JP7768082B2 - Liquid crystal alignment agent, liquid crystal alignment film, liquid crystal element and polymer - Google Patents

Description

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

In recent years, with the demand for higher resolution and more versatile liquid crystal elements, there has been a demand not only for further improvements in voltage retention characteristics and display quality, but also for suppressing variations in the orientation of liquid crystal molecules within pixels that occur due to variations in the manufacturing process. Variations in the orientation of liquid crystal molecules cause variations in brightness within the plane when displaying black, which can ultimately lead to a decrease in contrast in liquid crystal elements.

To suppress the above-mentioned decrease in contrast, it has been disclosed that a liquid crystal aligning agent contains a polyamic acid or polyimide obtained using a diamine having a triple bond in the main chain and a diamine having a naphthalene ring (see Patent Document 1).

International Publication No. 2021/140034

In order to prevent a decrease in contrast in liquid crystal devices, a relatively flexible skeleton can be introduced into the main chain of the polymer component of the liquid crystal alignment film. This improves the stretchability of liquid crystal alignment films formed by rubbing, and improves the thermal reorientation of photo-aligned films. However, introducing a highly flexible skeleton into the main chain of the polymer that makes up the liquid crystal alignment film raises concerns that this may cause a decrease in film density and lead to a decrease in voltage holding ratio. As a result, it has not yet been possible to achieve both low in-plane variation in the alignment orientation of the liquid crystal (hereinafter referred to as "alignment uniformity") and voltage holding characteristics at the currently required display quality level, and further improvement is required. Liquid crystal devices are also required to be resistant to deviations in the alignment orientation of the liquid crystal due to the application of stress, and to have good liquid crystal alignment properties.

The present invention has been made in consideration of the above-mentioned problems, and its main object is to provide a liquid crystal alignment agent that exhibits excellent liquid crystal alignment properties and alignment uniformity, and can produce liquid crystal elements with excellent voltage retention characteristics.

After extensive research, the inventors have resolved the above-mentioned problems by forming a liquid crystal alignment film using a polymer having a specific fused ring structure in its main chain. The present invention provides the following means:

[1] A liquid crystal aligning agent containing a polymer [A] having a partial structure (a) represented by the following formula (1) in its main chain:
(In formula (1), An ¹ has a substituted or unsubstituted fused ring structure comprising a plurality of aromatic monocycles, and is a divalent group obtained by removing one hydrogen atom from each of two different rings among the plurality of aromatic monocycles constituting the fused ring, or by removing one hydrogen atom from each of two different rings among the plurality of aromatic monocycles contained in a substituent of the fused ring structure. ^{X 1} and X ² each independently represent -S-, -NR ¹ -, -C(═O)-, -NR ¹ -C(═O)-, -NR ¹ -C(═O)-NR ² -, a substituted or unsubstituted alkanediyl group having 1 to 18 carbon atoms, or a substituted or unsubstituted alkanediyl group having 2 to 18 carbon atoms in which some methylene groups are -O-, -S-, -NR ¹ -, -C(═O)-, -NR ¹ -C(═O)-, or -NR ¹ a divalent group substituted with -C(=O)-NR ² - (excluding the case where X ¹ and X ² in formula (1) are simultaneously -NR ¹ - when An ¹ has a fluorene structure, and the case where X ¹ and X ² in formula (1) are simultaneously -NR ¹ -C(=O)- when An ^{1 has a carbazole structure). However, the aromatic monocycle in An 1 to} which X ¹ is bonded is different from the aromatic monocycle in An ¹ to which X ² is bonded. ^{R 1} and R ² are each independently a hydrogen atom or a monovalent organic group. ^{Ar 1} and Ar ² are each independently a divalent aromatic ring group. "*" represents a bond.)

[2] A liquid crystal alignment film formed using the liquid crystal alignment agent according to [1] above.
[3] A liquid crystal element comprising the liquid crystal alignment film of [3] above.
[4] A polymer which is a polyamic acid, a polyamic acid ester, or a polyimide and has a partial structure represented by the above formula (1) in its main chain.

The liquid crystal aligning agent of the present invention not only exhibits excellent liquid crystal alignment and alignment uniformity, but also enables the production of liquid crystal devices with excellent voltage retention characteristics.

Liquid crystal alignment agent
The liquid crystal aligning agent of the present disclosure contains a polymer [A] having a specific fused ring structure in the main chain. Below, each component contained in the liquid crystal aligning agent of the present disclosure and other components that are optionally blended as needed will be described. Note that, unless otherwise specified, each component may be used alone or in combination of two or more.

As used herein, the term "hydrocarbon group" includes chain-like hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. A "chain-like hydrocarbon group" refers to a linear or branched hydrocarbon group that does not contain a cyclic structure in its main chain and is composed solely of a chain structure. Chain-like hydrocarbon groups may be saturated or unsaturated. An "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. An alicyclic hydrocarbon group does not necessarily have to be composed solely of an alicyclic hydrocarbon structure and may also contain a chain structure as part of its structure. An "aromatic hydrocarbon group" refers to a hydrocarbon group that contains an aromatic ring structure as its ring structure. An aromatic hydrocarbon group does not necessarily have to be composed solely of an aromatic ring structure and may contain a chain structure or an alicyclic hydrocarbon structure as part of its structure. An "aromatic ring" includes aromatic hydrocarbon rings and aromatic heterocycles. An "organic group" refers to an atomic group formed by removing any hydrogen atom from a carbon-containing compound (i.e., an organic compound).

The "main chain" of a polymer refers to the "trunk" portion of the polymer, which is made up of the longest chain of atoms. It is permissible for this "trunk" portion to contain a ring structure. For example, "having a specific structure in the main chain" means that the specific structure constitutes part of the main chain. A "side chain" refers to a portion branching off from the "trunk" portion of the polymer. "(Meth)acrylo" is a term that encompasses acrylo and methacrylo, and "(meth)acrylate" is a term that encompasses acrylate and methacrylate.

<Polymer [A]>
The polymer [A] has a partial structure (a) represented by the following formula (1) in its main chain.
(In formula (1), An ¹ has a substituted or unsubstituted fused ring structure comprising a plurality of aromatic monocycles, and is a divalent group obtained by removing one hydrogen atom from each of two different rings among the plurality of aromatic monocycles constituting the fused ring, or by removing one hydrogen atom from each of two different rings among the plurality of aromatic monocycles contained in a substituent of the fused ring structure. ^{X 1} and X ² each independently represent -S-, -NR ¹ -, -C(═O)-, -NR ¹ -C(═O)-, -NR ¹ -C(═O)-NR ² -, a substituted or unsubstituted alkanediyl group having 1 to 18 carbon atoms, or a substituted or unsubstituted alkanediyl group having 2 to 18 carbon atoms in which some methylene groups are -O-, -S-, -NR ¹ -, -C(═O)-, -NR ¹ -C(═O)-, or -NR ¹ a divalent group substituted with -C(=O)-NR ² - (excluding the case where X ¹ and X ² in formula (1) are simultaneously -NR ¹ - when An ¹ has a fluorene structure, and the case where X ¹ and X ² in formula (1) are simultaneously -NR ¹ -C(=O)- when An ^{1 has a carbazole structure). However, the aromatic monocycle in An 1 to} which X ¹ is bonded is different from the aromatic monocycle in An ¹ to which X ² is bonded. ^{R 1} and R ² are each independently a hydrogen atom or a monovalent organic group. ^{Ar 1} and Ar ² are each independently a divalent aromatic ring group. "*" represents a bond.)

In the above formula (1), the fused ring structure of An ¹ may be a polycyclic structure containing a plurality of aromatic monocyclic rings, and is not particularly limited thereto. The aromatic monocyclic ring constituting the fused ring structure may be an aromatic hydrocarbon ring or an aromatic heterocyclic ring. The aromatic monocyclic ring constituting the fused ring structure is preferably a benzene ring or a pyridine ring. From the viewpoints of affinity and solubility with liquid crystals and ease of material availability, the number of aromatic monocyclic rings in the fused ring structure is preferably two or three. When the fused ring structure contains two aromatic monocyclic rings, specific examples of the fused ring structure include a naphthalene ring structure, a quinoline structure, an isoquinoline structure, a 1,8-naphthyridine structure, a fluorene structure, a carbazole structure, a dibenzofuran structure, a dibenzothiophene structure, and a dibenzothiophene-5,5-dioxide structure. When the fused ring structure of An ¹ contains three aromatic monocyclic rings, specific examples include an anthracene structure and an acridine structure.

When the fused ring structure of An ¹ has a substituent, examples of the substituent include a hydrocarbon group, a halogenated hydrocarbon group, an alkoxy group, a halogenated alkoxy group, an alkoxyalkyl group, an alkoxyalkoxyalkyl group, a halogen atom, and a hydroxyl group.

From the viewpoint of affinity and solubility with liquid crystal, An ¹ preferably has a substituted or unsubstituted fused ring structure containing two aromatic monocycles, and specific examples thereof include divalent groups obtained by removing one hydrogen atom from each of two different rings among two or more aromatic monocycles contained in the structure represented by the following formula (an-1):
(In formula (an-1), ^B1 and ^B2 each independently represent an aromatic monocycle. ^X3 is —C( ^R3 )( ^R4 )—, —O—, —S—, ^—NR5— , or _—SO2— . ^R3 and ^R4 each independently represent a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group. ^R5 is a hydrogen atom, an alkyl group of 1 to 5 carbon atoms, or a thermally eliminable group. ^Ya is an alkyl group of 1 to 5 carbon atoms, an alkoxy group of 1 to 5 carbon atoms, a halogenated alkyl group of 1 to 5 carbon atoms, a halogenated alkoxy group of 1 to 5 carbon atoms, an alkoxyalkyl group of 1 to 5 carbon atoms, an alkoxyalkoxyalkyl group of 1 to 5 carbon atoms, a halogen atom, or a hydroxyl group. r is an integer of 0 to 6. m is 0 or 1.)

In the above formula (an-1), B ¹ and B ² are preferably a benzene ring or a pyridine ring.
When ^X3 is a group represented by -C( ^R3 )( ^R4 )-, the monovalent hydrocarbon group represented by ^R3 and ^R4 is preferably an alkyl group having 1 to 5 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. The alkyl group having 1 to 5 carbon atoms may be linear or branched, and examples thereof include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. Examples of cycloalkyl groups having 3 to 12 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and groups in which an alkyl group is bonded to the ring of these groups. Examples of aryl groups having 6 to 12 carbon atoms include a phenyl group, a naphthyl group, and groups in which an alkyl group is bonded to the ring of these groups. When ^R3 and ^R4 are substituted monovalent hydrocarbon groups, examples of the substituent include an alkoxy group having 1 to 5 carbon atoms, a halogenated alkyl group having 1 to 5 carbon atoms, a halogenated alkoxy group having 1 to 5 carbon atoms, an alkoxyalkyl group having 1 to 5 carbon atoms, an alkoxyalkoxyalkyl group having 1 to 5 carbon atoms, a halogen atom, and a hydroxyl group.

