CN113366381A

CN113366381A - Liquid crystal aligning agent, liquid crystal alignment film, and liquid crystal display element using same

Info

Publication number: CN113366381A
Application number: CN202080011835.0A
Authority: CN
Inventors: 别府功一朗; 新津新平; 仲井崇; 望月大
Original assignee: Nissan Chemical Corp
Current assignee: Nissan Chemical Corp
Priority date: 2019-01-30
Filing date: 2020-01-29
Publication date: 2021-09-07
Also published as: JP7447817B2; TWI834805B; KR20210121002A; WO2020158818A1; JPWO2020158818A1; TW202035522A

Abstract

The invention provides a liquid crystal aligning agent which can obtain a liquid crystal aligning film with high DC brightness relaxation speed and flicker change inhibition. The liquid crystal aligning agent of the present invention is characterized by containing the following polymer (A), polymer (B) and polymer (C). Polymer (a): at least one polymer selected from the group consisting of the following (i) to (iii). (i) A polyamic acid obtained by polymerizing a diamine component containing at least one diamine selected from the group consisting of diamines represented by the formula [1] and diamines represented by the formula [2] with a tetracarboxylic acid component comprising an aromatic tetracarboxylic dianhydride. (ii) A polyamic acid ester obtained by polymerizing a tetracarboxylic acid component and a diamine component containing at least one diamine selected from the group consisting of a diamine represented by the formula [1] and a diamine represented by the formula [2 ]. (iii) A polyimide obtained by imidizing a polyimide precursor obtained by polymerizing a tetracarboxylic acid component and a diamine component, wherein the diamine component contains at least one diamine selected from the group consisting of a diamine represented by the formula [1] and a diamine represented by the formula [2 ]. Polymer (B): at least one polymer selected from the group consisting of a polyimide precursor obtained by polymerizing a diamine component containing a diamine represented by the formula [3] with a tetracarboxylic acid component, and a polyimide obtained from the polyimide precursor. Polymer (C): a polyamic acid obtained by polymerizing a diamine component (wherein the diamine component does not contain a diamine represented by the formula [3 ]) with a tetracarboxylic acid component comprising an alicyclic tetracarboxylic dianhydride and/or an aliphatic tetracarboxylic dianhydride. (the formulae [1] to [3] are defined in the specification).

Description

Liquid crystal aligning agent, liquid crystal alignment film, and liquid crystal display element using same

Technical Field

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

Background

As a liquid crystal alignment film used for a liquid crystal display element or the like, a polyimide-based resin film is widely used. The polyimide-based liquid crystal alignment film is produced by applying a liquid crystal alignment agent containing a polymer such as polyamic acid (also referred to as polyamic acid), polyamic acid ester, or polyimide, and a solvent as main components to a substrate.

In addition to recent advances in high performance and large area of liquid crystal display elements and power saving of display devices, liquid crystal display elements are increasingly used in various environments, and various problems are becoming remarkable. For example, static electricity is likely to accumulate in the liquid crystal cell, and charges accumulated in the liquid crystal alignment film affect display in the form of disturbance or afterimage of liquid crystal alignment, thereby significantly degrading the display quality of the liquid crystal display device. When the liquid crystal panel is driven for a long time, the magnitude of flicker (flicker) changes when a positive and negative asymmetrical voltage is applied due to the accumulation of electric charges generated by the driving.

Patent documents 1 to 4 describe liquid crystal alignment agents containing polyamic acid obtained from a low-resistance material such as 4, 4' -diaminodiphenylamine (DADPA).

However, when a low-resistance material is used in the production of polyamic acid, the DC luminance relaxation rate becomes fast, but the flicker change may become large. On the other hand, when a material in which the change of flicker is suppressed is used in the production of polyamic acid, the DC luminance relaxation rate may be slow. That is, in the conventional liquid crystal alignment film, the high DC luminance relaxation speed and the suppression of the flicker variation are in a mutually opposite relationship (trade-off), and both of them may not be compatible, which is a problem.

In addition, when a low-resistance material is used, the transmittance of the substrate may be lowered by coloring, which is a problem.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 5900328

Patent document 2: international publication No. 2018/062440

Patent document 3: japanese patent No. 6280701

Patent document 4: japanese patent No. 6314488

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a liquid crystal aligning agent capable of providing a liquid crystal alignment film having a high DC luminance relaxation speed and suppressed flicker variation. It is another object of the present invention to provide a liquid crystal aligning agent which can provide a liquid crystal alignment film having a high substrate transmittance even when a low-resistance material is used.

Means for solving the problems

The present inventors have intensively studied to solve the above problems, and as a result, they have found that the above problems are satisfied by a specific liquid crystal aligning agent.

A liquid crystal aligning agent, comprising: the following polymer (A), polymer (B) and polymer (C).

Polymer (a): at least one polymer selected from the group consisting of the following (i) to (iii).

(i) A polyamic acid obtained by polymerizing a diamine component containing at least one diamine selected from the group consisting of diamines represented by the following formula [1] and diamines represented by the following formula [2] with a tetracarboxylic acid component composed of an aromatic tetracarboxylic dianhydride.

(ii) A polyamic acid ester obtained by polymerizing a tetracarboxylic acid component with a diamine component containing at least one diamine selected from the group consisting of a diamine represented by the following formula [1] and a diamine represented by the following formula [2 ].

(iii) A polyimide obtained by imidizing a polyimide precursor obtained by polymerizing a diamine component and a tetracarboxylic acid component, wherein the diamine component contains at least one diamine selected from the group consisting of a diamine represented by the following formula [1] and a diamine represented by the following formula [2 ].

(formula [1]]And [2]]In (A)₁Is a single bond, an ether bond, an ester bond, -C ═ C-, -C ≡ C-, or a C2-20 subunitAlkyl group or-CH in the alkylene group₂A group in which a part or all of the group-A-B-C is substituted with at least one group selected from the group consisting of an ether bond, an ester bond, -C ═ C-, -C ≡ C-, a cyclohexylene group, and a phenylene group. A. the₂Is a fluorine atom or an alkyl group or alkoxy group having 1 to 5 carbon atoms (wherein any hydrogen atom of the alkyl group or alkoxy group is optionally substituted by a fluorine atom). a is an integer of 0 to 4, and when a is an integer of 2 or more, A is₂May be the same or different. b and c are each independently an integer of 1 to 2. )

Polymer (B): at least one polymer selected from the group consisting of a polyimide precursor obtained by polymerizing a diamine component and a tetracarboxylic acid component, and a polyimide obtained from the polyimide precursor, wherein the diamine component contains a diamine represented by the following formula [3 ].

H₂N-X-NH₂ [3]

(wherein X has a structure in which an aromatic hydrocarbon ring is bonded to a carbon atom of a nitrogen-containing aromatic heterocycle constituting a five-membered ring or a six-membered ring, or has a structure represented by the following formula,

bonded to a structure other than a carbonyl group, and at least one is bonded to an aromatic ring group. )

Polymer (C): a polyamic acid obtained by polymerizing a diamine component (wherein the diamine component does not contain a diamine represented by the formula [3 ]) with a tetracarboxylic acid component comprising an alicyclic tetracarboxylic dianhydride and/or an aliphatic tetracarboxylic dianhydride.

Effects of the invention

According to the liquid crystal aligning agent of the present invention, a liquid crystal alignment film having a high DC luminance relaxation speed and suppressed flicker variation can be obtained. Further, according to the liquid crystal aligning agent of the present invention, even when a low-resistance material is used, a liquid crystal alignment film having a high transmittance of a substrate can be obtained.

Detailed Description

< Polymer (A) >

The polymer (a) contained in the liquid crystal aligning agent of the present invention is the following polymer.

(ii) A polyamic acid ester obtained by polymerizing a tetracarboxylic acid component with a diamine component containing at least one diamine selected from the group consisting of diamines represented by the following formula [1] and diamines represented by the following formula [2 ].

(iii) A polyimide obtained by imidizing a polyimide precursor obtained by polymerizing a diamine component and a tetracarboxylic acid component, wherein the diamine component contains at least one diamine selected from the group consisting of diamines represented by the following formula [1] and diamines represented by the following formula [2 ].

