JP7643446B2 - 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.

Liquid crystal display devices have been widely used as display units for personal computers, smartphones, mobile phones, television receivers, etc. 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 it on an electrode substrate in one direction with a cloth such as cotton, nylon, or polyester, which is called a rubbing treatment. The rubbing treatment 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 apparent, such as scratches on the surface of the alignment film caused by the rubbing treatment, dust generation, effects due to mechanical force and static electricity, and even non-uniformity within the alignment treatment surface. As an alternative alignment treatment method to the rubbing treatment, 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).

A liquid crystal alignment film, which is a component of a liquid crystal display element, is a film for uniformly aligning liquid crystals, and liquid crystal alignment is one of its important characteristics. However, the liquid crystal alignment film obtained by the above-mentioned photoalignment method tends to have lower liquid crystal alignment properties than liquid crystal alignment films obtained by conventional rubbing treatments, and the range of application of liquid crystal display devices equipped with such liquid crystal alignment films has been limited.

Japanese Patent Publication 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

Furthermore, in actual liquid crystal display elements, the twist angle varies slightly within the plane of the liquid crystal display element due to manufacturing variations, etc. This in-plane variation then causes the brightness of the liquid crystal display element during black display to vary within the plane.
The present invention has been made in consideration of the above circumstances, and has as its object to provide a liquid crystal alignment agent suitable for use in a photoalignment method, which can obtain a liquid crystal display element having high liquid crystal alignment properties, suppressing in-plane brightness variations during black display, and improved contrast.

The present inventors have conducted extensive research and found that the above problems can be solved by using a liquid crystal aligning agent containing a specific component, and have completed the present invention.
Throughout this specification, examples of halogen atoms include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and * represents a bond.

（式（０）および式（１）中、Ｘは下記式（ｇ）で表される４価の有機基を表し、Ｙは以下の条件（１）及び条件（２）を満たす芳香族ジアミン（ｄ０）に由来する２価の有機基を表し、Ｙ_１は、以下の条件（１）及び条件（３）を満たす芳香族ジアミン（ｄ１）に由来する２価の有機基を表し、Ｒ、Ｚはそれぞれ独立して、水素原子又は炭素数１～６のアルキル基を表し、Xは互いに同一であっても異なっていても良い。）

（式（g）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し、また、上記アルキル基、アルケニル基、アルキニル基及びフッ素原子を含有する炭素数１～６の１価の有機基に含まれる－ＣＨ_２－の一部は、－Ｏ－で置き換えられてもよい。）
条件（１）：炭素数６以上の側鎖基を有しない。
条件（２）：アミノ基に由来する二つの炭素－窒素結合軸が互いに平行ではない。
条件（３）：アミノ基に由来する二つの炭素－窒素結合軸が互いに平行であり、下記式（Ｏ）で表される部分構造を有する。

（式（Ｏ）中、Ａｒはそれぞれ独立して、ベンゼン環、ビフェニル構造、又はナフタレン環を表し、環上の任意の水素原子は、ハロゲン原子又は１価の有機基で置き換えられてもよく、Ｑ_２は－（ＣＨ_２）_ｎ－（ｎは２～１８の整数である。）、又は上記－（ＣＨ_２）_ｎ－の任意の－ＣＨ_２－を－Ｏ－、－Ｃ（＝Ｏ）－又は－Ｏ－Ｃ（＝Ｏ）－のいずれかで置き換えた基を表し、＊は結合手を表す。）。 A liquid crystal aligning agent comprising: an imidized polymer of a polyimide precursor containing a repeating unit (a0) represented by the following formula (0) and a repeating unit (a1) represented by the following formula (1), wherein the imidization rate of the imidized polymer is 80 to 95%.

(In formula (0) and formula (1), X represents a tetravalent organic group represented by the following formula (g), Y represents a divalent organic group derived from an aromatic diamine (d0) satisfying the following conditions (1) and (2), _Y1 represents a divalent organic group derived from an aromatic diamine (d1) satisfying the following conditions (1) and (3), R and Z each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and X may be the same or different.)

(In formula (g), 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 containing a fluorine atom, or a phenyl group; at least one of R ₁ to R ₄ represents a group other than a hydrogen atom as defined above; and a portion of -CH ₂ - contained in the alkyl group, alkenyl group, alkynyl group, and monovalent organic group having 1 to 6 carbon atoms and containing a fluorine atom may be replaced by -O-.)
Condition (1): The compound has no side chain groups having six or more carbon atoms.
Condition (2): The axes of the two carbon-nitrogen bonds derived from the amino group are not parallel to each other.
Condition (3): The two carbon-nitrogen bond axes derived from the amino group are parallel to each other and have a partial structure represented by the following formula (O):

(In formula (O), each Ar independently represents a benzene ring, a biphenyl structure, or a naphthalene ring, any hydrogen atom on the ring may be replaced by a halogen atom or a monovalent organic group, _Q2 represents -( _CH2 ) _n- (n is an integer from 2 to 18) or a group in which any _-CH2- in the above-mentioned -( _CH2 ) _n- is replaced by -O-, -C(=O)- or -O-C(=O)-, and * represents a bond.)

According to the present invention, there is provided a liquid crystal display element having high liquid crystal alignment properties and excellent contrast with suppressed in-plane brightness variation during black display, and a liquid crystal alignment agent suitable for a photoalignment method by which this can be obtained.

（式（０）および式（１）中、Ｘは下記式（ｇ）で表される４価の有機基を表し、Ｙは以下の条件（１）及び条件（２）を満たす芳香族ジアミン（ｄ０）に由来する２価の有機基を表し、Ｙ_１は、以下の条件（１）及び条件（３）を満たす芳香族ジアミン（ｄ１）に由来する２価の有機基を表し、Ｒ、Ｚはそれぞれ独立して、水素原子又は炭素数１～６のアルキル基を表し、Ｘは互いに同一であっても異なっていても良い。）

（式（g）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し、また、上記アルキル基、アルケニル基、アルキニル基及びフッ素原子を含有する炭素数１～６の１価の有機基に含まれる－ＣＨ_２－の一部は、－Ｏ－で置き換えられてもよく、＊は結合手を表す。）
条件（１）：炭素数６以上の側鎖基を有しない。
条件（２）：アミノ基に由来する二つの炭素－窒素結合軸が互いに平行ではない。
条件（３）：アミノ基に由来する二つの炭素－窒素結合軸が互いに平行であり、下記式（Ｏ）で表される部分構造を有する。

（式（Ｏ）中、Ａｒはそれぞれ独立して、ベンゼン環、ビフェニル構造、又はナフタレン環を表し、環上の任意の水素原子は、ハロゲン原子又は１価の有機基で置き換えられてもよく、Ｑ_２は－（ＣＨ_２）_ｎ－（ｎは２～１８の整数である。）、又は上記－（ＣＨ_２）_ｎ－の任意の－ＣＨ_２－を－Ｏ－、－Ｃ（＝Ｏ）－又は－Ｏ－Ｃ（＝Ｏ）－のいずれかで置き換えた基を表し、＊は結合手を表す。）
このような構成とすることで、高い液晶配向性と、コントラストに優れた液晶表示素子を得ることができる。 <Polymer (A)>
The liquid crystal aligning agent of the present invention contains a polymer (A) which is an imidized polymer of a polyimide precursor containing a repeating unit (a0) represented by the above formula (0) and a repeating unit (a1) represented by the above formula (1), and the imidization rate of the imidized polymer is 80 to 95%.

