JP7764796B2 - Liquid crystal alignment agent, liquid crystal alignment film, liquid crystal element and polymer - Google Patents

Description

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

Conventionally, various driving methods have been developed for liquid crystal elements, with differences in electrode structure and the physical properties of the liquid crystal molecules used. Known types include TN type, STN type, VA type, MVA type, in-plane switching type (IPS type), FFS type, and optically compensated bend type (OCB type). These liquid crystal elements have a liquid crystal alignment film for aligning the liquid crystal molecules. Liquid crystal alignment films are generally formed on substrates by applying a liquid crystal alignment agent, consisting of a polymer component dissolved or dispersed in an organic solvent, to the substrate surface and then preferably heating the applied material.

In recent years, large-screen, high-definition LCD televisions have become mainstream, and small display devices such as smartphones and tablet PCs have become increasingly popular, further increasing the demand for higher quality liquid crystal elements. To meet this demand for higher quality, various liquid crystal alignment agents have been proposed (see, for example, Patent Document 1). Patent Document 1 discloses that the liquid crystal alignment agent contains, together with polyimide or a polyimide precursor, a crosslinkable compound as a low-molecular-weight compound that improves the hardness of the liquid crystal alignment film.

International Publication No. 2020/171128

As liquid crystal elements become increasingly high-definition, quality requirements are becoming increasingly stringent. For example, liquid crystal elements are required not only to further improve liquid crystal alignment and voltage holding ratio, but also to ensure that display quality is not impaired by physical pressure such as vibrations and tapping during transportation. In particular, glass panels, which form the base material for liquid crystal elements, are becoming thinner, and the physical pressure applied to internal components is increasing. At the same time, it is becoming increasingly difficult to maintain display quality simply by adding crosslinking compounds, as was done in the past.

The present invention has been made in consideration of the above-mentioned problems, and its main object is to provide a liquid crystal alignment agent that can produce liquid crystal devices that have good liquid crystal alignment properties, excellent voltage retention characteristics, and suppressed degradation of display quality due to exposure to external forces.

The inventors conducted extensive research to solve the above problems and discovered that the above problems can be solved by using a polymer with a specific carbon-carbon unsaturated structure, leading to the completion of the present invention. Specifically, the present invention provides the following means:

<1> A liquid crystal aligning agent containing a polymer [A] having a partial structure (a) represented by the following formula (1) in its main chain:
(In formula (1), R ¹ and R ² are each independently —C(R ⁵ )(R ⁶ )—, —O—, —S—, —CO—, —COO—, —NR ⁷ —, —NR ⁷ —NR ⁸ —, —NR 7 —CO—O—, —NR ⁷ —CO—NR ⁸ —, an aromatic hydrocarbon ring, an aromatic heterocycle, or a nitrogen-containing non-aromatic heterocycle, and are a divalent group bonded to the carbonyl ^group in formula (1). R ³ and R ⁴ are each independently a hydrogen atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms, or R ³ and R ⁴ taken together represent a ring structure formed with the carbon to which R ³ is bonded and the carbon to which R ⁴ is bonded. R ⁵ and R ^{R 7 and} R ⁸ are each independently a hydrogen atom or a monovalent organic group. "*" 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 polyamic acid, a polyamic acid ester, or a polyimide having a partial structure represented by the above formula (1) in the main chain.

<5> A method for producing a diamine, comprising producing a diamine represented by the following formula (2) using a compound represented by the following formula (5) as a raw material.
(In formula (5), ^R9 is a single bond or a divalent organic group.)
(In formula (2), A ¹ and A ² are each independently a single bond, a divalent alicyclic group, or a divalent aromatic ring group. R ¹ and R ² are each independently —C(R ⁵ )(R ⁶ )—, —O—, —S—, —CO—, —COO—, —NR 7 —, —NR ⁷ —NR ⁸ —, —NR ⁷ —CO—O—, —NR ⁷ —CO—NR ⁸ —, ^an aromatic hydrocarbon ring, an aromatic heterocycle, or a nitrogen-containing non-aromatic heterocycle, and are a divalent organic group bonded to the carbonyl group in formula (2). R ³ and R ⁴ are each independently a hydrogen atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms, or R ³ and R ⁴ taken together represent a ring structure formed with the carbon to which R ³ is bonded and the carbon to which R ⁴ is bonded. R ⁵ and R R 1 to R ⁶ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms. R ⁷ and R ⁸ are each independently a hydrogen atom or a monovalent organic group. m1 is an integer of 1 to 3. When m1 is 2 or 3, multiple R ¹ to R ⁴ are the same or different.

<6> A method for producing a tetracarboxylic dianhydride, comprising using the compound represented by the formula (5) as a raw material to produce tetracarboxylic dianhydrides represented by the following formulas (3) and (4):
In formula (3) and formula (4), ^A3 and ^A4 are each independently a trivalent aromatic ring group or aliphatic ring group. ^R1 and ^R2 are each independently -C( ^R5 )( ^R6 )-, -O-, -S-, -CO-, -COO-, -NR7-, -NR7 ^-NR8- , -NR7-CO ^- O-, ^{-NR7 -} CO- ^NR8- , an aromatic hydrocarbon ring, an aromatic heterocycle, ^or a nitrogen-containing non-aromatic heterocycle, and are a divalent organic group bonded to the carbonyl group in formula (3) and formula (4). ^R3 and ^R4 are each independently a hydrogen atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms, or ^R3 and ^R4 taken together represent a ring structure formed with the carbon to which ^R3 is bonded and the carbon to which ^R4 is bonded. ^R5 and R R 1 to R ⁶ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms. R ⁷ and R ⁸ are each independently a hydrogen atom or a monovalent organic group. m2 is an integer of 1 to 3. n1 and n2 are each independently an integer of 1 to 3. When m2 is 2 or 3, multiple R ¹ to R ⁴ are the same or different.

<7> A method for producing a polymer, comprising polymerizing a monomer containing at least one compound selected from the group consisting of a diamine obtained by the production method <5> above and a tetracarboxylic dianhydride obtained by the production method <6> above to produce the polyamic acid, polyamic acid ester, and polyimide of <4> above.

The liquid crystal aligning agent of the present invention makes it possible to obtain a liquid crystal device that has good liquid crystal alignment properties, excellent voltage retention characteristics, and suppresses degradation of display quality even when subjected to external forces (e.g., external forces due to vibration, tapping, etc.).

Liquid crystal alignment agent
Hereinafter, each component contained in the liquid crystal aligning agent of the present disclosure and other components that may be arbitrarily blended as necessary will be described.

In this specification, the term "hydrocarbon group" includes chain hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. A "chain hydrocarbon group" refers to a straight-chain hydrocarbon group or a branched hydrocarbon group that does not contain a cyclic structure in the main chain and is composed solely of a chain structure. However, it may be saturated or unsaturated. An "alicyclic hydrocarbon group" refers to 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 solely of an alicyclic hydrocarbon structure, and it may also contain a chain structure as part of it. An "aromatic hydrocarbon group" refers to a hydrocarbon group that contains an aromatic ring structure as a ring structure. However, it does not have to be composed solely of an aromatic ring structure, and it may contain a chain structure or an alicyclic hydrocarbon structure as part of it.

"Main chain" refers to the longest "trunk" portion of the atomic chain of a polymer. It is permissible for this "trunk" portion to contain a ring structure. "Side chain" refers to the portion branching off from the "trunk" of a polymer. "Aromatic ring" includes aromatic hydrocarbon rings and aromatic heterocycles. "Organic group" refers to an atomic group formed by removing any hydrogen atom from a carbon-containing compound (i.e., an organic compound). "Tetracarboxylic acid derivative" includes tetracarboxylic acid dianhydrides, tetracarboxylic acid diesters, and tetracarboxylic acid diester dihalides.

The liquid crystal aligning agent of the present disclosure contains a polymer [A] having a partial structure (a) represented by the following formula (1) in its main chain.
(In formula (1), R ¹ and R ² are each independently —C(R ⁵ )(R ⁶ )—, —O—, —S—, —CO—, —COO—, —NR ⁷ —, —NR ⁷ —NR ⁸ —, —NR 7 —CO—O—, —NR ⁷ —CO—NR ⁸ —, an aromatic hydrocarbon ring, an aromatic heterocycle, or a nitrogen-containing non-aromatic heterocycle, and are a divalent group bonded to the carbonyl ^group in formula (1). R ³ and R ⁴ are each independently a hydrogen atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms, or R ³ and R ⁴ taken together represent a ring structure formed with the carbon to which R ³ is bonded and the carbon to which R ⁴ is bonded. R ⁵ and R ^{R 7 and} R ⁸ are each independently a hydrogen atom or a monovalent organic group. "*" represents a bond.

<Polymer [A]>
Regarding partial structure (a): When ^R1 and ^R2 in the above formula (1) are -C( ^R5 )( ^R6 )-, which is a divalent group bonded to the carbonyl group in the above formula (1 ⁾ , the alkyl group having 1 to 8 carbon atoms, the alkenyl group having 1 to 8 carbon atoms, and the alkoxy group having 1 to 8 carbon atoms represented by R5 and ^R6 may be either linear or branched. ^R5 and ^R6 are preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and more preferably a hydrogen atom (i.e., when -C( ^R5 )( ^R6 )- is a methylene group).

When R ¹ and R ² in the above formula (1) are -NR ⁷ -, -NR ⁷ -NR ⁸ -, -NR ⁷ -CO-O-, and -NR ⁷ -CO-NR ⁸ -, which are divalent groups bonded to the carbonyl group in the above formula (1), the monovalent organic groups represented by R ⁷ and R ⁸ are preferably monovalent hydrocarbon groups having 1 to 10 carbon atoms, or monovalent leaving groups that are released by heat or light (hereinafter also simply referred to as "leaving groups").

When the monovalent organic groups represented by ^R7 and ^R8 are monovalent hydrocarbon groups, specific examples of the hydrocarbon groups include alkyl groups having 1 to 6 carbon atoms, cycloalkyl groups having 4 to 10 carbon atoms, aryl groups having 6 to 10 carbon atoms, and aralkyl groups having 6 to 10 carbon atoms. Of these, alkyl groups and phenyl groups having 1 to 3 carbon atoms are preferred, and alkyl groups having 1 to 3 carbon atoms are more preferred.

When the monovalent organic groups represented by ^R7 and ^R8 are monovalent leaving groups, the leaving group is preferably a thermally leaving group that is eliminated by heat (preferably by heating during film formation). Specific examples of thermally leaving groups include a tert-butoxycarbonyl group (Boc group), a benzyloxycarbonyl group, a 1,1-dimethyl-2-haloethyloxycarbonyl group, an allyloxycarbonyl group, and a 2-(trimethylsilyl)ethoxycarbonyl group. Of these, the Boc group is particularly preferred because it has excellent thermal elimination properties and can reduce the amount of the eliminated structure remaining in the film.

Among these, R ⁷ and R ⁸ are preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a monovalent thermally eliminable group, and more preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a tert-butoxycarbonyl group.

When ^R1 and ^R2 are an aromatic hydrocarbon ring, an aromatic heterocycle, or a nitrogen-containing non-aromatic heterocycle that bonds to the carbonyl group in formula (1), examples of the aromatic hydrocarbon ring include a benzene ring, a naphthalene ring, and an anthracene ring. Examples of the aromatic heterocycle include a nitrogen-containing aromatic heterocycle, an oxygen-containing aromatic heterocycle, and a sulfur-containing aromatic heterocycle. Specific examples of these include a pyridine ring, a pyrimidine ring, a pyridazine ring, and a pyrazine ring as the nitrogen-containing aromatic heterocycle; a furan ring as the oxygen-containing aromatic heterocycle; and a thiophene ring as the sulfur-containing aromatic heterocycle. Examples of the nitrogen-containing non-aromatic heterocycle include a piperidine ring and a piperazine ring. These rings may have a substituent. Examples of the substituent include an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a halogen atom, a hydrogen atom, and a cyano group.

