JP7484664B2 - Liquid crystal alignment agent for forming a liquid crystal alignment film for photoalignment, liquid crystal alignment film, and liquid crystal device using the same - Google Patents

Description

The present invention relates to a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal element using the same. More specifically, the present invention relates to a liquid crystal alignment agent for photo-alignment (hereinafter sometimes abbreviated as liquid crystal alignment agent) for forming a liquid crystal alignment film using a photo-alignment method (hereinafter sometimes abbreviated as a photo-alignment film), a liquid crystal alignment film using a photo-alignment method formed using the liquid crystal alignment agent, and a liquid crystal display element having the liquid crystal alignment film.

Liquid crystal elements are known that can cause optical phenomena such as refraction, scattering, and reflection of electromagnetic waves incident on the element by controlling or modulating the orientation state of the liquid crystal layer within the element. In addition to the liquid crystal display elements listed below, liquid crystal antennas, dimming windows, optical compensation materials, and variable phase shifters are also known.

Liquid crystal display elements are known to have various driving methods, such as TN (Twisted Nematic) mode, STN (Super Twisted Nematic) mode, IPS (In-Plane Switching) mode, FFS (Fringe Field Switching) mode, and vertical alignment VA (Multi-domain Vertical Alignment) mode. These liquid crystal display elements are used in image display devices of various electronic devices such as televisions and mobile phones, and development is underway to further improve display quality. Specifically, the performance of liquid crystal display elements is improved not only by improvements in the driving method and element structure, but also by the components used in the elements. Among the components used in liquid crystal display elements, the liquid crystal alignment film in particular is one of the important materials related to display quality, and research on this liquid crystal alignment film is being actively conducted in order to meet the demand for higher quality liquid crystal display elements.

Here, the liquid crystal alignment film is provided on a pair of substrates provided on both sides of the liquid crystal layer of the liquid crystal display element, in contact with the liquid crystal layer, and has the function of orienting the liquid crystal molecules that make up the liquid crystal layer with a certain regularity relative to the substrates. By using a liquid crystal alignment film with high liquid crystal alignment properties, it is possible to realize a liquid crystal display element with high contrast and improved afterimage characteristics (see, for example, Patent Documents 1 and 2).

Currently, solutions (varnishes) in which polyamic acid, soluble polyimide, or polyamic acid ester is dissolved in an organic solvent are mainly used to form such liquid crystal alignment films. To form liquid crystal alignment films using these varnishes, the varnish is applied to a substrate, and the coating is solidified by heating or other methods to form a polyimide-based liquid crystal alignment film, and an alignment treatment suitable for the display mode described above is performed as necessary. Known alignment treatment methods include the rubbing method, in which the surface of the alignment film is rubbed with a cloth or the like to align the direction of the polymer molecules, and the photoalignment method, in which the alignment film is irradiated with linearly polarized ultraviolet light to cause photochemical changes such as photoisomerization and dimerization in the polymer molecules to give the film anisotropy. Of these, the photoalignment method has the advantages of being more uniform in alignment than the rubbing method, being a non-contact alignment treatment method that does not scratch the film, and reducing the causes of display defects in liquid crystal display elements such as dust generation and static electricity.

For example, Patent Documents 1 to 6 describe liquid crystal alignment films produced using such photoalignment methods, in which diaminoazobenzene and the like are used as raw materials and photoisomerization technology is applied to obtain photoalignment films with large anchoring energy and good liquid crystal alignment properties.

Patent Publication 2010-197999 International Publication No. 2013/157463 JP2005-275364 Patent Publication 2007-248637 JP2009-069493 International Publication No. 2015/016118

In recent years, the applications of liquid crystal display elements have become diverse, including monitors for personal computers, LCD televisions, mobile phones, smartphone displays, and medical monitors. There is a demand for better display quality, and contrast is one of the important characteristics that affect display quality.

Therefore, the inventors have conducted extensive research with the objectives of providing an alignment film capable of forming a liquid crystal display element having good contrast and excellent display quality, and of providing a liquid crystal alignment agent for photo-alignment capable of forming such a liquid crystal alignment film.

As a result of intensive research to solve the above problems, the present inventors have found that an alignment film having high liquid crystal alignment properties can be obtained by using a compound having an azobenzene structure and a compound represented by formula (1), and that a liquid crystal display element having good contrast and excellent display quality can be formed by using this alignment film, thereby completing the present invention.
The present invention includes the following configurations.

式（１）において、Ｒ^１、Ｒ^２はそれぞれ独立に、水素原子、炭素数が１から４のアルキル基及び－Ｆから選択される１種を示し、ｉは１～４の整数を示す。
［２］ 前記式（１）で表されるテトラカルボン酸二無水物について、Ｒ^１、Ｒ^２が水素原子であり、ｉが２または３である、［１］に記載の光配向用液晶配向剤。
［３］ 前記アゾベンゼン構造を有する化合物が、下記式（２）で表される化合物の少なくとも１つであることを特徴とする、［１］または［２］に記載の光配向用液晶配向剤。

式（２）においてＸは炭素数１～１２のアルキレン基であり、前記アルキレン基の－（ＣＨ_２）_２－の隣り合わない１つ以上が－Ｏ－および－ＮＨ－のいずれかで置き換えられていてもよく、
Ｒ^ａおよびＲ^ｂはそれぞれ独立して水素原子、－ＣＨ_３、－ＯＣＨ_３、－ＣＦ_３、－Ｆ、－ＣＯＯＣＨ_３、または式（Ｐ１－１）もしくは式（Ｐ１－２）で表される１価の基であり、
Ｒ^ｃはそれぞれ独立して水素原子、－ＣＨ_３、－ＯＣＨ_３、－ＣＦ_３、－Ｆ、または式（Ｐ１－１）もしくは式（Ｐ１－２）で表される１価の基であり、ｊは０または１であり、ａ～ｃはそれぞれ独立に０～２の整数であり、

式（Ｐ１－１）および式（Ｐ１－２）において、Ｒ^６ａ、Ｒ^７ａおよびＲ^８ａは、それぞれ独立して、水素原子、置換もしくは無置換のアルキル基、置換もしくは無置換のアルカノイル基、置換もしくは無置換のアルコキシカルボニル基、または置換もしくは無置換のアリールカルボニル基を表し、Ｒ^６ａ、Ｒ^７ａおよびＲ^８ａは互いに同一であっても異なっていてもよく、＊は、式（２）におけるベンゼン環への結合位置を表し、
式（２）において、環を構成するいずれかの炭素原子に結合位置が固定されていない基は、その環における結合位置が任意であることを示す。
［４］ 式（２）で表される化合物が、下記式（２－１）から式（２－３）のいずれか１つである、［３］に記載の光配向用液晶配向剤。

式（２－１）において、Ｒ^１ａおよびＲ^１ｃは、それぞれ独立して、水素原子または式（Ｐ１－１）もしくは式（Ｐ１－２）で表される１価の基を表し、
式（２－２）において、Ｒ^２ａおよびＲ^２ｂは、それぞれ独立して、水素原子または式（Ｐ１－１）もしくは式（Ｐ１－２）で表される１価の基を表し、Ｒ^２ｃはそれぞれ独立して水素原子、－ＣＨ_３、－ＯＣＨ_３、－ＣＦ_３、－Ｆであり、Ｘ_１は炭素数１～１２のアルキレン基であり、前記アルキレンの－（ＣＨ_２）_２－の隣り合わない１つ以上が－Ｏ－および－ＮＨ－のいずれかで置き換えられていてもよく、ｋは０～２の整数であり、
式（２－３）において、Ｒ^３ａは、それぞれ独立して、水素原子または式（Ｐ１－１）もしくは式（Ｐ１－２）で表される１価の基を表し、Ｒ^４、Ｒ^５は、それぞれ独立して、水素原子または－Ｆであり、Ｒ^４およびＲ^５が同時に水素原子となることはなく、Ｒ^3ｃはそれぞれ独立して水素原子、－ＣＨ_３、－ＯＣＨ_３、－ＣＦ_３、－Ｆであり、Ｘ_１は炭素数１～１２のアルキレン基であり、前記アルキレン基の－（ＣＨ_２）_２－の隣り合わない１つ以上が－Ｏ－および－ＮＨ－のいずれかで置き換えられていてもよく、ｍは０～２の整数であり、

式（Ｐ１－１）および式（Ｐ１－２）において、Ｒ^６ａ、Ｒ^７ａおよびＲ^８ａは、それぞれ独立して、水素原子、置換もしくは無置換のアルキル基、置換もしくは無置換のアルカノイル基、置換もしくは無置換のアルコキシカルボニル基、または置換もしくは無置換のアリールカルボニル基を表し、Ｒ^６ａ、Ｒ^７ａおよびＲ^８ａは互いに同一であっても異なっていてもよく、＊は、式（１）におけるベンゼン環への結合位置を表し、
式（２－１）、式（２－２）および式（２－３）において、環を構成するいずれかの炭素原子に結合位置が固定されていない基は、その環における結合位置が任意であることを示す。
［５］ さらに、添加剤を含む、［１］～［４］のいずれか１項に記載の光配向用液晶配向剤。
［６］ 添加剤が、オキサゾリン化合物およびエポキシ化合物からなる群から選ばれる少なくとも１つである、［５］に記載の光配向用液晶配向剤。
［７］ ［１］～［６］のいずれか１項に記載の光配向用液晶配向剤から形成される液晶配向膜。
［８］ ［７］に記載の液晶配向膜を有する液晶素子。
［９］ ［１］～［６］のいずれか１項に記載の光配向用液晶配向剤を基板に塗布する工程と、その塗膜に偏光紫外線を照射する工程とを含む、液晶配向膜の製造方法。 [1] A liquid crystal alignment agent for photo-alignment, comprising at least one polymer and a solvent, wherein at least one of the polymers is a polymer obtained by reacting tetracarboxylic dianhydrides with diamines, and a raw material composition used as a raw material for the polymer obtained by reacting tetracarboxylic dianhydrides with diamines contains at least one compound represented by formula (1) and a compound having an azobenzene structure.

In formula (1), R ¹ and R ² each independently represent one selected from a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and -F; and i represents an integer of 1 to 4.
[2] The liquid crystal aligning agent for photo-alignment according to [1], wherein in the tetracarboxylic dianhydride represented by the formula (1), R ¹ and R ² are hydrogen atoms, and i is 2 or 3.
[3] The liquid crystal aligning agent for photo-alignment according to [1] or [2], characterized in that the compound having an azobenzene structure is at least one compound represented by the following formula (2):

In formula (2), X is an alkylene group having 1 to 12 carbon atoms, and one or more non-adjacent —(CH ₂ ) ₂ — groups in the alkylene group may be replaced with —O— or —NH—;
R ^a and R ^b each independently represent a hydrogen atom, -CH ₃ , -OCH ₃ , -CF ₃ , -F, -COOCH ₃ , or a monovalent group represented by formula (P1-1) or formula (P1-2);
R ^c each independently represents a hydrogen atom, —CH ₃ , —OCH ₃ , —CF ₃ , —F, or a monovalent group represented by formula (P1-1) or formula (P1-2); j is 0 or 1; a to c each independently represent an integer of 0 to 2;

In formula (P1-1) and formula (P1-2), R ^6a , R ^7a , and R ^8a each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkanoyl group, a substituted or unsubstituted alkoxycarbonyl group, or a substituted or unsubstituted arylcarbonyl group, R ^6a , R ^7a , and R ^8a may be the same or different, * represents the bonding position to the benzene ring in formula (2),
In formula (2), a group that is not bonded to any carbon atom constituting a ring indicates that the group may be bonded to any position on the ring.
[4] The compound represented by formula (2) is any one of the following formulas (2-1) to (2-3):

In formula (2-1), R ^1a and R ^1c each independently represent a hydrogen atom or a monovalent group represented by formula (P1-1) or formula (P1-2),
In formula (2-2), R ^2a and R ^2b each independently represent a hydrogen atom or a monovalent group represented by formula (P1-1) or formula (P1-2); R ^2c each independently represent a hydrogen atom, -CH ₃ , -OCH ₃ , -CF ₃ , or -F; X ₁ represents an alkylene group having 1 to 12 carbon atoms, and one or more non-adjacent -(CH ₂ ) ₂ - of the alkylene may be replaced by either -O- or -NH-; k represents an integer of 0 to 2;
In formula (2-3), R ^3a each independently represents a hydrogen atom or a monovalent group represented by formula (P1-1) or formula (P1-2); R ⁴ and R ⁵ each independently represent a hydrogen atom or -F, R ⁴ and R ⁵ are not simultaneously hydrogen atoms; R ^3c each independently represents a hydrogen atom, -CH ₃ , -OCH ₃ , -CF ₃ , -F; X ₁ represents an alkylene group having 1 to 12 carbon atoms, and one or more non-adjacent -(CH ₂ ) ₂ - in the alkylene group may be replaced by either -O- or -NH-; m represents an integer of 0 to 2;

In formula (P1-1) and formula (P1-2), R ^6a , R ^7a , and R ^8a each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkanoyl group, a substituted or unsubstituted alkoxycarbonyl group, or a substituted or unsubstituted arylcarbonyl group, R ^6a , R ^7a , and R ^8a may be the same or different, * represents the bonding position to the benzene ring in formula (1),
In the formulae (2-1), (2-2) and (2-3), a group that is not bonded to any carbon atom constituting a ring means that the bonding position in the ring is arbitrary.
[5] The liquid crystal aligning agent for photoalignment according to any one of [1] to [4], further comprising an additive.
[6] The liquid crystal aligning agent for photo-alignment according to [5], wherein the additive is at least one selected from the group consisting of oxazoline compounds and epoxy compounds.
[7] A liquid crystal alignment film formed from the liquid crystal alignment agent for photo-alignment according to any one of [1] to [6].
[8] A liquid crystal element having the liquid crystal alignment film according to [7].
[9] A method for producing a liquid crystal alignment film, comprising the steps of applying the liquid crystal alignment agent for photo-alignment according to any one of [1] to [6] to a substrate, and irradiating the coating with polarized ultraviolet light.

By using the liquid crystal alignment agent for photo-alignment of the present invention, a liquid crystal alignment film with high liquid crystal alignment properties can be obtained. Furthermore, by using this liquid crystal alignment film, a liquid crystal display element with good contrast and excellent display quality can be realized.

The present invention will be described in detail below. The following description of the constituent elements may be based on a representative embodiment or specific example, but the present invention is not limited to such an embodiment. The "liquid crystal alignment agent" in the present invention is a liquid crystal alignment agent that can impart anisotropy by irradiating a polarized ultraviolet ray when the film is formed on a substrate, and is sometimes simply referred to as a "liquid crystal alignment agent" or a "liquid crystal alignment agent for photoalignment" in this specification. In addition, in the present invention, "tetracarboxylic dianhydrides" refer to tetracarboxylic dianhydrides, tetracarboxylic diesters, or tetracarboxylic diester dihalides. In the present invention, diamines and dihydrazides are sometimes referred to as "diamines".

<Liquid crystal alignment agent for photoalignment of the present invention>
The liquid crystal aligning agent for photoalignment of the present invention is characterized in that it contains at least one polymer selected from the group consisting of polyamic acid and polyamic acid derivatives, which are obtained by reacting tetracarboxylic dianhydrides with diamines, and contains at least one compound represented by formula (1) and a compound having an azobenzene structure as raw materials for the polymer. In the present invention, the polyamic acid derivative refers to polyimide, partial polyimide, polyamic acid ester, polyamic acid-polyamide copolymer, and polyamideimide. Such a polymer may be referred to as the polymer of the present invention.

式（１）において、Ｒ^１、Ｒ^２はそれぞれ独立に、水素原子、炭素数が１から４のアルキル基及び－Ｆから選択される１種を示し、ｉは１～４の整数を示す。 <Compound represented by formula (1)>
The compound represented by formula (1) used in the polymer contained in the liquid crystal aligning agent of the present invention will be described.

In formula (1), R ¹ and R ² each independently represent one selected from a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and -F; and i represents an integer of 1 to 4.

In the formula (1), a compound in which R ¹ and R ² are hydrogen atoms and i is 2 or 3 is preferred, and a compound in which R ¹ and R ² are hydrogen atoms and i is 2 (formula (1-1)) is more preferred.

The acid dianhydrides used in the polymer contained in the liquid crystal aligning agent of the present invention may be entirely compounds represented by formula (1), or may be used in combination with other acid dianhydrides described below.

式（Ａ）において、＊は結合手であり、結合手のベンゼン環に対する結合位置はそれぞれ独立して任意であり、ベンゼン環の置換可能な水素は置換基を有していてもよい。 <Compounds Having an Azobenzene Structure>
The compound having an azobenzene structure used in the polymer contained in the liquid crystal alignment agent of the present invention will be described. By using a compound having an azobenzene structure as a raw material, a photoreactive structure can be incorporated into the polymer. In this specification, the azobenzene structure refers to a structure represented by the following formula (A).

In formula (A), * represents a bond, and the bonding positions of the bonds on the benzene ring are each independently arbitrary, and a substitutable hydrogen atom on the benzene ring may have a substituent.

