TWI890827B - Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal element - Google Patents

Abstract

The present invention provides a liquid crystal alignment agent that can produce a liquid crystal alignment film that is less likely to produce residual images, has good coating properties, and has high mechanical strength. A liquid crystal alignment agent comprises: a polymer [A] containing a structural unit (U1) and not containing a structural unit (U2); and a polymer [B] containing a structural unit (U2) and a structural unit (U3). Structural unit (U1): a structural unit derived from a diamine having a partial structure represented by formula (1). Structural unit (U2): a structural unit derived from a diamine having a partial structure represented by formula (2). Structural unit (U3): a structural unit derived from a diamine having a partial structure Y (-( _CH2 ) _n- , etc.). In formula (1), ^X1 and ^X2 are divalent aromatic ring groups. ^R1 and ^R2 are a single bond, an alkanediyl group having 1 to 4 carbon atoms, etc. ^Y1 and ^Y2 are ^-NR3- CO-. ^Z1 is a divalent organic group, etc. ^A1 and ^A2 are divalent aromatic cyclic groups. ^B1 is ^-NR4- or a divalent aromatic heterocyclic group.

Description

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

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

As the liquid crystal material for liquid crystal cells, negative-type liquid crystals are used in liquid crystal cells using vertical alignment (VA) or multi-domain vertical alignment (MVA) drive modes, while positive-type liquid crystals are used in liquid crystal cells using twisted nematic (TN), in-plane switching (IPS), or fringe field switching (FFS) drive modes. Furthermore, in recent years, in order to achieve further high-definition liquid crystal cells, the use of negative-type liquid crystals in liquid crystal cells using IPS or FFS drive modes has also been proposed (see, for example, Patent Document 1).

In recent years, liquid crystal devices have been used in a wide range of applications, from relatively large display devices such as LCD televisions and information displays to small display devices such as smartphones. With the increasing versatility of these liquid crystal devices, there is a demand for further improved quality. Therefore, it has been proposed to include a polymer having a nitrogen-containing meta-arylene structure in a liquid crystal alignment agent, thereby achieving a liquid crystal alignment film with low resistance and high transparency, and also achieving a liquid crystal device with minimal burn marks (direct current (DC) artifacts) caused by stored charge (see, for example, Patent Document 2). [Prior Art Document] [Patent Document]

[Patent Document 1] International Publication No. 2016/152928 [Patent Document 2] International Publication No. 2019/093037

[Problem to be Solved by the Invention] In addition to DC image artifacts, liquid crystal elements also produce alternating current (AC) image artifacts caused by the liquid crystal alignment direction deviating from its initial alignment. To suppress these artifacts and achieve higher resolution in liquid crystal elements, it is necessary to suppress not only DC image artifacts but also AC image artifacts. Furthermore, when introducing metastable aromatic structures into polymers, as in the technique of Patent Document 2, there is a concern that the introduction of rigid structures into the main chain may reduce the polymer's solubility and thus the coating properties of the liquid crystal alignment agent. Furthermore, when considering the use of rubbing to obtain a liquid crystal alignment film or to prevent yield degradation, the film formed using the liquid crystal alignment agent requires high mechanical strength. However, it is difficult to simultaneously satisfy all of these characteristics, and there is room for further improvement in liquid crystal alignment agents.

This invention was developed in response to the aforementioned challenges. Its primary purpose is to provide a liquid crystal alignment agent that can produce a liquid crystal alignment film that is less prone to residual imaging, has excellent coating properties, and exhibits high mechanical strength. [Technical Solution]

The inventors have conducted extensive research to address this issue and have discovered that using multiple polymers with different molecular structures can solve this problem, leading to the completion of the present invention. Specifically, the present invention provides the following solutions.

<1> A liquid crystal alignment agent comprising: a polymer [A] having the following structural unit (U1) and not having the following structural unit (U2); and a polymer [B] having the following structural unit (U2) and the following structural unit (U3). Structural unit (U1): Structural unit derived from a diamine having a partial structure represented by the following formula (1) Structural unit (U2): Structural unit derived from a diamine having a partial structure represented by the following formula (2) Structural unit (U3): Structural unit derived from a diamine having the following partial structure Y Partial structure Y: A structure represented by -(CH _{2 ) n} - (wherein n is an integer from 1 to 20), a structure in which any methylene group in a structure represented by -(CH 2 ) _n+1 - is substituted by -O-, -S-, -COO-, -NR ⁷ -, -NR ⁷ -CO-, -NR ⁷ -COO-, -NR ⁷ -CO-NR ⁸ -, or a nitrogen-containing non-aromatic heterocyclic group (wherein R ⁷ and R ⁸ are each independently a hydrogen atom or a monovalent organic group; when n is 2 or greater, -O-, -S-, -COO-, -NR ⁷ -, -NR ⁷ -CO-, -NR ⁷ -COO-, -NR ⁷ -CO-NR ⁸ -, and the nitrogen-containing non-aromatic heterocyclic group are not adjacent to each other), -O-, -S-, -COO-, -NR ⁷ -CO-, -NR ⁷ -COO-, or -NR ⁷ -CO-NR ⁸ - [Chemistry 1] (In formula (1), ^X1 and ^X2 are each independently a divalent aromatic ring group; wherein, in the aromatic ring possessed by ^X1 , no substituent is bonded to a position different from the bonding position of ^R1 and the bonding position of the group to which “*” is bonded, and in the aromatic ring possessed by ^X2 , no substituent is bonded to a position different from the bonding position of ^R2 and the bonding position of the group to which “*” is bonded; ^R1 and ^R2 are each independently a single bond, an alkanediyl group having 1 to 10 carbon atoms, or a substituted alkanediyl group having 1 to 10 carbon atoms; ^Y1 and ^Y2 are each independently * ¹ - ^NR3 -CO- or * ¹ -CO- ^NR3- ; ^R3 is a hydrogen atom or a monovalent organic group; “* ¹ ” represents a substituted alkyl radical with Z ¹ ; Z ¹ is a single bond or a divalent organic group; m is 0 or 1; when m is 0, at least one of R ¹ and R ² is an alkanediyl group or a substituted alkanediyl group having 1 to 10 carbon atoms; "*" indicates a bond) [Chemistry 2] (In formula (2), ^A1 and ^A2 are each independently a divalent aromatic cyclic group; ^B1 is ^-NR4- or a divalent aromatic heterocyclic group; when ^B1 is a divalent aromatic heterocyclic group, ^R5 and ^R6 are each independently a hydrogen atom or a monovalent organic group; when ^B1 is ^-NR4- , ^R4 , ^R5 and ^R6 are (i) or (ii) below; (i) ^R4 is a hydrogen atom or a monovalent organic group; ^R5 and ^R6 are each independently a hydrogen atom or a monovalent organic group, or ^R5 and ^R6 are each bonded to each other and form a ring structure together with ^A1 , ^-NR4- and ^A2 ; (ii) ^R4 and R6 are ^{(R 5} is independently a hydrogen atom or a monovalent organic group, or represents a ring structure formed by R ⁴ and R ⁵ combined with each other, A ¹ and the nitrogen atom; R ⁶ is a hydrogen atom or a monovalent organic group; "*" represents a bond)

<2> A liquid crystal alignment film formed from the liquid crystal alignment agent of <1>. <3> A liquid crystal element comprising the liquid crystal alignment film of <2>. [Effects of the Invention]

The liquid crystal alignment agent of the present invention can produce a liquid crystal alignment film that is less prone to image sticking, has excellent coatability, and exhibits high mechanical strength. In particular, the liquid crystal alignment agent of the present invention can produce a liquid crystal alignment film that achieves both AC and DC image sticking characteristics.

The liquid crystal alignment agent disclosed herein contains a polymer [A] and a polymer [B] that is a polymer different from polymer [A]. The following describes the components contained in the liquid crystal alignment agent disclosed herein and other components that may be optionally added.

In addition, in this specification, the term "alkyl group" is used to include chain alkyl groups, alicyclic alkyl groups, and aromatic alkyl groups. The term "chain alkyl group" refers to a straight chain alkyl group and a branched alkyl group that does not contain a ring structure in the main chain and consists only of a chain structure. These may be saturated or unsaturated. The term "alicyclic alkyl group" refers to a alkyl group that contains only an alicyclic alkyl structure as a ring structure and does not contain an aromatic ring structure. These groups do not need to be composed only of an alicyclic alkyl structure and include groups that have a chain structure in part. The term "aromatic alkyl group" refers to a alkyl group that contains an aromatic ring structure as a ring structure. However, it is not necessary to be composed solely of an aromatic ring structure; a chain structure or an alicyclic hydrocarbon structure may also be partially included. The term "structural unit" refers to a unit primarily constituting the main chain structure, and at least two units are included in the main chain structure. Unless otherwise specified, each component or compound may be used alone or in combination of two or more.

<Polymer [A]> Polymer [A] is a polymer containing a structural unit (U1) derived from a diamine (hereinafter also referred to as “specific diamine (A)”) having a partial structure represented by the following formula (1). [Chemical 3] (In formula (1), ^X1 and ^X2 are each independently a divalent aromatic ring group; wherein, in the aromatic ring possessed by ^X1 , no substituent is bonded to a position different from the bonding position of ^R1 and the bonding position of the group to which “*” is bonded, and in the aromatic ring possessed by ^X2 , no substituent is bonded to a position different from the bonding position of ^R2 and the bonding position of the group to which “*” is bonded; ^R1 and ^R2 are each independently a single bond, an alkanediyl group having 1 to 10 carbon atoms, or a substituted alkanediyl group having 1 to 10 carbon atoms; ^Y1 and ^Y2 are each independently * ¹ - ^NR3 -CO- or * ¹ -CO- ^NR3- ; ^R3 is a hydrogen atom or a monovalent organic group; “* ¹ ” represents a substituted alkyl radical with Z ¹ ; Z ¹ is a single bond or a divalent organic group; m is 0 or 1; at least one of R ¹ and R ² is an alkanediyl group or a substituted alkanediyl group having 1 to 10 carbon atoms; "*" indicates a bond)

Structural Unit (U1) Structural Unit (U1) is a structural unit derived from a diamine containing two aromatic rings and at least one amide bond (-NR ³ -CO-). In Formula (1), the divalent aromatic ring groups represented by X ¹ and X ² are preferably aromatic hydrocarbon groups. Specific examples of X ¹ and X ² include groups formed by removing any two hydrogen atoms bonded to carbon atoms constituting an aromatic hydrocarbon ring such as a benzene ring, a naphthalene ring, or an anthracene ring.