R ¹ and R ² may be groups that bond to the carbonyl group in formula (1) via -C(R ⁵ )(R ⁶ )-, -O-, -S-, -CO-, -COO-, -NR ⁷ -, -NR ⁷ -NR ⁸ -, -NR ⁷ -CO-O-, -NR ⁷ -CO-NR ⁸ -, an aromatic hydrocarbon ring, an aromatic heterocycle, or a nitrogen-containing non-aromatic heterocycle, and the structure of other portions is not particularly limited. When R ¹ and R ² are bonded to the carbonyl group in formula (1) via -COO-, R ¹ and R ² may be bonded to the carbonyl group in formula (1) via an oxygen atom or a carbon atom. Furthermore, when R ¹ and R ² are bonded to the carbonyl group in the above formula (1) via —NR ⁷ —CO—O—, R ¹ and R ² may be bonded to the carbonyl group in the above formula (1) via a nitrogen atom or a carbon atom.

Specific examples of R ¹ and R ² include —C(R ⁵ )(R ⁶ )—, —O—, —S—, —CO—, —COO—, —NR ⁷ —, —NR ⁷ —NR ⁸ —, —NR ⁷ —CO—O—, —NR ⁷ —CO—NR ⁸ —, a divalent chain hydrocarbon group, a divalent aromatic hydrocarbon ring group, a divalent aromatic heterocyclic group, and a divalent nitrogen-containing non-aromatic heterocyclic group. Furthermore, R ¹ and R ² may be divalent organic groups in which methylene groups in the divalent hydrocarbon group are replaced with —O—, —S—, —CO—, —COO—, —NR ⁷ —, —NR ⁷ —NR ⁸ —, —NR ⁷ —CO—O—, —NR ⁷ —CO—NR ⁸ — or heterocyclic groups, provided that the methylene groups are not adjacent to each other.

It is preferable that one or both of R1 and R2 be a group having a chain hydrocarbon structure having one or more carbon atoms, or a divalent nitrogen-containing non-aromatic heterocyclic group, from the viewpoints of being able to increase the voltage holding ratio (VHR) of the liquid crystal element, being able to obtain a highly reliable liquid crystal element with little decrease in voltage holding ratio even when driven for a long period of time, being able to obtain a liquid crystal element that exhibits good liquid crystal alignment properties, and being highly effective in suppressing deterioration in display quality due to ^vibration or ^tapping . Specifically, one or both of R ¹ and R ² are preferably a divalent chain hydrocarbon group having one or more carbon atoms, a divalent group in which any methylene groups in the chain hydrocarbon group having two or more carbon atoms are replaced by —O—, —S—, —CO—, —COO—, —NR ⁷ —, —NR ⁷ —NR ⁸ —, —NR ⁷ —CO—O— or —NR ⁷ —CO—NR ⁸ —, provided that they are not adjacent to each other (provided that they are bonded to the carbonyl group in formula (1) above via —C(R ⁵ )(R ⁶ )—, —O—, —S—, —CO—, —COO—, —NR ⁷ —, —NR ⁷ —NR ⁸ —, —NR ⁷ —CO—O— or —NR ⁷ —CO—NR ⁸ —), or a divalent nitrogen-containing non-aromatic heterocyclic group. Among these, it is particularly preferred that one or both of R ¹ and R ² are divalent chain hydrocarbon groups having one or more carbon atoms, or divalent groups in which any methylene groups in a chain hydrocarbon group having two or more carbon atoms are replaced by -O-, -S-, -CO-, -COO-, -NR ⁷ -, -NR ⁷ -NR ⁸ -, -NR ⁷ -CO-O- or -NR ⁷ -CO-NR ⁸ -, provided that they are not adjacent to each other. The above explanations can be used for specific examples and preferred examples of R ⁵ , R ⁶ , R ⁷ and R ⁸ .

When R ¹ and R ² are divalent chain hydrocarbon groups, the chain hydrocarbon groups may be saturated or unsaturated, and may be linear or branched. From the viewpoints of increasing the voltage holding ratio of the liquid crystal element, obtaining a highly reliable liquid crystal element with little decrease in voltage holding ratio even when driven for a long period of time, obtaining a liquid crystal element that exhibits good liquid crystal alignment, and suppressing deterioration in display quality due to vibration or tapping, the chain hydrocarbon groups represented by R ¹ and R ² are preferably alkanediyl groups, and more preferably linear alkanediyl groups. When R ¹ and R ² are divalent chain hydrocarbon groups, the number of carbon atoms in the chain hydrocarbon groups is preferably 2 or more, and more preferably 3 or more, from the viewpoints of obtaining a liquid crystal element that exhibits a high voltage holding ratio and good liquid crystal alignment. Furthermore, from the viewpoint of achieving both improved film strength (and thus improved rubbing resistance) and improved voltage holding ratio of the liquid crystal element, when R ¹ and R ² are chain hydrocarbon groups, the number of carbon atoms in R ¹ and R ² is preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less.

When R ¹ and R ² are divalent groups (hereinafter also referred to as "divalent group A") in which any methylene groups in a chain hydrocarbon group having two or more carbon atoms are replaced with -O-, -S-, -CO-, -COO-, -NR ⁷ -, -NR ⁷ -NR ⁸ -, -NR ⁷ -CO-O- or -NR ⁷ -CO-NR ⁸ -, provided that they are not adjacent to each other, it is preferable that one or both of R ¹ and R ² are groups represented by the following formula (6):
-R ¹⁰ -X ¹ -* ¹ ...(6)
(In formula (6), R ¹⁰ is an alkanediyl group. X ¹ is —O—, —S—, —CO—, —COO—, —NR ⁷ —, —NR ⁷ —NR ⁸ —, —NR ⁷ —CO—O—, or —NR ⁷ —CO—NR ⁸ —. “* ¹ ” represents a bond bonding to the carbonyl group in formula (1). R ⁷ and R ⁸ are defined as in formula (1).)

In the above formula (6), the alkanediyl group represented by R ¹⁰ is preferably linear. The number of carbon atoms in the alkanediyl group is preferably 1 to 10, more preferably 2 to 10, and even more preferably 2 to 5.

When ^R1 and ^R2 are divalent nitrogen-containing non-aromatic heterocyclic groups, the divalent nitrogen-containing non-aromatic heterocyclic group is preferably a substituted or unsubstituted 1,4-piperidinediyl group or a substituted or unsubstituted 1,4-piperazinediyl group.

In the above formula (1), it is preferable that ^R3 and ^R4 are a hydrogen atom, a fluorine atom, or a methyl group, or that ^R3 and ^R4 are combined together to form a ring structure constituted by the carbon to which ^R3 is bonded and the carbon to which ^R4 is bonded. Examples of the ring structure constituted by ^R3 and ^R4 combined together include a cycloolefin ring having 5 to 10 ring members. Of these, a cycloolefin ring having 5 to 8 ring members is preferable. Of these, ^R3 and ^R4 are preferably a hydrogen atom, a fluorine atom, or a methyl group, and a hydrogen atom is particularly preferable, in terms of being able to further enhance the effect of improving film strength.

The group represented by -R ⁴ C═CR ³ - in the above formula (1) may be either a cis-type or a trans-type, and it is preferable that the group represented by -R ⁴ C═CR ³ - in the above formula (1) be a cis-type in order to enhance the effect of improving film strength.

Partial structure (a) is preferably a structure represented by the following formula (1-1) or (1-2).
(In formula (1-1), R ¹¹ and R ¹³ represent a nitrogen-containing non-aromatic heterocyclic structure in which R ¹¹ is a hydrogen atom or a monovalent organic group and R ¹³ is a single bond or an alkanediyl group, or R ¹¹ and R ¹³ taken together and the nitrogen atom to which R ¹¹ is bonded. R ¹² and R ¹⁴ represent a nitrogen-containing non-aromatic heterocyclic structure in which R ¹² is a hydrogen atom or a monovalent organic group and R ¹⁴ is a single bond or an alkanediyl group, or R ¹² and R ¹⁴ taken together and the nitrogen atom to which R ¹² is bonded. R ³ and R ⁴ are each independently a hydrogen atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms. "*" represents a bond.
In formula (1-2), R ¹⁵ and R ¹⁶ each independently represent a single bond or an alkanediyl group. R ³ and R ⁴ each independently represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms. "*" represents a bond.

In the above formulas (1-1) and (1-2), examples of the monovalent organic groups represented by R ¹¹ and R ¹² include the same groups as those exemplified in the description of R ⁷ and R ⁸ in the above formula (1). Examples of ^{R 3} and R ⁴ include the same groups as those exemplified in the description of R ³ and R ⁴ in the above formula (1).

When R ¹³ and R ¹⁴ are alkanediyl groups, they are preferably linear, and more preferably linear alkanediyl groups having 1 to 5 carbon atoms. The ring structure formed by combining R ¹¹ and R ¹³ together, and the ring structure formed by combining R ¹² and R ¹⁴ together are preferably substituted or unsubstituted 1,4-piperidinediyl groups, or substituted or unsubstituted 1,4-piperazinediyl groups.

In order to obtain a liquid crystal device that exhibits good liquid crystal alignment properties and exhibits high VHR and high reliability, the content of structural units derived from monomers having partial structure (a) in polymer [A] is preferably 2 mol% or more, based on the total amount of monomer units in polymer [A]. From this perspective, the content of structural units derived from monomers having partial structure (a) is more preferably 5 mol% or more, and even more preferably 7 mol% or more, based on the total amount of monomer units in polymer [A]. The content of structural units derived from monomers having partial structure (a) can be appropriately set depending on the main chain of polymer [A], but is, for example, 60 mol% or less, and preferably 50 mol% or less, based on the total amount of monomer units in polymer [A]. Polymer [A] may contain only one type of structural unit derived from a monomer having partial structure (a), or two or more types of structural units.

The main skeleton of polymer [A] is not particularly limited. In terms of its high affinity with liquid crystals, its high mechanical strength, and its ability to form a highly reliable liquid crystal alignment film, polymer [A] is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide.

The method for producing polymer [A] is not particularly limited as long as it allows for the introduction of partial structure (a) into the main chain of the polymer. In terms of ease of introducing partial structure (a) into the main chain of the polymer, polymer [A] is preferably produced by a polymerization method using a monomer having partial structure (a) in its main chain. In terms of the ability to form a liquid crystal alignment film with high affinity for liquid crystals and mechanical strength, the monomer having partial structure (a) is preferably at least one selected from the group consisting of a diamine compound having partial structure (a) (hereinafter also referred to as a "specific diamine") and a tetracarboxylic dianhydride having partial structure (a) (hereinafter also referred to as a "specific acid anhydride").

(Specific diamine)
The specific diamine may be a monomer having the partial structure (a) and two primary amino groups, and the structure of the other portions is not particularly limited. Specifically, the specific diamine is preferably a compound represented by the following formula (2):
(In formula (2), ^A1 and ^A2 each independently represent a single bond, a divalent alicyclic group, or a divalent aromatic ring group. m1 is an integer of 1 to 3. ^R1 , ^R2 , ^R3 , and ^R4 have the same meanings as in formula (1) above. When m1 is 2 or 3, multiple ^R1 to ^R4 are the same as or different from one another.)

In the above formula (2), the divalent alicyclic groups represented by ^A1 and ^A2 are preferably groups obtained by removing two hydrogen atoms from the ring portion of a substituted or unsubstituted alicyclic hydrocarbon ring. Examples of such alicyclic hydrocarbon rings include a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, and a cycloheptane ring. Examples of substituents introduced into the ring portion of the alicyclic hydrocarbon ring include an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and a halogen atom.

The divalent aromatic ring groups represented by ^A1 and ^A2 are groups obtained by removing two hydrogen atoms from the ring portion of a substituted or unsubstituted aromatic ring. The aromatic ring is an aromatic hydrocarbon ring or an aromatic heterocycle, preferably an aromatic hydrocarbon ring or a nitrogen-containing aromatic heterocycle. Examples of substituents introduced into the ring portion of the aromatic ring include an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and a halogen atom.

Specific examples of divalent aromatic ring groups represented by ^A1 and ^A2 include, as divalent aromatic hydrocarbon ring groups, groups obtained by removing any hydrogen atom from the ring moiety of a benzene ring, a biphenyl ring, a naphthalene ring, or an anthracene ring; and as divalent nitrogen-containing aromatic heterocyclic groups, groups obtained by removing any two hydrogen atoms from the ring moiety of a pyridine ring, a pyrimidine ring, a pyridazine ring, or a pyrazine ring. From the viewpoint of increasing the density of the liquid crystal alignment film, the divalent aromatic ring groups represented by ^A1 and ^A2 are preferably substituted or unsubstituted phenylene groups, biphenylene groups, or pyridinediyl groups, and more preferably substituted or unsubstituted phenylene groups.

