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

Abstract

This liquid crystal alignment agent comprises a solvent and a polymer (P) having a side chain that includes a cinnamate structure and does not have a fluorinated alkyl group at an end of the side chain. The solvent has a first solvent and a second solvent. The first solvent has a boiling point of 185°C or higher and has a cyclic amide structure or a cyclic ester structure. The second solvent has a boiling point of lower than 185°C and a surface tension at 25°C of 25 mN / m or less. The content of the first solvent is 30 mass% to 70 mass% with respect to the total amount of the solvent, and the content of the second solvent is more than 0 mass% and 30 mass% or less with respect to the total amount of the solvent.

Description

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

[0001] [Cross-reference of related applications] This application claims priority under Japanese Patent Application No. 2025-18756, filed on February 6, 2025, which is incorporated herein by reference in its entirety. This disclosure relates to liquid crystal alignment agents, liquid crystal alignment films, and liquid crystal elements.

[0002] A liquid crystal element includes a liquid crystal alignment film, which is an organic film that has the function of aligning liquid crystal molecules in the liquid crystal layer in a specific direction. Generally, the liquid crystal alignment film is formed on the substrate by coating the substrate surface with a liquid crystal alignment agent, which is a polymer component dissolved in an organic solvent, and preferably by heating it.

[0003] Conventional methods for obtaining organic films with liquid crystal alignment control capabilities include rubbing an organic film, oblique deposition of silicon dioxide, and forming a monolayer having a long-chain alkyl group, as well as irradiating a photosensitive organic film with light (photo-alignment method). Of these, the photo-alignment method has been the subject of much research in recent years because it can uniformly impart liquid crystal alignment to the film while suppressing the generation of static electricity and dust (see, for example, Patent Documents 1 and 2). Patent Documents 1 and 2 disclose forming a liquid crystal alignment film by the photo-alignment method using a polymer having a cinnamate structure.

[0004] Japanese Patent Publication No. 2011-100099 Japanese Patent Publication No. 2024-091428

[0005] Conventional liquid crystal alignment agents used in photo-alignment methods ensure photoreactivity by incorporating cinnamate structure-containing side chains (hereinafter also referred to as "cinnamate side chains") into the polymer. Furthermore, by introducing fluorinated alkyl groups to the ends of the cinnamate side chains, the coatability of the liquid crystal alignment agent and the liquid crystal alignment of liquid crystal elements are improved. On the other hand, in recent years, from the perspective of reducing environmental impact, attempts have been made to minimize the fluorine content in organic materials, and it is desirable to minimize the fluorine content in liquid crystal alignment agents as well.

[0006] However, when using polymers that do not have a fluorinated alkyl group at the end of the cinnamate side chain, the surfactant effect unique to fluorinated alkyl groups cannot be enjoyed, and the wettability (also called leveling) of the liquid crystal alignment agent tends to be inferior to that of liquid crystal alignment agents using polymers that have a fluorinated alkyl group at the end of the cinnamate side chain. In particular, liquid crystal alignment agents containing polymers that do not have a fluorinated alkyl group at the end of the cinnamate side chain are prone to coating defects such as repellency and unevenness around contact holes formed on the substrate. Considering the need to meet the stringent demands for high quality in liquid crystal devices in recent years, it is important for liquid crystal alignment agents to ensure good coating properties (hereinafter also referred to as "contact hole coating properties") even in areas prone to coating defects, such as around contact holes.

[0007] One possible method to suppress coating defects around contact holes is to use a relatively large amount of a solvent with low surface tension (hereinafter also called "leveling solvent") as the solvent to be blended with a polymer that does not have a fluorinated alkyl group at the end of the cinnamate side chain. However, leveling solvents generally have low polymer solubility. Therefore, if the leveling solvent does not volatilize quickly during the liquid crystal alignment film formation process, there is a concern that it may cause the liquid crystal alignment agent to be repelled or the film to whiten. In addition, during the liquid crystal alignment film formation process, there is a concern that unintended volatilization of the solvent may cause uneven display due to temperature variations during heating during film formation.

[0008] This disclosure is made in view of the above circumstances, and one of its objectives is to provide a liquid crystal alignment agent that exhibits good contact hole coating properties, enables the production of a liquid crystal alignment film with excellent transparency, and also provides excellent process stability.

[0009] According to this disclosure, the following liquid crystal alignment agents, liquid crystal alignment films, and liquid crystal elements are provided.

[0010] [1] A liquid crystal alignment agent comprising a polymer (P) having a side chain containing a cinnamate structure and having no fluorinated alkyl group at the end of the side chain, and a solvent, wherein the solvent comprises a first solvent having a boiling point of 185°C or higher and having a cyclic amide structure or a cyclic ester structure, and a second solvent having a boiling point of less than 185°C and a surface tension of 25 mN / m or less at 25°C, wherein the content of the first solvent is 30% by mass or more and 70% by mass or less based on the total amount of the solvent, and the content of the second solvent is greater than 0% by mass and 30% by mass or less based on the total amount of the solvent. [2] The liquid crystal alignment agent according to [1], wherein the polymer (P) contains structural units derived from a diamine having a monovalent group containing a cinnamate structure and having no fluorinated alkyl group at the end of the monovalent group. [3] The liquid crystal alignment agent according to [1] or [2], wherein the polymer (P) is at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide. [4] A liquid crystal alignment agent according to any one of [1] to [3], further comprising a polymer (Q) that does not have a cinnamate structure. [5] A liquid crystal alignment agent according to [4], wherein the polymer (Q) is at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide. [6] A liquid crystal alignment agent according to any one of [1] to [5], wherein the second solvent is at least one selected from the group consisting of alcohols, ketones, ethers, and chain esters. [7] A liquid crystal alignment agent according to any one of [1] to [6], further comprising a third solvent different from the first solvent and the second solvent. [8] A liquid crystal alignment film formed with a liquid crystal alignment agent according to any one of [1] to [7]. [9] A method for producing a liquid crystal alignment film, comprising forming a coating film with a liquid crystal alignment agent according to any one of [1] to [7], and subjecting the coating film to an alignment treatment to impart liquid crystal alignment ability.

[10] A liquid crystal element comprising the liquid crystal alignment film according to [8].

[0011] The liquid crystal alignment agent of this disclosure makes it possible to obtain a liquid crystal alignment film with excellent transparency while exhibiting good contact hole coating properties. Furthermore, the liquid crystal alignment agent of this disclosure exhibits excellent process stability.

[0012] The following details the aspects of this disclosure.

[0013] In this specification, numerical ranges indicated using "~" include the values ​​indicated before and after "~" as the lower and upper limits, respectively. A "structural unit" is a unit that primarily constitutes the main chain structure and is present in at least two units in the main chain structure. A structural unit is typically a repeating unit composed of a single monomer. A structural unit may also be obtained by reacting a repeating unit having a reactive group with a compound having a functional group that can react with the reactive group.

[0014] In this specification, "hydrocarbon group" includes linear hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. "Linear hydrocarbon group" means a linear hydrocarbon group or a branched hydrocarbon group that does not contain a cyclic structure and consists only of a linear structure. However, it may be saturated or unsaturated. "Alicyclic hydrocarbon group" means a hydrocarbon group that contains only the structure of an alicyclic hydrocarbon as its ring structure and does not contain an aromatic ring structure. However, it is not necessary to consist only of the structure of an alicyclic hydrocarbon, and it may also include those that have a linear structure as part of it. "Aromatic hydrocarbon group" means a hydrocarbon group that contains an aromatic ring structure as its ring structure. However, it is not necessary to consist only of the structure of an aromatic ring, and it may also contain a linear structure or an alicyclic hydrocarbon structure as part of it. "Organic group" means an atomic group obtained by removing any hydrogen atom from a carbon-containing compound (i.e., an organic compound).

[0015] The "main chain" of a polymer refers to the "trunk" portion, which consists of the longest chain of atoms. This "trunk" portion may 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. "Side chains" refer to the parts of a polymer that branch off from the "trunk" portion.

[0016] ≪Liquid Crystal Alignment Agent≫ The liquid crystal alignment agent and its manufacturing method described herein will now be explained. The liquid crystal alignment agent described herein contains a polymer (P) having a side chain containing a cinnamate structure and no fluorinated alkyl group at the end of the side chain, and a solvent. The polymer (P) and solvent contained in the liquid crystal alignment agent described herein, as well as any optional components that may be added as needed, will be described in detail below. Unless otherwise specified, each component may be used alone or in combination of two or more.

[0017] <Polymer (P)> Polymer (P) has side chains containing a cinnamate structure (hereinafter also referred to as "specific side chains"). The specific side chains of polymer (P) do not have a fluorinated alkyl group at the end of the side chain. Here, "end of the side chain" means the tip of the side chain, and more specifically, the part of the side chain furthest from the main chain of the polymer (i.e., the side opposite to the root of the side chain). Polymer (P) preferably has an alkyl group, alkoxy group, cyanide alkyl group, or cyanide alkoxy group having 1 to 20 carbon atoms at the end of the specific side chain, and more preferably has an alkyl group or alkoxy group having 4 to 20 carbon atoms, in order to obtain a liquid crystal element that exhibits good liquid crystal alignment.

[0018] The main skeleton of polymer (P) is not particularly limited as long as it has specific side chains. Examples of the main skeleton of polymer (P) include polymers whose main skeleton is polyamic acid, polyamic acid ester, polyimide, polyamine, polyenamine, polyamide, polyamideimide, polyurea, polyimine, polyorganosiloxane, or addition polymer. Polyenamine is a polymer having a carbon-carbon double bond adjacent to the amino group of a polyamine, and examples include polyenaminoketone, polyenaminoester, polyenaminonitrile, and polyenaminosulfonyl. Examples of addition polymers include (meth)acrylic polymers, styrene polymers, maleimide polymers, (meth)acrylic-styrene copolymers, (meth)acrylic-maleimide copolymers, (meth)acrylic-styrene-maleimide copolymers, and styrene-maleimide copolymers.

[0019] In terms of being able to obtain a liquid crystal element excellent in liquid crystal alignment property, voltage holding property, and reliability, the polymer (P) is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, polyimide, polyamide, polyamideimide, polyurea, and polyimine. Among these, particularly, the polymer (P) is more preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide.

