Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal element

Abstract

This invention provides a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal element. The liquid crystal alignment agent can produce a liquid crystal element with good liquid crystal alignment, good DC accumulation characteristics and DC mitigation characteristics, and is less prone to image retention. A liquid crystal alignment agent contains a polymer P. Polymer P contains one or more partial structures U2-1, U2-2, and U2-3 and a partial structure U1 within the same molecule, and molecules containing partial structure U1 contain two or more partial structures U2-1, U2-2, and U2-3 within the same molecule or in different molecules. Partial structure U1 has a partial structure formed by removing two hydrogen atoms from the structure represented by formula (Y-1). Partial structure U2-1 contains a chain hydrocarbon structure and adjacent partial structures such as "* 1-NR 1-CO-". Partial structure U2-2 has a carboxylic acid group or a sulfonic acid group. Partial structure U2-3 has a nitrogen-containing heterocycle.

Description

[Technical Field]

[0001] This invention relates to a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal element. [Previous Technology]

[0002] Liquid crystal elements are used in a wide range of applications, from relatively large display devices such as LCD TVs or information displays to small display devices such as smartphones. The performance of a liquid crystal element is determined by various characteristics such as the alignment or pretilt angle of the liquid crystal and the voltage holding rate. In order to improve the performance of liquid crystal elements, improvements have been made to the liquid crystal alignment film used to align the liquid crystals in a certain direction.

[0003] When a voltage is applied to a liquid crystal element and charge accumulates within the liquid crystal cell, it is sometimes perceived by the observer as a residual image (direct current (DC) image), which degrades the display quality of the liquid crystal element. Therefore, as one of the required characteristics of liquid crystal alignment films, low charge accumulation is one such characteristic.

[0004] Therefore, various techniques for suppressing charge accumulation within liquid crystal cells and improving the display quality of liquid crystal elements have been proposed in the past (for example, see Patent Document 1 or Patent Document 2). Patent Document 1 discloses a method for reducing accumulated charge by reacting a polyamide compound containing a nitrogen-containing diamine, such as N4,N4'-bis(4-aminophenyl)-benzidine, with a tetracarboxylic acid dianhydride to a liquid crystal alignment agent. Patent Document 2 discloses a method for obtaining a liquid crystal alignment film with moderate and rapid charge accumulation by containing a polymer of a diamine having a structure in which a carbazole structure and a benzene ring are bonded through an amino group in a liquid crystal alignment agent. [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2008-107811 [Patent Document 2] International Publication No. 2018 / 110354 [Summary of the Invention]

[0006] [Problem to be Solved by the Invention] With the increasing demand for higher quality liquid crystal elements, there is a need to develop a liquid crystal element that is less prone to image retention. In order to suppress image retention and achieve higher quality liquid crystal elements, it is required that even when a voltage is applied, charge is not easily accumulated in the liquid crystal cells (hereinafter also referred to as "DC accumulation characteristic") and that the accumulated charge can be quickly mitigated (hereinafter also referred to as "DC mitigation characteristic"). In addition, in order to obtain a high-quality liquid crystal element, it is ideal to maintain good liquid crystal alignment, which is one of the basic characteristics of liquid crystal elements, while also having good DC accumulation characteristic and DC mitigation characteristic.

[0007] This invention was made in view of the aforementioned problems, and one of its objectives is to provide a liquid crystal alignment agent that can produce a liquid crystal element with good liquid crystal alignment, good DC accumulation characteristics and DC mitigation characteristics, and is less prone to image retention. [Technical Means for Solving the Problem]

[0008] The following means can be provided by the present invention.

[0009] <1> A liquid crystal alignment agent comprising a polymer (P), wherein the polymer (P) comprises any one or more of the partial structures represented by formula (1) and formula (2), formula (3) and formula (4) within the same molecule, and the molecules comprising the partial structures represented by formula (1) comprise any two or more of the partial structures represented by formula (2), formula (3) and formula (4) within the same molecule or in different molecules. [Chemistry 1] (In formula (1), X1 is a tetravalent organic group; Y1 is a divalent organic group having a partial structure obtained by removing two hydrogen atoms from the structure represented by formula (Y-1) below) [Chemistry 2] (In formula (Y-1), A1 and A2 are each independently a monovalent group having an aromatic hydrocarbon ring and the aromatic hydrocarbon ring is bonded to the nitrogen atom in formula (Y-1), or represent a nitrogen-containing condensed heterocyclic structure formed by A1 and A2 combined with each other and the nitrogen atoms bonded to A1 and A2; A3 is a hydrogen atom or a monovalent organic group; wherein, in the case that A1 and A2 represent a nitrogen-containing condensed heterocyclic structure formed by A1 and A2 combined with each other and the nitrogen atoms bonded to A1 and A2, the nitrogen-containing condensed heterocyclic structure has two or more aromatic hydrocarbon rings, and the two aromatic hydrocarbon rings of the nitrogen-containing condensed heterocyclic structure have a fused ring structure bonded by sharing the nitrogen atom in formula (Y-1), or A3 has an aromatic hydrocarbon ring and A 3. The aromatic hydrocarbon rings of the compound are bonded to the nitrogen atoms in formula (Y-1) [Chemical 3] (In formulas (2), (3) and (4), X2, X3 and X4 are each a tetravalent organic group; Y2 is a divalent group containing a chain hydrocarbon structure in the main chain and the partial structure adjacent to "*1-NR1-CO-", "*1-CO-NR1-", "*1-NR1-CO-NR2-" or "*1-CO-NR1-NR2-CO-"; R1 and R2 are each a hydrogen atom or a monovalent organic group; "*1" indicates a bond with the chain hydrocarbon structure; Y3 is a divalent organic group with a carboxylic acid group or a sulfonic acid group; Y4 is a divalent organic group with a nitrogen-containing heterocycle selected from "-R3-NR4-R5-" and "-R6-NR7R" R3, R5 and R6 are each independently a divalent aliphatic hydrocarbon group; R4, R7 and R8 are each independently a hydrogen atom, a thermally detachable group or a monovalent aliphatic hydrocarbon group.

[0010] <2> According to the liquid crystal alignment agent described in <1>, wherein the polymer (P) comprises any two or more of the partial structures represented by formula (1) and formula (2), the partial structures represented by formula (3), and the partial structures represented by formula (4) within the same molecule. <3> According to the liquid crystal alignment agent described in <1> or <2>, wherein the polymer (P) comprises a structural unit derived from aromatic tetracarboxylic dianhydride. <4> According to the liquid crystal alignment agent described in any one of <1> to <3>, it further comprises a polymer (Q) different from the polymer (P). <5> According to the liquid crystal alignment agent described in <4>, it comprises a polymer (Q) comprising at least one of the group consisting of the partial structures represented by formula (5) and the partial structures represented by formula (6) below. [Chemistry 4] (In formulas (5) and (6), X5 and X6 are tetravalent groups with alicyclic structures, respectively; Y5 and Y6 are divalent organic groups containing thermally detachable groups bonded to nitrogen atoms, respectively)

[0011] <6> The liquid crystal alignment agent according to <5>, wherein the alicyclic structure is a substituted or unsubstituted cyclobutane ring structure. <7> The liquid crystal alignment agent according to any one of <1> to <6> further comprises a compound having at least three groups selected from the group consisting of oxetyl, oxetyl, hydroxyl, mercapto, amino, and polymeric carbon-carbon double bond groups within one molecule. <8> The liquid crystal alignment agent according to any one of <1> to <7> further comprises a compound having a trialkoxysilyl group. <9> A liquid crystal alignment film formed using the liquid crystal alignment agent according to any one of <1> to <8>. <10> A liquid crystal element comprising the liquid crystal alignment film according to <9>. [Effects of the Invention]

[0012] With the liquid crystal alignment agent of the present invention, a liquid crystal element can be obtained that maintains good liquid crystal alignment while having good DC accumulation characteristics and DC mitigation characteristics, and is not prone to generating image retention caused by charge accumulation.

Implementation Method

[0013] Liquid Crystal Alignment Agent Hereinafter, the components contained in the liquid crystal alignment agent of this disclosure, as well as other components that may be arbitrarily formulated as needed, will be described. Furthermore, unless otherwise specifically mentioned, each component may be used alone or in combination of two or more.

[0014] Here, in this specification, the term "hydrocarbon group" includes chain hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. "Chain hydrocarbon group" refers to a straight-chain hydrocarbon group or a branched hydrocarbon group whose main chain does not contain a ring structure and only contains a chain structure. The chain hydrocarbon group can be saturated or unsaturated. "Alicyclic hydrocarbon group" refers to a hydrocarbon group that contains only an alicyclic hydrocarbon structure as its ring structure and does not contain an aromatic ring structure. The alicyclic hydrocarbon group does not necessarily need to contain only an alicyclic hydrocarbon structure; it may also include groups with a chain structure in a portion thereof. "Aromatic hydrocarbon group" refers to a hydrocarbon group that contains an aromatic ring structure as its ring structure. The aromatic hydrocarbon group does not necessarily need to contain only an aromatic ring structure; it may also contain a chain structure or an alicyclic hydrocarbon structure in a portion thereof. "Aromatic ring" includes aromatic hydrocarbon rings and aromatic heterocycles. "Organic group" refers to a group of atoms formed by removing any hydrogen atom from a carbon-containing compound (i.e., an organic compound).

[0015] The "main chain" of a polymer refers to the portion of the polymer containing the longest atomic chain, the "stem". The "stem" portion may contain ring structures. For example, "having a specific structure in the main chain" means that the specific structure constitutes part of the main chain. The term "side chain" refers to a portion that branches off from the "stem" of the polymer. "Tetracarboxylic acid derivative" means that it includes tetracarboxylic dianhydride, tetracarboxylic acid diester, and tetracarboxylic acid diester dihalides.

[0016] The liquid crystal alignment agent of this disclosure contains a polymer (P). The polymer (P) is at least one selected from the group consisting of polyamide, polyamide ester, and polyimide, and is an aggregate of polymers containing a partial structure (U1) within the molecule. Furthermore, the molecules constituting the polymer (P) contain any one or more of partial structures (U2-1), (U2-2), and (U2-3) and partial structure (U1) within the same molecule, and the molecules containing partial structure (U1) contain any two or more of partial structures (U2-1), (U2-2), and (U2-3) within the same molecule or in different molecules. Regarding each partial structure, partial structure (U1) has a specific nitrogen-containing structure that imparts hole transport to the polymer. Partial structure (U2-1) has a structure that imparts hydrogen bonding to the main chain of the polymer. Partial structure (U2-2) has an acidic functional group, and partial structure (U2-3) has a nitrogen-containing heterocycle.

[0017] Here, the phrase "any two or more of partial structures (U2-1), partial structures (U2-2), and partial structures (U2-3)" in the same molecule or in different molecules means that the polymer (P), as an aggregate of polymers, contains any two of the three partial structures (U2-1), partial structures (U2-2), and partial structures (U2-3), or contains all three. Specifically, when the polymer (P) contains any two of the three partial structures (U2-1), partial structures (U2-2), and partial structures (U2-3), the polymer (P) (i.e., the aggregate of polymers containing partial structure (U1)) contains partial structures (U2-1) and partial structures (U2-2), or partial structures (U2-1) and partial structures (U2-3), or partial structures (U2-2) and partial structures (U2-3) in the same molecule or in different molecules. Furthermore, when a polymer (P) contains all three of the following structures: partial structure (U2-1), partial structure (U2-2), and partial structure (U2-3), the polymer (P) contains partial structures (U2-1), partial structures (U2-2), and partial structures (U2-3) within the same molecule or within different molecules. Specific forms of polymer (P) can be listed as <1> to <4> below.

[0018] <1> A polymer, wherein a molecule containing a partial structure (U1) contains partial structures (U2-1) and partial structures (U2-2) within the same molecule or in different molecules. <2> A polymer, wherein a molecule containing a partial structure (U1) contains partial structures (U2-1) and partial structures (U2-3) within the same molecule or in different molecules. <3> A polymer, wherein a molecule containing a partial structure (U1) contains partial structures (U2-2) and partial structures (U2-3) within the same molecule or in different molecules. <4> A polymer, wherein a molecule containing a partial structure (U1) contains partial structures (U2-1), partial structures (U2-2), and partial structures (U2-3) within the same molecule or in different molecules.

[0019] Furthermore, each polymer of <1> to <4> may contain only one partial structure (U1) or may contain two or more. Each polymer of <1>, <2>, and <4> may contain only one partial structure (U2-1) or may contain two or more. Each polymer of <1>, <3>, and <4> may contain only one partial structure (U2-2) or may contain two or more. Each polymer of <2> to <4> may contain only one partial structure (U2-3) or may contain two or more.

