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

Abstract

The present invention addresses the problem of obtaining a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal element which have excellent liquid crystal alignment properties, mechanical strength, adhesion to a substrate, and high temperature and humidity resistance. The liquid crystal aligning agent contains polyimide, and the polyimide comprises: a structural unit (I) having a partial structure represented by formula (1); and structural unit (II) (excluding structural unit (I)) The present invention is characterized by having a partial structure in which at least one methylene group contained in an alkylene structure having 5 or more carbon atoms is substituted by the same or different groups selected from the group consisting of-COO-,-OCO-,-O-,-CO-NR4-,-NR4-CO-,-NR4-and-CO-under the condition that the methylene groups are not adjacent to each other, and in which the at least one methylene group contained in the alkylene structure having 5 or more carbon atoms is substituted by the same or different groups selected from the group consisting of-COO-,-OCO-,-O-,-CO-NR4-,-NR4-CO-,-NR4-and-CO-.

Description

[0001] This application is a divisional application of the patent application No. 202210570180.1 filed on May 24, 2022, with the title of “Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal element”. TECHNICAL FIELD

[0002] The present application relates to a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal element. BACKGROUND

[0003] Liquid crystal elements are widely used in televisions or mobile devices, various monitors, and the like. With such versatility, higher quality of liquid crystal elements is required. Therefore, while the driving method or the element structure of the liquid crystal element is improved, the improvement of the liquid crystal alignment film, which is one of the constituent components of the liquid crystal element, is also promoted (for example, refer to Patent Literature 1 and Patent Literature 2).

[0004] In Patent Literature 1, it is disclosed that a liquid crystal alignment film is formed by using a polyamic acid having a partial structure in which a urea bond and an alkylene structure are bonded to the main chain, thereby improving the liquid crystal alignment property, the transparency, and the rubbing resistance. In addition, in Patent Literature 2, it is disclosed that a liquid crystal alignment film having less image sticking, high transmittance, contrast, and voltage holding characteristics, and good reworkability is obtained by blending a polymer having a urea bond or an amino group in the main chain with a polymer having a carbazole structure in the main chain.

[0005] [Patent Literature]

[0006] [Patent Literature]

[0007] [Patent Literature 1] Japanese Patent Publication No. 2014-98887

[0008] [Patent Literature 2] International Publication No. 2020 / 218331 SUMMARY

[0009] [Problems to be Solved by the Invention]

[0010] In order to achieve higher quality of liquid crystal elements, the present inventors and others have conducted research and obtained the following insight: by using a diamine having a partial structure in which an aromatic ring and a specific heteroatom-containing group and a short-chain alkylene structure are bonded, a polyamic acid is manufactured, and in the case of using either rubbing treatment or photo-alignment treatment to produce a liquid crystal alignment film, a liquid crystal alignment film showing good liquid crystal alignment property can be obtained. On the other hand, if the polyamic acid is imidized, the mechanical properties of the liquid crystal alignment film are reduced, or the adhesion of the liquid crystal alignment film to the substrate is reduced. If the case of producing a liquid crystal alignment film by rubbing treatment, or the reduction of yield, and the like are considered, a high mechanical strength is required for the film formed using a liquid crystal alignment agent.

[0011] In recent years, with the diversification of liquid crystal elements, it is assumed that liquid crystal elements are used in various environments. Therefore, it is also required that the liquid crystal elements have excellent high-temperature and high-humidity resistance. However, it is difficult to satisfy multiple characteristics such as liquid crystal alignment property, mechanical strength, adhesion to a substrate, high-temperature and high-humidity resistance, and there is room for further improvement in the liquid crystal alignment film.

[0012] The present application was made in view of the above circumstances, and a main object thereof is to provide a liquid crystal alignment agent which can obtain a liquid crystal alignment film having excellent liquid crystal alignment property, mechanical strength, adhesion to a substrate, and high-temperature and high-humidity resistance.

[0013] [Means of Solving the Problem]

[0014] The present application employs the following means in order to solve the above problem.

[0015] <1> A liquid crystal alignment agent comprising a polyimide, the polyimide comprising: a structural unit (I) having a partial structure represented by the following formula (1); and a structural unit (II) (excluding the structural unit (I)), having an alkylene structure having a carbon number of 5 or more or a partial structure having at least one methylene group of the alkylene structure having a carbon number of 5 or more substituted with the same or different group selected from the group consisting of -COO-, -OCO-, -O-, -CO-NR 4 4 -CO-, -NR 4 - and -CO- (R 4 is a hydrogen atom or a monovalent organic group).

[0016] [Chemical Formula 1]

[0017]

[0018] (In formula (1), Ar 1 and Ar 2 are each independently a divalent aromatic ring group. X 1 and X 2 are each independently -NR 2 -, -O-, -S-, 1 -NR 2 -CO- or 1 -O-CO-. 1 represents a bonding group bonded to Ar 1 or Ar 2 . R 1 is an alkanediyl group having a carbon number of 2 or more or an alkanediyl group having a carbon number of 2 or more which contains -NR 3 ​-、-O-、-S-、-CO-NR 3 -、-NR 3 Divalent groups of -CO-, -COO-, or -OCO-. R 2 and R 3 Each can be independently a hydrogen atom or a monovalent organic group. "Indicates a bond."

[0019] <2> A liquid crystal alignment film formed using the liquid crystal alignment agent according to <1>.

[0020] <3> A liquid crystal element comprising a liquid crystal alignment film according to <2>.

[0021] [The effects of the invention]

[0022] According to the liquid crystal alignment agent of the present invention, a liquid crystal alignment film with excellent liquid crystal alignment, mechanical strength, adhesion to the substrate, and resistance to high temperature and high humidity can be obtained. Detailed Implementation

[0023] The following provides a detailed description of matters related to the form disclosed herein. Furthermore, in this specification, the term "hydrocarbon group" encompasses chain-like hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. "Chain-like hydrocarbon group" refers to a straight-chain hydrocarbon group or a branched hydrocarbon group that consists only of a chain structure and does not contain a ring structure. It can be saturated or unsaturated. "Alicyclic hydrocarbon group" refers to a hydrocarbon group that contains only an alicyclic hydrocarbon structure as its ring structure and does not contain an aromatic ring structure. It is not necessary for it to consist only of an alicyclic hydrocarbon structure; it may also include a group with a chain structure in a portion thereof. "Aromatic hydrocarbon group" refers to a hydrocarbon group that contains an aromatic ring structure as its ring structure. It is not necessary for it to consist only of an aromatic ring structure; it may also include a chain structure or an alicyclic hydrocarbon structure in a portion thereof. The "main chain" of a polymer refers to the longest "trunk" portion of the atomic chain of the polymer. The "side chain" of a polymer refers to the branched portion from the "trunk" of the polymer. The term "organic radical" refers to an atomic group formed by removing any hydrogen atom from a carbon-containing compound (i.e., an organic compound).

[0024] Liquid crystal alignment agent

[0025] The liquid crystal alignment agent disclosed herein contains a polyimide (hereinafter also referred to as "polyimide (P)") comprising the following structural units (I) and (II).

[0026] Structural unit (I): A structural unit having a partial structure (A) represented by the following equation (1).

[0027] [Chemistry 2]

[0028]

[0029] (In formula (1), Ar 1 and Ar 2 are each independently a divalent aromatic ring group. X 1 and X 2 are each independently -NR 2 -, -O-, -S-, 1 -NR 2 -CO- or 1 -O-CO-. 1 " indicates a bond to Ar 1 or Ar 2 . R 1 is an alkanediyl group having 2 or more carbons or a divalent group containing -NR 3 -, -O-, -S-, -CO-NR 3 -, -NR 3 -CO-, -COO- or -OCO- between carbon-carbon bonds of an alkanediyl group having 2 or more carbons. R 2 and R 3 are each independently a hydrogen atom or a monovalent organic group. " indicates a bond.

[0030] Structural unit (II): a structural unit of a partial structure (B) having an alkylene structure having 5 or more carbons or at least one methylene group of the alkylene structure having 5 or more carbons being substituted with the same or different group selected from the group consisting of -COO-, -OCO-, -O-, -CO-NR 4 -, -NR 4 -CO-, -NR 4 - and -CO- under the condition that they are not adjacent to each other (wherein structural unit (I) is excluded. R 4 is a hydrogen atom or a monovalent organic group.

[0031] Hereinafter, the polyimide (P) contained in the liquid crystal alignment agent of the present disclosure and other components, if any, are described in detail.

[0032] <Polyimide (P)>

[0033] Structural unit (I)

[0034] In the formula (1), Ar 1 and Ar 2The bivalent aromatic ring group represented is a group in which two hydrogen atoms are removed from a ring portion of a substituted or unsubstituted aromatic ring. As the bivalent aromatic ring group, a substituted or unsubstituted bivalent aromatic hydrocarbon group and a substituted or unsubstituted bivalent aromatic heterocyclic group can be exemplified. As the aromatic heterocyclic group, a nitrogen-containing aromatic heterocyclic group, an oxygen-containing aromatic heterocyclic group, a sulfur-containing aromatic heterocyclic group, and the like can be exemplified. Among them, the nitrogen-containing aromatic heterocyclic group is preferred. Further, Ar 1 and Ar 2 may also have a substituent in the aromatic ring portion. As the substituent, an alkyl group having 1 to 3 carbon atoms, a halogen atom, a cyano group, and the like can be exemplified.

[0035] As specific examples of Ar 1 , Ar 2 , a bivalent aromatic hydrocarbon group can exemplify a bivalent group having a benzene ring, a biphenyl ring, a naphthalene ring, or an anthracene ring; a bivalent nitrogen-containing aromatic heterocyclic group can exemplify a bivalent group having a pyridine ring, a pyrimidine ring, a pyridazine ring, or a pyrazine ring; a bivalent oxygen-containing aromatic heterocyclic group can exemplify a bivalent group using a furan ring; and a bivalent sulfur-containing aromatic heterocyclic group can exemplify a bivalent group having a thiophene ring. From the viewpoint of achieving improvement in mechanical strength and high transmittance by high densification of the liquid crystal alignment film, the bivalent aromatic ring group of Ar 1 and Ar 2 is preferably a substituted or unsubstituted bivalent aromatic hydrocarbon group or a substituted or unsubstituted bivalent nitrogen-containing aromatic heterocyclic group, and more preferably a substituted or unsubstituted phenylene group, a substituted or unsubstituted biphenylene group, or a pyridine diyl group. From the aspect that the improvement effect on the film strength of the liquid crystal alignment film is higher, further preferably a substituted or unsubstituted phenylene group or a substituted or unsubstituted biphenylene group. The substituent is preferably a methyl group or a halogen atom.

