TWI868339B - Liquid crystal alignment agent, liquid crystal alignment film, method for manufacturing liquid crystal alignment film, and liquid crystal element - Google Patents

Abstract

The present invention provides a liquid crystal alignment agent, a liquid crystal alignment film, a method for manufacturing the liquid crystal alignment film, and a liquid crystal element, which are used to obtain a liquid crystal element that shows a low pre-tilt angle even when using a negative liquid crystal, is not prone to afterimages, has a high voltage retention rate, and has excellent reliability. The liquid crystal alignment agent contains a polymer [P] having a partial structure represented by formula (1) in the main chain. In formula (1), ^A1 and ^A2 are independently divalent nitrogen-containing aromatic heterocyclic groups, and ^B1 and ^B2 are independently single bonds or divalent aromatic cyclic groups. ^X1 and ^X2 are independently -O- or ^-NR1- ( _CH2 ) _n- . ^R1 is a hydrogen atom or a monovalent organic group, and n is an integer of 1 to 3. ^Y1 is a divalent group having one or more aromatic rings and is bonded to ^X1 and ^X2 through the same or different aromatic rings. "*" indicates a bond.

Description

Liquid crystal alignment agent, liquid crystal alignment film, method for manufacturing liquid crystal alignment film, and liquid crystal element

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

As the liquid crystal material of the liquid crystal element, negative liquid crystal is used in liquid crystal elements of vertical alignment (VA) drive mode or multi-domain vertical alignment (MVA) drive mode, and positive liquid crystal is used in liquid crystal elements of twisted nematic (TN) type or in-plane switching (IPS) drive mode, fringe field switching (FFS) drive mode, etc. In addition, in recent years, in order to achieve further high-precision liquid crystal elements, it has been proposed to use negative liquid crystal in liquid crystal elements of IPS drive mode or FFS drive mode (see patent document 1).

Liquid crystal elements are used in a wide range of devices or applications, from large LCD TVs to small display devices such as smartphones. As such liquid crystal elements become more versatile, there is a demand for further high-quality liquid crystal elements. For example, due to the need for viewing angle characteristics, a lower pre-tilt angle than before (e.g., a pre-tilt angle of less than 1 degree) is sometimes required in a rubbed alignment film. In order to meet the above requirements, a liquid crystal alignment film using polyimide having a specific structure has been proposed (see Patent Document 2). [Prior Art Document]

[Patent Document] [Patent Document 1] International Publication No. 2016/152928 [Patent Document 2] International Publication No. 2019/082975

[Problem to be solved by the invention] The inventors of the present invention and others have conducted research and found that when a liquid crystal display element using negative liquid crystal is used for a long time, burn-in is likely to occur. In addition, as a liquid crystal element, it is required to have a high voltage retention rate and excellent reliability when used for a long time.

The present invention is made in view of the above-mentioned problem, and its main purpose is to provide a liquid crystal alignment agent, which can obtain a liquid crystal element that shows a low pre-tilt angle even when using negative liquid crystal, is not prone to afterimages, has a high voltage retention rate, and has excellent reliability. [Technical means to solve the problem]

The inventors of the present invention have conducted intensive research to solve the above-mentioned problems, and have found that the above-mentioned problems can be solved by using a polymer having a specific structure in the main chain, thereby completing the present invention. Specifically, the present invention provides the following means.

<1> A liquid crystal aligning agent comprising a polymer [P] having a partial structure represented by the following formula (1) in the main chain, [Chemical 1] (In formula (1), ^A1 and ^A2 are independently a divalent nitrogen-containing aromatic heterocyclic group, ^B1 and ^B2 are independently a single bond or a divalent aromatic cyclic group. ^X1 and ^X2 are independently -O- or ^-NR1- ( _CH2 ) _n- . ^R1 is a hydrogen atom or a monovalent organic group, and n is an integer of 1 to 3. ^Y1 is a divalent group having one or more aromatic rings and bonded to ^X1 and ^X2 respectively through the same or different aromatic rings. "*" represents a bond.) <2> A method for manufacturing a liquid crystal alignment film, comprising: a step of forming a coating using the liquid crystal alignment agent described in <1>, and a step of irradiating the coating with light to impart liquid crystal alignment ability. <3> A method for manufacturing a liquid crystal alignment film, comprising: a step of forming a coating using the liquid crystal alignment agent of <1>, and a step of imparting liquid crystal alignment capability to the coating by rubbing. <4> A liquid crystal alignment film is formed using the liquid crystal alignment agent of <1>. <5> A liquid crystal element comprises the liquid crystal alignment film of <4>. [Effect of the invention]

According to the liquid crystal alignment agent of the present invention, a liquid crystal element can be obtained which shows a low pre-tilt angle even when using negative liquid crystal, is not prone to afterimages, has a high voltage retention rate, and has excellent reliability.

Hereinafter, each component contained in the liquid crystal alignment agent of the present disclosure and other components arbitrarily formulated as needed will be described.

In addition, in this specification, the so-called "alkyl group" has the meaning of chain alkyl groups, alicyclic alkyl groups and aromatic alkyl groups. The so-called "chain alkyl group" refers to a straight chain alkyl group and a branched alkyl group whose main chain does not contain a ring structure and is composed only of a chain structure. Among them, it can be saturated or unsaturated. The so-called "alicyclic alkyl group" refers to a alkyl group that contains only the structure of alicyclic hydrocarbons as a ring structure and does not contain an aromatic ring structure. Among them, it is not necessary to be composed only of the structure of alicyclic hydrocarbons, and it also includes a group having a chain structure in part. The so-called "aromatic hydrocarbon group" refers to a hydrocarbon group containing an aromatic ring structure as a ring structure. It does not need to be composed of only an aromatic ring structure, and a chain structure or an alicyclic hydrocarbon structure may be contained in part thereof. The so-called "aromatic ring" means an aromatic hydrocarbon ring and an aromatic heterocyclic ring. The so-called "structural unit" refers to a unit mainly composed of a main chain structure and containing at least two or more units in the main chain structure.

<Polymer [P]> The liquid crystal alignment agent disclosed herein contains a polymer [P] having a partial structure represented by the following formula (1) (hereinafter also referred to as "specific structure") in the main chain. [Chemical 2] (In formula (1), ^A1 and ^A2 are each independently a divalent nitrogen-containing aromatic heterocyclic group, ^B1 and ^B2 are each independently a single bond or a divalent aromatic cyclic group. ^X1 and ^X2 are each independently -O- or ^-NR1- ( _CH2 ) _n- . ^R1 is a hydrogen atom or a monovalent organic group, and n is an integer of 1 to 3. ^Y1 is a divalent group having one or more aromatic rings and is bonded to ^X1 and ^X2 through the same or different aromatic rings. "*" indicates a bond.)

In the above formula (1), the divalent nitrogen-containing aromatic heterocyclic group represented by ^A1 and ^A2 is a residual group obtained by removing two arbitrary hydrogen atoms bonded to atoms constituting the ring of the nitrogen-containing aromatic heterocyclic group. Examples of the nitrogen-containing aromatic heterocyclic group constituting ^A1 and ^A2 include a pyrrole ring, an imidazole ring, a pyrazole ring, a triazole ring, a pyridine ring, a pyrimidine ring, an oxazine ring and a pyrazine ring, and heterocyclic groups having substituents (e.g., a methyl group, an ethyl group, etc.) on these rings. Among these, ^A1 and ^A2 are preferably divalent groups obtained by removing two arbitrary hydrogen atoms bonded to carbon atoms constituting the ring of the pyridine ring, the pyrimidine ring, the oxazine ring or the pyrazine ring.