(In formula (0) and formula (1), X represents a tetravalent organic group represented by the following formula (g), Y represents a divalent organic group derived from an aromatic diamine (d0) satisfying the following conditions (1) and (2), _Y1 represents a divalent organic group derived from an aromatic diamine (d1) satisfying the following conditions (1) and (3), R and Z each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and X may be the same or different.)

(In formula (g), 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 containing a fluorine atom, or a phenyl group; at least one of R ₁ to R ₄ represents a group other than a hydrogen atom as defined above; further, a portion of -CH ₂ - contained in the alkyl group, alkenyl group, alkynyl group, and monovalent organic group having 1 to 6 carbon atoms and containing a fluorine atom may be replaced by -O-; and * represents a bond.)
Condition (1): The compound has no side chain groups having six or more carbon atoms.
Condition (2): The axes of the two carbon-nitrogen bonds derived from the amino group are not parallel to each other.
Condition (3): The two carbon-nitrogen bond axes derived from the amino group are parallel to each other and have a partial structure represented by the following formula (O):

(In formula (O), each Ar independently represents a benzene ring, a biphenyl structure, or a naphthalene ring, any hydrogen atom on the ring may be replaced with a halogen atom or a monovalent organic group, _Q2 represents -( _CH2 ) _n- (n is an integer from 2 to 18) or a group in which _{any -CH2-} in the -( _CH2 ) _n- is replaced with -O-, -C(=O)- or -O-C(=O)-, and * represents a bond.)
With this configuration, a liquid crystal display device having high liquid crystal alignment properties and excellent contrast can be obtained.

Here, the above condition (3) "the two carbon-nitrogen bond axes derived from the amino groups are parallel to each other" means that when the aromatic diamine is represented by a ball-and-rod molecular structure model (for example, the HGS molecular structure model manufactured by Maruzen Publishing), the two carbon-nitrogen bond axes derived from the amino groups can be arranged so that they are parallel to each other. Also, the above condition (2) "the two carbon-nitrogen bond axes derived from the amino groups are not parallel to each other" means that when the aromatic diamine is represented by a ball-and-rod molecular structure model, the two carbon-nitrogen bond axes derived from the amino groups cannot be arranged so that they are parallel to each other.

As a method other than the above, for example, when molecular modeling (Chem3D Ultra Version 16.0.1.4) is used to optimize the molecular structure and minimize the energy with the default MM2 force field settings and converge to a minimum (root mean square) RMS gradient of 0.010, the case in which the two carbon-nitrogen bond axes derived from the amino groups are arranged so as to be parallel to each other can be defined as the above condition (3) of "the two carbon-nitrogen bond axes derived from the amino groups are parallel to each other," and the case in which the two carbon-nitrogen bond axes derived from the amino groups are not arranged so as to be parallel to each other can be defined as the above condition (2) of "the two carbon-nitrogen bond axes derived from the amino groups are not parallel to each other."

Specific examples of the alkyl group having 1 to 6 carbon atoms in R ₁ to R ₄ of the above formula (g) include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, and an n-pentyl group. Specific examples of the alkenyl group having 2 to 6 carbon atoms in R ₁ to R ₄ include a vinyl group, a propenyl group, and a butynyl group, which may be linear or branched. Specific examples of the alkynyl group having 2 to 6 carbon atoms in R ₁ to R ₄ include an ethynyl group, a 1-propynyl group, and a 2-propynyl group. Examples of the halogen atom in R ₁ to R ₄ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom include a fluoromethyl group and a trifluoromethyl group. In addition, a portion of the _--CH.sub.2-- contained in the alkyl group, alkenyl group, alkynyl group and fluorine atom-containing monovalent organic group having 1 to 6 carbon atoms may be replaced with --O--.
In order to efficiently obtain the effects of the present invention, at least one of R ₁ to R ₄ represents a group other than a hydrogen atom as defined above. With the above-mentioned configuration, the photoreactivity of the polyimide film is increased, and the in-plane anisotropy of the obtained liquid crystal alignment film is increased, so that the decrease in contrast caused by the variation in the twist angle in the plane of the liquid crystal display element generated during the production is suppressed.

From the viewpoint of high photoreactivity, the tetravalent organic group represented by the above formula (g) is preferably a tetravalent organic group represented by any one of the following formulae (g-1) to (g-5), and more preferably a tetravalent organic group represented by the following formula (g-1), where * represents a bond.

Any hydrogen atom on the ring of Ar in the above formula (O) may be replaced with a monovalent organic group such as 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 containing a fluorine atom having 1 to 6 carbon atoms, etc. Specific examples of these monovalent organic groups include the structures exemplified above for R ₁ to R ₄ .