Furthermore, the aromatic rings possessed by ^X1 and ^X2 do not have a substituent. That is, in the aromatic ring possessed by ^X1 , no substituent is bonded to a position that is different from the bonding position of ^R1 and the bonding position of the group represented by "*". Similarly, in the aromatic ring possessed by ^X2 , no substituent is bonded to a position that is different from the bonding position of ^R2 and the bonding position of the group represented by "*".

From the viewpoint of achieving high density of the liquid crystal alignment film, improving the effect of reducing residual images and the mechanical strength of the film, the divalent aromatic ring group represented by X ¹ and X ² is preferably a phenylene group, particularly preferably a 1,4-phenylene group.

When ^R1 and ^R2 are alkanediyl groups having 1 to 10 carbon atoms, examples of ^R1 and ^{R2 include linear alkanediyl groups such as methylene, ethylidene, 1,3-propanediyl, 1,4-butanediyl, and 1,5-pentanediyl; and branched alkanediyl groups such as 1,2-propanediyl, 1,2-butanediyl, and 2-methyl-1,3-propanediyl. When R1 and R2 are substituted} alkanediyl groups having 1 to 10 carbon atoms, examples of substituents include halogen atoms, hydroxyl groups, amino groups, cyano groups, alkoxy groups, protected hydroxyl groups, and protected amino groups.

To improve the voltage holding characteristics and reliability of the liquid crystal element, at least one of ^R1 and ^R2 is preferably an alkanediyl group having 1 to 10 carbon atoms or a substituted alkanediyl group having 1 to 10 carbon atoms. It is preferred that ^{both R1} and ^R2 are alkanediyl groups having 1 to 10 carbon atoms or a substituted alkanediyl group having 1 to 10 carbon atoms. To exhibit good voltage holding characteristics and liquid crystal alignment, ^R1 and ^R2 preferably have 1 to 8 carbon atoms, more preferably 2 to 8 carbon atoms. To improve liquid crystal alignment and achieve a high effect in reducing afterimages, ^R1 and ^R2 are preferably linear chains.

^Y1 and ^Y2 represent an amide bond (* ¹ - ^NR3 -CO- or * ¹ -CO- ^NR3- ). The monovalent organic group represented by ^R3 is preferably a monovalent alkyl group having 1 to 10 carbon atoms, or a group that generates a hydrogen atom upon cleavage (protecting group). When ^R3 is a monovalent alkyl group, the monovalent alkyl group is preferably a C1-3 alkyl group or a phenyl group, and more preferably a C1-3 alkyl group.

When ^R is a protecting group, the protecting group is preferably a monovalent group that is thermally releasable. Examples thereof include carbamate-based protecting groups, amide-based protecting groups, imide-based protecting groups, and sulfonamide-based protecting groups. Among these, carbamate-based protecting groups are preferred due to their high thermal releasability. Specific examples thereof include tert-butoxycarbonyl, benzyloxycarbonyl, 1,1-dimethyl-2-haloethoxycarbonyl, allyloxycarbonyl, 2-(trimethylsilyl)ethoxycarbonyl, 9-fluorenylmethoxycarbonyl, and allyloxycarbonyl. Among these, a tert-butoxycarbonyl group (Boc group) is particularly preferred because it has excellent thermal releasability and can reduce the amount of residue in the film at the deprotected portion.

R ³ is preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a protecting group, and particularly preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a tert-butoxycarbonyl group.

^Z1 is a single bond or a divalent organic group. From the perspective of improving the voltage holding characteristics and liquid crystal alignment of the liquid crystal element, ^Z1 is preferably a divalent organic group.

When ^Z1 is a divalent organic group, examples of the divalent organic group include a divalent alkyl group having 1 to 20 carbon atoms, and a divalent group having -O-, -S-, or ^-NR3- (where ^R3 has the same meaning as ^R3 in ^Y1 and ^Y2 ) between the carbon-carbon bonds of the alkyl group. Furthermore, ^Z1 is bonded to the amide bonds of ^Y1 and ^Y2 via a alkyl group.

From the perspective of improving the solubility of polymer [A], the divalent organic group represented by ^Z1 is preferably a divalent chain alkyl group having 1 to 20 carbon atoms, a divalent alicyclic alkyl group having 4 to 20 carbon atoms, or a divalent group having -O-, -S-, or ^-NR3- between the carbon-carbon bonds of the chain alkyl group. An alkanediyl group having 1 to 20 carbon atoms or a cycloalkylene group having 4 to 12 carbon atoms is particularly preferred. The number of carbon atoms in ^Z1 is preferably 1 to 12, more preferably 1 to 10. m is 0 or 1, and is preferably 1 from the perspective of further enhancing the effect of reducing AC residual images.

The specific diamine (A) is preferably an aromatic diamine, and particularly preferably an aromatic diamine having a structure capable of introducing a partial structure represented by the formula (1) into the main chain of the polymer [A]. Specifically, the specific diamine (A) is particularly preferably a compound represented by the following formula (DA). In addition, the so-called "main chain" refers to the part of the polymer that contains the "trunk" of the longest atomic chain. The part of the "trunk" is allowed to contain a ring structure. For example, "having a specific structure in the main chain" means that the specific structure constitutes a part of the main chain. The so-called "side chain" refers to the part that branches from the "trunk" of the polymer. [Chemistry 4] (In formula (DA), R ¹ , R ² , Y ¹ , Y ² , Z ¹ and m have the same meanings as in formula (1))

In the above formula (DA), the description of the above formula (1) can be applied to the examples and preferred examples of R ¹ , R ² , Y ¹ , Y ² , Z ¹ and m.

Specific examples of the specific diamine (A) include compounds represented by the following formulas (DA-1) to (DA-23). [Chemistry 6] [Chemistry 7] (wherein, "Boc" represents tert-butoxycarbonyl)

The polymer [A] may be any polymer having the structural unit (U1). From the perspective of forming a liquid crystal alignment film having high affinity with liquid crystals, high mechanical strength, and high reliability, the polymer [A] is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide. When the polymer [A] is at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide, the partial structure represented by formula (1) can be introduced into the main chain of the polymer [A]. Furthermore, by introducing the partial structure represented by formula (1) into the main chain of the polymer, it is preferred that the effects of reducing residual images and improving film strength can be further enhanced.

(Polyamide) When the polymer [A] is polyamide, the polyamide (hereinafter also referred to as "polyamide [A]") can be obtained, for example, by reacting tetracarboxylic dianhydride with a diamine compound containing the specific diamine (A).

Tetracarboxylic dianhydride Examples of the tetracarboxylic dianhydride used in the synthesis of polyamide [A] include aliphatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, and aromatic tetracarboxylic dianhydride. Specific examples of these include aliphatic tetracarboxylic dianhydrides such as 1,2,3,4-butanetetracarboxylic dianhydride and ethylenediaminetetraacetic dianhydride; alicyclic tetracarboxylic dianhydrides such as 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic dianhydride, 5-(2,5-dioxotetrahydrofuran-3-yl)-3a,4,5,9b-tetrahydronaphtho[1,2-c]furan-1,3-dione, 5-(2,5-dioxotetrahydrofuran-3-yl)-8-methyl-3a,4,5,9b-tetrahydronaphtho[1, Examples of the aromatic tetracarboxylic dianhydride include furan-1,3-dione, 2,4,6,8-tetracarboxybiscyclo[3.3.0]octane-2:4,6:8-dianhydride, cyclopentanetetracarboxylic dianhydride, and cyclohexanetetracarboxylic dianhydride. Examples of aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, ethylene glycol ditrimellityl anhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, and 4,4'-carbonyldiphthalic anhydride. In addition, the tetracarboxylic dianhydrides described in Japanese Patent Application Laid-Open No. 2010-97188 can also be used. The tetracarboxylic dianhydride may be used alone or in combination of two or more.

In order to obtain a liquid crystal alignment film having high solubility in solvents and exhibiting good electrical properties and low residual image properties, the tetracarboxylic dianhydride used in the synthesis of the polyamic acid [A] preferably comprises at least one compound selected from the group consisting of aliphatic tetracarboxylic dianhydrides and alicyclic tetracarboxylic dianhydrides, and more preferably comprises alicyclic tetracarboxylic dianhydride. The proportion of the alicyclic tetracarboxylic dianhydride used in the synthesis of the polyamic acid [A] is preferably 20 mol% or more, more preferably 40 mol% or more, and even more preferably 50 mol% or more.

·Diamine compound The diamine compound used in the synthesis of the polyamide [A] may be the specific diamine (A) alone, or a diamine different from the specific diamine (A) may be used together with the specific diamine (A) (hereinafter also referred to as "other diamine (A)"). Examples of the other diamine (A) include aliphatic diamines, alicyclic diamines, aromatic diamines, and diaminoorganosiloxanes. Specific examples of the other diamine (A) include p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4,4'-diaminodiphenylpropane, 4-aminophenyl-4-aminobenzoate, 2,5-diaminobenzoic acid, 3,5-diaminobenzoic acid, 1,5-bis(4-aminophenoxy)pentane, 1,2-bis(4-aminophenoxy)pentane, and 1,2-bis(4-aminophenoxy)pentane. 1,3-bis(4-aminophenoxy)ethane, 1,6-bis(4-aminophenoxy)hexane, 4,4'-diaminodiphenyl ether, N,N'-bis(5-amino-2-pyridyl)-N,N'-bis(tert-butoxycarbonyl)ethylenediamine, 6,6'-(pentamethylenedioxy)bis(3-aminopyridine), 2,2'-dimethyl-4,4'-diaminobiphenyl, etc.

