JP6974800B2 - Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element - Google Patents

Description

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

As the liquid crystal alignment film, a so-called polyimide-based liquid crystal alignment film, which is obtained by applying and firing a liquid crystal alignment agent containing a polyimide precursor such as polyamic acid or a solution of soluble polyimide as a main component, is widely used. As a film forming method of a film, spin coating, dip coating, flexographic printing and the like are generally known. In reality, it is often applied by flexographic printing. In addition, flexographic printing requires various resin plates depending on the type of liquid crystal panel, the plate replacement is complicated in the manufacturing process, and film formation is performed on a dummy substrate to stabilize the film formation process. In recent years, coating by the inkjet method (hereinafter referred to as inkjet coating) has been attracting attention because there are problems such as the fact that the plate must be manufactured and the production of the plate contributes to the increase in the manufacturing cost of the liquid crystal display panel.

The liquid crystal alignment film formed by various coating methods is required to have small film thickness unevenness inside the coated surface and high film forming accuracy in the coating peripheral portion due to display uniformity and influence on electrical characteristics. In particular, if there is uneven film thickness, the unevenness causes a difference in display quality, which can be a main cause of display defects. In addition, the total amount of ionic impurities that can be generated from the membrane may also be a major factor affecting the alignment membrane.

For the above reasons, it is preferable that the solvent contained in the alignment agent is less likely to cause uneven coating and can be uniformly coated.

In order to improve the film formation accuracy of the coating peripheral portion, a method of confining the alignment film within a predetermined range by a structure has been proposed (Patent Document 1, Patent Document 2, Patent Document 3). However, these methods have the disadvantage of requiring additional structures.

Japanese Unexamined Patent Publication No. 2004-361623 Japanese Unexamined Patent Publication No. 2008-14541 Japanese Unexamined Patent Publication No. 2010-281925

Therefore, the present invention provides a polyimide-based liquid crystal alignment agent capable of forming a coating film having excellent film thickness in the coating surface and linearity in the coating peripheral portion and having excellent electrical characteristics of the liquid crystal display element. The purpose.

As a result of repeated studies to achieve the above object, the present inventor has arrived at the present invention having the following gist.

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

A 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 is in the liquid crystal alignment agent of the embodiment.

A third aspect of the present invention that achieves the above object is the first aspect or the second aspect, wherein the solvent of the group (A) is 50% by weight to 95% by weight with respect to the total amount of the solvent. It is in the liquid crystal alignment agent of the above aspect.

A fourth aspect of the present invention that achieves the above object is characterized in that the solvent of the group (B) is 5% by weight to 50% by weight with respect to the total amount of the solvent, from the first aspect to the third aspect. The liquid crystal alignment agent according to any one of the above embodiments.

A fifth aspect of the present invention that achieves the above object is the liquid crystal alignment agent according to any one of the first to fourth aspects, which comprises 1% by mass to 5% by mass of the polymer. be.

A sixth aspect of the present invention that achieves the above object is the liquid crystal alignment agent according to any one of the first to fifth aspects, which comprises 95% by mass to 99% by mass of the solvent. ..

A 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 alignment agent of the present invention can obtain a coating film having excellent linearity in the peripheral portion of coating, particularly when inkjet coating is applied. Further, the liquid crystal alignment film obtained from the liquid crystal alignment agent of the present invention is excellent in voltage holding characteristics.

The liquid crystal alignment agent of the present invention contains at least one polymer selected from the group consisting of polyimide and a polyimide precursor, and an organic solvent containing the following groups (A) and (B). It is a feature. Hereinafter, the liquid crystal alignment agent of the present invention will be described in detail.

<Organic solvent>
The liquid crystal alignment agent of the present invention contains an organic solvent containing the following group (A) and the following group (B).
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.

<Solvents of group (A)>
The solvent of group (A) 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 them, 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 orienting agent.

<Solvent of group (B)>
The solvent of the 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. Solvent. These are mainly solvents for providing good coatability.