[0020] As a specific example when a polymer (P) contains any two or more of partial structures (U2-1), partial structures (U2-2), and partial structures (U2-3) in different molecules, for example in the case of the <1>, polymers (P) can be categorized as polymers having partial structures (U1) and partial structures (U2-1) in the same molecule, and polymers having partial structures (U1) and partial structures (U2-2) in the same molecule. In the case of <4>, examples include: polymers (P) having partial structures (U1) and partial structures (U2-1) within the same molecule, polymers having partial structures (U1) and partial structures (U2-2) within the same molecule, and polymers having partial structures (U1) and partial structures (U2-3) within the same molecule; polymers (P) having partial structures (U1), partial structures (U2-1) and partial structures (U2-2) within the same molecule, and polymers having partial structures (U1) and partial structures (U2-3) within the same molecule; polymers (P) having partial structures (U1) and partial structures (U2-1) within the same molecule, and polymers having partial structures (U1), partial structures (U2-2) and partial structures (U2-3) within the same molecule, etc.

[0021] In terms of obtaining a liquid crystal element with good DC accumulation characteristics and DC mitigation characteristics and low image retention while minimizing the amount of components constituting the liquid crystal alignment agent, the polymer (P) is preferably composed of any two or more of partial structures (U2-1), partial structures (U2-2) and partial structures (U2-3) and partial structure (U1) within the same molecule.

[0022] The following describes in detail the partial structures (U1), (U2-1), (U2-2) and (U2-3).

[0023] <Partial Structure (U1)> The partial structure (U1) is the structural unit represented by the following formula (1). [Chemistry 5] (In formula (1), X1 is a tetravalent organic group; Y1 is a divalent organic group having a partial structure obtained by removing two hydrogen atoms from the structure represented by the following formula (Y-1)) [Chemistry 6] (In formula (Y-1), A1 and A2 are respectively independently monovalent groups having aromatic hydrocarbon rings and the aromatic hydrocarbon rings are bonded to the nitrogen atom in formula (Y-1), or represent a nitrogen-containing condensed heterocyclic structure formed by A1 and A2 combined with each other and the nitrogen atoms bonded to A1 and A2; A3 is a hydrogen atom or a monovalent organic group; wherein, in the case that A1 and A2 represent a nitrogen-containing condensed heterocyclic structure formed by A1 and A2 combined with each other and the nitrogen atoms bonded to A1 and A2, the nitrogen-containing condensed heterocyclic structure has two or more aromatic hydrocarbon rings, and the two aromatic hydrocarbon rings of the nitrogen-containing condensed heterocyclic structure have a fused ring structure bonded by sharing the nitrogen atom in formula (Y-1), or A3 has an aromatic hydrocarbon ring and A 3. The aromatic hydrocarbon rings it possesses are bonded to the nitrogen atoms in formula (Y-1).

[0024] In the formula (1), Y1 is a group derived from a diamine (hereinafter also referred to as "specific diamine (D1)") having a partial structure obtained by removing two hydrogen atoms from the structure represented by the formula (Y-1). A1 and A2 in the formula (Y-1) each have an aromatic hydrocarbon ring. When the aromatic hydrocarbon rings of A1 and A2 are bonded to the nitrogen atom in the formula (Y-1) by a single bond, the aromatic hydrocarbon rings of A1 and A2 can be monocyclic or polycyclic. Examples of aromatic hydrocarbon rings in A1 and A2 include: benzene rings, naphthalene rings, anthracene rings, etc. Among these, the aromatic hydrocarbon rings in A1 and A2 are preferably benzene rings or naphthalene rings, and more preferably benzene rings. The aromatic hydrocarbon rings in A1 and A2 may have substituents. Examples of substituents include: methyl, ethyl, halogen atoms, etc.

[0025] When A1 and A2 represent nitrogen-containing condensed heterocyclic structures formed by mutual bonding and together with the nitrogen atoms bonded to A1 and A2, examples of such nitrogen-containing condensed heterocyclic structures include: indoline structure, indole structure, 1,2,3,4-tetrahydroquinoline structure, 1,2-dihydroquinoline structure, 1,2-dihydroisoquinoline structure, carbazole structure, phenoxazine structure, phenothiazine structure, etc. These heterocyclic structures may have substituents in the ring portion. Examples of such substituents include: methyl, ethyl, halogen atoms, etc. Among these, the nitrogen-containing condensed heterocyclic structures formed by the mutual bonding of A1 and A2 are preferably indoline structure, indole structure, 1,2,3,4-tetrahydroquinoline structure, 1,2-dihydroquinoline structure, 1,2-dihydroisoquinoline structure, and carbazole structure.

[0026] When A3 is a monovalent organic group, examples of such monovalent organic groups include monovalent hydrocarbon groups having 1 to 10 carbon atoms and thermally detachable groups. Examples of monovalent hydrocarbon groups include alkyl groups having 1 to 10 carbon atoms, cycloalkyl groups having 3 to 10 carbon atoms, and aryl groups having 6 to 10 carbon atoms.

[0027] The thermally removable group is a substituent that is removed and replaced with a hydrogen atom due to the heat imparted to the liquid crystal alignment agent during the formation of the liquid crystal alignment film, etc. Examples of thermally removable groups include: urethane-based protecting groups, amide-based protecting groups, amide-imine-based protecting groups, sulfonamide-based protecting groups, etc. Among these, urethane-based protecting groups are preferred in terms of high thermal removability. Specific examples include: tributoxycarbonyl, benzyloxycarbonyl, 1,1-dimethyl-2-haloethyloxycarbonyl, allyloxycarbonyl, 2-(trimethylsilyl)ethoxycarbonyl, 9-fluorenylmethyloxycarbonyl, etc. Among these, tributoxycarbonyl (Boc group) is particularly preferred in terms of excellent thermal removability and the reduction of the amount of deprotected portion remaining in the film.

[0028] When A1 and A2 represent the nitrogen-containing condensed heterocyclic structure, the nitrogen-containing condensed heterocyclic structure represented by A1 and A2 has two or more aromatic hydrocarbon rings, and the two aromatic hydrocarbon rings of the nitrogen-containing condensed heterocyclic structure are fused ring structures (hereinafter also referred to as "fused ring structure Cp") that share a nitrogen atom in formula (Y-1), or A3 has an aromatic hydrocarbon ring and the aromatic hydrocarbon ring is bonded to a nitrogen atom in formula (Y-1). Examples of fused ring structures Cp include carbazole structures, phenoxazine structures, phenothiazine structures, etc., with carbazole structures being preferred.

[0029] Y1 in formula (1) only needs to have a partial structure obtained by removing two hydrogen atoms from the structure represented by formula (Y-1). The hydrogen atoms removed from the structure represented by formula (Y-1) can be hydrogen atoms of any of A1, A2 and A3. Specifically, Y1 in formula (1) can be a divalent base having a partial structure obtained by removing one hydrogen atom from A1 and one hydrogen atom from A2, or it can be a divalent base having a partial structure obtained by removing one hydrogen atom from A1 and one hydrogen atom from A3.

[0030] From the viewpoint of fully realizing the reduction of image retention generated in the liquid crystal element, Y1 preferably has a partial structure derived from the formula (Y-1) in the main chain. The number of partial structures derived from the formula (Y-1) in Y1 may be one or more.

[0031] As a specific example of the divalent organic group represented by Y 1, the group represented by the following formula can be listed. [Chem. 7] (where "*" represents a bond)

[0032] In the polymer (P), the proportion of structural units derived from a specific diamine (D1) is preferably 3 mol% or more, more preferably 5 mol% or more, relative to the total amount of structural units derived from the diamine in the polymer (P). Furthermore, the proportion of structural units derived from a specific diamine (D1) is preferably 90 mol% or less, more preferably 80 mol% or less, relative to the total amount of structural units derived from the diamine in the polymer (P). By setting the proportion of structural units derived from a specific diamine (D1) within the aforementioned range, the DC image retention characteristics (especially the DC mitigation characteristics) of the liquid crystal element can be improved, and the generation of DC image retention can be sufficiently reduced.

[0033] Furthermore, when the polymer (P) comprises two or more polymers with different monomer compositions, the proportion of structural units derived from a specific diamine (D1) refers to the proportion relative to the total amount of structural units derived from the diamines constituting the polymer (P). For example, when the liquid crystal alignment agent of this disclosure comprises a first polymer and a second polymer with different monomer compositions as polymer (P), the proportion of structural units derived from a specific diamine (D1) represents the proportion of the total amount of structural units derived from the specific diamine (D1) constituting the first polymer and the specific diamine (D1) constituting the second polymer relative to the total amount of structural units derived from all diamines constituting the first polymer and all diamines constituting the second polymer (the same applies to the structural units below).

[0034] <Partial Structure (U2-1)> The partial structure (U2-1) is the structural unit represented by the following formula (2). [Chemical 8] (In formula (2), X2 is a tetravalent organic group; Y2 is a divalent group in the main chain containing a chain hydrocarbon structure adjacent to "*1-NR1-CO-", "*1-CO-NR1-", "*1-NR1-CO-NR2-" or "*1-CO-NR1-NR2-CO-"; R1 and R2 are independently hydrogen atoms or monovalent organic groups; "*1" represents the bond with the chain hydrocarbon structure)

[0035] In the formula (2), Y2 is a group derived from a diamine (hereinafter also referred to as "specific diamine (D2-1)") whose main chain contains a chain hydrocarbon structure adjacent to a portion of the structure of "*1-NR1-CO-", "*1-CO-NR1-", "*1-NR1-CO-NR2-" or "*1-CO-NR1-NR2-CO-". The chain hydrocarbon structure of Y2 can be saturated or unsaturated. The chain hydrocarbon structure of Y2 can be linear or branched, preferably linear saturated or unsaturated hydrocarbon groups, specifically, linear alkyl and alkylene groups can be listed. The number of carbon atoms in each chain hydrocarbon structure adjacent to "* 1-NR 1-CO-", "* 1-CO-NR 1-", "* 1-NR 1-CO-NR 2-" or "* 1-CO-NR 1-NR 2-CO-" is preferably 1 to 10, more preferably 2 to 8, and even more preferably 2 to 5.

[0036] Furthermore, Y2 may also have a cyclic structure as long as it has a chain hydrocarbon structure in the main chain adjacent to the structure of "*1-NR1-CO-", "*1-CO-NR1-", "*1-NR1-CO-NR2-" or "*1-CO-NR1-NR2-CO-". There is no particular limitation on the cyclic structure that Y2 may have. Specific examples of the cyclic structures that Y2 may have include: alicyclic groups such as cycloalkyldiyl and cycloalkenyl; aromatic hydrocarbon groups such as phenyl; heterocyclic groups such as pirimidinediyl, pirimidinediyl, pyridinidinediyl, and pyridazindiyl.

[0037] Among the groups represented by "*1-NR1-CO-", "*1-CO-NR1-", "*1-NR1-CO-NR2-" or "*1-CO-NR1-NR2-CO-", when R1 and R2 are monovalent organic groups, specific examples of R1 and R2 can be listed as monovalent hydrocarbon groups having 1 to 10 carbon atoms and thermally degradable groups. When R1 and R2 are monovalent hydrocarbon groups, the monovalent hydrocarbon group is preferably an alkyl or phenyl group having 1 to 3 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. Specific examples of thermally degradable groups can be listed as groups that are the same as those exemplified in the description of A3 in the above formula (1) when A3 is a thermally degradable group. In terms of excellent thermal degradability and the ability to reduce the amount of residual deprotected portion in the film, these are particularly preferably tributoxycarbonyl (Boc group).

[0038] In the above, R1 and R2 are preferably hydrogen atoms, alkyl groups having 1 to 3 carbon atoms or thermally detachable groups, more preferably hydrogen atoms, alkyl groups having 1 to 3 carbon atoms or third butoxycarbonyl groups, and even more preferably hydrogen atoms.

[0039] In "*1-NR1-CO-", "*1-CO-NR1-", "*1-NR1-CO-NR2-", or "*1-CO-NR1-NR2-CO-", a chain hydrocarbon structure is bonded to the side of "*1". A chain hydrocarbon structure may be adjacent to the side opposite to "*1", or a structure different from the chain hydrocarbon structure (specifically, a cyclic hydrocarbon group or a heterocyclic group). Furthermore, the group adjacent to the side opposite to "*1" may also have substituents such as halogen atoms or hydroxyl groups.

[0040] As a preferred example of Y 2, the divalent base represented by the following formula (y2-1) can be listed. *-Ar 1-R 3-Z 1-(R 4-Z 2) nR 5-Ar 2-* …(y2-1) (In formula (y2-1), Ar 1 and Ar 2 are independently divalent aromatic cyclic groups or alicyclic groups; Z 1 and Z 2 are independently "* 1-NR 1-CO-", "* 1-CO-NR 1-", "* 1-NR 1-CO-NR 2-" or "* 1-CO-NR 1-NR 2-CO-"; "* 1" indicates a bond with a chain hydrocarbon structure; R 3 and R 5 are independently single bonds or divalent chain hydrocarbon groups; R 4 is a divalent organic group; wherein, when R 3 is a single bond, R 4 bonded to Z 1 is a divalent chain hydrocarbon group; when R 5 is a single bond, R 4 bonded to Z 2 adjacent to Ar 2 is a divalent chain hydrocarbon group.) 4 represents a divalent chain hydrocarbon group; n is an integer from 0 to 2; "*" indicates a bond.