[0036] In the case where the group represented by X 1 and X 2 is -NR 2 -CO- or 1 -NR 2 , as the monovalent organic group represented by R 2 , an alkyl group having 1 to 5 carbon atoms, or a leaving group which is detached by at least either of heat and light is preferred, and an alkyl group having 1 to 5 carbon atoms or a heat leaving group is more preferred. From the viewpoint of achieving simplification of the process by detaching the group R 2 during the process of forming the liquid crystal alignment film by applying the liquid crystal alignment agent to a substrate and heating, the heat leaving group is preferably a group which is decomposed at a temperature of 120°C to 300°C and is substituted to a hydrogen atom. Specifically, a tert-butyloxycarbonyl group (Boc group) or a 9-fluorenylmethoxycarbonyl group is preferred, and a tert-butyloxycarbonyl group is particularly preferred. R 2 is preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a heat leaving group.

[0037] In terms of improving liquid crystal alignment, X 1 and X 2 Preferred is -NR 2 -、-O- or -S-.

[0038] In terms of obtaining liquid crystal elements with minimal retardation and good liquid crystal alignment even under prolonged backlight illumination, X 1 and X 2 For -NR 2 -or 1 -NR 2 In the case of -CO-, Ar is preferred. 1 and Ar 2 At least one of them is a substituted or unsubstituted divalent nitrogen-containing aromatic heterocyclic group, more preferably Ar 1 and Ar 2 Both are substituted or unsubstituted divalent nitrogen-containing aromatic heterocyclic groups, and are preferably Ar. 1 and Ar 2 Both are substituted or unsubstituted pyridinyl groups. Furthermore, from the same perspective, in X... 1 and X 2 In the case of -O- or -S-, Ar is preferred. 1 and Ar 2 At least one of them is a substituted or unsubstituted divalent aromatic hydrocarbon group, more preferably Ar. 1 and Ar 2 Both are substituted or unsubstituted divalent aromatic hydrocarbon groups, and Ar is preferred. 1 and Ar 2 Both are either substituted or unsubstituted phenylene compounds.

[0039] R 1 The alkyldiyl group with 2 or more carbon atoms is preferably linear. In terms of improving both adhesion to the substrate and film strength, the alkyldiyl group preferably has 2 to 8 carbon atoms, more preferably 2 to 6, and even more preferably 2 to 4, and even more preferably 2 or 3.

[0040] In R 1 The group represented is an alkane with two or more carbon atoms whose carbon-carbon bonds contain -NR. 3 -、-O-、-S-、-CO-NR 3 -、-NR 3In the case of a divalent group of -CO-, -COO-, or -OCO-, the alkandiyl group having 2 or more carbons is preferably linear. In terms of being able to improve adhesion to a substrate and film strength in balance, the alkandiyl group preferably has 2 to 7 carbons, more preferably 2 to 5 carbons, and even more preferably 2 or 3 carbons.

[0041] Regarding R 3 , the specific examples and preferred examples of R 2 apply.

[0042] In terms of being able to promote extension of the molecular chain of the polymer in rubbing treatment, and in terms of being able to promote rearrangement of the molecular chain of the polymer by heat treatment after exposure in photo-alignment treatment, R 1 in the above is preferably an alkandiyl group having 2 or more carbons, more preferably a linear alkandiyl group having 2 to 8 carbons, even more preferably a linear alkandiyl group having 2 to 6 carbons, and even more preferably a linear alkandiyl group having 2 to 4 carbons, and particularly preferably a linear alkandiyl group having 2 or 3 carbons.

[0043] As specific examples of the partial structure (A) represented by the formula (1), the partial structures represented by the following formulae (1-1) to (1-24), and the like can be given.

[0044] [Chemical Formula 3]

[0045]

[0046] [Chemical Formula 4]

[0047]

[0048] [Chemical Formula 5]

[0049]

[0050] [Chemical Formula 6]

[0051]

[0052] (In formulae (1-1) to (1-24), "— " represents a bond.)

[0053] ​In the polyimide (P), the content of the structural unit (I) is preferably 1 mol% or more, more preferably 5 mol% or more, further preferably 10 mol% or more, and further more preferably 15 mol% or more, with respect to all the structural units derived from the monomers constituting the polyimide (P). In addition, the content of the structural unit (I) is preferably 49 mol% or less, more preferably 45 mol% or less, and further preferably 40 mol% or less, with respect to all the structural units derived from the monomers constituting the polyimide (P). If the content of the structural unit (I) is 1 mol% or more, the effect of improving the mechanical properties can be sufficiently obtained by introducing the aromatic ring-specific heteroatom-containing group-alkylene structure derived from the structural unit (I), and is thus preferred in this respect. In addition, if the content of the structural unit (I) is 49 mol% or less, a sufficient amount of the structural unit (II), i.e., the relatively long chain unit derived from the structural unit (II), can be introduced into the polyimide (P), and the effects of improving the adhesion to the substrate and the high-temperature high-humidity resistance can be improved, and is thus preferred in this respect. In addition, the polyimide (P) can have one kind of the structural unit (I) alone, or two or more kinds of the structural unit (I).

[0054] Structural Unit (II)

[0055] The structural unit (II) is a structural unit having the partial structure (B). That is, the structural unit (II) is a structural unit (IIa) having an alkylene structure having 5 or more carbons, or a structural unit (IIb) having a partial structure in which at least one methylene group of the alkylene structure having 5 or more carbons is substituted with the same or different group selected from the group consisting of -COO-, -OCO-, -O-, -CO-NR 4 4 -CO-, -NR 4 - and -CO- (hereinafter, also referred to as "functional group F1"). 4 R is a hydrogen atom or a monovalent organic group. In addition, the structural unit (II) is a structural unit different from the structural unit (I).

[0056] In terms of the effect of improving the high-temperature high-humidity resistance of the liquid crystal element, the structural unit (II) is preferably a partial structure (R 4a 4a -CO-, -NR 4 - and -CO- (hereinafter, also referred to as "functional group F1") in the condition that the methylene groups are not adjacent to each other. R 4 R is a hydrogen atom or a monovalent organic group. R 4a is a monovalent thermally dissociable group.​​

[0057] The alkylene structure of the structural unit (IIa) is preferably linear. In terms of improving adhesion to the substrate, the alkylene structure preferably has 6 or more carbon atoms, more preferably 7 or more, and even more preferably 8 or more. Furthermore, from the viewpoint of suppressing a decrease in the mechanical strength of the film, the alkylene structure preferably has 15 or fewer carbon atoms, more preferably 12 or fewer, and even more preferably 10 or fewer.

[0058] From the viewpoint of achieving good mechanical strength and adhesion of the membrane, the structural unit (IIb) is preferably an alkylene structure having 5 or more carbon atoms, wherein at least one methylene group is selected from -COO- 2 , 2 -OCO-、-O-、-CO-NR 4 - 2 , 2 -NR 4 -CO-、-NR 4 - and -CO- (where, " 2 "This refers to a partial structure formed by substituting the same or different groups from the group consisting of groups that are different from aromatic ring groups (preferably alkyl diesters). In structural unit (IIb), the alkylene structure is preferably linear. From the viewpoint of further improving adhesion to the substrate, the number of carbons in the alkylene structure is preferably 6 or more, more preferably 7 or more, and even more preferably 8 or more. In addition, from the viewpoint of suppressing the decrease in the mechanical strength of the film, the number of carbons in the alkylene structure is preferably 15 or less, more preferably 12 or less, and even more preferably 10 or less."

[0059] The number of functional groups F1 in the structural unit (IIb), that is, the number of functional groups F1 that substitute the methylene group in the alkylene structure having 5 or more carbon atoms, is not particularly limited, but is preferably 1 to 4, more preferably 1 or 2. Furthermore, when the structural unit (II) has two or more functional groups F1, the two or more functional groups F1 are introduced into the structural unit (IIb) under the condition that they are not adjacent to each other.

[0060] As R 4 The monovalent organic group represented can be listed as R 2 The same group as the monovalent organic group exemplified in the description. Based on R 2 For the same reason, R 4 The monovalent organic group represented is preferably tert-butoxycarbonyl (Boc group) or 9-fluorenylmethoxycarbonyl, and particularly preferably tert-butoxycarbonyl. R 4Preferably, it is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a thermally detachable group; more preferably, it is an alkyl group having 1 to 3 carbon atoms or a thermally detachable group; and even more preferably, it is a thermally detachable group.

[0061] In terms of obtaining liquid crystal elements with superior resistance to high temperature and high humidity, the structural unit (IIb) is preferably selected from -COO-, -OCO-, -O-, and -CO-NR. 4a -、-NR 4a -CO-、-NR 4 Partial structures formed by substitution of the same or different groups in the group consisting of - and -CO- (R 4 It can be a hydrogen atom or a monovalent organic group. R 4a It is a monovalent thermally detachable group. More preferably, it is -COO- 2 , 2 -OCO-、-O-、-CO-NR 4a - 2 , 2 -NR 4a -CO- and at least one of -CO-. Furthermore, " 2 "This has the same meaning as the above."

[0062] As specific examples of partial structures (B) possessed by structural unit (II), the partial structures represented by equations (2-1) to (2-22) below can be listed.

[0063] [Chemistry 7]

[0064]

[0065] [Chemistry 8]

[0066]

[0067] In the polyimide (P), the content of the structural unit (II) is preferably 1 mol% or more, more preferably 5 mol% or more, further preferably 10 mol% or more, and further more preferably 15 mol% or more, with respect to all the structural units derived from the monomers constituting the polyimide (P). In addition, the content of the structural unit (II) is preferably 49 mol% or less, more preferably 45 mol% or less, and further preferably 40 mol% or less, with respect to all the structural units derived from the monomers constituting the polyimide (P). If the content of the structural unit (II) is 1 mol% or more, the adhesion to a substrate and the improvement effect on the high-temperature and high-humidity resistance can be improved by introducing a relatively long chain derived from the structural unit (II), and thus this is preferable in terms of this aspect. In addition, if the content of the structural unit (II) is 49 mol% or less, a sufficient amount of the structural unit (I) can be introduced into the polyimide (P), and the improvement effect on the mechanical properties by the introduction of the aromatic ring-specific heteroatom-containing group-alkylene structure can be improved, and thus this is preferable in terms of this aspect. Note that the polyimide (P) can have only one kind of the structural unit (II), or can have two or more kinds of the structural unit (II).

[0068] In the polyimide (P), the ratio of the structural unit (I) to the structural unit (II) (structural unit (I) / structural unit (II)) is preferably 1 / 10 to 10 / 1, more preferably 1 / 4 to 4 / 1, further preferably 1 / 3 to 3 / 1, and further more preferably 1 / 2 to 2 / 1, in terms of a molar ratio. If the ratio of the structural unit (I) to the structural unit (II) is in the above range, the improvement effect on the mechanical strength of the film, the adhesion to a substrate, and the improvement effect on the high-temperature and high-humidity resistance (particularly, the improvement effect on the mechanical strength of the film) can be further improved, and thus this is preferable in terms of this aspect.

[0069] Production of the polyimide (P)

[0070] The method for producing the polyimide (P) is not particularly limited. The polyimide (P) can be produced, for example, by obtaining a polyamic acid (hereinafter, also referred to as "polyamic acid (P)") having the structural unit (I) and the structural unit (II) by reacting a tetracarboxylic dianhydride with a diamine, and then, imidizing the polyamic acid (P) by dehydration ring closure.