In the synthesis of polyamic acid [A], from the viewpoint of sufficiently achieving reduction in residual images and obtaining a liquid crystal alignment film with high mechanical strength, the proportion of the specific diamine (A) relative to the total amount of the diamine compounds used in the synthesis of polyamic acid [A] is preferably 10 mol% or more, more preferably 15 mol% or more, further preferably 20 mol% or more, further preferably 30 mol% or more, particularly preferably 40 mol% or more, and particularly preferably 60 mol% or more. Furthermore, the proportion of the specific diamine (A) relative to the total amount of the diamine compounds used in the synthesis of polyamic acid [A] can be set within a range of 100 mol% or less.

Polyamine Synthesis Polyamine [A] can be obtained by reacting tetracarboxylic dianhydride with a diamine compound and, if necessary, a molecular weight modifier. In the polyamine synthesis reaction, the ratio of tetracarboxylic dianhydride to diamine compound is preferably such that the anhydride groups of the tetracarboxylic dianhydride are 0.2 to 2 equivalents per 1 equivalent of the amine groups of the diamine compound. Examples of molecular weight modifiers include 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 molecular weight modifier is preferably used in an amount of 20 parts by mass or less per 100 parts by mass of the total tetracarboxylic dianhydride and diamine compound used.

The polyamino acid synthesis reaction is preferably carried out in an organic solvent. The reaction temperature is preferably -20°C to 150°C, and the reaction time is preferably 0.1 to 24 hours. Examples of organic solvents used in the reaction include aprotic polar solvents, phenolic solvents, alcoholic solvents, ketone solvents, ester solvents, etheric solvents, halogenated hydrocarbons, and hydrocarbons. Specific examples of these solvents include preferably using one or more selected from the group consisting of N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, γ-butyrolactone, tetramethylurea, hexamethylphosphatamide, m-cresol, xylenol, and halogenated phenols as the reaction solvent, or using a mixture of one or more of these with another organic solvent (e.g., butyl solvent, diethylene glycol diethyl ether, etc.). The amount of the organic solvent used (a) is preferably such that the total amount of tetracarboxylic dianhydride and diamine (b) is 0.1% by mass to 50% by mass relative to the total amount (a+b) of the reaction solution.

In this manner, a polymer solution containing dissolved polyamine [A] is obtained. This polymer solution can be used directly to prepare a liquid crystal alignment agent, or the polyamine [A] contained in the polymer solution can be separated and then used to prepare a liquid crystal alignment agent.

(Polyamic Acid Ester) When the polymer [A] is a polyamic acid ester, the polyamic acid ester can be obtained, for example, by the following methods: [I] reacting the polyamic acid [A] with an esterifying agent; [II] reacting a tetracarboxylic acid diester with a diamine compound containing the specific diamine (A); [III] reacting a tetracarboxylic acid diester dihalide with a diamine compound containing the specific diamine (A). The polyamic acid ester may have only an aminate structure or may be a partially esterified product containing both aminate and aminate structures. The reaction solution containing the dissolved polyamic acid ester may be used directly for the preparation of the liquid crystal alignment agent, or the polyamic acid ester contained in the reaction solution may be isolated and then used for the preparation of the liquid crystal alignment agent.

(Polyimide) When polymer [A] is a polyimide, the polyimide can be obtained, for example, by dehydrating and ring-closing the polyimide [A] synthesized as described above and then subjecting it to imidization. The polyimide may be a fully imidized product, in which the entire amide structure of the polyimide precursor is dehydrated and ring-closed, or a partially imidized product, in which only a portion of the amide structure is dehydrated and ring-closed, resulting in the coexistence of amide and imide ring structures. The imidization ratio of the polyimide is preferably 20% to 99%, more preferably 30% to 90%. The imidization ratio is expressed as a percentage of the number of imide ring structures relative to the total number of amide structures and imide ring structures in the polyimide. Here, a portion of the imide rings may be isoimide rings.

Dehydration and ring closure of polyamine is preferably performed by dissolving the polyamine in an organic solvent, adding a dehydrating agent and a dehydration and ring closure catalyst to the solution, and optionally heating the solution. In this method, an anhydride such as acetic anhydride, propionic anhydride, or trifluoroacetic anhydride can be used as the dehydrating agent. The amount of the dehydrating agent used is preferably 0.01 to 20 mol per 1 mol of the polyamine structure. Tertiary amines such as pyridine, collidine, lutidine, and triethylamine can be used as the dehydration and ring closure catalyst. The amount of the dehydration ring-closing catalyst used is preferably 0.01 to 10 mol per 1 mol of the dehydrating agent. The organic solvent used in the dehydration ring-closing reaction includes those exemplified for the synthesis of polyamides. The reaction temperature for the dehydration ring-closing reaction is preferably 0°C to 180°C. The reaction time is preferably 1.0 to 120 hours. Furthermore, the reaction solution containing the polyimide can be used directly or after isolating the polyimide for the preparation of the liquid crystal alignment agent.

<Polymer [B]> Polymer [B] is a polymer having structural unit (U2) and structural unit (U3). Each structural unit of polymer [B] is described in detail below.

Structural unit (U2) Structural unit (U2) is a structural unit derived from a diamine (hereinafter also referred to as "specific diamine (B1)") having a partial structure represented by the following formula (2). Structural unit (U2) imparts to polymer [B] the function of moderating accumulated charges in the liquid crystal alignment film. Furthermore, polymer [A] does not have structural unit (U2), and in this respect, polymer [B] differs from polymer [A]. [Chemical 8] (In formula (2), ^A1 and ^A2 are each independently a divalent aromatic cyclic group; ^B1 is ^-NR4- or a divalent aromatic heterocyclic group; when ^B1 is a divalent aromatic heterocyclic group, ^R5 and ^R6 are each independently a hydrogen atom or a monovalent organic group; when ^B1 is ^-NR4- , ^R4 , ^R5 and ^R6 are (i) or (ii) below; (i) ^R4 is a hydrogen atom or a monovalent organic group; ^R5 and ^R6 are each independently a hydrogen atom or a monovalent organic group, or ^R5 and ^R6 are each bonded to each other and form a ring structure together with ^A1 , ^-NR4- and ^A2 ; (ii) ^R4 and R6 are ^{(R 5} is independently a hydrogen atom or a monovalent organic group, or represents a ring structure formed by R ⁴ and R ⁵ combined with each other, A ¹ and the nitrogen atom; R ⁶ is a hydrogen atom or a monovalent organic group; "*" represents a bond)

Furthermore, in this specification, the phrase "another polymer does not have" a structural unit (hereinafter referred to as a "specific unit") present in at least one of the multiple polymers contained in the liquid crystal alignment agent means that the other polymer is permitted to have the specific unit as long as the effects of the present invention are not impaired. In this specification, when it is stated that an other polymer "does not have" a specific unit, the content of the specific unit in the other polymer is preferably 1 mol% or less, more preferably 0.5 mol% or less, and even more preferably 0.1 mol% or less, relative to the total structural units present in the other polymer.

In formula (2), examples of the divalent aromatic cyclic group represented by ^A1 and ^A2 include divalent aromatic alkyl groups and divalent aromatic heterocyclic groups. Examples of the divalent aromatic heterocyclic group include nitrogen-containing aromatic heterocyclic groups, oxygen-containing aromatic heterocyclic groups, and sulfur-containing aromatic heterocyclic groups, with nitrogen-containing aromatic heterocyclic groups being preferred. Furthermore, ^A1 and ^A2 may have a substituent on the aromatic ring portion. Examples of such substituents include alkyl groups having 1 to 5 carbon atoms and halogen atoms.

Specific examples of A ¹ and A ² include divalent aromatic alkyl groups formed by removing any two hydrogen atoms bonded to carbon atoms constituting a benzene ring, naphthalene ring, or anthracene ring; divalent nitrogen-containing aromatic heterocyclic groups include groups formed by removing any two hydrogen atoms bonded to carbon atoms constituting a pyridine ring, pyrimidine ring, oxazine ring, or pyrazine ring; divalent oxygen-containing aromatic heterocyclic groups include groups formed by removing any two hydrogen atoms bonded to carbon atoms constituting a furan ring; and divalent sulfur-containing aromatic heterocyclic groups include groups formed by removing any two hydrogen atoms bonded to carbon atoms constituting a thiophene ring. From the viewpoint of achieving high density and high transmittance of the liquid crystal alignment film, the divalent aromatic ring group represented by ^A1 and ^A2 is preferably a divalent aromatic alkyl group, more preferably a phenylene group.

^B1 is ^-NR4- or a divalent aromatic heterocyclic group. When ^B1 is a divalent aromatic heterocyclic group, examples of the divalent aromatic heterocyclic group include the divalent aromatic heterocyclic groups exemplified for ^A1 and ^A2 . Among these, the divalent aromatic heterocyclic group represented by ^B1 is preferably a group formed by removing any two hydrogen atoms bonded to carbon atoms constituting the pyrrole ring, furan ring, or thiophene ring, from the viewpoint of achieving a high effect of mitigating accumulated charge.

When ^B1 is a divalent aromatic heterocyclic group, ^R5 and ^R6 are each independently a hydrogen atom or a monovalent organic group. Specific examples and preferred examples of ^R5 can be found in the description of ^R3 . Examples of monovalent organic groups for ^R6 include alkyl groups having 1 to 3 carbon atoms, halogen atoms, and cyano groups.

When ^B1 is ^-NR4- , ^R4 , ^R5 , and ^R6 satisfy (i) or (ii). When ^R4 , ^R5 , and ^R6 satisfy (i), ^R4 is a hydrogen atom or a monovalent organic group. Specific examples and preferred examples of ^R4 are as described above for ^R3 . Specific examples and preferred examples of ^R5 and ^R6 being a hydrogen atom or a monovalent organic group are as described above for ^R3 . Regarding ^R5 and ^R6 , when ^R5 and ^R6 are combined with each other and form a ring structure together with ^A1 , ^-NR4- , and ^A2 , examples of the ring structure include a carbazole structure, a 9-methylcarbazole structure, and a 9-ethylcarbazole structure.

