JP7469736B2 - 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.

Conventionally, liquid crystal display devices have been widely used as display units for personal computers, smartphones, mobile phones, television receivers, and the like. A liquid crystal display device includes, for example, a liquid crystal layer sandwiched between an element substrate and a color filter substrate, pixel electrodes and a common electrode that apply an electric field to the liquid crystal layer, an alignment film that controls the alignment of the liquid crystal molecules in the liquid crystal layer, and thin film transistors (TFTs) that switch the electric signal supplied to the pixel electrodes. Known methods for driving liquid crystal molecules include vertical electric field methods such as the TN method and the VA method, and horizontal electric field methods such as the IPS method and the FFS (fringe field switching) method.

Currently, the most widely used liquid crystal alignment film in the industry is produced by rubbing the surface of a film made of polyamic acid and/or polyimide formed by imidizing polyamic acid on an electrode substrate in one direction with a cloth such as cotton, nylon, or polyester. The rubbing process is a simple and highly productive industrially useful method. However, as liquid crystal display elements become more powerful, more precise, and larger, various problems have become evident, such as scratches on the surface of the alignment film caused by the rubbing process, dust generation, effects of mechanical force and static electricity, and even non-uniformity within the alignment treatment surface. As an alternative alignment method to the rubbing process, a photoalignment method is known in which liquid crystal alignment ability is imparted by irradiating polarized radiation. As for photoalignment methods, methods using photoisomerization reactions, photocrosslinking reactions, photodecomposition reactions, etc. have been proposed (see Non-Patent Document 1 and Patent Document 1).

The liquid crystal alignment film, which is a component of a liquid crystal display element, is a film for uniformly aligning liquid crystals, but the stability of the liquid crystal alignment is also important. If the alignment stability is low, the liquid crystal will not return to its initial state when driven for a long period of time, which can cause a decrease in contrast and image retention (hereinafter referred to as AC afterimages). Patent Document 2 discloses a specific liquid crystal alignment agent as a method for solving the above problem.

Japanese Patent Application Laid-Open No. 9-297313 International Publication No. 2015/050135

"Liquid Crystal Photo-Alignment Film" Kidowaki, Ichimura, Functional Materials, November 1997, Vol. 17, No. 11, pp. 13-22

However, in actual LCD elements, the twist angle varies slightly within the plane of the LCD element due to manufacturing variations, etc. This in-plane variation causes the brightness of the LCD element when displaying black to vary within the plane.

The present invention has been made in consideration of the above circumstances, and one of its objectives is to provide a liquid crystal alignment agent that can provide a liquid crystal display element with improved contrast and suppressed brightness variations within the plane during black display.

After extensive research, the inventors discovered that the above problems could be solved by using a liquid crystal alignment agent containing a specific component, and thus completed the present invention. Specifically, the gist of the invention is as follows:

（式中、Ｒ_１からＲ_４はそれぞれ独立して、水素原子、ハロゲン原子、炭素数１～６のアルキル基、炭素数２～６のアルケニル基、炭素数２～６のアルキニル基、フッ素原子を含有する炭素数１～６の１価の有機基、又はフェニル基を表し、Ｒ_１からＲ_４の少なくとも一つは上記定義中の水素原子以外の基を表す。Ｒ、Ｚはそれぞれ独立して、水素原子又は炭素数１～６のアルキル基を表す。Ｙ_１は下記式（Ｔ）で表される２価の有機基を表す。）

（Ｑ_１は、三重結合を有する炭素数２～１８の有機基を表す。＊は結合手を表す。）

（式中、Ｒ_１からＲ_４、Ｒ、Ｚは、前記式（１）と同義である。Ｙ_２は下記式（Ｏ）で表される２価の有機基を表す。）

（Ａｒは、ベンゼン環、ビフェニル、又はナフタレン環を表し、Ａｒの少なくとも一つはナフタレン環を表す。２つのＡｒは同一でも異なってもよく、環状の任意の水素原子は１価の有機基で置き換えられてもよい。Ｑ_２は－（ＣＨ_２）_ｎ－（ｎは２～１８の整数である。）、又は前記－（ＣＨ_２）_ｎ－の－ＣＨ_２－の少なくとも一部を－Ｏ－、－Ｃ（＝Ｏ）－又は－Ｏ－Ｃ（＝Ｏ）－のいずれかで置き換えた基を表す。＊は結合手を表す。） The liquid crystal aligning agent of the present invention is characterized in that it contains at least one polymer (A) selected from the group consisting of polyimide precursors having a repeating unit (a1) represented by the following formula (1) and a repeating unit (a2) represented by the following formula (2), and imidized polymers thereof:

(In the formula, _R1 to _R4 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom, or a phenyl group, and at least one of _R1 to _R4 represents a group other than a hydrogen atom as defined above. R and Z each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. _Y1 represents a divalent organic group represented by the following formula (T).)

( _Q1 represents an organic group having 2 to 18 carbon atoms and a triple bond. * represents a bond.)

(In the formula, _R1 to _R4 , R, and Z are the same as those in formula (1). _Y2 represents a divalent organic group represented by the following formula (O).)

(Ar represents a benzene ring, biphenyl, or naphthalene ring, and at least one of Ar represents a naphthalene ring. Two Ars may be the same or different, and any hydrogen atom on the ring may be replaced by a monovalent organic group. Q ₂ represents -(CH ₂ ) _n - (n is an integer from 2 to 18), or a group in which at least a portion of the -CH ₂ - of the -(CH ₂ ) _n - is replaced by any of -O-, -C(═O)-, or -O-C(═O)-. * represents a bond.)

The liquid crystal alignment agent of the present invention contains at least one polymer (A) selected from the group consisting of polyimide precursors having repeating units (a1) represented by the above formula (1) and repeating units (a2) represented by the above formula (2) and imidized polymers thereof, thereby suppressing the variation in brightness within the plane during black display, and achieving the effect of obtaining a liquid crystal display element with improved contrast.

The liquid crystal alignment agent of the present invention will be explained.

<Polymer (A)>
The liquid crystal aligning agent of the present invention contains at least one polymer (A) selected from the group consisting of a polyimide precursor having a repeating unit (a1) represented by the following formula (1) and a repeating unit (a2) represented by the following formula (2) and an imidized polymer thereof:

<Repeating Unit (a1)>
The repeating unit (a1) of the present invention is a repeating unit represented by the following formula (1).

式（１）中、Ｒ_１からＲ_４はそれぞれ独立して、水素原子、ハロゲン原子、炭素数１～６のアルキル基、炭素数２～６のアルケニル基、炭素数２～６のアルキニル基、フッ素原子を含有する炭素数１～６の１価の有機基、又はフェニル基を表し、Ｒ_１からＲ_４の少なくとも一つは上記定義中の水素原子以外の基を表す。Ｒ、Ｚはそれぞれ独立して、水素原子又は炭素数１～６のアルキル基を表す。Ｙ_１は下記式（Ｔ）で表される２価の有機基を表す。

ここで、Ｑ_１は、三重結合を有する炭素数２～１８の有機基を表す。＊は結合手を表す。

In formula (1), R ₁ to R ₄ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom, or a phenyl group, and at least one of R ₁ to R ₄ represents a group other than a hydrogen atom as defined above. R and Z each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Y ₁ represents a divalent organic group represented by the following formula (T):

Here, _Q1 represents an organic group having a triple bond and having 2 to 18 carbon atoms. * represents a bond.