When the coating of the photo-alignment liquid crystal alignment agent of the present invention is irradiated with ultraviolet light as described below in the process of forming a liquid crystal alignment film, the azobenzene structure of the polymer main chain, which is roughly parallel to the polarization direction, undergoes a photoisomerization reaction, and the components of the polymer chain that are oriented in a specific direction (roughly perpendicular to the polarization direction of the irradiated light) become dominant, imparting anisotropy to the coating. This state in which the components of the polymer chain that are oriented in a specific direction become dominant is expressed as the polymer chain being oriented. When the photo-alignment film formed by baking this coating is used in a liquid crystal display element, the interaction between the surface of the oriented film and the liquid crystal molecules results in the liquid crystal molecules being oriented with their long axes aligned in a certain direction (roughly perpendicular to the polarization direction of the irradiated light).

式（２）においてＸは炭素数１～１２のアルキレン基であり、前記アルキレン基の－（ＣＨ_２）_２－の隣り合わない１つ以上が－Ｏ－および－ＮＨ－のいずれかで置き換えられていてもよく、
Ｒ^ａおよびＲ^ｂはそれぞれ独立して水素原子、－ＣＨ_３、－ＯＣＨ_３、－ＣＦ_３、－Ｆ、－ＣＯＯＣＨ_３、または式（Ｐ１－１）もしくは式（Ｐ１－２）で表される１価の基であり、Ｒ^ｃはそれぞれ独立して水素原子、－ＣＨ_３、－ＯＣＨ_３、－ＣＦ_３、－Ｆ、または式（Ｐ１－１）もしくは式（Ｐ１－２）で表される１価の基であり、ｊは０または１であり、ａ～ｃはそれぞれ独立に０～２の整数であり、

式（Ｐ１－１）および式（Ｐ１－２）において、Ｒ^６ａ、Ｒ^７ａおよびＲ^８ａは、それぞれ独立して、水素原子、置換もしくは無置換のアルキル基、置換もしくは無置換のアルカノイル基、置換もしくは無置換のアルコキシカルボニル基、または置換もしくは無置換のアリールカルボニル基を表し、Ｒ^６ａ、Ｒ^７ａおよびＲ^８ａは互いに同一であっても異なっていてもよく、＊は、式（２）におけるベンゼン環への結合位置を表し、
式（２）において、環を構成するいずれかの炭素原子に結合位置が固定されていない基は、その環における結合位置が任意であることを示す。 The compound having an azobenzene structure used in the polymer contained in the photo-alignment liquid crystal aligning agent of the present invention is specifically a compound represented by formula (2).

In formula (2), X is an alkylene group having 1 to 12 carbon atoms, and one or more non-adjacent —(CH ₂ ) ₂ — groups in the alkylene group may be replaced with —O— or —NH—;
R ^a and R ^b are each independently a hydrogen atom, -CH ₃ , -OCH ₃ , -CF ₃ , -F, -COOCH ₃ , or a monovalent group represented by formula (P1-1) or formula (P1-2); R ^c are each independently a hydrogen atom, -CH ₃ , -OCH ₃ , -CF ₃ , -F, or a monovalent group represented by formula (P1-1) or formula (P1-2); j is 0 or 1; and a to c are each independently an integer of 0 to 2;

In formula (P1-1) and formula (P1-2), R ^6a , R ^7a , and R ^8a each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkanoyl group, a substituted or unsubstituted alkoxycarbonyl group, or a substituted or unsubstituted arylcarbonyl group, R ^6a , R ^7a , and R ^8a may be the same or different, * represents the bonding position to the benzene ring in formula (2),
In formula (2), a group that is not bonded to any carbon atom constituting a ring indicates that the group may be bonded to any position on the ring.

式（２－１）において、Ｒ^１ａおよびＲ^１ｃは、それぞれ独立して、水素原子、式（Ｐ１－１）または式（Ｐ１－２）で表される１価の基を表し、
式（２－２）において、Ｒ^２ａおよびＲ^２ｂは、それぞれ独立して、水素原子、式（Ｐ１－１）または式（Ｐ１－２）で表される１価の基を表し、Ｒ^２ｃはそれぞれ独立して水素原子、－ＣＨ_３、－ＯＣＨ_３、－ＣＦ_３、－Ｆであり、Ｘ_１は炭素数１～１２のアルキレン基であり、前記アルキレン基の－（ＣＨ_２）_２－の隣り合わない１つ以上が－Ｏ－および－ＮＨ－のいずれかで置き換えられていてもよく、ｋは０～２の整数であり、
式（２－３）において、Ｒ^３ａは、それぞれ独立して、水素原子、式（Ｐ１－１）または式（Ｐ１－２）で表される１価の基を表し、Ｒ^４、Ｒ^５は、それぞれ独立して、水素原子または－Ｆであり、Ｒ^４およびＲ^５が同時に水素原子となることはなく、Ｒ^3ｃはそれぞれ独立して水素原子、－ＣＨ_３、－ＯＣＨ_３、－ＣＦ_３、－Ｆであり、Ｘ_１は炭素数１～１２のアルキレン基であり、前記アルキレン基の－（ＣＨ_２）_２－の隣り合わない１つ以上が－Ｏ－および－ＮＨ－のいずれかで置き換えられていてもよく、ｍは０～２の整数であり、

式（Ｐ１－１）および式（Ｐ１－２）において、Ｒ^６ａ、Ｒ^７ａおよびＲ^８ａは、それぞれ独立して、水素原子、置換もしくは無置換のアルキル基、置換もしくは無置換のアルカノイル基、置換もしくは無置換のアルコキシカルボニル基、または置換もしくは無置換のアリールカルボニル基を表し、Ｒ^６ａ、Ｒ^７ａおよびＲ^８ａは互いに同一であっても異なっていてもよく、＊は、式（１）におけるベンゼン環への結合位置を表し、
式（２－１）、式（２－２）および式（２－３）において、環を構成するいずれかの炭素原子に結合位置が固定されていない基は、その環における結合位置が任意であることを示す。 The compound represented by formula (2) is specifically a compound represented by the following formulas (2-1) to (2-3).

In formula (2-1), R ^1a and R ^1c each independently represent a hydrogen atom or a monovalent group represented by formula (P1-1) or formula (P1-2).
In formula (2-2), R ^2a and R ^2b each independently represent a hydrogen atom or a monovalent group represented by formula (P1-1) or formula (P1-2); R ^2c each independently represent a hydrogen atom, -CH ₃ , -OCH ₃ , -CF ₃ , or -F; X ₁ represents an alkylene group having 1 to 12 carbon atoms, and one or more non-adjacent -(CH ₂ ) ₂ - in the alkylene group may be replaced by either -O- or -NH-; k represents an integer of 0 to 2;
In formula (2-3), R ^3a each independently represents a hydrogen atom or a monovalent group represented by formula (P1-1) or formula (P1-2); R ⁴ and R ⁵ each independently represent a hydrogen atom or -F, and R ⁴ and R ⁵ are not simultaneously hydrogen atoms; R ^3c each independently represents a hydrogen atom, -CH ₃ , -OCH ₃ , -CF ₃ , or -F; X ₁ represents an alkylene group having 1 to 12 carbon atoms, and one or more non-adjacent -(CH ₂ ) ₂ - in the alkylene group may be replaced by either -O- or -NH-; m represents an integer of 0 to 2;

In formula (P1-1) and formula (P1-2), R ^6a , R ^7a , and R ^8a each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkanoyl group, a substituted or unsubstituted alkoxycarbonyl group, or a substituted or unsubstituted arylcarbonyl group, R ^6a , R ^7a , and R ^8a may be the same or different, * represents the bonding position to the benzene ring in formula (1),
In the formulae (2-1), (2-2) and (2-3), a group that is not bonded to any carbon atom constituting a ring means that the bonding position in the ring is arbitrary.

式（２－１－２）において、Ｒ^６ａは炭素数１～４のアルキル基である。 Specific examples of the compound represented by formula (2-1) include the following compounds.

In formula (2-1-2), R ^6a is an alkyl group having 1 to 4 carbon atoms.

式（２－２－１）～式（２－２－６）において、Ｒ^６ａは炭素数１～４のアルキル基であり、ｌは１～１０の整数であり、ｍは１～１１の整数である。 Specific examples of the compound represented by formula (2-2) include the following compounds.

In formulas (2-2-1) to (2-2-6), R ^6a is an alkyl group having 1 to 4 carbon atoms, l is an integer of 1 to 10, and m is an integer of 1 to 11.

式（２－３－１）および式（２－３－２）において、ｌは１～１０の整数である。 Specific examples of the compound represented by formula (2-3) include the following compounds.

In formulas (2-3-1) and (2-3-2), l is an integer of 1 to 10.

When the transparency of the formed liquid crystal alignment film is important, it is preferable to use one or more compounds selected from the group consisting of formula (2-1-2), formula (2-1-3), formula (2-2-3), formula (2-2-4), formula (2-2-5), and formula (2-2-6), more preferably formula (2-1-2) and formula (2-1-3), and particularly preferably a compound of formula (2-1-2) in which R ^6a is an ethyl group.

In the case where importance is placed on obtaining a liquid crystal alignment film capable of forming an element having good afterimage characteristics even with a small amount of energy during the alignment treatment (i.e., a liquid crystal alignment agent with high sensitivity), it is preferable to use one or more compounds selected from the group consisting of formula (2-1-2), formula (2-1-3), formula (2-2-3), formula (2-2-4), formula (2-2-5), formula (2-2-6), formula (2-3-1), and formula (2-3-2), and formula (2-1-2), formula (2-3-1), and formula (2-3-2) are more preferable, and a compound in which R ^6a is an ethyl group in formula (2-1-2) or a compound represented by l = 2 to 6 in formula (2-3-1) is even more preferable.

In the case where importance is placed on obtaining a liquid crystal display element which maintains a high voltage holding ratio even in long-term use (i.e., has excellent VHR reliability), it is preferable to use any one or more compounds selected from the group consisting of formulas (2-1-2), (2-1-3), (2-2-1), (2-2-2), (2-2-3), (2-2-4), (2-2-5), and (2-2-6). More preferable are compounds in which l=2 to 6 in formula (2-1-2), (2-1-3), or (2-2-1), and even more preferable are compounds in which R ^6a is an ethyl group in formula (2-1-2) or compounds in which l=2 to 6 in formula (2-2-1).

When emphasis is placed on obtaining a liquid crystal display element with higher contrast, it is more preferable to use one or more compounds selected from the group consisting of formula (2-1-1), formula (2-2-1), and formula (2-2-2), and more preferable is a compound represented by formula (2-1-2) or formula (2-2-1) where l=2 to 6.

<Type of polymer>
The polyamic acid and the polyamic acid derivatives will be described in detail below.

Here, the polyamic acid is a polymer synthesized by a polymerization reaction between a diamine represented by formula (DI) and a tetracarboxylic dianhydride represented by formula (AN), and has a constitutional unit represented by formula (PAA). When a liquid crystal alignment agent containing a polyamic acid is heated and baked in the process of forming a liquid crystal alignment film, the polyamic acid is imidized, and a polyimide liquid crystal alignment film having a constitutional unit represented by formula (PI) can be formed.

In formula (AN), formula (PAA), and formula (PI), ^X1 is a tetravalent organic group. In formula (DI), formula (PAA), and formula (PI), ^X2 is a divalent organic group. For the preferred range and specific examples of the tetravalent organic group in ^X1 , reference can be made to the corresponding structure of the tetracarboxylic dianhydride described in formula (1) or the other tetracarboxylic dianhydride column below. For the preferred range and specific examples of the divalent organic group in ^X2 , reference can be made to the corresponding structure of the diamine or dihydrazide described in formula (2) or the other diamine column below.

式（ＰＡＥ）において、Ｘ^１は４価の有機基であり、Ｘ^２は２価の有機基であり、Ｙはアルキル基である。Ｘ^１、Ｘ^２の好ましい範囲と具体例については、式（ＰＡＡ）におけるＸ^１、Ｘ^２についての記載を参照することができる。Ｙにおいては、炭素数１～６の直鎖または分岐鎖のアルキル基が好ましく、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、またはターシャリーブチル基がより好ましい。 The polyamic acid derivative is a compound in which a part of the polyamic acid is replaced with another atom or atomic group to modify the properties, and is preferably one which has high solubility in a solvent used for a liquid crystal alignment agent. Specific examples of such polyamic acid derivatives include 1) polyimides in which all amino groups and carboxyl groups of a polyamic acid are subjected to a dehydration ring-closing reaction, 2) partial polyimides in which a part of the polyamic acid is subjected to a dehydration ring-closing reaction, 3) polyamic acid esters in which the carboxyl groups of a polyamic acid are converted into esters, 4) polyamic acid-polyamide copolymers obtained by replacing a part of the acid dianhydride contained in a tetracarboxylic dianhydride compound with an organic dicarboxylic acid and reacting the resulting mixture, and 5) polyamideimides in which a part or all of the polyamic acid-polyamide copolymer is subjected to a dehydration ring-closing reaction. Among these derivatives, for example, polyimides can be exemplified by those having a structural unit represented by the above formula (PI), and polyamic acid esters can be exemplified by those having a structural unit represented by the following formula (PAE).

In formula (PAE), ^X1 is a tetravalent organic group, ^X2 is a divalent organic group, and Y is an alkyl group. For preferred ranges and specific examples of ^X1 and ^X2 , the description of ^X1 and ^X2 in formula (PAA) can be referred to. Y is preferably a linear or branched alkyl group having 1 to 6 carbon atoms, and more preferably a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, or a tertiary butyl group.

Polyamic acids can be obtained as reaction products by polymerization reaction of tetracarboxylic dianhydrides and diamines. For explanations of tetracarboxylic dianhydrides, their preferred ranges, and specific examples, please refer to the description in the Tetracarboxylic Dianhydrides section below. For explanations of diamines, their preferred ranges, and specific examples, please refer to the description in the Diamines section below.

The tetracarboxylic dianhydrides and diamines used in the synthesis of the polyamic acid may each be one type or two or more types. The polyamic acid of the present invention can be obtained by using a compound represented by formula (1) as at least one of the tetracarboxylic dianhydrides and a compound represented by formula (2) as at least one of the diamines.

When the polyamic acid of the present invention is to be converted into a polyimide, which is a polyamic acid derivative, the polyimide can be obtained by imidizing the obtained polyamic acid solution with an acid anhydride such as acetic anhydride, propionic anhydride, or trifluoroacetic anhydride as a dehydrating agent, and a tertiary amine such as triethylamine, pyridine, or collidine as a dehydration ring-closing catalyst at a temperature of 20 to 150°C. Alternatively, the polyamic acid can be precipitated from the obtained polyamic acid solution using a large amount of a poor solvent (an alcohol-based solvent such as methanol, ethanol, or isopropanol, or a glycol-based solvent), and the precipitated polyamic acid can be imidized in a solvent such as toluene or xylene at a temperature of 20 to 150°C together with the above-mentioned dehydrating agent and dehydration ring-closing catalyst to obtain a polyimide.

In the imidization reaction, the ratio of the dehydrating agent to the dehydration ring-closing catalyst is preferably 0.1 to 10 (molar ratio). The total amount of the dehydrating agent and the dehydration ring-closing catalyst used is preferably 1.5 to 10 times the molar amount of the tetracarboxylic dianhydride used in the synthesis of the polyamic acid. The degree of imidization can be controlled by adjusting the amount of the dehydrating agent and catalyst used in the imidization reaction, the reaction temperature, and the reaction time, thereby obtaining a partial polyimide in which only a portion of the polyamic acid is imidized. The obtained polyimide can be separated from the solvent used in the reaction and redissolved in another solvent and used as a liquid crystal alignment agent, or it can be used as a liquid crystal alignment agent without separating it from the solvent.

The polyamic acid ester can be obtained by a synthesis method of reacting a polyamic acid with a hydroxyl group-containing compound, a halide, an epoxy group-containing compound, or the like, or by a synthesis method of reacting a tetracarboxylic acid diester or a tetracarboxylic acid diester dichloride derived from a tetracarboxylic acid dianhydride with a diamine. The tetracarboxylic acid diester derived from a tetracarboxylic acid dianhydride can be obtained, for example, by reacting the tetracarboxylic acid dianhydride with two equivalents of an alcohol to open the ring, and the tetracarboxylic acid diester dichloride can be obtained by reacting the tetracarboxylic acid diester with two equivalents of a chlorinating agent (e.g., thionyl chloride, etc.). The polyamic acid ester may have only an amic acid ester structure, or may be a partial ester in which an amic acid structure and an amic acid ester structure coexist. The polyamic acid ester of the present invention can be obtained by using a compound represented by formula (1) as at least one of the tetracarboxylic acid dianhydrides and a compound represented by formula (2) as at least one of the diamines.

The polyamic acid or its derivative of the present invention can be produced in the same manner as known polyamic acids or their derivatives used in forming polyimide films. The total amount of tetracarboxylic dianhydrides charged is preferably 0.9 to 1.1 moles per mole of diamines in total.

