JP7620264B2 - Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element - Google Patents

Description

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

The most widely used liquid crystal alignment films are polyimide-based ones, which are made by applying and baking a liquid crystal alignment agent whose main component is a solution of a polyimide precursor such as polyamic acid (also called polyamide acid) or a soluble polyimide.

In recent years, as liquid crystal display elements have become larger and more precise, the substrates used and the unevenness of the substrate steps have become larger. In such circumstances, there is a demand for uniform liquid crystal alignment films even for large substrates with large unevenness.

In the process of producing a liquid crystal alignment film, when a liquid crystal alignment agent containing polyamic acid or a solvent-soluble polyimide (also called a resin) is applied to a substrate, this is generally done industrially by a flexographic printing method or an inkjet coating method.
In this case, if the coating property of the liquid crystal alignment agent is poor, repellency or pinholes will occur, and when the liquid crystal display element is made, these parts will become display defects. In response to this, in addition to N-methyl-2-pyrrolidone or γ-butyrolactone, which are solvents with excellent resin solubility (also called good solvents), ethylene glycol monobutyl ether, which is a solvent with low resin solubility (also called poor solvent), is mixed into the solvent for the liquid crystal alignment agent in order to improve the coating property of the liquid crystal alignment agent (for example, see Patent Document 1).

However, poor solvents have poor ability to dissolve polyamic acid and solvent-soluble polyimide, so mixing in large quantities causes the problem of resin precipitation. In addition, in recent years, in mobile liquid crystal display elements such as smartphones and mobile phones, in order to secure as much display surface as possible, the sealant used to bond the substrates of the liquid crystal display element is located close to the edge of the liquid crystal alignment film. Therefore, if the coating properties of the edge of the liquid crystal alignment film are reduced, that is, if the edge of the liquid crystal alignment film is not straight or if the edge is raised, the adhesive effect between the liquid crystal alignment film and the sealant is reduced, which causes a problem of degrading the display characteristics and reliability of the liquid crystal display element.

On the other hand, the inkjet method has attracted attention as a method for forming liquid crystal alignment films without using flexographic printing plates. The inkjet method involves dropping fine droplets onto a substrate and forming a film by the liquid wetting and spreading. Not only does it not require printing plates, but it also allows the printing pattern to be freely set, simplifying the manufacturing process for liquid crystal display elements. Another advantage is that it does not require film formation on a dummy substrate, as is necessary with flexographic printing, so less coating liquid is wasted. It is expected that the inkjet method will reduce the cost of liquid crystal panels and improve production efficiency.

However, while the inkjet method has the advantage of reducing the cost of liquid crystal panels and improving production efficiency, liquid crystal alignment films formed by the inkjet method generally have a trade-off between the uniformity of film thickness within the coating surface and the film formation accuracy around the periphery of the coating. In other words, materials with high in-plane uniformity usually have low dimensional stability around the periphery of the coating, which can lead to the film extending beyond the set dimensions.

Therefore, in order to form a polyimide film, a composition containing a specific poor solvent, such as dipropylene glycol dimethyl ether, has been proposed as a composition with excellent coating properties (see Patent Document 2).

Furthermore, Patent Document 3 describes that a liquid crystal alignment film containing a solvent-soluble polyimide containing a specific diamine can be made extremely reliable even for negative liquid crystals that are very susceptible to contamination, and Patent Document 4 discloses that by using a liquid crystal alignment agent containing a solvent-soluble polyimide with a high imidization rate containing a specific diamine, it is possible to obtain a liquid crystal alignment film with a low pretilt angle of less than 1 degree, excellent voltage retention rate, and liquid crystal alignment properties.

Japanese Patent Application Publication No. 2-37324 JP 2018-83943 A WO2015/199149 WO2019/082975

When a composition containing ethylene glycol monobutyl ether, a poor solvent, added to the N-methyl-2-pyrrolidone and γ-butyrolactone disclosed in Patent Document 1 in order to improve the coating properties of the liquid crystal alignment agent is used in an inkjet method, there is a problem that when standby shots, in which liquid is sprayed periodically to prevent nozzle clogging, are performed over a long period of time, the liquid consisting of the polyimide solution adheres to the surface of the inkjet head, and problems are likely to occur, particularly when the composition contains polyimide with a high imidization rate.

In view of the above circumstances, the present invention aims to provide a liquid crystal alignment agent that has excellent bonding between liquids and good coating properties, and can be used stably over a long period of time even in the inkjet method, as well as a liquid crystal alignment film and a liquid crystal display element manufactured using the same.

As a result of intensive research, the inventors discovered that, for example, by introducing butyl cellosolve acetate as a poor solvent into N-methyl-2-pyrrolidone (NMP), γ-butyrolactone (GBL), and ethylene glycol monobutyl ether (butyl cellosolve; BCS), good coating properties and dimensional stability of the coated area are achieved, and the inkjet method can be used stably for a long period of time, leading to the completion of the present invention. Furthermore, the inventors discovered that the properties of such a solvent are particularly effective when dissolving a specific polyimide, leading to the completion of the present invention.

式中、Ａ_１は単結合、メチレン基、エーテル結合、エステル結合、アミド結合、シクロヘキシレン基、又は炭素数２～２０のアルキレン基である。但し、該アルキレン基の任意の－ＣＨ_２－はエーテル基、エステル基、アミド基、シクロヘキシレン基、フェニレン基、ウレア基、アミノ基、又はカルバメート基で置換されていてもよく、該アミド基、該ウレア基、該アミノ基の任意の水素原子はメチル基、又はｔｅｒｔ－ブトキシカルボニル基に置き換えられてもよい。Ａ_２は、フッ素原子、又は炭素数１～５のアルキル基若しくはアルコキシ基であり、該アルキル基若しくは該アルコキシ基の任意の水素原子はフッ素原子で置換されていてもよく、任意の炭素原子はｔｅｒｔ－ブトキシカルボニル基で保護されたアミノ基で置換されていてもよい。複数のａはそれぞれ独立して０～４の整数であり、Ａ_２が複数存在する場合、Ａ_２は同一でも異なってもよい。ｂ及びｃは、それぞれ独立して０～２の整数であり、ｂが０の場合、ｃは１又は２であり、Ａ_１はアルキレン基である。
（Ｂ）：ブチルセロソルブ及びブチルセロソルブアセテートを含有する有機溶媒。 The liquid crystal aligning agent of the present invention for achieving the above object is
It contains the following (A) and (B).
(A): A polyimide obtained by imidizing a polyimide precursor which is a reaction product between a diamine component containing at least one diamine selected from the following formulae [1] and [2] and a tetracarboxylic acid component.

In the formula, A ₁ is a single bond, a methylene group, an ether bond, an ester bond, an amide bond, a cyclohexylene group, or an alkylene group having 2 to 20 carbon atoms. However, any -CH ₂ - in the alkylene group may be substituted with an ether group, an ester group, an amide group, a cyclohexylene group, a phenylene group, a urea group, an amino group, or a carbamate group, and any hydrogen atom in the amide group, the urea group, or the amino group may be substituted with a methyl group or a tert-butoxycarbonyl group. _{A 2} is a fluorine atom, or an alkyl group or alkoxy group having 1 to 5 carbon atoms, and any hydrogen atom in the alkyl group or the alkoxy group may be substituted with a fluorine atom, and any carbon atom may be substituted with an amino group protected with a tert-butoxycarbonyl group. A's are each independently an integer of 0 to 4, and when there are multiple A _'s , A _'s may be the same or different. b and c each independently represent an integer of 0 to 2, and when b is 0, c is 1 or 2, and A ₁ is an alkylene group.
(B): An organic solvent containing butyl cellosolve and butyl cellosolve acetate.

According to the present invention, it is possible to provide a liquid crystal alignment agent that has good coating properties, good dimensional stability around the application edge, and can be used stably for a long period of time even in the inkjet method, as well as a liquid crystal alignment film and a liquid crystal display element manufactured using the same.

The present invention will now be described in more detail.
The liquid crystal aligning agent of the present invention contains the following (A) and (B).
(A): A polyimide obtained by imidizing a polyimide precursor, which is a reaction product between a diamine component containing at least one diamine selected from the above formulae [1] and [2] and a tetracarboxylic acid component.
(B): An organic solvent containing butyl cellosolve and butyl cellosolve acetate.

The diamine used in the present invention includes at least one selected from the above formula [1] or [2].
In the above formula [1], _A2 is preferably a methyl group, and a is preferably an integer of 0 to 1.
In the above formula [2], A ₁ is preferably a single bond, a methylene group, an ether bond, an ester bond, or an alkylene group having 2 to 10 carbon atoms (with the proviso that at least one -CH ₂ - of the alkylene group is substituted with an ether group or an ester group) from the viewpoint of improving liquid crystal alignment.
In the above formula [2], _A2 is preferably a methyl group. a is preferably an integer of 0 to 1. b is preferably 1. c is preferably an integer of 1 to 2.
More preferred specific structures of the diamine represented by the above formula [1] and the diamine represented by the formula [2] include any of the structures of the following formulas [d1-1] to [d1-2] or [d2-1] to [d2-28].

（式［ｄ１－１］中、Ｒはフッ素原子、又は炭素数１～５のアルキル基若しくはアルコキシ基であり、該アルキル基若しくは該アルコキシ基の任意の水素原子はフッ素原子で置換されていてもよい。式［ｄ１－２］中、Ｂｏｃはｔｅｒｔ－ブトキシカルボニル基を表す。）

(In formula [d1-1], R represents a fluorine atom, or an alkyl or alkoxy group having 1 to 5 carbon atoms, and any hydrogen atom of the alkyl or alkoxy group may be substituted with a fluorine atom. In formula [d1-2], Boc represents a tert-butoxycarbonyl group.)

（式［ｄ２－８］中、Ｒ、Ｒ’は、それぞれ独立して、フッ素原子、又は炭素数１～５のアルキル基若しくはアルコキシ基であり、該アルキル基若しくは該アルコキシ基の任意の水素原子はフッ素原子で置換されていてもよい。）

(In formula [d2-8], R and R' each independently represent a fluorine atom, or an alkyl or alkoxy group having 1 to 5 carbon atoms, and any hydrogen atom of the alkyl or alkoxy group may be substituted with a fluorine atom.)