^R5 is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a thermally detachable group. Examples of the thermally detachable group include a tert-butoxycarbonyl group (Boc group), a benzyloxycarbonyl group, a 1,1-dimethyl-2-haloethyloxycarbonyl group, an allyloxycarbonyl group, a 2-(trimethylsilyl)ethoxycarbonyl group, and a 9-fluorenylmethyloxycarbonyl group. Of these, the Boc group is particularly preferred because it has excellent thermal detachment properties and can reduce the amount of the detached structure remaining in the film.

Of the two or more aromatic monocyclic rings contained in the structure represented by formula (an-1), the ring bonded to ^X1 and the ring bonded to ^X2 are not particularly limited as long as they are different rings. Specifically, when m is 0, or when m is 1 and ^X3 is -O-, -S-, -NR ⁵ - or -SO ₂ -, ^X1 is bonded to one of the two aromatic monocyclic rings constituting the fused ring in formula (an-1), and ^X2 is bonded to the other aromatic monocyclic ring. When m is 1 and ^X3 is -C(R ³ )(R ⁴ )-, ^X1 or X2 may be bonded to at least one of the two aromatic monocyclic rings constituting the fused ring in formula (an-1), or at least one of R ³ and R ⁴ may be an aryl group, and ^X1 or ^X2 may be bonded to an aromatic monocyclic ring in R ³ or ^{R 4} .

Y ^a in the above formula (an-1) may be bonded to either of the two aromatic monocyclic rings contained in An ^1. For example, when the aromatic ring structure in the above formula (an-1) is a naphthalene ring structure, the monovalent group represented by Y ^a may be bonded to the benzene ring on the side bonded to X ¹ , or may be bonded to the benzene ring on the side bonded to X ^2. Furthermore, when the aromatic ring structure in the above formula (an-1) is a naphthalene ring structure and r is 2 or greater, only one benzene ring may have a substituent, or both benzene rings may have a substituent.
r is preferably 0 to 4, and more preferably 0 to 2.

Specific preferred examples of An ¹ include groups represented by the following formula (an-1-1), formula (an-1-2), formula (an-1-3), or formula (an-1-4). Formulas (an-1-1) and (an-1-2) below correspond to the case where m is 0 in formula (an-1) above. Formula (an-1-3) below corresponds to the case where m is 1 in formula (an-1) above, and X ¹ is bonded to one of the two benzene rings constituting the fused ring, and X ² is bonded to the other benzene ring. Formula (an-1-4) below corresponds to the case where m is 1 in formula (an-1) above, X ³ is -C(R ³ )(R ⁴ )-, R ³ and R ⁴ are substituted or unsubstituted phenyl groups, X ¹ is bonded to the benzene ring in R ³ , and X ² is bonded to the benzene ring in R ⁴ .
(In formulas (an-1-1), (an-1-2), (an-1-3), and (an-1-4), Y ¹ to Y ⁶ each independently represent an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a halogenated alkyl group having 1 to 5 carbon atoms, a halogenated alkoxy group having 1 to 5 carbon atoms, an alkoxyalkyl group having 1 to 5 carbon atoms, an alkoxyalkoxyalkyl group having 1 to 5 carbon atoms, a halogen atom, or a hydroxyl group. r1 to r4 each independently represent an integer of 0 to 6. r5 and r6 each independently represent an integer of 0 to 4. X ⁴ is —C(R ⁶ )(R ⁷ )—, —O—, —S—, —NR ⁸ —, or —SO ₂ —. R ⁶ and R ⁷ each independently represent a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group. R ⁸ is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a thermally detachable group. "* ¹ " represents a bond to one of ^X1 and ^X2 in formula (1), and "* ² " represents a bond to the other.

In the above formulas (an-1-1) to (an-1-4), examples of the substituted or unsubstituted monovalent hydrocarbon group represented by ^R6 or ^R7 include the same groups as those exemplified as specific examples of ^R3 and ^R4 .
Examples of the thermally eliminable group represented by ^R8 include the same groups as those exemplified as specific examples when ^R5 is a thermally eliminable group.
r1 to r4 are preferably 0 to 4, and more preferably 0 to 2. r5 and r6 are preferably 0 to 2, and more preferably 0 or 1.

Further specific examples of the group represented by formula (an-1-1), formula (an-1-2), formula (an-1-3) or formula (an-1-4) include groups represented by each of the following formulas (g-1) to (g-22).
(In formulas (g-1) to (g-22), "*" represents a bond.)

From the viewpoint of improving the liquid crystal alignment property in a liquid crystal element, An ¹ is preferably a group having a naphthalene ring structure among the above, and specifically, a group represented by the above formula (an-1-1) is preferred.

When An ¹ has a naphthalene ring structure, it is sufficient ^{that one of the two benzene rings constituting the naphthalene ring in An 1 is bonded to X 1 and the} other is bonded to X ² , and the bonding position between the benzene ring in An ¹ and X ¹ or X ² is not particularly limited. From the viewpoint of obtaining a liquid crystal element exhibiting good liquid crystal alignment properties and alignment uniformity, the naphthalene diyl group represented by An ¹ is preferably a naphthalene-1,5-diyl group (a group represented by the above formula (g-3)), a naphthalene-2,6-diyl group (a group represented by the above formula (g-2)), or a naphthalene-3,7-diyl group (a group represented by the above formula (g-1)). Among these, a naphthalene-2,6-diyl group or a naphthalene-3,7-diyl group is more preferred, and a naphthalene-3,7-diyl group is even more preferred, from the viewpoint of being able to enhance the effect of improving liquid crystal alignment properties.

In ^X1 and ^X2 , examples of the monovalent organic group represented by ^R1 and ^R2 include a monovalent hydrocarbon group having 1 to 10 carbon atoms and a monovalent thermally eliminable group. When ^R1 and ^R2 are monovalent hydrocarbon groups having 1 to 10 carbon atoms, examples of the hydrocarbon group include an alkyl group having 1 to 10 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 10 carbon atoms, and a monovalent aromatic hydrocarbon group having 5 to 10 carbon atoms. Of these, an alkyl group having 1 to 5 carbon atoms, a cyclohexyl group, or a phenyl group is preferred, and an alkyl group having 1 to 3 carbon atoms is more preferred.

Examples of the monovalent thermally detachable group include the same groups as those exemplified as specific examples when R ⁵ is a thermally detachable group. Among these, the Boc group is particularly preferred because it has excellent thermal detachment properties and can reduce the amount of the detached structure remaining in the film.

Among these, R ¹ and R ² are preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a monovalent thermally eliminable group, and more preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a Boc group.

When X ¹ and X ² are alkanediyl groups having 1 to 18 carbon atoms, the alkanediyl group may be linear or branched. Specific examples of alkanediyl groups when X ¹ and X ² are alkanediyl groups having 1 to 18 carbon atoms include methylene, ethylene, propane-1,3-diyl, propane-1,2-diyl, propane-1,1-diyl, butane-1,4-diyl, butane-1,2-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, decane-1,10-diyl, and dodecane-1,12-diyl. From the viewpoint of improving the liquid crystal alignment property and alignment uniformity of the liquid crystal element, and from the viewpoint of obtaining a liquid crystal alignment film having high adhesion to the substrate, among these, the alkanediyl group having 1 to 18 carbon atoms represented by X ¹ and X ² is preferably linear, and a linear alkanediyl group having 2 to 18 carbon atoms is more preferred.

Furthermore, from the viewpoint of suppressing a decrease in the voltage holding ratio in a liquid crystal element, the number of carbon atoms in the alkanediyl group represented by X ¹ or X ² is preferably 15 or less, more preferably 10 or less, and even more preferably 5 or less. When ^{X 1} or X ² is a substituted alkanediyl group having 1 to 18 carbon atoms, examples of the substituent include a halogen atom (such as a fluorine atom, a chlorine atom, an iodine atom, or a bromine atom), a hydroxyl group, etc.

X ¹ and X ² may each be a divalent group in which some methylene groups in a substituted or unsubstituted alkanediyl group having 2 to 18 carbon atoms have been replaced with -O-, -S-, -NR ¹ -, -C(═O)-, -NR ¹ -C(═O)-, or -NR ¹ -C(═O)-NR ² - (hereinafter also referred to as "divalent group F ¹ "). Note that in the divalent group F ¹ , methylene groups have been replaced with the above heteroatom-containing groups, provided that they are not adjacent to each other. Furthermore, when X ¹ and X ² are divalent groups F ¹ , the number of methylene groups replaced by the above heteroatom-containing groups is not particularly limited and may be one or more.

In the divalent group F ¹ , the substituted or unsubstituted alkanediyl group having 2 to 18 carbon atoms may be linear or branched. From the viewpoint of improving the liquid crystal alignment property and alignment uniformity of the liquid crystal element and from the viewpoint of obtaining a liquid crystal alignment film having high adhesion to the substrate, it is preferable that the alkanediyl group in the divalent group F ¹ is linear. Examples of the substituent include a halogen atom (such as a fluorine atom, a chlorine atom, an iodine atom, or a bromine atom), a hydroxyl group, etc.

When X ¹ and X ² are divalent groups F ¹ , the divalent group F ¹ is preferably a substituted or unsubstituted alkanediyl group having 2 to 18 carbon atoms in which some methylene groups have been replaced with —O—, —NR ¹ —, or —NR ¹ —C(═O)—.

From the viewpoint of improving the liquid crystal alignment property and alignment uniformity in a liquid crystal element, X ¹ and X ² are preferably a substituted or unsubstituted alkanediyl group having 2 to 18 carbon atoms or a divalent group F ¹ , more preferably a divalent group F ¹ , and even more preferably a divalent group in which some methylene groups in a substituted or unsubstituted alkanediyl group having 4 to 18 carbon atoms have been replaced by —O—, —S—, —NR ¹ —, —C(═O)—, —NR ¹ —C(═O)— or —NR ¹ —C(═O)—NR ² —. Furthermore, from the viewpoint of suppressing a decrease in voltage holding ratio while improving the liquid crystal alignment property and alignment uniformity in a liquid crystal element, it is preferable that one or both of ^X1 and ^X2 are bonded to the aromatic monocyclic ring in ^An1 via —O—, —S—, —NR ¹ — or —C(═O)—, and it is more preferable that both of ^X1 and ^X2 are bonded to the aromatic monocyclic ring in ^An1 via —O—, —S—, —NR ¹ — or —C(═O)—.

When X ¹ and X ² are bonded to the aromatic monocyclic ring in An ¹ via —NR ¹ —, —NR ¹ — may be —NR ¹ — in “—NR ¹ —C(═O)—” or —NR ¹ — in “—NR ¹ —C(═O)—NR ² —”. When X ¹ and X ² are bonded to the aromatic monocyclic ring in An ¹ via —C(═O)—, —C(═O)— may be —C(═O)— in “—NR ¹ —C(═O)—”.