（上記式中において、Ｒは、ヒドロキシ基、炭素数１～５のアルキル基、炭素数１～５のアルコキシ基、カルボキシ基、ハロゲン原子、フッ素原子を含有する炭素数１～５の１価の有機基、又は上記炭素数１～５のアルキル基上の水素原子の一部がヒドロキシ基で置換された基を表し、Ｒ’は、水素原子又は炭素数１～５のアルキル基を表す。また、ＲおよびＲ’が複数ある場合、各ＲおよびＲ’は互いに同一であっても異なっていても良い。Ｌは－ＣＨ_２－、－Ｃ（ＣＨ_３）_２－、－Ｏ－、－Ｃ（＝Ｏ）－、－Ｏ－Ｃ（＝Ｏ）－Ｏ－、－ＮＲ－Ｃ（＝Ｏ）－ＮＲ－、－ＮＲ－（Ｒは水素原子、炭素数１～５のアルキル基、フェニル基、又はｔｅｒｔ-ブトキシカルボニル基を表す。）、炭素数２～２０のアルキレン基又は該アルキレン基の－ＣＨ_２－の一部が－Ｏ－、－Ｓｉ（ＣＨ_３）_２－、－Ｃ（＝Ｏ）－、－Ｏ－Ｃ（＝Ｏ）－、－ＮＲ－Ｃ（＝Ｏ）－又は－ＮＲ－で置き換えられた２価の有機基を表し、主鎖方向の炭素原子、酸素原子、珪素原子及び窒素原子の合計数が奇数個である。Ｌ’は、上記Ｌで定義した２価の有機基のうち、－ＮＲ－以外の２価の有機基を表す。Ｑ、Ｑ’、Ｑ”は複素環を表す。但し、Ｑ’とベンゼン環との間で形成されるそれぞれの結合は、互いに平行ではなく、式（ｄ０－１０）、式（ｄ０－１１）において、Ｑ”と窒素原子との間で形成されるそれぞれの結合は、互いに平行ではない。式（ｄ０－９）において、ｎが０の場合、Ｑ”と窒素原子との間で形成されるそれぞれの結合は互いに平行であり、ｎが１の場合、Ｑ”と窒素原子との間で形成されるそれぞれの結合は互いに平行ではない。また、式（ｄ０－１３）において、Ｑと隣接する窒素原子および炭素原子との間でそれぞれ形成される結合は、互いに平行でない。上記式中にＱが複数ある場合、各Ｑは互いに同一であっても異なっていても良い。また、上記同一式中のｎは互いに同一であっても異なっていても良い。）
上記Ｑ、Ｑ’、Ｑ”における複素環の具体例としては、ピロール、イミダゾール、ピラゾール、トリアゾール、ピリジン、ピリミジン、ピリダジン、ピラジン、インドール、ベンゾイミダゾール、プリン、キノリン、イソキノリン、ナフチリジン、キノキサリン、フタラジン、トリアジン、カルバゾール、アクリジン、ピペリジン、ピペラジン、ピロリジン、ヘキサメチレンイミン、オキサゾリン等が挙げられる。尚、上記複素環上の任意の水素原子は、炭素数１～３のアルキル基、炭素数１～３のアルコキシ基、炭素数１～３のフッ素含有アルキル基、炭素数１～３のフッ素含有アルコキシ基及びフッ素原子からなる群から選ばれる少なくとも１種で置換されていてもよい。複素環のより好ましい具体例は、ピロール、ピリジン、ピリミジン、ピリダジン、ピラジン、ベンゾイミダゾール、カルバゾール、ピペリジン、ピペラジン、オキサゾリンである。上記「Ｑ’とベンゼン環との間で形成されるそれぞれの結合は、互いに平行ではない」とは、例えばピリジンを例に挙げると、ベンゼン環と結合するピリジンの結合位置が２，４－位、２，６－位、３，５－位であることを表し、「Ｑ”と窒素原子との間で形成されるそれぞれの結合は、互いに平行ではない」とは、ピリジンを例に挙げると、窒素原子と結合するピリジンの結合位置が２，４－位、２，６－位又は３，５－位であることを表す。「Ｑ”と窒素原子との間で形成されるそれぞれの結合は、互いに平行である」とは、ピリジンを例に挙げると、窒素原子と結合するピリジンの結合位置が２，５－位であることを表す。また、「Ｑと隣接する窒素原子および炭素原子との間でそれぞれ形成される結合は、互いに平行でない」とは、ピリジンを例に挙げると、隣接する窒素原子又は炭素原子と結合するピリジンの結合位置が２，４－位、２，６－位又は３，５－位であることを表す。
更に好ましい芳香族ジアミン（ｄ０）の具体例として、１，３－ジアミノベンゼン、２，４－ジアミノトルエン、２，６－ジアミノトルエン、２，４－ジアミノフェノール、３，５－ジアミノフェノール、２，４－ジアミノベンジルアルコール、４，６－ジアミノレソルシノール、３，５－ジアミノベンジルアルコール、２，４－ジアミノ安息香酸、３，５－ジアミノ安息香酸、３，３’－ジアミノジフェニルメタン、４，４’－ジアミノジフェニルメタン、ビス（４－アミノフェノキシ）メタン、１，５－ビス（４－アミノフェノキシ）ペンタン、１，３－ビス（４－アミノフェネチル）ウレア、４，４’－ジアミノジフェニルエーテル、２，２－ビス（３－アミノフェニル）プロパン、２，２－ビス（４－アミノフェニル）プロパン、４，４’－ジアミノベンゾフェノン、１－（４－アミノフェニル）－１，３，３－トリメチル－１Ｈ－インダン－５－アミン、１－（４－アミノフェニル）－２，３－ジヒドロ－１，３，３－トリメチル－１Ｈ－インデン－６－アミン、下記式（Ｄｐ－１）～（Ｄｐ－２）で表されるジアミン、下記式（５－１）～（５－４）で表されるジアミン、１，３－ビス（４－アミノフェノキシ）ベンゼン、ビス［４－（４－アミノフェノキシ）フェニル］エーテル、２，６－ジアミノピリジン、３，４－ジアミノピリジン、２，４－ジアミノピリミジン、３，６－ジアミノカルバゾール、Ｎ－メチル－３，６－ジアミノカルバゾール、３，６－ジアミノアクリジン、Ｎ－エチル－３，６－ジアミノカルバゾール、下記式（ｚ－１）～式（ｚ－１７）、下記式（Ｏｘ－１）～式（Ｏｘ－２）などの複素環を分子内に含有する芳香族ジアミン、又は下記式（Ｓｉ－１）で表されるジアミンが挙げられる。下記式（５－１）～（５－４）中、「Ｂｏｃ」はｔｅｒｔ-ブトキシカルボニル基を表す。

(Aromatic diamine (d0))
From the viewpoint of efficiently achieving the effects of the present invention, the aromatic diamine (d0) is preferably an aromatic diamine having 4 to 40 carbon atoms. Specific examples include aromatic diamines containing one aromatic ring in the molecule, aromatic diamines containing two aromatic rings in the molecule, the two aromatic rings being -CH ₂ -, -C(CH ₃ ) ₂ -, -O-, -C(═O)-, -O-C(═O)-, -NR-C(═O)-, -NR- (R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a phenyl group, or a tert-butoxycarbonyl group), an alkylene group having 2 to 20 carbon atoms, or a part of the -CH ₂ - in the alkylene group being -O-, -Si(CH ₃ ) _{2 -} , or the like. Examples of the aromatic diamine include aromatic diamines linked by divalent organic groups substituted with -, -C(=O)-, -O-C(=O)-, -NR-C(=O)-, and having an odd number of carbon atoms, oxygen atoms, silicon atoms, and nitrogen atoms in the main chain direction of the linking group, aromatic diamines having one aromatic ring and an indane structure in the molecule, aromatic diamines having three or more aromatic rings in the molecule, and aromatic diamines having a heterocyclic structure. Examples of the aromatic ring include a benzene ring, a naphthalene ring, and an anthracene ring, with a benzene ring and a naphthalene ring being preferred, and a benzene ring being more preferred. In addition, some of the hydrogen atoms on the aromatic ring may be replaced by a hydroxy group, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a carboxy group, a halogen atom, a fluorine-containing monovalent organic group having 1 to 5 carbon atoms, a group in which some of the hydrogen atoms on the alkyl group having 1 to 5 carbon atoms have been substituted with a hydroxy group, or -NH(Boc) (Boc represents a tert-butoxycarbonyl group).
More specifically, examples of the aromatic diamines include those represented by the following formulas (d0-1) to (d0-15), 1,3-bis(4-aminophenoxy)benzene, and bis[4-(4-aminophenoxy)phenyl]ether.