As the divalent aromatic ring group of ^B1 and ^B2 , there can be listed divalent aromatic alkyl groups and divalent aromatic heterocyclic groups, preferably divalent aromatic alkyl groups or divalent nitrogen-containing aromatic heterocyclic groups. ^B1 and ^B2 may have a substituent in the aromatic ring part. As the substituent, there can be listed an alkyl group having 1 to 5 carbon atoms, a halogen atom, etc. As specific examples of ^B1 and ^B2 , the divalent aromatic hydrocarbon group includes a group formed by removing any hydrogen atom bonded to a carbon atom constituting a benzene ring, a naphthalene ring or an anthracene ring; and the divalent nitrogen-containing aromatic heterocyclic group includes a group formed by removing two hydrogen atoms bonded to a carbon atom constituting a pyridine ring, a pyrimidine ring, a oxadiazine ring or a pyrazine ring. From the viewpoint of achieving a high density of the liquid crystal alignment film, the divalent aromatic cyclic group of ^B1 and ^B2 is preferably a divalent aromatic hydrocarbon group, and more preferably a phenylene group. From the viewpoint of further increasing the density of the liquid crystal alignment film, suppressing the increase in ion density or reducing afterimages, and achieving low pretilt angle, at least one of ^B1 and ^B2 is preferably a single bond, and more preferably both are single bonds.

Regarding ^X1 and ^X2 , the monovalent organic group of ^R1 in " ^-NR1- ( _CH2 ) _n- " is preferably a monovalent hydrocarbon group or a protecting group having 1 to 10 carbon atoms. When ^R1 is a monovalent hydrocarbon group, the monovalent hydrocarbon group is preferably an alkyl group having 1 to 3 carbon atoms or a phenyl group, and more preferably an alkyl group having 1 to 3 carbon atoms. When ^R1 is a protecting group, the protecting group is preferably a monovalent group that is released by heat, for example, carbamate-based protecting groups, amide-based protecting groups, imide-based protecting groups, sulfonamide-based protecting groups, etc. Among these, carbamate-based protecting groups are preferred in terms of high releasability by heat, and specific examples thereof include tert-butoxycarbonyl, benzyloxycarbonyl, 1,1-dimethyl-2-haloethoxycarbonyl, allyloxycarbonyl, 2-(trimethylsilyl)ethoxycarbonyl, etc. Among these, tert-butoxycarbonyl (Boc group) is particularly preferred in terms of excellent releasability by heat and the ability to reduce the amount of residues in the film of the deprotected portion.

^R1 is preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a protecting group, and is particularly preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a tert-butyloxycarbonyl group. From the viewpoint of both improving the alignment restriction force of the liquid crystal alignment film and reducing the residual image property, n is preferably 1 or 2. When ^X1 and ^X2 are " ^-NR1- ( _CH2 ) _n- ", from the viewpoint of achieving a high density of the liquid crystal alignment film and obtaining a polymer with higher photoreactivity, ^X1 and ^X2 are preferably nitrogen atoms (i.e., " ^-NR1- ") bonded to ^B1 and ^B2 , and more preferably ^B1 and ^B2 are single bonds and directly bonded to ^A1 and ^A2 . From the viewpoint of obtaining a polymer having higher photoreactivity, at least one of ^X1 and ^X2 is preferably " ^-NR1- ( _CH2 ) _n- ", and more preferably both ^X1 and ^X2 are " ^-NR1- ( _CH2 ) _n- ".

^Y1 is a divalent group having one or more aromatic rings and bonded to ^X1 and ^X2 respectively through the same or different aromatic rings. The aromatic ring possessed by ^Y1 may be any one of an aromatic hydrocarbon ring and an aromatic heterocyclic ring. The aromatic ring is preferably an aromatic hydrocarbon ring or a nitrogen-containing aromatic heterocyclic ring, and specifically, is preferably a benzene ring, a naphthalene ring, a pyridine ring, a pyrimidine ring, an oxazine ring or a pyrazine ring. In addition, when ^Y1 has two or more aromatic rings, these aromatic rings are the same ring or different rings. The aromatic ring possessed by ^Y1 may also have a substituent in the ring portion. As the substituent, an alkyl group having 1 to 5 carbon atoms, a halogen atom, etc. can be listed.

^Y1 is preferably a divalent group represented by the following formula (2). (In formula (2), ^B3 and ^B4 are each independently a divalent aromatic cyclic group, ^X3 is a single bond, -O- or ^-NR1- ( _CH2 ) _n- . ^R1 and n have the same meanings as in formula (1). m is an integer from 0 to 3. When m is 2 or 3, multiple ^B4 in the formula are the same group or different groups, and multiple ^X3 are the same group or different groups. "*" represents a bond.)

In the above formula (2), as examples of divalent aromatic ring groups for ^B3 and ^B4 , the same as described above for divalent aromatic ring groups for ^B1 and ^B2 can be applied. When ^X3 is " ^-NR1- ( _CH2 ) _n- ", ^R1 and n can be applied to the same as described above for ^R1 and n for ^X1 and ^X2 . From the viewpoint of improving the solubility of the polymer [P] in the solvent, m is preferably 0 to 2, more preferably 0 or 1.

Preferred specific examples of ^Y1 include groups represented by the following formulae (Y-1) to (Y-15). (In formula (Y-1) to formula (Y-15), "Boc" is tert-butyloxycarbonyl. "*" represents a bond.)

As preferred specific examples of the specific structure, the structures represented by the following formulas (1-1) to (1-21) can be cited. [Chemistry 6] [Chemistry 7] [Chemistry 8] (In formula (1-14) to formula (1-19), R ¹¹ is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a tert-butoxycarbonyl group. "*" represents a bond.)

The specific structure is particularly preferably a structure represented by each of the above formulas (1-1) to (1-21), (1-1) to (1-11), and (1-14) to (1-18).

The main chain of the polymer [P] is not particularly limited as long as a specific structure can be introduced into the main chain. In terms of facilitating the introduction of the polymer [P] into the main chain, the polymer [P] is preferably a polymer comprising a structural unit derived from a monomer having a specific structure, and more preferably a polymer comprising a structural unit derived from a diamine compound having a specific structure (hereinafter also referred to as "specific diamine"). Among these, in terms of being able to form a liquid crystal alignment film having high affinity with liquid crystals and mechanical strength and high reliability, the polymer [P] is preferably a polymer comprising at least one selected from the group consisting of polyamic acid, polyamic acid ester and polyimide.

Here, the main chain refers to the part of the polymer that contains the longest atomic chain, the "trunk". In addition, the "trunk" part is allowed to contain a ring structure. In other words, "having a specific structure in the main chain" means that the specific structure constitutes a part of the main chain. The so-called "side chain" refers to the part that branches from the "trunk" of the polymer.

In the polymer [P], the content ratio of the structural unit derived from the monomer having a specific structure relative to the total amount of the monomer units possessed by the polymer [P] is preferably 5 mol% or more, more preferably 10 mol% or more, further preferably 20 mol% or more, and further preferably 30 mol% or more.

The specific diamine used in the synthesis of the polymer [P] is preferably a compound represented by the following formula (3). (In formula (3), ^B5 and ^B6 are independently a single bond or a divalent aromatic cyclic group. When ^B1 is a divalent aromatic cyclic group, ^B5 is a single bond, and when ^B2 is a divalent aromatic cyclic group, ^B6 is a single bond. ^A1 , ^A2 , ^{B1 ,} B2, ^X1 , ^X2 and ^Y1 have the same meanings as in formula (1).)

In the formula (3), the description of the divalent aromatic ring group of ^B1 and ^B2 is applicable to the examples and preferred examples of the divalent aromatic ring group of ^B5 and ^B6 . From the viewpoint of achieving a high density of the liquid crystal alignment film, ^B5 and ^B6 are preferably a single bond or a divalent aromatic hydrocarbon, more preferably a single bond or a phenylene group, and particularly preferably a single bond. The description of the formula (1) is applicable to the examples and preferred examples of ^A1 , ^A2 , ^B1 , ^B2 , ^X1 , ^X2 and ^Y1 .

Preferred examples of the specific diamine include compounds represented by the following formulas (3-1) to (3-25). [Chemistry 11] [Chemistry 12] [Chemistry 13] (In formula (3-14) to formula (3-19), R ¹¹ is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a tert-butoxycarbonyl group.)