[0020] The cinnamate structure is a partial structure containing cinnamic acid or its derivative as a basic skeleton. Examples of the cinnamate structure include the partial structure represented by the following formula (1). (In formula (1), R １ , ４ , ０ , ７ , ３ , ８ , ６ , ５ ,

[0021] , ３ , ５ , ８ , ２ , ６ , ０ , １ , ３ , ４ , ７ , and R ２ are each independently a hydrogen atom, a halogen atom, a cyano group, a nitro group, a hydroxyl group, a carboxy group, -SiR ４ R ５ R ６ ; -NR ７ R ８ , a phosphate group, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a monovalent oxyhydrocarbon group having 1 to 10 carbon atoms. R ４ , R ５ , R ６ , R ７ and R ８ are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. R ３ is a halogen atom, a cyano group, a nitro group, a hydroxyl group, a carboxy group, an amino group, a monovalent hydrocarbon group having 1 to 1 carbon atoms, or a monovalent oxyhydrocarbon group having 1 to 10 carbon atoms. a is an integer of 0 to (5 - b). b is 0 or 1. When a is 2 or more, the plurality of R ３ are the same or different. X<​​​​​​​​​​​​​​​​​​６ , R ７ , R ８ or R ０ Examples of monovalent hydrocarbon groups having 1 to 10 carbon atoms represented by R include saturated or unsaturated chain hydrocarbon groups, saturated or unsaturated alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ , R ８ or R ０ Of the monovalent hydrocarbon groups having 1 to 10 carbon atoms represented by , saturated or unsaturated chain hydrocarbon groups are preferred, and alkyl groups having 1 to 3 carbon atoms are more preferred.

[0022] Examples of monovalent oxy hydrocarbon groups having 1 to 10 carbon atoms include groups formed by bonding the group exemplified as a monovalent hydrocarbon group having 1 to 10 carbon atoms with an -O- group. １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ or R ８ The monovalent oxy hydrocarbon group having 1 to 10 carbon atoms represented by is preferably a saturated or unsaturated oxy-chain hydrocarbon group, and more preferably an alkoxy group having 1 to 3 carbon atoms. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms.

[0023] R １ and R ２ It is preferable that each of these elements independently be a hydrogen atom, a halogen atom, a C1-C3 alkyl group, a C1-C3 alkoxy group, or a cyano group. ３ Preferably, it is an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a halogen atom, or a cyano group.

[0024] X １ ga-NR ０ - If R ０Preferably, the group is a hydrogen atom, a monovalent hydrocarbon group having 1 to 6 carbon atoms, or a monovalent leaving group, and more preferably, a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a monovalent leaving group.

[0025] The monovalent leaving group is preferably a group that is removed by heat or light and replaced by a hydrogen atom. Among the monovalent leaving groups, carbamate-type leaving groups are preferred because they exhibit high thermal leaving properties. Specific examples of these include isopropyloxycarbonyl group, tert-butoxycarbonyl group (Boc group), 2-methyl-2-butyloxycarbonyl group, benzyloxycarbonyl group, 1,1-dimethyl-2-haloethyloxycarbonyl group, allyloxycarbonyl group, 2-(trimethylsilyl)ethoxycarbonyl group, and 9-fluorenylmethyloxycarbonyl group. Among these, branched alkyloxycarbonyl groups having 3 to 6 carbon atoms are particularly preferred, and tert-butoxycarbonyl group (Boc group) is more preferred, because they exhibit excellent thermal leaving properties and can reduce the amount of residue remaining in the film of the deprotected portion. a is preferably 0 or 1.

[0026] X １ In terms of being able to increase the photoreactivity of the substructure represented by formula (1) above, an oxygen atom or a sulfur atom is preferred, and an oxygen atom is more preferred.

[0027] The polymer (P) has a cinnamate structure, as shown in formula (1) above, "-CR １ =CR ２ -CO-X １ "-CR" is attached to the benzene ring to which "-" is attached. １ =CR ２ -CO-X １ The polymer may have a substructure in its side chains in which the "-" is located on the main chain side (hereinafter also referred to as the "forward cinnamate structure"). １ =CR ２ -CO-X １ "-CR" is attached to the benzene ring to which "-" is attached. １ =CR ２ -CO-X １ The side chain may have a substructure in which the "-" symbol is located at the terminal end of the side chain (hereinafter also referred to as the "reverse cinnamate structure").

[0028] A specific example of a forward cinnamate structure is the substructure represented by the following formula (cn-1). A specific example of an inverse cinnamate structure is the substructure represented by the following formula (cn-2). (In formula (cn-1), R ９ R is a hydrogen atom, a chlorine atom, a bromine atom, an iodine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cyano group, an alkyl cyanide group having 2 to 20 carbon atoms, or an alkoxy cyanide group having 2 to 20 carbon atoms. １０ This refers to a phenylene group or a cyclohexylene group, or a group in which at least some of the hydrogen atoms of these groups are substituted with a chlorine atom, a bromine atom, an iodine atom, a C1-C10 alkyl group, a C1-C10 alkoxy group, or a cyano group. １ This includes a single bond, an oxygen atom, a sulfur atom, an alkanediyl group with 1 to 3 carbon atoms, -CH=CH-, -NH-, and * １ -COO-, * １ -OCO-, * １ -NH-CO-, * １ -CO-NH-, * １ -CH ２ -O- or * １ -O-CH ２ - ("* １ " is R １０ This represents a combination with ). c is an integer from 0 to 3. If c is 2 or greater, multiple A １ They are the same or different, multiple R １０ They are the same or different. In formula (cn-2), R １１ A is an alkyl group having 1 to 20 carbon atoms. ２ * is an oxygen atom. ２ -COO-, * ２ -OCO-, * ２ -NH-CO- or * ２ -CO-NH- (“* ２ " is R １２ This represents a combination with . １２ R is an alkanediyl group having 1 to 6 carbon atoms. d is 0 or 1. R in formulas (cn-1) and (cn-2) １ , R ２ , R３ and X １ and a have the same meanings as in the above formula (1). "*" represents a bond.)

[0029] In the above formula (cn-1), "-(A １ -R １０ ) ｃ -R ９ " The monovalent group represented by does not have a fluorinated alkyl group. Here, the "fluorinated alkyl group" without a specific side chain is a group in which any hydrogen atom of the alkyl group is substituted with a fluorine atom. Note that the fluorinated alkyl group in the fluorinated alkoxy group also corresponds to the "fluorinated alkyl group" without a specific side chain.)

[0030] In terms of being able to make the liquid crystal alignment property, reliability, and afterimage characteristics of the liquid crystal element more excellent, it is preferable that the specific side chain has a partial structure represented by the above formula (cn-1). Among these, c is 2 or 3, and R ９ The R １０ to which binds is preferably a substituted or unsubstituted cyclohexylene group. R ９ in the above formula (cn-1) is preferably 4 or more carbon atoms in terms of obtaining a liquid crystal element showing good liquid crystal alignment property, and a linear alkyl group or alkoxy group having 4 to 18 carbon atoms is more preferable.)

[0031] Preferred specific examples of the specific side chain include a side chain containing a partial structure represented by the following formula (1A). (In formula (1A), L １ is the group represented by the above formula (1). However, b in the above formula (1) is 1. Z Ｉ , Z ＩＩ and Z ＩＩＩ are each independently a single bond, -O-, * １ -COO-, * １ -OCO-, *1] １ -CH ２ O-, * １ -OCH ２ - or an alkanediyl group having 1 to 3 carbon atoms. "*9] １ " represents a bond to the group on the terminal side of the specific side chain. R ２０k is an alkyl group, alkoxy group, cyanide alkyl group, or cyanide alkoxy group having 1 to 20 carbon atoms. k is 0 or 1. m is an integer from 0 to 3. n is an integer from 0 to 2. However, 1 ≤ k + m + n ≤ 3. (* represents a bond.)

[0032] In the above formula (1A), the benzene ring in formula (1) and Z in formula (1A) １ When the group represented by formula (1) above is arranged so that it bonds with L, １ It has a forward cinnamate structure, and X in formula (1) above １ and Z in the above equation (1A) １ When arranged so that they are joined together, L １ It has an inverse cinnamate structure. Of these, L １ It is preferable that the side chain has a forward cinnamate structure. Furthermore, in order to improve the liquid crystal alignment, reliability, and afterimage characteristics of the liquid crystal element, it is preferable that the specific side chain has n = 0 and m = 1 or more. In this case, Z ＩＩＩ A single bond is preferred. ２０ The group preferably has four or more carbon atoms, and more preferably a linear alkyl or alkoxy group having four to eighteen carbon atoms.

[0033] Further specific examples of the specific side chains of the polymer (P) include, for example, a side chain having a substructure represented by the following formula; and a side chain having a substructure in which the terminal alkyl group or terminal alkoxy group in the substructure represented by the following formula is replaced by an alkyl group, alkoxy group, cyanide alkyl group, or cyanide alkoxy group having 2 to 20 carbon atoms. (In the formula, "*" represents a bond.)

[0034] The substructure represented by the above formula, and the substructure in which the terminal alkyl group or terminal alkoxy group in said substructure is replaced with an alkyl group, alkoxy group, cyanide alkyl group, or cyanide alkoxy group having 2 to 20 carbon atoms, may be bonded to the main chain of the polymer by single bonds or by divalent linking groups. Examples of divalent linking groups include alkanediyl groups having 1 to 10 carbon atoms, and divalent groups containing -O- or the like between the carbon-carbon bonds of alkanediyl groups having 2 to 10 carbon atoms.

[0035] The content of specific side chains in polymer (P) is preferably 15 mol% or more, more preferably 20 mol% or more, and even more preferably 25 mol% or more, relative to the total amount of structural units derived from monomers contained in polymer (P). By setting the content of specific side chains within the above range, a liquid crystal alignment film exhibiting good liquid crystal alignment can be obtained by photo-alignment.

