TWI899393B - Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal element - Google Patents

Abstract

The present invention provides a liquid crystal alignment agent that can obtain a liquid crystal element with good liquid crystal alignment, high voltage retention, and low residual image generation, and can also form a liquid crystal alignment film with high film strength, good reworkability, and good adhesion. The present invention provides a liquid crystal alignment agent containing a polymer [P] having a partial structure (A) represented by formula (1) or formula (2) at the end of the main chain. In formula (1) and formula (2), ^R1 and ^R5 are monovalent organic groups that are released by at least one of heat and light. ^R2 is a monovalent organic group. (i) ^R6 is a monovalent organic group and ^R7 is a divalent alicyclic group, or (ii) ^R6 and ^R7 represent a ring structure formed by ^R6 and ^R7 together with the nitrogen atom to which they are bonded.

Description

Liquid crystal alignment agent, 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.

Liquid crystal devices are used in a wide range of applications, from relatively large display devices like LCD TVs and information displays to smaller displays like smartphones. The performance of liquid crystal devices is determined by various properties, including the liquid crystal's alignment, pretilt angle, and voltage holding ratio. To improve the performance of liquid crystal devices, efforts have been made not only to improve liquid crystal materials but also to improve the liquid crystal alignment films that align the liquid crystals in a specific direction (for example, see Patent Documents 1 and 2).

Patent Document 1 discloses the use of a polyimide precursor and polyimide having a structure in which an amino group bonded to a methylene group is protected by a t-butyloxycarbonyl (Boc) group on the polymer side chain to form a liquid crystal alignment film. Patent Document 2 discloses the use of a polymer to form a liquid crystal alignment film by reacting a post-polymerization polyamide with di-t-butyl dicarbonate to introduce Boc groups into the ends of the polyamide backbone.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] International Publication No. 2010/050523

[Patent Document 2] International Publication No. 2019/022215

In recent years, with the increasing sophistication of liquid crystal devices, quality requirements have become increasingly stringent. To meet these demands, liquid crystal devices are required to have even better liquid crystal alignment, voltage retention, and residual image characteristics (the degree of residual image generation). Furthermore, considering the application of rubbing methods, improvements in liquid crystal alignment and voltage retention, and the suppression of yield degradation, organic films formed using liquid crystal alignment agents are required to have sufficiently high strength.

To maximize the display area, liquid crystal display devices employ a method where a liquid crystal alignment film is formed across the entire substrate surface, a sealant is applied to the film, and the substrates are bonded together, achieving narrow LCD panel edges. This structure is susceptible to stress on the portion of the liquid crystal alignment film where the sealant is applied. If the adhesion between the liquid crystal alignment film and the substrates is poor, the sealant can easily peel off, potentially reducing the reliability of the liquid crystal element.

During the manufacturing process of liquid crystal alignment films, defects such as pinholes and uneven coating may occur in the liquid crystal alignment film formed on a substrate. This often requires peeling the liquid crystal alignment film from the substrate for reuse (reworking). This reworking requires the coating to be easily peelable from the substrate (i.e., excellent reworkability).

However, it is difficult to simultaneously satisfy all of these characteristics, and there is room for further improvement in liquid crystal alignment agents.

This invention was developed in response to the aforementioned challenges. Its primary purpose is to provide a liquid crystal alignment agent that can produce liquid crystal devices with excellent liquid crystal alignment, high voltage retention, and low residual image generation. Furthermore, it can form a liquid crystal alignment film with high film strength, good reworkability, and excellent adhesion.

The present inventors have conducted extensive research to address this issue and discovered that the problem can be solved by using a polymer with a specific structure at the end of the main chain, leading to the completion of the present invention. Specifically, the present invention provides the following solutions.

<1> A liquid crystal alignment agent comprising a polymer [P] having a partial structure (A) represented by the following formula (1) or formula (2) at the end of the main chain.

(In formula (1), ^R1 is a monovalent organic group that is released by at least one of heat and light. ^R2 is a monovalent organic group. ^R3 and ^R4 are each independently a hydrogen atom or a monovalent organic group. "*" represents a bond.

In formula (2), ^R5 is a monovalent organic group that is released by at least one of heat and light. ^R6 and ^R7 satisfy the following (i) or (ii).

(i) ^R6 is a monovalent organic group. ^R7 is a divalent alicyclic group.

(ii) R ⁶ and R ⁷ represent a ring structure formed ^together with the nitrogen atom to which ^they are bonded.

"*" indicates a keystroke.)

<2> A liquid crystal alignment agent comprising a polymer [P], wherein the polymer [P] is obtained by polymerizing monomers comprising tetracarboxylic dianhydride, an acid derivative of at least one selected from the group consisting of tetracarboxylic dianhydride and tetracarboxylic diester dihalides, and a diamine compound in the presence of a monoamine compound having a partial structure (A) represented by formula (1) or (2), or by reacting the monomers with the monoamine compound after polymerization.

<3> A liquid crystal alignment film formed using the liquid crystal alignment agent described in <1> or <2> above.

<4> A liquid crystal element comprising the liquid crystal alignment film described in <3>.

The liquid crystal alignment agent of the present invention can produce a liquid crystal element with excellent liquid crystal alignment, high voltage retention, and low residual image generation. Furthermore, it can form a liquid crystal alignment film with high film strength, excellent reworkability, and good adhesion.

Liquid Crystal Alignment Agents

The following describes the various components contained in the liquid crystal alignment agent disclosed herein, as well as other components that may be optionally blended.

In this specification, the term "alkyl group" encompasses chain alkyl groups, alicyclic alkyl groups, and aromatic alkyl groups. "Chain alkyl groups" refer to linear and branched alkyl groups whose main chains contain no ring structures but consist solely of chain structures. These groups may be saturated or unsaturated. "Alicyclic alkyl groups" refer to alkyl groups that contain only alicyclic hydrocarbon structures as ring structures and do not contain aromatic ring structures. These groups do not necessarily need to consist solely of alicyclic hydrocarbon structures and include groups that have a chain structure in part. An "aromatic alkyl group" refers to a alkyl group containing an aromatic ring structure. These groups do not necessarily have to consist solely of aromatic ring structures and may also partially contain a chain structure or an alicyclic hydrocarbon structure. "Aromatic ring" encompasses both aromatic alkyl rings and aromatic heterocyclic rings. An "organic group" refers to an atomic group formed by removing any hydrogen atom from a carbon-containing compound (i.e., an organic compound).

The liquid crystal alignment agent disclosed herein contains a polymer [P] having a partial structure represented by the following formula (1) or formula (2) (hereinafter also referred to as "partial structure (A)") at the end of the main chain.

[Chemistry 2]

(In formula (1), ^R1 is a monovalent organic group that is released by at least one of heat and light. ^R2 is a monovalent organic group. ^R3 and ^R4 are each independently a hydrogen atom or a monovalent organic group. "*" represents a bond.

In formula (2), ^R5 is a monovalent organic group that is released by at least one of heat and light. ^R6 and ^R7 satisfy the following (i) or (ii).

(i) ^R6 is a monovalent organic group. ^R7 is a divalent alicyclic group.

(ii) R ⁶ and R ⁷ represent a ring structure formed ^together with the nitrogen atom to which ^they are bonded.

"*" indicates a keystroke.)

<Polymer[P]>

．About Partial Structure (A)

In formulas (1) and (2), the monovalent organic groups represented by ^R1 and ^R5 are preferably groups that are thermally detachable and substituted with hydrogen atoms (hereinafter also referred to as "thermally detachable groups"). When the monovalent organic groups represented by ^R1 and ^R5 are thermally detachable groups, it is preferred that the groups represented by ^R1 and ^R5 be detached by heating (post-baking) during film formation, and replaced with hydrogen atoms. This is preferred from the perspectives of simplifying the process and allowing the partial structure (A) to be introduced into the terminal of the polymer backbone.

Specific examples of thermally releasable groups include tert-butoxycarbonyl, benzyloxycarbonyl, 1,1-dimethylpropynyloxycarbonyl, 1,1-dimethyl-2-haloethoxycarbonyl, allyloxycarbonyl, vinyloxycarbonyl, cyclohexyloxycarbonyl, methylcyclohexyloxycarbonyl, 2-(trimethylsilyl)ethoxycarbonyl, 9-fluorenylmethoxycarbonyl, 2,2,2-trichloroethoxycarbonyl, o-phthalyl, p-toluenesulfonyl, and 2-nitrobenzenesulfonyl. Of these, the thermally releasable groups represented by R ¹ and R ⁵ are preferably those that are released at a temperature of 130°C to 250°C, from the perspective of being released by heating during film formation. Specifically, a tert-butoxycarbonyl group and a 9-fluorenylmethoxycarbonyl group are preferred. A tert-butoxycarbonyl group (Boc group) is particularly preferred because of its excellent thermal removability and the ability to reduce the amount of the removable structure remaining in the film.