Among the above, the specific diamine is preferably a compound represented by each of the above formula (3-1) to (3-11) and formula (3-14) to (3-18). In addition, the specific diamine may be used alone or in combination of two or more.

(Polyamide) When the polymer [P] is polyamide, the polyamide (hereinafter, also referred to as "polyamide [P]") can be obtained by reacting tetracarboxylic dianhydride with a diamine compound containing a specific diamine.

(Tetracarboxylic dianhydride) Examples of tetracarboxylic dianhydrides used in the synthesis of polyamide [P] include aliphatic tetracarboxylic dianhydrides, alicyclic tetracarboxylic dianhydrides, aromatic tetracarboxylic dianhydrides, and the like. As specific examples of these, aliphatic tetracarboxylic dianhydrides include 1,2,3,4-butanetetracarboxylic dianhydride and ethylenediaminetetraacetic dianhydride; alicyclic tetracarboxylic dianhydrides include 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic dianhydride, 5-(2,5-dioxotetrahydrofuran-3-yl)-3a,4,5,9b-tetrahydronaphtho[1,2-c]furan-1,3-dione, 5-(2,5-dioxotetrahydrofuran-3-yl)-8-methyl-3a,4,5,9 b-tetrahydronaphtho[1,2-c]furan-1,3-dione, 2,4,6,8-tetracarboxybiscyclo[3.3.0]octane-2:4,6:8-dianhydride, cyclopentanetetracarboxylic dianhydride, cyclohexanetetracarboxylic dianhydride, etc.; aromatic tetracarboxylic dianhydride includes pyromellitic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, ethylene glycol ditrimellitate, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 4,4'-carbonyldiphthalic anhydride, etc., and in addition, tetracarboxylic dianhydrides described in Japanese Patent Laid-Open No. 2010-97188 can be used. As the tetracarboxylic dianhydride, one kind can be used alone or two or more kinds can be used in combination.

In terms of obtaining a liquid crystal alignment film having high solubility in a solvent and exhibiting good electrical properties and low residual image properties, the tetracarboxylic dianhydride used in the synthesis of polyamide [P] is preferably a compound comprising at least one selected from the group consisting of aliphatic tetracarboxylic dianhydride and alicyclic tetracarboxylic dianhydride, and more preferably alicyclic tetracarboxylic dianhydride. The proportion of alicyclic tetracarboxylic dianhydride used relative to the total amount of tetracarboxylic dianhydride used in the synthesis of polyamide [P] is preferably 20 mol% or more, more preferably 40 mol% or more, and further preferably 50 mol% or more.

(Diamine compound) The diamine compound used in the synthesis of polyamide [P] may be only a specific diamine, or a diamine different from the specific diamine (hereinafter also referred to as "other diamine") may be used together with the specific diamine. Examples of the other diamine include aliphatic diamines, alicyclic diamines, aromatic diamines, diaminoorganosiloxanes, and the like.

Specific examples of other diamines include aliphatic diamines such as m-xylene diamine and hexamethylene diamine; alicyclic diamines such as 1,4-diaminocyclohexane and 4,4'-methylenebis(cyclohexylamine); aromatic diamines such as p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4-aminophenyl-4-aminobenzoate, 4,4'-diaminoazobenzene, 3,5-diaminobenzoic acid, 1,5-bis(4-aminophenoxy)pentane, 1,2-bis(4-aminophenoxy)ethane, 1,3-bis(4 -aminophenoxy) propane, 1,6-bis(4-aminophenoxy)hexane, bis[2-(4-aminophenyl)ethyl]adipic acid, 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis(4-aminophenyl)hexafluoropropane, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-diaminodiphenylamine, 2,2'-dimethyl-4,4'-diaminobiphenyl, 4,4'-(phenylenediamine) isopropyl) dianiline, 2,6-diaminopyridine, 2,4-diaminopyrimidine, 3,6-diaminooxazole, N-methyl-3,6-diaminooxazole, 3,6-diaminoacridine and other main chain diamines; hexadecyloxy-2,4-diaminobenzene, octadecyloxy-2,4-diaminobenzene, octadecyloxy-2,5-diaminobenzene, cholesteryloxy-3,5-diaminobenzene, cholesteryloxy-3,5-diaminobenzene, cholesteryloxy-2,4-diaminobenzene, cholesteryloxy-2,4-diaminobenzene, 3 ,5-diaminobenzoic acid cholesteryl ester, 3,5-diaminobenzoic acid cholesteryl, 3,5-diaminobenzoic acid lanosteryl ester, 3,6-bis(4-aminobenzyloxy)cholestane, 3,6-bis(4-aminophenoxy)cholestane, 4-(4'-trifluoromethoxybenzyloxy)cyclohexyl-3,5-diaminobenzoate, 1,1-bis(4-((aminophenyl)methyl)phenyl)-4-butylcyclohexane, 3,5-diaminobenzoic acid = 5ξ-cholestane-3-yl, the following formula (E-1) [Chemistry 14] (In formula (E-1), X ^I and X ^II are independently a single bond, -O-, *-COO- or *-OCO- (where "*" represents a bond to X ^I ), R ^I is an alkanediyl group having 1 to 3 carbon atoms, R ^II is a single bond or an alkanediyl group having 1 to 3 carbon atoms, a is 0 or 1, b is an integer from 0 to 2, c is an integer from 1 to 20, and d is 0 or 1. Wherein a and b are not 0 at the same time) compounds represented by side-chain diamines, etc., diaminoorganosiloxanes include 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, etc. Examples of the compounds represented by formula (E-1) include compounds represented by the following formulas (E-1-1) to (E-1-4), etc. [Chemistry 15]

When synthesizing polyamide [P], from the viewpoint of obtaining a liquid crystal element that exhibits a low pretilt angle, is not prone to afterimages, exhibits a high voltage holding ratio (VHR), and has high reliability, the specific diamine is preferably used in an amount of 20 mol% or more, more preferably 30 mol% or more, and further preferably 50 mol% or more relative to the total amount of the diamine compound used in the synthesis of polyamide [P]. In addition, as other diamines, one type may be used alone or two or more types may be used in combination.

(Synthesis of polyamide) Polyamide [P] can be obtained by reacting tetracarboxylic dianhydride and diamine compound, and optionally with a molecular weight modifier. In the synthesis reaction of polyamide [P], the ratio of tetracarboxylic dianhydride to diamine compound is preferably such that the anhydride group of tetracarboxylic dianhydride is 0.2 to 2 equivalents per 1 equivalent of the amino group of the diamine compound. Examples of molecular weight modifiers include: monoanhydrides such as maleic anhydride, phthalic anhydride, and itaconic anhydride; monoamine compounds such as aniline, cyclohexylamine, and n-butylamine; and monoisocyanate compounds such as phenyl isocyanate and naphthyl isocyanate. The molecular weight modifier is preferably used in an amount of 20 parts by mass or less per 100 parts by mass of the total of the tetracarboxylic dianhydride and diamine compound used.

The synthesis reaction of polyamine [P] is preferably carried out in an organic solvent. The reaction temperature is preferably -20°C to 150°C, and the reaction time is preferably 0.1 hour to 24 hours. Examples of the organic solvent used in the reaction include aprotic polar solvents, phenolic solvents, alcoholic solvents, ketone solvents, ester solvents, etheric solvents, halogenated hydrocarbons, hydrocarbons, etc. As specific examples thereof, it is preferred to use one or more selected from the group consisting of N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, γ-butyrolactone, tetramethylurea, hexamethylphosphatamide, m-cresol, xylenol and halogenated phenol as the reaction solvent, or to use a mixture of one or more of these and other organic solvents (e.g., butyl solvent, diethylene glycol diethyl ether, etc.). The amount of the organic solvent used (a) is preferably an amount in which the total amount (b) of tetracarboxylic dianhydride and diamine is 0.1 mass % to 50 mass % relative to the total amount (a+b) of the reaction solution.

In the above manner, a polymer solution in which polyamine [P] is dissolved is obtained. The polymer solution can be directly used for the preparation of a liquid crystal alignment agent, or the polymer solution can be used for the preparation of a liquid crystal alignment agent after the polyamine [P] contained in the polymer solution is separated.

