JP7593271B2 - Liquid crystal alignment agent, liquid crystal alignment film and method for producing the same, and liquid crystal element - Google Patents

Description

The present invention relates to a liquid crystal alignment agent, a liquid crystal alignment film and its manufacturing method, and a liquid crystal element.

Polyimide is generally used as the polymer component of liquid crystal alignment films because of its high heat resistance. On the other hand, polyimide has low solubility in solvents, and therefore, when a relatively large hydrophobic group (mesogen structure, etc.) is introduced into the polymer side chain, the solubility is insufficient, and it is thought that the coatability will decrease. Therefore, as an alternative to polyimide, it has been proposed to use acrylic polymers or styrene-maleimide polymers as materials for liquid crystal alignment films (see, for example, Patent Document 1).

International Publication No. 2018/074547

A liquid crystal alignment film is usually formed on a substrate by applying a liquid crystal alignment agent, in which a polymer component is dissolved or dispersed in a solvent, onto the substrate and heating at high temperatures (e.g., 200 to 250°C). For this reason, if the polymer component does not have sufficient heat resistance, there is a concern that the polymer component may be thermally decomposed by the heat treatment during film formation, causing display defects, or that the components generated by thermal decomposition may become impurities and reduce reliability. Such concerns are thought to be particularly likely to occur in areas where the thickness of the liquid crystal alignment film has become thin due to poor coating, etc. On the other hand, there is a demand for even higher quality liquid crystal elements, and they are required to have the property of exhibiting the desired pretilt angle (hereinafter also referred to as "pretilt angle stability") even when the thickness of the liquid crystal alignment film has become thin due to poor coating, etc. during the formation of the alignment film.

In addition, if components resulting from thermal decomposition caused by heating at relatively high temperatures remain in the film as impurities, there is concern that exposure of the liquid crystal element to a high-temperature environment for a long period of time could cause a decrease in performance due to the impurities in the film, i.e., poor long-term heat resistance.

The present invention has been made in consideration of the above circumstances, and its main object is to provide a liquid crystal alignment agent that can provide a liquid crystal element having a stable pretilt angle and excellent long-term heat resistance even when the thickness of the liquid crystal alignment film is thinned due to poor coating or the like.

The present invention employs the following measures to solve the above problems.

（式（１）中、Ｒ^１及びＲ^２は、それぞれ独立して、水素原子、ハロゲン原子、炭素数１～１０の１価の炭化水素基、若しくは炭化水素基の任意の水素原子がハロゲン原子に置き換えられてなる炭素数１～１０の１価の基であるか、又は、Ｒ^１及びＲ^２が互いに結合してＲ^１及びＲ^２が結合する炭素原子と共に構成される環構造を表す。Ｘ^１は、光照射によりラジカルを発生するラジカル発生機能及び光照射により増感作用を示す光増感機能のうち少なくともいずれかの機能を発現可能な部分構造を有するか、又は重合性炭素－炭素不飽和結合を有する１価の基である。Ｒ^３は、１価の置換基である。ｍ１は０～４の整数である。ｎ１は０～２の整数である。ｍ１が２以上の場合、複数のＲ^３は互いに同一又は異なる。「＊」は結合手であることを表す。
式（２）中、Ｒ^４及びＲ^５は、それぞれ独立して、水素原子、ハロゲン原子、炭素数１～１０の１価の炭化水素基、若しくは炭化水素基の任意の水素原子がハロゲン原子に置き換えられてなる炭素数１～１０の１価の基であるか、又は、Ｒ^４及びＲ^５が互いに結合してＲ^４及びＲ^５が結合する炭素原子と共に構成される環構造を表す。Ｒ^６は、水素原子又は１価の有機基である。Ｘ^２は、光照射によりラジカルを発生するラジカル発生機能及び光照射により増感作用を示す光増感機能のうち少なくともいずれかの機能を発現可能な部分構造を有するか、又は重合性炭素－炭素不飽和結合を有する１価の基である。Ｒ^７は、１価の置換基である。ｍ２は０～４の整数である。ｎ２は０～２の整数である。ｍ２が２以上の場合、複数のＲ^７は互いに同一又は異なる。「＊」は結合手であることを表す。
式（３）中、Ｒ^８は、水素原子、ハロゲン原子、炭素数１～１０の１価の炭化水素基、若しくは炭化水素基の任意の水素原子がハロゲン原子に置き換えられてなる炭素数１～１０の１価の基である。Ｘ^３は、光照射によりラジカルを発生するラジカル発生機能及び光照射により増感作用を示す光増感機能のうち少なくともいずれかの機能を発現可能な部分構造を有するか、又は重合性炭素－炭素不飽和結合を有する１価の基である。Ｒ^９は、１価の置換基である。ｍ３は０～４の整数である。ｍ３が２以上の場合、複数のＲ^９は互いに同一又は異なる。「＊」は結合手であることを表す。
式（４）中、Ｒ^１０は、水素原子、ハロゲン原子、炭素数１～１０の１価の炭化水素基、若しくは炭化水素基の任意の水素原子がハロゲン原子に置き換えられてなる炭素数１～１０の１価の基である。Ｚ^１は、酸素原子又は－ＮＨ－である。Ｘ^４は、光照射によりラジカルを発生するラジカル発生機能及び光照射により増感作用を示す光増感機能のうち少なくともいずれかの機能を発現可能な部分構造を有するか、又は重合性炭素－炭素不飽和結合を有する１価の基である。「＊」は結合手であることを表す。） <1> A liquid crystal aligning agent comprising a polymer [P] which is an addition polymer having, in a polymer side chain, a partial structure capable of exhibiting at least one of a radical generating function of generating radicals upon light irradiation and a photosensitizing function of exhibiting a sensitizing effect upon light irradiation, or a polymerizable carbon-carbon unsaturated bond, and the polymer [P] has at least one selected from the group consisting of a structural unit represented by the following formula (1), a structural unit represented by the following formula (2), a structural unit represented by the following formula (3), and a structural unit represented by the following formula (4):

(In formula (1), R ¹ and R ² are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group is replaced with a halogen atom, or R ¹ and R ² are bonded to each other to represent a ring structure constituted together with the carbon atom to which R ¹ and R ² are bonded. X ¹ has a partial structure capable of exhibiting at least either of a radical generating function that generates radicals upon light irradiation and a photosensitizing function that exhibits a sensitizing effect upon light irradiation, or is a monovalent group having a polymerizable carbon-carbon unsaturated bond. R ³ is a monovalent substituent. m1 is an integer of 0 to 4. n1 is an integer of 0 to 2. When m1 is 2 or more, multiple R ^3s are the same or different. "*" represents a bond.
In formula (2), R ⁴ and R ⁵ are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group is replaced with a halogen atom, or R ⁴ and R ⁵ are bonded to each other to form a ring structure together with the carbon atom to which R ⁴ and R ⁵ are bonded. R ⁶ is a hydrogen atom or a monovalent organic group. X ² has a partial structure capable of exhibiting at least one of a radical generating function that generates radicals upon light irradiation and a photosensitizing function that exhibits a sensitizing effect upon light irradiation, or is a monovalent group having a polymerizable carbon-carbon unsaturated bond. R ⁷ is a monovalent substituent. m2 is an integer of 0 to 4. n2 is an integer of 0 to 2. When m2 is 2 or more, multiple R ^7s are the same or different from each other. "*" represents a bond.
In formula (3), R ⁸ is a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group has been replaced with a halogen atom. ^{X 3} is a monovalent group having a partial structure capable of exhibiting at least one of a radical generating function of generating radicals upon light irradiation and a photosensitizing function of exhibiting a sensitizing effect upon light irradiation, or having a polymerizable carbon-carbon unsaturated bond. R ⁹ is a monovalent substituent. m3 is an integer of 0 to 4. When m3 is 2 or more, multiple R ^9s are the same or different from each other. "*" represents a bond.
In formula (4), R ¹⁰ is a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group has been replaced with a halogen atom. Z ¹ is an oxygen atom or -NH-. X ⁴ is a monovalent group having a partial structure capable of exhibiting at least one of a radical generating function that generates radicals upon light irradiation and a photosensitizing function that exhibits a sensitizing effect upon light irradiation, or having a polymerizable carbon-carbon unsaturated bond. "*" represents a bond.)

<2> A liquid crystal alignment film formed using the liquid crystal aligning agent according to <1> above.
<3> A liquid crystal element comprising the liquid crystal alignment film according to <2> above.
<4> A method for producing a liquid crystal element, comprising: a step of applying the liquid crystal aligning agent according to <1> above onto each conductive film of a pair of substrates having a conductive film to form a coating film; a step of constructing a liquid crystal cell by disposing the pair of substrates on which the coating films have been formed so that the coating films face each other via a liquid crystal layer; and a step of irradiating the liquid crystal cell with light while applying a voltage between the conductive films.

The liquid crystal alignment agent of the present invention makes it possible to obtain a liquid crystal element that has a stable pretilt angle and excellent long-term heat resistance even when the thickness of the liquid crystal alignment film is thin due to poor coating or the like.

The following describes in detail matters related to the aspects of the present disclosure. In this specification, the term "hydrocarbon group" includes linear hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. The term "linear hydrocarbon group" means a linear hydrocarbon group and a branched hydrocarbon group that does not include a cyclic structure and is composed only of a linear structure. However, it may be saturated or unsaturated. The term "alicyclic hydrocarbon group" means a hydrocarbon group that contains only an alicyclic hydrocarbon structure as a ring structure and does not contain an aromatic ring structure. However, it does not have to be composed only of an alicyclic hydrocarbon structure, and it also includes those that have a linear structure as a part of it. The term "aromatic hydrocarbon group" means a hydrocarbon group that contains an aromatic ring structure as a ring structure. However, it does not have to be composed only of an aromatic ring structure, and it may contain a linear structure or an alicyclic hydrocarbon structure as a part of it. The term "main chain" of a polymer refers to the longest "trunk" part of the atomic chain of the polymer. The term "side chain" of a polymer refers to a part branched from the "trunk" of the polymer. An "organic group" is an atomic group formed by removing any hydrogen atom from a carbon-containing compound (i.e., an organic compound).

（式（１）中、Ｒ^１及びＲ^２は、それぞれ独立して、水素原子、ハロゲン原子、炭素数１～１０の１価の炭化水素基、若しくは炭化水素基の任意の水素原子がハロゲン原子に置き換えられてなる炭素数１～１０の１価の基であるか、又は、Ｒ^１及びＲ^２が互いに結合してＲ^１及びＲ^２が結合する炭素原子と共に構成される環構造を表す。Ｘ^１は、光照射によりラジカルを発生するラジカル発生機能及び光照射により増感作用を示す光増感機能のうち少なくともいずれかの機能を発現可能な部分構造を有するか、又は重合性炭素－炭素不飽和結合を有する１価の基である。Ｒ^３は、１価の置換基である。ｍ１は０～４の整数である。ｎ１は０～２の整数である。ｍ１が２以上の場合、複数のＲ^３は互いに同一又は異なる。「＊」は結合手であることを表す。
式（２）中、Ｒ^４及びＲ^５は、それぞれ独立して、水素原子、ハロゲン原子、炭素数１～１０の１価の炭化水素基、若しくは炭化水素基の任意の水素原子がハロゲン原子に置き換えられてなる炭素数１～１０の１価の基であるか、又は、Ｒ^４及びＲ^５が互いに結合してＲ^４及びＲ^５が結合する炭素原子と共に構成される環構造を表す。Ｒ^６は、水素原子又は１価の有機基である。Ｘ^２は、光照射によりラジカルを発生するラジカル発生機能及び光照射により増感作用を示す光増感機能のうち少なくともいずれかの機能を発現可能な部分構造を有するか、又は重合性炭素－炭素不飽和結合を有する１価の基である。Ｒ^７は、１価の置換基である。ｍ２は０～４の整数である。ｎ２は０～２の整数である。ｍ２が２以上の場合、複数のＲ^７は互いに同一又は異なる。「＊」は結合手であることを表す。
式（３）中、Ｒ^８は、水素原子、ハロゲン原子、炭素数１～１０の１価の炭化水素基、若しくは炭化水素基の任意の水素原子がハロゲン原子に置き換えられてなる炭素数１～１０の１価の基である。Ｘ^３は、光照射によりラジカルを発生するラジカル発生機能及び光照射により増感作用を示す光増感機能のうち少なくともいずれかの機能を発現可能な部分構造を有するか、又は重合性炭素－炭素不飽和結合を有する１価の基である。Ｒ^９は、１価の置換基である。ｍ３は０～４の整数である。ｍ３が２以上の場合、複数のＲ^９は互いに同一又は異なる。「＊」は結合手であることを表す。
式（４）中、Ｒ^１０は、水素原子、ハロゲン原子、炭素数１～１０の１価の炭化水素基、若しくは炭化水素基の任意の水素原子がハロゲン原子に置き換えられてなる炭素数１～１０の１価の基である。Ｚ^１は、酸素原子又は－ＮＨ－である。Ｘ^４は、光照射によりラジカルを発生するラジカル発生機能及び光照射により増感作用を示す光増感機能のうち少なくともいずれかの機能を発現可能な部分構造を有するか、又は重合性炭素－炭素不飽和結合を有する１価の基である。「＊」は結合手であることを表す。） Liquid crystal alignment agent
The liquid crystal aligning agent of the present disclosure contains the following polymer [P].
Polymer [P]: An addition polymer having, in a polymer side chain, a partial structure capable of exhibiting at least one of a radical generating function of generating radicals upon light irradiation and a photosensitizing function of exhibiting a sensitizing effect upon light irradiation, or a polymerizable carbon-carbon unsaturated bond, and having at least one structural unit (hereinafter also referred to as a "first structural unit") selected from the group consisting of a structural unit represented by the following formula (1), a structural unit represented by the following formula (2), a structural unit represented by the following formula (3), and a structural unit represented by the following formula (4):

(In formula (1), R ¹ and R ² are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group is replaced with a halogen atom, or R ¹ and R ² are bonded to each other to represent a ring structure constituted together with the carbon atom to which R ¹ and R ² are bonded. X ¹ has a partial structure capable of exhibiting at least either of a radical generating function that generates radicals upon light irradiation and a photosensitizing function that exhibits a sensitizing effect upon light irradiation, or is a monovalent group having a polymerizable carbon-carbon unsaturated bond. R ³ is a monovalent substituent. m1 is an integer of 0 to 4. n1 is an integer of 0 to 2. When m1 is 2 or more, multiple R ^3s are the same or different. "*" represents a bond.
In formula (2), R ⁴ and R ⁵ are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group is replaced with a halogen atom, or R ⁴ and R ⁵ are bonded to each other to form a ring structure together with the carbon atom to which R ⁴ and R ⁵ are bonded. R ⁶ is a hydrogen atom or a monovalent organic group. X ² has a partial structure capable of exhibiting at least one of a radical generating function that generates radicals upon light irradiation and a photosensitizing function that exhibits a sensitizing effect upon light irradiation, or is a monovalent group having a polymerizable carbon-carbon unsaturated bond. R ⁷ is a monovalent substituent. m2 is an integer of 0 to 4. n2 is an integer of 0 to 2. When m2 is 2 or more, multiple R ^7s are the same or different from each other. "*" represents a bond.
In formula (3), R ⁸ is a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group has been replaced with a halogen atom. ^{X 3} is a monovalent group having a partial structure capable of exhibiting at least one of a radical generating function of generating radicals upon light irradiation and a photosensitizing function of exhibiting a sensitizing effect upon light irradiation, or having a polymerizable carbon-carbon unsaturated bond. R ⁹ is a monovalent substituent. m3 is an integer of 0 to 4. When m3 is 2 or more, multiple R ^9s are the same or different from each other. "*" represents a bond.
In formula (4), R ¹⁰ is a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group has been replaced with a halogen atom. Z ¹ is an oxygen atom or -NH-. X ⁴ is a monovalent group having a partial structure capable of exhibiting at least one of a radical generating function that generates radicals upon light irradiation and a photosensitizing function that exhibits a sensitizing effect upon light irradiation, or having a polymerizable carbon-carbon unsaturated bond. "*" represents a bond.)