(In the above formula, R represents a hydroxy group, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a carboxy group, a halogen atom, a monovalent organic group having 1 to 5 carbon atoms containing a fluorine atom, or a group in which some of the hydrogen atoms on the alkyl group having 1 to 5 carbon atoms have been substituted with a hydroxy group; R' represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. When there are a plurality of R and R', each R and R' may be the same or different. L represents -CH ₂ -, -C(CH ₃ ) ₂ -, -O-, -C(═O)-, -O-C(═O)-O-, -NR-C(═O)-NR-, -NR- (R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a phenyl group, or a tert-butoxycarbonyl group), an alkylene group having 2 to 20 carbon atoms, or a group in which some of the -CH ₂ - of the alkylene group is -O-, -Si(CH ₃ ) ₂ represents a divalent organic group replaced by -, -C(=O)-, -O-C(=O)-, -NR-C(=O)- or -NR-, and the total number of carbon atoms, oxygen atoms, silicon atoms and nitrogen atoms in the main chain direction is an odd number. L' represents a divalent organic group other than -NR- among the divalent organic groups defined for L above. Q, Q' and Q" represent heterocycles, with the proviso that the bonds formed between Q' and a benzene ring are not parallel to each other, and in formulas (d0-10) and (d0-11), the bonds formed between Q" and a nitrogen atom are In formula (d0-9), when n is 0, the bonds formed between Q" and the nitrogen atom are parallel to each other, and when n is 1, the bonds formed between Q" and the nitrogen atom are not parallel to each other. In formula (d0-13), the bonds formed between Q and the adjacent nitrogen atom and carbon atom are not parallel to each other. When there are multiple Qs in the above formula, each Q may be the same as or different from each other. In the same formula, each n may be the same as or different from each other.)
Specific examples of the heterocycle in Q, Q', and Q" include pyrrole, imidazole, pyrazole, triazole, pyridine, pyrimidine, pyridazine, pyrazine, indole, benzimidazole, purine, quinoline, isoquinoline, naphthyridine, quinoxaline, phthalazine, triazine, carbazole, acridine, piperidine, piperazine, pyrrolidine, hexamethyleneimine, and oxazoline. Any hydrogen atom on the heterocycle is at least one selected from the group consisting of 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, and a fluorine atom. The heterocycle may be substituted with. More preferred examples of the heterocycle include pyrrole, pyridine, pyrimidine, pyridazine, pyrazine, benzimidazole, carbazole, piperidine, piperazine, and oxazoline. The above phrase "respective bonds formed between Q' and a benzene ring are not parallel to each other" means that, for example, in the case of pyridine, the bonding positions of the pyridine bonded to the benzene ring are 2,4-positions, 2,6-positions, or 3,5-positions, and the phrase "respective bonds formed between Q" and a nitrogen atom are not parallel to each other" means that, for example, in the case of pyridine, the bonding positions of the pyridine bonded to the nitrogen atom are 2,4-positions, 2,6-positions, or 3,5-positions. The phrase "respective bonds formed between Q" and a nitrogen atom are parallel to each other" means that, for example, in the case of pyridine, the bonding positions of the pyridine bonded to the nitrogen atom are 2,5-positions. Furthermore, "the bonds formed between Q and the adjacent nitrogen atom and carbon atom, respectively, are not parallel to each other" means that, taking pyridine as an example, the bonding positions of the pyridine bonding to the adjacent nitrogen atom or carbon atom are the 2,4-positions, 2,6-positions, or 3,5-positions.
More preferred specific examples of the aromatic diamine (d0) include 1,3-diaminobenzene, 2,4-diaminotoluene, 2,6-diaminotoluene, 2,4-diaminophenol, 3,5-diaminophenol, 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzoic acid, 3,5-diaminobenzoic acid, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, bis(4-aminophenoxy)methane, 1,5-bis(4-aminophenoxy)pentane, 1,3-bis(4-aminophenethyl)urea, 4,4'-diaminodiphenyl ether, 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 4,4'-diaminobenzophenone, 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, diamines represented by the following formulas (Dp-1) to (Dp-2), diamines represented by the following formulas (5-1) to (5-4), 1,3-bis(4-aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]ether, 2,6-diaminopyridinyl Examples of the heterocyclic diamines include aromatic diamines having a heterocycle in the molecule, such as those represented by the following formulae (z-1) to (z-17) and (Ox-1) to (Ox-2), or diamines represented by the following formula (Si-1). In the following formulae (5-1) to (5-4), "Boc" represents a tert-butoxycarbonyl group.

（式中、Ｐｙは、それぞれ独立して２，５－ピリジニレン基又は２，５－ピリミジニレン基を表す。）

(In the formula, each Py independently represents a 2,5-pyridinylene group or a 2,5-pyrimidinylene group.)

From the viewpoint of enhancing liquid crystal alignment, Y in the above formula (1) is preferably a divalent organic group derived from 1,3-diaminobenzene, 2,4-diaminotoluene, 2,6-diaminotoluene, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, bis(4-aminophenoxy)methane, 1,5-bis(4-aminophenoxy)pentane, 1,3-bis(4-aminophenethyl)urea, 4,4'-diaminodiphenyl ether, 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 4,4'-diaminobenzophenone or 1,3-bis(4-aminophenoxy)benzene.

(Aromatic diamine (d1))
From the viewpoint of efficiently obtaining the effects of the present invention, the aromatic diamine (d1) is preferably an aromatic diamine having 4 to 40 carbon atoms. Furthermore, it is preferable that the total number of carbon atoms and oxygen atoms in the main chain direction of _Q2 in (d1) is an even number. A preferred total number of carbon atoms and oxygen atoms in the main chain direction is 2n (n represents an integer of 1 to 9, preferably 1 to 8, and more preferably 1 to 6). Specific examples of aromatic diamines include aromatic diamines in which two amino groups are bonded to the partial structure represented by the above formula (O).

In terms of improving liquid crystal alignment properties, _Y1 in the above formula (1) is preferably a divalent organic group derived from a diamine represented by the following formulas (d1-1) to (d1-14).

The polymer (A) may be an imidized polymer of a polyimide precursor further having a repeating unit (a2) represented by the following formula (2) which is different from the repeating unit (a0) or (a1).

In the above formula (2), _X2 represents a tetravalent organic group, _Y2 represents a divalent organic group derived from an aromatic diamine having no side chain group having 6 or more carbon atoms, and R and Z are the same as R and Z in the above formula (0). However, when _X2 is the same as the tetravalent organic group represented by the above formula (g), _Y2 represents a structure other than the divalent organic group defined by Y in the above formula (0) or the divalent organic group defined by _Y1 in the above formula (1). Specific examples of _X2 include, in addition to the tetravalent organic group represented by the above formula (g), tetravalent organic groups represented by any of the following formulas (X-1) to (X-25), and tetravalent organic groups derived from aromatic tetracarboxylic dianhydrides.

Here, aromatic tetracarboxylic dianhydrides refer to acid dianhydrides obtained by intramolecular dehydration of a carboxy group bonded to an aromatic ring such as a benzene ring or a naphthalene ring. Specific examples include tetravalent organic groups represented by any of the following formulae (Xa-1) to (Xa-2) and tetravalent organic groups represented by the following formulae (Xr-1) to (Xr-7).

（上記式（Ｘａ－１）～（Ｘａ－２）中、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１～１０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。）

(In the above formulas (Xa-1) to (Xa-2), x and y each independently represent a single bond, an ether, a carbonyl, an ester, an alkanediyl group having 1 to 10 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 above formula (Xa-1) or (Xa-2) may have a structure represented by any of the following formulas (Xa-3) to (Xa-19).

本発明の効果を効率的に得る観点から、Ｘ_２は上記式（ｇ）で表される４価の有機基又は上記式（Ｘ－１）～（Ｘ－２５）のいずれかで表される４価の有機基であることが好ましく、上記式（ｇ）で表される４価の有機基であることがより好ましい。

From the viewpoint of efficiently obtaining the effects of the present invention, _X2 is preferably a tetravalent organic group represented by the above formula (g) or a tetravalent organic group represented by any one of the above formulas (X-1) to (X-25), and more preferably a tetravalent organic group represented by the above formula (g).

Specific examples of the divalent organic group of _Y2 include the divalent organic groups defined as Y in the above formula (0) or the divalent organic groups defined as _Y1 in the above formula (1), as well as groups in which two amino groups have been removed from diamines such as p-phenylenediamine, 4,4'-diamino-2,2'-dimethylbiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4,4'-diaminobiphenyl, 3,3'-difluoro-4,4'-diaminobiphenyl, 3,3'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, and 4,4'-diaminobenzanilide, and divalent organic groups represented by the following formula (h-1): group, a divalent organic group having a photoalignment group such as the following formulas (h-2) to (h-4), a divalent organic group represented by (h-5), 4-(2-(methylamino)ethyl)aniline, 4-(2-aminoethyl)aniline, 2,5-diaminobenzoic acid, 4,4'-diaminobiphenyl-3,3'-dicarboxylic acid, diamines having a diphenylamine skeleton such as the following formulas (Dp-5) to (Dp-6), diamines having "-N(D)- (D represents a carbamate-based protecting group, more preferably a tert-butoxycarbonyl group)" in the molecule such as the following formulas (5-5) to (5-9), and groups obtained by removing two amino groups from diamines such as diamines represented by (z-18) to (z-23).