When ^R6 and ^R7 in the formula (2) satisfy the above (i), the monovalent organic group represented by ^R6 , and the monovalent organic group represented by ^R2 in the formula (1) are preferably a monovalent chain alkyl group having 1 or more carbon atoms, or a monovalent group having -O-, -S-, -CO-, -COO-, -NR8a-, -CO- ^NR8a- , -NR8a-CO-O-, or ^-NR8a -CO- ^NR9a- between the carbon-carbon bonds of the chain alkyl ^group having 2 or ^more carbon atoms (wherein ^R8a and ^R9a are each independently a hydrogen atom or a monovalent organic group. The same shall apply hereinafter). The monovalent organic group represented by R ^8a and R ^9a is preferably a monovalent alkyl group having 1 to 10 carbon atoms or a monovalent thermally ionizable group, and more preferably an alkyl group having 1 to 3 carbon atoms or a Boc group.

Furthermore, the direction of the bond between -COO-, -CO-NR ^8a -, -NR ^8a -CO-O-, and -NR ^8a -CO-NR ^9a - is not determined. Therefore, for example, when R ² in the formula (1) is a monovalent group having -COO- between carbon-carbon bonds of a chain alkyl group having two or more carbon atoms, -COO- may be arranged with -CO- on the nitrogen atom side in the formula (1) or with -O- on the nitrogen atom side in the formula (1).

When ^R6 and ^R7 in the formula (2) satisfy the condition (i), the monovalent organic group represented by ^R6 , and the monovalent organic group represented by ^R2 in the formula (1), are preferably an alkyl group having 1 to 5 carbon atoms, or a monovalent group having -O- between the carbon-carbon bonds of the alkyl group, and more preferably an alkyl group having 1 to 3 carbon atoms, or an alkoxyalkyl group having 1 to 3 carbon atoms, from the viewpoint of improving the reactivity of the nitrogen atom in the formula (1).

Examples of the monovalent organic group represented by ^R3 and ^R4 in the formula (1) include a monovalent chain alkyl group having 1 to 10 carbon atoms, a monovalent alicyclic alkyl group having 5 to 12 carbon atoms, a monovalent aromatic alkyl group having 6 to 12 carbon atoms, and a monovalent group in which any methylene group of a chain alkyl group having 2 or more carbon atoms is substituted with -O-, -S-, -CO-, -COO-, ^-NR8a- , -CO- ^NR8a- , ^-NR8a -CO-O-, or ^-NR8a -CO- ^NR9- . Among these, the monovalent organic group represented by ^R3 and ^R4 is preferably an alkyl group or alkoxy group having 1 to 5 carbon atoms, and more preferably an alkyl group or alkoxy group having 1 to 3 carbon atoms.

With respect to ^R3 and ^R4 in the formula (1), from the viewpoint of improving the reactivity of the nitrogen atom in the formula (1) and thus improving the liquid crystal alignment, voltage retention, afterimage characteristics, and mechanical strength of the film, preferably they are a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group, more preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or an alkoxy group, further preferably a hydrogen atom or a methyl group, and particularly preferably a hydrogen atom.

When ^R6 and ^R7 in the formula (2) satisfy the above (i), examples of the divalent alicyclic group represented by ^R7 include cyclopentanediyl, cyclohexanediyl, cycloheptanediyl, or divalent groups having a substituent such as a methyl group, an ethyl group, or a methoxy group on the ring of these groups.

When ^R6 and ^R7 in the above formula (2) satisfy the above (ii), examples of the ring structure formed by ^R6 and ^R7 together with the nitrogen atom to which they are bonded include a pyrrolidine ring, a piperidine ring, a hexamethyleneimine ring, or a ring having a substituent such as a methyl group, an ethyl group, or a methoxy group on these rings, wherein two hydrogen atoms (a hydrogen atom bonded to a nitrogen atom and a hydrogen atom bonded to a carbon atom) are removed from the ring portion.

Specific examples of partial structure (A) include the structures represented by the following formulas (A-1) to (A-15).

[Chemistry 3]

(In the formula, TMS represents trimethylsilyl. "*" represents a bond.)

Regarding the partial structure (A), the partial structure represented by formula (1) is preferred, and a partial structure in which R ^<3> and R ^<4> in formula (1) are hydrogen atoms is more preferred, in terms of having a high effect on improving liquid crystal alignment, voltage holding ratio, and afterimage characteristics. The polymer [P] may have one partial structure (A) or two or more partial structures (A). The number of partial structures (A) in the polymer [P] is preferably one or two.

．About polymers[P]

The main chain of polymer [P] is not particularly limited. In terms of forming a liquid crystal alignment film with high affinity for liquid crystals, mechanical strength, and reliability, and in terms of significantly improving various properties by introducing partial structure (A) into the main chain terminus, polymer [P] is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide.

When the polymer [P] is at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide, the polymer [P] can be obtained, for example, by a method comprising polymerizing monomers comprising tetracarboxylic dianhydride, an acid derivative of at least one selected from the group consisting of tetracarboxylic dianhydride and tetracarboxylic acid diester dihalide, and a diamine compound.

(Polyamine)

When the polymer [P] is polyamine (hereinafter also referred to as "polyamine [P]"), the method for producing the polyamine (hereinafter also referred to as "polyamine [P]") is not particularly limited as long as the partial structure (A) can be introduced into the terminal end of the main chain. Here, the "main chain" of a polymer refers to the portion of the polymer containing the "trunk" of the longest atomic chain. Furthermore, the "trunk" portion may contain a ring structure. The "side chains" of a polymer refer to the portions branching from the "trunk" of the polymer.

In order to introduce the partial structure (A) into the terminal of the polyamine main chain, a method can be listed in which a compound having the partial structure (A) (hereinafter also referred to as "compound [A]") is used as an end-capping agent for terminating the polymerization reaction during or after the polymerization reaction. Specifically, the following methods [1] and [2] can be listed.

[1] A method of polymerizing monomers comprising tetracarboxylic dianhydride and a diamine compound in the presence of compound [A].

[2] A method of polymerizing monomers containing tetracarboxylic dianhydride and a diamine compound, and then reacting the polymer obtained by the polymerization with compound [A].

Among these methods, the method [1] is preferred as a method for producing polyamine [P]. According to the method [1], by reacting the polymer terminal (more specifically, the structural unit derived from tetracarboxylic dianhydride) with the compound [A] during the polymerization reaction, a polymer having a structural unit derived from the compound [A] at the main chain terminal can be obtained as polyamine [P]. Therefore, the step for introducing the partial structure (A) into the main chain terminal of the polyamine can be performed without being separated from the polymerization step, which is preferred in terms of simplifying the production steps.

(Tetracarboxylic dianhydride)

Examples of the tetracarboxylic dianhydride used in the synthesis of polyamine [P] include aliphatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, and aromatic tetracarboxylic dianhydride. Specific examples of these include aliphatic tetracarboxylic dianhydrides such as 1,2,3,4-butanetetracarboxylic dianhydride and ethylenediaminetetraacetic dianhydride; alicyclic tetracarboxylic dianhydrides such as 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,4,5,9b-tetrahydronaphtho[1,2-c]furan-1,3-dione, Examples of the aromatic tetracarboxylic dianhydride include pyromellitic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, ethylene glycol bis(trimellitic anhydride), 4,4'-carbonyldiphthalic anhydride, and 3,3',4,4'-biphenyltetracarboxylic dianhydride. Furthermore, the tetracarboxylic dianhydride described in Japanese Patent Application Laid-Open No. 2010-97188 can be used. The tetracarboxylic dianhydride can be used alone or in combination of two or more.

In order to obtain a liquid crystal alignment film having high solubility and exhibiting excellent liquid crystal alignment and electrical properties, the tetracarboxylic dianhydride used in the synthesis of the polyamic acid [P] preferably comprises at least one selected from the group consisting of aliphatic tetracarboxylic dianhydrides and alicyclic tetracarboxylic dianhydrides, and more preferably comprises alicyclic tetracarboxylic dianhydride. The proportion of the alicyclic tetracarboxylic dianhydride used in the synthesis of the polyamic acid [P] is preferably 20 mol% or more, more preferably 40 mol% or more, and even more preferably 50 mol% or more.

(Diamine compound)

Examples of diamine compounds used in the synthesis of polyamine [P] include aliphatic diamines, alicyclic diamines, aromatic diamines, and diaminoorganosiloxanes.

Specific examples of diamine compounds include aliphatic diamines such as m-xylenediamine and hexamethylenediamine; alicyclic diamines such as 1,4-diaminocyclohexane and 4,4'-methylenebis(cyclohexylamine); and aromatic diamines such as p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4-aminophenyl-4-aminobenzoate, 4,4'-diaminoazobenzene, and 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, 6,6'-(pentamethylenedioxy)bis(3-aminopyridine), N,N'-bis(5-amino-2-pyridyl)-N,N'-bis(tert-butoxycarbonyl)ethylenediamine, bis[2-(4-aminophenyl)ethyl]adipic acid, 4 ,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylamine, 4,4'-diaminodiphenylethyl urea, 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, 2,2'-dimethyl-4,4'-diaminobiphenyl, 4,4'-(phenylenediisopropylidene)bis(1,4-diaminophenoxy)benzene, Aniline, 2,6-diaminopyridine, 2,4-diaminopyrimidine, 3,6-diaminocarbazole, N-methyl-3,6-diaminocarbazole, 3,6-diaminoacridine, monomers containing a diphenylamine structure (e.g., N4,N4'-bis(4-aminophenyl)-N4,N4'-dimethylbenzidine, etc.), N,N'-bis(5-aminopyridin-2-yl)-N,N'-di(tert-butoxycarbonyl)ethylenediamine, the following formula (D-1):

(In formula (D-1), R ¹¹ and R ¹² are each independently an alkanediyl group. R ¹³ is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a protecting group. n1 is an integer from 1 to 3. When n1 is 2 or 3, multiple R ^12s are the same or different, and multiple R ^13s are the same or different.)