(formula [1]]And [2]]In (A)₁Is a single bond, an ether bond, an ester bond, -C ═ C-, -C ≡ C-, or an alkylene group having 2 to 20 carbon atoms, or-CH in the alkylene group₂A group in which a part or all of the group-A-B-C is substituted with at least one group selected from the group consisting of an ether bond, an ester bond, -C ═ C-, -C ≡ C-, a cyclohexylene group, and a phenylene group. A. the₂Is a fluorine atom or an alkyl group or alkoxy group having 1 to 5 carbon atoms (wherein any hydrogen atom of the alkyl group or alkoxy group is optionally substituted by a fluorine atom). a is an integer of 0 to 4, and when a is an integer of 2 or more, A is₂May be the same or different. b and c are each independently an integer of 1 to 2. )

(diamine component for producing Polymer (A))

The diamine component for producing the polymer (A) contains at least one diamine selected from the group consisting of the diamines represented by the above formula [1] and the diamines represented by the above formula [2 ].

The above formula [1]-formula [2]In (B), preferably, A₁Is a single bond, -C ═ C-, -C ≡ C-, C2-10 alkylene group, or-CH in the alkylene group₂A group substituted with at least one group selected from the group consisting of an ether bond, an ester bond, -C ═ C-, -C ≡ C-, a cyclohexylene group and a phenylene group, and a₂Is CH₃Wherein a is an integer of 0 to 1, b is 1, and c is an integer of 1 to 2.

Examples of the diamine represented by the formulae [1] to [2] include the following diamines.

The amount of the diamine represented by the formulae [1] and [2] used is 30 to 100 mol%, more preferably 40 to 100 mol%, and still more preferably 50 to 100 mol% based on the total amount of the diamine component used for producing the polymer (A).

Further, as the diamine component used for producing the polymer (a) contained in the liquid crystal aligning agent of the present invention, any diamine other than the diamines represented by the formulae [1] and [2] (hereinafter, also referred to as "other diamine") may be used. Specific examples of the other diamines include: 4, 4 ' -diaminodiphenylmethane, 3, 4 ' -diaminodiphenylmethane, 4- (2- (methylamino) ethyl) aniline, 4- (2-aminoethyl) aniline, 4 ' -diaminobenzophenone, 4 ' -diaminoazobenzene, 1- (4-aminophenyl) -1, 3, 3-trimethyl-1H-indan-5-amine, 1- (4-aminophenyl) -2, 3-dihydro-1, 3, 3-trimethyl-1H-inden-6-amine, 1, 4-diaminonaphthalene, 1, 5-diaminonaphthalene, 2, 6-diaminonaphthalene, 2, 7-diaminonaphthalene, 2 ' -bis [ 4- (4-aminophenoxy) phenyl ] propane, 2 ' -bis [ 4- (4-aminophenoxy) phenyl ] hexafluoropropane, 2 ' -bis (4-aminophenyl) propane, 2- (2, diamines having a photopolymerizable group at the terminal, such as 4-diaminophenoxy) ethyl ester and 2, 4-diamino-N, N-diallylaniline; diamines having a steroid (steroid) skeleton, such as cholestanyl (cholestanyl) oxy-3, 5-diaminobenzene, cholestanyl oxy-2, 4-diaminobenzene, cholestanyl alcohol 3, 5-diaminobenzoate, cholesteryl ester 3, 5-diaminobenzoate, lanosterol ester 3, 5-diaminobenzoate, and cholestane 3, 6-bis (4-aminobenzoyloxy); diamines represented by the following formulae (V-1) to (V-6); diamines having a siloxane bond such as 1, 3-bis (3-aminopropyl) -tetramethyldisiloxane; aromatic diamines such as diamines having a group "-N (D) -" (D represents a protecting group which is eliminated by heating and is substituted with a hydrogen atom, and is preferably a t-butoxycarbonyl group) and represented by the following formulae (5-1) to (5-11); aliphatic diamines such as m-xylylenediamine, ethylenediamine, 1, 3-propylenediamine, tetramethylenediamine and hexamethylenediamine; and alicyclic diamines such as p-cyclohexanediamine and 4, 4' -methylenebis (cyclohexylamine).

(in the above formulae (V-1) to (V-6), X^v1～X^v4、X^p1～X^p8Each independently represents- (CH)₂)_a- (a is an integer of 1 to 15), -CONH-, -NHCO-, -CON (CH)₃)－、－NH－、－O－、－CH₂O－、－CH₂OCO-, -COO-or-OCO-, X^v5represents-O-, -CH₂O－、－CH₂OCO-, -COO-or-OCO-. Xa represents a single bond, -O-, -NH-, -O- (CH)₂)_m-O- (m represents an integer of 1 to 6), R^v1～R^v4、R^1a～R^1bEach independently represents an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms)

(Boc represents a tert-butoxycarbonyl group.)

The diamine component used for producing the polymer (a) of the present invention may be used alone or in combination of two or more depending on the solubility of the polymer (a) in a solvent, the coatability of a liquid crystal aligning agent, the liquid crystal alignment properties when a liquid crystal alignment film is formed, the voltage holding ratio, the accumulated charge, and other properties.

(tetracarboxylic acid component for producing Polymer (A))

The tetracarboxylic acid component of the polyamic acid (i) used for producing the polymer (a) is composed of an aromatic tetracarboxylic dianhydride.

The aromatic tetracarboxylic dianhydride is an acid dianhydride obtained by intramolecular dehydration of four carboxyl groups bonded to the same or different aromatic rings. In this case, when there is one aromatic ring, it is preferable to use acid dianhydride obtained by intramolecular dehydration of four carboxyl groups bonded to the aromatic ring. In addition, if the aromatic ring is two or more, the following acid dianhydride is preferred: acid dianhydride obtained by intramolecular dehydration of two carboxyl groups bonded to one aromatic ring and intramolecular dehydration of two carboxyl groups bonded to the other aromatic ring; or an acid dianhydride obtained by intramolecular dehydration of a carboxyl group bonded to one of two adjacent aromatic rings and a carboxyl group bonded to the other, and intramolecular dehydration of a carboxyl group bonded to one of two adjacent aromatic rings and a carboxyl group bonded to the other.

Examples of the aromatic tetracarboxylic dianhydride include compounds represented by the following formula (3 a-1).

In the above formula, X₁Is any of the following formulae (A-1) to (A-28). Denotes a bond.

As the tetracarboxylic acid component of the (ii) polyamic acid ester or (iii) polyimide used for producing the polymer (a), any tetracarboxylic dianhydride or its derivative (tetracarboxylic acid, tetracarboxylic acid dihalide, tetracarboxylic acid dialkyl ester or tetracarboxylic acid dialkyl ester dihalide) can be used.

The tetracarboxylic acid component of the (ii) polyamic acid ester or (iii) polyimide used for producing the polymer (a) is preferably composed of an aromatic tetracarboxylic acid dianhydride, an alicyclic tetracarboxylic acid dianhydride, or an aliphatic tetracarboxylic acid dianhydride, or a derivative thereof. Examples of the aromatic tetracarboxylic dianhydride include the aromatic tetracarboxylic dianhydrides described above, and examples of the alicyclic tetracarboxylic dianhydride or the aliphatic tetracarboxylic dianhydride include the alicyclic tetracarboxylic dianhydride or the aliphatic tetracarboxylic dianhydride in the polymer (C). Preferred specific examples of the (ii) polyamic acid ester or (iii) aromatic tetracarboxylic dianhydride used for producing the polymer (A) include the compounds represented by the above formula (3 a-1), and preferred specific examples of the alicyclic tetracarboxylic dianhydride or aliphatic tetracarboxylic dianhydride include the compounds represented by the following formula (3 c-1).

The tetracarboxylic acid component used for producing the polymer (a) of the present invention may be used alone or in combination of two or more depending on the solubility of the polymer (a) in a solvent, the coatability of a liquid crystal aligning agent, the liquid crystal alignment properties in the case of forming a liquid crystal alignment film, the voltage holding ratio, the accumulated charge, and other properties.

< Polymer (B) >

The polymer (B) contained in the liquid crystal aligning agent of the present invention is the following polymer.

H₂N-X-NH₂ [3]

The "aromatic ring group" refers to an n-valent group obtained by removing n hydrogen atoms from an aromatic ring, and specific examples of the aromatic ring include: benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, pyrene ring, perylene ring, and terylene ring, etc. Specific examples of the nitrogen-containing aromatic heterocyclic ring having a five-membered ring or a six-membered ring include: pyrrole rings, pyridine rings, and the like. Specific examples of the aromatic hydrocarbon ring include: benzene rings, naphthalene rings, and the like.