（上記式中、＊は結合手を表す。）

(In the above formula, * represents a bond.)

（上記式中、Ｂｏｃは、ｔｅｒｔ－ブトキシカルボニル基を表す。）

（上記式中、Ｐｙは、それぞれ独立して２，５－ピリジニレン基又は２，５－ピリミジニレン基を表す。）

(In the above formula, Boc represents a tert-butoxycarbonyl group.)

(In the above formula, each Py independently represents a 2,5-pyridinylene group or a 2,5-pyrimidinylene group.)

The polymer (A) may be an imidized polymer of a polyimide precursor having a repeating unit (a3) represented by the following formula (3) which is different from the repeating units (a0), (a1) and (a2).

In the formula, _X3 represents a tetravalent organic group, _Y3 represents a divalent organic group other than the divalent organic group defined by _Y2 in the above formula (2), and R and Z are the same as R and Z in the above formula (0). However, when _X3 is the same as the tetravalent organic group represented by the above formula (g), _Y3 represents a structure other than the divalent organic group defined by Y in the above formula (0) or the divalent organic group defined by _Y1 in the above formula (1). Specific examples of _X3 include the structures exemplified by _X2 in the above formula (2), and from the viewpoint of suitably obtaining the effects of the present invention, it is preferably a tetravalent organic group represented by the above formula (g).

Specific examples of the divalent organic group of _Y3 include diamines having a photopolymerizable group at the end, such as N-phenyl-3,6-diaminocarbazole, 2-(2,4-diaminophenoxy)ethyl methacrylate, and 2,4-diamino-N,N-diallylaniline; diamines having a steroid skeleton, such as cholestanyloxy-3,5-diaminobenzene, cholestanyloxy-3,5-diaminobenzene, cholestanyloxy-2,4-diaminobenzene, cholestanyl 3,5-diaminobenzoate, cholestanyl 3,5-diaminobenzoate, lanostannyl 3,5-diaminobenzoate, and 3,6-bis(4-aminobenzoyloxy)cholestane; diamines represented by the following formulae (V-1) to (V-6); diamines represented by the following formulas (5-10) to (5-13), alicyclic diamines such as bis(4-aminocyclohexyl)methane and bis(4-amino-3-methylcyclohexyl)methane, groups in which two amino groups have been removed from diamines such as aliphatic diamines such as 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, and 1,12-diaminododecane, and groups represented by any of formulas (Y-1) to (Y-167) described in WO2018/117239. In order to suitably obtain the effects of the present invention, _Y3 is preferably a group in which two amino groups have been removed from a diamine represented by any of the formulas (5-10) to (5-13).

(In the above formulas (V-1) to (V-6), 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); and 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.

（上記式中、Ｂｏｃは、ｔｅｒｔ－ブトキシカルボニル基を表す。）

(In the above formula, Boc represents a tert-butoxycarbonyl group.)

From the viewpoint of obtaining the effects of the present invention, it is preferable that the sum of the repeating units (a0), repeating units (a1) and their imidized repeating units in polymer (A) is 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, it is preferable that polymer (A) contains repeating unit (a1) and its imidized repeating unit in an amount of 1 to 40 mol %, more preferably 1 to 35 mol %, and even more preferably 1 to 30 mol %, of all repeating units.

From the viewpoint of obtaining the effects of the present invention, it is preferable that polymer (A) contains repeating unit (a2) and its imidized repeating unit in an amount of 1 to 95 mol %, more preferably 1 to 90 mol %, and even more preferably 5 to 90 mol %, of all repeating units.

From the viewpoint of obtaining the effects of the present invention, it is preferable that polymer (A) contains repeating unit (a3) and its imidized repeating unit in an amount of 1 to 40 mol %, more preferably 1 to 30 mol %, and even more preferably 1 to 25 mol %, of all repeating units.

The imidized repeating units contained in the polymer (A) are 95 mol % or less.
When the polymer (A) contains a repeating unit other than the repeating unit (a0), the repeating unit (a1), and imidized repeating units thereof, the total content of the repeating unit (a0), the repeating unit (a1), and imidized repeating units thereof is preferably 95 mol % or less, and more preferably 90 mol % or less.

（上記式（４）中、Ｘ_４は４価の有機基であり、Ｙ_４は２価の有機基である。Ｚ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し、Ｒは、それぞれ独立して、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 at least one polymer (B) selected from the group consisting of polyimide precursors and polyimides having an imidization rate of less than 80%, in addition to the polymer (A). From the viewpoint of efficiently obtaining the effects of the present invention, the polymer (B) may be a polymer having a repeating unit represented by the following formula (4).

(In the above formula (4), _X4 is a tetravalent organic group, and _Y4 is a divalent organic group. Each Z is independently 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, and each R is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

Examples of the tetravalent organic group in _X4 in the above formula (4) include a tetravalent organic group derived from an aliphatic tetracarboxylic dianhydride, a tetravalent organic group derived from an alicyclic tetracarboxylic dianhydride, or a tetravalent organic group derived from an aromatic tetracarboxylic dianhydride, and specific examples include the tetravalent organic groups exemplified for the above _X2 . From the viewpoint of efficiently obtaining the effects of the present invention, _X4 is preferably a tetravalent organic group represented by the above formula (g), a tetravalent organic group represented by any one of the above formulas (X-1) to (X-25), a tetravalent organic group represented by the above formulas (Xa-1) to (Xa-2), or a tetravalent organic group represented by the above formulas (Xr-1) to (Xr-7) (collectively referred to as "specific tetravalent organic groups").

From the viewpoint of efficiently obtaining the effects of the present invention, the polymer (B) preferably contains repeating units in which _X4 is the specific tetravalent organic group in an amount of 5 mol % or more, and more preferably 10 mol % or more, of all repeating units contained in the polymer (B).

Examples of the divalent organic group in Y ₄ in the above formula (4) include the divalent organic groups exemplified as Y in the above formula (0) or Y ₁ to Y ₃ in the above formulas (1) to (3). 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 Y ₄ is a divalent organic group selected from the group consisting of 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, a divalent organic group obtained by removing two amino groups from a diamine having a carboxy group, and a divalent organic group obtained by removing two amino groups from a diamine having a urea bond such as 1,3-bis(4-aminophenethyl)urea (these are also collectively referred to as "specific divalent organic groups").

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, hexamethyleneimine, etc. Among these, pyridine, pyrimidine, pyrazine, piperidine, piperazine, quinoline, carbazole, and acridine are preferred.

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, and "*" represents a bond bonded to the hydrocarbon group.
Examples of the monovalent hydrocarbon group represented by R in the above formula (n) include alkyl groups such as methyl, ethyl, and propyl groups, cycloalkyl groups such as cyclohexyl groups, and aryl groups such as phenyl and methylphenyl groups. R is preferably a hydrogen atom or a methyl group.

Specific examples of diamines having a nitrogen-containing structure include, for example, 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, diamines represented by the above formulas (Dp-1) to (Dp-6), or diamines represented by the above formulas (z-1) to (z-25).

Specific examples of the diamine having the above-mentioned carboxy group include 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid, 3,5-diaminobenzoic acid, and 4,4'-diaminobiphenyl-3,3'-dicarboxylic acid.