[0036] The method for obtaining a polymer (P) having a specific side chain is not particularly limited. It is preferable that the polymer (P) contains structural units derived from a diamine having a monovalent group corresponding to the specific side chain (hereinafter also referred to as "specific diamine"), in order to obtain a polymer with high affinity for liquid crystals, to increase the mechanical strength of the liquid crystal alignment film, and to easily introduce the specific side chain into the polymer.

[0037] (Specific Diamine) A specific diamine has a monovalent group corresponding to a specific side chain, that is, a monovalent group containing a cinnamate structure, and has a substructure in which the terminal (i.e., tip) of the monovalent group does not have a fluorinated alkyl group. From the viewpoint of ease of synthesis of the specific diamine and affinity with liquid crystals, it is preferable that the specific diamine is an aromatic diamine. Here, an aromatic diamine is a compound in which the two primary amino groups of the diamine are bonded to the same or different aromatic rings. In one molecule of a specific diamine, the number of monovalent groups corresponding to a specific side chain may be one or more, and one or two is preferred.

[0038] Specific examples of specific diamines include diamines in which the aforementioned specific side chains are bonded to a diaminophenyl group via a single bond or a divalent linking group. Further specific examples of specific diamines include, for example, the compounds represented by formulas (1-1) to (1-20) below, and compounds in which the terminal alkyl group or terminal alkoxy group in the compounds represented by formulas (1-1) to (1-20) below is replaced with an alkyl group, alkoxy group, cyanide alkyl group, or cyanide alkoxy group having 2 to 20 carbon atoms.

[0039] The content of structural units derived from a specific diamine in polymer (P) is preferably 25 mol% or more, more preferably 30 mol% or more, and even more preferably 40 mol% or more, relative to the total amount of structural units derived from diamine contained in polymer (P). By setting the content of structural units derived from a specific diamine within the above range, it is possible to form an organic film with good photo-alignment properties while ensuring good coatability of the liquid crystal alignment agent.

[0040] (Synthesis of Polymer (P)) Polymer (P) is preferably a polymer obtained by using a specific diamine as a monomer. Examples of such polymers (P) include polyamic acid, polyamic acid ester, polyimide, polyamide, polyamideimide, polyurea, and polyimine. Among these, polymer (P) is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide, as it can form a liquid crystal alignment film with excellent liquid crystal alignment properties, mechanical strength, and affinity to liquid crystals.

[0041] (Polyamic Acid) When the polymer (P) is a polyamic acid, the polyamic acid (hereinafter also referred to as "polyamic acid (P)") can be obtained by reacting a tetracarboxylic dianhydride with a diamine (polycondensation reaction).

[0042] Examples of tetracarboxylic dianhydrides used in the synthesis of tetracarboxylic dianhydrides polyamic acids (P) include aliphatic tetracarboxylic dianhydrides and aromatic tetracarboxylic dianhydrides. Examples of aliphatic tetracarboxylic dianhydrides include linear tetracarboxylic dianhydrides and alicyclic tetracarboxylic dianhydrides.

[0043] Specific examples of tetracarboxylic dianhydrides include, as chain-type tetracarboxylic dianhydrides, for example, 1,2,3,4-butanetetracarboxylic dianhydride, ethylenediaminetetraacetic acid dianhydride, etc.; as alicyclic tetracarboxylic dianhydrides, for example, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 5-(2,5-dioxotetrahydrofuran-3-yl)-3a,4,5,9b-tetrahydronaphtho[1,2-c]furan-1,3-dione, 5-(2,5-dioxotetrahydrofuran-3-yl)-8-methyl-3a,4,5,9b-tetrahydronaphtho[1,2-c]furan-1,3-dione, 3-oxabicyclo[3 2.1] Octane-2,4-dione-6-spiro-3'-(tetrahydrofuran-2',5'-dione), 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic acid 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 ２，６Undecane-3,5,8,10-tetraone, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bicyclo[2.2.2]octo-7-ene-2,3,5,6-tetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, etc. Examples of aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, p-phenylenebis(trimellitic monoester anhydride), ethylene glycol bis(anhydrotrimellitate), 1,3-propylene glycol bis(anhydrotrimellitate), 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 4,4'-biphthalic dianhydride, 4,4'-oxydiphthalic dianhydride, 4,4'-carbonyldiphthalic anhydride, etc. In addition, tetracarboxylic dianhydrides described in Japanese Patent Application Publication No. 2010-97188 can be used.

[0044] The tetracarboxylic dianhydride preferably includes an aliphatic tetracarboxylic dianhydride, and more preferably an alicyclic tetracarboxylic dianhydride, in that it can increase the solubility of the polymer (P) and allow for the production of a liquid crystal alignment film exhibiting good voltage retention characteristics. Specifically, it is preferable to include at least one selected from the group consisting of 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 2,4,6,8-tetracarboxybicyclo[3.3.0]octane-2:4,6:8-dianhydride, cyclopentanetetracarboxylic dianhydride, and cyclohexanetetracarboxylic dianhydride.

[0045] In polyamic acid (P), the content of structural units derived from alicyclic tetracarboxylic dianhydrides is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 50 mol% or more, and particularly preferably 70 mol% or more, relative to the total amount of structural units derived from tetracarboxylic dianhydrides contained in polyamic acid (P).

[0046] • In the synthesis of diamine polyamic acid (P), only specific diamines may be used as the diamine. Alternatively, diamines that do not have a cinnamate structure (hereinafter also referred to as "other diamines") may be used together with the specific diamine. Examples of other diamines include aliphatic diamines, aromatic diamines, and diaminoorganosiloxanes. Examples of aliphatic diamines include linear diamines and alicyclic diamines.

[0047] Other specific examples of diamines include, as chain-type diamines, metaxylylenediamine and hexamethylenediamine; and as alicyclic diamines, 1,4-diaminocyclohexane and 4,4'-methylenebis(cyclohexylamine).

[0048] Specific examples of aromatic diamines include p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4,4'-diaminodiphenyl ether, 4-aminophenyl-4-aminobenzoate, 4,4'-diaminoazobenzene, 3,5-diaminobenzoic acid, 1,5-bis(4-aminophenoxy)pentane, 1,2-bis(4-aminophenoxy)ethane, 1,3-bis(4-aminophenoxy)propane, 1,6-bis(4-aminophenoxy)hexane, bis[2-(4-aminophenyl)ethyl]hexanediacid, 1,4-bis-(4-aminophenyl)-piperazine, 2,2'-dimethyl-4, Main-chain diamines such as 4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-(phenylenediisopropylidene)bisaniline, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-[4,4'-propane-1,3-diylbis(piperidine-1,4-diyl)]dianiline, 4,4'-diaminobenzanilide, 4,4'-diaminostilbene, and 4,4'-diaminodiphenethylurea;Dodecanoxy-2,4-diaminobenzene, pentadecanoxy-2,4-diaminobenzene, hexadecanoxy-2,4-diaminobenzene, octadecanoxy-2,4-diaminobenzene, pentadecanoxy-2,5-diaminobenzene, octadecanoxy-2,5-diaminobenzene, cholestanyloxy-3,5-diaminobenzene, cholestanyloxy-3,5-diaminobenzene, cholestanyloxy-2,4-diaminobenzene, cholestanyloxy-2,4-diaminobenzene, 3,5-di Cholestanyl aminobenzoate, 3,5-Cholestenyl diaminobenzoate, 3,5-Lanostanyl diaminobenzoate, 3,6-Bis(4-aminobenzoyloxy)cholestane, 3,6-Bis(4-aminophenoxy)cholestane, 4-(4'-Trifluoromethoxybenzoyloxy)cyclohexyl-3,5-diaminobenzoate, 1,1-Bis(4-((aminophenyl)methyl)phenyl)-4-butylcyclohexane, 3,5-Diaminobenzoic acid = 5ξ-Cholestan-3-yl, formula (E-1) below; (In formula (E-1), X I and X II These are, independently of each other, single bonds, -O-, *-COO-, or *-OCO- (where "*" indicates a bond with the diaminophenyl group). Ｉ This is an alkanediyl group having 1 to 3 carbon atoms. ＩＩ R is a single bond or an alkanediyl group having 1 to 3 carbon atoms. ＩＩＩ (a1) is an alkyl group, alkoxy group, fluoroalkyl group, or fluoroalkoxy group having 1 to 20 carbon atoms. a1 is 0 or 1. b1 is an integer from 0 to 3. c1 is an integer from 0 to 2. d1 is 0 or 1. However, 1 ≤ (a1) + (b1) + (c1) ≤ 3.) Examples include side-chain type diamines such as compounds represented by (a1).

[0049] Examples of compounds represented by formula (E-1) include those represented by formulas (E-1-1) to (E-1-4) below.

[0050] Specific examples of diaminoorganosiloxanes include 1,3-bis(3-aminopropyl)-tetramethyldisiloxane. In addition to the above, other diamines can be used, such as those described in Japanese Patent Publication No. 2010-97188.

[0051] When the polymer (P) contains structural units derived from other diamines, the content of structural units derived from other diamines is preferably 1 mol% or more, more preferably 2 mol% or more, and even more preferably 5 mol% or more, relative to the total amount of structural units derived from diamines contained in the polymer (P). Furthermore, the content of structural units derived from other diamines is preferably 75 mol% or less, more preferably 65 mol% or less, and even more preferably 60 mol% or less, relative to the total amount of structural units derived from diamines contained in the polymer (P). By setting the content of structural units derived from other diamines within the above range, it is possible to form an organic film with good photo-alignment properties while ensuring good coatability of the liquid crystal alignment agent.

[0052] Furthermore, from the viewpoint of avoiding the use of fluorine as much as possible, diamines that do not contain fluorine atoms can preferably be used as the other diamines. The proportion of diamines that do not contain fluorine atoms among the other diamines is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 95 mol% or more, based on the total amount of other diamines.

[0053] Polyamic acid (P) can be obtained by reacting a tetracarboxylic dianhydride with a diamine, along with a molecular weight modifier as needed. The preferred ratio of tetracarboxylic dianhydride to diamine used in the synthesis reaction of polyamic acid (P) is such that the acid anhydride groups of the tetracarboxylic dianhydride are 0.2 to 2 equivalents per 1 equivalent of the amino groups of the diamine.