The diamine represented by the formula [3] preferably has a structure represented by the following formulae [ 3-1 ] to [ 3-3 ].

(wherein in the formula [ 3-3 ], at least one bond derived from a carbon atom constituting a nitrogen-containing aromatic heterocycle is bonded to an aromatic hydrocarbon ring.)

Examples of the diamine represented by the formula [3] include the following diamines.

The amount of the diamine represented by the formula [3] is 30 to 100 mol%, more preferably 40 to 100 mol%, and still more preferably 50 to 100 mol% based on the total amount of the diamine component used in the polymer (B).

As the diamine component used for producing the polymer (B) contained in the liquid crystal aligning agent of the present invention, any diamine other than the diamine represented by the formula [3], for example, the other diamines can be used.

The diamine component used for producing the polymer (B) of the present invention may be used alone or in combination of two or more depending on the solubility of the polymer (B) in a solvent, the coatability of a liquid crystal aligning agent, the liquid crystal alignment properties when a liquid crystal alignment film is formed, the voltage holding ratio, the accumulated charge, and other properties.

As the tetracarboxylic acid component used for producing the polymer (B) contained in the liquid crystal aligning agent of the present invention, any tetracarboxylic dianhydride or a derivative thereof can be used. More preferable specific examples of the tetracarboxylic dianhydride used for producing the polymer (B) include: an aromatic tetracarboxylic dianhydride, an alicyclic tetracarboxylic dianhydride or an aliphatic tetracarboxylic dianhydride for producing the polymer (A). As a preferred specific example of the aromatic tetracarboxylic dianhydride, a compound represented by the above formula (3 a-1) is mentioned, and as a preferred specific example of the alicyclic tetracarboxylic dianhydride or the aliphatic tetracarboxylic dianhydride, a compound represented by the following formula (3 c-1) is mentioned.

The tetracarboxylic acid component used for producing the polymer (B) of the present invention may be used alone or in combination of two or more depending on the solubility of the polymer (B) in a solvent, the coatability of a liquid crystal aligning agent, the liquid crystal alignment properties in the case of forming a liquid crystal alignment film, the voltage holding ratio, the accumulated charge, and other properties.

< Polymer (C) >

The polymer (C) contained in the liquid crystal aligning agent of the present invention is the following polymer.

The diamine component used for producing the polymer (C) does not contain a diamine represented by the formula [3 ].

Examples of the diamine component used for producing the polymer (C) include diamines represented by the following formula [4 ].

H₂N-Y-NH₂ [4]

(wherein Y has one or more structures represented by the following formulae,

is a bonding bond. )

As a more preferable specific example of Y, a divalent organic group having at least one of the partial structures shown above and having at least one benzene ring is preferable. More preferable specific examples of the diamine represented by the above formula [4] include diamines represented by the following formulae (4-1) to (4-2).

(in the formula, A)₁A hydroxyl group, a carboxyl group, a fluorine atom, or an alkyl or alkoxy group having 1 to 5 carbon atoms (wherein any hydrogen atom of the alkyl or alkoxy group is optionally substituted by a fluorine atom), A₁At least one of them represents a hydroxyl group or a carboxyl group. A. the₂A divalent organic group in which a part of the alkylene group having 1 to 20 carbon atoms is substituted with a urea bond or an amide bond, or-CH in the divalent organic group₂A group in which a part or all of the group-A-B-is substituted with at least one group selected from the group consisting of an ether bond, an ester bond, a cyclohexylidene group and a phenylene group. a1 is an integer of 1-4. a21 and a22 are 0 ℃ to4, or a pharmaceutically acceptable salt thereof. When a1, a21 or a22 is an integer of 2 or more, A₁May be the same or different. In A₂When the group represents a single bond or an alkylene group having 1 to 20 carbon atoms, either a21 or a22 is an integer other than 0. b and c are each independently an integer of 1 to 2. )

The diamine represented by the formula [4] is preferably a diamine represented by the following formula, and particularly preferably 1, 3-bis (4-aminophenylethyl) urea represented by the following formula.

The diamine component used for producing the polymer (C) of the present invention may be used singly or in combination of two or more depending on the solubility of the polymer (C) in a solvent, the coatability of a liquid crystal aligning agent, the liquid crystal alignment properties in the case of forming a liquid crystal alignment film, the voltage holding ratio, the accumulated charge, and other properties. As the diamine component used for producing the polymer (C), the diamine represented by the above formula [3] or any diamine other than the diamine represented by the above formula [4], for example, the other diamines can be used.

The tetracarboxylic acid component used for producing the polymer (C) is composed of an alicyclic tetracarboxylic dianhydride and/or an aliphatic tetracarboxylic dianhydride.

Here, the aliphatic tetracarboxylic dianhydride is an acid dianhydride obtained by intramolecular dehydration of four carboxyl groups bonded to a chain hydrocarbon structure. Among them, it is not necessary to constitute only a chain hydrocarbon structure, and a part thereof may have an alicyclic structure or an aromatic ring structure.

The alicyclic tetracarboxylic dianhydride is an acid dianhydride obtained by intramolecular dehydration of four carboxyl groups including at least one carboxyl group bonded to an alicyclic structure. Wherein none of the four carboxyl groups are bonded to an aromatic ring. Further, the alicyclic structure need not be solely formed, and a part thereof may have a chain hydrocarbon structure or an aromatic ring structure.

Examples of the aliphatic tetracarboxylic dianhydride or alicyclic tetracarboxylic dianhydride include compounds represented by the following formula (3 c-1).

In the above formula, X₂Is any of the following formulae (B-1) to (B-18). Denotes a bond.

The tetracarboxylic acid component used for producing the polymer (C) of the present invention may be used alone or in combination of two or more depending on the solubility of the polymer (C) in a solvent, the coatability of a liquid crystal aligning agent, the liquid crystal alignment properties in the case of a liquid crystal alignment film, the voltage holding ratio, the accumulated charge, and other properties.

< method for producing polymers (A) to (C) >

The polyimide precursor that can be contained in the liquid crystal aligning agent of the present invention is polyamic acid or polyamic acid ester.

The reaction of the diamine component with the tetracarboxylic acid component is usually carried out in a solvent. The solvent used in this case is not particularly limited as long as the polyimide precursor formed by dissolution is dissolved. Specific examples of the solvent used in the reaction are listed below, but the solvent is not limited to these examples.

For example, there may be mentioned: n-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ -butyrolactone, N-dimethylformamide, N-dimethylacetamide, 3-methoxy-N, N-dimethylpropane amide, 3-butoxy-N, N-dimethylpropane amide, dimethyl sulfoxide or 1, 3-dimethyl-imidazolidinone. When the polyimide precursor has high solubility in a solvent, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, and the like can be used.

These solvents may be used alone or in combination. Further, even if the solvent is a solvent that does not dissolve the polyimide precursor, the solvent may be used in a mixture within a range in which the produced polyimide precursor is not precipitated. Further, since moisture in the solvent inhibits the polymerization reaction and causes hydrolysis of the polyimide precursor to be produced, it is preferable to use a dehydrated and dried solvent as the solvent.

When the diamine component and the tetracarboxylic acid component are reacted in a solvent, the following methods may be mentioned: a method of adding the tetracarboxylic acid component directly or by dispersing or dissolving the tetracarboxylic acid component in a solvent by stirring a solution obtained by dispersing or dissolving the diamine component in the solvent; conversely, a method of adding a diamine component to a solution in which a tetracarboxylic acid component is dispersed or dissolved in a solvent; a method of alternately adding a diamine component and a tetracarboxylic acid component to the reaction system, and any of these methods can be used. In addition, in the case of using a plurality of diamine components or tetracarboxylic acid components and reacting them, they may be reacted in a state of being mixed in advance, or may be reacted in sequence individually, or may be reacted by mixing low molecular weight substances obtained by reacting individually to produce a polymer.