（式中、Ｂｏｃはｔｅｒｔ－ブトキシカルボニル基を表す。式［ｄ２－１７］において、ｍが複数存在する場合、複数のｍは同一でも異なっても良い。）

(In the formula, Boc represents a tert-butoxycarbonyl group. When multiple m's are present in formula [d2-17], the multiple m's may be the same or different.)

As for the diamine represented by the above formula [1] and the diamine represented by the above formula [2], the following structure can be given as a more preferred specific structure.

The content of the diamines represented by the above formulas [1] and [2] is preferably 50 mol% or more, and more preferably 70 mol% or more, per mole of the total diamine components.

In the present invention, the diamine constituting the polyimide (A) may include, in addition to the diamine selected from the above formulas [1] and [2], the diamine described below.

The diamines selected from the above formulae [1] and [2] may be used in combination of two or more, or three or more.
Among them, it is preferable to use two or more kinds of diamines selected from the above formula [2].

<Diamine having specific side chain structure>
The diamine having a specific side chain structure exhibits vertical alignment properties and has at least one side chain structure selected from the group represented by the following formulas [S1] to [S3]. Hereinafter, examples of the second diamine having such a specific side chain structure, that is, the diamine having the specific side chain structure represented by formulas [S1] to [S3], will be described in order.

上記式［Ｓ１］中、Ｘ^１及びＸ^２は、それぞれ独立して、単結合、－（ＣＨ_２）_ａ－（ａは１～１５の整数を示す。）、－ＣＯＮＨ－、－ＮＨＣＯ－、－ＣＯＮ（ＣＨ_３）－、－ＮＨ－、－Ｏ－、－ＣＯＯ－、－ＯＣＯ－又は－（（ＣＨ_２）_ａ１－Ａ_１）_ｍ１－を表す。このうち、ａ１は１～１５の整数を示し、Ａ_１は酸素原子又は－ＣＯＯ－を示し、ｍ１は１～２の整数を示す。ｍ１が２の場合、複数のａ１及びＡ_１はそれぞれ独立して上記定義を有する。 [a]: Diamine having a specific side chain structure represented by the following formula [S1]

In the above formula [S1], ^X1 and ^X2 each independently represent a single bond, -( _CH2 ) _a- (a represents an integer of 1 to 15), -CONH-, -NHCO-, -CON( _CH3 )-, -NH-, -O-, -COO-, -OCO- or -(( _CH2 ) _a1 - _A1 ) _m1- . Of these, a1 represents an integer of 1 to 15, _A1 represents an oxygen atom or -COO-, and m1 represents an integer of 1 to 2. When m1 is 2, multiple a1s and _A1s each independently have the above definition.

Among these, from the viewpoints of availability of raw materials and ease of synthesis, ^X1 and ^X2 are each preferably independently a single bond, -( _CH2 ) _a- (a is an integer of 1 to 15), -O-, _-CH2O- or -COO-, and more preferably a single bond, -( _CH2 ) _a- (a is an integer of 1 to 10), -O-, _-CH2O- or -COO-.

In the above formula [S1], ^G1 and ^G2 each independently represent a divalent cyclic group selected from the group consisting of a divalent aromatic group having 6 to 12 carbon atoms and a divalent alicyclic group having 3 to 8 carbon atoms. Any hydrogen atom on the cyclic group may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxy group having 1 to 3 carbon atoms, or a fluorine atom. m and n each independently represent an integer of 0 to 3, and the sum of m and n is 1 to 6, preferably 1 to 4.

In the above formula [S1], R ¹ represents an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an alkoxyalkyl group having 2 to 20 carbon atoms. Any hydrogen atom forming R ¹ may be substituted with a fluorine atom. Among these, examples of the divalent aromatic group having 6 to 12 carbon atoms include a phenylene group, a biphenyl structure, and a naphthylene group. Examples of the divalent alicyclic group having 3 to 8 carbon atoms include a cyclopropylene group and a cyclohexylene group.

Therefore, preferred specific examples of the above formula [S1] include the following formulas [S1-x1] to [S1-x7].

In the above formulas [S1-x1] to [S1-x7], R ¹ is the same as in the above formula [S1]. ^{X p} represents -(CH ₂ ) _a - (a represents an integer of 1 to 15), -CONH-, -NHCO-, -CON(CH ₃ )-, -NH-, -O-, -CH ₂ O-, -CH ₂ OCO-, -COO- or -OCO-. _{A 1} represents an oxygen atom or -COO-* (the bond marked with "*" is bonded to (CH ₂ ) _a2 ). _{A 2} represents an oxygen atom or *-COO- (the bond marked with "*" is bonded to (CH ₂ ) _a2 ). _{a 3} represents an integer of 0 or 1, and a ₁ and a ₂ each independently represent an integer of 2 to 10. Cy represents a 1,4-cyclohexylene group or a 1,4-phenylene group.

上記式［Ｓ２］中、Ｘ^３は単結合、－ＣＯＮＨ－、－ＮＨＣＯ－、－ＣＯＮ（ＣＨ_３）－、－ＮＨ－、－Ｏ－、－ＣＨ_２Ｏ－、－ＣＯＯ－又は－ＯＣＯ－を表す。なかでも、液晶配向剤の液晶配向性の点から、Ｘ^３は－ＣＯＮＨ－、－ＮＨＣＯ－、－Ｏ－、－ＣＨ_２Ｏ－、－ＣＯＯ－又は－ＯＣＯ－が好ましい。 [b]: Diamine having a specific side chain structure represented by the following formula [S2]

In the above formula [S2], ^X3 represents a single bond, -CONH-, -NHCO-, -CON( _CH3 )-, -NH-, -O-, _-CH2O- , -COO- or -OCO-. Among these, from the viewpoint of the liquid crystal alignment property of the liquid crystal aligning agent, ^X3 is preferably -CONH-, -NHCO-, -O-, _-CH2O- , -COO- or -OCO-.

In the above formula [S2], ^R2 represents an alkyl group having 1 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms. Any hydrogen atom forming ^R2 may be substituted with a fluorine atom. Among them, from the viewpoint of the liquid crystal alignment property of the liquid crystal aligning agent, ^R2 is preferably an alkyl group having 3 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms.
As a preferred specific example of formula [S2], X ³ is any one of -O-, -CH ₂ O-, -COO- or -OCO-, and R ² is preferably an alkyl group having 3 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms, more preferably an alkyl group having 3 to 20 carbon atoms, and any hydrogen atom ^{forming R 2 may} be substituted with a fluorine atom.

上記式［Ｓ３］中、Ｘ^４は－ＣＯＮＨ－、－ＮＨＣＯ－、－Ｏ－、－ＣＨ_２Ｏ－、－ＣＯＯ－又は－ＯＣＯ－を表す。Ｒ^３はステロイド骨格を有する構造を表す。ここでのステロイド骨格は、３つの六員環及び１つの五員環が結合した下記式（ｓｔ）で表される骨格を有する。尚、該ステロイド骨格が有する環は二重結合を有してもよい。

[c]: Diamine having a specific side chain structure represented by the following formula [S3]

In the above formula [S3], ^X4 represents -CONH-, -NHCO-, -O-, -CH ₂ O-, -COO- or -OCO-. ^R3 represents a structure having a steroid skeleton. The steroid skeleton here has a skeleton represented by the following formula (st) in which three six-membered rings and one five-membered ring are bonded. The ring in the steroid skeleton may have a double bond.

An example of the above formula [S3] is the following formula [S3-x]. Me represents a methyl group.

In the above formula [S3-x], X represents the above formula [X1], [X2] or [X3]. Col represents any of the above formulas [Col1] to [Col3], and G represents any of the above formulas [G1] to [G4]. * represents a bond.

In the above formula [S3-x], preferred examples of combinations of X, Col, and G include the following combinations: [X1], [Col1], and [G1], [X1], [Col1], and [G2], [X1], [Col2], and [G1], [X1], [Col2], and [G2], [X1], [Col3], and [G2], [X1], [Col3], and [G1], [X2], [Col1], and [G2], [X2], [Col2], and [G2], [X2], [Col2], and [G1], [X2], [Col3], and [G2], [X2], [Col1], and [G1], [X3], [Col2], and [G1], [X3], [Col2], and [G2], [X3], [Col2], and [G3].

Specific examples of the above formula [S3] include the structure obtained by removing a hydroxyl group (hydroxy group) from the steroid compound described in paragraph [0024] of JP-A-4-281427, the structure obtained by removing an acid chloride group from the steroid compound described in paragraph [0030] of the same publication, the structure obtained by removing an amino group from the steroid compound described in paragraph [0038] of the same publication, the structure obtained by removing a halogen atom from the steroid compound described in paragraph [0042] of the same publication, and the structure described in paragraphs [0018] to [0022] of JP-A-8-146421.

A typical example of a steroid skeleton is cholesterol (the combination of [Col1] and [G2] in the above formula [S3-x]), but a steroid skeleton that does not contain cholesterol can also be used. That is, an example of a diamine having a steroid skeleton is cholestanyl 3,5-diaminobenzoate, but it is also possible to use a diamine component that does not contain a diamine having a cholesterol skeleton. In addition, as a diamine having a specific side chain structure, one that does not contain an amide bond at the linking position between the diamine and the side chain can also be used. In this embodiment, a liquid crystal alignment agent can be provided that can obtain a liquid crystal alignment film or liquid crystal display element that can maintain a high voltage retention rate for a long period of time even if a diamine component that does not contain a diamine having a cholesterol skeleton is used.

The diamines having side chain structures represented by the above formulas [S1] to [S3] are represented by the structures of the following formulas [1-S1] to [1-S3], respectively.

上記式［１－Ｓ１］中、Ｘ^１、Ｘ^２、Ｇ^１、Ｇ^２、Ｒ^１、ｍ及びｎは、上記式［Ｓ１］における場合と同様である。上記式［１－Ｓ２］中、Ｘ^３及びＲ^２は、上記式［Ｓ２］における場合と同様である。上記式［１－Ｓ３］中、Ｘ^４及びＲ^３は、上記式［Ｓ３］における場合と同様である。

In the above formula [1-S1], ^X1 , ^X2 , ^G1 , ^G2 , ^R1 , m and n are the same as those in the above formula [S1]. In the above formula [1-S2], ^X3 and ^R2 are the same as those in the above formula [S2]. In the above formula [1-S3], ^X4 and ^R3 are the same as those in the above formula [S3].