The liquid crystal alignment agent of the present invention may contain only one of these polyamic acids, polyamic acid esters, and polyimides obtained by imidizing these, or may contain two or more of them.

The molecular weight of the polyamic acid or its derivative of the present invention is preferably 5,000 to 500,000, more preferably 5,000 to 50,000, in terms of polystyrene equivalent weight average molecular weight (Mw). The molecular weight of the polyamic acid or its derivative can be determined by measurement using gel permeation chromatography (GPC).

The presence of the polyamic acid or its derivative of the present invention can be confirmed by analyzing the solid content obtained by precipitating the polyamic acid or its derivative with a large amount of poor solvent using IR (infrared spectroscopy) or NMR (nuclear magnetic resonance analysis). The monomers used can also be confirmed by analyzing an organic solvent extract of the decomposition product of the polyamic acid or its derivative with an aqueous solution of a strong alkali such as KOH or NaOH using GC (gas chromatography), HPLC (high performance liquid chromatography) or GC-MS (gas chromatography mass spectrometry).

<Other tetracarboxylic acid dianhydrides>
The tetracarboxylic dianhydrides other than the compound represented by formula (1) used as the raw material for the polymer of the present invention can be selected from known tetracarboxylic dianhydrides without any limitation.

Other examples of tetracarboxylic dianhydrides are given below. These tetracarboxylic dianhydrides may be converted into tetracarboxylic diesters or tetracarboxylic diester dichlorides and used as raw materials for polymers.

Such tetracarboxylic dianhydrides may belong to either the aromatic system (including heteroaromatic ring systems) in which the dicarboxylic anhydride is directly bonded to the aromatic ring, or the aliphatic system (including heterocyclic ring systems) in which the dicarboxylic anhydride is not directly bonded to the aromatic ring.

Examples of such tetracarboxylic dianhydrides include compounds represented by the following formulae (AN-1) to (AN-9), (AN-11), (AN-12), (AN-15), (AN-10-1), (AN-10-2), and (AN-16-1) to (AN-16-15).

式（ＡＮ－１）において、Ｇ^１１は単結合、炭素数１～１２のアルキレン基、１，４－フェニレン基、または１，４－シクロヘキシレン基である。Ｘ^１１は独立して単結合または－ＣＨ_２－である。Ｇ^１２は独立して下記の３価の基のいずれかである。

Ｇ^１２が＞ＣＨ－であるとき、＞ＣＨ－の水素原子はメチル基で置換されていてもよい。Ｇ^１２が＞Ｎ－であるとき、Ｇ^１１は単結合および－ＣＨ_２－であることはなく、Ｘ^１１は単結合であることはない。Ｒ^１１は独立して水素原子またはメチル基である。 [Tetracarboxylic acid dianhydride represented by formula (AN-1)]

In formula (AN-1), G ¹¹ is a single bond, an alkylene group having 1 to 12 carbon atoms, a 1,4-phenylene group, or a 1,4-cyclohexylene group. X ¹¹ is independently a single bond or —CH ₂ —. G ¹² is independently any of the following trivalent groups:

When G ¹² is >CH-, the hydrogen atom of >CH- may be substituted with a methyl group. When G ¹² is >N-, G ¹¹ is not a single bond or -CH ₂ -, and X ¹¹ is not a single bond. R ¹¹ is independently a hydrogen atom or a methyl group.

式（ＡＮ－１－２）および（ＡＮ－１－１４）において、ｍはそれぞれ独立して１～１２の整数である。 Examples of the tetracarboxylic dianhydride represented by formula (AN-1) include the compounds represented by the following formulas (AN-1-1) to (AN-1-15).

In formulas (AN-1-2) and (AN-1-14), each m is independently an integer of 1 to 12.

式（ＡＮ－２）において、Ｒ^６１は独立して、水素原子、炭素数１～５のアルキル基、またはフェニル基である。 [Tetracarboxylic acid dianhydride represented by formula (AN-2)]

In formula (AN-2), R ⁶¹ is independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a phenyl group.

Examples of the tetracarboxylic dianhydride represented by formula (AN-2) include the compounds represented by the following formulas (AN-2-1) to (AN-2-3).

式（ＡＮ－３）において、環Ａ^１１はシクロヘキサン環またはベンゼン環である。 [Tetracarboxylic acid dianhydride represented by formula (AN-3)]

In formula (AN-3), ring A ¹¹ is a cyclohexane ring or a benzene ring.

Examples of the tetracarboxylic dianhydride represented by formula (AN-3) include compounds represented by the following formulas (AN-3-1) and (AN-3-2).

式（ＡＮ－４）において、Ｇ^１３は単結合、－（ＣＨ_２）_ｍ－、－Ｏ－、－Ｓ－、－Ｃ（ＣＨ_３）_２－、－ＳＯ_２－、－ＣＯ－、－Ｃ（ＣＦ_３）_２－、または下記式（Ｇ１３－１）で表される２価の基であり、ｍは１～１２の整数である。環Ａ^１１はそれぞれ独立してシクロヘキサン環またはベンゼン環である。Ｇ^１３は環Ａ^１１の任意の位置に結合してよい。

式（Ｇ１３－１）において、Ｇ^１３ａおよびＧ^１３ｂはそれぞれ独立して、単結合、－Ｏ－、－ＣＯＮＨ－、または－ＮＨＣＯ－で表される２価の基である。フェニレン基は、１，４－フェニレン基または１，３－フェニレン基であることが好ましい。 [Tetracarboxylic acid dianhydride represented by formula (AN-4)]

In formula (AN-4), G ¹³ is a single bond, -(CH ₂ ) _m -, -O-, -S-, -C(CH ₃ ) ₂ -, -SO ₂ -, -CO-, -C(CF ₃ ) ₂ -, or a divalent group represented by the following formula (G13-1), where m is an integer of 1 to 12. Each ring A ¹¹ is independently a cyclohexane ring or a benzene ring. G ¹³ may be bonded to any position of ring A ¹¹ .

In formula (G13-1), G ^13a and G ^13b each independently represent a single bond, or a divalent group represented by -O-, -CONH-, or -NHCO-. The phenylene group is preferably a 1,4-phenylene group or a 1,3-phenylene group.

式（ＡＮ－４－１７）において、ｍは１～１２の整数である。 Examples of the tetracarboxylic dianhydride represented by formula (AN-4) include the compounds represented by the following formulas (AN-4-1) to (AN-4-31).

In formula (AN-4-17), m is an integer from 1 to 12.

式（ＡＮ－５）において、Ｒ^１１は独立して水素原子またはメチル基である。２つのＲ^１１のうちベンゼン環におけるＲ^１１は、ベンゼン環の置換可能な位置のいずれかに結合する。 [Tetracarboxylic acid dianhydride represented by formula (AN-5)]

In formula (AN-5), R ¹¹ is independently a hydrogen atom or a methyl group. Of the two R ¹¹ , the R ¹¹ in the benzene ring is bonded to any substitutable position of the benzene ring.

Examples of the tetracarboxylic dianhydride represented by formula (AN-5) include the compounds represented by the following formulas (AN-5-1) to (AN-5-3).

式（ＡＮ－６）において、Ｘ^１１は独立して単結合または－ＣＨ_２－である。Ｘ^１２は－ＣＨ_２－、－ＣＨ_２ＣＨ_２－または－ＣＨ＝ＣＨ－である。ｎは１または２である。ｎが２であるとき、２つのＸ^１２は互いに同一であっても異なっていてもよい。 [Tetracarboxylic acid dianhydride represented by formula (AN-6)]

In formula (AN-6), X ¹¹ is independently a single bond or -CH ₂ -. X ¹² is -CH ₂ -, -CH ₂ CH ₂ - or -CH=CH-. n is 1 or 2. When n is 2, two X ¹² may be the same or different.

Examples of the tetracarboxylic dianhydride represented by formula (AN-6) include the compounds represented by the following formulas (AN-6-1) to (AN-6-12).

式（ＡＮ－７）において、Ｘ^１１は単結合または－ＣＨ_２－である。 [Tetracarboxylic acid dianhydride represented by formula (AN-7)]

In formula (AN-7), X ¹¹ is a single bond or —CH ₂ —.

Examples of the tetracarboxylic dianhydride represented by formula (AN-7) include compounds represented by the following formulas (AN-7-1) and (AN-7-2).

式（ＡＮ－８）において、Ｘ^１１は単結合または－ＣＨ_２－である。Ｒ^１２は水素原子、メチル基、エチル基、またはフェニル基である。環Ａ^１２はシクロヘキサン環またはシクロヘキセン環である。 [Tetracarboxylic acid dianhydride represented by formula (AN-8)]

In formula (AN-8), X ¹¹ is a single bond or —CH ₂ —. R ¹² is a hydrogen atom, a methyl group, an ethyl group, or a phenyl group. Ring A ¹² is a cyclohexane ring or a cyclohexene ring.

Examples of the tetracarboxylic dianhydride represented by formula (AN-8) include compounds represented by the following formulas (AN-8-1) and (AN-8-2).

式（ＡＮ－９）において、ｒはそれぞれ独立して０または１である。 [Tetracarboxylic acid dianhydride represented by formula (AN-9)]

In formula (AN-9), each r is independently 0 or 1.

Examples of the tetracarboxylic dianhydride represented by formula (AN-9) include the compounds represented by the following formulas (AN-9-1) to (AN-9-3).

[Tetracarboxylic acid dianhydrides represented by formulas (AN-10-1) and (AN-10-2)]

式（ＡＮ－１１）において、環Ａ^１１は独立してシクロヘキサン環またはベンゼン環である。 [Tetracarboxylic acid dianhydride represented by formula (AN-11)]

In formula (AN-11), ring A ¹¹ is independently a cyclohexane ring or a benzene ring.

Examples of the tetracarboxylic dianhydride represented by formula (AN-11) include the compounds represented by the following formulas (AN-11-1) to (AN-11-3).

式（ＡＮ－１２）において、環Ａ^１１はそれぞれ独立してシクロヘキサン環またはベンゼン環である。 [Tetracarboxylic acid dianhydride represented by formula (AN-12)]

In formula (AN-12), each ring A ¹¹ independently represents a cyclohexane ring or a benzene ring.

Examples of the tetracarboxylic dianhydride represented by formula (AN-12) include the compounds represented by the following formulas (AN-12-1) to (AN-12-3).

式（ＡＮ－１５）において、ｗは１～１０の整数である。 [Tetracarboxylic acid dianhydride represented by formula (AN-15)]

In formula (AN-15), w is an integer of 1 to 10.

Examples of the tetracarboxylic dianhydride represented by formula (AN-15) include compounds represented by the following formulas (AN-15-1) to (AN-15-3).

Other tetracarboxylic dianhydrides include the compounds represented by the following formulae (AN-16-1) to (AN-16-15).

Among the above tetracarboxylic dianhydrides, preferred materials for improving the properties of the liquid crystal alignment film described below will be described. When emphasis is placed on further improving the liquid crystal alignment properties, compounds represented by formula (AN-1-2), formula (AN-4-17), formula (AN-4-21), or formula (AN-4-29) are more preferred, and in formula (AN-1-2), m is preferably 4 to 8, and in formula (AN-4-17), m is preferably 4 to 8.

When emphasis is placed on improving the transmittance of the liquid crystal display element, compounds represented by formula (AN-1-1), (AN-1-2), (AN-2-1), (AN-3-1), (AN-4-17), (AN-4-30), (AN-5-1), (AN-7-2), (AN-10-1), (AN-16-3), or (AN-16-4) are preferred, and among these, in formula (AN-1-2), m=4 or 8 is preferred, and in formula (AN-4-17), m=4 to 8 is preferred, with m=8 being more preferred.

When emphasis is placed on improving the VHR of the liquid crystal display element, compounds represented by formula (AN-1-1), (AN-1-2), (AN-3-1), (AN-4-17), (AN-4-30), (AN-7-2), (AN-10-1), (AN-16-3), (AN-16-4), or (AN-2-1) are preferred, and in formula (AN-1-2), m=4 or 8 is preferred, and in formula (AN-4-17), m=4 or 8 is preferred, with m=8 being more preferred.

One effective method for preventing image sticking is to improve the relaxation speed of the residual charge (residual DC) in the liquid crystal alignment film by reducing the volume resistance of the liquid crystal alignment film. When this objective is important, compounds represented by formula (AN-1-13), formula (AN-3-2), formula (AN-4-21), formula (AN-4-29), or formula (AN-11-3) are preferred.

<Other diamines>
Diamines other than the compound represented by formula (2) used as raw materials for the polymer of the present invention can be selected from known diamines without any limitation.

Diamines can be divided into two types based on their structure. That is, when the skeleton connecting the two amino groups is viewed as the main chain, there are diamines that have groups branching from the main chain, i.e., side chain groups, and diamines that do not have side chain groups. In the following explanation, diamines that have such side chain groups may be referred to as side chain type diamines. And diamines that do not have such side chain groups may be referred to as non-side chain type diamines. The side chain groups are groups that have the effect of increasing the pretilt angle.
By appropriately using the non-side chain type diamine and the side chain type diamine, it is possible to meet the pretilt angle required for each.

It is preferable to use side chain diamines in combination to the extent that the characteristics of the present invention are not impaired. It is also preferable to selectively use side chain diamines and non-side chain diamines in order to improve characteristics such as vertical alignment properties for liquid crystals, VHR, and afterimage characteristics.

上記の式（ＤＩ－１）において、Ｇ^２０は、－ＣＨ_２－または式（ＤＩ－１－ａ）で表される基である。Ｇ^２０が－ＣＨ_２－であるとき、ｍ個の－ＣＨ_２－の少なくとも１つは－ＮＨ－、－Ｏ－に置き換えられてもよく、ｍ個の－ＣＨ_２－の少なくとも１つの水素原子は水酸基またはメチル基で置換されてもよい。ｍは１～１２の整数である。ＤＩ－１におけるｍが２以上であるとき、複数のＧ^２０は互いに同一であっても異なっていてもよい。ただし、Ｇ^２０が式（ＤＩ－１－ａ）であるとき、ｍは１である。

式（ＤＩ－１－ａ）において、ｖはそれぞれ独立して１～６の整数である。 Known diamines having no side chains are shown in the following formulas (DI-1) to (DI-16).

In the above formula (DI-1), G ²⁰ is -CH ₂ - or a group represented by formula (DI-1-a). When G ²⁰ is -CH ₂ -, at least one of the m -CH ₂ - may be replaced by -NH- or -O-, and at least one hydrogen atom of the m -CH ₂ - may be replaced by a hydroxyl group or a methyl group. m is an integer of 1 to 12. When m in DI-1 is 2 or more, multiple G ²⁰ may be the same or different from each other. However, when G ²⁰ is formula (DI-1-a), m is 1.

In formula (DI-1-a), each v is independently an integer of 1 to 6.

In formulae (DI-3), (DI-6) and (DI-7), G ²¹ independently represents a single bond, -NH-, -NCH ₃ -, -O-, -S-, -S-S-, -SO ₂ -, -CO-, -COO-, -CONCH ₃ -, -CONH-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -(CH ₂ ) _m -, -O-(CH ₂ ) _m -O-, -N(CH ₃ )-(CH ₂ ) _k -N(CH ₃ )-, -(O-C ₂ H ₄ ) _m -O-, -O-CH ₂ -C(CF ₃ ) ₂ -CH ₂ -O-, -O-CO-(CH ₂ ) _m -CO-O-, -CO-O-(CH ₂ ) _m -O-CO-, -( _CH2 ) _m -NH-( _CH2 ) _m- , -CO-( _CH2 ) _k -NH-( _CH2 ) _k- , -(NH-( _CH2 ) _{m )k-NH-, -CO-C3H6-(NH-C3H6 ) n - CO- ,} or -S-( _CH2 ) _m -S-, where m is independently an integer of 1 to 12, k is an integer of 1 to 5, and n is 1 or 2. In formula (DI-4), s is independently an integer of 0 to 2.

In formula (DI-5), G ³³ is a single bond, -NH-, -NCH ₃ -, -O-, -S-, -S-S-, -SO ₂ -, -CO-, -COO-, -CONCH ₃ -, -CONH-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -(CH ₂ ) _m -, -O-(CH 2 ) _m -O- _, -N(CH ₃ )-(CH ₂ ) _k -N(CH ₃ )-, -(O-C ₂ H ₄ ) _m -O-, -O-CH ₂ -C(CF ₃ ) ₂ -CH ₂ -O-, -O-CO-(CH ₂ ) _m -CO-O-, -CO-O-(CH ₂ ) _m -O-CO-, -(CH ₂ ) _m -NH-( _CH2 ) _m- , -CO-( _CH2 ) _k -NH-( _CH2 ) _k- , -(NH-( _CH2 ) _m ) _k -NH- _, -CO- _C3H6- (NH- _C3H6 ) _n -CO-, or -S-( _CH2 ) _m -S-, -N( _Boc ) _- (CH2) _e -N(Boc)-, -NH-( _CH2 ) _e -N(Boc)-, -N(Boc)-( _CH2 ) _e- , -( _CH2 ) _m -N(Boc)-CONH-( _CH2 ) _m- , -( _CH2 ) _m -N(Boc)-( _CH2 ) _m -, a group represented by the following formula (DI-5-a) or the following formula (DI-5-b), m is independently an integer of 1 to 12, k is an integer of 1 to 5, e is an integer of 2 to 10, and n is 1 or 2. Boc is a t-butoxycarbonyl group.