[0041] In formula (y2-1), the divalent aromatic ring group represented by Ar1 or Ar2 is a group formed by removing two hydrogen atoms from the ring portion of an aromatic ring. Examples of such aromatic rings include: benzene rings, naphthyl rings, pyridine rings, pyrimidine rings, etc. The divalent alicyclic group represented by Ar1 or Ar2 is a group formed by removing two hydrogen atoms from the ring portion of an aliphatic ring such as a cyclohexane ring. The divalent aromatic ring group or alicyclic group represented by Ar1 or Ar2 may have substituents in the ring portion. Examples of such substituents include: methyl groups, ethyl groups, halogen atoms, etc. From the viewpoint of forming a liquid crystal alignment film exhibiting good liquid crystal alignment properties, Ar1 and Ar2 are preferably phenyl groups.

[0042] When R3 and R5 are divalent chain hydrocarbon groups, straight-chain alkyldiyl and alkenediyl groups can be used as R3 and R5. The divalent chain hydrocarbon group represented by R3 and R5 is preferably a straight-chain alkyldiyl group, and more preferably a straight-chain alkyldiyl group with 1 to 5 carbon atoms.

[0043] Examples of divalent organic groups represented by R 4 include divalent hydrocarbon groups and heterocyclic groups. Examples of divalent hydrocarbon groups include: chain hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. Specific examples of divalent organic groups represented by R 4 include: alkyldiyl, alkenyl, cycloalkyldiyl, cycloalkenyl, phenyl, piperidinediyl, piperazinediyl, pyridinediyl, pyridazinediyl, etc.

[0044] As a specific example of the divalent organic group represented by Y 2, the groups represented by the following formulas can be listed. [Chem. 9][Chem. 10][Chem. 11] (where "Boc" represents the third butoxycarbonyl group; "*" represents the bond)

[0045] When the polymer (P) contains structural units derived from a specific diamine (D2-1), the proportion of structural units derived from the specific diamine (D2-1) is preferably 5 mol% or more, and more preferably 10 mol% or more, relative to the total amount of structural units derived from the diamine contained in the polymer (P). Furthermore, the proportion of structural units derived from the specific diamine (D2-1) is preferably 90 mol% or less, and more preferably 80 mol% or less, relative to the total amount of structural units derived from the diamine contained in the polymer (P). By setting the proportion of structural units derived from the specific diamine (D2-1) within the aforementioned range, the DC image retention characteristics (especially the DC accumulation characteristics) of the liquid crystal element can be improved, and the generation of DC image retention can be sufficiently reduced.

[0046] <Partial Structure (U2-2)> The partial structure (U2-2) is the structural unit represented by the following formula (3). [Chemical 12] (In formula (3), X3 is a tetravalent organic group; Y3 is a divalent organic group with a carboxylic acid group or a sulfonic acid group)

[0047] In the formula (3), Y3 is a group derived from a diamine having a carboxylic acid group or a sulfonic acid group (hereinafter also referred to as "specific diamine (D2-2)"). The carboxylic acid group or the sulfonic acid group in Y3 can be bonded to a chain structure or a ring structure. Y3 is preferably bonded to an aromatic ring structure directly or via a divalent linker, and more preferably directly to an aromatic ring structure. When the carboxylic acid group or the sulfonic acid group is bonded to an aromatic ring structure via a divalent linker, examples of divalent linkers include: alkyldiyl groups with 1 to 3 carbon atoms, and divalent groups formed by replacing any extended methyl group in alkyldiyl groups with -O-, -CO-, -COO-, -NR 6- or -CO-NR 6- (R 6 is a hydrogen atom or a monovalent organic group). The number of carboxylic acid groups or sulfonic acid groups in Y3 is not particularly limited, for example, one to four, preferably one or two.

[0048] As a specific example of the divalent base represented by Y 3, the base represented by the following formula can be listed. [Chemistry 13] (where "*" represents a bond)

[0049] When the polymer (P) contains structural units derived from a specific diamine (D2-2), the proportion of structural units derived from the specific diamine (D2-2) is preferably 5 mol% or more, and more preferably 10 mol% or more, relative to the total amount of structural units derived from the diamine contained in the polymer (P). Furthermore, the proportion of structural units derived from the specific diamine (D2-2) is preferably 90 mol% or less, and more preferably 60 mol% or less, relative to the total amount of structural units derived from the diamine contained in the polymer (P). By setting the proportion of structural units derived from the specific diamine (D2-2) within the aforementioned range, the DC image retention characteristics (especially the DC accumulation characteristics) of the liquid crystal element can be improved, and the generation of DC image retention can be sufficiently reduced.

[0050] <Partial Structure (U2-3)> The partial structure (U2-3) is the structural unit represented by the following formula (4). [Chemical 14] (In formula (4), X4 is a tetravalent organic group; Y4 is a divalent organic group having at least one partial structure selected from the group consisting of nitrogen-containing heterocycles, "-R3-NR4-R5-" and "-R6-NR7R8" (except for the group equivalent to Y2); R3, R5 and R6 are each independently a divalent aliphatic hydrocarbon group; R4, R7 and R8 are each independently a hydrogen atom, a thermally detachable group or a monovalent aliphatic hydrocarbon group)

[0051] In the formula (4), Y4 is a group derived from a diamine (hereinafter also referred to as "specific diamine (D2-3)") having at least one partial structure (hereinafter also referred to as "nitrogen-containing structure Ny") selected from the group consisting of nitrogen-containing heterocycles, "-R3-NR4-R5-", and "-R6-NR7R8". When Y4 has a nitrogen-containing heterocycle, the nitrogen-containing heterocycle may be an aromatic heterocycle or a non-aromatic heterocycle. In addition, the nitrogen-containing heterocycle in Y4 may be a monocyclic or a fused ring. Specific examples of nitrogen-containing heterocycles in Y4 include, for example, pyrrole rings, imidazole rings, pyrazole rings, triazole rings, pyridine rings, pyrimidine rings, pyridazine rings, quinoline rings, benzimidazole rings, carbazole rings, and pyrazine rings, as well as heterocycles having substituents (e.g., methyl, ethyl, etc.) on these rings. Examples of nitrogen-containing non-aromatic heterocycles include: piracene rings, piracene rings, morpholine rings, and hexamethyleneimine rings, as well as heterocycles with substituents (e.g., methyl, ethyl, etc.) introduced onto these rings. Among these, the nitrogen-containing heterocycle in Y4 is preferably a structure having at least one structure selected from the group consisting of pyridine rings, pyrimidine rings, pyrazine rings, piracene rings, quinoline rings, benzimidazole rings, and carbazole rings.

[0052] The divalent aliphatic hydrocarbon group represented by R3, R5, or R6 can be exemplified by: alkyldiyl, alkenediyl, cycloalkanediyl, etc. Among these, the divalent aliphatic hydrocarbon group represented by R3, R5, or R6 is preferably alkyldiyl. The monovalent aliphatic hydrocarbon group represented by R4, R7, or R8 is preferably alkyl, more preferably alkyl having 1 to 3 carbon atoms. As a specific example of a thermally detachable group represented by R4, R7, or R8, the same group as the group exemplified in the description of A3 in the above formula (1) as a thermally detachable group can be cited. Among these, a third butoxycarbonyl (Boc group) is particularly preferred.

[0053] Y4 may have a nitrogen-containing structure Ny in the main chain of the polymer, or in the side chain, or in both the main chain and the side chain. From the viewpoint of obtaining a liquid crystal element with sufficiently reduced image retention, Y4 preferably has a nitrogen-containing structure Ny in the side chain of the polymer. The number of nitrogen-containing structures Ny in Y4 is not particularly limited, for example, one to four, preferably one to three.

[0054] Y4 may be a group containing only a nitrogen-containing heterocycle, or it may also have a nitrogen-containing heterocycle and a ring structure or chain structure different from the nitrogen-containing heterocycle. Furthermore, these ring structures and chain structures may be located in the main chain of the polymer or in the side chain. Examples of chain structures include: alkyl dienes with 1 to 10 carbon atoms, and divalent groups (where R7 is a hydrogen atom or a monovalent organic group) formed by replacing any extended methyl group in the alkyl diene with -O-, -CO-, -COO-, -NR7-, or -CO-NR7-. Examples of ring structures different from the nitrogen-containing heterocycle include aromatic hydrocarbon rings (benzene rings, naphthalene rings, etc.).

[0055] Where Y4 is a group different from Y2 in formula (2). That is, the specific diamine (D2-3) is a compound different from the specific diamine (D2-1), and Y4 is a divalent group in the main chain that does not have a chain hydrocarbon structure adjacent to the partial structure of "*1-NR1-CO-", "*1-CO-NR1-", "*1-NR1-CO-NR2-" or "*1-CO-NR1-NR2-CO-". In addition, the specific diamine (D1), specific diamine (D2-1), specific diamine (D2-2) and specific diamine (D2-3) constituting the polymer (P) are compounds that are different from each other.

[0056] Specific examples of divalent organic groups represented by Y 4, as groups having a nitrogen-containing structure Ny in the main chain, can be listed as groups represented by the following formula. [Chemical 15] (where "*" represents a bond)

[0057] In addition, regarding specific examples of the divalent organic group represented by Y 4, as a group having a nitrogen-containing structure Ny in the side chain, the group represented by the following formula can be listed. [Chemical 16] (where "*" indicates a bond)

[0058] When the polymer (P) contains structural units derived from a specific diamine (D2-3), the proportion of structural units derived from the specific diamine (D2-3) is preferably 3 mol% or more, and more preferably 5 mol% or more, relative to the total amount of structural units derived from the diamine contained in the polymer (P). Furthermore, the proportion of structural units derived from the specific diamine (D2-3) is preferably 90 mol% or less, and more preferably 60 mol% or less, relative to the total amount of structural units derived from the diamine contained in the polymer (P). By setting the proportion of structural units derived from the specific diamine (D2-3) within the aforementioned range, the DC image retention characteristics (especially the DC accumulation characteristics) of the liquid crystal element can be improved, and the generation of DC image retention can be sufficiently reduced.

[0059] In the polymer (P), the total content of structural units derived from a specific diamine (D2-1), structural units derived from a specific diamine (D2-2), and structural units derived from a specific diamine (D2-3) is preferably 10 mol% or more, more preferably 20 mol% or more, relative to the total amount of structural units derived from the diamine in the polymer (P). Furthermore, the total content of structural units derived from a specific diamine (D2-1), structural units derived from a specific diamine (D2-2), and structural units derived from a specific diamine (D2-3) is preferably 97 mol% or less, more preferably 95 mol% or less, relative to the total amount of structural units derived from the diamine in the polymer (P).

[0060] The tetravalent groups represented by X1 in formula (1), X2 in formula (2), X3 in formula (3), and X4 in formula (4) are structural units derived from tetracarboxylic anhydrides. Examples of tetracarboxylic anhydrides include aliphatic tetracarboxylic dianhydrides and aromatic tetracarboxylic dianhydrides. Examples of aliphatic tetracarboxylic dianhydrides include chain tetracarboxylic dianhydrides and alicyclic tetracarboxylic dianhydrides.

[0061] Examples of chain-like tetracarboxylic dianhydrides include 1,2,3,4-butanetetracarboxylic dianhydride and ethylenediaminetetraacetic acid dianhydride. Examples of alicyclic tetracarboxylic dianhydrides include: 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 2,3,5-tricarboxylated cyclopentylacetic acid 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)-3a,4,5,9b-tetrahydronaphtho[1,2-c]furan-1,3-dione, etc. Examples of aromatic tetracarboxylic dianhydrides include: oxotetrahydrofuran-3-yl)-8-methyl-3a,4,5,9b-tetrahydronaphtho[1,2-c]furan-1,3-dione, 2,4,6,8-tetracarboxylic bicyclo[3.3.0]octane-2:4,6:8-dianhydride, cyclopentanetetracarboxylic dianhydride, cyclohexanetetracarboxylic dianhydride, 3,5,6-tricarboxylic-2-carboxymethylnorbornene-2:3,5:6-dianhydride, etc. Examples of aromatic tetracarboxylic dianhydrides include: pyromellitic dianhydride, 4,4'-(hexafluoroethylene isopropyl)diphthalic anhydride, ethylene glycol bis(triphenyl)-2-diphenyl anhydride, 4,4'-carbonyldiphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, etc.

[0062] In terms of obtaining a liquid crystal element that significantly improves the DC mitigation characteristics and substantially reduces image retention, the tetracarboxylic dianhydride constituting each partial structure (U1) and partial structures (U2-1) to (U2-3) preferably comprises structural units derived from aromatic tetracarboxylic dianhydrides. In the polymer (P), the proportion of structural units derived from aromatic tetracarboxylic dianhydrides is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more, relative to the total amount of structural units derived from the tetracarboxylic dianhydrides constituting the polymer (P).