The compounds represented by the 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, cholesteryloxy-3,5-diaminobenzoate, cholesteryl 3,5-diaminobenzoate 3,5-diaminobenzoic acid lanostanyl 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)

(In formula (E-1), ^X1 and ^XII each independently represent a single bond, -O-, *-COO-, or *-OCO- (where "*" represents a bond to ^X1 ). ^R1 is an alkanediyl group having 1 to 3 carbon atoms. ^RII is a single bond or an alkanediyl group having 1 to 3 carbon atoms. ^RIII is an alkyl group, alkoxy group, fluoroalkyl group, or fluoroalkoxy group having 1 to 20 carbon atoms. a is 0 or 1. b is an integer from 0 to 3. c is an integer from 0 to 2. d is 0 or 1. 1≦a+b+c≦3.)

The compounds represented include side-chain diamines, and examples of diaminoorganosiloxanes include 1,3-bis(3-aminopropyl)tetramethyldisiloxane.

Examples of the compound represented by formula (D-1) include compounds represented by formulas (D-1-1) to (D-1-3) below. Examples of the compound represented by formula (E-1) include compounds represented by formulas (E-1-1) to (E-1-4) below. When producing polyamine [P], the diamine compound may be used alone or in combination of two or more. In the structural formula, "Boc" represents a tert-butyloxycarbonyl group (the same shall apply hereinafter).

(Compound [A])

Compound [A] is a compound having a partial structure (A), for example, monoanhydrides, monoamine compounds, monoisocyanate compounds, etc. Among these, compound [A] is preferably a monoamine compound, and more specifically, a compound represented by the following formula (3) is preferred.

(In formula (3), ^A1 is a monovalent group having a partial structure represented by formula (1) or (2). ^R8 is a single bond, -O-, -S-, -CO-, -COO-, ^-NR10- , -CO- ^NR10- , ^-NR10 -CO-O-, ^-NR10 -CO- ^NR11- , a divalent chain alkyl group having 1 or more carbon atoms, a divalent alicyclic alkyl group having 3 or more carbon atoms, or a divalent chain alkyl group having 2 or more carbon atoms in which any methylene group is substituted with -O-, -S-, -CO-, -COO-, -NR10-, -CO ^{- NR10-} , ^-NR10 -CO-O-, or ^-NR10 -CO- ^NR11- . ^R10 and ^R11 are each independently a hydrogen atom or a monovalent organic group. R ^{R 9} is a single bond or an (m+1)-valent aromatic ring group. m is 1 or 2. When R ⁹ is a single bond, m is 1, and R ⁸ is a single bond or is bonded to the primary amino group in formula (3) through a alkyl group. When m is 2, multiple R ^8s are the same or different, and multiple A ^1s are the same or different.

In formula (3), ^A1 is a monovalent group represented by formula (1) or formula (2). Specific examples and preferred embodiments of formula (1) and formula (2) can be referred to the above description. Specific examples of the monovalent group represented by ^A1 include the groups represented by formulas (A-1) to (A-15), respectively.

When ^R8 is a divalent chain alkyl group having 1 or more carbon atoms, the chain alkyl group is preferably an alkanediyl group, more preferably a linear alkanediyl group, from the perspective of improving reactivity with the crosslinking agent described below. When ^R8 is a divalent chain alkyl group, the carbon number of the chain alkyl group is preferably 7 or less, more preferably 5 or less, and even more preferably 3 or less, from the perspective of achieving excellent film adhesion while simultaneously improving film strength (and, consequently, friction resistance), achieving high voltage retention of the liquid crystal cell, and improving liquid crystal alignment and residual image characteristics.

When R ⁸ is a divalent group formed by replacing any methylene group of a chain alkyl group with -O-, -S-, -CO-, -COO-, -NR ¹⁰ -, -CO-NR ¹⁰ -, -NR ¹⁰ -CO-O-, or -NR ¹⁰ -CO-NR ¹¹ -, the above description can be used for specific examples and preferred examples of the chain alkyl group. When R ¹⁰ and R ¹¹ are monovalent organic groups, examples of the monovalent organic group include monovalent alkyl groups having 1 to 10 carbon atoms and thermally detachable groups. Among these, R ¹⁰ and R ¹¹ are preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a thermally detachable group, and more preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a tert-butoxycarbonyl group.

When R ⁸ is a divalent alicyclic alkyl group having 3 or more carbon atoms, examples of the alicyclic alkyl group include 1,4-cyclohexanediyl, 2-methyl-1,4-cyclohexanediyl, and 2,5-dimethyl-1,4-cyclohexanediyl.

From the perspective of improving the reactivity with the crosslinking agent (more specifically, compound [B]) and obtaining a liquid crystal cell having excellent voltage retention and liquid crystal alignment, among the above, ^R8 is preferably a single bond, -O-, -S-, -CO-, -COO-, an alkanediyl group having 1 to 7 carbon atoms, or a divalent group having 1 to 7 carbon atoms in which any methylene group possessed by an alkanediyl group having 2 or more carbon atoms is substituted with -O- or -S-.

Furthermore, -COO-, -CO-NR ¹⁰ -, -NR ¹⁰ -CO-O-, and -NR ¹⁰ -CO-NR ¹¹ - do not define the direction of the bond. Therefore, for example, when R ⁸ in formula (3) is -COO-, -COO- may bond with either -CO- or -O- to A ¹ in formula ( ³ ).

When R is an (m+1) ^-valent aromatic cyclic group, examples of the aromatic cyclic group include (m+1)-valent aromatic alkyl groups and (m+1)-valent aromatic heterocyclic groups. Among these, (m+1)-valent aromatic alkyl groups and (m+1)-valent nitrogen-containing aromatic heterocyclic groups are preferred. ^R may have a substituent on the aromatic ring portion. The substituent is preferably an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a halogen atom.

Specific examples of R ⁹ being an (m+1)-valent aromatic cyclic group include (m+1)-valent aromatic alkyl groups formed by removing (m+1) arbitrary hydrogen atoms bonded to carbon atoms constituting a benzene ring, biphenyl ring, naphthalene ring, or anthracene ring. Examples of (m+1)-valent nitrogen-containing aromatic heterocyclic groups include (m+1) arbitrary hydrogen atoms bonded to carbon atoms constituting a pyridine ring, pyrimidine ring, oxazine ring, or pyrazine ring. When R ⁹ is an (m+1)-valent aromatic cyclic group, R ⁹ is preferably a group formed by removing (m+1) hydrogen atoms from a substituted or unsubstituted benzene ring or pyridine ring.

As compound [A], among these, particularly preferably used are compounds wherein, when ^A1 is a group represented by formula (1), ^R8 is a single bond, -O-, -S-, -CO-, -COO-, an alkanediyl group having 1 to 7 carbon atoms, or a divalent group having 1 to 7 carbon atoms in which any methylene group possessed by an alkanediyl group having 2 or more carbon atoms is substituted with -O- or -S-, and ^R9 is a single bond or an (m+1)-valent aromatic ring group; and compounds wherein, when ^A1 is a group represented by formula (2), ^R8 and ^R9 are single bonds.

Specific examples of compound [A] include compounds represented by the following formulas (CA-1) to (CA-29). Compound [A] may be used alone or in combination of two or more.

[Chemistry 11]

(In the formula, k, k1, and k2 are independently integers between 0 and 7.)

(Synthesis of polyamine)

The synthesis reaction of polyamine [P] is preferably carried out in an organic solvent. The ratio of tetracarboxylic dianhydride to diamine compound used in the synthesis reaction of polyamine [P] is preferably 0.2 to 2 equivalents of tetracarboxylic dianhydride anhydride groups per 1 equivalent of diamine compound amino groups.

In the above synthesis reaction, from the perspective of introducing structural units derived from compound [A] into the terminals of the polymer backbone and obtaining a polymer within an appropriate molecular weight range, the proportion of compound [A] used relative to the total amount of the diamine compound and compound [A] used in the synthesis is preferably 1 mol% or more, more preferably 2 mol%, and even more preferably 5 mol% or more. Furthermore, the proportion of compound [A] used relative to the total amount of the diamine compound and compound [A] used in the synthesis is preferably 30 mol% or less, more preferably 20 mol% or less, and even more preferably 15 mol% or less.

Furthermore, during the synthesis reaction, a compound not having partial structure (A) may be used together with compound [A] as a capping agent. Examples of such compounds 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 proportion of these compounds used relative to the total amount of the capping agent used in the synthesis reaction is preferably 10 mol% or less, more preferably 5 mol% or less, and even more preferably 1 mol% or less.

