WO2018038160A1

WO2018038160A1 - Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element

Info

Publication number: WO2018038160A1
Application number: PCT/JP2017/030130
Authority: WO
Inventors: 大輝山極
Original assignee: 日産化学工業株式会社
Priority date: 2016-08-24
Filing date: 2017-08-23
Publication date: 2018-03-01
Also published as: JPWO2018038160A1; CN109643038B; KR20190044642A; JP6974800B2; CN109643038A; TWI735635B; TW201825658A; KR102430123B1

Abstract

This liquid crystal alignment agent is characterized by containing: at least one type of polymer selected from the group consisting of polyimides and polyimide precursors; and an organic solvent containing solvents specified by group (A) and group (B). Group (A): at least one type of solvent selected from N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and γ-butyrolactone. Group (B): at least one type of solvent selected from 4-methoxy-4-methyl-2-pentanone, 4-hydroxy-2-butanone, and 2-methyl-2-hexanol.

Description

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

The present invention relates to a liquid crystal aligning agent suitable for application by an inkjet method, a liquid crystal aligning film obtained from the liquid crystal aligning agent, and a liquid crystal display element.

As the liquid crystal alignment film, a so-called polyimide liquid crystal alignment film obtained by applying and baking a liquid crystal alignment agent mainly composed of a polyimide precursor such as polyamic acid or a solution of soluble polyimide is widely used. As film formation methods, spin coating, dip coating, flexographic printing, and the like are generally known. Actually, there are many applications by flexographic printing. In addition, flexographic printing requires various resin plates due to the different types of liquid crystal panels, the plate replacement in the manufacturing process is complicated, and film formation on a dummy substrate is performed to stabilize the film formation process. In recent years, application by an ink jet method (hereinafter referred to as ink jet application) has been attracting attention because there are problems such as the necessity of manufacturing the plate and the manufacturing cost of the liquid crystal display panel. *

A liquid crystal alignment film formed by various coating methods is required to have uniform film thickness unevenness inside the coating surface and high film forming accuracy in the periphery of the coating because of uniform display and influence on electrical characteristics. In particular, when the film thickness is uneven, the display quality is different due to the unevenness, which can be a main cause of display defects. In addition, the total amount of ionic impurities that can be generated from the film may be a main factor affecting the alignment film. *

For the above reasons, it is preferable that the solvent contained in the aligning agent does not cause coating unevenness and can be applied uniformly. *

In order to increase the film forming accuracy in the periphery of the coating, methods for confining the alignment film within a predetermined range with a structure have been proposed (Patent Document 1, Patent Document 2, and Patent Document 3). However, these methods have the disadvantage that additional structures are required.

JP 2004-361623 A JP 2008-145461 A JP 2010-281925 A

Therefore, the present invention provides a polyimide-based liquid crystal aligning agent that can form a coating film with excellent uniformity of the film thickness within the coating surface and linearity of the peripheral portion of the coating, and that has excellent electrical characteristics of the liquid crystal display element. Objective.

The inventor has conducted research to achieve the above object, and has reached the present invention having the following summary.

A first aspect of the present invention that achieves the above-described object is a solvent containing at least one polymer selected from the group consisting of a polyimide and a polyimide precursor, and a solvent of the following groups (A) and (B): In a liquid crystal aligning agent characterized by containing.
Group (A): at least one solvent selected from N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and γ-butyrolactone (B) group: 4-methoxy-4-methyl-2-pentanone, 4 At least one solvent selected from -hydroxy-2-butanone and 2-methyl-2-hexanol

The second aspect of the present invention that achieves the above object is characterized in that the solvent of the group (A) contains at least one selected from the group consisting of N-methylpyrrolidone and γ-butyrolactone. It exists in the liquid crystal aligning agent of an aspect.

According to a third aspect of the present invention for achieving the above object, the solvent of the group (A) is 50% by weight to 95% by weight with respect to the total amount of the solvent. In the liquid crystal aligning agent of the embodiment.

According to a fourth aspect of the present invention for achieving the above object, the solvent of the group (B) is 5 to 50% by weight based on the total amount of the solvent. The liquid crystal aligning agent according to any one of the embodiments is provided.

According to a fifth aspect of the present invention for achieving the above object, in the liquid crystal aligning agent according to any one of the first to fourth aspects, the polymer is contained in an amount of 1% by mass to 5% by mass. is there.