The temperature for polycondensation of the diamine component and the tetracarboxylic acid component can be selected from any of-20 to 150 ℃, and preferably from-5 to 100 ℃. The reaction may be carried out at any concentration, but if the concentration is too low, it becomes difficult to obtain a polymer having a high molecular weight, and if the concentration is too high, the viscosity of the reaction solution becomes too high, and uniform stirring becomes difficult. Therefore, the concentration of the polymer is preferably 1 to 50% by mass, more preferably 5 to 30% by mass. The reaction is carried out at a high concentration in the initial stage, and then a solvent may be added.

In the polymerization reaction for obtaining the polyimide precursor, the ratio of the total mole number of the tetracarboxylic acid component to the total mole number of the diamine component is preferably 0.8 to 1.2. Similarly to the ordinary polycondensation reaction, the molecular weight of the polyimide precursor to be produced is increased as the molar ratio is closer to 1.0.

The polyimide is obtained by ring-closing a polyimide precursor. In this polyimide, the ring-closure ratio (also referred to as imidization ratio) of the amic acid (amic acid) group (amic acid) does not need to be 100%, and can be arbitrarily adjusted depending on the application and purpose.

Examples of the method for imidizing the polyimide precursor include: thermal imidization in which a solution of a polyimide precursor is directly heated, or imidization in which a catalyst is added to a solution of a polyimide precursor.

The temperature for thermal imidization of the polyimide precursor in the solution is preferably 100 to 400 ℃, more preferably 120 to 250 ℃, and a method of performing imidization while removing water generated by imidization reaction from the system is preferable. The catalyst imidization of the polyimide precursor can be carried out by: a basic catalyst and an acid anhydride are added to a solution of a polyimide precursor, and the mixture is stirred at-20 to 250 ℃, preferably at 0 to 180 ℃.

The amount of the basic catalyst is preferably 0.5 to 30 times, more preferably 2 to 20 times, the amount of the acid anhydride is preferably 1 to 50 times, more preferably 3 to 30 times, the amount of the acid amide group.

Examples of the basic catalyst include: pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine, and the like. Among them, pyridine is preferable because it has a moderate basicity for proceeding the reaction.

Examples of the acid anhydride include: acetic anhydride, trimellitic anhydride, pyromellitic anhydride (pyromellitic anhydride), and the like. In particular, the use of acetic anhydride is preferable because purification after completion of the reaction is easy. The imidization rate obtained by the imidization of the catalyst can be controlled by adjusting the amount of the catalyst, the reaction temperature, and the reaction time.

When the polyimide precursor formed from the reaction solution or the polyimide obtained therefrom is recovered, the reaction solution may be put into a solvent to precipitate the polyimide. As the solvent for precipitation, there may be mentioned: methanol, ethanol, isopropanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, toluene, benzene, water, etc. The polymer precipitated by charging the solvent may be recovered by filtration, and then dried at normal temperature or under reduced pressure or by heating. Further, the operation of dissolving the polymer recovered by precipitation in the solvent again and recovering the polymer by reprecipitation is repeated 2 to 10 times, whereby impurities in the polymer can be reduced. Examples of the solvent in this case include: alcohols, ketones, hydrocarbons, and the like. It is preferable to use three or more solvents selected from them because the purification efficiency is further improved.

In the present invention, when the polyimide precursor is a polyamic acid ester, specific examples of the method for producing the polyimide precursor include the methods described in paragraphs to of international publication No. WO 2011-115077.

The polyimide precursor or the polyimide obtained therefrom may also be modified at its ends by an end modifier. By modifying the terminal, the effect of improving the adhesion between the sealant and the liquid crystal alignment film can be obtained.

Examples of the terminal modifier include t-butyloxycarbonylating agents, and examples thereof include: n-t-butoxycarbonylimidazole, t-butyl-phenyl carbonate, t-butyl carbazate, t-butyl chloroformate, di-t-butyl dicarbonate, and the like. The terminal modifier is preferably di-tert-butyl dicarbonate.

< liquid Crystal Aligning agent >

An embodiment of the present invention is a liquid crystal aligning agent comprising a polymer (A), a polymer (B) and a polymer (C).

The content of the polymer (a) in the liquid crystal aligning agent is preferably 10 to 50% by mass, and more preferably 10 to 30% by mass, based on 100% by mass of the total amount of the polymers (a) to (C), from the viewpoint of alignment regulating power of liquid crystal.

From the viewpoint of the relaxation property of the accumulated charge, the content of the polymer (B) in the liquid crystal aligning agent is preferably 10 to 70% by mass, more preferably 40 to 60% by mass, based on 100% by mass of the total amount of the polymers (a) to (C).

The content of the polymer (C) in the liquid crystal aligning agent is preferably 10 to 50% by mass, and more preferably 10 to 30% by mass, based on 100% by mass of the total amount of the polymers (a) to (C), from the viewpoint of the amount of charge accumulated in the DC.

The liquid crystal aligning agent of the present invention may contain other polymers than the polymers (a) to (C). Examples of other polymers include: cellulosic polymers, acrylic polymers, methacrylic polymers, polystyrene, polyamides, silicones, and the like. The content of the other polymer other than the above is preferably 0.5 to 15 parts by mass, more preferably 1 to 10 parts by mass, based on 100 parts by mass of the total of the polymers (A) to (C).

The liquid crystal aligning agent usually contains an organic solvent, and the content of the organic solvent is preferably 70 to 99.9 mass% relative to the liquid crystal aligning agent. The content may be appropriately changed depending on the method of applying the liquid crystal aligning agent and the target film thickness of the liquid crystal alignment film.

The organic solvent used for the liquid crystal aligning agent is preferably a solvent (also referred to as a good solvent) for dissolving the polymers (a) to (C). For example, there may be mentioned: n, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ -butyrolactone, 1, 3-dimethyl-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, 3-methoxy-N, N-dimethylpropane amide, 3-butoxy-N, N-dimethylpropane amide, and the like. Among them, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 3-methoxy-N, N-dimethylpropane amide, 3-butoxy-N, N-dimethylpropane amide or γ -butyrolactone is preferably used.

The preferable solvent in the liquid crystal aligning agent of the present invention is preferably 20 to 99% by mass, more preferably 20 to 90% by mass, and particularly preferably 30 to 80% by mass of the entire solvent contained in the liquid crystal aligning agent.

The liquid crystal aligning agent of the present invention may be a solvent (also referred to as a poor solvent) that improves the film coatability and surface smoothness of the liquid crystal alignment film when the liquid crystal aligning agent is applied. Specific examples thereof are listed below.

For example, there may be mentioned: diisopropyl ether, diisobutyl methanol (2, 6-dimethyl-4-heptanol), ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, 1, 2-butoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, 4-hydroxy-4-methyl-2-pentanone, diethylene glycol methyl ethyl ether, diethylene glycol dibutyl ether, 3-ethoxybutyl acetate, 1-methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene glycol monoacetate, ethylene glycol diacetate, propylene carbonate, ethylene glycol monobutyl ether, ethylene glycol monoisoamyl ether, ethylene glycol monohexyl ether, propylene glycol monobutyl ether, 1- (2-butoxyethoxy) -2-propanol, 2- (2-butoxyethoxy) -1-propanol, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether, dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, 1, 2-ethylbutyl ether, 2-ethylbutyl acetate, ethylene glycol monohexyl ether, propylene glycol isoamyl ether, propylene glycol monohexyl ether, propylene glycol mono, Dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monobutyl ether acetate, ethylene glycol monoacetate, ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, ethyl 2- (2-ethoxyethoxy) acetate, diethylene glycol acetate, propylene glycol diacetate, n-butyl acetate, propylene glycol monoethyl ether acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, propyl 3-methoxypropionate, butyl 3-methoxypropionate, n-butyl lactate, isoamyl lactate, diethylene glycol monoethyl ether, diisobutyl ketone (2, 6-dimethyl-4-heptanone), and the like.