In formulae (DI-6) and (DI-7), G ²² independently represents a single bond, —O—, —S—, —CO—, —C(CH ₃ ) ₂ —, —C(CF ₃ ) ₂ —, or an alkylene group having 1 to 10 carbon atoms.

At least one hydrogen atom of the cyclohexane ring and the benzene ring in formulae (DI-2) to (DI- ₇ ) may be substituted with -F, -Cl, an alkylene group having 1 to 3 carbon atoms, _-OCH3 , -OH, _-CF3 , _-CO2H , _-CONH2 , _-NHC6H5 , a phenyl group, or a benzyl group; in addition, in formula (DI-4), at least one hydrogen atom of the cyclohexane ring and the benzene ring may be substituted with one selected from the group of groups represented by any of the following formulae (DI-4-a) to (DI-4-i); and in formula (DI-5), when ^G33 is a single bond, at least one hydrogen atom of the cyclohexane ring and the benzene ring may be substituted with NHBoc or N(Boc) ₂ .

式（ＤＩ－４－ａ）および式（ＤＩ－４－ｂ）において、Ｒ^２０は独立して水素原子または－ＣＨ_３である。式（ＤＩ－４－ｆ）および式（ＤＩ－４－ｇ）において、ｍはそれぞれ独立して０～１２の整数であり、Ｂｏｃはｔ－ブトキシカルボニル基である。 A group that is not fixed to a carbon atom constituting a ring indicates that the bonding position in the ring is arbitrary. And, the bonding position of _-NH2 to the cyclohexane ring or benzene ring is arbitrary except for the bonding position of G ²¹ , G ²² or G ³³ .

In formulae (DI-4-a) and (DI-4-b), R ²⁰ is independently a hydrogen atom or -CH _3. In formulae (DI-4-f) and (DI-4-g), m is independently an integer of 0 to 12, and Boc is a t-butoxycarbonyl group.

式（ＤＩ－５－ａ）において、ｑはそれぞれ独立して０～６の整数である。Ｒ^４４は水素原子、－ＯＨ、炭素数１～６のアルキル基、または炭素数１～６のアルコキシ基である。

In formula (DI-5-a), q is independently an integer of 0 to 6. R ⁴⁴ is a hydrogen atom, —OH, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

式（ＤＩ－１１）において、ｒは０または１である。式（ＤＩ－８）～式（ＤＩ－１１）において、環に結合する－ＮＨ_２の結合位置は、任意の位置である。

In formula (DI-11), r is 0 or 1. In formulas (DI-8) to (DI-11), the bonding position of --NH ₂ bonded to the ring is any position.

式（ＤＩ－１２）において、Ｒ^２１およびＲ^２２は、それぞれ独立して炭素数１～３のアルキル基またはフェニル基であり、Ｇ^２３は独立して炭素数１～６のアルキレン基、フェニレン基またはアルキル基で置換されたフェニレン基であり、ｗは１～１０の整数である。
式（ＤＩ－１３）において、Ｒ^２３は独立して炭素数１～５のアルキル基、炭素数１～５のアルコキシ基または－Ｃｌであり、ｐは独立して０～３の整数であり、ｑは０～４の整数である。
式（ＤＩ－１４）において、環Ｂは単環の複素環式芳香族基であり、Ｒ^２４は水素原子、－Ｆ、－Ｃｌ、炭素数１～６のアルキル基、アルコキシ基、アルケニル基、またはアルキニル基であり、ｑは独立して０～４の整数である。ｑが２以上であるとき、複数のＲ^２４は互いに同一であっても異なっていてもよい。式（ＤＩ－１５）において、環Ｃは複素環式芳香族基または複素環式脂肪族基である。式（ＤＩ－１６）において、Ｇ^２４は単結合、炭素数２～６のアルキレン基または１，４－フェニレン基であり、ｒは０または１である。そして、環を構成する炭素原子に結合位置が固定されていない基は、その環における結合位置が任意であることを示す。式（ＤＩ－１３）～式（ＤＩ－１６）において、環に結合する－ＮＨ_２の結合位置は、任意の位置である。

In formula (DI-12), R ²¹ and R ²² each independently represent an alkyl group having 1 to 3 carbon atoms or a phenyl group; G ²³ independently represents an alkylene group having 1 to 6 carbon atoms, a phenylene group, or a phenylene group substituted with an alkyl group; and w is an integer of 1 to 10.
In formula (DI-13), R ²³ independently represents an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or -Cl; p independently represents an integer of 0 to 3; and q independently represents an integer of 0 to 4.
In formula (DI-14), ring B is a monocyclic heteroaromatic group, R ²⁴ is a hydrogen atom, -F, -Cl, an alkyl group, an alkoxy group, an alkenyl group, or an alkynyl group having 1 to 6 carbon atoms, and q is independently an integer of 0 to 4. When q is 2 or more, the multiple R ²⁴ may be the same or different from each other. In formula (DI-15), ring C is a heteroaromatic group or a heterocyclic aliphatic group. In formula (DI-16), G ²⁴ is a single bond, an alkylene group having 2 to 6 carbon atoms, or a 1,4-phenylene group, and r is 0 or 1. And, a group that is not fixedly bonded to a carbon atom constituting a ring indicates that the bonding position in the ring is arbitrary. In formulas (DI-13) to (DI-16), the bonding position of -NH ₂ bonded to the ring is arbitrary.

式（ＤＩ－１－７）および式（ＤＩ－１－８）において、ｋはそれぞれ独立して、１～３の整数である。式（ＤＩ－１－９）において、ｖはそれぞれ独立して１～６の整数である。 Examples of the diamine represented by formula (DI-1) are shown in the following formulas (DI-1-1) to (DI-1-9).

In formula (DI-1-7) and formula (DI-1-8), k is independently an integer of 1 to 3. In formula (DI-1-9), v is independently an integer of 1 to 6.

Examples of the diamines represented by formulas (DI-2) to (DI-3) are shown in the following formulas (DI-2-1), (DI-2-2), and (DI-3-1) to (DI-3-3).

式（ＤＩ－４－２０）および（ＤＩ－４－２１）において、ｍはそれぞれ独立して１～１２の整数である。

Examples of the diamine represented by formula (DI-4) are shown in the following formulas (DI-4-1) to (DI-4-27).

In formulas (DI-4-20) and (DI-4-21), each m is independently an integer of 1 to 12.

式（ＤＩ－５－１）において、ｍは１～１２の整数である。 Examples of the diamine represented by formula (DI-5) are shown in the following formulas (DI-5-1) to (DI-5-50).

In formula (DI-5-1), m is an integer of 1 to 12.

式（ＤＩ－５－１２）および式（ＤＩ－５－１３）において、ｍはそれぞれ独立して１～１２の整数である。

In formulae (DI-5-12) and (DI-5-13), each m is independently an integer of 1 to 12.

式（ＤＩ－５－１６）において、ｖは１～６の整数である。

In formula (DI-5-16), v is an integer of 1 to 6.

式（ＤＩ－５－３０）において、ｋは１～５の整数である。

In formula (DI-5-30), k is an integer of 1 to 5.

式（ＤＩ－５－３５）～式（ＤＩ－５－３７）、および式（ＤＩ－５－３９）において、ｍはそれぞれ独立して１～１２の整数であり、式（ＤＩ－５－３８）および式（ＤＩ－５－３９）において、ｋはそれぞれ独立して１～５の整数であり、式（ＤＩ－５－４０）において、ｎは１または２の整数である。

In formulas (DI-5-35) to (DI-5-37), and (DI-5-39), m each independently represents an integer of 1 to 12; in formulas (DI-5-38) and (DI-5-39), k each independently represents an integer of 1 to 5; and in formula (DI-5-40), n is an integer of 1 or 2.

式（ＤＩ－５－４２）～式（ＤＩ－５－４４）において、ｅはそれぞれ独立して２～１０の整数であり、式（ＤＩ－５－４５）においてＲ^４３は水素原子、－ＮＨＢｏｃ、または－Ｎ（Ｂｏｃ）_２である。式（ＤＩ－５－４２）～式（ＤＩ－５－４４）において、Ｂｏｃはｔ－ブトキシカルボニル基である。

In formulae (DI-5-42) to (DI-5-44), e is each independently an integer of 2 to 10, and in formula (DI-5-45), R ⁴³ is a hydrogen atom, -NHBoc, or -N(Boc) _2. In formulae (DI-5-42) to (DI-5-44), Boc is a t-butoxycarbonyl group.

Examples of the diamine represented by formula (DI-6) are shown in the following formulas (DI-6-1) to (DI-6-7).

式（ＤＩ－７－３）および式（ＤＩ－７－４）において、ｍはそれぞれ独立して１～１２の整数であり、ｎは独立して１または２である。 Examples of the diamine represented by formula (DI-7) are shown in the following formulas (DI-7-1) to (DI-7-11).

In formulae (DI-7-3) and (DI-7-4), m is each independently an integer of 1 to 12; n is independently 1 or 2.

Examples of the diamine represented by formula (DI-8) are shown in the following formulas (DI-8-1) to (DI-8-4).

Examples of the diamine represented by formula (DI-9) are shown in the following formulas (DI-9-1) to (DI-9-3).

Examples of the diamine represented by formula (DI-10) are shown in the following formulas (DI-10-1) and (DI-10-2).

Examples of the diamine represented by formula (DI-11) are shown in the following formulas (DI-11-1) to (DI-11-3).

An example of the diamine represented by formula (DI-12) is shown in the following formula (DI-12-1).

Examples of the diamine represented by formula (DI-13) are shown in the following formulas (DI-13-1) to (DI-13-13).

Examples of the diamine represented by formula (DI-14) are shown in the following formulas (DI-14-1) to (DI-14-9).

Examples of the diamine represented by formula (DI-15) are shown in the following formulas (DI-15-1) to (DI-15-12).

An example of the diamine represented by formula (DI-16) is shown in the following formula (DI-16-1).

式（ＤＩＨ－１）において、Ｇ^２５は単結合、炭素数１～２０のアルキレン基、－ＣＯ－、－Ｏ－、－Ｓ－、－ＳＯ_２－、－Ｃ（ＣＨ_３）_２－、または－Ｃ（ＣＦ_３）_２－である。
式（ＤＩＨ－２）において、環Ｄはシクロヘキサン環、ベンゼン環またはナフタレン環であり、この基の少なくとも１つの水素原子はメチル基、エチル基、またはフェニル基で置換されてもよい。式（ＤＩＨ－３）において、環Ｅはそれぞれ独立してシクロヘキサン環、またはベンゼン環であり、この基の少なくとも１つの水素原子はメチル基、エチル基、またはフェニル基で置換されてもよい。複数の環Ｅは互いに同一であっても異なっていてもよい。Ｙは単結合、炭素数１～２０のアルキレン、－ＣＯ－、－Ｏ－、－Ｓ－、－ＳＯ_２－、－Ｃ（ＣＨ_３）_２－、または－Ｃ（ＣＦ_３）_２－である。式（ＤＩＨ－２）および式（ＤＩＨ－３）において、環に結合する－ＣＯＮＨＮＨ_２の結合位置は、任意の位置である。 Next, the dihydrazide used as the raw material for the polymer of the present invention will be described. Known dihydrazides having no side chains include compounds represented by any of the following formulas (DIH-1) to (DIH-3).

In formula (DIH-1), G ²⁵ is a single bond, an alkylene group having 1 to 20 carbon atoms, -CO-, -O-, -S-, -SO ₂ -, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ -.
In formula (DIH-2), ring D is a cyclohexane ring, a benzene ring, or a naphthalene ring, and at least one hydrogen atom of this group may be substituted with a methyl group, an ethyl group, or a phenyl group. In formula (DIH-3), ring E is each independently a cyclohexane ring or a benzene ring, and at least one hydrogen atom of this group may be substituted with a methyl group, an ethyl group, or a phenyl group. A plurality of rings E may be the same or different from each other. Y is a single bond, an alkylene having 1 to 20 carbon atoms, -CO-, -O-, -S-, -SO ₂ -, -C(CH ₃ ) ₂ -, or -C(CF ₃ ) ₂ -. In formulas (DIH-2) and (DIH-3), the bonding position of -CONHNH ₂ bonded to the ring is any position.

式（ＤＩＨ－１－２）において、ｍは１～１２の整数である。 Examples of the compounds represented by any of formulas (DIH-1) to (DIH-3) are shown in the following formulas (DIH-1-1), (DIH-1-2), (DIH-2-1) to (DIH-2-3), and (DIH-3-1) to (DIH-3-6).

In formula (DIH-1-2), m is an integer of 1 to 12.

Diamines suitable for increasing the pretilt angle will now be described. The compound of the present invention can be suitably used as a liquid crystal aligning agent for use in a horizontal electric field type liquid crystal display element, but it is also possible to increase the pretilt angle by using it in combination with the following diamines. Diamines having a side chain group suitable for increasing the pretilt angle include diamines represented by any of formulas (DI-31) to (DI-35) and formulas (DI-36-1) to (DI-36-8).

In formula (DI-31), G ²⁶ is a single bond, -O-, -COO-, -OCO-, -CO-, -CONH-, -CH ₂ O-, -OCH ₂ -, -CF ₂ O-, -OCF ₂ -, or -(CH ₂ ) _ma -, where ma is an integer of 1 to 12. Preferred examples of G ²⁶ are a single bond, -O-, -COO-, -OCO-, -CH ₂ O-, and an alkylene group having 1 to 3 carbon atoms, and particularly preferred examples are a single bond, -O-, -COO-, -OCO-, -CH ₂ O-, -CH ₂ -, and -CH ₂ CH ₂ -. R ²⁵ is an alkyl group having 3 to 30 carbon atoms, a phenyl group, a group having a steroid skeleton, or a group represented by the following formula (DI-31-a). In this alkyl group, at least one hydrogen atom may be substituted with -F, and at least one -CH ₂ - may be substituted with -O-, -CH=CH- or -C≡C-. The hydrogen atom of this phenyl group may be substituted with -F, -CH ₃ , -OCH ₃ , -OCH ₂ F, -OCHF _{2 ,} -OCF _3, an alkyl group having 3 to 30 carbon atoms, or an alkoxy group having 3 to 30 carbon atoms. The bonding position of -NH ₂ bonded to the benzene ring indicates any position in the ring, but the bonding position is preferably the meta position or para position. That is, when the bonding position of the group "R ²⁵ -G ²⁶ -" is the 1st position, the two bonding positions are preferably the 3rd and 5th positions, or the 2nd and 5th positions.

式（ＤＩ－３１－ａ）において、Ｇ^２７、Ｇ^２８およびＧ^２９は結合基であり、これらは、それぞれ独立して単結合、または炭素数１～１２のアルキレン基であり、このアルキレン基の１以上の－ＣＨ_２－は、－Ｏ－、－ＣＯＯ－、－ＯＣＯ－、－ＣＯＮＨ－、または－ＣＨ＝ＣＨ－で置換されていてもよい。環Ｂ^２１、環Ｂ^２２、環Ｂ^２３および環Ｂ^２４は、それぞれ独立して１，４－フェニレン基、１，４－シクロへキシレン基、１，３－ジオキサン－２，５－ジイル基、ピリミジン－２，５－ジイル基、ピリジン－２，５－ジイル基、ナフタレン－１，５－ジイル基、ナフタレン－２，７－ジイル基またはアントラセン－９，１０－ジイル基であり、環Ｂ^２１、環Ｂ^２２、環Ｂ^２３および環Ｂ^２４において、少なくとも１つの水素原子は－Ｆまたは－ＣＨ_３で置換されてもよく、ｓ、ｔ、およびｕは、それぞれ独立して０～２の整数であって、これらの合計は１～５であり、ｓ、ｔ、またはｕが２であるとき、各々の括弧内の２つの結合基は同じであっても異なってもよく、そして、２つの環は同じであっても異なっていてもよい。Ｒ^２６は水素原子、－Ｆ、－ＯＨ、炭素数１～３０のアルキル基、炭素数１～３０のフッ素置換アルキル基、炭素数１～３０のアルコキシ基、－ＣＮ、－ＯＣＨ_２Ｆ、－ＯＣＨＦ_２、または－ＯＣＦ_３であり、この炭素数１～３０のアルキル基の少なくとも１つの－ＣＨ_２－は下記式（ＤＩ－３１－ｂ）で表される２価の基で置換されていてもよい。

式（ＤＩ－３１－ｂ）において、Ｒ^２７およびＲ^２８は、それぞれ独立して炭素数１～３のアルキル基であり、ｖは１～６の整数である。Ｒ^２６の好ましい例は炭素数１～３０のアルキル基および炭素数１～３０のアルコキシ基である。

In formula (DI-31-a), G ²⁷ , G ²⁸ and G ²⁹ are bonding groups, each of which independently represents a single bond or an alkylene group having 1 to 12 carbon atoms, and one or more -CH ₂ - in this alkylene group may be substituted by -O-, -COO-, -OCO-, -CONH- or -CH═CH-. Ring B ²¹ , ring B ²² , ring B ²³ and ring B ²⁴ are each independently a 1,4-phenylene group, a 1,4-cyclohexylene group, a 1,3-dioxane-2,5-diyl group, a pyrimidine-2,5-diyl group, a pyridine-2,5-diyl group, a naphthalene-1,5-diyl group, a naphthalene-2,7-diyl group or an anthracene-9,10-diyl group; in ring B ²¹ , ring B ²² , ring B ²³ and ring B ²⁴ , at least one hydrogen atom may be replaced by -F or -CH ₃ ; s, t and u are each independently an integer of 0 to 2, the sum of which is 1 to 5; and when s, t or u is 2, the two bonding groups in each parentheses may be the same or different, and the two rings may be the same or different. R ²⁶ is a hydrogen atom, -F, -OH, an alkyl group having 1 to 30 carbon atoms, a fluorine-substituted alkyl group having 1 to 30 carbon atoms, an alkoxy group having 1 to 30 carbon atoms, -CN, -OCH ₂ F, -OCHF ₂ , or -OCF ₃ , and at least one -CH ₂ - in this alkyl group having 1 to 30 carbon atoms may be substituted with a divalent group represented by the following formula (DI-31-b).