^X1 and ^X2 preferably have an alkylene chain having two or more carbon atoms, in order to improve the adhesion of the liquid crystal alignment film to the substrate while maintaining the liquid crystal alignment property and alignment uniformity in the liquid crystal element. The alkylene chain preferably has 2 to 10 carbon atoms, in order to suppress a decrease in the voltage holding ratio. When ^X1 and ^X2 have an alkylene chain having two or more carbon atoms, ^X1 and ^X2 may be a substituted or unsubstituted alkanediyl group, or may be a divalent group ^F1 .

From the viewpoint of improving the liquid crystal alignment property and alignment uniformity in a liquid crystal element, and from the viewpoint of increasing the adhesion of a liquid crystal alignment film to a substrate, X ¹ and X ² are preferably divalent groups F ¹ having an alkylene chain having two or more carbon atoms among the above, and more preferably both X ¹ and X ² are bonded to an aromatic monocycle in An ¹ via —O—, —S—, —NR ¹ — or —C(═O)—.

Specific examples of ^X1 and ^X2 include groups represented by the following formulae (x-1) to (x-46).

The divalent aromatic ring groups represented by ^Ar1 and ^Ar2 are groups obtained by removing two hydrogen atoms from the ring portion of a substituted or unsubstituted aromatic ring. Examples of the aromatic ring include aromatic hydrocarbon rings such as a benzene ring, a naphthalene ring, and an anthracene ring; nitrogen-containing aromatic heterocycles such as a pyridine ring, a pyrazine ring, a pyrimidine ring, a pyridazine ring, and an imidazole ring; and sulfur-containing aromatic heterocycles such as a thiophene ring. When the aromatic ring has a substituent, examples of the substituent include the same groups as the group represented by Y ^a in formula (an-1) above.

From the viewpoint of improving the liquid crystal alignment property and voltage retention characteristics, it is preferable that Ar ¹ and Ar ² have a ring structure selected from the group consisting of a benzene ring, a pyridine ring, a pyrazine ring, a pyrimidine ring, a pyridazine ring, and an imidazole ring. Preferred specific examples of ^{Ar 1} and Ar ² include groups represented by the following formulas (a-1) to (a-11), respectively.
(In the formula, "*" represents a bond.)

In terms of being able to form a liquid crystal alignment film excellent in liquid crystal alignment property and voltage retention characteristics, Ar ¹ and Ar ² are preferably groups represented by formula (a-1) to formula (a-6) among the above, and more preferably groups represented by formula (a-1) or formula (a-6).

The main skeleton of polymer [A] is not particularly limited. From the viewpoints of affinity with liquid crystal molecules, mechanical strength, liquid crystal alignment, and ease of incorporation of partial structure (a) into the main chain, polymer [A] is preferably a polymer containing a structural unit derived from a diamine having partial structure (a). Specific examples of such polymer [A] include polyamic acid, polyamic acid ester, polyimide, polyamide, polyenamine, etc. Among these, polymer [A] is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide.

The methods for producing the polyamic acid, polyamic acid ester, and polyimide used as polymer [A] are not particularly limited, and they can be produced by appropriately combining standard organic chemistry methods. The polyamic acid, polyamic acid ester, and polyimide used as polymer [A] are described in detail below.

[Polyamic acid]
The polyamic acid as the polymer [A] (hereinafter also referred to as "polyamic acid (A)") can be obtained, for example, by reacting a tetracarboxylic dianhydride with a diamine.

(Tetracarboxylic acid dianhydride)
Examples of the tetracarboxylic acid dianhydride used in the synthesis of the polyamic acid (A) include aliphatic tetracarboxylic acid dianhydrides and aromatic tetracarboxylic acid dianhydrides. The aliphatic tetracarboxylic acid dianhydrides include chain tetracarboxylic acid dianhydrides and alicyclic tetracarboxylic acid dianhydrides.

Specific examples of the chain tetracarboxylic dianhydride include butane tetracarboxylic dianhydride, etc. Specific examples of the alicyclic tetracarboxylic dianhydride include 1,2,3,4-cyclobutane tetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic dianhydride, 5-(2,5-dioxotetrahydrofuran-3-yl)-3a,4,5,9b-tetrahydronaphtho[1,2-c]furan-1,3-dione, 5-(2,5-dioxotetrahydrofuran-3-yl)-8-methyl-3a,4,5,9b-tetrahydronaphtho[1,2-c]furan-1,3-dione, 3-oxabicyclo[3.2.1]octane-2,4-dione, 2,3,5-tricarboxycyclopentylacetic dianhydride, 5-(2,5-dioxotetrahydrofuran-3-yl)-8-methyl-3a,4,5,9b-tetrahydronaphtho[1,2-c]furan-1,3-dione, 2,3,5-tricarboxycyclopentylacetic dianhydride ... Benzene-6-spiro-3'-(tetrahydrofuran-2',5'-dione), 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 3,5,6-tricarboxy-2-carboxymethylnorbornane-2:3,5:6-dianhydride, bicyclo[3.3.0]octane-2,4,6,8-tetracarboxylic acid 2:4,6:8-dianhydride, bicyclo[2.2.1]heptane-2,3,5,6-tetracarboxylic acid 2:3,5:6-dianhydride, 4,9-dioxatricyclo[5.3.1.0]octane-2,4,6,8-tetracarboxylic acid 2:3,5:6-dianhydride ^2,6 ]undecane-3,5,8,10-tetraone, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, ethylenediaminetetraacetic acid dianhydride, cyclopentanetetracarboxylic dianhydride, and the like.

Examples of aromatic tetracarboxylic acid dianhydrides include pyromellitic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, p-phenylene bis(trimellitic acid monoester anhydride), ethylene glycol bis(anhydrotrimellitate), 1,3-propylene glycol bis(anhydrotrimellitate), 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, and 4,4'-biphthalic dianhydride. In addition to the above, the tetracarboxylic acid dianhydrides described in JP 2010-97188 A can also be used as the tetracarboxylic acid dianhydride used in the synthesis of polyamic acid (A).

When imparting liquid crystal alignment ability to a coating film by photoalignment treatment, it is preferable to use a substituted cyclobutanetetracarboxylic dianhydride in synthesizing the polyamic acid (A), because the photoreactivity of the coating film can be further increased in combination with a specific diamine. Specific examples of the substituted cyclobutanetetracarboxylic dianhydride include the compounds represented by the following formulas (t-1) to (t-6).

When a substituted cyclobutanetetracarboxylic dianhydride is used in the synthesis of polyamic acid (A), the proportion of the substituted cyclobutanetetracarboxylic dianhydride used is preferably 10 mol % or more, based on the total amount of tetracarboxylic dianhydride used in the synthesis, in order to sufficiently increase the photoreactivity of the coating film. It is more preferably 30 mol % or more, and even more preferably 50 mol % or more.

(Diamine compound)
In synthesizing the polyamic acid (A), a diamine having the partial structure (a) (hereinafter also referred to as a "specific diamine") can be preferably used. The specific diamine is only required to have the partial structure represented by the above formula (1), and other structures are not particularly limited. A preferred specific example of the specific diamine is a compound represented by the following formula (2):
(In formula (2), Ar ¹ , X ¹ , An ¹ , X ² and Ar ² have the same meanings as in formula (1) above.)

The explanations for formula (1) above apply to specific examples and preferred examples of Ar ¹ , X ¹ , An ¹ , X ² and Ar ² in formula (2) above.

Specific examples of the specific diamine include compounds in which the specific examples of Ar ¹ , X ¹ , An ¹ , X ² and Ar ² explained above are combined in any order. Examples of the specific diamine include compounds represented by the following formulas (d-1) to (d-22), and compounds in which the naphthalenediyl group in the compounds represented by the following formulas (d-1) to (d-22) is replaced with a group represented by the above formula (g-4) to (g-22). Note that "Boc" in the structural formula represents a tert-butoxycarbonyl group (the same applies hereinafter).

Of these, the specific diamine is preferably a compound having a naphthalenediyl group, as it allows the production of a liquid crystal device with excellent liquid crystal alignment properties. Furthermore, among the compounds represented by the above formulas (d-1) to (d-22), the compounds represented by formulas (d-1) to (d-8) and formulas (d-13) to (d-17) are particularly preferred, with the compounds represented by formulas (d-1) to (d-8) and formulas (d-13) to (d-15) being even more preferred.

The diamine compound used in the synthesis of polyamic acid (A) may be the specific diamine alone. Alternatively, the diamine compound used in the synthesis of polyamic acid (A) may be a combination of the specific diamine and a diamine that does not have the partial structure represented by formula (1) above (hereinafter also referred to as "other diamines").

Other diamines include, for example, aliphatic diamines, aromatic diamines, and diaminoorganosiloxanes. Aliphatic diamines include chain diamines and alicyclic diamines.

Specific examples of other diamines include chain diamines such as m-xylylenediamine, 1,3-propanediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, and 1,3-bis(aminomethyl)cyclohexane; alicyclic diamines such as 1,4-diaminocyclohexane and 4,4'-methylenebis(cyclohexylamine);
Examples of aromatic diamines include dodecanoxydiaminobenzene, tetradecanoxydiaminobenzene, pentadecanoxydiaminobenzene, hexadecanoxydiaminobenzene, octadecanoxydiaminobenzene, cholestanyloxydiaminobenzene, cholesteryloxydiaminobenzene, cholestanyl diaminobenzoate, cholesteryl diaminobenzoate, lanostannyl diaminobenzoate, 3,6-bis(4-aminobenzoyloxy)cholestane, 3,6-bis(4-aminophenoxy)cholestane, 1,1 ... , 1-bis(4-((aminophenyl)methyl)phenyl)-4-butylcyclohexane, 1,1-bis(4-((aminophenyl)methyl)phenyl)-4-heptylcyclohexane, 1,1-bis(4-((aminophenoxy)methyl)phenyl)-4-heptylcyclohexane, 1,1-bis(4-((aminophenyl)methyl)phenyl)-4-(4-heptylcyclohexyl)cyclohexane, N-(2,4-diaminophenyl)-4-(4-heptylcyclohexyl)benzamide, and compounds represented by the following formula (E-1):
(In formula (E-1), X ^I and X ^II each independently represent a single bond, —O—, *-COO—, or *-OCO— (wherein “*” represents a bond to the diaminophenyl group). R ^I represents an alkanediyl group having 1 to 3 carbon atoms. R ^II represents a single bond or an alkanediyl group having 1 to 3 carbon atoms. R ^III represents an alkyl group, alkoxy group, fluoroalkyl group, or fluoroalkoxy group having 1 to 20 carbon atoms. a is 0 or 1. b is an integer of 0 to 3. c is an integer of 0 to 2. d is 0 or 1, provided that 1≦a+b+c≦3.)
Directing group-containing diamines such as compounds represented by the formula:
paraphenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylamine, 4,4'-diaminodiphenyl sulfide, 4-aminophenyl-4'-aminobenzoate, 4,4'-diaminoazobenzene, 1,2-bis(4-aminophenoxy)ethane, 1,2-bis(4-aminophenoxy)ethane, 1,3-bis(4-aminophenoxy)propane, 1,5-bis(4-aminophenoxy)pentane, 1,6-bis(4-aminophenoxy)hexane, 1,7-bis(4-aminophenoxy) ) heptane, bis[2-(4-aminophenyl)ethyl]hexanedioic acid, N,N-bis(4-aminophenyl)methylamine, N,N'-di(5-amino-2-pyridyl)-N,N'-di(tert-butoxycarbonyl)ethylenediamine, 4,4'-(2,2'-oxybis(ethane-2,1-diyl)bis(oxy))dianiline, 1,5-diaminonaphthalene, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 9,9-bis(4-aminophenyl)fluorene, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-(p-phenylenediisopropylidene)bisaniline, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 2,6-diaminopyridine, 2,4-diaminopyrimidine, 3,6- Diaminoacridine, 3,6-diaminocarbazole, N-methyl-3,6-diaminocarbazole, N,N'-bis(4-aminophenyl)-benzidine, N,N'-bis(4-aminophenyl)-N,N'-dimethylbenzidine, 1,4-bis-(4-aminophenyl)-piperazine, 3,5-diaminobenzoic acid, 1-(4-aminophenoxy)-2-(4-(4'-aminophenyl)phenoxy)ethane, 3,5-diamino-N,N-bis(pyridin-3-ylmethyl)benzamide, compounds represented by the following formulas (f-1) to (f-33):
Diamines represented by the following formula:
Examples of diaminoorganosiloxanes include 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, and the diamines described in JP-A-2010-97188 can also be used. As the other diamines used in the synthesis of the polyamic acid (A), one type can be used alone, or two or more types can be appropriately selected and used.