The divalent organic group represented by _Q1 includes -C≡C-, a group (t1) in which a portion of the -CH ₂ - of -(CH ₂ ) _n - (n is an integer of 2 to 18) is replaced with -C≡C-, or a group in which at least a portion of the -CH ₂ - of the group (t1) is replaced with any one of -O-, -C(═O)-, -O-C(═O)- or a phenylene group.

Here, the divalent organic group represented by formula (T) is, for example, a divalent organic group represented by the following formulas (t-1) to (t-3), but is not limited thereto.

式（２）中、Ｒ_１からＲ_４、Ｒ、Ｚは、前記式（１）と同義である。Ｙ_２は下記式（Ｏ）で表される２価の有機基を表す。

<Repeating unit (a2)>
The repeating unit (a2) of the present invention is a repeating unit represented by the following formula (2).

In formula (2), _R1 to _R4 , R and Z are the same as those in formula (1), _{and Y2} represents a divalent organic group represented by the following formula (O).

Here, Ar represents a benzene ring, biphenyl, or naphthalene ring, and at least one of Ar represents a naphthalene ring. Two Ar's may be the same or different, and any hydrogen atom in the ring may be replaced with a monovalent organic group. _Q2 represents -( _CH2 ) _n- (n is an integer of 2 to 18), or a group in which at least a portion of the _-CH2- in the -( _CH2 ) _n- is replaced with any of -O-, -C(=O)-, or -O-C(=O)-. * represents a bond.

Here, examples of the divalent organic group represented by formula (O) include, but are not limited to, divalent organic groups represented by the following formulas (o-1) to (o-6).

ここで、式（３）中、Ｘ_３は４価の有機基を表し、Ｙ_３は下記式（３ｄ）で表される２価の有機基を表す。Ｒ、Ｚは、前記式（１）と同義である。

ここで、Ａｒ_３は、ベンゼン環又はビフェニルを表し、２つのＡｒ_３は同一でも異なってもよく、環状の任意の水素原子は１価の有機基で置き換えられてもよい。Ｑ_３は－（ＣＨ_２）_ｎ－（ｎは２～１８の整数である。）、又は前記－（ＣＨ_２）_ｎ－の－ＣＨ_２－の少なくとも一部を－Ｏ－、－Ｃ（＝Ｏ）－又は－Ｏ－Ｃ（＝Ｏ）－のいずれかで置き換えた基を表す。＊は結合手を表す。 <Repeating unit (a3)>
The polymer (A) may be at least one selected from the group consisting of polyimide precursors having a repeating unit (a3) represented by the following formula (3) in addition to the repeating units (a1) and (a2) and imidized polymers thereof:

In the formula (3), _X3 represents a tetravalent organic group, and _Y3 represents a divalent organic group represented by the following formula (3d): R and Z are the same as those in the formula (1).

Here, Ar ₃ represents a benzene ring or biphenyl, two Ar ₃ may be the same or different, and any hydrogen atom in the ring may be replaced with a monovalent organic group. Q ₃ represents -(CH ₂ ) _n - (n is an integer of 2 to 18), or a group in which at least a part of the -CH ₂ - of the -(CH ₂ ) _n - is replaced with any of -O-, -C(═O)-, or -O-C(═O)-. * represents a bond.

Here, examples of the divalent organic group represented by formula (3d) include, but are not limited to, divalent organic groups represented by the following formulas (3d-1) to (3d-8).

The polymer (A) may be at least one selected from the group consisting of polyimide precursors having repeating units (a1) and (a2) as well as repeating units (a4) represented by the following formula (4) and imidized polymers thereof.

式（４）中、Ｒ、Ｚは、前記式（１）と同義である。Ｘ_４は４価の有機基を表し、Ｙ_４は基「－Ｎ（Ｄ）－（Ｄはカルバメート系保護基を表す。）」を分子内に有する炭素数６～３０の２価の有機基を表す。

In formula (4), R and Z are the same as those in formula (1), _X4 represents a tetravalent organic group, and _Y4 represents a divalent organic group having 6 to 30 carbon atoms and containing the group "-N(D)- (D represents a carbamate protecting group)" in the molecule.

Specific examples of the divalent organic group having 6 to 30 carbon atoms and having a group "-N(D)- (D represents a carbamate protecting group)" in the molecule in _Y4 include a divalent organic group having a partial structure represented by the following formula (4-1) or a divalent organic group represented by the following formula (4-2).

In the formula, Q ₅ represents a single bond, -(CH ₂ ) _n - (n is an integer of 1 to 20), or a group in which any -CH ₂ - in -(CH ₂ ) _n - is replaced by -O-, -COO-, -OCO-, -NQ ₉ -, -NQ ₉ CO-, -CONQ ₉ -, -NQ ₉ CONQ ₁₀ -, -NQ ₉ COO- or -OCOO-, and Q ₉ and Q ₁₀ each independently represent a hydrogen atom or a monovalent organic group;
Q ₆ and Q ₇ each independently represent -H, -NHD, -N(D) ₂ , a group having -NHD, or a group having -N(D) ₂ . Q ₈ represents -NHD, -N(D) ₂ , a group having -NHD, or a group having -N(D) ₂ . D represents a carbamate-based protecting group, and examples of the carbamate-based protecting group include a tert-butoxycarbonyl group and a 9-fluorenylmethoxycarbonyl group. However, at least one of Q ₅ , Q ₆ , and Q ₇ has a carbamate-based protecting group in the group. * represents a bond. Specific examples of the monovalent organic group in Q ₉ and Q ₁₀ include an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, an alkyl group having 1 to 6 carbon atoms containing a fluorine atom, the carbamate-based protecting group, and an alkoxyalkyl group having 1 to 6 carbon atoms.

（Ｂｏｃは、ｔｅｒｔ－ブトキシカルボニル基を表す。＊は結合手を表す。） Here, examples of _Y4 include structures represented by the following formulae (Y4-1) to (Y4-4), but are not limited thereto.

(Boc represents a tert-butoxycarbonyl group. * represents a bond.)

式（５）中、Ｒ、Ｚは、前記式（１）と同義である。Ｘ_５は４価の有機基を表し、Ｙ_５は２価の有機基を表す。但し、Ｙ_５は前記式（３ｄ）で表される２価の有機基、又は基「－Ｎ（Ｄ）－（Ｄはカルバメート系保護基を表す。）」を分子内に有する炭素数６～３０の２価の有機基以外の構造を表し、Ｘ_５が下記式（ｇ）で表される４価の有機基と同義である場合は、Ｙ_５は前記式（Ｔ）で表される２価の有機基又は前記式（Ｏ）で表される２価の有機基以外の構造を表す。

（Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４は、上記式（１）のＲ_１、Ｒ_２、Ｒ_３、Ｒ_４と同義である。） The polymer (A) may be at least one selected from the group consisting of polyimide precursors having a repeating unit (a5) represented by the following formula (5) in addition to the repeating units (a1) and (a2) and imidized polymers thereof:

In formula (5), R and Z are the same as those in formula (1). _X5 represents a tetravalent organic group, and _Y5 represents a divalent organic group. However, when _Y5 represents a structure other than the divalent organic group represented by formula (3d) or the divalent organic group having 6 to 30 carbon atoms and having a group "-N(D)- (D represents a carbamate-based protecting group)" in the molecule, and _X5 is the same as the tetravalent organic group represented by formula (g) below, _Y5 represents a structure other than the divalent organic group represented by formula (T) or the divalent organic group represented by formula (O).