(Diamine having a specific two-side chain structure exhibiting vertical alignment properties)
The diamine having a specific two-side chain structure that exhibits vertical alignment properties is represented, for example, by the following formula [N1].

In the above formula [N1], X represents a single bond, -O-, -C(CH ₃ ) ₂ -, -NH-, -CO-, -NHCO-, -COO-, -(CH ₂ ) _m -, -SO ₂ -, or a divalent organic group consisting of any combination thereof. Among these, X is preferably a single bond, -O-, -NH-, or -O-(CH ₂ ) _m -O-. Examples of "any combination thereof" include -O-( _CH2 ) _m -O-, -O-C( _CH3 ) _2- , -CO-( _CH2 ) _m- , -NH-(CH2)m-, _-SO2- ( _CH2 ) _m- , -CONH-( _CH2 ) _m- , -CONH-( _CH2 ) _m- NHCO-, -COO-( _CH2 ) _m -OCO-, -NH-( _CH2 ) _m -NH-, _-SO2- ( _CH2 ) _{m - SO2-} , and the like, where m is an integer of 1 to ₈ .
In the above formula [N1], two Y's each independently represent a monovalent group selected from the side chain structures represented by the above formulas [S1] to [S3].

In addition, in the above formula [N1], Y may be in the meta position or the ortho position relative to the position of X, but is preferably in the ortho position. In other words, the above formula [N1] is preferably the following formula [1'].

In addition, in the above formula [N1], the positions of the two amino groups (-NH ₂ ) may be any positions on the benzene ring, but the positions represented by the following formulas [1]-a1 to [1]-a3 are preferred, and the following formula [1]-a1 is more preferred. In the following formulas, X is the same as in the above formula [N1]. Note that the following formulas [1]-a1 to [1]-a3 explain the positions of the two amino groups, and the notation of Y represented in the above formula [N1] is omitted.

Therefore, based on the above formulas [1'] and [1]-a1 to [1]-a3, the above formula [N1] is preferably any structure selected from the group consisting of the following formulas [1]-a1-1 to [1]-a3-2, and more preferably a structure represented by the following formula [1]-a1-1. In the following formulas, X and Y are each the same as in formula [N1].

Furthermore, examples of the above formulas [S1] to [S3] include the following formulas [S]-1 to [S]-20. Of these, preferred examples of the above formula [S1] are the following formulas [S]-1 to [S]-4, [S]-8 and [S]-10. In the following formulas, * represents the bonding position with the phenyl group in the above formulas [1], [1'] and [1]-a1 to [1]-a3. In addition, in [S]-1 to [S]-20, n is an integer from 1 to 20, and m is an integer from 1 to 6.

<Other diamines: diamines having photoreactive side chains>
The diamine component of the present embodiment may contain a diamine having a photoreactive side chain as the other diamine. When the diamine component contains a diamine having a photoreactive side chain, the photoreactive side chain can be introduced into the specific polymer or other polymers.
Specific examples of diamines having a photoreactive side chain include, but are not limited to, those described in paragraphs [0124] to [0132] of Republished Patent Publication No. 2016/140328.

These diamines having photoreactive side chains can be used alone or in combination of two or more. Whether to use alone or in combination of two or more, and if to use in combination of two or more, the ratio, etc., can be appropriately adjusted depending on the liquid crystal alignment properties, pretilt angle, voltage retention characteristics, stored charge, and other characteristics when used as a liquid crystal alignment film, and the response speed of the liquid crystal when used as a liquid crystal display element.

In this embodiment, when the diamine component contains a photoreactive side chain diamine, the photoreactive side chain diamine preferably accounts for 10 to 70 mol %, and more preferably 10 to 60 mol %, of the total diamine component.

<Other diamines: diamines other than those listed above>
The other diamines that may be contained in the diamine component for obtaining the specific polymer are not limited to the above-mentioned diamines having a photoreactive side chain.
When producing a polyimide precursor and/or a polyimide, diamines other than the above-mentioned diamines can be used in combination as a diamine component. Specifically, in addition to the diamines listed below, those described in paragraph [0135] of the republished patent publication WO2016/140328 can be mentioned.

Diamines having a photo-alignable group such as 4,4'-diaminoazobenzene or diaminotran; 4,4'-diaminodiphenylamine, 4,4'-diaminodiphenylmethylamine, 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol; 4,4'-diamino-3,3'-dihydroxybiphenyl, 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid , 3,5-diaminobenzoic acid, and diamines having a carboxyl group such as diamines represented by the following formulae (3b-1) to (3b-4); 4-(2-(methylamino)ethyl)aniline, 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; 2-(2,4-diaminophenoxy)ethyl methacrylate, 2,4-diamino-N,N-di Allylaniline; 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, diamines having a siloxane bond such as the diamine represented by the following formula (Ds-1); diamines represented by the following formulas (Ox-1) to (Ox-2), 2,6-diaminopyridine, 3,4-diaminopyridine, 2,4-diaminopyrimidine, 3,6-diaminocarbazole, N-methyl-3,6-diaminocarbazole, 1,4-bis-(4-aminophenyl)-piperazine, 3,6-diaminoacrylonitrile, Lysine, N-ethyl-3,6-diaminocarbazole, N-phenyl-3,6-diaminocarbazole, diamines having a heterocyclic structure such as diamines represented by the following formulas (z-1) to (z-18); metaxylylenediamine, 1,3-propanediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-diaminocyclohexane, 4,4'-methylenebis(cyclohexylamine), and the like.

（上記（３ｂ－１）中、Ａ^１は単結合、－ＣＨ_２－、－Ｃ_２Ｈ_４－、－Ｃ（ＣＨ_３）_２－、－ＣＦ_２－、－Ｃ（ＣＦ_３）_２－、－Ｏ－、－ＣＯ－、－ＮＨ－、－Ｎ（ＣＨ_３）－、－ＣＯＮＨ－、－ＮＨＣＯ－、－ＣＨ_２Ｏ－、－ＯＣＨ_２－、－ＣＯＯ－、－ＯＣＯ－、－ＣＯＮ（ＣＨ_３）－又は－Ｎ（ＣＨ_３）ＣＯ－を示し、ｍ１及びｍ２はそれぞれ独立して、０～４の整数を示し、かつｍ１＋ｍ２は１～４の整数を示す。式（３ｂ－２）中、ｍ３及びｍ４はそれぞれ独立して、１～５の整数を示す。式（３ｂ－３）中、Ａ^２は炭素数１～５の直鎖又は分岐アルキル基を示し、ｍ５は１～５の整数を示す。式（３ｂ－４）中、Ａ^３及びＡ^４はそれぞれ独立して、単結合、－ＣＨ_２－、－Ｃ_２Ｈ_４－、－Ｃ（ＣＨ_３）_２－、－ＣＦ_２－、－Ｃ（ＣＦ_３）_２－、－Ｏ－、－ＣＯ－、－ＮＨ－、－Ｎ（ＣＨ_３）－、－ＣＯＮＨ－、－ＮＨＣＯ－、－ＣＨ_２Ｏ－、－ＯＣＨ_２－、－ＣＯＯ－、－ＯＣＯ－、－ＣＯＮ（ＣＨ_３）－又は－Ｎ（ＣＨ_３）ＣＯ－を示し、ｍ６は１～４の整数を示す。）

(In the above (3b-1), A ¹ represents a single bond, —CH ₂ —, —C ₂ H ₄ —, —C(CH ₃ ) ₂ —, —CF ₂ —, —C(CF ₃ ) ₂ —, —O—, —CO—, —NH—, —N(CH ₃ )—, —CONH—, —NHCO—, —CH ₂ O—, —OCH ₂ —, —COO—, —OCO—, —CON(CH ₃ )— or —N(CH ₃ )CO—; m1 and m2 each independently represent an integer of 0 to 4, and m1+m2 represents an integer of 1 to 4. In formula (3b-2), m3 and m4 each independently represent an integer of 1 to 5. In formula (3b-3), A In formula (3b-4), A ³ and A ⁴ each independently represent a single bond, —CH ₂ —, —C ₂ H ₄ —, —C(CH ₃ ) ₂ —, —CF ₂ —, —C(CF ₃ ) ^{2 —} , _—O— , —CO—, —NH—, —N(CH 3 )—, —CONH—, —NHCO—, —CH ₂ O—, _{—OCH 2} —, —COO—, —OCO—, —CON(CH ₃ )— or —N(CH ₃ )CO—, and m6 represents an integer from 1 to 4.

The above-mentioned other diamines can also be used alone or in a mixture of two or more types depending on the properties such as liquid crystal alignment, pretilt angle, voltage retention characteristics, and stored charge when formed into a liquid crystal alignment film.

When the liquid crystal alignment film of the present invention is used in an IPS or FFS liquid crystal display element, it is preferable that the diamine constituting the polyimide (A) in the present invention does not have a side chain group having 6 or more carbon atoms. Examples of diamines having a side chain group having 6 or more carbon atoms include diamines having the above-mentioned specific side chain structure and diamines having a two-side chain type specific side chain structure that exhibits the above-mentioned vertical alignment property.

<Polyimide>
The polyimide of the present invention is obtained by imidizing a polyimide precursor, which is a reaction product between the above diamine and a tetracarboxylic acid component.

<Tetracarboxylic acid component>
As the tetracarboxylic acid component for obtaining the polyimide of the present invention, a tetracarboxylic acid dianhydride represented by the following formula [3] or a derivative thereof (tetracarboxylic acid, tetracarboxylic acid dihalide, tetracarboxylic acid dialkyl ester, or tetracarboxylic acid dialkyl ester dihalide) (collectively referred to as specific tetracarboxylic acid) can be used.

（式［３］中、Ｘ_１は、下記式（Ｂ－１）～（Ｂ－２０）のいずれかから選択される。特に、Ｘ_１が（Ｂ－１）、（Ｂ－２）、（Ｂ－３）のいずれかであることが好ましい。

In formula [3], X ₁ is selected from any one of the following formulas (B-1) to (B-20). It is particularly preferable that X ₁ is any one of (B-1), (B-2), or (B-3).

