Liquid crystal alignment agent, liquid crystal alignment film, liquid crystal element, and method for manufacturing the same

Abstract

To provide a liquid crystal alignment agent that enables low-voltage driving of liquid crystal elements, forms a liquid crystal alignment film with excellent adhesion, and exhibits excellent coatability. [Solution] A liquid crystal alignment agent containing an addition polymer [P] comprising a structural unit [A] having a hydroxyl group bonded to a carbon atom in a chain structure or an aliphatic ring (excluding carbon atoms in the carbonyl group and carbon atoms constituting the main chain of the polymer), and a structural unit [B] having a substructure represented by formula (1) and different from the structural unit [A].

Description

Technical Field

[0001] The present invention relates to a liquid crystal aligning agent, a liquid crystal alignment film, a liquid crystal element, and a method for manufacturing the same.

Background Art

[0002] In a liquid crystal element, the initial alignment of liquid crystal molecules is generally defined by the anchoring of liquid crystal molecules by a liquid crystal alignment film. In recent years, in liquid crystal elements with a horizontal alignment mode such as the IPS type or the FFS type, a liquid crystal alignment film having strong anchoring energy (hereinafter, also referred to as "strong anchoring liquid crystal alignment film") is formed on one of a pair of substrates, and a liquid crystal alignment film having no anchoring energy or very small anchoring energy (hereinafter, also referred to as "weak anchoring liquid crystal alignment film") is formed on the other substrate. Various liquid crystal elements have been proposed. In a liquid crystal element utilizing a weak anchoring state, it is possible to achieve an improvement in brightness and contrast ratio, low voltage driving, high-speed response (fast rise), etc. compared to a normal liquid crystal element in which strong anchoring liquid crystal alignment films are formed on both substrates, and further improvement is expected. Note that "weak anchoring" is also referred to as "zero surface anchoring".

[0003] For example, Patent Document 1 discloses a method for forming a zero surface anchoring film on a first substrate by a method including a step of applying an energy sufficient for a polymerization reaction of a radically polymerizable compound to a liquid crystal composition containing a liquid crystal and a radically polymerizable compound in a state of contacting a radical generating film, and forming a liquid crystal alignment film on the second substrate with a known liquid crystal aligning agent to manufacture a liquid crystal cell.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technology described in Patent Document 1, the fabrication of a weakly anchored liquid crystal alignment film requires a step in which a liquid crystal composition containing liquid crystal and a radical polymerizable compound is brought into contact with a radical generating film formed on a first substrate, and sufficient energy is provided to cause a polymerization reaction of the radical polymerizable compound in that state, which does not result in good production efficiency. Therefore, it is desirable to obtain a liquid crystal element that can achieve low-voltage driving derived from a weakly anchored state and exhibit good liquid crystal alignment properties using conventional simple fabrication methods such as inkjet coating.

[0006] In recent years, in addition to mobile applications such as smartphones and tablet PCs, bezel narrowing has been pursued for large-screen televisions and PC monitors from the perspectives of design and miniaturization of display devices. One method for achieving bezel narrowing is to form a liquid crystal alignment film over the entire substrate surface, and then apply a sealant on the liquid crystal alignment film to bond the substrates together. On the other hand, placing a sealant on the liquid crystal alignment film tends to reduce the adhesion between substrates, raising concerns that the substrates may easily peel off due to external forces.

[0007] However, achieving both low-voltage drive and inkjet coating properties and adhesion is difficult, and there is still room for further improvement in liquid crystal alignment agents and liquid crystal elements.

[0008] The present invention has been made in view of the above problems, and its main objective is to provide a liquid crystal alignment agent that can drive liquid crystal elements at a low voltage, form a liquid crystal alignment film with excellent adhesion, and has excellent coatability. [Means for solving the problem]

[0009] According to the present invention, the following liquid crystal alignment agents, liquid crystal alignment films, liquid crystal elements, and methods for manufacturing the same are provided.

[0010] [1] A liquid crystal alignment agent comprising a structural unit [A] having a hydroxyl group bonded to a carbon atom in a chain structure or an aliphatic ring (excluding carbon atoms in a carbonyl group and carbon atoms constituting the main chain of the polymer), and an addition polymer [P] having a substructure represented by the following formula (1) and different from the structural unit [A]. * 1 -CO-OR 1 …(1) (In formula (1), R 1 It is a monovalent, chain-like hydrocarbon group with a branched structure. 1 (This symbol represents a bond with a carbon atom that makes up the main chain of the polymer.)

[0011] [2] A liquid crystal alignment film formed using the liquid crystal alignment agent described in [1] above. [3] A liquid crystal element comprising the liquid crystal alignment film described in [2] above. [4] A method for manufacturing a liquid crystal element comprising a pair of substrates consisting of a first substrate and a second substrate, and a liquid crystal layer disposed between the pair of substrates, the method comprising the step of applying the liquid crystal alignment agent of [1] to the surface of one of the pair of substrates to form a liquid crystal alignment film. [Effects of the Invention]

[0012] The liquid crystal alignment agent of the present invention enables low-voltage driving of liquid crystal elements and the formation of a liquid crystal alignment film with excellent adhesion. Furthermore, the liquid crystal alignment agent of the present invention exhibits excellent coatability. [Brief explanation of the drawing]

[0013] [Figure 1] Schematic diagram of an FFS type liquid crystal display element. [Figure 2] A schematic plan view of the top electrode used in the manufacturing of a liquid crystal display element. (a) is a top view of the top electrode, and (b) is a magnified view of a portion of the top electrode. [Figure 3] A diagram showing four drive electrodes. [Modes for carrying out the invention]

[0014] Liquid crystal alignment agent The liquid crystal alignment agent of this disclosure contains an addition polymer (hereinafter also referred to as "addition polymer [P]") comprising two types of structural units having a specific structure (hereinafter also referred to as "structural unit [A]" and "structural unit [B]", respectively). The components contained in the liquid crystal alignment agent of this disclosure, and other components that may be optionally added as needed, are described below. Unless otherwise specified, each component may be used alone or in combination of two or more. Furthermore, in this specification, numerical ranges indicated using "~" include the values ​​indicated before and after "~" as the lower and upper limits, respectively.

[0015] Herein, in this specification, "hydrocarbon group" means a group of hydrocarbons that 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, linear hydrocarbon groups 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, an alicyclic hydrocarbon group does not have to consist only of the structure of an alicyclic hydrocarbon, and may also include 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, an aromatic hydrocarbon group does not have to consist only of an aromatic ring structure, and may also include a linear structure or an alicyclic hydrocarbon structure as part of it. "Aromatic ring" means an aromatic hydrocarbon ring and an aromatic heterocycle. "Organic group" means an atomic group obtained by removing any hydrogen atom from a carbon-containing compound (i.e., an organic compound).

[0016] The "main chain" of a polymer refers to the "trunk" portion of the polymer, 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. A "side chain" refers to a portion of a polymer that branches off from the "trunk" portion. A "structural unit" is a unit that mainly constitutes the main chain structure and is present in the main chain structure in groups of two or more. Structural units are typically monomeric units. However, a monomeric unit having a reactive group is also included as a "structural unit" if it is reacted with a compound having a functional group that can react with that reactive group. "(meth)acrylic" is a term that encompasses acrylic and methacrylic, and "(meth)acrylo" is a term that encompasses acrylo and methacrylo.

[0017] <Addition polymer [P]> The addition polymer [P] contained in the liquid crystal alignment agent of this disclosure is a polymer containing structural units derived from monomers having polymerizable unsaturated carbon-carbon bonds, and is not particularly limited as long as it contains structural units [A] and structural units [B]. In other words, it is sufficient if one or more of the monomers constituting the addition polymer [P] are monomers that give structural unit [A], and one or more of the monomers constituting the addition polymer [P] are monomers that give structural unit [B]. Examples of addition polymers [P] include polymers whose main skeleton is a (meth)acrylic polymer, a (meth)acrylic-styrene copolymer, a (meth)acrylic-maleimide copolymer, a (meth)acrylic-styrene-maleimide copolymer, a (meth)acrylic-vinyl ether-maleic anhydride copolymer, and a (meth)acrylic-styrene-maleamide copolymer, and which contain structural units [A] and structural units [B].

[0018] (Structural unit [A]) The structural unit [A] has a hydroxyl group bonded to a carbon atom in a chain structure or in an aliphatic ring (excluding the carbon atom in the carbonyl group and the carbon atoms constituting the main chain of the polymer). For the structural unit [A], it is sufficient that the carbon atom to which the hydroxyl group is bonded is a carbon atom in a chain structure or in an aliphatic ring (excluding the carbon atom in the carbonyl group and the carbon atoms constituting the main chain of the polymer), and it may have a carbonyl group or an aromatic ring. Further, the carbon atom to which the hydroxyl group is bonded may be directly bonded to the main chain of the addition polymer [P], or may be bonded to the main chain of the addition polymer [P] via a divalent organic group.