From the viewpoint of obtaining a highly reliable liquid crystal element that shows little decrease in voltage holding ratio (VHR) even when driven for a long period of time, and from the viewpoint of obtaining a liquid crystal element that shows good liquid crystal alignment properties, ^A1 and ^A2 are preferably, among others, a divalent alicyclic group or a divalent aromatic ring group, and more preferably a divalent aromatic ring group.
From the viewpoints of liquid crystal alignment and ease of synthesis, m1 is preferably 1 or 2. Furthermore, from the viewpoint of enhancing the improving effect of the introduction of the partial structure (a), m1 is preferably 2 or more. From the viewpoints of enhancing the liquid crystal alignment and ease of synthesis, and enhancing the improving effect of the voltage holding ratio by the introduction of the partial structure (a), m is particularly preferably 2.

Preferable specific examples of the specific diamine include a compound represented by the following formula (2-1) and a compound represented by the following formula (2-2).
(In formula (2-1) and formula (2-2), Ar ¹ and Ar ² each independently represent a divalent aromatic ring group. m1 represents an integer of 1 to 3. R ³ , R ⁴ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶ have the same meanings as in formula (1-1) and formula (1-2) above.)

Specific examples of the specific diamine include compounds represented by the following formulas (3-1) to (3-30): In the compounds represented by the following formulas (3-1) to (3-30), the carbon-carbon unsaturated bond between the two carbonyl groups does not specify structural isomerism, and the compound may be either a cis or trans isomer.

(Synthesis of specific diamine)
The synthesis method of the specific diamine is not particularly limited. The specific diamine can be produced, for example, by a method of reacting maleic anhydride with an amine compound having a partial structure corresponding to "-R ¹ -A ¹ -NH ₂ " in the above formula (2) (Method 1A); or a method of reacting fumaryl chloride with an amine compound having a partial structure corresponding to "-R ¹ -A ¹ -NH ₂ " in the above formula (2) (Method 2A). The specific diamine can also be produced using a compound represented by the following formula (5) as a raw material (Method 3A). From an industrial perspective, it is desirable to obtain a useful diamine with a small number of steps. In this regard, Method 3A is advantageous in that it allows the introduction of two or more partial structures (a) into the specific diamine with a small number of steps.
(In formula (5), ^R9 is a single bond or a divalent organic group.)

In Method 3A, the compound represented by the above formula (5) is reacted with an amine compound having a partial structure corresponding to "-R ¹ -A ¹ -NH ₂ " in the above formula (2), if necessary, in a solvent. The solvent is preferably an organic solvent capable of dissolving the raw materials. In Method 3A, the reaction temperature is, for example, 0 to 80°C, and the reaction time is, for example, 30 minutes to 12 hours.

In the above formula (5), examples of the divalent organic group represented by ^R9 include divalent hydrocarbon groups having 1 to 20 carbon atoms and divalent groups containing -O-, -S-, etc. between the carbon-carbon bonds of the hydrocarbon group. For example, by reacting a compound represented by the above formula (5) with a compound represented by the following formula (7), a compound represented by the following formula (8) can be obtained as the specific diamine.
(In the scheme, ^R9 is a single bond or a divalent organic group. ^A1 has the same meaning as in formula (2) above, and ^R1 has the same meaning as in formula (1) above.)

(Specified acid anhydride)
The specific acid anhydride may be a monomer having the partial structure (a) and two acid anhydride groups, and the structure of the other parts is not particularly limited. Specifically, the specific acid anhydride is preferably at least one selected from the group consisting of a compound represented by the following formula (3) and a compound represented by the following formula (4):
(In formula (3) and formula (4), ^A3 and ^A4 each independently represent a trivalent aromatic ring group or aliphatic ring group. m2 is an integer of 1 to 3. n1 and n2 each independently represent an integer of 1 to 3. ^R1 , ^R2 , ^R3 , and ^R4 have the same meanings as in formula (1) above. When m2 is 2 or 3, multiple ^R1 to ^R4 are the same as or different from one another.)

In the above formulas (3) and (4), examples of the trivalent aliphatic cyclic group represented by ^A3 and ^A4 include groups obtained by removing three hydrogen atoms from the ring portion of an alicyclic hydrocarbon ring such as a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, or a cycloheptane ring. The alicyclic hydrocarbon ring may have a substituent. Examples of the substituent include an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and a halogen atom.

The trivalent aromatic ring groups represented by ^A3 and ^A4 are groups obtained by removing three hydrogen atoms from the ring portion of a substituted or unsubstituted aromatic ring. The aromatic ring is an aromatic hydrocarbon ring or an aromatic heterocycle, preferably an aromatic hydrocarbon ring or a nitrogen-containing aromatic heterocycle. Examples of substituents introduced into the ring portion of the aromatic ring include an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and a halogen atom. From the viewpoint of increasing the density of the liquid crystal alignment film, the trivalent aromatic ring groups represented by ^A3 and ^A4 are preferably groups having a benzene ring, a biphenyl ring, or a pyridine ring, and more preferably groups having a benzene ring.

From the viewpoint of obtaining a highly reliable liquid crystal element that shows little decrease in voltage holding ratio (VHR) even when driven for a long period of time, and from the viewpoint of obtaining a liquid crystal element that shows good liquid crystal alignment properties, ^A3 and ^A4 are preferably trivalent aromatic ring groups, and more preferably trivalent groups having a benzene ring.
From the viewpoints of liquid crystal alignment properties and ease of synthesis, m2 is preferably 1 or 2. Furthermore, from the viewpoint of enhancing the improving effect due to the introduction of the partial structure (a), m2 is preferably 2 or more.

Preferable specific examples of the specific acid anhydride include a compound represented by the following formula (3-1), a compound represented by the following formula (3-2), a compound represented by the following formula (4-1), and a compound represented by the following formula (4-2).
(In formulas (3-1) and (3-2), Ar ³ and Ar ⁴ each independently represent a trivalent aromatic ring group. m2 represents an integer of 1 to 3. R ³ , R ⁴ , R ¹¹ , R ^{12 , R 13 ,} R ¹⁴ , R ¹⁵ and R ¹⁶ have the same meanings as in formulas (1-1) and (1-2) above.)
(In formulas (4-1) and (4-2), m2 is an integer of 1 to 3. n1 and n2 are each independently an integer of 1 to 3. R ³ , R ⁴ , R 11 , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and ^{R 16 are} the same as defined in formulas (1-1) and (1-2) above.)

In the above formulas (3-1), (3-2), (4-1) and (4-2), R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶ are preferably single bonds from the viewpoint of ease of compound synthesis.

Specific examples of the specific acid anhydride include compounds represented by the following formulas (4-1) to (4-3): In the compounds represented by the following formulas (4-1) to (4-3), the carbon-carbon unsaturated bond between the two carbonyl groups does not specify structural isomerism, and the compounds may be either cis or trans.

(Synthesis of specific acid anhydride)
The method for synthesizing the specific acid anhydride is not particularly limited. The specific acid anhydride can be produced, for example, by a method (Method 1B) in which fumaryl chloride is reacted with an amine compound having a partial structure corresponding to the "-R ¹ -acid anhydride group" in the above formula (3) or (4). The specific acid anhydride can also be produced using a compound represented by the following formula (5) as a raw material (Method 2B). From an industrial perspective, it is desirable to obtain a useful tetracarboxylic dianhydride with a small number of steps. In this regard, Method 2B is advantageous in that two or more partial structures (a) can be introduced into the specific acid anhydride with a small number of steps.
(In formula (5), ^R9 is a single bond or a divalent organic group.)

In Method 2B, a compound represented by the above formula (5) is reacted with an amine compound having a partial structure corresponding to the "-R ¹ -acid anhydride group" in the above formula (3) or (4), if necessary, in a solvent. The solvent is preferably an organic solvent capable of dissolving the raw materials. In Method 2B, the reaction temperature is, for example, 0 to 80°C, and the reaction time is, for example, 30 minutes to 12 hours.

In the above formula (5), examples of the divalent organic group represented by ^R9 include divalent hydrocarbon groups having 1 to 20 carbon atoms and divalent groups containing -O-, -S-, etc. between the carbon-carbon bonds of the hydrocarbon group. For example, by reacting a compound represented by the above formula (5) with a compound represented by the following formula (9), a compound represented by the following formula (10) can be obtained as a specific acid anhydride.
(In the scheme, ^R9 is a single bond or a divalent organic group. ^A5 is a single bond or an alkanediyl group. ^R1 has the same meaning as in formula (1) above. n1 is an integer of 1 to 3.)

<Polyamic acid>
When the polymer [A] is a polyamic acid, the polyamic acid (hereinafter also referred to as "polyamic acid [A]") can be prepared by, for example, [1] a method of reacting a tetracarboxylic dianhydride containing a specific acid-free dihydrate with a diamine compound; [2] a method of reacting a tetracarboxylic dianhydride with a diamine compound containing a specific diamine; etc. Method [1] and method [2] may be combined.

(Tetracarboxylic acid dianhydride)
In synthesizing the polyamic acid [A], one tetracarboxylic dianhydride may be used alone, or two or more tetracarboxylic dianhydrides may be used in combination. The tetracarboxylic dianhydride used in synthesizing the polyamic acid [A] may consist solely of the specific acid anhydride, or may contain a tetracarboxylic dianhydride not having the partial structure (a) (hereinafter also referred to as "other acid dianhydrides"). Examples of other acid dianhydrides include linear aliphatic tetracarboxylic dianhydrides, alicyclic tetracarboxylic dianhydrides, and aromatic tetracarboxylic dianhydrides.

Specific examples of other acid dianhydrides include, as chain aliphatic tetracarboxylic dianhydrides, 1,2,3,4-butanetetracarboxylic dianhydride, ethylenediaminetetraacetic dianhydride, etc.; as alicyclic tetracarboxylic dianhydrides, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic 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-tetracarboxylic dianhydride, Examples of suitable tetracarboxylic dianhydrides include 2,4,6,8-tricarboxybicyclo[3.3.0]octane dianhydride, cyclopentane tetracarboxylic dianhydride, cyclohexane tetracarboxylic dianhydride, and 3,5,6-tricarboxy-2-carboxymethylnorbornane dianhydride; aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, ethylene glycol bisanhydrotrimate, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 4,4'-carbonyldiphthalic anhydride, and 3,3',4,4'-biphenyl tetracarboxylic dianhydride; and the tetracarboxylic dianhydrides described in JP 2010-97188 A can also be used.

The other acid dianhydrides used in the synthesis of polyamic acid [A] preferably include at least one selected from the group consisting of linear aliphatic tetracarboxylic acid dianhydrides and alicyclic tetracarboxylic acid dianhydrides, and more preferably alicyclic tetracarboxylic acid dianhydrides, in that they are highly soluble and can produce a liquid crystal alignment film that exhibits good liquid crystal alignment properties and electrical characteristics. The proportion of the alicyclic tetracarboxylic acid dianhydride used is preferably 20 mol% or more, more preferably 40 mol% or more, and even more preferably 50 mol% or more, based on the total amount of tetracarboxylic acid dianhydrides used in the synthesis of polyamic acid [A].

When polyamic acid [A] is produced by method [1] above, the proportion of the specific acid dianhydride used is preferably 20 mol% or more, more preferably 30 mol% or more, and even more preferably 40 mol% or more, based on the total amount of tetracarboxylic acid dianhydride used in the synthesis of polyamic acid [A].

(Diamine compound)
In synthesizing the polyamic acid [A], one diamine compound may be used alone, or two or more diamine compounds may be used in combination. The diamine compound used in synthesizing the polyamic acid [A] may consist solely of the specific diamine, or may contain a diamine compound not having the partial structure (a) (hereinafter also referred to as "other diamine"). Examples of other diamines include linear aliphatic diamines, alicyclic diamines, aromatic diamines, and diaminoorganosiloxanes.