<First structural unit>
In the above formulas (1) to (4), when X ¹ , X ² , X ³ and X ⁴ are groups having a partial structure (hereinafter also referred to as "partial structure A") capable of expressing at least one of a radical generating function that generates radicals by light irradiation and a photosensitizing function that exhibits a sensitizing effect by light irradiation, it is preferable that the partial structure A is a group having a photoinitiator structure that absorbs light and generates radicals. Examples of this photoinitiator structure include structures derived from known photoradical generators. Examples of the photoradical generator include radical generating group-containing compounds such as alkylphenone compounds, benzoin compounds, ketal compounds, acetophenone compounds, benzophenone compounds, thioxanthone compounds, and anthraquinone compounds.

（式（ａ－１）中、Ａｒ^１及びＡｒ^２は、Ａｒ^１が２価の芳香環基であり、かつＡｒ^２がアルキル基又は１価の芳香環基であるか、又は、Ａｒ^１とＡｒ^２とが互いに合わせられ、Ａｒ^１及びＡｒ^２が結合するカルボニル基と共に構成される環構造を表す。Ｒ^３１は、単結合又は２価の有機基である。「＊」は結合手であることを表す。）

（式（ａ－２）中、Ａｒ^３は２価の芳香環基である。Ｒ^３２及びＲ^３３は、それぞれ独立して１価の有機基であるか、又はＲ^３２とＲ^３３とが合わせられ、Ｒ^３２及びＲ^３３が結合する炭素原子と共に構成される環構造を表す。Ｒ^３４は、水酸基又は１価の有機基である。Ｒ^３５は、単結合又は２価の有機基である。「＊」は結合手であることを表す。） When X ¹ , X ² , X ³ and X ⁴ are groups having a partial structure A, X ¹ , X ² , X ³ and X ⁴ are preferably groups represented by the following formula (a-1) or groups represented by the following formula (a-2).

(In formula (a-1), Ar ¹ and Ar ² are a divalent aromatic ring group, and Ar ² is an alkyl group or a monovalent aromatic ring group, or Ar ¹ and Ar ² are combined with each other to form a ring structure together with the carbonyl group to which Ar ¹ and Ar ² are bonded. ^{R 31} is a single bond or a divalent organic group. "*" represents a bond.)

(In formula (a-2), Ar ³ is a divalent aromatic ring group. R ³² and R ³³ are each independently a monovalent organic group, or R ³² and R ³³ taken together represent a ring structure formed together with the carbon atom to which R ³² and R ³³ are bonded. R ³⁴ is a hydroxyl group or a monovalent organic group. R ³⁵ is a single bond or a divalent organic group. "*" represents a bond.)

The divalent aromatic ring group represented by Ar ¹ and Ar ² in the above formula (a-1) and Ar ³ in the above formula (a-2) is a group obtained by removing two hydrogen atoms from the ring portion of a substituted or unsubstituted aromatic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and the like, and a benzene ring is preferred. Examples of the substituent that the aromatic ring may have include an alkyl group, an alkoxy group, and a fluoroalkyl group having 1 to 6 carbon atoms, a fluorine atom, and a hydroxyl group. Examples of the ring structure formed by combining ^{Ar 1} and Ar ² together include a structure in which two benzene rings are bonded via -O-, -S-, a carbonyl group, or -NR ³⁶ - (R ³⁶ is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms. The same applies below).

Examples of the monovalent organic groups represented by R ³² to R ³⁴ in the above formula (a-2) include an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a benzyl group, a phenethyl group, a phenyloxy group, a phenylalkyloxy group, -NR ³⁹ R ⁴⁰ (wherein R ³⁹ and R ⁴⁰ are each independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms), a nitrogen-containing heterocyclic group, and the like, and any hydrogen atom possessed by these groups may be substituted. Examples of the substituent include a fluorine atom and a hydroxyl group. Examples of the ring structure formed by combining R ³² and R ³³ together include a cycloalkyl group having 4 to 10 carbon atoms.

In R ³¹ in formula (a-1) and R ³⁵ in formula (a-2) above, examples of the divalent organic group include a divalent hydrocarbon group having 1 to 20 carbon atoms, a group having 2 to 20 carbon atoms in which any methylene group in the hydrocarbon group is replaced with -O-, -S- or -NR ³⁶ -, and a group having 2 to 20 carbon atoms in which any hydrogen atom in the hydrocarbon group is replaced with a fluorine atom, an alkoxy group, a hydroxyl group, etc. When R ³¹ and R ³⁵ are divalent organic groups, they preferably have 1 to 10 carbon atoms, and more preferably have 1 to 5 carbon atoms.

In terms of achieving both pretilt angle stability and ease of production in a liquid crystal alignment film when the film thickness is reduced, preferred examples of R ³¹ and R ³⁵ include groups represented by the following formula (r-1).
* ¹ -R ³⁸ -Z ² -*...(r-1)
(In formula (r-1), R ³⁸ is a divalent organic group. Z ² is -O-, * ² -COO-, * ² -OCO-, * ² -NH-CO-, * ² -CO-NH- or * ² -NH-COO-. "* ² " represents a bond to R ^38. "* ¹ " represents a bond to Z ^1. "*" represents a bond.)

（式中、Ｒ^３１は、単結合又は２価の基である。「＊」は結合手であることを表す。）

（式中、Ｒ^３５は、単結合又は２価の基である。「＊」は結合手であることを表す。） When X ¹ , X ² , X ³ and X ⁴ have the partial structure A, specific examples of X ¹ , X ² , X ³ and X ⁴ include, as a group having the partial structure represented by the above formula (a-1), groups represented by each of the following formulas (a-1-1) to (a-1-5), and as a group represented by the above formula (a-2), groups represented by each of the following formulas (a-2-1) to (a-2-9), respectively.

(In the formula, R ³¹ is a single bond or a divalent group. "*" represents a bond.)

(In the formula, R ³⁵ is a single bond or a divalent group. "*" represents a bond.)

When X ¹ , X ² , X ³ and X ⁴ are monovalent groups having a polymerizable carbon-carbon unsaturated bond, examples of X ¹ , X ² , X ³ and X ⁴ include groups represented by the following formula (a-3).
*-R ³⁷ -D ¹ ...(a-3)
(In formula (a-3), D ¹ is a (meth)acryloyl group, a vinyl group, a vinylphenyl group, or a vinyl ether group. R ³⁷ is a single bond or a divalent organic group.)

In R ³⁷ in the above formula (a-3), examples of the divalent organic group include a divalent hydrocarbon group having 1 to 20 carbon atoms, a group having 2 to 20 carbon atoms in which any methylene group in the hydrocarbon group is replaced with -O-, -S- or -NR ³⁶ -, and a group having 2 to 20 carbon atoms in which any hydrogen atom in the hydrocarbon group is replaced with a fluorine atom, an alkoxy group, a hydroxyl group or the like. In this specification, "(meth)acrylic" includes both "acrylic" and "methacrylic". "(meth)acryloyl" includes both "acryloyl" and "methacryloyl".

In ^R1 and ^R2 in the above formula (1), and ^R4 and ^R5 in the above formula (2), examples of the hydrocarbon group having 1 to 10 carbon atoms include a linear or branched alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 4 to 10 carbon atoms, a phenyl group, a methylphenyl group, etc. Examples of the ring structure formed by bonding ^R1 and ^R2 or ^R3 and ^R4 to each other include a cycloalkyl group having 4 to 10 carbon atoms, etc. From the viewpoint of further improving the long-term heat resistance and pretilt angle stability of the liquid crystal element, n1 and n2 are preferably single bonds.

When R ⁶ in the above formula (2) is a monovalent organic group, examples of the monovalent organic group include a monovalent hydrocarbon group having 1 to 30 carbon atoms, a group in which at least one methylene group of the hydrocarbon group is substituted with -O-, -CO-, -COO- or -NR ²⁰ - (wherein R ²⁰ is a hydrogen atom or a monovalent hydrocarbon group) (hereinafter also referred to as "group α"), a monovalent hydrocarbon group having 1 to 30 carbon atoms or a group in which at least one hydrogen atom of the group α is substituted with a fluorine atom or a cyano group, and the like.

Examples of the monovalent substituents of R ³ in the above formula (1), R ⁷ in the above formula (2), and R ⁹ in the above formula (3) include an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 4 to 10 carbon atoms, a phenyl group, an alkoxy group having 1 to 10 carbon atoms, a halogen atom, a cyano group, etc. Each of m1 to m3 is preferably 0 to 2, and more preferably 0 or 1.
R ⁸ in the above formula (3) and R ¹⁰ in the above formula (4) are preferably a hydrogen atom, a fluorine atom, an alkyl group having 1 to 3 carbon atoms, or a fluoroalkyl group having 1 to 3 carbon atoms.

From the viewpoint of further improving the long-term heat resistance of the liquid crystal element, the first structural unit is preferably at least one selected from the group consisting of the partial structure represented by the above formula (1), the partial structure represented by the above formula (2), and the partial structure represented by the above formula (3). In addition, in order to obtain a liquid crystal alignment film that exhibits a desired pretilt angle even when formed into a thin film, the first structural unit preferably has a group represented by the above formula (a-1) or (a-2), and more preferably has a group represented by the above formula (a-2).

（式中、Ｘ^５は、上記式（ａ－１－１）～式（ａ－１－５）及び上記式（ａ－２－１）～式（ａ－２－９）のいずれかで表される１価の基である。「＊」は結合手であることを表す。） Specific examples of the first structural unit include structural units represented by the following formulas (U1-1) to (U1-21).

(In the formula, ^X5 is a monovalent group represented by any one of the above formulas (a-1-1) to (a-1-5) and (a-2-1) to (a-2-9). "*" represents a bond.)

In the polymer [P], the preferred range of the content of the first structural unit varies depending on whether the polymer [P] contains the following second structural unit. When the polymer [P] contains the second structural unit together with the first structural unit, the content of the first structural unit in the polymer [P] is preferably 1 mol% or more, more preferably 2 mol% or more, and even more preferably 5 mol% or more, based on the total amount of the structural units constituting the polymer [P]. In addition, the content of the first structural unit is preferably 50 mol% or less, more preferably 40 mol% or less, and even more preferably 30 mol% or less, based on the total amount of the structural units constituting the polymer [P]. When the content of the first structural unit is in the above range, it is preferable that the desired pretilt angle is exhibited even when the thickness of the liquid crystal alignment film is thin due to poor coating during the formation of the alignment film, and the effect of improving the long-term heat resistance of the liquid crystal element can be enhanced.

When the polymer [P] does not contain the second structural unit, the content ratio of the first structural unit in the polymer [P] is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 25 mol% or more, based on the total amount of the structural units constituting the polymer [P]. The content ratio of the first structural unit is preferably 80 mol% or less, more preferably 70 mol% or less, based on the total amount of the structural units constituting the polymer [P]. When the polymer [P] does not contain the second structural unit, if the content ratio of the first structural unit is in the above range, the desired pretilt angle is exhibited even when the thickness of the liquid crystal alignment film is thin, and the long-term heat resistance of the liquid crystal element is highly improved, which is preferable.

<Second structural unit>
The polymer [P] comprises the following structural units (a) and (b) together with the first structural unit:
(a) a non-photosensitive monovalent group having a total of two or more aromatic rings and/or aliphatic rings (hereinafter also referred to as "non-photosensitive group B");
(b) a non-photosensitive monovalent group having an alkyl group, an alkoxy group, a fluoroalkyl group, or a fluoroalkoxy group having 5 or more carbon atoms (excluding groups corresponding to (a)). Hereinafter, this group may also be referred to as "non-photosensitive group C");
It is preferable that the polymer [P] further contains a structural unit having at least one of the following structural units (hereinafter also referred to as a "second structural unit"). By containing the second structural unit, the polymer [P] is advantageous in that it can more stably exhibit a desired pretilt angle even when the thickness of the liquid crystal alignment film is thinned due to poor coating or the like, and a highly reliable liquid crystal device can be obtained.

From the viewpoint of achieving both the liquid crystal alignment property and the solubility of the polymer [A], the total number of aromatic rings and aliphatic rings possessed by the non-photosensitive group B is preferably 2 or more, and more preferably 2 to 6. When the ring possessed by the non-photosensitive group B is a condensed ring, the number of single rings constituting the condensed ring represents the total number of aromatic rings and aliphatic rings possessed by the non-photosensitive group B. For example, a cholestanyl group is a group having four aliphatic rings, and corresponds to a non-photosensitive monovalent group having a total of at least two aromatic rings and at least one aliphatic ring.