[0019] Examples of the chain structure containing the carbon atom to which the hydroxyl group is bonded include, for example, a chain hydrocarbon group, -O-, -CO-, -COO-, -NR 11 -, or -CO-NR 11 -containing groups, and groups in which some of the hydrogen atoms thereof are replaced by halogen atoms (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.). Examples of the aliphatic ring containing the carbon atom to which the hydroxyl group is bonded include, for example, an aliphatic hydrocarbon ring, an aliphatic heterocyclic ring, and rings in which some of the hydrogen atoms thereof are replaced by halogen atoms. R 11 is a hydrogen atom or a monovalent chain hydrocarbon group having 1 to 10 carbon atoms.

[0020] The hydroxyl group possessed by the structural unit [A] is preferably bonded to a carbon atom in a chain structure (excluding the carbon atom in the carbonyl group and the carbon atoms constituting the main chain of the polymer), and more preferably exists as a hydroxyl group constituting a hydroxyalkyl group. The number of hydroxyl groups possessed by the structural unit [A] may be 1 or more, preferably 1 or 2, and more preferably 1.

[0021] Preferred specific examples of the structural unit [A] include structural units having a partial structure represented by the following formula (2). * 2 -CO-O-A 1 -C(B 1 )(B 2)-OH …(2) (In formula (2), A 1 This is a single bond or a divalent organic group. 1 and B 2 These are, independently of each other, a hydrogen atom, a halogen atom, or a monovalent organic group. 2 (This symbol represents a bond with a carbon atom that makes up the main chain of the polymer.)

[0022] In the above equation (2), A 1 The divalent organic groups represented by include substituted or unsubstituted divalent hydrocarbon groups, and -O-, -CO-, -COO-, -NR between the carbon-carbon bonds in substituted or unsubstituted divalent hydrocarbon groups. 12 -, or -CO-NR 12 Examples of divalent groups include divalent groups containing -. Examples of divalent hydrocarbon groups include divalent chain hydrocarbon groups having 1 to 20 carbon atoms, divalent alicyclic hydrocarbon groups having 3 to 12 carbon atoms, and divalent aromatic hydrocarbon groups having 6 to 10 carbon atoms. Examples of substituents introduced into divalent hydrocarbon groups include hydroxyl groups and halogen atoms. A 1 From the viewpoint of low-voltage driving, a single bond or a divalent organic group without an aromatic ring is preferred, a substituted or unsubstituted divalent linear hydrocarbon group is preferred, a substituted or unsubstituted divalent linear hydrocarbon group containing -O- or -CO- between carbon-carbon bonds is more preferred, an alkanediyl group is even more preferred, an alkanediyl group having 1 to 5 carbon atoms is even more preferred, and a linear alkanediyl group having 1 to 5 carbon atoms is particularly preferred. R 12 This is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

[0023] B 1 and B 2 The monovalent organic groups represented by each of these include substituted or unsubstituted monovalent hydrocarbon groups, and -O-, -CO-, -COO-, and -NR between the carbon-carbon bonds in the substituted or unsubstituted monovalent hydrocarbon groups. 13 -, or -CO-NR 13Examples of monovalent groups include monovalent groups containing -. Examples of monovalent hydrocarbon groups include monovalent linear hydrocarbon groups having 1 to 20 carbon atoms, monovalent alicyclic hydrocarbon groups having 3 to 12 carbon atoms, and monovalent aromatic hydrocarbon groups having 6 to 10 carbon atoms. Examples of substituents introduced into monovalent hydrocarbon groups include hydroxyl groups and halogen atoms. B 1 and B 2 Preferably, the group is a hydrogen atom, a substituted or unsubstituted monovalent hydrocarbon group, or a monovalent group containing -O- between the carbon-carbon bonds of a substituted or unsubstituted monovalent hydrocarbon group; more preferably, a hydrogen atom, a monovalent hydrocarbon group, a monovalent halogenated hydrocarbon group, or a monovalent group containing -O- between the carbon-carbon bonds of a monovalent hydrocarbon group or a monovalent halogenated hydrocarbon group; even more preferably, a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms; and particularly preferably, a hydrogen atom. R 13 This is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

[0024] Specific examples of monomers that give structural unit [A] include, for example, the compounds represented by formulas (1-1) to (1-13) below. [ka] (In formulas (1-1) to (1-13), R is a hydrogen atom or a methyl group.) In equation (1-13), n is an integer between 2 and 10.

[0025] As monomers that provide structural unit [A], compounds represented by formulas (1-1) to (1-8), formula (1-12), and formula (1-13) are preferred from the viewpoint of improving low-voltage driving, compounds represented by formulas (1-1) to (1-8), and formula (1-12) are more preferred, and compounds represented by formulas (1-1) to (1-7) are even more preferred.

[0026] From the viewpoint of improving adhesion and coatability, the content of structural units [A] in the addition polymer [P] is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 15 mol% or more, relative to the total structural units constituting the addition polymer [P]. Furthermore, from the viewpoint of low-voltage driving and improved coatability, the content of structural units [A] is preferably 70 mol% or less, more preferably 60 mol% or less, and even more preferably 50 mol% or less, relative to the total structural units constituting the addition polymer [P].

[0027] (Structural unit [B]) Structural unit [B] has a substructure represented by the following formula (1) and is different from structural unit [A]. * 1 -CO-OR 1 …(1) (In formula (1), R 1 It is a monovalent, chain-like hydrocarbon group with a branched structure. 1 (This symbol represents a bond with a carbon atom that makes up the main chain of the polymer.)

[0028] Structural unit [B] differs from structural unit [A] in that it does not have a hydroxyl group bonded to a carbon atom in the chain structure or aliphatic ring. In other words, even if a structural unit has a substructure represented by formula (1) above, the structural unit having such a hydroxyl group belongs to structural unit [A].

[0029] In the above equation (1), R 1 Examples of monovalent chain hydrocarbon groups having a branched structure represented by include chain hydrocarbon groups having a branched structure with 3 to 50 carbon atoms. 1 A branched alkyl group having 3 to 50 carbon atoms is preferred. The number of carbon atoms in the branched alkyl group is more preferably 4 or more, even more preferably 6 or more, and particularly preferably 8 or more. Furthermore, the number of carbon atoms in the branched alkyl group is more preferably 40 or less, even more preferably 30 or less, even more preferably 20 or less, and particularly preferably 15 or less.

[0030] R 1The monovalent chain hydrocarbon group having a branched structure represented by formula (1) is preferably a group that does not detach from the substructure represented by formula (1) by heat (mainly heat during film formation), from the viewpoint of improving adhesion and suppressing the elution of impurities into the liquid crystal. Specifically, it is preferable that it does not detach at 150°C, more preferably at 200°C, and even more preferably at 250°C.

[0031] R 1 In this, the number of branched structures in a monovalent linear hydrocarbon group is not particularly limited, and it is sufficient that the monovalent linear hydrocarbon group has at least one branched structure. Furthermore, the carbon atom at the starting point of the branching may be either a tertiary carbon atom or a quaternary carbon atom, but it is preferable that it be a tertiary carbon atom. Furthermore, the portion of the monovalent linear hydrocarbon group having a branched structure is not particularly limited, but from the viewpoint of improving adhesion, at least an ester group (the group "* in formula (1)) is preferred. 1 It is preferable that the -CO-O-) group is branched at an adjacent carbon atom (α-carbon), or at an even further adjacent carbon atom (β-carbon), and more preferably at an adjacent carbon atom (α-carbon) to the ester group.

[0032] As monomers that give structural unit [B], (meth)acrylic compounds having a monovalent chain hydrocarbon group with a branched structure are preferred. Specific examples of monomers that give structural unit [B] include compounds represented by formulas (2-1) to (2-12) below. [ka] (In formulas (2-1) to (2-12), R is either a hydrogen atom or a methyl group.)

[0033] As monomers that provide structural units [B], compounds represented by formulas (2-1), (2-3), (2-5) to (2-8), (2-11), and (2-12) are preferred from the viewpoint of improving adhesion, and compounds represented by formulas (2-5) to (2-8) are more preferred.

[0034] From the viewpoint of low-voltage driving and improved coating properties, the content of structural units [B] in the addition 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 structural units constituting the addition polymer [P]. Furthermore, from the viewpoint of improving adhesion and coating properties, the content of structural units [B] is preferably 90 mol% or less, more preferably 80 mol% or less, and even more preferably 70 mol% or less, relative to the total structural units constituting the addition polymer [P].

[0035] (Structural unit [C]) The addition polymer [P] may be an addition polymer that contains only structural units [A] and structural unit [B] as structural units, but from the viewpoint of further improving adhesion, it is preferable to include structural units (hereinafter also referred to as "structural unit [C]") that have a structure represented by the following formula (3) and are different from structural units [A] and structural unit [B]. * 3 -CO-OR 2 …(3) (In formula (3), R 2 It is a monovalent linear hydrocarbon group. 3 (This symbol represents a bond with a carbon atom that makes up the main chain of the polymer.)