[0071] The method for producing the polyamic acid (P) is also not particularly limited. In terms of the high degree of freedom in the selection of the monomers, it is preferable to introduce the structural unit (I) into the polymer using a diamine having the partial structure (A) (hereinafter also referred to as "specific diamine A"). In addition, it is preferable to introduce the structural unit (II) into the polymer using a diamine having the partial structure (B) (hereinafter also referred to as "specific diamine B"). One preferable form of the polyimide (P) is a polyimide having a structural unit derived from a diamine having the partial structure (A) and a structural unit derived from a diamine having the partial structure (B).

[0072] (tetracarboxylic dianhydride)

[0073] As the tetracarboxylic dianhydride used in the synthesis of the polyamic acid (P), for example, aliphatic tetracarboxylic dianhydrides, alicyclic tetracarboxylic dianhydrides, aromatic tetracarboxylic dianhydrides, and the like can be exemplified. As specific examples thereof, the aliphatic tetracarboxylic dianhydrides can include 1,2,3,4-butanetetracarboxylic dianhydride, ethylenediaminetetraacetic dianhydride, and the like; the alicyclic tetracarboxylic dianhydrides can include 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic dianhydride, 5-(2,5-dioxotetrahydrofuran-3-yl)-3a,4,5,9b-tetrahydronaphtho[1,2-c]furan-1,3-dione, 5-(2,5-dioxotetrahydrofuran-3-yl)-8-methyl-3a,4,5,9b-tetrahydronaphtho[1,2-c]furan-1,3-dione, 2,4,6,8-tetracarboxybicyclo[3.3.0]octane-2:4,6:8-dianhydride, cyclopentanetetracarboxylic dianhydride, cyclohexanetetracarboxylic dianhydride, 3,5,6-tricarboxy-2-carboxymethyl-norbornane-2:3,5:6-dianhydride, and the like; the aromatic tetracarboxylic dianhydrides can include pyromellitic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, ethylene glycol bis-trimellitate anhydride, 4,4'-carbonylbiphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and the like, and in addition thereto, the tetracarboxylic dianhydrides described in Japanese Patent Application Publication No. 2010-97188 can be used. One kind or two or more kinds in combination can be used as the tetracarboxylic dianhydride.

[0074] In terms of high solubility and the ability to obtain a liquid crystal alignment film that exhibits good electrical properties, the tetracarboxylic dianhydride used in the synthesis of the polyamic acid (P) preferably contains at least one selected from the group consisting of aliphatic tetracarboxylic dianhydrides and alicyclic tetracarboxylic dianhydrides, and more preferably contains an alicyclic tetracarboxylic dianhydride. The proportion of the alicyclic tetracarboxylic dianhydride used is preferably 20 mol% or more, more preferably 50 mol% or more, and further preferably 80 mol% or more, relative to the total amount of the tetracarboxylic dianhydride used in the synthesis of the polyamic acid (P).

[0075] In the case of forming a liquid crystal alignment film by a photo-alignment method, as the tetracarboxylic dianhydride used in the synthesis of the polyamic acid (P), a tetracarboxylic dianhydride having a cyclobutane structure (hereinafter, also referred to as "specific acid dianhydride") can be preferably used. The specific acid dianhydride is preferably a compound represented by the following formula (4).

[0076] [Chem. 9]

[0077]

[0078] (In formula (4), R 11 , R 12 , R 13 , and R 14 are each independently a hydrogen atom, a halogen atom, an alkyl group having a carbon number of 1 to 3, a halogenated alkyl group having a carbon number of 1 to 3, or an alkoxy group having a carbon number of 1 to 3.)

[0079] Among them, the specific acid dianhydride is particularly preferably one or both of 1,2,3,4-cyclobutane tetracarboxylic dianhydride and 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride. In addition, as the specific acid dianhydride, only one kind can be used, or two or more kinds can be used.

[0080] In the case of using the specific acid dianhydride at the time of synthesizing the polyamic acid (P), from the viewpoint of imparting a good liquid crystal alignment property by light irradiation, the use ratio of the specific acid dianhydride with respect to the total amount of the tetracarboxylic dianhydride used in the synthesis of the polyamic acid (P) is preferably 20 mol% or more, more preferably 50 mol% or more, more preferably 80 mol% or more, and further preferably 90 mol% or more.

[0081] (Specific diamine A)

[0082] The specific diamine A is not particularly limited as long as it has the partial structure (A) represented by the above formula (1). As specific examples of the specific diamine A, for example, compounds represented by the following formulas (5-1) to (5-24), and the like can be exemplified.

[0083] [Chem. 10]

[0084]

[0085] [Chem. 11]

[0086]

[0087] [Chem. 12]

[0088]

[0089] [Chem. 13]

[0090]

[0091] In the synthesis of the polyimide (P), the use amount of the specific diamine A is preferably 2 mol% or more, more preferably 10 mol% or more, further preferably 20 mol% or more, and still further preferably 30 mol% or more, relative to the total amount of the diamine compound used in the synthesis of the polyimide (P). In addition, the use amount of the specific diamine A is preferably 98 mol% or less, more preferably 90 mol% or less, further preferably 80 mol% or less, and still further preferably 70 mol% or less, relative to the total amount of the diamine compound used in the synthesis of the polyimide (P). If the use amount of the specific diamine A is 2 mol% or more, the improvement effect on the mechanical properties due to the introduction of the aromatic ring-specific heteroatom-containing group-alkylene structure can be increased, which is preferable in this respect. In addition, if the use amount of the specific diamine A is 98 mol% or less, a sufficient amount of the structural unit derived from the specific diamine B, i.e., a relatively long chain unit, can be introduced into the polyimide (P), and the improvement effect on the adhesion to a substrate and the high-temperature high-humidity resistance can be increased, which is preferable in this respect. As the specific diamine A, one kind can be used alone, or two or more kinds can be used in combination.

[0092] (Specific diamine B)

[0093] The specific diamine B is not particularly limited as long as it has the partial structure (B). The specific diamine B is preferably an aromatic diamine, and for example, a compound represented by the following formula (6) can be given.

[0094] [Chem. 14]

[0095]

[0096] (In formula (6), Ar 5 and Ar 6 are each independently a divalent aromatic ring group. R 6 is an alkanediyl group having 5 or more carbon atoms, or a dimethyl group in which at least one methylene group of an alkanediyl group having 5 or more carbon atoms is substituted with the same or different group selected from the group consisting of -COO-, -OCO-, -O-, -CO-NR 4 -, -NR 4 -CO-, -NR 4 -, and -CO- in such a manner that they are not adjacent to each other. R 4 is a hydrogen atom or a monovalent organic group.)

[0097] In the formula (6), as the divalent aromatic ring group represented by Ar 5 and Ar 6 , the divalent aromatic ring group in the formula (1) can be given. 1 and Ar 2The divalent aromatic ring group represented by Ar 5 and Ar 6 may also have a substituent in the aromatic ring portion. As the substituent, an alkyl group having a carbon number of 1 to 3, a halogen atom, a cyano group, and the like can be exemplified. From the viewpoint of achieving high densification and high transmittance of the liquid crystal alignment film, Ar 5 and Ar 6 represented by Ar are preferably a divalent group having a benzene ring, a naphthalene ring, a pyridine ring, or a pyrimidine ring, and more preferably a divalent group having a benzene ring or a pyridine ring.

[0098] The divalent group represented by R 6 may be exemplified. As the divalent group represented by R 6 may be exemplified.

[0099] As specific examples of the specific diamine B, for example, compounds represented by the following formulas (6-1) to (6-23), and the like can be exemplified.

[0100] [Chemical Formula 15]

[0101]

[0102] [Chemical Formula 16]

[0103]

[0104] [Chemical Formula 17]

[0105]

[0106] [Chemical Formula 18]

[0107]

[0108] In the polyimide (P), the use amount of the specific diamine B is preferably 2 mol% or more, more preferably 10 mol% or more, further preferably 20 mol% or more, and further more preferably 30 mol% or more, relative to the total amount of diamines used in the synthesis of the polyimide (P). In addition, the use amount of the specific diamine B is preferably 98 mol% or less, more preferably 90 mol% or less, further preferably 80 mol% or less, and further more preferably 70 mol% or less, relative to the total amount of diamines used in the synthesis of the polyimide (P). If the use amount of the specific diamine B is 2 mol% or more, the adhesion to a substrate and the improvement effect on high-temperature and high-humidity resistance can be improved by introducing a relatively long chain derived from the specific diamine B, and thus this is preferable in terms of this aspect. In addition, if the use amount of the specific diamine B is 98 mol% or less, a sufficient amount of the structural unit (I) can be introduced into the polyimide (P), and the improvement effect on the mechanical properties by the introduction of the aromatic ring-specific heteroatom-containing group-alkylene structure can be improved, and thus this is preferable in terms of this aspect. As the specific diamine B, one kind can be used alone, or two or more kinds can be used in combination.

[0109] In the polyimide (P), the ratio of the specific diamine A to the specific diamine B (specific diamine A / specific diamine B) is preferably 1 / 10 to 10 / 1, more preferably 1 / 4 to 4 / 1, further preferably 1 / 3 to 3 / 1, and further more preferably 1 / 2 to 2 / 1, in terms of molar ratio. If the ratio of the specific diamine A to the specific diamine B is in the range described above, the improvement effect on the mechanical strength of the film and the improvement effect on the adhesion to a substrate and the high-temperature and high-humidity resistance are further improved, and thus this is preferable.

[0110] (Other diamines)

[0111] The diamines used in the synthesis of the polyimide (P) can be only the specific diamine A and the specific diamine B, but can also include the specific diamine A and the specific diamine B, and a diamine (hereinafter also referred to as "other diamine") that does not have either of the partial structure (A) and the partial structure (B). As the other diamine, aliphatic diamines, alicyclic diamines, aromatic diamines, diaminoorganosiloxanes, and the like can be exemplified.

[0112] As specific examples of the other diamines, aliphatic diamines can include ethylenediamine, tetramethylenediamine, and the like; alicyclic diamines can include p-cyclohexanediamine, 4,4'-methylenebis(cyclohexylamine), and the like; and diaminoorganosiloxanes can include 1,3-bis(aminopropyl)-tetramethyldisiloxane, and the like.

[0113] As the aromatic diamine, the following can be mentioned: p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4,4'-diaminodiphenylamine, 4-aminophenyl-4'-aminobenzoate, 4,4'-diaminoazobenzene, 3,5-diaminobenzoic acid, N,N-bis(4-aminophenyl)methylamine, N,N'-bis(4-aminophenyl)-benzidine, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 4,4'-diaminodiphenylether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-(phenylenediisopropylidene)dianiline, 1,4-bis(4-aminophenoxy)benzene, 4-(4-aminophenoxy carbonyl)-1-(4-aminophenyl)piperidine, 4,4'-[4,4'-propane-1,3-diylbis(piperidine-1,4-diyl)]dianiline, cholexyl oxydiaminobenzene, cholexyl diamino benzoate, cholexyl diamino benzoate, lanoxyl diamino benzoate, 3,6-bis(4-aminobenzoyloxy)cholestan, 3,6-bis(4-aminophenoxy)cholestan, 1,1-bis(4-((aminophenyl)methyl)phenyl)-4-butylcyclohexane, 2,5-diamino-N,N-diallylaniline, compounds represented by the following formulae (7-1) to (7-5) (in formulae (7-1) to (7-4), n is an integer of 1 to 20), and the like.

