CN108604029B

CN108604029B - Liquid crystal aligning agent, liquid crystal alignment film, and liquid crystal display element using same

Info

Publication number: CN108604029B
Application number: CN201680080871.6A
Authority: CN
Inventors: 山极大辉
Original assignee: Nissan Chemical Corp
Current assignee: Nissan Chemical Corp
Priority date: 2015-12-03
Filing date: 2016-12-02
Publication date: 2021-11-26
Anticipated expiration: 2036-12-02
Also published as: WO2017094898A1; JP6891814B2; TW201734131A; KR20180089487A; TWI751995B; JPWO2017094898A1; CN108604029A

Abstract

Provided is a liquid crystal aligning agent for obtaining a liquid crystal alignment film having good liquid crystal alignment properties, voltage holding ratio and aging resistance. A liquid crystal aligning agent comprising the following component (A) and component (B): a copolymer having a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2), (X)₁、X₂Independently is a 4-valent organic radical, Y₁、Y₂Independently is a 2-valent organic radical, R₁Is an alkyl group having 1 to 5 carbon atoms, A₁And A₂Each independently represents a hydrogen atom, or an optionally substituted alkyl group having 1 to 10 carbon atoms, alkenyl group having 2 to 10 carbon atoms or alkynyl group having 2 to 10 carbon atoms. ) (ii) a Component (B): a compound having 2 or more crosslinkable functional groups.

Description

Liquid crystal aligning agent, liquid crystal alignment film, and liquid crystal display element using same

Technical Field

The present invention relates to a liquid crystal alignment agent containing a polyamic acid ester-polyamic acid copolymer, a liquid crystal alignment film, and a liquid crystal display element using the same.

Background

In a liquid crystal display device used in a liquid crystal television, a liquid crystal display, or the like, a liquid crystal alignment film for controlling the alignment state of liquid crystal is generally provided in the device. A liquid crystal alignment film is a film for controlling the alignment of liquid crystal molecules in a constant direction in a liquid crystal display element, a retardation plate using polymerizable liquid crystal, or the like. For example, a liquid crystal display element has a structure in which liquid crystal molecules forming a liquid crystal layer are sandwiched between liquid crystal alignment films formed on respective surfaces of a pair of substrates. In the liquid crystal display element, liquid crystal molecules are aligned in a constant direction with a pretilt angle by the liquid crystal alignment film, and respond by applying a voltage to an electrode provided between the substrate and the liquid crystal alignment film. As a result, the liquid crystal display element displays a desired image by utilizing the change in orientation caused by the response of the liquid crystal molecules.

As the liquid crystal alignment film, a polyimide-based liquid crystal alignment film obtained by applying a liquid crystal alignment agent containing a polyimide precursor such as polyamic acid (polyamide acid) or a solution of a soluble polyimide as a main component to a glass substrate or the like and baking the applied liquid crystal alignment agent has been mainly used.

As the liquid crystal display device has been highly functionalized, in addition to the fact that excellent liquid crystal alignment properties and stable pretilt angle are important for the liquid crystal alignment film, characteristics such as a high voltage holding ratio, a small amount of residual charge when a dc voltage is applied, and/or a rapid relaxation of residual charge accumulated by the dc voltage are also important for the liquid crystal alignment film.

In order to respond to the above-mentioned requirements, various polyimide-based liquid crystal alignment films have been proposed. For example, a liquid crystal aligning agent containing a specific structure of a tertiary amine in addition to a polyamic acid and a polyamic acid containing an imide group (see patent document 1), an additive having an isocyanate structure (see patent document 2), and the like have been proposed.

On the other hand, it has been reported that a liquid crystal aligning agent using a polyamic acid ester as a polymer component constituting the liquid crystal aligning agent is excellent in alignment stability and voltage holding characteristics of liquid crystal compared to a liquid crystal aligning agent using a polyamic acid because a decrease in molecular weight does not occur by a heat treatment at the time of imidization (see patent document 3).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 9-316200

Patent document 2: WO2014/178406 publication

Patent document 3: japanese patent laid-open publication No. 2003-26918

Disclosure of Invention

Problems to be solved by the invention

However, when a liquid crystal aligning agent containing various crosslinking agents in a polyamic acid is used, a liquid crystal display element having excellent voltage holding characteristics is obtained, but the liquid crystal aligning property may be impaired.

Further, as described above, since the liquid crystal display element having excellent voltage holding characteristics is obtained by using the liquid crystal aligning agent using polyamic acid ester as compared with the liquid crystal aligning agent using polyamic acid, it is estimated that the voltage holding characteristics are further improved by adding a crosslinking agent thereto, but contrary to expectation, such an effect cannot be obtained.

An object of the present invention is to provide a liquid crystal aligning agent that can provide a liquid crystal alignment film having good liquid crystal alignment properties, Voltage Holding Ratio (hereinafter, also referred to as VHR), and aging resistance.

Means for solving the problems

The present inventors have conducted extensive studies and as a result, have found that the above problems can be solved by using a copolymer of a polyamic acid ester and a polyamic acid (hereinafter also referred to as a PAE-PAA copolymer) in combination with a crosslinking agent having a specific structure, and have completed the present invention.

That is, the present invention is based on the above findings, and the gist thereof is as follows.

1. A liquid crystal aligning agent comprising the following component (A) and component (B).

Component (A): a copolymer having a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2).

In the above formulae (1) and (2), X₁And X₂Each independently is a 4-valent organic radical, Y₁And Y₂Each independently is a 2-valent organic radical, R₁Is an alkyl group having 1 to 5 carbon atoms, A₁And A₂Each independently represents a hydrogen atom, or an optionally substituted alkyl group having 1 to 10 carbon atoms, alkenyl group having 2 to 10 carbon atoms or alkynyl group having 2 to 10 carbon atoms.