[0063] [Other Diamines] When synthesizing polymers (P), diamines different from the specific diamines (D1), (D2-1), (D2-2), and (D2-3) (hereinafter also referred to as "other diamines") may be used. Examples of other diamines include: aliphatic diamines, aromatic diamines, and diamino organosilicones. Examples of aliphatic diamines include chain diamines and alicyclic diamines.

[0064] Specific examples of other diamines include, as chain diamines, meta-xylylenediamine, hexamethylenediamine, etc. As alicyclic diamines, 1,4-diaminocyclohexane, 4,4'-amethylenebis(cyclohexylamine), etc.

[0065] Examples of aromatic diamines include: p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4-aminophenyl-4-aminobenzoate, 4,4'-diaminoazobenzene, 1,5-bis(4-aminophenoxy)pentane, 1,2-bis(4-aminophenoxy)ethane, 1,3-bis(4-aminophenoxy)propane, 1,6-bis(4-aminophenoxy)hexane, and 6,6'-(pentanedimethyldioxy) Main-chain diamines include bis(3-aminopyridine), bis[2-(4-aminophenyl)ethyl] adipic acid, 4,4'-diaminodiphenyl ether, 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, and 4,4'-(extrinsic phenyl diextrinsic)bisaniline. Hexadecyloxy-2,4-diaminobenzene, Octadecyloxy-2,4-diaminobenzene, Octadecyloxy-2,5-diaminobenzene, Cholesteryloxy-3,5-diaminobenzene, Cholesteryloxy-3,5-diaminobenzene, Cholesteryloxy-2,4-diaminobenzene, Cholesteryloxy-2,4-diaminobenzene, Cholesteryl 3,5-diaminobenzoate, Cholesteryl 3,5-diaminobenzoate, 3,5-diaminobenzoate (Sheep) Side-chain diamines such as roostane esters, 3,6-bis(4-aminobenzoyloxy)cholestan, 3,6-bis(4-aminophenoxy)cholestan, 4-(4'-trifluoromethoxybenzoyloxy)cyclohexyl-3,5-diaminobenzoate, 1,1-bis(4-((aminophenyl)methyl)phenyl)-4-butylcyclohexane, 3,5-diaminobenzoic acid = 5ξ-cholestan-3-yl, and compounds represented by the following formula (E-1); [Chem. 17] (In formula (E-1), XI and XII are independently single bonds, -O-, *-COO- or *-OCO- (where "*" indicates a bond with the diaminophenyl side); RI is an alkyldiyl group with 1 to 3 carbon atoms; RII is a single bond or an alkyldiyl group with 1 to 3 carbon atoms; RIII is an alkyl, alkoxy, fluoroalkyl or fluoroalkoxy group with 1 to 20 carbon atoms; a is 0 or 1; b is an integer from 0 to 3; c is an integer from 0 to 2; d is 0 or 1; where 1≦a+b+c≦3) Examples of diaminoorganosiloxanes include 1,3-bis(3-aminopropyl)-tetramethyldisiloxane.

[0066] Examples of compounds represented by formula (E-1) include compounds represented by formulas (E-1-1) to (E-1-4). [Chemical 18]

[0067] When synthesizing polymer (P), the proportion of other diamines used is preferably 75 mol% or less, and more preferably 65 mol% or less, relative to the total amount of diamines used in the synthesis of polymer (P).

[0068] [Synthesis of Polymer (P)] • Polyamide When the polymer (P) is polyamide, the polyamide (hereinafter also referred to as "polyamide (P)") can be obtained by reacting a tetracarboxylic dianhydride with a diamine and a molecular weight modifier as needed.

[0069] In the synthesis reaction of polyacrylic acid (P), the ratio of tetracarboxylic dianhydride to diamine is preferably 0.2 to 2 equivalents of anhydride group to diamine group. Examples of molecular weight modifiers include: maleic anhydride, phthalic anhydride, itaconic anhydride, etc.; monoamine compounds such as aniline, cyclohexylamine, n-butylamine, etc.; and monoisocyanate compounds such as phenyl isocyanate, naphthyl isocyanate, etc. The ratio of the molecular weight modifier to the total 100 parts by mass of tetracarboxylic dianhydride and diamine used is preferably 20 parts by mass or less.

[0070] In the synthesis reaction of polyacrylic acid (P), the reaction temperature is preferably -20°C to 150°C, and the reaction time is preferably 0.1 hours to 24 hours. Examples of organic solvents used for the reaction include: aprotic polar solvents, phenolic solvents, alcoholic solvents, ketone solvents, ester solvents, ether solvents, halogenated hydrocarbons, and hydrocarbons. Among these, it is preferred 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, hexamethylphosphoric acid triamine, m-cresol, xylenol, and halogenated phenols, or to use a mixture of one or more of these solvents with other organic solvents (e.g., butyl cellosolve, diethylene glycol diethyl ether, etc.). The amount of organic solvent used is preferably set relative to the total amount of the reaction solution, while the total amount of tetracarboxylic acid dianhydride and diamine compound is 0.1% to 50% by mass.

[0071] When a polymer solution containing polyacrylic acid (P) is obtained by the polymerization, the polymer solution can be directly used in the preparation of a liquid crystal alignment agent, or it can be used in the preparation of a liquid crystal alignment agent after separating the polyacrylic acid (P) contained in the polymer solution.

[0072] • When the polymer (P) is a polyamide, the polyamide can be obtained, for example, by the following methods: [I] reacting polyamide (P) with an esterifying agent; [II] reacting a tetracarboxylic acid diester with a diamine; [III] reacting a tetracarboxylic acid diester dihalide with a diamine. The polyamide may have only a polyamide structure, or it may be a partial esterification in which both a polyamide structure and a polyamide structure coexist. The reaction solution obtained by dissolving the polyamide can be directly used in the preparation of a liquid crystal alignment agent. Alternatively, the polyamide contained in the reaction solution can be separated, and the separated polyamide can be used in the preparation of a liquid crystal alignment agent.

[0073] • Polyimide: When the polymer (P) is polyimide, the polyimide (hereinafter also referred to as "polyimide (P)") can be obtained, for example, by dehydrating and ring-closing polyamide (P) and then amide-imidizing it. The polyimide (P) preferably has an amide-imidization rate of 20% to 99%, more preferably 30% to 90%. Furthermore, the amide-imidization rate is expressed as a percentage, representing the proportion of the number of amide ring structures relative to the total number of amide acid structures and amide ring structures in the polyimide.

[0074] The dehydration and ring-closing of polyacrylic acid (P) is preferably carried out by the following method: dissolving polyacrylic acid (P) in an organic solvent, adding a dehydrating agent and a dehydration and ring-closing catalyst to the solution, and heating as needed. In this method, anhydrides such as acetic anhydride, propionic anhydride, and trifluoroacetic anhydride can be used as dehydrating agents. The amount of dehydrating agent used is preferably 0.01 mol to 20 mol relative to 1 mol of the polyacrylic acid structure of polyacrylic acid (P). Tertiary amines such as pyridine, trimethylpyridine, dimethylpyridine, and triethylamine can be used as dehydration and ring-closing catalysts. The amount of dehydration and ring-closing catalyst used is preferably 0.01 mol to 10 mol relative to 1 mol of the dehydrating agent used.

[0075] Examples of organic solvents used in the dehydration ring-closing reaction include those used in the synthesis of polyamide (P). The reaction temperature for the dehydration ring-closing reaction is preferably 0°C to 180°C. The reaction time is preferably 1.0 hour to 120 hours. Furthermore, the reaction solution containing polyimide (P) can be directly used in the preparation of liquid crystal alignment agents. Alternatively, polyimide (P) can be separated from the reaction solution and used in the preparation of liquid crystal alignment agents. Polyimide (P) can also be obtained through the dehydration ring-closing of polyamide esters.

[0076] When preparing a solution with a concentration of 10% by mass, the solution viscosity of polymer (P) is preferably between 10 mPa·s and 800 mPa·s, and more preferably between 15 mPa·s and 500 mPa·s. Furthermore, the solution viscosity (mPa·s) is a value obtained by measuring a 10% by mass polymer solution prepared using a good solvent for polymer (P) (e.g., γ-butyrolactone, N-methyl-2-pyrrolidone, etc.) at 25°C using an E-type rotational viscometer.

[0077] The weight-average molecular weight (Mw) of the polymer (P) converted from polystyrene, as determined by gel permeation chromatography (GPC), is preferably 1,000 to 500,000, more preferably 2,000 to 300,000. The molecular weight distribution (Mw / Mn) expressed as the ratio of Mw to the number-average molecular weight (Mn) of polystyrene determined by GPC is preferably 7 or less, more preferably 5 or less.

[0078] Relative to the total amount of solid components contained in the liquid crystal alignment agent (i.e., the total mass of components other than the solvent in the liquid crystal alignment agent), the content of polymer (P) in the liquid crystal alignment agent is preferably 20% by mass or more, more preferably 40% by mass or more, and even more preferably 60% by mass or more.

[0079] <Other Components> In addition to the polymer (P), the liquid crystal alignment agent may also contain components different from the polymer (P) as needed (hereinafter also referred to as "other components").

[0080] • Polymer (Q) The liquid crystal alignment agent disclosed herein may also contain a polymer (Q) different from the polymer (P). By co-blending the polymer (P) and the polymer (Q), a liquid crystal alignment film with good liquid crystal alignment and providing a highly reliable liquid crystal element can be formed.

[0081] The main skeleton of polymer (Q) is not particularly limited. Examples of polymer (Q) include: polyamide, polyamide ester, polyimide, polyorganosiloxane, polyester, polyenamine, polyurea, polyamide, polyamide-imide, polybenzoxazole precursor, polybenzoxazole, cellulose derivative, polyacetal, addition polymer (e.g., (meth)acrylic acid polymer, styrene polymer, maleimide polymer, styrene-maleimide copolymer), etc. Among these, polymer (Q) is preferably at least one selected from the group consisting of polyamide, polyamide ester, and polyimide. Furthermore, when polymer (Q) is at least one selected from the group consisting of polyamide, polyamide ester, and polyimide, polymer (Q) is a polymer that does not have a partial structure (U1).

[0082] The liquid crystal alignment agent of this disclosure is preferably a polymer (hereinafter also referred to as "polymer (Q-1)") having at least one of the group consisting of a partial structure represented by formula (5) and a partial structure represented by formula (6) below. By including both polymer (P) and polymer (Q-1) in the liquid crystal alignment agent, the layer separation of the polymer component can be promoted, and the liquid crystal alignment can be improved, which is suitable in this respect. [Chemical 19] (In formula (5) and formula (6), X5 and X6 are each independently tetravalent groups having an alicyclic structure; Y5 and Y6 are each independently divalent organic groups containing a thermally detachable group bonded to a nitrogen atom)

[0083] In formulas (5) and (6), the tetravalent groups represented by X5 and X6 are groups derived from tetracarboxylic dianhydrides having an alicyclic structure (i.e., alicyclic tetracarboxylic dianhydrides). Specific examples of alicyclic tetracarboxylic dianhydrides can be listed as compounds identical to those exemplified as alicyclic tetracarboxylic dianhydrides constituting polymer (P). The alicyclic structure of X5 and X6 is preferably a substituted or unsubstituted cyclobutane ring structure.

[0084] In the substituted cyclobutane ring structure, examples of substituents include: alkyl groups having 1 to 6 carbon atoms, alkyl halogenates having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, alkoxy halogenates having 1 to 6 carbon atoms, and halogen atoms. Among these, the substituents in the cyclobutane ring structure are preferably alkyl groups having 1 to 3 carbon atoms, alkyl halogenates having 1 to 3 carbon atoms, alkoxy groups having 1 to 3 carbon atoms, alkoxy halogenates having 1 to 3 carbon atoms, or halogen atoms; more preferably alkyl groups having 1 to 3 carbon atoms, fluoroalkyl groups having 1 to 3 carbon atoms, or fluorine atoms; and most preferably methyl groups.

[0085] Specific examples of tetracarboxylic dianhydrides constituting the tetravalent groups represented by X5 and X6 include: 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1-methyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3-trimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1-ethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-diethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1-ethyl-3 1,3-Methyl-1,2,3,4-cyclobutanetetracarboxylic anhydride, 1,3-dimethoxy-1,2,3,4-cyclobutanetetracarboxylic anhydride, 1,3-diethoxy-1,2,3,4-cyclobutanetetracarboxylic anhydride, 1-trifluoromethyl-1,2,3,4-cyclobutanetetracarboxylic anhydride, 1,3-di(trifluoromethyl)-1,2,3,4-cyclobutanetetracarboxylic anhydride, 1,3-di(trifluoromethoxy)-1,2,3,4-cyclobutanetetracarboxylic anhydride, 1,2,3-tris(trifluoromethyl)-1,2,3,4-cyclobutanetetracarboxylic anhydride, 1,2,3,4-tetra(trifluoromethyl)-1,2,3,4-cyclobutanetetracarboxylic anhydride, etc. Among these, at least one is selected from the group consisting of 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride.