[0054] 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 the molecular weight modifier used is preferably 20 parts by mass or less per 100 parts by mass of the total amount of tetracarboxylic dianhydride and diamine used.

[0055] The synthesis reaction of polyamic acid (P) 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.

[0056] Examples of organic solvents used in the reaction include aprotic polar solvents, phenolic solvents, alcohols, ketones, esters, ethers, halogenated hydrocarbons, and hydrocarbons. 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 phenol, or a mixture of one or more of these and another organic solvent (e.g., butyl cellosolve, diethylene glycol diethyl ether, etc.). The amount of organic solvent used (a) is preferably such that the total amount of tetracarboxylic dianhydride and diamine (b) is 0.1 to 50% by mass of the total amount of the reaction solution (a + b).

[0057] As described above, a reaction solution is obtained by dissolving polyamic acid (P). This reaction solution may be used as is for the preparation of the liquid crystal alignment agent, or the polyamic acid (P) contained in the reaction solution may be isolated and then used for the preparation of the liquid crystal alignment agent, or the isolated polyamic acid (P) may be purified and then used for the preparation of the liquid crystal alignment agent. When dehydrating and cyclizing the polyamic acid (P) to obtain polyimide, the above reaction solution may be used as is for the dehydration and cyclization reaction, or the polyamic acid (P) contained in the reaction solution may be isolated and then used for the dehydration and cyclization reaction, or the isolated polyamic acid (P) may be purified and then used for the dehydration and cyclization reaction. The isolation and purification of polyamic acid (P) can be carried out according to known methods.

[0058] (Polyamic acid esters) Polyamic acid esters as polymers (P) (hereinafter also referred to as "polyamic acid esters (P)") can be obtained, for example, by [I] reacting the polyamic acid (P) obtained by the above synthesis reaction with an esterifying agent; [II] reacting a tetracarboxylic acid diester with a diamine; [III] reacting a tetracarboxylic acid dihalide with a diamine; and so on.

[0059] Examples of esterifying agents used in Method [I] include hydroxyl group-containing compounds, acetal compounds, halides, and epoxy group-containing compounds. Specific examples include, as hydroxyl group-containing compounds, alcohols such as methanol, ethanol, and propanol, and phenols such as phenol and cresol; as acetal compounds, N,N-dimethylformamide diethyl acetal and N,N-diethylformamide diethyl acetal; as halides, methyl bromide, ethyl bromide, stearyl bromide, methyl chloride, stearyl chloride, and 1,1,1-trifluoro-2-iodoethane; and as epoxy group-containing compounds, propylene oxide.

[0060] The tetracarboxylic acid diester used in Method [II] can be obtained, for example, by opening the ring of a tetracarboxylic acid dianhydride, as exemplified in the description of the synthesis of polyamic acid (P), using an alcohol such as methanol or ethanol. Note that the tetracarboxylic acid derivative used in Method [II] may be a tetracarboxylic acid diester alone, but a tetracarboxylic acid dianhydride may also be used in combination.

[0061] The tetracarboxylic acid diester dihalides 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. Note that the tetracarboxylic acid derivative used in Method [III] may be solely a tetracarboxylic acid diester dihalide, but a tetracarboxylic acid dianhydride may also be used in combination.

[0062] The polyamic acid ester (P) contained in the liquid crystal alignment agent may have only an amic acid ester structure, or it may be a partially esterified product in which both an amic acid structure and an amic acid ester structure coexist. The reaction solution obtained by dissolving the polyamic acid ester (P) may be used as is for the preparation of the liquid crystal alignment agent, or the polyamic acid ester (P) contained in the reaction solution may be isolated and then used for the preparation of the liquid crystal alignment agent, or the isolated polyamic acid ester (P) may be purified and then used for the preparation of the liquid crystal alignment agent. The isolation and purification of the polyamic acid ester (P) can be carried out according to known methods.

[0063] (Polyimide) Polyimide as a polymer (P) (hereinafter also referred to as "polyimide (P)") can be obtained, for example, by dehydrating and cyclizing a polyamic acid (P) synthesized as described above to imidize it.

[0064] Polyimide (P) may be a complete imidide obtained by dehydrating and cyclizing all of the amic acid structure present in its precursor, polyamic acid (P), or it may be a partial imidide obtained by dehydrating and cyclizing only a portion of the amic acid structure, resulting in the coexistence of amic acid and imide ring structures. The imidation rate of polyimide (P) is preferably 20% or more, and more preferably 30-99%. This imidation rate is expressed as a percentage of the ratio of the number of imide ring structures to the total number of amic acid structures and imide ring structures in polyimide (P). Here, a portion of the imide ring may be an isoimide ring.

[0065] Dehydration and ring closure of polyamic acid (P) is preferably carried out by heating the polyamic acid (P), or by dissolving the polyamic acid (P) in an organic solvent, adding a dehydrating agent and a dehydration ring-closing catalyst to the solution, and heating as necessary.

[0066] In a method of adding a dehydrating agent and a dehydration ring-closing catalyst to a solution of polyamic acid (P), the dehydrating agent can be an acid anhydride such as acetic anhydride, propionic anhydride, or trifluoroacetic anhydride. The amount of dehydrating agent used is preferably 0.01 to 20 moles per mole of the amic acid structure of polyamic acid (P). As the dehydration ring-closing catalyst, a tertiary amine such as pyridine, colidine, lutidine, triethylamine, or 1-methylpiperidine can be used. The amount of dehydration ring-closing catalyst used is preferably 0.01 to 10 moles per mole of the dehydrating agent used. Examples of organic solvents used in the dehydration ring-closing reaction include those exemplified as those used in the synthesis of polyamic acid (P). 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.

[0067] In this way, a reaction solution containing polyimide (P) is obtained. This reaction solution may be used as is for the preparation of the liquid crystal alignment agent, or the dehydrating agent and dehydration ring-closing catalyst may be removed from the reaction solution before preparing the liquid crystal alignment agent, or the polyimide (P) may be isolated before preparing the liquid crystal alignment agent, or the isolated polyimide (P) may be purified before preparing the liquid crystal alignment agent. These purification operations can be carried out according to known methods. In addition, polyimide (P) can also be obtained by imidization of polyamic acid ester (P).

[0068] Polyamides, polyamide-imides, polyureas, and polyimines, as polymers (P), can be obtained in the same way as polyamic acids (P), polyamic acid esters (P), and polyimides (P) by using specific diamines as monomers. Specifically, polyamides can be obtained by reacting a dicarboxylic acid derivative with a diamine containing a specific diamine, etc. Polyamide-imides can be obtained by reacting a tricarboxylic acid derivative with a diamine containing a specific diamine, etc. Polyureas can be obtained by reacting an isocyanate compound with a polyamine containing a specific diamine, etc. Polyimines can be obtained by reacting a dialdehyde compound with a diamine containing a specific diamine, etc. In each of these reactions, the specific diamine can be the same compound as the one exemplified in the description of polyamic acids (P).

[0069] The polymer (P) obtained as described above preferably has a solution viscosity of 20 to 1,800 mPa·s when it is prepared as a 15% by mass solution, and more preferably has a solution viscosity of 50 to 1,500 mPa·s. The solution viscosity (mPa·s) of polymer (P) 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 polymer (P) (e.g., γ-butyrolactone, N-methyl-2-pyrrolidone, etc.).

[0070] The weight-average molecular weight (Mw) of the polymer (P), measured by gel permeation chromatography (GPC), is preferably 1,000 to 500,000, and more preferably 2,000 to 300,000. Furthermore, for the polymer (P), the molecular weight distribution (Mw / Mn), expressed as the ratio of Mw to the number-average molecular weight (Mn) measured by GPC, is preferably 8 or less, and more preferably 7 or less. By ensuring that the Mw and Mw / Mn of the polymer (P) are within the above ranges, good liquid crystal alignment of the liquid crystal element can be ensured.

[0071] The polymer (P) content in the liquid crystal alignment agent is preferably 2% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, based on the total amount of solids contained in the liquid crystal alignment agent (i.e., the total mass of components other than the solvent in the liquid crystal alignment agent).

[0072] <Solvents> The liquid crystal alignment agent of this disclosure contains, together with the polymer (P), the following first solvent and second solvent as solvent components: First solvent: A compound having a boiling point of 185°C or higher and having a cyclic amide structure or a cyclic ester structure. Second solvent: A compound having a boiling point of less than 185°C and a surface tension of 25 mN / m or less at 25°C.

[0073] (First Solvent) The first solvent is a component that contributes to improving the solubility of the polymer (P). In order to ensure sufficient solubility of the polymer (P), the boiling point of the first solvent is preferably 190°C or higher, and more preferably 195°C or higher. Furthermore, from the viewpoint of keeping the heating temperature during film formation as low as possible, the boiling point of the first solvent is preferably 300°C or lower, more preferably 280°C or lower, and even more preferably 250°C or lower. In this specification, the boiling point of the solvent is the value measured under conditions of 1 atmosphere.

[0074] The first solvent is at least one selected from the group consisting of compounds having a cyclic amide structure and compounds having a cyclic ester structure. The first solvent is typically a good solvent for polymer (P). Hereinafter, the determination of whether a solvent is a good or poor solvent for polymer (P) is made by adding 1 g of solvent Sp to 0.1 g of a 20% by mass polymer solution prepared by adding polymer (P) to the solvent Sp of the subject at 25°C. If no turbidity occurs, solvent Sp is determined to be a good solvent for polymer (P), and if turbidity occurs, solvent Sp is determined to be a poor solvent.

[0075] Compounds having a cyclic amide structure (hereinafter also referred to as "cyclic amides") and compounds having a cyclic ester structure (hereinafter also referred to as "cyclic esters") preferably have 5 to 7 ring members. Cyclic amides and cyclic esters may have substituents on the ring portion. Examples of substituents include monovalent hydrocarbon groups having 1 to 5 carbon atoms and monovalent groups containing -O- between the carbon-carbon bonds of the hydrocarbon group.

[0076] As the first solvent, a compound with relatively high surface tension can preferably be used. The surface tension of the first solvent at 25°C is preferably greater than 25 mN / m, more preferably 30 mN / m or more, and even more preferably 32 mN / m or more. The surface tension of the solvent is measured at 25°C using the Wilhelmy plate method.