In formula (DI-31-b), R ²⁷ and R ²⁸ each independently represent an alkyl group having 1 to 3 carbon atoms, and v represents an integer of 1 to 6. Preferred examples of R ²⁶ include an alkyl group having 1 to 30 carbon atoms and an alkoxy group having 1 to 30 carbon atoms.

式（ＤＩ－３２）および式（ＤＩ－３３）において、Ｇ^３０は独立して単結合、－ＣＯ－または－ＣＨ_２－であり、Ｒ^２９は独立して水素原子または－ＣＨ_３であり、Ｒ^３０は独立して水素原子、炭素数１～２０のアルキル基、または炭素数２～２０のアルケニル基である。式（ＤＩ－３３）におけるベンゼン環の少なくとも１つの水素原子は、炭素数１～２０のアルキル基またはフェニル基で置換されてもよい。そして、環を構成するいずれかの炭素原子に結合位置が固定されていない基は、その環における結合位置が任意であることを示す。式（ＤＩ－３２）における２つの基「－フェニレン－Ｇ^３０－Ｏ－」の一方はステロイド核の３位に結合し、もう一方はステロイド核の６位に結合していることが好ましい。式（ＤＩ－３３）における２つの基「－フェニレン－Ｇ^３０－Ｏ－」のベンゼン環への結合位置は、ステロイド核の結合位置に対して、それぞれメタ位またはパラ位であることが好ましい。式（ＤＩ－３２）および式（ＤＩ－３３）において、ベンゼン環に結合する－ＮＨ_２はその環における結合位置が任意であることを示す。

In formula (DI-32) and formula (DI-33), G ³⁰ is independently a single bond, -CO- or -CH ₂ -, R ²⁹ is independently a hydrogen atom or -CH ₃ , and R ³⁰ is independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an alkenyl group having 2 to 20 carbon atoms. At least one hydrogen atom of the benzene ring in formula (DI-33) may be substituted with an alkyl group having 1 to 20 carbon atoms or a phenyl group. A group not fixedly bonded to any carbon atom constituting the ring indicates that the bonded position in the ring is arbitrary. It is preferable that one of the two groups "-phenylene-G ³⁰ -O-" in formula (DI-32) is bonded to the 3-position of the steroid nucleus, and the other is bonded to the 6-position of the steroid nucleus. The bonding positions of the two groups "-phenylene-G ³⁰ -O-" in formula (DI-33) to the benzene ring are preferably meta or para relative to the bonding position of the steroid nucleus. In formulae (DI-32) and (DI-33), -NH ₂ bonded to the benzene ring indicates that the bonding position in the ring is arbitrary.

式（ＤＩ－３４）および式（ＤＩ－３５）において、Ｇ^３１は独立して－Ｏ－または炭素数１～６のアルキレン基であり、Ｇ^３２は単結合または炭素数１～３のアルキレン基である。Ｒ^３１は水素原子または炭素数１～２０のアルキル基であり、このアルキル基の少なくとも１つの－ＣＨ_２－は、－Ｏ－、－ＣＨ＝ＣＨ－または－Ｃ≡Ｃ－で置き換えられてもよい。Ｒ^３２は炭素数６～２２のアルキル基であり、Ｒ^３３は水素原子または炭素数１～２２のアルキル基である。環Ｂ^２５は１，４－フェニレン基または１，４－シクロヘキシレン基であり、ｒは０または１である。そしてベンゼン環に結合する－ＮＨ_２はその環における結合位置が任意であることを示すが、独立してＧ^３１の結合位置に対してメタ位またはパラ位であることが好ましい。

In formula (DI-34) and formula (DI-35), G ³¹ is independently -O- or an alkylene group having 1 to 6 carbon atoms, and G ³² is a single bond or an alkylene group having 1 to 3 carbon atoms. R ³¹ is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and at least one -CH ₂ - of this alkyl group may be replaced by -O-, -CH=CH- or -C≡C-. R ³² is an alkyl group having 6 to 22 carbon atoms, and R ³³ is a hydrogen atom or an alkyl group having 1 to 22 carbon atoms. Ring B ²⁵ is a 1,4-phenylene group or a 1,4-cyclohexylene group, and r is 0 or 1. And -NH ₂ bonded to the benzene ring indicates that the bonding position in the ring is arbitrary, but it is preferably independently a meta position or a para position with respect to the bonding position of G ³¹ .

Examples of the compound represented by formula (DI-31) are shown in the following formulas (DI-31-1) to (DI-31-55).

In formulae (DI-31-1) to (DI-31-11), R ³⁴ is independently an alkyl group having 1 to 30 carbon atoms or an alkoxy group having 1 to 30 carbon atoms, preferably an alkyl group having 5 to 25 carbon atoms or an alkoxy group having 5 to 25 carbon atoms. R ³⁵ is independently an alkyl group having 1 to 30 carbon atoms or an alkoxy group having 1 to 30 carbon atoms, preferably an alkyl group having 3 to 25 carbon atoms or an alkoxy group having 3 to 25 carbon atoms.

In formulae (DI-31-12) to (DI-31-17), R ³⁶ is independently an alkyl group having 4 to 30 carbon atoms, preferably an alkyl group having 6 to 25 carbon atoms. R ³⁷ is independently an alkyl group having 6 to 30 carbon atoms, preferably an alkyl group having 8 to 25 carbon atoms.

In formulae (DI-31-18) to (DI-31-43), R ³⁸ is independently an alkyl group having 1 to 20 carbon atoms or an alkoxy group having 1 to 20 carbon atoms, preferably an alkyl group having 3 to 20 carbon atoms or an alkoxy group having 3 to 20 carbon atoms. R ³⁹ is independently a hydrogen atom, -F, an alkyl group having 1 to 30 carbon atoms, an alkoxy group having 1 to 30 carbon atoms, -CN, -OCH ₂ F, -OCHF ₂ or -OCF ₃ , preferably an alkyl group having 3 to 25 carbon atoms or an alkoxy group having 3 to 25 carbon atoms. And G ³³ is an alkylene group having 1 to 20 carbon atoms.

Examples of the compound represented by formula (DI-32) are shown in the following formulas (DI-32-1) to (DI-32-4).

Examples of the compound represented by formula (DI-33) are shown in the following formulas (DI-33-1) to (DI-33-8).

式（ＤＩ－３４－１）～式（ＤＩ－３４－１２）において、Ｒ^４０はそれぞれ独立して水素原子または炭素数１～２０のアルキル基、好ましくは水素原子または炭素数１～１０のアルキル基であり、そしてＲ^４１はそれぞれ独立して水素原子または炭素数１～１２のアルキル基である。 Examples of the compound represented by formula (DI-34) are shown in the following formulas (DI-34-1) to (DI-34-12).

In formulae (DI-34-1) to (DI-34-12), R ⁴⁰ is independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and R ⁴¹ is independently a hydrogen atom or an alkyl group having 1 to 12 carbon atoms.

式（ＤＩ－３５－１）～式（ＤＩ－３５－３）において、Ｒ^３７はそれぞれ独立して炭素数６～３０のアルキル基であり、Ｒ^４１はそれぞれ独立して水素原子または炭素数１～１２のアルキル基である。 Examples of the compound represented by formula (DI-35) are shown in the following formulas (DI-35-1) to (DI-35-3).

In formulae (DI-35-1) to (DI-35-3), R ³⁷ each independently represents an alkyl group having 6 to 30 carbon atoms, and R ⁴¹ each independently represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms.

式（ＤＩ－３６－１）～式（ＤＩ－３６－８）において、Ｒ^４２はそれぞれ独立して炭素数３～３０のアルキル基である。 The compounds represented by formulae (DI-36-1) to (DI-36-8) are shown below.

In formulae (DI-36-1) to (DI-36-8), R ⁴² each independently represents an alkyl group having 3 to 30 carbon atoms.

Among the above diamines, preferred materials for improving the properties of the liquid crystal alignment film described below will be described. When emphasis is placed on improving the liquid crystal alignment, it is preferred to use a compound represented by formula (DI-1-3), formula (DI-5-1), formula (DI-5-5), formula (DI-5-9), formula (DI-5-12), formula (DI-5-13), formula (DI-5-29), formula (DI-6-7), formula (DI-7-3), or formula (DI-11-2). In formula (DI-5-1), m is preferably 2 to 8, and more preferably m is 4 to 8. In formula (DI-5-12), m is preferably 2 to 6, and more preferably m is 5. In formula (DI-5-13), m is preferably 1 or 2, and more preferably m is 1.

When emphasis is placed on improving the transmittance, it is preferable to use a diamine represented by formula (DI-1-3), formula (DI-2-1), formula (DI-5-1), formula (DI-5-5), formula (DI-5-24), or formula (DI-7-3), and more preferably a compound represented by formula (DI-2-1). In formula (DI-5-1), m is preferably 2 to 8, and more preferably m is 8. In formula (DI-7-3), m is preferably 2 or 3, n is preferably 1 or 2, and more preferably m is 3, n is 1.

When emphasis is placed on improving the VHR of the liquid crystal display element, it is preferable to use a compound represented by formula (DI-2-1), formula (DI-4-1), formula (DI-4-2), formula (DI-4-10), formula (DI-4-15), formula (DI-4-22), formula (DI-5-1), formula (DI-5-28), formula (DI-5-30), or formula (DI-13-1), and more preferable is a diamine represented by formula (DI-2-1), formula (DI-5-1), or formula (DI-13-1). In formula (DI-5-1), m=1 is preferable. In formula (DI-5-30), k=2 is preferable.

One effective method for preventing image sticking is to improve the relaxation speed of the residual charge (residual DC) in the liquid crystal alignment film by reducing the volume resistance of the liquid crystal alignment film. When this purpose is important, it is preferable to use a compound represented by formula (DI-4-1), formula (DI-4-2), formula (DI-4-10), formula (DI-4-15), formula (DI-5-1), formula (DI-5-12), formula (DI-5-13), formula (DI-5-28), formula (DI-4-20), formula (DI-4-21), formula (DI-7-12), or formula (DI-16-1), and more preferable is a compound represented by formula (DI-4-1), formula (DI-5-1), or formula (DI-5-13). In formula (DI-5-1), m=2 to 8 is preferable, and m=4 to 8 is more preferable. In formula (DI-5-12), m is preferably 2 to 6, and more preferably m is 5. In formula (DI-5-13), m is preferably 1 or 2, and more preferably m is 1. In formula (DI-7-12), m is preferably 3 or 4, and more preferably m is 4.

In the raw material composition used as the raw material for the polymer of the present invention, a part of the diamines may be replaced with at least one selected from the group consisting of monoamines and monohydrazides. The ratio of at least one selected from the group consisting of monoamines and monohydrazides to the diamines is preferably in the range of 40 mol% or less. Such a replacement can cause the termination of the polymerization reaction when producing polyamic acid, and can suppress further progress of the polymerization reaction. For this reason, such a replacement can easily control the molecular weight of the resulting polymer (polyamic acid or its derivative), and can improve the coating properties of the liquid crystal alignment agent, for example, without impairing the effects of the present invention. The diamines that may be replaced with monoamines or monohydrazides may be one type or two or more types, as long as the effects of the present invention are not impaired. Examples of the monoamine include aniline, 4-hydroxyaniline, cyclohexylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, n-undecylamine, n-dodecylamine, n-tridecylamine, n-tetradecylamine, n-pentadecylamine, n-hexadecylamine, n-heptadecylamine, n-octadecylamine, n-eicosylamine, paraaminophenyltrimethoxysilane, and 3-aminopropyltriethoxysilane.

When the polymer of the present invention is a polyamic acid or a derivative thereof, the raw material composition may further contain a monoisocyanate compound as a monomer. By including a monoisocyanate compound in the monomer, the terminal of the resulting polyamic acid or its derivative is modified, and the molecular weight is adjusted. By using this terminal-modified polyamic acid or its derivative, for example, it is possible to improve the coating properties of the liquid crystal alignment agent without impairing the effect of the present invention. From the above viewpoint, it is preferable that the content of the monoisocyanate compound in the monomer is 1 to 10 mol% based on the total amount of the diamine and tetracarboxylic dianhydride in the monomer. Examples of the monoisocyanate compound include phenyl isocyanate and naphthyl isocyanate.

The liquid crystal alignment agent of the present invention may be composed of one type of polymer of the present invention, or may be a mixture of the polymer of the present invention and a polymer other than the present invention. In this specification, a liquid crystal alignment agent composed of one type of polymer may be referred to as a single-layer type liquid crystal alignment agent. A liquid crystal alignment agent that is a mixture of two or more types of the above polymers may be referred to as a blend type liquid crystal alignment agent. A blend type liquid crystal alignment agent is used particularly when VHR reliability and other electrical characteristics are important.

As the polymer other than that of the present invention used in the blend type liquid crystal alignment agent, one or more of polyamic acid and polyamic acid derivatives are preferable. As for the polymer other than that of the present invention, the above description of the polymer of the present invention can be referred to for polyamic acid and polyamic acid derivatives, except that the raw material composition does not simultaneously contain a compound having a photoreactive structure and a compound represented by formula (1).

When using a two-component polymer, for example, one polymer is selected that has excellent performance in aligning liquid crystals, and the other is selected that has excellent performance in improving the electrical properties of liquid crystal display elements. This is suitable for obtaining an alignment agent with a good balance between liquid crystal alignment properties and electrical properties.

In this case, by controlling the structure and molecular weight of each polymer, the liquid crystal alignment agent in which these polymers are dissolved in a solvent is applied to a substrate as described below, and in the process of forming a thin film by pre-drying, the polymer with excellent performance in aligning liquid crystals can be segregated to the upper layer of the thin film, and the polymer with excellent performance in improving the electrical properties of the liquid crystal display element can be segregated to the lower layer of the thin film. This can be achieved by applying the phenomenon in which a polymer with a small surface energy is separated into the upper layer and a polymer with a large surface energy is separated into the lower layer in a mixed polymer. Such layer separation can be confirmed by checking that the surface energy of the formed liquid crystal alignment film is the same as or close to the surface energy of a film formed by a liquid crystal alignment agent containing only the polymer intended to be segregated to the upper layer.

One way to induce layer separation is to reduce the molecular weight of the polymer that you want to segregate to the upper layer.

When using liquid crystal alignment agents consisting of a mixture of polymers, layer separation can be achieved by using polyimide as the polymer to be segregated to the upper layer.

The compound represented by formula (1) may be used as a raw material for the polymer that segregates in the upper layer of the thin film, or may be used as a raw material for the polymer that segregates in the lower layer of the thin film, or may be used as a raw material for both polymers, but is more preferably used as a raw material for the polymer that segregates in the upper layer of the thin film.

The compound represented by formula (2) may be used as a raw material for the polymer that segregates in the upper layer of the thin film, or may be used as a raw material for the polymer that segregates in the lower layer of the thin film, or may be used as a raw material for both polymers, but is more preferably used as a raw material for the polymer that segregates in the upper layer of the thin film.

The tetracarboxylic acid dianhydride other than the compound represented by formula (1) used to synthesize the polyamic acid or its derivative segregated in the upper layer of the thin film and the polyamic acid or its derivative segregated in the lower layer of the thin film can be selected without limitation from the known tetracarboxylic acid dianhydrides exemplified above.

The tetracarboxylic dianhydride used to synthesize the polyamic acid or its derivative that segregates in the upper layer of the thin film is preferably a compound represented by formula (AN-1-1), (AN-1-2), (AN-2-1), (AN-3-1), (AN-4-5), (AN-4-17), or (AN-4-21), more preferably formula (AN-4-17) or (AN-4-21). In formula (AN-4-17), m is preferably 4 to 8.