From the viewpoint of reducing afterimages derived from residual DC, the polymer (B) may contain repeating units in which _Y4 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 used in the present invention, that is, polyamic acid ester, polyamic acid, and polyimide which is an imidized polymer thereof, can be synthesized by known methods such as those described in International Publication WO2013/157586.

The polymer (A) of the present invention can be obtained by imidizing the polyimide precursor described above. In the polymer (A), the repeating units of the polyimide precursor are ring-closed, and the ratio of the ring-closed repeating units to the total repeating units of the polyimide precursor (also referred to as the ring-closure rate or imidization rate) is 80 to 95%, preferably 82 to 95%, and more preferably 85 to 95%.
With the above-mentioned configuration, the obtained liquid crystal alignment film has high liquid crystal alignment properties, so that the above-mentioned effects of the present invention can be obtained.

<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 mass 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 mass 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 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. With the molecular weight in 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 aligning agent.

In addition, the organic solvent contained in the liquid crystal alignment agent is preferably a mixed solvent containing a solvent (also called a poor solvent) that improves the coating property and the surface smoothness of the coating film when applying the liquid crystal alignment agent in addition to the above solvent. Specific examples of the poor solvent to be used in combination are shown 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-butoxy)-2-propanol, diethoxy)-1-propanol, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monobutyl ether acetate, ethylene glycol monoacetate, ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 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.

The content of the poor solvent is preferably 1 to 80% by mass, more preferably 20 to 80% by mass, and particularly preferably 20 to 70% by mass, of the total solvent contained in the liquid crystal alignment agent. The type and content of the poor solvent are appropriately selected depending on the application device, application conditions, application environment, etc. of the liquid crystal alignment agent.

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, propylene glycol monobutyl ether, and diisobutyl ketone, N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether, and diisopropyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether, and diisobutyl carbinol, N-methyl-2-pyrrolidone, γ-butyrolactone, and dipropylene glycol dimethyl ether, N-methyl-2-pyrrolidone, propylene glycol monobutyl ether, and dipropylene glycol dimethyl ether.

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 increasing the adhesion between the liquid crystal alignment film and the substrate or between the liquid crystal alignment film and the sealant, compounds for promoting imidization, 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.

（式（ｄ）中、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」であり、＊は結合手を表す。式（e）中、Ａは芳香環を有する（ｍ＋ｎ）価の有機基を表し、Ｒは、水素原子又は炭素数１～５のアルキル基を表し、ｍは１～６の整数を表し、ｎは０～４の整数を表す。）
式（e）において、上記Ａの芳香環上の水素原子は、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価の有機基などの１価の有機基で置き換えられてもよい。 From the viewpoint of exhibiting good resistance to AC afterimages and highly improving film strength, the crosslinkable compound may be at least one compound selected from the group consisting of 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), and a compound represented by the following formula (e) (hereinafter these may be collectively referred to as compound (C)).

(In formula (d), _R2 and _R3 each independently represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or "*-CH2 _- OH", where * represents a bond. In formula (e), A represents an (m+n)-valent organic group having an aromatic ring, R represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, m represents an integer of 1 to 6, and n represents an integer of 0 to 4.)
In formula (e), a hydrogen atom on the aromatic ring of A may be replaced by a monovalent organic group such as 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, or a monovalent organic group having 1 to 6 carbon atoms and containing a fluorine atom.

Specific examples of the compound having an oxiranyl group include compounds having two or more oxiranyl groups, such as the compound described in paragraph [0037] of JP-A-10-338880 and the compound having a triazine ring as a skeleton described in International Publication WO2017/170483. Among these, the compound may be a compound containing a nitrogen atom, 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, or the compounds represented by the following formulae (r-1) to (r-3).

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 International Publication No. 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, and may be 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 described in JP 2016-200798 A.
Specific examples of the compound having a group containing an oxazoline ring structure include compounds containing two or more oxazoline ring structures described in paragraph [0115] of JP-A-2007-286597.

Specific examples of the compound having a group containing a Meldrum's acid structure include compounds having two or more Meldrum's acid structures described in International Publication WO2012/091088.
Specific examples of the compound having a cyclocarbonate group include the compounds described in International Publication WO2011/155577.
Examples of the alkyl group having 1 to 3 carbon atoms for R ₂ and R ₃ in the group represented by formula (d) include a methyl group, an ethyl group, a propyl group, and an isopropyl 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 International Publication WO2015/072554 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 formula (e) include an (m+n)-valent aromatic hydrocarbon group having 6 to 30 carbon atoms, an (m+n)-valent organic group to which an aromatic hydrocarbon group having 6 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 group 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 -NR- (R is a hydrogen atom or a methyl group), an alkylene group having 1 to 10 carbon atoms, a group obtained by removing one hydrogen atom from an alkylene group, and a divalent or trivalent cyclohexane ring. Any hydrogen atom in the alkylene group may be substituted with a fluorine atom or an organic group such as a trifluoromethyl group. Specific examples of the alkyl group having 1 to 5 carbon atoms for R in formula (e) include the alkyl groups exemplified as R ₁ to R ₄ in formula (g) above.
Specific examples include the compounds described in International Publication WO2010/074269 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 International Publication No. 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 relative to 100 parts by mass of the polymer component contained in the liquid crystal aligning agent, and from the viewpoint of proceeding with the crosslinking reaction and exhibiting good resistance to AC afterimages, it is more preferably 1 to 15 parts by mass.

Examples of the adhesion aids 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 preferably 0.1 to 30 parts by mass, 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.

（上記式中（Ｂ－１）～（Ｂ－１７）中、Ｄは、加熱によって脱離する有機基を表し、好ましくは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のいずれかであり、Ｄが複数ある場合、各Ｄは互いに同一であっても異なっていても良い。） The compound for promoting imidization is preferably a compound having a basic site (e.g., a primary amino group, an aliphatic heterocycle (e.g., a pyrrolidine skeleton), an aromatic heterocycle (e.g., an imidazole ring, an indole ring), or a guanidino group) (excluding the crosslinkable compound and the adhesion aid) or a compound that generates the basic site upon baking. More preferably, it is a compound that generates the basic site upon baking, and specific examples include the compounds represented by the following formulas (B-1) to (B-17). The content of the compound for promoting imidization is preferably 2 mols or less, more preferably 1 mol or less, and even more preferably 0.5 mols or less, relative to 1 mol of the amic acid or amic acid ester site in the polymer (A).

(In the above formulas (B-1) to (B-17), D represents an organic group which is eliminated by heating, and is preferably either a tert-butoxycarbonyl group or a 9-fluorenylmethoxycarbonyl group. When there are a plurality of Ds, each D may be the same or different.)

<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)), heating the applied liquid crystal alignment agent to obtain a film (step (2)), irradiating the film obtained in step (2) with polarized ultraviolet light (step (3)), and, if necessary, further 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 of applying the liquid crystal alignment agent is not particularly limited, but in industry, it is generally performed by screen printing, offset printing, flexographic printing, inkjet printing, etc. Other application methods include a dip method, a roll coater method, a slit coater method, a spinner method, a spray method, etc., and these may be used depending on the purpose.