Specific examples of other diamines include: chain aliphatic diamines such as metaxylylenediamine and hexamethylenediamine; alicyclic diamines such as 1,4-diaminocyclohexane and 4,4'-methylenebis(cyclohexylamine); aromatic diamines such as p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4-aminophenyl-4-aminobenzoate, 4,4'-diaminoazobenzene, 3,5-diaminobenzoic acid, 1,5-bis(4-aminophenoxy)pentane, 1,2-bis(4-aminophenoxy)ethane, 1,3-bis(4-aminophenoxy)propane, 1,6-bis(4-aminophenoxy)hexane, 6,6'-(pentamethylenedioxy)bis(3-aminopyridine), N,N'-di(5-amino-2-pyridyl)-N,N'-di( tert-butoxycarbonyl)ethylenediamine, bis[2-(4-aminophenyl)ethyl]hexanedioic acid, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylamine, 4,4'-diaminodiphenethyl urea, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis(4-aminophenyl)hexafluoropropane, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 4,4'-(phenylenediisopropylidene)bisaniline, 2,6-diaminopyridine, 2,4-diaminopyrimidine, 3,6-diaminocarbazole, N-methyl-3,6-diaminocarbazole, 3,6-diaminoacridine, diphenylamine structure-containing monomers, and monomers represented by the following formula (F-1):
(In formula (F-1), R ²¹ and R ²² each independently represent an alkanediyl group. R ²³ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a protecting group. r1 represents an integer of 1 to 3. When r1 is 2 or 3, multiple R ^22s may be the same or different, and multiple R ^23s may be the same or different.)
Main chain diamines such as compounds represented by the following formula:
Hexadecanoxy-2,4-diaminobenzene, octadecanoxy-2,4-diaminobenzene, octadecanoxy-2,5-diaminobenzene, cholestanyloxy-3,5-diaminobenzene, cholesteryloxy-3,5-diaminobenzene, cholestanyloxy-2,4-diaminobenzene, cholesteryloxy-2,4-diaminobenzene, cholestanyl 3,5-diaminobenzoate, cholesteryl 3,5-diaminobenzoate , lanostannyl 3,5-diaminobenzoate, 3,6-bis(4-aminobenzoyloxy)cholestane, 3,6-bis(4-aminophenoxy)cholestane, 4-(4'-trifluoromethoxybenzoyloxy)cyclohexyl-3,5-diaminobenzoate, 1,1-bis(4-((aminophenyl)methyl)phenyl)-4-butylcyclohexane, 3,5-diaminobenzoic acid=5ξ-cholestan-3-yl, compounds of the following formula (E-1):
(In formula (E-1), X ^I and X ^II each independently represent a single bond, —O—, *-COO—, or *-OCO— (wherein “*” represents a bond to the diaminophenyl group). R ^I represents an alkanediyl group having 1 to 3 carbon atoms. R ^II represents a single bond or an alkanediyl group having 1 to 3 carbon atoms. R ^III represents an alkyl group, alkoxy group, fluoroalkyl group, or fluoroalkoxy group having 1 to 20 carbon atoms. a represents 0 or 1. b represents an integer of 0 to 3. c represents an integer of 0 to 2. d represents 0 or 1, provided that 1≦a+b+c≦3.)
A side chain type diamine or the like, such as a compound represented by
Examples of diaminoorganosiloxanes include 1,3-bis(3-aminopropyl)-tetramethyldisiloxane.

Examples of the compound represented by formula (F-1) above include compounds represented by the following formulas (F-1-1) to (F-1-3). Examples of the compound represented by formula (E-1) above include compounds represented by the following formulas (E-1-1) to (E-1-4). As the other diamines, one type can be used alone, or two or more types can be used in combination. In the formulas, "Boc" represents a tert-butoxycarbonyl group (the same applies hereinafter).

When producing polyamic acid [A] by method [2] above, the proportion of the specific diamine used is preferably 20 mol% or more, more preferably 30 mol% or more, and even more preferably 40 mol% or more, based on the total amount of diamine compounds used in the synthesis of polyamic acid [A].

(Synthesis of Polyamic Acid)
The polyamic acid [A] can be obtained by reacting a tetracarboxylic dianhydride with a diamine compound, optionally together with a molecular weight modifier. One preferred embodiment of the method for producing the polyamic acid [A] includes reacting a tetracarboxylic dianhydride with a diamine compound using a monomer containing at least one selected from the group consisting of the specific diamine obtained by the above method 3A and the specific acid dianhydride obtained by the above method 2B.

In the synthesis reaction of polyamic acid [A], the ratio of tetracarboxylic dianhydride to diamine compound is preferably such that 0.2 to 2 equivalents of acid anhydride groups in the tetracarboxylic dianhydride are used per 1 equivalent of amino groups in the diamine compound. Examples of molecular weight modifiers include acid monoanhydrides such as maleic anhydride, phthalic anhydride, and itaconic anhydride; monoamine compounds such as aniline, cyclohexylamine, and n-butylamine; and monoisocyanate compounds such as phenyl isocyanate and naphthyl isocyanate. The ratio of molecular weight modifier used is preferably 20 parts by mass or less per 100 parts by mass of the total of the tetracarboxylic dianhydride and diamine compound used.

The synthesis reaction of polyamic acid [A] 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, alcoholic solvents, ketone solvents, ester solvents, ether solvents, halogenated hydrocarbons, and hydrocarbons. Among these, it is preferable to use one or more solvents selected from the group consisting of N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, tetramethylurea, hexamethylphosphortriamide, m-cresol, xylenol, and halogenated phenols as the reaction solvent, or to use a mixture of one or more of these solvents with another organic solvent (e.g., butyl cellosolve, diethylene glycol diethyl ether, etc.). The amount of organic solvent used is preferably such that the total amount of the tetracarboxylic dianhydride and diamine compound is 0.1 to 50% by mass based on the total amount of the reaction solution.

In this manner, a polymer solution containing dissolved polyamic acid [A] is obtained. This polymer solution may be used directly to prepare a liquid crystal aligning agent, or the polyamic acid [A] contained in the polymer solution may be isolated and then used to prepare a liquid crystal aligning agent.

Polyamic Acid Ester When the polymer [A] is a polyamic acid ester, the polyamic acid ester (hereinafter also referred to as "polyamic acid ester [A]") can be obtained, for example, by a method such as [I] reacting a polyamic acid [A] with an esterifying agent, [II] reacting a tetracarboxylic acid diester with a diamine compound containing a specific diamine, or [III] reacting a tetracarboxylic acid diester dihalide with a diamine compound containing a specific diamine. The polyamic acid ester [A] may have only an amic acid ester structure, or may be a partially esterified product in which an amic acid structure and an amic acid ester structure coexist. The reaction solution in which the polyamic acid ester [A] is dissolved may be used directly for preparing a liquid crystal aligning agent, or the polyamic acid ester [A] contained in the reaction solution may be isolated and then used for preparing a liquid crystal aligning agent.

Polyimide When the polymer [A] is a polyimide, the polyimide (hereinafter also referred to as "polyimide [A]") can be obtained, for example, by imidizing the polyamic acid [A] synthesized as described above through dehydration and cyclization. The polyimide [A] may be a fully imidized product in which all of the amic acid structures contained in its precursor polyamic acid [A] have been dehydrated and cyclized, or a partially imidized product in which only a portion of the amic acid structures have been dehydrated and cyclized, resulting in both amic acid structures and imide ring structures. The polyimide [A] preferably has an imidization rate of 20 to 99%, more preferably 30 to 90%. The 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. Some of the imide rings may be isoimide rings.

The dehydration ring-closing of polyamic acid [A] is preferably carried out by dissolving polyamic acid [A] in an organic solvent, adding a dehydrating agent and a dehydration ring-closing catalyst to the solution, and heating as needed. In this method, the dehydrating agent may be an acid anhydride such as acetic anhydride, propionic anhydride, or trifluoroacetic anhydride. The amount of dehydrating agent used is preferably 0.01 to 20 moles per mole of the amic acid structure of polyamic acid [A]. The dehydration ring-closing catalyst may be a tertiary amine such as pyridine, collidine, lutidine, or triethylamine. The amount of dehydration ring-closing catalyst used is preferably 0.01 to 10 moles per mole of the dehydrating agent used. Examples of organic solvents used in the dehydration ring-closing reaction include those exemplified for the synthesis of polyamic acid [A]. The reaction temperature for the dehydration ring-closing reaction is preferably 0 to 180°C. The reaction time is preferably 1.0 to 120 hours. The reaction solution containing polyimide [A] may be used as is to prepare a liquid crystal aligning agent, or polyimide [A] may be isolated and then used to prepare a liquid crystal aligning agent.

When polymer [A] is at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide, the solution viscosity of polymer [A] is preferably 10 to 800 mPa·s when prepared as 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 polymer [A] (e.g., γ-butyrolactone, N-methyl-2-pyrrolidone, etc.).

The polystyrene-equivalent weight-average molecular weight (Mw) of polymer [A] measured by gel permeation chromatography (GPC) is preferably 1,000 to 500,000, and more preferably 2,000 to 300,000. Furthermore, the molecular weight distribution (Mw/Mn), expressed as the ratio of Mw to the polystyrene-equivalent number-average molecular weight (Mn) measured by GPC, is preferably 7 or less, and more preferably 5 or less. When preparing the liquid crystal aligning agent, one type of polymer [A] may be used alone, or two or more types may be used in combination.

<Other ingredients>
The liquid crystal aligning agent may contain, in addition to the polymer [A], components different from the polymer [A] (hereinafter also referred to as "other components"), if necessary.

Polymer [Q]
The liquid crystal aligning agent of the present disclosure may further contain, as a polymer component, a polymer not having the partial structure (a) (hereinafter also referred to as "polymer [Q]").

The main skeleton of polymer [Q] is not particularly limited. Examples of polymer [Q] include polyamic acid, polyamic acid ester, polyimide, polyorganosiloxane, polyester, polyenamine, polyurea, polyamide, polyamideimide, polybenzoxazole precursor, polybenzoxazole, cellulose derivative, polyacetal, (meth)acrylic polymer, styrene polymer, maleimide polymer, styrene-maleimide copolymer, etc. From the viewpoint of obtaining a highly reliable liquid crystal device, polymer [Q] is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, polyimide, polyorganosiloxane, and addition polymer. Examples of addition polymers include (meth)acrylic polymer, styrene polymer, maleimide polymer, styrene-maleimide copolymer, etc.

When the liquid crystal aligning agent of the present disclosure contains polymer [Q] together with polymer [A], the content of polymer [Q] is preferably 1% by mass or more, and more preferably 2% by mass or more, based on the total amount of polymer [A] and polymer [Q]. Furthermore, the content of polymer [Q] is preferably 95% by mass or less, and more preferably 90% by mass or less, based on the total amount of polymer [A] and polymer [Q]. Polymer [Q] can be used alone or in combination of two or more types.

Solvent The liquid crystal aligning agent of the present disclosure is prepared as a liquid composition in which the polymer component and other components used as needed are dispersed or dissolved preferably in a suitable solvent.

Organic solvents are preferably used as the solvent. Specific examples include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 1,2-dimethyl-2-imidazolidinone, 1,3-dimethyl-2-imidazolidinone, phenol, γ-butyrolactone, γ-butyrolactam, N,N-dimethylformamide, N,N-dimethylacetamide, 4-hydroxy-4-methyl-2-pentanone, diacetone alcohol, 1-hexanol, 2-hexanol, propane-1,2-diol, 3-methoxy-1-butanol, ethylene glycol monomethyl ether, methyl lactate, ethyl lactate, butyl lactate, methyl acetate, ethyl acetate, butyl acetate, methyl acetoacetate, ethyl acetoacetate, ethyl propionate, 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 solvents 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, propylene carbonate, propylene glycol monomethyl ether (PGME), diethylene glycol diethyl ether acetate, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol diacetate, cyclopentanone, and cyclohexanone. These solvents can be used alone or in combination.

Other components contained in the liquid crystal aligning agent include, in addition to those mentioned above, crosslinking agents, antioxidants, metal chelate compounds, curing accelerators, surfactants, fillers, dispersants, photosensitizers, etc. The blending ratio of other components can be selected appropriately depending on each compound, as long as the effects of the present disclosure are not impaired.

The solids concentration in the liquid crystal aligning agent (the proportion of the total mass of the liquid crystal aligning agent's components other than the solvent to the total mass of the liquid crystal aligning agent) is selected appropriately taking into consideration viscosity, volatility, etc., but is preferably in the range of 1 to 10% by mass. A solids concentration of 1% by mass or more is preferable in that it ensures a sufficient coating film thickness and allows for the production of a liquid crystal alignment film that exhibits better liquid crystal alignment properties. On the other hand, a solids concentration of 10% by mass or less allows for the coating film to have an appropriate thickness, making it easier to produce a liquid crystal alignment film that exhibits good liquid crystal alignment properties, and also tends to provide an appropriate viscosity for the liquid crystal aligning agent, resulting in good coatability.