When ^R4 , ^R5 , and ^R6 satisfy (ii) above, the specific examples and preferred examples of ^R4 being a hydrogen atom or a monovalent organic group can be cited as those described above for ^R3 . When ^R5 and ^R6 are a hydrogen atom or a monovalent organic group, examples of the monovalent organic group include an alkyl group having 1 to 3 carbon atoms, a halogen atom, and a cyano group. Regarding ^R4 and ^R5 , when ^R4 and ^R5 are bonded to each other and form a ring structure together with ^A1 and a nitrogen atom, examples of the ring structure include an indoline structure and an isoindoline structure.

Preferred specific examples of the partial structure represented by the formula (2) include, when B ¹ is -NR ⁴ -, the partial structures represented by the following formulas (2-1) to (2-7), and when B ¹ is a divalent aromatic heterocyclic group, the partial structures represented by the following formulas (2-8) to (2-10), respectively. [Chemistry 9] (In formulas (2-1) to (2-10), ^R4 and ^R33 are each independently a hydrogen atom or a monovalent organic group; "*" represents a bond)

The specific diamine (B1) may have only one partial structure represented by the formula (2) or may have two or more. From the viewpoint of ensuring the solubility of the polymer [B], one or two are preferred. The specific diamine (B1) is preferably an aromatic diamine, and particularly preferably an aromatic diamine having a structure capable of introducing the partial structure represented by the formula (2) into the main chain of the polymer [B]. Specific examples of the specific diamine (B1) include compounds represented by the following formulas (DB-1) to (DB-21). In addition, the specific diamine (B1) does not have the partial structure Y possessed by the structural unit (U3). [Chemistry 10] [Chemistry 11] [Chemistry 12]

Structural unit (U3) Structural unit (U3) is a structural unit derived from a diamine (hereinafter also referred to as "specific diamine (B2)") having the following partial structure Y. Furthermore, specific diamine (B2) is a compound that does not have the partial structure represented by formula (2) and is different from specific diamine (B1). The presence of structural unit (U2) and structural unit (U3) in polymer [B2] improves the solubility of polymer [B2] and enables the production of a liquid crystal alignment film exhibiting low afterimage characteristics (particularly reduced AC afterimages). Partial structure Y: a structure represented by -(CH ₂ ) _n - (wherein n is an integer from 1 to 20), a structure in which any methylene group in a structure represented by -(CH ₂ ) _n+1 - is substituted by -O-, -S-, -COO-, -NR ⁷ -, -NR ⁷ -CO-, -NR ⁷ -COO-, -NR ⁷ -CO-NR ⁸ -, or a nitrogen-containing non-aromatic heterocyclic group (wherein R ⁷ and R ⁸ are each independently a hydrogen atom or a monovalent organic group; when n is 2 or greater, -O-, -S-, -COO-, -NR ⁷ -, -NR ⁷ -CO-, -NR ⁷ -COO-, -NR ⁷ -CO-NR ⁸ -, and the nitrogen-containing non-aromatic heterocyclic group are not adjacent to each other), -O-, -S-, -COO-, -NR ⁷ -CO-, -NR ⁷ -COO- or -NR ⁷ -CO-NR ⁸ -

In the partial structure Y, n is preferably 1 to 14, more preferably 1 to 12, from the viewpoint of enhancing the effect of improving the solubility of the polymer [B], improving the low afterimage characteristics (reduction of AC afterimage and DC afterimage), and improving the mechanical strength of the liquid crystal alignment film. When the partial structure Y is a structure represented by -(CH ₂ ) _n+1 - in which any methylene group is substituted with -O- or the like (hereinafter also referred to as a "hetero-atom-containing structure"), n is preferably 2 or more, more preferably 2 to 14. Examples of the nitrogen-containing non-aromatic heterocyclic group in the partial structure Y include piperidine-1,4-diyl, piperazine-1,4-diyl, and 2-oxo-4-imidazolidinone-1,3-diyl. The examples and preferred examples of R ⁷ and R ⁸ are the same as those described above for R ^3. As the partial structure Y, among these, preferred are structures represented by -(CH ₂ ) _n -, structures containing heteroatoms, or -O-, and more preferred are structures represented by -(CH ₂ ) _n - or structures containing heteroatoms.

The specific diamine (B2) is not particularly limited as long as it is a diamine having a partial structure Y. Examples thereof include aliphatic diamines, alicyclic diamines, aromatic diamines, and diaminoorganosiloxanes. The specific diamine (B2) preferably has a structure capable of incorporating the partial structure Y into the main chain of the polymer [B]. Specifically, a compound represented by the following formula (DB2) is preferred. [Chemical 13] (In formula (DB2), Y ³ is a structure represented by -(CH ₂ ) _n -, a structure in which any methylene group in a structure represented by -(CH ₂ ) _n+1 - is substituted by -O-, -S-, -COO-, -NR ⁷ -, -NR ⁷ -CO-, -NR ⁷ -COO-, -NR ⁷ -CO-NR ⁸ -, or a nitrogen-containing non-aromatic heterocyclic group (a structure containing a hetero atom), -O-, -S-, -COO-, -NR ⁷ -CO-, -NR ⁷ -COO-, or -NR ⁷ -CO-NR ⁸ -; A ³ and A ⁴ are each independently a single bond, a substituted or unsubstituted cyclohexylene group, or a substituted or unsubstituted phenylene group; n, R ⁷ and R ⁸ has the same meaning as described above; when n is 2 or greater, in the structure containing a heteroatom, -O-, -S-, -COO-, -NR ⁷ -, -NR ⁷ -CO-, -NR ⁷ -COO-, -NR ⁷ -CO-NR ⁸ -, and the nitrogen-containing non-aromatic heterocyclic group are not adjacent to each other.

Specific examples of the specific diamine (B2) include aliphatic diamines such as m-xylylenediamine, pentamethylenediamine, and hexamethylenediamine; alicyclic diamines such as 4,4'-methylenebis(cyclohexylamine); and aromatic diamines such as 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, and 4,4'-diamine. diphenylpropane, 4-aminophenyl-4-aminobenzoate, 4,4'-diaminobenzanilide, 1,3-bis(4-aminophenyl)urea, 1,3-bis(4-aminophenethyl)urea, 1,3-bis(4-aminobenzyl)urea, 1,5-bis(4-aminophenoxy)pentane, 1,2-bis(4-aminophenoxy)ethane, 1,3-bis(4-aminophenoxy)propane Alkane, 1,6-bis(4-aminophenoxy)hexane, bis[2-(4-aminophenyl)ethyl]adipic acid, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-[4,4'-propane-1,3-diylbis(piperidin-1,4-diyl)]diphenylamine, diethylene glycol bis(4 -aminophenyl) ether, 1,4-bis(4-aminophenoxy)benzene, compounds represented by the aforementioned formulas (DA-1) to (DA-15) and (DA-17) to (DA-20), and compounds represented by the following formulas (DC-1) to (DC-7), etc.; examples of diaminoorganosiloxanes include 1,3-bis(3-aminopropyl)-tetramethyldisiloxane. [Chemistry 14]

As the specific diamine (B2), among these, it is preferred to use at least one selected from the group consisting of 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4,4'-diaminodiphenyl ether, 1,2-bis(4-aminophenoxy)ethane, 4,4'-[4,4'-propane-1,3-diylbis(piperidin-1,4-diyl)]diphenylamine, bis[2-(4-aminophenyl)ethyl]adipic acid, diethylene glycol bis(4-aminophenyl) ether, hexamethylenediamine, hexamethylenediamine, and the compound represented by formula (DC-5).

In terms of high affinity with polymer [A], polymer [B] is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide. In particular, polymer [B] having the partial structure represented by formula (2) and the partial structure Y in its main chain improves the solubility of polymer [B], rapidly alleviates accumulated charge, and sufficiently reduces AC residual images, which is particularly preferred.

When polymer [B] is polyamic acid, the polyamic acid (hereinafter also referred to as "polyamic acid [B]") can be obtained by reacting tetracarboxylic dianhydride with a diamine compound containing a specific diamine (B1) and a specific diamine (B2). Polyamic acid [B], polyamic acid ester, and polyimide serving as polymer [B] can also be produced in the same manner as polymer [A].

As the tetracarboxylic dianhydride used in the synthesis of polymer [B], the examples and preferred examples of the tetracarboxylic dianhydride used in the synthesis of polymer [A] can be cited. That is, the tetracarboxylic dianhydride used in the synthesis of polyamic acid [B] preferably comprises at least one compound selected from the group consisting of aliphatic tetracarboxylic dianhydrides and alicyclic tetracarboxylic dianhydrides, and more preferably comprises alicyclic tetracarboxylic dianhydride. The proportion of alicyclic tetracarboxylic dianhydride used relative to the total amount of tetracarboxylic dianhydride used in the synthesis of polyamic acid [B] is preferably 20 mol% or more, more preferably 40 mol% or more, and further preferably 50 mol% or more.

Furthermore, when synthesizing the polyamic acid [B], polyamic acid ester, and polyimide serving as the polymer [B], a compound different from the specific diamine (B1) and the specific diamine (B2) (hereinafter also referred to as "other diamine (B)") may be further used as the diamine compound. Examples of the other diamine (B) include p-phenylenediamine, 3,5-diaminobenzoic acid, 2,5-diaminobenzoic acid, 4,4-diamino-2,2'-dimethylbiphenyl, and 3,5-diamino-N,N-bis(pyridin-3-ylmethyl)benzamide. During the synthesis, the amount of the other diamine (B) used is preferably 20 mol% or less, and more preferably 10 mol% or less, relative to the total amount of the diamine compounds used in the synthesis of the polymer [B].

In order to rapidly alleviate residual charge and effectively reduce DC residual image distortion during the synthesis of polymer [B], the amount of the specific diamine (B1) used is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 15 mol% or more, relative to the total amount of diamine compounds used in the synthesis of polymer [B]. Furthermore, from the perspective of suppressing AC residual image distortion and ensuring the solubility of polymer [B], the amount of the specific diamine (B1) used is preferably 95 mol% or less, more preferably 80 mol% or less, and even more preferably 70 mol% or less, relative to the total amount of diamine compounds used in the synthesis of polymer [B].