<Step (2)>
Step (2) is a step of heating the liquid crystal alignment agent applied on the substrate to form a film. Specifically, the liquid crystal alignment agent applied on the substrate in step (1) can be heated by a heating means such as a hot plate, a heat circulation type oven, or an IR (infrared) type oven to evaporate the solvent or to thermally imidize the amic acid or amic acid ester in the polymer. The heating step of the liquid crystal alignment agent applied on the substrate in step (1) can be performed at any temperature and time, and may be performed multiple times. The heating temperature can be, for example, 40 to 180°C, and from the viewpoint of shortening the process, it is preferable to perform it at 40 to 150°C, and more preferably at 40 to 120°C. The heating time is not particularly limited, but can be 1 to 10 minutes or 1 to 5 minutes. When thermally imidizing the amic acid or amic acid ester in the polymer, a heating step can be performed at a temperature range of, for example, 190 to 250°C or 200 to 240°C after the above step. The heating time is not particularly limited, but may be from 5 to 40 minutes, or from 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. 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 the linearly polarized UV light is preferably 10:1 or more, and more preferably 20:1 or more.

<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.
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.

Furthermore, after carrying out either the above 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 product 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 them, from the viewpoint of versatility and safety of the solvent, water, 2-propanol, 1-methoxy-2-propanol, and ethyl lactate are preferred, and 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 method of treating 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 in order to efficiently dissolve the decomposition products generated from the liquid crystal alignment film by ultraviolet light. In particular, immersion treatment for 1 to 30 minutes is preferable. The solvent during the above-mentioned 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 in terms of the solubility of the decomposition products.

After the contact treatment, it is preferable to rinse with a low boiling point solvent such as water, methanol, ethanol, 2-propanol, acetone, or methyl ethyl ketone, or to 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, more preferably 180 to 250°C, and even more preferably 200 to 230°C. The baking time is preferably 10 seconds to 30 minutes, and more preferably 1 to 10 minutes.

<Liquid crystal alignment film>
The liquid crystal alignment film of the present invention is obtained from the above liquid crystal aligning agent.
The liquid crystal alignment film of the present invention is suitable as a liquid crystal alignment film for a lateral electric field type liquid crystal display element such as an IPS type or an FFS type, and is particularly useful as a liquid crystal alignment film for an FFS type liquid crystal display element.

<Liquid crystal display element>
The liquid crystal display element of the present invention comprises the above liquid crystal alignment film.
A liquid crystal display element can be obtained by preparing a substrate having a liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention, and then preparing a liquid crystal cell by a known method, and using the liquid crystal cell.
As an example of a method for fabricating a liquid crystal cell, a liquid crystal display element having a passive matrix structure will be described below. However, a liquid crystal display element having an active matrix structure in which a switching element such as a TFT (Thin Film Transistor) is provided in each pixel portion constituting an 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. In order to control the gap between the substrates, a spacer is usually mixed into the sealant, and it is also preferable to scatter spacers for controlling the gap between the substrates on the inner surface where the sealant is not provided. An opening is provided in a part of the sealant, through which liquid crystal can be filled from the outside. Next, a 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 the opening is sealed with an adhesive. For the 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 is attached to the surface 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 drive system or FFS drive system. 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 including a step of removing the organic solvent in the temperature range of 40 to 150°C in step (2) and then performing step (3).

The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. The abbreviations of compounds and the measuring methods of each property are as follows.
(solvent)
NMP: N-methyl-2-pyrrolidone BCS: Butyl cellosolve (diamine)
DA-1 to DA-13: Compounds (tetracarboxylic dianhydrides) represented by the following formulas (DA-1) to (DA-13), respectively.
CA-1 to CA-3: Compounds (additives) represented by the following formulas (CA-1) to (CA-3), respectively.
C-1: Compound represented by the following formula (C-1) S-1: Compound represented by the following formula (S-1) F-1: Compound represented by the following formula (F-1)

（上記式中、Ｂｏｃは、ｔｅｒｔ－ブトキシカルボニル基を表す。）

(In the above formula, Boc represents a tert-butoxycarbonyl group.)

（上記式中、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。）

(In the above formula, 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 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%).

[Polymer synthesis example]
<Synthesis Example 1>
5.62g (19.2mmol) of DA-2, 4.18g (10.5mmol) of DA-10, and 2.92g (5.24mmol) of DA-7 were weighed out into a 100mL eggplant flask equipped with a stirring device and a nitrogen inlet tube, 50.9g of NMP was added, and the mixture was dissolved by stirring while feeding nitrogen. While stirring this diamine solution under water cooling, 4.50g (22.7mmol) of CA-3 was added, and 18.0g of NMP was further added, and the mixture was stirred at 50°C for 1 hour under a nitrogen atmosphere. Furthermore, 2.63g (11.7mmol) of CA-1 was added, and NMP was added so that the concentration was 20% by mass, and the mixture was stirred at 40°C for 24 hours to obtain a polyamic acid solution.
25.0 g of this polyamic acid solution was taken into a 100 mL Erlenmeyer flask containing a stirrer, 8.33 g of NMP, 2.96 g of acetic anhydride (3 equivalents relative to the molar amount of polyamic acid), and 0.766 g of pyridine (equivalent to the molar amount of polyamic acid) were added, and the mixture was stirred at room temperature for 30 minutes, and then reacted at 55 ° C. for 3 hours. This reaction solution was poured into 170 g of methanol, and the resulting precipitate was filtered off. This precipitate was washed with methanol, and then dried under reduced pressure at a temperature of 80 ° C. to obtain a polyimide resin powder (imidization rate: 86%). Furthermore, 4.00 g of this polyimide resin powder was taken into a 500 mL Erlenmeyer flask containing a stirrer, and 29.3 g of NMP was added, and the mixture was stirred at 70 ° C. for 24 hours to dissolve, and a polyimide solution (PI-1) was obtained.
<Synthesis Example 2>
In a 200 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, 2.44 g (10.0 mmol) of DA-1, 2.37 g (10.0 mmol) of DA-3, 2.30 g (10.0 mmol) of DA-4, 2.98 g (10.0 mmol) of DA-6, and 3.44 g (10.0 mmol) of DA-9 were weighed out, 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, 10.6 g (47.2 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.
35 g (8.7 mmol) of the obtained polyamic acid solution was taken into a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and 11.7 g of NMP was added and stirred for 30 minutes. 2.67 g of acetic anhydride (3 equivalents relative to the molar amount of polyamic acid) and 0.69 g of pyridine (equivalent to the molar amount of polyamic acid) were added to the obtained polyamic acid solution, and the mixture was heated at 55 ° C. for 3 hours to perform chemical imidization. The obtained reaction solution was poured into 150 ml of methanol while stirring, and the precipitate was filtered out. The same operation was carried out twice to wash the resin powder, and then the resin powder was dried under reduced pressure at 60 ° C. for 12 hours to obtain a polyimide resin powder. The imidization rate of this polyimide resin powder was 86%. 3.60 g of the obtained polyimide resin powder was dispensed into a 100 ml Erlenmeyer flask, and NMP was added so that the solid concentration became 12% by mass. The mixture was stirred at 70° C. for 24 hours to dissolve the powder, thereby obtaining a polyimide solution (PI-2).

<Synthesis Examples 3 to 5>
Polyimide solutions (PI-3) to (PI-5) were obtained in the same manner as in Synthesis Example 2, except that the types and amounts of monomers used were changed as shown in Table 1 below.

<Synthesis Example 6>
2.69 g (9.0 mmol) of DA-6 and 7.17 g (36.0 mmol) of DA-11 were placed in a 200 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and NMP was added to give a concentration of 12 mass%, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this diamine solution, 12.2 g (41.4 mmol) of CA-2 was added, and NMP was added to give a concentration of 12 mass%, and the mixture was stirred at 70° C. for 24 hours to obtain a polyamic acid solution (PAA-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 components, 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 components, and the blending ratio (parts by mole) of each organic solvent relative to 100 parts by mass of the total amount of organic solvents used in the preparation of the polyimide solution for the organic solvents.