According to the present disclosure described above, the following liquid crystal aligning agent is provided.
<1> A liquid crystal aligning agent containing a polymer [A] having a partial structure (a) represented by the above formula (1) in its main chain.
<2> The liquid crystal aligning agent according to the above <1>, wherein the polymer [A] contains a structural unit derived from a diamine having the partial structure (a).
<3> The liquid crystal aligning agent according to the above <2>, wherein the diamine is a compound represented by the above formula (2).
<4> The liquid crystal aligning agent according to any one of the above <1> to <3>, wherein the polymer [A] contains a structural unit derived from a tetracarboxylic acid derivative having the partial structure (a).
<5> The liquid crystal aligning agent according to the above <4>, wherein the tetracarboxylic acid derivative is at least one selected from the group consisting of a compound represented by the above formula (3) and a compound represented by the above formula (4).
<6> The liquid crystal aligning agent according to any one of the above <1> to <5>, wherein the polymer [A] is at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide.
<7> The liquid crystal aligning agent according to any one of the above <1> to <6>, wherein the polymer [A] contains a structural unit derived from an alicyclic tetracarboxylic dianhydride.
<8> The liquid crystal aligning agent according to any one of the above <1> to <7>, further comprising a polymer [Q] that does not have the partial structure (a).

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

<Step 1: Formation of coating film>
First, a liquid crystal alignment agent is applied to a substrate, and the coated surface is preferably heated to form a coating film on the substrate. Examples of substrates that can be used include transparent substrates made of glass such as float glass and soda glass; and plastics such as polyethylene terephthalate, polybutylene terephthalate, polyethersulfone, polycarbonate, and poly(alicyclic olefin). Examples of transparent conductive films that can be provided on one side of the substrate include a NESA film (registered trademark of PPG Corporation, USA) made of tin oxide (SnO ₂ ) and an ITO film made of indium oxide-tin oxide (In ₂ O ₃ -SnO ₂ ). When manufacturing TN-, STN-, or VA-type liquid crystal devices, two substrates each having a patterned transparent conductive film are used. On the other hand, when manufacturing IPS- or FFS-type liquid crystal devices, a substrate having a comb-shaped patterned electrode and an opposing substrate without an electrode are used.

The method for applying the liquid crystal alignment agent to the substrate is not particularly limited. The liquid crystal alignment agent can be applied to the substrate by, for example, a spin coating method, a printing method (e.g., offset printing method, flexographic printing method, etc.), an inkjet method, a slit coating method, a bar coater method, an extrusion die method, a direct gravure coater method, a chamber doctor coater method, an offset gravure coater method, an impregnation coater method, an MB coater method, etc.

After applying the liquid crystal alignment agent, preheating (pre-baking) is preferably performed to prevent dripping of the applied liquid crystal alignment agent. The pre-baking temperature is preferably 30 to 200°C, and the pre-baking time is preferably 0.25 to 10 minutes. The solvent is then completely removed, and if necessary, a baking (post-baking) step is performed to thermally imidize the amic acid structure present in the polymer. The baking temperature (post-baking temperature) at this time is preferably 80 to 280°C, more preferably 80 to 250°C. The post-baking time is preferably 5 to 200 minutes. The thickness of the formed film is preferably 0.001 to 1 μm.

<Step 2: Alignment Treatment>
When producing a TN-type, STN-type, IPS-type, or FFS-type liquid crystal element, the coating film formed in step 1 above is subjected to a treatment (alignment treatment) to impart liquid crystal alignment ability. This imparts the ability to align liquid crystal molecules to the coating film, thereby forming a liquid crystal alignment film. As the alignment treatment, a rubbing treatment in which the surface of the coating film formed on the substrate is rubbed with cotton, nylon, or the like, or a photoalignment treatment in which the coating film is irradiated with light to impart liquid crystal alignment ability is preferably used. When producing a vertical alignment type liquid crystal element, the coating film formed in step 1 above may be used as a liquid crystal alignment film as is, or the coating film may be subjected to an alignment treatment to further enhance the liquid crystal alignment ability.

Light irradiation for photo-alignment can be performed by irradiating the coating film after the post-bake step, by irradiating the coating film after the pre-bake step but before the post-bake step, or by irradiating the coating film while it is being heated in at least one of the pre-bake and post-bake steps. The radiation irradiated onto 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 contains 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, irradiation may be performed perpendicular to the substrate surface, obliquely, or a combination of these. When using unpolarized radiation, the irradiation direction is oblique.

Examples of light sources 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 200 to 30,000 J/ ^m² , and more preferably 500 to 10,000 J/ ^m² . After light irradiation to impart alignment ability, the substrate surface may be washed with, for example, water, an organic solvent (e.g., methanol, isopropyl alcohol, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, etc.), or a mixture thereof, or the substrate may be heated.

<Step 3: Construction of liquid crystal cell>
Two substrates each having a liquid crystal alignment film formed thereon are prepared as described above, and a liquid crystal cell is fabricated by disposing a liquid crystal between the two substrates facing each other. Examples of methods for fabricating a liquid crystal cell include disposing two substrates facing each other with a gap between them so that the liquid crystal alignment films face each other, bonding the peripheries of the two substrates together with a sealant, injecting liquid crystal into the cell gap surrounded by the substrate surfaces and the sealant, and sealing the injection hole, and using the ODF method. Examples of sealants that can be used include epoxy resins containing a curing agent and aluminum oxide spheres as spacers. Examples of liquid crystals include nematic liquid crystals and smectic liquid crystals, with nematic liquid crystals being preferred.

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

When manufacturing a liquid crystal display device, a polarizing plate is then attached to the outer surface of the liquid crystal cell. Examples of polarizing plates include a polarizing film called an "H film," which is made by stretching and aligning polyvinyl alcohol and absorbing iodine, sandwiched between cellulose acetate protective films, or a polarizing plate made of the H film itself.

The liquid crystal element of the present disclosure can be effectively applied to a variety of applications. Specifically, it can be used in various display devices such as watches, portable game consoles, word processors, notebook computers, car navigation systems, camcorders, PDAs, digital cameras, mobile phones, smartphones, various monitors, LCD televisions, and information displays, as well as in light control devices and retardation films.

The following examples will explain the present invention in more detail, but the present invention should not be construed as being limited by these examples.

In the following examples, the imidization rate of polyimide in the polymer solution was measured by the following method. The required amounts of raw material compounds and polymers used in the following examples were secured by repeating synthesis on the synthesis scale shown in the synthesis examples below as necessary.

[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. The precipitate was then dissolved in deuterated dimethyl sulfoxide and subjected to ^1H -NMR measurement at room temperature using tetramethylsilane as a reference substance. The imidization rate [%] was calculated from the obtained ^1H -NMR spectrum using the following formula (1).
Imidization rate [%] = (1 - (A ¹ / (A ² × α))) × 100 (1)
(In formula (1), ^A1 is the peak area derived from the proton of the NH group appearing at a chemical shift of around 10 ppm, ^A2 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).)

The abbreviations for the compounds are as follows. Note that hereinafter, the compound represented by formula (X) may be referred to simply as "compound (X)."

(Tetracarboxylic acid dianhydride)

(Diamine compound)

(Other compounds)

<Synthesis of Monomer>
1. Synthesis of Compounds (DA-1), (DA-8), and (DA-9) Compounds (DA-1), (DA-8), and (DA-9) were synthesized by a method similar to the method described in Japanese Patent No. 6013823. The production recipe for compound (DA-1) is shown below.

Synthesis of Compound (DA-1) 30 g (0.2 mol) of 4-(2-methylamino-ethyl)-phenylamine and 200 ml of tetrahydrofuran were added to a reaction vessel. Under ice cooling, a solution of 20 g (0.2 mol) of maleic anhydride dissolved in 30 ml of tetrahydrofuran was added dropwise, and the mixture was stirred overnight at room temperature. After the reaction was completed, the precipitated solid was collected by filtration, washed three times with 20 ml of tetrahydrofuran, and dried at 60°C for 3 hours to obtain a brown solid. Subsequently, 30 g (0.2 mol) of 4-(2-methylamino-ethyl)-phenylamine, 0.5 g of dimethylaminopyridine, and 100 ml of dimethylformamide were charged to the reaction vessel containing the obtained solid. Under ice cooling, 38 g (0.2 mol) of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride was added, and the mixture was stirred overnight at room temperature. After the reaction was completed, 300 ml of water was added, and the mixture was extracted three times with 300 ml of ethyl acetate. After drying with sodium sulfate, the solvent was distilled off to obtain 28 g of a brown viscous solid. 80 ml of methanol was added to the obtained solid, and the insoluble solid was collected by filtration to obtain 20 g of compound (DA-1) as a brown solid. The results of ¹ H-NMR measurement of compound (DA-1) are as follows.
¹ H-NMR (300 MHz, DMSO-d ⁶ ) δppm: 7.02 (4H, d), 6.53 (4H, d), 6.44 (2H, s), 3.22-3.57 (10H, m), 2.62 (4H, t).

2. Synthesis of Compounds (DA-2) to (DA-7) Compounds (DA-2) to (DA-7) were produced by a synthetic method in which compounds (D-1) to (D-4) were first produced with reference to the method described in a reference document (Journal of Polymer Science: Polymer Chemistry Edition 1975, Vol. 13, 1691-1698), and the resulting compounds (D-1) to (D-4) were used as intermediates. The production recipe for compound (DA-2) is shown below. Note that compounds (DA-2) to (DA-7) are cis-isomers.

Synthesis of Compound (DA-2) To a reaction vessel, 19.6 g (0.2 mol) of maleic anhydride and 100 ml of acetic acid were added. A solution of 5.0 g (0.1 mol) of hydrazine monohydrate dissolved in 25 ml of acetic acid was added dropwise. During the dropwise addition, the reaction temperature was controlled using an ice bath so that the reaction solution did not exceed 25°C. After the dropwise addition, the mixture was left to stand for 3 hours, and the precipitate was collected by filtration and washed three times with 30 ml of ethanol. This was then dried at 60°C for 5 hours to obtain 21 g of a pale yellow solid. The obtained solid was transferred to a reaction vessel, and 110 ml of thionyl chloride was added, followed by stirring at 75°C for 6 hours. After the reaction, the mixture was cooled to room temperature, and the precipitate was collected by filtration. The precipitate was washed with hexane and dried at 60°C for 5 hours to obtain 10 g (0.05 mol) of compound (D-1). The obtained compound (D-1) was dissolved in 50 ml of N-methyl-2-pyrrolidone, and 14 g (0.1 mol) of 2-(4-aminophenyl)ethylamine was added dropwise over 30 minutes. After the dropwise addition, the mixture was stirred at room temperature for 1 hour, and the reaction solution was added to 500 ml of water to obtain a precipitate. The obtained precipitate was collected by filtration, washed with water, and then dried at 60°C for 5 hours to obtain 20 g of compound (DA-2). The ¹ H-NMR measurement results of compound (DA-2) are as follows:
¹ H-NMR (300 MHz, DMSO-d ⁶ ) δppm: 8.96 (2H, s), 6.89 (4H, m), 6.51 (4H, m), 6.19-6.31 (4H, m), 3.29 (4H, m), 2.60 (4H, m).

3. Synthesis of Compound (DA-10) To a reaction vessel were added 13.9 g (0.1 mol) of 2-amino-5-nitropyridine, 7.9 g (0.1 mol) of pyridine, and 50 ml of tetrahydrofuran. A solution of 7.6 g (0.05 mol) of fumaryl chloride dissolved in 25 ml of tetrahydrofuran was added dropwise. After the addition was completed, the mixture was stirred at room temperature for 8 hours. The resulting reaction solution was poured into water, and the precipitate was collected by filtration. The resulting solid was washed with water and ethanol and dried at 60°C for 5 hours to obtain 14.5 g of the intermediate as a brown solid. The resulting intermediate was transferred to a reaction vessel, and 10 wt% palladium/carbon (2 g) and N,N-dimethylformamide (30 ml) were added, followed by heating at 50°C for 8 hours under a hydrogen atmosphere. The reaction solution was filtered to remove the catalyst, and the filtrate was poured into ice water, and the resulting precipitate was collected by filtration. The obtained solid was washed with ethanol and dried at 60° C. for 5 hours to obtain 12.2 g of compound (DA-10). The ¹ H-NMR measurement results of compound (DA-10) are as follows.
¹ H-NMR (300 MHz, DMSO-d ⁶ ) δppm: 11.2 (2H, s), 7.13-7.44 (6H, m), 6.18 (2H, s).