[0077] Preferred specific examples of the first solvent include the compound represented by the following formula (3) and the compound represented by the following formula (4). (In equations (3) and (4), R ２１ and R ２２ These are, independently of each other, monovalent hydrocarbon groups having 1 to 5 carbon atoms, or monovalent groups containing -O- between the carbon-carbon bonds of said hydrocarbon groups. n is an integer from 1 to 3. m is an integer from 0 to 4.

[0078] In equations (3) and (4) above, R ２１ or R ２２The monovalent hydrocarbon group having 1 to 5 carbon atoms represented by is preferably a chain-like hydrocarbon group, and more preferably an alkyl group. Examples of monovalent groups containing -O- between carbon-carbon bonds in the hydrocarbon group include alkoxyalkyl groups having 1 to 5 carbon atoms and alkoxyalkoxyalkyl groups having 2 to 5 carbon atoms. ２１ Of the above, alkyl groups or alkoxyalkyl groups having 1 to 5 carbon atoms are preferred, and alkyl groups or alkoxyalkyl groups having 1 to 3 carbon atoms are more preferred. ２２ The alkyl group is preferably a C1-C5 alkyl group, and more preferably a C1-C3 alkyl group. n is preferably 1 or 2, and more preferably 1. m is preferably 0-2, and more preferably 0 or 1.

[0079] Specific examples of the first solvent include cyclic amides such as N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-(n-propyl)-2-pyrrolidone, N-isopropyl-2-pyrrolidone, N-(n-butyl)-2-pyrrolidone, N-(tert-butyl)-2-pyrrolidone, N-(n-pentyl)-2-pyrrolidone, N-methoxypropyl-2-pyrrolidone, N-ethoxyethyl-2-pyrrolidone, and N-methoxybutyl-2-pyrrolidone. Among these cyclic amides, N-ethyl-2-pyrrolidone, N-(n-pentyl)-2-pyrrolidone, N-(tert-butyl)-2-pyrrolidone, and N-methoxypropyl-2-pyrrolidone can be preferably used.

[0080] Examples of cyclic esters include γ-butyrolactone, γ-valerolactone, δ-valerolactone, and ε-caprolactone. Among these, γ-butyrolactone and γ-valerolactone are preferred.

[0081] In the liquid crystal alignment agent of this disclosure, the content of the first solvent is 30% by mass or more and 70% by mass or less of the total amount of solvent contained in the liquid crystal alignment agent. If the content of the first solvent is less than 30% by mass, the liquid crystal alignment agent applied to the substrate tends to dry out easily during the liquid crystal alignment film formation process. As a result, if temperature unevenness occurs during the heat treatment (especially pre-baking) during film formation, the distribution of specific side chains tends to become non-uniform within the plane of the liquid crystal alignment film, making it easy for display unevenness to occur. Furthermore, if the content of the first solvent exceeds 70% by mass, the wettability and spreadability of the liquid crystal alignment agent cannot be sufficiently ensured, and it tends to have poor contact hole coating properties.

[0082] From the viewpoint of ensuring sufficient process margin when forming the liquid crystal alignment film, the content of the first solvent is preferably 35% by mass or more, and more preferably 40% by mass or more, relative to the total amount of solvent contained in the liquid crystal alignment agent. Furthermore, from the viewpoint of achieving excellent contact hole coating properties, the content of the first solvent is preferably 65% ​​by mass or less, and more preferably 60% by mass or less, relative to the total amount of solvent contained in the liquid crystal alignment agent.

[0083] (Second Solvent) The second solvent is a component that contributes to improving the wettability of the liquid crystal alignment agent. In order to ensure sufficient process margin when manufacturing liquid crystal elements, the boiling point of the second solvent is preferably 182°C or lower, and more preferably 180°C or lower. Furthermore, from the viewpoint of improving the storage stability of the liquid crystal alignment agent, the boiling point of the second solvent is preferably 50°C or higher, more preferably 70°C or higher, and even more preferably 90°C or higher.

[0084] The surface tension of the second solvent at 25°C is 25 mN / m or less. By incorporating such a low-surface-tension solvent into the liquid crystal alignment agent, a liquid crystal alignment agent exhibiting good coatability (especially contact hole coatability) can be obtained. Furthermore, from the viewpoint of ensuring sufficient film thickness of the liquid crystal alignment film, the surface tension of the second solvent at 25°C is preferably 10 mN / m or more, and more preferably 15 mN / m or more.

[0085] As the second solvent, a poor solvent of the polymer (P) can preferably be used. Specifically, the second solvent is preferably at least one selected from the group consisting of alcohols, ketones, ethers, and linear esters.

[0086] Specific examples of these include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, 1-heptanol, 1-hexanol, 2-hexanol, 3-hexanol, 2-methyl-1-pentanol, and 2-octanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and diisobutyl ketone; ethers such as diethyl ether, dibutyl ether, diisopentyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether (PGME), and dipropylene glycol dimethyl ether; and chain esters such as methyl acetate, ethyl acetate, butyl acetate, isoamyl butyrate, and isoamyl propionate.

[0087] As the second solvent, at least one selected from the group consisting of 2-octanol, 1-hexanol, 2-methyl-1-pentanol, diisobutyl ketone, dibutyl ether, diisopentyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether, dipropylene glycol dimethyl ether, isoamyl butyrate, and isoamyl propionate is preferred, as it can further improve the coating properties (especially the coating properties for contact holes). Among these, at least one selected from the group consisting of 2-octanol, diisobutyl ketone, dibutyl ether, dipropylene glycol dimethyl ether, and isoamyl butyrate is more preferred, with diisobutyl ketone being particularly preferred.

[0088] In the liquid crystal alignment agent of this disclosure, the content of the second solvent is greater than 0% by mass and less than or equal to 30% by mass relative to the total amount of solvent contained in the liquid crystal alignment agent. If the content of the second solvent is 0% by mass (i.e., if the second solvent is not present), the wettability of the liquid crystal alignment agent will be insufficient. In this case, when the liquid crystal alignment agent is applied to a substrate in which contact holes are formed, unevenness and repulsion are likely to occur in the contact hole areas, which can easily lead to defects. Furthermore, if the content of the second solvent exceeds 30% by mass, the solubility of the polymer (P) cannot be sufficiently ensured, and when the liquid crystal alignment agent is applied to the substrate, repulsion and unevenness may occur, or whitening may occur in the resulting coating film.

[0089] From the viewpoint of ensuring sufficient wettability of the liquid crystal alignment agent and sufficiently suppressing coating defects around contact holes, the content of the second solvent is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, based on the total amount of solvent contained in the liquid crystal alignment agent. Furthermore, from the viewpoint of obtaining a highly transparent liquid crystal alignment film and ensuring sufficient process margin when forming the liquid crystal alignment film, the content of the second solvent is preferably 25% by mass or less, and more preferably 20% by mass or less, based on the total amount of solvent contained in the liquid crystal alignment agent.

[0090] The total amount of the first solvent and the second solvent contained in the liquid crystal alignment agent of this disclosure is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more, based on the total amount of solvent contained in the liquid crystal alignment agent, from the viewpoint of sufficiently obtaining the effect of improving the coatability and process stability of the liquid crystal alignment agent and sufficiently obtaining the effect of suppressing the whitening of the liquid crystal alignment film. The total amount of the first solvent and the second solvent can be any value of 100% by mass or less based on the total amount of solvent contained in the liquid crystal alignment agent.

[0091] (Third Solvent) The liquid crystal alignment agent of this disclosure may further contain a solvent component that is different from the first solvent and also different from the second solvent (hereinafter also referred to as the "third solvent"). The third solvent can be included in the liquid crystal alignment agent of this disclosure for the purpose of ensuring the solubility of the polymer in the solvent component or suppressing the decrease in product yield due to the precipitation of the polymer in the coating process.

[0092] As the third solvent, a poor solvent of the polymer (P) can preferably be used. The third solvent is preferably a compound having a boiling point of 185°C or higher, or a surface tension of more than 25 mN / m at 25°C, or a compound having a boiling point of 185°C or higher and a surface tension of more than 25 mN / m at 25°C, and more preferably at least one selected from the group consisting of alcohols, ethers, cyclic carbonates, and linear esters.

[0093] Specific examples of the third solvent include alcohols such as 2-heptanol, ethylene glycol, propylene glycol, 1,4-butanediol, triethylene glycol, diacetone alcohol, 3-methoxy-1-butanol, 3-methoxy-3-methylbutanol, and benzyl alcohol; ethers such as ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-i-propyl ether, ethylene glycol monobutyl ether (butyl cellosolve), ethylene glycol ethyl ether acetate, diethylene glycol diethyl ether, diethylene glycol butyl methyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol methyl ethyl ether, and propylene glycol monobutyl ether; and cyclic carbonates such as ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, vinylethylene carbonate, and 1,3-dioxan-2-one. Examples include chain-like esters such as diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate (PGMEA), methyl methoxypropionate, ethyl ethoxypropionate, isobutyl isobutyrate, diethyl oxalate, and diethyl malonate.

[0094] In the liquid crystal alignment agent of this disclosure, the content of the third solvent is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less, based on the total amount of solvent contained in the liquid crystal alignment agent. By setting the content of the third solvent within the above range, it is possible to sufficiently obtain the effect of improving the coatability and process stability of the liquid crystal alignment agent, as well as the effect of suppressing whitening of the liquid crystal alignment film. When the liquid crystal alignment agent of this disclosure contains the third solvent, the content of the third solvent may be, for example, 1% by mass or more, based on the total amount of solvent contained in the liquid crystal alignment agent.

[0095] <Other Components> The liquid crystal alignment agent of this disclosure may further contain components other than polymer (P) and solvent (hereinafter also referred to as "other components"). Examples of other components include polymers that do not have a cinnamate structure (hereinafter also referred to as "polymer (Q)"), crosslinking agents, adhesion aids, etc.