The divalent group represented by "-X ^I -(R ^I -X ^II ) _d -" in the above formula (E-1) is preferably an alkanediyl group having 1 to 3 carbon atoms, *-O-, *-COO-, or *-O-C ₂ H ₄ -O- (wherein the bond marked with "*" is bonded to the diaminophenyl group). The group represented by R ^III is preferably linear. The two amino groups in the diaminophenyl group are preferably in the 2,4-position or 3,5-position relative to other groups.

Specific examples of the compound represented by formula (E-1) above include compounds represented by formulas (E-1-1) to (E-1-4) below.

When synthesizing polyamic acid (A), the proportion of the specific diamine used is preferably 2 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more, relative to the total amount of diamine compounds used in synthesizing polyamic acid (A). A proportion of the specific diamine used within the above range is advantageous in that it allows for sufficient compatibility between liquid crystal alignment and alignment uniformity and voltage retention characteristics in a liquid crystal element. Furthermore, when synthesizing polyamic acid (A), the proportion of the specific diamine used may be 100 mol% or less, relative to the total amount of diamine compounds used in synthesizing polyamic acid (A). When other diamines are used to impart desired properties, the proportion of the specific diamine used is preferably 90 mol% or less, more preferably 80 mol% or less, relative to the total amount of diamine compounds used in synthesizing polyamic acid (A).

(Synthesis of Polyamic Acid)
The polyamic acid (A) can be obtained by reacting the above-mentioned tetracarboxylic dianhydride with a diamine compound, optionally together with a molecular weight modifier. The ratio of the tetracarboxylic dianhydride and the diamine compound used in the synthesis reaction of the polyamic acid (A) is preferably such that 0.2 to 2 equivalents, and more preferably 0.3 to 1.2 equivalents, of the acid anhydride groups of the tetracarboxylic dianhydride are used per equivalent of the amino groups of the diamine compound.

Examples of molecular weight modifiers include acid monoanhydrides such as maleic anhydride, phthalic anhydride, and itaconic anhydride; monoamine compounds such as aniline, cyclohexylamine, and n-butylamine; and monoisocyanate compounds such as phenyl isocyanate and naphthyl isocyanate. The proportion of molecular weight modifier used is preferably 20 parts by weight or less, and more preferably 10 parts by weight or less, per 100 parts by weight of the total of the tetracarboxylic dianhydride and diamine compounds used.

The synthesis reaction of polyamic acid (A) is preferably carried out in an organic solvent. The reaction temperature is preferably -20°C to 150°C, more preferably 0°C to 100°C. The reaction time is preferably 0.1 to 24 hours, more preferably 0.5 to 12 hours.

Examples of organic solvents used in the reaction include aprotic polar solvents, phenolic solvents, alcohols, ketones, esters, ethers, halogenated hydrocarbons, and hydrocarbons. Among these organic solvents, it is preferable to use one or more selected from the group consisting of aprotic polar solvents and phenolic solvents (Group 1 organic solvents), or a mixture of one or more selected from Group 1 organic solvents with one or more selected from the group consisting of alcohols, ketones, esters, ethers, halogenated hydrocarbons, and hydrocarbons (Group 2 organic solvents). In the latter case, the proportion of Group 2 organic solvent used is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, based on the total amount of Group 1 organic solvents and Group 2 organic solvents.

Particularly preferred organic solvents are one or more selected from the group consisting of N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, tetramethylurea, hexamethylphosphortriamide, m-cresol, xylenol, and halogenated phenols, or a mixture of one or more of these with other organic solvents in the above-mentioned proportions. The amount of organic solvent (x) used is preferably an amount such that the total amount (y) of the tetracarboxylic dianhydride and diamine compound is 0.1 to 50% by mass relative to the total amount (x + y) of the reaction solution.

In this manner, a reaction solution containing dissolved polyamic acid (A) is obtained. This reaction solution may be used directly to prepare a liquid crystal aligning agent, or the polyamic acid (A) contained in the reaction solution may be isolated and then used to prepare a liquid crystal aligning agent, or the isolated polyamic acid (A) may be purified and then used to prepare a liquid crystal aligning agent. When polyamic acid (A) is to be dehydrated and cyclized to form a polyimide, the reaction solution may be used directly to the dehydration and cyclization reaction, or the polyamic acid (A) contained in the reaction solution may be isolated and then used to prepare a dehydration and cyclization reaction, or the isolated polyamic acid (A) may be purified and then used to prepare a dehydration and cyclization reaction. Isolation and purification of polyamic acid (A) can be performed according to known methods.

[Polyamic acid ester]
The polyamic acid ester as the polymer [A] can be obtained, for example, by [I] a method of reacting the polyamic acid (A) obtained by the above synthesis reaction with an esterifying agent, [II] a method of reacting a tetracarboxylic acid diester with a diamine compound, or [III] a method of reacting a tetracarboxylic acid diester dihalide with a diamine compound.

In this specification, "tetracarboxylic acid diester" refers to a compound in which two of the four carboxy groups in a tetracarboxylic acid are esterified and the remaining two are carboxy groups. "Tetracarboxylic acid diester dihalide" refers to a compound in which two of the four carboxy groups in a tetracarboxylic acid are esterified and the remaining two are halogenated.

Esterifying agents used in method [I] include, for example, hydroxyl group-containing compounds, acetal compounds, halides, and epoxy group-containing compounds. Specific examples of these include: hydroxyl group-containing compounds such as alcohols (e.g., methanol, ethanol, and propanol), and phenols (e.g., phenol and cresol); acetal compounds such as N,N-dimethylformamide diethyl acetal and N,N-diethylformamide diethyl acetal; halides such as methyl bromide, ethyl bromide, stearyl bromide, methyl chloride, stearyl chloride, and 1,1,1-trifluoro-2-iodoethane; and epoxy group-containing compounds such as propylene oxide.

The tetracarboxylic acid diester used in method [II] can be obtained, for example, by ring-opening the tetracarboxylic acid dianhydride exemplified in the description of the synthesis of polyamic acid (A) using an alcohol such as methanol or ethanol. The tetracarboxylic acid derivative used in method [II] may be the tetracarboxylic acid diester alone, or it may be used in combination with a tetracarboxylic acid dianhydride. As for the diamine compound, the specific diamine exemplified in the synthesis of polyamic acid may be used alone, or it may be used in combination with other diamines.

The reaction in method [II] is preferably carried out in an organic solvent in the presence of a suitable dehydration catalyst. Examples of organic solvents include those exemplified for use in the synthesis of polyamic acid (A). Examples of dehydration catalysts include 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium halide, carbonylimidazole, and phosphorus-based condensing agents. The reaction temperature is preferably -20 to 150°C, more preferably 0 to 100°C. The reaction time is preferably 0.1 to 24 hours, more preferably 0.5 to 12 hours.

The tetracarboxylic acid diester dihalide used in Method [III] can be obtained, for example, by reacting the tetracarboxylic acid diester obtained as described above with a suitable chlorinating agent such as thionyl chloride. The tetracarboxylic acid derivative used in Method [III] may be the tetracarboxylic acid diester dihalide alone, or it may be used in combination with a tetracarboxylic acid dianhydride. Furthermore, with regard to the diamine compound, the specific diamines exemplified in the description of the synthesis of polyamic acid (A) may be used alone or in combination with other diamines.

The reaction in method [III] is preferably carried out in an organic solvent in the presence of a suitable base. Examples of organic solvents include those listed as examples of organic solvents used in the synthesis of polyamic acid (A). Examples of bases that can be used include tertiary amines such as pyridine and triethylamine; and alkali metals such as sodium hydride, potassium hydride, sodium hydroxide, potassium hydroxide, sodium, and potassium. The reaction temperature is preferably -20 to 150°C, more preferably 0 to 100°C. The reaction time is preferably 0.1 to 24 hours, more preferably 0.5 to 12 hours.

The polyamic acid ester contained in the liquid crystal aligning agent may have only an amic acid ester structure, or may be a partially esterified product in which an amic acid structure and an amic acid ester structure coexist. The reaction solution in which the polyamic acid ester is dissolved may be used directly to prepare the liquid crystal aligning agent, or the polyamic acid ester contained in the reaction solution may be isolated and then used to prepare the liquid crystal aligning agent, or the isolated polyamic acid ester may be purified and then used to prepare the liquid crystal aligning agent. The polyamic acid ester can be isolated and purified according to known methods.

[Polyimide]
The polyimide as the polymer [A] can be obtained, for example, by imidizing the polyamic acid (A) synthesized as described above by dehydration and ring closure.

The polyimide may be a fully imidized product in which all of the amic acid structures contained in its precursor polyamic acid have been dehydrated and cyclized, or a partially imidized product in which only a portion of the amic acid structures have been dehydrated and cyclized, resulting in both amic acid structures and imide ring structures. The polyimide used in the reaction preferably has an imidization rate of 20% or more, more preferably 30 to 99%, and even more preferably 40 to 99%. This imidization rate is the ratio, expressed as a percentage, of the number of imide ring structures to the total number of amic acid structures and imide ring structures in the polyimide. Some of the imide rings may be isoimide rings.

The dehydration and ring-closure of polyamic acid is preferably carried out by heating the polyamic acid, or by dissolving the polyamic acid in an organic solvent, adding a dehydrating agent and a dehydration and ring-closure catalyst to the solution, and heating as necessary.