（式中、ｊ及びｋは、０又は１の整数であり、Ａ_１及びＡ_２は、それぞれ独立して、単結合、－Ｏ－、－ＣＯ－、－ＣＯＯ－、フェニレン、スルホニル、又はアミド基を表す。上記式（Ｂ－２０）において、２個のＡ_２は、互いに同一であっても異なっていてもよい。式中、＊は結合手を表す。）

(In the formula, j and k are integers of 0 or 1, and A ₁ and A ₂ each independently represent a single bond, -O-, -CO-, -COO-, phenylene, sulfonyl, or an amide group. In the above formula (B-20), the two A ₂ may be the same or different. In the formula, * represents a bond.)

Specific examples of the specific tetracarboxylic acid include, in addition to those listed below, 2,3,3',4-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride.

The specific tetracarboxylic acid is preferably 50 to 100 mol % of the total tetracarboxylic acid components (100 mol %). Of these, 70 to 100 mol % is more preferable. Even more preferable is 80 to 100 mol %.

Specific tetracarboxylic acids can be used alone or in a mixture of two or more types depending on the properties such as the solubility of the specific polymer in the solvent, the coatability of the liquid crystal alignment agent, the alignment of the liquid crystal when made into a liquid crystal alignment film, the voltage retention rate, and the stored charge.

The tetracarboxylic acid component for obtaining the polyimide of the present invention may contain tetracarboxylic acids other than the above-mentioned specific tetracarboxylic acids (hereinafter, also referred to as other tetracarboxylic acids).
Examples of other tetracarboxylic acids include the following tetracarboxylic acid compounds, tetracarboxylic dianhydrides, tetracarboxylic acid dihalide compounds, tetracarboxylic acid dialkyl ester compounds, and tetracarboxylic acid dialkyl ester dihalide compounds.

That is, examples of other tetracarboxylic acids include 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 1,2,5,6-anthracene tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 1,1,1,3,3,3-hexafluoro-2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride, bis(3,4-dicarboxyphenyl)diphenylsilane dianhydride, 2,3,4,5-pyridine tetracarboxylic dianhydride, 2,6-bis(3,4-dicarboxyphenyl)pyridine dianhydride, 3,4,9,10-perylene tetracarboxylic dianhydride, and 1,3-diphenyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride.
Other tetracarboxylic acids can be used alone or in combination depending on the solubility of the specific polymer in a solvent, the coatability of the liquid crystal alignment agent, and properties such as liquid crystal alignment, voltage holding rate, and stored charge when used as a liquid crystal alignment film.

<Method of producing polyimide>
The polyimide of the present invention can be obtained by a method of reacting the diamine component and the tetracarboxylic acid component described above. For example, the method includes a method of reacting a diamine component consisting of one or more diamines with at least one tetracarboxylic acid component selected from the group consisting of tetracarboxylic dianhydrides and derivatives of the tetracarboxylic acid to obtain a polyamic acid. Specifically, a method of polycondensing a primary or secondary diamine with a tetracarboxylic dianhydride to obtain a polyamic acid is used.

To obtain a polyamic acid alkyl ester, a method of polycondensing a tetracarboxylic acid in which the carboxylic acid group has been dialkyl esterified with a primary or secondary diamine, a method of polycondensing a tetracarboxylic acid dihalide in which the carboxylic acid group has been halogenated with a primary or secondary diamine, or a method of converting the carboxy group of a polyamic acid into an ester is used. To obtain a polyimide, a method of ring-closing the above polyamic acid or polyamic acid alkyl ester to form a polyimide is used.

The reaction between the diamine component and the tetracarboxylic acid component is usually carried out in a solvent. The solvent used is not particularly limited as long as the generated polyimide precursor dissolves in the solvent. Examples of the solvent include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, and 1,3-dimethyl-2-imidazolidinone. In addition, when the polyimide precursor has high solvent solubility, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or solvents represented by the following formulas [D-1] to [D-3] can be used.

In formula [D-1], D ¹ represents an alkyl group having 1 to 3 carbon atoms. In formula [D-2], D ² represents an alkyl group having 1 to 3 carbon atoms. In formula [D-3], D ³ represents an alkyl group having 1 to 4 carbon atoms.

These solvents can be used alone or in combination of two or more. Even if the solvent does not dissolve the polyimide precursor, it may be mixed with the above-mentioned solvent as long as the generated polyimide precursor does not precipitate. Furthermore, moisture in the solvent inhibits the polymerization reaction and may even cause hydrolysis of the generated polyimide precursor, so it is preferable to use a solvent that has been dehydrated and dried.

When reacting the diamine component and the tetracarboxylic acid component in a solvent, any of the following methods may be used: a solution in which the diamine component is dispersed or dissolved in a solvent is stirred, and the tetracarboxylic acid component is added as is or dispersed or dissolved in the solvent; conversely, the diamine component is added to a solution in which the tetracarboxylic acid component is dispersed or dissolved in a solvent; or the diamine component and the tetracarboxylic acid component are added alternately. When reacting multiple diamine components or multiple tetracarboxylic acid components, they may be reacted in a premixed state, or may be reacted individually in sequence, or low molecular weight compounds that have been reacted individually may be mixed and reacted to form a polymer.

The temperature at which the diamine component and the tetracarboxylic acid component are polycondensed can be selected from -20 to 150°C, but is preferably in the range of -5 to 100°C. The reaction can be carried out at any concentration, but if the concentration is too low it becomes difficult to obtain a high molecular weight polymer, and if the concentration is too high the viscosity of the reaction liquid becomes too high, making uniform stirring difficult. Therefore, the concentration is preferably 1 to 50% by mass, and more preferably 5 to 30% by mass. The reaction can also be carried out at a high concentration at the beginning, with additional solvent added later.

In the polymerization reaction of the polyimide precursor, the ratio of the total number of moles of the diamine component to the total number of moles of the tetracarboxylic acid component is preferably 0.8 to 1.2. As in a normal polycondensation reaction, the closer this molar ratio is to 1.0, the higher the molecular weight of the resulting polyimide precursor will be.

Polyimide is a polyimide obtained by ring-closing the polyimide precursor. In this polyimide, the ring-closing rate of the amic acid group (also called the imidization rate) does not necessarily have to be 100% and can be adjusted as desired depending on the application and purpose. The imidization rate of the polyimide, which is the specific polymer used in the present invention, is preferably 20 to 100% from the viewpoint of reducing the occurrence rate of display defects, more preferably 50 to 99%, and even more preferably 70 to 95%. Methods for imidizing the polyimide precursor include thermal imidization, in which a solution of the polyimide precursor is heated as is, and catalytic imidization, in which a catalyst is added to a solution of the polyimide precursor.

The temperature when thermally imidizing the polyimide precursor in a solution is 100 to 400°C, preferably 120 to 250°C, and it is preferable to carry out the process while removing the water generated by the imidization reaction from the system. Catalytic imidization of the polyimide precursor can be carried out by adding a basic catalyst and an acid anhydride to a solution of the polyimide precursor and stirring at -20 to 250°C, preferably 0 to 180°C.

The amount of the basic catalyst is 0.5 to 30 molar times, preferably 2 to 20 molar times, the amount of the amide acid group, and the amount of the acid anhydride is 1 to 50 molar times, preferably 3 to 30 molar times, the amount of the amide acid group. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine, etc. Among them, pyridine is preferred because it has an appropriate basicity for promoting the reaction. Examples of the acid anhydride include acetic anhydride, trimellitic anhydride, pyromellitic anhydride, etc. In particular, the use of acetic anhydride is preferred because it makes purification after the reaction easier. The imidization rate by catalytic imidization can be controlled by adjusting the amount of catalyst, reaction temperature, and reaction time.

When recovering the polyimide produced from the polyimide reaction solution, the reaction solution may be poured into a solvent to cause precipitation. Examples of solvents used for precipitation include methanol, ethanol, isopropyl alcohol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, toluene, benzene, and water. The polymer precipitated by pouring into the solvent can be recovered by filtration and then dried at normal or reduced pressure, or at room temperature or by heating. In addition, the polymer precipitated and recovered can be redissolved in a solvent and the reprecipitation and recovery operation repeated 2 to 10 times to reduce impurities in the polymer. Examples of solvents used in this case include alcohols, ketones, and hydrocarbons. It is preferable to use three or more types of solvents selected from these because this further increases the efficiency of purification.

<Terminal Modifier>
In synthesizing the polyimide precursor or polyimide of the present invention, a terminal-modified polymer may be synthesized using a suitable terminal modifier together with the above-mentioned tetracarboxylic acid derivative component and diamine component. The terminal-modified polymer has the effect of improving the film hardness of the liquid crystal alignment film obtained by coating and improving the adhesion property between the sealant and the liquid crystal alignment film.
Examples of the terminals of the polyimide precursor or polyimide in the present invention include an amino group, a carboxyl group, an acid anhydride group, an isocyanate group, a thioisocyanate group, or derivatives thereof. The amino group, the carboxyl group, the acid anhydride group, the isocyanate group, and the thioisocyanate group can be obtained by a normal condensation reaction, and the above-mentioned derivatives can be obtained by modifying the terminals, for example, with the following terminal modifiers.

Examples of terminal modifiers include acid monoanhydrides such as acetic anhydride, maleic anhydride, nadic anhydride, phthalic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride, 3-hydroxyphthalic anhydride, trimellitic anhydride, compounds represented by the following formulas (m-1) to (m-6), 3-(3-trimethoxysilyl)propyl)-3,4-dihydrofuran-2,5-dione, 4,5,6,7-tetrafluoroisobenzofuran-1,3-dione, and 4-ethynylphthalic anhydride;

Examples of such compounds include dicarbonate diester compounds such as di-tert-butyl dicarbonate and diallyl dicarbonate; chlorocarbonyl compounds such as acryloyl chloride, methacryloyl chloride and nicotinic acid chloride; monoamine compounds such as aniline, 2-aminophenol, 3-aminophenol, 4-aminosalicylic acid, 5-aminosalicylic acid, 6-aminosalicylic acid, 2-aminobenzoic acid, 3-aminobenzoic acid, 4-aminobenzoic acid, cyclohexylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine and n-octylamine; monoisocyanate compounds such as ethyl isocyanate, phenyl isocyanate and naphthyl isocyanate; and thioisocyanate compounds such as ethyl isothiocyanate and allyl isothiocyanate.

The proportion of terminal modifier used is preferably 0.01 to 20 molar parts, and more preferably 0.01 to 10 molar parts, per 100 molar parts of the total diamine components used.