<Polyamide> When the polymer [P] is a polyamide, the polyamide (hereinafter also referred to as "polyamide [P]") can be obtained, for example, by the following methods: [I] a method of reacting a polyamide [P] with an esterifying agent; [II] a method of reacting a tetracarboxylic acid diester with a diamine compound containing a specific diamine; [III] a method of reacting a tetracarboxylic acid diester dihalide with a diamine compound containing a specific diamine. The polyamide [P] may have only an amide structure, or may be a partially esterified product in which an amide structure and an amide structure coexist. The reaction solution in which the polyamic acid ester [P] is dissolved may be directly used for the preparation of the liquid crystal alignment agent, or the polyamic acid ester [P] contained in the reaction solution may be separated and then used for the preparation of the liquid crystal alignment agent.

<Polyimide> When the polymer [P] is a polyimide, the polyimide (hereinafter also referred to as "polyimide [P]") can be obtained, for example, by subjecting the polyamine [P] synthesized in the above manner to dehydration and ring closure and imidization. The polyimide [P] may be a complete imidization product in which all the amide structures of the polyamine [P] as a precursor thereof are dehydrated and ring closed, or a partial imidization product in which only a part of the amide structure is dehydrated and ring closed, so that the amide structure and the imide ring structure coexist. The polyimide [P] preferably has an imidization rate of 20% to 99%, more preferably 30% to 90%. In addition, the imidization rate is expressed as a percentage of the number of imide ring structures relative to the total number of amide structures and imide ring structures of the polyimide. Here, a part of the imide ring may be an isoimide ring.

The dehydration and ring closure of polyamine [P] is preferably carried out by dissolving polyamine [P] in an organic solvent, adding a dehydrating agent and a dehydration and ring closure catalyst to the solution, and heating as needed. In the method, as a dehydrating agent, for example, an acid anhydride such as acetic anhydride, propionic anhydride, trifluoroacetic anhydride, etc. can be used. The amount of the dehydrating agent used is preferably set to 0.01 mol to 20 mol relative to 1 mol of the amide structure of polyamine [P]. As a dehydration and ring closure catalyst, for example, a tertiary amine such as pyridine, coltidine, dimethylpyridine, triethylamine, etc. can be used. The amount of the dehydration ring-closing catalyst used is preferably set to 0.01 mol to 10 mol relative to 1 mol of the dehydrating agent used. As the organic solvent used in the dehydration ring-closing reaction, the organic solvent exemplified as the organic solvent used in the synthesis of polyamide [P] can be listed. The reaction temperature of the dehydration ring-closing reaction is preferably 0°C to 180°C. The reaction time is preferably 1.0 hour to 120 hours. In addition, the reaction solution containing polyimide [P] can be directly used for the preparation of a liquid crystal alignment agent, or it can be used for the preparation of a liquid crystal alignment agent after the polyimide [P] is separated.

Regarding the solution viscosity of the polymer [P] used in the preparation of the liquid crystal alignment agent, when a solution with a concentration of 10 mass % is prepared, it is preferably 10 mPa·s to 800 mPa·s, and more preferably 15 mPa·s to 500 mPa·s. In addition, the solution viscosity (mPa·s) is a value measured at 25°C using an E-type rotational viscometer for a 10 mass % polymer solution prepared using a good solvent for the polymer (P) (for example, γ-butyrolactone, N-methyl-2-pyrrolidone, etc.).

The weight average molecular weight (Mw) of the polymer [P] measured by colloid permeation chromatography (GPC) in terms of polystyrene is preferably 1,000 to 500,000, more preferably 2,000 to 300,000. In addition, the molecular weight distribution (Mw/Mn) represented by the ratio of Mw to the number average molecular weight (Mn) in terms of polystyrene measured by GPC is preferably 7 or less, more preferably 5 or less. In the preparation of the liquid crystal alignment agent, the polymer (P) may be used alone or in combination of two or more.

<Other components> In addition to the polymer [P], the liquid crystal alignment agent may contain components different from the polymer [P] (hereinafter also referred to as "other components") as needed.

(Other polymers) The liquid crystal alignment agent disclosed in the present invention may also contain a polymer having no specific structure (hereinafter also referred to as "other polymers") as a polymer component. The main skeleton of the other polymer is not particularly limited. As other polymers, for example: polyamic acid, polyamic acid ester, polyimide, polysiloxane, polyester, polyenamine, polyurea, polyamide, polyamide imide, polybenzoxazole precursor, polybenzoxazole, cellulose derivative, polyacetal, (meth) acrylic polymer, styrene polymer, maleimide polymer, or styrene-maleimide polymer. From the viewpoint of having high affinity with liquid crystal when used together with the polymer [P] and improving the reliability of the liquid crystal element, the other polymer is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester and polyimide.

When other polymers are contained in the liquid crystal alignment agent, the content ratio of polymer [P] relative to the total amount of polymer [P] and other polymers is preferably 5 mass % or more, more preferably 10 mass % or more, further preferably 20 mass % or more, further preferably 30 mass % or more. As other polymers, one kind may be used alone or two or more kinds may be used in combination.

(Solvent) The liquid crystal alignment agent disclosed in the present invention is prepared in the form of a liquid composition in which the polymer [P] and other components used as needed are preferably dispersed or dissolved in an appropriate solvent.

As the solvent, an organic solvent is preferably used. Specific examples thereof include: N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 1,2-dimethyl-2-imidazolidinone, 1,3-dimethyl-2-imidazolidinone, phenol, γ-butyrolactone, γ-butyrolactamide, N,N-dimethylformamide, N,N-dimethylacetamide, 4-hydroxy-4-methyl-2-pentanone, diacetone alcohol, 1-hexanol, 2-hexanol, propane-1,2-diol, 3-methoxy-1-butanol, ethylene glycol monomethyl ether, methyl lactate, ethyl lactate, butyl lactate, methyl acetate, ethyl acetate, butyl acetate, acetic acid Methyl ester, ethyl acetylacetate, ethyl propionate, methyl methoxypropionate, ethyl ethoxypropionate, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-isopropyl ether, ethylene glycol-n-butyl ether (butyl solvent), ethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diisobutyl ketone, isoamyl propionate, isoamyl isobutyrate, diisoamyl ether, ethyl carbonate, propyl carbonate, propylene glycol monomethyl ether (Propylene glycol monomethyl ether (PGME), diethylene glycol diethyl ether acetate, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol diacetate, cyclopentane, cyclohexane, etc. These can be used alone or in combination of two or more.

As other components contained in the liquid crystal alignment agent, in addition to the above, for example, there can be listed: antioxidants, metal chelate compounds, hardening accelerators, surfactants, fillers, dispersants, photosensitizers, etc. The mixing ratio of other components can be appropriately selected according to each compound within the range that does not impair the effects of the present invention.

The solid component concentration in the liquid crystal alignment agent (the ratio of the total mass of the components other than the solvent of the liquid crystal alignment agent to the total mass of the liquid crystal alignment agent) is appropriately selected in consideration of viscosity, volatility, etc., and is preferably in the range of 1 mass % to 10 mass %. If the solid component concentration is 1 mass % or more, the film thickness of the coating can be fully ensured, and a liquid crystal alignment film showing good liquid crystal alignment can be easily obtained. On the other hand, if the solid component concentration is 10 mass % or less, the coating can be made to have an appropriate thickness, and a liquid crystal alignment film showing good liquid crystal alignment can be easily obtained. In addition, the viscosity of the liquid crystal alignment agent becomes moderate and there is a tendency to make the coating property better.