Component (B): a compound having 2 or more crosslinkable functional groups.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the liquid crystal aligning agent of the present invention, a liquid crystal alignment film having excellent liquid crystal alignment properties, voltage holding ratio, aging resistance and the like can be formed. The main reason for this is considered to be that fine irregularities on the surface of a liquid crystal alignment film formed from the liquid crystal alignment agent of the present invention can be reduced.

Detailed Description

< ingredient (a): PAE-PAA copolymer >

The PAE-PAA copolymer used in the present invention is a polyimide precursor for obtaining polyimide, and is a polymer having a site capable of undergoing an imidization reaction shown below by heating.

(R is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.)

The PAE-PAA copolymer contained in the liquid crystal aligning agent of the present invention has a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2).

In the above formula (1), R₁Is an alkyl group having 1 to 5 carbon atoms, and is preferably a methyl group or an ethyl group from the viewpoint of ease of application to a glass substrate.

In the above formulae (1) and (2), A₁And A₂Each independently represents a hydrogen atom, or an optionally substituted alkyl group having 1 to 10 carbon atoms, alkenyl group having 2 to 10 carbon atoms or alkynyl group having 2 to 10 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a tert-butyl group, a hexyl group, an octyl group, a decyl group, a cyclopentyl group, a cyclohexyl group, and a dicyclohexyl group. As the alkenyl group, 1 or more CH-substituted groups present in the alkyl group can be mentionedExamples of the alkenyl group having a CH structure substituted by a C ═ C structure include vinyl, allyl, 1-propenyl, isopropenyl, 2-butenyl, 1, 3-butadienyl, 2-pentenyl, 2-hexenyl, cyclopropenyl, cyclopentenyl and cyclohexenyl. As the alkynyl group, 1 or more CH groups present in an alkyl group are exemplified₂-CH₂Examples of the alkynyl group having a structure substituted by a C.ident.C structure include an ethynyl group, a 1-propynyl group, and a 2-propynyl group.

The alkyl group, the alkenyl group, and the alkynyl group may have a substituent, and a ring structure may be formed by the substituent. The term "ring structure formed by substituents" means that the substituents are bonded to each other or to a part of the parent skeleton to form a ring structure.

Examples of the substituent include a halogen group, a hydroxyl group, a mercapto group, a nitro group, an aryl group, an organooxy group, an organothio group, an organosilyl group, an acyl group, an ester group, a thioester group, a phosphate group, an amide group, an alkyl group, an alkenyl group, and an alkynyl group.

Examples of the halogen group as a substituent include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

As the aryl group as a substituent, a phenyl group is exemplified. The aryl group may be further substituted with the aforementioned other substituents.

The organic oxy group as a substituent may have a structure represented by O-R. The R may be the same or different, and examples thereof include the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group and the like. The aforementioned substituents may be further substituted on these R. Specific examples of the organoxy group include methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, and the like.

As the organic thio group as a substituent, a structure represented by-S-R can be shown. Examples of the R include the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group, and the like. The aforementioned substituents may be further substituted on these R. Specific examples of the organic thio group include a methylthio group, an ethylthio group, a propylthio group, a butylthio group, a pentylthio group, a hexylthio group, a heptylthio group, and an octylthio group.

As the substituent, an organosilyl group represented by-Si- (R)₃The structure shown. The R may be the same or different, and examples thereof include the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group and the like. The aforementioned substituents may be further substituted on these R. Specific examples of the organosilyl group include a trimethylsilyl group, a triethylsilyl group, a tripropylsilyl group, a tributylsilyl group, a tripentylsilyl group, a trihexylsilyl group, a pentyldimethylsilyl group, and a hexyldimethylsilyl group.

The acyl group as a substituent may have a structure represented by-C (O) -R. Examples of the R include the alkyl group, the alkenyl group, and the aryl group. The aforementioned substituents may be further substituted on these R. Specific examples of the acyl group include formyl group, acetyl group, propionyl group, butyryl group, isobutyryl group, valeryl group, isovaleryl group, benzoyl group and the like.

The ester group as a substituent may have a structure represented by-C (O) O-R or OC (O) R. Examples of the R include the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group, and the like. The aforementioned substituents may be further substituted on these R.

The thioester group as a substituent may have a structure represented by-C (S) O-R or OC (S) -R. Examples of the R include the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group, and the like. The aforementioned substituents may be further substituted on these R.

As the phosphate group as a substituent, there may be mentioned-OP (O) - (OR)₂The structure shown. The R may be the same or different, and examples thereof include the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group and the like. The aforementioned substituents may be further substituted on these R.

As the amide group as a substituent, there may be shown-C (O) NH₂、-C(O)NHR、-NHC(O)R、-C(O)N(R)₂or-NRC (O) R. The R may be the same or different, and examples thereof include the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group and the like. The aforementioned substituents may be further substituted on these R.

Examples of the aryl group as a substituent include the same aryl groups as those described above. The aryl group may be further substituted with the aforementioned other substituents.

Examples of the alkyl group as the substituent include the same alkyl groups as those described above. The aforementioned other substituents may be further substituted on the alkyl group.

Examples of the alkenyl group as the substituent include the same alkenyl groups as those described above. The aforementioned other substituents may be further substituted on the alkenyl group.

Examples of the alkynyl group as a substituent include the same alkynyl groups as those described above. The alkynyl group may be further substituted with the aforementioned other substituents.