<Liquid crystal alignment agent>
The liquid crystal alignment agent of the present invention contains the above polyimide (referred to as the specific polymer), but may contain two or more polymers with different structures. In addition to the polymer, it may contain other polymers. Examples of the polymer type include polyamic acid, polyimide, polyamic acid ester, polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivative, polyacetal, polystyrene or its derivative, poly(styrene-phenylmaleimide) derivative, poly(meth)acrylate, etc. When the liquid crystal alignment agent of the present invention contains other polymers, the ratio of the specific polymer to the total polymer components is preferably 5% by mass or more, for example, 5 to 95% by mass.

Among the above other polymers, from the viewpoint of enhancing liquid crystal alignment, polyamic acid not containing an imide ring structure or polyamic acid ester not containing an imide ring structure (hereinafter also referred to as polyimide precursor (PA)) is preferred.

Tetracarboxylic acid derivative components for obtaining the polyimide precursor (pa) include acyclic aliphatic tetracarboxylic acid dianhydrides, alicyclic tetracarboxylic acid dianhydrides, aromatic tetracarboxylic acid dianhydrides, or derivatives thereof. Specific examples of acyclic aliphatic tetracarboxylic acid dianhydrides, alicyclic tetracarboxylic acid dianhydrides, and aromatic tetracarboxylic acid dianhydrides include the tetracarboxylic acid dianhydrides or derivatives thereof exemplified in the above specific polymer. Among them, the preferred tetracarboxylic acid derivative components are the compounds represented by the above formula [3] or derivatives thereof. As the tetracarboxylic acid derivative component, one type of tetracarboxylic acid dianhydride or its derivative may be used alone, or two or more types may be used in combination.

The tetracarboxylic acid derivative component for obtaining the polyimide precursor (pa) is preferably a tetracarboxylic acid dianhydride represented by formula [3] in which X ₁ in formula [3] is selected from the above formulas (B-1) to (B-8) and (B-13) to (B-20), or a derivative thereof.

The proportion of the tetracarboxylic dianhydride represented by the above formula [3] or a derivative thereof used is preferably 1 to 100 mol%, more preferably 5 to 100 mol%, and even more preferably 10 to 100 mol%, relative to 1 mole of the total tetracarboxylic acid derivative components used in the synthesis of the polyimide precursor (pa).

Examples of the diamine component for obtaining the polyimide precursor (pa) include the diamine components exemplified in the specific polymer above. Among them, it is preferable to include at least one diamine selected from the group consisting of a diamine having at least one group selected from the group consisting of a urea bond, an amide bond, a carboxy group, and a hydroxy group in the molecule (hereinafter also referred to as diamine (b1)), and a diamine having a nitrogen-containing structure (excluding urea bonds, amide bonds, and imide bonds) selected from the group consisting of a secondary amino group, a tertiary amino group, and a heterocycle (hereinafter also referred to as diamine (b2)). The diamine component may be a single diamine, or two or more diamines may be used in combination. In the above, the total amount of diamines (b1) and (b2) used is preferably 10 to 100 mol%, more preferably 10 to 90 mol%, and even more preferably 20 to 80 mol% based on the total amount of the diamine components for producing the polyimide precursor (pa).

The polyimide precursor (pa) may be composed of one or more polyimide precursor components. More preferred specific aspects of the polyimide precursor (pa) include at least one polymer (hereinafter also referred to as copolymer) selected from the group consisting of a polyimide precursor which is a reaction product of a diamine component containing the above diamine (b1) and the above diamine (b2) and a tetracarboxylic acid derivative component, at least one polyimide precursor (pa-p1) selected from the group consisting of a diamine component containing the above diamine (b1) and a polyimide precursor which is a reaction product of a tetracarboxylic acid derivative component, and at least one polyimide precursor (pa-p2) selected from the group consisting of a diamine component containing the above diamine (b2) and a polyimide precursor which is a reaction product of a tetracarboxylic acid derivative component (hereinafter also referred to as polymer blend). The above copolymers or polymer blends may be used alone or in combination.

In the above copolymer, the amount of diamine (b1) used is preferably 30 to 100 mol %, more preferably 40 to 100 mol %, and even more preferably 50 to 100 mol %, based on the total amount of diamine components used to produce the polyimide precursor (pa).
In the above copolymer, the amount of diamine (b2) used is preferably 30 to 100 mol %, more preferably 40 to 100 mol %, and even more preferably 50 to 100 mol %, based on the total amount of diamine components used to produce the polyimide precursor (pa).
In the above polymer blend, the diamine (b1) and the diamine (b2) are preferably used in an amount of 20 to 100 mol % based on the total amount of the diamine components for producing the polyimide precursor (pa-p1) and the polyimide precursor (pa-p2), respectively. The diamine (b1) is more preferably used in an amount of 20 to 90 mol %, and even more preferably 20 to 80 mol %, based on the total amount of the diamine components for producing the polyimide precursor (pa-p1). The diamine (b2) is more preferably used in an amount of 20 to 80 mol %, and even more preferably 30 to 80 mol %, based on the total amount of the diamine components for producing the polyimide precursor (pa-p2).

Specific examples of the diamine (b1) include the diamines represented by the above formulas [d2-10] to [d2-16], 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol, 4,4'-diamino-3,3'-dihydroxybiphenyl, 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid, or 3,5-diaminobenzoic acid, or the diamines represented by the above formulas (3b-1) to (3b-4).

Specific examples of the diamine (b2) include the diamines represented by the above formulas [d2-23] to [d2-28], 4,4'-diaminodiphenylamine, 4,4'-diaminodiphenylmethylamine, and the diamines represented by the above formulas (z-1) to (z-18).

The mass ratio of the content of the polyimide precursor (pa-p1) to the content of the polyimide precursor (pa-p2) is preferably 5/95 to 95/5, and more preferably 10/90 to 90/10.

From the viewpoint of minimizing afterimages resulting from residual DC, the content ratio of the specific polymer polyimide and the polyimide precursor (pa) may be 5/95 to 95/5 in terms of the mass ratio of [specific polymer polyimide]/[polyimide precursor (pa)], or may be 20/80 to 90/10, or may be 20/80 to 80/20.

Liquid crystal alignment agents are generally in the form of a coating solution in order to form a uniform thin film. The liquid crystal alignment agent of the present invention is also preferably a coating solution containing the above-mentioned polymer component and an organic solvent in which the polymer component is dissolved. In this case, the concentration of the polymer in the liquid crystal alignment agent can be appropriately changed depending on the thickness of the coating film to be formed. In order to form a uniform and defect-free coating film, a concentration of 1% by mass or more is preferable, and in order to ensure the storage stability of the solution, a concentration of 10% by mass or less is preferable. A particularly preferable polymer concentration is 2 to 8% by mass.

The organic solvent contained in the liquid crystal alignment agent contains butyl cellosolve and butyl cellosolve acetate (B), and also contains other organic solvents in which the polymer components are uniformly dissolved.
The liquid crystal aligning agent of the present invention contains butyl cellosolve and butyl cellosolve acetate as poor solvents, and therefore has excellent bonding between liquids and good coating properties, and can be stably used for a long period of time even in the inkjet method.

The content of butyl cellosolve is preferably 5 to 20% by mass, based on the total organic solvents contained in the liquid crystal alignment agent, and the content of butyl cellosolve acetate is preferably 5 to 20% by mass, based on the total organic solvents contained in the liquid crystal alignment agent. The total amount of butyl cellosolve and butyl cellosolve acetate is preferably 10% by mass or more, more preferably 12% by mass or more, and even more preferably 15% by mass or more, based on the total organic solvents contained in the liquid crystal alignment agent.

The other organic solvent is not particularly limited as long as it dissolves the polymer component. Specific examples include N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethyllactamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethylsulfoxide, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone, N-(n-propyl)-2-pyrrolidone, N-isopropyl-2-pyrrolidone, N-(n-butyl)-2-pyrrolidone, N-(tert-butyl)-2-pyrrolidone, N-(n-pentyl)-2-pyrrolidone, N-methoxypropyl-2-pyrrolidone, N-ethoxyethyl-2-pyrrolidone, N-methoxybutyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, 3-methoxy-N,N-dimethylpropane, amide, 3-butoxy-N,N-dimethylpropanamide, methyl ethyl ketone, cyclohexanone, cyclopentanone (these are also collectively referred to as "solvent (C1)"); diisopropyl ether, diisobutyl ether, diisobutyl carbinol (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 ether acetate, 1-methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene glycol monoacetate, ethylene glycol diacetate, propylene carbonate, ethylene carbonate, 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, propylene glycol diacetate, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol di Methyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2-(2-ethoxyethoxy)ethyl acetate, diethylene glycol acetate, propylene glycol diacetate, n-butyl acetate, propylene 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) (collectively referred to as "solvent (C2)"). As the solvent (C1), it is preferable to use N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, or γ-butyrolactone, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, N,N-dimethyllactamide, or 1,3-dimethyl-2-imidazolidinone. The content of the solvent (C1) is preferably 60 to 90 mass%, more preferably 60 to 88 mass%, and particularly preferably 60 to 85 mass%, based on the total organic solvent contained in the liquid crystal alignment agent.
Among them, the solvent (C2) is preferably diisobutyl carbinol, propylene glycol monobutyl ether, propylene glycol diacetate, diethylene glycol diethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, 4-hydroxy-4-methyl-2-pentanone or diisobutyl ketone. The content of the solvent (C2) is preferably 1 to 20% by mass, more preferably 5 to 20% by mass, based on the total organic solvent contained in the liquid crystal alignment agent.
When the solvent (C1) and the solvent (C2) are contained, the total content of the solvent (C1) and the solvent (C2) is preferably 60 to 90 mass%, more preferably 60 to 88 mass%, and particularly preferably 60 to 85 mass%, based on the total organic solvent contained in the liquid crystal alignment agent.

In addition to the above-mentioned solvents, the organic solvent contained in the liquid crystal alignment agent of the present invention may also be a solvent that improves the coatability of the liquid crystal alignment agent when applied and the surface smoothness of the coating film. Specific examples of such organic solvents include those described in paragraph [0177] of the republished patent publication WO2016/140328.