《Liquid crystal alignment film and liquid crystal element》 The liquid crystal alignment film disclosed herein can be manufactured by using a liquid crystal alignment agent prepared as described above. In addition, the liquid crystal element disclosed herein includes a liquid crystal alignment film formed using the liquid crystal alignment agent described above. The driving method of the liquid crystal in the liquid crystal element is not particularly limited, and can be applied to various modes such as twisted nematic (TN), super twisted nematic (STN), vertical alignment (VA) (including vertical alignment-multi-domain vertical alignment (VA-MVA), vertical alignment-patterned vertical alignment (VA-PVA), in-plane switching (IPS), fringe field switching (FFS), optically compensated bend (OCB), polymer sustained alignment (PSA), etc. The liquid crystal element can be manufactured, for example, by a method including the following steps 1 to 3. Step 1 uses different substrates depending on the desired operation mode. Step 2 and step 3 are common in all operation modes.

<Step 1: Formation of coating film> First, a coating film is formed on a substrate by coating a liquid crystal alignment agent on the substrate, preferably by heating the coated surface. As the substrate, for example, glass such as float glass and sodium glass; transparent substrates containing plastics such as polyethylene terephthalate, polybutylene terephthalate, polyether sulfone, polycarbonate, and poly(aliphatic cycloolefin) can be used. As a transparent conductive film provided on one side of the substrate, a NESA film (registered trademark of PPG, USA) containing tin oxide (SnO ₂ ), an indium tin oxide (ITO) film containing indium oxide-tin oxide (In ₂ O ₃ -SnO ₂ ), etc. can be used. When manufacturing TN, STN or VA type liquid crystal elements, two substrates provided with patterned transparent conductive films are used. On the other hand, when manufacturing IPS or FFS type liquid crystal elements, a substrate provided with electrodes patterned in a comb shape and an opposing substrate without electrodes are used.

The method for applying the liquid crystal alignment agent to the substrate is not particularly limited, and it can be carried out, for example, by spin coating, printing (for example, offset printing, flexographic printing, etc.), inkjet, slit coating, rod coating, extrusion die, direct gravure coater, chamber doctor coater, offset gravure coater, impregnation coater, MB coater, etc.

After applying the liquid crystal alignment agent, it is preferred to perform preheating (pre-baking) for the purpose of preventing the applied liquid crystal alignment agent from flowing. The pre-baking temperature is preferably 30°C to 200°C, and the pre-baking time is preferably 0.25 minutes to 10 minutes. Thereafter, the solvent is completely removed, and a calcination (post-baking) step is performed as needed for the purpose of thermally imidizing the amide structure present in the polymer. The calcination temperature (post-baking temperature) at this time is preferably 80°C to 280°C, and more preferably 80°C to 250°C. The post-baking time is preferably 5 minutes to 200 minutes. The film thickness of the formed film is preferably 0.001 μm to 1 μm.

<Step 2: Alignment treatment> In the case of manufacturing TN type, STN type, IPS type or FFS type liquid crystal elements, a treatment (alignment treatment) is performed to impart liquid crystal alignment ability to the coating formed in the step 1. Thereby, the alignment ability of the liquid crystal molecules is imparted to the coating to form a liquid crystal alignment film. As the alignment treatment, it is preferred to use a friction treatment in which the surface of the coating formed on the substrate is wiped with cotton or the like, or a light alignment treatment in which the coating is irradiated with light to impart liquid crystal alignment ability to it. In the case of manufacturing a vertical alignment type liquid crystal element, the coating formed in the step 1 can be directly used as a liquid crystal alignment film, and in order to further improve the liquid crystal alignment ability, the coating can also be subjected to an alignment treatment.

Light irradiation for photo-alignment can be performed using the following methods, etc.: a method of irradiating the coating after the post-baking step; a method of irradiating the coating after the pre-baking step and before the post-baking step; a method of irradiating the coating while the coating is heated in at least one of the pre-baking step and the post-baking step. As radiation irradiated to the coating, for example, ultraviolet light and visible light containing a wavelength of 150 nm to 800 nm can be used. Ultraviolet light containing a wavelength of 200 nm to 400 nm is preferred. When the radiation is polarized, it can be linearly polarized or partially polarized. When the radiation used is linearly polarized or partially polarized, the irradiation can be performed from a direction perpendicular to the substrate surface, from an oblique direction, or a combination of these directions. The irradiation direction of non-polarized radiation is set to be an oblique direction.

Examples of the light source used include low-pressure mercury lamps, high-pressure mercury lamps, deuterium lamps, metal halide lamps, argon resonance lamps, xenon lamps, and excimer lasers. The radiation dose is preferably 200 J/m ² to 30,000 J/m ² , and more preferably 500 J/m ² to 10,000 J/m ² . After irradiation with light for imparting alignment ability, the substrate surface may be cleaned with water, an organic solvent (e.g., methanol, isopropyl alcohol, 1-methoxy-2-propanol acetate, butyl solvent, ethyl lactate, etc.) or a mixture thereof, or the substrate may be heated.

<Step 3: Construction of liquid crystal cell> Prepare two substrates with liquid crystal alignment films formed in the above manner, and arrange liquid crystal between the two substrates arranged opposite to each other, thereby manufacturing a liquid crystal cell. When manufacturing a liquid crystal cell, for example, the following methods can be listed: arrange the two substrates opposite to each other with a gap in between so that the liquid crystal alignment films face each other, use a sealant to bond the periphery of the two substrates, inject liquid crystal into the cell gap surrounded by the substrate surface and the sealant and seal the injection hole, and use a liquid crystal drop (One Drop Fill, ODF) method. As a sealant, for example, an epoxy resin containing a hardener and aluminum oxide balls as a spacer can be used. As a liquid crystal, either a positive type or a negative type can be used, preferably a negative type. Examples of negative liquid crystals include "MLC-6608", "MLC-6609", "MLC-6610", and "MLC-7026-100" manufactured by Merck. In particular, when negative liquid crystals are used in IPS-type and FFS-type liquid crystal elements, they are preferred in terms of reducing the transmission loss above the electrode and improving the contrast. In addition, examples of liquid crystals include nematic liquid crystals and discotic liquid crystals, and nematic liquid crystals are preferred.

When manufacturing a liquid crystal display device, a polarizing plate is then attached to the outer surface of the liquid crystal unit to obtain a liquid crystal display element. Examples of polarizing plates include a polarizing plate formed by sandwiching a polarizing film called "H film" between cellulose acetate protective films or a polarizing plate containing the H film itself. The "H film" is a film formed by stretching and aligning polyvinyl alcohol on one side and absorbing iodine on the other side.

The reason why a liquid crystal element that exhibits a low pretilt angle, is less likely to produce afterimages, has a high voltage holding ratio, and is excellent in reliability even when a negative liquid crystal is used, by forming a liquid crystal alignment film using a polymer [P] is not certain, but is considered to be as follows. The polymer [P] has a nitrogen-containing aromatic heterocyclic structure in the main chain, and has an aromatic ring bonded to -O- or -NR ¹ -(CH ₂ ) _n - at a specific position (see the above formula (1)). It is considered that due to the interaction between the molecules of the polymers, the liquid crystal alignment film is made denser, and ionic impurities generated due to long-term use are fixed on the film to suppress the increase in ion density, thereby exhibiting good low pretilt angle characteristics and low afterimage characteristics.

The liquid crystal element of the present invention can be effectively applied to various purposes. Specifically, for example, it can be used as a clock, a portable game console, a word processor, a notebook-type personal computer, a car navigation system, a camera, a personal digital assistant (PDA), a digital camera, a mobile phone, a smart phone, various monitors, a liquid crystal television, an information display, and other display devices or dimming devices, a phase difference film, etc.

[Examples] The following describes the implementation method in more detail based on the examples, but the present invention is not to be interpreted as being limited to the following examples.