As the above-mentioned A₁And A₂In general, the reactivity of amino groups and the liquid crystal alignment property may be lowered when a bulky structure is introduced, and therefore, a hydrogen atom or an optionally substituted alkyl group having 1 to 5 carbon atoms is more preferable, and a hydrogen atom, a methyl group or an ethyl group is particularly preferable.

In the above formulae (1) and (2), if X₁And X₂The structure of the 4-valent organic group is not particularly limited, and 2 or more kinds thereof may be mixed. If X is shown₁And X₂Specific examples of such compounds include X-1 to X-47 shown below. Among them, X is preferable from the viewpoints of availability of monomers, light irradiation sensitivity, and rubbing resistance strength₁、X₂And X-1, X-2, X-3, X-4, X-5, X-6, X-8, X-16, X-19, X-21, X-25, X-26, X-27, X-28, X-32 or X-47.

In the formulae (1) and (2), Y₁And Y₂Is a 2-valent organic group, and is not particularly limited. Y is₁And Y₂May be the same or different.

If it shows Y₁And Y₂Specific examples thereof include the following Y-1 to Y-99. Among them, Y-7, Y-8, Y-20, Y-21, Y-22, Y-28, Y-29, Y-30, Y-31, Y-41, Y-43, Y-64, Y-65, Y-66, Y-68, Y-71, Y-72, Y-98 or Y-99 are preferable from the viewpoint of availability of the monomer, and Y-22, Y-28, Y-30, Y-31, Y-72, Y-98, Y-99, Y-100, Y-101, Y-102, Y-103 or Y-104 are more preferable.

In the PAE-PAA copolymer, the ratio of the structural unit represented by formula (1) (contained) is preferably 50 to 95 mol%, more preferably 70 to 90 mol%, based on the total structural units. In the PAE-PAA copolymer, the ratio of the structural unit represented by formula (2) (contained) is preferably 5 to 50 mol%, more preferably 10 to 30 mol%, based on the total structural units.

< method for producing PAE-PAA copolymer >

The PAE-PAA copolymer of the present invention is produced by the following method.

Forming X in the structural unit represented by the formula (1) in the presence of a condensing agent, a base, and an organic solvent₁A tetracarboxylic acid diester of (1) and (2) to form Y₁And Y₂The diamine(s) is (are) subjected to a polycondensation reaction at-20 to 150 ℃, preferably 0 to 50 ℃, for 30 minutes to 24 hours, preferably 1 to 12 hours, to neutralizeAnd a base, adding diphenyl phosphate to the reaction mixture, and adding the diphenyl phosphate to the structural unit represented by the formula (2) to form X₂The above-mentioned PAE-PAA copolymer is produced by reacting a tetracarboxylic acid or a dianhydride thereof at a temperature of 0 to 50 ℃ for 30 minutes to 24 hours, preferably 1 to 12 hours.

The organic solvent used in the above reaction is preferably N, N-dimethylformamide, N-methyl-2-pyrrolidone or γ -butyrolactone from the viewpoint of solubility of the monomer and the polymer, and 1 kind or 2 or more kinds mixed may be used. The concentration of the polymer is preferably 1 to 30% by mass, more preferably 5 to 20% by mass, from the viewpoint that precipitation of the polymer is not likely to occur and a high molecular weight material is easily obtained.

As the condensing agent, triphenyl phosphite, dicyclohexylcarbodiimide, 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride, N, N ' -carbonyldiimidazole, dimethoxy-1, 3, 5-triazinylmethyl morpholinium, O- (benzotriazol-1-yl) -N, N, N ', N ' -tetramethyltetrafluoroboric acid urea, O- (benzotriazol-1-yl) -N, N, N ', N ' -tetramethylhexafluorophosphoric acid urea, diphenyl (2, 3-dihydro-2-thio-3-benzoxazolyl) phosphonate, and the like can be used. The amount of the condensing agent to be added is preferably 2 to 3 times by mol based on the tetracarboxylic acid diester.

As the base, tertiary amines such as pyridine and triethylamine can be used. The amount of the base to be added is preferably 2 to 4 times by mole relative to the diamine component, from the viewpoint of ease of removal and availability of a high molecular weight product.

The polymer can be precipitated and recovered by injecting the PAE-PAA copolymer obtained as described above into a poor solvent while sufficiently stirring the reaction solution. Further, the PAE-PAA copolymer is precipitated several times, washed with a poor solvent, and dried at room temperature or under heating to obtain a purified PAE-PAA copolymer powder. The poor solvent is not particularly limited, and examples thereof include water, methanol, ethanol, hexane, butyl cellosolve, acetone, toluene, and the like.

The weight average molecular weight of the PAE-PAA copolymer is preferably 10000-305000, more preferably 10000-210000. The number average molecular weight is preferably 5000 to 152500, more preferably 10000 to 105000.

< ingredient (B): compound having 2 or more crosslinkable functional groups >

The component (B) contained in the liquid crystal aligning agent of the present invention is a compound containing 2 or more crosslinkable functional groups.

The crosslinkable functional group includes at least one selected from the group consisting of a hydroxyl group, a hydroxyalkylamide group, a (meth) acrylate group, a blocked isocyanate group, an oxetanyl group, and an epoxy group, but is not limited thereto.

Among them, from the viewpoint of availability and the voltage holding ratio improving effect, a hydroxyl group, a blocked isocyanate group, or an epoxy group is preferable, and a hydroxyl group or an epoxy group is more preferable.

The compound of the component (B) may have 2 or more of the same crosslinkable functional groups or 2 or more of different crosslinkable functional groups in its structure.