[0114] [Chemical 19]

[0115]

[0116] In addition, as the other diamine, in addition to the above, the diamine described in Japanese Patent Application Publication No. 2010-97188 can be used. Furthermore, as the other diamine, one kind can be used alone, or two or more kinds can be used in combination.

[0117] (Synthesis of polyimide (P))

[0118] In the case where the polyimide (P) is obtained by imidization of the polyamic acid (P), first, the polyamic acid (P) is obtained by reacting the tetracarboxylic dianhydride with the diamine, as necessary, together with a molecular weight adjustor.

[0119] In the synthesis reaction of the polyamic acid (P), the ratio of the use of the tetracarboxylic dianhydride to the diamine is preferably 1 equivalent of the amino group of the diamine to 0.2 to 2 equivalents of the acid anhydride group of the tetracarboxylic dianhydride. As the molecular weight adjusting agent, for example, acid monomers such as maleic anhydride, phthalic anhydride, itaconic anhydride, monoamine compounds such as aniline, cyclohexylamine, n-butylamine, monoisocyanate compounds such as phenyl isocyanate, naphthyl isocyanate, and the like can be exemplified. The use ratio of the molecular weight adjusting agent is preferably 20 mass% or less relative to 100 mass% of the total of the tetracarboxylic dianhydride and the diamine used.

[0120] The synthesis reaction of the polyamic acid (P) is preferably performed in an organic solvent. The reaction temperature at this time is preferably -20°C to 150°C, and the reaction time is preferably 0.1 hour to 24 hours. As the organic solvent used in the reaction, for example, aprotic polar solvents, phenol-based solvents, alcohol-based solvents, ketone-based solvents, ester-based solvents, ether-based solvents, halogenated hydrocarbons, hydrocarbons, and the like can be exemplified. Among them, it is preferable to use one or more selected from the group consisting of N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, tetramethyl urea, hexamethylphosphoric triamide, m-cresol, dimethylphenol, and halogenated phenol as the reaction solvent, or to use a mixture of one or more of them with another organic solvent (for example, butyl cellosolve, diethylene glycol diethyl ether, and the like). The amount of the organic solvent used is preferably an amount in which the total amount of the tetracarboxylic dianhydride and the diamine becomes 0.1 to 50 mass% relative to the total amount of the reaction solution.

[0121] Subsequently, the obtained polyamic acid (P) is subjected to dehydration ring closure. The dehydration ring closure of the polyamic acid (P) is preferably performed by a method in which the polyamic acid (P) is dissolved in an organic solvent, a dehydrating agent and a dehydration ring closure catalyst are added to the solution, and heating is performed as necessary. In the method, as the dehydrating agent, for example, acid anhydrides such as acetic anhydride, propionic anhydride, trifluoroacetic anhydride, and the like can be used. The amount of the dehydrating agent used is preferably 0.01 to 20 moles relative to 1 mole of the amic acid structure of the polyamic acid (P). As the dehydration ring closure catalyst, for example, tertiary amines such as pyridine, collidine, lutidine, triethylamine, and the like can be used. The amount of the dehydration ring closure catalyst used is preferably 0.01 to 10 moles relative to 1 mole of the dehydrating agent used. As the organic solvent used in the dehydration ring closure reaction, the organic solvents exemplified as the organic solvent used in the synthesis of the polyamic acid (P) can be exemplified. The reaction temperature of the dehydration ring closure reaction is preferably 0°C to 180°C. The reaction time is preferably 1.0 to 120 hours.

[0122] In this way, a solution containing the polyimide (P) is obtained. The reaction solution containing the polyimide (P) can be directly used for the production of the liquid crystal alignment agent, or the polyimide (P) can be isolated and then used for the production of the liquid crystal alignment agent.

[0123] The polyimide (P) preferably has an imidization rate of 30% or more. Here, by introducing the partial structure (A) into the main chain of the polyimide, the organic film formed using the liquid crystal alignment agent can be imparted with good liquid crystal alignment properties, regardless of whether rubbing treatment or photo-alignment treatment is used. On the other hand, it is known that if a polyamic acid having the partial structure (A) is imidized, a decrease in mechanical properties or a decrease in adhesion to a substrate tends to easily occur. With regard to the decrease in mechanical properties or the decrease in adhesion to a substrate of the liquid crystal alignment film caused by imidization of the polyamic acid having the partial structure (A), there is a tendency that the greater the imidization rate, the greater the influence.

[0124] In view of this aspect, by introducing the partial structure (A) and the partial structure (B) into the main chain of the polyimide, even if the polyimide (P) has a high imidization rate, a liquid crystal alignment film that can suppress a decrease in mechanical properties and a decrease in adhesion to a substrate, and further has excellent high-temperature high-humidity resistance can be formed. From the viewpoint of improving the high-temperature high-humidity resistance of the liquid crystal alignment film, the imidization rate of the polyimide (P) is more preferably 40% or more, further preferably 45% or more, further more preferably 60% or more, and particularly preferably 80% or more. In addition, from the viewpoint of sufficiently improving the film strength, the imidization rate of the polyimide (P) is preferably 99% or less, and more preferably 90% or less.

[0125] Further, the imidization rate is expressed as a percentage of the number of imide ring structures with respect to the total number of amic acid structures and imide ring structures of the polyimide (P). In addition, part of the imide ring can be an iso-imide ring.

[0126] With regard to the solution viscosity of the polyimide (P), when a solution having a concentration of 10 mass% is prepared, it is preferably a solution having a solution viscosity of 10 mPa s to 800 mPa s, and more preferably a solution having a solution viscosity of 15 mPa s to 500 mPa s. Further, the solution viscosity (mPa s) is a value obtained by measuring a polymer solution having a concentration of 10 mass% of a good solvent (for example, γ-butyrolactone, N-methyl-2-pyrrolidone, or the like) of the polyimide (P) using an E-type rotational viscometer at 25°C.

[0127] The weight average molecular weight (Mw) of the polyimide (P) in terms of polystyrene as determined by gel permeation chromatography (GPC) is preferably from 1,000 to 500,000, more preferably from 2,000 to 300,000. In addition, the molecular weight distribution (Mw / Mn) represented by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) in terms of polystyrene as determined by GPC is preferably 7 or less, more preferably 5 or less.

[0128] The content ratio of the polyimide (P) in the liquid crystal alignment agent is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 15 parts by mass or more, relative to 100 parts by mass of the total of the solid components (i.e., components other than the solvent) in the liquid crystal alignment agent. In addition, one kind of polyimide (P) alone or two or more kinds of polyimide (P) in combination can be used in the preparation of the liquid crystal alignment agent.

[0129] <Other Components>

[0130] The liquid crystal alignment agent of the present disclosure can also contain components other than the polyimide (P) (hereinafter also referred to as "other components"). Hereinafter, the other components are described.

[0131] (Other Polymers)

[0132] The liquid crystal alignment agent of the present disclosure can also contain a polymer other than the polyimide (P) (hereinafter also referred to as "other polymer") in order to further improve the liquid crystal alignment properties and electrical properties of the liquid crystal alignment film formed using the liquid crystal alignment agent.

[0133] The main skeleton of the other polymer is not particularly limited, and examples thereof include polyamide acid, polyamide acid ester, polyimide (except for the polyimide (P)), polyorganosiloxane, polyester, polyenamine, polyurea, polyamide, polyamide-imide, polybenzoxazole precursor, polybenzoxazole, cellulose derivative, polyacetal, and the like. The other polymer is preferably a polymer that does not have either of the structural unit (I) and the structural unit (II).

[0134] As the other polymer, at least one polymer selected from the group consisting of polyamide acid and polyamide acid ester (hereinafter also referred to as "polymer (Q)") can be preferably used. It is considered that, according to the liquid crystal alignment agent in which the polyimide (P) and the polymer (Q) are blended, phase separation of the polyimide (P) and the polymer (Q) is easily generated in the liquid crystal alignment film, the polyimide (P) easily deviates to exist in the upper layer, and thus the liquid crystal alignment properties and the rubbing resistance of the liquid crystal alignment film are improved, and a liquid crystal alignment film having excellent adhesion to a substrate can be obtained.

[0135] As the other polymer, it is preferable to use a polymer containing a structural unit having a partial structure represented by the following formula (3) (hereinafter, also referred to as "structural unit (III)"). By containing both the polymer containing the structural unit (III) and the polyimide (P) in the liquid crystal alignment agent, accumulated electric charges in the liquid crystal alignment film can be sufficiently reduced, and thus generation of a residual image in the obtained liquid crystal element can be suppressed, which is preferable in this respect.

[0136] [Chemical Formula 20]

[0137]

[0138] (In formula (3), Ar 3 , Ar 4 and R 5 satisfy (i), (ii) or (iii) below.

[0139] (i) Ar 3 and Ar 4 are each independently a divalent aromatic ring group. R 5 is a hydrogen atom or a monovalent organic group.

[0140] (ii) Ar 3 and Ar 4 represent a condensed ring structure containing nitrogen formed by combining with each other and with the aromatic ring possessed by Ar 3 , -NR 5 - and the aromatic ring possessed by Ar 4 . R 5 is a hydrogen atom or a monovalent organic group.

[0141] (iii) Ar 3 and R 5 represent a condensed ring structure containing nitrogen formed by combining with each other and with the aromatic ring possessed by Ar 3 , R 5 and the nitrogen atom to which R 5 is bonded. Ar 4 is a divalent aromatic ring group.

[0142] " represents a bond. " represents a bond.

[0143] In the formula (3), as the divalent aromatic ring group represented by Ar 3 and Ar 4 , a substituted or unsubstituted divalent aromatic hydrocarbon group and a substituted or unsubstituted divalent aromatic heterocyclic group can be exemplified. As specific examples of the divalent aromatic heterocyclic group, the same groups as those exemplified as Ar 1 and Ar 2 in the formula (1) can be exemplified.The bivalent aromatic ring group represented by Ar is the same group as that described above. From the viewpoint of achieving high densification and high transmittance of the liquid crystal alignment film, Ar 3 and Ar 4 is preferably a substituted or unsubstituted bivalent aromatic hydrocarbon group, and more preferably a substituted or unsubstituted phenylene group.

[0144] As Ar 3 and Ar 4 together with the aromatic ring possessed by Ar 3 -NR 5 - and Ar 4 together with the aromatic ring possessed by Ar 3 and R 5 together with the aromatic ring possessed by Ar 3 and the nitrogen atom to which R 5 is bonded, can be exemplified by an indoline structure, an isoindoline structure, a carbazole structure, and the like.