From the perspective of improving the solubility of polymer [B], the amount of the specific diamine (B2) used is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 15 mol% or more, relative to the total amount of diamine compounds used in the synthesis of polymer [B]. Furthermore, from the perspective of sufficiently achieving reduction in DC residual image, the amount of the specific diamine (B2) used is preferably 90 mol% or less, more preferably 80 mol% or less, and even more preferably 70 mol% or less, relative to the total amount of diamine compounds used in the synthesis of polymer [B].

In addition, regarding various conditions and the like in the synthesis method of each polymer such as polyamine [B], the description of the polymer [A] can be cited.

The solution viscosity of polymers [A] and [B] used in preparing the liquid crystal alignment agent is preferably 10 mPa·s to 800 mPa·s, and more preferably 15 mPa·s to 500 mPa·s, when prepared as a 10% by mass solution. Solution viscosity (mPa·s) is the value measured at 25°C using an E-type rotational viscometer for a 10% by mass solution of the polymers prepared in a good solvent for the polymers (e.g., γ-butyrolactone, N-methyl-2-pyrrolidone, etc.).

For each of polymer [A] and polymer [B], the weight average molecular weight (Mw) as measured by gel permeation chromatography (GPC) is preferably 1,000 to 500,000, more preferably 2,000 to 300,000. Furthermore, the molecular weight distribution (Mw/Mn), represented by the ratio of Mw to the number average molecular weight (Mn) as measured by GPC, is preferably 7 or less, more preferably 5 or less.

In a liquid crystal alignment agent, from the perspective of sufficiently reducing AC residual image, the content of polymer [A] is preferably 1% by mass or more, more preferably 2% by mass or more, further preferably 5% by mass or more, and further preferably 10% by mass or more, relative to the total amount of polymer components contained in the liquid crystal alignment agent. Furthermore, from the perspective of reducing DC residual image by mitigating residual charge, the content of polymer [A] is preferably 90% by mass or less, more preferably 80% by mass or less, and further preferably 70% by mass or less, relative to the total amount of polymer components contained in the liquid crystal alignment agent.

The content of polymer [B] relative to the total amount of polymer components contained in the liquid crystal alignment agent is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. Furthermore, the content of polymer [B] relative to the total amount of polymer components contained in the liquid crystal alignment agent is preferably 99% by mass or less, more preferably 98% by mass or less, even more preferably 95% by mass or less, and even more preferably 90% by mass or less.

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

(Other Polymers) The liquid crystal alignment agent disclosed herein may also contain a polymer different from polymer [A] and polymer [B] (hereinafter also referred to as "other polymer") as a polymer component. The main skeleton of the other polymer is not particularly limited. Examples of other polymers include polyamic acid, polyamic acid ester, polyimide, polyorganosiloxane, polyester, polyenamine, polyurea, polyamide, polyamide imide, polybenzoxazole precursor, polybenzoxazole, cellulose derivative, polyacetal, (meth)acrylic polymer, styrene polymer, maleimide polymer, or styrene-maleimide polymer. From the perspective of having high affinity with liquid crystals and improving the reliability of the liquid crystal element when used in combination with polymer [A] and polymer [B], the other polymer is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide.

When the liquid crystal alignment agent contains other polymers, the content of the other polymers in the liquid crystal alignment agent is preferably 30 mass% or less, more preferably 20 mass% or less, further preferably 10 mass% or less, and further preferably 5 mass% or less, relative to the total amount of polymer [A], polymer [B] and other polymers.

(Solvent) The liquid crystal alignment agent disclosed herein is prepared as a liquid composition in which polymer [A], polymer [B], and other components used as needed are preferably dispersed or dissolved in an appropriate solvent.

As the solvent, an organic solvent can be preferably used. Specific examples thereof include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 1,2-dimethyl-2-imidazolidinone, 1,3-dimethyl-2-imidazolidinone, phenol, γ-butyrolactone, γ-butyrolactamide, N,N-dimethylformamide, N,N-dimethylacetamide, 4-hydroxy-4-methyl-2-pentanone, diacetone alcohol, 1-hexanol, 2-hexanol, propane-1,2-diol, 3-methoxy-1-butanol, ethylene glycol monomethyl ether, methyl lactate, ethyl lactate, butyl lactate, methyl acetate, ethyl acetate, butyl acetate, acetic acid Methyl ester, ethyl acetate, ethyl propionate, methyl methoxypropionate, ethyl ethoxypropionate, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-isopropyl ether, ethylene glycol-n-butyl ether (butyl solvent), ethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diisobutyl ketone, isoamyl propionate, isoamyl isobutyrate, diisoamyl ether, ethyl carbonate, propylene carbonate, propylene glycol monomethyl ether (Propylene Glycol Monomethyl Ether, PGME), Diethylene Glycol Diethyl Ether Acetate, Propylene Glycol Monomethyl Ether Acetate (PGMEA), Propylene Glycol Diacetate, Cyclopentanone, Cyclohexanone, etc.

Other components included in the liquid crystal alignment agent, in addition to those mentioned above, include antioxidants, metal chelate compounds, curing accelerators, surfactants, fillers, dispersants, and photosensitizers. The proportions of these other components can be appropriately selected for each compound, within a range that does not compromise the effects of the present disclosure.

The solids concentration (the ratio of the total mass of the liquid crystal alignment agent's components other than the solvent) in the liquid crystal alignment agent should be appropriately selected in consideration of viscosity, volatility, and other factors, preferably ranging from 1% to 10% by mass. A solids concentration of 1% by mass or greater ensures sufficient film thickness, facilitating the production of a liquid crystal alignment film exhibiting excellent liquid crystal alignment properties. On the other hand, a solids concentration of 10% by mass or less ensures an appropriate film thickness, facilitating the production of a liquid crystal alignment film exhibiting excellent liquid crystal alignment properties. Furthermore, the viscosity of the liquid crystal alignment agent is moderate, tending to improve coating properties.

Liquid Crystal Alignment Film and Liquid Crystal Device The liquid crystal alignment film disclosed herein can be produced using a liquid crystal alignment agent prepared as described above. Furthermore, the liquid crystal device disclosed herein includes a liquid crystal alignment film formed using the liquid crystal alignment agent described above. The liquid crystal driving method in the liquid crystal device is not particularly limited and can be applied to various modes, including TN, Super Twisted Nematic (STN), VA (including Vertical Alignment-Multi-domain Vertical Alignment (VA-MVA) and Vertical Alignment-Patterned Vertical Alignment (VA-PVA)), IPS, FFS, Optically Compensated Bend (OCB), and Polymer Sustained Alignment (PSA). A liquid crystal element can be manufactured, for example, by a method including the following steps 1 to 3. Step 1 uses different substrates depending on the desired operating mode. Steps 2 and 3 are common to all operating modes.

<Step 1: Coating Film Formation> First, a liquid crystal alignment agent is applied to a substrate, preferably by heating the coated surface to form a coating film on the substrate. Examples of substrates include glass such as float glass and sodium glass, and transparent substrates made of plastics such as polyethylene terephthalate, polybutylene terephthalate, polyether sulfide, polycarbonate, and poly(aliphatic cycloolefin). Examples of transparent conductive films applied to one side of the substrate include NESA film (a registered trademark of PPG Corporation, USA) containing tin oxide ( _SnO₂ ) and indium tin oxide (ITO) film containing indium oxide-tin oxide ( _{In₂O₃ -SnO₂ )} . When manufacturing TN, STN, or VA liquid crystal devices, two substrates with patterned transparent conductive films are used. On the other hand, when manufacturing IPS or FFS liquid crystal devices, a substrate with electrodes patterned into a comb shape and an opposing substrate without electrodes are used.

There are no particular limitations on the method for applying the liquid crystal alignment agent to the substrate. For example, it can be applied by spin coating, printing (e.g., offset printing, flexographic printing, etc.), inkjet, slit coating, rod coater, extrusion die, direct gravure coater, chamber doctor coater, offset gravure coater, impregnation coater, MB coater, and the like.

After applying the liquid crystal alignment agent, preheating (prebaking) is preferably performed to prevent the applied liquid crystal alignment agent from dripping. The prebaking temperature is preferably 30°C to 200°C, and the prebaking time is preferably 0.25 to 10 minutes. The solvent is then completely removed, and a calcination (postbaking) step is optionally performed to thermally imidize the amide structures present in the polymer. The calcination temperature (postbaking temperature) is preferably 80°C to 280°C, more preferably 80°C to 250°C. The postbaking time is preferably 5 to 200 minutes. The resulting film thickness is preferably 0.001 μm to 1 μm.

<Step 2: Alignment Treatment> When manufacturing TN, STN, IPS, or FFS liquid crystal devices, the coating formed in Step 1 is treated to impart liquid crystal alignment properties (alignment treatment). This imparts alignment properties to the liquid crystal molecules, forming a liquid crystal alignment film. Preferred alignment treatments include rubbing the surface of the coating formed on the substrate with cotton or other materials, or photo-alignment treatments that impart alignment properties by irradiating the coating with light. When manufacturing vertically aligned liquid crystal devices, the coating formed in Step 1 can be used directly as the liquid crystal alignment film. Alternatively, the coating can be subjected to an alignment treatment to further enhance alignment properties.

Light irradiation for photo-alignment can be performed by the following methods, among others: a method of irradiating the coating after the post-baking step; a method of irradiating the coating after the pre-baking step and before the post-baking step; a method of irradiating the coating while the coating is being heated in at least one of the pre-baking step and the post-baking step. As radiation irradiated onto the coating, for example, ultraviolet light and visible light having a wavelength of 150 nm to 800 nm can be used. Ultraviolet light having a wavelength of 200 nm to 400 nm is preferred. When the radiation is polarized, it can be linearly polarized or partially polarized. When the radiation used is linearly polarized or partially polarized, irradiation can be performed from a direction perpendicular to the substrate surface, from an oblique direction, or a combination of these directions. In the case of non-polarized radiation, the irradiation direction is set to be oblique.