[0036] Structural unit [C] differs from structural unit [A] in that it does not have a hydroxyl group bonded to a carbon atom in the chain structure or aliphatic ring, and differs from structural unit [B] in that it does not have the substructure represented by formula (1) above. In other words, even if a structural unit has the substructure represented by formula (3) above, the structural unit having the hydroxyl group belongs to structural unit [A], and the structural unit that does not have the hydroxyl group but has the substructure represented by formula (1) above belongs to structural unit [B]. For example, the structural unit derived from the monomer represented by formula (2-12) above has the substructure represented by formula (3) above, but at the same time also has the substructure represented by formula (1) above, and therefore belongs to structural unit [B].

[0037] In equation (3) above, R 2Examples of monovalent linear hydrocarbon groups represented by include linear alkyl groups having 1 to 50 carbon atoms. 2 A linear alkyl group having 1 to 20 carbon atoms is preferred, and a linear alkyl group having 1 to 10 carbon atoms is more preferred.

[0038] Specific examples of monomers that provide the structural unit [C] include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tetradecyl (meth)acrylate, and n-icosyl (meth)acrylate.

[0039] When structural units [C] are included in the addition polymer [P], the content of structural units [C] is preferably 10 mol% or more, more preferably 15 mol% or more, and even more preferably 20 mol% or more, relative to the total structural units constituting the addition polymer [P], from the viewpoint of improving adhesion. Furthermore, from the viewpoint of improving adhesion and coatability, the content of structural units [C] is preferably 60 mol% or less, more preferably 50 mol% or less, and even more preferably 40 mol% or less, relative to the total structural units constituting the addition polymer [P].

[0040] (Other structural units) The addition polymer [P] may further contain structural units (hereinafter also referred to as "other structural units") that are different from structural units [A] and [B], and also different from structural unit [C]. Other structural units are those that do not have hydroxyl groups bonded to carbon atoms in the chain structure or aliphatic ring, and do not have the substructure represented by formula (1) and the substructure represented by formula (3). Examples of monomers that give other structural units (hereinafter also referred to as "other monomers") include (meth)acrylic compounds, aromatic vinyl compounds, conjugated diene compounds, maleimide compounds, vinyl ether compounds, maleamide compounds, and the like.

[0041] Other specific examples of monomers include (meth)acrylic compounds such as unsaturated carboxylic acids like (meth)acrylic acid, maleic acid, and fumaric acid; and unsaturated carboxylic acid esters such as cycloalkyl (meth)acrylate, benzyl (meth)acrylate, trimethoxysilylpropyl (meth)acrylate, glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxybutyl (meth)acrylate, 4-hydroxybutyl glycidyl ether (meth)acrylate, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, 6-(meth)acryloyloxyhexyltrimethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane.

[0042] Aromatic vinyl compounds include styrene, methylstyrene, divinylbenzene, p-styryltrimethoxysilane, 4-(glycidyloxymethyl)styrene, and vinylbenzoic acid. Conjugated diene compounds include 1,3-butadiene and 2-methyl-1,3-butadiene. Maleimide compounds include N-methylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-(4-glycidyloxyphenyl)maleimide, N-(4-glycidyloxymethylphenyl)maleimide, N-glycidylmaleimide, N-(4-carboxyphenyl)maleimide, and N-(4-terr-butoxycarbonylphenyl)maleimide. Vinyl ether compounds include n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, cyclohexyl vinyl ether, 1,4-butanediol divinyl ether, and diethylene glycol divinyl ether. Examples of maleamide compounds include N,N'-dimethylmaleamide, N,N'-diisopropylmaleamide, N,N'-diisobutylmaleamide, and N,N'-diphenylmaleamide.

[0043] Furthermore, other unsaturated monomers may be used that have photodirecting groups (e.g., cinnamate structures, coumarin structures, azobenzene structures), C4-C30 alkyl groups, C4-C30 halogenated alkyl groups, C4-C30 alkoxy groups, C4-C30 halogenated alkoxy groups, structures in which one or more rings from among benzene rings and cyclohexane rings are linked via single bonds or linking groups, or vertically oriented groups such as steroid skeletons, and are not monomers that give structural unit [A], monomers that give structural unit [B], or monomers that give structural unit [C].

[0044] When the addition polymer [P] contains other structural units, the proportion of these other structural units can be appropriately selected within a range that does not impair the effects of the present disclosure. Specifically, the proportion of these other structural units is preferably 30 mol% or less, more preferably 20 mol% or less, and even more preferably 10 mol% or less, relative to the total structural units constituting the addition polymer [P].

[0045] (Synthesis of addition polymers [P]) The addition polymer [P] is a polymer obtained by addition polymerization, and the details of its synthesis method are not particularly limited. The addition polymer [P] can be obtained, for example, by polymerizing monomers in the presence of a polymerization initiator. Radical polymerization initiators can be preferably used as polymerization initiators, and specific examples include azo compounds such as 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile). The proportion of polymerization initiator used is preferably 0.01 to 30 parts by mass per 100 parts by mass of the total monomers used in the reaction.

[0046] The polymerization reaction is preferably carried out in an organic solvent. Examples of organic solvents used in the reaction include alcohols, ethers, ketones, amides, esters, and hydrocarbon compounds, with diethylene glycol ethyl methyl ether and propylene glycol monomethyl ether acetate being preferred. The reaction temperature is preferably 30°C to 120°C, and the reaction time is preferably 1 to 36 hours. The amount of organic solvent used (a) is preferably such that the total amount of monomers used in the reaction (b) is 0.1 to 60% by mass of the total amount of the reaction solution (a + b). The addition polymer [P] contained in the reaction solution may be isolated from the reaction solution obtained by dissolving the polymer by applying known isolation methods, such as pouring the reaction solution into a large amount of poor solvent and drying the precipitate obtained under reduced pressure, or distilling the reaction solution under reduced pressure using an evaporator, and then used to prepare the liquid crystal alignment agent.

[0047] Furthermore, when synthesizing addition polymers having functional groups such as vertically oriented groups or photoinitiator groups in their side chains, in addition to polymerizing using monomers containing functional groups, addition polymers having functional groups in their side chains may also be synthesized by first using epoxy group-containing monomers as at least a portion of the raw materials to synthesize an addition polymer having epoxy groups in its side chains, and then reacting it with a carboxylic acid containing functional groups.

[0048] The addition polymer [P] preferably has a weight-average molecular weight (Mw) in polystyrene terms measured by gel permeation chromatography (GPC) of 250 to 500,000, and more preferably 500 to 100,000. Furthermore, the molecular weight distribution (Mw / Mn), expressed as the ratio of Mw to the number-average molecular weight (Mn) in polystyrene terms measured by GPC, is preferably 8 or less, and more preferably 6 or less.

[0049] The content of the addition polymer [P] in the liquid crystal alignment agent of this disclosure is preferably 3% by mass or more, more preferably 5% by mass or more, and from the viewpoint of achieving stable low-voltage driving, even more preferably 10% by mass or more, and particularly preferably 15% by mass or more.

[0050] <Other ingredients> The liquid crystal alignment agent of this disclosure may contain, in addition to the addition polymer [P], components other than the addition polymer [P] (hereinafter also referred to as "other components") as needed. Examples of other components include polymers other than the addition polymer [P] (hereinafter also referred to as "other polymers"), solvents, crosslinking agents, adhesion aids, etc.

[0051] [Other polymers] Other polymers may be polymers that do not have structural units [A] and [B], and the type of their main skeleton is not particularly limited. Examples of other polymers include polymers whose main skeletons are polyamic acid, polyamic acid esters, polyimides, polyorganosiloxanes, polyesters, polyenamines, polyureas, polyamides, polyamideimides, addition polymers, polybenzoxazoles, etc.

[0052] From the viewpoint of obtaining a liquid crystal alignment film with excellent adhesion while achieving low-voltage driving, the other polymer is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, polyimide, and addition polymer, and more preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide (hereinafter also referred to as "polyimide polymer").

[0053] When the liquid crystal alignment agent of this disclosure contains a polyimide polymer having a photo-aligning group as another polymer, examples of such photo-aligning groups include photo-crosslinking type, photo-isomerizing type, and photo-degrading type. In particular, from the viewpoint of improving adhesion, it is preferable that the photo-aligning group of the polyimide polymer be at least one selected from the group consisting of photo-crosslinking type and photo-isomerizing type.

[0054] When other polymers are included in the liquid crystal alignment agent, the content of the other polymers is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the polymer components contained in the liquid crystal alignment agent (i.e., the total amount of addition polymer [P] and other polymers). Furthermore, the content of the other polymers is preferably 95 parts by mass or less, per 100 parts by mass of the polymer components contained in the liquid crystal alignment agent, more preferably 90 parts by mass or less, and even more preferably 85 parts by mass or less, from the viewpoint of achieving stable low-voltage driving.