Examples of the compound having 2 or more hydroxyl groups include compounds represented by the following formula (3).

In the above formula (3), X₃Is an n-valent organic group containing an aliphatic hydrocarbon group or an aromatic hydrocarbon group having 1 to 20 carbon atoms. Among them, preferred is an aliphatic hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, and more preferably 1 to 5 carbon atoms. R₂And R₃Each independently represents a hydrogen atom, an optionally substituted alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms or an alkynyl group having 2 to 4 carbon atoms, R₂And R₃At least one of them is represented by the following formula (4), but R is preferred₂And R₃Any one of them is represented by the following formula (4). n is preferably an integer of 2 to 6, particularly preferably 2.

In the above formula (4), R₄～R₇Each independently is a hydrogen atom, a hydrocarbon group, or a hydrocarbon group substituted with a hydroxyl group, preferably a hydrogen atom.

X₃The aliphatic hydrocarbon group is preferably one having 1 to 10 carbon atoms from the viewpoint of liquid crystal alignment properties and solubility, as described above. n represents an integer of 2 to 6, but n is preferably 2 to 4 from the viewpoint of solubility.

Specific examples of the compound having 2 or more hydroxyl groups include the following compounds.

Examples of the compound containing 2 or more blocked isocyanate groups include compounds represented by the following formula (5).

In the formula (5), Z is alkyl with 1-3 carbon atoms, hydroxyl or organic group shown in the formula (6) independently, and at least one of Z is organic group shown in the formula (6).

Specific examples of the compound containing 2 or more blocked isocyanate groups include the following compounds.

Examples of the compound containing 2 or more blocked isocyanate groups other than the compound represented by the above formula (7) include the following compounds.

Specific examples of the compound containing 2 or more epoxy groups include the following compounds.

Specific examples of the compound having 2 or more (meth) acrylate groups include the following compounds.

As the compound having 2 or more crosslinkable functional groups, the following compounds can be exemplified.

The compound of component (B) is contained in the liquid crystal aligning agent of the present invention preferably in an amount of 1 to 30% by weight, more preferably 3 to 15% by weight, based on the component (A).

< liquid Crystal alignment agent >

The liquid crystal aligning agent of the present invention is in the form of a solution in which the above-mentioned PAE-PAA copolymer and a compound having 2 or more crosslinkable functional groups are dissolved in an organic solvent. When the respective components are synthesized in an organic solvent, the reaction solution itself may be obtained, or the reaction solution may be diluted with an appropriate solvent. When each component is obtained as a powder, it may be dissolved in an organic solvent to form a solution.

The content (concentration) of the polymer component containing the PAE-PAA copolymer in the liquid crystal aligning agent of the present invention may be appropriately changed depending on the thickness of the polyimide film to be formed, but the content of the polymer component is preferably 0.5 mass% or more with respect to the organic solvent from the viewpoint of forming a uniform and defect-free coating film, and is preferably 15 mass% or less, more preferably 1 to 10 mass% from the viewpoint of the storage stability of the solution.

In this case, a concentrated solution of the polymer may be prepared in advance and diluted when the liquid crystal alignment agent is formed from the concentrated solution. The concentration of the concentrated solution of the polymer component is preferably 10 to 30% by mass, more preferably 10 to 15% by mass. Alternatively, the heating may be performed when the powder of the polymer component is dissolved in the organic solvent to prepare a solution. The heating temperature is preferably 20 to 150 ℃, and particularly preferably 20 to 80 ℃.

The organic solvent contained in the liquid crystal aligning agent of the present invention is not particularly limited as long as the polymer component is uniformly dissolved. Specific examples thereof include N, N-dimethylformamide, N-diethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-methylcaprolactam, 2-pyrrolidone, N-vinyl-2-pyrrolidone, dimethyl sulfoxide, dimethyl sulfone, γ -butyrolactone, 1, 3-dimethyl-imidazolidinone, and 3-methoxy-N, N-dimethylpropanamide. These may be used in a mixture of 1 or 2 or more. In addition, even if the single use of polymer components can not be dissolved in the solvent, if the polymer does not precipitate in the range of the solvent, can also be mixed with the organic solvent.

The liquid crystal aligning agent of the present invention may contain a solvent for improving the uniformity of a coating film when the liquid crystal aligning agent is applied to a substrate, in addition to an organic solvent for dissolving the polymer component. As the solvent, a solvent having a lower surface tension than the organic solvent is usually used. Specific examples thereof include ethyl cellosolve, butyl cellosolve acetate, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, ethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-butoxy-2-propanol, 1-phenoxy-2-propanol, propylene glycol monoacetate, propylene glycol diacetate, propylene glycol-1-monomethyl ether-2-acetate, propylene glycol-1-monoethyl ether-2-acetate, dipropylene glycol, 2- (2-ethoxypropoxy) propanol, methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, and isoamyl lactate. These solvents may be used in combination of 2 or more.

The liquid crystal aligning agent of the present invention may contain various additives such as a compound for improving film thickness uniformity and surface smoothness when the liquid crystal aligning agent is applied, a silane coupling agent, and a crosslinking agent, in addition to the above.

Examples of the compound for improving the uniformity of the film thickness and the surface smoothness include a fluorine-based surfactant, a silicone-based surfactant, and a nonionic surfactant.

More specifically, there may be mentioned, for example, EFTOP (Tochem Products Co., Ltd. trade name, EF301, EF303, EF352), Megaface (Dainippon Ink Co., Ltd. trade name, F171, F173, R-30, Fluorad (Sumitomo 3M Limited trade name, FC430, FC431, Asahi Guard (Asahi Niger trade name, AG710, Surflon (Asahi Niger trade name, S-382, SC101, SC102, SC103, SC104, SC105, SC106, etc.).