A preferred specific example of the non-photosensitive group B is a group represented by the following formula (8): The group represented by the following formula (8) is preferable in that it is difficult to thermally decompose and can further increase the long-term heat resistance of the liquid crystal element.
A ¹ -B ¹ -L ¹ -B ² -L ² -*...(8)
(In formula (8), A ¹ is a hydrogen atom, a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a fluoroalkyl group having 1 to 20 carbon atoms, or a fluoroalkoxy group having 1 to 20 carbon atoms. ^{B 1} is a divalent group represented by any one of the following formulas (1-1) to (1-8). ^{L 1} is a single bond or a divalent group represented by any one of the following formulas (2-1) to (2-6). B ² is a single bond or a divalent aromatic ring group. L ² is a divalent group represented by any one of the following formulas (3-1) to (3-9). "*" represents a bond.)

In the above formula (8), when A ¹ is an alkyl group, alkoxy group, fluoroalkyl group or fluoroalkoxy group having 1 to 20 carbon atoms, these are preferably linear. In terms of improving the liquid crystal alignment property, A ¹ is preferably an alkyl group, alkoxy group, fluoroalkyl group or fluoroalkoxy group having 2 to 20 carbon atoms, and more preferably an alkyl group, alkoxy group, fluoroalkyl group or fluoroalkoxy group having 3 to 15 carbon atoms.

When ^B2 is a divalent aromatic ring group, the aromatic ring group is preferably a substituted or unsubstituted phenylene group or naphthalene group, more preferably a phenylene group. Examples of the substituent of the aromatic ring group include a methyl group and a halogen atom.

（式（ｍ２－１）～式（ｍ２－１６）中、Ａ^１は、上記式（８）と同義である。「＊」は結合手であることを表す。） Specific examples of the group represented by formula (8) include groups represented by each of the following formulas (m2-1) to (m2-16).

(In formulas (m2-1) to (m2-16), A ¹ has the same meaning as in formula (8) above. "*" represents a bond.)

The non-photosensitive group C is a non-photosensitive monovalent group having an alkyl group, an alkoxy group, a fluoroalkyl group, or a fluoroalkoxy group having 5 or more carbon atoms. The alkyl group, alkoxy group, fluoroalkyl group, and fluoroalkoxy group of the non-photosensitive group C are preferably linear. Specific examples of these include an alkyl group such as n-pentyl group, n-hexyl group, n-octyl group, n-nonyl group, n-decyl group, n-dodecyl group, n-tetradecyl group, n-hexadecyl group, n-octadecyl group, and n-nonadecyl group. Examples of the alkoxy group include the above-mentioned groups in which an alkyl group and an oxygen atom are bonded. Examples of the fluoroalkyl group include the above-mentioned groups in which at least one hydrogen atom in the alkyl group and an oxygen atom is replaced with a fluorine atom. Examples of the fluoroalkoxy group include the above-mentioned groups in which at least one hydrogen atom in the alkyl group and an oxygen atom is replaced with a fluorine atom.

The non-photosensitive group C may be a monovalent group in which an alkyl group, an alkoxy group, a fluoroalkyl group, or a fluoroalkoxy group having 5 or more carbon atoms is bonded to an aromatic ring or an aliphatic ring. The ring possessed by the non-photosensitive group C is preferably a benzene ring or a cyclohexane ring, and more preferably a benzene ring. However, the non-photosensitive group C has one ring.

The alkyl group, alkoxy group, fluoroalkyl group, and fluoroalkoxy group of the non-photosensitive group C preferably have 6 or more carbon atoms, and particularly preferably have 8 or more carbon atoms, in order to increase the pretilt angle stability of the liquid crystal alignment film when it is formed into a thin film.

（式（５）中、Ｒ^１１及びＲ^１２は、それぞれ独立して、水素原子、ハロゲン原子、炭素数１～１０の１価の炭化水素基、若しくは炭化水素基の任意の水素原子がハロゲン原子に置き換えられてなる炭素数１～１０の１価の基であるか、又は、Ｒ^１１及びＲ^１２が互いに結合してＲ^１１及びＲ^１２が結合する炭素原子と共に構成される環構造を表す。Ｙ^１は、芳香族環及び脂肪族環のうち少なくともいずれかを合計２個以上有する非感光性の１価の基である。Ｒ^１３は、１価の置換基である。ｍ４は０～４の整数である。ｎ３は０～２の整数である。ｍ４が２以上の場合、複数のＲ^１３は互いに同一又は異なる。「＊」は結合手であることを表す。
式（６）中、Ｒ^１４及びＲ^１５は、それぞれ独立して、水素原子、ハロゲン原子、炭素数１～１０の１価の炭化水素基、若しくは炭化水素基の任意の水素原子がハロゲン原子に置き換えられてなる炭素数１～１０の１価の基であるか、又は、Ｒ^１４及びＲ^１５が互いに結合してＲ^１４及びＲ^１５が結合する炭素原子と共に構成される環構造を表す。Ｒ^１６は、水素原子又は１価の有機基である。Ｙ^２は、芳香族環及び脂肪族環のうち少なくともいずれかを合計２個以上有する非感光性の１価の基である。Ｒ^１７は、１価の置換基である。ｍ５は０～４の整数である。ｎ４は０～２の整数である。ｍ５が２以上の場合、複数のＲ^１７は互いに同一又は異なる。「＊」は結合手であることを表す。
式（７）中、Ｒ^１８は、水素原子、ハロゲン原子、炭素数１～１０の１価の炭化水素基、若しくは炭化水素基の任意の水素原子がハロゲン原子に置き換えられてなる炭素数１～１０の１価の基である。Ｙ^３は、芳香族環及び脂肪族環のうち少なくともいずれかを合計２個以上有する非感光性の１価の基である。Ｒ^１９は、１価の置換基である。ｍ６は０～４の整数である。ｍ６が２以上の場合、複数のＲ^１９は互いに同一又は異なる。「＊」は結合手であることを表す。） In order to more stably exhibit a desired pretilt angle even when the thickness of the liquid crystal alignment film is reduced, and to obtain a highly reliable liquid crystal element, the second structural unit of the polymer [P] preferably has a non-photosensitive group B, and is particularly preferably at least one structural unit selected from the group consisting of a structural unit represented by the following formula (5), a structural unit represented by the following formula (6), and a structural unit represented by the following formula (7).

(In formula (5), R ¹¹ and R ¹² are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group is replaced with a halogen atom, or R ¹¹ and R ¹² are bonded to each other to represent a ring structure formed together with the carbon atom to which R ¹¹ and R ¹² are bonded. Y ¹ is a non-photosensitive monovalent group having a total of two or more of at least either an aromatic ring or an aliphatic ring. R ¹³ is a monovalent substituent. m4 is an integer of 0 to 4. n3 is an integer of 0 to 2. When m4 is 2 or more, multiple R ^13s are the same or different. "*" represents a bond.
In formula (6), R ¹⁴ and R ¹⁵ are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group is replaced with a halogen atom, or R ¹⁴ and R ¹⁵ are bonded to each other to form a ring structure together with the carbon atom to which R ¹⁴ and R ¹⁵ are bonded. R ¹⁶ is a hydrogen atom or a monovalent organic group. Y ² is a non-photosensitive monovalent group having a total of two or more of at least any one of aromatic rings and aliphatic rings. R ¹⁷ is a monovalent substituent. m5 is an integer of 0 to 4. n4 is an integer of 0 to 2. When m5 is 2 or more, multiple R ^17s are the same or different from each other. "*" represents a bond.
In formula (7), R ¹⁸ is a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group has been replaced with a halogen atom. Y ³ is a non-photosensitive monovalent group having a total of two or more aromatic rings and/or aliphatic rings. R ¹⁹ is a monovalent substituent. m6 is an integer of 0 to 4. When m6 is 2 or more, the multiple R ^19s are the same or different from each other. "*" represents a bond.)

^Y1 in the above formula (5), ^Y2 in the above formula (6), and ^Y3 in the above formula (7) are non-photosensitive monovalent groups (non-photosensitive group B) having a total of two or more aromatic rings and/or aliphatic rings. Specific examples and preferred examples of the non-photosensitive group B are the same as those of the non-photosensitive group B in the second structural unit.

The same explanation as for R ¹ , R ^{2 , R 3} , ⁿ¹ and m1 in the above formula (1) applies to R ¹¹ , R ¹² , R ¹³ , n3 and m4 in the above formula (5), respectively.
The same explanations as for R ⁴ , R 5 , R ⁶ , R ⁷ , n2 and m2 in the above formula (2) apply to R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , n4 and m5 in the above formula (6) ^, respectively.
The same explanation as for R ⁸ , R ⁹ and m3 in the above formula (3) applies to R ¹⁸ , R ¹⁹ and m6 in the above formula (7), respectively.

Specific examples of the second structural unit include structural units represented by the above formulas (U1-1) to (U1-17), in which X ⁵ is a group represented by any one of the above formulas (m2-1) to (m2-16), and structural units represented by the above formulas (U1-1) to (U1-17), in which X ⁵ is an alkyl group, alkoxy group, fluoroalkyl group, or fluoroalkoxy group having 5 or more carbon atoms. A preferred specific example of the second structural unit is a structural unit represented by the above formulas (U1-1) to (U1-17), in which X ⁵ is a group represented by any one of the above formulas (m2-1) to (m2-16).

When the polymer [P] contains the second structural unit, the content of the second structural unit is preferably 1 mol% or more, more preferably 2 mol% or more, and even more preferably 5 mol% or more, based on the total amount of the structural units constituting the polymer [P]. When the polymer [P] contains the second structural unit, the content of the second structural unit is preferably 40 mol% or less, more preferably 35 mol% or less, and even more preferably 30 mol% or less, based on the total amount of the structural units constituting the polymer [P]. When the content of the second structural unit is in the above range, it is preferable in that the effect of improving the pretilt angle stability and long-term heat resistance can be further improved.

<Third structural unit>
The polymer [P] preferably further has a structural unit (hereinafter also referred to as "third structural unit") having at least one selected from the group consisting of a cyclic ether group and a cyclic carbonate group. When the polymer [P] has a third structural unit, the cyclic ether group or cyclic carbonate group in the third structural unit is preferable in that it can improve the pretilt angle stability and heat resistance of the liquid crystal alignment film by reacting with a carboxyl group, a hydroxyl group, an amino group, or the like of a component contained in the liquid crystal alignment agent. The cyclic ether group preferably has 3 to 7 ring members, and at least one of an oxetanyl group and an oxiranyl group is more preferable in terms of high reactivity. In this specification, the oxetanyl group and the oxiranyl group are also referred to as "epoxy group".

The polymer [P] having the third structural unit can be obtained, for example, by using an unsaturated monomer having at least one of a cyclic ether group and a cyclic carbonate group (hereinafter also referred to as the "third monomer") as a monomer that provides the third structural unit when synthesizing the polymer [P]. Examples of the third monomer include maleimide-based compounds, styrene-based compounds, and (meth)acrylic-based compounds.

Specific examples of the third monomer include compounds having a cyclic ether group, such as (3-ethyloxetan-3-yl)methyl (meth)acrylate, N-(4-glycidyloxyphenyl)maleimide, N-glycidylmaleimide, 3-(glycidyloxymethyl)styrene, 4-(glycidyloxymethyl)styrene, 4-glycidyl-α-methylstyrene, glycidyl (meth)acrylate, glycidyl α-ethylacrylate, glycidyl α-n-propylacrylate, glycidyl α-n-butylacrylate, 3,4-epoxybutyl (meth)acrylate, 3,4-epoxybutyl α-ethylacrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 6,7-epoxyheptyl (meth)acrylate, 6,7-epoxyheptyl α-ethylacrylate, and 4-hydroxybutyl glycidyl ether (meth)acrylate;
Examples of the compound having a cyclic carbonate group include (2-oxo-1,3-dioxolan-4-yl)methyl (meth)acrylate, 2-((2-oxo-1,3-dioxolan-4-yl)methoxy)ethyl (meth)acrylate, and the like. In addition, when synthesizing the polymer [P], as the third monomer, one of these may be used alone, or two or more of them may be used in combination.

When the polymer [P] contains a third structural unit, the content ratio of the third structural unit is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 20 mol% or more, based on the total amount of the structural units constituting the polymer [P]. When the polymer [P] contains a third structural unit, the content ratio of the third structural unit is preferably 80 mol% or less, more preferably 75 mol% or less, and even more preferably 70 mol% or less, based on the total amount of the structural units constituting the polymer [P]. By having the content ratio of the third structural unit in the above range, a crosslinked structure can be appropriately formed between the components, and even when the liquid crystal alignment film is thinned, pretilt angle stability can be ensured, and the effect of improving long-term heat resistance can be enhanced. This is preferable.

<Fourth structural unit>
It is preferable that the polymer [P] further includes a structural unit (hereinafter also referred to as a "fourth structural unit") having a functional group (hereinafter also referred to as a "reactive functional group") that is capable of forming a bond between compounds and is different from an oxetanyl group and an oxiranyl group. The reactive functional group of the fourth structural unit includes a functional group (hereinafter also referred to as a "functional group D") that reacts with at least one of an oxetanyl group and an oxiranyl group upon heating. When the polymer [P] has the functional group D, it is preferable in that the effect of improving the liquid crystal alignment (particularly the pretilt angle stability in a thin film) can be sufficiently obtained.

Examples of functional group D include a carboxy group, a protected carboxy group, a hydroxyl group, a protected hydroxyl group, an isocyanate group, a protected isocyanate group, an amino group, a protected amino group, and an alkoxymethyl group. Among them, functional group D is preferably at least one selected from the group consisting of a carboxyl group, a protected carboxyl group, an amino group, and a protected amino group, in that it has good storage stability and is highly reactive with an oxetane ring and an oxirane ring upon heating.

When the reactive functional group of the fourth structural unit is at least one selected from the group consisting of a carboxy group, a protected carboxy group, an amino group, and a protected amino group, it reacts with a functional group of a component contained in the liquid crystal alignment agent (e.g., an oxetanyl group or an oxiranyl group of the polymer [P], or an amino group, a hydroxyl group, or a carboxyl group of a polymer other than the polymer [P]) to form a crosslinked structure, which is advantageous in that it can improve the pretilt angle stability and heat resistance of the liquid crystal alignment film.