[0055] [solvent] The liquid crystal alignment agent of this disclosure is preferably prepared as a liquid composition in which an addition polymer [P] and optionally added components are dissolved or dispersed in a solvent. The solvent is preferably an organic solvent, such as aprotic polar solvents, phenolic solvents, alcohols, ketones, esters, ethers, halogenated hydrocarbons, hydrocarbons, etc. Specific examples of organic solvents used include, for example, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 1,2-dimethyl-2-imidazolidinone, 1,3-dimethyl-2-imidazolidinone, γ-butyrolactone, γ-butyrolactam, N,N-dimethylformamide, N,N-dimethylacetamide, 4-hydroxy-4-methyl-2-pentanone (diacetone alcohol), ethylene glycol monomethyl ether, butyl lactate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-i-propyl ether, and Examples include ethylene glycol-n-butyl ether (butyl cellosolve), ethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diisobutyl ketone, isoamyl propionate, isoamyl isobutyrate, diisopentyl ether, ethylene carbonate, propylene carbonate, cyclohexanone, diisobutyl ketone, and 3-methoxy-1-butanol.

[0056] [Crosslinking agent] The liquid crystal alignment agent of this disclosure may contain a crosslinking agent. By further containing a crosslinking agent, a liquid crystal alignment film with superior adhesion can be obtained while achieving low-voltage driving. Examples of crosslinking agents include oxyranyl groups, oxetanyl groups, cyclic thioether groups, cyclic carbonate groups, hydroxyl groups, protected hydroxyl groups, mercapto groups, protected mercapto groups, amino groups, protected amino groups, isocyanate groups, protected isocyanate groups, alkoxysilyl groups, polymerizable carbon-carbon unsaturated bond groups (alkenyl groups, vinyl ether groups, vinylphenyl groups, maleimide groups, (meth)acryloyl groups, etc.), β-alkoxyalkylamide groups, oxazoline groups, aldehyde groups, carbodiimide groups, carboxyl groups, protected carboxyl groups, and groups "-CR 60 =CR 61 -R 62 -" However, R 60 R is a monovalent organic group that is eliminated by reaction with an amino group. 61 R is a hydrogen atom or an alkyl group. 62 Examples include compounds having two or more crosslinkable groups selected from the group consisting of electron-withdrawing groups, silanol groups, and alkoxysilyl groups (excluding addition polymers [P]).

[0057] From the viewpoint of obtaining a liquid crystal alignment film with excellent adhesion while exhibiting good weak anchoring characteristics, the number of crosslinkable groups in one molecule of the crosslinking agent is preferably 2 to 10, and more preferably 2 to 6. 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.

[0058] Specific examples of crosslinking agents include compounds having an oxyranil group or an oxetanil 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 trimethylol Examples include epoxidation reaction products of 1,2'-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 2,2'-diallylbisphenol A diallyl ether with hydrogen peroxide.

[0059] Examples of compounds having a cyclic carbonate group include those represented by the following formulas (d1-1) and (d1-2).

[0060] Compounds having a hydroxyl group or a protected hydroxyl group can preferably include compounds having a methylol group, a protected methylol group, a hydroxyalkylamide group, or a protected hydroxyalkylamide group. Specific examples of these include compounds represented by formulas (d2-1) to (d2-5) and (d3-1) to (d3-5) below.

[0061] Examples of compounds having a carboxyl group or a protected carboxyl group include maleic acid, itaconic acid, trimellitic acid, tetracarboxylic acid, cis-1,2,3,4-tetrahydrophthalic acid, ethylene glycol bistrimate, propylene glycol bistrimate, 4,4'-oxydiphthalic acid, and their protected derivatives.

[0062] Examples of compounds having a mercapto group or a protected mercapto group include 1,2-ethanedithiol, 1,3-propanedithiol, 1,3,4-thiadiazole-2,5-dithiol, 1,10-decanedithiol, pentaerythritol tetrakis(3-mercaptobutyrate), and 1,3,5-tris(2-(3-sulfanylbutanoyloxy)ethyl)-1,3,5-triazinan-2,4,6-trione.

[0063] Examples of compounds having an amino group or a protected amino group include those represented by formulas (d4-1) to (d4-5) below.

[0064] Examples of compounds having a protected isocyanate group include compounds in which the isocyanate group in tolylene diisocyanate, xylylene diisocyanate, chlorphenyl diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, or diphenylmethane diisocyanate is protected with 3,6-dimethylpyrazole, methyl ethyl ketoxime, diethyl malonate, or ε-caprolactam, and compounds represented by the following formula (d5-1).

[0065] Examples of compounds having polymerizable carbon-carbon unsaturated bond 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 (d6-1) to (d6-8) below.

[0066] [ka] [ka] (In formula (d2-4), Ac represents an acetyl group.) [ka] [ka] [ka] [ka]

[0067] As a crosslinking agent, compounds without aromatic rings (hereinafter also referred to as "aliphatic crosslinking agents") can be preferably used, from the viewpoint of obtaining a superior liquid crystal element by driving the liquid crystal element at a low voltage. Aliphatic crosslinking agents may be compounds having a chain structure or a cyclic structure. Specific examples of aliphatic crosslinking agents include compounds without aromatic rings among the compounds exemplified above.

[0068] From the viewpoint of improving adhesion while enabling low-voltage driving, the crosslinking agent content is preferably 0.5 parts by mass or more, 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 components contained in the liquid crystal alignment agent (i.e., the total amount of addition polymer [P] and other polymers). Furthermore, from the viewpoint of obtaining good coating properties, 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 components.

[0069] [Adhesion enhancer] Adhesion aids are components that improve the adhesion between a liquid crystal alignment film formed using a liquid crystal alignment agent and a substrate or sealant. 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, and isocyanate groups.

[0070] 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.

[0071] 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 components contained in the liquid crystal alignment agent.

[0072] Other components to be included in the liquid crystal alignment agent include, in addition to those mentioned above, surfactants, antioxidants, metal chelating compounds, curing accelerators, fillers, dispersants, photosensitizers, and the like. The proportion of these other components can be appropriately selected for each compound, as long as it does not impair the effects of the present disclosure.

[0073] The solid content concentration in the liquid crystal alignment agent (the ratio of the total mass of components other than the solvent to the total mass of the liquid crystal alignment agent) is appropriately selected considering viscosity, volatility, etc. The solid content concentration of the liquid crystal alignment agent is preferably in the range of 1 to 10% by mass. A solid content concentration of 1% by mass or more is preferable because it allows for sufficient film thickness of the coating and enables the production of a liquid crystal alignment film exhibiting better liquid crystal alignment properties. Furthermore, a solid content concentration of 10% by mass or less allows for a coating with an appropriate thickness, making it easier to obtain a liquid crystal alignment film exhibiting good liquid crystal alignment properties. In addition, the viscosity of the liquid crystal alignment agent becomes appropriate, ensuring good coatability.

[0074] ≪Liquid Crystal Alignment Film≫ The liquid crystal alignment film of this disclosure is a weakly anchored liquid crystal alignment film formed by a liquid crystal alignment agent prepared as described above. Here, "weak anchoring" means that the orientation restricting force of liquid crystal molecules is substantially zero in the in-plane direction, and even if the horizontal orientation of liquid crystal molecules is forced, the orientation restricting force in the in-plane direction is substantially zero. Specifically, weak anchoring means, for example, that the azimuthal anchoring strength (A2) is 10 -4 J / m 2 This refers to the case where the azimuth anchoring strength (A2) is less than 10 -5 J / m 2 It is preferable that it be smaller than . In the weak anchoring state (also called zero-plane anchoring), the orientation direction in the plane can be freely rotated 360° by control with an external field such as an electric field or magnetic field. On the other hand, a strongly anchored liquid crystal alignment film has a stronger anchoring energy than a weakly anchored liquid crystal alignment film, specifically, an azimuthal anchoring intensity (A2) of 10 -4 J / m 2It is preferable that it be greater than [value]. In this specification, the azimuthal angle anchoring intensity of the liquid crystal alignment film is a value calculated from the electric field response threshold.

[0075] The method for producing a weakly anchored liquid crystal alignment film using the liquid crystal alignment agent of this disclosure is not particularly limited and can be carried out in the same manner as when producing a liquid crystal alignment film using conventionally known liquid crystal alignment agents. In terms of the ease of forming a weakly anchored liquid crystal alignment film, a method of forming it by coating the liquid crystal alignment agent of this disclosure onto a substrate and preferably heating the coated surface is preferred.

[0076] The substrate on which the weakly anchored liquid crystal alignment film is formed is not particularly limited. Examples of substrates include glass such as float glass and soda glass; and transparent substrates made of plastics such as polyethylene terephthalate, polybutylene terephthalate, polyethersulfone, polycarbonate, and poly(alicyclic olefin).

[0077] The method for applying the liquid crystal alignment agent to the substrate is not particularly limited. The liquid crystal alignment agent can be applied by, for example, spin coating, printing (e.g., offset printing, flexographic printing, etc.), inkjet, slit coating, bar coater, extrusion die, direct gravure coater, chamber doctor coater, offset gravure coater, impregnation coater, MB coater, etc. Of these, it is preferable to apply the liquid crystal alignment agent by inkjet.