(R ₁ , R ₂ , R ₃ , and R ₄ are the same as R ₁ , R ₂ , R ₃ , and R ₄ in the above formula (1).)

In the formula (5), specific examples of _Y5 include p-phenylenediamine, 2,3,5,6-tetramethyl-p-phenylenediamine, 2,5-dimethyl-p-phenylenediamine, m-phenylenediamine, 2,4-dimethyl-m-phenylenediamine, 2,5-diaminotoluene, 2,6-diaminotoluene, 4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-difluoro-4,4'-biphenyl, 3,3'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,4'-diaminobiphenyl, 3,3'-diaminobiphenyl, 2,2'-diaminobiphenyl, 2,3'-diaminobiphenyl, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenyl. Examples of the divalent organic group include divalent organic groups obtained by removing two amino groups from aromatic diamines such as 4,4'-diaminomethane, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 4,4'-diaminobenzanilide, 4,4'-diaminoazobenzene, 1,5-diaminonaphthalene, 1,6-diaminonaphthalene, 1,7-diaminonaphthalene, 2,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,7-diaminonaphthalene, 2,8-diaminonaphthalene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, and 1,4-bis(4-aminobenzyl)benzene, as well as divalent organic groups exemplified by _Y7 described later.

式（Ｘ１－１）～（Ｘ１－４）において、Ｒ^３～Ｒ^２３は、それぞれ独立して、水素原子、ハロゲン原子、炭素数１～６のアルキル基、炭素数２～６のアルケニル基、炭素数２～６のアルキニル基、フッ素原子を含有する炭素数１～６の１価の有機基、又はフェニル基である。液晶配向性の点から、Ｒ^３～Ｒ^２３は、水素原子、ハロゲン原子、メチル基、又はエチル基が好ましく、水素原子、又はメチル基がより好ましい。 In formula (3), formula (4) and formula (5), the structure of the tetravalent organic group of _X3 , _X4 and _X5 is not particularly limited, and any structure can be independently selected. Preferred specific examples include the following formulae (X1-1) to (X1-44).

In formulae (X1-1) to (X1-4), R ³ to R ²³ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom, or a phenyl group. From the viewpoint of liquid crystal alignment, R ³ to R ²³ are preferably a hydrogen atom, a halogen atom, a methyl group, or an ethyl group, and more preferably a hydrogen atom or a methyl group.

Specific examples of formula (X1-1) include the following formulas (X1-1-1) to (X1-1-6). From the viewpoints of liquid crystal alignment and photoreaction sensitivity, (X1-1-1) to (X1-1-2) are more preferred, with (X1-1-2) being particularly preferred.

From the viewpoint of obtaining the effects of the present invention, polymer (A) preferably contains repeating units (a1) in an amount of 1 to 40 mol % of all repeating units, more preferably 1 to 35 mol %, and even more preferably 1 to 30 mol %.

From the viewpoint of obtaining the effects of the present invention, the sum of the repeating units (a1) and (a2) in the polymer (A) is preferably 5 mol % or more, and more preferably 10 mol % or more, of the total repeating units.

From the viewpoint of obtaining the effects of the present invention, polymer (A) preferably contains 1 to 95 mol % of repeating units (a3) based on the total repeating units, more preferably 1 to 90 mol %, and even more preferably 5 to 90 mol %. In this case, the upper limit of the total of repeating units (a1) and repeating units (a2) is preferably 99 mol % or less, more preferably 95 mol % or less.

From the viewpoint of obtaining the effects of the present invention, polymer (A) preferably contains 1 to 40 mol % of repeating units (a4) based on the total repeating units, more preferably 1 to 30 mol %, and even more preferably 1 to 25 mol %.

（Ｘ_７は４価の有機基であり、Ｙ_７は、２価の有機基である。Ｚ_７１、Ｚ_７２は、それぞれ独立して、水素原子、置換基を有してもよい炭素数１～１０のアルキル基、置換基を有してもよい炭素数２～１０のアルケニル基、置換基を有してもよい炭素数２～１０のアルキニル基、ｔｅｒｔ－ブトキシカルボニル基、又は９－フルオレニルメトキシカルボニル基を表す。Ｒ_７は水素原子、又は炭素数１～４のアルキル基を表す。） <Polymer (B)>
The liquid crystal aligning agent of the present invention may contain a polymer (B) having a repeating unit represented by the following formula (7) from the viewpoint of reducing afterimages caused by residual DC.

( _X7 is a tetravalent organic group, and _Y7 is a divalent organic group. _Z71 and _Z72 each independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms which may have a substituent, an alkenyl group having 2 to 10 carbon atoms which may have a substituent, an alkynyl group having 2 to 10 carbon atoms which may have a substituent, a tert-butoxycarbonyl group, or a 9-fluorenylmethoxycarbonyl group. _R7 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

（上記式（ｘ－１）～（ｘ－１３）中、Ｒ^１～Ｒ^４は、それぞれ独立して、水素原子、ハロゲン原子、炭素数１～６のアルキル基、炭素数２～６のアルケニル基、炭素数２～６のアルキニル基、フッ素原子を有する炭素数１～６の１価の有機基又はフェニル基を表す。Ｒ^５及びＲ^６は、それぞれ独立して、水素原子又はメチル基を表す。＊は結合手を表す。） Examples of the tetravalent organic group in formula _X7 include a tetravalent organic group derived from an aliphatic tetracarboxylic dianhydride, a tetravalent organic group derived from an alicyclic tetracarboxylic dianhydride, a tetravalent organic group derived from an aromatic tetracarboxylic dianhydride, etc. Specific examples of the tetravalent organic group derived from an aliphatic tetracarboxylic dianhydride and the tetravalent organic group derived from an alicyclic tetracarboxylic dianhydride include structures selected from the following formulae (x-1) to (x-13).

(In the above formulas (x-1) to (x-13), R ¹ to R ⁴ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms and a fluorine atom, or a phenyl group. R ⁵ and R ⁶ each independently represent a hydrogen atom or a methyl group. * represents a bond.)

上記式（ｘ１－１）～（ｘ１－６）において、＊１は一方の酸無水物基に結合する結合手を表し、また、＊２は他方の酸無水物基に結合する結合手を表す。 The above formula (x-1) is preferably one selected from the group consisting of the following formulas (x1-1) to (x1-6).

In the above formulae (x1-1) to (x1-6), *1 represents a bond bonded to one acid anhydride group, and *2 represents a bond bonded to the other acid anhydride group.

（ｘ及びｙは、それぞれ独立に、単結合、エーテル、カルボニル、エステル、炭素数１～５のアルカンジイル基、１，４－フェニレン、スルホニル又はアミド基である。ｊ及びｋは、０又は１の整数である。＊は結合手を表す。）

The aromatic tetracarboxylic acid dianhydride is an acid dianhydride obtained by intramolecular dehydration of a carboxyl group bonded to an aromatic ring such as a benzene ring or a naphthalene ring. Specific examples include tetravalent organic groups represented by any one of the following formulae (X3-1) to (X3-2) and tetravalent organic groups represented by the following formulae (Xr-1) to (Xr-7).

(x and y each independently represent a single bond, an ether, a carbonyl, an ester, an alkanediyl group having 1 to 5 carbon atoms, 1,4-phenylene, a sulfonyl, or an amide group. j and k each represent an integer of 0 or 1. * represents a bond.)