[0145] As R 5 represents a monovalent organic group, the same group as that exemplified in the description of R 2 is exemplified. For the same reason as R 2 , R 5 is preferably a tert-butyloxycarbonyl group (Boc group) or a 9-fluorenylmethyloxycarbonyl group, and particularly preferably a tert-butyloxycarbonyl group. R 5 is preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a thermally dissociable group, and more preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a tert-butyloxycarbonyl group.

[0146] In other polymers, the partial structure represented by the formula (3) is preferably introduced into the main chain of the polymer. As specific examples of the partial structure represented by the formula (3), the partial structures represented by the following formulae (3-1) to (3-9), and the like, can be exemplified.

[0147] [Chemical Formula 21]

[0148]

[0149] (In the formulae (3-1) to (3-9), “— ” represents a bond.)

[0150] ​The polymer having the structural unit (III) is preferably at least one polymer selected from the group consisting of polyamic acid and polyamic acid ester (i.e., the polymer (Q)). By including both the polymer (Q) having the structural unit (III) and the polyimide (P) in the liquid crystal aligning agent, the function of alleviating the accumulated electric charge in the liquid crystal aligning film can be imparted while the effects of improving the liquid crystal aligning property and the adhesion to the substrate are sufficiently obtained. The polymer (Q) having the structural unit (III) can be obtained, for example, by polymerization using a diamine having the partial structure represented by the formula (3) (hereinafter, also referred to as "specific diamine C").

[0151] As specific examples of the specific diamine C, compounds represented by the following formulas (8-1) to (8-17), and the like can be given.

[0152] [Chem. 22]

[0153]

[0154] [Chem. 23]

[0155]

[0156] The polymer (Q) can be synthesized according to a method known in the art. For example, the polyamic acid can be obtained by reacting a tetracarboxylic dianhydride with a diamine. As the tetracarboxylic dianhydride, the same compounds as those exemplified as the tetracarboxylic dianhydride which can be used for the synthesis of the polyimide (P) can be given. As the diamine, only the specific diamine C can be used, or the specific diamine C and other diamines exemplified as the diamine which can be used for the synthesis of the polyimide (P) can be used together.

[0157] In the case where the polymer (Q) is a polyamic acid ester, the polyamic acid ester can be obtained, for example, by a method in which the polyamic acid obtained in the above is reacted with an esterification agent (e.g., methanol or ethanol, N,N-dimethylformamide diethyl acetal, or the like), a method in which a tetracarboxylic diester is reacted with a diamine compound in the presence of a suitable dehydration catalyst, a method in which a tetracarboxylic diester dihalide is reacted with a diamine in the presence of a suitable base, or the like.

[0158] As for the solution viscosity of the polymer (Q), when a solution having a concentration of 10 mass% is prepared, it is preferably a solution having a solution viscosity of 10 mPa s to 800 mPa s, and more preferably a solution having a solution viscosity of 15 mPa s to 500 mPa s. Furthermore, the solution viscosity (mPa s) is a value determined using an E-type rotational viscometer at 25°C on a 10 mass% concentration of the polymer solution prepared using a good solvent (e.g., γ-butyrolactone, N-methyl-2-pyrrolidone, etc.) for the polymer (Q).

[0159] The weight average molecular weight (Mw) of the polymer (Q) determined by GPC in terms of polystyrene is preferably 1,000 to 500,000, more preferably 5,000 to 100,000. The molecular weight distribution (Mw / Mn) represented by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) determined by GPC in terms of polystyrene is preferably 15 or less, more preferably 10 or less. Furthermore, the polymer (Q) contained in the liquid crystal alignment agent can be only one, or two or more can be combined.

[0160] In the case where the polymer (Q) is formulated in the liquid crystal alignment agent of the present disclosure, the proportion of the polyimide (P) with respect to the content of the polyimide (P) and the polymer (Q) is preferably 1 mass part or more, more preferably 10 mass parts or more, and further preferably 20 mass parts or more, with respect to 100 mass parts of the total amount of the polyimide (P) and the polymer (Q). In addition, in the case where the polymer (Q) is formulated, the content of the polyimide (P) is preferably 95 mass parts or less, more preferably 70 mass parts or less, with respect to 100 mass parts of the total amount of the polyimide (P) and the polymer (Q). By setting the content of the polyimide (P) to the range, the accumulated electric charge in the liquid crystal alignment film can be moderated, and the adhesion to a substrate, the mechanical properties, and the high-temperature high-humidity resistance of the film can be excellent, which is preferable in this respect.

[0161] As other components that the liquid crystal alignment agent of the present disclosure can contain, in addition to the polymer (Q), for example, a compound having one or more epoxy groups in the molecule, a compound having two or more methylol groups in the molecule, a functional silane compound, a compound having one or more (meth)acryloyl groups in the molecule, an antioxidant, a metal chelate compound, a hardening accelerator, a surfactant, a filler, a dispersant, a photosensitizer, and the like can be listed. The formulation ratio thereof can be appropriately selected depending on each compound within a range that does not impair the effects of the present disclosure.

[0162] (Solvent)

[0163] The liquid crystal alignment agent is generally prepared as a liquid composition in which the polyimide (P) and other components, if necessary, are preferably dispersed or dissolved in an appropriate solvent.

[0164] As the organic solvent used, for example, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 1,2-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, 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, and the like can be exemplified. They can be used alone or in a mixture of two or more kinds.

[0165] The solid content concentration (the proportion of the total mass of components other than the solvent of the liquid crystal alignment agent in the total mass of the liquid crystal alignment agent) in the liquid crystal alignment agent can be appropriately selected in consideration of viscosity, volatility, and the like, and is preferably in the range of 1 to 10 mass%. That is, the liquid crystal alignment agent is applied to the surface of a substrate as described later, preferably with heating, thereby forming a coating film that is a liquid crystal alignment film or becomes a liquid crystal alignment film. At this time, if the solid content concentration is 1 mass% or more, the film thickness of the coating film can be sufficiently secured, and a good liquid crystal alignment film can be easily obtained, which is preferable from this viewpoint. In addition, if the solid content concentration is 10 mass% or less, the film thickness of the coating film does not become excessively large, a good liquid crystal alignment film can be obtained, and the viscosity of the liquid crystal alignment agent can be moderately secured, and the application properties can be made good.

[0166] Liquid crystal alignment film and liquid crystal element

[0167] The liquid crystal alignment film of the present disclosure can be formed from the liquid crystal alignment agent prepared as described. In addition, the liquid crystal element of the present disclosure includes a liquid crystal alignment film formed using the liquid crystal alignment agent described. The mode of operation of the liquid crystal in the liquid crystal element is not particularly limited, and for example, various modes such as a Twisted Nematic (TN) mode, a Super Twisted Nematic (STN) mode, a Vertical Alignment (VA) mode (including a Vertical Alignment-Multi-domain Vertical Alignment (VA-MVA) mode, a Vertical Alignment-Patterned Vertical Alignment (VA-PVA) mode, and the like), an In-Plane Switching (IPS) mode, a Fringe Field Switching (FFS) mode, an Optically Compensated Bend (OCB) mode, a Polymer Sustained Alignment (PSA) mode, and the like can be applied. The liquid crystal element can be manufactured, for example, by a method including the following Process 1 to Process 3. In Process 1, the substrate differs depending on the desired mode of operation. Process 2 and Process 3 are common to each mode of operation.

[0168] (Process 1: Formation of a Film)

[0169] First, a liquid crystal alignment agent is applied to a substrate, and preferably the coated surface is heated, thereby forming a coating film on the substrate. As the substrate, for example, a float glass, a soda glass, or the like; a transparent substrate including polyethylene terephthalate, polybutylene terephthalate, polyethersulfone, polycarbonate, poly(alicyclic olefin), or the like plastic can be used. As a transparent conductive film provided on one surface of the substrate, a NESA (NESA is a registered trademark of PPG Industries, Inc.) film including tin oxide (Sn02), an indium tin oxide (ITO) film including indium oxide-tin oxide (In203-Sn02), or the like can be used. In the case of manufacturing a liquid crystal element of a TN type, a STN type, or a VA type, two pieces of substrates provided with a patterned transparent conductive film are used. On the other hand, in the case of manufacturing a liquid crystal element of an IPS type or an FFS type, a substrate provided with an electrode including a transparent conductive film or a metal film patterned in a comb shape, and an opposing substrate not provided with an electrode are used. As the metal film, for example, a film including a metal such as chromium can be used. The application of the liquid crystal alignment agent to the substrate is preferably performed on the electrode formation surface by a flexographic printing method, a spin coating method, a roll coater method, or an inkjet printing method.

[0170] After the application of the liquid crystal alignment agent, preheating (pre-baking) is preferably performed for the purpose of preventing sagging of the applied liquid crystal alignment agent or the like. The pre-baking temperature is preferably 30°C to 150°C, and more preferably 40°C to 120°C. The pre-baking time is preferably 0.25 minutes to 10 minutes.

[0171] Subsequently, a calcination (post-baking) process is performed for the purpose of removing a solvent and, as necessary, thermally imidizing an amide acid structure present in a polymer. The calcination temperature (post-baking temperature) at this time is preferably 280°C or lower, and more preferably 250°C or lower. In addition, from the viewpoint of suppressing a decrease in liquid crystal alignment properties or reliability due to the influence of a solvent component remaining in the film, the post-baking temperature is preferably 80°C or higher, and more preferably 90°C or higher. The post-baking time is preferably 5 minutes to 150 minutes. The film thickness of the film thus formed is preferably 0.001 μm to 1 μm. After the application of the liquid crystal alignment agent to the substrate, the organic solvent is removed, thereby forming a liquid crystal alignment film or a film that becomes a liquid crystal alignment film.

[0172] (Process 2: Alignment treatment)

[0173] In the case of manufacturing a liquid crystal element of TN type, STN type, IPS type, or FFS type, a treatment for imparting a liquid crystal aligning ability to the coating film formed in the above-mentioned step 1 (alignment treatment) is performed. By this, the aligning ability of the liquid crystal molecules is imparted to the film to become a liquid crystal alignment film. As the alignment treatment, rubbing treatment using rubbing of the surface of the film formed on the substrate with cotton or the like, or photo-alignment treatment for imparting a liquid crystal aligning ability to the film formed on the substrate by light irradiation is preferable. In the case of manufacturing a liquid crystal element of vertical alignment type, the film formed in the above-mentioned step 1 can be directly used as a liquid crystal alignment film, and in order to further improve the liquid crystal aligning ability, the film can also be subjected to the alignment treatment.