As the tetracarboxylic dianhydride used to synthesize the polyamic acid or its derivative that segregates in the lower layer of the thin film, a compound represented by formula (AN-1-1), formula (AN-1-13), formula (AN-2-1), formula (AN-3-2), or formula (AN-4-21) is preferred, and formula (AN-1-1), formula (AN-2-1), or formula (AN-3-2) is more preferred.

The tetracarboxylic dianhydride used to synthesize the polyamic acid or its derivative that segregates in the lower layer of the thin film preferably contains 10 mol % or more, and more preferably 30 mol % or more, of aromatic tetracarboxylic dianhydride in the total amount of tetracarboxylic dianhydride.

Diamines other than the compound represented by formula (2) used to synthesize the polyamic acid or its derivative that segregates in the upper layer of the thin film and the polyamic acid or its derivative that segregates in the lower layer of the thin film can be selected without limitation from the known diamines exemplified above.

As the diamines used to synthesize the polyamic acid or its derivatives that segregate in the upper layer of the thin film, it is preferable to use a compound represented by formula (DI-4-1), formula (DI-4-13), formula (DI-4-15), formula (DI-5-1), formula (DI-7-3), or formula (DI-13-1). Among them, it is more preferable to use a compound represented by formula (DI-4-13), formula (DI-4-15), formula (DI-5-1), or formula (DI-13-1). In formula (DI-5-1), m=4 to 8 is preferable. In formula (DI-7-3), m=3, n=1 is preferable.

As the diamines used to synthesize the polyamic acid or its derivatives that segregate in the lower layer of the thin film, compounds represented by formula (DI-4-1), formula (DI-4-2), formula (DI-4-10), formula (DI-4-18), formula (DI-4-19), formula (DI-5-1), formula (DI-5-9), formula (DI-5-28), formula (DI-5-30), formula (DI-13-1), or formula (DIH-1-2) are preferred. In formula (DI-5-1), compounds in which m=1 or 2 are preferred, and in formula (DI-5-30), compounds in which k=2 are preferred. Among them, compounds represented by formula (DI-4-1), formula (DI-4-18), formula (DI-4-19), formula (DI-5-9), formula (DI-13-1), or formula (DIH-1-2) are more preferred.

The diamines used to synthesize the polyamic acid or its derivatives that segregate in the lower layer of the thin film preferably contain at least one selected from the group consisting of aromatic diamines and aromatic dihydrazides in an amount of 30 mol % or more, and more preferably 50 mol % or more, based on the total amount of diamines.

The ratio of polyamic acid or its derivative segregated in the upper layer of the thin film to the total amount of polyamic acid or its derivative segregated in the upper layer of the thin film and polyamic acid or its derivative segregated in the lower layer of the thin film is preferably 5% by weight to 60% by weight, and more preferably 20% by weight to 50% by weight.

The polyamic acid or derivative thereof of the present invention may be a block polymer including a first polymer chain and a second polymer chain having a structure different from that of the first polymer chain. The block polymer may further include another polymer chain having a structure different from that of the first polymer chain and the second polymer chain. For example, a block polymer of polyamic acid may be formed by mixing a solution of a specific polyamic acid (PAA1) represented by formula (PAA) with a solution of a polyamic acid (PAA1) and a polyamic acid (PAA2) having a different combination of ^X1 and ^X2 , and heating the mixture. The block polymer of polyamic acid thus formed includes a block represented by (PAA1) _n1 and a block represented by (PAA2) _n2 . _n1 and n2 in (PAA1)n1 and (PAA2) _n2 are each independently an integer of 1 or more, and preferably each independently an integer of 2 or more. In the block polymer, the polymer chains using the compound represented by formula (1) and the compound represented by formula (2) in the raw material composition may be any one, may be two or more, or may be all of the polymer chains.

Here, the polyamic acid block polymer may be synthesized by mixing two or more kinds of polyamic acids that are produced separately and then heating them. Alternatively, two or more kinds of polyamic acids may be synthesized in the same reaction vessel and then heated, such as by synthesizing the first kind of polyamic acid and then adding the raw material for the second kind of polyamic acid to the same reaction vessel.

When a block polymer is produced, in the raw material composition used as the raw material for the polymer of the present invention, the compound represented by formula (1) is preferably 10 mol % or more, more preferably 20 mol % or more, based on the total amount of the acid dianhydrides used as raw materials. The compound represented by formula (2) is preferably 10 mol % or more, more preferably 20 mol % or more, based on the total amount of the diamines used as raw materials.

When not forming a block polymer, in the raw material composition used as the raw material for the polymer of the present invention, the compound represented by formula (1) is preferably 20 mol % or more, more preferably 50 mol %, based on the total amount of the acid dianhydrides used as raw materials. The compound represented by formula (2) is preferably 20 mol % or more, more preferably 50 mol % or more, based on the total amount of the diamines used as raw materials.

The liquid crystal aligning agent of the present invention may further contain a solvent from the viewpoint of adjusting the coatability of the liquid crystal aligning agent and the concentration of the polyamic acid or its derivative. The solvent can be applied without any particular restrictions as long as it has the ability to dissolve polymer components. The solvent includes a wide range of solvents that are commonly used in the manufacturing process and applications of polymer components such as polyamic acid and soluble polyimide, and can be appropriately selected depending on the purpose of use. The solvent may be one type or a mixed solvent of two or more types.

Solvents include those that are compatible with the polyamic acid or its derivatives, and other solvents that are intended to improve coating properties.

Examples of aprotic polar organic solvents that are compatible with polyamic acid or its derivatives include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethylimidazolidinone, N-methylcaprolactam, N-methylpropionamide, N,N-dimethylacetamide, dimethylsulfoxide, N,N-dimethylformamide, N,N-diethylformamide, diethylacetamide, N,N-dimethylisobutyramide, γ-butyrolactone, and γ-valerolactone. Among these, N-methyl-2-pyrrolidone, dimethylimidazolidinone, γ-butyrolactone, and γ-valerolactone are preferred.

Examples of other solvents for improving coating properties include ethylene glycol monoalkyl ethers such as ethylene glycol monobutyl ether and ethylene glycol monotertiary butyl ether, diethylene glycol monoalkyl ethers such as diethylene glycol monoethyl ether, and diethylene glycol dialkyl ethers such as diethylene glycol ethyl methyl ether, diethylene glycol diethyl ether, and diethylene glycol butyl methyl ether. Other examples include propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether and 1-butoxy-2-propanol, dipropylene glycol monoalkyl ethers such as dipropylene glycol monomethyl ether, triethylene glycol monoalkyl ethers, butyl cellosolve acetate, phenyl acetate, and ester compounds such as these acetates. Other examples include dialkyl malonates such as diethyl malonate, alkyl lactates, diisobutyl ketone, diacetone alcohol, 3-methyl-3-methoxybutanol, 4-methyl-2-pentanol, diisobutyl carbinol, tetralin, and isophorone.

Among these, diisobutyl ketone, 4-methyl-2-pentanol, diisobutyl carbinol, ethylene glycol monobutyl ether, ethylene glycol monotertiary butyl ether, diethylene glycol monoethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol diethyl ether, diethylene glycol butyl methyl ether, 1-butoxy-2-propanol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, or butyl cellosolve acetate are preferred.

The solids concentration in the liquid crystal alignment agent of the present invention is not particularly limited, and an optimal value may be selected according to the various coating methods described below. In general, to prevent unevenness and pinholes during coating, the solids concentration is preferably 0.1 to 30% by weight, more preferably 1 to 10% by weight, based on the weight of the varnish.

The preferred range of the viscosity of the liquid crystal alignment agent of the present invention varies depending on the application method, the concentration of the polyamic acid or its derivative, the type of polyamic acid or its derivative used, and the type and ratio of the solvent. For example, in the case of application by a printer, the viscosity is 5 to 100 mPa·s (more preferably 10 to 80 mPa·s). If the viscosity is 5 mPa·s or more, a sufficient film thickness is easily obtained, and if the viscosity is 100 mPa·s or less, printing unevenness is easily suppressed. In the case of application by spin coating, the viscosity is suitable for 5 to 200 mPa·s (more preferably 10 to 100 mPa·s). In the case of application using an inkjet coating device, the viscosity is suitable for 5 to 50 mPa·s (more preferably 5 to 20 mPa·s). The viscosity of the liquid crystal alignment agent is measured by a rotational viscosity measurement method, for example, using a rotational viscometer (Toki Sangyo TVE-20L type) (measurement temperature: 25°C).

The liquid crystal alignment agent of the present invention may further contain various additives. Various additives can be selected and used according to the respective purposes in order to improve various properties of the alignment film. Examples are shown below.

<Alkenyl-substituted nadimide compound>
For example, the liquid crystal alignment agent of the present invention may further contain an alkenyl-substituted nadimide compound for the purpose of stabilizing the electrical properties of the liquid crystal display element for a long period of time. The alkenyl-substituted nadimide compound may be used alone or in combination of two or more. For the above purpose, the content of the alkenyl-substituted nadimide compound is preferably 1 to 50% by weight, more preferably 1 to 30% by weight, and even more preferably 1 to 20% by weight, based on the polyamic acid or its derivative. The alkenyl-substituted nadimide compound is preferably a compound that can be dissolved in a solvent that dissolves the polyamic acid or its derivative used in the present invention. Preferred alkenyl-substituted nadimide compounds include the alkenyl-substituted nadimide compounds disclosed in JP-A-2008-096979, JP-A-2009-109987, and JP-A-2013-242526. Particularly preferred alkenyl-substituted nadimide compounds include bis{4-(arylbicyclo[2.2.1]hept-5-ene-2,3-dicarboximide)phenyl}methane, N,N'-m-xylylene-bis(arylbicyclo[2.2.1]hept-5-ene-2,3-dicarboximide), or N,N'-hexamethylene-bis(arylbicyclo[2.2.1]hept-5-ene-2,3-dicarboximide).

<Compound Having Radically Polymerizable Unsaturated Double Bond>
For example, the liquid crystal aligning agent of the present invention may further contain a compound having a radical polymerizable unsaturated double bond for the purpose of stabilizing the electrical characteristics of the liquid crystal display element for a long period of time. The compound having a radical polymerizable unsaturated double bond may be one type of compound, or two or more types of compounds. The compound having a radical polymerizable unsaturated double bond does not include an alkenyl-substituted nadiimide compound. Preferred compounds having a radical polymerizable unsaturated double bond include N,N'-methylenebisacrylamide, N,N'-dihydroxyethylene-bisacrylamide, ethylenebisacrylate, 4,4'-methylenebis(N,N-dihydroxyethyleneacrylateaniline), triallyl cyanurate, and other compounds having a radical polymerizable unsaturated double bond disclosed in JP 2009-109987 A, JP 2013-242526 A, WO 2014/119682, and WO 2015/152014. For the above-mentioned purposes, the content of the compound having a radically polymerizable unsaturated double bond is preferably 1 to 50% by weight, more preferably 1 to 30% by weight, based on the polyamic acid or its derivative.

<Oxazine Compound>
For example, the liquid crystal aligning agent of the present invention may further contain an oxazine compound for the purpose of stabilizing the electrical characteristics of a liquid crystal display element for a long period of time. The oxazine compound may be one type of compound or two or more types of compounds. For the above purpose, the content of the oxazine compound is preferably 0.1 to 50% by weight, more preferably 1 to 40% by weight, and even more preferably 1 to 20% by weight, based on the polyamic acid or its derivative.

The oxazine compound is preferably an oxazine compound that is soluble in a solvent that dissolves polyamic acid or a derivative thereof and has ring-opening polymerizability. Preferred oxazine compounds include the oxazine compounds represented by formula (OX-3-1), formula (OX-3-9), and formula (OX-3-10), as well as the oxazine compounds disclosed in JP-A-2007-286597 and JP-A-2013-242526.

<Oxazoline Compound>
For example, the liquid crystal aligning agent of the present invention may further contain an oxazoline compound for the purpose of stabilizing the electrical characteristics of a liquid crystal display element for a long period of time. The oxazoline compound is a compound having an oxazoline structure. The oxazoline compound may be one type of compound or two or more types of compounds. For the above purpose, the content of the oxazoline compound is preferably 0.1 to 50% by weight, more preferably 1 to 40% by weight, and even more preferably 1 to 20% by weight, based on the polyamic acid or its derivative. Preferred oxazoline compounds include the oxazoline compounds disclosed in JP-A-2010-054872 and JP-A-2013-242526. More preferably, 1,3-bis(4,5-dihydro-2-oxazolyl)benzene is used.

<Epoxy Compound>
For example, the liquid crystal aligning agent of the present invention may further contain an epoxy compound for the purpose of stabilizing the electrical characteristics of a liquid crystal display element for a long period of time, improving the hardness of the film, or improving the adhesion to a sealant. The epoxy compound may be one type of compound or two or more types of compounds. For the above purposes, the content of the epoxy compound is preferably 0.1 to 50% by weight, more preferably 1 to 20% by weight, and even more preferably 1 to 10% by weight, based on the polyamic acid or its derivative.

As the epoxy compound, various compounds having one or more epoxy rings in the molecule can be used.
For the purpose of improving the hardness of the film or the adhesion to a sealant, a compound having two or more epoxy rings in the molecule is preferred, and a compound having three or four epoxy rings is more preferred.

Examples of epoxy compounds include those disclosed in JP 2009-175715 A, JP 2013-242526 A, JP 2016-170409 A, and WO 2017/217413. Preferred epoxy compounds include N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, (3,3',4,4'-diepoxy)bicyclohexyl, 1,4-butanediol glycidyl ether, tris(2,3-epoxypropyl) isocyanurate, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, or N,N,N',N'-tetraglycidyl-m-xylylenediamine. More preferred are 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane. In addition to the above, oligomers or polymers having epoxy rings can also be added. The oligomers and polymers having epoxy rings can be those disclosed in JP 2013-242526 A.

<Silane Compound>
For example, the liquid crystal aligning agent of the present invention may further contain a silane compound for the purpose of improving adhesion to a substrate and a sealant. For the above purpose, the content of the silane compound is preferably 0.1 to 30% by weight, more preferably 0.5 to 20% by weight, and even more preferably 0.5 to 10% by weight, based on the polyamic acid or its derivative.

As the silane compound, the silane coupling agents disclosed in JP 2013-242526 A, JP 2015-212807 A, JP 2018-173545 A, and International Publication No. 2018/181566 can be used. Preferred silane coupling agents include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, paraaminophenyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-isocyanatopropyltriethoxysilane, and 3-ureidopropyltriethoxysilane.

In addition to the additives described above, a compound having a cyclocarbonate group, a hydroxyalkylamide moiety, or a hydroxyl group may be added for the purpose of increasing the strength of the alignment film or stabilizing the electrical properties of the liquid crystal display element for a long period of time. Specific examples of the compound include those disclosed in JP 2016-118753 A and WO 2017/110976 A. Preferred examples of the compound include the following formulae (HD-1) to (HD-4). The amount of these compounds is preferably 0.5 to 50% by weight, more preferably 1 to 30% by weight, and even more preferably 1 to 10% by weight, based on the polyamic acid or its derivative.

When improved antistatic properties are required, antistatic agents can be used, and when imidization is to proceed at low temperatures, imidization catalysts can be used. Examples of imidization catalysts include the imidization catalysts disclosed in JP 2013-242526 A.

<Liquid crystal alignment film>
Next, the liquid crystal alignment film of the present invention will be described. The liquid crystal alignment film of the present invention is formed using the liquid crystal alignment agent of the present invention. When the liquid crystal alignment agent of the present invention is used to form a liquid crystal alignment film, heating and baking causes an imidization reaction, and a polyimide-based liquid crystal alignment film can be formed. The liquid crystal alignment agent of the present invention is suitable as a liquid crystal alignment agent for photo-alignment, and a photo-alignment method can be applied to the alignment treatment in the process of forming the liquid crystal alignment film.

The following describes a method for forming a liquid crystal alignment film using the liquid crystal alignment agent for photoalignment of the present invention.

The liquid crystal alignment film of the present invention can be obtained by a normal method for producing a liquid crystal alignment film from a liquid crystal alignment agent for photo-alignment. The liquid crystal alignment film of the present invention can be obtained, for example, through a process of forming a coating film of the liquid crystal alignment agent for photo-alignment of the present invention, a process of heating and drying the coating film to form a film of the liquid crystal alignment agent, a process of irradiating the film of the liquid crystal alignment agent with light to impart anisotropy, and a process of heating and baking the film of the liquid crystal alignment agent to which anisotropy has been imparted. For the liquid crystal alignment film of the present invention, it is preferable to irradiate light after the coating process and the heating and drying process to impart anisotropy, and then to undergo a heating and baking process.

The coating film can be formed by applying the liquid crystal aligning agent of the present invention to a substrate of a liquid crystal display element in the same manner as in the preparation of a normal liquid crystal alignment film. The substrate may be made of glass, silicon nitride, acrylic, polycarbonate, polyimide, or the like, which may be provided with an electrode such as ITO (indium tin oxide), IZO (In ₂ O ₃ -ZnO), or IGZO (In-Ga-ZnO ₄ ) electrode, or a color filter, or the like.