According to a sixth aspect of the present invention for achieving the above object, there is provided the liquid crystal aligning agent according to any one of the first to fifth aspects, wherein the solvent is contained in an amount of 95% by mass to 99% by mass. .

The seventh aspect of the present invention that achieves the above object is a liquid crystal alignment film obtained from the liquid crystal alignment agent according to any one of the first to sixth aspects.

An eighth aspect of the present invention that achieves the above object is a liquid crystal display element comprising the liquid crystal alignment film of the seventh aspect.

The liquid crystal aligning agent of the present invention can provide a coating film having excellent linearity at the periphery of the coating, particularly when inkjet coating is applied. Furthermore, the liquid crystal alignment film obtained from the liquid crystal aligning agent of this invention is excellent in a voltage holding characteristic.

The liquid crystal aligning agent of this invention contains at least 1 sort (s) of polymer chosen from the group which consists of a polyimide and a polyimide precursor, and the organic solvent containing the solvent of the following (A) group and (B) group. Features. Hereinafter, the liquid crystal aligning agent of the present invention will be described in detail.

<Organic solvent>
The liquid crystal aligning agent of this invention contains the organic solvent containing the solvent of the following (A) group and the following (B) group.
Group (A): At least one solvent selected from N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and γ-butyrolactone.
Group (B): At least one solvent selected from 4-methoxy-4-methyl-2-pentanone, 4-hydroxy-2-butanone and 2-methyl-2-hexanol.

<Solvent of Group (A)>
The group (A) solvent contained in the organic solvent of the present invention is at least one solvent selected from N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and γ-butyrolactone. These are mainly solvents for dissolving the polymer. Among these, from the viewpoint of solubility, at least one selected from the group consisting of N-methylpyrrolidone and γ-butyrolactone is preferable.

The content of the solvent in the group (A) is preferably 50% by weight to 95% by weight with respect to the total amount of the solvent from the viewpoint of the solubility of the aligning agent.

<Solvent of Group (B)>
The solvent of group (B) contained in the organic solvent of the present invention is at least one selected from 4-methoxy-4-methyl-2-pentanone, 4-hydroxy-2-butanone and 2-methyl-2-hexanol. It is a solvent. These are mainly solvents for providing good coating properties.

The content of the solvent in the group (B) is preferably 5% by weight to 50% by weight with respect to the total solvent amount from the viewpoint of the stability of the solution.

<Other solvents>
The liquid crystal aligning agent of the present invention can contain a solvent other than the above solvents (hereinafter also referred to as other solvents) to the extent that the effects of the present invention are exhibited. Examples of other solvents are listed below, but are not limited thereto.

For example, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N-ethyl-2-pyrrolidone, N-methylcaprolactam, 2-pyrrolidone, N-vinyl-2-pyrrolidone, dimethyl sulfoxide Dimethylsulfone, 1,3-dimethyl-2-imidazolidinone, 3-methoxy-N, N-dimethylpropanamide, ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, ethylene glycol, 1 -Methoxy-2-propanol, 1-ethoxy-2-propanol, 1-butoxy-2-propanol, 2-butoxy-1-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, butyl cellosolve acetate, dipropylene glycol, 2- (2-ethoxypropoxy) propanol, methyl lactate, lactic acid Examples include ethyl ester, lactic acid n-propyl ester, lactic acid n-butyl ester, lactic acid isoamyl ester, and diacetone alcohol.

Examples of preferable solvents as other solvents and combinations of solvents that are preferably combined with the group (A) and the group (B) are shown below. *

For example, N, N-dimethylformamide, butyl cellosolve, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, diisobutyl carbinol, diisopropyl ether, diisobutyl ketone, ethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2 -Propanol, 1-butoxy-2-propanol, 2-butoxy-1-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, butyl cellosolve acetate, dipropylene glycol, dipropylene glycol dimethyl ether, Propylene glycol dimethyl -n- propyl ether and the like.

<Polymer>
The polymer contained in the liquid crystal aligning agent of the present invention is at least one polymer selected from the group consisting of polyimide and polyimide precursor.

The polyimide precursor can be represented by the following formula (1). *

In the above formula (1), X ₁ is a tetravalent organic group derived from a tetracarboxylic acid derivative, Y ₁ is a divalent organic group derived from a diamine, and R ₁ is a hydrogen atom or a carbon atom number of 1 Represents an alkylene of .about.5. From the viewpoint of easy progress of the imidization reaction during heating, R ₁ is preferably a hydrogen atom, a methyl group, or an ethyl group, and more preferably a hydrogen atom or a methyl group.
A ₁ and A ₂ are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms. From the viewpoint of liquid crystal orientation, A ₁ and A ₂ are preferably a hydrogen atom or a methyl group.