[0174] In the case of manufacturing a liquid crystal alignment film by photo-alignment treatment, the light irradiation to the film can be performed by the following methods or the like: a method of irradiating the film after the post-baking step, a method of irradiating the film after the pre-baking step and before the post-baking step, or a method of irradiating the film during the heating of the film in at least either one of the pre-baking step and the post-baking step. In the photo-alignment treatment, as the radiation to be irradiated to the coating film, for example, ultraviolet rays and visible rays including light of a wavelength of 150 nm to 800 nm can be used. Ultraviolet rays including light of a wavelength of 200 nm to 400 nm are preferable. In the case where the radiation is polarized, it can be linearly polarized, or it can be partially polarized. In addition, in the case where the radiation used is linearly polarized or partially polarized, the irradiation can be performed from a direction perpendicular to the surface of the substrate, it can be performed from an oblique direction, or it can be performed in combination of these. In the case of irradiating non-polarized radiation, the irradiation direction is set to an oblique direction.

[0175] As the light source used, for example, a low-pressure mercury lamp, a high-pressure mercury lamp, a deuterium lamp, a metal halide lamp, an argon resonance lamp, a xenon lamp, an excimer laser, or the like can be used. The irradiation amount of the radiation is preferably 400 J / m 2 to 20,000 J / m 2 , more preferably 1,000 J / m 2 to 5,000 J / m 2 In order to improve the reactivity, the light irradiation to the film can be performed while the film is warmed.

[0176] In the manufacturing of a liquid crystal alignment film, the film subjected to the light irradiation treatment can be further subjected to heating. In addition, a contact step of bringing the film subjected to the light irradiation treatment into contact with water, a water-soluble organic solvent, or a mixed solvent of water and a water-soluble organic solvent can also be included. As the water-soluble organic solvent, for example, methanol, ethanol, 1-propanol, isopropanol, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone can be exemplified. The heating treatment of the film can be performed after the contact step.

[0177] (Step 3: construction of liquid crystal cell)

[0178] Two substrates each of which the liquid crystal alignment film is formed in the above-described manner are prepared, and liquid crystal is disposed between the two substrates disposed facing each other, whereby a liquid crystal cell is manufactured. In manufacturing the liquid crystal cell, for example, (1) a method in which the two substrates are disposed facing each other with a gap (spacer) therebetween, and the periphery of the two substrates is bonded using a sealant, liquid crystal is injected and filled into a cell gap divided by the surfaces of the substrates and the sealant, and then the injection hole is sealed, (2) a method (one drop filling (ODF) method) in which a sealant is applied to a prescribed site on one of the substrates on which the liquid crystal alignment film is formed, liquid crystal is further dropped at prescribed several places on the liquid crystal alignment film surface, then the other substrate is bonded facing the liquid crystal alignment film, and liquid crystal is allowed to spread over the entire surface of the substrate, and the like can be exemplified. It is preferable that, for the manufactured liquid crystal cell, further, a process of heating to a temperature at which the liquid crystal used attains an isotropic phase, and then slowly cooling to room temperature is performed, whereby the flow alignment at the time of filling of the liquid crystal is removed.

[0179] As the sealant, for example, a hardening agent and an epoxy resin containing alumina balls as spacers, and the like can be used. As the spacers, a photospacer, a bead spacer, and the like can be used.

[0180] As the liquid crystal, either one of a positive type and a negative type can be used. In the case where a negative type liquid crystal is used in a liquid crystal element of an IPS type and an FFS type, the transmission loss at the upper portion of the electrode can be reduced, and an increase in contrast can be achieved, which is preferable in this respect. As the liquid crystal used, a nematic liquid crystal, a smectic liquid crystal, and the like can be exemplified, of which a nematic liquid crystal is preferable. As the nematic liquid crystal, for example, a Schiff base type liquid crystal, an azoxy type liquid crystal, a biphenyl type liquid crystal, a phenylcyclohexane type liquid crystal, an ester type liquid crystal, a terphenyl type liquid crystal, a biphenylcyclohexane type liquid crystal, a pyrimidine type liquid crystal, a dioxane type liquid crystal, a bicyclooctane type liquid crystal, a cubane type liquid crystal, and the like can be used. In addition, for example, a cholesteric liquid crystal, a chiral agent, a ferroelectric liquid crystal, and the like can be added to these liquid crystals and used.

[0181] In the PSA mode, the following treatment is performed: a polymerizable compound (for example, a multifunctional (meth)acrylate compound or the like) is filled into the cell gap together with the liquid crystal, and after the liquid crystal cell is constructed, light is irradiated to the liquid crystal cell in a state where a voltage is applied between the conductive films possessed by the pair of substrates. In the production of a liquid crystal element of the PSA mode, the use ratio of the polymerizable compound is 0.01 parts by mass to 3 parts by mass, preferably 0.1 parts by mass to 1 part by mass, with respect to 100 parts by mass of the total of the liquid crystal.

[0182] Subsequently, a polarizing plate is attached to the outer surface of the liquid crystal cell as necessary. As the polarizing plate, a polarizing plate in which a polarizing film called an "H film" that is formed by stretching and orienting polyvinyl alcohol and absorbing iodine is sandwiched by a cellulose acetate protective film or a polarizing plate including the H film itself can be cited. Thereby, a liquid crystal element is obtained.

[0183] The liquid crystal element of the present disclosure can be effectively applied to various uses, for example, can be used in a clock, a portable game machine, a word processor, a notebook personal computer, a car navigation system, a video camera, a personal digital assistant (PDA), a digital camera, a mobile phone, a smartphone, various monitors, a liquid crystal television, an information display, or the like, or a dimming film or the like. In addition, the liquid crystal element formed using the liquid crystal aligning agent of the present disclosure can also be applied to an optical film such as a phase difference film.

[0184] According to the present disclosure described above, the following means can be provided.

[0185] [Means 1] A liquid crystal aligning agent containing a polyimide, the polyimide including: a structural unit (I) having a partial structure represented by the formula (1); and a structural unit (II) (excluding the structural unit (I)), having a partial structure in which an alkylene structure having 5 or more carbons or at least one methylene group of the alkylene structure having 5 or more carbons is substituted with the same or different group selected from the group consisting of -COO-, -OCO-, -O-, -CO-NR 4 4 -CO-, -NR 4 - and -CO- (R 4 is a hydrogen atom or a monovalent organic group).

[0186] [Means 2] The liquid crystal aligning agent according to [Means 1], in which the imidization rate of the polyimide is 30% or more.

[0187] ​[Method 3] According to [Method 1] or [Method 2], wherein the structural unit (II) has an alkylene structure having 5 or more carbon atoms, or at least one methylene group of the alkylene structure having 5 or more carbon atoms is selected from -COO-, -OCO-, -O-, -CO-NR under the condition that they are not adjacent to each other. 4a -、-NR 4a -CO-、-NR 4 Partial structures formed by substitution of the same or different groups in the group consisting of - and -CO- (R 4 It can be a hydrogen atom or a monovalent organic group. R 4a (This is due to the detachment of monovalent heat.)

[0188] [Method 4] The liquid crystal alignment agent according to any one of [Method 1] to [Method 3] further comprises a polymer having a structural unit having a partial structure represented by the formula (3) and different from the polyimide.

[0189] [Method 5] The liquid crystal alignment agent according to any one of [Method 1] to [Method 4] further comprises at least one polymer selected from the group consisting of polyamic acid and polyamic acid ester.

[0190] [Method 6] A liquid crystal alignment film formed using a liquid crystal alignment agent according to any one of [Method 1] to [Method 5].

[0191] [Method 7] A liquid crystal element comprising a liquid crystal alignment film according to [Method 6].

[0192] [Example]

[0193] The present invention will be described in more detail below through embodiments, but the present invention is not limited to these embodiments.

[0194] <Determination Method>

[0195] In the following examples, the solution viscosity of the polymer and the imidization rate of the polyimide were determined by the following methods.

[0196] [Solution viscosity of the polymer]

[0197] The solution viscosity of the polymer was measured using an E-type viscometer at 25°C.

[0198] [Imidification rate of polyimide]

[0199] The polyimide solution was added to pure water, and the resulting precipitate was dried under reduced pressure at room temperature. It was then dissolved in deuterated dimethyl sulfoxide, and proton NMR spectroscopy was performed at room temperature using tetramethylsilane as a reference. 1H-Nuclear Magnetic Resonance, 1 H-NMR) measurement. From the obtained 1 H-NMR spectrum, the imidization ratio [%] was calculated using the following equation (a).

[0200] Imidization ratio [%] = (1 - (β 1 / (β 2 x α)) x 100... (a)

[0201] (In equation (a), β 1 is the peak area of the proton source of the NH group appearing near a chemical shift of 10 ppm, β 2 is the peak area of other proton sources, and α is the ratio of the number of other protons to one proton of the NH group in the precursor (polyamic acid) of the polymer.)

[0202] <Short Name of Compound>

[0203] The short names of the compounds used in the following examples are shown below. Furthermore, the "compound represented by formula (X) (X is a symbol)" is sometimes simply referred to as "compound (X)" for convenience below.

[0204] [Four Carboxylic Acid Dianhydride]

[0205] [Chemical Formula 24]

[0206]

[0207] [Di-amine]

[0208] Specific Di-amine B

[0209] [Chemical Formula 25]

[0210]

[0211] [Chemical Formula 26]

[0212]

[0213] Specific Di-amine A

[0214] [Chemical Formula 27]

[0215]

[0216] Other Di-amine

[0217] [Chemical Formula 28]

[0218]

[0219] [Synthesis Example 1]

[0220]

[0221]

[0222] 1. Synthesis of polyimide

[0223] [Synthesis Example 2]

[0224] A compound (DB-1) as a diamine, 50 mol parts, and a compound (DC-11) as a diamine, 50 mol parts, were dissolved in N-methyl-2-pyrrolidone (NMP), and a compound (TA-1) as a tetracarboxylic dianhydride, 100 mol parts, was added, and reacted at 40°C for 24 hours, whereby a solution containing 15 mass% of polyamic acid was obtained. Subsequently, NMP was added to the obtained polyamic acid solution, and pyridine and acetic anhydride, each 1.80 mol equivalents with respect to the carboxyl group derived from the tetracarboxylic dianhydride possessed by the polyamic acid, were added, and dehydration ring closure reaction was performed at 80°C for 4 hours. After the dehydration ring closure reaction, solvent replacement was performed with fresh NMP, and further concentration was performed, whereby a solution containing 15 mass% of polyimide (which will be referred to as polymeric body (PI-1)) having an imidization rate of 80% was obtained. A small amount of this solution was separated, and a solution having a concentration of 10 mass% was prepared by adding NMP, and the solution viscosity of this solution was measured to be 100 mPa s.

[0225] [Synthesis Examples 3 to 11, and Synthesis Examples 13 to 17]

[0226] The kind and amount of the tetracarboxylic dianhydride and diamine used in the polymerization were changed as described in Table 1, and the polymerization was performed in the same manner as in Synthesis Example 2 except for this aspect, whereby a solution containing a polymeric body (PI-2) to a polymeric body (PI-10), a polymeric body (PI-12) to a polymeric body (PI-16) as polyimides was obtained, respectively. Further, the polymerization was performed in such a manner that the viscosity of an NMP solution having a polymeric body concentration of 10 mass% becomes 40 mPa s to 100 mPa s, and the molar ratio of the diamine to the tetracarboxylic dianhydride (diamine / tetracarboxylic dianhydride) was adjusted to 0.85 to 1.0. In Table 1, the values of the dianhydride represent the proportion (mol parts) of each compound with respect to the total amount of the tetracarboxylic dianhydride used in the synthesis, 100 mol parts. The values of the diamine represent the proportion (mol parts) of each compound with respect to the total amount of the diamine used in the synthesis, 100 mol parts.