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

<Other solvents>
The liquid crystal alignment agent of the present invention may contain a solvent other than the above-mentioned solvent (hereinafter, also referred to as other solvent) to the extent that the effect of the present invention is 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-methylcaprolactum, 2-pyrrolidone, N-vinyl-2-pyrrolidone, dimethylsulfoxide. , Dimethylsulfone, 1,3-dimethyl-2-imidazolidinone, 3-methoxy-N, N-dimethylpropanamide, ethylserosolve, butylserosolve, ethylcarbitol, butylcarbitol, ethylcarbitol 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, lactic acid methyl ester, lactic acid ethyl ester, lactic acid Examples thereof include n-propyl ester, lactic acid n-butyl ester, lactic acid isoamyl ester, and diacetone alcohol.

The following is an example of a solvent that is preferable as another solvent and a combination of the solvent that is preferable in combination with the group (A) and the group (B).

For example, N, N-dimethylformamide, butyl cellosolve, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, diisobutylcarbinol, diisopropyl ether, diisobutylketone, 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, dipropylene glycol dimethyl-n-propyl ether and the like can be mentioned.

<Polymer>
The polymer contained in the liquid crystal alignment agent of the present invention is at least one polymer selected from the group consisting of polyimide and a 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 1. Represents an alkylene of ~ 5. From the viewpoint of ease of 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 independently hydrogen atoms or alkyl groups having 1 to 5 carbon atoms, alkenyl groups having 2 to 5 carbon atoms, and alkynyl groups having 2 to 5 carbon atoms. From the viewpoint of liquid crystal orientation, A ₁ and A ₂ are preferably hydrogen atoms or methyl groups.

Hereinafter, each component that is a raw material for forming a polymer will be described in detail.

<Diamine>
The structure of the diamine component used in the liquid crystal alignment agent of the present invention is not particularly 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 of the above formula (2) have the same definition as _{A 1} and A ₂ of the above formula (1), including preferable 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 to 6.

Boc in the above formula (Y-175), the above formula (Y-176), the above formula (Y-179) and the above formula (Y-180) 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) contained in the liquid crystal alignment agent of the present invention includes not only the tetracarboxylic acid dianhydride but also the tetracarboxylic acid thereof. 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 dianhydride 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 formulas (X1-1) to the following formulas (X1-44).

In the above formula (X1-1) to the above formula (X1-4), R ₃ to R ₂₃ independently have a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, and 2 to 6 carbon atoms. It is 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, and 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 structures of the above formula (X1-1) include structures represented by the following formulas (X1-1-1) to the following formulas (X1-1-6). The following formula (X1-1-1) is particularly preferable from the viewpoint of liquid crystal orientation and sensitivity of photoreaction.

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

(1) When Synthesized from Polyamic Acid The polyamic acid ester can be synthesized by esterifying the 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 by.

The esterifying agent is preferably one that can be easily removed by purification, and is preferably N, N-dimethylformamide dimethylacetal, N, N-dimethylformamide diethylacetal, N, N-dimethylformamide dipropylacetal, N, N-dimethylformamide. Gineopentylbutylacetal, N, N-dimethylformamide di-t-butylacetal, 1-methyl-3-p-tolyltriasel, 1-ethyl-3-p-tolyltriasel, 1-propyl-3-p -Tolyltriase, 4- (4,6-dimethoxy-1,3,5-triazine-2-yl) -4-methylmorpholinium chloride and the like can be mentioned. The amount of the esterifying agent added is preferably 2 molar equivalents to 6 molar equivalents with respect to 1 mol of the repeating unit of the polyamic acid.

The solvent used for the above reaction is preferably N, N-dimethylformamide, N-methyl-2-pyrrolidone, or γ-butyrolactone because of the solubility of the polymer, and 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, more preferably 5% by mass to 20% by mass, from the viewpoint that precipitation of the polymer is unlikely to occur and a high molecular weight substance is easily obtained.

(2) When Synthesized by Reaction of Tetracarboxylic Acid Diester Dichloride with Diamine The polyamic acid ester can be synthesized from the tetracarboxylic acid diester dichloride and diamine.

Specifically, the tetracarboxylic dianester dichloride and diamine are mixed 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 be synthesized by reacting for a time.

As the base, pyridine, triethylamine, 4-dimethylaminopyridine and the like can be used, but pyridine is preferable because the reaction proceeds moderately. The amount of the base added is preferably 2 to 4 times the molar amount of the tetracarboxylic dianester dichloride from the viewpoint of easy removal and easy acquisition of a high molecular weight substance.