Hereafter, each component used as the raw material which forms a polymer is explained in full detail.

<Diamine>
The structure of the diamine component used for the liquid crystal aligning agent of this invention is not specifically limited.

The diamine used for the polymerization of the polymer having the structure of the above formula (1) can be generalized by the following formula (2). *

A ₁ and A _{2 in} the above formula (2) have the same definitions as A ₁ and A _{2 in} the above formula (1), including preferred examples. An example of the structure of Y ₁ is as follows.

In the above formula (Y-165) and the above formula (Y-166), n is an integer of 1-6. *

In the above formula (Y-175), the above formula (Y-176), the above formula (Y-179) and the above formula (Y-180), Boc represents a tert-butoxycarbonyl group.

<Tetracarboxylic acid derivative>
The tetracarboxylic acid derivative component for producing the polymer having the structural unit of the above formula (1), which is contained in the liquid crystal aligning agent of the present invention, includes not only tetracarboxylic dianhydride but also its tetracarboxylic acid. Derivatives such as tetracarboxylic acid, tetracarboxylic acid dihalide compound, tetracarboxylic acid dialkyl ester compound or tetracarboxylic acid dialkyl ester dihalide compound can also be used.

As the tetracarboxylic dianhydride or a derivative thereof, it is more preferable to use at least one selected from the tetracarboxylic dianhydrides represented by the following formula (3) or a derivative thereof. *

In the above formula (3), X ₁ is a tetravalent organic group having an alicyclic structure, and the structure is not particularly limited. Specific examples include the following formula (X1-1) to the following formula (X1-44).

In the above formulas (X1-1) to (X1-4), R ₃ to R ₂₃ each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkyl group having 2 to 6 carbon atoms. An alkenyl group, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom, or a phenyl group, which may be the same or different. From the viewpoint of liquid crystal orientation, R ₃ to R ₂₃ are preferably a hydrogen atom, a halogen atom, a methyl group, or an ethyl group, and more preferably a hydrogen atom or a methyl group. Specific examples of the structure of the above formula (X1-1) include structures represented by the following formulas (X1-1-1) to (X1-1-6). The following formula (X1-1-1) is particularly preferable from the viewpoint of liquid crystal alignment and photoreaction sensitivity.

<Method for producing polyamic acid ester>
The polyamic acid ester which is one of the polyimide precursors used in the present invention can be synthesized by the following method (1), (2) or (3).

(1) When synthesizing from polyamic acid The polyamic acid ester can be synthesized by esterifying a polyamic acid obtained from tetracarboxylic dianhydride and diamine.

Specifically, the polyamic acid and the esterifying agent are reacted in the presence of an organic solvent at −20 ° C. to 150 ° C., preferably 0 ° C. to 50 ° C., for 30 minutes to 24 hours, preferably 1 hour to 4 hours. Can be synthesized. *

The esterifying agent is preferably one that can be easily removed by purification, and N, N-dimethylformamide dimethyl acetal, N, N-dimethylformamide diethyl acetal, N, N-dimethylformamide dipropyl acetal, N, N-dimethylformamide Dineopentyl butyl acetal, N, N-dimethylformamide di-t-butyl acetal, 1-methyl-3-p-tolyltriazene, 1-ethyl-3-p-tolyltriazene, 1-propyl-3-p -Tolyltriazene, 4- (4,6-dimethoxy-1,3,5-triazin-2-yl) -4-methylmorpholinium chloride and the like. The addition amount of the esterifying agent is preferably 2 to 6 molar equivalents relative to 1 mol of the polyamic acid repeating unit. *

The solvent used in the above reaction is preferably N, N-dimethylformamide, N-methyl-2-pyrrolidone, or γ-butyrolactone in view of polymer solubility. These may be used alone or in combination of two or more. Good. The concentration at the time of synthesis is preferably 1% by mass to 30% by mass and more preferably 5% by mass to 20% by mass from the viewpoint that polymer precipitation is unlikely to occur and a high molecular weight product is easily obtained.

(2) When synthesized by reaction of tetracarboxylic acid diester dichloride and diamine Polyamic acid ester can be synthesized from tetracarboxylic acid diester dichloride and diamine.