[0227] [Synthesis Example 12]

[0228] ​A compound (DA-6) as a diamine, 20 mol parts, and a compound (DB-4) as a compound (DB-4), 80 mol parts, were dissolved in N-methyl-2-pyrrolidone (NMP), a compound (TA-1) as a tetracarboxylic dianhydride, 80 mol parts, and a compound (TA-3), 20 mol parts, were added, and the mixture was reacted at 40°C for 24 hours, whereby a solution containing 15 mass% of polyamic acid was obtained. Subsequently, the obtained polyamic acid solution was subjected to dehydration ring closure reaction at 180°C for 2 hours. After the dehydration ring closure reaction, solvent replacement was performed using fresh NMP, and then concentration was performed, whereby a solution containing 15 mass% of polyimide (which will be referred to as polymer (PI-11)) having an imidization rate of 100% was obtained. A small amount of this solution was taken out, and a solution having a concentration of 10 mass% was prepared by adding NMP. The solution viscosity of this solution was measured to be 80 mPa s.

[0229] 2. Synthesis of polyamic acid

[0230] [Synthesis Example 1]

[0231] A compound (DA-1) as a diamine, 50 mol parts, and a compound (DB-1), 50 mol parts, were dissolved in N-methyl-2-pyrrolidone (NMP), a compound (TA-1) as a tetracarboxylic dianhydride, 100 mol parts, was added, and the mixture was reacted at 40°C for 24 hours, whereby a solution containing 15 mass% of polyamic acid (which will be referred to as polymer (PA-1)) was obtained.

[0232] [Synthesis Examples 18 to 25]

[0233] The kind and amount of the tetracarboxylic dianhydride and the diamine used in the polymerization were changed as described in Table 2, and the polymerization was performed in the same manner as in Synthesis Example 1 except for this, whereby a solution containing the polymer (PA-2) to the polymer (PA-9) as polyamic acid was obtained, respectively. Further, the polymerization was performed so that the viscosity of the NMP solution of the polymer concentration of 10 mass% became 40 mPa s to 100 mPa s, by adjusting the molar ratio of the diamine to the tetracarboxylic dianhydride (diamine / tetracarboxylic dianhydride) to 0.85 to 1.0. In Table 2, the values of the dianhydride represent the proportion (mol parts) of each compound with respect to 100 mol parts of the total amount of the tetracarboxylic dianhydride used in the synthesis. The values of the diamine represent the proportion (mol parts) of each compound with respect to 100 mol parts of the total amount of the diamine used in the synthesis.

[0234] [Table 1]

[0235]

[0236] [Table 2]

[0237]

[0238] Manufacture and Evaluation of Liquid Crystal Element

[0239] [Example 1: FFS-type liquid crystal display element]

[0240] 1. Preparation of liquid crystal alignment agent

[0241] A solution of the polymer (PI-8) obtained in Synthesis Example 9 was diluted with NMP and butyl cellosolve (BC) to prepare a solution having a solvent composition of NMP / BC = 80 / 20 (mass ratio) and a solid content concentration of 3.5 mass%. The solution was filtered using a filter having a pore size of 0.2 μm, thereby preparing a liquid crystal alignment agent (AL-1).

[0242] 2. Evaluation of adhesiveness

[0243] The liquid crystal alignment agent (AL-1) was applied to a glass substrate using a spinner, and after pre-baking using a hot plate at 80°C for 2 minutes, the glass substrate was heated (post-baking) in an oven in which nitrogen substitution had been performed at 230°C for 30 minutes, thereby forming a coating film having an average film thickness of 0.10 μm. Two glass substrates on which coating films were formed were prepared by repeating the same operation. An ODF sealant (manufactured by Shikoku Chemicals Corporation, S-WB42) was applied to the coating film of one of the glass substrates on which a coating film was formed in such a manner that the width became 1 mm, and the coating film of the other glass substrate was attached to the coating film of the one glass substrate in such a manner that the ODF sealant was in contact with the coating film. Then, after irradiation with light of 30,000 J / m 2 (converted at 365 nm) using a metal halide lamp, the glass substrates were heated in an oven at 120°C for 1 hour. The adhesion of the film to the substrate was evaluated by measuring the adhesion force using a tensile compression tester (Model: SDWS-0201-100SL) manufactured by Imoto Mfg. Co., Ltd. In the evaluation, the case where the adhesion force was 175 N / cm 2 or more was rated as "good (O)", the case where the adhesion force was 125 N / cm 2 or more and less than 175 N / cm 2 was rated as "fair (D)", and the case where the adhesion force was less than 125 N / cm 2 was rated as "poor (X)". As a result, in this example, the adhesion force was 160 N / cm 2 , and the adhesiveness was rated as "fair (D)".

[0244] 3. Evaluation of high-temperature high-humidity resistance

[0245] (1) Manufacture of liquid crystal cell for evaluation

[0246] The liquid crystal alignment agent (AL-1) prepared in the above was applied to the transparent electrode surface of a glass substrate with a transparent electrode including an ITO film using a spinner, and prebaked for 1 minute using a hot plate at 80°C. Then, in an oven in which the inside of the oven was subjected to nitrogen substitution, heating was performed at 230°C for 1 hour to form a coating film having a film thickness of 0.1 μm. The same operation was repeated to produce a pair (two pieces) of substrates having a liquid crystal alignment film.

[0247] An epoxy resin adhesive in which alumina balls having a diameter of 3.5 μm were loaded was applied to the outer periphery of the surface having a liquid crystal alignment film of one of the substrates by screen printing, and then the liquid crystal alignment film surfaces of the pair of substrates were brought into opposition and pressure-bonded, and the adhesive was heat-hardened at 150°C for 1 hour. Subsequently, a negative type liquid crystal (manufactured by Merck, MLC-6608) was filled into the gap between the substrates from the liquid crystal injection port, and then the liquid crystal injection port was sealed with an epoxy-based adhesive. Further, in order to remove the flow alignment at the time of liquid crystal injection, it was heated at 130°C and then slowly cooled to room temperature, whereby an evaluation liquid crystal cell was obtained.

[0248] (2) Measurement of voltage holding ratio (VHR)

[0249] For the evaluation liquid crystal cell produced in the above (1), a voltage of 5 V was applied at a temperature of 60°C for an application time of 60 microseconds and a span of 167 milliseconds, and then the voltage holding ratio after 167 milliseconds from the time of removal of the application (initial voltage holding ratio VH1) was measured. The measuring device used was a product of TOYO Corporation, trade name "VHR-1". Subsequently, the evaluation liquid crystal cell after measurement of the initial voltage holding ratio VH1 was stored in an oven set at 85°C and a humidity of 85% for 300 hours, and then the voltage holding ratio was measured in the same manner as the initial voltage holding ratio VH1. The value thereof was taken as the voltage holding ratio after application of stress VH2. The reduction ratio of the voltage holding ratio calculated using the following equation (b) was taken as ΔVHR (%), and the high temperature and high humidity resistance was evaluated using ΔVHR.

[0250] ΔVHR = (VH2 / VH1) x 100... (b)

[0251] In the evaluation, the case where ΔVHR was 80% or more was taken as "good (◎)", the case where ΔVHR was 60% or more and less than 80% was taken as "fair (△)", and the case where ΔVHR was less than 60% was taken as "poor (x)". As a result, in this Example 1, ΔVHR = 80%, and the evaluation was "good (◎)".

[0252] 4. Evaluation of film strength (rubbing resistance)

[0253] The liquid crystal alignment agent (AL-1) prepared in 1. above was coated on a glass substrate using a spinner, and heated (pre-baked) for 3 minutes using a hot plate at 110°C. Then, drying (post-baking) was performed for 30 minutes using an oven at 230°C with nitrogen substitution in the oven, to form a coating film having an average film thickness of 0.08 μm, and the haze value of the coating film was measured using a hazemeter. Subsequently, rubbing treatment was performed five times on the coating film using a rubbing machine having a roller with cotton cloth wound thereon, at a roller rotation speed of 1000 rpm, a stage moving speed of 3 cm / sec, and a bristle penetration length of 0.3 mm. Then, the haze value of the liquid crystal alignment film was measured using a hazemeter, and the difference from the haze value before the rubbing treatment (haze change value) was calculated. In the case where the haze value of the film before the rubbing treatment is assumed to be Hzl (%) and the haze value of the film after the rubbing treatment is assumed to be Hz2 (%), the haze change value is represented by the following equation (c).

[0254] Haze change value (%) = Hz2 - Hzl... (c)

[0255] The case where the haze change value in the liquid crystal alignment film is less than 1.0 was evaluated as "good (O)", the case where the haze change value is 1.0 or more and 1.5 or less was evaluated as "fair (Δ)", and the case where the haze change value is more than 1.5 was evaluated as "poor (X)". If the haze change value is 1.5 or less (more preferably less than 1.0), it can be said that the film strength is sufficiently high and the rubbing resistance is high, that is, the mechanical properties of the film are good. As a result, in this example, the evaluation was "good (O)" for the film strength.

[0256] 5. Production of FFS-type liquid crystal display element using rubbing method

[0257] A glass substrate (assumed to be a first substrate) on which a flat electrode (bottom electrode), an insulating layer, and a comb-shaped electrode (top electrode) were sequentially layered on one surface, and a glass substrate (assumed to be a second substrate) on which no electrode was provided were prepared. Subsequently, a liquid crystal alignment agent (AL-1) was coated on the electrode formation surface of the first substrate and on one surface of the second substrate using a spinner, and heated (pre-baked) for 3 minutes using a hot plate at 110°C. Then, drying (post-baking) was performed for 30 minutes using an oven at 230°C with nitrogen substitution in the oven, to form a coating film having an average film thickness of 0.08 μm. Subsequently, rubbing treatment was performed using a rubbing machine having a roller with rayon cloth wound thereon, at a roller rotation speed of 1000 rpm, a stage moving speed of 3 cm / sec, and a bristle penetration length of 0.3 mm. Then, ultrasonic cleaning was performed for 1 minute in ultrapure water, and then drying was performed for 10 minutes in a clean oven at 100°C, to thereby obtain a pair of substrates having a liquid crystal alignment film.