In the following examples, the weight average molecular weight Mw of the polymer, the imidization rate of the polyimide in the polymer solution, the solution viscosity of the polymer solution and the epoxy equivalent are measured by the following method. The required amount of the raw material compound and the polymer used in the following examples is ensured by repeating the synthesis under the synthesis scale shown in the following synthesis example as needed. [Weight average molecular weight Mw of polymer] The weight average molecular weight Mw is a polystyrene conversion value measured by GPC under the following conditions. Column: TSKgelGRCXLII manufactured by Tosoh Co., Ltd. Solvent: N,N-dimethylformamide solution containing lithium bromide and phosphoric acid Temperature: 40°C Pressure: 68 kgf/ ^cm2 [Imidization rate of polyimide] The polyimide solution was added to pure water, the obtained precipitate was fully dried under reduced pressure at room temperature, and then dissolved in deuterated dimethyl sulfoxide. ^1H -NMR ( ^1H -NMR) was measured at room temperature using tetramethylsilane as ^a reference substance. The imidization rate [%] was calculated from the obtained ^1H -NMR spectrum using the following formula (1). Imidization rate [%] = (1-( ^A1 /( ^A2 ×α)))×100 …(1) (In formula (1), ^A1 is the peak area of protons derived from NH groups appearing around the chemical shift of 10 ppm, ^A2 is the peak area derived from other protons, and α is the ratio of other protons to the number of protons in the NH group in the polymer precursor (polyamine).)

The abbreviations of the compounds are as follows. In addition, in the following, the compound represented by formula (X) is sometimes simply represented as "compound (X)". [Chemistry 17] [Chemistry 18]

<Synthesis of polymer> 1. Synthesis of polyamine [Synthesis Example 1] 100 mol parts of 1,3-dimethylcyclobutane-1,2:3,4-tetracarboxylic dianhydride as tetracarboxylic dianhydride and 100 mol parts of compound (DA-1) as diamine compound were dissolved in N-methyl-2-pyrrolidone (NMP) and reacted at room temperature for 6 hours to obtain a solution containing 15% by mass of polyamine (referred to as "polymer (PA-1)"). [Synthesis Example 2 to Synthesis Example 12] Except that the types and amounts of tetracarboxylic dianhydride and diamine compounds used were changed as shown in Table 1 below, the same operation as in Synthesis Example 1 was performed to obtain polyamides (polymers (PA-2) to (PA-7), polymers (PB-1) to (PB-5)).

2. Synthesis of polyimide [Synthesis Example 13] 100 mol parts of 1,3-dimethylcyclobutane-1,2:3,4-tetracarboxylic dianhydride as tetracarboxylic dianhydride and 100 mol parts of compound (DA-1) as diamine compound were dissolved in NMP and reacted at room temperature for 6 hours to obtain a solution containing 15% by mass of polyimide. Then, NMP was added to the obtained polyimide solution to prepare a solution having a polyimide concentration of 10% by mass, and pyridine and acetic anhydride were added to perform a dehydration ring-closing reaction at 60°C for 4 hours. After the dehydration ring-closing reaction, the solvent in the system was replaced with new NMP to obtain a solution containing 15% by mass of a polyimide (hereinafter referred to as "polymer (PI-1)") having an imidization rate of about 70%. [Synthesis Examples 14 to 16] Except that the types and amounts of the tetracarboxylic dianhydride and diamine compound used were changed as shown in Table 1 below, the same operation as in Synthesis Example 13 was performed to obtain polyimides (polymers (PI-2) to (PI-4)).

[Table 1] [Table 1] Synthesis of polymer Polymer Name Monomer (molar parts) Anhydride 1 Anhydride 2 Diamine 1 Diamine 2 Synthesis Example 1 PA-1 TA-2 (100) - DA-1 (100) Synthesis Example 2 PA-2 TA-2 (100) - DA-2 (100) Synthesis Example 3 PA-3 TA-2 (100) - DA-3 (100) Synthesis Example 4 PA-4 TA-2 (100) - DA-5 (100) Synthesis Example 5 PA-5 TA-1 (70) TA-3 (30) DA-1 (100) Synthesis Example 6 PA-6 TA-2 (100) - DA-6 (100) Synthesis Example 7 PA-7 TA-1 (70) TA-3 (30) DA-4 (80) DB-5 (20) Synthesis Example 8 PB-1 TA-2 (100) - DB-1 (100) Synthesis Example 9 PB-2 TA-2 (100) - DB-2 (100) Synthesis Example 10 PB-3 TA-2 (100) - DB-3 (100) Synthesis Example 11 PB-4 TA-2 (100) - DB-4 (100) Synthesis Example 12 PB-5 TA-1 (50) TA-3 (50) DB-5 (100) Synthesis Example 13 PI-1 TA-2 (100) - DA-1 (100) Synthesis Example 14 PI-2 TA-2 (100) - DA-1 (60) DA-5 (40) Synthesis Example 15 PI-3 TA-1 (70) TA-3 (30) DA-1 (100) Synthesis Example 16 PI-4 TA-2 (100) - DA-5 (100)

[Example 1] 1. Preparation of liquid crystal alignment agent The solution of the polymer (PA-1) obtained in Synthesis Example 1 was diluted with NMP and butyl cellosolve (BC) to prepare a solution having a solvent composition of NMP/BC = 80/20 (mass ratio) and a solid content of 3.5 mass %. The solution was filtered using a filter with a pore size of 0.2 μm to prepare a liquid crystal alignment agent (AL-1).

2. Manufacture of FFS-type liquid crystal unit using rubbing method A glass substrate (set as the first substrate) with a flat electrode (bottom electrode), an insulating layer and a comb-shaped electrode (top electrode) stacked in sequence on one side, and a glass substrate (set as the second substrate) without an electrode were prepared. Then, a liquid crystal alignment agent (AL-1) was applied to the electrode formation surface of the first substrate and the single side of the second substrate using a rotator, and heated on a hot plate at 110°C for 3 minutes (pre-baking). After that, it was dried for 30 minutes in a 230°C oven with nitrogen substituted in the chamber (post-baking), and a coating with an average film thickness of 0.08 μm was formed. Next, the coated surface was rubbed using a rubbing machine with a roller wrapped with rayon cloth at a roller speed of 1000 rpm, a platform moving speed of 3 cm/sec, and a hair pressing length of 0.3 mm. After that, ultrasonic cleaning was performed in ultrapure water for 1 minute, and then dried in a clean oven at 100°C for 10 minutes, thereby obtaining a pair of substrates with a liquid crystal alignment film. Next, for a pair of substrates with a liquid crystal alignment film, a liquid crystal injection port was left at the edge of the surface where the liquid crystal alignment film was formed, and an epoxy resin adhesive with alumina balls of 3.5 μm in diameter was added by screen printing. After that, the substrates are overlapped and pressed together, and the adhesive is thermally cured at 150°C for 1 hour. Then, negative liquid crystal (MLC-6608 manufactured by Merck) is filled into the gap between the pair of substrates from the liquid crystal injection port, and then the liquid crystal injection port is sealed with an epoxy adhesive. Furthermore, in order to remove the flow alignment during the injection of the liquid crystal, it is heated at 120°C and then slowly cooled to room temperature, thereby manufacturing a liquid crystal unit. In addition, when overlapping a pair of substrates, the friction method of each substrate is made anti-parallel. As the top electrode, a comb electrode with a plurality of parallel linear electrodes bent in the middle into a "ㄑ" shape is used, and the electrode line width is 3 μm, and the distance between the electrodes is 6 μm (refer to Figure 3 of Japanese Patent Publication No. 2014-77845). The obtained liquid crystal unit has two pixel areas (first area and second area) with different liquid crystal orientations, with the bent part of the linear electrode as the boundary, and can perform multi-domain driving.

3. Evaluation of low pre-tilt angle characteristics For the liquid crystal cell manufactured in 2. above, the tilt angle of the liquid crystal molecules relative to the substrate surface was measured by the crystal rotation method using He-Ne laser according to the method described in the non-patent document "T.J. Scheffer et al. Journal of Applied Physics (J. Appl. Phys.) Vol. 19, p. 2013 (1980)", and the value was used as the pre-tilt angle. When the measured value of the pre-tilt angle is less than 0.7 degrees, it is set as "excellent (◎)", when it is 0.7 degrees or more and less than 0.9 degrees, it is set as "good (○)", when it is 0.9 degrees or more and less than 1.1 degrees, it is set as "acceptable (△)", and when it is 1.1 degrees or more, it is set as "unacceptable (×)". As a result, the evaluation of the low pre-tilt angle characteristics of the above-mentioned embodiment is "excellent".