Specifically, tetracarboxylic acid diester dichloride and diamine in the presence of a base and an organic solvent at −20 ° C. to 150 ° C., preferably 0 ° C. to 50 ° C., for 30 minutes to 24 hours, preferably 1 hour to 4 hours. It can synthesize | combine by making it react for time. *

As the base, pyridine, triethylamine, 4-dimethylaminopyridine and the like can be used, but pyridine is preferable because the reaction proceeds gently. The addition amount of the base is preferably 2 to 4 times mol with respect to tetracarboxylic acid diester dichloride from the viewpoint of easy removal and high molecular weight. *

The solvent used in the above reaction is preferably N-methyl-2-pyrrolidone or γ-butyrolactone from the solubility of the monomer and polymer, and these may be used alone or in combination. The polymer concentration at the time of synthesis is preferably 1% by mass to 30% by mass and more preferably 5% by mass to 20% by mass from the viewpoint that polymer precipitation is difficult to occur and a high molecular weight product is easily obtained. In order to prevent hydrolysis of the tetracarboxylic acid diester dichloride, the solvent used for the synthesis of the polyamic acid ester is preferably dehydrated as much as possible, and it is preferable to prevent mixing of outside air in a nitrogen atmosphere.

(3) When synthesizing polyamic acid ester from tetracarboxylic acid diester and diamine Polyamic acid ester can be synthesized by polycondensation of tetracarboxylic acid diester and diamine.

Specifically, tetracarboxylic acid diester and diamine in the presence of a condensing agent, a base, and an organic solvent at 0 ° C. to 150 ° C., preferably 0 ° C. to 100 ° C., for 30 minutes to 24 hours, preferably 3 hours to It can be synthesized by reacting for 15 hours. *

Examples of the condensing agent include triphenyl phosphite, dicyclohexylcarbodiimide, 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride, N, N′-carbonyldiimidazole, dimethoxy-1,3,5-triazide. Nylmethylmorpholinium, O- (benzotriazol-1-yl) -N, N, N ′, N′-tetramethyluronium tetrafluoroborate, O- (benzotriazol-1-yl) -N, N , N ′, N′-tetramethyluronium hexafluorophosphate, (2,3-dihydro-2-thioxo-3-benzoxazolyl) phosphonate diphenyl, and the like. The addition amount of the condensing agent is preferably 2 to 3 times mol with respect to the tetracarboxylic acid diester. *

As the base, tertiary amines such as pyridine and triethylamine can be used. The addition amount of the base is preferably 2 to 4 mols relative to the diamine component from the viewpoint of easy removal and high molecular weight. *

In the above reaction, the reaction proceeds efficiently by adding Lewis acid as an additive. As the Lewis acid, lithium halides such as lithium chloride and lithium bromide are preferable. The addition amount of the Lewis acid is preferably 0 to 1.0 times mol with respect to the diamine component. *

Among the methods for synthesizing the three polyamic acid esters, since the high molecular weight polyamic acid ester is obtained, the synthesis method (1) or (2) is particularly preferable. *

The polymer solution can be precipitated by injecting the polyamic acid ester solution obtained as described above into a poor solvent while stirring well. Precipitation is performed several times, and after washing with a poor solvent, a purified polyamic acid ester powder can be obtained at room temperature or by heating and drying. Although a poor solvent is not specifically limited, Water, methanol, ethanol, hexane, butyl cellosolve, acetone, toluene etc. are mentioned.

<Method for producing polyamic acid>
The polyamic acid which is a polyimide precursor used in the present invention can be synthesized by the following method.

Specifically, tetracarboxylic dianhydride and diamine are -20 ° C to 150 ° C, preferably 0 ° C to 50 ° C in the presence of an organic solvent, for 30 minutes to 24 hours, preferably 1 hour to 12 hours. It can be synthesized by reacting. *

The organic solvent used in the above reaction is preferably N, N-dimethylformamide, N-methyl-2-pyrrolidone, or γ-butyrolactone in view of the solubility of the monomer and polymer. These may be used alone or in combination of two or more. It may be used. The concentration of the polymer is preferably 1% by mass to 30% by mass and more preferably 5% by mass to 20% by mass from the viewpoint that polymer precipitation is difficult to occur and a high molecular weight body is easily obtained. *

The polyamic acid obtained as described above can be recovered by precipitating the polymer by pouring into the poor solvent while thoroughly stirring the reaction solution. Moreover, the powder of polyamic acid refine | purified by performing precipitation several times, washing | cleaning with a poor solvent, and normal temperature or heat-drying can be obtained. Although a poor solvent is not specifically limited, Water, methanol, ethanol, hexane, butyl cellosolve, acetone, toluene etc. are mentioned.