Among them, preferable combinations of solvents include: n-methyl-2-pyrrolidone with ethylene glycol monobutyl ether; n-methyl-2-pyrrolidone, gamma-butyrolactone, and ethylene glycol monobutyl ether; n-methyl-2-pyrrolidone, gamma-butyrolactone and propylene glycol monobutyl ether; n-ethyl-2-pyrrolidone with propylene glycol monobutyl ether; n-methyl-2-pyrrolidone, γ -butyrolactone, 4-hydroxy-4-methyl-2-pentanone, and diethylene glycol diethyl ether; n-methyl-2-pyrrolidone, gamma-butyrolactone, propylene glycol monobutyl ether, and 2, 6-dimethyl-4-heptanone; n-methyl-2-pyrrolidone, gamma-butyrolactone, propylene glycol monobutyl ether, and diisopropyl ether; n-methyl-2-pyrrolidone, gamma-butyrolactone, propylene glycol monobutyl ether, and 2, 6-dimethyl-4-heptanol; n-methyl-2-pyrrolidone, gamma-butyrolactone and dipropylene glycol dimethyl ether; and the like. The poor solvent is preferably 1 to 80% by mass, more preferably 10 to 80% by mass, and particularly preferably 20 to 70% by mass of the entire solvent contained in the liquid crystal aligning agent. The kind and content of such a solvent can be appropriately selected depending on the coating apparatus, coating conditions, coating environment, and the like of the liquid crystal aligning agent.

The liquid crystal aligning agent of the present invention may contain: a dielectric material for changing electrical characteristics such as dielectric constant and conductivity of the liquid crystal alignment film; a silane coupling agent for the purpose of improving the adhesion between the liquid crystal alignment film and the substrate; a crosslinkable compound for the purpose of improving the hardness and density of the film when the liquid crystal alignment film is produced; and an imidization accelerator for efficiently performing imidization by heating a polyimide precursor when a coating film is fired.

Examples of the compound for improving the adhesion between the liquid crystal alignment film and the substrate include: examples of the functional silane-containing compound and the epoxy-containing compound include: 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropyltriethylenetriamine, N-trimethoxysilylpropyltriethylenetriamine, N-glycidoxypropyltriethylenetriamine, N-glycidoxypropyltriethoxysilane, N-glycidoxypropyltrimethoxysilane, N-triethoxysilane, N-glycidoxypropyltrimethoxysilane, N-methoxysilane, N-triethoxysilane, N-methoxysilane, N-2-hydroxysilane, N-type-2, N-hydroxysilane, N-1-hydroxysilane, and a, 10-trimethoxysilyl-1, 4, 7-triazodecane, 10-triethoxysilyl-1, 4, 7-triazodecane, 9-trimethoxysilyl-3, 6-diaza-nonyl acetate, 9-triethoxysilyl-3, 6-diaza-nonyl acetate, N-benzyl-3-aminopropyltrimethoxysilane, N-benzyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, N-bis (oxyethylene) -3-aminopropyltrimethoxysilane, N-bis (oxyethylene) -3-aminopropyltriethoxysilane, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, Neopentyl glycol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, glycerol diglycidyl ether, 2-dibromoneopentyl glycol diglycidyl ether, 1, 3, 5, 6-tetraglycidyl-2, 4-hexanediol, N ', -tetraglycidyl m-xylylenediamine, 1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane, or N, N ', -tetraglycidyl-4, 4 ' -diaminodiphenylmethane, and the like.

In addition, the following additives (CL-1) to (CL-15) may be added to the liquid crystal aligning agent of the present invention in order to improve the mechanical strength of the liquid crystal alignment film.

The content of the additive is preferably 0.1 to 30 parts by mass per 100 parts by mass of the polymer component contained in the liquid crystal aligning agent. More preferably 0.5 to 20 parts by mass.

< method for producing liquid crystal alignment film >

The liquid crystal alignment film is obtained by coating the liquid crystal alignment agent on a substrate to form a coating film, preferably drying the coating film, and then baking the coating film. As the substrate, a substrate having high transparency is preferable, and as the material thereof, ceramics such as glass and silicon nitride; and plastics such as acrylic and polycarbonate. As the substrate, a substrate formed with an ITO (Indium Tin Oxide) electrode or the like for driving a liquid crystal is preferably used in view of simplification of the process. In the reflective liquid crystal display element, an opaque substrate such as a silicon wafer may be used as a single-sided substrate, and a material that reflects light such as aluminum may be used as an electrode.

The method of forming a coating film on a substrate with a liquid crystal aligning agent may be industrially used, for example, screen printing, offset printing, flexographic printing, and inkjet printing, and may also be used, depending on the purpose, immersion, roll coating, slit coating, spin coating, and spray coating.

After the coating of the liquid crystal aligning agent is formed on the substrate, the coating is preferably dried by a heating means such as a hot plate, a thermal cycle oven, or an IR (infrared ray) oven, preferably at 30 to 120 ℃, more preferably at 50 to 120 ℃, for preferably 1 to 10 minutes, and more preferably for 1 to 5 minutes, to evaporate the solvent.

When the imide precursor in the polymer is thermally imidized, the coating film obtained from the liquid crystal aligning agent is then subjected to a firing treatment by the same heating means as the above-mentioned drying treatment, preferably at 120 to 250 ℃, more preferably at 150 to 230 ℃. The time of the firing treatment varies depending on the firing temperature, and is preferably 5 minutes to 1 hour, and more preferably 5 minutes to 40 minutes.

The thickness of the film after the baking treatment is not particularly limited, but if it is too thin, the reliability of the liquid crystal display element may be lowered, and if it is too thick, the resistance of the obtained liquid crystal alignment film may be increased, and therefore, it is preferably 5 to 300nm, and more preferably 10 to 200 nm.

After the above firing treatment, the obtained coating film is subjected to an alignment treatment. Examples of the orientation treatment include: brushing treatment, photo-alignment treatment, and the like.

As a specific example of the photo-alignment treatment, the surface of the coating film is irradiated with radiation deflected in a certain direction. As the radiation, ultraviolet rays or visible rays having a wavelength of 100 to 800nm can be used. Among them, ultraviolet rays having a wavelength of 100 to 400nm are preferable, and ultraviolet rays having a wavelength of 200 to 400nm are more preferable. In order to improve the liquid crystal alignment properties, the substrate coated with the liquid crystal alignment film may be irradiated with ultraviolet rays while being heated at 50 to 250 ℃. The irradiation amount of the radiation is preferably 1 to 10000mJ/cm 2. Among them, it is preferably 100 to 5000mJ/cm 2. The liquid crystal alignment film thus produced can stably align liquid crystal molecules in a certain direction.

The higher the extinction ratio of the polarized ultraviolet ray, the higher the anisotropy can be imparted, and therefore, the higher the extinction ratio is preferable. Specifically, the extinction ratio of ultraviolet rays polarized in a straight line is preferably 10: 1 or more, and more preferably 20: 1 or more.

The film subjected to the alignment treatment may be further subjected to at least one treatment selected from the group consisting of a heating treatment and a contact treatment with a solvent.

The heat treatment after the orientation treatment may be performed by the same heating means as the above-mentioned drying treatment and firing treatment, and is preferably performed at 180 to 250 ℃, and more preferably at 180 to 230 ℃. When the temperature of the heat treatment is in the above range, the contrast of the liquid crystal display element obtained from the liquid crystal alignment film obtained can be improved.

The time of the heat treatment varies depending on the heating temperature, but is preferably 5 minutes to 1 hour, and more preferably 5 to 40 minutes.

The solvent used for the contact treatment with the solvent is not particularly limited as long as it dissolves impurities and the like adhering to the liquid crystal alignment film.

Specific examples thereof include: water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, methyl lactate, diacetone alcohol, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate, cyclohexyl acetate, and the like. Among them, water, 2-propanol, 1-methoxy-2-propanol, or ethyl lactate is preferable from the viewpoint of versatility and safety of the solvent. More preferably water, 1-methoxy-2-propanol or ethyl lactate. One or two or more of these solvents may be used.

Examples of the contact treatment include: dipping treatment, and spraying treatment (also referred to as spray treatment). The treatment time in these treatments is preferably 10 seconds to 1 hour, and particularly, the immersion treatment may be performed for 1 to 30 minutes. The temperature during the contact treatment may be normal temperature or heating, and is preferably 10 to 80 ℃ and 20 to 50 ℃ may be mentioned. In the contact treatment, ultrasonic treatment or the like may be performed as necessary.

After the contact treatment, washing (also referred to as rinsing) with a low boiling point solvent such as water, methanol, ethanol, 2-propanol, acetone, or methyl ethyl ketone, and drying may be performed. In this case, either rinsing or drying may be performed, or both may be performed. The drying temperature is preferably 50 to 150 ℃, and 80 to 120 ℃ can be mentioned. The drying time is preferably 10 seconds to 30 minutes, and preferably 1 to 10 minutes.