The liquid crystal alignment agent of the present invention may additionally contain components other than the polymer component and the organic solvent. Examples of such additional components include adhesion aids for improving the adhesion between the liquid crystal alignment film and the substrate, or between the liquid crystal alignment film and the sealant, crosslinking agents for increasing the strength of the liquid crystal alignment film, and dielectrics and conductive substances for adjusting the dielectric constant and electrical resistance of the liquid crystal alignment film. Specific examples of these additional components include poor solvents and crosslinkable compounds disclosed in paragraphs [0104] on page 53 to [0116] on page 60 of WO 2015/060357.

In addition to the above, the liquid crystal alignment agent of the present invention may contain polymers other than the specific polymers described in the present invention, dielectrics for changing the electrical properties such as the dielectric constant and conductivity of the liquid crystal alignment film, silane coupling agents for improving adhesion between the liquid crystal alignment film and the substrate, crosslinking compounds for increasing the hardness and density of the film when made into a liquid crystal alignment film, and imidization accelerators for efficiently promoting imidization by heating the polyimide precursor when baking the coating film.

Compounds that improve the adhesion between the liquid crystal alignment film and the substrate include functional silane-containing compounds. Specific examples include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldiethoxymethylsilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, and N-ethoxycarbonyl-3-aminopropyltrimethoxysilane. Propyltriethoxysilane, N-triethoxysilylpropyltriethylenetriamine, N-trimethoxysilylpropyltriethylenetriamine, 10-trimethoxysilyl-1,4,7-triazadecane, 10-triethoxysilyl-1,4,7-triazadecane, 9-trimethoxysilyl-3,6-diazanonyl acetate, 9-triethoxysilyl-3,6-diazanonyl acetate, N-benzyl-3-aminopropyltrimethoxysilane, N-benzyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, Phenyl-3-aminopropyltriethoxysilane, N-bis(oxyethylene)-3-aminopropyltrimethoxysilane, N-bis(oxyethylene)-3-aminopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloyltrimethoxysilane, Examples of the compound include acryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, and those described in paragraph [0180] of republished patent publication WO2016/140328. The content is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, relative to 100 parts by mass of the polymer component contained in the liquid crystal alignment agent.

In order to further increase the film strength of the liquid crystal alignment film, a crosslinking compound such as a compound having two or more of at least one group selected from the group consisting of an oxiranyl group, an oxetanyl group, a protected isocyanate group, a protected isothiocyanate group, a group containing an oxazoline ring structure, a group containing a Meldrum's acid structure, a cyclocarbonate group, and a hydroxyalkylamide group (hereinafter also referred to as a compound having two or more specific crosslinking groups), or a phenolic compound such as 2,2-bis(4-hydroxy-3,5-dihydroxymethylphenyl)propane or tetra(methoxymethyl)bisphenol may be added. The amount of these crosslinking compounds is preferably 0.1 to 30 parts by mass, more preferably 1 to 20 parts by mass, per 100 parts by mass of the total amount of the polymer contained in the liquid crystal alignment agent. Examples of the compound having two or more of the specific crosslinking groups include the following compounds.

<Liquid crystal alignment film>
The liquid crystal alignment film of the present invention is obtained from the liquid crystal alignment agent. The use of the liquid crystal alignment agent of the present invention is particularly suitable for the IPS system or FFS system in which liquid crystal molecules aligned horizontally to the substrate are made to respond to an electric field, and a liquid crystal alignment film and a liquid crystal display element having excellent voltage retention, rapid relaxation of accumulated charges, and excellent afterimage characteristics can be provided. As an example of a method for obtaining a liquid crystal alignment film, the liquid crystal alignment agent of the present invention can be applied to a substrate, and then dried and baked as necessary to obtain a cured film, which can be used as a liquid crystal alignment film as it is. In addition, the cured film can be rubbed, irradiated with polarized light or light of a specific wavelength, or treated with an ion beam, or irradiated with UV light while a voltage is applied to the liquid crystal display element after filling with liquid crystal as an alignment film for PSA.

The substrate on which the liquid crystal alignment agent is applied is not particularly limited as long as it is a highly transparent substrate, and in addition to glass substrates and silicon nitride substrates, plastic substrates such as acrylic substrates and polycarbonate substrates can also be used. In this case, it is preferable to use a substrate on which an ITO electrode for driving the liquid crystal is formed in terms of simplifying the process. In addition, in a reflective liquid crystal display element, an opaque material such as a silicon wafer can be used for only one substrate, and in this case, a light-reflecting material such as aluminum can be used for the electrode.

The method of applying the liquid crystal alignment agent is not particularly limited, but industrially, screen printing, offset printing, flexographic printing, inkjet printing, etc. are generally used. Other application methods include dip method, roll coater method, slit coater method, spinner method, spray method, etc., and these may be used depending on the purpose. After the liquid crystal alignment agent is applied to the substrate, the solvent is evaporated and baked by heating means such as a hot plate, a heat circulation type oven, or an IR (infrared) type oven. The temperature and time can be selected for the drying and baking process after the liquid crystal alignment agent is applied. Although the drying process is not necessarily required, it is preferable to perform a drying process when the time from application to baking is not constant for each substrate, or when baking is not performed immediately after application. This drying is sufficient as long as the solvent is removed to an extent that the coating film shape is not deformed by transportation of the substrate, etc., and the drying means are not particularly limited. For example, a method of drying for 0.5 to 30 minutes, preferably 1 to 5 minutes, on a hot plate at a temperature of 40 to 150 ° C., preferably 60 to 100 ° C., can be mentioned.

When the liquid crystal alignment agent of the present invention is used, particularly when applied by the inkjet method, the inclusion of butyl cellosolve and butyl cellosolve acetate as poor solvents prevents the liquid consisting of the polyimide solution from adhering to the surface of the inkjet head, even when standby shots are performed over a long period of time, enabling stable ejection without precipitation on the head.

The baking temperature of the coating film formed by applying the liquid crystal alignment agent is not limited, and is, for example, 100 to 350°C, preferably 120 to 300°C, and more preferably 150 to 250°C. The baking time is 5 to 240 minutes, preferably 10 to 90 minutes, and more preferably 20 to 90 minutes. Heating can be performed by a commonly known method, such as a hot plate, a hot air circulation oven, or an infrared oven.

The thickness of the liquid crystal alignment film after baking is preferably 5 to 300 nm, more preferably 10 to 200 nm, since if it is too thin, the reliability of the liquid crystal display element may decrease. The liquid crystal alignment film of the present invention is particularly useful as a liquid crystal alignment film for IPS-type and FFS-type liquid crystal display elements.

<Liquid crystal display element and its manufacturing method>
The liquid crystal display element can be produced by forming a liquid crystal alignment film on the substrate by the above method, and then producing a liquid crystal cell by a known method. A specific example of the liquid crystal display element is a horizontal alignment type liquid crystal display element having a liquid crystal cell having two substrates arranged to face each other, a liquid crystal layer provided between the substrates, and the above liquid crystal alignment film formed by a liquid crystal alignment agent provided between the substrates and the liquid crystal layer. Specifically, the liquid crystal alignment agent is applied to the two substrates and baked, and then subjected to an alignment treatment such as rubbing treatment or photoalignment treatment, and can be used as a liquid crystal alignment film without alignment treatment for vertical alignment applications. The two substrates are arranged so that the liquid crystal alignment films face each other, and a liquid crystal layer made of liquid crystal is sandwiched between the two substrates, i.e., the liquid crystal layer is provided in contact with the liquid crystal alignment film, producing a liquid crystal cell.

The substrate of the liquid crystal display element is not particularly limited as long as it is a highly transparent substrate, but is usually a substrate on which a transparent electrode for driving liquid crystal is formed. Specific examples include the same substrates as those described for the liquid crystal alignment film above. A transparent glass substrate is prepared, and a common electrode is provided on one substrate, and a segment electrode is provided on the other substrate. These electrodes can be, for example, ITO electrodes, and are patterned so as to display a desired image. Next, an insulating film is provided on each substrate so as to cover the common electrode and the segment electrode. The insulating film can be, for example, a SiO ₂ -TiO ₂ film formed by a sol-gel method.

In addition, in high-performance elements such as TFT-type elements, transistor-like elements are formed between the electrodes for driving the liquid crystal and the substrate.

In the case of transmissive liquid crystal display elements, the above-mentioned substrates are generally used, but in the case of reflective liquid crystal display elements, an opaque substrate such as a silicon wafer can be used for only one of the substrates. In such cases, a light-reflecting material such as aluminum can be used for the electrodes formed on the substrate.

There are no particular limitations on the liquid crystal material that constitutes the liquid crystal layer of the liquid crystal display element, and liquid crystal materials used in conventional horizontal alignment methods, such as positive-type liquid crystals such as MLC-3019 manufactured by Merck, and negative-type liquid crystals such as MLC-7026-100 manufactured by the same company, can be used. In addition, in the PSA mode, liquid crystals containing a polymerizable compound, such as that represented by the following formula, can be used.

A known method can be used to sandwich a liquid crystal layer between two substrates. For example, a method can be used in which a pair of substrates on which a liquid crystal alignment film is formed is prepared, spacers such as beads are dispersed on the liquid crystal alignment film of one substrate, the other substrate is bonded to the substrate so that the surface on which the liquid crystal alignment film is formed faces inward, and liquid crystal is injected under reduced pressure and sealed. A liquid crystal cell can also be produced by a method in which a pair of substrates on which a liquid crystal alignment film is formed is prepared, spacers such as beads are dispersed on the liquid crystal alignment film of one substrate, liquid crystal is then dripped onto the substrate, and the other substrate is bonded to the substrate so that the surface on which the liquid crystal alignment film is formed faces inward, and sealed. The thickness of the spacer is preferably 1 to 30 μm, more preferably 2 to 10 μm.

The process of producing a liquid crystal cell by irradiating ultraviolet light while applying a voltage to the liquid crystal alignment film and the liquid crystal layer can be, for example, a method of applying an electric field to the liquid crystal alignment film and the liquid crystal layer by applying a voltage between electrodes disposed on a substrate, and irradiating ultraviolet light while maintaining this electric field. Here, the voltage applied between the electrodes is, for example, 5 to 30 Vpp, preferably 5 to 20 Vpp. The amount of ultraviolet light irradiation is, for example, 1 to 60 J/ ^cm2 , preferably 40 J/cm2 ^or less. A smaller amount of ultraviolet light irradiation is preferable because it can suppress a decrease in reliability caused by destruction of the members constituting the liquid crystal display element, and because it can increase manufacturing efficiency by reducing the ultraviolet light irradiation time.