4. Synthesis of Compound (DA-12) Compound (DA-12) was synthesized in the same manner as in the synthesis of compound (DA-10), except that 4-nitroaniline was used instead of 2-amino-5-nitropyridine as the starting material.

5. Synthesis of Compound (DA-11) To a reaction vessel, 13.9 g (0.1 mol) of 2-amino-5-nitropyridine, 7.9 g (0.1 mol) of pyridine, and 50 ml of tetrahydrofuran were added. A solution of 7.6 g (0.05 mol) of fumaryl chloride dissolved in 25 ml of tetrahydrofuran was added dropwise. After the addition was completed, the mixture was stirred at room temperature for 8 hours. The resulting reaction solution was poured into water, and the precipitate was collected by filtration. The resulting solid was washed with water and ethanol and dried at 60°C for 5 hours to obtain 14.5 g of an intermediate as a brown solid. The resulting intermediate was transferred to a reaction vessel, and 25 ml of dimethylformamide was added. 18 g (0.08 mol) of di-tert-butyl dicarbonate was added thereto, and the mixture was stirred at room temperature for 16 hours. The reaction solution was added dropwise to water, and the precipitate was collected by filtration, washed with water, and then dried at 60°C for 3 hours to obtain 13.2 g of a light brown solid. The obtained solid was transferred to a reaction vessel, and 10 wt % palladium/carbon (1.8 g) and N,N-dimethylformamide (30 ml) were added, followed by heating at 50°C for 8 hours under a hydrogen atmosphere. The reaction solution was filtered to remove the catalyst, and the filtrate was poured into ice water, and the resulting precipitate was collected by filtration. The obtained solid was washed with ethanol and dried at 60°C for 5 hours, yielding 9.8 g of compound (DA-11). The ¹ H-NMR measurement results of compound (DA-11) are as follows:
¹ H-NMR (300 MHz, DMSO-d ⁶ ) δppm: 8.09 (2H, m), 7.28-7.44 (4H, m), 6.93 (2H, s), 1.39 (18H, s).

6. Synthesis of Compound (DA-13) Compound (DA-13) was synthesized in the same manner as in the synthesis of (DA-11), except that 4-nitroaniline was used instead of 2-amino-5-nitropyridine as the starting material.

7. Synthesis of Compound (TA-1) 11.5 g (0.1 mol) of 3-aminodihydrofuran-2,5-dione, 7.9 g (0.1 mol) of pyridine, and 300 ml of tetrahydrofuran were added to a reaction vessel. The reaction solution was cooled to 0°C in an ice bath, and a solution of 7.6 g (0.05 mol) of fumaryl chloride dissolved in 50 ml of tetrahydrofuran was added dropwise thereto. After the dropwise addition was completed, the mixture was stirred at room temperature for 4 hours. After the reaction, the solvent was removed under reduced pressure. Subsequently, 50 g of acetic acid and 50 g of acetic anhydride were added, and the mixture was stirred at 100°C for 3 hours. The resulting precipitate was collected by filtration, washed with acetic acid and normal hexane, and then dried under reduced pressure at 60°C for 5 hours to obtain Compound (TA-1).

8. Synthesis of Compound (TA-2) Compound (TA-2) was synthesized in the same manner as in the synthesis of compound (TA-1), except that 5-hydroxyisobenzofuran-1,3-dione was used instead of 3-aminodihydrofuran-2,5-dione as the starting material.

9. Synthesis of Compound (TA-3) To a reaction vessel, 19.6 g (0.2 mol) of maleic anhydride and 100 ml of acetic acid were added. A solution of 5.0 g (0.1 mol) of hydrazine monohydrate dissolved in 25 ml of acetic acid was added dropwise. During the dropwise addition, the reaction temperature was controlled using an ice bath to prevent the reaction solution from exceeding 25°C. After the dropwise addition, the mixture was left to stand for 3 hours, and the precipitate was collected by filtration and washed three times with 30 ml of ethanol. This was then dried at 60°C for 5 hours to obtain 21 g of a pale yellow solid. The resulting solid was transferred to a reaction vessel, and 110 ml of thionyl chloride was added, followed by stirring at 75°C for 6 hours. After the reaction, the mixture was cooled to room temperature, and the precipitate was collected by filtration. The precipitate was washed with hexane and dried at 60°C for 5 hours to obtain 10 g (0.05 mol) of compound (D-1). The obtained compound (D-1) was dissolved in 50 ml of N-methyl-2-pyrrolidone, and 11.5 g (0.1 mol) of 3-aminodihydrofuran-2,5-dione was added dropwise over 30 minutes. After the addition was completed, the mixture was stirred at room temperature for 4 hours. After the reaction, the solvent was removed under reduced pressure. Subsequently, 50 g of acetic acid and 50 g of acetic anhydride were added, and the mixture was stirred at 100°C for 3 hours. The obtained precipitate was collected by filtration, washed with acetic acid and normal hexane, and then dried under reduced pressure at 60°C for 5 hours to obtain compound (TA-3). Note that compound (TA-3) is a cis-isomer.

<Synthesis of Polymer>
1. Synthesis of polyamic acid [Synthesis Example 1]
100 parts by mole of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (compound (TB-1)) as a tetracarboxylic dianhydride and 100 parts by mole of compound (DA-2) as a diamine compound were dissolved in N-methyl-2-pyrrolidone (NMP), and the mixture was allowed to react at room temperature for 6 hours, thereby obtaining a solution containing 15% by mass of polyamic acid (referred to as polymer (PAA-1)).

The polymer (PAA-1) can also be obtained by polymerizing the intermediate compound (D-1) without using the isolated compound (DA-2). Different methods for synthesizing the polymer (PAA-1) are shown below.
[Alternative synthesis of PAA-1]
100 parts by mole of compound (D-1) was dissolved in N-methyl-2-pyrrolidone, and 200 parts by mole of 2-(4-aminophenyl)ethylamine was added dropwise over 30 minutes. After the dropwise addition, the mixture was stirred at room temperature for 1 hour. Thereafter, 100 parts by mole of 1,2,3,4-cyclobutanetetracarboxylic dianhydride was added as a tetracarboxylic dianhydride, and the mixture was reacted at room temperature for 6 hours to obtain a solution containing 15% by mass of polymer (PAA-1).

[Synthesis Examples 2 to 24]
Polyamic acids (polymers (PAA-2) to (PAA-20) and polymers (paa-1) to (paa-4)) were obtained by the same procedure as in Synthesis Example 1, except that the types and amounts of the tetracarboxylic dianhydrides and diamine compounds used were changed as shown in Table 1. In Table 1, the numerical values for the tetracarboxylic dianhydrides (acid dianhydrides 1 and 2) represent the ratio (molar ratio) of each compound relative to 100 parts by mole of the total amount of the tetracarboxylic dianhydrides used in the synthesis of the polyamic acid. The numerical values for the diamine compounds (diamines 1 to 3) represent the ratio (molar ratio) of each compound relative to 100 parts by mole of the total amount of the diamine compounds used in the synthesis of the polyamic acid.

2. Synthesis of polyimide [Synthesis Example 25]
60 parts by mole of compound (TB-1) and 40 parts by mole of compound (TB-3) as tetracarboxylic dianhydrides, and 20 parts by mole of compound (DA-2), 60 parts by mole of compound (DB-2), and 20 parts by mole of compound (DB-3) as diamine compounds were dissolved in NMP, and the reaction was carried out at room temperature for 6 hours to obtain a solution containing 15% by mass of polyamic acid. Next, NMP was added to the obtained polyamic acid solution to obtain a solution with a polyamic acid concentration of 10% by mass, and pyridine and acetic anhydride were added, and a dehydration ring-closing reaction was carried out at 60°C for 4 hours. After the dehydration ring-closing reaction, the solvent in the system was replaced with fresh NMP to obtain a solution containing 15% by mass of polyimide (referred to as polymer (PI-1)) with an imidization rate of approximately 80%.

[Synthesis Examples 26 to 30]
Polyimides (polymers (PI-2), (PI-3), and (PI-1) to (PI-3)) were obtained by the same procedure as in Synthesis Example 25, except that the types and amounts of the tetracarboxylic dianhydrides and diamine compounds used were changed as shown in Table 2. In Table 2, the numerical values for the tetracarboxylic dianhydrides (acid dianhydrides 1 to 3) represent the ratio (molar ratio) of each compound relative to 100 parts by mole of the total amount of the tetracarboxylic dianhydrides used in the synthesis of the polyimide. The numerical values for the diamine compounds (diamines 1 to 4) represent the ratio (molar ratio) of each compound relative to 100 parts by mole of the total amount of the diamine compounds used in the synthesis of the polyimide.

3. Synthesis of polyorganosiloxane [Synthesis Example 31]
A 1000 ml three-neck flask was charged with 100.0 g of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (compound (s-1)), 500 g of methyl isobutyl ketone, and 10.0 g of triethylamine, and mixed at room temperature. Next, 100 g of deionized water was added dropwise from the dropping funnel over 30 minutes, and the mixture was then mixed under reflux at 80 ° C. for 6 hours while reacting. After completion of the reaction, the organic layer was removed and washed with a 0.2 mass% aqueous ammonium nitrate solution until the water after washing was neutral, and then the solvent and water were distilled off under reduced pressure. An appropriate amount of methyl isobutyl ketone was added to obtain a 50 mass% solution of polymer (ESSQ-1), which is a polyorganosiloxane having epoxy groups.
In a 500 ml three-neck flask, 3.10 g of compound (c-1) (20 mol% relative to the amount of epoxy groups in the polymer (ESSQ-1)), 3.24 g of compound (c-2) (10 mol% relative to the amount of epoxy groups in the polymer (ESSQ-1)), 1.00 g of tetrabutylammonium bromide, 20.0 g of the polymer (ESSQ-1)-containing solution, and 290.0 g of methyl isobutyl ketone were added and stirred at 90 ° C. for 18 hours. After cooling to room temperature, the separation and washing operation with distilled water was repeated 10 times. Thereafter, the organic layer was recovered, concentrated using a rotary evaporator and diluted with NMP twice, and then adjusted to a solids concentration of 10% by mass using NMP to obtain an NMP solution of polyorganosiloxane (this is referred to as polymer (PSQ-1)).

4. Synthesis of styrene-maleimide copolymer [Synthesis Example 32]
Under nitrogen, 5.00 g of compound (M-1), 1.05 g of compound (M-2), 4.80 g of compound (M-3), and 2.26 g of compound (M-4) were added as polymerization monomers to a 100 mL two-neck flask, 0.39 g of 2,2'-azobis(2,4-dimethylvaleronitrile) as a radical polymerization initiator, 0.39 g of 2,4-diphenyl-4-methyl-1-pentene as a chain transfer agent, and 52.5 ml of N-methyl-2-pyrrolidone (NMP) as a solvent, and polymerization was carried out for 6 hours at 70°C. After reprecipitation in methanol, the precipitate was filtered and dried in vacuum at room temperature for 8 hours to obtain the target polymer (referred to as polymer (MI-1)).

5. Synthesis of polyamide [Synthesis Example 33]
The synthesis was carried out with reference to the method described in the reference document (Journal of Polymer Science: Polymer Chemistry Edition 1975, Vol. 13, 1691-1698). 100 parts by mole of compound (D-1) as a biisomaleimide and 100 parts by mole of compound (DB-18) as a diamine compound were dissolved in N-methyl-2-pyrrolidone (NMP), and the reaction was carried out at room temperature for 6 hours to obtain a solution containing 15% by mass of polyamide (referred to as polymer (pa-1)).

<Evaluation as a polymer>
Example 1: Evaluation of residual amine and storage stability
1. Evaluation of Residual Amine A solution of the polymer (PAA-1) obtained in Synthesis Example 1 was added dropwise to acetone to precipitate the polymer. A portion of the supernatant was removed and evaluated by liquid chromatography (LC). When a peak of the diamine used as a raw material was observed, it was rated as "present," and when it was not observed, it was rated as "absent." As a result, the residual amine peak in Example 1 was "absent."

2. Evaluation of Storage Stability With regard to the solution of polymer (PAA-1) obtained in Synthesis Example 1, the storage stability was evaluated based on the rate of change ([(D2-D1)/D1)] x 100(%)) between the solution viscosity D1 immediately after preparation of the polymer solution and the solution viscosity D2 after storage at room temperature for 7 days. A rate of change in viscosity of 5% or more was evaluated as "poor (x)," and a rate of change in viscosity of less than 5% was evaluated as "good (○)." As a result, the storage stability of Example 1 was evaluated as "good (○)."