After the contact treatment with the solvent, the heat treatment after the alignment treatment may be performed. By adopting such a constitution, a liquid crystal alignment film having excellent liquid crystal alignment properties can be obtained.

< liquid crystal display element >

The liquid crystal Alignment film of the present invention can be applied to various driving modes such as a TN (Twisted Nematic) mode, an STN (Super Twisted Nematic) mode, an IPS (In-Plane Switching) mode, an FFS (Fringe Field Switching) mode, a VA (Vertical Alignment) mode, an MVA (Multi-domain Vertical Alignment) mode, and a PSA (Polymer stabilized Alignment) mode, and is preferably used as a liquid crystal Alignment film of a liquid crystal display device of a transverse electric Field system such as an IPS mode and an FFS mode, and is particularly useful as a liquid crystal display device of an FFS mode. The liquid crystal display element of the present invention is an element produced by obtaining a substrate with a liquid crystal alignment film from the liquid crystal alignment agent, then producing a liquid crystal cell by a known method, and using the liquid crystal cell.

As an example of a method for manufacturing a liquid crystal cell, a liquid crystal display element having a passive matrix structure will be described. Note that each pixel portion constituting image display may be a liquid crystal display element having an active matrix (active matrix) structure in which a conversion element such as a TFT (Thin Film Transistor) is provided.

Specifically, a transparent glass substrate is prepared, a common electrode is provided on one substrate, and a segment electrode is provided on the other substrate. These electrodes may be, for example, ITO electrodes, and may be patterned so as to display a desired image. Next, an insulating film is provided on each substrate so as to cover the common electrode and the segment electrode. The insulating film may be formed of, for example, SiO formed by a sol-gel method₂－TiO₂And (3) a film of the composition. Next, under the above conditions, liquid crystal alignment films were formed on the respective substrates, one substrate and the other substrate were stacked so that the liquid crystal alignment films faced each other, and the peripheries thereof were bonded with a sealant. In the sealant, it is generally preferable to mix a spacer in order to control the substrate gap. Further, it is preferable that spacers for controlling the substrate gap are scattered also in the surface portion where the sealing agent is not provided. In a part of the sealant, an opening portion capable of being filled with liquid crystal from the outside is provided in advance.

Then, a liquid crystal material is injected into a space surrounded by the two substrates and the sealant through an opening provided in the sealant. Next, the opening is sealed with an adhesive. For the injection, there may be mentioned: the vacuum infusion method, a method utilizing the capillary phenomenon in the atmosphere, or an ODF (One Drop Fill: liquid crystal Drop) method may be used. As the liquid crystal material, either positive or negative dielectric anisotropy may be used. In the present invention, from the viewpoint of liquid crystal alignment properties, one having negative dielectric anisotropy is preferable, and can be used depending on the application.

After a liquid crystal material is injected into a liquid crystal cell (cell), a polarizing plate is disposed. Specifically, a pair of polarizing plates is preferably attached to the surfaces of the two substrates opposite to the liquid crystal layer.

[ examples ]

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited thereto. The following abbreviations for the compounds and the methods for measuring the respective properties are as follows.

(diamine)

(tetracarboxylic dianhydride)

(end-modifying agent)

Di-tert-butyl dicarbonate (Boc 2O).

(additives)

(s-1): 3-glycidoxypropyltriethoxysilane.

(organic solvent)

NMP: n-methyl-2-pyrrolidone.

GBL: gamma-butyrolactone.

BCS: butyl cellosolve.

< measurement of imidization Rate >

To an NMR sample tube (. phi.5 (manufactured by Softweed scientific Co.)) was added 20mg of polyimide powder, and to this tube was added 0.53ml of deuterated dimethyl sulfoxide (DMSO-d 6, 0.05% TMS (tetramethylsilane) mixture), followed by completely dissolving the mixture with ultrasonic waves. The proton NMR of the solution at 500MHz was measured by an NMR spectrometer (JNW-ECA 500) (manufactured by electronic DATUM, Japan). The imidization ratio was determined as follows: the proton derived from a structure which does not change before and after imidization was defined as a reference proton, and the proton peak integral value was obtained by the following formula using the peak integral value of the proton and the peak integral value of the proton derived from the NH group of amic acid appearing in the vicinity of 9.5ppm to 10.0 ppm.

Imidization ratio (%) - (1-. alpha.x/y). times.100

In the above formula, x is a peak integral value of a proton derived from an NH group of amic acid, y is a peak integral value of a reference proton, and α is a ratio of the number of reference protons to the number of protons of one NH group of amic acid in the case of polyamic acid (imidization ratio of 0%).

[ Synthesis of Polymer ]

< Synthesis example 1 >

10.3g (42.5mmol) of DA-1, 7.8g (14.0mmol) of DA-3, and 4.78g (14.0mmol) of DA-4 were weighed into a four-necked flask equipped with a stirrer and a nitrogen inlet tube, NMP was added so that the solid content concentration became 15 mass%, and the mixture was dissolved with stirring while feeding nitrogen. While the diamine solution was stirred, 10.2g (45.5mmol) of CA-1 was added, and NMP was further added so that the solid content concentration became 18 mass%. After stirring at 40 ℃ for 1 hour, 3.57g (18.2mmol) of CA-2 was added at room temperature, and NMP was further added so that the solid content concentration became 18 mass%. The polymerization solution was stirred for 3 hours to obtain a polyamic acid solution (PA-I).

100.0g of the obtained polyamic acid solution (PA-I) was weighed into a 100mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 4.06g (18.6mmol) of di-tert-butyl dicarbonate (Boc2O) as a terminal modifier was added, and the mixture was stirred at 40 ℃ for 15 hours to obtain a terminal-modified polyamic acid solution (PAboc-I).

100.0g of the obtained terminal-modified polyamic acid solution (PAboc-I) was weighed into a 100mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, NMP was added so that the solid content concentration became 12 mass%, and the mixture was stirred for 30 minutes. To the obtained polyamic acid solution were added 10.54g of acetic anhydride and 2.72g of pyridine, and the mixture was stirred at room temperature for 30 minutes, and then heated and stirred at 55 ℃ for 2 hours and 15 minutes to perform chemical imidization. The obtained reaction solution was poured into methanol in an amount of 3.5 times the mass of the reaction solution while stirring, and the precipitated precipitate was filtered, followed by washing 3 times with methanol. The obtained resin powder was vacuum-dried at 80 ℃ for 12 hours, whereby a powder of polyimide (SPI 1-1) was obtained. The imidization ratio of the polyimide resin powder was 75%. NMP was added to the obtained polyimide (SPI 1-1) so that the solid content concentration became 15 mass%, and the mixture was stirred at 70 ℃ for 15 hours to obtain a polyimide (SPI 1-1) solution having a solid content concentration of 15 mass%.

< Synthesis examples 2 to 6 >

By using the diamines and tetracarboxylic acid derivatives shown in Table 1 below, solutions of the polyimides (SPI 1-1) to (SPI 1-6) shown in Table 1 below were obtained in the same order as in Synthesis example 1. In table 1, the numerical values indicated below the compound names indicate the mass (g) of the tetracarboxylic acid derivative used for the synthesis for the tetracarboxylic acid component, and the mass (g) of the diamine used for the synthesis for the diamine acid component. The terminal modification treatment was performed in the same manner as in synthesis example 1 in the case of Boc2O, and the end modification treatment was not performed in the case of nothing.

[ Table 1]

< Synthesis examples 7 to 28 >

By using the diamines and tetracarboxylic acid derivatives shown in Table 2 below, solutions of polyamic acids (PAA 2-1 to PAA 2-15, PAA 3-1 to PAA 3-7) shown in Table 1 below were obtained in the same procedure as in Synthesis example 1. In table 2, the numerical values indicated below the compound names indicate the mass (g) of the tetracarboxylic acid derivative used for the synthesis for the tetracarboxylic acid component, and the mass (g) of the diamine used for the synthesis for the diamine acid component.