In the method of adding a dehydrating agent and a dehydration ring-closing catalyst to a polyamic acid solution, the dehydrating agent can be, for example, an acid anhydride such as acetic anhydride, propionic anhydride, or trifluoroacetic anhydride. The amount of dehydrating agent used is preferably 0.01 to 20 moles per mole of the amic acid structure of the polyamic acid. The dehydration ring-closing catalyst can be, for example, a tertiary amine such as pyridine, collidine, lutidine, triethylamine, or 1-methylpiperidine. The amount of dehydration ring-closing catalyst used is preferably 0.01 to 10 moles per mole of the dehydrating agent used. Examples of organic solvents used in the dehydration ring-closing reaction include the organic solvents exemplified for use in synthesizing polyamic acid. The reaction temperature for the dehydration ring-closing reaction is preferably 0 to 180°C, more preferably 10 to 150°C. The reaction time is preferably 1.0 to 120 hours, more preferably 2.0 to 30 hours.

In this way, a reaction solution containing polyimide is obtained. This reaction solution may be used directly to prepare a liquid crystal aligning agent, or the dehydrating agent and dehydration ring-closing catalyst may be removed from the reaction solution before use in the preparation of a liquid crystal aligning agent. The polyimide may be isolated and then used in the preparation of a liquid crystal aligning agent, or the isolated polyimide may be purified and then used in the preparation of a liquid crystal aligning agent. These purification procedures can be carried out according to known methods. Alternatively, polyimide can also be obtained by imidizing a polyamic acid ester.

The polymer [A] obtained in this manner preferably has a solution viscosity of 20 to 1,800 mPa·s when made into a 15% by mass solution, and more preferably 50 to 1,500 mPa·s. The solution viscosity (mPa·s) of the polymer is the value measured at 25°C using an E-type rotational viscometer for a 15% by mass polymer solution prepared using a good solvent for the polymer (e.g., γ-butyrolactone, N-methyl-2-pyrrolidone, etc.).

The polystyrene-equivalent weight-average molecular weight (Mw) of polymer [A] measured by gel permeation chromatography (GPC) is preferably 1,000 to 500,000, and more preferably 2,000 to 300,000. Furthermore, the molecular weight distribution (Mw/Mn) of polymer [A], expressed as the ratio of Mw to the polystyrene-equivalent number-average molecular weight (Mn) measured by GPC, is preferably 8 or less, and more preferably 6 or less. Having Mw and Mw/Mn of polymer [A] within the above ranges ensures good liquid crystal alignment properties in liquid crystal devices.

The content of polymer [A] in the liquid crystal aligning agent of the present disclosure is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, per 100 parts by mass of the solid content (components of the liquid crystal aligning agent other than the solvent) contained in the liquid crystal aligning agent.

<Other ingredients>
The liquid crystal aligning agent of the present disclosure may contain components (other components) other than the polymer [A]. Examples of other components include a polymer not having the partial structure represented by the above formula (1) in its main chain (hereinafter also referred to as "polymer [B]"), a crosslinking agent, a functional silane compound, an antioxidant, a metal chelate compound, a curing accelerator, a surfactant, a filler, a dispersant, a photosensitizer, an acid generator, a base generator, and a radical generator. The blending ratio of these components can be appropriately selected depending on each compound within a range that does not impair the effects of the present disclosure.

(Polymer [B])
The polymer [B] is used, for example, for the purpose of suppressing a decrease in voltage holding ratio and improving liquid crystal alignment. The main skeleton of the polymer [B] is not particularly limited, but examples include polymers having a main skeleton of polyamic acid, polyimide, polyamic acid ester, polyorganosiloxane, polyester, cellulose derivative, polyacetal, and addition polymer. The addition polymer is a polymer containing a structural unit derived from a monomer having a polymerizable unsaturated carbon-carbon bond, and examples include styrene-based polymers, (meth)acrylic polymers, maleimide-based polymers, and styrene-maleimide copolymers. Of these, the polymer [B] is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, polyimide, polyorganosiloxane, and addition polymer.

When used as a liquid crystal alignment agent for photo-alignment treatment, the polymer [A] may contain a photosensitive polymer and the polymer [B] may contain a non-photosensitive polymer. Alternatively, the polymer [A] may contain a non-photosensitive polymer and the polymer [B] may contain a photosensitive polymer. Furthermore, both the polymer [A] and the polymer [B] may contain photosensitive polymers.

When polymer [B] is contained in the liquid crystal aligning agent, the content of polymer [B] is preferably 95 parts by mass or less, and more preferably 90 parts by mass or less, per 100 parts by mass of the polymer components contained in the liquid crystal aligning agent (i.e., the total amount of polymer [A] and polymer [B]).

(solvent)
The liquid crystal aligning agent of the present disclosure is prepared as a liquid composition obtained by dispersing or dissolving the polymer [A] and components used as needed, preferably in a suitable solvent.

Examples of the organic solvent used include N-methyl-2-pyrrolidone, γ-butyrolactone, γ-butyrolactam, N,N-dimethylformamide, N,N-dimethylacetamide, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monomethyl ether, butyl lactate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-i-propyl 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, diisopentyl ether, ethylene carbonate, and propylene carbonate. These can be used alone or in combination of two or more.

The solids concentration in the liquid crystal aligning agent (the proportion of the total mass of the liquid crystal aligning agent's components other than the solvent to the total mass of the liquid crystal aligning agent) is selected appropriately taking into consideration viscosity, volatility, etc., but is preferably in the range of 1 to 10% by mass. That is, the liquid crystal aligning agent is applied to the substrate surface as described below, and preferably heated to form a coating film that is a liquid crystal alignment film or a coating film that will become a liquid crystal alignment film. In this case, if the solids concentration is 1% by mass or more, the coating film can be sufficiently thick, and a good liquid crystal alignment film tends to be easily obtained. If the solids concentration is 10% by mass or less, the coating film thickness does not become too large, and an increase in the viscosity of the liquid crystal aligning agent can be suppressed, tending to improve applicability.

The particularly preferred solid content range varies depending on the application of the liquid crystal alignment agent and the method used to apply the agent to a substrate. For example, when applying a liquid crystal alignment agent for a liquid crystal display device to a substrate using a spinner method, a solid content range (the ratio of the total mass of all components in the liquid crystal alignment agent other than the solvent to the total mass of the liquid crystal alignment agent) of 1.5 to 4.5 mass% is particularly preferred. When using a printing method, a solid content range of 3 to 9 mass% is particularly preferred, thereby resulting in a solution viscosity of 12 to 50 mPa·s. When using an inkjet method, a solid content range of 1 to 5 mass% is particularly preferred, thereby resulting in a solution viscosity of 3 to 15 mPa·s. The temperature when preparing the liquid crystal alignment agent is preferably 10 to 50°C, more preferably 20 to 30°C. Furthermore, with regard to liquid crystal aligning agents for retardation films, from the viewpoint of ensuring the coatability of the liquid crystal aligning agent and the appropriate thickness of the coating film formed, the solids concentration of the liquid crystal aligning agent is preferably in the range of 0.2 to 10% by mass, and more preferably in the range of 3 to 10% by mass.

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

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

After applying the liquid crystal alignment agent, preheating (pre-baking) is preferably performed to prevent dripping of the applied liquid crystal alignment agent. The pre-baking temperature is preferably 30 to 200°C, and the pre-baking time is preferably 0.25 to 10 minutes. If necessary, a baking (post-baking) process is then performed to completely remove the solvent or thermally imidize the amic acid structure present in the polymer. The baking temperature (post-baking temperature) is preferably 80 to 300°C, and the post-baking time is preferably 5 to 200 minutes. The film formed in this manner preferably has a thickness of 0.001 to 1 μm. After applying the liquid crystal alignment agent to the substrate, the organic solvent is removed to form a liquid crystal alignment film, or a coating film that will become a liquid crystal alignment film.

(Step 2: Alignment Treatment)
When manufacturing a TN-type, STN-type, IPS-type, or FFS-type liquid crystal device, a treatment (alignment treatment) is carried out to impart liquid crystal alignment ability to the coating film formed in step 1. This imparts the alignment ability of liquid crystal molecules to the coating film, resulting in a liquid crystal alignment film. Examples of alignment treatments include a rubbing treatment in which the surface of the coating film formed on the substrate is rubbed with cotton or the like, and a photo-alignment treatment in which the coating film is irradiated with light to impart liquid crystal alignment ability. In particular, the liquid crystal alignment agent of the present disclosure is preferably used as a photo-alignment agent in which a coating film formed using the liquid crystal alignment agent is subjected to a photo-irradiation treatment to impart liquid crystal alignment ability. On the other hand, when manufacturing a vertical alignment type (VA type) liquid crystal device, the coating film formed in step 1 can be used as a liquid crystal alignment film as is, or the coating film may be subjected to an alignment treatment. Liquid crystal alignment films suitable for vertical alignment type liquid crystal devices can also be preferably used for PSA type liquid crystal devices.

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

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

When producing a liquid crystal alignment film, the coating film that has been subjected to light irradiation treatment may be heated at a temperature ranging from 120°C to 280°C. This heat treatment is preferable in that it further improves the liquid crystal alignment (thermal realignment) and results in a liquid crystal device with improved display quality. This heating may be post-baking, or it may be a heat treatment performed separately from post-baking and after post-baking. When heat-treating the coating film that has been subjected to light irradiation treatment, the heating temperature is preferably 140°C or higher, and more preferably 150°C to 250°C, from the perspective of promoting molecular chain realignment due to heating. The heating time is preferably 5 to 200 minutes, more preferably 10 to 60 minutes.

The production of a liquid crystal alignment film may further include a step of contacting the light-irradiated coating film with water, a water-soluble organic solvent, or a mixed solvent of water and a water-soluble organic solvent. Examples of water-soluble organic solvents include methanol, ethanol, 1-propanol, isopropanol, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclopentanone. Of these, water, isopropanol, and mixtures thereof are preferred as the solvent used in this step. Methods for contacting the coating film with the solvent include, but are not limited to, spraying, showering, immersion, and puddling. The contact time between the coating film and the solvent is not particularly limited, but is, for example, 5 seconds to 15 minutes. After contact with the solvent, the coating film may be heat-treated.

(Step 3: Construction of liquid crystal cell)
Two substrates each having a liquid crystal alignment film formed thereon are prepared as described above, and a liquid crystal cell is fabricated by disposing a liquid crystal between the two substrates. Examples of methods for fabricating a liquid crystal cell include: (1) arranging the two substrates facing each other with a gap (spacer) between them so that the liquid crystal alignment films face each other, bonding the peripheries of the two substrates together with a sealant, injecting liquid crystal into the substrate surfaces and the cell gap defined by the sealant, and then sealing the injection hole; and (2) applying a sealant to a predetermined location on one of the substrates on which the liquid crystal alignment film is formed, dropping liquid crystal onto several predetermined locations on the liquid crystal alignment film, and then bonding the other substrate so that the liquid crystal alignment film faces each other, and spreading the liquid crystal over the entire surface of the substrate (ODF method). The fabricated liquid crystal cell is then preferably heated to a temperature at which the liquid crystal used assumes an isotropic phase, and then slowly cooled to room temperature to remove the flow orientation that occurred during liquid crystal filling.