[0096] • Polymer (Q) Polymer (Q) can be any polymer that does not have a cinnamate structure, and its main skeleton is not particularly limited. Examples of polymer (Q) include polyamic acid, polyamic acid ester, polyimide, polyamine, polyenamine, polyamide, polyamideimide, polyurea, polyimine, polyorganosiloxane, polyester, polybenzoxazole precursor, polybenzoxazole, cellulose derivative, polyacetal, addition polymer, etc.

[0097] In terms of exhibiting good liquid crystal alignment and voltage retention characteristics when used in combination with polymer (P), polymer (Q) is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, polyimide, polyorganosiloxane, and addition polymer, and more preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide. Polyamic acid, polyamic acid ester, and polyimide as polymer (Q) can be obtained using the tetracarboxylic acid derivatives and other diamines exemplified in the description of polymer (P).

[0098] From the viewpoint of minimizing the use of fluorine, it is preferable that the content of structural units derived from monomers containing fluorine atoms in the polymer (Q) be as low as possible. Specifically, in the polymer (Q), the content of structural units derived from monomers containing fluorine atoms is preferably 10 mol% or less, more preferably 5 mol% or less, and even more preferably 1 mol% or less, relative to the total amount of structural units constituting the polymer (Q).

[0099] When polymer (Q) is included in the liquid crystal alignment agent, the content of polymer (Q) is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more, based on the total amount of polymer (P) and polymer (Q). Furthermore, the content of polymer (Q) is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less, based on the total amount of polymer (P) and polymer (Q).

[0100] - Crosslinking agent By further incorporating a crosslinking agent into the liquid crystal alignment agent of this disclosure, it is possible to further improve film strength and the reliability of liquid crystal elements. Examples of crosslinking agents include compounds having two or more groups in the molecule of at least one group selected from the group consisting of cyclic ether groups, cyclic thioether groups, isocyanate groups, protected isocyanate groups, methylol groups, protected methylol groups, hydroxyalkylamide groups, protected hydroxyalkylamide groups, cyclic carbonate groups, polymerizable carbon-carbon bond-containing groups, amino groups, and protected amino groups.

[0101] The number of crosslinking groups in one molecule of the crosslinking agent is preferably 2 to 10, and more preferably 2 to 6, from the viewpoint of sufficiently improving the reliability of the liquid crystal element. Furthermore, the molecular weight of the crosslinking agent is preferably 100 to 1,000, more preferably 100 to 800, and even more preferably 100 to 700.

[0102] Specific examples of crosslinking agents include compounds having a cyclic ether group or a cyclic thioether group, such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, triglycidyl isocyanurate, glycerol polyglycidyl ether, pentaerythritol tetraglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, N,N',N',N'-tetraglycidyl glycol uryl, 1,6-hexanediol diglycidyl ether, and trimeth Examples include rolpropane triglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, N,N-diglycidyl-benzylamine, N,N-diglycidyl-aminomethylcyclohexane, N,N-diglycidyl-cyclohexylamine, and epoxidation products of 2,2'-diallylbisphenol A diallyl ether with hydrogen peroxide.

[0103] Compounds having an isocyanate group or a protected isocyanate group include tolylene diisocyanate, xylylene diisocyanate, chlorphenyl diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, or compounds in which the isocyanate group of these compounds is protected with 3,6-dimethylpyrazole, methyl ethyl ketoxime, diethyl malonate, or ε-caprolactam, and compounds represented by the following formula (d1-1).

[0104] Examples of compounds having a methylol group or a protected methylol group include the compounds represented by formulas (d2-1) to (d2-5) below. Examples of compounds having a hydroxyalkylamide group or a protected hydroxyalkylamide group include the compounds represented by formulas (d3-1) to (d3-8) below. Examples of compounds having a cyclic carbonate group include the compounds represented by formulas (d4-1) and (d4-2) below.

[0105] Compounds having polymerizable carbon-carbon bond-containing groups include compounds having (meth)acryloyl groups, maleimide groups, alkenyl groups, vinylphenyl groups, vinyl ether groups, or 3-methylenetetrahydrofuran-2(3H)-on-5-yl groups. Specific examples of these include ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, pentaerythritol tri(meth)acrylate, and compounds represented by formulas (d5-1) to (d5-7) below. Compounds having amino groups or protected amino groups include compounds represented by formulas (d6-1) to (d6-5) below.

[0106] (In formula (d2-4), Ac is an acetyl group.)

[0107] When a crosslinking agent is included in the liquid crystal alignment agent of this disclosure, the crosslinking agent content is preferably 0.5 parts by mass or more per 100 parts by mass of the total amount of polymer (P) and polymer (Q) contained in the liquid crystal alignment agent, from the viewpoint of improving the mechanical properties of the liquid crystal alignment film and further improving the reliability of the liquid crystal element. From the above viewpoint, the crosslinking agent content is more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, per 100 parts by mass of the total amount of polymer (P) and polymer (Q). Furthermore, from the viewpoint of obtaining a liquid crystal element with good liquid crystal alignment and voltage holding characteristics, and from the viewpoint of improving the storage stability of the liquid crystal alignment agent, the crosslinking agent content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the total amount of polymer (P) and polymer (Q).

[0108] • Adhesion aids: Adhesion aids are components that improve the adhesion between the liquid crystal alignment film formed using a liquid crystal alignment agent and the substrate or sealing material. Functional silane coupling agents having reactive functional groups are preferably used as adhesion aids. Examples of reactive functional groups in functional silane coupling agents include carboxyl groups, (meth)acryloyl groups, oxyranyl groups, oxetanyl groups, vinyl groups, isocyanate groups, etc.

[0109] Specific examples of functional coupling agents include, for example, trimethoxysilyl benzoic acid, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, vinyltriacetoxysilane, vinyltrimethoxysilane, and 3-isocyanatepropyltriethoxysilane.

[0110] When the liquid crystal alignment agent of this disclosure contains an adhesion aid, the content of the adhesion aid is preferably 0.1 to 20 parts by mass, and more preferably 0.2 to 10 parts by mass, based on 100 parts by mass of the total amount of polymer (P) and polymer (Q) contained in the liquid crystal alignment agent.

[0111] Other components, in addition to those mentioned above, include, for example, antioxidants, metal chelating compounds, curing accelerators, surfactants, fillers, dispersants, photosensitizers, acid generators, base generators, and radical generators. The proportion of each of these components can be appropriately selected depending on the compound, as long as it does not impair the effects of this disclosure.

[0112] The solid content concentration in the liquid crystal alignment agent (the ratio of the total mass of components other than the solvent in the liquid crystal alignment agent to the total mass of the liquid crystal alignment agent) is appropriately selected considering viscosity, volatility, etc., but is preferably in the range of 1 to 10% by mass. That is, the liquid crystal alignment agent is applied to the substrate surface as described later, 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. When the solid content concentration is 1% by mass or more, the film thickness of the coating film can be sufficiently secured, and a good liquid crystal alignment film tends to be obtained. When the solid content concentration is 10% by mass or less, the film thickness of the coating film does not become excessive, and the increase in viscosity of the liquid crystal alignment agent can be suppressed, and the coatability tends to be good.

[0113] The preferred range of solid content concentration varies depending on the application of the liquid crystal alignment agent and the method used to coat the liquid crystal alignment agent onto the substrate. For example, when applying a liquid crystal alignment agent for a liquid crystal display element to a substrate using the spinner method, the solid content concentration (the ratio of the total mass of all components other than the solvent in the liquid crystal alignment agent to the total mass of the liquid crystal alignment agent) is particularly preferred to be in the range of 1.5 to 4.5% by mass. When using the printing method, the solid content concentration is particularly preferred to be in the range of 3 to 9% by mass, thereby resulting in a solution viscosity in the range of 12 to 50 mPa·s. When using the inkjet method, the solid content concentration is particularly preferred to be in the range of 1 to 5% by mass, thereby resulting in a solution viscosity in the range of 3 to 15 mPa·s. The temperature when preparing the liquid crystal alignment agent is preferably 10 to 50°C, and more preferably 20 to 30°C. Furthermore, with respect to the liquid crystal alignment agent for phase difference films, from the viewpoint of ensuring appropriate coatability and film thickness of the formed coating, the solid content concentration of the liquid crystal alignment 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.

[0114] ≪Liquid Crystal Alignment Film and Liquid Crystal Element≫ The liquid crystal alignment film of this disclosure is formed from a liquid crystal alignment agent prepared as described above. The liquid crystal element of this disclosure has 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 can be applied to various modes such as TN type, STN type, VA type (including VA-MVA type, VA-PVA type, etc.), IPS (In-Plane Switching) type, FFS (Fringe Field Switching) type, OCB (Optically Compensated Bend) type, and PSA (Polymer Sustained Alignment) type. The liquid crystal element can be manufactured by a method including, for example, the following steps 1 to 3. In step 1, the substrate used differs depending on the desired operating mode. Steps 2 and 3 are common to each operating mode.

[0115] <Step 1: Formation of Coating Film> First, a liquid crystal alignment agent is applied to the substrate, and preferably the coated surface is heated to form a coating film on the substrate. As the substrate, for example, glass such as float glass or soda glass; a transparent substrate made of resin such as polyethylene terephthalate, polybutylene terephthalate, polyethersulfone, polycarbonate, or poly(alicyclic olefin) can be used. When manufacturing TN type, STN type, or VA type liquid crystal elements, two substrates with patterned transparent conductive films are used. On the other hand, when manufacturing IPS type or FFS type liquid crystal elements, a substrate with comb-shaped patterned electrodes and a counter substrate without electrodes are used. As the transparent conductive film, tin oxide (SnO ２ ) consisting of NESA film (registered trademark of PPG Corporation, USA), indium oxide-tin oxide (In ２ O ３ -SnO ２ An ITO film or the like can be used. The liquid crystal alignment agent is applied to the substrate surface, preferably by offset printing, flexographic printing, spin coating, roll coating, or inkjet printing.