<Production method of polyimide>
The polyimide used in the present invention can be produced by imidizing the polyamic acid ester or polyamic acid. When a polyimide is produced from a polyamic acid ester, chemical imidization in which a basic catalyst is added to a polyamic acid solution obtained by dissolving the polyamic acid ester solution or the polyamic acid ester resin powder in an organic solvent is simple. Chemical imidization is preferable because the imidization reaction proceeds at a relatively low temperature and the molecular weight of the polymer is unlikely to decrease during the imidization process.

Chemical imidation can be performed by stirring the polyamic acid ester to be imidized in an organic solvent in the presence of a basic catalyst. As an organic solvent, the solvent used at the time of the polymerization reaction mentioned above can be used. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine and the like. Of these, triethylamine is preferred because it has sufficient basicity to allow the reaction to proceed. *

The temperature for carrying out the imidization reaction is −20 ° C. to 140 ° C., preferably 0 ° C. to 100 ° C., and the reaction time can be 1 hour to 100 hours. The amount of the basic catalyst is 0.5 mol times to 30 mol times, preferably 2 mol times to 20 mol times of the amic acid ester group. The imidation ratio of the resulting polymer can be controlled by adjusting the amount of catalyst, temperature, and reaction time. Since the added catalyst or the like remains in the solution after the imidation reaction, the obtained imidized polymer is recovered by the means described below, redissolved in an organic solvent, and the liquid crystal alignment according to the present invention. It is preferable to use an agent. *

When a polyimide is produced from a polyamic acid, chemical imidization in which a catalyst is added to the polyamic acid solution obtained by the reaction of a diamine component and tetracarboxylic dianhydride is simple. Chemical imidization is preferable because the imidization reaction proceeds at a relatively low temperature and the molecular weight of the polymer is unlikely to decrease during the imidization process. *

Chemical imidation can be performed by stirring a polymer to be imidized in an organic solvent in the presence of a basic catalyst and an acid anhydride. As an organic solvent, the solvent used at the time of the polymerization reaction mentioned above can be used. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine and the like. Of these, pyridine is preferable because it has an appropriate basicity for proceeding with the reaction. Examples of the acid anhydride include acetic anhydride, trimellitic anhydride, pyromellitic anhydride and the like. Among them, use of acetic anhydride is preferable because purification after completion of the reaction is facilitated. *

The temperature for carrying out the imidization reaction is −20 ° C. to 140 ° C., preferably 0 ° C. to 100 ° C., and the reaction time can be 1 hour to 100 hours. The amount of the basic catalyst is 0.5 to 30 mol times, preferably 2 to 20 mol times the amic acid group, and the amount of the acid anhydride is 1 to 50 mol times the amic acid group, The amount is preferably 3 mole times to 30 mole times. The imidation ratio of the resulting polymer can be controlled by adjusting the amount of catalyst, temperature, and reaction time. *

In the solution after the imidation reaction of polyamic acid ester or polyamic acid, the added catalyst and the like remain, so the obtained imidized polymer is recovered by the means described below, and redissolved in an organic solvent. Thus, the liquid crystal aligning agent of the present invention is preferable. *

The polyimide solution obtained as described above can be polymerized by pouring into a poor solvent while stirring well. Precipitation is performed several times, and after washing with a poor solvent, a purified polyamic acid ester powder can be obtained at room temperature or by heating and drying. *

The poor solvent is not particularly limited, and examples thereof include methanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, and benzene.

<Liquid crystal aligning agent>
The liquid crystal aligning agent used in the present invention has a form of a solution in which a polymer having a specific structure is dissolved in an organic solvent. The molecular weight of the polyimide precursor and polyimide described in the present invention is preferably 2,000 to 500,000 in weight average molecular weight, more preferably 5,000 to 300,000, and still more preferably 10,000 to 100. , 000. The number average molecular weight is preferably 1,000 to 250,000, more preferably 2,500 to 150,000, and still more preferably 5,000 to 50,000.