[0086] The divalent organic groups represented by Y5 and Y6 are groups derived from diamines having a partial structure (hereinafter also referred to as "partial structure (Np)") with a thermally detachable group bonded to a nitrogen atom. As a specific example of the thermally detachable group possessed by the partial structure Np, the same group as the group exemplified in the description of A3 in the above formula (1) as a specific example when A3 is a thermally detachable group can be listed. Among them, the thermally detachable group possessed by the partial structure Np is preferably a third butoxycarbonyl group.

[0087] The polymer (Q-1) may have a partial structure Np in the main chain, or in the side chain, or in both. Specific examples of the partial structure Np include the monovalent group represented by formula (Np-1) and the divalent group represented by formula (Np-2). [Chemical 20] (In formulas (Np-1) and (Np-2), R10 is a thermally detachable group; R11 is a hydrogen atom, a monovalent hydrocarbon group with 1 to 10 carbon atoms, or a thermally detachable group; "*" indicates a bond; "*2" indicates a bond with the atoms constituting the main chain)

[0088] Specific examples of diamines having a partial structure (Np) include compounds represented by the following formulas. [Chemical 21]

[0089] When the liquid crystal alignment agent contains polymer (Q), the content of polymer (Q) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, relative to 100 parts by mass of the total mass of polymer (P) and polymer (Q) contained in the liquid crystal alignment agent. Furthermore, the content of polymer (Q) is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 40 parts by mass or less, relative to 100 parts by mass of the total mass of polymer (P) and polymer (Q) contained in the liquid crystal alignment agent.

[0090] Relative to 100 parts by mass of the total amount of polymer (P) and polymer (Q) contained in the liquid crystal alignment agent, the content of polymer (Q-1) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more. Furthermore, relative to 100 parts by mass of the total amount of polymer (P) and polymer (Q) contained in the liquid crystal alignment agent, the content of polymer (Q-1) is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 40 parts by mass or less.

[0091] • Crosslinking agent: In the liquid crystal alignment agent disclosed herein, a crosslinking agent may also be formulated for purposes such as improving the mechanical strength of the film. As a crosslinking agent, a compound having at least three crosslinking groups selected from the group consisting of oxetyl, oxetyl, hydroxyl, mercapto, amino, and polymerizable carbon-carbon double bond groups (hereinafter also referred to as "compound (Z)") within one molecule is preferably used. From the viewpoint of ensuring the toughness of the film while improving its mechanical strength, the number of crosslinking groups in compound (Z) is preferably three to ten, more preferably three to six.

[0092] When the liquid crystal alignment agent contains compound (Z), the content of compound (Z) is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, relative to 100 parts by mass of the total amount of polymer components (the total amount of polymer (P) and polymer (Q)) contained in the liquid crystal alignment agent. Furthermore, the content of compound (Z) is preferably 15 parts by mass or less, and more preferably 10 parts by mass or less, relative to 100 parts by mass of the total amount of polymer components contained in the liquid crystal alignment agent.

[0093] • Adhesion aid In the liquid crystal alignment agent disclosed herein, an adhesion aid may also be formulated for the purpose of improving the adhesion of the liquid crystal alignment film. As an adhesion aid, a compound having a trialkoxysilane group (hereinafter also referred to as "compound (Y)") is preferably used. Compound (Y) is preferably a compound having at least one reactive functional group selected from the group consisting of oxetyl, oxetyl, hydroxyl, mercapto, amino, and polymerizable carbon-carbon double bond groups. As such a compound (Y), a known silane coupling agent having said reactive functional group can be suitable.

[0094] When the liquid crystal alignment agent contains compound (Y), the content of compound (Y) is preferably 0.1 parts by mass or more, and more preferably 0.3 parts by mass or more, relative to 100 parts by mass of the total amount of polymer components (the total amount of polymer (P) and polymer (Q)) contained in the liquid crystal alignment agent. Furthermore, the content of compound (Y) is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, relative to 100 parts by mass of the total amount of polymer components contained in the liquid crystal alignment agent.

[0095] • Solvent The liquid crystal alignment agent disclosed herein is prepared as a liquid composition in which the polymer (P) and other components used as needed are preferably dispersed or dissolved in a suitable solvent.

[0096] Organic solvents are preferably used as solvents. Specific examples include: N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 1,2-dimethyl-2-imidazolium ketone, 1,3-dimethyl-2-imidazolium ketone, phenol, γ-butyrolactone, γ-butyrolactamine, 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, acetoacetic acid. Methyl acetate, ethyl acetate, ethyl propionate, methyl methoxypropionate, ethyl ethoxypropionate, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-isopropyl ether, 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, diisoamyl ether, ethyl carbonate, propyl carbonate, propylene glycol monomethyl ether (PGME), diethylene glycol diethyl ether acetate, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol diacetate, cyclopentanone, cyclohexanone, etc. As a solvent, it can be used alone or in combination with two or more.

[0097] Other components formulated into the liquid crystal alignment agent, besides those described above, may include, for example, antioxidants, metal chelate compounds, curing accelerators, surfactants, fillers, dispersants, photosensitizers, etc. The formulation ratio of other components may be appropriately selected according to each compound, within the range that does not impair the effects of this disclosure.

[0098] The solid content concentration of the liquid crystal alignment agent (the ratio of the total mass of the liquid crystal alignment agent's components other than the solvent to the total mass of the liquid crystal alignment agent) is appropriately selected considering factors such as viscosity and volatility. The solid content concentration of the liquid crystal alignment agent is preferably in the range of 1% to 10% by mass. If the solid content concentration is 1% by mass or more, the film thickness of the coating can be sufficiently ensured, and a liquid crystal alignment film exhibiting better liquid crystal alignment properties can be obtained, which is suitable in this respect. On the other hand, if the solid content concentration is 10% by mass or less, there is a tendency that the coating can be set to an appropriate thickness, a liquid crystal alignment film exhibiting good liquid crystal alignment properties can be easily obtained, and the viscosity of the liquid crystal alignment agent becomes moderate, resulting in good coatability.

[0099] Liquid Crystal Alignment Film and Liquid Crystal Element The liquid crystal alignment film disclosed herein can be manufactured using a liquid crystal alignment agent prepared as described above. Furthermore, the liquid crystal element disclosed herein includes a liquid crystal alignment film formed using the liquid crystal alignment agent described above. The driving method of the liquid crystal in a liquid crystal element is not particularly limited. For example, it can be applied to various modes such as twisted nematic (TN), super twisted nematic (STN), vertical alignment (VA) (including vertical alignment-multi-domain vertical alignment (VA-MVA) and vertical alignment-patterned vertical alignment (VA-PVA), in-plane switching (IPS), fringe field switching (FFS), optically compensated bending (OCB), and polymer-stable alignment (PSA). The liquid crystal element can be manufactured, for example, using a method including steps 1 to 3. In step 1, the substrate used varies depending on the desired operating mode. Steps 2 and 3 are common in all operating modes.

[0100] <Step 1: Coating Formation> First, a coating is formed on the substrate by coating a liquid crystal alignment agent onto the substrate, preferably by heating the coated surface. Examples of substrates that can be used include: float glass, soda glass, etc.; and transparent substrates containing plastics such as polyethylene terephthalate, polybutylene terephthalate, polyethersulfone, polycarbonate, and poly(alicyclic olefins). As a transparent conductive film disposed on one side of the substrate, a NESA film (a registered trademark of PPG Industries, Inc.) containing tin oxide (SnO 2) or an indium tin oxide (ITO) film containing indium oxide-tin oxide (In 2O 3-SnO 2) can be used. In the case of manufacturing TN, STN, or VA type liquid crystal elements, two substrates with patterned transparent conductive films are used. On the other hand, when manufacturing IPS or FFS type liquid crystal elements, a substrate with electrodes patterned into a comb shape and an opposing substrate without electrodes are used.

[0101] There is no particular limitation on the method of coating the substrate with the liquid crystal alignment agent. The coating of the liquid crystal alignment agent onto the substrate can be performed by, for example, spin coating, printing (e.g., offset printing, flexographic printing, etc.), inkjet printing, slot coating, bar coating, extrusion die coating, direct gravure coating, chamber doctor coating, offset gravure coating, impregnation coating, MB coating, etc.

[0102] After coating the liquid crystal alignment agent, it is preferable to perform preheating (pre-baking) to prevent sagging of the coated liquid crystal alignment agent. The pre-baking temperature is preferably 30°C to 200°C, and the pre-baking time is preferably 0.25 minutes to 10 minutes. Afterward, the solvent is completely removed, and a calcination (post-baking) step is performed as needed for the purpose of thermally imidizing the amide structure present in the polymer. The calcination temperature (post-baking temperature) is preferably 80°C to 280°C, more preferably 80°C to 250°C. The post-baking time is preferably 5 minutes to 200 minutes. The thickness of the formed film is preferably 0.001 μm to 1 μm.

[0103] <Step 2: Alignment Processing> In the case of manufacturing TN, STN, IPS, or FFS type liquid crystal elements, a process (alignment processing) is performed to impart liquid crystal alignment capability to the coating film formed in step 1. As a result, the alignment capability of the liquid crystal molecules is imparted to the coating film, forming a liquid crystal alignment film. Preferably, the alignment processing involves rubbing the surface of the coating film formed on the substrate with cotton or nylon, or photoalignment processing by irradiating the coating film with light to impart liquid crystal alignment capability. In the case of manufacturing vertically aligned liquid crystal elements, the coating film formed in step 1 can be used directly as a liquid crystal alignment film. Alternatively, alignment processing can be performed on the coating film to further improve the liquid crystal alignment capability. A liquid crystal alignment film suitable for vertically aligned liquid crystal elements is also preferably used for PSA type liquid crystal elements.

[0104] Light irradiation for photoalignment can be performed by methods such as: irradiating the coating after the post-baking step; irradiating the coating after the pre-baking step and before the post-baking step; or irradiating the coating during the heating process of the coating in at least one of the pre-baking and post-baking steps. As the radiation irradiating the coating, for example, ultraviolet light and visible light containing wavelengths of 150 nm to 800 nm can be used. Ultraviolet light containing wavelengths of 200 nm to 400 nm is preferred. When the radiation is polarized, it can be linearly polarized or partially polarized. When the radiation used is linearly polarized or partially polarized, irradiation can be performed from a direction perpendicular to the substrate surface, from an oblique direction, or a combination of these directions. The irradiation direction for unpolarized radiation is set to an oblique direction.

[0105] Examples of light sources used include: low-pressure mercury lamps, high-pressure mercury lamps, deuterium lamps, metal halide lamps, argon resonant lamps, xenon lamps, excimer lasers, etc. The radiation dose is preferably 200 J / m² to 30,000 J / m², more preferably 500 J / m² to 10,000 J / m². After irradiation with light to impart alignment capability, the substrate surface may be cleaned using, for example, water, an organic solvent (e.g., methanol, isopropanol, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, etc.), or a mixture thereof, or the substrate may be heated.

[0106] <Step 3: Construction of the Liquid Crystal Cell> Prepare two substrates on which liquid crystal alignment films are formed as described above, and manufacture a liquid crystal cell by distributing liquid crystal between the two substrates arranged facing each other. When manufacturing the liquid crystal cell, methods such as: arranging the two substrates facing each other with the liquid crystal alignment films facing each other and a gap between them; bonding the peripheries of the two substrates together using a sealant; injecting and filling liquid crystal into the cell gap surrounded by the substrate surface and the sealant and sealing the injection hole; or using a liquid crystal drop filling (ODF) method. As a sealant, for example, epoxy resin containing a hardener and alumina spheres as spacers can be used. As a liquid crystal, nematic liquid crystal and smectic liquid crystal can be used, with nematic liquid crystal being preferred.

[0107] In PSA mode, the following process is performed: a polymeric compound (e.g., a polyfunctional (meth)acrylate compound, etc.) 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 a pair of substrates. When manufacturing a PSA type liquid crystal element, the proportion of the polymeric compound used relative to 100 parts by mass of the total liquid crystal is, for example, 0.01 parts by mass to 3 parts by mass, preferably 0.05 parts by mass to 1 part by mass.

[0108] In the case of 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 plate made by clamping a polarizing film called an "H film" which is formed by extending and aligning polyvinyl alcohol on one side and absorbing iodine on the other side using a cellulose acetate protective film, or a polarizing plate that includes the H film itself.

[0109] The liquid crystal element disclosed herein can be effectively applied to a variety of uses. Specifically, it can be used, for example, in clocks, handheld game consoles, word processors, laptops, car navigation systems, camcorders, personal digital assistants (PDAs), digital cameras, mobile phones, smartphones, various monitors, LCD TVs, information displays, and other display devices or dimming devices, retardation films, etc. [Examples]

[0110] Hereinafter, the invention will be described in more detail by way of examples, but the invention is not limited to these examples.