4. Evaluation of low afterimage characteristics In a constant temperature environment of 60°C, an AC voltage of 10 V was applied between the electrodes of the FFS-type liquid crystal unit manufactured in 2. for 72 hours. Thereafter, the top electrode and the bottom electrode of the liquid crystal unit were short-circuited, and the state was maintained and placed at room temperature for 1 day. After being placed for 1 day, the liquid crystal unit was arranged between two polarizing plates arranged in a manner such that the polarization axes were orthogonal, and the backlight was turned on without applying a voltage, and the arrangement angle of the liquid crystal unit was adjusted to minimize the brightness of the transmitted light. The rotation angle when the liquid crystal unit is rotated from the darkest angle of one of the two pixel areas of the FFS-type liquid crystal unit to the darkest angle of the other area is set to angle Δθ. It can be said that the smaller the angle Δθ, the less likely afterimages are to occur, and the better the low afterimage characteristics. When the angle Δθ was less than 0.10 degrees, it was evaluated as "excellent (◎)", when it was greater than 0.10 degrees and less than 0.15 degrees, it was evaluated as "good (○)", when it was greater than 0.15 degrees and less than 0.20 degrees, it was evaluated as "acceptable (△)", and when it was greater than 0.20 degrees, it was evaluated as "unacceptable (×)". As a result, the low afterimage characteristic of the embodiment was evaluated as "excellent".

5. Evaluation of electrical properties The liquid crystal cell manufactured in 2. was placed in an oven at 60°C, and the voltage holding rate (also referred to as "initial VHR") was measured at 1 V and 1670 msec using a VHR measuring device manufactured by Toyo Technica. As the evaluation standard, an initial VHR of 80% or more was rated as "excellent (◎)", a value of less than 80% and more than 70% was rated as "good (○)", a value of less than 70% and more than 60% was rated as "acceptable (△)", and a value of less than 60% was rated as "unacceptable (×)". As a result, the initial VHR of the embodiment was evaluated as "good".

6. Evaluation of reliability after light irradiation The reliability of the liquid crystal unit manufactured in 2. was evaluated. The evaluation was performed as follows. First, a voltage of 1 V was applied to the liquid crystal unit for 60 microseconds, and the voltage holding rate (VHR1) was measured 1670 milliseconds after the application was released. Then, the liquid crystal unit was irradiated with cold cathode fluorescent lamps (CCFL) (backlight) for one week at 60°C, and then left at room temperature to cool naturally to room temperature. After cooling, a voltage of 1 V was applied to the liquid crystal unit for 60 microseconds, and the voltage holding rate (VHR2) was measured 1670 milliseconds after the application was released. In addition, the measuring device used was "VHR-1" manufactured by Toyo Technica (Co., Ltd.). The change rate of VHR at that time (ΔVHR) was calculated from the difference between VHR1 and VHR2 (ΔVHR = VHR1-VHR2), and the reliability was evaluated based on ΔVHR. When ΔVHR was less than 10%, it was judged as "excellent (◎)", when it was greater than 10% and less than 15%, it was judged as "good (○)", when it was greater than 15% and less than 20%, it was judged as "acceptable (△)", and when it was greater than 20%, it was judged as "unacceptable (×)". As a result, the reliability of the above embodiment was "good".

[Example 2 to Example 11 and Comparative Example 1 to Comparative Example 4] The composition of the liquid crystal alignment agent was changed as shown in Table 2 below, and the liquid crystal alignment agent was prepared in the same manner as in Example 1. In addition, the obtained liquid crystal alignment agent was used to produce an FFS type liquid crystal unit by a rubbing method in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2 below. In addition, in Examples 10 and 11, two polymers were used as polymer components. In Table 2, the numerical values in parentheses in the polymer component column represent the mixing ratio (mass parts) of each polymer used in the preparation of the liquid crystal alignment agent relative to the total amount of the polymer component in terms of solid components.

[Table 2] [Table 2] Evaluation Polymer composition Feature Evaluation Polymer 1 Polymer 2 Low pre-tilt characteristics Low afterimage characteristics Electrical characteristics (initial VHR) VHR Reliability Embodiment 1 PA-1 (100) - ◎ ◎ ○ ○ Embodiment 2 PA-2 (100) - ○ ○ ○ ○ Embodiment 3 PA-3 (100) - ○ ○ ○ ○ Embodiment 4 PA-4 (100) - ◎ ◎ ◎ ○ Embodiment 5 PA-5 (100) - ◎ ○ ○ ○ Embodiment 6 PA-7 (100) - △ ○ ○ ○ Embodiment 7 PI-1 (100) - ○ ○ ○ ○ Embodiment 8 PI-2 (100) - ○ ○ ○ ○ Embodiment 9 PI-3 (100) - ○ ○ ○ ○ Embodiment 10 PI-1 (50) PB-5 (50) ○ ○ ○ ◎ Embodiment 11 PI-3 (50) PB-5 (50) ○ ○ ○ ◎ Comparison Example 1 PB-1 (100) - × △ △ × Comparison Example 2 PB-2 (100) - × △ △ × Comparison Example 3 PB-3 (100) - △ ○ △ △ Comparison Example 4 PB-4 (100) - △ ○ ○ △

As shown in Table 2, compared with Comparative Examples 1 to 4, Examples 1 to 11 have achieved a balance of various characteristics, including low pre-tilt angle characteristics, low afterimage characteristics, initial VHR, and reliability. In particular, in Examples 1 to 5 and Examples 7 to 11, any characteristic is evaluated as "◎" or "○", and is excellent. Among these, in particular, the low pre-tilt angle characteristics of Examples 1, 4, and 5 are "◎", and the low afterimage characteristics are also good.

[Example 12] 1. Preparation of liquid crystal alignment agent The solution of the polymer (PA-4) obtained in Synthesis Example 4 was used and diluted with NMP and BC to prepare a solution having a solvent composition of NMP/BC = 80/20 (mass ratio) and a solid content of 3.5 mass%. The solution was filtered using a filter with a pore size of 0.2 μm to prepare a liquid crystal alignment agent (AL-12).

2. Manufacture of FFS-type liquid crystal display element using photo-alignment method Prepare the same first substrate and second substrate as in Example 1. Then, use a rotator to apply the liquid crystal alignment agent (AL-12) on the electrode forming surface of the first substrate and one of the substrate surfaces of the second substrate, respectively, and heat (pre-bake) for 1 minute using a hot plate at 80°C. Thereafter, dry (post-bake) for 30 minutes in a 230°C oven in which the interior of the chamber is replaced with nitrogen, and form a coating with an average film thickness of 0.1 μm. Use a Hg-Xe lamp to irradiate the obtained coating with 1,000 J/ ^m2 of ultraviolet light containing a bright line of 254 nm with linear polarization from the normal direction of the substrate for photo-alignment treatment. In addition, the irradiation amount is a value measured using a light meter that measures with a wavelength of 254 nm as a reference. Then, the coating that has been subjected to the photo-alignment treatment is heated in a clean oven at 230°C for 30 minutes to perform a heat treatment to form a liquid crystal alignment film. Next, for one of the pair of substrates on which the liquid crystal alignment film is formed, an epoxy resin adhesive to which aluminum oxide balls with a diameter of 3.5 μm are added is applied by screen printing on the outer edge of the surface having the liquid crystal alignment film. Thereafter, the substrates are overlapped and pressed together in such a way that the projection direction of the polarization axis on the substrate surface during light irradiation becomes antiparallel, and the adhesive is thermally cured at 150°C for 1 hour. Next, negative liquid crystal (Merck, MLC-6608) was filled between a pair of substrates from the liquid crystal injection port, and the liquid crystal injection port was sealed with an epoxy adhesive to obtain a liquid crystal unit. Furthermore, in order to remove the flow alignment during the liquid crystal injection, it was heated at 120°C and then slowly cooled to room temperature. After that, polarizing plates were attached to both sides of the outer side of the substrate of the liquid crystal unit to obtain a liquid crystal display element. In addition, by performing the above series of operations by varying the UV exposure after post-baking within the range of 100 J/ ^m2 to 10,000 J/ ^m2 , three or more liquid crystal display elements with different UV exposure amounts were manufactured, and the liquid crystal display element with the exposure amount (optimal exposure amount) showing the best alignment characteristics was used for the following evaluations of liquid crystal alignment, low afterimage characteristics, electrical characteristics, and reliability.