The concentration of the polymer of the liquid crystal aligning agent used in the present invention can be appropriately changed depending on the setting of the thickness of the coating film to be formed, but it is 1 weight from the viewpoint of forming a uniform and defect-free coating film. % From the viewpoint of storage stability of the solution, and preferably 10% by weight or less. *

The liquid crystal aligning agent of the present invention may contain various additives such as a silane coupling agent and a crosslinking agent. The silane coupling agent is added for the purpose of improving the adhesion between the substrate on which the liquid crystal alignment agent is applied and the liquid crystal alignment film formed thereon. Existing silane coupling agents are added. *

If the amount of the silane coupling agent added is too large, unreacted ones may adversely affect the liquid crystal orientation, and if too small, the effect on adhesion will not appear, so the amount of the silane coupling agent is 0 with respect to the solid content of the polymer. 0.01 wt% to 5.0 wt% is preferable, and 0.1 wt% to 1.0 wt% is more preferable. When adding the said silane coupling agent, in order to prevent precipitation of a polymer, it is preferable to add before adding the solvent for improving the above-mentioned coating-film uniformity. *

In addition, an imidization accelerator may be added to the liquid crystal aligning agent of the present invention in order to efficiently advance the imidization of the polyimide precursor when the coating film is baked. Existing imidation accelerators are used. *

In the case of adding an imidization accelerator, since imidization may proceed by heating, it is preferably added after dilution with a good solvent and a poor solvent.

<Liquid crystal alignment film>
The liquid crystal alignment film of the present invention is a film obtained by applying the liquid crystal aligning agent to a substrate, drying and baking. The substrate on which the liquid crystal aligning agent of the present invention is applied is not particularly limited as long as it is a highly transparent substrate, and a glass substrate, a silicon nitride substrate, an acrylic substrate, a polycarbonate substrate such as a polycarbonate substrate, or the like can be used. From the viewpoint of simplification of the process, it is preferable to use a substrate on which an ITO electrode or the like is formed. In the reflective liquid crystal display element, an opaque material such as a silicon wafer can be used as long as only one substrate is used. In this case, a material that reflects light, such as aluminum, can also be used.

As a method for applying the liquid crystal aligning agent of the present invention, a spin coating method, a printing method, or the like can be used. As described above, the liquid crystal aligning agent of the present invention is particularly suitable for the ink jet method. When the liquid crystal aligning agent of this invention is apply | coated by the inkjet method and a coating film is formed (inkjet application | coating), the coating film excellent in the uniformity of the film thickness in a coating surface and the linearity of a coating peripheral part is obtained. *

In the drying and baking process after applying the liquid crystal aligning agent of the present invention, any temperature and time can be selected. Usually, in order to sufficiently remove the organic solvent contained, drying is performed at 50 ° C. to 120 ° C. for 1 minute to 10 minutes, and then baking is performed at 150 ° C. to 300 ° C. for 5 minutes to 120 minutes. 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 element may be lowered, and therefore it is 5 nm to 300 nm, preferably 10 nm to 200 nm. *

The liquid crystal alignment treatment agent of the present invention can be used as a liquid crystal alignment film after being applied and baked on a substrate, then subjected to alignment treatment by rubbing treatment, photo-alignment treatment, or the like, or without alignment treatment in vertical alignment applications. it can.

<Liquid crystal display element>
The liquid crystal display element of the present invention is a liquid crystal display element obtained by obtaining a substrate with a liquid crystal alignment film from the liquid crystal aligning agent of the present invention by the above-described method, performing an alignment treatment, and then preparing a liquid crystal cell by a known method. It is.

The manufacturing method of the liquid crystal cell is not particularly limited. For example, a pair of substrates on which the liquid crystal alignment film is formed is preferably 1 μm to 30 μm, more preferably 2 μm to 10 μm with the liquid crystal alignment film surface inside. A method is generally employed in which the spacer is fixed with a sealing agent after the spacer is sandwiched, and liquid crystal is injected and sealed. The method for enclosing the liquid crystal is not particularly limited, and examples thereof include a vacuum method of injecting liquid crystal after reducing the pressure inside the produced liquid crystal cell, and a dropping method of sealing after dropping the liquid crystal.

Hereinafter, the present invention will be described more specifically with reference to examples. However, it is needless to say that the present invention is not construed as being limited to these examples. *

In addition, the symbol used by an Example and a comparative example and the measuring method of each characteristic are as follows.
1,3DMCBDA: 1,3-dimethyl 1,2,3,4 cyclobutanetetracarboxylic dianhydride CBDA: 1,2,3,4-cyclobutanetetracarboxylic dianhydride DA-1: of the following formula DA-1 Diamine DA-2: Diamine DA-3 of formula DA-2 below: Diamine of formula DA-3 below

Boc in the above formula DA-2 and the above formula DA-3 represents a tert-butoxycarbonyl group.