[0116] After applying the liquid crystal alignment agent, preheating (pre-bake) is preferably performed to prevent dripping of the applied liquid crystal alignment agent. The pre-bake temperature is preferably 30 to 200°C, and the pre-bake time is preferably 0.25 to 10 minutes. Subsequently, a baking (post-bake) process is performed to remove the solvent in the applied liquid crystal alignment agent. The baking temperature (post-bake temperature) at this time is preferably 80 to 250°C, more preferably 80 to 200°C. The post-bake time is preferably 5 to 200 minutes. The thickness of the film formed in this way is preferably 0.001 to 1 μm.

[0117] <Step 2: Alignment Treatment> When manufacturing TN-type, STN-type, IPS-type, or FFS-type liquid crystal elements, a treatment (alignment treatment) is performed to impart liquid crystal alignment ability to the coating film formed in Step 1. This imparts the liquid crystal molecule alignment ability to the coating film, making it a liquid crystal alignment film. As alignment treatments, rubbing treatments can be used, in which the coating film formed on the substrate is rubbed in a certain direction with a roll wrapped with a cloth made of fibers such as nylon, rayon, or cotton; or photo-alignment treatments, in which the coating film formed on the substrate is irradiated with light to impart liquid crystal alignment ability to the coating film. Since the liquid crystal alignment agent of this disclosure contains a polymer (P), photo-alignment treatment is particularly preferable as the alignment treatment. When manufacturing vertically aligned (VA) type liquid crystal elements, the coating film formed in Step 1 can be used as is as a liquid crystal alignment film. Furthermore, to further enhance the liquid crystal alignment ability, an alignment treatment may be applied to the coating film. A liquid crystal alignment film suitable for vertically aligned liquid crystal elements is also suitable for PSA-type liquid crystal elements.

[0118] In the photo-alignment process, light irradiation can be performed by methods such as irradiating the coating film after the post-bake process; irradiating the coating film after the pre-bake process but before the post-bake process; or irradiating the coating film while it is being heated in at least one of the pre-bake or post-bake processes. As radiation to irradiate the coating film, for example, ultraviolet light and visible light including wavelengths of 150 to 800 nm can be used. Preferably, ultraviolet light including wavelengths of 200 to 400 nm is used. If the radiation is polarized, it may be linearly polarized or partially polarized. If the radiation used is linearly polarized or partially polarized, irradiation may be performed from a direction perpendicular to the substrate surface, from an oblique direction, or a combination of these. In the case of unpolarized radiation, the irradiation direction should be oblique.

[0119] 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 to the substrate surface is preferably 400 to 50,000 J / m². ２ More preferably, 1,000 to 20,000 J / m ２ In addition, after light irradiation to impart orientation ability, the substrate surface may be washed with, for example, water, an organic solvent (e.g., methanol, isopropyl alcohol, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, etc.), or a mixture thereof, or the substrate may be heated.

[0120] <Step 3: Construction of Liquid Crystal Cells> Two substrates on which liquid crystal alignment films have been formed as described above are prepared, and a liquid crystal cell is manufactured between the two substrates so that liquid crystal is arranged adjacent to the liquid crystal alignment film. Methods for manufacturing a liquid crystal cell include, for example, placing two substrates opposite each other with a gap in between so that the liquid crystal alignment films face each other, bonding the periphery of the two substrates with a sealant, injecting and filling the cell gap surrounded by the substrate surface and the sealant, and sealing the injection hole; the ODF method; etc. As the sealant, epoxy resin containing a curing agent and aluminum oxide spheres as spacers can be used. As the liquid crystal, nematic liquid crystals and smectic liquid crystals can be used, with nematic liquid crystals being preferred. In PSA mode, a liquid crystal cell is constructed by placing a photopolymerizable compound together with liquid crystal between the two substrates, and after the construction of the liquid crystal cell, a voltage is applied between the conductive films of the pair of substrates, and the liquid crystal cell is irradiated with light.

[0121] For each mode of liquid crystal cell, a polarizing plate is then attached to the outer surface of the liquid crystal cell as needed to form a liquid crystal element. Examples of polarizing plates include a polarizing plate made by sandwiching a polarizing film called an "H film," which is made by stretching and oriented polyvinyl alcohol while absorbing iodine, between cellulose acetate protective films, or a polarizing plate made of the H film itself.

[0122] The liquid crystal elements disclosed herein can be effectively applied to a variety of applications. Specifically, they can be applied to various display devices such as watches, portable game consoles, word processors, notebook computers, car navigation systems, camcorders, PDAs, digital cameras, mobile phones, smartphones, various monitors, liquid crystal televisions, information displays, as well as dimming films, phase difference films, and the like.

[0123] The present invention will be described in detail below with reference to examples, but it is not limited to the following examples.

[0124] In the following example, the imidation rate of polyimide, the weight-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of the polymer were measured by the following method. [Imidation rate of polyimide] A solution of polyimide was added to pure water, and the resulting precipitate was thoroughly dried under reduced pressure at room temperature. Then it was dissolved in deuterated dimethyl sulfoxide, and tetramethylsilane was used as a reference substance at room temperature. １ H-NMR was measured. １ The imidization rate [%] was determined from the 1H-NMR spectrum (400 MHz) using the following formula (1): Imidization rate [%] = (1 - α × A) １ / A ２ ) × 100 … (1) (In formula (1), A １ This represents the peak area of ​​protons originating from the amide group of the amico acid, appearing around a chemical shift of 10 ppm. ２ α represents the peak area of ​​protons originating from aromatic groups appearing around chemical shift 6–9 ppm. α is the ratio of protons from aromatic groups to one proton from the amide group of the amic acid in the polymer precursor (polyamic acid).

[0125] The compounds used in the following examples are shown below. For convenience, in the following, "compound represented by formula (X)" may simply be referred to as "compound (X)".

[0126] ・Tetracarboxylic acid dianhydride

[0127] Cinnamate structure-containing diamines

[0128] Other diamines

[0129] • Additives

[0130] 1. Synthesis of Polymers [Synthesis Example 1] Under a stream of dry nitrogen, 50 mole parts of compound (RD-1), 10 mole parts of compound (DA-1), and 40 mole parts of compound (DA-5) were dissolved in 20 g of N-methyl-2-pyrrolidone (NMP) as diamines. To this, 100 mole parts of compound (TA-1) as a tetracarboxylic dianhydride were added, and the mixture was reacted at 40°C for 6 hours. This yielded a solution containing 20% ​​by mass of the target polyamic acid (referred to as "polymer (PI-1)").

[0131] [Synthesis Examples 3, 5, 7-15, 17] Polymerization was carried out in the same manner as in Synthesis Example 1, except that the types and amounts of tetracarboxylic dianhydrides and diamines used in polymerization were changed as shown in Table 1, to obtain polymers (PI-3) to (PI-5), (PI-7) to (PI-15), and (PI-17), which are polyamic acids. In Table 1, the values ​​in the column for acidic dianhydrides represent the molar ratio of each compound used relative to 100 moles of the total amount of tetracarboxylic dianhydrides used in synthesis. The values ​​in the columns for cinnamate structure-containing diamines and other diamines represent the molar ratio of each compound used relative to 100 moles of the total amount of diamines used in synthesis.

[0132] [Synthesis Example 2] Polymerization was carried out in the same manner as in Synthesis Example 1 to obtain a solution containing 20% ​​by mass of polyamic acid. To the obtained solution, 0.50 molar equivalents of 1-methylpiperidine and acetic anhydride were added relative to the carboxyl groups of the polyamic acid as dehydrating agents, and the mixture was heated and stirred at 60°C for 3 hours. The obtained solution was repeatedly concentrated under reduced pressure and diluted with NMP to obtain a 15% by mass solution of the target polyimide (referred to as "polymer (PI-2)"). The imidization rate of polymer (PI-2) was 55%.

[0133] [Synthesis Examples 4, 6, 16] Polymers (PI-4), (PI-6), and (PI-16), which are polyimides, were obtained in the same manner as in Synthesis Example 2, except that the types and molar ratios of tetracarboxylic dianhydride and diamine were changed as shown in Table 1.

[0134]

[0135] 2. Manufacturing and Evaluation of Optically Perpendicular Liquid Crystal Display Elements [Example 1] (1) Preparation of Liquid Crystal Alignment Agent (AL-1) A mixture of 20 parts by mass of polymer (PI-1) obtained in Synthesis Example 1 and 100 parts by mass (solid content of polymer) of polymer (PI-15) obtained in Synthesis Example 15 was mixed with N-ethyl-2-pyrrolidone (NEP), N-methyl-2-pyrrolidone (NMP), 2-octanol (2ON), diethylene glycol diethyl ether (DEDG), and butyl cellosolve (BC) as solvents, to obtain a solution with a solvent composition of NEP / NMP / 2ON / DEDG / BC = 20 / 30 / 5 / 20 / 25 (mass ratio) and a solid content concentration of 4.0% by mass. Liquid crystal alignment agent (AL-1) was prepared by filtering this solution through a filter with a pore size of 0.5 μm.

[0136] (2) Evaluation of the appearance of the coating The liquid crystal alignment agent (AL-1) was stored in a refrigerator at 4°C for one month and then returned to room temperature. The liquid crystal alignment agent, which had returned to room temperature, was continuously coated onto an ITO substrate using a JET-CM continuous inkjet printer (manufactured by Kishu Giken Kogyo Co., Ltd.) at a volume that resulted in a dry film thickness of 0.1 μm. The time required from the start of coating the liquid crystal alignment agent to the completion of coating the entire substrate surface and baking was 10 minutes. The substrate coated with the liquid crystal alignment agent was pre-baked on a hot plate at 90°C for 1 minute, and then post-baked at 230°C for 30 minutes in a clean oven under a nitrogen atmosphere. After that, the coating on the substrate was visually observed. If whitening of the coating occurred at this point, it was evaluated as "unacceptable (××)" and no further evaluation was performed. If the coating was transparent, the peripheral and central parts of the coating were observed with a 20x microscope. In this study, the presence or absence of pinholes and uneven coating (such as uneven film thickness) was judged as "good (○)", the presence of one or more but less than three pinholes and uneven coating locations was judged as "acceptable (△)", and the presence of three or more pinholes and uneven coating locations was judged as "poor (×)". As a result, the appearance of the coating film in this example was evaluated as "good (○)".