The tetravalent organic group represented by the formula (X3-1) or (X3-2) may have a structure represented by any one of the following formulas (X3-3) to (X3-19).

（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、ｍ^３及びｍ^４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レン基を示し、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。）

（Ｘ^ｖ１～Ｘ^ｖ４、Ｘ^ｐ１～Ｘ^ｐ２は、それぞれ独立に、－（ＣＨ_２）_ａ－（ａは１～１５の整数である。－ＣＯＮＨ－、－ＮＨＣＯ－、－ＣＯＮ（ＣＨ_３）－、－ＮＨ－、－Ｏ－、－ＣＨ_２Ｏ－、－ＣＨ_２ＯＣＯ－、－ＣＯＯ－、又は－ＯＣＯ－を表し、Ｘ^ｖ５は－Ｏ－、－ＣＨ_２Ｏ－、－ＣＨ_２ＯＣＯ－、－ＣＯＯ－、又は－ＯＣＯ－を表す。Ｘａは、単結合、－Ｏ－、－ＮＨ－、－Ｏ－（ＣＨ_２）_ｍ－Ｏ－（ｍは１～６の整数を表す。）を表し、Ｒ^ｖ１～Ｒ^ｖ４、Ｒ^１ａ～Ｒ^１ｂは、それぞれ独立に、炭素数１～２０のアルキル基、炭素数１～２０のアルコキシ基又は炭素数２～２０のアルコキシアルキル基を表す。）

The divalent organic group in the formula _Y7 includes a diamine having at least one nitrogen-containing structure (hereinafter also referred to as a nitrogen-containing structure) selected from the group consisting of a nitrogen-containing heterocycle, a secondary amino group, and a tertiary amino group, 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol, 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid, 3,5-diaminobenzoic acid, diamines represented by the following formulae (3b-1) to (3b-4): diamines having a carboxyl group such as amine compounds, 4-(2-(methylamino)ethyl)aniline, 4-(2-aminoethyl)aniline, 4,4'-diaminodiphenylmethane, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenylether, 4,4'-diaminobenzanilide, 4,4'-diaminoazobenzene, 1-(4-aminophenyl)-1,3,3-trimethyl-1H-indan-5-amine, 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl-1H-indene- 6-amine, diamines having a urea bond such as 1,3-bis(4-aminophenethyl)urea, diamines having a photopolymerizable group at the end such as 2-(2,4-diaminophenoxy)ethyl methacrylate, 2,4-diamino-N,N-diallylaniline, cholestanyloxy-3,5-diaminobenzene, cholestanyloxy-3,5-diaminobenzene, cholestanyloxy-2,4-diaminobenzene, cholestanyl 3,5-diaminobenzoate, cholestanyl 3,5-diaminobenzoate, lanosta 3,5-diaminobenzoate diamines having a steroid skeleton such as 3,6-bis(4-aminobenzoyloxy)cholestane, diamines represented by the following formulas (V-1) to (V-6), diamines having a siloxane bond such as 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, diamines having an oxazoline structure such as the following formulas (Ox-1) to (Ox-2), divalent organic groups obtained by removing two amino groups from diamines, and groups represented by any of the formulas (Y-1) to (Y-167) described in WO 2018/117239.

( ^A1 represents a single bond, _-CH2- , _-C2H4- , -C( _CH3 ) _2- , _{-CF2- ,} -C( _CF3 ) _2- , -O-, -CO-, -NH-, -N( _CH3 )-, -CONH-, -NHCO-, -CH2O-, _-OCH2- , -COO-, -OCO-, -CON( _CH3 )- or N( _CH3 )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.

(X ^v1 to X ^v4 and X ^p1 to X ^p2 each independently represent -(CH ₂ ) _a - (a is an integer of 1 to 15), -CONH-, -NHCO-, -CON(CH ₃ )-, -NH-, -O-, -CH ₂ O- _, -CH 2 OCO-, -COO-, or -OCO-; X ^v5 represents -O-, -CH ₂ O-, -CH ₂ OCO-, -COO-, or -OCO-; Xa represents a single bond, -O-, -NH-, or -O-(CH ₂ ) _m -O- (m is an integer of 1 to 6); R ^v1 to R ^v4 and R ^1a to R Each of ^1b 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.

Examples of the nitrogen-containing heterocycle include pyrrole, imidazole, pyrazole, triazole, pyridine, pyrimidine, pyridazine, pyrazine, indole, benzimidazole, purine, quinoline, isoquinoline, naphthyridine, quinoxaline, phthalazine, triazine, carbazole, acridine, piperidine, piperazine, pyrrolidine, and hexamethyleneimine. Among these, pyridine, pyrimidine, pyrazine, piperidine, piperazine, quinoline, carbazole, and acridine are preferred.

上記式（ｎ）において、Ｒは、水素原子又は炭素数１～１０の１価の炭化水素基を表す。「＊」は、炭化水素基に結合する結合手を表す。 The secondary amino group and tertiary amino group that the diamine having a nitrogen-containing structure may have are represented, for example, by the following formula (n).

In the above formula (n), R represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. "*" represents a bond bonded to the hydrocarbon group.

Examples of the monovalent hydrocarbon group of the above formula R include alkyl groups such as methyl, ethyl, and propyl; cycloalkyl groups such as cyclohexyl; and aryl groups such as phenyl and methylphenyl. R is preferably a hydrogen atom or a methyl group.

Specific examples of diamines having a nitrogen-containing structure include 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-diaminoacridine, N-ethyl-3,6-diaminocarbazole, N-phenyl-3,6-diaminocarbazole, N,N'-bis(4-aminophenyl)-benzidine, N,N'-bis(4-aminophenyl)-N,N'-dimethylbenzidine, 4,4'-diaminodiphenylamine, N,N-bis(4-aminophenyl)-methylamine, and compounds represented by the following formulae (z-1) to (z-18).

From the viewpoint of reducing the residual image caused by residual DC, the polymer (B) is preferably a polymer containing a repeating unit in which _Y7 is a divalent organic group (collectively referred to as a specific divalent organic group) selected from the group consisting of diamines having a nitrogen-containing structure, 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol, 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid, 3,5-diaminobenzoic acid, diamines having a carboxyl group such as the diamine compounds represented by the formulas (3b-1) to (3b-4), or diamines having a urea bond, from which two amino groups have been removed.

From the viewpoint of reducing afterimages derived from residual DC, the polymer (B) may contain repeating units in which _Y7 is the specific divalent organic group in an amount of 1 mol % or more, or 5 mol % or more, of all repeating units contained in the polymer (B).

From the viewpoint of minimizing afterimages caused by residual DC, the content ratio of polymer (A) to polymer (B) may be 10/90 to 90/10 in terms of the mass ratio of [polymer (A)]/[polymer (B)], or may be 20/80 to 90/10, or may be 20/80 to 80/20.

<Methods of producing polyamic acid, polyamic acid ester, and polyimide>
The polyimide precursors, ie, polyamic acid ester, polyamic acid and polyimide, used in the present invention can be synthesized by known methods such as those described in WO 2013/157586.