（式（４）中、Ｒ^４１、Ｒ^４２及びＲ^４３は、次の（１）又は（２）を満たす。
（１）Ｒ^４１、Ｒ^４２及びＲ^４３は、それぞれ独立して、炭素数１～１０のアルキル基又は炭素数３～２０の１価の脂環式炭化水素基である。
（２）Ｒ^４１及びＲ^４２は、互いに合わせられＲ^４１及びＲ^４２が結合する炭素原子とともに構成される炭素数４～２０の脂環式炭化水素構造又は環状エーテル構造を表す。Ｒ^４３は、炭素数１～１０のアルキル基、炭素数２～１０のアルケニル基又は炭素数６～２０のアリール基である。
「＊」は結合手であることを表す。） The protected carboxy group is not particularly limited as long as it is one that is eliminated by heat to generate a carboxy group. Preferred examples of the protected carboxy group include a structure represented by the following formula (4), an acetal ester structure of a carboxylic acid, and a ketal ester structure of a carboxylic acid.

In formula (4), R ⁴¹ , R ⁴² and R ⁴³ satisfy the following (1) or (2).
(1) R ⁴¹ , R ⁴² and R ⁴³ each independently represent an alkyl group having 1 to 10 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.
(2) ^R41 and ^R42 , taken together with the carbon atom to which ^R41 and ^R42 are bonded, represent an alicyclic hydrocarbon structure or a cyclic ether structure having 4 to 20 carbon atoms. ^R43 represents an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.
"*" indicates a bond.)

Specific examples of the structure represented by the above formula (4) include a tert-butoxycarbonyl group, a 1-cyclopentylethoxycarbonyl group, a 1-cyclopentyl-2-methylpropoxycarbonyl group, a 1-cyclohexylethoxycarbonyl group, a 1-norbornylethoxycarbonyl group, a 1-phenylethoxycarbonyl group, a 1-(1-naphthyl)ethoxycarbonyl group, a 1-benzylethoxycarbonyl group, and a 1-phenethylethoxycarbonyl group.

Specific examples of acetal ester structures of carboxylic acids include 1-methoxyethoxycarbonyl group, 1-ethoxyethoxycarbonyl group, 1-propoxyethoxycarbonyl group, 1-butoxyethoxycarbonyl group, 1-cyclohexyloxyethoxycarbonyl group, 2-tetrahydropyranyloxycarbonyl group, 1-phenoxyethoxycarbonyl group, 2-tetrahydrofuranyloxycarbonyl group, and 2-tetrahydropyranyloxycarbonyl group.

Specific examples of ketal ester structures of carboxylic acids include 1-methyl-1-methoxyethoxycarbonyl group, 1-methyl-1-ethoxyethoxycarbonyl group, 1-methyl-1-propoxyethoxycarbonyl group, 1-methyl-1-butoxyethoxycarbonyl group, 1-methyl-1-cyclohexyloxyethoxycarbonyl group, 2-(2-methyltetrahydrofuranyl)oxycarbonyl group, 2-(2-methyltetrahydropyranyl)oxycarbonyl group, 1-methoxycyclopentyloxycarbonyl group, and 1-methoxycyclohexyloxycarbonyl group.

The protected amino group is a group that is eliminated by heat to generate an amino group. Specific examples of thermally eliminable groups that are eliminated by heat include, for example, tert-butoxycarbonyl group, benzyloxycarbonyl group, 1,1-dimethylpropynyloxycarbonyl group, 1,1-dimethyl-2-haloethyloxycarbonyl group, allyloxycarbonyl group, vinyloxycarbonyl group, cyclohexyloxycarbonyl group, methylcyclohexyloxycarbonyl group, 2-(trimethylsilyl)ethoxycarbonyl group, 9-fluorenylmethyloxycarbonyl group, 2,2,2-trichloroethoxycarbonyl group, phthaloyl group, p-toluenesulfonyl group, and 2-nitrobenzenesulfonyl group. Among these, the tert-butoxycarbonyl group and the 9-fluorenylmethyloxycarbonyl group are preferred from the viewpoint of being removed by heating during film formation, and the tert-butoxycarbonyl group (Boc group) is particularly preferred because it has excellent thermal removal properties and can reduce the amount of the removed structure remaining in the film.

When the polymer [P] contains a fourth structural unit, the reactive functional group of the fourth structural unit is preferably a carboxy group or a protected carboxy group, more preferably a protected carboxy group, in that it has high reactivity with cyclic ether groups and cyclic carbonate groups and can improve the storage stability of the liquid crystal alignment agent.

The polymer [P] having the fourth structural unit can be obtained, for example, by carrying out a polymerization reaction using an unsaturated monomer having a reactive functional group (hereinafter also referred to as the "fourth monomer"). Examples of the fourth monomer include maleimide-based compounds, styrene-based compounds, (meth)acrylic-based compounds, vinyl-based compounds, etc.

（式（ｍ４－１）～式（ｍ４－１２）中、Ｒ^５０は水素原子又はメチル基である。）
のそれぞれで表される保護カルボニル基含有化合物等を；
ビニル系化合物として、例えばビシクロ［２．２．１］ヘプト－５－エン－２－カルボン酸等を；挙げることができる。なお、重合体［Ｐ］の合成に際し、第４単量体としては１種を単独で使用してもよく、２種以上を組み合わせて使用してもよい。 Specific examples of these include maleimide compounds such as 3-(2,5-dioxo-3-pyrrolin-1-yl)benzoic acid, 4-(2,5-dioxo-3-pyrrolin-1-yl)benzoic acid, methyl 4-(2,5-dioxo-3-pyrrolin-1-yl)benzoate, and tert-butyl 4-(2,5-dioxopyrrol-1-yl)benzoate;
Examples of styrene-based compounds include 3-vinylbenzoic acid, 4-vinylbenzoic acid, 4-aminostyrene, and 4-(N-tert-butoxycarbonyl)styrene;
Examples of the (meth)acrylic compound include (meth)acrylic acid, α-ethylacrylic acid, maleic acid, fumaric acid, vinylbenzoic acid, crotonic acid, citraconic acid, mesaconic acid, itaconic acid, 3-maleimidobenzoic acid, 3-maleimidopropionic acid, 2-aminoethyl (meth)acrylate, and compounds represented by the following formulae (m4-1) to (m4-12):

(In formulas (m4-1) to (m4-12), R ⁵⁰ is a hydrogen atom or a methyl group.)
A compound containing a protected carbonyl group represented by each of the following formulas:
Examples of vinyl compounds include bicyclo[2.2.1]hept-5-ene-2-carboxylic acid. In the synthesis of the polymer [P], the fourth monomer may be used alone or in combination of two or more.

When the polymer [P] contains a fourth structural unit, the content ratio of the fourth structural unit is preferably 2 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more, based on the total amount of the structural units constituting the polymer [P]. When the polymer [P] contains a fourth structural unit, the content ratio of the fourth structural unit is preferably 65 mol% or less, more preferably 60 mol% or less, and even more preferably 55 mol% or less, based on the total amount of the structural units constituting the polymer [P]. By having the content ratio of the fourth structural unit in the above range, a crosslinked structure is appropriately formed between the functional group of the third structural unit or the functional group of a polymer different from the polymer [P], which is advantageous in that the effect of improving the pretilt angle stability and long-term heat resistance in the liquid crystal element can be enhanced.

<Other structural units>
The polymer [P] may further have a structural unit (hereinafter also referred to as "other structural unit") different from the first structural unit to the fourth structural unit. Examples of the monomer (hereinafter also referred to as "other monomer") that gives the other structural unit include (meth)acrylic compounds such as alkyl (meth)acrylate, cycloalkyl (meth)acrylate, benzyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate; aromatic vinyl compounds such as styrene, methylstyrene, and divinylbenzene; conjugated diene compounds such as 1,3-butadiene and 2-methyl-1,3-butadiene; maleimide compounds such as N-methylmaleimide, N-cyclohexylmaleimide, and N-phenylmaleimide; and the like. As the other monomer, one type may be used alone, or two or more types may be used in combination.

In the polymer [P], the preferred range of the content of the other structural units varies depending on whether the polymer [P] contains the second structural unit. When the polymer [P] contains the second structural unit together with the first structural unit, the content of the other structural units in the polymer [P] is preferably 20 mol % or less, and more preferably 15 mol % or less, based on the total amount of the structural units constituting the polymer [P].

When polymer [P] does not contain the second structural unit together with the first structural unit, the proportion of other structural units in polymer [P] is preferably 40 mol % or less, and more preferably 35 mol % or less, based on the total amount of structural units constituting polymer [P].

In the polymer [P], the proportion of the structural units derived from the maleimide-based compound (i.e., the proportion of the structural units derived from the maleimide-based compound among the first to fourth structural units and other structural units) is preferably 20 mol% or more with respect to the total amount of the structural units constituting the polymer [P]. If it is 20 mol% or more, it is preferable in that the solubility of the polymer [P] and the coatability on the substrate can be ensured while the effect of improving the pretilt angle stability of the liquid crystal alignment film can be sufficiently obtained. From the above viewpoint, the proportion of the structural units derived from the maleimide-based compound is more preferably 25 mol% or more, and more preferably 30 mol% or more with respect to the total amount of the structural units constituting the polymer [P]. In addition, from the viewpoint of suppressing the decrease in the liquid crystal alignment property and the voltage holding ratio of the liquid crystal element, the proportion of the structural units derived from the maleimide-based compound is more preferably 95 mol% or less, and even more preferably 90 mol% or less with respect to the total amount of the structural units constituting the polymer [P].

When introducing structural units derived from a styrene-based compound into the polymer [P], the ratio of structural units derived from the styrene-based compound (i.e., the ratio of structural units derived from the styrene-based compound among the first to fourth structural units and other structural units) is preferably 1 mol% or more, more preferably 2 mol% or more, and even more preferably 5 mol% or more, based on the total amount of structural units constituting the polymer [P], from the viewpoint of increasing the effect of improving the heat resistance of the liquid crystal alignment film. In addition, the ratio of structural units derived from the styrene-based compound is preferably 90 mol% or less, more preferably 80 mol% or less, based on the total amount of structural units constituting the polymer [P]. Furthermore, when the polymer [P] is a copolymer of a styrene-based compound and a maleimide-based compound, the styrene-based compound and the maleimide-based compound are alternately copolymerized to form a main chain structure with high heat resistance, which is advantageous in that it is possible to reduce unreacted monomers after polymerization and further improve long-term heat resistance from the main chain heat resistance. From the above viewpoints, the ratio of the styrene-based compound and the maleimide-based compound constituting the polymer [P] is preferably 0.8 to 1.2 moles of the maleimide-based compound per mole of the styrene-based compound.

The proportion of structural units derived from (meth)acrylic compounds in polymer [P] (i.e., the proportion of structural units derived from (meth)acrylic compounds among the first to fourth structural units and other structural units) is preferably 30 mol % or less, more preferably 25 mol % or less, and even more preferably 20 mol % or less, based on the total amount of structural units in polymer [A], from the viewpoints of forming a liquid crystal alignment film with high heat resistance and sufficiently ensuring the liquid crystal alignment and electrical characteristics of the liquid crystal element.

<Synthesis of Polymer [P]>
The polymer [P] is a polymer obtained by addition polymerization, and the details of the synthesis method are not particularly limited. The polymer [P] can be obtained, for example, by polymerizing (addition polymerizing) a monomer in an organic solvent in the presence of a polymerization initiator. As the polymerization initiator, a radical polymerization initiator can be preferably used, and specific examples thereof include azo compounds such as 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile). The proportion of the polymerization initiator used is preferably 0.01 to 30 parts by mass with respect to 100 parts by mass of the total monomers used in the reaction. As the organic solvent used, for example, alcohols, ethers, ketones, amides, esters, hydrocarbon compounds, etc. can be mentioned.

In the above polymerization reaction, the reaction temperature is preferably 30°C to 120°C, and the reaction time is preferably 1 to 36 hours. The amount of organic solvent (a) used is preferably such that the total amount of monomers (b) used in the reaction is 0.1 to 60 mass% relative to the total amount of the reaction solution (a + b). The polymer [P] contained in the reaction solution may be isolated and used for the preparation of a liquid crystal alignment agent by applying a known isolation method to the reaction solution in which the polymer is dissolved, such as a method of pouring the reaction solution into a large amount of poor solvent and drying the resulting precipitate under reduced pressure, or a method of distilling the reaction solution under reduced pressure using an evaporator.

The weight average molecular weight (Mw) of the polymer [P] in terms of polystyrene measured by gel permeation chromatography (GPC) is preferably 1,000 to 300,000, more preferably 2,000 to 100,000. The molecular weight distribution (Mw/Mn), which is expressed as the ratio of Mw to the number average molecular weight (Mn) in terms of polystyrene measured by GPC, is preferably 10 or less, more preferably 8 or less. The polymer [P] used to prepare the liquid crystal alignment agent may be one type or a combination of two or more types.

The preferred content ratio of the polymer [P] in the liquid crystal alignment agent varies depending on whether the polymer [P] contains the second structural unit. When the polymer [P] contains the second structural unit together with the first structural unit, from the viewpoint of obtaining a liquid crystal element having excellent long-term heat resistance while improving the pretilt angle characteristics even when the liquid crystal alignment film becomes thinner than the desired film thickness due to poor coating or the like, the content ratio of the polymer [P] is preferably 2 parts by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, relative to a total of 100 parts by mass of the solid components (i.e., components other than the solvent) in the liquid crystal alignment agent. In addition, the content ratio of the polymer [P] in the liquid crystal alignment agent is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 25% by mass or less, relative to a total of 100 parts by mass of the solid components in the liquid crystal alignment agent.

When the polymer [P] does not contain a second structural unit, the content of the polymer [P] is, for the same reasons as above, preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, relative to a total of 100 parts by mass of the solid components in the liquid crystal alignment agent. In addition, the content of the polymer [P] in the liquid crystal alignment agent is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3% by mass or less, relative to a total of 100 parts by mass of the solid components in the liquid crystal alignment agent.

<Other ingredients>
The liquid crystal aligning agent of the present disclosure may further contain components other than the polymer [P] (hereinafter also referred to as “other components”).

(Polymer [Q])
The liquid crystal alignment agent of the present disclosure may further contain, as another component, a polymer different from the polymer [P], i.e., a polymer not containing a first structural unit (hereinafter also referred to as "polymer [Q]"), for the purpose of further improving the liquid crystal alignment properties and electrical properties of a liquid crystal alignment film formed using the liquid crystal alignment agent.

The main skeleton of the polymer [Q] is not particularly limited, but examples thereof include polyamic acid, polyamic acid ester, polyimide, polyorganosiloxane, polyester, polyenamine, polyurea, polyamide, polyamideimide, polybenzoxazole precursor, polybenzoxazole, cellulose derivative, polyacetal, etc. Among these, the polymer [Q] is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide. A blend system of polyamic acid or the like and polymer [P] can easily cause phase separation between the polymer [P] and the polymer [Q] in the liquid crystal alignment film, which is thought to make it easier to unevenly distribute the polymer [P] in the upper layer. As a result, it is thought that a liquid crystal alignment film that shows high pretilt angle stability that is not easily affected by differences in film thickness can be obtained.