[0258] Next, for a pair of substrates with a liquid crystal alignment film, a liquid crystal injection port is left at the edge of the surface where the liquid crystal alignment film is formed, and an epoxy resin adhesive containing alumina balls with a diameter of 3.5 μm is screen-printed onto the substrates. Then, the substrates are overlapped and pressed together, and the adhesive is thermosetting at 150°C for 1 hour. Next, negative liquid crystal (manufactured by Merck, MLC-6608) is filled into the gap between the two substrates from the liquid crystal injection port, and then the liquid crystal injection port is sealed with an epoxy adhesive. Furthermore, to remove the flow alignment during liquid crystal injection, it is heated at 120°C and then slowly cooled to room temperature, thereby manufacturing a liquid crystal cell. In addition, when the pair of substrates are overlapped, the friction directions of each substrate are made antiparallel. Next, polarizing plates are attached to the outer two sides of the substrates in the liquid crystal cell, thereby obtaining a triboelectric FFS type liquid crystal display element.

[0259] 6. Evaluation of Charge Storage Capacity (RDC)

[0260] Using the triboelectric FFS type liquid crystal display element manufactured in section 5, a 2 V DC voltage was applied at 71°C for 10 minutes, followed by a 0.2-second short circuit, and then kept open for 10 minutes. The voltage accumulated in the liquid crystal display element during this period was measured by dielectric absorption method. In the evaluation, a charge accumulation of less than 0.1 V was designated as "Good (◎)", a charge accumulation greater than 0.1 V but less than 0.2 V was designated as "Acceptable (○)", and a charge accumulation greater than 0.2 V was designated as "Poor (×)". As a result, in this embodiment, the charge accumulation was evaluated as "Acceptable (○)".

[0261] 7. Evaluation of liquid crystal orientation

[0262] The friction-type FFS liquid crystal display element manufactured in step 5. was subjected to a temperature of 27,000 cd / m². 2 The liquid crystal alignment was evaluated by placing the device on a high-brightness backlight for 500 hours and measuring the rate of change in retardation before and after backlight illumination. First, for the FFS-type liquid crystal display element manufactured in section 5, the retardation was measured using an Axoscan instrument manufactured by Optoscience, and the rate of change in retardation α before and after backlight illumination was calculated using the following formula (d). The smaller the rate of change α, the better the liquid crystal alignment. A rate of change α of less than 1% was designated as "good (◎)", a rate of change α greater than 1% and less than 2% was designated as "acceptable (○)", and a rate of change α greater than 2% was designated as "poor (×)".

[0263] α=(Δθ / θ1)×100…(d)

[0264] (In formula (d), Δθ represents a difference in retardation before and after irradiation, and θ1 represents a retardation value before irradiation.)

[0265] As a result, the liquid crystal alignment property of this example was evaluated as "good (◎)".

[0266] 8. Production of FFS-type liquid crystal display element using photo-alignment method

[0267] The same first substrate and second substrate as in the case of 5. were prepared. Then, a liquid crystal alignment agent (AL-1) was applied to one of the substrate surfaces of the first substrate and the second substrate using a spinner, and heated (pre-baked) using a hot plate at 80°C for 1 minute. Then, drying (post-baking) was performed in an oven at 230°C for 30 minutes under nitrogen replacement in the oven, to form a coating film having an average film thickness of 0.1 μm. The obtained coating film was irradiated with ultraviolet rays including a bright line at 254 nm polarized in a straight line at 1,000 J / m 2 from the normal line direction of the substrate, using a Hg-Xe lamp. Then, photo-alignment treatment was performed. The amount of irradiation was measured using a light amount meter based on the wavelength of 254 nm. Then, the coating film subjected to the photo-alignment treatment was heat-treated in a clean oven at 230°C for 30 minutes to form a liquid crystal alignment film.

[0268] Next, to one of the pair of substrates on which the liquid crystal alignment film was formed, an epoxy resin adhesive containing alumina balls having a diameter of 3.5 μm was applied to the outer edge of the surface having the liquid crystal alignment film by screen printing. Then, the substrates were overlapped and pressure-bonded in such a manner that the projection direction of the polarization axis at the time of light irradiation on the substrate surface became antiparallel, and the adhesive was heat-hardened at 150°C for 1 hour. Then, after filling a negative-type liquid crystal (manufactured by Merck Co., Ltd., MLC-6608) between the pair of substrates from the liquid crystal injection port, the liquid crystal injection port was sealed with an epoxy-based adhesive to obtain a liquid crystal cell. Furthermore, in order to remove the flow alignment at the time of liquid crystal injection, it was heated at 120°C and then slowly cooled to room temperature. Then, polarizing plates were attached to the outer sides of both surfaces of the substrate of the liquid crystal cell to obtain a photo-aligned FFS-type liquid crystal display element. In addition, the series of operations were performed while changing the amount of ultraviolet irradiation after post-baking in the range of 100 J / m 2 to 10,000 J / m 2 Thus, three or more liquid crystal display elements different in the amount of ultraviolet irradiation were produced, and the liquid crystal display element showing the best exposure amount (optimum exposure amount) of alignment characteristics was used for the following evaluation.

[0269] 9. Evaluation of charge accumulation amount (RDC)

[0270] The optical orientation FFS-type liquid crystal display element produced in the above 8. was subjected to the RDC measurement and evaluation in the same manner as in the above 6. As a result, the evaluation was "OK" in this example.

[0271] 10. Evaluation of liquid crystal alignment property

[0272] The liquid crystal alignment property of the optical orientation FFS-type liquid crystal display element produced in the above 8. was evaluated in the same manner as in the above 7. As a result, the evaluation was "Good" in this example.

[0273] [Examples 2 to 13 and Comparative Examples 1 to 6]

[0274] A liquid crystal alignment agent was produced in the same manner as in Example 1, except that the composition of the liquid crystal alignment agent was changed as shown in Table 3. Further, using the obtained liquid crystal alignment agent, an FFS-type liquid crystal cell and an FFS-type liquid crystal display element were produced in the same manner as in Example 1, and various evaluations were performed. The results thereof are shown in Table 3. Furthermore, in Examples 5 to 12 and Comparative Example 3, two kinds of polymer were used as the polymer component. In Example 13, three kinds of polymer were used as the polymer component. In Examples 4 and 6, the FFS-type liquid crystal display element was produced by the rubbing method, and the FFS-type liquid crystal display element was not produced by the optical orientation method. In Table 3, the numerical value in the column of polymer indicates the blending ratio (mass parts) of each polymer used in the production of the liquid crystal alignment agent, in terms of the solid component, relative to the total amount of the polymer component (100 mass parts).

[0275] [Table 3]

[0276]

[0277] As shown in Table 3, with respect to the liquid crystal alignment agents of Examples 1 to 13, the evaluations of the adhesiveness of the film, the high-temperature high-humidity resistance, and the film strength were all good or OK, and a balance of various properties was obtained. Further, the liquid crystal alignment films formed using the liquid crystal alignment agents of Examples 1 to 13 also had less accumulated electric charge, and the liquid crystal alignment property was also good.

[0278] On the other hand, in Comparative Example 1 in which polyamic acid (P) was used instead of polyimide (P), the high-temperature high-humidity resistance of the film was poor. Further, in Comparative Examples 2 to 6 in which polyimides having one or both of the structural unit (I) and the structural unit (II) were used, at least one of the adhesiveness of the film, the high-temperature high-humidity resistance, and the film strength was poor.

Claims

1. A liquid crystal aligning agent comprising a polyimide, the polyimide comprising: a structural unit (I) having a partial structure represented by the following formula (1); and a structural unit (II), wherein, Except for the structural unit (I), the alkylene structure having 5 or more carbon atoms or the at least one methylene group in the alkylene structure having 5 or more carbon atoms is selected from -COO-, -OCO-, -O-, -CO-NR under the condition that they are not adjacent to each other. 4 -、-NR 4 -CO-、-NR 4 Partial structures formed by substitution of the same or different groups in the group consisting of - and -CO-, R 4 It can be a hydrogen atom or a monovalent organic group. In formula (1), Ar 1 and Ar 2 are each independently a divalent aromatic ring group; X 1 and X 2 are each independently -NR 2 -, -O-, -S-, 1 -NR 2 -CO- or 1 -O-CO-; 1 " indicates a bond to Ar 1 or Ar 2 ; R 1 is an alkanediyl group having 2 or more carbons or a divalent group containing -NR 3 -, -O-, -S-, -CO-NR 3 -, -NR 3 -CO-, -COO- or -OCO- between the carbon-carbon bonds of an alkanediyl group having 2 or more carbons; R 2 and R 3 are each independently a hydrogen atom or a monovalent organic group; " indicates a bond.

2. The liquid crystal aligning agent according to claim 1, wherein The imidization rate of the polyimide is 30% or more.

3. The liquid crystal aligning agent according to claim 1, wherein The structural unit (II) has a part structure in which an alkylene structure having 5 or more carbons or at least one methylene group of the alkylene structure having 5 or more carbons is substituted with the same or different groups selected from the group consisting of -COO-, -OCO-, -O-, -CO-NR 4a -CO-, -NR 4a -CO-, -NR 4 -CO-, and -CO- in a condition that they are not adjacent to each other, R 4 is a hydrogen atom or a monovalent organic group; and R 4a is a monovalent thermally dissociable group.

4. The liquid crystal aligning agent according to claim 1, further comprising a polymer different from the polyimide, which contains a structural unit having a partial structure represented by the following formula (3), In formula (3), Ar 3 , Ar 4 , and R 5 satisfy (i), (ii), or (iii) below. (i) Ar 3 and Ar 4 are each independently a divalent aromatic ring group; R 5 is a hydrogen atom or a monovalent organic group; (ii) Ar 3 and Ar 4 denote that they are bound to each other and to Ar 3 the aromatic ring, -NR 5 - and the aromatic ring of Ar 4 together form a condensed ring structure containing nitrogen; R 5 is a hydrogen atom or a monovalent organic group; (iii) Ar 3 and R 5 denote that the aromatic ring, R 3 and the nitrogen atom to which R 5 and R 5 are bonded together form a condensed ring structure containing nitrogen; Ar 4 is a divalent aromatic ring group; "represents a bond.​ 5. The liquid crystal aligning agent according to claim 1, further comprising at least one polymer (Q) selected from the group consisting of polyamic acid and polyamic acid ester.

6. The liquid crystal aligning agent according to claim 5, which contains, as the polymer (Q), a polymer containing a structural unit having a partial structure represented by the following formula (3), In formula (3), Ar 3 , Ar 4 , and R 5 satisfy (i), (ii), or (iii) below. (i) Ar 3 and Ar 4 are each independently a divalent aromatic ring group; R 5 is a hydrogen atom or a monovalent organic group; (ii)Ar 3 and Ar 4 This indicates that they combine with each other and with Ar 3 The aromatic ring it possesses, -NR 5 -and Ar 4 The aromatic rings together form a nitrogen-containing condensation ring structure; R 5 It can be a hydrogen atom or a monovalent organic group; (iii) Ar 3 and R 5 denote that the aromatic ring, R 3 and the nitrogen atom to which R 5 and R 5 are bonded together form a condensed ring structure containing nitrogen; Ar 4 is a divalent aromatic ring group; "represents a bond.​ 7. A liquid crystal aligning film formed using the liquid crystal aligning agent according to any one of claims 1 to 6.

8. A liquid crystal element comprising the liquid crystal aligning film according to claim 7.

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