Examples of sealing agents that can be used include epoxy resins containing a curing agent and aluminum oxide spheres as spacers. Examples of spacers that can be used include photospacers and bead spacers. Examples of liquid crystals that can be used include nematic liquid crystals and smectic liquid crystals. Nematic liquid crystals are preferred, and examples that can be used include Schiff-based liquid crystals, azoxy liquid crystals, biphenyl liquid crystals, phenylcyclohexane liquid crystals, ester liquid crystals, terphenyl liquid crystals, biphenylcyclohexane liquid crystals, pyrimidine liquid crystals, dioxane liquid crystals, bicyclooctane liquid crystals, and cubane liquid crystals. Cholesteric liquid crystals, chiral agents, ferroelectric liquid crystals, etc. may also be added to these liquid crystals.

In PSA mode, a polymerizable compound (e.g., a polyfunctional (meth)acrylate compound) is filled into the cell gap along with the liquid crystal, and after the liquid crystal cell is constructed, the liquid crystal cell is irradiated with light while a voltage is applied between the conductive films of the pair of substrates. When manufacturing PSA-type liquid crystal elements, the proportion of the polymerizable compound used is, for example, 0.01 to 3 parts by weight, preferably 0.05 to 1 part by weight, per 100 parts by weight of the total liquid crystal.

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

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

According to the present disclosure described above, the following means are provided.
[Means 1] A liquid crystal aligning agent containing a polymer [A] having a partial structure (a) represented by the above formula (1) in its main chain.
[Means 2] The liquid crystal aligning agent according to [Means 1], wherein the polymer [A] contains a structural unit derived from a diamine having the partial structure (a).
[Means 3] One or both of the X ¹ and X ² are bonded to the aromatic monocycle in the An ¹ via —O—, —S—, —NR ¹ — or —C(═O)—, the liquid crystal aligning agent according to [Means 1] or [Means 2].
[Means 4] The liquid crystal aligning agent according to any one of [Means 1] to [Means 3], wherein the polymer [A] is at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide.
[Means 5] The An ¹ is represented by the above formula (an-1-1), formula (an-1-2), formula (an-1-3) or formula (an-1-4), [Means 1] to [Means 4], A liquid crystal aligning agent according to any one of the above.
[Means 6] The liquid crystal aligning agent according to any one of [Means 1] to [Means 5], wherein An ¹ is a substituted or unsubstituted naphthalene-2,6-diyl group or naphthalene-3,7-diyl group.
[Means 7] The liquid crystal aligning agent according to any one of [Means 1] to [Means 6], further comprising a polymer [B] that does not have the partial structure (a) in its main chain.
[Means 8] The liquid crystal aligning agent according to [Means 7], wherein the polymer [B] is at least one selected from the group consisting of polyamic acid, polyamic acid ester, polyimide, polyorganosiloxane, and addition polymer.
[Means 9] A liquid crystal alignment film formed by using the liquid crystal aligning agent according to any one of [Means 1] to [Means 8].
[Means 10] A liquid crystal device comprising the liquid crystal alignment film according to [Means 9].
[Means 11] A polymer which is a polyamic acid, a polyamic acid ester or a polyimide and has a partial structure represented by the above formula (1) in its main chain.

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

In the following examples, the imidization rate of polyimide in a polymer solution was measured by the following method.
[Imidization rate of polyimide]
The polyimide solution was poured into pure water, and the resulting precipitate was thoroughly dried under reduced pressure at room temperature. The precipitate was then dissolved in deuterated dimethyl sulfoxide and subjected to ^1H -NMR measurement at room temperature using tetramethylsilane as a reference substance. The imidization rate [%] was calculated from the obtained ^1H -NMR spectrum using the following formula (1).
Imidization rate [%] = (1 - (A ¹ / (A ² × α))) × 100 (1)
(In formula (1), ^A1 is the peak area derived from the proton of the NH group, which appears at a chemical shift of about 10 ppm. ^A2 is the peak area derived from other protons. α is the ratio of the number of other protons to one proton of the NH group in the polymer precursor (polyamic acid).)

The required amounts of raw material compounds and polymers used in the following examples were obtained by repeating synthesis on the scale shown in the synthesis examples below as necessary. Note that "parts" and "%" in the examples and comparative examples are by mass unless otherwise specified.

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

(Tetracarboxylic acid dianhydride)

(Diamine compound)

(Other compounds)

<Synthesis of Polymer>
1. Synthesis of polyamic acid [Synthesis Example 1]
100 parts by mole of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride (compound (TB-1)) as a tetracarboxylic dianhydride, 40 parts by mole of compound (DA-1), 10 parts by mole of compound (DB-1), and 50 parts by mole of compound (DB-5) as diamine compounds were dissolved in N-methyl-2-pyrrolidone (NMP), and the mixture was reacted at 40°C for 6 hours to obtain a solution containing 15% by mass of polyamic acid (referred to as polymer (PAA-1)).

[Synthesis Examples 2 to 39]
Polyamic acids (polymers (PAA-2) to (PAA-28) and polymers (paa-1) to (paa-11)) were obtained by the same procedure as in Synthesis Example 1, except that the types and amounts of the tetracarboxylic dianhydrides and diamine compounds used were changed as shown in Table 1. In Table 1, the numerical values for the tetracarboxylic dianhydrides (acid dianhydrides 1 to 3) represent the ratio (molar ratio) of each compound relative to 100 parts by mole of the total amount of the tetracarboxylic dianhydrides used in the synthesis of the polyamic acid. The numerical values for the diamine compounds (diamines 1 to 4) represent the ratio (molar ratio) of each compound relative to 100 parts by mole of the total amount of the diamine compounds used in the synthesis of the polyamic acid.

2. Synthesis of polyimide [Synthesis Example 40]
100 parts by mole of compound (TB-1) as a tetracarboxylic dianhydride, 10 parts by mole of compound (DA-1) as a diamine compound, 50 parts by mole of compound (DB-5), 20 parts by mole of compound (DB-8), and 20 parts by mole of compound (DB-9) were dissolved in NMP and reacted at 40°C for 6 hours to obtain a solution containing 15% by mass of polyamic acid. Next, NMP was added to the obtained polyamic acid solution to obtain a solution with a polyamic acid concentration of 10% by mass, and pyridine and acetic anhydride were added, followed by a dehydration ring-closing reaction at 60°C for 4 hours. After the dehydration ring-closing reaction, the solvent in the system was replaced with fresh NMP to obtain a solution containing 15% by mass of polyimide (referred to as polymer (PI-1)) with an imidization rate of approximately 60%.

[Synthesis Examples 41 to 51]
Polyimides (polymers (PI-2) to (PI-9) and (PI-1) to (PI-3)) were obtained by the same procedure as in Synthesis Example 40, except that the types and amounts of the tetracarboxylic dianhydrides and diamine compounds used were changed as shown in Table 2. In Table 2, the numerical values for the tetracarboxylic dianhydrides (acid dianhydrides 1 and 2) represent the ratio (molar ratio) of each compound relative to 100 parts by mole of the total amount of the tetracarboxylic dianhydrides used in the synthesis of the polyimide. The numerical values for the diamine compounds (diamines 1 to 4) represent the ratio (molar ratio) of each compound relative to 100 parts by mole of the total amount of the diamine compounds used in the synthesis of the polyimide.

3. Synthesis of polyorganosiloxane [Synthesis Example 52]
A 1000 mL three-neck flask was charged with 100.0 g of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (compound (s-1)), 500 g of methyl isobutyl ketone, and 10.0 g of triethylamine, and mixed at room temperature. Next, 100 g of deionized water was added dropwise from the dropping funnel over 30 minutes, and the mixture was then mixed under reflux at 80 ° C. for 6 hours while reacting. After completion of the reaction, the organic layer was removed and washed with a 0.2 mass% aqueous ammonium nitrate solution until the water after washing was neutral, and then the solvent and water were distilled off under reduced pressure. An appropriate amount of methyl isobutyl ketone was added to obtain a 50 mass% solution of polymer (ESSQ-1), which is a polyorganosiloxane having epoxy groups.
In a 500 mL three-neck flask, 3.10 g of compound (c-1) (20 mol% relative to the amount of epoxy groups in the polymer (ESSQ-1)), 3.24 g of compound (c-2) (10 mol% relative to the amount of epoxy groups in the polymer (ESSQ-1)), 1.00 g of tetrabutylammonium bromide, 20.0 g of the polymer (ESSQ-1)-containing solution, and 290.0 g of methyl isobutyl ketone were added and stirred at 90 ° C. for 18 hours. After cooling to room temperature, the separation and washing operation with distilled water was repeated 10 times. Thereafter, the organic layer was recovered, concentrated using a rotary evaporator and diluted with NMP twice, and then adjusted to a solids concentration of 10% by mass using NMP to obtain an NMP solution of polyorganosiloxane (this is referred to as polymer (PSQ-1)).

4. Synthesis of styrene-maleimide copolymer [Synthesis Example 53]
Under nitrogen, 5.00 g of compound (M-1), 1.05 g of compound (M-2), 4.80 g of compound (M-3), and 2.26 g of compound (M-4) were added as polymerization monomers to a 100 mL two-neck flask, 0.39 g of 2,2'-azobis(2,4-dimethylvaleronitrile) as a radical polymerization initiator, 0.39 g of 2,4-diphenyl-4-methyl-1-pentene as a chain transfer agent, and 52.5 mL of N-methyl-2-pyrrolidone (NMP) as a solvent, and polymerization was carried out for 6 hours at 70°C. After reprecipitation in methanol, the precipitate was filtered and dried in vacuum at room temperature for 8 hours to obtain the target polymer (referred to as polymer (MI-1)).

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

2. Fabrication of FFS-Type Liquid Crystal Display Devices Using a Photo-Alignment Method A glass substrate (referred to as the first substrate) with a flat electrode (bottom electrode), an insulating layer, and a comb-shaped electrode (top electrode) laminated in this order on one side, and a glass substrate (referred to as the second substrate) without an electrode, were prepared. Next, a liquid crystal alignment agent (AL-1) was applied to the electrode-forming surface of the first substrate and one substrate surface of the second substrate using a spinner, and the substrates were pre-baked at 80°C on a hot plate for 1 minute. The substrates were then dried (post-baked) for 30 minutes in a nitrogen-purged oven at 230°C to form a coating film with an average thickness of 0.1 μm. The resulting coating film was subjected to a photo-alignment treatment by irradiating the substrate normal with 1,000 J/ ^m² of linearly polarized ultraviolet light containing a 254 nm emission line using an Hg-Xe lamp. Note that this exposure dose was measured using an actinometer measuring at a wavelength of 254 nm. Next, the coating film that had been subjected to the photo-alignment treatment was heat-treated by heating in a clean oven at 230° C. for 30 minutes to form a liquid crystal alignment film.
Next, an epoxy resin adhesive containing 3.5 μm diameter aluminum oxide spheres was applied by screen printing to the outer edge of the surface of one of the pair of substrates bearing the liquid crystal alignment film. The substrates were then superimposed and pressed together so that the projection direction of the polarization axis onto the substrate surface during light irradiation was antiparallel. The adhesive was then thermally cured at 150°C for 1 hour. Next, a negative liquid crystal (MLC-6608, manufactured by Merck) was filled between the pair of substrates through the liquid crystal injection port, which was then sealed with an epoxy adhesive to obtain a liquid crystal cell. To eliminate flow alignment during liquid crystal injection, the cell was heated to 120°C and then slowly cooled to room temperature. The above series of operations was repeated, varying the UV exposure dose after post-baking between 100 and 10,000 J/ ^m² , to produce three or more liquid crystal cells with different UV exposure doses. The liquid crystal cell with the best exposure dose (optimum exposure dose) was used for the evaluation of liquid crystal alignment, alignment uniformity, and VHR reliability described below.