[0111] <Structure and Abbreviation of Compounds> The structures and abbreviations of the main compounds used in the following examples are as follows.

[0112] [Tetracarboxylic dianhydride] Compounds (TA-1) to (TA-7): The compounds represented by each of the following formulas (TA-1) to (TA-7) [Chemical 22]

[0113] [Diamine] Compounds (DA-1) to (DA-6): The compounds represented by each of the following formulas (DA-1) to (DA-6) [Chemistry 23]

[0114] Compounds (DB-1) to (DB-6): The compounds represented by each of the following formulas (DB-1) to (DB-6) [Chemistry 24]

[0115] Compound (DC-1), Compound (DC-2): Compounds represented by the following formula (DC-1) or formula (DC-2) [Chemical 25]

[0116] Compounds (DD-1) to (DD-4): The compounds represented by each of the following formulas (DD-1) to (DD-4) [Chemistry 26]

[0117] Compounds (DE-1) to (DE-13): The compounds represented by each of the following formulas (DE-1) to (DE-13) [Chemistry 27][Chemistry 28]

[0118] [Additives] Compounds (AD-1) to (AD-4): Compounds represented by each of the following formulas (AD-1) to (AD-4) [Chemistry 29]

[0119] [Solvents] NMP: N-methyl-2-pyrrolidone (NMP) BC: Butyl Cellosolve (BC)

[0120] <Polymer Synthesis and Evaluation> Polymers were synthesized in the following Synthesis Examples 1 to 52. In addition, in the following examples, the amide content of polyimide in the polymer solution was determined by the following method. [Aamide content of polyimide] The polyimide solution was added to pure water, and the obtained precipitate was thoroughly dried under reduced pressure at room temperature, dissolved in deuterated dimethyl sulfoxide, and measured by 1H-nuclear magnetic resonance (1H-NMR) at room temperature using tetramethylsilane as a reference substance. The amide content [%] was calculated using the following formula (1) based on the obtained 1H-NMR spectrum (400 MHz). Acrylimide rate [%] = (1 - (A1 / (A2×α)))×100 … (1) (In formula (I), A1 is the peak area of ​​protons originating from acetyl groups appearing near a chemical shift of 10 ppm, A2 is the peak area of ​​protons originating from aromatic groups appearing near a chemical shift of 6 ppm to 9 ppm, and α is the ratio of the number of protons from aromatic groups to the number of protons of acetyl groups in the polymer precursor (polyacrylic acid))

[0121] [Synthesis Example 1] Diamine (10 mol of diamine (DA-1), 40 mol of diamine (DB-2), 20 mol of diamine (DC-1) and 30 mol of diamine (DE-3) relative to 100 mol of all diamines) was dissolved in NMP, and tetracarboxylic dianhydride (40 mol of acid dianhydride (TA-1) and 60 mol of acid dianhydride (TA-5) relative to 100 mol of all tetracarboxylic dianhydride) was added. The reaction was carried out at room temperature for 6 hours to obtain a 15% by mass solution of polyacrylic acid (which is designated as polymer (PA-1)).

[0122] [Synthesis Examples 2 to 32] The types and molar ratios of tetracarboxylic dianhydride and diamine were changed as described in Table 1 below. Otherwise, polyamides (polymers (PA-2) to (PA-32)) were obtained in the same manner as in Synthesis Example 1.

[0123] [Synthesis Examples 33 to 38] The types and molar ratios of tetracarboxylic dianhydride and diamine were changed as described in Table 2 below. Otherwise, polyamides (polymers (PA-33) to (PA-38)) were obtained in the same manner as in Synthesis Example 1.

[0124] [Synthesis Example 39] Diamines (50 mol of diamine (DE-11), 30 mol of diamine (DE-12), and 20 mol of diamine (DE-2) relative to 100 mol of all diamines) were dissolved in NMP, and tetracarboxylic acid dianhydride (TA-2) in an amount of 0.95 mol equivalent relative to the total stoichiometry of the diamines was added. The reaction was carried out at room temperature for 6 hours to obtain a solution of polyacrylic acid. 1-methylpiperidine and acetic anhydride in an amount of 0.75 mol equivalent relative to the carboxyl group of polyacrylic acid were added as dehydrating agents to the obtained solution, and the mixture was heated and stirred at 60°C for 3 hours. The obtained solution was repeatedly concentrated under reduced pressure and diluted with NMP to obtain a 10% by mass solution of polyimide (designated as polymer (PI-1)). The amide content of polyimide (PI-1) was 78%.

[0125] [Synthesis Example 40] The types and molar ratios of tetracarboxylic dianhydride and diamine were changed as described in Table 2 below. Otherwise, polyimide (which was set as polymer (PI-2)) was obtained in the same manner as in Synthesis Example 39.

[0126] [Synthesis Examples 41 to 51] The types and molar ratios of the tetracarboxylic dianhydride and diamine were changed as described in Table 3 below. Otherwise, polyamides (polymers (PA-39) to (PA-49)) were obtained in the same manner as in Synthesis Example 1. [Synthesis Example 52] The molar ratio of the dehydrating agent was changed to 0.40 molar equivalents. Otherwise, a 10% by mass solution of polymer (PI-3) as polyimide was obtained in the same manner as in Synthesis Example 39. The amide content of polymer (PI-3) was 50%.

[0127] [Table 1] polymer Acid dianhydride 1 acid dianhydride 2 Specific diamines (D1) Specific diamine (D2-1) Specific diamine (D2-2) Specific diamines (D2-3) Other diamines type type Mörby type Mörby type Mörby type Mörby type Mörby type Mörby type Mörby Synthesis example 1 PA-1 TA-1 40 TA-5 60 DA-1 10 DB-2 40 DC-1 20 - - DE-3 30 Synthesis example 2 PA-2 TA-1 40 TA-5 60 DA-1 10 - - DC-1 20 DD-2 10 DE-3 60 Synthesis example 3 PA-3 TA-1 40 TA-5 60 DA-1 10 DB-2 40 - - DD-2 10 DE-3 40 Synthesis example 4 PA-4 TA-1 40 TA-5 60 DA-1 10 DB-2 40 DC-1 20 DD-2 10 DE-3 20 Synthesis example 5 PA-5 TA-1 100 - - DA-2 60 DB-3 20 DC-1 20 - - - - Synthesis example 6 PA-6 TA-1 100 - - DA-2 60 - - DC-1 20 DD-1 20 - - Synthesis Example 7 PA-7 - - TA-6 100 DA-2 60 DB-3 20 DC-1 20 - - - - Synthesis example 8 PA-8 - - TA-6 100 DA-2 60 - - DC-1 20 DD-1 20 - - Synthesis example 9 PA-9 TA-4 20 TA-6 80 DA-3 40 DB-3 40 DC-1 20 - - - - Synthesis example 10 PA-10 TA-3 20 TA-6 80 DA-4 20 DB-1 50 DC-1 20 - - DE-1 10 Synthesis Example 11 PA-11 TA-3 20 TA-6 80 DA-4 20 DB-1 50 DC-1 20 DD-2 10 - - Synthesis Example 12 PA-12 TA-1 60 TA-5 40 DA-5 20 DB-3 50 DC-1 20 - - DE-1 10 Synthesis Example 13 PA-13 TA-1 60 TA-5 40 DA-6 10 DB-1 50 DC-1 20 - - DE-2 20 Synthesis Example 14 PA-14 TA-1 60 TA-5 40 DA-6 10 DB-4 50 DC-1 20 - - DE-2 20 Synthesis Example 15 PA-15 TA-1 60 TA-5 40 DA-6 10 - - DC-1 40 DD-2 20 DE-2 30 Synthesis Example 16 PA-16 TA-1 60 TA-5 40 DA-6 10 DB-1 50 DC-1 30 DD-2 10 - - Synthesis Example 17 PA-17 TA-1 60 TA-5 40 DA-6 10 DB-1 50 DC-1 30 DD-3 10 - - Synthesis Example 18 PA-18 TA-1 100 - - - - - - - - - - DE-3 100 Synthesis example 19 PA-19 TA-1 100 - - - - DB-2 40 DC-1 20 - - DE-3 40 Synthesis example 20 PA-20 TA-1 100 - - - - DB-2 40 - - DD-2 20 DE-3 40 Synthesis Example 21 PA-21 TA-1 100 - - - - - - DC-1 40 DD-2 20 DE-3 40 Synthesis example 22 PA-22 TA-1 100 - - DA-1 10 - - - - - - DE-3 90 Synthesis Example 23 PA-23 TA-1 100 - - DA-1 20 - - - - - - DE-3 80 Synthesis Example 24 PA-24 TA-1 40 TA-5 60 DA-1 10 - - - - - - DE-3 90 Synthesis Example 25 PA-25 TA-1 40 TA-5 60 DA-1 10 DB-2 40 - - - - DE-3 50 Synthesis Example 26 PA-26 TA-1 40 TA-5 60 DA-1 10 - - DC-1 20 - - DE-3 70 Synthesis Example 27 PA-27 TA-1 40 TA-5 60 DA-1 10 - - - - DD-2 20 DE-3 70 Synthesis Example 28 PA-28 TA-1 40 TA-5 60 DA-1 10 - - DC-1 20 - - DE-4 70 Synthesis Example 29 PA-29 TA-1 40 TA-5 60 DA-1 10 - - DC-1 20 - - DE-5 70 Synthesis Example 30 PA-30 - - TA-6 100 DA-2 60 DB-3 20 - - - - DE-1 20 Synthesis Example 31 PA-31 - - TA-6 100 DA-2 60 - - DC-1 20 - - DE-1 20 Synthesis example 32 PA-32 TA-1 100 - - DA-6 10 DB-1 50 DC-1 20 - - DE-2 20

[0128] [Table 2] polymer Acid dianhydride 1 acid dianhydride 2 Diamine 1 Diamine 2 Diamine 3 Diamine 4 Kind Kind Mörby Kind Mörby Kind Mörby Kind Mörby type Mörby type Mörby Synthesis example 33 PA-33 TA-2 100 - - DE-6 30 DE-7 30 DE-1 20 DE-8 20 Synthesis example 34 PA-34 TA-2 70 TA-1 30 DE-6 60 DE-9 20 DE-10 20 - - Synthesis Example 35 PA-35 TA-1 100 - - DB-1 100 - - - - - - Synthesis Example 36 PA-36 TA-6 100 - - DB-3 100 - - - - - - Synthesis Example 37 PA-37 TA-1 100 - - DB-4 100 - - - - - - Synthesis example 38 PA-38 TA-5 100 - - DB-4 100 - - - - - - Synthesis Example 39 PI-1 TA-2 100 - - DE-11 50 DE-12 30 DE-2 20 - - Synthesis Example 40 PI-2 TA-2 70 TA-3 30 DE-11 30 DE-13 50 DD-3 20 - -

[0129] [Table 3] polymer Acid dianhydride 1 acid dianhydride 2 Specific diamines (D1) Specific diamine (D2-1) Specific diamine (D2-2) Specific diamines (D2-3) Other diamines type type Mörby type Mörby type Mörby type Mörby type Mörby type Mörby type Mörby Synthesis Example 41 PA-39 TA-1 40 TA-6 60 DA-6 10 DB-1 50 DC-1 20 - - DE-2 20 Synthesis Example 42 PA-40 TA-1 40 TA-6 60 DA-6 10 DB-5 50 DC-1 20 - - DE-2 20 Synthesis Example 43 PA-41 TA-1 40 TA-6 60 DA-6 10 DB-6 50 DC-1 20 - - DE-2 20 Synthesis Example 44 PA-42 TA-1 40 TA-6 60 DA-6 10 DE-8 20 DC-1 20 - - DE-2 50 Synthesis Example 45 PA-43 TA-1 40 TA-6 60 DA-6 10 DE-9 20 DC-1 20 - - DE-2 50 Synthesis Example 46 PA-44 TA-1 40 TA-6 60 DA-6 10 - - DC-1 40 DD-2 20 DE-2 30 Synthesis Example 47 PA-45 TA-1 40 TA-6 60 DA-6 10 - - DC-2 40 DD-2 20 DE-2 30 Synthesis Example 48 PA-46 TA-1 40 TA-6 60 DA-6 10 - - DC-1 40 DD-4 20 DE-2 30 Synthesis Example 49 PA-47 TA-1 40 TA-6 60 DA-6 10 - - DC-1 60 DD-4 30 - - Synthesis Example 50 PA-48 TA-1 40 TA-6 60 DA-6 10 - - DC-1 40 DE-10 20 DE-2 30 Synthesis Example 51 PA-49 TA-1 40 TA-6 60 DA-6 10 - - DC-1 40 DE-11 20 DE-2 30

[0130] Regarding the values ​​in Tables 1 to 3, for acid dianhydrides, it indicates the proportion of each compound used relative to the total amount (100 mol%) of acid dianhydrides used in the synthesis (mol%), and for diamines, it indicates the proportion of each compound used relative to the total amount (100 mol%) of diamines used in the synthesis (mol%).