The amount of the surfactant is preferably 0.01 to 2 parts by mass, more preferably 0.01 to 1 part by mass, based on 100 parts by mass of the resin component contained in the liquid crystal aligning agent.

The silane coupling agent is added to improve the adhesion between the substrate coated with the liquid crystal alignment agent and the liquid crystal alignment film formed thereon. Examples of the silane coupling agent include, but are not limited to, the following silane coupling agents.

Amine systems such as 3-aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-phenylaminopropyltrimethoxysilane, 3-triethoxysilyl-N- (1, 3-dimethyl-butylidene) propylamine, and 3-aminopropyldiethoxymethylsilane; vinyl systems such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, vinylmethyldimethoxysilane, vinyltriacetoxysilane, vinyltriisopropoxysilane, allyltrimethoxysilane and p-vinyltrimethoxysilane; epoxy systems such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane and 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane; methacrylic acid series such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane; acrylic acid series such as 3-acryloxypropyltrimethoxysilane; ureide systems such as 3-ureide propyltriethoxysilane; thioether-based compounds such as bis (3- (triethoxysilyl) propyl) disulfide and bis (3- (triethoxysilyl) propyl) tetrasulfide; mercapto systems such as 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane and 3-octanoylthio-1-propyltriethoxysilane; isocyanate groups such as 3-isocyanatopropyltriethoxysilane and 3-isocyanatopropyltrimethoxysilane; aldehydes such as triethoxysilylbutanal; and carbamates such as triethoxysilylpropylmethylcarbamate and (3-triethoxysilylpropyl) -tert-butylcarbamate.

If the amount of the silane coupling agent added is too large, the unreacted product may adversely affect the liquid crystal alignment properties, and if it is too small, the effect on the adhesion properties cannot be exhibited, and therefore, it is preferably 0.01 to 5.0% by weight, more preferably 0.1 to 1.0% by weight, based on the solid content of the polymer.

In the liquid crystal alignment film of the present invention, an imidization accelerator may be added to effectively imidize the PAE-PAA copolymer or the polyamic acid ester during baking of the coating film.

< liquid Crystal alignment film >

The liquid crystal alignment film of the present invention is a film obtained by applying the liquid crystal alignment agent of the present invention to a substrate, drying the applied liquid crystal alignment agent as needed, and then baking the dried liquid crystal alignment agent. The substrate to which the liquid crystal aligning agent of the present invention is applied is not particularly limited as long as it is a substrate having high transparency, and for example, a plastic substrate such as an acrylic substrate or a polycarbonate substrate may be used in addition to a glass substrate. When the liquid crystal aligning agent of the present invention is used for manufacturing a liquid crystal display device, it is preferable to form a liquid crystal alignment film using a substrate on which an ITO (Indium Tin Oxide) electrode or the like for driving a liquid crystal is formed. In the case of manufacturing a reflective liquid crystal display element, an opaque substrate such as a silicon wafer may be used as the single-sided substrate, and a material that reflects light such as aluminum may be used as the electrode in this case.

Examples of the method for applying the liquid crystal aligning agent of the present invention to a substrate include screen printing, offset printing, flexographic printing, and ink jet printing. As other coating methods, there are a dipping method, a roll coating method, a slit coating method, a spin coating method, a spray method, and the like, and they can be used as necessary.

The coating film is usually dried at 50 to 120 ℃ for 1 to 10 minutes and then baked at 150 to 300 ℃ for 5 to 120 minutes in order to sufficiently remove the organic solvent contained therein. The thickness of the coating film after baking is not particularly limited, but if it is too thin, the reliability of the liquid crystal display device may be lowered, and therefore, it is 5 to 300nm, preferably 10 to 200 nm.

Examples of the method for aligning the obtained liquid crystal alignment film include a rubbing method and a photo-alignment treatment method.

The rubbing treatment of the coating film formed on the substrate may be performed by using a conventional rubbing device. Examples of the material of the rubbing cloth include cotton, rayon, and nylon. The conditions for the rubbing treatment are generally 300 to 2000rpm in rotation speed, 5 to 100mm/s in feed speed, 0.1 to 1.0mm in pressing amount, and the like. Then, the residue generated by the friction is removed by ultrasonic washing using pure water, alcohol, or the like.

The photo-alignment treatment method includes a method of applying a radiation beam deflected in a constant direction to the surface of the coating film and, if necessary, further performing a heat treatment at a temperature of 150 to 250 ℃ to impart an alignment ability to the liquid crystal. As the radiation ray, violet having a wavelength of 100 to 800nm can be usedOuter lines and visible rays. Among them, ultraviolet rays having a wavelength of 100 to 400nm are preferable, and a wavelength of 200 to 400nm is particularly preferable. In addition, in order to improve the liquid crystal alignment, the coated substrate may be irradiated with radiation while being heated at 50 to 250 ℃. The irradiation amount of the radiation is preferably 1 to 10000mJ/cm²Particularly preferably 100 to 5000mJ/cm²。

< liquid Crystal display element >

In the liquid crystal display element of the present invention, a substrate with a liquid crystal alignment film is obtained from the liquid crystal alignment agent of the present invention by the above-described method, and then a liquid crystal cell is produced by a known method to form the liquid crystal display element.