The polymer [Q] can be synthesized according to a conventional method. For example, a polyamic acid can be obtained by reacting a tetracarboxylic dianhydride with a diamine. In this specification, the term "tetracarboxylic acid derivative" includes tetracarboxylic dianhydrides, tetracarboxylic diesters, and tetracarboxylic diester dihalides.

The tetracarboxylic dianhydride used in the polymerization is not particularly limited, and various tetracarboxylic dianhydrides can be used. Specific examples thereof include aliphatic tetracarboxylic dianhydrides such as butane tetracarboxylic dianhydride and ethylenediaminetetraacetic dianhydride; 1,2,3,4-cyclobutane tetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic dianhydride, 5-(2,5-dioxotetrahydrofuran-3-yl)-3a,4,5,9b-tetrahydronaphtho[1,2-c]furan-1,3-dione, 5-(2,5-dioxotetrahydrofuran-3-yl)-8-methyl-3a,4,5,9b-tetrahydronaphtho[1,2-c]furan-1,3-dione, 2,4,6,8 Alicyclic tetracarboxylic dianhydrides such as tetracarboxybicyclo[3.3.0]octane-2:4,6:8-dianhydride, cyclopentane tetracarboxylic dianhydride, and cyclohexane tetracarboxylic dianhydride; aromatic tetracarboxylic dianhydrides such as pyromellitic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, p-phenylene bis(trimellitic monoester anhydride), ethylene glycol bis(anhydrotrimellitate), and 1,3-propylene glycol bis(anhydrotrimellitate); and tetracarboxylic dianhydrides described in JP-A-2010-97188 can be used. Note that the tetracarboxylic dianhydrides may be used alone or in combination of two or more.

（式（５－０）～式（５－４）中、ｎは１～２０の整数である。）

Examples of the diamine used in the polymerization include aliphatic diamines such as ethylenediamine and tetramethylenediamine; alicyclic diamines such as p-cyclohexanediamine and 4,4'-methylenebis(cyclohexylamine);
Dodecanoxydiaminobenzene, pentadecanoxydiaminobenzene, hexadecanoxydiaminobenzene, octadecanoxydiaminobenzene, cholestanyloxydiaminobenzene, cholestanyl diaminobenzoate, cholesteryl diaminobenzoate, lanostannyl diaminobenzoate, 3,6-bis(4-aminobenzoyloxy)cholestane, 3,6-bis(4-aminophenoxy)cholestane, 1,1-bis(4-((aminophenyl)methyl)phenyl)-4-butylcyclohexane, 2,5-diamino-N,N-diallylaniline, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylamine, 4-aminophenyl-4'-aminobenzoate, 4,4'-diaminoazobenzene, 3,5-diaminobenzoic acid, 1,5-bis(4-aminophenoxy)pentane, bis[2- (4-aminophenyl)ethyl]hexanedioic acid, bis(4-aminophenyl)amine, N,N-bis(4-aminophenyl)methylamine, N,N'-bis(4-aminophenyl)-benzidine, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-(phenylenediisopropylidene)bisaniline, 1,4-bis(4-aminophenoxy)benzene, 4-(4-aminophenoxycarbonyl)-1-(4-aminophenyl)piperidine, 4,4'-[4,4'-propane-1,3-diylbis(piperidine-1,4-diyl)]dianiline, aromatic diamines such as compounds represented by each of the following formulas (5-0) to (5-10);
Examples of the diamine include diaminoorganosiloxanes such as 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, and the like. In addition, the diamines described in JP 2010-97188 A can be used. As the diamine, a diamine in which any one of the monovalent groups of the above formulae (m2-1) to (m2-16) is bonded to diaminobenzene can also be used. The diamines may be used alone or in combination of two or more kinds.

(In formulas (5-0) to (5-4), n is an integer of 1 to 20.)

The synthesis reaction of polyamic acid is preferably carried out in an organic solvent. The reaction temperature is preferably -20°C to 150°C, and the reaction time is preferably 0.1 to 24 hours. Examples of organic solvents used in the reaction include aprotic polar solvents, phenolic solvents, alcohols, ketones, esters, ethers, halogenated hydrocarbons, and hydrocarbons. The amount of organic solvent used is preferably such that the total amount of tetracarboxylic dianhydride and diamine compound is 0.1 to 50% by mass relative to the total amount of the reaction solution.

When the polymer [Q] is a polyamic acid ester, the polyamic acid ester can be obtained, for example, by reacting the polyamic acid obtained above with an esterifying agent (e.g., methanol, ethanol, N,N-dimethylformamide diethyl acetal, etc.), by reacting a tetracarboxylic acid diester with a diamine compound in the presence of a suitable dehydration catalyst, or by reacting a tetracarboxylic acid diester dihalide with a diamine in the presence of a suitable base.

When the polymer [Q] is a polyimide, the polyimide can be obtained, for example, by dehydrating and ring-closing the polyamic acid obtained above to convert it into an imidized product. The polyimide preferably has an imidization rate of 20 to 95%, more preferably 30 to 85%, and even more preferably 40 to 80 mol%. This imidization rate is the ratio, expressed as a percentage, of the number of imide ring structures to the total number of amic acid structures and imide ring structures in the polyimide.

The solution viscosity of the polymer [Q] is preferably 10 to 800 mPa·s when made into a 10% by mass solution, and more preferably 15 to 500 mPa·s. The solution viscosity (mPa·s) is the value measured at 25°C using an E-type rotational viscometer for a 10% by mass polymer solution prepared using a good solvent for the polymer [Q] (e.g., γ-butyrolactone, N-methyl-2-pyrrolidone, etc.).

The weight average molecular weight (Mw) of the polymer [Q] measured by GPC in terms of polystyrene is preferably 1,000 to 500,000, more preferably 5,000 to 100,000. The molecular weight distribution (Mw/Mn), which is expressed as the ratio of Mw to the number average molecular weight (Mn) measured by GPC in terms of polystyrene, is preferably 15 or less, more preferably 10 or less. The polymer [Q] contained in the liquid crystal alignment agent may be of only one type, or may be of a combination of two or more types.

When the polymer [P] does not contain the second structural unit, the liquid crystal alignment agent of the present disclosure preferably contains, together with the polymer [P] (i.e., a polymer that contains the first structural unit and does not contain the second structural unit), a polymer [Q] that has at least one of the non-photosensitive groups of the non-photosensitive B and non-photosensitive C described above and does not contain the first structural unit (hereinafter also referred to as "polymer [Q1]"). When the polymer [P] does not contain the second structural unit, by containing the polymer [Q1] together with the polymer [P], it is possible to exhibit good pretilt angle characteristics in the resulting liquid crystal alignment film.

The non-photosensitivity of the polymer [Q1] is particularly preferably non-photosensitive B, since this has a greater effect of improving the pretilt angle stability in a thin liquid crystal alignment film. Specific examples and preferred examples of non-photosensitive group B and non-photosensitive group C are the same as those described above.

The polymer [Q1] is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide, in that it can facilitate phase separation between the polymer [P] and the polymer [Q1] in the liquid crystal alignment film. When the polymer [Q1] is at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide, the polymer can be obtained, for example, by polymerization using a diamine having non-photosensitive B or non-photosensitive C (hereinafter also referred to as "vertically aligning diamine").

When the polymer [Q1] is at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide, the content ratio of structural units derived from vertically aligning diamine in the polymer [Q1] is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 20 mol% or more, based on the total amount of diamine constituting the polymer [Q1]. The content ratio of structural units derived from vertically aligning diamine is preferably 80 mol% or less, more preferably 70 mol% or less, and even more preferably 60 mol% or less, based on the total amount of diamine constituting the polymer [Q1].

When the polymer [Q] is blended into the liquid crystal alignment agent of the present disclosure, the preferred range of the ratio of the polymer [Q] to the polymer [P] in the liquid crystal alignment agent varies depending on whether the polymer [P] contains the second structural unit. When the polymer [P] contains the second structural unit together with the first structural unit, the ratio of the polymer [P] to the content of the polymer [Q] is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the polymer [Q]. The content of the polymer [P] is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 25 parts by mass or less, per 100 parts by mass of the polymer [Q]. By setting the content of the polymer [P] within the above range, a stable pretilt angle can be expressed even when the thickness of the liquid crystal alignment film is thinner than the desired film thickness, and it is preferable in that the long-term heat resistance of the liquid crystal element can be excellent.

When the polymer [P] does not contain the second structural unit together with the first structural unit, the ratio of the polymer [P] to the content of the polymer [Q] (preferably the polymer [Q1]) is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.2 parts by mass or more, relative to 100 parts by mass of the polymer [Q]. The content of the polymer [P] is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the polymer [Q]. By setting the content of the polymer [P] within the above range, a stable pretilt angle can be expressed even when the thickness of the liquid crystal alignment film is thinner than the desired film thickness, and it is also preferable in that the long-term heat resistance of the liquid crystal element can be excellent.

Other components that may be contained in the liquid crystal alignment agent of the present disclosure include, in addition to the polymer [Q], for example, a compound having one or more epoxy groups in the molecule, a compound having two or more methylol groups in the molecule, a functional silane compound, a compound having one or more (meth)acryloyl groups in the molecule, an antioxidant, a metal chelate compound, a curing accelerator, a surfactant, a filler, a dispersant, a photosensitizer, etc. The blending ratio of these can be appropriately selected according to each compound within a range that does not impair the effects of the present disclosure.

(solvent)
The liquid crystal aligning agent is usually prepared as a liquid composition in which the polymer [P] and other components used as necessary are preferably dispersed or dissolved in a suitable solvent.

Examples of organic solvents that can be used include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 1,2-dimethyl-2-imidazolidinone, γ-butyrolactone, γ-butyrolactam, N,N-dimethylformamide, N,N-dimethylacetamide, 4-hydroxy-4-methyl-2-pentanone (diacetone alcohol), ethylene glycol monomethyl ether, butyl lactate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, and ethylene glycol-i-propyl ether. Examples of suitable ethers include ethylene glycol n-butyl ether (butyl cellosolve), ethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diisobutyl ketone, isoamyl propionate, isoamyl isobutyrate, diisopentyl ether, ethylene carbonate, and propylene carbonate. These can be used alone or in combination of two or more.

The solid content concentration in the liquid crystal alignment agent (the ratio of the total mass of the components other than the solvent of the liquid crystal alignment agent to the total mass of the liquid crystal alignment agent) is appropriately selected taking into consideration the viscosity, volatility, etc., but is preferably in the range of 1 to 10 mass%. That is, the liquid crystal alignment agent is applied to the substrate surface as described below, and preferably heated to form a coating film that is a liquid crystal alignment film or a coating film that will become a liquid crystal alignment film. In this case, if the solid content concentration is 1 mass% or more, the thickness of the coating film can be sufficiently ensured, which is preferable in that a good liquid crystal alignment film can be easily obtained. In addition, if the solid content concentration is 10 mass% or less, the thickness of the coating film is not too large, and a good liquid crystal alignment film can be obtained, and the viscosity of the liquid crystal alignment agent can be appropriately ensured, making the coating property good.

Preferred embodiments of the liquid crystal aligning agent of the present disclosure include the following embodiments <1> to <4>. However, the embodiments of the liquid crystal aligning agent of the present disclosure are not limited to the following embodiments.
<1> An embodiment in which the polymer [P] contains a polymer that includes a first structural unit, a second structural unit, and a third structural unit, and optionally further contains other structural units, and the polymer [Q] contains a polyamic acid, a polyamic acid ester, or a polyimide.
<2> An embodiment in which the polymer [P] contains a polymer that includes a first structural unit, a second structural unit, a third structural unit, and a fourth structural unit, and further includes other structural units as necessary, and the polymer [Q] contains a polyamic acid, a polyamic acid ester, or a polyimide.
<3> An embodiment in which the polymer [P] contains a polymer that includes a first structural unit, a second structural unit, and a fourth structural unit, and further includes other structural units as necessary, and the polymer [Q] contains a polyamic acid, a polyamic acid ester, or a polyimide.
<4> An embodiment in which the polymer [P] contains a polymer that includes a first structural unit and a fourth structural unit and, if necessary, further contains other structural units, and the polymer [Q1] contains a polyamic acid, a polyamic acid ester, or a polyimide.
<5> An embodiment in which the polymer [P] contains a polymer that includes a first structural unit, a third structural unit, and a fourth structural unit, and further includes other structural units as necessary, and the polymer [Q1] contains a polyamic acid, a polyamic acid ester, or a polyimide.
<6> An embodiment in which the polymer [P] contains a polymer that includes a first structural unit and a third structural unit and, if necessary, further contains other structural units, and the polymer [Q1] contains a polyamic acid, a polyamic acid ester, or a polyimide.

Among the above aspects, <1>, <2>, <4> and <5> are preferred in that they are highly effective in achieving a stable pretilt angle even when the thickness of the liquid crystal alignment film is thinner than the desired film thickness, and can provide the liquid crystal element with excellent long-term heat resistance.

<Liquid crystal alignment film and liquid crystal element>
The liquid crystal alignment film of the present disclosure is formed by the liquid crystal alignment agent prepared as described above. The liquid crystal element of the present disclosure includes a liquid crystal alignment film formed by using the liquid crystal alignment agent described above. The operation mode of the liquid crystal in the liquid crystal element is not particularly limited, and can be applied to various modes such as TN (Twisted Nematic) type, STN (Super Twisted Nematic) type, VA (Vertical Alignment) type (including VA-MVA type, VA-PVA type, etc.), IPS (In-Plane Switching) type, FFS (Fringe Field Switching) type, OCB (Optically Compensated Bend) type, PSA (Polymer Sustained Alignment) type, etc. The liquid crystal element can be manufactured by a method including, for example, the following steps 1 to 3. In step 1, the substrate used differs depending on the desired operation mode. Steps 2 and 3 are common to each operation mode.