Examples of light sources include low-pressure mercury lamps, high-pressure mercury lamps, deuterium lamps, metal halide lamps, argon resonance lamps, xenon lamps, and excimer lasers. The radiation dose is preferably 200 J/ ^m² to 30,000 J/ ^m² , more preferably 500 J/ ^m² to 10,000 J/ ^m² . Following irradiation with light to impart alignment, the substrate surface may be cleaned with water, an organic solvent (e.g., methanol, isopropyl alcohol, 1-methoxy-2-propanol acetate, butyl solvent, ethyl lactate), or a mixture thereof, or heated.

<Step 3: Liquid Crystal Cell Construction> Prepare two substrates with liquid crystal alignment films formed as described above, and arrange liquid crystal between the two opposing substrates to produce a liquid crystal cell. Examples of methods for producing a liquid crystal cell include: placing the two substrates facing each other with a gap between them, bonding the perimeters of the two substrates together with a sealant, and then injecting liquid crystal into the cell gap surrounded by the substrate surfaces and the sealant, sealing the injection hole; or using the one-drop fill (ODF) method. For example, the sealant can be an epoxy resin containing a hardener and aluminum oxide balls as spacers. The liquid crystal can be either positive or negative, with negative being preferred. Examples of negative-type liquid crystals include Merck's "MLC-6608," "MLC-6609," "MLC-6610," and "MLC-7026-100." Using negative-type liquid crystals in IPS and FFS liquid crystal devices is particularly advantageous because it reduces transmission loss above the electrodes and improves contrast. Examples of liquid crystals include nematic and smectic liquid crystals, with nematic liquid crystals being particularly preferred.

When manufacturing a liquid crystal display (LCD), a polarizing plate is then attached to the outer surface of the liquid crystal cell to produce a liquid crystal display element. Examples of polarizing plates include those made by sandwiching a polarizing film called an "H film" between cellulose acetate protective films, or those consisting solely of the H film. The "H film" is a film made by stretching and aligning polyvinyl alcohol while allowing it to absorb iodine.

The liquid crystal element of the present invention can be effectively used in a variety of applications. Specifically, it can be used as a display device or dimming device, or as a retardation film in clocks, portable game consoles, word processors, notebook personal computers, car navigation systems, camcorders, personal digital assistants (PDAs), digital cameras, mobile phones, smartphones, various monitors, LCD televisions, information displays, and other display devices. [Examples]

Hereinafter, the embodiments will be described in more detail based on the embodiments, but the present invention is not limited to the following embodiments.

In the following examples, the imidization rate of the polyimide in the polymer solution was measured by the following method. The required amounts of the raw material compounds and polymers used in the following examples were ensured by repeating the synthesis on the synthesis scale shown in the following synthesis examples as needed. [Imidization rate of polyimide] A solution of polyimide was added to pure water, and the obtained precipitate was ^fully dried under reduced pressure at room temperature. It was then dissolved in deuterated dimethyl sulfoxide and ^1H -nuclear magnetic resonance ( ^1H -NMR) was measured 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-(β1/(β2×α)))×100 …(1) (In formula (1), β1 is the peak area of protons derived from NH groups appearing around a chemical shift of 10 ppm, β2 is the peak area of protons derived from other protons, and α is the ratio of the number of other protons to one proton of the NH group in the polymer precursor (polyamine))

The abbreviations of the monomers used in the examples are as follows. (Tetracarboxylic dianhydride) Compounds (c-1) to (c-5): compounds represented by the following formulas (c-1) to (c-5) [Chemical 15]

(Diamine compound) Compounds (DA-1) to (DA-14): Compounds represented by the aforementioned formulas (DA-1) to (DA-14) Compounds (DB-1) to (DB-20): Compounds represented by the aforementioned formulas (DB-1) to (DB-20) Compounds (d-1) to (d-5): Compounds represented by the following formulas (d-1) to (d-5) Compounds (b-1) to (b-11): Compounds represented by the following formulas (b-1) to (b-11) [Chemical 16] [Chemistry 17]

<Polymer Synthesis> 1. Synthesis of Polyamine [Synthesis Example 1] 100 mol parts of compound (c-2) as a tetracarboxylic dianhydride and 100 mol parts of compound (DA-1) as a diamine compound were dissolved in N-methyl-2-pyrrolidone (NMP) and reacted at room temperature for 6 hours to obtain a solution containing 15% by mass of polyamine (hereinafter referred to as "Polymer (PAA-1)"). [Synthesis Examples 2 to 17, Synthesis Examples 23 to 46] The same procedures as in Synthesis Example 1 were followed, except that the types and amounts of tetracarboxylic dianhydride and diamine compounds used were changed as shown in Tables 1 and 2 below, to obtain solutions containing polyamines (Polymers (PAA-2) to (PAA-41)). In Tables 1 and 2, the amount of tetracarboxylic dianhydride added represents the ratio (molar %) to the total amount of tetracarboxylic dianhydride used in the synthesis of each polymer. The amount of the diamine compound added represents the ratio (molar %) to the total amount of the diamine compound used in the synthesis of each polymer.

2. Synthesis of Polyimide [Synthesis Example 18] 90 mol parts of compound (c-1) and 10 mol parts of compound (c-5) as tetracarboxylic dianhydride, and 100 mol parts of compound (DA-2) as a diamine compound were dissolved in NMP and reacted at room temperature for 6 hours to obtain a solution containing 15% by mass of polyimide. Subsequently, additional NMP was added to the obtained polyimide solution to obtain a solution having a polyimide concentration of 10% by mass. Pyridine and acetic anhydride were added, and a dehydration ring-closure reaction was carried out at 60°C for 4 hours. After the dehydration and ring-closure reaction, the solvent in the system was replaced with fresh NMP, yielding a solution containing 15% by mass of a polyimide (referred to as "Polymer (PI-1)") with an imidization ratio of approximately 80%. [Synthesis Examples 19-22] The same procedures as in Synthesis Example 18 were followed, except that the types and amounts of tetracarboxylic dianhydride and diamine compounds used were changed as shown in Table 1 below, to yield solutions containing polyimides (Polymers (PI-2) to (PI-5)).

[Table 1] Synthesis example Polymer name Acid dianhydride 1 Acid dianhydride 2 Specific diamine (A) Other diamines 1 Other diamines 2 Kind quantity Kind quantity Kind quantity Kind quantity Kind quantity 1 PAA-1 c-2 100 DA-1 100 2 PAA-2 c-1 100 DA-2 100 3 PAA-3 c-1 80 c-4 20 DA-3 100 4 PAA-4 c-1 100 DA-4 100 5 PAA-5 c-2 100 DA-5 100 6 PAA-6 c-1 100 DA-6 100 7 PAA-7 c-1 100 DA-7 100 8 PAA-8 c-2 70 c-1 30 DA-8 60 b-7 30 b-1 10 9 PAA-9 c-1 100 DA-9 100 10 PAA-10 c-1 100 DA-10 100 11 PAA-11 c-2 100 DA-11 100 12 PAA-12 c-1 100 DA-12 100 13 PAA-13 c-2 80 c-4 20 DA-13 70 b-4 30 14 PAA-14 c-2 100 DA-14 70 b-4 30 15 PAA-15 c-1 100 d-1 100 16 PAA-16 c-1 100 d-2 100 17 PAA-17 c-2 100 d-3 100 18 PI-1 c-1 90 c-5 10 DA-2 100 19 PI-2 c-2 70 c-1 30 DA-5 80 b-7 20 20 PI-3 c-2 70 c-1 30 DA-9 100 twenty one PI-4 c-2 100 DA-2 30 b-7 70 twenty two PI-5 c-2 100 DA-2 15 B-11 85

[Table 2] Synthesis example Polymer name Acid dianhydride 1 Acid dianhydride 2 Specific diamine (B1) Specific diamine (B2) Specific diamine (B2) Other diamines Kind quantity Kind quantity Kind quantity Kind quantity Kind quantity Kind quantity twenty three PAA-18 c-3 70 c-1 30 DB-1 70 d-1 30 twenty four PAA-19 c-5 70 c-1 30 DB-2 60 DA-1 40 25 PAA-20 c-3 70 c-1 30 DB-3 70 b-2 30 26 PAA-21 c-1 100 DB-4 70 b-2 30 27 PAA-22 c-5 50 c-1 50 DB-5 50 b-4 50 28 PAA-23 c-5 50 c-1 50 DB-6 60 b-3 40 29 PAA-24 c-5 50 c-1 50 DB-7 50 b-8 50 30 PAA-25 c-5 50 c-1 50 DB-8 40 b-5 60 31 PAA-26 c-5 50 c-1 50 DB-9 50 b-10 50 32 PAA-27 c-5 80 c-1 20 DB-10 40 d-1 50 b-8 10 33 PAA-28 c-5 60 c-4 40 DB-11 60 b-6 40 34 PAA-29 c-5 60 c-3 40 DB-12 40 b-5 60 35 PAA-30 c-5 60 c-4 40 DB-13 70 b-5 20 b-8 10 36 PAA-31 c-1 70 c-5 30 DB-14 40 b-5 60 37 PAA-32 c-3 60 c-1 40 DB-15 50 b-8 50 38 PAA-33 c-1 50 c-5 50 DB-16 40 b-10 60 39 PAA-34 c-1 60 c-5 40 DB-17 40 b-9 60 40 PAA-35 c-1 80 c-5 20 DB-18 30 b-2 70 41 PAA-36 c-1 50 c-5 50 DB-19 40 b-7 60 42 PAA-37 c-1 100 DB-20 40 b-2 60 43 PAA-38 c-1 100 DB-20 100 44 PAA-39 c-1 100 b-3 30 d-4 70 45 PAA-40 c-1 100 b-3 30 d-5 70 46 PAA-41 c-1 100 DB-19 70 b-1 30

[Example 1] 1. Preparation of a Liquid Crystal Alignment Agent A solution of the polymer (PAA-1) obtained in Synthesis Example 1 and a solution of the polymer (PAA-36) obtained in Synthesis Example 41 were diluted with NMP and butyl cellosolve (BC) to obtain a solution having a solids concentration of 4.0% by mass and a solvent composition ratio of NMP:BC = 80:20 (mass ratio). This solution was filtered through a 0.2 μm pore size filter to prepare a liquid crystal alignment agent (R-1).