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

(3) When synthesizing a polyamic acid ester from a tetracarboxylic acid diester and a diamine The polyamic acid ester can be synthesized by polycondensing a tetracarboxylic acid diester and a diamine.

Specifically, the tetracarboxylic acid diester and the diamine are mixed 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. It can be synthesized by reacting for 15 hours.

The condensing agent includes triphenylphosphite, dicyclohexylcarbodiimide, 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride, N, N'-carbonyldiimidazole, dimethoxy-1,3,5-triazole. Nylmethylmorpholinium, O- (benzotriazole-1-yl) -N, N, N', N'-tetramethyluronium tetrafluoroborate, O- (benzotriazole-1-yl) -N, N , N', N'-tetramethyluronium hexafluorophosphate, (2,3-dihydro-2-thioxo-3-benzoxazolyl) phosphonate diphenyl and the like can be used. The amount of the condensing agent added is preferably 2 to 3 times the molar amount of the tetracarboxylic diandies.

A tertiary amine such as pyridine or triethylamine can be used as the base. The amount of the base added is preferably 2 to 4 times the molar amount with respect to the diamine component from the viewpoint that the amount of the base added is easy to remove and a high molecular weight substance can be easily obtained.

Further, in the above reaction, the reaction proceeds efficiently by adding Lewis acid as an additive. As the Lewis acid, lithium halide such as lithium chloride and lithium bromide is preferable. The amount of Lewis acid added is preferably 0 to 1.0 times the molar amount of the diamine component.

Among the above three methods for synthesizing polyamic acid esters, the above-mentioned (1) or (2) synthesis method is particularly preferable because a high molecular weight polyamic acid ester can be obtained.

The solution of the polyamic acid ester obtained as described above can be injected into a poor solvent with good stirring to precipitate a polymer. Precipitation is carried out several times, and after washing with a poor solvent, the powder of the polyamic acid ester purified at room temperature or by heating and drying can be obtained. The antisolvent is not particularly limited, and examples thereof include water, methanol, ethanol, hexane, butyl cellosolve, acetone, and toluene.

<Manufacturing method of polyamic acid>
The polyamic acid, which is a polyimide precursor used in the present invention, can be synthesized by the method shown below.

Specifically, tetracarboxylic dianhydride and diamine are mixed 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 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 because of the solubility of the monomer and the polymer, and these are one or a mixture of two or more. You may use it. The concentration of the polymer is preferably 1% by mass to 30% by mass, more preferably 5% by mass to 20% by mass, from the viewpoint that precipitation of the polymer is unlikely to occur and a high molecular weight polymer is easily obtained.

The polyamic acid obtained as described above can be recovered by precipitating a polymer by injecting the reaction solution into a poor solvent while stirring well. Further, the purified polyamic acid powder can be obtained by performing precipitation several times, washing with a poor solvent, and then drying at room temperature or by heating. The antisolvent is not particularly limited, and examples thereof include water, methanol, ethanol, hexane, butyl cellosolve, acetone, and toluene.

<Polyimide manufacturing method>
The polyimide used in the present invention can be produced by imidizing the polyamic acid ester or polyamic acid. When polyimide is produced from a polyamic acid ester, chemical imidization in which a basic catalyst is added to the polyamic acid solution obtained by dissolving the polyamic acid ester solution or the polyamic acid ester resin powder in an organic solvent is convenient. 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 imidization can be performed by stirring the polyamic acid ester to be imidized in an organic solvent in the presence of a basic catalyst. As the organic solvent, the solvent used in the above-mentioned polymerization reaction can be used. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine and the like. Of these, triethylamine is preferable because it has sufficient basicity to allow the reaction to proceed.

The temperature at which the imidization reaction is carried out 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 to 30 mol times, preferably 2 mol times to 20 mol times, that of the amic acid ester group. The imidization rate of the obtained polymer can be controlled by adjusting the amount of catalyst, the temperature, and the reaction time. Since the added catalyst and the like remain in the solution after the imidization reaction, the obtained imidized polymer is recovered by the means described below and redissolved in an organic solvent to orient the liquid crystal of the present invention. It is preferable to use it as an agent.