[0137] (3) Evaluation of contact hole coating properties The liquid crystal alignment agent (AL-1) was stored in a refrigerator at 4°C for one month, and then returned to room temperature. The liquid crystal alignment agent returned to room temperature was filled into a Shibaura inkjet device, and inkjet coating was performed on a glass substrate having contact holes (C / H) and an ITO layer. The contact holes were formed by coating a photosensitive resin onto the glass substrate to form a resin layer with a thickness of 3.5 μm, exposing it through a mask to create a hole diameter of 25 μm and an inter-hole distance of 200 μm, and then developing it. After the contact holes were formed, an ITO layer was formed on the contact hole formation surface of the glass substrate by sputtering. After coating the glass substrate with the liquid crystal alignment agent (AL-1), it was then pre-baked on a hot plate at 90°C for one minute. Subsequently, it was heated in an oven with nitrogen purged at 230°C for one hour to form a liquid crystal alignment film with a thickness of 0.1 μm. The contact holes of this liquid crystal alignment film were visually inspected using a scanning electron microscope (SEM) at 50x magnification, counting 200 holes. The contact hole coating performance was evaluated based on the percentage of contact holes where coating defects occurred (coating defect rate [%]). Coating defect rate [%] = [(Number of contact holes with coating defects) / 200] × 100 A coating defect rate of 0% was evaluated as "Excellent (◎)", a rate between 0% and 10% was evaluated as "Good (○)", a rate between 10% and 20% was evaluated as "Acceptable (△)", and a rate above 20% was evaluated as "Poor (×)". As a result, the contact hole coating performance of this example was evaluated as "Good (○)".

[0138] (4) Manufacturing of optically perpendicular liquid crystal display elements The liquid crystal alignment agent (AL-1) prepared above was applied to the transparent electrode surface of a glass substrate with a transparent electrode made of ITO film using a spinner, and pre-baked on a hot plate at 90°C for 1 minute. Then, it was heated in an oven with nitrogen purged at 230°C for 1 hour to form a coating film with a thickness of 0.1 μm. Next, polarized ultraviolet light containing an emission line of 313 nm was applied to the surface of this coating film at 200 J / m using an Hg-Xe lamp and a Gran-Taylor prism. ２The substrate was irradiated with a light source at a 40° angle from the substrate normal to impart liquid crystal alignment capability. The same operation was repeated to create a pair (two) of substrates with a liquid crystal alignment film. Next, an epoxy resin adhesive containing 3.5 μm diameter aluminum oxide spheres was screen printed onto the outer circumference of the surface of one of the substrates that had the liquid crystal alignment film. Then, the liquid crystal alignment film surfaces of the pair of substrates were placed facing each other, and they were pressed together so that the projection direction of the ultraviolet light axis of each substrate onto the substrate surface was opposite parallel. The adhesive was then heat-cured at 150°C for one hour. Next, negative liquid crystal (Merck MLC-6608) was filled into the gap between the substrates through the liquid crystal injection port, and the liquid crystal injection port was sealed with epoxy adhesive. Furthermore, to eliminate the flow orientation during liquid crystal injection, this was heated to 130°C and then slowly cooled to room temperature to obtain a liquid crystal cell. Next, a liquid crystal display element was manufactured by bonding polarizing plates to both outer surfaces of the substrate such that their polarization directions are orthogonal to each other and that they form a 45° angle with the projection direction of the ultraviolet light axis of the liquid crystal alignment film onto the substrate surface.

[0139] (5) Evaluation of process stability (pre-bake margin) Liquid crystal cells were manufactured by fabricating liquid crystal alignment films at different pre-bake temperatures (45°C and 90°C), and the pre-tilt angles of the liquid crystal cells were measured. The difference Δθ between the measured pre-tilt angles was determined, and process stability was evaluated based on Δθ. The smaller Δθ, the smaller the variation in the pre-tilt angle due to temperature unevenness during pre-bake, and the better the process stability. The pre-tilt angle was measured in accordance with the method described in Non-Patent Literature (T. J. Scheffer et al. J. Appl. Phys. vol. 19, p. 2013 (1980)), using a crystal rotation method with He-Ne laser light. The value of the tilt angle of the liquid crystal molecules from the substrate surface was defined as the pre-tilt angle [°]. The evaluation criteria were as follows: Δθ less than 0.10° was rated "Good (○)", Δθ between 0.10° and 0.15° was rated "Acceptable (△)", and Δθ greater than or equal to 0.15° was rated "Poor (×)". As a result, the process stability of this embodiment was rated "Good (○)".

[0140] [Examples 2-28 and Comparative Examples 1-12] Liquid crystal alignment agents were 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 2. The obtained liquid crystal alignment agents were also evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3. In Table 3, the "-" notation in the columns for contact hole coating properties and process stability indicates that these evaluations were not performed because the evaluation of the coating film appearance was unsatisfactory.

[0141]

[0142] In Table 2, the abbreviations for additives and solvents represent the following compounds. The surface tension of the solvent is measured at 25°C using the Wilhelmy plate method. (Additives) Add-1 to Add-6: Compounds represented by the above formulas (Add-1) to (Add-6) Add-7: Silicone-based surfactant (product name "SH8400FLUID", manufactured by Toray Dow Corning Silicone Co., Ltd.) (Solvents) ・First solvent NEP: N-ethyl-2-pyrrolidone (boiling point: 218°C, surface tension: 37 mN / m) GBL: γ-butyrolactone (boiling point: 204°C, surface tension: 44 mN / m) NMP: N-methyl-2-pyrrolidone (boiling point: 202°C, surface tension: 41 mN / m) ・Second solvent 2ON: 2-octanol (boiling point: 179°C, surface tension: 25 mN / m) DMM: Dipropylene glycol dimethyl ether (boiling point: 171°C, surface tension: 25 mN / m) DIBK: Diisobutyl ketone (boiling point: 169°C, surface tension: 24 mN / m) DBE: Dibutyl ether (boiling point: 142°C, surface tension: 23 mN / m) MBA: Isoamyl butyrate (boiling point: 142°C, surface tension: 24 mN / m) Third solvent PC: Propylene carbonate (boiling point: 242°C, surface tension: 41 mN / m) BDM: Diethylene glycol butyl methyl ether (boiling point: 212°C, surface tension: 24 mN / m) DEDG: Diethylene glycol diethyl ether (boiling point: 189°C, surface tension: 25 mN / m) BC: Butyl cellosolve (boiling point: 170°C, surface tension: 28 mN / m) PNB: Propylene glycol monobutyl ether (boiling point: 170°C, surface tension: 28 mN / m) DAA: Diacetone alcohol (boiling point: 168°C, surface tension: 30 mN / m) MB: 3-Methoxy-1-butanol (boiling point: 161°C, surface tension: 29 mN / m) 2HN: 2-Heptanol (boiling point: 160°C, surface tension: 30 mN / m) IB: Isobutyl isobutyrate (boiling point: 147°C, surface tension: 28 mN / m)

[0143]

[0144] As shown in Table 3, the liquid crystal alignment agents of Examples 1 to 28, which contain a polymer without a fluorinated alkyl group at the end of the cinnamate side chain and contain the first solvent and the second solvent in predetermined proportions, all showed a well-balanced improvement in various properties such as coating appearance, contact hole coating properties, and process stability.

[0145] In contrast, among liquid crystal alignment agents containing polymers that do not have fluorinated alkyl groups at the end of the cinnamate side chain, the liquid crystal alignment agents of Comparative Examples 10 to 12, which did not contain a second solvent, showed good coating film appearance and process stability, but poor contact hole coating performance (×), which was inferior to Examples 1 to 28. Furthermore, the liquid crystal alignment agents of Comparative Examples 1 to 3, in which the second solvent content was 35% by mass of the total solvent, showed whitening of the coating film, resulting in a poor coating film appearance. The liquid crystal alignment agents of Comparative Examples 4 to 6, in which the first solvent content was 25% by mass of the total solvent, showed poor process stability, and the liquid crystal alignment agents of Comparative Examples 7 to 9, in which the first solvent content was 80% by mass of the total solvent, showed poor contact hole coating performance.

[0146] From the above results, it has become clear that by including a first solvent and a second solvent in predetermined amounts in a liquid crystal alignment agent containing a polymer that does not have a fluorinated alkyl group at the end of the cinnamate side chain, it is possible to obtain a liquid crystal alignment film that exhibits good contact hole coating properties, has excellent transparency, and has excellent process stability.

Claims

1. A liquid crystal alignment agent comprising: a polymer (P) having a side chain containing a cinnamate structure and having no fluorinated alkyl group at the end of the side chain; a solvent; wherein the solvent comprises a first solvent having a boiling point of 185°C or higher and having a cyclic amide structure or a cyclic ester structure; and a second solvent having a boiling point of less than 185°C and a surface tension of 25 mN / m or less at 25°C; wherein the content of the first solvent is 30% by mass or more and 70% by mass or less of the total amount of the solvent; and the content of the second solvent is greater than 0% by mass and 30% by mass or less of the total amount of the solvent.

2. The liquid crystal alignment agent according to claim 1, wherein the polymer (P) comprises structural units derived from a diamine having a monovalent group containing a cinnamate structure, and the monovalent group does not have a fluorinated alkyl group at its terminal end.

3. The liquid crystal alignment agent according to claim 1, wherein the polymer (P) is at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide.

4. The liquid crystal alignment agent according to claim 1, further comprising a polymer (Q) that does not have a cinnamate structure.

5. The liquid crystal alignment agent according to claim 4, wherein the polymer (Q) is at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide.

6. The liquid crystal alignment agent according to claim 1, wherein the second solvent is at least one selected from the group consisting of alcohols, ketones, ethers, and linear esters.

7. The liquid crystal alignment agent according to claim 1, further comprising a third solvent different from the first and second solvents.

8. A liquid crystal alignment film formed with the liquid crystal alignment agent described in any one of claims 1 to 7.

9. A method for manufacturing a liquid crystal alignment film, comprising forming a coating film with a liquid crystal alignment agent according to any one of claims 1 to 7, and subjecting the coating film to an alignment treatment to impart liquid crystal alignment ability.

10. A liquid crystal element comprising the liquid crystal alignment film described in claim 8.

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