<Solvent>
NMP: N-methyl-2-pyrrolidone BCS: butyl cellosolve GBL: γ-butyrolactone BCA: butyl cellosolve acetate PB: propylene glycol monobutyl ether DME: dipropylene glycol dimethyl ether DEDG: diethylene glycol diethyl ether DAA: diacetone alcohol 4M4M2P: 4-methoxy-4 -Methyl-2-pentanone 4H2B: 4-hydroxy-2-butanone 2M2H: 2-methyl-2-hexanol

<Viscosity>
In the synthesis example, the viscosity of the polymer solution was measured using an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.), a sample amount of 1.1 mL, cone rotor TE-1 (1 ° 34 ′, R24), temperature 25 Measured at ° C.

<Molecular weight>
In the synthesis examples, the molecular weight of the polymer is measured by a GPC (room 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) in terms of polyethylene glycol and polyethylene oxide. Say).
GPC device: manufactured by Shodex (GPC-101)
Column: manufactured by Shodex (series of KD803 and KD805)
Column temperature: 50 ° C
Eluent: N, N-dimethylformamide (as additives, lithium bromide-hydrate (LiBr · H ₂ O) 30 mmol / L, phosphoric acid / anhydrous crystals (o-phosphoric acid) 30 mmol / L, tetrahydrofuran) (THF) is 10 ml / L)
Flow rate: 1.0 ml / min Standard sample for preparation of calibration curve: TSK standard polyethylene oxide (weight average molecular weight (Mw) of about 900,000, 150,000, 100,000, 30,000) manufactured by Tosoh Corporation, and polymer laboratory Polyethylene glycol manufactured by the company (peak top molecular weight (Mp) of about 12,000, 4,000, 1,000). In order to avoid the overlapping of peaks, the measurement was performed by mixing four types of 900,000, 100,000, 12,000, and 1,000, and three types of 150,000, 30,000, and 4,000. Two samples of the mixed sample were measured separately.

<Synthesis example>
(Synthesis Example 1)
In a 50 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 1.88 g (7.70 mmol) of DA-1, 1.17 g (2.11 mmol) of DA-3, 1.67 g of DA-2 ( 4.20 mmol), 40.00 g of NMP was added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this diamine solution, 2.04 g (9.10 mmol) of 1,3DMCBDA was added and further stirred. When the viscosity was stabilized, 0.62 g (3.16 mmol) of CBDA was added, and the solid content concentration was 15%. NMP was added so that it might become the mass%, and it stirred at room temperature for 24 hours, and obtained the solution of polyamic acid (PAA-1). The viscosity of this polyamic acid solution at 25 ° C. was 212 mPa · S.

(Synthesis Example 2)
30 g of PAA-1 obtained in Synthesis Example 1 was weighed into a 100 mL four-necked flask equipped with a stirrer and a nitrogen introduction tube, and diluted with NMP so that the solid content concentration was 8% by mass.

Next, 2.61 g (25.5 mmol) of acetic anhydride and 0.67 g (8.47 mmol) of pyridine were added and dissolved. Next, this solution was heated to 55 ° C. with stirring and reacted for 3 hours. The obtained polyamic acid-soluble polyimide acid solution was poured into methanol in an amount equivalent to 3.5 times the total solution while stirring to cause reprecipitation. The powder after reprecipitation is filtered by natural filtration or suction filtration, and then further washed with 0.188 l (5.86 mmol) of methanol in two portions and dried to give white polyamic acid- A soluble polyimide resin powder (PWD-1) was obtained. The molecular weight of this resin powder was Mn = 13,493 and Mw = 27,207. *

The PWD-1 obtained above was dissolved in NMP to obtain a polyamic acid-soluble polyimide resin powder solution (SPI-1) having a solid content concentration of 12% by mass.

(Example 1)
To a 20 ml sample tube containing a stir bar, 6.75 g of the polyamic acid solution (PAA-1) obtained in Synthesis Example 1 was weighed and diluted to 1.0% by mass with NMP. 0.81 g of ethoxysilane solution and 6.84 g of NMP were added. Thereafter, 3.60 g of DAA was added and stirred with a magnetic stirrer for 30 minutes to obtain a liquid crystal aligning agent (A-1). When the liquid crystal aligning agent A-1 was stored at −20 ° C. for 1 week, precipitation of solid matter was not observed, and the solution was uniform.