In the synthesis reaction of polyamine [P], the reaction temperature is preferably -20°C to 150°C, and the reaction time is preferably 0.1 hour to 24 hours. Examples of organic solvents used in the reaction include aprotic polar solvents, phenolic solvents, alcoholic solvents, ketone solvents, ester solvents, etheric solvents, halogenated hydrocarbons, and hydrocarbons. Among these, 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, hexamethylphosphatriaine, m-cresol, xylenol, and halogenated phenol as the reaction solvent, or to use a mixture of one or more of these with another organic solvent (e.g., butyl solvent, diethylene glycol diethyl ether, etc.). The amount of the organic solvent used is preferably such that the total amount of the tetracarboxylic dianhydride, diamine compound, and compound [A] is 0.1% by mass to 50% by mass relative to the total amount of the reaction solution.

In this manner, a polymer solution containing dissolved polyamine [P] is obtained. This polymer solution can be used directly to prepare a liquid crystal alignment agent, or it can be used to prepare a liquid crystal alignment agent after the polyamine [P] contained in the polymer solution is separated.

．Polyamide

When the polymer [P] is a polyamic acid ester, the polyamic acid ester (hereinafter also referred to as "polyamic acid ester [P]") can be obtained, for example, by the following methods: [I] reacting the polyamic acid [P] with an esterifying agent; [II] reacting the compound [A] with a tetracarboxylic acid diester and a diamine compound, or reacting the compound [A] after polymerizing the tetracarboxylic acid diester and the diamine compound; [III] reacting the compound [A] with a tetracarboxylic acid diester dihalide and a diamine compound, or reacting the compound [A] after polymerizing the tetracarboxylic acid diester dihalide and the diamine compound. The polyamic acid ester [P] may have only an aminate structure or may be a partially esterified product having both an aminate structure and an aminate structure. The reaction solution obtained by dissolving the polyamine [P] can be used directly for the preparation of the liquid crystal alignment agent, or the polyamine [P] contained in the reaction solution can 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 polyimide [P] synthesized in the above manner to dehydration and ring closure followed by imidization. The polyimide [P] may be a fully imidized product, in which the entire amide structure of the precursor polyimide [P] is dehydrated and ring-closed, or a partially imidized product, in which only a portion of the amide structure is dehydrated and ring-closed, resulting in the coexistence of an amide structure and an imide ring structure. The polyimide [P] preferably has an imidization ratio of 20% to 99%, more preferably 30% to 90%. The imidization ratio is expressed as a percentage of the number of imide ring structures relative to the total number of amide structures and imide ring structures in the polyimide. Here, a portion of the imide rings may be isoimide rings.

Dehydration and ring closure of polyamine [P] is preferably carried out by dissolving the polyamine [P] in an organic solvent, adding a dehydrating agent and a dehydration and ring closure catalyst to the solution, and optionally heating. In this method, an anhydride such as acetic anhydride, propionic anhydride, or trifluoroacetic anhydride can be used as the dehydrating agent. The amount of dehydrating agent used is preferably 0.01 mol to 20 mol per 1 mol of the amide structure of the polyamine [P]. Tertiary amines such as pyridine, colidine, collidine, and triethylamine can be used as the dehydration and ring closure catalyst. The amount of the dehydration and ring-closing catalyst used is preferably 0.01 mol to 10 mol per 1 mol of the dehydrating agent. The organic solvent used in the dehydration and ring-closing reaction includes those exemplified as organic solvents used in the synthesis of polyamide [P]. The reaction temperature for the dehydration and ring-closing reaction is preferably 0°C to 180°C. The reaction time is preferably 1.0 hour to 120 hours. Furthermore, the reaction solution containing polyimide [P] can be used directly or after isolating the polyimide [P] for the preparation of the liquid crystal alignment agent.

Regarding the solution viscosity of polymer [P], when prepared as a 10% by mass solution, it is preferably 10 mPa·s to 800 mPa·s, and more preferably 15 mPa·s to 500 mPa·s. The solution viscosity (mPa·s) is measured at 25°C using an E-type rotational viscometer on a 10% by mass solution of polymer [P] prepared in a good solvent (e.g., γ-butyrolactone, N-methyl-2-pyrrolidone, etc.).

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

<Other ingredients>

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

．Polymer[Q]

The liquid crystal alignment agent disclosed herein may further contain a polymer (hereinafter also referred to as polymer [Q]) that does not have the partial structure (A) as a polymer component. The main skeleton of polymer [Q] is not particularly limited. Examples of polymer [Q] include polyamic acid, polyamic acid ester, polyimide, polyorganosiloxane, polyester, polyenamine, polyurea, polyamide, polyamide imide, polybenzoxazole precursor, polybenzoxazole, cellulose derivative, polyacetal, (meth)acrylic polymer, styrene polymer, maleimide polymer, styrene-maleimide copolymer, and the like. Of these, from the perspective of achieving a highly reliable liquid crystal element, the polymer [Q] is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, polyimide, polyorganosiloxane, and polymers containing structural units derived from monomers having polymerizable unsaturated carbon-carbon bonds. Examples of polymers containing structural units derived from monomers having polymerizable unsaturated carbon-carbon bonds include (meth)acrylic polymers, styrene polymers, maleimide polymers, and styrene-maleimide copolymers.

When polymer [Q] is included in the liquid crystal alignment agent, the content of polymer [Q] is preferably 1% by mass or greater, more preferably 2% by mass or greater, relative to the total amount of polymer [P] and polymer [Q]. Furthermore, the content of polymer [Q] is preferably 95% by mass or less, more preferably 90% by mass or less, relative to the total amount of polymer [P] and polymer [Q]. Polymer [Q] may be used singly or in combination of two or more.

． Crosslinking agent

The liquid crystal alignment agent disclosed herein may further contain a crosslinking agent. As the crosslinking agent, a compound having a functional group capable of reacting with an amino group (hereinafter also referred to as a "crosslinking group") is preferably used. Preferred specific examples of the crosslinking agent contained in the liquid crystal alignment agent of the present disclosure include compounds (hereinafter also referred to as "compound [B]") containing as a crosslinking group at least one group selected from the group consisting of the following groups: a group having a polymerizable carbon-carbon bond, a cyclic ether group, a cyclic sulfide group, an isocyanate group, a protected isocyanate group, a hydroxymethyl group, a protected hydroxymethyl group, a cyclic carbonate group, a group " ^-CR20 = ^CR21 - ^R22- " (wherein ^R20 is a monovalent group that is liberated by reaction with an amino group; ^R21 is a hydrogen atom or an alkyl group, and ^R22 is an electron-withdrawing group), a silanol group, and an alkoxysilyl group.

Among the crosslinking groups, groups having a polymerizable carbon-carbon bond include (meth)acryloyl, maleimide, alkenyl, vinylphenyl, vinyl ether, and 3-methylenetetrahydrofuran-2(3H)-one-5-yl. In the group "-CR ²⁰ =CR ²¹ -R ²² -," examples of the monovalent organic group represented by R ²⁰ include an alkoxy group having 1 to 5 carbon atoms, a pyrrolidinone-1-yl group, and a halogen atom (fluorine, chlorine, bromine, or iodine). Examples of electron-withdrawing groups represented by R ²² include a carbonyl group and a sulfonyl group.

From the perspective of achieving a well-balanced improvement in liquid crystal alignment, voltage retention, and film strength while suppressing a decrease in reworkability, the number of crosslinking groups contained in one molecule of compound [B] is preferably 2 to 12, more preferably 2 to 10. From the perspective of storage stability, the molecular weight of compound [B] is preferably 3,000 or less, more preferably 2,000 or less, and even more preferably 1,000 or less.

Specific examples of compound [B] include compounds having a polymerizable carbon-carbon bond such as ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, pentaerythritol tri(meth)acrylate, and compounds represented by the following formulas (b-1) to (b-6). Examples of compounds having a cyclic (thio)ether group include ethylene glycol dihydrate. Glyceryl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, triglycidyl isocyanurate, 1,6-hexanediol diglycidyl ether, trihydroxymethylpropane triglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-di N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, N,N-diglycidyl-benzylamine, N,N-diglycidyl-aminomethylcyclohexane, N,N-diglycidyl-cyclohexylamine, etc.; compounds having an isocyanate group or a protected isocyanate group include, for example, the compounds represented by the following formulas (b-7) to (b-11); compounds having a hydroxymethyl group or a protected hydroxymethyl group include, for example, the compounds represented by the following formulas (b-12) to (b-17); compounds having a cyclic carbonate group include, for example, the compounds represented by the following formulas (b-18) and (b-19); compounds having the group "-CR Examples of the compound expressing " ^R20 = ^CR21 - ^R22- " include compounds represented by the following formulas (b-20) to (b-26), respectively. Examples of the compound having an alkoxysilyl group or a silanol group include 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, vinyltriethoxysilane, and trimethoxysilylpropylsuccinic anhydride.

[Chemistry 16]

(In formula (b-7) and formula (b-8), ^R23 is a thermally deionizable group.)

(In formula (b-16), Ac is an acetyl group.)