2. Fabrication of FFS-Type Liquid Crystal Cells Using the Rubbing Method A glass substrate (the first substrate) with a flat electrode (bottom electrode), an insulating layer, and a comb-shaped electrode (top electrode) laminated sequentially on one surface was prepared, along with a glass substrate (the second substrate) without an electrode. A liquid crystal aligner (R-1) was then applied to the electrode-forming surface of the first substrate and one surface of the second substrate using a spinner. The layers were then heated on a 110°C hotplate for 3 minutes (pre-baking). The layers were then dried for 30 minutes (post-baking) in a 230°C oven with the chamber purged of nitrogen, resulting in a coating with an average thickness of 0.08 μm. The coated surfaces were then rubbed using a rubbing machine equipped with a roll wrapped with rayon cloth at a roll speed of 1000 rpm, a stage movement speed of 3 cm/s, and a bristle indentation length of 0.3 mm. The surfaces were then ultrasonically cleaned in ultrapure water for one minute and dried in a 100°C oven for 10 minutes, yielding a pair of substrates with liquid crystal alignment films. Next, an epoxy resin adhesive containing 3.5 μm diameter aluminum oxide balls was screen-printed onto the edges of the substrates with the liquid crystal alignment films, leaving a liquid crystal injection port at the edges of the surfaces with the liquid crystal alignment films. The substrates are then stacked and pressed together, and the adhesive is thermally cured at 150°C for one hour. Negative liquid crystal (MLC-6608, manufactured by Merck) is then injected into the gap between the two substrates through the liquid crystal injection port, and the port is sealed with an epoxy adhesive. Furthermore, to eliminate the flow alignment caused by the liquid crystal injection, the substrates are heated at 120°C and then slowly cooled to room temperature, thus producing a liquid crystal cell. Furthermore, when stacking the two substrates, the rubbing angles of the two substrates are set to be antiparallel.

3. Evaluation of Inkjet Coating Properties (Solubility Evaluation) As the substrate for coating the liquid crystal alignment agent, a glass substrate with an ITO-containing transparent electrode was used. The substrate was heated on a 200°C hot plate for 1 minute, then cleaned with UV light and ozone to reduce the water contact angle on the transparent electrode surface to 10° or less. The liquid crystal alignment agent (R-1) prepared in 1. was applied to the transparent electrode surface of the glass substrate with a transparent electrode using an inkjet coater (manufactured by Shibaura Mechatronics Co., Ltd.). The coating conditions were 2,500 strokes/(nozzle/minute), a spray amount of 250 mg/10 seconds, and two reciprocating strokes (a total of four strokes). After coating, the film was left to stand for 1 minute and then heated at 80°C to form a coating with an average film thickness of 0.1 μm. The resulting coating was visually inspected for unevenness and depressions under illumination with an interference fringe light (sodium lamp). Evaluation was performed by rating the film "Excellent (◎)" if the total number of areas with unevenness and depressions was 0, "Good (○)" if the total number of areas with unevenness and depressions was 1 or more but less than 3, and "Poor (×)" if the total number of areas with unevenness and depressions was 3 or more. Good inkjet coating properties indicate good solubility of the polymer used in preparing the liquid crystal alignment agent. As a result, the inkjet coating properties of the liquid crystal alignment agent of the embodiment were rated as "excellent".

4. Evaluation of AC afterimage characteristics For the FFS type liquid crystal cell manufactured in 2. above, after being driven with an AC voltage of 10 V for 72 hours, the minimum relative transmittance (%) expressed by the following formula (2) was measured using a device with a polarizer and an analyzer arranged between the light source and the light intensity detector. Minimum relative transmittance (%) = (β-B0)/(B100-B0)×100   …(2) (In formula (2), B0 is the light transmittance under blank and crossed Nicols; B100 is the light transmittance under blank and parallel Nicols; β is the light transmittance that is minimum under crossed Nicols with the liquid crystal cell sandwiched between the polarizer and the analyzer) The black level in the dark state is represented by the minimum relative transmittance of the liquid crystal cell. In FFS type liquid crystal cells, the smaller the black level in the dark state, the better the contrast characteristics, and it can be said that the AC afterimage characteristics are excellent. A minimum relative transmittance of less than 0.3% was rated "Excellent (◎)", a minimum relative transmittance of 0.3% or more but less than 2.0% was rated "Good (○)", and a minimum relative transmittance of 2.0% or more was rated "Poor (×)". The result was a "Good" rating in the embodiment described above.

5. Evaluation of Electrical Properties The FFS liquid crystal cell produced in 2. was placed in a 60°C oven and its voltage holding ratio (VHR) was measured using a VHR measuring device "VHR-1" manufactured by Toyo Technica Corporation at 1 V and 1670 msec. The evaluation criteria were: a VHR of 80% or higher was rated "Excellent (◎)", a VHR of less than 80% but greater than 70% was rated "Good (○)", a VHR of less than 70% but greater than 60% was rated "Acceptable (△)", and a VHR of less than 60% was rated "Unacceptable (×)". The VHR of the example described above was rated "Excellent".

6. Reliability Evaluation after Light Irradiation The reliability of the FFS-type liquid crystal cell produced in 2. above was evaluated. The evaluation was conducted as follows. First, a voltage of 1 V was applied to the liquid crystal cell for 60 μs. The voltage holding ratio (VHR1) was measured 1670 milliseconds after the voltage application was removed. Next, the liquid crystal cell was exposed to a cold cathode fluorescent lamp (CCFL) (backlight) at 60°C for one week and then allowed to cool naturally to room temperature. After cooling, a voltage of 1 V was applied to the liquid crystal cell for 60 μs. The voltage holding ratio (VHR2) was measured 1670 milliseconds after the voltage application was removed. The measurement apparatus used was the "VHR-1" VHR measuring apparatus manufactured by Toyo Technica. The VHR change rate (ΔVHR) at that time is calculated from the difference between VHR1 and VHR2 (ΔVHR = VHR1 - VHR2), and reliability is evaluated based on ΔVHR. A ΔVHR of less than 10% is rated "Excellent (◎)", a ΔVHR of 10% to less than 15% is rated "Good (○)", a ΔVHR of 15% to less than 20% is rated "Acceptable (△)", and a ΔVHR of 20% or more is rated "Unacceptable (×)". The result is "Excellent" reliability in this embodiment.

7. Evaluation of DC Image Posterization Characteristics The liquid crystal cell fabricated in step 2 was driven at 2.5 V AC, with the luminance difference between any two pixels set to 0. Then, it was driven at 2.5 V AC, with 1 V DC applied to only one pixel for 20 minutes, allowing charge to accumulate. When the 1 V DC application was terminated and the drive returned to 2.5 V AC only, a luminance difference between the two pixels occurred due to the accumulated charge. By observing the change in this luminance difference over time, the time required for the residual DC value to decay was calculated. A relaxation time of less than 10 seconds was rated "Excellent (◎)", a relaxation time of 10 seconds or more but less than 20 seconds was rated "Good (○)", and a relaxation time of 20 seconds or more was rated "Poor (×)". The result was rated "Excellent" in the embodiment described above.

8. Evaluation of Abrasion Resistance The liquid crystal alignment agent (R-1) prepared in step 1 was applied to a glass substrate using a spinner and heated on a 110°C hot plate for 3 minutes (pre-baking). The coating was then dried for 30 minutes in a 230°C oven purged with nitrogen (post-baking). This resulted in a coating with an average film thickness of 0.08 μm. The haze value of the coating was measured using a haze meter. The coating was then rubbed five times using a rubbing machine equipped with a roll wrapped with cotton cloth, at a roll speed of 1000 rpm, a stage travel speed of 3 cm/s, and a bristle indentation length of 0.3 mm. Thereafter, the haze value of the liquid crystal alignment film was measured using a haze meter, and the difference from the haze value before the rubbing treatment (haze change value) was calculated using the following formula (3). Haze change value (%) = [Haze value of the film after rubbing treatment (%)] - [Haze value of the film before rubbing treatment (%)] …(3) Regarding the rubbing resistance of the liquid crystal alignment film, a haze change value of less than 0.8 was evaluated as "excellent (◎)", a haze change value of 0.8 or more and less than 1.5 was evaluated as "good (○)", and a haze change value of 1.5 or more was evaluated as "poor (×)". If the haze change value is less than 1.5 (more preferably less than 0.8), the film strength is considered sufficiently high and the abrasion resistance is excellent. The abrasion resistance in the example was rated "Excellent."

[Examples 2-21 and Comparative Examples 1-8] 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 modified as shown in Table 3 below. Furthermore, using the resulting liquid crystal alignment agent, an FFS liquid crystal cell was produced by the rubbing method, similar to Example 1, and various evaluations were performed. The results are shown in Table 4 below. In Table 3, the amount of each polymer added is expressed as a solids content (parts by mass) relative to the total amount of polymer components used to prepare the liquid crystal alignment agent.

[Example 22, Example 23] 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 below, and that the liquid crystal alignment film was formed using a photoalignment method instead of a rubbing method. FFS-type liquid crystal cells were manufactured and various evaluations were performed. The results are shown in Table 4. The liquid crystal alignment film was formed using the photoalignment method according to the following procedure. (Formation of Liquid Crystal Alignment Film Using the Photoalignment Method) The liquid crystal alignment agent was applied using a spinner to each of a glass substrate with a flat electrode (bottom electrode), an insulating layer, and a comb-shaped electrode (top electrode) laminated sequentially on one surface, and an opposing glass substrate without electrodes. The coating was then heated (pre-baked) on an 80°C hot plate for one minute. Afterwards, the coating was dried (post-baked) for 30 minutes in a nitrogen-purged oven at 230°C, forming a coating with an average thickness of 0.1 μm. The resulting coating was then photo-aligned using a Hg-Xe lamp, irradiated with 1,000 J/ ^m² of linearly polarized UV light at 254 nm from the direction normal to the substrate. The irradiation dose was measured using a light meter based on a wavelength of 254 nm. The photo-aligned coating was then heat-treated in a clean oven at 230°C for 30 minutes to form a liquid crystal alignment film. Furthermore, the above series of operations were performed by varying the UV exposure dose after post-baking within a range of 100 J/ ^m² to 10,000 J/ ^m² , thereby producing three or more liquid crystal cells with different UV exposure doses. The liquid crystal cell exhibiting the best alignment characteristics (optimal exposure dose) was then subjected to various evaluations similar to those in Example 1.