Methods commonly known for applying a liquid crystal alignment agent to a substrate include the spinner method, printing method, dipping method, dropping method, inkjet method, etc. These methods can also be applied to the present invention.

The commonly known heat drying process involves heating in an oven or infrared furnace, or on a hot plate. The heat drying process is preferably carried out at a temperature within a range in which the solvent can evaporate, and more preferably at a temperature relatively low compared to the temperature in the heat baking process. Specifically, the heat drying temperature is preferably in the range of 30°C to 150°C, and more preferably in the range of 50°C to 120°C.

The heating and baking process can be carried out under conditions necessary for the polyamic acid or its derivatives to undergo an imidization reaction. Commonly known methods for baking a coating film include a method of heating in an oven or infrared furnace, and a method of heating on a hot plate. These methods can also be applied to the present invention. In general, it is preferable to perform the baking at a temperature of about 90 to 300°C for 1 minute to 3 hours, more preferably 120 to 280°C, and even more preferably 150 to 250°C.

When emphasis is placed on improving the anisotropy of the film or the afterimage characteristics when the liquid crystal display element is produced, it is preferable to raise the temperature gradually in the heating process. For example, the temperature can be raised stepwise and the film can be heated and baked multiple times at different temperatures, or the temperature can be changed from low to high. Also, both heating methods can be used in combination.

When heating and firing multiple times at different temperatures, multiple heating devices set to different temperatures may be used, or one heating device may be used and the temperature may be changed sequentially to different temperatures.

When firing multiple times at different temperatures, it is preferable to fire the product at 90 to 180°C for the first firing, and 185 to 300°C for the final firing. For example, it is preferable to fire the product at 110°C and then at 220°C, fire the product at 110°C and then at 230°C, fire the product at 130°C and then at 220°C, fire the product at 150°C and then at 200°C, fire the product at 150°C and then at 220°C, fire the product at 150°C and then at 230°C, or fire the product at 170°C and then at 200°C. It is also preferable to fire the product in more stages while gradually increasing the temperature. When firing the product in two or more stages with different heating temperatures, it is preferable that the heating time for each heating step is 5 to 30 minutes.

When firing is performed by changing the temperature from a low temperature to a high temperature, the initial temperature is preferably 90 to 180°C. The final temperature is preferably 185 to 300°C, more preferably 190 to 230°C. The heating time is preferably 5 to 60 minutes, more preferably 20 to 60 minutes. The temperature rise speed can be, for example, 0.5°C/min to 40°C/min. The temperature rise speed during the temperature rise does not have to be constant.

In the method for forming a liquid crystal alignment film of the present invention, a known photoalignment method can be suitably used as a means for imparting anisotropy to the thin film in order to align the liquid crystal in one direction relative to the horizontal and/or vertical directions.

The method for forming the liquid crystal alignment film of the present invention using the photo-alignment method will be described in detail. The liquid crystal alignment film of the present invention using the photo-alignment method can be formed by heating and drying the coating film, irradiating the thin film with light to impart anisotropy to the thin film, and then heating and baking the film. Alternatively, the film can be formed by heating and drying the coating film, heating and baking it, and then irradiating the thin film with light. From the viewpoint of liquid crystal alignment, it is preferable to carry out the light irradiation process before the heating and baking process.

Furthermore, in order to increase the liquid crystal alignment ability of the liquid crystal alignment film, the coating film can be irradiated with light while being heated. The light irradiation can be performed in the process of heating and drying the coating film or in the process of heating and baking, or between the heating and baking processes. The heating temperature when irradiating light in the process of heating and drying the coating film or in the process of heating and baking can be determined by referring to the description of the heating and baking process above. When irradiating light between the heating and drying process and the heating and baking process, the heating temperature is preferably in the range of 30°C to 150°C, and more preferably in the range of 50°C to 110°C.

As the light, for example, ultraviolet light or visible light containing light with a wavelength of 150 to 800 nm can be used, but ultraviolet light containing light with a wavelength of 300 to 400 nm is preferred. Polarized or unpolarized light can also be used. There are no particular limitations on the type of light as long as it is capable of imparting liquid crystal alignment ability to the thin film, but if it is desired to exert a strong alignment control force on the liquid crystal, polarized light is preferred, and linearly polarized light is even more preferred.

The irradiation dose of the linearly polarized light in the light irradiation step is preferably 0.05 to 10 J/ ^cm2 , more preferably 0.1 to 5 J/ ^cm2 . The wavelength of the linearly polarized light is preferably 200 to 400 nm, more preferably 300 to 400 nm. The irradiation angle of the linearly polarized light to the film surface is not particularly limited, but in order to express a strong alignment control force for the liquid crystal, it is preferable that the irradiation angle is as perpendicular as possible to the film surface from the viewpoint of shortening the alignment treatment time. In addition, the liquid crystal alignment film of the present invention can align the liquid crystal in a direction perpendicular to the polarization direction of the linearly polarized light by irradiating the linearly polarized light.

Light sources used in the light irradiation process can include, without limitation, ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, deep UV lamps, halogen lamps, metal halide lamps, high power metal halide lamps, xenon lamps, mercury xenon lamps, excimer lamps, KrF excimer lasers, fluorescent lamps, LED lamps, sodium lamps, microwave excited electrodeless lamps, etc.

The liquid crystal alignment film of the present invention can be suitably obtained by a method that further includes steps other than those described above.

The liquid crystal alignment film of the present invention does not require a step of washing the film with a washing solution after baking or light irradiation, but a washing step can be provided for the convenience of other steps. Examples of washing methods using a washing solution include brushing, jet spray, steam washing, and ultrasonic washing. These methods may be performed alone or in combination. The washing solution may be, but is not limited to, pure water or various alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, aromatic hydrocarbons such as benzene, toluene, and xylene, halogenated solvents such as methylene chloride, and ketones such as acetone and methyl ethyl ketone. Of course, these washing solutions are sufficiently purified and contain few impurities. Such washing methods can also be applied to the washing step in the formation of the liquid crystal alignment film of the present invention.

In order to enhance the liquid crystal alignment ability of the liquid crystal alignment film of the present invention, an annealing treatment using heat or light can be used before or after the heating and baking process, or before or after irradiation with polarized or unpolarized light. In the annealing treatment, the annealing temperature is 30 to 180°C, preferably 50 to 150°C, and the time is preferably 1 minute to 2 hours. The annealing light used in the annealing treatment may be a UV lamp, a fluorescent lamp, an LED lamp, or the like. The light irradiation dose is preferably 0.3 to 10 J/ ^cm2 .

The thickness of the liquid crystal alignment film of the present invention is not particularly limited, but is preferably 10 to 300 nm, and more preferably 30 to 150 nm. The thickness of the liquid crystal alignment film of the present invention can be measured using a known film thickness measuring device such as a step gauge or an ellipsometer.

The liquid crystal alignment film of the present invention is characterized by having a particularly large alignment anisotropy. The magnitude of such anisotropy can be evaluated by a method using polarized IR as described in JP-A-2005-275364, etc. It can also be evaluated by a method using ellipsometry. More specifically, the retardation value of the liquid crystal alignment film can be measured by a spectroscopic ellipsometer. The retardation value of the film increases in proportion to the degree of orientation of the polymer main chain.

The liquid crystal alignment film of the present invention can be suitably used for controlling the alignment of liquid crystal compositions in liquid crystal display elements. In addition to the use of aligning liquid crystal compositions in liquid crystal display elements, it can be used for controlling the alignment of liquid crystal materials in all other liquid crystal elements, such as liquid crystal antennas, dimming windows, optical compensation materials, variable phase shifters, etc. In addition, since the liquid crystal alignment film of the present invention has a large anisotropy, it can be used alone as an optical compensation material.

<Liquid crystal display element>
The liquid crystal display element of the present invention is characterized by having the liquid crystal alignment film of the present invention, and can realize high display quality due to its excellent contrast.

The liquid crystal display element of the present invention will be described in detail. The present invention is a liquid crystal display element having a pair of substrates arranged opposite to each other, electrodes formed on one or both of the opposing surfaces of each of the pair of substrates, a liquid crystal alignment film formed on the opposing surfaces of each of the pair of substrates, a liquid crystal layer formed between the pair of substrates, a pair of polarizing films arranged to sandwich the opposing substrates, a backlight, and a driving device, in which the liquid crystal alignment film is composed of the liquid crystal alignment film of the present invention.

The electrode is not particularly limited as long as it is an electrode formed on one side of the substrate. Examples of such electrodes include ITO and a metal deposition film. The electrode may be formed on the entire surface of one side of the substrate, or may be formed in a desired shape, for example, patterned. Examples of the desired shape of the electrode include a comb-shaped or zigzag structure. The electrode may be formed on one of the pair of substrates, or on both substrates. The form of electrode formation differs depending on the type of liquid crystal display element. For example, in the case of an IPS type liquid crystal display element (horizontal electric field type liquid crystal display element), an electrode is arranged on one of the pair of substrates, and in the case of other liquid crystal display elements, an electrode is arranged on both of the pair of substrates. The liquid crystal alignment film is formed on the substrate or the electrode.

In the case of a homogeneously aligned liquid crystal display element (e.g., IPS, FFS, etc.), the structure includes at least, from the backlight side, a backlight, a first polarizing film, a first substrate, a first liquid crystal alignment film, a liquid crystal layer, a second substrate, and a second polarizing film, and the polarizing axis of the polarizing film is set so that the polarizing axis of the first polarizing film (direction of polarized light absorption) crosses (preferably perpendicular) with the polarizing axis of the second polarizing film. In this case, the polarizing axis of the first polarizing film can be set so that it is parallel to the liquid crystal alignment direction or perpendicular to the liquid crystal alignment direction. A liquid crystal display element in which the polarizing axis of the first polarizing film is set so that it is parallel to the liquid crystal alignment direction is called O-mode, and a liquid crystal display element in which it is set so that it is perpendicular to the liquid crystal alignment direction is called E-mode. The liquid crystal alignment film of the present invention can be applied to either O-mode or E-mode, and can be selected according to the purpose.

Many photoisomerization materials use compounds with dichroism. Therefore, if the polarization axis of the polarized light irradiated to impart anisotropy to the liquid crystal alignment agent is aligned parallel to the polarization axis of the polarized light from the polarizing film placed on the backlight side (when the liquid crystal alignment agent of the present invention is used, this is the O-mode arrangement), the transmittance of the liquid crystal alignment film in the light absorption wavelength range increases. This can further improve the transmittance of the liquid crystal display element.

The liquid crystal layer is formed by sandwiching a liquid crystal composition between the pair of substrates with the surfaces on which the liquid crystal alignment film is formed facing each other. When forming the liquid crystal layer, spacers such as fine particles or a resin sheet that are interposed between the pair of substrates to form an appropriate gap can be used as necessary.

Known methods for forming liquid crystal layers are the vacuum injection method and the ODF (One Drop Fill) method.

In the vacuum injection method, a gap (cell gap) is provided so that the liquid crystal alignment film surfaces face each other, and a sealant is printed leaving an inlet for the liquid crystal, and then the substrates are bonded together. The cell gap defined by the substrate surface and the sealant is filled with liquid crystal using a vacuum pressure difference, and the inlet is then sealed to produce a liquid crystal display element.

In the ODF method, a sealant is printed on the outer periphery of the liquid crystal alignment film surface of one of a pair of substrates, liquid crystal is dropped into the area inside the sealant, and then the other substrate is attached so that the liquid crystal alignment film surface faces the other. The liquid crystal is then spread over the entire surface of the substrate, and then the entire surface of the substrate is irradiated with ultraviolet light to harden the sealant, thereby producing a liquid crystal display element.

In addition to UV-curing types, heat-curing types are also known as sealants used to bond substrates. The sealant can be printed, for example, by screen printing.

There are no particular limitations on the liquid crystal composition, and various liquid crystal compositions with positive or negative dielectric anisotropy can be used. Preferred liquid crystal compositions with positive dielectric anisotropy are described in Japanese Patent No. 3,086,228, Japanese Patent No. 2,635,435, JP-T-5-501735, JP-A-8-157826, JP-A-8-231960, JP-A-9-241644 (EP 885,272 A1), JP-A-9-302,346 (EP 806,466 A1), and JP-A-8-199,168 (EP 722,998 A1). Examples of such liquid crystal compositions include those disclosed in JP-A-9-235552, JP-A-9-255956, JP-A-9-241643 (EP885271A1), JP-A-10-204016 (EP844229A1), JP-A-10-204436, JP-A-10-231482, JP-A-2000-087040, and JP-A-2001-48822.

Preferred examples of the liquid crystal composition having the negative dielectric anisotropy include JP-A-57-114532, JP-A-2-4725, JP-A-4-224885, JP-A-8-40953, JP-A-8-104869, JP-A-10-168076, JP-A-10-168453, JP-A-10-236989, JP-A-10-236990, JP-A-10-236992, JP-A-10-236993, JP-A-10-236994, JP-A-10-237000, JP-A-10-237004, JP-A-10-237024, JP-A-10-237035, JP-A-10-237075, and JP-A-10-237076. , JP-A-10-237448 (EP967261A1), JP-A-10-287874, JP-A-10-287875, JP-A-10-291945, JP-A-11-029581, JP-A-11-080049, JP-A-2000-256307, JP-A-2001-019965, JP-A-2001-072626, JP-A-2001-192657, JP-A-2010-037428, WO 2011/024666, WO 2010/072370, JP-T-2010-537010, JP-A-2012-077201, JP-A-2009-084362, and the like.

There is no problem with adding one or more optically active compounds to a liquid crystal composition having a positive or negative dielectric anisotropy.

For example, the liquid crystal composition used in the liquid crystal display element of the present invention may further contain additives, for example, from the viewpoint of improving the alignment. Such additives include photopolymerizable monomers, optically active compounds, antioxidants, UV absorbers, dyes, defoamers, polymerization initiators, and polymerization inhibitors. Preferred photopolymerizable monomers, optically active compounds, antioxidants, UV absorbers, dyes, defoamers, polymerization initiators, and polymerization inhibitors include the compounds disclosed in International Publication WO 2015/146330 and the like.

A polymerizable compound can be mixed into the liquid crystal composition to make it compatible with a liquid crystal display element in a PSA (polymer sustained alignment) mode. Preferred examples of the polymerizable compound include compounds having a polymerizable group, such as acrylates, methacrylates, vinyl compounds, vinyloxy compounds, propenyl ethers, epoxy compounds (oxiranes, oxetanes), and vinyl ketones. Preferred compounds include those disclosed in International Publication WO 2015/146330, etc.

The present invention will be described below with reference to examples. The evaluation methods and compounds used in the examples are as follows.

Weight average molecular weight (Mw)
The weight average molecular weight of the polyamic acid was measured by GPC using a 2695 Separation Module-2414 Differential Refractometer (Waters) and calculated in terms of polystyrene. The obtained polyamic acid was diluted with a phosphoric acid-DMF mixed solution (phosphoric acid/DMF=0.6/100: weight ratio) so that the polyamic acid concentration was about 2 wt%. The column used was HSPgel RT MB-M (Waters), and the mixed solution was used as a developer at a column temperature of 50°C and a flow rate of 0.40 mL/min. The standard polystyrene used was TSK standard polystyrene manufactured by Tosoh Corporation.

<Tetracarboxylic acid dianhydride>

<Diamine>

<Solvent>
NMP: N-methyl-2-pyrrolidone BC: Butyl cellosolve (ethylene glycol monobutyl ether)
<Additives>
Additive 1: 1,3-bis(4,5-dihydro-2-oxazolyl)benzene Additive 2: (3,3',4,4'-diepoxy)bicyclohexyl

The compound represented by formula (1-1) was obtained by referring to the method described in International Publication No. 2011/099518.

The compound represented by formula (2-2-1; l = 4) was obtained by the following method. A solution of 4-nitrophenol (50.0 g, 359 mmol), 1,4-dibromobutane (310.4 g, 1438 mmol), and potassium carbonate (74.5 g, 539 mmol) in DMF (500 mL) was reacted at 60 degrees for 2 hours. The reaction mixture was cooled to room temperature, ethyl acetate (1 L) was added, washed three times with water (1 L), dried over sodium sulfate, and the solvent was distilled off under reduced pressure to obtain a crude product. This crude product was purified by silica gel column chromatography using a mixed solvent of heptane:ethyl acetate = 100:1 as the eluent, and 1-(4-bromo-butoxy)-4-nitrobenzene was obtained in a yield of 45.9 g and 47%.