3. Evaluation of Photoreactivity The liquid crystal alignment agent (AL-12) prepared in 1. was applied to a quartz substrate using a rotator, heated on a hot plate at 80°C for 1 minute, and dried for 30 minutes in an oven at 230°C in which the interior was replaced with nitrogen, to form a coating having an average film thickness of 0.1 μm. The coating surface was irradiated with 1,000 J/m ² of ultraviolet light containing a bright line of 254 nm with linear polarization from a Hg-Xe lamp in the normal direction of the substrate. Thereafter, the photoreactivity was evaluated based on the absorption of the substituted maleimide compound generated by photodecomposition. Specifically, the absorbance of the coating after irradiation with light at the maximum absorption wavelength in the region of 220 nm to 250 nm was measured, and the increase rate relative to the absorbance of the coating before irradiation with light at the wavelength was calculated. When the increase rate of absorbance was 20% or more, it was rated as "excellent (◎)", when the increase rate of absorbance was 10% or more and less than 20%, it was rated as "good (○)", and when the increase rate of absorbance was less than 10%, it was rated as "unacceptable (×)". As a result, the evaluation of the embodiment was "excellent".

4. Evaluation of liquid crystal alignment For the liquid crystal display element manufactured in 2. above, the liquid crystal alignment was evaluated based on the change in brightness when the voltage was turned on/off (ON/OFF) (applied/released) and the presence or absence of abnormal domains observed under a microscope (magnification 50 times). At this time, the case where no abnormal domain was observed was set as "good (○)", and the case where an abnormal domain was observed was set as "unacceptable (×)". As a result, the liquid crystal alignment in the above embodiment was judged to be "good".

5. Evaluation of low afterimage characteristics Except that the polarizing plates were not attached to the outer sides of the substrate, the same operation as in 2. was performed to produce an FFS type liquid crystal unit, and the low afterimage characteristics were evaluated using the same method as in Example 1. As a result, the low afterimage characteristics in the example were judged to be "excellent". 6. Evaluation of electrical characteristics For the liquid crystal display element manufactured in 2., the electrical characteristics were evaluated using the same method as in Example 1. As a result, the electrical characteristics in the example were judged to be "excellent". 7. Evaluation of reliability For the liquid crystal display element manufactured in 2., the reliability was evaluated using the same method as in Example 1. As a result, the reliability in the example was judged to be "good".

[Example 13 to Example 16 and Comparative Example 5, Comparative Example 6] The composition of the liquid crystal alignment agent was changed as shown in Table 3 below, and the liquid crystal alignment agent was prepared in the same manner as in Example 12. In addition, the obtained liquid crystal alignment agent was used to manufacture an FFS type liquid crystal display element by a photoalignment method in the same manner as in Example 12, and various evaluations were performed. The results are shown in Table 3 below. In addition, in Example 15 and Example 16, two polymers were used as polymer components. In Table 3, the numerical values in parentheses in the polymer component column represent the mixing ratio (mass parts) of each polymer used in the preparation of the liquid crystal alignment agent relative to the total amount of the polymer component in terms of solid components. Regarding Example 15 and Example 16, since the photoreactivity was not evaluated, "-" is expressed in the photoreactivity column.

[Table 3] [Table 3] Evaluation Polymer composition Feature Evaluation Polymer 1 Polymer 2 Photoreactivity Liquid crystal alignment Low afterimage characteristics Electrical characteristics (initial VHR) VHR Reliability Embodiment 12 PA-4 (100) - ◎ ○ ◎ ◎ ○ Embodiment 13 PA-6 (100) - ◎ ○ ◎ ◎ ○ Embodiment 14 PI-4 (100) - ◎ ○ ◎ ◎ ○ Embodiment 15 PA-4 (100) PB-5 (50) - ○ ○ ◎ ◎ Embodiment 16 PI-4 (100) PB-5 (50) - ○ ○ ◎ ◎ Comparison Example 5 PB-3 (100) - × ○ △ △ △ Comparison Example 6 PB-4 (100) - ○ ○ ○ ○ △

As shown in Table 3, Examples 12 to 16 have achieved a balance of various characteristics including liquid crystal alignment, low afterimage characteristics, initial VHR, and reliability compared to Comparative Examples 5 and 6. In addition, the liquid crystal alignment agents of Examples 12 to 14 also have excellent light reactivity.

without.

without.

Claims (9)

A liquid crystal alignment agent comprises a polymer [P] having a partial structure represented by the following formula (1) in the main chain: * ^-A1 - ^B1 - ^X1 - ^Y1 - ^X2 - ^B2 - ^A2- * (1) In the formula (1), ^A1 and ^A2 are independently two divalent nitrogen-containing aromatic heterocyclic groups formed by removing any hydrogen atoms bonded to atoms constituting a pyrrole ring, an imidazole ring, a pyrazole ring, a triazole ring, a pyridine ring, a pyrimidine ring, an oxadiazine ring and a pyrazine ring; ^B1 and ^B2 are independently single-bonded or divalent aromatic cyclic groups; ^X1 and ^X2 are independently -O- or ^-NR1- ( _CH2 ) _n- ; R ¹ is a hydrogen atom or a monovalent organic group, and n is an integer of 1 to 3; ^Y1 is a divalent group having one or more aromatic rings and bonded to ^X1 and ^X2 respectively through the same or different aromatic rings; "*" indicates a bond. The liquid crystal alignment agent as described in claim 1, wherein ^Y1 is a divalent group represented by the following formula (2):

In formula (2), B ³ and B ⁴ are independently divalent aromatic cyclic groups, X ³ is a single bond, -O- or -NR ¹ -(CH ₂ ) _n -; R ¹ and n have the same meanings as in formula (1); m is an integer from 0 to 3; when m is 2 or 3, multiple B ⁴ in the formula are the same group or different groups, and multiple X ³ are the same group or different groups; "*" represents a bond. A liquid crystal alignment agent as described in claim 1 or claim 2, wherein the polymer [P] has a structural unit derived from a diamine compound represented by the following formula (3): H ₂ NB ⁵ -A ¹ -B ¹ -X ¹ -Y ¹ -X ² -B ² -A ² -B ⁶ -NH ₂ (3) In formula (3), B ⁵ and B ⁶ are independently a single bond or a divalent aromatic ring group; wherein when B ¹ is a divalent aromatic ring group, B ⁵ is a single bond, and when B ² is a divalent aromatic ring group, B ⁶ is a single bond; A ¹ , A ² , B ¹ , B ² , X ¹ , X ² and Y ¹ have the same meanings as in formula (1). The liquid crystal alignment agent as described in claim 1 or claim 2, wherein the polymer [P] is at least one selected from the group consisting of polyamine, polyamine ester and polyimide. The liquid crystal alignment agent as described in claim 1 or claim 2, wherein the polymer [P] is a polymer having structural units derived from tetracarboxylic acid derivatives and structural units derived from diamine compounds, and the tetracarboxylic acid derivatives include alicyclic tetracarboxylic dianhydride. A method for manufacturing a liquid crystal alignment film, comprising: a step of forming a coating using a liquid crystal alignment agent as described in any one of claim 1 to claim 5, and a step of irradiating the coating with light to impart liquid crystal alignment capability. A method for manufacturing a liquid crystal alignment film, comprising: a step of forming a coating using a liquid crystal alignment agent as described in any one of claim 1 to claim 5, and a step of rubbing the coating to impart liquid crystal alignment capability. A liquid crystal alignment film, which is formed using a liquid crystal alignment agent as described in any one of claim 1 to claim 5. A liquid crystal element, comprising a liquid crystal alignment film as described in claim 8.