<Polymer solution viscosity and molecular weight>
The polyamic acid, polyamic acid ester, and polyimide used in the present invention preferably have a solution viscosity of, for example, 10 to 1000 mPa·s when made into a solution of 10 to 15% by weight from the viewpoint of workability, but are not particularly limited thereto. The solution viscosity (mPa·s) of the above polymer is a value measured at 25° C. using an E-type rotational viscometer for a polymer solution of 10 to 15% by weight prepared using a good solvent for the polymer (e.g., γ-butyrolactone, N-methyl-2-pyrrolidone, etc.).

The polystyrene-equivalent weight average molecular weight (Mw) of the above polyamic acid, polyamic acid ester, and polyimide measured by gel permeation chromatography (GPC) is preferably 1,000 to 500,000, and more preferably 2,000 to 300,000. The molecular weight distribution (Mw/Mn), expressed as the ratio of Mw to the polystyrene-equivalent number average molecular weight (Mn) measured by GPC, is preferably 15 or less, and more preferably 10 or less. By having the molecular weight within this range, good alignment and stability of the liquid crystal display element can be ensured.

<Liquid crystal alignment agent>
The liquid crystal aligning agent of the present invention contains a polymer (A) and, if necessary, a polymer (B). The liquid crystal aligning agent of the present invention may contain other polymers in addition to the polymer (A) and the polymer (B). Examples of the other polymers include polyesters, polyamides, polyureas, polyorganosiloxanes, cellulose derivatives, polyacetals, polystyrene or derivatives thereof, poly(styrene-phenylmaleimide) derivatives, and poly(meth)acrylates.

The liquid crystal alignment agent is used to prepare a liquid crystal alignment film, and takes the form of a coating liquid from the viewpoint of forming a uniform thin film. The liquid crystal alignment agent of the present invention is also preferably a coating liquid containing the above-mentioned polymer component and an organic solvent. 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. From the viewpoint of forming a uniform and defect-free coating film, 1% by mass or more is preferable, and from the viewpoint of storage stability of the solution, 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 is not particularly limited as long as the polymer component is dissolved uniformly. Specific examples include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethylsulfoxide, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide (collectively referred to as "good solvents"). Among these, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, or γ-butyrolactone is preferred. The content of the good solvent is preferably 20 to 99% by mass, more preferably 20 to 90% by mass, and particularly preferably 30 to 80% by mass, of the total solvent contained in the liquid crystal alignment agent.

The organic solvent contained in the liquid crystal alignment agent is preferably a mixed solvent that uses, in addition to the above-mentioned solvent, a solvent (also called a poor solvent) that improves the coatability when applying the liquid crystal alignment agent and the surface smoothness of the coating film. Specific examples of the organic solvent to be used in combination are listed below, but are not limited to these.

For example, 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 acetate, 1-methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene glycol monoacetate, ethylene glycol diacetate, propylene carbonate, ethylene 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, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monobutyl ether acetate, 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), and the like.

Among these, 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, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, or diisobutyl ketone are preferred.

Preferred solvent combinations of good and poor solvents include N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone and ethylene glycol monobutyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone and propylene glycol monobutyl ether, N-ethyl-2-pyrrolidone and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone and diethylene glycol diethyl ether, and N-methyl-2-pyrrolidone and γ-butyrolactone. Examples of the poor solvent include 1 to 80% by mass of the entire solvent contained in the liquid crystal alignment agent, more preferably 10 to 80% by mass, and particularly preferably 20 to 70% by mass. The type and content of the poor solvent are appropriately selected depending on the coating device, coating conditions, and coating environment of the liquid crystal alignment agent.

The liquid crystal alignment agent of the present invention may additionally contain components other than the polymer component and the organic solvent (hereinafter also referred to as additive components). Such additive components include adhesion assistants for improving the adhesion between the liquid crystal alignment film and the substrate or between the liquid crystal alignment film and the sealant, compounds for increasing the strength of the liquid crystal alignment film (hereinafter also referred to as cross-linking compounds), dielectrics and conductive substances for adjusting the dielectric constant and electrical resistance of the liquid crystal alignment film, etc.

（Ｒ_１は、水素原子、炭素数１～３のアルキル基又は「＊－ＣＨ_２－ＯＨ」であり、Ｒ_２及びＲ_３は、それぞれ独立に水素原子、炭素数１～３のアルキル基又は「＊－ＣＨ_２－ＯＨ」である。＊は結合手であることを示す。Ａは芳香環を有する（ｍ＋ｎ）価の有機基を表す。ｍは１～６の整数を表し、ｎは０～４の整数を表す。） From the viewpoint of exhibiting good resistance to AC afterimages and highly improving film strength, the crosslinkable compound may be a compound having 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 group represented by the following formula (d), or a compound selected from compounds represented by the following formula (e) (hereinafter these may be collectively referred to as compound (C)).

( _R1 is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or "* _-CH2 -OH", _R2 and _R3 are each independently a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or "* _-CH2 -OH". * indicates a bond. A represents an (m+n)-valent organic group having an aromatic ring. m represents an integer of 1 to 6, and n represents an integer of 0 to 4.)

Specific examples of the compound having an oxiranyl group include compounds having two or more oxiranyl groups, such as the compounds described in paragraph [0037] of JP-A-10-338880 and compounds having a triazine ring as a skeleton described in WO 2017/170483. Among these, compounds containing nitrogen atoms, such as N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-p-phenylenediamine, and compounds represented by the following formulas (r-1) to (r-3), may be used.

Specific examples of compounds having an oxetanyl group include compounds having two or more oxetanyl groups, such as those described in paragraphs [0170] to [0175] of WO 2011/132751.

Specific examples of the compound having a protected isocyanate group include the compound having two or more protected isocyanate groups described in paragraphs [0046] to [0047] of JP 2014-224978 A, and the compound having three or more protected isocyanate groups described in paragraphs [0119] to [0120] of WO 2015/141598 A. Also includes compounds represented by the following formulae (bi-1) to (bi-3).

Specific examples of compounds having a protected isothiocyanate group include compounds having two or more protected isothiocyanate groups, as described in JP 2016-200798 A.

Specific examples of compounds having a group containing an oxazoline ring structure include compounds containing two or more oxazoline structures, as described in paragraph [0115] of JP 2007-286597 A.

Specific examples of compounds having a group containing a Meldrum's acid structure include compounds having two or more Meldrum's acid structures described in WO 2012/091088.

Specific examples of compounds having a cyclocarbonate group include the compounds described in WO 2011/155577.

Examples of the alkyl group having 1 to 3 carbon atoms for R ₁ , R ₂ and R ₃ in the group represented by formula (d) include a methyl group, an ethyl group and a propyl group.

Specific examples of the compound having a group represented by formula (d) include compounds having two or more groups represented by formula (d) described in WO 2015/072554 and paragraph [0058] of JP 2016-118753 A, and compounds described in JP 2016-200798 A. Also includes compounds represented by the following formulae (hd-1) to (hd-8).

Examples of the (m+n)-valent organic group having an aromatic ring in A of the formula (e) include an (m+n)-valent aromatic hydrocarbon group having 5 to 30 carbon atoms, an (m+n)-valent organic group to which an aromatic hydrocarbon group having 5 to 30 carbon atoms is bonded directly or via a linking group, and an (m+n)-valent group having an aromatic heterocycle. Examples of the aromatic hydrocarbon include benzene and naphthalene. Examples of the aromatic heterocycle include a pyrrole ring, an imidazole ring, a pyrazole ring, a pyridine ring, a pyrimidine ring, a quinoline ring, an isoquinoline ring, a carbazole ring, a pyridazine ring, a pyrazine ring, a benzimidazole ring, an indole ring, a quinoxaline ring, and an acridine ring. Examples of the linking group include an alkylene group having 1 to 10 carbon atoms, a group obtained by removing one hydrogen atom from the alkylene group, and a divalent or trivalent cyclohexane ring. Any hydrogen atom in the alkylene group may be substituted with an organic group such as a fluorine atom or a trifluoromethyl group. Specific examples include the compounds described in WO 2010/074269 and the compounds represented by the following formulas (e-1) to (e-10).