[Reference example 1]
The residual amine content and storage stability were evaluated in the same manner as in Example 1, except that the polymer was changed as shown in Table 3. The results are shown in Table 3.

As shown in Table 3, polymer (PAA-1) had less residual amine than polyamide polymer (pa-1), and exhibited good storage stability as a solution.

<Preparation and Evaluation of Liquid Crystal Alignment Agent>
[Example 2: Rubbed FFS-type liquid crystal display element]
1. Preparation of liquid crystal aligning agent The solution of the polymer (PAA-2) obtained in Synthesis Example 2 was diluted with NMP and butyl cellosolve (BC) to prepare a solution with a solvent composition of NMP/BC = 80/20 (mass ratio) and a solid content concentration of 3.5 mass %. This solution was filtered through a filter with a pore size of 0.2 μm to prepare a liquid crystal aligning agent (AL-1).

2. Fabrication of FFS-Mode Liquid Crystal Display Element Using Rubbing Method A glass substrate (referred to as the first substrate) with a flat electrode (bottom electrode), an insulating layer, and a comb-shaped electrode (top electrode) laminated in this order on one side, and a glass substrate (referred to as the second substrate) without an electrode, were prepared. Next, a liquid crystal alignment agent (AL-1) was applied to the electrode-formed surface of the first substrate and one side of the second substrate using a spinner, and heated (pre-baked) on a hot plate at 110°C for 3 minutes. This was then dried (post-baked) for 30 minutes in a nitrogen-purged oven at 230°C, forming a coating film with an average film thickness of 0.08 μm. Next, the coating film surface was rubbed using a rubbing machine equipped with a roll wrapped around a rayon cloth at a roll rotation speed of 1000 rpm, a stage movement speed of 3 cm/sec, and a pile indentation length of 0.3 mm. Thereafter, the substrate was subjected to ultrasonic cleaning in ultrapure water for 1 minute, and then dried in a clean oven at 100° C. for 10 minutes to obtain a pair of substrates having a liquid crystal alignment film.
Next, a pair of substrates with liquid crystal alignment films were screen-printed with an epoxy resin adhesive containing 3.5 μm diameter aluminum oxide spheres, leaving a liquid crystal injection port at the edge of the surface where the liquid crystal alignment film was formed. The substrates were then superimposed and pressed together, and the adhesive was thermally cured at 150°C for 1 hour. Next, negative liquid crystal (MLC-6608, manufactured by Merck) was filled into the gap between the pair of substrates through the liquid crystal injection port, which was then sealed with an epoxy adhesive. Furthermore, to eliminate flow alignment during liquid crystal injection, the substrate was heated at 120°C and then slowly cooled to room temperature to produce a liquid crystal cell. When the pair of substrates were superimposed, the rubbing directions of the respective substrates were antiparallel.

3. Evaluation of Liquid Crystal Alignment The liquid crystal cell manufactured in 2. above was left standing for 500 hours in front of a high-brightness backlight of 27,000 cd/ ^m² , and the liquid crystal alignment was evaluated by the rate of change in retardation before and after backlight irradiation. First, the retardation of the liquid crystal display element manufactured in 2. above was measured using an Axoscan manufactured by Optoscience, and the rate of change α of retardation before and after backlight irradiation was calculated using the following formula (z-1). The smaller the rate of change α, the better the liquid crystal alignment. When the rate of change α was 1% or less, it was rated as "good (○)", when it was greater than 1% and less than 2% it was rated as "fair (△)", and when it was greater than 2% it was rated as "poor (×)".
α=Δθ/θ1...(z-1)
(In formula (z-1), Δθ represents the difference in retardation before and after irradiation, and θ1 represents the retardation value before irradiation.)
As a result, the liquid crystal alignment property of this example was evaluated as "good (◯)".

4. Evaluation of Initial VHR The liquid crystal cell manufactured in 2. above was placed in an oven at 60°C, and then the voltage holding ratio (VHR) was measured under conditions of 1 V and 1670 msec using a VHR measuring device "VHR-1" manufactured by Toyo Corporation. The evaluation criteria were as follows: if the VHR was higher than 70%, it was rated "good (○)", if it was 70% or less and 60% or more, it was rated "fair (△)", and if it was less than 60%, it was rated "poor (×)". As a result, the initial VHR of this example was rated "good (○)".

5. Evaluation of VHR Reliability The reliability (VHR reliability) of the liquid crystal cells manufactured in Section 2 above was evaluated based on the voltage holding ratio. The evaluation was performed as follows. First, a voltage of 1 V was applied to the liquid crystal cell for 60 microseconds, and then the voltage holding ratio (VHR1) was measured 1670 milliseconds after the application was removed. Next, the liquid crystal cell was irradiated with a CCFL (backlight) at 60°C for one week, and then left to cool naturally to room temperature. After cooling, a voltage of 1 V was applied to the liquid crystal cell for 60 microseconds, and then the voltage holding ratio (VHR2) was measured 1670 milliseconds after the application was removed. The measurement device used was a VHR measuring device "VHR-1" manufactured by Toyo Corporation. The rate of change in VHR (ΔVHR) at this time was calculated as the difference between VHR1 and VHR2 (ΔVHR = VHR1 - VHR2), and VHR reliability was evaluated based on ΔVHR. When ΔVHR was less than 15%, it was judged as "good (◯)", when it was 15% or more and 20% or less it was judged as "fair (△)", and when it was more than 20%, it was judged as "poor (×)". As a result, in this example, the VHR reliability was "good (◯)".

6. Evaluation of Film Strength (Rubbing Resistance) The liquid crystal alignment agent (AL-1) prepared in 1 above was applied to a glass substrate using a spinner and heated (pre-baked) on a hot plate at 110 ° C. for 3 minutes. The substrate was then dried (post-baked) for 30 minutes in a 230 ° C. oven with the interior substituted with nitrogen, forming a coating film with an average film thickness of 0.08 μm. The haze value of this coating film was measured using a hazemeter. Next, the coating film was subjected to rubbing treatment five times using a rubbing machine with a roll wrapped around a cotton cloth at a roll rotation speed of 1000 rpm, a stage movement speed of 3 cm/sec, and a pile indentation length of 0.3 mm. The haze value of the liquid crystal alignment film was then measured using a haze meter, and the difference from the haze value before and after rubbing treatment (haze change value) was calculated. When the haze value of the film before rubbing treatment is Hz1 (%) and the haze value of the film after rubbing treatment is Hz2 (%), the haze change value is expressed by the following formula (z-2).
Haze change value (%) = Hz2 - Hz1 ... (z-2)
When the haze change value of the liquid crystal alignment film was less than 0.5, it was evaluated as "best (◎)", when the haze change value was 0.5 or more and less than 1.0, it was evaluated as "good (○)", when the haze change value was 1.0 or more and 1.5 or less, it was evaluated as "fair (△)", and when it was more than 1.5, it was evaluated as "poor (×)". If the haze change value is 1.5 or less (more preferably less than 1.0, even more preferably less than 0.5), it can be said that the film strength is sufficiently high and the rubbing resistance is high, that is, the mechanical properties of the film are good. As a result, in this example, the film strength was evaluated as "good (○)".

7. Evaluation of Film Strength (Keying Test Resistance) The keying test resistance of the liquid crystal cell produced in 2. above was evaluated. The evaluation was performed as follows. First, the liquid crystal cell was observed under a polarizing microscope with crossed Nicols, and the number of bright spots was counted. Next, the liquid crystal cell was fixed on a fixed plate, and a keying rod was moved up and down to apply a repeated load to the liquid crystal cell. The load was 250 gf, the number of repetitions was 100,000, and the speed was 10 Hz/sec. After keying, the liquid crystal cell was observed again, and the number of bright spots was counted. If the difference in the number of bright spots before and after keying was less than 5, it was evaluated as "best (◎)," if it was 5 to 10, it was evaluated as "good (○)," if it was 10 to 50, it was evaluated as "fair (△)," and if it was 50 or more, it was evaluated as "poor (×)." If the difference in the number of bright spots was less than 10 (more preferably less than 5), it can be said that the mechanical strength of the film against keying was good. As a result, in this example, the film strength was evaluated as "good (○)."

[Examples 2 to 15 and Comparative Examples 2 and 3]
A liquid crystal alignment agent was prepared in the same manner as in Example 2, except that the composition of the liquid crystal alignment agent was changed as shown in Table 4. Furthermore, using the obtained liquid crystal alignment agent, an FFS-type liquid crystal cell was produced by a rubbing method in the same manner as in Example 2, and various evaluations were performed. The results are shown in Table 4. In Examples 3, 4, 7, and 12 to 15, two types of polymers were used as the polymer component. In Table 4, the numerical values in the polymer column represent the blending ratio (parts by mass) of the solid content of each polymer relative to 100 parts by mass of the total amount of the polymer components used in preparing the liquid crystal alignment agent.

As shown in Table 4, Examples 2 to 15, which used a liquid crystal alignment agent containing polymer [A], achieved good or even the best results in film strength, particularly in the keystroke test resistance, compared to Comparative Examples 2 and 3, which used a liquid crystal alignment agent that did not contain polymer [A]. Furthermore, Examples 2 to 15 also demonstrated good liquid crystal alignment, initial VHR, and VHR reliability.

[Example 16: Optical FFS-type liquid crystal display element]
1. Preparation of Liquid Crystal Alignment Agent A solution containing 30 parts by mass of the polymer (PAA-15) obtained in Synthesis Example 15 and a solution containing 70 parts by mass of the polymer (paa-2) obtained in Synthesis Example 18 were mixed and diluted with NMP and BC to obtain a solution with a solvent composition of NMP/BC = 80/20 (mass ratio) and a solids concentration of 3.5 mass%. This solution was filtered through a filter with a pore size of 0.2 μm to prepare a liquid crystal alignment agent (AL-17).

2. Fabrication of FFS-Type Liquid Crystal Display Element Using Photo-Alignment Method The same first and second substrates as in Example 1 were prepared. Next, a liquid crystal alignment agent (AL-17) was applied to the electrode-forming surface of the first substrate and one of the substrate surfaces of the second substrate using a spinner and pre-baked on a hot plate at 80°C for 1 minute. This was then dried (post-baked) for 30 minutes in a nitrogen-purged oven at 230°C, forming a coating film with an average thickness of 0.1 μm. The resulting coating film was subjected to a photo-alignment treatment by irradiating it with 1,000 J/ ^m² of linearly polarized ultraviolet light containing a 254 nm emission line from an Hg-Xe lamp in the direction normal to the substrate. Note that this exposure dose was measured using an actinometer measuring at a wavelength of 254 nm. The photo-aligned coating film was then heat-treated in a clean oven at 230°C for 30 minutes to form a liquid crystal alignment film.
Next, for one of the pair of substrates with a liquid crystal alignment film, an epoxy resin adhesive containing 3.5 μm diameter aluminum oxide spheres was applied by screen printing to the outer edge of the surface bearing the liquid crystal alignment film. The substrates were then superimposed and pressed together so that the projection direction of the polarization axis onto the substrate surface during light irradiation was antiparallel, and the adhesive was thermally cured at 150°C for 1 hour. Next, a negative liquid crystal (MLC-6608, manufactured by Merck) was filled between the pair of substrates through the liquid crystal injection port, which was then sealed with an epoxy adhesive to obtain a liquid crystal cell. Furthermore, to eliminate flow alignment during liquid crystal injection, the cell was heated to 120°C and then slowly cooled to room temperature. Furthermore, by performing the above series of operations, varying the UV exposure dose after post-baking between 100 and 10,000 J/ ^m² , three or more liquid crystal cells with different UV exposure doses were produced. The liquid crystal cell with the exposure dose that showed the best alignment characteristics (optimal exposure dose) was used for the following evaluations of liquid crystal alignment, initial VHR, VHR reliability, and film strength.

3. Evaluation The liquid crystal cells produced in 2. above were evaluated for liquid crystal alignment property, initial VHR, and VHR reliability in the same manner as in Example 2. In addition, the film strength was evaluated in the same manner as in Example 2 using a liquid crystal alignment agent (AL-17). The evaluation results are shown in Table 5.