[ Table 2]

[ preparation of liquid Crystal Aligning agent ]

< example 1 >

The solution of polyimide (SPI 1-1) obtained in synthesis example 1, the polyamic acid solution (PAA 2-1) obtained in synthesis example 7, and the polyamic acid solution (PAA 3-3) obtained in synthesis example 24 were diluted with NMP, GBL, and BCS, and the additive (c-1) was added in an amount of 3 parts by mass per 100 parts by mass of all the polymers, and the additive (s-1) was further added in an amount of 1 part by mass per 100 parts by mass of all the polymers, and stirred at room temperature. Subsequently, the obtained solution was filtered through a filter having a pore size of 0.5 μm, thereby obtaining a liquid crystal aligning agent (1) having a polymer component ratio of (SPI 1-1): (PAA 2-1): (PAA 3-3) of 30: 40: 30 (solid content conversion mass ratio), a solvent composition ratio of NMP: GBL: BCS of 30: 35.5: 30 (mass ratio), and a polymer solid content concentration of 4.5 mass% (table 3 below). The liquid crystal aligning agent was not observed in abnormalities such as clouding and precipitation, and was confirmed to be a uniform solution.

< examples 2 to 33, comparative examples 1 to 7 >

Liquid crystal alignment agents (2) to (33) and (R1) to (R7) were obtained in the same manner as in example 1, except that the polymers shown in table 3 below were used.

[ Table 3]

[ production of liquid Crystal display element ]

A liquid crystal cell having a configuration of a Fringe Field Switching (FFS) mode liquid crystal display element was manufactured.

First, a substrate with electrodes is prepared. The substrate was a glass substrate having a size of 35mm × 40mm and a thickness of 0.7 mm. An ITO electrode having a dense pattern constituting a counter electrode is formed as a first layer on a substrate. On the counter electrode of the first layer, a SiN (silicon nitride) film formed by a CVD method is formed as a second layer. The SiN film of the second layer has a film thickness of 500nm and functions as an interlayer insulating film. On the SiN film of the second layer, a comb-shaped pixel electrode formed by patterning an ITO film is disposed as a third layer, and two kinds of pixels, i.e., a first pixel and a second pixel, are formed. The size of each pixel is 10mm in length and about 5mm in width. At this time, the counter electrode of the first layer and the pixel electrode of the third layer are electrically insulated by the SiN film of the second layer.

The pixel electrode of the third layer has a comb-tooth shape in which a plurality of "<" -shaped electrode elements each having a central portion bent are arranged. The width of each electrode element in the short dimension direction was 3 μm, and the interval between the electrode elements was 6 μm. Since the pixel electrode forming each pixel is configured by an electrode element of a "<" symbol shape in which a plurality of central portions are bent, the shape of each pixel is not rectangular, but has a shape similar to a bold "< symbol" in which the pixel electrode is bent at the central portion like the electrode element. Each pixel is divided vertically at a central bent portion into a boundary, and has a first region above the bent portion and a second region below the bent portion.

The first region and the second region of each pixel are compared, and the formation directions of the electrode elements constituting the pixel electrodes are different. That is, when the brushing direction of the liquid crystal alignment film described later is used as a reference, the electrode element of the pixel electrode is formed so as to be at an angle of +10 ° (clockwise) in the first region of the pixel, and the electrode element of the pixel electrode is formed so as to be at an angle of-10 ° (clockwise) in the second region of the pixel. That is, in the first region and the second region of each pixel, the directions of the in-plane switching (in-plane switching) of the liquid crystal in the substrate plane induced by the voltage application between the pixel electrode and the counter electrode are opposite to each other.

Next, by spin coating, a liquid crystal aligning agent was coated on the substrate with electrodes and a glass substrate having a height of 4 μm and a columnar spacer on the back surface of which an ITO film was formed, the liquid crystal aligning agent was filtered through a 1.0 μm filter, and the resultant was dried on a hot plate at 80 ℃ for 2 minutes. Then, the resulting film was baked in a hot air circulating oven at 230 ℃ for 30 minutes to obtain a substrate with a liquid crystal alignment film having a film thickness of 100 nm. The surface of the substrate with the liquid crystal alignment film was brushed with rayon cloth (YA-20R, manufactured by JICHUAN chemical Co., Ltd.), and then washed by ultrasonic wave irradiation in pure water for 1 minute (roll diameter: 120mm, roll rotation speed: 1000rpm, moving speed: 20mm/sec, pressing length: 0.4mm), and after water droplets were removed by air blowing, the substrate was dried at 80 ℃ for 15 minutes to obtain a substrate with a liquid crystal alignment film. The two substrates with liquid crystal alignment films obtained were used as a set, a sealant was printed so that a liquid crystal injection port remained on the substrates, and the other substrate was bonded so that the liquid crystal alignment films were opposed to each other and the rubbing directions were antiparallel to each other. Then, the sealant was cured to produce an empty cell having a cell gap of 4 μm. Liquid crystal MLC-3019 (manufactured by MERCK) was injected into the empty cell by a reduced pressure injection method, and the injection port was sealed, thereby obtaining an FFS type liquid crystal display element. Then, the resulting liquid crystal display element was heated at 120 ℃ for 1 hour and placed at 23 ℃ late for evaluation.

[ evaluation of DC accumulation amount ]

The FFS driving liquid crystal cell prepared as described above was placed between two polarizing plates arranged so that the polarization axes were orthogonal to each other, and LED backlights were irradiated from below the two polarizing plates in a state where the pixel electrodes and the counter electrodes were short-circuited to have the same potential, and the angle of the liquid crystal cell was adjusted so that the luminance of the light transmitted through the LED backlights measured on the two polarizing plates was minimized. This evaluation was performed under a temperature condition in which the temperature of the liquid crystal cell was 23 ℃.

Then, while applying an ac voltage having a frequency of 30Hz to the cell, a V-T curve (voltage-transmittance curve) was measured, and an ac voltage having a relative transmittance of 23% or 100% was calculated as a driving voltage. A30 minute square wave with a frequency of 1kHz and 20mV was applied to the cell at 23 ℃.

Then, an ac drive with a relative transmittance of 100% was applied for 45 minutes, and during this period, the amount of change from the start of measurement to 45 minutes after was calculated as the DC accumulation amount while measuring the minimum offset voltage value every 3 minutes.

The accumulated electric charges affect display as disorder or afterimage of the liquid crystal alignment, and the display quality level of the liquid crystal element is significantly lowered, so that it can be said that the smaller the DC accumulation amount generated during driving, the better. In the present invention, it is particularly preferable that the DC accumulation amount is 150mV or less.

[ relaxation characteristics of accumulated Charge ]

Then, while applying a rectangular wave having a frequency of 30Hz to the cell, the V-T characteristics (voltage-transmittance characteristics) at a temperature of 23 ℃ were measured, and an AC voltage at which the relative transmittance became 23% was calculated. Since the ac voltage corresponds to a region where the change in luminance with respect to voltage is large, it is appropriate to evaluate the accumulated charge through the luminance.

Subsequently, a rectangular wave having a frequency of 30Hz was applied for 5 minutes under an AC voltage having a relative transmittance of 23%, and then a DC voltage of +1.0V was applied thereto for 30 minutes. Then, the dc voltage was cut off, and a rectangular wave having a frequency of 30Hz was applied for 30 minutes under an ac voltage with a relative transmittance of 23% again.

Since the charge stored in the liquid crystal cell is stored more quickly when the dc voltage is applied, the relaxation characteristics of the stored charge are evaluated in a time period required until the relative transmittance immediately after the dc voltage is applied is reduced from a state of 30% or more to 23%. It can be said that the shorter the time, the better the relaxation property of the accumulated charge. Specifically, the time for which the relative transmittance was reduced to 30% or less was expressed as a numerical value from the time when the dc voltage was started to be applied until 30 minutes elapsed. The case where the relative transmittance was reduced to 30% or less within 10 minutes was evaluated as "very excellent", the case where the relative transmittance was reduced to 20% or less within 10 minutes was evaluated as "o", the case where the relative transmittance was reduced to 30% or less within 20 minutes was evaluated as "Δ", and the case where the relative transmittance was not reduced to 30% or less within 30 minutes was evaluated as "x".

[ evaluation of afterimage characteristics based on Long-term AC drive ]

The FFS driving liquid crystal cell thus produced was applied with an ac voltage of 60Hz ± 5V at a frequency of 120 hours in a constant temperature environment of 60 ℃. Then, the pixel electrode and the counter electrode of the liquid crystal cell were short-circuited, and the liquid crystal cell was left in this state at room temperature for one day.

In the liquid crystal cell subjected to the above-described processing, the deviation between the alignment direction of the liquid crystal in the first region and the alignment direction of the liquid crystal in the second region of the pixel in the voltage-non-applied state is calculated as an angle.