As described above, when the liquid crystal alignment film and the liquid crystal layer are irradiated with ultraviolet light while applying a voltage, the polymerizable compound reacts to form a polymer, and this polymer memorizes the direction in which the liquid crystal molecules tilt, thereby increasing the response speed of the resulting liquid crystal display element. In addition, when the liquid crystal alignment film and the liquid crystal layer are irradiated with ultraviolet light while applying a voltage, the photoreactive side chains of at least one polymer selected from a polyimide precursor having a side chain that vertically aligns the liquid crystal and a photoreactive side chain, and a polyimide obtained by imidizing this polyimide precursor, react with each other, or the photoreactive side chain of the polymer reacts with the polymerizable compound, thereby increasing the response speed of the resulting liquid crystal display element.

Next, polarizing plates are installed. Specifically, it is preferable to attach a pair of polarizing plates to the surfaces of the two substrates opposite the liquid crystal layer.

The liquid crystal alignment film and liquid crystal display element of the present invention are not limited to the above configuration and manufacturing method as long as the liquid crystal alignment agent of the present invention is used, and may be manufactured by other known methods. The process of obtaining a liquid crystal display element from a liquid crystal alignment agent is disclosed, for example, in paragraphs [0074] on page 17 to [0082] on page 19 of JP 2015-135393 A.

When the polymer has photoreactive side chains, the polymerizable compound is polymerized and the photoreactive side chains are reacted with each other or with the polymerizable compound, thereby more efficiently fixing the alignment of the liquid crystal and producing a liquid crystal display element with excellent response speed.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these. The abbreviations of the compounds and the methods for measuring the respective properties are as follows:

(Diamine)

(Tetracarboxylic acid dianhydride)

(Terminal Modifier)
Boc ₂ O: di-tert-butyl dicarbonate

(Additives)

s-1: 3-glycidoxypropyltriethoxysilane (organic solvent)
NMP: N-methyl-2-pyrrolidone GBL: γ-butyrolactone BCS: Ethylene glycol monobutyl ether BCA: Ethylene glycol monobutyl ether acetate DME: Dipropylene glycol dimethyl ether PB: Propylene glycol monobutyl ether

<Measurement of imidization rate>
20 mg of polyimide powder was placed in an NMR sample tube (NMR sampling tube standard, φ5 (Kusano Scientific Co., Ltd.)), deuterated dimethyl sulfoxide (DMSO-d6, 0.05% TMS (tetramethylsilane) mixture) (0.53 ml) was added, and the mixture was sonicated to completely dissolve. This solution was measured for proton NMR at 500 MHz using an NMR measurement device (JNW-ECA500) (JEOL Datum Co., Ltd.). The imidization rate was calculated by the following formula, using a proton derived from a structure that does not change before and after imidization as a reference proton, and the peak integrated value of this proton and the proton peak integrated value derived from the NH group of the amic acid that appears around 9.5 to 10.0 ppm.
Imidization rate (%)=(1−α·x/y)×100
In the above formula, x is the integrated value of the proton peak derived from the NH group of the amic acid, y is the integrated value of the peak of the reference proton, and α is the ratio of the number of reference protons to one NH group proton of the amic acid in the case of polyamic acid (imidization rate 0%).

[Synthesis of polymer]
<Synthesis Example 1>
In a four-neck flask equipped with a stirrer and a nitrogen inlet tube, 10.3 g (42.5 mmol) of DA-1, 7.8 g (14.0 mmol) of DA-3, and 4.78 g (14.0 mmol) of DA-4 were weighed out, and NMP was added so that the solid content concentration was 15% by mass, and stirred and dissolved while feeding nitrogen. While stirring this diamine solution, 10.2 g (45.5 mmol) of CA-1 was added, and further NMP was added so that the solid content concentration was 18% by mass. After stirring at 40 ° C. for 1 hour, 3.57 g (18.2 mmol) of CA-2 was added at room temperature, and further NMP was added so that the solid content concentration was 18% by mass. This polymerization solution was stirred for 3 hours to obtain a polyamic acid solution (PA-I).
100.0 g of the above-obtained polyamic acid solution (PA-I) was placed in a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and 4.06 g (18.6 mmol) of a terminal modifier, Boc ₂ O, was added. After stirring at 40° C. for 15 hours, a terminal-modified polyamic acid solution (PAboc-I) was obtained.
100.0 g of the above-obtained terminal-modified polyamic acid solution (PAboc-I) was taken in a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and NMP was added so that the solid content concentration was 12 mass%, and the mixture was stirred for 30 minutes. 10.54 g of acetic anhydride and 2.72 g of pyridine were added to the obtained polyamic acid solution, and the mixture was stirred at room temperature for 30 minutes, and then heated and stirred at 55 ° C for 2 hours and 15 minutes to perform chemical imidization. The obtained reaction solution was poured into methanol in an amount 3.5 times the reaction solution mass while stirring, and the precipitate was filtered and then washed three times with methanol. The obtained resin powder was vacuum dried at 80 ° C for 12 hours to obtain a powder of polyimide (SPI1-1). The imidization rate of this polyimide resin powder was 75%. NMP was added to the obtained polyimide (SPI1-1) so that the solid content concentration was 15% by mass, and the mixture was stirred at 70° C. for 15 hours to obtain a solution of polyimide (SPI1-1) having a solid content concentration of 15% by mass.

<Synthesis Example 2>
In a four-neck flask equipped with a stirrer and a nitrogen inlet tube, 4.18 g (10.5 mmol) of DA-2, 2.92 g (5.2 mmol) of DA-3, and 5.63 g (19.3 mmol) of DA-5 were weighed out, and NMP was added so that the solid content concentration was 19% by mass, and stirred and dissolved while feeding nitrogen. While stirring this diamine solution, 4.51 g (22.7 mmol) of CA-5 was added, and NMP was further added so that the solid content concentration was 20% by mass. After stirring at 50 ° C. for 1 hour, 2.31 g (11.8 mmol) of CA-2 was added at room temperature, and NMP was further added so that the solid content concentration was 20% by mass. This polymerization solution was stirred for 3 hours to obtain a polyamic acid solution (PA-II).
50.0 g of the above-obtained polyamic acid solution (PA-II) was placed in a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and 0.30 g (1.37 mmol) of a terminal modifier, Boc ₂ O, was added. After stirring at 40° C. for 15 hours, a terminal-modified polyamic acid solution (PAboc-II) was obtained.
50.0 g of the above-obtained terminal-modified polyamic acid solution (PAboc-II) was taken in a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and NMP was added so that the solid content concentration was 12 mass%, and the mixture was stirred for 30 minutes. 6.40 g of acetic anhydride and 2.12 g of pyridine were added to the obtained polyamic acid solution, and the mixture was stirred at room temperature for 30 minutes, and then heated and stirred at 60 ° C. for 4 hours to perform chemical imidization. The obtained reaction solution was poured into methanol in an amount 3.5 times the mass of the reaction solution while stirring, and the precipitate was filtered and then washed three times with methanol. The obtained resin powder was vacuum dried at 80 ° C. for 12 hours to obtain a powder of polyimide (SPI1-2). The imidization rate of this polyimide resin powder was 95%. NMP was added to the obtained polyimide (SPI1-2) so that the solid content concentration was 15% by mass, and the mixture was stirred at 70° C. for 15 hours to obtain a solution of polyimide (SPI1-2) having a solid content concentration of 15% by mass.

<Synthesis Example 3>
20.2 g (47.9 mmol) of DA-9 and 6.35 g (32.0 mmol) of DA-7 were weighed into a four-neck flask equipped with a stirrer and a nitrogen inlet tube, and NMP was added so that the solid content concentration was 9% by mass, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this diamine solution, 15.3 g (78.0 mmol) of CA-2 was added, and NMP was further added so that the solid content concentration was 12% by mass. This polymerization solution was stirred for 5 hours to obtain a polyamic acid solution (PAA2-1).

<Synthesis Example 4>
In a four-neck flask equipped with a stirrer and a nitrogen inlet tube, 14.3 g (47.9 mmol) of DA-10 and 4.81 g (32.0 mmol) of DA-11 were weighed out, and NMP was added so that the solid content concentration was 15% by mass, and stirred and dissolved while feeding nitrogen. While stirring this diamine solution, 6.67 g (34.0 mmol) of CA-2 was added, and NMP was further added so that the solid content concentration was 15% by mass. After stirring at room temperature for 2 hours, 10.0 g (40.0 mmol) of CA-4 was added, and NMP was further added so that the solid content concentration was 15% by mass. This polymerization solution was stirred at 50 ° C. for 12 hours to obtain a polyamic acid solution (PAA2-2).

<Synthesis Example 5>
In a four-neck flask equipped with a stirrer and a nitrogen inlet tube, 29.3 g (148 mmol) of DA-7, 46.8 g (111 mmol) of DA-9, and 12.0 g (111 mmol) of DA-12 were weighed out, 451 g of NMP and 194 g of GBL were added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this diamine solution under water cooling, 55.1 g (281 mmol) of CA-2 and GBL were added so that the solid content concentration was 14.5% by mass, and the mixture was stirred for 2 hours under water cooling in a nitrogen atmosphere. Further, 16.1 g (74.0 mmol) of CA-3 was added, and GBL was further added so that the solid content concentration was 15%, and the mixture was stirred for 15 hours at 50 ° C. under a nitrogen atmosphere to obtain a polyamic acid solution (PAA2-3) having a solid content concentration of 15% and NMP / GBL = 50 / 50 (mass ratio).

<Synthesis Example 6>
7.45 g (26.0 mmol) of DA-8 was weighed out into a four-neck flask equipped with a stirrer and a nitrogen inlet tube, and 60.2 g of NMP was added so that the solid content concentration was 11% by mass, and the mixture was dissolved by stirring while feeding nitrogen. While stirring this diamine solution under water cooling, 5.16 g (23.6 mmol) of CA-3 and NMP were added so that the solid content concentration was 12%, and the polymerization solution was stirred at 50° C. for 15 hours to obtain a polyamic acid solution (PAA2-4).