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

4. Evaluation of Alignment Uniformity For the liquid crystal cell manufactured in 2. above, retardation was measured at 20 points within one pixel plane using an Axoscan manufactured by Optoscience, and the standard deviation was calculated. The evaluation was as follows: if the standard deviation of retardation was 0.05 or less, it was "good (○)", if it was greater than 0.05 and less than 0.07, it was "fair (△)", and if it was greater than 0.07, it was "poor (×)". As a result, the alignment uniformity of this example was evaluated as "good (○)".

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

6. Evaluation of Adhesion to Substrates The liquid crystal alignment agent (AL-1) was applied to a glass substrate using a spinner, prebaked on a hot plate at 80°C for 2 minutes, and then postbaked in a nitrogen-purged oven at 230°C for 30 minutes to form a coating film with an average thickness of 0.10 μm. This same procedure was repeated to produce two glass substrates with coating films. An ODF sealant (S-WB42, manufactured by Sekisui Chemical Co., Ltd.) was applied to the coating film of one glass substrate with a coating film formed thereon to a width of 1 mm, and the other glass substrate was bonded so that the coating film and the ODF sealant were in contact. The substrate was then irradiated with light of 30,000 J/m ² (equivalent to 365 nm) using a metal halide lamp and then heated in an oven at 120°C for 1 hour. After heating, the adhesion of the film to the substrate was evaluated by measuring the adhesion force using a tension and compression tester (model number: SDWS-0201-100SL) manufactured by Imada Manufacturing Co., Ltd. The evaluation was as follows: an adhesion force of 200 N/ ^cm2 or more was "good (○)", an adhesion force of 100 N/cm2 ^{or more} but less than 200 N/ ^cm2 was "fair (△)", and an adhesion force of less than 100 N/ ^cm2 was "poor (×)". As a result, in this example, the adhesion force was 212 N/ ^cm2 , and the adhesion was evaluated as "good (○)".

[Examples 2 to 17 and Comparative Examples 1 to 7]
A liquid crystal alignment agent was prepared in the same manner as in Example 1, except that the composition of the liquid crystal alignment agent was changed as shown in Table 3. Furthermore, using the obtained liquid crystal alignment agent, an FFS-type liquid crystal cell was produced by a photoalignment method in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 3. In Examples 11 to 14, 16, and 17 and Comparative Examples 2, 3, and 5 to 7, two types of polymers were used as the polymer component. In Table 3, the numerical values in the polymer column represent the blending ratio (parts by mass) of the solid content of each polymer relative to 100 parts by mass of the total amount of the solid content (polymer component) used in preparing the liquid crystal alignment agent.

As shown in Table 3, Examples 1 to 17, which used a liquid crystal alignment agent containing polymer [A] having partial structure (a), showed a well-balanced improvement in liquid crystal alignment, alignment uniformity, and VHR reliability compared to Comparative Examples 1 to 7, which used a liquid crystal alignment agent that did not contain polymer [A]. Furthermore, Examples 1 to 17 also showed adhesion to the substrate that was rated "good" or "fair."

Among these, in Examples 1 to 17, Examples 1 to 5, 9 to 13, and 15 to 17 were rated as "good (○)" for liquid crystal alignment and adhesion, indicating that film adhesion could be improved while maintaining liquid crystal alignment. This is thought to be due to the fact that the inclusion of a naphthalene-2,6-diyl group or a naphthalene-3,7-diyl group in the partial structure (a) further improved liquid crystal alignment, and that the inclusion of an alkylene chain having two or more carbon atoms in the partial structure (a) improved film adhesion while maintaining liquid crystal alignment. Note that in Comparative Example 7, although a naphthalene ring structure was introduced into the polymer by using compound (DB-22) as part of the diamine compound, the results were inferior to those of Examples 1 to 16. This is presumably because the introduction of a structural unit derived from compound (DB-22) into the polymer main chain caused bending of the molecular chain, resulting in insufficient VHR reliability, and the absence of a structure corresponding to ^X2 resulted in the evaluation of liquid crystal alignment and adhesion being "fair (△)."

[Example 18: Rubbed FFS-type liquid crystal display element]
1. Preparation of liquid crystal aligning agent The solution of the polymer (PAA-14) obtained in Synthesis Example 14 was diluted with NMP and butyl cellosolve (BC) to prepare a solution with a solvent composition of NMP/BC = 80/20 (mass ratio) and a solid content concentration of 3.5 mass %. This solution was filtered through a filter with a pore size of 0.2 μm to prepare a liquid crystal aligning agent (AL-25).

2. Fabrication of FFS-Mode Liquid Crystal Display Element Using Rubbing Method A glass substrate (referred to as the first substrate) with a flat electrode (bottom electrode), an insulating layer, and a comb-shaped electrode (top electrode) laminated in this order on one side, and a glass substrate (referred to as the second substrate) without an electrode, were prepared. Next, a liquid crystal alignment agent (AL-25) was applied to the electrode-formed surface of the first substrate and one side of the second substrate using a spinner, and heated (pre-baked) on a hot plate at 110°C for 3 minutes. This was then dried (post-baked) for 30 minutes in a nitrogen-purged oven at 230°C, forming a coating film with an average film thickness of 0.08 μm. Next, the coating film surface was rubbed using a rubbing machine equipped with a roll wrapped around a rayon cloth at a roll rotation speed of 1000 rpm, a stage movement speed of 3 cm/sec, and a pile indentation length of 0.3 mm. Thereafter, the substrate was subjected to ultrasonic cleaning in ultrapure water for 1 minute, and then dried in a clean oven at 100° C. for 10 minutes to obtain a pair of substrates having a liquid crystal alignment film.
Next, a pair of substrates with liquid crystal alignment films were screen-printed with an epoxy resin adhesive containing 3.5 μm diameter aluminum oxide spheres, leaving a liquid crystal injection port at the edge of the surface where the liquid crystal alignment film was formed. The substrates were then superimposed and pressed together, and the adhesive was thermally cured at 150°C for 1 hour. Next, negative liquid crystal (MLC-6608, manufactured by Merck) was filled into the gap between the pair of substrates through the liquid crystal injection port, which was then sealed with an epoxy adhesive. Furthermore, to eliminate flow alignment during liquid crystal injection, the substrate was heated at 120°C and then slowly cooled to room temperature to produce a liquid crystal cell. When the pair of substrates were superimposed, the rubbing directions of the respective substrates were antiparallel.

3. Evaluation The liquid crystal cells produced in 2. above were evaluated for liquid crystal alignment, alignment uniformity, and VHR reliability in the same manner as in Example 1. In addition, the liquid crystal alignment agent (AL-25) was used to evaluate adhesion in the same manner as in Example 1. The evaluation results are shown in Table 4.

[Examples 19 to 37 and Comparative Examples 8 to 11]
A liquid crystal aligning agent was prepared in the same manner as in Example 18, except that the composition of the liquid crystal aligning agent was changed as shown in Table 4. Furthermore, using the obtained liquid crystal aligning agent, an FFS-type liquid crystal cell was produced by a rubbing method in the same manner as in Example 18, and various evaluations were performed. The results are shown in Table 4. In Examples 28 to 30 and Comparative Example 10, two types of polymers were used as the polymer component. In Table 4, the numerical values in the polymer column represent the blending ratio (parts by mass) of the solid content of each polymer relative to 100 parts by mass of the total amount of the polymer components used in preparing the liquid crystal aligning agent.

As shown in Table 4, Examples 18 to 37, which used a liquid crystal alignment agent containing polymer [A] having partial structure (a), achieved better alignment uniformity and VHR reliability than Comparative Examples 8 to 11, which used a liquid crystal alignment agent that did not contain polymer [A]. Furthermore, Examples 18, 21, 23, and 27 to 30 also demonstrated good liquid crystal alignment and adhesion to the substrate.

In Comparative Example 11, although a naphthalene ring structure (naphthalene-1,4-diyl group) was introduced into the polymer by using compound (DB-23) as part of the diamine compound, the liquid crystal alignment was "poor (×)" and the alignment uniformity was "fair (△)."

[Example 38: PSA type liquid crystal display element]
1. Preparation of Liquid Crystal Alignment Agent A solution containing 5 parts by mass of the polymer (PSQ-1) obtained in Synthesis Example 52 and a solution containing 95 parts by mass of the polymer (PI-7) obtained in Synthesis Example 46 were mixed and diluted with NMP and BC to obtain a solution with a solvent composition of NMP/BC = 50/50 (mass ratio) and a solids concentration of 3.5 mass%. This solution was filtered through a filter with a pore size of 0.2 μm to prepare a liquid crystal alignment agent (AL-49).

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

3. Manufacturing of PSA-Type Liquid Crystal Display Element The liquid crystal alignment agent (AL-49) prepared above was applied to the transparent electrode surface of a glass substrate with a transparent electrode made of an ITO film using a spinner. After pre-baking for 1 minute on a hot plate at 80°C, the substrate was heated at 200°C for 1 hour in a nitrogen-substituted oven to remove the solvent, forming a coating film (liquid crystal alignment film) with a thickness of 0.08 μm. This coating film was subjected to a rubbing treatment using a rubbing machine equipped with a roll wrapped around a rayon cloth at a roll rotation speed of 400 rpm, a stage movement speed of 3 cm/sec, and a pile indentation length of 0.1 mm. The substrate was then ultrasonically cleaned in ultrapure water for 1 minute and then dried in a clean oven at 100°C for 10 minutes to obtain a substrate with a liquid crystal alignment film. This operation was repeated to obtain a pair (two substrates) with a liquid crystal alignment film. Note that this rubbing treatment was a weak rubbing treatment performed to control liquid crystal collapse and easily achieve alignment division.
An epoxy resin adhesive containing aluminum oxide spheres with a diameter of 3.5 μm was applied by screen printing to the outer periphery of the surface of one of the substrates having a liquid crystal alignment film, and then the liquid crystal alignment film surfaces of the pair of substrates were placed facing each other, overlapped, and pressed together, and the adhesive was thermally cured by heating for 1 hour at 150° C. Next, liquid crystal composition LC1 was filled into the gap between the substrates through the liquid crystal injection port, which was then sealed with an epoxy adhesive. To prevent flow alignment during liquid crystal injection, the resulting mixture was heated at 150° C. for 10 minutes and then slowly cooled to room temperature.
Next, a 10 V AC voltage with a frequency of 60 Hz was applied between the electrodes of the resulting liquid crystal cell. While the liquid crystal was in a driving state, the cell was irradiated with ultraviolet light at a dose of 50,000 J/ ^m² using an ultraviolet irradiation device with a metal halide lamp as the light source. Note that this dose was measured using an actinometer measuring at a wavelength of 365 nm. This resulted in the production of a PSA-type liquid crystal cell.