Specifically, a liquid crystal cell is provided between two polarizing plates arranged so that the polarization axes are orthogonal to each other, a backlight is turned on, the arrangement angle of the liquid crystal cell is adjusted so that the transmission light intensity in the first region of the pixel becomes minimum, and then the rotation angle required to rotate the liquid crystal cell so that the transmission light intensity in the second region of the pixel becomes minimum is obtained.

It can be said that the smaller the value of the rotation angle, the better the afterimage characteristics by the long-term ac drive. Specifically, the case where the rotation angle is 0.5 degrees or less is evaluated as "excellent", the case where the rotation angle exceeds 0.5 degrees and is 1.0 degrees or less is evaluated as "o", the case where the rotation angle exceeds 1.0 degrees and is 1.5 degrees or less is evaluated as "Δ", and the case where the rotation angle further exceeds 2.0 degrees is evaluated as "x".

[ evaluation of optical Properties (transparency) ]

A quartz substrate having a size of 40mm × 40mm and a thickness of 1.0mm was prepared. Next, the liquid crystal alignment agent was filtered with a 1.0 μm filter, and then spin-coated on the quartz substrate. Then, the film was dried on a hot plate at 80 ℃ for 2 minutes and fired at 230 ℃ for 20 minutes to obtain a polyimide film having a film thickness of 100nm on each substrate.

The transparency was evaluated by measuring the transmittance of the substrate obtained by the above method. Specifically, the transmittance of the sample was measured by using a UV-3600 (manufactured by Shimadzu corporation) measuring device under the conditions of a temperature of 25 ℃ and a scanning wavelength of 300 to 800 nm. At this time, the reference (reference example) used a quartz substrate which was not coated with any substance. For the evaluation, the average transmittance at a wavelength of 400 to 800nm was calculated, and the higher the transmittance, the more excellent the transparency.

The evaluation results of the DC storage amount, the relaxation characteristics of the stored charge, the afterimage characteristics by long-term ac drive, and the optical characteristics of the liquid crystal display elements using the liquid crystal aligning agents of examples 1 to 33 and comparative examples 1 to 7 are shown in table 4 below.

[ Table 4]

It is understood that the liquid crystal display element using the liquid crystal aligning agent of the embodiment of the present invention has a suppressed DC storage amount and has a high balance with other characteristics.

Industrial applicability

The liquid crystal aligning agent of the present invention is useful for forming a liquid crystal alignment film in a wide range of liquid crystal display devices such as IPS drive systems and FFS drive systems.

It should be noted that the entire contents of the specification, claims and abstract of japanese patent application No. 2019-014146 applied on 30/01/2019 and japanese patent application No. 2019-100642 applied on 29/05/2019 are incorporated herein by reference as disclosure of the specification of the present invention.

Claims

1. A liquid crystal aligning agent, comprising: the following polymers A, B and C,

polymer A: at least one polymer selected from the group consisting of (i) to (iii) below,

(i) a polyamic acid obtained by polymerizing a diamine component containing at least one diamine selected from the group consisting of a diamine represented by the following formula [1] and a diamine represented by the following formula [2] with a tetracarboxylic acid component composed of an aromatic tetracarboxylic dianhydride,

(ii) a polyamic acid ester obtained by polymerizing a tetracarboxylic acid component with a diamine component containing at least one diamine selected from the group consisting of a diamine represented by the following formula [1] and a diamine represented by the following formula [2],

(iii) a polyimide obtained by imidizing a polyimide precursor obtained by polymerizing a diamine component containing at least one diamine selected from the group consisting of a diamine represented by the following formula [1] and a diamine represented by the following formula [2] with a tetracarboxylic acid component,

formula [1]And [2]]In (A)₁Is a single bond, an ether bond, an ester bond, -C ═ C-, -C ≡ C-, or an alkylene group having 2 to 20 carbon atoms, or-CH in the alkylene group₂A group substituted with at least one group selected from the group consisting of an ether bond, an ester bond, -C ═ C-, -C ≡ C-, a cyclohexylene group and a phenylene group, and a₂Is a fluorine atom or an alkyl or alkoxy group having 1 to 5 carbon atoms, wherein any hydrogen atom of the alkyl or alkoxy group is optionally substituted by a fluorine atom, a is an integer of 0 to 4, and when a is an integer of 2 or more, A is a₂B and c are each independently an integer of 1 to 2,

polymer B: at least one polymer selected from the group consisting of a polyimide precursor obtained by polymerizing a diamine component and a tetracarboxylic acid component, and a polyimide obtained from the polyimide precursor, wherein the diamine component contains a diamine represented by the following formula [3],

H₂N-X-NH₂ [3]

wherein X has a structure in which an aromatic hydrocarbon ring is bonded to a carbon atom of a nitrogen-containing aromatic heterocycle constituting a five-membered ring or a six-membered ring, or a structure represented by the following formula,

bonded to a structure other than a carbonyl group, and at least one is bonded to an aromatic ring group,

polymer C: a polyamic acid obtained by polymerizing a diamine component and a tetracarboxylic acid component, wherein the diamine component does not contain a diamine represented by the formula [3], and the tetracarboxylic acid component is composed of an alicyclic tetracarboxylic dianhydride and/or an aliphatic tetracarboxylic dianhydride.

2. The liquid crystal aligning agent according to claim 1,

the formula [1] in Polymer A]And [2]]In (A)₁Is a single bond, an alkylene group having 1 to 10 carbon atoms or a phenylene group, wherein at least one-CH group of the alkylene group₂Substituted by ether or ester groups, A₂Is CH₃Wherein a is an integer of 0 to 1, b is 1, and c is an integer of 1 to 2.

3. The liquid crystal aligning agent according to claim 1 or 2,

the diamine represented by the formula [3] in the polymer B has a structure represented by the following formulae [ 3-1 ] to [ 3-3 ],

wherein in formula [ 3-3 ], at least one bond derived from a carbon atom constituting the nitrogen-containing aromatic heterocycle is bonded to the aromatic hydrocarbon ring.

4. The liquid crystal aligning agent according to any one of claims 1 to 3, wherein the diamine represented by the formula [3] in the polymer B is a diamine selected from the group consisting of,

5. the liquid crystal aligning agent according to any one of claims 1 to 4,

the diamine component in the polymer C contains a diamine represented by the following formula [4],

H₂N-Y-NH₂ [41

wherein Y is a bond and has at least one structure represented by the following formula,

6. the liquid crystal aligning agent according to claim 5,

the diamine represented by the formula [4] is a diamine selected from the group consisting of the following formulae,

7. the liquid crystal aligning agent according to any one of claims 1 to 6,

the tetracarboxylic acid component in (ii) and (iii) of the polymer a is composed of an aromatic tetracarboxylic acid dianhydride, an alicyclic tetracarboxylic acid dianhydride, an aliphatic tetracarboxylic acid dianhydride, or a derivative thereof.

8. The liquid crystal aligning agent according to any one of claims 1 to 7,

the aromatic tetracarboxylic dianhydride in the polymer A is a compound represented by the following formula (3 a-1),

in the above formula, X₁Is any of the following formulae (A-1) to (A-28) wherein a represents a bond,

9. the liquid crystal aligning agent according to any one of claims 1 to 8,

the alicyclic tetracarboxylic dianhydride and/or aliphatic tetracarboxylic dianhydride in the polymer C is a compound represented by the following formula (3C-1),

in the above formula, X₂Is any of the following formulae (B-1) to (B-18) wherein a represents a bond,

10. the liquid crystal aligning agent according to any one of claims 1 to 9,

the polymer A is contained in an amount of 10 to 50% by mass based on 100% by mass of the total amount of the polymers A to C.

11. The liquid crystal aligning agent according to any one of claims 1 to 10,

the polymer B is contained in an amount of 10 to 70% by mass based on 100% by mass of the total amount of the polymers A to C.

12. The liquid crystal aligning agent according to any one of claims 1 to 11,

the polymer (C) is contained in an amount of 10 to 50% by mass based on 100% by mass of the total amount of the polymers (A to C).

13. A liquid crystal alignment film obtained from the liquid crystal aligning agent according to any one of claims 1 to 12.

14. A liquid crystal display element having the liquid crystal alignment film according to claim 13.