[0131] <Preparation and Evaluation of Liquid Crystal Orientation Agent> [Example 1: Photo-aligned FFS type liquid crystal display element] (1) Preparation of liquid crystal orientation agent The polymer components (solid component conversion: 20 parts by mass of polymer (PI-1), 80 parts by mass of polymer (PA-1), 5 parts by mass of crosslinking agent (N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamine (the compound represented by formula (AD-1))) and 1 part by mass of bonding agent (3-glycidoxypropyltrimethoxysilane (the compound represented by formula (AD-4))) were diluted with NMP and BC to obtain a solution with a solid component concentration of 4.0% by mass and a solvent composition ratio of NMP:BC = 70:30 (mass ratio). The solution was filtered using a filter with a pore size of 0.2 μm to prepare liquid crystal orientation agent (AL-1).

[0132] (2) Formation of the liquid crystal alignment film based on photoalignment method: The liquid crystal alignment agent (AL-1) prepared in (1) is coated onto the surfaces of a glass substrate on which a planar electrode, an insulating layer and a comb-shaped electrode are sequentially deposited on one side, and an opposing glass substrate without electrodes. After heating on a hot plate at 80°C for 1 minute, the coating is heated for 30 minutes in an oven at 230°C with nitrogen purging in the chamber, forming a coating with an average film thickness of 100 nm. The surface of the coating is photoaligned by irradiating the surface of the coating with 200 mJ / cm² of ultraviolet light containing a 254 nm bright line with linear polarization from the substrate normal direction using an Hg-Xe lamp. The photoaligned coating is then heat-treated by heating it for 30 minutes in an oven at 230°C with nitrogen purging in the chamber, forming the liquid crystal alignment film.

[0133] (3) Manufacturing of FFS type liquid crystal display element: A liquid crystal injection port is left on the outer periphery of the surface of one of the substrates with the liquid crystal alignment film prepared in (2). After applying epoxy resin adhesive containing alumina balls with a diameter of 3.5 μm using a dispenser, the surfaces of the two substrates with the liquid crystal alignment films are facing each other and pressed together with the alignment processing directions of each substrate being antiparallel. The adhesive is then heat-cured at 150°C for 1 hour. Subsequently, negative nematic liquid crystal (Merck, MJ20195NCMP) is filled into the gap between the substrates through the liquid crystal injection port, and the liquid crystal injection port is sealed with epoxy adhesive. Furthermore, in order to remove the flow alignment during liquid crystal injection, the liquid crystal is heated at 120°C and then slowly cooled to room temperature. Next, polarizing plates are attached to the outer sides of the substrates with their polarization directions orthogonal to each other and at an angle of 45° to the alignment processing direction of the liquid crystal alignment film, thereby manufacturing an FFS type liquid crystal display element.

[0134] (4) Evaluation of liquid crystal alignment: For the liquid crystal display element manufactured in (3), an abnormal region (domain) was observed in the brightness change when a voltage of 5 V was applied / removed (ON / OFF) using a microscope at a magnification of 50x. Regarding the evaluation, the case where no abnormal region was observed was set as "good", and the case where an abnormal region was observed was set as "bad". As a result, the evaluation in this embodiment is "good".

[0135] (5) Evaluation of long-term image retention at room temperature (DC mitigation characteristics): The liquid crystal display element manufactured in (3) was placed in an environment of 25°C and 1 atmosphere. Using a 30 Hz alternating current (AC) rectangular wave, the image was driven at 100% relative transmittance. After setting the brightness difference between any two pixels to 0, AC driving was performed under backlight illumination, while a DC 0.5 V was applied to only a single pixel for 30 minutes to accumulate charge. When the DC 0.5 V application ended and the image was driven back to AC with a relative transmittance of 50%, a brightness difference ΔL was generated between the two pixels due to the accumulated charge. The change in brightness difference ΔL over time was observed, and the time from the end of the DC 0.5 V application until the brightness difference ΔL reached less than 36.8% of its initial value was defined as the image retention time. Furthermore, the shorter the time, the easier it is for the image retention caused by the accumulated charge to disappear, indicating a better DC mitigation characteristic. Regarding the evaluation, cases where the afterimage removal time is less than 10 minutes are rated as "Excellent," cases where it is more than 10 minutes but less than 20 minutes are rated as "Good," cases where it is more than 20 minutes but less than 30 minutes are rated as "Acceptable," and cases where it is more than 30 minutes are rated as "Unacceptable." In this embodiment, the evaluation is "Good."

[0136] (6) Evaluation of short-term high-temperature image retention (DC accumulation characteristics): The liquid crystal display element manufactured in (3) was placed in an environment of 60°C and 1 atmosphere. A 30 Hz AC rectangular wave was used to drive the image at 100% relative transmittance. After setting the brightness difference between any two pixels to 0, AC driving was performed under backlight illumination, while a DC 0.2 V was applied to a single pixel for 30 minutes to accumulate charge. When the DC 0.2 V application ended and the driving returned to AC only with 50% relative transmittance, a brightness difference ΔL was generated between the two pixels due to the accumulated charge. Furthermore, the smaller the brightness difference, the less likely charge is to accumulate, indicating a better DC accumulation characteristic. A value less than 1% of the brightness difference ΔL divided by the average brightness of the two pixels was rated as "excellent," 1% or more but less than 2% as "good," 2% or more but less than 3% as "acceptable," and 3% or more as "unacceptable." The result is rated as "acceptable" in this embodiment.

[0137] [Examples 2-17, Examples 26-29] In Example 1, the types and amounts of polymer components contained in the liquid crystal alignment agent were changed as shown in Table 4 below. Otherwise, the liquid crystal alignment agent was prepared in the same manner as in Example 1, a liquid crystal alignment film was formed by photoalignment, and an FFS type liquid crystal display element was manufactured and various evaluations were performed. The evaluation results are shown in Table 4 below. In addition, the exposure amount of ultraviolet light after linear polarization was set to 200 mJ / cm2 in Examples 2-4, Examples 10-11, Examples 13-17, Examples 26, and Examples 28-29, and to 500 mJ / cm2 in other examples.

[0138] [Comparative Examples 1 to 14] In Example 1, the types and amounts of polymer components contained in the liquid crystal alignment agent were changed as shown in Table 5 below. Otherwise, the liquid crystal alignment agent was prepared in the same manner as in Example 1, a liquid crystal alignment film was formed by photoalignment, and an FFS type liquid crystal display element was manufactured and various evaluations were performed. The evaluation results are shown in Table 5 below. In addition, the exposure amount of linearly polarized ultraviolet light was set to 200 mJ / cm² in Comparative Examples 1 to 12, and to 500 mJ / cm² in Comparative Examples 13 and 14.

[0139] [Example 18: Friction-aligned FFS type liquid crystal display element] (1) Preparation of liquid crystal alignment agent The polymer components (solid component conversion: 20 parts by mass of polymer (PI-2), 80 parts by mass of polymer (PA-1), 5 parts by mass of crosslinking agent (N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamine (the compound represented by formula (AD-1))) and 1 part by mass of bonding agent (3-glycidoxypropyltrimethoxysilane (the compound represented by formula (AD-4))) were diluted with NMP and BC to obtain a solution with a solid component concentration of 4.0% by mass and a solvent composition ratio of NMP:BC = 70:30 (mass ratio). The solution was filtered using a filter with a pore size of 0.2 μm to prepare the liquid crystal alignment agent (AL-18).

[0140] (2) Formation of the liquid crystal alignment film based on the friction method: The liquid crystal alignment agent (AL-18) prepared in (1) was coated onto the surfaces of a glass substrate on which a planar electrode, an insulating layer and a comb-shaped electrode were sequentially deposited on one side, and an opposing glass substrate without electrodes. After heating on a hot plate at 80°C for 1 minute, the coating was heated in an oven at 230°C with nitrogen purging for 30 minutes to form a coating with an average thickness of 100 nm. For the surface of the coating, a friction machine with a roller with a nylon cloth wound on it was used to perform two friction treatments at a roller speed of 1000 rpm, a platform movement speed of 30 mm / s, and a bristle indentation length of 0.3 mm. The coating that had undergone friction alignment treatment was ultrasonically cleaned in ultrapure water for 1 minute and then dried in an oven at 100°C for 10 minutes to form the liquid crystal alignment film.

[0141] (3)The FFS type liquid crystal display element is manufactured using a pair of substrates having a liquid crystal alignment film produced by the friction method in (2) as a substrate having a liquid crystal alignment film. Otherwise, the FFS type liquid crystal display element is manufactured in the same manner as in Example 1.

[0142] (4) Evaluation of liquid crystal alignment The liquid crystal alignment of the FFS type liquid crystal display element manufactured in (3) was evaluated in the same manner as in Example 1. The result was "good" in this example.

[0143] (5) Evaluation of long-term image retention at room temperature (DC mitigation characteristics) The DC mitigation characteristics of the FFS type liquid crystal display element manufactured in (3) were evaluated in the same manner as in Example 1. The result was "good" in this example.

[0144] (6) Evaluation of high-temperature short-term image retention (DC accumulation characteristics) For the FFS type liquid crystal display element manufactured in (3), the DC accumulation characteristics were evaluated in the same manner as in Example 1. The result was "acceptable" in this example.

[0145] [Examples 19 to 25] In Example 18, the types and amounts of polymer components contained in the liquid crystal alignment agent were changed as shown in Table 4 below. Otherwise, the liquid crystal alignment agent was prepared in the same manner as in Example 18, a liquid crystal alignment film was formed by a rubbing method, and an FFS type liquid crystal display element was manufactured and various evaluations were performed. The evaluation results are shown in Table 4 below.

[0146] [Table 4] Liquid crystal alignment agent Polymer 1 Polymer 2 Polymer 3 Liquid crystal display element type type mass ratio type mass ratio type mass ratio Liquid crystal alignment Long-term residual image at room temperature High temperature short-term afterimage Example 1 AL-1 PA-1 80 PI-1 20 - - good good Can Example 2 AL-2 PA-2 80 PI-1 20 - - good good good Example 3 AL-3 PA-3 80 PI-1 20 - - good good Can Example 4 AL-4 PA-4 80 PI-1 20 - - good good good Example 5 AL-5 PA-5 60 PA-33 40 - - good Can Can Example 6 AL-6 PA-6 60 PA-33 40 - - good Can good Example 7 AL-7 PA-7 60 PA-33 40 - - good good Can Example 8 AL-8 PA-8 60 PA-33 40 - - good good good Example 9 AL-9 PA-9 60 PA-33 40 - - good Can Can Example 10 AL-10 PA-10 80 PI-1 20 - - good Can Can Example 11 AL-11 PA-11 80 PI-1 20 - - good Can Can Example 12 AL-12 PA-12 60 PA-33 40 - - good good Can Example 13 AL-13 PA-13 80 PI-1 20 - - good good good Example 14 AL-14 PA-14 80 PI-1 20 - - good good Can Example 15 AL-15 PA-15 80 PI-1 20 - - good excellent good Example 16 AL-16 PA-16 80 PI-1 20 - - good excellent excellent Example 17 AL-17 PA-17 80 PI-1 20 - - good good good Example 18 AL-18 PA-1 80 PI-2 20 - - good good Can Example 19 AL-19 PA-2 80 PI-2 20 - - good good good Example 20 AL-20 PA-7 60 PA-34 40 - - good good Can Example 21 AL-21 PA-8 60 PA-34 40 - - good good good Example 22 AL-22 PA-9 60 PA-34 40 - - good Can Can Example 23 AL-23 PA-10 80 PI-2 20 - - good Can Can Example 24 AL-24 PA-12 60 PA-34 40 - - good good Can Example 25 AL-25 PA-13 80 PI-2 20 - - good good good Example 26 AL-26 PA-1 60 PI-1 20 PA-35 20 good good good Example 27 AL-27 PA-5 50 PA-33 30 PA-36 20 good good good Example 28 AL-28 PA-10 60 PI-1 20 PA-37 20 good Can good Example 29 AL-29 PA-32 60 PI-1 20 PA-38 20 good excellent excellent

[0147] [Table 5] Liquid crystal alignment agent Polymer 1 Polymer 2 Polymer 3 Liquid crystal display element type type mass ratio type mass ratio type mass ratio Liquid crystal alignment Long-term residual image at room temperature High temperature short-term afterimage Comparative Example 1 AL-30 PA-18 80 PI-1 20 - - good No good Comparative Example 2 AL-31 PA-19 80 PI-1 20 - - good No excellent Comparative Example 3 AL-32 PA-20 80 PI-1 20 - - good No excellent Comparative Example 4 AL-33 PA-21 80 PI-1 20 - - good No excellent Comparative Example 5 AL-34 PA-22 80 PI-1 20 - - good Can No Comparative Example 6 AL-35 PA-23 80 PI-1 20 - - good Can No Comparative Example 7 AL-36 PA-24 80 PI-1 20 - - good good No Comparative Example 8 AL-37 PA-25 80 PI-1 20 - - good good No Comparative Example 9 AL-38 PA-26 80 PI-1 20 - - good good No Comparative Example 10 AL-39 PA-27 80 PI-1 20 - - good good No Comparative Example 11 AL-40 PA-28 80 PI-1 20 - - good good No Comparative Example 12 AL-41 PA-29 80 PI-1 20 - - good good No Comparative Example 13 AL-42 PA-30 60 PA-33 40 - - good Can No Comparative Example 14 AL-43 PA-31 60 PA-33 40 - - good good No

[0148] In Tables 4 and 5, the mass ratio of each polymer in the liquid crystal alignment agent represents the proportion (parts by mass) of each polymer relative to the total 100 parts by mass of the polymer components used in the preparation of the liquid crystal alignment agent. In each example, the liquid crystal alignment agent is prepared with 5 parts by mass of a crosslinking agent (N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamine (the compound represented by formula (AD-1)) and 1 part by mass of a bonding agent (3-glycidoxypropyltrimethoxysilane (the compound represented by formula (AD-4)) relative to the total 100 parts by mass of the polymer components.