[0078] After applying the liquid crystal alignment agent, preheating (pre-bake) is preferably performed to prevent dripping of the 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 further remove the solvent. The baking temperature (post-bake temperature) is preferably 80 to 280°C, more preferably 80 to 250°C. The post-bake time is preferably 5 to 200 minutes. The film thickness of the formed film is preferably 0.001 to 2.5 μm. By the above operation, a weakly anchored liquid crystal alignment film can be easily manufactured. After post-bake, the coating film may be subjected to orientation treatment (e.g., rubbing orientation treatment or photo-alignment treatment) as needed to obtain a weakly anchored liquid crystal alignment film.

[0079] ≪Liquid crystal elements and methods for manufacturing the same≫ The liquid crystal element of this disclosure comprises a weakly anchored liquid crystal alignment film formed using the liquid crystal alignment agent described above. The liquid crystal driving method in the liquid crystal element is not particularly limited and can be applied to various modes such as TN type, STN type, VA type (including VA-MVA type, VA-PVA type, etc.), IPS type, FFS type, OCB (Optically Compensated Bend) type, PSA (Polymer Sustained Alignment) type, and ECB (Electrically Controlled Birefringence) type. Of these, it is preferably applicable to horizontal mode liquid crystal elements such as IPS type and FFS type.

[0080] The liquid crystal element of this disclosure can be manufactured, for example, by a method including the following steps A and B. The order of steps A and B is not particularly limited; step A may be performed before step B, or step B may be performed before step A. Steps A and B may also be performed simultaneously. Step A: A step of forming a weak anchoring liquid crystal alignment film on one of a pair of substrates using a liquid crystal alignment agent for forming a weak anchoring film. Step B: A step of forming a strongly anchoring liquid crystal alignment film on the other substrate of the pair (i.e., the substrate on which the weakly anchoring liquid crystal alignment film has not been formed).

[0081] Step A is preferably performed according to Step 1 shown below, and Step B is preferably performed according to Steps 1 and 2 shown below. Furthermore, a liquid crystal element can be obtained by constructing a liquid crystal cell in Step 3 using a substrate on which a liquid crystal alignment film has been formed, obtained in Steps A and B. Note that the substrate used in Step 1 differs depending on the desired operating mode. Steps 2 and 3 are common to all operating modes.

[0082] <Step 1: Formation of the coating> First, a liquid crystal alignment agent is applied to each substrate surface of a pair of substrates, and preferably the applied surface is heated to form a coating on the substrate. Conventional known liquid crystal alignment agents can be used as appropriate for forming a strongly anchoring liquid crystal alignment film.

[0083] When manufacturing, for example, an IPS-type or FFS-type liquid crystal element using a pair of substrates, a substrate with comb-shaped patterned electrodes (hereinafter also referred to as the "first substrate") and a counter substrate without electrodes (hereinafter also referred to as the "second substrate") are used. Transparent conductive films can be used as electrodes. Examples of transparent conductive films include NESA films (registered trademark of PPG, Inc., USA) made of tin oxide (SnO2), and ITO films made of indium oxide-tin oxide (In2O3-SnO2). When forming liquid crystal alignment films on the first and second substrates, examples include a first embodiment in which a strongly anchored liquid crystal alignment film is formed on the first substrate and a weakly anchored liquid crystal alignment film is formed on the second substrate; and a second embodiment in which a weakly anchored liquid crystal alignment film is formed on the first substrate and a strongly anchored liquid crystal alignment film is formed on the second substrate. Of these, the first embodiment is preferred from the viewpoint of driving the liquid crystal element at a low voltage.

[0084] <Step 2: Orientation Treatment> When manufacturing an IPS-type or FFS-type liquid crystal element, at least one of the coating films formed on the first substrate and the second substrate in step 1 is subjected to a process (alignment process) to impart liquid crystal alignment ability. Preferably, the alignment process involves rubbing the surface of the coating film formed on the substrate with cotton or nylon, or photo-alignment, which involves irradiating the coating film with light to impart liquid crystal alignment ability. The alignment process may be performed on both the coating film formed on the first substrate and the coating film formed on the second substrate, or on only one of them. From the viewpoint of obtaining a liquid crystal element exhibiting good liquid crystal alignment, it is preferable to apply a liquid crystal alignment agent to form a strongly anchoring liquid crystal alignment film to one of the first or second substrate, and then perform the alignment process only on the resulting coating film. In this case, the strongly anchoring liquid crystal alignment film may be a rubbing alignment film formed by the rubbing alignment process, or a photo-alignment film formed by the photo-alignment process. The liquid crystal alignment agent used to form a strongly anchored liquid crystal alignment film preferably contains a crosslinking agent in that it can improve liquid crystal alignment and adhesion, and it is even more preferable that the crosslinking agent does not have an aromatic ring in that it has a high effect in improving the low-voltage driving of the liquid crystal element.

[0085] Furthermore, with the weakly anchored liquid crystal alignment film formed by the liquid crystal alignment agent of this disclosure, a liquid crystal element exhibiting good liquid crystal alignment can be obtained without performing alignment treatments such as rubbing alignment or photo-alignment. Taking advantage of these characteristics, the weakly anchored liquid crystal alignment film formed by the liquid crystal alignment agent of this disclosure may be arranged as a protective film provided on a color filter in a liquid crystal element, and the weakly anchored liquid crystal alignment film may be given the function of a protective film (specifically, planarization, protection from impurities or humidity, etc.).

[0086] <Step 3: Liquid Crystal Cell Construction> A liquid crystal cell is manufactured by using a substrate on which a strongly anchoring liquid crystal alignment film is formed and a substrate on which a weakly anchoring liquid crystal alignment film is formed, with a liquid crystal layer placed between two opposing substrates. Methods for manufacturing the 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; an ODF method; and so on. As the sealant, for example, an epoxy resin containing a curing agent and aluminum oxide spheres as spacers can be used. Examples of liquid crystals constituting the liquid crystal layer include nematic liquid crystals and smectic liquid crystals, with nematic liquid crystals being preferred.

[0087] When manufacturing liquid crystal display devices, a polarizing plate is then bonded to the outer surface of the liquid crystal cell. Examples of polarizing plates include a polarizing film called an "H film," which is made by stretching and oriented polyvinyl alcohol while absorbing iodine, sandwiched between cellulose acetate protective films, or a polarizing plate made of the H film itself.

[0088] The liquid crystal elements of this disclosure can be effectively applied to a variety of uses. Specifically, they can be used, for example, in various display devices such as watches, portable game consoles, word processors, notebook computers, car navigation systems, camcorders, PDAs, digital cameras, mobile phones, smartphones, various monitors, liquid crystal televisions, information displays, as well as in dimming devices, phase difference films, and the like.

[0089] According to this disclosure, the following means are provided: [Method 1] A liquid crystal alignment agent comprising a structural unit [A] having a hydroxyl group bonded to a carbon atom in a chain structure or an aliphatic ring (excluding carbon atoms in a carbonyl group and carbon atoms constituting the main chain of the polymer), and an addition polymer [P] having a substructure represented by the above formula (1) and different from the structural unit [A]. [Method 2] The liquid crystal alignment agent according to [Method 1], wherein the structural unit [A] has a substructure represented by the above formula (2). [Method 3] A in formula (2) above 1 The liquid crystal alignment agent according to [Method 2], wherein it does not have an aromatic ring. [Method 4] A in formula (2) above 1 The liquid crystal alignment agent according to [Method 2] or [Method 3], wherein is a substituted or unsubstituted divalent linear hydrocarbon group, or a divalent group containing -O- or -CO- between carbon-carbon bonds in a substituted or unsubstituted divalent linear hydrocarbon group. [Method 5] B in formula (2) above 1 and B 2 The liquid crystal orientation agent according to any one of [Method 2] to [Method 4], wherein each is independently a hydrogen atom, a monovalent hydrocarbon group, a monovalent halogenated hydrocarbon group, or a monovalent group containing -O- between the carbon-carbon bonds of a monovalent hydrocarbon group or halogenated hydrocarbon group. [Method 6] The liquid crystal alignment agent according to any one of [Method 1] to [Method 5], wherein the addition polymer [P] has a substructure represented by the above formula (3) and further comprises a structural unit [C] different from the structural unit [A] and the structural unit [B]. [Method 7] A liquid crystal alignment agent according to any one of [Method 1] to [Method 6], further comprising at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide. [Method 8] A liquid crystal alignment agent according to any one of [Method 1] to [Method 7], further comprising a crosslinking agent. [Method 9] The liquid crystal alignment agent according to [Method 8], wherein the crosslinking agent does not have an aromatic ring. [Method 10] A liquid crystal alignment agent according to any one of [Method 1] to [Method 9] for forming a weakly anchored liquid crystal alignment film. [Method 11] A liquid crystal alignment film formed using a liquid crystal alignment agent described in any of [Method 1] to [Method 10]. [Method 12] A liquid crystal element comprising the liquid crystal alignment film described in [Method 11]. [Method 13] A method for manufacturing a liquid crystal element comprising a pair of substrates consisting of a first substrate and a second substrate, and a liquid crystal layer disposed between the pair of substrates, the method comprising the step of applying a liquid crystal alignment agent described in any of [Method 1] to [Method 10] to the surface of one of the pair of substrates to form a liquid crystal alignment film. [Method 14] The liquid crystal alignment film formed with the liquid crystal alignment agent described in any of [Method 1] to [Method 10] is a weak anchoring liquid crystal alignment film, and the method for manufacturing a liquid crystal element according to [Method 13] further includes the step of forming a strongly anchoring liquid crystal alignment film having a stronger anchoring energy than the weak anchoring liquid crystal alignment film on the surface of a substrate different from the substrate on which the weak anchoring liquid crystal alignment film was formed, among the first substrate and the second substrate. [Method 15] The method for manufacturing a liquid crystal element according to [Method 14], wherein the strongly anchoring liquid crystal alignment film is a rubbing alignment film or a photo-alignment film. [Method 16] A method for manufacturing a liquid crystal element according to [Method 14] or [Method 15], wherein the first substrate has a pair of electrodes, the second substrate does not have electrodes, the strongly anchored liquid crystal alignment film is formed on the surface of the first substrate, and the weakly anchored liquid crystal alignment film is formed on the surface of the second substrate. [Examples]

[0090] The present invention will be described in detail below with reference to examples, but it is not limited to the following examples. In the examples and comparative examples, "parts" and "%" refer to mass unless otherwise specified.