4. Evaluation The liquid crystal cells produced in the above 3. were evaluated for liquid crystal alignment, alignment uniformity, VHR reliability, and adhesion in the same manner as in Example 1. The evaluation results are shown in Table 5.

[Examples 39 to 41 and Comparative Examples 12 and 13]
A liquid crystal alignment agent was prepared in the same manner as in Example 38, except that the composition of the liquid crystal alignment agent was changed as shown in Table 5. Furthermore, a PSA type liquid crystal cell was produced using the obtained liquid crystal alignment agent in the same manner as in Example 38, and various evaluations were performed. The evaluation results are shown in Table 5. In Table 5, the numerical values in the polymer column represent the blending ratio (parts by mass) of the solid content of each polymer relative to 100 parts by mass of the total amount of the polymer components used in the preparation of the liquid crystal alignment agent.

As shown in Table 5, Examples 38 to 41, which used a liquid crystal alignment agent containing polymer [A], were all rated as good in alignment uniformity, VHR reliability, and adhesion. Of these, Example 38, which used a liquid crystal alignment agent containing polymer (PI-7) having a naphthalene ring structure in the partial structure (a), was also rated as good in liquid crystal alignment. In contrast, Comparative Examples 12 and 13, which used liquid crystal alignment agents that did not contain polymer [A], were rated as "fair (△)" for alignment uniformity and "poor (×)" for VHR reliability, and Comparative Example 13 was also rated as "poor (×)" for adhesion.

[Example 42: Optical VA type liquid crystal display element]
1. Preparation of Liquid Crystal Alignment Agent A solution containing 30 parts by mass of the polymer (MI-1) obtained in Synthesis Example 53 and 70 parts by mass of the polymer (PAA-14) obtained in Synthesis Example 14 was mixed and diluted with NMP and BC to obtain a solution with a solvent composition of NMP/BC = 80/20 (mass ratio) and a solids concentration of 3.5 mass%. This solution was filtered through a filter with a pore size of 0.2 μm to prepare a liquid crystal alignment agent (AL-55).

2. Manufacture of VA-type liquid crystal display elements using a photoalignment method. The liquid crystal alignment agent (AL-55) prepared above was applied to the transparent electrode surface of a glass substrate with a transparent electrode made of an ITO film using a spinner and prebaked on a hot plate at 80°C for 1 minute. The substrate was then heated at 230°C for 1 hour in an oven with the interior purged with nitrogen to form a coating film with a thickness of 0.1 μm. The coating film surface was then irradiated with 1,000 J/ ^m² of polarized ultraviolet light containing a 313 nm emission line using an Hg-Xe lamp and a Glan-Taylor prism from a direction tilted 40° from the substrate normal to impart liquid crystal alignment ability. The same procedure was repeated to prepare a pair (two substrates) of substrates with liquid crystal alignment films.
An epoxy resin adhesive containing 3.5 μm diameter aluminum oxide spheres was applied by screen printing to the outer periphery of the surface of one of the substrates bearing the liquid crystal alignment film. The pair of substrates were then placed with the liquid crystal alignment film surfaces facing each other and pressed together so that the projection directions of the ultraviolet light axes of each substrate onto the substrate surface were antiparallel. The adhesive was then thermally cured at 150°C for 1 hour. Next, negative liquid crystal (MLC-6608, manufactured by Merck) was filled into the gap between the substrates through the liquid crystal injection port, which was then sealed with an epoxy adhesive. Furthermore, to eliminate flow alignment during liquid crystal injection, the substrate was heated at 130°C and then slowly cooled to room temperature.

3. Evaluation The liquid crystal cells produced in 2. above were evaluated for liquid crystal alignment, alignment uniformity, VHR reliability, and adhesion in the same manner as in Example 1. Table 6 shows the evaluation results.

[Comparative Example 14]
A liquid crystal alignment agent was prepared in the same manner as in Example 42, except that the composition of the liquid crystal alignment agent was changed as shown in Table 6. In addition, an optical VA-type liquid crystal cell was produced using the obtained liquid crystal alignment agent in the same manner as in Example 42, and various evaluations were performed. The results are shown in Table 6. In Table 6, the numerical values in the polymer column represent the blending ratio (parts by mass) of the solid content of each polymer relative to 100 parts by mass of the total amount of the polymer components used in the preparation of the liquid crystal alignment agent.

As shown in Table 6, Example 42, which used a liquid crystal alignment agent containing polymer [A], was rated as good in liquid crystal alignment, alignment uniformity, VHR reliability, and adhesion. In contrast, Comparative Example 14, which used a liquid crystal alignment agent not containing polymer [A], was rated as "fair (△)" for alignment uniformity and "poor (×)" for VHR reliability.

These results demonstrate that a liquid crystal alignment agent containing polymer [A] having partial structure (a) can be used to obtain liquid crystal devices with excellent liquid crystal alignment properties, alignment uniformity, and VHR reliability, as well as to form a liquid crystal alignment film with excellent adhesion to the substrate.

Claims (11)

A liquid crystal aligning agent comprising a polymer [A] having a partial structure (a) represented by the following formula (1) (excluding the partial structure represented by the following formula (DA-6E)) in its main chain.
(In formula (1), An ¹ has a substituted or unsubstituted fused ring structure comprising a plurality of aromatic monocycles, and is a divalent group obtained by removing one hydrogen atom from each of two different rings among the plurality of aromatic monocycles constituting the fused ring, or by removing one hydrogen atom from each of two different rings among the plurality of aromatic monocycles contained in a substituent of the fused ring structure. ^{X 1} and X ² are each independently a substituted or unsubstituted alkanediyl group having 2 to 18 carbon atoms, or a divalent group in which some methylene groups in a substituted or unsubstituted alkanediyl group having 2 to 18 carbon atoms are replaced by —O—, —S—, —NR ¹ —, —C(═O)—, —NR ¹ —C(═O)— or —NR ¹ —C(═O)—NR ² —; provided that the aromatic monocycle in An 1 to which X ¹ is bonded and the aromatic monocycle in An ¹ to which X ² is bonded are mutually exclusive .) ^R1 and ^R2 are each independently a ^{hydrogen atom or a monovalent organic group. Ar1 and Ar2} are each independently a divalent aromatic ring group. "*" represents a bond.
(In formula (DA-6E), "*" represents a bond.) The liquid crystal aligning agent according to claim 1, wherein the polymer [A] contains a structural unit derived from a diamine having the partial structure (a). 2. The liquid crystal aligning agent according to claim 1, wherein one or both of X ¹ and X ² are bonded to the aromatic monocyclic ring in An ¹ via -O-, -S-, -NR ¹ - or -C(=O)-. The liquid crystal aligning agent according to claim 1, wherein the polymer [A] is at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide. The liquid crystal aligning agent according to claim 1, wherein An ¹ is represented by the following formula (an-1-1), formula (an-1-2), formula (an-1-3) or formula (an-1-4).
(In formulas (an-1-1), (an-1-2), (an-1-3), and (an-1-4), Y ¹ to Y ⁶ each independently represent an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a halogenated alkyl group having 1 to 5 carbon atoms, a halogenated alkoxy group having 1 to 5 carbon atoms, an alkoxyalkyl group having 1 to 5 carbon atoms, an alkoxyalkoxyalkyl group having 1 to 5 carbon atoms, a halogen atom, or a hydroxyl group. r1 to r4 each independently represent an integer of 0 to 6. r5 and r6 each independently represent an integer of 0 to 4. X ⁴ is —C(R ⁶ )(R ⁷ )—, —O—, —S—, —NR ⁸ —, or —SO ₂ —. R ⁶ and R ⁷ each independently represent a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group. R ⁸ is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a thermally detachable group. "* ¹ " represents a bond to one of ^X1 and ^X2 in formula (1), and "* ² " represents a bond to the other. 2. The liquid crystal aligning agent according to claim 1, wherein An ¹ is a substituted or unsubstituted naphthalene-2,6-diyl group or naphthalene-3,7-diyl group. The partial structure represented by the above formula (1) (wherein X ¹ and X ² in formula (1) each independently represent -S-, -NR ¹ -, -C(═O)-, -NR ¹ -C(═O)-, -NR ¹ -C(═O)-NR ² -, a substituted or unsubstituted alkanediyl group having 1 to 18 carbon atoms, or a divalent group in which some methylene groups in a substituted or unsubstituted alkanediyl group having 2 to 18 carbon atoms are replaced by -O-, -S-, -NR ¹ -, -C(═O)-, -NR ¹ -C( ═O)- or -NR ¹ -C(═O)-NR ² -) (wherein when An ¹ has a fluorene structure, X ¹ and X ² in formula (1) are simultaneously -NR ¹ -, and when An 2. The liquid crystal aligning agent according to claim 1 , further comprising a polymer [B] having no —NR ¹ —C(═O)— in the main chain, except that when X ¹ has a carbazole structure, X ¹ and X ² in formula (1) are simultaneously —NR 1 —C(═O)—. The liquid crystal aligning agent according to claim 7, wherein the polymer [B] is at least one selected from the group consisting of polyamic acid, polyamic acid ester, polyimide, polyorganosiloxane, and addition polymer. A liquid crystal alignment film formed using the liquid crystal alignment agent according to any one of claims 1 to 8. A liquid crystal element comprising the liquid crystal alignment film according to claim 9. A polymer which is a polyamic acid, a polyamic acid ester, or a polyimide and has a partial structure represented by the following formula (1) (excluding the partial structure represented by the following formula (DA-6E)) in its main chain.
(In formula (1), An ¹ has a substituted or unsubstituted fused ring structure comprising a plurality of aromatic monocycles, and is a divalent group obtained by removing one hydrogen atom from each of two different rings among the plurality of aromatic monocycles constituting the fused ring, or by removing one hydrogen atom from each of two different rings among the plurality of aromatic monocycles contained in a substituent of the fused ring structure. ^{X 1} and X ² are each independently a substituted or unsubstituted alkanediyl group having 2 to 18 carbon atoms, or a divalent group in which some methylene groups in a substituted or unsubstituted alkanediyl group having 2 to 18 carbon atoms are replaced by —O—, —S—, —NR ¹ —, —C(═O)—, —NR ¹ —C(═O)— or —NR ¹ —C(═O)—NR ² —; provided that the aromatic monocycle in An 1 to which X ¹ is bonded and the aromatic monocycle in An ¹ to which X ² is bonded are mutually exclusive .) ^R1 and ^R2 are each independently a ^{hydrogen atom or a monovalent organic group. Ar1 and Ar2} are each independently a divalent aromatic ring group. "*" represents a bond.
(In formula (DA-6E), "*" represents a bond.)