(Step 1: Formation of coating film)
First, a liquid crystal alignment agent is applied onto a substrate, and a coating film is formed on the substrate, preferably by heating the applied surface. As the substrate, for example, a transparent substrate made of glass such as float glass or soda glass; or plastic such as polyethylene terephthalate, polybutylene terephthalate, polyethersulfone, polycarbonate, or poly(alicyclic olefin) can be used. As the transparent conductive film provided on the substrate surface, a NESA film (registered trademark of PPG Corporation, USA) made of tin oxide (SnO ₂ ), an ITO film made of indium oxide-tin oxide (In ₂ O ₃ -SnO ₂ ), or the like can be used. When manufacturing a TN-type, STN-type, or VA-type liquid crystal element, two substrates on which a patterned transparent conductive film is provided are used. On the other hand, when manufacturing an IPS-type or FFS-type liquid crystal element, a substrate on which an electrode made of a transparent conductive film or metal film patterned into a comb tooth shape is provided, and an opposing substrate on which no electrode is provided are used. As the metal film, for example, a film made of a metal such as chromium can be used. The liquid crystal alignment agent is applied to the substrate on the surface on which the electrodes are formed, preferably by offset printing, spin coating, roll coating or inkjet printing.

After the liquid crystal alignment agent is applied, preliminary heating (pre-baking) is preferably performed for the purpose of preventing dripping of the applied liquid crystal alignment agent. The pre-baking temperature is preferably 30 to 150°C, and more preferably 40 to 120°C. The pre-baking time is preferably 0.25 to 10 minutes.

Then, the solvent is further removed, and a baking (post-baking) step is carried out, if necessary, to thermally imidize the amic acid structure present in the polymer. The baking temperature (post-baking temperature) at this time is preferably 280°C or lower, more preferably 250°C or lower. In addition, from the viewpoint of suppressing the deterioration of the liquid crystal alignment property and reliability due to the influence of the solvent components remaining in the film, the post-baking temperature is preferably 80°C or higher, more preferably 90°C or higher. The post-baking time is preferably 5 to 150 minutes. The film thickness of the film thus formed is preferably 0.001 to 1 μm. After applying the liquid crystal alignment agent to the substrate, the organic solvent is removed to form a liquid crystal alignment film or a coating film that will become a liquid crystal alignment film.

(Step 2: Alignment Treatment)
When a TN-type, STN-type, IPS-type or FFS-type liquid crystal element is manufactured, a treatment (alignment treatment) is carried out to impart liquid crystal alignment ability to the coating film formed in the above step 1. This imparts the alignment ability of liquid crystal molecules to the coating film, forming a liquid crystal alignment film. As the alignment treatment, it is preferable to use a rubbing treatment in which the surface of the coating film formed on the substrate is rubbed with cotton or the like, or a photo-alignment treatment in which the coating film is irradiated with light to impart liquid crystal alignment ability. When a vertical alignment type liquid crystal element is manufactured, the coating film formed in the above step 1 may be used as it is as a liquid crystal alignment film, or an alignment treatment may be carried out on the coating film to further enhance the liquid crystal alignment ability.

The light irradiation in the photo-alignment treatment can be performed by a method of irradiating the coating film after the post-bake step, a method of irradiating the coating film after the pre-bake step but before the post-bake step, or a method of irradiating the coating film while it is being heated in at least one of the pre-bake step and the post-bake step. In the photo-alignment treatment, the radiation to be irradiated to the coating film can be, for example, ultraviolet light and visible light containing light with a wavelength of 150 to 800 nm. Preferably, ultraviolet light containing light with a wavelength of 200 to 400 nm. When the radiation is polarized, it may be linearly polarized or partially polarized. When the radiation used is linearly polarized or partially polarized, the radiation may be performed from a direction perpendicular to the substrate surface, from an oblique direction, or a combination of these. When non-polarized radiation is irradiated, the direction of irradiation is oblique.

Examples of light sources that can be used include low-pressure mercury lamps, high-pressure mercury lamps, deuterium lamps, metal halide lamps, argon resonance lamps, xenon lamps, and excimer lasers. The radiation dose is preferably 400 to 20,000 J/ ^m2 , and more preferably 1,000 to 5,000 J/ ^m2 . The coating film may be irradiated with light while being heated in order to increase the reactivity.

When manufacturing the liquid crystal alignment film, the organic film that has been subjected to the light irradiation treatment may be further heated. The method may further include a contacting step in which the organic film that has been subjected to the light irradiation treatment is brought into contact with water, a water-soluble organic solvent, or a mixed solvent of water and a water-soluble organic solvent. Examples of water-soluble organic solvents include methanol, ethanol, 1-propanol, isopropanol, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclopentanone. After the contacting step, the organic film may be subjected to a heat treatment.

(Step 3: Construction of liquid crystal cell)
Two substrates on which the liquid crystal alignment film is formed as described above are prepared, and a liquid crystal is disposed between the two substrates arranged opposite to each other to manufacture a liquid crystal cell. For example, the liquid crystal cell can be manufactured by (1) arranging two substrates opposite to each other through a gap (spacer) so that the liquid crystal alignment film faces each other, bonding the peripheries of the two substrates using a sealant, injecting liquid crystal into the cell gap partitioned by the substrate surface and the sealant, and then sealing the injection hole, or (2) applying a sealant to a predetermined location on one substrate on which the liquid crystal alignment film is formed, dropping liquid crystal at a predetermined number of locations on the liquid crystal alignment film surface, bonding the other substrate so that the liquid crystal alignment film faces each other, and spreading the liquid crystal over the entire surface of the substrate (ODF method). It is preferable to further heat the manufactured liquid crystal cell to a temperature at which the liquid crystal used has an isotropic phase, and then slowly cool it to room temperature to remove the flow orientation during liquid crystal filling.

As a sealing agent, for example, an epoxy resin containing a hardener and aluminum oxide spheres as spacers can be used. As spacers, photospacers, bead spacers, etc. can be used.

As the liquid crystal, either positive type or negative type may be used. When negative type liquid crystal is used in IPS type and FFS type liquid crystal elements, it is preferable because the transmission loss at the upper part of the electrode can be reduced and the contrast can be improved. In addition, the liquid crystal used can be nematic liquid crystal or smectic liquid crystal, and among them, nematic liquid crystal is preferable. As the nematic liquid crystal, for example, Schiff base type liquid crystal, azoxy type liquid crystal, biphenyl type liquid crystal, phenylcyclohexane type liquid crystal, ester type liquid crystal, terphenyl type liquid crystal, biphenylcyclohexane type liquid crystal, pyrimidine type liquid crystal, dioxane type liquid crystal, bicyclooctane type liquid crystal, cubane type liquid crystal, etc. can be used. In addition, for example, cholesteric liquid crystal, chiral agent, ferroelectric liquid crystal, etc. may be added to these liquid crystals.

In the PSA mode, a polymerizable compound (e.g., a polyfunctional (meth)acrylate compound) is filled into the cell gap together with the liquid crystal, and after the liquid crystal cell is constructed, a process is performed in which the liquid crystal cell is irradiated with light while a voltage is applied between the conductive films of the pair of substrates. When manufacturing a PSA mode liquid crystal element, the proportion of the polymerizable compound used is 0.01 to 3 parts by mass, preferably 0.1 to 1 part by mass, per 100 parts by mass of the total liquid crystal.

In the manufacturing process of PSA mode liquid crystal elements, it is necessary to apply a relatively large amount of light to the liquid crystal cell in order to react the polymerizable compound in the liquid crystal, and there is a concern that such ultraviolet irradiation will cause the liquid crystal components to decompose and cause a decrease in display quality. On the other hand, if the amount of light irradiation to the liquid crystal cell is reduced, unreacted polymerizable compounds will remain in the film or liquid crystal. If unreacted polymer components remain in the film or liquid crystal as impurities, there is a concern that the quality of the liquid crystal element will decrease if it is exposed to a high temperature environment for a long period of time. In this regard, by forming a liquid crystal alignment film using the liquid crystal alignment agent of the present disclosure, it is possible to efficiently react the polymerizable compound in the liquid crystal with a small amount of light irradiation, and it is possible to express a high liquid crystal alignment control force, which is thought to have resulted in the expression of a stable pretilt angle even in the thin film region and improved long-term heat resistance.

Next, if necessary, a polarizing plate is attached to the outer surface of the liquid crystal cell. Examples of polarizing plates include a polarizing film called an "H film" made by absorbing iodine while stretching and aligning polyvinyl alcohol, sandwiched between cellulose acetate protective films, or a polarizing plate made of the H film itself. This results in a liquid crystal element.

The liquid crystal element of the present disclosure can be effectively applied to various applications, for example, in various display devices such as watches, portable game machines, word processors, notebook computers, car navigation systems, camcorders, PDAs, digital cameras, mobile phones, smartphones, various monitors, liquid crystal televisions, and information displays, as well as in light control films. In addition, liquid crystal elements formed using the liquid crystal alignment agent of the present disclosure can also be applied to optical films such as retardation films.

The following provides a more detailed explanation using examples, but the present invention is not limited to these examples.

<Measurement method>
In the following examples, the solution viscosity, weight average molecular weight (Mw) and imidization rate of the polymer were measured by the following methods.
[Polymer solution viscosity]
The solution viscosity of the polymer was measured at 25° C. using an E-type viscometer.
[Weight average molecular weight (Mw) of polymer]
The Mw was measured by gel permeation chromatography (GPC) under the following conditions.
Apparatus: Showa Denko Co., Ltd. "GPC-101"
GPC column: Shimadzu GLC's "GPC-KF-801", "GPC-KF-802", "GPC-KF-803" and "GPC-KF-804" combined Mobile phase: Tetrahydrofuran (THF)
Column temperature: 40°C
Flow rate: 1.0 mL/min Sample concentration: 1.0% by mass
Sample injection volume: 100 μL
Detector: Differential refractometer Standard material: Monodisperse polystyrene

[Imidization rate of polyimide]
The polyimide solution was poured into pure water, and the resulting precipitate was thoroughly dried under reduced pressure at room temperature, then dissolved in deuterated dimethyl sulfoxide and subjected to ^1H -NMR measurement at room temperature using tetramethylsilane as a standard substance. From the obtained ^1H -NMR spectrum, the imidization rate [%] was calculated using the following formula (1).
Imidization rate [%] = (1 - (β ¹ / (β ² × α))) × 100 ... (1)
(In formula (1), ^β1 is the peak area derived from the proton of the NH group appearing at a chemical shift of about 10 ppm, ^β2 is the peak area derived from other protons, and α is the ratio of the number of other protons to one proton of the NH group in the polymer precursor (polyamic acid).)

<Abbreviation of compound>
The abbreviations of the compounds used in the following examples are shown below. For convenience, hereinafter, a "compound represented by formula (X)" (X is a symbol) may be simply referred to as "compound (X)".

[Photoreactive monomer]

[Vertical alignment monomer]

[Cyclic Group-Containing Monomer]

[Reactive functional group-containing monomer]

[Other monomers]

[Tetracarboxylic acid dianhydride]

[Diamine]

[Additives]

<Synthesis of Compounds>
1. Synthesis of liquid crystal alignment monomer [Synthesis Example 1-1: Synthesis of compound (M-01)]

3.05 g of 4-(chloromethyl)styrene, 4.93 g of 4-(4-pentylcyclohexyl)phenol, and 5.48 g of potassium carbonate were dissolved in 40 mL of dimethylformamide and reacted at 60°C for 12 hours. After confirming the disappearance of the raw materials by HPLC, the reaction solution was dropped into 400 mL of water and the resulting solid was filtered. After that, recrystallization was performed using THF solvent, and the resulting solid was filtered and dried to obtain 5.80 g of compound (M-01).

[Synthesis Example 1-2: Synthesis of compound (M-02)]

2.46 g of 4-(4-pentylcyclohexyl)phenol, 12.5 g of 2-bromoethanol, and 16.6 g of potassium carbonate were dissolved in 200 mL of dimethylformamide and reacted for 5 hours at 100° C. After the reaction, the reaction solution was poured into 1 L of water, and the resulting solid was filtered and dried to obtain 28.1 g of compound (M-02-1).
Next, 26.1 g of compound (M-02-1) was dissolved in 200 ml of dichloromethane, 10 mL of pyridine was further added, and the mixture was ice-cooled to 0°C. 100 mL of dichloromethane in which 17.2 g of tosyl chloride was dissolved was added dropwise thereto, and the mixture was reacted at room temperature overnight. After the reaction, the mixture was separated three times with 200 mL of water, and the organic layer was distilled off. The obtained solid was purified by column chromatography to obtain 17.2 g of compound (M-02-2).
13.3 g of compound (M-02-2), 5.68 g of 4-hydroxyphenylmaleimide, and 3.33 g of triethylamine were dissolved in 200 mL of tetrahydrofuran and reacted under reflux for 4 hours. After the reaction, 200 mL of ethyl acetate was added, and the mixture was separated twice with 200 mL of 1N hydrochloric acid and three times with 200 mL of water. The organic layer was distilled off under reduced pressure. The obtained solid was dissolved in 150 mL of THF, and 60 mL of ethanol and 50 mL of water were added thereto. The good solvent was slowly distilled off using a rotary evaporator, and the precipitated solid was filtered and dried to obtain 8.58 g of compound (M-02).

[Synthesis Example 1-3: Synthesis of compound (M-03)]

20 mL of thionyl chloride and a catalytic amount of DMF were added to 2.74 g of 4-(4-pentylcyclohexyl)benzoic acid, and the mixture was reacted at 60°C for 2 hours. After the reaction, thionyl chloride was distilled off under reduced pressure. The obtained solid was dissolved in 20 mL of dehydrated THF to obtain solution A. On the other hand, 1.90 g of 4-hydroxyphenylmaleimide and 1.20 g of triethylamine were dissolved in 20 mL of dehydrated THF, and the mixture was ice-cooled to 0°C. Solution A was added dropwise to the mixture, and the mixture was reacted at room temperature overnight. After the reaction, the reaction solution was separated twice with 1N hydrochloric acid and three times with water, and the organic layer was distilled off under reduced pressure. Furthermore, the obtained solid was dissolved in 50 mL of THF, and 30 mL of ethanol and 10 mL of water were added thereto. The good solvent was slowly distilled off using a rotary evaporator, and the precipitated solid was filtered and dried to obtain 3.81 g of compound (M-03).

[Synthesis Example 1-4: Synthesis of compound (M-04)]
9.25 g of compound (M-04) was obtained by the same method as in Synthesis Example 1-3, except that 4'-pentyl-[1,1'-bi(cyclohexane)]-4-carboxylic acid was used instead of 4-(4-pentylcyclohexyl)benzoic acid and 4-(2-hydroxyethyl)phenylmaleimide was used instead of 4-hydroxyphenylmaleimide in Synthesis Example 1-3.