(Examples 2 to 5, Comparative Examples 1 to 6)
Example 1 except that a polyamic acid-soluble polyimide resin powder solution (SPI-1) was used instead of polyamic acid (PAA-1), or the solvent shown in the table below was used instead of DAA as the solvent. Thus, liquid crystal aligning agents (A-2) to (A-5) and (B-1) to (B-6) were obtained. When all the liquid crystal aligning agents obtained as described above were stored at −20 ° C. for 1 week, no solid precipitate was observed and the solution was uniform. The results are shown in Table 1 below.

In order to evaluate the electrical characteristics of the liquid crystal cell, a substrate with electrodes was first prepared. The substrate is a glass substrate having a size of 30 mm × 40 mm and a thickness of 1.1 mm. An ITO electrode having a film thickness of 35 nm is formed on the substrate, and the electrode is a stripe pattern having a length of 40 mm and a width of 10 mm. *

Next, the liquid crystal aligning agent was filtered through a 1.0 μm filter, and then applied to the prepared substrate with electrodes by spin coating. After drying on a hot plate at 50 ° C. for 5 minutes, baking was performed in an IR oven at 230 ° C. for 20 minutes to form a coating film having a thickness of 100 nm to obtain a substrate with a liquid crystal alignment film. This liquid crystal alignment film is rubbed with a rayon cloth (roller diameter: 120 mm, roller rotation speed: 1000 rpm, moving speed: 20 mm / sec, indentation length: 0.4 mm), and then irradiated with ultrasonic waves in pure water for 1 minute. After washing and removing water droplets by air blow, drying was performed at 80 ° C. for 15 minutes to obtain a substrate with a liquid crystal alignment film. Prepare two substrates with this liquid crystal alignment film, spray a 4μm spacer on the surface of one liquid crystal alignment film, print a sealant on it, and reverse the rubbing direction of the other substrate. And after bonding together so that the film surfaces face each other, the sealing agent was cured to produce an empty cell. Liquid crystal ML-7026-100 (manufactured by Merck Japan) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain a liquid crystal cell. Thereafter, the obtained liquid crystal cell was heated at 120 ° C. for 60 minutes, then cooled to room temperature and the cell was observed. The orientation was good.

<Measurement of voltage holding ratio>
(Example 6)
A voltage of 1 V was applied to the liquid crystal cell at a temperature of 60 ° C. for 60 μs, the voltage after 50 ms was measured, and how much the voltage was held was calculated as a voltage holding ratio.

As a result, the voltage holding ratio at 60 ° C. of the alignment film made of the alignment agent A-1 was 96.7%.

(Examples 7 to 10 and Comparative Examples 7 to 12)
Alignment agent (A-2) to Alignment agent (A-5) and Alignment agent (B-1) to Alignment agent (B-6) obtained in Examples 2 to 5 and Comparative Examples 1 to 6 A liquid crystal cell was prepared by the same method, and the voltage holding ratio was measured by the measurement method described in Example 6. Each result is shown in Table 2 below.

Widely useful for TN elements, STN elements, TFT liquid crystal elements, and vertical alignment type liquid crystal display elements.

Claims

A liquid crystal aligning agent comprising at least one polymer selected from the group consisting of a polyimide and a polyimide precursor, and an organic solvent containing a solvent of the following groups (A) and (B).
Group (A): at least one solvent selected from N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and γ-butyrolactone (B) group: 4-methoxy-4-methyl-2-pentanone, 4 At least one solvent selected from -hydroxy-2-butanone and 2-methyl-2-hexanol
2. The liquid crystal aligning agent according to claim 1, wherein the solvent of the group (A) contains at least one selected from the group consisting of N-methylpyrrolidone and γ-butyrolactone.
3. The liquid crystal aligning agent according to claim 1, wherein the solvent of the group (A) is 50% by weight to 95% by weight with respect to the total amount of the solvent.
The liquid crystal aligning agent according to any one of claims 1 to 3, wherein the solvent of the group (B) is 5 to 50% by weight based on the total amount of the solvent.
The liquid crystal aligning agent according to any one of claims 1 to 4, wherein the polymer is contained in an amount of 1% by mass to 5% by mass.
The liquid crystal aligning agent according to any one of claims 1 to 5, wherein the solvent contains 95% by mass to 99% by mass.
A liquid crystal alignment film obtained from the liquid crystal alignment agent according to any one of claims 1 to 6.
A liquid crystal display element comprising the liquid crystal alignment film according to claim 7.