[Chemistry 18]

When a crosslinking agent is included in the liquid crystal alignment agent disclosed herein, from the perspective of improving the adhesion of the liquid crystal alignment film and obtaining a liquid crystal element with excellent liquid crystal alignment and electrical properties, the content of the crosslinking agent is preferably 0.02 parts by mass or more relative to 100 parts by mass of the total amount of the polymer components contained in the liquid crystal alignment agent. The content of the crosslinking agent is more preferably 0.5 parts by mass or more, and further preferably 1 part by mass or more relative to 100 parts by mass of the total amount of the polymer components. In addition, from the perspective of obtaining a liquid crystal element that satisfies the liquid crystal alignment, electrical properties, storage stability, and reprocessability, the content of the crosslinking agent is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less relative to 100 parts by mass of the total amount of the polymer components. As a crosslinking agent, one type can be used alone or in combination of two or more types.

．Solvent

The liquid crystal alignment agent disclosed herein 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, and acetylacetic acid. Methyl ester, ethyl acetate, 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, ethylene carbonate, propylene 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. As a solvent, one type can be used alone or in combination of two or more.

Other ingredients included in liquid crystal alignment agents, in addition to those mentioned above, include antioxidants, metal chelate compounds, curing accelerators, surfactants, fillers, dispersants, and photosensitizers. The proportions of these other ingredients can be appropriately selected for each compound, within a range that does not compromise the effects of the present disclosure.

The solids concentration (the ratio of the total mass of the components other than the solvent in the liquid crystal alignment agent) in the liquid crystal alignment agent should be appropriately selected in consideration of viscosity, volatility, and other factors. It is preferably in the range of 1% to 10% by mass. A solids concentration of 1% by mass or greater is preferred because it allows for a sufficient coating thickness, resulting in a liquid crystal alignment film exhibiting better liquid crystal alignment properties. On the other hand, a solids concentration of 10% by mass or less allows for an appropriate coating thickness, facilitating the production of a liquid crystal alignment film exhibiting good liquid crystal alignment properties. Furthermore, the viscosity of the liquid crystal alignment agent is moderate, tending to improve coating properties.

Liquid crystal alignment film and liquid crystal element

The liquid crystal alignment film disclosed herein can be manufactured using the liquid crystal alignment agent prepared as described above. Furthermore, 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. For example, it 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) and vertical alignment-patterned vertical alignment (VA-PVA)), in-plane switching (IPS), fringe field switching (FFS), optically compensated bend (OCB), and polymer-stabilized alignment (PSA). Liquid crystal elements can be manufactured, for example, using a method comprising the following steps 1 to 3. Step 1 utilizes different substrates depending on the desired operating mode. Steps 2 and 3 are common to all operating modes.

<Step 1: Film Formation>

First, a liquid crystal alignment agent is applied to a substrate, preferably by heating the coated surface, to form a coating film on the substrate. Examples of substrates include glass such as float glass and sodium glass, and transparent substrates made of plastics such as polyethylene terephthalate, polybutylene terephthalate, polyether sulfide, polycarbonate, and poly(aliphatic cycloolefin). When manufacturing TN, STN, VA, or PSA liquid crystal elements, two substrates with patterned transparent conductive films are used. On the other hand, when manufacturing IPS or FFS liquid crystal elements, a substrate with electrodes patterned into a comb shape and an opposing substrate without electrodes are used. As the transparent conductive film, a NESA film (registered trademark of PPG Corporation, USA) containing tin oxide (SnO ₂ ), an indium tin oxide (ITO) film containing indium oxide-tin oxide (In ₂ O ₃ -SnO ₂ ), or the like can be used.

The method for applying the liquid crystal alignment agent to the substrate is not particularly limited. Application of the liquid crystal alignment agent to the substrate can be performed, for example, by spin coating, printing (e.g., 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, and the like.

After applying the liquid crystal alignment agent, it is preferably preheated (prebaked) to prevent the applied liquid crystal alignment agent from dripping. The prebaking temperature is preferably 30°C to 200°C, and the prebaking time is preferably 0.25 minutes to 10 minutes. Subsequently, the solvent is completely removed, and a calcination (postbaking) step is optionally performed to thermally imidize the amide structures present in the polymer. The calcination temperature (postbaking temperature) is preferably 80°C to 280°C, more preferably 80°C to 250°C. The postbaking time is preferably 5 minutes to 200 minutes. The film thickness of the formed film is preferably 0.001μm to 1μm.

<Step 2: Alignment Processing>

When manufacturing TN, STN, IPS, or FFS liquid crystal devices, the coating formed in step 1 is subjected to a treatment to impart liquid crystal alignment (alignment treatment). This imparts alignment properties to the coating, forming a liquid crystal alignment film. Preferred alignment treatments include rubbing the surface of the coating formed on the substrate with cotton or nylon, or photo-alignment treatments that impart alignment properties by irradiating the coating with light. When manufacturing vertical alignment liquid crystal devices, the coating formed in step 1 can be used directly as the liquid crystal alignment film. Alternatively, the coating can be subjected to an alignment treatment to further enhance alignment properties. Liquid crystal alignment films that are preferred for vertical alignment liquid crystal cells can also be used preferably for PSA liquid crystal cells.

Light irradiation for photo-alignment can be performed by the following methods, among others: 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 being heated in at least one of the pre-baking step and the post-baking step. As radiation irradiated onto the coating, for example, ultraviolet light and visible light having a wavelength of 150 nm to 800 nm can be used. Ultraviolet light having 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, irradiation can be performed from a direction perpendicular to the substrate surface, from an oblique direction, or a combination of these directions. For non-polarized radiation, the irradiation direction is set to an oblique direction.

Examples of light sources 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 between 200 J/ ^m² and 30,000 J/ ^m² , more preferably between 500 J/ ^m² and 10,000 J/ ^m² . Following the irradiation with light to impart alignment, 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), or a mixture thereof, or heated.

<Step 3: Construction of the Liquid Crystal Cell>

Two substrates with liquid crystal alignment films formed in the above manner are prepared, and liquid crystal is placed between the two opposing substrates to produce a liquid crystal cell. Examples of methods for producing a liquid crystal cell include placing the two substrates facing each other with a gap between them, bonding the peripheries of the two substrates together using a sealant, and then injecting liquid crystal into the cell gap surrounded by the substrate surfaces and the sealant, sealing the injection hole, or using a one-drop fill (ODF) method. For example, the sealant can be an epoxy resin containing a hardener and aluminum oxide balls as spacers. Examples of liquid crystals include nematic and discotic liquid crystals, with nematic liquid crystals being preferred.

In the PSA mode, a polymerizable compound (e.g., a polyfunctional (meth)acrylate compound) is filled into the cell gap along with liquid crystal. After the liquid crystal cell is constructed, a voltage is applied between the conductive films on a pair of substrates, and the liquid crystal cell is then irradiated with light. When manufacturing a PSA-type liquid crystal element, the polymerizable compound is used in an amount of, for example, 0.01 to 3 parts by mass, preferably 0.05 to 1 part by mass, per 100 parts by mass of the liquid crystal.

When manufacturing a liquid crystal display device, a polarizing plate is then attached to the outer surface of the liquid crystal cell. Examples of such polarizing plates include a polarizing film called an "H film" sandwiched between cellulose acetate protective films, or a polarizing plate containing the H film itself. The "H film" is formed by absorbing iodine while stretching and aligning polyvinyl alcohol.

The liquid crystal element disclosed herein can be effectively used in a variety of applications. Specifically, it can be used as a display device, dimming device, or retardation film in clocks, portable game consoles, word processors, notebook computers, car navigation systems, camcorders, personal digital assistants (PDAs), digital cameras, mobile phones, smartphones, various monitors, LCD televisions, and information displays.

[Example]

The following describes the embodiments in more detail, but the present invention is not to be construed as being limited by the following embodiments.

In the following examples, the imidization ratio of the polyimide in the polymer solution and the weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the styrene-maleimide copolymer were measured using the following methods. The required amounts of the starting compounds and polymers used in the following examples were determined by repeating the synthesis on the scale shown in the following synthesis examples as needed.

[Imidization rate of polyimide]

A polyimide solution was added to pure water. The resulting precipitate was thoroughly dried under reduced pressure at room temperature and then dissolved in deuterated dimethylsulfoxide. Hydrogen ^ion nuclear magnetic resonance ( ¹ H-NMR) measurements were performed at room temperature using tetramethylsilane as a reference. The imidization rate (%) was calculated from the obtained ¹ H-NMR spectrum using the following formula (1).

Imidization rate [%] = (1-(A ¹ /(A ² ×α))) × 100...(1)

(In formula (1), ^A1 is the peak area of protons originating from the NH group appearing near the chemical shift of 10 ppm, ^A2 is the peak area of protons originating from other protons, and α is the ratio of the number of other protons to the number of protons in the NH group in the polymer precursor (polyamine).)

[Weight average molecular weight (Mw) and number average molecular weight (Mn)]

Mw and Mn are polystyrene-equivalent values measured by GPC under the following conditions.

Column: Tosoh Corporation, TSKgelGRCXLII

Solvent: Tetrahydrofuran

Temperature: 40°C

Pressure: 68kgf/ ^cm2

The abbreviations of the compounds are as follows. In the following, the compound represented by formula (X) may be simply referred to as "Compound (X)".