[Synthesis Example 1-5: Synthesis of compound (M-05)]
Compound (M-05) (12.1 g) was obtained in the same manner as in Synthesis Example 1-2, except that 4-hydroxystyrene was used instead of 4-hydroxyphenylmaleimide.

[Synthesis Example 1-6: Synthesis of compound (M-06)]
Compound (M-06) (8.08 g) was obtained in the same manner as in Synthesis Example 1-1, except that β-cholestanol was used instead of 4-(4-pentylcyclohexyl)phenol in Synthesis Example 1-1.

[Synthesis Example 1-7: Synthesis of compound (M-07)]
5.82 g of compound (M-07) was obtained in the same manner as in Synthesis Example 1-2, except that 4-(4'-pentyl-[1,1'-bicyclohexane]-4-yl)phenol was used instead of 4-(4-pentylcyclohexyl)phenol and 4-hydroxy-3-methylphenylmaleimide was used instead of 4-hydroxyphenylmaleimide in Synthesis Example 1-2.

[Synthesis Example 1-8: Synthesis of compound (M-08)]
Compound (M-08) (7.11 g) was obtained in the same manner as in Synthesis Example 1-1, except that 4-(4-pentylcyclohexyl)phenol was replaced with 4-(4'-pentyl-[1,1'-bicyclohexyl]-4-yl)phenol.

[Synthesis Example 1-9: Synthesis of compound (M-09)]

10.0 g of 4-(4-heptylcyclohexyl)phenol, 8.8 g of 1-(4-fluorophenethyl)-1H-pyrrole-2,5-dione, 5.6 g of potassium carbonate, and 200 mL of N,N-dimethylformamide were added to a 500 mL three-neck flask containing a stirrer, and stirred at room temperature for 30 minutes. After confirming that the raw materials had dissolved, the mixture was reacted at 80°C for 12 hours. After the reaction, the reaction solution was poured into 1500 mL of distilled water, and the precipitated solid was filtered. The solid was then vacuum dried and recrystallized to obtain 13.7 g of compound (M-09). 1-(4-fluorophenethyl)-1H-pyrrole-2,5-dione was synthesized according to the method described in Molecules, 2016, 21, 1198.

[Synthesis Example 1-10: Synthesis of compound (M-10)]
7.56 g of compound (M-10) was obtained by the same method as in Synthesis Example 1-1, except that 4-(2-(4'-pentyl-[1,1'-bicyclohexane]-4-yl)ethyl)phenol was used instead of 4-(4-pentylcyclohexyl)phenol in Synthesis Example 1-1. 4-(2-(4'-pentyl-[1,1'-bicyclohexane]-4-yl)ethyl)phenol was synthesized according to the method described in JP2013-228672A.

[Synthesis Example 1-11: Synthesis of compound (M-11)]
6.49 g of compound (M-11) was obtained in the same manner as in Synthesis example 1-3, except that 4-(4'-(4,4,4-trifluorobutyl)-[1,1'-bicyclohexane]-4-yl)benzoic acid was used instead of 4-(4-pentylcyclohexyl)benzoic acid and 4-hydroxy-3-methylphenylmaleimide was used instead of 4-hydroxyphenylmaleimide in Synthesis example 1-3.

[Synthesis Example 1-12: Synthesis of compound (M-12)]

Compound (M-12-1) (12.1 g) was obtained in the same manner as in Synthesis Example 1-9, except that 1-fluoro-3-nitrobenzene was used instead of 1-(4-fluorophenethyl)-1H-pyrrole-2,5-dione in Synthesis Example 1-9.
Next, 12.0 g of compound (M-12-1), 1.94 g of 5% palladium carbon, 60 mL of tetrahydrofuran, and 60 mL of ethanol were added to a 500 mL three-necked flask containing a stirrer, and then heated to 80° C. 9.11 g of hydrazine monohydrate was added dropwise thereto, and then the mixture was heated under reflux for 6 hours. After cooling to room temperature, the filtered solution was reprecipitated in 600 mL of water. The obtained solid was filtered, washed with water, and then vacuum dried to obtain 9.8 g of compound (M-12-2).
The mixture was placed in a 500 mL three-neck flask containing a stirrer, 100 mL of tetrahydrofuran was added, and the mixture was placed in an ice bath. A solution consisting of 2.15 g of maleic anhydride and 50 mL of tetrahydrofuran was added dropwise thereto, and the mixture was stirred at room temperature for 3 hours. The precipitated solid was then collected by filtration. The obtained solid was dried in a vacuum to obtain 9.5 g of compound (M-12).

[Synthesis Example 1-13: Synthesis of compound (M-13)]

In Synthesis Example 1-12, 11.1 g of compound (M-13-1) was obtained in the same manner as compound (M-12-1), except that 4'-(4,4,4-trifluorobutyl)-[1,1'-bicyclohexyl]-4-ol was used instead of 4-(4-heptylcyclohexyl)phenol and 1-fluoro-4-nitrobenzene was used instead of 1-fluoro-3-nitrobenzene. Then, 7.5 g of compound (M-13-2) was obtained in the same manner as compound (M-12-2), except that compound (M-13-1) was used instead of compound (M-12-1).
In a 300 mL eggplant flask containing a stirrer, 3.00 g of monomethyl maleate, 15 g of thionyl chloride, and 0.01 g of N,N-dimethylformamide were added and stirred at 60°C for 2 hours. Thereafter, excess thionyl chloride was removed with a diaphragm pump, and 30 g of tetrahydrofuran was added to obtain solution A. A new 500 mL three-neck flask containing a stirrer was added with 8.84 g of compound (M-13-2), 100 g of tetrahydrofuran, and 4.7 g of triethylamine, and the flask was placed in an ice bath. Solution A was added dropwise thereto, and the mixture was stirred at room temperature for 8 hours. The reaction solution was reprecipitated with 750 mL of water, and the resulting white solid was vacuum dried to obtain 9.8 g of compound (M-13).

[Synthesis Example 1-17: Synthesis of compound (M-17)]
Compound (M-17) (4.58 g) was obtained in the same manner as in Synthesis Example 1-1, except that 4-pentylcyclohexanol was used instead of 4-(4-pentylcyclohexyl)phenol.

[Synthesis Examples 1-14 to 1-16, 1-18, and 1-19: Synthesis of Compounds (M-14 to M-16, M-18, and M-19)]
The compounds (M-14 to M-16, M-18, and M-19) were each synthesized according to the methods described in the following documents.
Compound (M-14): JP 2006-178149 A Compound (M-15): JP 2004-2373 A Compound (M-16): JP 2004-99446 A Compound (M-18): JP 2008-191337 A Compound (M-19): WO 2006/001096 A

[Synthesis Example 1-20: Synthesis of compound (E-2)]
Compound (E-2) (4.76 g) was obtained in the same manner as in Synthesis Example 1-1, except that 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone and sodium hydride were used instead of 4-(4-pentylcyclohexyl)phenol and potassium carbonate, respectively.

[Synthesis Example 1-21: Synthesis of compound (E-3)]
Compound (E-3) (4.68 g) was obtained in the same manner as in Synthesis Example 1-2, except that 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone was used instead of compound (M-02-1).

[Synthesis Example 1-22: Synthesis of compound (E-4)]

7.93 g of 4-hydroxybenzophenone, 5.0 g of 2-bromoethanol, and 11.06 g of potassium carbonate were dissolved in 80 mL of dimethylformamide and reacted for 10 hours at 100° C. After confirming the disappearance of the raw materials by HPLC, the reaction solution was added dropwise to 500 mL of water, and the resulting solid was filtered and dried to obtain 9.21 g of intermediate (E-4-1).
Next, 2.42 g of intermediate (E-4-1) was dissolved in 20 mL of dimethylformamide and stirred at 0° C. Then, 0.60 g of sodium hydride (60%, liquid paraffin dispersion) was added, and the mixture was stirred at 0° C. for 30 minutes. Then, 1.53 g of 4-(chloromethyl)styrene was added, and the mixture was further reacted at 0° C. for 3 hours. After confirming the disappearance of the raw materials by HPLC, the reaction solution was dropped into 150 mL of water, and purification was performed by separation with ethyl acetate. The separated organic layer was distilled under reduced pressure to remove the solvent, and dried to obtain 3.40 g of compound (E-4).

[Synthesis Example 1-23: Synthesis of compound (E-5)]
Compound (E-5) (4.50 g) was obtained in the same manner as in Synthesis Example 1-1, except that 4'-hydroxyacetophenone was used instead of 4-(4-pentylcyclohexyl)phenol.

<Synthesis of Polymer>
1. Synthesis of polymer [P] [Synthesis Example 2-1]
Under nitrogen, a 100 mL two-neck flask was charged with 10 mol parts of compound (M-01), 10 mol parts of compound (E-2), 30 mol parts of compound (A-5), 10 mol parts of compound (A-6), 20 mol parts of compound (B-3), and 20 mol parts of compound (B-6) as polymerization monomers, 2 mol parts of 2,2'-azobis(2,4-dimethylvaleronitrile) as a radical polymerization initiator, and 50 ml of tetrahydrofuran as a solvent, and polymerized at 70 ° C. for 6 hours. After reprecipitation in methanol, the precipitate was filtered and dried in vacuum at room temperature for 8 hours to obtain a styrene-maleimide copolymer (referred to as polymer (P-1)). The weight average molecular weight Mw measured in terms of polystyrene by GPC was 92700, and the molecular weight distribution Mw/Mn was 4.78.

[Synthesis Examples 2-2 to 2-10, 2-12 to 2-24: Synthesis of Polymers (P-2) to (P-10), (P-12), (P-13), (P-16) to (P-19), and (P-20) to (P-26)]
Polymerization was carried out in the same manner as in Synthesis Example 2-1, except that the types and amounts of monomers used in the polymerization were changed as shown in Table 1, to obtain polymers (P-2) to (P-10), (P-12), (P-16) to (P-19), and (P-20) to (P-26), respectively.

[Synthesis Example 2-11: Synthesis of Polymer (P-11)]
Polymerization was carried out in the same manner as in Synthesis Example 2-1, except that the types and amounts of monomers used in polymerization were changed as shown in Table 1, to obtain a solution containing a polymer (P-11-1). Next, to this polymer solution, 1 mole of a compound represented by the following formula (MO-1) was added relative to 2-hydroxyethyl methacrylate in the polymer, and the mixture was reacted at 50° C. for 6 hours to obtain a solution containing a polymer (P-11). After reprecipitation in methanol, the precipitate was filtered and vacuum dried at room temperature for 8 hours to obtain a polymer (P-11).

[Comparative Synthesis Examples 2-1 to 2-3: Synthesis of Polymers (P-14), (P-15), and (P-27)]
Polymerization was carried out in the same manner as in Synthesis Example 2-1, except that the types and amounts of monomers used in polymerization were changed as shown in Table 1, to obtain polymers (P-14), (P-15), and (P-27), respectively.

2. Synthesis of polymer [Q] [Synthesis Example 2-25]
30 mol parts of compound (DA-1) as diamine, 50 mol parts of compound (DA-8), and 20 mol parts of compound (DA-9) were dissolved in N-methyl-2-pyrrolidone (NMP), 100 mol parts of 2,3,5-tricarboxycyclopentylacetic dianhydride as tetracarboxylic dianhydride were added, and the mixture was reacted at 40° C. for 24 hours to obtain a solution containing 20% by mass of polyamic acid. Next, NMP was added to the obtained polyamic acid solution, and pyridine and acetic anhydride were added in amounts of 1.80 molar equivalents each relative to the carboxyl groups derived from the acid dianhydride possessed by the polyamic acid, and a dehydration ring-closing reaction was carried out at 80° C. for 4 hours. After the dehydration ring-closing reaction, the solvent in the system was replaced with fresh NMP, and the mixture was further concentrated to obtain a solution containing 20% by mass of polyimide with an imidization rate of 70% (this is referred to as polymer (PI-1)). A small amount of this solution was taken, and NMP was added to make a 10% by mass solution, which had a viscosity of 46.4 mPa·s.

[Synthesis Examples 2-26, 2-27, 2-29 to 2-36]
Polymerization was performed in the same manner as in Synthesis Example 2-18, except that the type and amount of tetracarboxylic dianhydride and diamine used in polymerization were changed as shown in Table 2, and solutions containing polyimide polymers (PI-2), (PI-3), (PI-5) to (PI-12) were obtained. The polymerization was performed with the molar ratio of diamine to tetracarboxylic dianhydride (diamine/tetracarboxylic dianhydride) adjusted to 0.95 to 1.00 so that the viscosity of an NMP solution with a polymer concentration of 10% by mass was 40 to 60 mPa·s. In Table 2, the numerical value of the acid anhydride represents the ratio (molar part) of each compound relative to 100 mole parts of the total amount of tetracarboxylic dianhydride used in the synthesis. The numerical value of the diamine represents the ratio (molar part) of each compound relative to 100 mole parts of the total amount of diamine used in the synthesis.

[Synthesis Example 2-28]
30 parts by mole of compound (DA-1) as a diamine, 50 parts by mole of compound (DA-3), and 20 parts by mole of compound (DA-8) were dissolved in N-methyl-2-pyrrolidone (NMP), and 100 parts by mole of 2,3,5-tricarboxycyclopentylacetic dianhydride as a tetracarboxylic dianhydride was added thereto and reacted at 40° C. for 24 hours to obtain a solution containing 20% by mass of polyamic acid (referred to as polymer (PI-4)).

<Production and Evaluation of Liquid Crystal Devices>
[Example 1: PSA type liquid crystal display element]
(1) Preparation of liquid crystal alignment agent (AL-1) 10 parts by mass of the polymer (P-1) obtained in Synthesis Example 2-1, and NMP and butyl cellosolve (BC) as a solvent were added to a solution containing 100 parts by mass of the polymer (PI-1) obtained in Synthesis Example 2-25, to obtain a solution with a solvent composition of NMP/BC=50/50 (mass ratio) and a solid content concentration of 4.0% by mass. The liquid crystal alignment agent (AL-1) was prepared by filtering this solution with a filter having a pore size of 0.2 μm.

(2) Preparation of Liquid Crystal Composition 5% by mass of a liquid crystal compound represented by the following formula (L1-1) and 0.3% by mass of a photopolymerizable compound represented by the following formula (L2-1) were added to 10 g of a nematic liquid crystal (MLC-6608, manufactured by Merck) and mixed to obtain a liquid crystal composition LC1.