The above compounds are examples of crosslinkable compounds, and are not limited thereto. For example, components other than those described above disclosed on pages 53 [0105] to 55 [0116] of WO 2015/060357 may be mentioned. In addition, two or more types of crosslinkable compounds may be combined.

The content of the crosslinkable compound in the liquid crystal aligning agent of the present invention is preferably 0.5 to 20 parts by mass per 100 parts by mass of the polymer component contained in the liquid crystal aligning agent, and more preferably 1 to 15 parts by mass from the viewpoint of proceeding with the crosslinking reaction and exhibiting good resistance to AC afterimages.

Examples of the adhesion aid 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, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, and N-ethoxycarbonyl-3-aminopropyltrimethoxysilane. N-trimethoxysilylpropyltriethylenetriamine, 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-aminopropyltriethoxysilane Aminopropyltrimethoxysilane, N-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 Examples of silane coupling agents include silane coupling agents such as xysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-isocyanatepropyltriethoxysilane. When using a silane coupling agent, from the viewpoint of exhibiting good resistance to AC afterimages, it is preferable that the amount of the silane coupling agent is 0.1 to 30 parts by mass, and more preferably 0.1 to 20 parts by mass, per 100 parts by mass of the polymer component contained in the liquid crystal alignment agent.

<Method of manufacturing liquid crystal alignment film>
The method for producing a liquid crystal alignment film using the liquid crystal alignment agent of the present invention is characterized by sequentially carrying out the steps of applying the above-mentioned liquid crystal alignment agent onto a substrate (step (1)), baking the applied liquid crystal alignment agent (step (2)), irradiating the film obtained in step (2) with polarized ultraviolet light (step (3)), and baking the film obtained in step (3) at a temperature of 100° C. or higher and at a temperature higher than that of step (2) (step (4)).

<Step (1)>
The substrate to which the liquid crystal alignment agent used in the present invention is applied is not particularly limited as long as it is a highly transparent substrate, and a glass substrate, a silicon nitride substrate, an acrylic substrate, a plastic substrate such as a polycarbonate substrate, etc. 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 from the viewpoint 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 also be used for the electrode.

The method for applying the liquid crystal alignment agent is not particularly limited, but in industry, screen printing, offset printing, flexographic printing, inkjet printing, or the like is generally used. Other application methods include the dip method, roll coater method, slit coater method, spinner method, and spray method, and these may be used depending on the purpose.

<Step (2)>
Step (2) is a step of baking the liquid crystal alignment agent applied on the substrate to form a film. After the liquid crystal alignment agent is applied on the substrate, the solvent can be evaporated or the amic acid or amic acid ester in the polymer can be thermally imidized by a heating means such as a hot plate, a heat circulation type oven, or an IR (infrared) type oven. The drying and baking steps after the application of the liquid crystal alignment agent of the present invention can be performed at any temperature and time, and may be performed multiple times. The temperature for removing the organic solvent of the liquid crystal alignment agent can be, for example, 40 to 150°C. From the viewpoint of shortening the process, it may be performed at 40 to 120°C. The baking time is not particularly limited, but may be 1 to 10 minutes or 1 to 5 minutes. When the amic acid or amic acid ester in the polymer is thermally imidized, a baking step can be performed at a temperature range of, for example, 190 to 250°C or 200 to 240°C after the step of removing the organic solvent. The baking time is not particularly limited, but may be 5 to 40 minutes or 5 to 30 minutes.

<Step (3)>
Step (3) is a step of irradiating the film obtained in step (2) with polarized ultraviolet light. The wavelength of the ultraviolet light is preferably 200 to 400 nm, and more preferably, ultraviolet light having a wavelength of 200 to 300 nm is used. In order to improve the liquid crystal alignment, the substrate coated with the liquid crystal alignment film may be irradiated with ultraviolet light while being heated at 50 to 250°C. The radiation dose is preferably 1 to 10,000 mJ/ ^cm2 , and more preferably 100 to 5,000 mJ/ ^cm2 . The liquid crystal alignment film thus prepared can stably align liquid crystal molecules in a certain direction.

The higher the extinction ratio of the polarized UV light, the higher the anisotropy that can be imparted, which is preferable. Specifically, the extinction ratio of linearly polarized UV light is preferably 10:1 or greater, and more preferably 20:1 or greater.

<Step (4)>
Step (4) is a step of baking the film obtained in step (3) at 100° C. or higher and at a temperature higher than that in step (2). The baking temperature is not particularly limited as long as it is 100° C. or higher and higher than the baking temperature in step (2), but is preferably 150 to 300° C., more preferably 150 to 250° C., and even more preferably 200 to 250° C. The baking time is preferably 5 to 120 minutes, more preferably 5 to 60 minutes, and even more preferably 5 to 30 minutes.

If the thickness of the liquid crystal alignment film after baking is too thin, the reliability of the liquid crystal display element may decrease, so the thickness is preferably 5 to 300 nm, and more preferably 10 to 200 nm.

Furthermore, after carrying out either step (3) or (4), the obtained liquid crystal alignment film can be subjected to a contact treatment using water or a solvent.

The solvent used in the contact treatment is not particularly limited as long as it dissolves the decomposition products generated from the liquid crystal alignment film by irradiation with ultraviolet light. Specific examples include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, methyl lactate, diacetone alcohol, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate, and cyclohexyl acetate. Among these, water, 2-propanol, 1-methoxy-2-propanol, and ethyl lactate are preferred from the viewpoint of versatility and solvent safety. Water, 1-methoxy-2-propanol, and ethyl lactate are more preferred. The solvent may be one type or a combination of two or more types.

The above-mentioned contact treatment, i.e., the treatment of the liquid crystal alignment film irradiated with polarized ultraviolet light with water or a solvent, includes immersion treatment and spray treatment (also called spray treatment). The treatment time in these treatments is preferably 10 seconds to 1 hour from the viewpoint of efficiently dissolving the decomposition products generated from the liquid crystal alignment film by the ultraviolet light. In particular, immersion treatment for 1 to 30 minutes is preferable. The solvent during the contact treatment may be at room temperature or heated, but is preferably 10 to 80°C, and more preferably 20 to 50°C. In addition, ultrasonic treatment or the like may be performed as necessary from the viewpoint of the solubility of the decomposition products.

After the contact treatment, it is preferable to rinse the liquid crystal alignment film with a low boiling point solvent such as water, methanol, ethanol, 2-propanol, acetone, or methyl ethyl ketone (also called rinsing), and then bake the liquid crystal alignment film. In this case, either rinsing or baking may be performed, or both may be performed. The baking temperature is preferably 150 to 300°C. Of these, 180 to 250°C is more preferable, and 200 to 230°C is even more preferable. The baking time is preferably 10 seconds to 30 minutes, and of these, 1 to 10 minutes is more preferable.