An example of a method for manufacturing the liquid crystal display element is as follows. First, 1 pair of substrates on which liquid crystal alignment films are formed are prepared, and they are disposed so that the rubbing direction forms an arbitrary angle of 0 ° to 270 ° with a spacer of preferably 1 to 30 μm, more preferably 2 to 10 μm interposed therebetween, and the periphery is fixed with a sealant. Then, liquid crystal is injected between the substrates and sealed. The method of sealing the liquid crystal is not particularly limited, and examples thereof include a vacuum method in which the pressure in the prepared liquid crystal cell is reduced and then the liquid crystal is injected, a dropping method in which the liquid crystal is dropped and then sealed, and the like.

Examples

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The abbreviations of the compounds used hereinafter and the methods for measuring the respective characteristics are as follows.

< monomer >

1,3 DMCBDE-Cl: dimethyl 1, 3-bis (chlorocarbonyl) -1, 3-dimethylcyclobutane-2, 4-dicarboxylate

1,3 DMCBDA: 1, 3-dimethyl-1, 2,3, 4-cyclobutanetetracarboxylic dianhydride

And (3) PMDA: pyromellitic dianhydride

PMDE-me: 2, 5-bis (methoxycarbonyl) benzene-1, 4-dicarboxylic acid

CBDE: 2, 4-bis (methoxycarbonyl) cyclobutane 1, 3-dicarboxylic acid

CBDA: 1,2,3, 4-cyclobutanetetracarboxylic dianhydride

DADPA: 4, 4' -diaminodiphenylamine

p-PDA: p-phenylenediamine

DBOP: diphenyl (2, 3-dihydro-2-thio-3-benzoxazolyl) phosphonates

< solvent >

NMP: n-methyl-2-pyrrolidone

BCS: butyl cellosolve

GBL: gamma-butyrolactone

< viscosity >

The viscosity of the polymer solution was measured using an E-type viscometer TVE-22H (manufactured by Toyobo industries Co., Ltd.) under conditions of a sample volume of 1.1mL, conical rotors TE-1(1 ℃ C., 34' and R24) and a temperature of 25 ℃.

< molecular weight >

The molecular weight of the polymer was measured by a GPC (normal temperature gel permeation chromatography) apparatus, and the number average molecular weight (hereinafter, also referred to as Mn) and the weight average molecular weight (hereinafter, also referred to as Mw) were calculated as values converted from polyethylene glycol and polyethylene oxide.

GPC apparatus: shodex Ltd (GPC-101)

A chromatographic column: shodex products (series KD803 and KD 805)

Temperature of the column: 50 deg.C

Eluent: n, N-dimethylformamide (containing lithium bromide-hydrate (LiBr. H) as an additive₂O)30 mmol/L, phosphoric acid-anhydrous crystal (orthophosphoric acid) 30 mmol/L, Tetrahydrofuran (THF)10ml/L)

Flow rate: 1.0 ml/min

Standard curve preparation standard samples: TSK standard polyethylene oxide (weight average molecular weight (Mw) of about 900000, 150000, 100000, 30000) manufactured by TOSOH CORPORATION, and polyethylene glycol (peak molecular weight (Mp) of about 12000, 4000, 1000) manufactured by Polymer Laboratories Ltd. In order to avoid overlapping of peaks, 2 samples, i.e., 4 mixed samples of 900000, 100000, 12000, and 1000, and 3 mixed samples of 150000, 30000, and 4000, were measured.

(Synthesis example 1)

In a 2L four-necked flask equipped with a stirrer and a nitrogen inlet, 1.30g (12.02 mmol) of p-PDA, 1.76g (7.21 mmol) of DA-A, and 1.64g (4.81 mmol) of DA-B were taken, and 46.10g of NMP, 106.9g of GBL, and 3.58g (0.44 mol) of pyridine were added and dissolved. Then, 1.07g (4.81 mmol) of 1,3d mcbda was added to the solution while stirring, and the mixture was reacted for 5 hours under water cooling. To the thus-obtained solution, 6.02g (18.5 mmol) of 1,3DMCBDE-Cl was added, and the reaction was further carried out under water cooling for 14 hours.

After 2.39g (2.64 mmol) of acryloyl chloride was added to the obtained polyamic acid ester-polyamic acid copolymer solution and reacted for 4 hours, the solution was poured into 1061ml of isopropyl alcohol while stirring, and the precipitated white precipitate was collected by filtration. Then, the mixture was washed with 2655ml of isopropyl alcohol 5 times and dried, thereby obtaining a white polyamic acid ester-polyamic acid copolymer resin powder (PWD-1). The molecular weight of the polyamic acid ester-polyamic acid copolymer was Mn-13493 and Mw-27207.

The polyamic acid ester-polyamic acid Copolymer resin powder (PWD-1) obtained above was dissolved in GBL to obtain a polyamic acid ester-polyamic acid Copolymer solution (biopolymer-1) having a solid content concentration of 12% by mass.

(Synthesis example 2)

In a 200mL four-necked flask equipped with a stirrer and a nitrogen inlet, 8.40g (3.23 mmol) of CBDE, 5.57g (2.28 mmol) of DA-A, and 3.03g (1.52 mmol) of DADPA were taken, and 106.57g of NMP and 6.92g (6.84 mmol) of triethylamine were added and dissolved. Then, 24.77g (6.46 mmol) of DBOP was added to the solution while stirring, and the reaction was carried out for 5 hours under water cooling. Then, while the solution was further stirred, 1.90g (0.76 mmol) of diphenyl phosphate, 1.08g (0.49 mmol) of PMDA and 22.84g of NMP were added thereto, and the reaction was further carried out for 5 hours under water cooling.