When the polyimide is produced from a polyamic acid, it is convenient to chemically imidize by adding a catalyst to the solution of the polyamic acid obtained by the reaction of the diamine component and the tetracarboxylic acid dianhydride. 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 imidization can be carried out by stirring the polymer to be imidized in the presence of a basic catalyst and an acid anhydride in an organic solvent. As the organic solvent, the solvent used in the above-mentioned polymerization reaction can be used. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine and the like. Among them, pyridine is preferable because it has an appropriate basicity for advancing the reaction. Examples of the acid anhydride include acetic anhydride, trimellitic anhydride, pyromellitic anhydride and the like. Among them, acetic anhydride is preferable because it facilitates purification after the reaction is completed.

The temperature at which the imidization reaction is carried out 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 mol to 20 mol times the amount of the amic acid group, and the amount of the acid anhydride is 1 mol to 50 mol times the amic acid group. It is preferably 3 to 30 mol times. The imidization rate of the obtained polymer can be controlled by adjusting the amount of catalyst, the temperature, and the reaction time.

Since the added catalyst and the like remain in the solution after the imidization reaction of the polyamic acid ester or the polyamic acid, the obtained imidized polymer is recovered by the means described below and redissolved in an organic solvent. Therefore, it is preferable to use the liquid crystal alignment agent of the present invention.

The polyimide solution obtained as described above can be injected into a poor solvent with good stirring to precipitate a polymer. Precipitation is carried out several times, and after washing with a poor solvent, the powder of the polyamic acid ester purified at room temperature or by heating and drying can be obtained.

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

<Liquid crystal alignment agent>
The liquid crystal alignment agent used in the present invention has the 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 the polyimide described in the present invention is preferably 2,000 to 500,000, more preferably 5,000 to 300,000, still more preferably 10,000 to 100, in terms of weight average molecular weight. It is 000. The number average molecular weight is preferably 1,000 to 250,000, more preferably 2,500 to 150,000, and even more preferably 5,000 to 50,000.

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

The liquid crystal alignment agent of the present invention may contain various additives such as a silane coupling agent and a cross-linking agent. The silane coupling agent is added for the purpose of improving the adhesion between the substrate to which the liquid crystal alignment agent is applied and the liquid crystal alignment film formed therein. Existing silane coupling agents are added.

If the amount of the silane coupling agent added is too large, the unreacted one may adversely affect the liquid crystal orientation, and if it is too small, the effect on adhesion does not appear. Therefore, it is 0 with respect to the solid content of the polymer. It is preferably 0.01% by weight to 5.0% by weight, more preferably 0.1% by weight to 1.0% by weight. When the silane coupling agent is added, it is preferable to add it before adding the solvent for improving the uniformity of the coating film in order to prevent the precipitation of the polymer.

Further, an imidization accelerator may be added to the liquid crystal alignment agent of the present invention in order to efficiently promote the imidization of the polyimide precursor when firing the coating film. Existing ones are used as the imidization accelerator.

When an imidization accelerator is added, it is preferable to add it after diluting it with a good solvent and a poor solvent because imidization may proceed by heating.

<Liquid crystal alignment film>
The liquid crystal alignment film of the present invention is a film obtained by applying the above liquid crystal alignment agent to a substrate, drying and firing. The substrate to which the liquid crystal alignment 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 plastic substrate such as a polycarbonate substrate, or the like can be used, and the liquid crystal display can be driven. From the viewpoint of simplifying the process, it is preferable to use a substrate on which an ITO electrode or the like is formed. Further, in the reflective liquid crystal display element, an opaque object such as a silicon wafer can be used if only one side of the substrate is used, and in this case, a material that reflects light such as aluminum can also be used as the electrode.

As a method for applying the liquid crystal alignment agent of the present invention, a spin coating method, a printing method and the like can also be used, but as described above, the liquid crystal alignment agent of the present invention is particularly suitable for the inkjet method. When the liquid crystal alignment agent of the present invention is applied by an inkjet method to form a coating film (inkjet coating), a coating film having excellent film thickness in the coating surface and linearity in the coating peripheral portion can be obtained.