The liquid crystal alignment film of the present invention is suitable as a liquid crystal alignment film for a liquid crystal display element of a horizontal electric field type such as an IPS type or an FFS type, and is particularly useful as a liquid crystal alignment film for a liquid crystal display element of an FFS type. The liquid crystal display element is obtained by obtaining a substrate with a liquid crystal alignment film obtained from the liquid crystal alignment agent of the present invention, and 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 with a passive matrix structure will be described. Note that a liquid crystal display element with an active matrix structure in which switching elements such as TFTs (Thin Film Transistors) are provided in each pixel portion that constitutes the image display may also be used.

Specifically, transparent glass substrates are prepared, and 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 are patterned to display a desired image. Next, an insulating film is provided on each substrate so as to cover the common electrode and the segment electrodes. The insulating film may be, for example, a SiO ₂ -TiO ₂ film formed by a sol-gel method.

Next, a liquid crystal alignment film is formed on each substrate, and one substrate is superimposed on the other substrate so that the liquid crystal alignment film faces each other, and the periphery is bonded with a sealant. Spacers are usually mixed into the sealant in order to control the gap between the substrates, and it is also preferable to disperse spacers for controlling the gap between the substrates in the in-plane portion where the sealant is not provided. An opening is provided in a part of the sealant so that liquid crystal can be filled from the outside. Next, liquid crystal material is injected into the space surrounded by the two substrates and the sealant through the opening provided in the sealant, and then this opening is sealed with an adhesive. For injection, a vacuum injection method or a method utilizing capillary action in the atmosphere may be used. The liquid crystal material may be either a positive type liquid crystal material or a negative type liquid crystal material. Next, a polarizing plate is installed. Specifically, a pair of polarizing plates are attached to the surfaces of the two substrates opposite to the liquid crystal layer.

By using the manufacturing method of the present invention, it is possible to suppress image retention caused by long-term AC driving in liquid crystal display elements using the IPS driving method or FFS driving method. In addition, by removing the organic solvent in the temperature range of 40 to 150°C in step (2) and then performing step (3), a liquid crystal alignment film can be obtained with fewer steps than in the past. The liquid crystal alignment agent of the present invention can be particularly preferably used in a manufacturing method for a liquid crystal alignment film that includes a step of removing the organic solvent in the temperature range of 40 to 150°C in step (2) and then performing step (3).

（Ｂｏｃは、ｔｅｒｔ－ブトキシカルボニル基を表す。）

（Ｂｏｃは、ｔｅｒｔ－ブトキシカルボニル基を表す。Ｆｍｏｃは、９－フルオレニルメチルオキシカルボニル基を表す。） (solvent)
NMP: N-methyl-2-pyrrolidone,
GBL: gamma-butyrolactone,
BCS: butyl cellosolve,
(Diamine)
DA-1 to DA-5: Compounds represented by the following formulas (DA-1) to (DA-5), respectively:
DA-t-1: a compound represented by the following formula (DA-t-1):
(Tetracarboxylic acid dianhydride)
CA-1 to CA-2: Compounds represented by the following formulas (CA-1) to (CA-2), respectively:
(Additive)
C-1: A compound represented by the following formula (C-1):
S-1: A compound represented by the following formula (S-1):
F-1: A compound represented by the following formula (F-1)

(Boc represents a tert-butoxycarbonyl group.)

(Boc represents a tert-butoxycarbonyl group. Fmoc represents a 9-fluorenylmethyloxycarbonyl group.)

<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 ppm 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 amide 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 amide acid in the case of polyamide acid (imidization rate 0%).

[Polymer synthesis example]
<Synthesis Example 1>
In a 500 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, 4.16 g (20.0 mmol) of DA-t-1, 11.00 g (45.0 mmol) of DA-1, 3.55 g (15.0 mmol) of DA-3 and 5.90 g (20.0 mmol) of DA-2 were taken, and NMP was added so that the concentration was 12% by mass, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this diamine solution, 21.0 g (93.7 mmol) of CA-1 was added, and NMP was added so that the concentration was 12% by mass, and the mixture was stirred at 40 ° C. for 24 hours to obtain a solution of polyamic acid (PAA-1).

<Synthesis Example 2, Comparative Synthesis Examples 1 and 2>
As shown in Table 1 below, Synthesis Example 2 and Comparative Synthesis Examples 1 and 2 were carried out in the same manner as Synthesis Example 1. In Table 1, the numbers in parentheses indicate the blending ratio (parts by mole) of each compound relative to 100 parts by mole of the total amount of tetracarboxylic acid derivatives used in the synthesis for the tetracarboxylic acid component, the blending ratio (parts by mole) of each compound relative to 100 parts by mole of the total amount of diamines used in the synthesis for the diamine component, and the blending ratio (parts by mole) of each compound relative to 100 parts by mole of the total amount of organic solvents used in the synthesis for the organic solvents.

<Synthesis Example 3>
100 g of the obtained polyamic acid solution (PAA-1) was taken in a 200 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, 33.3 g of NMP was added, and the mixture was stirred for 30 minutes. 7.82 g of acetic anhydride and 2.02 g of pyridine were added to the obtained polyamic acid solution, and the mixture was heated at 50 ° C. for 3 hours to perform chemical imidization. The obtained reaction solution was poured into 600 mL of methanol while stirring, and the precipitate was filtered off. The same operation was performed twice to wash the resin powder, and then the resin powder was dried at 60 ° C. for 12 hours to obtain a polyimide resin powder. 3.60 g of the obtained polyimide resin powder was taken in a 100 mL Erlenmeyer flask, NMP was added so that the solid concentration was 12 mass%, and the mixture was stirred and dissolved at 70 ° C. for 24 hours to obtain a polyimide solution (SPI-1).

Comparative Synthesis Examples 3 and 4
Polyimide solutions (R-SPI-1) and (R-SPI-2) were obtained by carrying out the same procedure as in Synthesis Example 3, except that the polyamic acid solution in Table 2 below was used instead of the polyamic acid solution (PAA-1). In Table 2, the numerical values in parentheses indicate the blending ratio (parts by mass) of each organic solvent relative to 100 parts by mass of the total amount of the organic solvents in the polyimide solution.

[Preparation of liquid crystal alignment agent]
Example 1
The polyimide solution (SPI-1) obtained in Synthesis Example 3, NMP, GBL, and BCS were added to a sample tube containing a stirrer, and stirred for 30 minutes. After stirring, a liquid crystal alignment agent (1) was obtained in which the solid content concentration of the polyimide solution (SPI-1) was 4 mass % and the solvent composition was NMP:GBL:BCS=50:30:20 by mass ratio.

Example 2
In a sample tube containing a stirrer, the polyimide solution (SPI-1) obtained in Synthesis Example 3 and the polyamic acid solution (PAA-2) obtained in Synthesis Example 2 were mixed so that the polymer solid content ratio was 50:50 by mass, NMP, GBL, and BCS were added to dilute, and S-1, C-1, and F-1 were added so that they were 1 mass%, 10 mass%, and 15 mass%, respectively, relative to the total amount of the polymer solid content, and the mixture was stirred for 30 minutes. After stirring, a liquid crystal alignment agent (2) was obtained in which the mass ratio of the polymer solid content of the polyimide solution (SPI-1) and the polyamic acid solution (PAA-2) was 50:50, the solid content concentration was 6 mass%, and the solvent composition was NMP:GBL:BCS=50:30:20 by mass.