The obtained polyamic acid ester-polyamic acid copolymer solution was put into 2000ml of isopropyl alcohol while stirring, and the precipitated white precipitate was collected by filtration, washed with 407.83ml of methanol in 4 times, and dried to obtain a white polyamic acid ester-polyamic acid copolymer resin powder (PWD-2).

The polyamic acid ester-polyamic acid Copolymer resin powder (PWD-2) obtained above was dissolved in NMP to obtain a polyamic acid ester-polyamic acid Copolymer solution (biopolymer-2) having a solid content concentration of 12 mass%.

(comparative Synthesis example 1)

10.00g (92.4 mmol) of p-PDA, 13.60g (55.5 mmol) of DA-A, and 12.60g (37.0 mmol) of DA-B were taken in a 2L four-necked flask equipped with a stirrer and a nitrogen inlet, and 379.00g of NMP, 1023.00g of GBL, and 34.60g (0.43 mol) of pyridine were added and dissolved. Then, 1,3d mcbde-Cl 58.30g (179.4 mmol) was added while the solution was stirred, and the reaction was carried out under water cooling for 14 hours.

To the obtained polyamic acid solution was added 2.41g (26.6 mmol) of acryloyl chloride, and after a further reaction for 4 hours, the solution was charged with 8653ml of isopropyl alcohol while stirring, and the precipitated white precipitate was collected by filtration. Subsequently, the mixture was washed with 21635ml of isopropyl alcohol 5 times and dried, thereby obtaining a white polyamic acid ester resin powder (PWD-3). The polyamic acid ester had a molecular weight of Mn 24366 and Mw 54808.

The polyamic acid ester resin powder (PWD-3) obtained above was dissolved in GBL to obtain a polyamic acid ester solution (PAE-1) having a solid content concentration of 12% by mass.

(comparative Synthesis example 2)

In a 15L four-necked flask equipped with a stirrer and a nitrogen inlet, 761.05g (1.75 mol) of p-PDA, 256.50g (1.05 mol) of DA-A, and 258.56g (0.7 mol) of DA-B were taken, and 9671.41g of NMP was added and dissolved. Then, 761.05g (3.39 mol) of 1,3DMCBDA was added to the solution while stirring, and the solution was diluted with NMP so that the solid content concentration of the solution became 12%. The solution was reacted under water cooling for 14 hours to obtain a polyamic acid solution (PAA-1). The molecular weight of the polyamic acid was Mn-14366 and Mw-28508.

(example 1)

5.50g of the polyamic acid ester-polyamic acid Copolymer solution (Copolymer-1) obtained in Synthesis example 1 was taken in a 20ml sample tube equipped with a stirrer, and 0.28g of NMP (10 mass% dilution) solution of AD-A, 0.55g of 3-glycidoxypropylmethyldiethoxysilane solution diluted to 1.0 mass% with NMP, and 1.70g of NMP were added. Then, 2.00g of BCS was added and stirred with a magnetic stirrer for 30 minutes to obtain a liquid crystal aligning agent (A-1). The viscosity of A-1 was 35 mPaS. Even when the liquid crystal aligning agent (A-1) was stored at-20 ℃ for 1 week, no solid deposition was observed, and the solution was homogeneous.

(example 2)

7.50g of the polyamic acid ester-polyamic acid Copolymer solution (Copolymer-2) obtained in Synthesis example 2 was taken in a 20ml sample tube equipped with a stirrer, and 0.45g of NMP (10 mass% dilution) solution of AD-A, 0.9g of 3-glycidoxypropylmethyldiethoxysilane solution diluted to 1.0 mass% with NMP, and 3.12g of NMP were added. Then, 3.00g of BCS was added and stirred with a magnetic stirrer for 30 minutes to obtain a liquid crystal aligning agent (A-2). The viscosity of A-2 was 37 mPaS. Even when the liquid crystal aligning agent A-2 was stored at-20 ℃ for 1 week, no solid deposition was observed, and the solution was homogeneous.

Comparative example 1

7.50g of the polyamic acid ester solution (PAE-1) obtained in comparative Synthesis example 1 was taken in a 20ml sample tube equipped with a stirrer, 0.45g of a 10 mass% solution of AD-A in NMP was added, and 0.90g of a 1.0 mass% solution of 3-glycidoxypropylmethyldiethoxysilane and 2.48g of NMP were added. Then, 3.00g of BCS was added and stirred with a magnetic stirrer for 30 minutes to obtain a liquid crystal aligning agent (B-1). The viscosity of B-1 was 32 mPaS. The liquid crystal aligning agent B-1 was stored at-20 ℃ for 1 week, and as a result, no solid deposition was observed, and the solution was homogeneous.

Comparative example 2

8.21g of the polyamic acid solution (PAA-1) obtained in comparative Synthesis example 2 was taken out of a 20ml sample tube equipped with a stirrer, 0.45g of an NMP (10 mass% dilution) solution of AD-A was added, and 0.90g of a 3-glycidoxypropylmethyldiethoxysilane solution diluted to 1.0 mass% with NMP and 3.12g of NMP were added. Then, 3.00g of BCS was added and stirred with a magnetic stirrer for 30 minutes to obtain a liquid crystal aligning agent (B-2). The viscosity of B-2 was 35 mPaS. The liquid crystal aligning agent B-2 was stored at-20 ℃ for 1 week, and as a result, no solid deposition was observed, and the solution was homogeneous.

(example 3)

The liquid crystal aligning agent (A-1) obtained in example 1 was filtered through a 1.0 μm filter, spin-coated on a glass substrate with a transparent electrode, and dried on a hot plate at a temperature of 80 ℃ for 5 minutes. Then, the film was baked in a hot air circulating oven at 230 ℃ for 10 minutes to obtain an imidized film having a film thickness of 100 nm. Irradiating the baked film with 254nm ultraviolet ray of 250mJ/cm through a polarizing plate². Thus, a substrate with a liquid crystal alignment film was obtained.