[Preparation of liquid crystal alignment agent]
<Comparative Example 1>
In a sample tube containing a stirrer, NMP and BCS were added to the polyimide solution (PI-1) obtained in Synthesis Example 1 to dilute it, and S-1, C-1 and F-1 were added in amounts of 1 part by mass, 10 parts by mass and 15 parts by mass, respectively, relative to 100 parts by mass of polymer solid content, and the mixture was stirred for 30 minutes. In this way, a liquid crystal alignment agent (R1) was obtained in which the solid content concentration of polyimide (PI-1) was 6% by mass and the solvent composition was NMP:BCS=80:20 by mass ratio.

<Examples 1 to 8>
Liquid crystal alignment agents (1) to (8) were obtained by the same method as in Comparative Example 1 except that the polymer components used were changed as shown in Table 2 below. In Table 2, 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 numbers indicate the blending ratio (parts by mass) of each organic solvent relative to 100 parts by mass of the total amount of the organic solvent used in the preparation of the liquid crystal alignment agent.

Using the liquid crystal alignment agent obtained as described above, an FFS-driven liquid crystal cell was fabricated using 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 a 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 having a columnar spacer with a height of 3.5 μm on the surface and an ITO film for preventing static electricity 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 internal angle of 160° at the center are arranged in parallel with a gap 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 dividing the interior angles of the pixel bends 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]
A liquid crystal alignment agent filtered through a 1.0 μm filter was applied by spin coating to the surface of each of the above glass substrates, and dried for 2 minutes on a hot plate at 80° C. After that, the coating surface was irradiated with 150 to 350 mJ/ ^cm2 of linearly polarized ultraviolet light with an extinction ratio of 26:1 and a wavelength of 254 nm through a polarizing plate, and then baked for 30 minutes in a hot air circulation oven at 230° C. to obtain two substrates 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, and the sealant was cured to prepare an empty cell. Liquid crystal (MLC-3019, manufactured by Merck) was vacuum-injected into this empty cell at room temperature by a reduced pressure injection method, and the injection port was sealed to obtain an FFS drive liquid crystal cell. The obtained liquid crystal cell was then heated at 120°C for 1 hour (hereinafter also referred to as "ISO treatment") and left overnight before being used for each evaluation.

<Evaluation of Liquid Crystal Alignment>
The liquid crystal cells before the ISO treatment were used and the evaluation was performed by defining those with initial flow alignment as "bad" and those without initial flow alignment as "good".
<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 fabricated 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 a twist angle standard deviation of 0.5 or more as "poor" and a twist angle standard deviation of less than 0.5 as "good."

<Evaluation Results>
Table 3 shows the evaluation results of the liquid crystal display devices obtained by using the liquid crystal alignment agents (1) to (8) and (R1) obtained in the above Examples 1 to 8 and Comparative Example 1.

The liquid crystal aligning agent of the present invention is widely used in liquid crystal display elements of vertical electric field modes such as TN mode and VA mode, and particularly in horizontal electric field modes such as IPS mode and FFS mode.
The entire contents of the specifications, claims and abstracts of Japanese Patent Application No. 2020-039387 filed on March 6, 2020 and Japanese Patent Application No. 2020-123014 filed on July 17, 2020 are hereby incorporated by reference as the disclosure of the specification of the present invention.

Claims (13)

An imidized polymer of a polyimide precursor containing a repeating unit (a0) represented by the following formula (0) and a repeating unit (a1) represented by the following formula (1),
The liquid crystal aligning agent comprises the imidized polymer (A) having an imidization rate of 80 to 95%.

(In formula (0) and formula (1), X represents a tetravalent organic group represented by the following formula (g); Y represents a divalent organic group derived from an aromatic diamine (d0) satisfying the following conditions (1) and (2); Y is a divalent organic group derived from 2,6-diaminotoluene, 3,3'-diaminodiphenylmethane, or 1,5-bis(4-aminophenoxy)pentane, or a compound represented by the following formula (DA-4), (DA-5 ), (DA-8), (DA-11), or (DA-13); _Y1 represents a divalent organic group derived from an aromatic diamine (d1) satisfying the following conditions (1) and (3); R and Z each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; and X may be the same or different from each other.)

(In formula (g), 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 containing a fluorine atom, or a phenyl group; at least one of R ₁ to R ₄ represents a group other than a hydrogen atom as defined above; further, a portion of -CH ₂ - contained in the alkyl group, alkenyl group, alkynyl group, and monovalent organic group having 1 to 6 carbon atoms and containing a fluorine atom may be replaced by -O-; and * represents a bond.)
Condition (1): The compound has no side chain groups having six or more carbon atoms.
Condition (2): The axes of the two carbon-nitrogen bonds derived from the amino group are not parallel to each other.
Condition (3): The two carbon-nitrogen bond axes derived from the amino group are parallel to each other and have a partial structure represented by the following formula (O):

(In formula (O), each Ar independently represents a benzene ring, a biphenyl structure, or a naphthalene ring, any hydrogen atom on the ring may be replaced with a halogen atom or a monovalent organic group, _Q2 represents -( _CH2 ) _n- (n is an integer from 2 to 18) or a group in which any _-CH2- in the -( _CH2 ) _n- is replaced with -O-, -C(=O)- or -O-C(=O)-, and * represents a bond.)

The liquid crystal aligning agent according to claim 1, wherein Y ₁ in the formula (1) is a divalent organic group derived from a diamine represented by the following formulas (d1-1) to (d1-14).

The liquid crystal aligning agent according to claim 1 or 2, wherein the sum of the repeating units (a0), (a1) and their imidized repeating units is 5 mol % or more based on the total repeating units. The tetravalent organic group represented by the formula (g) is a tetravalent organic group represented by any one of the following formulas (g-1) to (g-5). The liquid crystal aligning agent according to any one of claims 1 to 3.

(In formulas (g-1) to (g-5), * represents a bond.) The polymer (A) is an imidized polymer of a polyimide precursor having a repeating unit (a2) represented by the following formula (2) different from the repeating unit (a0) or (a1), according to any one of claims 1 to 4. The liquid crystal aligning agent according to any one of claims 1 to 4.

(In the formula, _X2 represents a tetravalent organic group, _Y2 represents a divalent organic group derived from an aromatic diamine having no side chain group having 6 or more carbon atoms, and R and Z are defined as R and Z in the formula (0).) The liquid crystal aligning agent according to any one of claims 1 to 5, wherein either or both of the aromatic diamine (d0) and the aromatic diamine (d1) are aromatic diamines having 4 to 40 carbon atoms. The liquid crystal alignment agent according to any one of claims 1 to 6, which is for use in a photoalignment method. A liquid crystal alignment film obtained from the liquid crystal alignment agent according to any one of claims 1 to 7. A liquid crystal display element comprising the liquid crystal alignment film according to claim 8. 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 alignment agent according to any one of claims 1 to 7 onto a substrate; Step (2): A step of heating the liquid crystal alignment agent applied in step (1) 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 10, 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 10 or 11, wherein the step (2) is a step of obtaining a film by heating in a temperature range of 40 to 180°C. A liquid crystal display element having a liquid crystal alignment film obtained by the method for producing a liquid crystal alignment film according to any one of claims 10 to 12.