(Tetracarboxylic dianhydride)

(Diamine compound)

[Chemistry 22]

(Blocked Amine)

(Siloxane monomers and reactive compounds)

(Styrene-maleimide copolymer monomer)

(Crosslinking agent)

[Chemistry 26]

[Chemistry 27]

(In formula (AD-5), R is a tert-butoxycarbonyl group or a group derived from methyl ethyl ketoxime (*-ON=C(CH ₃ )(C ₂ H ₅ )).)

<Polymer Synthesis>

1. Synthesis of polyamine

[Synthesis example 1]

70 mol parts of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride and 30 mol parts of 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 60 mol parts of 1,2-bis(4-aminophenoxy)ethane as a diamine compound, and 40 mol parts of compound (DB-13) 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, Synthesis Example 4 to Synthesis Example 13]

Solutions containing polyamides (Polymers (PA-2) to (PA-5), and Polymers (PA-16) to (PA-23)) were obtained by the same procedures as in Synthesis Example 1, except that the types and amounts of tetracarboxylic dianhydride and diamine compounds used were changed as described in Tables 1 and 2. Furthermore, in Synthesis Examples 4 and 5, a blocked amine was dissolved in NMP along with the tetracarboxylic dianhydride and diamine compounds for reaction.

[Synthesis example 3]

Polymerization was carried out in the same manner as in Synthesis Example 1, except that the types and amounts of tetracarboxylic dianhydride and diamine compounds used were changed as shown in Table 1, yielding a polymer solution containing polyamide. Blocked amine (MA-3) was then added to the resulting polymer solution, and the reaction was allowed to proceed at room temperature for 3 hours to yield a solution containing polymer (PA-3).

2. Synthesis of polyimide

[Synthesis Example 14]

Polymerization was carried out in the same manner as in Synthesis Example 1 to obtain a solution containing 15% by mass of the polymer (PA-1). NMP was then added to the obtained polymer solution to prepare a solution with a polyimide concentration of 10% by mass. Pyridine and acetic anhydride were then added to allow a dehydration and ring-closure reaction to proceed at 60°C for 4 hours. After the dehydration and ring-closure reaction, the solvent in the system was replaced with fresh NMP, yielding a solution containing 15% by mass of polyimide (referred to as polymer (PI-1)) with an imidization ratio of approximately 80%.

[Synthesis Example 15 to Synthesis Example 21, Synthesis Example 23 to Synthesis Example 26]

The same procedures as in Synthesis Example 14 were followed, except that the types and amounts of the tetracarboxylic dianhydride and diamine compound used were changed as described in Tables 3 and 4, to obtain solutions containing polyimides (Polymers (PI-2) to (PI-8), (PI-10), and (PI-11)). Furthermore, in Synthesis Examples 15, 17 to 21, 24, and 25, a blocked amine was dissolved in NMP along with the tetracarboxylic dianhydride and diamine compound, and the reaction was carried out.

[Synthesis Example 22]

Polymerization was carried out in the same manner as in Synthesis Example 1, except that the types and amounts of tetracarboxylic dianhydride and diamine compounds used were changed as described in Table 3, to obtain a polymer solution containing polyamide. Blocked amine (MA-1) was then added to the resulting polymer solution, and the reaction was allowed to proceed at room temperature for 3 hours. Subsequently, imidization of the polyamide was carried out in the same manner as in Synthesis Example 14, to obtain a solution containing polymer (PI-9) as a polyimide.

3. Synthesis of polyorganosiloxane

[Synthesis Example 27]

A 1000 mL three-necked flask was charged with 100.0 g of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (the compound represented by Formula (s-1)), 500 g of methyl isobutyl ketone, and 10.0 g of triethylamine and mixed at room temperature. Subsequently, 100 g of deionized water was added dropwise from a dropping funnel over 30 minutes. The mixture was then reacted at 80°C for 6 hours while mixing under reflux. After the reaction, the organic layer was removed and washed with a 0.2% by mass aqueous ammonium nitrate solution until the washed water became neutral. The solvent and water were then distilled off under reduced pressure. An appropriate amount of methyl isobutyl ketone was added to obtain a 50% by mass solution of a polyorganosiloxane polymer (ESSQ-1) having an epoxy group.

To a 500 mL three-necked flask were added 3.10 g of compound (c-1) (20 mol% of epoxy groups relative to the polymer (ESSQ-1)), 3.24 g of compound (c-2) (10 mol% of epoxy groups relative to the polymer (ESSQ-1)), 1.00 g of tetrabutylammonium bromide, 20.0 g of the solution containing polymer (ESSQ-1), and 290.0 g of methyl isobutyl ketone. The mixture was stirred at 90°C for 18 hours. After cooling to room temperature, the mixture was washed with distilled water 10 times. The organic layer was then recovered and repeatedly concentrated and diluted with NMP twice using a rotary evaporator. The solid content was then adjusted to 10% by mass using NMP to obtain an NMP solution of polyorganosiloxane (referred to as polymer (PSQ-1)).

4. Synthesis of Styrene-Maleimide Copolymers

[Synthesis Example 28]

Under nitrogen, a 100 mL two-necked flask was charged with 10 mol parts of Compound (M-1), 10 mol parts of Compound (M-2), 30 mol parts of Compound (M-3), 10 mol parts of Compound (M-4), 20 mol parts of Compound (M-5), and 20 mol parts of Compound (M-6) as polymerization monomers, 2 mol parts of 2,2'-azobis(2,4-dimethylvaleronitrile) as a free radical polymerization initiator, and 50 ml of tetrahydrofuran as a solvent. Polymerization was carried out at 70°C for 6 hours. After reprecipitation in methanol, the precipitate was filtered and vacuum-dried at room temperature for 8 hours to obtain a styrene-maleimide copolymer (referred to as Polymer (MI-1)). The weight average molecular weight (Mw) of the polymer (MI-1) measured by GPC in terms of polystyrene was 92,700, and the molecular weight distribution (Mw/Mn) was 4.78.

<Preparation and Evaluation of Liquid Crystal Alignment Agents>

[Example 1: Friction-treated FFS liquid crystal display element]

1. Preparation of Liquid Crystal Alignment Agent

To the solution of the polymer (PI-4) obtained in Synthesis Example 17, 5 parts by mass of compound (AD-1) as a crosslinker was added relative to 100 parts by mass of the polymer (solid content). The solution was diluted with NMP and butyl cellosolve (BC) to prepare a solution with a solvent composition of NMP/BC = 80/20 (mass ratio) and a solid content concentration of 3.5% by mass. The solution was filtered through a filter with a pore size of 0.2 μm to prepare a liquid crystal alignment agent (AL-1).

2. Manufacturing of FFS-type liquid crystal cells using the rubbing method

A glass substrate (the first substrate) with a flat electrode (bottom electrode), an insulating layer, and a comb-shaped electrode (top electrode) laminated sequentially on one side was prepared, along with a glass substrate (the second substrate) without an electrode. A liquid crystal alignment agent (AL-1) was then applied to the electrode-forming surface of the first substrate and one side of the second substrate using a spinner. The coatings were then heated for 3 minutes on a 110°C hot plate (pre-baked). The coatings were then dried for 30 minutes in a nitrogen-purged oven at 230°C (post-baked), resulting in a coating with an average thickness of 0.08μm. The coated surface was then rubbed using a rubbing machine equipped with a roll wrapped with rayon cloth at a roll speed of 1000 rpm, a stage movement speed of 3 cm/sec, and a bristle penetration length of 0.3 mm. The surface was then ultrasonically cleaned in ultrapure water for one minute and dried in a 100°C oven for 10 minutes, yielding a pair of substrates with liquid crystal alignment films.

Next, a pair of substrates with liquid crystal alignment films were screen-printed with an epoxy resin adhesive containing 3.5μm-diameter aluminum oxide balls, leaving a liquid crystal injection port at the edge of the film-coated surface. The substrates were then stacked and pressed together, and the adhesive was heat-cured at 150°C for one hour. Negative liquid crystal (MLC-6608, manufactured by Merck) was then injected into the gap between the two substrates through the liquid crystal injection port, and the port was sealed with an epoxy adhesive. Furthermore, to eliminate the flow alignment caused by liquid crystal injection, the film was heated at 120°C and then slowly cooled to room temperature, thus producing a liquid crystal cell. In addition, when a pair of substrates are stacked, the rubbing directions of the substrates are made antiparallel.

3. Evaluation of Liquid Crystal Orientation

The liquid crystal cell manufactured in 2. was placed under a high-brightness backlight of 27,000 cd/ ^m2 for 500 hours, and the liquid crystal alignment was evaluated based on the delay change rate before and after backlight irradiation. First, for the liquid crystal cell manufactured in 2., the delay was measured using an Axoscan manufactured by Optoscience, and the delay change rate α before and after backlight irradiation was calculated using the following formula (z-1). The smaller the change rate α, the better the liquid crystal alignment. A change rate α of less than 1% was rated as "good (○)", a change rate of 1% or more and less than 2% was rated as "acceptable (△)", and a change rate of 2% or more was rated as "poor (×)".

α=△θ/θ1...(z-1)

(In formula (z-1), △θ represents the delay difference before and after irradiation, and θ1 represents the delay value before irradiation.)

As a result, the evaluation of the liquid crystal alignment of the embodiment was "good (○)".