[0091] In the following examples, the imidization rate of the polyimide, the weight-average molecular weight (Mw) of the polymer, and the number-average molecular weight (Mn) were measured by the following methods. <Imidification rate of polyimides> A polyimide solution 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, with tetramethylsilane as the reference substance, at room temperature. 1 1H-NMR measurements were performed. 1The imidization rate [%] was determined from the 1H-NMR spectrum using the following formula (1). Imidization rate [%] = (1 - (β 1 / ( β 2 ×α)))×100 …(1) (In formula (1), β 1 This represents the peak area originating from the proton of the NH group, appearing around a chemical shift of 10 ppm, and β 2 α represents the peak area derived from other protons, and α is the ratio of other protons to one proton of the NH group in the polymer precursor (polyamic acid).

[0092] <Weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polymers> The weight-average molecular weight (Mw) and number-average molecular weight (Mn) were measured by gel permeation chromatography (GPC) under the following conditions. The molecular weight distribution (Mw / Mn) was calculated from the obtained Mw and Mn values. Equipment: Showa Denko Corporation's "GPC-101" GPC columns: Combining "GPC-KF-801", "GPC-KF-802", "GPC-KF-803", and "GPC-KF-804" manufactured by Shimadzu GLC Co., Ltd. Mobile phase: Tetrahydrofuran (THF) Column temperature: 40℃ Flow rate: 1.0mL / min Sample concentration: 1.0% by mass Sample injection volume: 100 μL Detector: Differential refractometer Standard material: Monodisperse polystyrene

[0093] The abbreviations for the compounds are as follows. In the following, the compound represented by formula (X) may simply be referred to as "compound (X)".

[0094] <Monomers containing unsaturated bonds> [ka] [ka] [ka] [ka]

[0095] <Tetracarboxylic acid dianhydride> [ka]

[0096] <Diamine> [ka]

[0097] <Additives> [ka]

[0098] <Synthesis of polymers> 1. Synthesis of addition polymers [Synthesis Example 1] Under nitrogen, in a 100 mL two-necked flask, 100 moles of polymerization monomers were mixed with 45 moles of compound (MA-1), 25 moles of compound (MA-7), 25 moles of compound (MB-2), and 5 moles of compound (M-1) as polymerization monomers, 2 moles of 2,2'-azobis(2,4-dimethylvaleronitrile) as a radical polymerization initiator, and N-methyl-2-pyrrolidone (NMP) as a solvent. Polymerization was carried out at 70°C for 6 hours. After reprecipitation in methanol, the precipitate was filtered and vacuum-dried at room temperature for 8 hours to obtain the desired addition polymer (referred to as polymer (PM-1)).

[0099] [Synthesis Examples 2-10] Except for changing the type and amount of polymerization monomer used in the reaction as shown in Table 1, the same procedure as in Synthesis Example 1 was performed to obtain addition polymers (referred to as polymers (PM-2) to polymers (PM-10)).

[0100] In Table 1, the monomer values ​​represent the molar ratio of each compound to 100 moles of the total amount of monomers used in the synthesis. "Branched alkyl monomers" correspond to monomers that give structural unit [B], "aliphatic OH monomers" correspond to monomers that give structural unit [A], "linear alkyl monomers" correspond to monomers that give structural unit [C], and "other monomers" correspond to monomers that give other structural units.

[0101] [Table 1]

[0102] 2. Synthesis of polyamic acids [Synthesis Example 11] 100 moles of compound (T-3) as a tetracarboxylic dianhydride and 100 moles of compound (D-1) as a diamine compound were dissolved in NMP, and the reaction was carried out at 60°C for 6 hours to obtain a solution containing 20% ​​by mass of polyamic acid (referred to as polymer (PI-1)).

[0103] [Synthesis Examples 12-17, 19 and 20] The same procedure as in Synthesis Example 11 was followed, except that the types and amounts of tetracarboxylic dianhydride and diamine compounds used were changed as shown in Table 2, to obtain polyamic acids (these were designated as polymers (PI-2) to (PI-7), (PI-9), and (PI-10)).

[0104] 3. Synthesis of polyimides [Synthesis Example 18] 100 moles of compound (T-5) as a tetracarboxylic dianhydride and 100 moles of compound (D-14) as a diamine compound were dissolved in NMP and reacted at 60°C for 6 hours to obtain a solution containing 20% ​​by mass of polyamic acid. Next, NMP was added to the obtained polyamic acid solution to make a 10% by mass solution of polyamic acid, and pyridine and acetic anhydride were added to carry out a dehydration and cyclization reaction at 80°C for 4 hours. After the dehydration and cyclization reaction, the solvent in the system was replaced with fresh NMP to obtain a solution containing 15% by mass of polyimide (referred to as polymer (PI-8)) with an imidization rate of approximately 30%.

[0105] In Table 2, the values ​​for tetracarboxylic dianhydrides (acid dianhydrides 1-3) represent the molar ratio of each compound to 100 moles of the total amount of tetracarboxylic dianhydrides used in the synthesis of the polymer. The values ​​for diamine compounds (diamines 1-4) represent the molar ratio of each compound to 100 moles of the total amount of diamine compounds used in the synthesis of the polymer.

[0106] [Table 2]

[0107] <Preparation of liquid crystal alignment agent and evaluation of inkjet coating properties> 1. Preparation of liquid crystal alignment agent for weak anchoring film formation [Example 1] A solution containing 10 parts by mass of polymer (PM-1) obtained in Synthesis Example 1 and a solution containing 90 parts by mass of polymer (PI-5) obtained in Synthesis Example 15 were diluted with N-methyl-2-pyrrolidone (NMP), gamma-butyrolactone (GBL), butyl cellosolve (BC), diacetone alcohol (DAA), and diethylene glycol diethyl ether (DEDG) to obtain a solution with a solvent composition of NMP:GBL:BC:DAA:DEDG = 30:30:15:15:10 (mass ratio) and a solid content concentration of 3.5% by mass. This solution was filtered through a 0.2 μm pore size filter to prepare a liquid crystal alignment agent (AL-1) for weak anchoring film formation.

[0108] 2. Evaluation of inkjet coating properties As the substrate to which the liquid crystal alignment agent was applied, a glass substrate with transparent electrodes made of ITO was heated on a hot plate at 200°C for 1 minute, and then subjected to ultraviolet / ozone cleaning to reduce the water contact angle on the transparent electrode surface to 10° or less. On this substrate, a liquid crystal alignment agent for weak anchoring film formation (AL-1) was applied to the transparent electrode surface of the glass substrate with transparent electrodes using an inkjet coating machine (manufactured by Shibaura Mechatronics Co., Ltd.). The application conditions were 2,500 strokes / (nozzle·minute), with a discharge rate of 250 mg / 10 seconds, and applied in two passes (a total of four passes). After letting it stand for 1 minute after application, the substrate was heated at 50°C to form a coating with an average film thickness of 0.1 μm. The obtained coating was observed with the naked eye under the irradiation of an interference fringe measurement lamp (sodium lamp) to evaluate unevenness and repulsion. Furthermore, the same procedure as above was performed, except that the heating temperature during coating film formation was changed from 50°C to 60°C and 80°C, and the presence or absence of unevenness and repulsion in the coating film was observed. If neither unevenness nor repulsion was observed at any of the heating temperatures of 50°C, 60°C, and 80°C, the inkjet coating performance was rated as "particularly good (◎)". If at least one of unevenness or repulsion was observed at one of the heating temperatures of 50°C, 60°C, and 80°C, it was rated as "good (○)". If at least one of unevenness or repulsion was observed at two of the heating temperatures, it was rated as "acceptable (△)". If at least one of unevenness or repulsion was observed at all heating temperatures, it was rated as "poor (×)". As a result, this example was evaluated as "good (○)".