In order to evaluate the electric characteristics of the liquid crystal cell, 2 substrates with the liquid crystal alignment films were prepared, and 6 μm spacers were scattered on 1 of the substrates. The sealant was printed thereon, and another 1 substrate was bonded to the liquid crystal alignment film surface so that the photo-alignment directions were perpendicular to each other, and then the sealant was cured to prepare an empty cell. Liquid crystals ML-7026-100 (manufactured by Merck Japan) were injected into the empty cell by a reduced pressure injection method, and the injection port was sealed to obtain an IPS liquid crystal cell. The liquid crystal cell was subjected to heat treatment at 120 ℃ for 30 minutes, and then slowly cooled to room temperature, and the cell was observed to have good alignment properties.

< measurement of Voltage holding ratio >

The voltage applied to the liquid crystal cell at 60 ℃ was 1V for 60. mu.s, and the voltage after 500ms was measured, and how much the voltage could be held was calculated as the voltage holding ratio.

As a result, the voltage holding ratio of the alignment film 1 formed from the alignment agent A-1 at 60 ℃ was 85.4%.

(example 4)

The same evaluation as in example 3 was carried out using the liquid crystal aligning agent of the present invention obtained in synthesis example 2. However, the rubbing treatment (roll diameter 120mm, rotation speed 1000rpm, moving speed 20 mm/sec, pressing length 0.3mm) was performed by the orientation treatment of the rayon cloth. The results are shown in table 1 described later.

Comparative example 3

The liquid crystal aligning agent of the present invention obtained in comparative example 1 was used to perform the same evaluation as in example 3. The results are shown in table 1 described later.

Comparative example 4

The liquid crystal aligning agent of the present invention obtained in comparative example 1 was used to perform the same evaluation as in example 3. However, the irradiation was carried out by irradiating 254nm ultraviolet rays of 500mJ/cm through a polarizing plate²To proceed with.

The results of examples 3 and 4 and comparative examples 3 and 4 are shown in table 1 below.

[ Table 1]

Industrial applicability

The liquid crystal alignment film formed by using the liquid crystal alignment agent of the present invention has not only improved liquid crystal alignment property but also improved electric characteristics such as voltage holding ratio and residual direct current voltage. As a result, the liquid crystal display device is widely used for TN devices, STN devices, TFT liquid crystal devices, vertical alignment liquid crystal display devices, and the like.

The entire contents of the specification, claims, drawings and abstract of japanese patent application 2015-236340 filed on 12/3/2015 are incorporated herein as the disclosure of the specification of the present invention.

Claims

1. A liquid crystal aligning agent comprising a component (A) and a component (B),

component (A): a copolymer having a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2),

in the formulae (1) and (2), X₁And X₂Each independently is a 4-valent organic radical, Y₁And Y₂Each independently is a 2-valent organic radical, R₁Is an alkyl group having 1 to 5 carbon atoms, A₁And A₂Each independently represents a hydrogen atom, an optionally substituted alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms or an alkynyl group having 2 to 10 carbon atoms,

component (B): a compound having 2 or more functional groups selected from at least one of a hydroxyl group, a hydroxyalkylamide group, a (meth) acrylate group, a blocked isocyanate group, and an oxetanyl group.

2. The liquid crystal aligning agent according to claim 1, wherein the component (B) is a compound represented by the following formula (3),

in the formula (3), X₃Is an n-valent organic group containing an aliphatic hydrocarbon group or an aromatic hydrocarbon group having 1 to 20 carbon atoms, R₂And R₃Each independently represents a hydrogen atom, or an optionally substituted alkyl group having 1 to 4 carbon atoms, alkenyl group having 2 to 4 carbon atoms or alkynyl group having 2 to 4 carbon atoms, R₂And R₃At least one of which is represented by the following formula (4), n is an integer of 2 to 6,

in the formula (4), R₄～R₇Each independently is a hydrogen atom, a hydrocarbyl group, or a hydrocarbyl group substituted with a hydroxyl group.

3. The liquid crystal aligning agent according to claim 1, wherein the copolymer of the component (A) has 50 to 95 mol% of the structural unit represented by the formula (1) and 5 to 50 mol% of the structural unit represented by the formula (2) based on all the structural units.

4. The liquid crystal aligning agent according to any one of claims 1 to 3, wherein the component (B) is contained in an amount of 1 to 30 wt% relative to the component (A).

5. The liquid crystal aligning agent according to any one of claims 1 to 3, further comprising an organic solvent, wherein the total content of the component (A) and the component (B) is 0.5 to 15% by mass relative to the organic solvent.

6. The liquid crystal aligning agent according to any one of claims 1 to 3, wherein X in the formulae (1) and (2)₁And X₂Each independently is at least one selected from the group consisting of structures represented by the following formulae,

7. the liquid crystal aligning agent according to any one of claims 1 to 3, wherein Y in the formulae (1) and (2)₁And Y₂Each independently is at least one selected from the group consisting of structures represented by the following formulae,

8. the liquid crystal aligning agent according to any one of claims 1 to 3, wherein the blocked isocyanate group is an organic group represented by the following formula (6),

9. the liquid crystal aligning agent according to claim 2, wherein the compound represented by formula (3) is a compound,

10. a liquid crystal alignment film obtained from the liquid crystal aligning agent according to any one of claims 1 to 9.

11. A liquid crystal display element having the liquid crystal alignment film according to claim 10.