4. Evaluation of AC afterimage characteristics

For the liquid crystal cell manufactured in 2. above, after being driven with an AC voltage of 10V for 72 hours, the minimum relative transmittance (%) expressed by the following formula (2) was measured using a device with a polarizer and an analyzer arranged between the light source and the light intensity detector.

Minimum relative transmittance (%) = (β-B0)/(B100-B0)×100...(2)

(In formula (2), B0 is the light transmittance under a blank and crossed Nicol prism. B100 is the light transmittance under a blank and parallel Nicol prism. β is the light transmittance that is minimum when the liquid crystal cell is sandwiched between the polarizer and the analyzer under crossed Nicol prisms.

The black level in the dark state is represented by the minimum relative transmittance of the liquid crystal cell. In FFS liquid crystal cells, the lower the black level in the dark state, the better the contrast. A minimum relative transmittance of less than 0.3% is rated "Excellent (◎)", 0.3% or more and less than 1.3% is rated "Good (○)", 1.3% or more and less than 2.0% is rated "Acceptable (△)", and 2.0% or more is rated "Poor (×)". The results were rated "Excellent (◎)" in the example described above.

5. Evaluation of initial voltage holding ratio (VHR)

The liquid crystal cell produced in step 2. was placed in a 60°C oven and then measured for voltage holding ratio (VHR) using a VHR measuring device "VHR-1" manufactured by Toyo Technica under the conditions of 1V and 1670msec. The evaluation criteria were "good (○)" for a VHR greater than 80%, "acceptable (△)" for a VHR between 80% and 60%, and "poor (×)" for a VHR less than 60%. The initial VHR of the example was evaluated as "good (○)".

6. Evaluation of film strength (friction resistance)

The liquid crystal alignment agent (AL-1) prepared in step 1 was applied to a glass substrate using a spinner and heated on a 110°C hot plate for 3 minutes (pre-baking). The coating was then dried for 30 minutes in a 230°C oven purged of nitrogen (post-baking) to form a film with an average film thickness of 0.08 μm. The haze value of the film was measured using a haze meter. The film was then rubbed five times using a rubbing machine equipped with a roll wrapped with cotton cloth, at a roll speed of 1000 rpm, a stage travel speed of 3 cm/sec, and a bristle indentation length of 0.3 mm. The haze value of the liquid crystal alignment film was then measured using a haze meter, and the difference from the haze value before rubbing was calculated (the haze change). The haze change is expressed by the following formula (z-2), where the haze value of the film before rubbing is Hz1 (%) and the haze value of the film after rubbing is Hz2 (%).

Fog density change (%) = Hz2-Hz1...(z-2)

A haze change value of less than 0.5 was rated "Excellent (◎)", a haze change value of 0.5 or more but less than 0.8 was rated "Good (○)", a haze change value of 0.8 or more but less than 1.0 was rated "Acceptable (△)", and a haze change value of 1.0 or more was rated "Poor (×)". A haze change value of less than 1.0 indicates that the film strength is sufficiently high and the friction resistance is high, meaning that the film's mechanical properties are good. Consequently, the film strength in the example described was rated "Excellent (◎)".

7. Evaluation of film adhesion

The liquid crystal alignment agent (AL-1) prepared in step 1 was applied to a glass substrate using a spinner. After pre-baking for 1 minute on an 80°C hot plate, the coating was heated (post-baked) for 1 hour in a 230°C oven purged of nitrogen, resulting in a coating with an average thickness of 0.1 μm. This same procedure was repeated to create two coated glass substrates. An ODF sealant (S-WB42, manufactured by Sekisui Chemical) was applied to the coating on one of the glass substrates to a diameter of 4.8 mm to 5.2 mm. The two glass substrates were then bonded together so that the coating on the other glass substrate was in contact with the ODF sealant. The films were then irradiated with 30,000 J/m ² (365 nm) of light from a metal halide lamp and heated in a 120°C oven for 1 hour. The film's adhesion was then evaluated by measuring adhesion strength using an Imada Seisakusho tension-compression tester (model: SDWS-0201-100SL).

In the evaluation, adhesion strength of 300 gf/mm² or ^greater was rated as "excellent (◎)", adhesion strength of 200 gf/ ^mm² or greater but less than 300 gf/ ^mm² was rated as "good (○)", adhesion strength of 100 gf/ ^mm² or greater but less than 200 gf/ ^mm² was rated as "acceptable (△)", and adhesion strength of less than 100 gf/ ^mm² was rated as "poor (×)". The results showed that the adhesion in the example described above was rated as "excellent (◎)".

8. Evaluation of Reprocessability

On a transparent conductive film including an ITO film provided on one side of a 1mm thick glass substrate, the liquid crystal alignment agent (AL-1) prepared as described above was applied using a spinner, and pre-baked at 100°C for 90 seconds using a hot plate to form a coating with a film thickness of approximately 0.08μm. The above operation was repeated to produce two substrates with coatings. The two obtained substrates were then stored in a dark room at 25°C under a nitrogen environment. After 12 hours and 48 hours from the start of storage, one substrate was taken out respectively, immersed in a beaker containing NMP at a temperature adjusted to 40°C for 2 minutes, and then rinsed several times with ultrapure water. Water droplets on the surface were removed using an air blow. The substrate was observed under an optical microscope to check for coating residue, thereby evaluating the ease of peeling the liquid crystal alignment film from the substrate (reworkability).

Regarding the evaluation, if no coating residue was observed after NMP immersion even on a substrate removed 48 hours after storage, reworkability was rated "good (○)." If coating residue was observed on a substrate after 48 hours but not on a substrate after 12 hours, reworkability was rated "acceptable (△)." If coating residue was observed on a substrate after 12 hours, reworkability was rated "poor (×)." The results showed that the reworkability of the example described above was "good (○)."

[Example 2 to Example 20 and Comparative Example 1 to Comparative Example 4]

A liquid crystal alignment agent was prepared in the same manner as in Example 1, except that the composition of the liquid crystal alignment agent was modified as shown in Table 5. Furthermore, using the resulting liquid crystal alignment agent, an FFS liquid crystal cell was produced by rubbing in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 5. Furthermore, in Examples 3 to 5, 7, 8, 12, 14, 19, and 20, two or three polymers were used as polymer components. The numerical values of the alignment agent composition in Table 5 represent the proportion (parts by mass) of each compound per 100 parts by mass of the total polymer components used in preparing the liquid crystal alignment agent (the same applies to Tables 6 and 7).

In Table 5, the abbreviations of the crosslinking agents are as follows.

AD-6: Product name: TRIXENE 7982, manufactured by Baxenden.

As shown in Table 5, Examples 1 to 20, which use liquid crystal alignment agents containing polymer [P], achieve a good balance among liquid crystal alignment, afterimage characteristics, initial VHR, film strength (friction resistance), film adhesion, and reworkability, compared to Comparative Examples 1 to 4, which use liquid crystal alignment agents not containing polymer [P].

[Example 21: Optical FFS Type Liquid Crystal Display Element]

1. Preparation of Liquid Crystal Alignment Agent

To a solution containing the polymer (PI-6) obtained in Synthesis Example 19, 3 parts by mass of compound (AD-3) as a crosslinker was added relative to 100 parts by mass of the polymer (solid content). The solution was then diluted with NMP and BC to prepare a solution with a solvent composition of NMP/BC = 80/20 (mass ratio) and a solid content concentration of 3.5% by mass. The solution was filtered through a filter with a pore size of 0.2 μm to prepare a liquid crystal alignment agent (AL-21).

2. Manufacturing of FFS-type liquid crystal display devices using photoalignment

Prepare the same first and second substrates as in Example 1. Then, use a rotator to apply a liquid crystal alignment agent (AL-21) to 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 an 80°C heating plate. Thereafter, dry (post-bake) for 30 minutes in a 230°C oven with nitrogen substituted inside the box to 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 of linear polarization from the normal direction of the substrate to perform a photoalignment treatment. In addition, the irradiation amount is a value measured using a light meter measured with a wavelength of 254 nm as the reference. The photo-aligned coating was then heated in a clean oven at 230°C for 30 minutes to form a liquid crystal alignment film.

Next, an epoxy resin adhesive containing 3.5μm-diameter aluminum oxide spheres was screen-printed onto the outer edge of one of the paired substrates, which had a liquid crystal alignment film formed on it. The substrates were then stacked and press-bonded so that the polarization axes of light projected onto the substrate surfaces were antiparallel during irradiation. The adhesive was then thermally cured at 150°C for one hour. Negative liquid crystal (MLC-6608, manufactured by Merck) was then injected into the gap between the two substrates through the liquid crystal injection port. The port was then sealed with an epoxy adhesive to produce a liquid crystal cell. Furthermore, to eliminate the flow alignment caused during liquid crystal injection, the cells were heated at 120°C and then slowly cooled to room temperature. Furthermore, the above series of operations were repeated, varying the UV exposure after post-baking from 100 J/ ^m² to 10,000 J/ ^m² . Three or more liquid crystal cells with different UV exposure levels were produced, and the cell with the exposure that exhibited the best alignment characteristics (optimal exposure) was used for evaluation.

3. Evaluation

Using the liquid crystal alignment agent prepared in 1. and the liquid crystal cell manufactured in 2., various evaluations were performed in the same manner as in Example 1. The evaluation results are shown in Table 6.