[0109] [Examples 2-9, Comparative Examples 1-3] Liquid crystal alignment agents (AL-2) to (AL-12) for weak anchoring film formation were prepared with the same solvent composition and solid content concentration as in Example 1, except that the types and amounts of polymers and additives were changed as shown in Table 3, and the inkjet coating properties were evaluated. The evaluation results are shown in Table 3.

[0110] 3. Preparation of liquid crystal alignment agent for forming strong anchoring film [Preparation Examples 1-3] Liquid crystal alignment agents (AL-13) to (AL-15) for strong anchoring film formation were prepared with the same solvent composition and solid content concentration as in Example 1, except that the types and amounts of polymers and additives were changed as shown in Table 3. The inkjet coating properties of the liquid crystal alignment agents (AL-13) to (AL-15) for strong anchoring film formation were also evaluated, and it was confirmed that there were no problems with coating properties. The evaluation results are shown in Table 3.

[0111] [Table 3]

[0112] As shown in Table 3, in Examples 1 to 9, where the liquid crystal alignment agent contained an addition polymer [P] containing structural unit [A] and structural unit [B], the inkjet coating performance was rated as good (○). In contrast, in Comparative Example 1, where an addition polymer without structural unit [A] was used instead of addition polymer [P], Comparative Example 2, where an addition polymer without structural unit [B] was used, and Comparative Example 3, where an addition polymer without structural unit [A] and structural unit [B] was used, the inkjet coating performance was rated as poor (×).

[0113] In Comparative Example 1, where an addition polymer was used that did not contain structural unit [A] among structural unit [A] and structural unit [B] instead of addition polymer [P], and in Comparative Example 3, where an addition polymer was used that did not contain structural unit [A] and structural unit [B] but contained structural unit [C], it is presumed that the increased hydrophobicity of the liquid crystal alignment agent resulted in poor spreadability during inkjet coating (poor edge linearity), leading to unevenness in the coating film. Furthermore, in Comparative Example 2, where an addition polymer was used that did not contain structural unit [B] among structural unit [A] and structural unit [B] instead of addition polymer [P], it is presumed that the increased water absorption and surface activity of the liquid crystal alignment agent resulted in excessively high spreadability during inkjet coating (poor edge linearity).

[0114] <Manufacturing of liquid crystal elements, and evaluation of adhesion and low-voltage driving (FFS type liquid crystal display elements)> FFS-type liquid crystal cells were manufactured and various characteristics were evaluated. In manufacturing the FFS-type liquid crystal cells, first, a substrate (electrode substrate) having an electrode pair formed in the order of a bottom electrode without a pattern, an insulating layer made of silicon nitride film, and a top electrode patterned in a comb-like manner on one side of the glass substrate, and a counter glass substrate (counter substrate) without electrodes were prepared. A schematic plan view of the top electrode used is shown in Figure 2. Figure 2(a) is a top view of the top electrode, and Figure 2(b) is an enlarged view of the portion C1 enclosed by the dashed line in Figure 2(a). In this embodiment, the electrode line width d1 was 4 μm and the distance between electrodes d2 was 6 μm. In addition, four drive electrodes, electrodes A, B, C and D, were used as the top electrode (Figure 3). The bottom electrode acts as a common electrode that acts on all four drive electrodes, and each of the regions of the four drive electrodes becomes a pixel region.

[0115] [Example 10: Photo-aligned FFS type liquid crystal display element] 1. Manufacturing of liquid crystal display elements (1) Formation of weakly anchored liquid crystal alignment film A weak anchoring liquid crystal alignment agent (AL-1) was applied to one substrate surface of opposing substrates using a spin coater, heated on an 80°C hot plate for 1 minute, and then heated in a 230°C oven with nitrogen purging for 30 minutes to form a weak anchoring liquid crystal alignment film with an average thickness of 100 nm.

[0116] (2) Formation of strongly anchored liquid crystal alignment films by photo-alignment method A liquid crystal alignment agent for strong anchoring film formation (AL-13) was applied to the electrode formation surface of an electrode substrate using a spin coater. After heating on an 80°C hot plate for 1 minute, the substrate was heated in a 230°C oven with nitrogen purging for 30 minutes to form a coating with an average thickness of 100 nm. The surface of this coating was exposed to 200 mJ / cm² of ultraviolet light containing linearly polarized emission lines at 254 nm using an Hg-Xe lamp. 2Photo-alignment treatment was performed by irradiating the substrate from the direction normal to the substrate. At this time, the direction of the polarization plane was set so that the direction of the line segment obtained by projecting the polarization plane of polarized ultraviolet light onto the substrate was parallel to the direction of the double-headed arrow in Figure 2(b). The photo-aligned coating was heat-treated by heating it in a 230°C oven with nitrogen purged for 30 minutes to form a strongly anchored liquid crystal alignment film.

[0117] (3) Manufacturing of photo-aligned FFS type liquid crystal display elements On the outer periphery of one of the substrates prepared in (1) and (2) above, the side with the liquid crystal alignment film, an epoxy resin adhesive containing aluminum oxide spheres with a diameter of 3.5 μm was dispensed, leaving a liquid crystal injection port. Then, the sides of the pair of substrates with the liquid crystal alignment film were pressed together, and the adhesive was heat-cured at 150°C for 1 hour. Next, negative nematic liquid crystal (Merck, MLC-6608, Δn=0.083) 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 remove the flow orientation during liquid crystal injection, it was heated at 120°C and then slowly cooled to room temperature.

[0118] 2. Evaluation (1) Evaluation of adhesion Two glass substrates were prepared by applying a liquid crystal alignment agent for weak anchoring film formation (AL-1) and a liquid crystal alignment agent for strong anchoring film formation (AL-13) to a glass substrate using a spin coater. The substrates were then heated on an 80°C hot plate for 1 minute, followed by heating in a 230°C oven with nitrogen purging for 30 minutes, resulting in two glass substrates with a coating film of average thickness of 100 nm. Next, a liquid crystal sealant (Sekisui Chemical Co., Ltd., S-WB21) was applied to the center of the coated surface of one glass substrate, and the two glass substrates were bonded together so that the coating film and the liquid crystal sealant were in contact. The amount of liquid crystal sealant applied was set so that the diameter of the sealant after bonding the substrates was 4 mm. Subsequently, a metal halide lamp was used to apply 30,000 J / m² of heat. 2After irradiating with light (equivalent to 365 nm), the cells were heated in a 120°C oven for 1 hour to obtain evaluation cells. Subsequently, the evaluation cells were pressed using a small desktop test machine (model: EZ-LX) from Shimadzu Corporation, and the pressure (N) at which the film peeled off (mainly due to interfacial failure between the liquid crystal sealant and the film, or cohesive failure within the liquid crystal sealant) was measured. The pressure (N) at the time of peeling was measured across the area (mm²) of the liquid crystal sealant. 2 By dividing by ), the adhesion (N / mm²) of the liquid crystal sealant and the film to the substrate is determined. 2 The value was calculated. The evaluation was based on a pressure measurement of 1.5 N / mm². 2 If the result is above this, it is marked as "Excellent (◎)", 1.0 N / mm 2 More than 1.5N / mm 2 If the value is less than 1.0 N / mm², it is considered "Good (○)". 2 A result below this value was classified as "Poor (×)". As a result, this example received a "Good (○)" rating.

[0119] (2) Evaluation of low-voltage drive The liquid crystal display element manufactured in 1.(3) above was sandwiched between two polarizing plates so that its brightness was minimized, and the liquid crystal display element was placed between a backlight and a luminance meter, with the optical axes aligned. Then, a voltage was applied to the liquid crystal display element in 0.1V increments up to 10V. A VT curve was obtained by measuring the brightness as a function of the applied voltage, and the voltage value at which the brightness was maximized was estimated. For evaluation, a liquid crystal display element with a liquid crystal alignment film formed by photoalignment using a liquid crystal alignment agent (AL-13) for strong anchoring film formation, similar to the electrode substrate, was prepared as a reference cell, and the evaluation was judged by how much the maximum brightness voltage of the liquid crystal display element manufactured in each example was reduced relative to the maximum brightness voltage of the reference cell. In the liquid crystal display element manufactured in 1.(3) above, those with a maximum brightness voltage lowered by more than 0.6V compared to the maximum brightness voltage of the reference cell were rated as "particularly good (◎)", those with a voltage lowered by more than 0.2V but 0.6V or less compared to the maximum brightness voltage of the reference cell were rated as "good (○)", those with a voltage lowered by more than 0V but 0.2V or less compared to the maximum brightness voltage of the reference cell were rated as "acceptable (△)", and those with a voltage lowering of 0V or less compared to the maximum brightness voltage of the liquid crystal display element of the reference cell were rated as "poor (×)". As a result, in this embodiment, the evaluation was "particularly good (◎)".