[Table 3] polymer [A] Other polymers 1 polymer [B] Other polymers 2 Kind Mixing quantity (weight) Kind Mixing quantity (weight) Kind Mixing quantity (weight) Kind Mixing quantity (weight) Example 1 PAA-1 40 - - PAA-36 60 - - Example 2 PAA-2 30 - - PAA-37 70 - - Example 3 PAA-3 40 - - PAA-18 60 - - Example 4 PAA-4 40 - - PAA-19 60 - - Example 5 PAA-5 50 - - PAA-35 50 - - Example 6 PAA-6 50 - - PAA-34 50 - - Example 7 PAA-7 50 - - PAA-22 50 - - Example 8 PAA-8 40 - - PAA-20 60 - - Example 9 PAA-9 50 - - PAA-21 50 - - Example 10 PAA-10 40 - - PAA-23 60 - - Example 11 PAA-11 50 - - PAA-24 50 - - Example 12 PAA-12 30 - - PAA-26 70 - - Example 13 PAA-13 40 - - PAA-25 60 - - Example 14 PAA-14 50 - - PAA-27 50 - - Example 15 PI-1 30 - - PAA-33 70 - - Example 16 PI-2 30 - - PAA-28 70 - - Example 17 PI-3 40 - - PAA-29 60 - - Example 18 PI-1 20 - - PAA-30 80 - - Example 19 PAA-1 50 - - PAA-31 50 - - Example 20 PI-2 30 - - PAA-32 70 - - Example 21 PAA-2 50 - - PAA-34 50 - - Example 22 PI-4 40 - - PAA-21 60 - - Example 23 PI-5 40 - - PAA-35 60 - - Comparative example 1 PAA-1 100 - - - - - - Comparative example 2 - - PAA-15 50 PAA-26 50 - - Comparative example 3 - - PAA-16 30 PAA-26 70 - - Comparative example 4 - - PAA-17 50 PAA-34 50 - - Comparative example 5 PAA-2 30 - - - - PAA-38 70 Comparative example 6 PAA-1 40 - - - - PAA-39 60 Comparative example 7 PAA-2 30 - - - - PAA-40 70 Comparative example 8 PAA-1 40 - - - - PAA-41 60

[Table 4] Reviews Inkjet coating properties AC afterimage characteristics VHR reliability DC afterimage characteristics Friction resistance Example 1 ◎ ◎ ◎ ◎ ◎ ◎ Example 2 ◎ ◎ ◎ ◎ ◎ ◎ Example 3 ◎ ◎ ◎ ◎ ◎ ◎ Example 4 ◎ ◎ ◎ ◎ ◎ ◎ Example 5 ◎ ◎ ◎ ◎ ◎ ◎ Example 6 ◎ ◎ ◎ ◎ ◎ ◎ Example 7 ◎ ◎ ○ ○ ◎ ◎ Example 8 ◎ ◎ ◎ ◎ ◎ ◎ Example 9 ◎ ◎ ◎ ◎ ◎ ◎ Example 10 ◎ ◎ ○ ○ ◎ ◎ Example 11 ◎ ◎ ◎ ◎ ◎ ◎ Example 12 ◎ ◎ ○ ○ ◎ ◎ Example 13 ◎ ◎ ◎ ○ ◎ ◎ Example 14 ◎ ◎ ◎ ◎ ◎ ◎ Example 15 ◎ ◎ ◎ ◎ ◎ ◎ Example 16 ◎ ◎ ◎ ◎ ◎ ◎ Example 17 ◎ ◎ ◎ ◎ ◎ ◎ Example 18 ◎ ◎ ◎ ◎ ◎ ◎ Example 19 ◎ ◎ ◎ ◎ ◎ ◎ Example 20 ◎ ◎ ◎ ◎ ◎ ◎ Example 21 ◎ ◎ ◎ ◎ ◎ ◎ Example 22 ◎ ◎ ◎ ◎ ◎ ◎ Example 23 ◎ ◎ ◎ ◎ ◎ ○ Comparative example 1 ◎ ◎ ◎ ◎ × ◎ Comparative example 2 ◎ × ◎ ◎ ◎ ◎ Comparative example 3 ◎ × ◎ ◎ ◎ ◎ Comparative example 4 ○ ◎ ○ ○ ◎ × Comparative example 5 × × ○ ○ ◎ × Comparative example 6 ◎ ◎ ◎ ◎ × ◎ Comparative example 7 × × ○ × ◎ × Comparative example 8 × × ○ ○ ◎ ×

As shown in Table 4, compared to Comparative Examples 1 through 8, Examples 1 through 23 achieved a good balance of inkjet coatability, AC image sticking characteristics, VHR, reliability, DC image sticking characteristics, and abrasion resistance. In particular, Examples 1 through 6, 8, 9, 11, and 14 through 22 all received a "◎" rating, indicating they were excellent. In contrast, Comparative Examples 1 through 8 received a "×" rating for at least one of the following: inkjet coatability, AC image sticking characteristics, reliability, DC image sticking characteristics, and abrasion resistance.

The above results demonstrate that a liquid crystal alignment agent comprising polymer [A] and polymer [B] can produce a liquid crystal alignment film that reduces image artifacts in liquid crystal display devices and exhibits high mechanical strength. Furthermore, it was demonstrated that a liquid crystal alignment agent exhibiting good solubility of polymer [A] and polymer [B] and excellent coating properties can be obtained.

without

Claims (6)

A liquid crystal alignment agent comprises: a polymer [A] having the following structural unit (U1) and not having the following structural unit (U2); and a polymer [B] having the following structural unit (U2) and the following structural unit (U3); wherein the structural unit (U1) is a structural unit derived from a diamine having a partial structure represented by the following formula (1); the structural unit (U2) is a structural unit derived from a diamine having a partial structure represented by the following formula (2); and the structural unit (U3) is a structural unit derived from a diamine having the following partial structure Y; the partial structure Y is a structure represented by -( _CH2 ) _n- (wherein n is an integer from 1 to 20), wherein any methylene group in the structure represented by -( _CH2 ) _n+1- is replaced by -O-, -S-, -COO-, ^-NR7- , ^-NR7 -CO-, -NR7 ^- COO-, -NR7- -O-, -S-, -COO-, -NR 7 -, -NR ^{7 -CO-} , -NR 7 -COO-, -NR 7 -CO-NR ⁸ - ^, or a nitrogen-containing non-aromatic heterocyclic group (wherein R ⁷ and R ⁸ are each independently a hydrogen atom or a monovalent organic group; when n is 2 or greater, -O-, -S-, -COO-, -NR ⁷ -CO-, -NR ⁷ -COO-, -NR ⁷ -CO-NR ⁸ -, and the nitrogen-containing non-aromatic heterocyclic group are not adjacent to each other), -O-, -S-, -COO-, -NR ⁷ -CO-, -NR ⁷ -COO-, or -NR ⁷ -CO-NR ⁸ -; (In formula (1), ^X1 and ^X2 are each independently a divalent aromatic ring group; wherein, in the aromatic ring possessed by ^X1 , no substituent is bonded to a position different from the bonding position of ^R1 and the bonding position of the group to which “*” is bonded, and in the aromatic ring possessed by ^X2 , no substituent is bonded to a position different from the bonding position of ^R2 and the bonding position of the group to which “*” is bonded; ^R1 and ^R2 are each independently a single bond, an alkanediyl group having 1 to 10 carbon atoms, or a substituted alkanediyl group having 1 to 10 carbon atoms; at least one of ^R1 and ^R2 is an alkanediyl group having 1 to 10 carbon atoms or a substituted alkanediyl group having 1 to 10 carbon atoms; ^Y1 and ^Y2 are each independently * ¹ - ^NR3 -CO- or * ¹ -CO- ^NR3 -; R ³ is a hydrogen atom or a monovalent organic group; "* ¹ " represents a bond with Z ¹ ; Z ¹ is a single bond or a divalent organic group; m is 0 or 1; "*" represents a bond); (In formula (2), ^A1 and ^A2 are each independently a divalent aromatic cyclic group; ^B1 is ^-NR4- or a divalent aromatic heterocyclic group; when ^B1 is a divalent aromatic heterocyclic group, ^R5 and ^R6 are each independently a hydrogen atom or a monovalent organic group; when ^B1 is ^-NR4- , ^R4 , ^R5 and ^R6 are (i) or (ii) below; (i) ^R4 is a hydrogen atom or a monovalent organic group; ^R5 and ^R6 are each independently a hydrogen atom or a monovalent organic group, or ^R5 and ^R6 are each bonded to each other and form a ring structure together with ^A1 , ^-NR4- and ^A2 ; (ii) ^R4 and R6 are ^{(R 5} is independently a hydrogen atom or a monovalent organic group, or represents a ring structure formed by R ⁴ and R ⁵ combined with each other, A ¹ and the nitrogen atom; R ⁶ is a hydrogen atom or a monovalent organic group; "*" represents a bond). The liquid crystal alignment agent according to claim 1, wherein the polymer [A] and the polymer [B] are at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide. The liquid crystal alignment agent according to claim 1 or claim 2, wherein the diamine having the partial structure represented by formula (1) is a compound represented by the following formula (DA): (In formula (DA), R ¹ , R ² , Y ¹ , Y ² and Z ¹ have the same meanings as in formula (1)). The liquid crystal alignment agent according to claim 1 or claim 2, wherein the polymer [B] comprises 5 mol% to 95 mol% of the structural unit (U2) relative to the total amount of diamine units in the polymer [B]. A liquid crystal alignment film is formed using the liquid crystal alignment agent described in any one of claims 1 to 4. A liquid crystal element comprising the liquid crystal alignment film as described in claim 5.