[Examples 17 to 23, Comparative Examples 4 and 5]
A liquid crystal aligning agent was prepared in the same manner as in Example 16, except that the composition of the liquid crystal aligning agent was changed as shown in Table 5. Furthermore, using the obtained liquid crystal aligning agent, an FFS-type liquid crystal cell was produced by a photoalignment method in the same manner as in Example 16, and various evaluations were performed. The results are shown in Table 5. In Example 23 and Comparative Example 5, N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane (referred to as compound (N-1)) was blended as an additive component together with the polymer component. In Table 5, the numerical values in the "Polymer" column represent the blending ratio (parts by mass) of the solid content of each polymer relative to 100 parts by mass of the total amount of the solid content (polymer component and additive component) used in the preparation of the liquid crystal aligning agent. The numerical values in the "Additive" column represent the blending ratio (parts by mass) of the solid content of compound (N-1) relative to 100 parts by mass of the total amount of the solid content (polymer component and additive component) used in the preparation of the liquid crystal aligning agent.

As shown in Table 5, Examples 16 to 23, which used a liquid crystal alignment agent containing polymer [A], achieved good or even the best results in film strength, particularly in keystroke test resistance, compared to Comparative Examples 4 and 5, which used a liquid crystal alignment agent not containing polymer [A], and demonstrated well-balanced performance in terms of liquid crystal alignment, initial VHR, and VHR reliability.

[Example 24: PSA type liquid crystal display element]
1. Preparation of Liquid Crystal Alignment Agent A solution containing 5 parts by mass of the polymer (PSQ-1) obtained in Synthesis Example 31 and a solution containing 95 parts by mass of the polymer (PI-3) obtained in Synthesis Example 27 were mixed and diluted with NMP and BC to obtain a solution with a solvent composition of NMP/BC = 50/50 (mass ratio) and a solids concentration of 3.5 mass%. This solution was filtered through a filter with a pore size of 0.2 μm to prepare a liquid crystal alignment agent (AL-27).

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 nematic liquid crystal (MLC-6608, manufactured by Merck) and mixed to obtain liquid crystal composition LC1.

3. Manufacturing of PSA-Type Liquid Crystal Display Element The liquid crystal alignment agent (AL-27) prepared above was applied to the transparent electrode surface of a glass substrate with a transparent electrode made of an ITO film using a spinner. After pre-baking for 1 minute on a hot plate at 80°C, the substrate was heated at 200°C for 1 hour in a nitrogen-substituted oven to remove the solvent, forming a coating film (liquid crystal alignment film) with a thickness of 0.08 μm. This coating film was subjected to a rubbing treatment using a rubbing machine equipped with a roll wrapped around a rayon cloth at a roll rotation speed of 400 rpm, a stage movement speed of 3 cm/sec, and a pile indentation length of 0.1 mm. The substrate was then subjected to ultrasonic cleaning in ultrapure water for 1 minute, followed by drying for 10 minutes in a 100°C clean oven to obtain a substrate with a liquid crystal alignment film. This operation was repeated to obtain a pair (two substrates) with a liquid crystal alignment film. Note that this rubbing treatment was a weak rubbing treatment performed to control liquid crystal collapse and easily achieve alignment division.
An epoxy resin adhesive containing aluminum oxide spheres with a diameter of 3.5 μm was applied by screen printing to the outer periphery of the surface of one of the substrates having a liquid crystal alignment film, and then the liquid crystal alignment film surfaces of the pair of substrates were placed facing each other, overlapped, and pressed together, and the adhesive was thermally cured by heating for 1 hour at 150° C. Next, liquid crystal composition LC1 was filled into the gap between the substrates through the liquid crystal injection port, which was then sealed with an epoxy adhesive. To prevent flow alignment during liquid crystal injection, the resulting mixture was heated at 150° C. for 10 minutes and then slowly cooled to room temperature.
Next, a 10 V AC voltage with a frequency of 60 Hz was applied between the electrodes of the resulting liquid crystal cell. While the liquid crystal was in a driving state, the cell was irradiated with ultraviolet light at a dose of 50,000 J/ ^m² using an ultraviolet irradiation device with a metal halide lamp as the light source. Note that this dose was measured using an actinometer measuring at a wavelength of 365 nm. This resulted in the production of a PSA-type liquid crystal cell.

4. Evaluation The liquid crystal cells produced in the above 3. were evaluated for liquid crystal alignment, initial VHR, VHR reliability, and film strength in the same manner as in Example 2. The evaluation results are shown in Table 6.

[Comparative Example 6]
A liquid crystal alignment agent was prepared in the same manner as in Example 24, except that the composition of the liquid crystal alignment agent was changed as shown in Table 6. Furthermore, a PSA type liquid crystal cell was produced using the obtained liquid crystal alignment agent in the same manner as in Example 24, and various evaluations were carried out. The evaluation results are shown in Table 6. In Table 6, the numerical values in the polymer column represent the blending ratio (parts by mass) of the solid content of each polymer relative to 100 parts by mass of the total amount of the polymer components used in the preparation of the liquid crystal alignment agent.

As shown in Table 6, Example 24, which used a liquid crystal alignment agent containing polymer [A], was rated as good for liquid crystal alignment, initial VHR, and VHR reliability, and was rated as best for film strength. In contrast, Comparative Example 6, which used a liquid crystal alignment agent not containing polymer [A], was rated as "fair" for film strength (rubbing resistance) and "poor" for film strength (keystroke test resistance).

[Example 25: Optical VA type liquid crystal display element]
1. Preparation of Liquid Crystal Alignment Agent A solution containing 30 parts by mass of the polymer (MI-1) obtained in Synthesis Example 32 and 70 parts by mass of the polymer (PAA-14) obtained in Synthesis Example 14 was mixed and diluted with NMP and BC to obtain a solution with a solvent composition of NMP/BC = 80/20 (mass ratio) and a solids concentration of 3.5 mass%. This solution was filtered through a filter with a pore size of 0.2 μm to prepare a liquid crystal alignment agent (AL-29).

2. Fabrication of an Optical VA-Type Liquid Crystal Display Element The liquid crystal alignment agent (AL-29) prepared above was applied to the transparent electrode surface of a glass substrate with a transparent electrode made of an ITO film using a spinner and pre-baked on a hot plate at 80°C for 1 minute. The substrate was then heated at 230°C for 1 hour in an oven with the interior purged with nitrogen to form a coating film with a thickness of 0.1 μm. Next, the surface of this coating film was irradiated with 1,000 J/ ^m² of polarized ultraviolet light containing a 313 nm emission line using an Hg-Xe lamp and a Glan-Taylor prism from a direction tilted 40° from the substrate normal to impart liquid crystal alignment ability. The same procedure was repeated to prepare a pair (two substrates) with liquid crystal alignment films.
An epoxy resin adhesive containing 3.5 μm diameter aluminum oxide spheres was applied by screen printing to the outer periphery of the surface of one of the substrates bearing the liquid crystal alignment film. The pair of substrates were then placed with the liquid crystal alignment film surfaces facing each other and pressed together so that the projection directions of the ultraviolet light axes of each substrate onto the substrate surface were antiparallel. The adhesive was then thermally cured at 150°C for 1 hour. Next, negative liquid crystal (MLC-6608, manufactured by Merck) was filled into the gap between the substrates through the liquid crystal injection port, which was then sealed with an epoxy adhesive. Furthermore, to eliminate flow alignment during liquid crystal injection, the substrate was heated at 130°C and then slowly cooled to room temperature.

3. Evaluation The liquid crystal cells produced in 2. above were evaluated for liquid crystal alignment, initial VHR, VHR reliability, and film strength in the same manner as in Example 2. The evaluation results are shown in Table 7.

[Comparative Example 7]
A liquid crystal alignment agent was prepared in the same manner as in Example 25, except that the composition of the liquid crystal alignment agent was changed as shown in Table 7. In addition, an optical VA-type liquid crystal cell was produced using the obtained liquid crystal alignment agent in the same manner as in Example 25, and various evaluations were performed. The results are shown in Table 7. In Table 7, the numerical values in the polymer column represent the blending ratio (parts by mass) of the solid content of each polymer relative to 100 parts by mass of the total amount of the polymer components used in the preparation of the liquid crystal alignment agent.

As shown in Table 7, Example 25, which used a liquid crystal alignment agent containing polymer [A], was rated as good for liquid crystal alignment, initial VHR, and VHR reliability, and was rated as best for film strength. In contrast, Comparative Example 7, which used a liquid crystal alignment agent not containing polymer [A], was rated as "fair" for film strength (rubbing resistance) and "poor" for film strength (keystroke test resistance).

These results demonstrate that a liquid crystal alignment agent containing a polymer having partial structure (a) in its main chain not only provides good liquid crystal alignment, a high voltage holding ratio, and a highly reliable liquid crystal device, but also provides high cured film strength.

Claims (11)

A liquid crystal aligning agent comprising a polymer [A] having a partial structure (a) represented by the following formula (1) in its main chain:
(In formula (1), R ¹ and R ² are each independently —C(R ⁵ )(R ⁶ )—, —O—, —S—, —CO—, —COO—, —NR ⁷ —, —NR ⁷ —NR ⁸ —, —NR 7 —CO—O—, —NR ⁷ —CO—NR ⁸ —, an aromatic hydrocarbon ring, an aromatic heterocycle, or a nitrogen-containing non-aromatic heterocycle, and are a divalent group bonded to the carbonyl ^group in formula (1). R ³ and R ⁴ are each independently a hydrogen atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms, or R ³ and R ⁴ taken together represent a ring structure formed with the carbon to which R ³ is bonded and the carbon to which R ⁴ is bonded. R ⁵ and R ⁶ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, a ^R7 and ^R8 are each independently a hydrogen atom or a monovalent organic group. "*" represents a bond. The liquid crystal aligning agent according to claim 1, wherein the polymer [A] contains a structural unit derived from a diamine having the partial structure (a). The liquid crystal aligning agent according to claim 2 , wherein the diamine is a compound represented by the following formula (2):
(In formula (2), ^A1 and ^A2 each independently represent a single bond, a divalent alicyclic group, or a divalent aromatic ring group. m1 is an integer of 1 to 3. ^R1 , ^R2 , ^R3 , and ^R4 have the same meanings as in formula (1) above. When m1 is 2 or 3, multiple ^R1 to ^R4 are the same as or different from one another.) The liquid crystal aligning agent according to claim 1, wherein the polymer [A] contains a structural unit derived from a tetracarboxylic acid derivative having the partial structure (a). The liquid crystal aligning agent according to claim 4, wherein the tetracarboxylic acid derivative is at least one selected from the group consisting of compounds represented by the following formula (3) and compounds represented by the following formula (4):
(In formula (3) and formula (4), ^A3 and ^A4 each independently represent a trivalent aromatic ring group or aliphatic ring group. m2 is an integer of 1 to 3. n1 and n2 each independently represent an integer of 1 to 3. ^R1 , ^R2 , ^R3 , and ^R4 have the same meanings as in formula (1) above. When m2 is 2 or 3, multiple ^R1 to ^R4 are the same as or different from one another.) The liquid crystal aligning agent according to claim 1, wherein the polymer [A] is at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide. The liquid crystal aligning agent according to claim 6, wherein the polymer [A] contains structural units derived from an alicyclic tetracarboxylic dianhydride. The liquid crystal aligning agent according to claim 1, further comprising a polymer [Q] that does not have the partial structure (a). A liquid crystal alignment film formed using the liquid crystal alignment agent according to any one of claims 1 to 8. A liquid crystal element comprising the liquid crystal alignment film according to claim 9. A polyamic acid, a polyamic acid ester, and a polyimide each having a partial structure represented by the following formula (1) in the main chain:
(In formula (1), R ¹ and R ² are each independently —C(R ⁵ )(R ⁶ )—, —O—, —S—, —CO—, —COO—, —NR ⁷ —, —NR ⁷ —NR ⁸ —, —NR 7 —CO—O—, —NR ⁷ —CO—NR ⁸ —, an aromatic hydrocarbon ring, an aromatic heterocycle, or a nitrogen-containing non-aromatic heterocycle, and are a divalent group bonded to the carbonyl ^group in formula (1). R ³ and R ⁴ are each independently a hydrogen atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms, or R ³ and R ⁴ taken together represent a ring structure formed with the carbon to which R ³ is bonded and the carbon to which R ⁴ is bonded. R ⁵ and R ⁶ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, a ^R7 and ^R8 are each independently a hydrogen atom or a monovalent organic group. "*" represents a bond.