４－ニトロアニリン（２９．４ｇ，２１３ｍｍｏｌ）の水（１３０ｍＬ）溶液に、濃塩酸（５３ｍＬ）を氷冷下（氷浴）で加えた。次いで、この溶液に、亜硝酸ナトリウム（１４．７ｇ，２１３ｍｍｏｌ）の水（４５ｍＬ）溶液を氷冷下（氷浴）で滴下後、３０分間撹拌し、４－ニトロベンゼンジアゾニウム塩酸塩の水溶液を調製した。得られた４－ニトロベンゼンジアゾニウム塩酸塩の水溶液を、氷冷したフェノール（２０．０ｇ，２１３ｍｍｏｌ）と酢酸ナトリウム（１３９．５ｇ，１７００ｍｍｏｌ）のエタノール（１０ｍＬ）と水（４００ｍＬ）の混合溶液に撹拌しながらゆっくりと加えた。反応溶液を氷冷下（氷浴）で２時間撹拌した後、ろ過した。得られた固体を酢酸エチル（２Ｌ）に溶解し、水（１Ｌ）で３回洗浄し、硫酸ナトリウムで乾燥させた後、溶媒を減圧留去して、アゾベンゼン誘導体１を収量４０．１ｇ、収率７８％で得た。

To a solution of 4-nitroaniline (29.4 g, 213 mmol) in water (130 mL), concentrated hydrochloric acid (53 mL) was added under ice-cooling (ice bath). Next, to this solution, a solution of sodium nitrite (14.7 g, 213 mmol) in water (45 mL) was added dropwise under ice-cooling (ice bath), and the mixture was stirred for 30 minutes to prepare an aqueous solution of 4-nitrobenzenediazonium hydrochloride. The obtained aqueous solution of 4-nitrobenzenediazonium hydrochloride was slowly added to an ice-cooled mixed solution of phenol (20.0 g, 213 mmol) and sodium acetate (139.5 g, 1700 mmol) in ethanol (10 mL) and water (400 mL) while stirring. The reaction solution was stirred under ice-cooling (ice bath) for 2 hours, and then filtered. The obtained solid was dissolved in ethyl acetate (2 L), washed three times with water (1 L), and dried over sodium sulfate. The solvent was then distilled off under reduced pressure to obtain 40.1 g of azobenzene derivative 1 in a yield of 78%.

１－（４－ブロモ－ブトキシ）－４－ニトロベンゼン（２０．０ｇ，７３ｍｍｏｌ）、アゾベンゼン誘導体１（１７．７ｇ，７３ｍｍｏｌ）、および炭酸カリウム（１５．１ｇ，１０９ｍｍｏｌ）のＤＭＦ（２００ｍＬ）溶液を６０度で６時間反応させた。反応混合物を室温まで冷却し、ジクロロメタン（４Ｌ）を加え、水（２Ｌ）で３回洗浄し、硫酸ナトリウムで乾燥させた後、溶媒を減圧留去して粗体を得た。この粗体を、ジクロロメタンを溶離液に用いてシリカゲルカラムクロマトグラフィーで精製し、アゾベンゼン誘導体２を収量３０．５ｇ、収率９６％で得た。

A solution of 1-(4-bromo-butoxy)-4-nitrobenzene (20.0 g, 73 mmol), azobenzene derivative 1 (17.7 g, 73 mmol), and potassium carbonate (15.1 g, 109 mmol) in DMF (200 mL) was reacted at 60° C. for 6 hours. The reaction mixture was cooled to room temperature, dichloromethane (4 L) was added, washed three times with water (2 L), dried over sodium sulfate, and the solvent was distilled off under reduced pressure to obtain a crude product. This crude product was purified by silica gel column chromatography using dichloromethane as an eluent to obtain azobenzene derivative 2 in a yield of 30.5 g and 96%.

アゾベンゼン誘導体２（２９．４ｇ，６７ｍｍｏｌ）のエタノール（６０ｍＬ）溶液に、水（６０ｍＬ）及び硫化ナトリウム九水和物（９７．２ｇ，４０５ｍｍｏｌ）を加え、２時間加熱還流した。反応混合物を室温まで冷却し、減圧濃縮した後、酢酸エチル（３Ｌ）を加え、水（１Ｌ）で３回洗浄し、硫酸ナトリウムで乾燥させた後、溶媒を減圧留去して粗体を得た。この粗体をトルエン：酢酸エチル＝３：１の混合溶媒を溶離液に用いてシリカゲルカラムクロマトグラフィーで精製し、式（２－２－１；ｌ＝４）の化合物を収量３．９ｇ、収率１５％で得た。

Water (60 mL) and sodium sulfide nonahydrate (97.2 g, 405 mmol) were added to a solution of azobenzene derivative 2 (29.4 g, 67 mmol) in ethanol (60 mL), and the mixture was heated to reflux for 2 hours. The reaction mixture was cooled to room temperature and concentrated under reduced pressure, after which ethyl acetate (3 L) was added, washed three times with water (1 L), dried over sodium sulfate, and the solvent was distilled off under reduced pressure to obtain a crude product. This crude product was purified by silica gel column chromatography using a mixed solvent of toluene:ethyl acetate = 3:1 as the eluent, and the compound of formula (2-2-1; l = 4) was obtained in a yield of 3.9 g and 15%.

Preparation of Varnishes The varnishes used in this example were prepared according to the following procedure. Here, varnishes A1 to A6 and R1 to R6 prepared in varnish preparation examples 1 to 12 are solutions of polyamic acid obtained by reaction using a compound having an azobenzene structure as one of the raw materials. Blend varnishes B1 to B3 prepared in varnish preparation examples 13 to 15 are solutions of polyamic acid obtained without using a compound having an azobenzene structure as a raw material, and are used by blending with varnishes A1 to A6 or varnishes R1 to R6.

[Preparation Example 1 of Varnish] Preparation of Varnish A1 In a 100mL three-neck flask equipped with a stirring blade and a nitrogen inlet tube, 2.184g of the compound represented by formula (2-1-1) was placed, and 34.0g of N-methyl-2-pyrrolidone was added and stirred. To this solution, 2.374g of the compound represented by formula (1-1) and 1.442g of the compound represented by formula (AN-4-17) (m = 4) were added, and the mixture was stirred at room temperature for 12 hours. Thereto, 30.0g of NMP and 30.0g of BC were added, and the solution was heated and stirred at 60 ° C. until the weight average molecular weight of the solute polymer reached the desired weight average molecular weight, and a varnish A1 was obtained in which the weight average molecular weight of the solute was approximately 13,500 and the resin concentration (solid concentration) was 6% by weight.

[Preparation Examples 2 to 15 of Varnish] Preparation of Varnishes A2 to A6, Varnishes R1 to R6, and Varnishes B1 to B3 Varnishes A2 to A6 and comparative varnishes R1 to R6 with a solid content concentration of 6% by weight were prepared in the same manner as in Preparation Example 1, except that the compounds used as diamines and tetracarboxylic dianhydrides were changed as shown in Table 1 or Table 2. The compositions of varnishes A1 to A6 are those in which a part of the tetracarboxylic dianhydride in the composition of the corresponding varnishes R1 to R6 (for example, A1 corresponds to R1, and A3 corresponds to R3) is replaced with formula (1-1). Varnishes B1 to B3 were prepared in the same manner as in Preparation Example 1, except that the compounds used as diamines and tetracarboxylic dianhydrides were changed as shown in Table 2. In varnishes B1 to B3, the conditions of heating and stirring were adjusted so that the weight average molecular weight of the polymer was about 50,000. The weight average molecular weight of the produced polymer is shown in Tables 1 and 2. In Table 1, in a preparation example in which two or more compounds are listed as diamines, it means that all of the compounds were used together as diamines, and in a preparation example in which two or more compounds are listed as tetracarboxylic dianhydrides, it means that all of the compounds were used together as tetracarboxylic dianhydrides. The numbers in square brackets indicate the compounding ratio (mol%), and blank spaces mean that the compound corresponding to that space was not used. The same applies to Table 2.

[Example 1]
Varnish A1 was diluted with an NMP-BC mixed solution (NMP/BC = 7/3 weight ratio) so that the solid content concentration was 4 wt%, and stirred. Then, additive 1 was added so that the amount was 6 parts by weight relative to the solid content, and stirred to prepare liquid crystal alignment agent 1. The prepared liquid crystal alignment agent was applied to a glass substrate with FFS electrodes and a glass substrate with column spacers by a spinner method. After application, the substrate was heated at 60 ° C for 80 seconds to evaporate the solvent, and then, using a Multilight ML-501C/B manufactured by Ushio Electric Co., Ltd., linearly polarized ultraviolet light was irradiated from the vertical direction to the substrate through a polarizing plate. The exposure energy at this time was measured using an ultraviolet integrating light meter UIT-150 (photoreceiver: UVD-S365) manufactured by Ushio Electric Co., Ltd., and the exposure time was adjusted so that the light amount was 2.0 ± 0.1 J / cm ² at a wavelength of 365 nm. Then, the substrate was baked at 220° C. for 30 minutes to form an alignment film with a thickness of about 100 nm. Next, the two substrates on which the alignment films were formed were laminated together with the surfaces on which the liquid crystal alignment films were formed facing each other, and a gap was provided between the facing liquid crystal alignment films for injecting the liquid crystal composition. At this time, the polarization directions of the linearly polarized light irradiated on each liquid crystal alignment film were parallel. Positive liquid crystal composition A was injected into these cells to prepare liquid crystal cells (liquid crystal display elements) with a cell thickness of 5 μm. The brightness-voltage characteristics (BV characteristics) of the prepared liquid crystal cells were measured, and the contrast (CR) was calculated using the ratio of the minimum brightness to the maximum brightness. The larger the CR value, the clearer the light and dark display and the better the contrast.
CR = B _max / B _min
In the formula, B _max indicates the maximum luminance in the BV characteristics, and B _min indicates the minimum luminance in the BV characteristics.
The contrast (CR) was evaluated according to the following criteria.
CR 3300 or more: ◎
CR is between 3000 and 3300: 〇 CR is between 2700 and 3000: △
CR less than 2700: ×
The evaluation results of the contrast in Examples 1 to 9 and Comparative Examples 1 to 9 are shown in Tables 3 and 4 together with the preparation conditions of the varnish.

[Examples 2 to 3, Comparative Examples 1 to 3]
Alignment agents 2 to 3 and comparative alignment agents 1 to 3 were prepared in the same manner as in Example 1, except that varnishes A2 to A3 and R1 to R3 were used instead of varnish A1 and no additive was added. For each of alignment agents 2 to 3 and comparative alignment agents 1 to 3, liquid crystal cells were prepared in the same manner as in Example 1, and the contrast was measured and evaluated.

[Example 4]
Varnish A1 and varnish B1 were blended in a weight ratio of 3:7 to obtain a blend varnish with a solid content of 6% by weight. The blend was further diluted with an NMP-BC mixed solution (NMP/BC=7/3 weight ratio) to obtain a solid content of 4% by weight, and stirred. Additive 1 was then added in an amount of 6 parts by weight relative to the solid content, and stirred to prepare alignment agent 4. A liquid crystal cell was prepared in the same manner as in Example 1, except that alignment agent 4 was used instead of alignment agent 1, and the contrast was measured and evaluated.

[Examples 5 to 9, Comparative Examples 4 to 9]
Alignment agents 5 to 9 and comparative alignment agents 4 to 9 were prepared in the same manner as in Example 4, except that the varnishes shown in Table 4 were used instead of varnish A1 and varnish B1, and the blend ratio was changed to that shown in Table 4. For those with descriptions in the column of additive and amount added, the corresponding additive was added in the described amount. The amount of additive added is in parts by weight relative to the solid content. For example, in alignment agent 4, 8 parts by weight of additive 1 was added. For those without descriptions in the column of additive and amount added, no additive was added. For each of alignment agents 5 to 9 and comparative alignment agents 4 to 9, liquid crystal cells were prepared in the same manner as in Example 1, and the contrast was measured and evaluated.

（物性値）
相転移温度ＮＩ：１００．１℃、誘電率異方性Δε：５．１、屈折率異方性Δｎ：０．０９３、粘度η：２５．６ｍＰａ・ｓ． <Positive Liquid Crystal Composition A>

(Physical properties)
Phase transition temperature NI: 100.1° C., dielectric anisotropy Δε: 5.1, refractive index anisotropy Δn: 0.093, viscosity η: 25.6 mPa·s.

The contrast in Examples 1 to 9 was higher than that of the corresponding Comparative Examples (for example, Example 1 corresponds to Comparative Example 1). It was found that by using a polymer obtained by polymerizing the tetracarboxylic dianhydride represented by formula (1) with a compound having an azobenzene structure as a liquid crystal alignment agent for photoalignment, an alignment film capable of realizing a high-contrast liquid crystal display element can be obtained.

By using the liquid crystal alignment agent for photo-alignment of the present invention, it is possible to manufacture a liquid crystal alignment film that realizes a high-contrast liquid crystal display element. The liquid crystal alignment agent for photo-alignment of the present invention can be suitably applied to a horizontal electric field type liquid crystal display element.

Claims (9)

A liquid crystal aligning agent comprising at least one polymer and a solvent, wherein at least one of the polymers is a polymer obtained by reacting a tetracarboxylic dianhydride with a diamine,
A liquid crystal alignment agent for photoalignment, characterized in that a raw material composition used as a raw material for a polymer obtained by reacting the tetracarboxylic dianhydrides with diamines contains at least one compound represented by formula (1) and a compound having an azobenzene structure.

In formula (1), R ¹ and R ² each independently represent one selected from a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and -F; and i represents an integer of 1 to 4.
The liquid crystal aligning agent for photo-alignment according to claim 1 , wherein in the tetracarboxylic dianhydride represented by the formula (1), R ¹ and R ² are hydrogen atoms, and i is 2 or 3. 3. The liquid crystal aligning agent for photo-alignment according to claim 1, wherein the compound having an azobenzene structure is at least one compound represented by the following formula (2):

In formula (2), X is an alkylene group having 1 to 12 carbon atoms, and one or more non-adjacent —(CH ₂ ) ₂ — groups in the alkylene group may be replaced with —O— or —NH—;
R ^a and R ^b each independently represent a hydrogen atom, -CH ₃ , -OCH ₃ , -CF ₃ , -F, -COOCH ₃ , or a monovalent group represented by formula (P1-1) or formula (P1-2);
R ^c each independently represents a hydrogen atom, —CH ₃ , —OCH ₃ , —CF ₃ , —F, or a monovalent group represented by formula (P1-1) or formula (P1-2); j is 0 or 1; a to c each independently represent an integer of 0 to 2;

In formula (P1-1) and formula (P1-2), R ^6a , R ^7a , and R ^8a each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkanoyl group, a substituted or unsubstituted alkoxycarbonyl group, or a substituted or unsubstituted arylcarbonyl group, R ^6a , R ^7a , and R ^8a may be the same or different, * represents the bonding position to the benzene ring in formula (2),
In formula (2), a group that is not bonded to any carbon atom constituting a ring indicates that the group may be bonded to any position on the ring. The compound represented by formula (2) is any one of the following formulas (2-1) to (2-3):

In formula (2-1), R ^1a and R ^1c each independently represent a hydrogen atom or a monovalent group represented by formula (P1-1) or formula (P1-2),
In formula (2-2), R ^2a and R ^2b each independently represent a hydrogen atom or a monovalent group represented by formula (P1-1) or formula (P1-2); R ^2c each independently represent a hydrogen atom, -CH ₃ , -OCH ₃ , -CF ₃ , or -F; X ₁ represents an alkylene group having 1 to 12 carbon atoms, and one or more non-adjacent -(CH ₂ ) ₂ - in the alkylene group may be replaced by either -O- or -NH-; k represents an integer of 0 to 2;
In formula (2-3), R ^3a each independently represents a hydrogen atom or a monovalent group represented by formula (P1-1) or formula (P1-2); R ⁴ and R ⁵ each independently represent a hydrogen atom or -F, R ⁴ and R ⁵ are not simultaneously hydrogen atoms; R ^3c each independently represents a hydrogen atom, -CH ₃ , -OCH ₃ , -CF ₃ , -F; X ₁ represents an alkylene group having 1 to 12 carbon atoms, and one or more non-adjacent -(CH ₂ ) ₂ - in the alkylene group may be replaced by either -O- or -NH-; m represents an integer of 0 to 2;

In formula (P1-1) and formula (P1-2), R ^6a , R ^7a , and R ^8a each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkanoyl group, a substituted or unsubstituted alkoxycarbonyl group, or a substituted or unsubstituted arylcarbonyl group, R ^6a , R ^7a , and R ^8a may be the same or different, * represents the bonding position to the benzene ring in formula (1),
In the formulae (2-1), (2-2) and (2-3), a group that is not bonded to any carbon atom constituting a ring means that the bonding position in the ring is arbitrary. The liquid crystal alignment agent for photoalignment according to any one of claims 1 to 4, further comprising an additive. The liquid crystal alignment agent for photoalignment according to claim 5, wherein the additive is at least one selected from the group consisting of oxazoline compounds and epoxy compounds. A liquid crystal alignment film formed from the liquid crystal alignment agent for photoalignment according to any one of claims 1 to 6. A liquid crystal element having the liquid crystal alignment film according to claim 7. A method for producing a liquid crystal alignment film, comprising the steps of applying the liquid crystal alignment agent for photo-alignment described in any one of claims 1 to 6 to a substrate, and irradiating the coating with polarized ultraviolet light.