<Synthesis Example 7>
7.97g (40.0mmol) of DA-6 was weighed out into a four-neck flask equipped with a stirrer and a nitrogen inlet tube, 55.6g of NMP and 59.1g of GBL were added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this diamine solution under water cooling, 6.37g (32.5mmol) of CA-2 was added, and 31.3g of NMP was further added, and the mixture was stirred for 3 hours under water cooling while feeding nitrogen. Next, 1.98g (10.0mmol) of DA-7 and 13.9g of GBL were added and stirred to dissolve, and then 3.00g (10.0mmol) of CA-6 and 13.9g of GBL were added, and the mixture was stirred for 3 hours under water cooling while feeding nitrogen, to obtain a polyamic acid solution (PAA2-5) having a solid content concentration of 10% and NMP/GBL=50/50 (mass ratio).

<Synthesis Example 8>
In a four-neck flask equipped with a stirrer and a nitrogen inlet tube, 16.4 g (82.5 mmol) of DA-7 and 16.4 g (82.5 mmol) of DA-6 were weighed out, and 240.5 g of NMP was added and stirred while feeding nitrogen to dissolve. While stirring this diamine solution under water cooling, 20.6 g (82.5 mmol) of CA-4 and NMP were added so that the solid content concentration was 15.0 mass%, and stirred at 50 ° C. under a nitrogen atmosphere for 5 hours. Further, 22.4 g (76.2 mmol) of CA-7 was added, and further NMP was added so that the solid content concentration was 15%, and stirred at 50 ° C. under a nitrogen atmosphere for 15 hours to obtain a polyamic acid solution (PAA2-6) having a solid content of 15%.

[Preparation of liquid crystal alignment agent]
Example 1
The solution of polyimide (SPI1-1) obtained in Synthesis Example 1, the polyamic acid solution (PAA2-1) obtained in Synthesis Example 3, and the polyamic acid solution (PAA2-2) obtained in Synthesis Example 4 were diluted with NMP, GBL, BCS, and BCA, and compound c-1 was added so that it was 3 parts by mass relative to 100 parts by mass of all polymers, and further compound s-1 was added so that it was 1 part by mass relative to 100 parts by mass of all polymers and stirred at room temperature. Next, the resulting solution was filtered through a filter having a pore size of 0.5 μm, and the polymer component ratio was (SPI1-1): (PAA2-1): (PAA2-2) = 30: 40: 30 (solid content equivalent mass ratio), the solvent composition ratio was NMP: GBL: BCS: BCA = 30: 45.9: 5: 15 (mass ratio), and the polymer solid content concentration was 4.1 mass%. A liquid crystal alignment agent (1) was obtained. The liquid crystal alignment agent was found to have no abnormalities such as turbidity or precipitation, and was confirmed to be a homogeneous solution.

<Examples 2 to 8, Comparative Examples 1 to 7>
According to the ratio of polymer and solvent shown in Table 1 below, liquid crystal alignment agents (2) to (15) were obtained in the same manner as in Example 1 using the solutions obtained in Synthesis Examples 1 to 8.

[Evaluation of Printing Properties]
The liquid crystal alignment agents (1) to (15) obtained above were filtered through a filter having a pore size of 1.0 μm, and then filled into an inkjet printer (IP-1212NC1180L, manufactured by Ishii Hyoku) and various evaluations were carried out.

1. Evaluation of initial coating properties Coating was performed on a glass substrate on which chromium had been vapor-deposited at a scan speed of 500 mm/sec, a meniscus value of -4500 Pa, and a coating area of 65 mm (perpendicular to the scan direction) x 75 mm (parallel to the scan direction), and the substrate was left at 23°C for 35 seconds. The substrate was then dried on a hot plate at 90°C for 2 minutes, and then baked in a hot air circulating oven at 230°C for 20 minutes to obtain a substrate with a polyimide film having a thickness of 600 Å. Note that the scan pitch during coating was set to a value specific to each liquid crystal alignment agent so that the film thickness was the same.
The obtained film-coated substrate was then visually observed and observed under an optical microscope (Nikon Corporation, ECLIPSE L300ND). If a uniform film was formed, it was evaluated as "good", and if unevenness or streaks were observed, it was evaluated as "poor".

2. Evaluation of ejection stability Standby shots were performed over a long period of time to evaluate leakage, precipitation, and coating properties on the head surface. The standby shot is a process in which the liquid is periodically ejected to prevent nozzle clogging.

(1) Leakage of liquid from the head surface Standby shots were performed for 15 hours with an interval of 1 minute and a discharge time of 3 seconds, and then the head surface was visually observed. The case where there was no leakage of liquid from the nozzles of the head was defined as "good", and the case where liquid was attached to the head surface was defined as "poor".
(2) Coatability Thereafter, a substrate with a polyimide film having a thickness of 600 Å was obtained in the same manner as in the evaluation of the initial coatability described above, and was observed visually and under an optical microscope. The evaluation was defined as "good" if a uniform film was formed, and "poor" if streaks were observed.
(3) Precipitates on the Head Surface Furthermore, the head surface was wiped with a cloth (ASPURE Wiper AS-909, manufactured by AS ONE), and then the cloth surface was observed visually and under an optical microscope. The case where no precipitates were observed was defined as "good", and the case where precipitates were observed was defined as "poor".

The results of the evaluation of each of the liquid crystal aligning agents of Examples 1 to 8 and Comparative Examples 1 to 7 carried out as described above are shown in Table 2 below.

In the evaluation of the initial coatability of the liquid crystal alignment agents of Comparative Examples 2 and 5, scale-like unevenness occurred due to insufficient bonding between the liquids, and the result was "poor." In addition, in the evaluation of the ejection stability of the liquid crystal alignment agents of Comparative Examples 1, 3, 4, and 6, liquid leakage and precipitation were observed on the head after a long standby shot, and streaks along the scanning direction were observed, and the result was "poor." In addition, liquid leakage was observed for the liquid crystal alignment agent of Comparative Example 7, but no precipitation was observed, and no streaks or unevenness were confirmed.
On the other hand, the liquid crystal alignment agents of the Examples did not show any streaks or unevenness either in the initial state or after the long-term standby shot, and no liquid leakage or precipitate was observed on the head surface.

For the liquid crystal alignment agents of Example 3 and Comparative Examples 4, 5, and 6, the polyimide film on the substrate obtained in the above-mentioned evaluation of initial coatability was measured in the vertical and horizontal scan directions. In addition, 65 mm was subtracted from the measured values in the vertical scan direction and 75 mm in the horizontal direction, and the average value was calculated as the wetting spread of the liquid from the coating area. In other words, the smaller this value, the better the dimensional stability. The evaluation results are shown in Table 3 below.

Example 3, like Comparative Examples 4 to 6, had little spreading and good dimensional stability.

In addition, the liquid crystal alignment agents of Examples 1 to 8 made it possible to create liquid crystal display elements without alignment defects using known methods.

Claims (12)

A liquid crystal aligning agent comprising the following (A) and (B):
(A): A polyimide obtained by imidizing a polyimide precursor, which is a reaction product between a diamine component containing at least one diamine selected from the formula [2] and a tetracarboxylic acid component.

In the formula, A ₁ is a single bond, a methylene group, an ester bond, an amide bond, a cyclohexylene group, or an alkylene group having 2 to 20 carbon atoms. However, any -CH ₂ - in the alkylene group may be substituted with an ether group, an ester group, an amide group, a cyclohexylene group, a phenylene group, a urea group, an amino group, or a carbamate group, and any hydrogen atom in the amide group, the urea group, or the amino group may be substituted with a methyl group or a tert-butoxycarbonyl group. _{A 2} is a fluorine atom, or an alkyl group or alkoxy group having 1 to 5 carbon atoms, and any hydrogen atom in the alkyl group or the alkoxy group may be substituted with a fluorine atom, and any carbon atom may be substituted with an amino group protected with a tert-butoxycarbonyl group. A's are each independently an integer of 0 to 4, and when there are multiple A ₂ 's, A ₂ 's may be the same or different. b and c each independently represent an integer of 0 to 2, and when b is 0, c is 1 or 2, and A ₁ is an alkylene group.
(B): An organic solvent containing butyl cellosolve and butyl cellosolve acetate. In the above [2], A ₁ is a single bond, an alkylene group having 2 to 10 carbon atoms (provided that at least one -CH ₂ - of the alkylene group is substituted with an ether group or an ester group), A ₂ is CH ₃ , a is an integer of 0 to 1, b is 1, and c is an integer of 1 to 2. The liquid crystal aligning agent according to claim 1. The liquid crystal aligning agent according to claim 1 or 2, wherein the tetracarboxylic acid component (A) is represented by the following formula [3]:

In the formula, _X1 is any one of the following formulas (B-1) to (B-18).

The liquid crystal alignment agent according to any one of claims 1 to 3, wherein the content of the diamine represented by the above formula [2] is 50 mol% or more per mol of the total diamine components. The liquid crystal aligning agent according to claim 3 , wherein X ₁ in the formula [3] is any one of (B-1), (B-2) and (B-3). The liquid crystal alignment agent according to any one of claims 1 to 5, wherein the content of butyl cellosolve is 5 to 20 mass% relative to the total organic solvents, and the content of butyl cellosolve acetate is 5 to 20 mass% relative to the total organic solvents. The liquid crystal alignment agent according to any one of claims 1 to 6, wherein the organic solvent further contains any one of solvents (C1) selected from N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, N,N-dimethyllactamide, and 1,3-dimethyl-2-imidazolidinone. The liquid crystal alignment agent according to claim 7, wherein the solvent (C1) is contained in an amount of 60 to 90 mass% based on the total organic solvents contained in the liquid crystal alignment agent. The liquid crystal alignment agent according to any one of claims 1 to 8, wherein the organic solvent further comprises any one of solvents (C2) selected from diisobutyl carbinol, propylene glycol monobutyl ether, propylene glycol diacetate, diethylene glycol diethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, 4-hydroxy-4-methyl-2-pentanone, and diisobutyl ketone. The liquid crystal alignment agent according to any one of claims 1 to 9, further comprising a crosslinkable compound and/or a functional silane-containing compound. A liquid crystal alignment film obtained from the liquid crystal alignment agent according to any one of claims 1 to 10. A liquid crystal display element having the liquid crystal alignment film according to claim 11.