[0149] As shown in Table 4, the liquid crystal alignment agents of Examples 1 to 29 containing polymer (P) exhibited "good" liquid crystal alignment properties, and both long-term image retention at room temperature (DC mitigation characteristics) and short-term image retention at high temperature (DC accumulation characteristics) were "excellent," "good," or "acceptable," achieving a balance of various properties. In contrast, the liquid crystal alignment agents of Comparative Examples 1 to 14, which did not contain polymer (P), showed "unacceptable" DC mitigation and DC accumulation characteristics in their liquid crystal display elements, which were worse than those of the Examples.

[0150] The mechanism by which the image retention characteristics of the liquid crystal display element are improved in Examples 1 to 29 is not yet certain, but it is speculated as follows.

[0151] The polymers contained in the liquid crystal alignment agents of Examples 1 to 29 have a partial structure (U1) (a partial structure with hole transport capability), and any two or all of the following three partial structures: partial structure (U2-1) (a partial structure with hydrogen bonding capability), partial structure (U2-2) (a partial structure with acidic functional groups), and partial structure (U2-3) (a partial structure with basic functional groups). In contrast, in the liquid crystal alignment agents of Comparative Examples 1 to 4, the polymers do not have a partial structure (U1); in the liquid crystal alignment agents of Comparative Examples 5 to 7, the polymers do not have partial structures (U2-1), (U2-2), and (U2-3); and in the liquid crystal alignment agents of Comparative Examples 8 to 14, the polymers have only one of the following three partial structures: partial structure (U2-1), partial structure (U2-2), and partial structure (U2-3).

[0152] From the viewpoint of long-term post-image at room temperature (DC mitigation properties), the polymer preferably has a partial structure exhibiting hole transport, and more preferably has a partial structure derived from aromatic tetracarboxylic dianhydride. In the liquid crystal alignment agents of Examples 1 to 29, the polymer has a partial structure (U1), and the DC mitigation properties are evaluated as "acceptable" or better. In contrast, in the liquid crystal alignment agents of Comparative Examples 1 to 4, the polymer does not have a partial structure (U1), and therefore the DC mitigation properties are considered "unacceptable".

[0153] From the viewpoint of high-temperature short-term image retention (DC accumulation characteristics), it is preferable that the physical or electrical properties of the liquid crystal alignment film are not easily changed and are stable under high temperature and backlight, and further preferably that the movement or bias of ionic impurities in the liquid crystal cell is suppressed. In the liquid crystal alignment agents of Examples 1 to 29, the polymer has two or all of the partial structures (U2-1), partial structures (U2-2), and partial structures (U2-3), and the DC accumulation characteristics are evaluated as "acceptable" or above. In contrast, in the liquid crystal alignment agents of Comparative Examples 5 to 14, the polymer has only one of the partial structures (U2-1), partial structures (U2-2), and partial structures (U2-3), or none of them, and therefore the DC accumulation characteristics are considered to be "unacceptable".

[0154] Regarding this aspect, it is believed that: by having two or all of the partial structures (U2-1), partial structures (U2-2), and partial structures (U2-3) in the polymer, the intermolecular interaction between the polymers in the liquid crystal alignment film is enhanced, the swelling or thermal expansion of the liquid crystal is suppressed, thereby suppressing the changes in physical or electrical properties under high temperature and backlight, and further suppressing the diffusion of ionic impurities in the liquid crystal alignment film in the liquid crystal layer or the movement caused by the electric field.

[0155] Furthermore, in polymer (P), it is believed that: amide or urea bonds in some structures (U2-1) can function as hydrogen bond donors and acceptors; carboxylic acid or sulfonic acid groups in some structures (U2-2) can function as hydrogen bond donors and acceptors; and basic functional groups in some structures (U2-3) can function as hydrogen bond acceptors. Moreover, it is believed that: when acidic and basic functional groups coexist, intermolecular interactions can also be formed through acid-base group interactions (ionic interactions).

[0156] From the viewpoint of liquid crystal alignment, it is preferable to include a polymer (P) and a polymer (Q), wherein the polymer (Q), which is mainly responsible for imparting and improving liquid crystal alignment, and the polymer (P), which is mainly responsible for imparting and improving electrical properties, are separated into upper and lower layers respectively. When a liquid crystal alignment agent is prepared that includes both polymer (P) and a polymer (Q-1) having a polar group protected by a Boc group as polymer (Q), the hydrophobicity of polymer (Q) is improved, and it tends to be present on the film surface more easily than polymer (P), thus easily exhibiting liquid crystal alignment. Furthermore, it is also believed that the generation of polar groups through thermal desorption of Boc groups can facilitate crosslinking or intermolecular interactions between polymers.

[0157] In addition, the liquid crystal alignment agents of Examples 26 to 29 also contain a polymer (third polymer) that does not have a partial structure (U1) and a partial structure (U2-2) and tends to be present on the substrate interface side compared with polymers (P) and (Q-1). The DC accumulation characteristics are all "excellent" or "good", and the balance of various characteristics is excellent. It is speculated that by adjusting the third polymer, charge acceptance (hole injection, etc.) with the ITO electrode can be suppressed, and the accumulation of charge can be further reduced. It is believed that the highest occupied molecular orbital (HOMO) of diamines with hole transport capability is usually high. When it exceeds the work function of ITO, hole injection from the ITO electrode is easily generated.

[0158] [Examples 30 to 40] In Example 1, the polymer components and the type and amount of crosslinking agent contained in the liquid crystal alignment agent were changed as shown in Table 6 below. Otherwise, the liquid crystal alignment agent was prepared in the same manner as in Example 1, a liquid crystal alignment film was formed by photoalignment, and an FFS type liquid crystal display element was manufactured and various evaluations were performed. The evaluation results are shown in Table 6 below.

[0159] [Table 6] Liquid crystal alignment agent Polymer 1 Polymer 2 Crosslinking agent Liquid crystal display element type type mass ratio type mass ratio type mass ratio Liquid crystal alignment Long-term residual image at room temperature High temperature short-term afterimage Example 30 AL-44 PA-39 80 PI-3 20 AD-2 5 good good good Example 31 AL-45 PA-40 80 PI-3 20 AD-2 5 good good excellent Example 32 AL-46 PA-41 80 PI-3 20 AD-2 5 good good excellent Example 33 AL-47 PA-42 80 PI-3 20 AD-2 5 good good good Example 34 AL-48 PA-43 80 PI-3 20 AD-2 5 good good good Example 35 AL-49 PA-44 80 PI-3 20 AD-3 10 good excellent good Example 36 AL-50 PA-45 80 PI-3 20 AD-3 10 good excellent good Example 37 AL-51 PA-46 80 PI-3 20 AD-3 10 good good good Example 38 AL-52 PA-47 80 PI-3 20 AD-3 10 good good good Example 39 AL-53 PA-48 80 PI-3 20 AD-3 10 good good good Example 40 AL-54 PA-49 80 PI-3 20 AD-3 10 good good good

[0160] In Table 6, the mass ratio of each polymer in the liquid crystal alignment agent represents the proportion (parts by mass) of each polymer relative to the total 100 parts by mass of the polymer components used in the preparation of the liquid crystal alignment agent. In each example, a bonding agent (3-glycidoxypropyltrimethoxysilane (the compound represented by formula (AD-4))) is prepared in the liquid crystal alignment agent in a proportion of 1 part by mass relative to the total 100 parts by mass of the polymer components.

[0161] As shown in Table 6, the liquid crystal display elements containing the liquid crystal alignment agents of Examples 30 to 40 (P) have "good" liquid crystal alignment properties, and both "excellent" or "good" DC mitigation and DC accumulation properties, achieving a balance of various properties.

[0162] Based on the above, it is clear that the liquid crystal display element containing the liquid crystal alignment agent of polymer (P) has good liquid crystal alignment, good DC accumulation characteristics and DC mitigation characteristics, and is not prone to image retention.

Claims

1. A liquid crystal alignment agent comprising a polymer (P) and a polymer (Q) different from said polymer (P), said polymer (P) comprising, within the same molecule, any one or more of the partial structures represented by formula (1) and formula (2), formula (3) and formula (4), and molecules comprising the partial structure represented by formula (1) comprising, within the same molecule or in different molecules, any two or more of the partial structures represented by formula (2), formula (3) and formula (4); said polymer (Q) is at least one selected from the group consisting of polyamide, polyamide ester and polyimide, and does not have the partial structure represented by formula (1); in formula (1), X1 is a tetravalent organic group; Y1 is a divalent organic group having a partial structure formed by removing two hydrogen atoms from the structure represented by formula (Y-1), In formula (Y-1), A1 and A2 are each independently a monovalent group with an aromatic hydrocarbon ring bonded to the nitrogen atom in formula (Y-1), or represent a nitrogen-containing condensed heterocyclic structure formed by the combination of A1 and A2 and the nitrogen atoms bonded to A1 and A2; A3 is a hydrogen atom or a monovalent organic group; wherein, In the case where A1 and A2 represent nitrogen-containing condensed heterocyclic structures that are mutually bonded and together with nitrogen atoms bonded to A1 and A2, the nitrogen-containing condensed heterocyclic structure has two or more aromatic hydrocarbon rings, and the two aromatic hydrocarbon rings of the nitrogen-containing condensed heterocyclic structure have a fused ring structure that shares a nitrogen atom in formula (Y-1), or A3 has an aromatic hydrocarbon ring and the aromatic hydrocarbon ring of A3 is bonded to a nitrogen atom in formula (Y-1). In formulas (2), (3), and (4), X2, X3, and X4 are each independently tetravalent organic groups; Y2 is a divalent group that contains a chain hydrocarbon structure in the main chain and a portion of the structure adjacent to "*1-NR1-CO-", "*1-CO-NR1-", "*1-NR1-CO-NR2-", or "*1-CO-NR1-NR2-CO-"; R1 and R2 are each independently hydrogen atoms or monovalent organic groups; "*1" represents a chain hydrocarbon structure. The structure is defined by the following bonds: Y3 is a divalent organic group having a carboxylic acid group or a sulfonic acid group; Y4 is a divalent organic group having at least one partial structure selected from the group consisting of nitrogen-containing heterocycles, "-R3-NR4-R5-", and "-R6-NR7R8", except for the group equivalent to Y2; R3, R5, and R6 are each independently a divalent aliphatic hydrocarbon group; R4, R7, and R8 are each independently a hydrogen atom, a thermally detachable group, or a monovalent aliphatic hydrocarbon group.

2. The liquid crystal alignment agent as claimed in claim 1, wherein the polymer (P) comprises, within the same molecule, any two or more of the partial structures represented by formula (1), formula (2), formula (3), and formula (4).

3. The liquid crystal alignment agent as claimed in claim 1, wherein the polymer (P) comprises structural units derived from aromatic tetracarboxylic acid dianhydrides.

4. The liquid crystal alignment agent as claimed in claim 1, comprising a polymer (Q) comprising at least one of the group consisting of a partial structure represented by formula (5) and a partial structure represented by formula (6); wherein in formulas (5) and (6), X5 and X6 are each independently a tetravalent group having an alicyclic structure; and Y5 and Y6 are each independently a divalent organic group comprising a partial structure having a thermally detachable group bonded to a nitrogen atom.

5. The liquid crystal alignment agent as claimed in claim 4, wherein the alicyclic structure is a substituted or unsubstituted cyclobutane ring structure.

6. The liquid crystal alignment agent as claimed in claim 1 further comprises a compound having at least three groups selected from the group consisting of oxetyl, oxetyl, hydroxyl, mercapto, amino, and polymerizable carbon-carbon double bond groups within one molecule.

7. The liquid crystal alignment agent as claimed in claim 1 further comprises a compound having a trialkoxysilyl group.

8. A liquid crystal alignment film formed using a liquid crystal alignment agent as described in any one of claims 1 to 7.

9. A liquid crystal element comprising a liquid crystal alignment film as described in claim 8.