<Comparative Examples 1 to 3>
Comparative Examples 1 to 3 were also carried out in the same manner as in Example 1 or 2, to obtain liquid crystal alignment agents (R1) to (R3), respectively. In Table 3, the numbers in parentheses indicate the blending ratio (parts by mass) of each polymer component or additive relative to 100 parts by mass of the total polymer components used in the preparation of the liquid crystal alignment agent, for the polymer and additive, respectively. For the organic solvent, the blending ratio (parts by mass) of each organic solvent relative to 100 parts by mass of the total amount of the organic solvent in the liquid crystal alignment agent is indicated.

Using the liquid crystal alignment agent obtained in the above manner, an FFS-driven liquid crystal cell was fabricated according to the procedure described below, and its characteristics were evaluated.

[Configuration of FFS driving liquid crystal cell]
The liquid crystal cell for Fringe Field Switching (FFS) mode is a set of a first glass substrate on which an FOP (Finger on Plate) electrode layer consisting of a surface-shaped common electrode, an insulating layer, and a comb-shaped pixel electrode is formed on the surface, and a second glass substrate on which a columnar spacer having a height of 3.5 μm is formed on the surface and an ITO film for preventing static electricity is formed on the back surface. The pixel electrode has a comb-like shape in which a plurality of electrode elements each having a width of 3 μm and bent at an inner angle of 160° at the center are arranged in parallel at intervals of 6 μm, and one pixel has a first region and a second region with a line connecting the bent parts of the plurality of electrode elements as a boundary.

The liquid crystal alignment film formed on the first glass substrate is oriented so that the direction that equally divides the inner angle of the pixel bend is perpendicular to the alignment direction of the liquid crystal, and the liquid crystal alignment film formed on the second glass substrate is oriented so that the alignment direction of the liquid crystal on the first substrate coincides with the alignment direction of the liquid crystal on the second substrate when the liquid crystal cell is fabricated.

[Preparation of Liquid Crystal Cell]
The liquid crystal alignment agent was filtered through a filter with a pore size of 1.0 μm, and then spin-coated on the above-mentioned electrode-attached substrate and counter substrate. Then, after drying for 2 minutes on a hot plate at 80° C., the coating surface was irradiated with 250 mJ/cm ² of linearly polarized ultraviolet light with an extinction ratio of 26:1 and a wavelength of 254 nm through a polarizing plate. Furthermore, this substrate was baked at 230° C. for 30 minutes to obtain a substrate with a liquid crystal alignment film having a thickness of 100 nm.

Next, a sealant was printed on one of the pair of substrates with liquid crystal alignment film, and the other substrate was attached so that the liquid crystal alignment film faces each other. The sealant was then cured to create an empty cell. Liquid crystal (MLC-3019, manufactured by Merck) was vacuum injected into this empty cell at room temperature using a reduced pressure injection method, and the injection port was sealed to obtain an FFS-driven liquid crystal cell.

<Evaluation of in-plane uniformity of contrast>
The twist angle of the liquid crystal display element was evaluated using an OPTIPRO-micro manufactured by Shintech Co., Ltd. The prepared liquid crystal cell was placed on a measurement stage, and 20 points within the first pixel plane were measured without applying voltage, and the standard deviation was calculated. The evaluation was performed by defining the twist angle standard deviation as "x" when it was 2.0 or more, "△" when it was less than 2.0 and 1.6 or more, and "○" when it was less than 1.6.

<Evaluation Results>
Table 4 shows the results of evaluation carried out on the liquid crystal display devices using the liquid crystal alignment agents of the above Examples and Comparative Examples.

Claims (11)

A liquid crystal aligning agent comprising at least one polymer (A) selected from the group consisting of a polyimide precursor having a repeating unit (a1) represented by the following formula (1) and a repeating unit (a2) represented by the following formula (2), and further having a repeating unit (a3) represented by the following formula (3), and an imidized polymer thereof:

(In the formula, _R1 to _R4 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom, or a phenyl group, and at least one of _R1 to _R4 represents a group other than a hydrogen atom as defined above. R and Z each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. _Y1 represents a divalent organic group represented by the following formula (T).)

( _Q1 represents an organic group having 2 to 18 carbon atoms and a triple bond. * represents a bond.)

(In the formula, _R1 to _R4 , R, and Z are each independently defined as in formula (1). _Y2 represents a divalent organic group represented by the following formula (O).)

(Ar represents a benzene ring, biphenyl, or naphthalene ring, and at least one of Ar represents a naphthalene ring. Two Ars may be the same or different, and any hydrogen atom on the ring may be replaced by a monovalent organic group. _Q2 represents -( _CH2 ) _n- (n is an integer from 2 to 18), or a group in which at least a portion of the _-CH2- in the -( _CH2 ) _n- is replaced by any of -O-, -C(=O)-, or -O-C(=O)-. * represents a bond.)

(In the formula, X3 _represents a tetravalent organic group, and Y3 _represents a divalent organic group represented by the following formula (3d). R and Z are the same as those in the formula (1).)

(Ar ₃ represents a benzene ring or biphenyl, two Ar _3s may be the same or different, and any hydrogen atom in the ring may be replaced by a monovalent organic group. Q ₃ represents -(CH ₂ ) _n - (n is an integer from 2 to 18), or a group in which at least a part of the -CH ₂ - of the -(CH ₂ ) _n - is replaced by any of -O-, -C(═O)-, or -O-C(═O)-. * represents a bond.) The liquid crystal aligning agent according to claim 1, wherein the divalent organic group represented by the formula (T) is a divalent organic group represented by the following formulas (t-1) to (t-3):

The liquid crystal aligning agent according to claim 1 or 2, wherein the divalent organic group represented by the formula (O) is a divalent organic group represented by the following formulas (o-1) to (o-6):

The liquid crystal aligning agent according to any one of claims 1 to 3 , wherein the polymer (A) is at least one selected from the group consisting of a polyimide precursor having a repeating unit (a4) represented by the following formula (4) and an imidized polymer thereof:

(In the formula, R and Z are the same as those in the formula (1). _X4 represents a tetravalent organic group, and _Y4 represents a divalent organic group having 6 to 30 carbon atoms and containing a group "-N(D)- (D represents a carbamate protecting group)" in the molecule.) The liquid crystal aligning agent according to claim 4 , wherein _Y4 is a structure represented by the following formulas (Y4-1) to (Y4-4).

(Boc represents a tert-butoxycarbonyl group. * represents a bond.) A liquid crystal alignment film obtained from the liquid crystal aligning agent according to any one of claims 1 to 5 . A liquid crystal display device comprising the liquid crystal alignment film according to claim 6 . A method for producing a liquid crystal alignment film, comprising the following steps (1) to (3):
Step (1): A step of applying the liquid crystal aligning agent according to any one of claims 1 to 5 onto a substrate.
Step (2): A step of heating the applied liquid crystal alignment agent to obtain a film.
Step (3): A step of irradiating the film obtained in step (2) with polarized ultraviolet light. The method for producing a liquid crystal alignment film according to claim 8 , further comprising the following step (4):
Step (4): A step of baking the film obtained in step (3) at a temperature of 100° C. or higher and higher than that in step (2). The method for producing a liquid crystal alignment film according to claim 8 or 9 , wherein the step (2) is a step of obtaining a film by heating at a temperature in the range of 40 to 180° C. A liquid crystal display device comprising a liquid crystal alignment film obtained by the method for producing a liquid crystal alignment film according to any one of claims 8 to 10 .