[Example 22 to Example 24 and Comparative Example 5 to Comparative Example 7]

A liquid crystal alignment agent was prepared in the same manner as in Example 21, except that the composition of the liquid crystal alignment agent was modified as shown in Table 6. Furthermore, using the obtained liquid crystal alignment agent, an FFS liquid crystal cell was fabricated by photoalignment in the same manner as in Example 21, and various evaluations were performed. The results are shown in Table 6.

As shown in Table 6, Examples 21 to 24, which use liquid crystal alignment agents containing polymer [P], achieve a balance of liquid crystal alignment properties, afterimage characteristics, initial VHR, film strength, film adhesion, and reworkability compared to Comparative Examples 5 to 7, which use liquid crystal alignment agents not containing polymer [P]. These results are comparable to those achieved when liquid crystal alignment films are manufactured using the rubbing method, demonstrating excellent results.

[Example 25: PSA-type liquid crystal display device]

1. Preparation of Liquid Crystal Alignment Agent

A solution containing 5 parts by mass of the polymer (PSQ-1) obtained in Synthesis Example 27 and a solution containing 95 parts by mass of the polymer (PI-12) obtained in Synthesis Example 25 were mixed and diluted with NMP and BC to prepare a solution with a solvent composition of NMP/BC = 50/50 (mass ratio) and a solids concentration of 3.5% by mass. This solution was filtered through a 0.2 μm pore size filter to prepare a liquid crystal alignment agent (AL-25).

2. Preparation of Liquid Crystal Compositions

To 10 g of nematic liquid crystal (MLC-6608, manufactured by Merck), 5% by mass of a liquid crystal compound represented by the following formula (L1-1) and 0.3% by mass of a photopolymerizable compound represented by the following formula (L2-1) were added and mixed to obtain a liquid crystal composition LC1.

3. Manufacturing of PSA-type liquid crystal cells

The liquid crystal alignment agent (AL-25) prepared above was applied to the transparent electrode surface of a glass substrate with an ITO film using a spinner. After pre-baking on a hot plate at 80°C for one minute, the solution was removed by heating at 200°C in a nitrogen oven for one hour to form a 0.08μm thick film (liquid crystal alignment film). The film was then rubbed using a rubbing machine equipped with a roll wrapped with rayon cloth at a roll speed of 400 rpm, a stage travel speed of 3 cm/sec, and a bristle indentation length of 0.1 mm. The film was then ultrasonically cleaned in ultrapure water for one minute and dried in a clean oven at 100°C for 10 minutes to obtain a substrate with a liquid crystal alignment film. Repeating this process yields a pair (two substrates) of liquid crystal alignment films. The rubbing treatment is a weak rubbing process performed to control the collapse of the liquid crystal and achieve alignment division in a simple manner.

An epoxy resin adhesive containing 3.5μm diameter aluminum oxide balls was screen-printed around the periphery of the surface of one of the substrates with the liquid crystal alignment film. The two substrates were then stacked and press-bonded with their liquid crystal alignment film surfaces facing each other. The adhesive was then heated at 150°C for one hour to thermally cure. The gap between the substrates was then filled with liquid crystal composition PLC1 through a liquid crystal injection port. The port was then sealed with an epoxy adhesive. Furthermore, to eliminate the flow alignment caused by liquid crystal injection, the substrates were heated at 150°C for 10 minutes and then slowly cooled to room temperature.

The resulting liquid crystal cell was then irradiated with ultraviolet light at a dose of 50,000 J/ ^m² using a UV irradiation device using a metal halide lamp as a light source, while a 10V AC voltage at a frequency of 60 Hz was applied between the electrodes to drive the liquid crystal. The dose was measured using a light meter with a wavelength of 365 nm. This produced a PSA-type liquid crystal cell.

4. Evaluation

The liquid crystal cell produced in step 3 was evaluated for liquid crystal alignment, initial VHR, film adhesion, and reworkability using the same methods as in Example 1. The evaluation results are shown in Table 7.

[Example 26, Example 27, and Comparative Example 8, Comparative Example 9]

A liquid crystal alignment agent was prepared in the same manner as in Example 25, except that the composition of the liquid crystal alignment agent was changed as shown in Table 7. Furthermore, a PSA-type liquid crystal cell was produced using the obtained liquid crystal alignment agent in the same manner as in Example 25, and various evaluations were performed. The evaluation results are shown in Table 7.

As shown in Table 7, Examples 25-27, which used liquid crystal alignment agents containing polymer [P], achieved a balance of liquid crystal alignment, initial VHR, film adhesion, and reworkability compared to Comparative Examples 8 and 9, which used liquid crystal alignment agents without polymer [P], achieving excellent results comparable to those of FFS-type liquid crystal display devices. In particular, the use of polymer [P] demonstrated a significant improvement in film adhesion. This is presumably due to the enhanced mechanical strength of the film resulting from the use of polymer [P].

The above results clearly demonstrate that a liquid crystal alignment agent containing polymer [P] can produce a liquid crystal element with high voltage retention and low residual image generation, and can also form a liquid crystal alignment film with high film strength, good reworkability, and excellent adhesion.

Claims (9)

A liquid crystal aligner comprising a polymer [P] having a partial structure (A) represented by the following formula (1) or (2) at the end of the main chain, In formula (1), ^R1 is a monovalent organic group that is released by heat; ^R2 is a monovalent organic group; ^R3 and ^R4 are each independently a hydrogen atom or a monovalent organic group; and "*" indicates a bond. In formula (2), ^R5 is a monovalent organic group that is released by heat; ^R6 and ^R7 satisfy the following (i) or (ii): (i) ^R6 is a monovalent organic group; ^R7 is a divalent alicyclic group; (ii) ^R6 and ^R7 represent a ring structure formed by ^R6 and ^R7 together with the nitrogen atom to which they are bonded; and "*" indicates a bond. The liquid crystal aligner according to claim 1, wherein the polymer [P] has a structural unit derived from a compound represented by the following formula (3) at the end of the main chain, In formula (3), ^A1 is a monovalent group having a partial structure represented by formula (1) or (2); ^R8 is a single bond, -O-, -S-, -CO-, -COO-, ^-NR10- , -CO- ^NR10- , ^-NR10 -CO-O-, ^-NR10 -CO- ^NR11- , a divalent chain alkyl group having 1 or more carbon atoms, a divalent alicyclic alkyl group having 3 or more carbon atoms, or a divalent chain alkyl group having 2 or more carbon atoms in which any methylene group is substituted with -O-, -S-, -CO-, -COO-, ^{-NR10-, -CO-NR10- , -NR10 -} CO-O-, or ^-NR10 -CO- ^NR11- ; ^R10 and ^R11 are each independently a hydrogen atom or a monovalent organic group; R ^{R 9} is a single bond or an (m+1)-valent aromatic ring group; m is 1 or 2; wherein, when R ⁹ is a single bond, m is 1, and R ⁸ is a single bond or is bonded to the primary amine group in formula (3) through a alkyl group; when m is 2, multiple R ^8s are the same or different, and multiple A ^1s are the same or different. The liquid crystal alignment agent according to claim 1 or claim 2, wherein the polymer [P] is at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide. The liquid crystal alignment agent according to claim 3, wherein the polymer [P] has structural units derived from alicyclic tetracarboxylic dianhydride. The liquid crystal alignment agent as described in claim 1 or claim 2 further contains a compound having at least one group selected from the group consisting of the following groups: a group having a polymerizable carbon-carbon bond, a cyclic ether group, a cyclic thioether group, an isocyanate group, a protected isocyanate group, a hydroxymethyl group, a protected hydroxymethyl group, a cyclic carbonate group, and the group " ^-CR20 = ^CR21 - ^R22- ", wherein ^R20 is a monovalent group that is released by reaction with an amino group; ^R21 is a hydrogen atom or an alkyl group; and ^R22 is an electron-withdrawing group, a silanol group, and an alkoxysilane group. The liquid crystal alignment agent as described in claim 1 or claim 2 further contains a polymer that does not have the partial structure (A) at the end of the main chain. A liquid crystal alignment agent comprises a polymer [P] obtained by polymerizing monomers comprising tetracarboxylic dianhydride, an acid derivative of at least one selected from the group consisting of tetracarboxylic dianhydride and tetracarboxylic diester dihalides, and a diamine compound in the presence of a monoamine compound having a partial structure (A) represented by the following formula (1) or (2), or by reacting the monomers with the monoamine compound after polymerization. In formula (1), ^R1 is a monovalent organic group that is released by heat; ^R2 is a monovalent organic group; ^R3 and ^R4 are each independently a hydrogen atom or a monovalent organic group; and "*" indicates a bond. In formula (2), ^R5 is a monovalent organic group that is released by heat; ^R6 and ^R7 satisfy the following (i) or (ii): (i) ^R6 is a monovalent organic group; ^R7 is a divalent alicyclic group; (ii) ^R6 and ^R7 represent a ring structure formed by ^R6 and ^R7 together with the nitrogen atom to which they are bonded; and "*" indicates a bond. A liquid crystal alignment film is formed using the liquid crystal alignment agent described in any one of claims 1 to 7. A liquid crystal element comprising the liquid crystal alignment film as described in claim 8.