[0120] [Examples 11-18, Comparative Examples 4-6, and Comparative Example 10] Except for changing the liquid crystal alignment agent used as shown in Table 4, a liquid crystal alignment film was formed in the same manner as in Example 10, and a photo-aligned FFS type liquid crystal display element was manufactured to evaluate adhesion and low-voltage driving. The reference cell used in the low-voltage driving evaluation of Example 18 was manufactured using a liquid crystal alignment agent for strong anchoring film formation (AL-15). The evaluation results are shown in Table 4.

[0121] [Example 19: Rubbing-oriented FFS type liquid crystal display element] 1. Manufacturing of liquid crystal display elements The FFS-type liquid crystal display element 10 shown in Figure 1 was manufactured and various characteristics were evaluated. (1) Formation of weakly anchored liquid crystal alignment film Similar to Example 10, a weakly anchored liquid crystal alignment film was formed using a liquid crystal alignment agent for weak anchoring film formation (AL-1).

[0122] (2) Formation of strongly anchored liquid crystal alignment film by rubbing orientation method A liquid crystal alignment agent for strong anchoring film formation (AL-14) was applied to the electrode formation surface of an electrode substrate using a spin coater. After heating on an 80°C hot plate for 1 minute, the substrate was heated in a 230°C oven with nitrogen purging for 30 minutes to form a coating with an average thickness of 100 nm. The surface of this coating was then rubbed twice using a rubbing machine with a roll wrapped in rayon cloth, at a roll rotation speed of 1,000 rpm, a stage movement speed of 30 mm / second, and a pile insertion length of 0.3 mm. At this time, the rubbing direction was set so that it was parallel to the direction of the double-headed arrow in Figure 2(b). The rubbing-oriented coating was ultrasonically cleaned in ultrapure water for 1 minute, and then dried in a 100°C oven for 10 minutes to form a strong anchoring liquid crystal alignment film.

[0123] (3) Manufacturing of FFS type liquid crystal display elements Using the pair of substrates prepared in (1) and (2) above, an FFS-type liquid crystal display element was manufactured in the same manner as in Example 10.

[0124] 2. Evaluation Adhesion and low-voltage driving were evaluated in the same manner as in Example 10, except that the liquid crystal display element manufactured in 1.(3) above was used. The reference cell for the low-voltage driving evaluation was manufactured using a liquid crystal alignment agent for strong anchoring film formation (AL-14). The evaluation results are shown in Table 4.

[0125] [Examples 20-27, Comparative Examples 7-9, and Comparative Example 11] Except for changing the liquid crystal alignment agent used as shown in Table 4, a rubbing-aligned FFS type liquid crystal display element was manufactured in the same manner as in Example 19, and its adhesion and low-voltage driving performance were evaluated. The evaluation results are shown in Table 4.

[0126] [Table 4]

[0127] As shown in Table 4, in Examples 10-27, which used the weak anchoring film formation liquid crystal alignment agents (AL-1)-(AL-9) of Examples 1-9, which have excellent inkjet coating properties, both adhesion and low-voltage driving were rated as particularly good (◎) or good (○), indicating a good balance of various properties. In particular, in Examples 11-14 and 20-23, which used the weak anchoring film formation liquid crystal alignment agents (AL-2)-(AL-5) in which the addition polymer [P] contains structural unit [C] in addition to structural unit [A] and structural unit [B], adhesion tended to be even better than in the other examples, and were rated as particularly good (◎). To achieve low-voltage driving while simultaneously achieving both adhesion and inkjet coating properties, it is preferable to include the addition polymer [P] in the liquid crystal alignment agent.

[0128] In contrast, Comparative Examples 4-9, which used the weak anchoring film-forming liquid crystal alignment agents (AL-10)-(AL-12) of Comparative Examples 1-3, which had poor inkjet coating properties, showed inferiority to the Examples in at least one of the following evaluations: adhesion and low-voltage driving. Specifically, Comparative Examples 4 and 7, which used an addition polymer that did not contain structural unit [A] instead of addition polymer [P], and Comparative Examples 6 and 9, which used an addition polymer that did not contain structural unit [A] or structural unit [B], showed poor adhesion (×). Furthermore, Comparative Examples 5 and 8, which used an addition polymer that did not contain structural unit [B] instead of addition polymer [P], showed a low-voltage driving evaluation of acceptable (△), which was inferior to Examples 10-27. In addition, Comparative Examples 10 and 11, which used only the strong anchoring film-forming liquid crystal alignment agent, showed particularly good adhesion (◎), but poor low-voltage driving (×), demonstrating the usefulness of the liquid crystal alignment agent of this disclosure.

[0129] From the results above, it has become clear that the liquid crystal alignment agent of this disclosure can enable low-voltage driving of liquid crystal elements, form a liquid crystal alignment film with excellent adhesion, and exhibit excellent coatability. [Explanation of Symbols]

[0130] 10...Liquid crystal element, 11...First substrate, 12...Second substrate, 13...Liquid crystal layer, 14...Common electrode, 15...Insulating film, 16...Pixel electrode, 17...Color filter, 18...Overcoat film, 19...Slit, 21,22...Liquid crystal alignment film, 23,24...Polarizing plate, 25...Liquid crystal molecule

Claims

1. A liquid crystal alignment agent comprising a structural unit [A] having a hydroxyl group bonded to a carbon atom in a chain structure or an aliphatic ring (excluding carbon atoms in a carbonyl group and carbon atoms constituting the main chain of the polymer), and an addition polymer [P] having a substructure represented by the following formula (1) and different from the structural unit [A]. * １ -C-O-R １ …(1) (In formula (1), R １ This is a monovalent, chain-like hydrocarbon group with a branched structure. １ (This symbol represents a bond with a carbon atom that makes up the main chain of the polymer.)

2. The liquid crystal alignment agent according to claim 1, wherein the structural unit [A] has a substructure represented by the following formula (2). * ２ ---O-A １ -C(B １ )(B ２ )-O+ …(2) (In formula (2), A １ is a single bond or a divalent organic group. B １ and B ２ are, independently of each other, a hydrogen atom, a halogen atom or a monovalent organic group. "* ２ " represents a bond with a carbon atom constituting the main chain of the polymer.)

3. A in formula (2) above １ The liquid crystal alignment agent according to claim 2, wherein the liquid crystal alignment agent does not have an aromatic ring.

4. A in formula (2) above １ The liquid crystal alignment agent according to claim 2, wherein is a substituted or unsubstituted divalent linear hydrocarbon group, or a divalent group containing -O- or -CO- between the carbon-carbon bonds in a substituted or unsubstituted divalent linear hydrocarbon group.

5. In the above formula (2), B １ and B ２ The liquid crystal alignment agent according to claim 2, wherein each of the members is independently a hydrogen atom, a monovalent hydrocarbon group, a monovalent halogenated hydrocarbon group, or a monovalent group containing -O- between the carbon-carbon bonds of a monovalent hydrocarbon group or halogenated hydrocarbon group.

6. The liquid crystal alignment agent according to claim 1, wherein the addition polymer [P] has a substructure represented by the following formula (3) and further comprises a structural unit [C] different from the structural unit [A] and the structural unit [B]. * ３ -C-O-R ２ …(3) (In formula (3), R ２ It is a monovalent linear hydrocarbon group. ３ (This symbol represents a bond with a carbon atom that makes up the main chain of the polymer.)

7. Furthermore, the liquid crystal alignment agent according to claim 1 contains at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide.

8. Furthermore, the liquid crystal alignment agent according to claim 1, further containing a crosslinking agent.

9. The liquid crystal alignment agent according to claim 8, wherein the crosslinking agent does not have an aromatic ring.

10. A liquid crystal alignment agent according to claim 1, for forming a weakly anchored liquid crystal alignment film.

11. A liquid crystal alignment film formed using the liquid crystal alignment agent described in any one of claims 1 to 10.

12. A liquid crystal element comprising the liquid crystal alignment film described in claim 11.

13. A method for manufacturing a liquid crystal element comprising a pair of substrates consisting of a first substrate and a second substrate, and a liquid crystal layer disposed between the pair of substrates, A method for manufacturing a liquid crystal element, comprising the step of applying a liquid crystal alignment agent according to any one of claims 1 to 10 to the surface of one of the pair of substrates to form a liquid crystal alignment film.

14. A liquid crystal alignment film formed with the liquid crystal alignment agent according to any one of claims 1 to 10 is a weakly anchored liquid crystal alignment film. The method for manufacturing a liquid crystal element according to claim 13, further comprising the step of forming a strongly anchoring liquid crystal alignment film having a stronger anchoring energy than the weakly anchoring liquid crystal alignment film on the surface of a substrate different from the substrate on which the weakly anchoring liquid crystal alignment film is formed, among the first substrate and the second substrate.

15. The method for manufacturing a liquid crystal element according to claim 14, wherein the strongly anchoring liquid crystal alignment film is a rubbing alignment film or a photo-alignment film.

16. The first substrate has a pair of electrodes, and the second substrate does not have electrodes. The strongly anchoring liquid crystal alignment film is formed on the surface of the first substrate. A method for manufacturing a liquid crystal element according to claim 14, wherein the weakly anchoring liquid crystal alignment film is formed on the surface of the second substrate.

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