(3) Manufacture of PSA type liquid crystal display element The liquid crystal alignment agent (AL-1) prepared above was applied to each electrode surface of two glass substrates each having a conductive film consisting of an ITO electrode patterned in a slit shape, using a liquid crystal alignment film printer (manufactured by Nissha Printing Co., Ltd.), heated (pre-baked) for 2 minutes on a hot plate at 80 ° C. to remove the solvent, and then heated (post-baked) for 30 minutes on a hot plate at 230 ° C. to form a coating film with an average thickness of 100 nm. These coating films were subjected to ultrasonic cleaning in ultrapure water for 1 minute, and then dried in a 100 ° C. clean oven for 10 minutes to obtain a pair (2 sheets) of substrates having a liquid crystal alignment film. The electrode pattern used was the same type of pattern as the electrode pattern in the PSA mode.
Next, an epoxy resin adhesive containing aluminum oxide spheres having a diameter of 5.5 μm was applied to the outer edge of the surface having the liquid crystal alignment film of one of the pair of substrates, and then the substrates were laminated and pressed so that the liquid crystal alignment film surfaces faced each other, and the adhesive was cured. Next, the liquid crystal composition LC1 prepared above was filled between the pair of substrates through the liquid crystal injection port, and the liquid crystal injection port was sealed with an acrylic photocurable adhesive to produce a liquid crystal cell. Then, an AC voltage of 10 V with a frequency of 60 Hz was applied between the conductive films of the liquid crystal cell, and while the liquid crystal was driven, ultraviolet rays were irradiated at an irradiation dose of 100,000 J/m ² using an ultraviolet irradiation device using a metal halide lamp as a light source. Note that this irradiation dose is a value measured using an actinometer that measures with a wavelength of 365 nm as a standard. Then, a polarizing plate was attached to both outer surfaces of the substrate so that the polarization directions of the polarizing plates were perpendicular to each other and formed an angle of 45° with the projection direction of the optical axis of the ultraviolet light of the liquid crystal alignment film onto the substrate surface, thereby producing a PSA type liquid crystal display element.

(4) Evaluation of liquid crystal alignment (normal film thickness)
The PSA type liquid crystal display element manufactured in (3) above was observed with an optical microscope to see whether there was an abnormal domain in the change in brightness when a voltage of 5V was turned on and off (applied and released), and the liquid crystal alignment was evaluated. The evaluation was as follows: "Excellent (◎)" when there were no abnormal domains and unevenness, "Good (○)" when there were no abnormal domains and only some unevenness, "Fair (△)" when there were some abnormal domains, and "Bad (×)" when there were abnormal domains all over. As a result, in this example, the liquid crystal alignment was evaluated as "Excellent (◎)".

(5) Evaluation of liquid crystal alignment (thin film)
A PSA type liquid crystal display element was prepared in the same manner as in (3) above, except that the average thickness of the coating film was changed from 100 nm to 30 nm. The prepared PSA type liquid crystal display element was observed by an optical microscope for the presence or absence of abnormal domains in the change in brightness when a voltage of 5 V was turned on and off (applied and removed), and the liquid crystal alignment was evaluated by the same four-level evaluation as in (4) above. As a result, in this example, the liquid crystal alignment when made into a thin film was evaluated as "excellent (◎)".

(6) Evaluation of Electrical Characteristics by Voltage Holding Ratio (VHR) A voltage of 5 V was applied to the PSA type liquid crystal display element manufactured as above for a time of 60 microseconds and a span of 167 milliseconds, and then the voltage holding ratio was measured 167 milliseconds after the application was removed. A VHR-1 manufactured by Toyo Corporation was used as the measuring device. At this time, a voltage holding ratio of 98% or more was rated as "good (○)", a voltage holding ratio of 95% or more and less than 98% was rated as "passable (△)", and a voltage holding ratio of less than 95% was rated as "poor (×)". As a result, in this example, the electrical characteristics were rated as "good (○)".

(7) Evaluation of long-term heat resistance A PSA type liquid crystal cell was manufactured by the same operation as in (3) above, except that no polarizing plate was attached to both outer sides of the substrate. The voltage retention rate was measured for this PSA type liquid crystal cell by the same operation as in (6) above. In addition, the obtained liquid crystal cell was stored in a thermostatic chamber at 100° C. for 21 days (about 500 hours), and then the voltage retention rate was measured again. When the decrease in the voltage retention rate due to storage in a thermostatic chamber at 100° C. (voltage retention rate (%) after liquid crystal cell production - voltage retention rate (%) after storage in a thermostatic chamber) was less than 20%, it was rated as "good (○)", when it was 20% or more and less than 40%, it was rated as "passable (△)", and when it was 40% or more, it was rated as "poor (×)". As a result, in this example, it was rated as "good (○)".

[Examples 2 to 35 and Comparative Examples 1 to 5]
Liquid crystal alignment agents (AL-2) to (AL-40) were prepared with the same solvent composition and solid content concentration as in Example 1, except that the blending composition was changed as shown in Tables 3 and 4. In addition, using each liquid crystal alignment agent, a PSA type liquid crystal display element was manufactured in the same manner as in Example 1, and various evaluations were performed. The evaluation results are shown in Tables 3 and 4.

As shown in Table 3, the liquid crystal alignment agents of Examples 1 to 18 were all rated as "◎", "○" or "△" for the liquid crystal alignment (normal film thickness, thin film), voltage holding rate and long-term heat resistance, and the various properties were well-balanced. In particular, Examples 1 to 14, which used a polymer containing a vertically aligning monomer unit having a group represented by the above formula (8) as the polymer [P], showed excellent or good results in the evaluation of the liquid crystal alignment property of the thin film compared to Examples 15 to 18, which used a polymer not containing a monomer unit having a group represented by the above formula (8). This is thought to be because the photopolymerizable compound mixed into the liquid crystal layer reacted efficiently and the alignment fixing ability was improved by using the polymer [P] of a specific main chain structure having the partial structure A as the polymer component of the liquid crystal alignment agent.

As shown in Table 4, the liquid crystal alignment agents of Examples 19 to 35 were all rated as "◎" or "○" for liquid crystal alignment (normal film thickness, thin film), voltage holding ratio, and long-term heat resistance, and the various properties were well-balanced. In particular, when a polymer containing a vertically aligning monomer unit having two or more ring structures was used as the polymer [Q], there was a tendency for excellent results to be obtained in the evaluation of the liquid crystal alignment of the thin film.

In contrast, the liquid crystal alignment agents of Comparative Examples 1 to 3, which do not contain the polymer [P] of the present disclosure, show good liquid crystal alignment properties at normal film thickness (0.1 μm), but when the liquid crystal alignment film is thin, the alignment of the liquid crystal cannot be sufficiently controlled, and the evaluation of the liquid crystal alignment properties of the thin film shows poor results. Furthermore, the liquid crystal alignment agent of Comparative Example 4 showed poor results in the evaluation of the liquid crystal alignment properties of the thin film, and the liquid crystal alignment agent of Comparative Example 5 showed poor results in the evaluation of the liquid crystal alignment properties of both normal film thickness and thin film.

Claims (12)

The polymer contains, in a side chain thereof, a polymer [P] which is an addition polymer having a partial structure capable of exhibiting at least one of a radical generating function which generates radicals upon light irradiation and a photosensitizing function which exhibits a sensitizing effect upon light irradiation, or a polymerizable carbon-carbon unsaturated bond;
The polymer [P] is a liquid crystal aligning agent having at least one selected from the group consisting of a structural unit represented by the following formula (1), a structural unit represented by the following formula (2), a structural unit represented by the following formula (3), and a structural unit represented by the following formula (4), and at least one selected from the group consisting of a structural unit represented by the following formula (5), a structural unit represented by the following formula (6), and a structural unit represented by the following formula (7) .

(In formula (1), R ¹ and R ² are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group is replaced with a halogen atom, or R ¹ and R ² are bonded to each other to represent a ring structure constituted together with the carbon atom to which R ¹ and R ² are bonded. X ¹ has a partial structure capable of exhibiting at least either of a radical generating function that generates radicals upon light irradiation and a photosensitizing function that exhibits a sensitizing effect upon light irradiation, or is a monovalent group having a polymerizable carbon-carbon unsaturated bond. R ³ is a monovalent substituent. m1 is an integer of 0 to 4. n1 is an integer of 0 to 2. When m1 is 2 or more, multiple R ^3s are the same or different. "*" represents a bond.
In formula (2), R ⁴ and R ⁵ are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group is replaced with a halogen atom, or R ⁴ and R ⁵ are bonded to each other to form a ring structure together with the carbon atom to which R ⁴ and R ⁵ are bonded. R ⁶ is a hydrogen atom or a monovalent organic group. X ² has a partial structure capable of exhibiting at least one of a radical generating function that generates radicals upon light irradiation and a photosensitizing function that exhibits a sensitizing effect upon light irradiation, or is a monovalent group having a polymerizable carbon-carbon unsaturated bond. R ⁷ is a monovalent substituent. m2 is an integer of 0 to 4. n2 is an integer of 0 to 2. When m2 is 2 or more, multiple R ^7s are the same or different from each other. "*" represents a bond.
In formula (3), R ⁸ is a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group has been replaced with a halogen atom. ^{X 3} is a monovalent group having a partial structure capable of exhibiting at least one of a radical generating function of generating radicals upon light irradiation and a photosensitizing function of exhibiting a sensitizing effect upon light irradiation, or having a polymerizable carbon-carbon unsaturated bond. R ⁹ is a monovalent substituent. m3 is an integer of 0 to 4. When m3 is 2 or more, multiple R ^9s are the same or different from each other. "*" represents a bond.
In formula (4), R ¹⁰ is a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group has been replaced with a halogen atom. Z ¹ is an oxygen atom or -NH-. X ⁴ is a monovalent group having a partial structure capable of exhibiting at least one of a radical generating function that generates radicals upon light irradiation and a photosensitizing function that exhibits a sensitizing effect upon light irradiation, or having a polymerizable carbon-carbon unsaturated bond. "*" represents a bond.)

(In formula (5), R ¹¹ and R ¹² are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group is replaced with a halogen atom, or R ¹¹ and R ¹² are bonded to each other to represent a ring structure formed together with the carbon atom to which R ¹¹ and R ¹² are bonded. Y ¹ is a non-photosensitive monovalent group having a total of two or more of at least either an aromatic ring or an aliphatic ring. R ¹³ is a monovalent substituent. m4 is an integer of 0 to 4. n3 is an integer of 0 to 2. When m4 is 2 or more, multiple R ^13s are the same or different. "*" represents a bond.
In formula (6), R ¹⁴ and R ¹⁵ are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group is replaced with a halogen atom, or R ¹⁴ and R ¹⁵ are bonded to each other to form a ring structure together with the carbon atom to which R ¹⁴ and R ¹⁵ are bonded. R ¹⁶ is a hydrogen atom or a monovalent organic group. Y ² is a non-photosensitive monovalent group having a total of two or more of at least any one of aromatic rings and aliphatic rings. R ¹⁷ is a monovalent substituent. m5 is an integer of 0 to 4. n4 is an integer of 0 to 2. When m5 is 2 or more, multiple R ^17s are the same or different from each other. "*" represents a bond.
In formula (7), R ¹⁸ is a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent group having 1 to 10 carbon atoms in which any hydrogen atom of a hydrocarbon group has been replaced with a halogen atom. Y ³ is a non-photosensitive monovalent group having a total of two or more aromatic rings and/or aliphatic rings. R ¹⁹ is a monovalent substituent. m6 is an integer of 0 to 4. When m6 is 2 or more, the multiple R ^19s are the same or different from each other. "*" represents a bond.) As the polymer [P] or a polymer different from the polymer [P] , the following (b) :
( b) a non-photosensitive monovalent group having an alkyl group, an alkoxy group, a fluoroalkyl group, or a fluoroalkoxy group having 5 or more carbon atoms (excluding non-photosensitive monovalent groups having a total of two or more of at least either an aromatic ring or an aliphatic ring ).
The liquid crystal alignment agent according to claim 1 , comprising a polymer having the formula : The liquid crystal aligning agent according to claim 1 or 2 , wherein Y ¹ , Y ² and Y ³ are groups represented by the following formula (8).
A ¹ -B ¹ -L ¹ -B ² -L ² -*...(8)
(In formula (8), A ¹ is a hydrogen atom, a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a fluoroalkyl group having 1 to 20 carbon atoms, or a fluoroalkoxy group having 1 to 20 carbon atoms. ^{B 1} is a divalent group represented by any one of the following formulas (1-1) to (1-8). ^{L 1} is a single bond or a divalent group represented by any one of the following formulas (2-1) to (2-6). B ² is a single bond or a divalent aromatic ring group. L ² is a divalent group represented by any one of the following formulas (3-1) to (3-9). "*" represents a bond.)

The liquid crystal aligning agent according to any one of claims 1 to 3 , further comprising a polymer [Q] different from the polymer [P]. Further containing a polymer [Q] different from the polymer [P],
The polymer [Q] has at least one of a non-photosensitive monovalent group having a total of two or more of at least any one of aromatic rings and aliphatic rings and the (b) non-photosensitive monovalent group. The liquid crystal aligning agent according to claim 2 or 3. The liquid crystal aligning agent according to claim 4 or 5 , wherein the polymer [Q] is at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide. The liquid crystal aligning agent according to any one of claims 1 to 6 , wherein X ¹ , X ² , X ³ and X ⁴ are groups having a photoinitiator structure that absorbs light to generate radicals. The liquid crystal aligning agent according to any one of claims 1 to 7 , wherein the polymer [P] has at least one selected from the group consisting of a cyclic ether group and a cyclic carbonate group. The liquid crystal aligning agent according to any one of claims 1 to 8 , wherein the polymer [P] has at least one selected from the group consisting of a carboxy group, a protected carboxy group, an amino group, and a protected amino group. A liquid crystal alignment film formed by using the liquid crystal aligning agent according to any one of claims 1 to 9 . A liquid crystal element comprising the liquid crystal alignment film according to claim 10 . A step of applying the liquid crystal aligning agent according to any one of claims 1 to 9 onto each conductive film of a pair of substrates having a conductive film to form a coating film;
a step of constructing a liquid crystal cell by disposing a pair of substrates on which the coating film is formed such that the coating film faces each other via a liquid crystal layer;
irradiating the liquid crystal cell with light while applying a voltage between the conductive films;
A method for manufacturing a liquid crystal element comprising the steps of: