anhydrous crystalline phosphoric acid (o-phosphoric acid) 30 mmol/L, tetrahydrofuran (THF) 10 mL/L), flow rate: 1.0 ml/min. Standard samples for creating calibration curves: TSK standard polyethylene oxide (molecular weight: approximately 900,000, 150,000, 100,000, 30,000) manufactured by Tosoh Corporation, and polyethylene glycol (molecular weight: approximately 12,000, 4,000, 1,000) manufactured by Polymer Laboratory.

<Imidization rate measurement>
20 mg of polyimide powder was placed in an NMR sample tube (Kusano Scientific NMR Sampling Tube Standard φ5), 1.0 mL of deuterated dimethyl sulfoxide (DMSO-d ₆ , 0.05% TMS mixture) was added, and the mixture was sonicated to completely dissolve. This solution was measured for proton NMR at 500 MHz using an NMR analyzer (JNW-ECA500) manufactured by JEOL Datum Co., Ltd. The imidization rate was determined by the following formula, using a proton derived from a structure that remains unchanged before and after imidization as the reference proton, and the integrated peak value of this proton and the integrated peak value of the proton derived from the NH group of the amic acid that appears around 9.5 to 10.0 ppm.
In the following formula, x represents the integrated value of the proton peak derived from the NH group of the amic acid, y represents the integrated value of the peak of the reference proton, and α represents the ratio of the number of the reference protons to one proton of the NH group of the amic acid in the case of polyamic acid (imidization rate 0%).
Imidization rate (%) = (1 - α x/y) x 100

<Viscosity measurement>
The viscosity of the liquid crystal alignment agent was measured at 25° C. using an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.) with a sample amount of 1.1 mL and a cone rotor TE-1 (1°34′, R24).

(Synthesis Example 1)
BODA (15.0 g, 60.0 mmol), DBA (18.3 g, 120 mmol), 3AMPDA (21.8 g, 90.0 mmol), and DA-1 (34.3 g, 90.0 mmol) were dissolved in NMP (357 g) and reacted at 60°C for 3 hours. PMDA (13.1 g, 60.0 mmol), followed by CBDA (34.1 g, 174 mmol) and NMP (137 g) were then added, and the mixture was reacted at 25°C for 10 hours to obtain a polyamic acid solution.
This polyamic acid solution (500 g) was diluted to 6.5% by mass with NMP, and then acetic anhydride (111 g) and pyridine (34.5 g) were added as imidization catalysts and reacted at 60°C for 3 hours. This reaction solution was poured into methanol (7000 mL), and the resulting precipitate was filtered off. This precipitate was washed with methanol and dried under reduced pressure at 100°C to obtain polyimide powder (A). The imidization rate of this polyimide was 80%, and the number average molecular weight was 12,000 and the weight average molecular weight was 24,000.

(Synthesis Example 2)
TCA (43.9 g, 196 mmol), DA-2 (30.3 g, 40.0 mmol), DA-4 (9.49 g, 40.0 mmol), DA-5 (13.9 g, 70.0 mmol), and DA-6 (16.5 g, 50.0 mmol) were mixed in NMP (455 g) and reacted at 60°C for 15 hours to obtain a polyamic acid solution with a resin solids concentration of 20% by mass.
This polyamic acid solution (100 g) was diluted to 6.5% by mass with NMP, and then acetic anhydride (17.9 g) and pyridine (5.55 g) were added as imidization catalysts and reacted at 100°C for 3 hours. This reaction solution was poured into methanol (1160 ml), and the resulting precipitate was filtered off. This precipitate was washed with methanol and dried under reduced pressure at 60°C to obtain polyimide powder (B). The imidization rate of this polyimide was 72%, and the number average molecular weight was 13,300 and the weight average molecular weight was 40,500.

(Synthesis Example 3)
TDA (30.0 g, 100 mmol), PDA (9.73 g, 90 mmol), and DA-3 (3.77 g, 10.0 mmol) were dissolved in NMP (247 g) and reacted at 40° C. for 3 hours to obtain a polyamic acid solution.
This polyamic acid solution (50 g) was diluted to 5% by mass with NMP, and then acetic anhydride (17.6 g) and pyridine (8.20 g) were added as imidization catalysts and reacted at 40°C for 3 hours. This reaction solution was poured into methanol (600 ml), and the resulting precipitate was filtered off. This precipitate was washed with methanol and dried under reduced pressure at 100°C to obtain polyimide powder (C). The imidization rate of this polyimide was 85%, and the number average molecular weight was 13,400 and the weight average molecular weight was 27,000.

(Synthesis Example 4)
13DM-CBDA (17.1 g, 76.4 mmol), PDA (1.73 g, 16.0 mmol), DA-7 (5.86 g, 24.0 mmol), DA-8 (7.69 g, 24.0 mmol), and DA-9 (5.46 g, 16.0 mmol) were dissolved in NMP (277 g) and reacted at 50°C for 15 hours to obtain a polyamic acid solution.
This polyamic acid solution (100 g) was diluted to 9% by mass with NMP, and then acetic anhydride (7.60 g) and pyridine (0.98 g) were added as imidization catalysts and reacted at 55°C for 3 hours. This reaction solution was poured into methanol (530 ml), and the resulting precipitate was filtered off. This precipitate was washed with methanol and dried under reduced pressure at 60°C to obtain polyimide powder (D). The imidization rate of this polyimide was 66%, and the number average molecular weight was 14,300 and the weight average molecular weight was 35,800.

(Synthesis Example 5)
MA-1 (10.2 g, 20.0 mmol), MA-2 (2.61 g, 30.0 mmol), MA-3 (2.35 g, 16.5 mmol), and NMP (60.6 g) were added to a four-neck flask, and each monomer component was completely dissolved. This solution was degassed using a diaphragm pump, and AIBN (0.550 g, 3.33 mmol) was added as a polymerization initiator, followed by degassing again. The mixture was then reacted at 60°C for 13 hours, yielding a methacrylic polymer solution (E). The number average molecular weight of this polymer was 15,800, and the weight average molecular weight was 68,200.

Example 1
NMP (44.0 g) was added to the obtained polyimide powder (A) (6.00 g), and the mixture was dissolved by stirring at 70° C. for 20 hours. To this solution, Me-3AMP (2 mass % NMP solution, 6.00 g) was added as the amine compound (B), and further, NMP (4.00 g) and BCS (40.0 g) were added, and the mixture was stirred at room temperature for 3 hours to obtain a liquid crystal aligning agent (A1).

(Examples 2 and 3 and Comparative Examples 1 and 2)
Liquid crystal aligning agents (A2) to (A5) were prepared in the same manner as in Example 1, except that the type of the added amine compound (B) was changed. The obtained liquid crystal aligning agents and the amine compound (B) used therein are shown in Table 1 below.
In Comparative Example 2, the amine compound (B) was not added.

<Storage stability test>
The liquid crystal aligning agents obtained in Examples 1 to 3 and Comparative Examples 1 or 2 were placed in vials and sealed, and left standing in a light-shielded environment at 25°C. The change in viscosity of the liquid crystal aligning agent during standing and the molecular weight of the polyimide contained in the liquid crystal aligning agent were tracked.
Table 2 below shows the change in viscosity of the liquid crystal alignment agent, and Table 3 shows the change in molecular weight (number average molecular weight) of the polyimide contained in the liquid crystal alignment agent.

<Evaluation of whitening properties>
0.1 mL of the liquid crystal alignment agent obtained in Examples 1 to 3 and Comparative Examples 1 or 2 was dropped onto a chrome substrate and left to stand in an environment of a temperature of 23°C and a humidity of 70%. The edge and center of the droplet were observed with an optical microscope, and the time until a precipitate was generated was measured.
In this evaluation, the whitening phenomenon is defined as the phenomenon in which the droplets become cloudy due to precipitation or aggregation of dissolved polyimide. A state in which the droplets are not whitened at all is rated as "Good", a state in which only the edges of the droplets are whitened is rated as "Good", and a state in which the entire surface of the droplets is whitened is rated as "Poor".
Table 4 shows the evaluation results of the whitening property after 3 days of the storage stability test of the liquid crystal aligning agent.

The results in Tables 2 and 3 show that, compared to the changes in viscosity and molecular weight in Comparative Example 1, the decreases in viscosity and molecular weight in Examples 1 to 3 were significantly suppressed, and the storage stability of the polyimide varnish was improved.
Furthermore, the results of the whitening test in Table 4 show that Examples 1 to 3 have significantly improved whitening properties compared to Comparative Example 2.
Furthermore, the results in Table 4 show that the whitening properties of Examples 1 to 3 are less likely to deteriorate than those of Comparative Example 1. This is thought to be because the aliphatic amine in 3AMP is a primary amine, which makes it more likely to make a nucleophilic attack on the polyimide main chain, whereas the nucleophilicity of secondary and tertiary amines to the polyimide main chain is suppressed due to the influence of steric hindrance.

(Examples 4 to 8, Comparative Examples 3 to 12, Synthesis Examples 6 to 8)
In Example 1, except that the polyimide powder, amine compound and organic solvent were changed as shown in Table 5 below, the same procedure was carried out to prepare liquid crystal aligning agents (B1) to (B2), (C1) to (C3) and (D1) to (D3).
In addition, NMP (24.0 g), BCS (40.0 g), and 6.00 g of MBA (2 mass% NMP solution) were added to the methacrylic polymer solution (E) (30.0 g) obtained in Synthesis Example 5, and the mixture was stirred at room temperature for 3 hours to obtain a liquid crystal aligning agent (E1) (Synthesis Example 6). Furthermore, by carrying out the same procedure as in Synthesis Example 6, except that the amine compound was changed as shown in Table 5 below, liquid crystal aligning agents (E2) to (E3) were prepared (Synthesis Examples 7 and 8).
Table 5 shows the combinations of each liquid crystal alignment agent and the additives used therein.

Subsequently, the liquid crystal aligning agents (B1) to (B3) and (E1) to (E3) obtained up to this point were blended with the liquid crystal aligning agents (A2), (A4) and (A5).
Table 6 shows the combinations of the blended liquid crystal alignment agents and the combinations of the additives contained in the liquid crystal alignment agents.
The liquid crystal aligning agent obtained above was subjected to a storage stability test and evaluation of whitening properties in the same manner as above. The results are shown in Tables 7 to 10 below.

<Storage stability test>

<Evaluation of whitening properties>
The results of the evaluation carried out on the day of preparation of the liquid crystal aligning agent are shown in Table 9, and the results of the evaluation after 3 days of the storage stability test are shown in Tables 9 and 10.

The results in Tables 7 and 8 show that in Examples 5 to 8, the decrease in viscosity and molecular weight was significantly suppressed, and the storage stability was improved.
Furthermore, the results of the whitening test in Tables 9 and 10 show that Examples 5 to 8 have significantly improved whitening properties compared to Comparative Examples 5 to 12.

The polyimide varnish of the present invention is widely used in a wide range of fields, including as a liquid crystal alignment agent for forming liquid crystal alignment films in liquid crystal display elements, insulating films for semiconductors, and particularly as film-like protective and insulating materials in the electrical and electronic fields.

The entire contents of the specification, claims and abstract of Japanese Patent Application No. 2020-30729, filed on February 26, 2020, are hereby incorporated by reference as part of the disclosure of the specification of the present invention.

Claims (13)

A polyimide varnish characterized by containing the following components (A) and (B):
Component (A): Polyimide (A) which is an imidized product of a polyimide precursor.
Component (B): An amine compound (B) having, in the molecule, either a secondary amino group or a tertiary amino group and either a nitrogen-containing aromatic heterocycle or an aromatic hydrocarbon group as a cyclic group, wherein the amino group is bonded to an acyclic aliphatic hydrocarbon group or a non-aromatic cyclic hydrocarbon group, and the amine compound (B) is one or more compounds represented by any of the following formulas (b-1) and (b-3) to (b-14):
2. The polyimide varnish according to claim 1, wherein the polyimide precursor of the polyimide (A) is obtained using a tetracarboxylic acid component containing a tetracarboxylic acid dianhydride represented by the following formula (3) or a derivative thereof:
(X represents a structure selected from the group consisting of the following (x-1) to (x-13)).
(R ¹ to R ⁴ each independently represent a hydrogen atom, a methyl group, an ethyl group, a propyl group, a chlorine atom, a fluorine atom, a monovalent organic group containing 1 to 6 carbon atoms and a fluorine atom, or a phenyl group. R ⁵ and R ⁶ each independently represent a hydrogen atom or a methyl group. j and k each independently represent an integer of 0 or 1. A ₁ and A ₂ each independently represent a single bond, —O—, —CO—, —COO—, phenylene, a sulfonyl group, or an amide group. *1 represents a bond bonding to one of the acid anhydride groups, and *2 represents a bond bonding to the other acid anhydride group. The two A _2s may be the same or different.) The tetracarboxylic dianhydride or derivative thereof represented by the formula (3) is a tetracarboxylic dianhydride or derivative thereof, wherein X is any one of the formulae (x-1) to (x-7) and (x-11) to (x-13). The polyimide varnish according to claim 2. The polyimide varnish according to any one of claims 1 to 3, wherein the polyimide precursor of the polyimide (A) is obtained using a diamine (a) having at least one side chain structure selected from the group consisting of the following formulae (S1) to (S3):
( ^X1 and ^X2 each independently represent a single bond, -( _CH2 ) _a- (a is an integer of 1 to 15), -CONH-, -NHCO-, -CON( _CH3 )-, -NH-, -O-, -COO-, -OCO-, or -(( _CH2 ) _a1 - _A1 ) _m1- . In these, a1 is an integer of 1 to 15, _A1 represents an oxygen atom or -COO-, and _m1 is 1 or 2. ^G1 and ^G2 each independently represent a divalent cyclic group that is a divalent aromatic group having 6 to 12 carbon atoms or a divalent alicyclic group having 3 to 8 carbon atoms. Any hydrogen atom on the cyclic group may be substituted. m and n each independently represent an integer of 0 to 3, and m+n is 1 to 6. R ¹ represents an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an alkoxyalkyl group having 2 to 20 carbon atoms, and any hydrogen atom forming R ¹ may be substituted with a fluorine atom. When there are two or more X ¹ , X ² , G ¹ , G ² , a1, and A ₁ , the two or more X ¹ , X ² , G ¹ , G ² , a1, and A ₁ may each independently be the same or different.
( ^X3 represents a single bond, -CONH-, -NHCO-, -CON( _CH3 )-, -NH-, -O-, _-CH2O- , -COO- or -OCO-. ^R2 represents an alkyl group having 1 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms, and any hydrogen atom forming ^R2 may be substituted with a fluorine atom.)
( ^X4 represents -CONH-, -NHCO-, -O-, -CH ₂ O-, -OCH ₂ -, -COO- or -OCO-. ^R3 represents a structure having a steroid skeleton.) The polyimide varnish according to claim 4, wherein the diamine (a) is at least one diamine selected from the group consisting of the following formulas (V-1) to (V-13):
(In the above formula, X ^v1 to X ^v4 and X ^p1 to X ^p8 each independently represent —(CH ₂ ) _a — (a is an integer of 1 to 15), —CONH—, —NHCO—, —CON(CH ₃ )—, —NH—, —O—, —CH ₂ O—, —CH ₂ OCO—, —COO—, or —OCO—; X ^v5 represents —O—, —CH ₂ O— , —COO—, or —OCO—; X ^v6 to X ^v7 and X ^s1 to X ^s4 each independently represent —O—, —CH ₂ O—, —OCH ₂ —, —COO—, or —OCO—; _{X a} to X _f each independently represent a single bond, —O—, —NH—, —O—(CH ₂ ) _m -O-, -C(CH ₃ ) ₂ -, -CO-, -COO-, -CONH-, -(CH ₂ ) _m -, -SO ₂ -, -O-C(CH ₃ ) ₂ -, -CO-(CH ₂ ) _m -, -NH-(CH ₂ ) _m -, -NH-(CH ₂ ) _m -NH-, _-SO2- ( _CH2 ) _m- , _{-SO2-(CH2)m-SO2-, -CONH-(CH2)m- , -CONH- ( CH2 )m-NHCO-, or -COO-(CH2 ) m - OCO-} , R ^v1 ~R ^v4 , R ^1a ~R Each ^1h independently represents an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an alkoxyalkyl group having 2 to 20 carbon atoms. m represents an integer of 1 to 8. The polyimide varnish according to any one of claims 1 to 5, wherein the polyimide (A) has a ring-closed structure in which 20 to 90% of the total repeating units contained in the polyimide precursor are ring-closed. The polyimide varnish according to any one of claims 1 to 6, wherein the amine compound (B) is contained in an amount of 0.1 to 50 parts by mass per 100 parts by mass of the polyimide (A). A liquid crystal alignment agent obtained from the polyimide varnish described in any one of claims 1 to 7. The liquid crystal aligning agent according to claim 8, further comprising at least one other polymer selected from the group consisting of polyimide precursors, polysiloxanes, polyesters, polyamides, polyureas, polyorganosiloxanes, cellulose derivatives, polyacetals, and polymers of monomers having polymerizable unsaturated bonds. The liquid crystal aligning agent according to claim 9, wherein the polymer of the monomer having a polymerizable unsaturated bond is obtained using at least one compound selected from the group consisting of (meth)acrylic compounds, (meth)acrylic acid amide compounds, aromatic vinyl compounds, conjugated diene compounds, maleimide group-containing compounds, α-methylene-γ-butyrolactone compounds, vinyl compounds other than aromatic vinyl compounds, and compounds containing a maleic anhydride structure. The polymer of the monomer having a polymerizable unsaturated bond is obtained using at least one monomer selected from the group consisting of a monomer represented by the following formula (S-m A ), a monomer having a carboxy group and a polymerizable unsaturated bond, and a monomer having an epoxy skeleton and a polymerizable unsaturated bond, the liquid crystal aligning agent according to claim 9 or 10.
(P represents a (meth)acryloyloxy group, a styryl group, a vinyloxy group (CH ₂ ═CH—O—), a maleimide group, or an α-methylene-γ-butyrolactone structure.
X represents a single bond, -(CH ₂ ) _a - (a is an integer of 1 to 15), -CONH-, -NHCO-, -CON(CH ₃ )-, -NH-, -O-, -COO-, -OCO- or -((CH ₂ ) _a1 -A ₁ ) _m1 - (a1 is an integer of 1 to 15, A ₁ represents an oxygen atom or -COO-, and m ₁ is an integer of 1 or 2; when m ₁ is 2, multiple a1s and A _1s each independently have the same definition as above), or a group "-L-OCO-CR'═CR"-". However, when P is a (meth)acryloyloxy group, a vinyloxy group (CH ₂ ═CH—O—) or a maleimide group, X represents a single bond or a divalent organic group bonded to P via a carbon atom.
J represents a monovalent organic group having at least one group selected from the group consisting of alicyclic hydrocarbon groups having 4 to 40 carbon atoms and aromatic hydrocarbon groups having 6 to 40 carbon atoms, provided that at least one hydrogen atom possessed by the alicyclic hydrocarbon group and the aromatic hydrocarbon group is substituted with a substituent selected from the group consisting of a halogen atom, a halogen-atom-containing alkyl group, a halogen-atom-containing alkoxy group, an alkyl group having 3 to 10 carbon atoms, an alkoxy group having 3 to 10 carbon atoms, an alkenyl group having 3 to 10 carbon atoms, and a heteroatom-containing group in which a carbon-carbon bond possessed by any methylene group of the halogen-atom-containing alkyl group, halogen-atom-containing alkoxy group, alkyl group, alkoxy group, and alkenyl group is interrupted by an oxygen atom.
In the group "-L-OCO-CR'=CR"-", L represents a single bond or -(B ₁ -(CH ₂ ) _b1 ) _m' - (b1 is an integer of 1 to 15. _{B 1} represents a single bond, -CONH-, -NHCO-, -CON(CH ₃ )-, -NH-, -O-, -COO- or -OCO-. ^m' is an integer of 1 to 2. When m ^' is 2, multiple b1s and B _1s each independently have the same definition as above, and at least one B ₁ is not a single bond.) R' and R" represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. A liquid crystal alignment film formed using the liquid crystal aligning agent according to any one of claims 8 to 11. A liquid crystal display element comprising the liquid crystal alignment film according to claim 12.