Any temperature and time can be selected for the drying and firing steps after applying the liquid crystal alignment agent of the present invention. Usually, it is dried at 50 ° C. to 120 ° C. for 1 minute to 10 minutes and then calcined at 150 ° C. to 300 ° C. for 5 minutes to 120 minutes in order to sufficiently remove the contained organic solvent. The thickness of the coating film after firing is not particularly limited, but is 5 nm to 300 nm, preferably 10 nm to 200 nm because the reliability of the liquid crystal display element may decrease if it is too thin.

The liquid crystal alignment treatment agent of the present invention can be used as a liquid crystal alignment film after being applied and fired on a substrate and then subjected to alignment treatment such as rubbing treatment or photoalignment treatment, or without alignment treatment in vertical alignment applications. 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 method, performing alignment treatment, and then producing a liquid crystal cell by a known method. Is.

The method for manufacturing the liquid crystal cell is not particularly limited, but to give an 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. After installing the spacer with the spacer in between, the surrounding area is fixed with a sealing agent, and a liquid crystal display is injected to seal the liquid crystal display. The method of enclosing the liquid crystal is not particularly limited, and examples thereof include a vacuum method in which the inside of the produced liquid crystal cell is depressurized and then the liquid crystal is injected, and a dropping method in which the liquid crystal is dropped and then sealed.

Hereinafter, the present invention will be specifically described with reference to examples. However, it goes without saying that the present invention is not construed as being limited to these examples.

The abbreviations used in Examples and Comparative Examples and the measurement method for 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 of the following formula DA-2 DA-3: Diamine of the following formula DA-3

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: Butylcellosolve GBL: γ-Butyrolactone BCA: Butylcellosolve 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 by using an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.), a sample volume of 1.1 mL, a cone rotor TE-1 (1 ° 34', R24), and a temperature of 25. Measured at ° C.

<Molecular weight>
In the synthesis example, 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 measured as polyethylene glycol and polyethylene oxide equivalent values. Say.) Was calculated.
GPC device: manufactured by Shodex (GPC-101)
Column: Made by Shodex (series of KD803 and KD805)
Column temperature: 50 ° C
Eluent: N, N-dimethylformamide (as an additive, lithium bromide-hydrate (LiBr · H ₂ O) 30 mmol / L, phosphoric acid / anhydrous crystal (o-phosphate) 30 mmol / L, tetrahydrofuran (THF) is 10 ml / L)
Flow rate: 1.0 ml / Standard sample for preparing a calibration curve: Tosoh TSK standard polyethylene oxide (weight average molecular weight (Mw) about 900,000, 150,000, 100,000, 30,000), and polymer laboratory Polyethylene glycol manufactured by the company (peak top molecular weight (Mp) of about 12,000, 4,000, 1,000). In the measurement, in order to avoid overlapping peaks, a sample in which 4 types of 900,000, 100,000, 12,000, and 1,000 are mixed, and 3 types of 150,000, 30,000, and 4,000 are used. Two samples of the mixed sample were measured separately.

<Synthesis example>
(Synthesis Example 1)
1.88 g (7.70 mmol) of DA-1 and 1.17 g (2.11 mmol) of DA-3 and 1.67 g of DA-2 (1.77 g) in a 50 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube. 4.20 mmol) was taken, 40.00 g of NMP was added, and the mixture was stirred while feeding nitrogen to dissolve it. While stirring this diamine solution, add 2.04 g (9.10 mmol) of 1,3 DMCBDA and further stir, add 0.62 g (3.16 mmol) of CBDA when the viscosity is stable, and further add a solid content concentration of 15. NMP was added so as to be in mass%, and the mixture was stirred at room temperature for 24 hours to obtain a 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 in a 100 mL four-necked flask equipped with a stirrer and a nitrogen introduction tube, and NMP was added to dilute the solid content concentration to 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, the solution was heated to 55 ° C. with stirring and reacted for 3 hours. The obtained polyamic acid-soluble polyimide acid solution was added to methanol in an equal volume of 3.5 times the total solution with stirring and reprecipitated. The powder after reprecipitation is collected by filtration by natural filtration or suction filtration, and then 0.188 liters (5.86 mmol) of methanol are washed in two portions and dried to obtain white polyamic acid-. 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)
In a 20 ml sample tube containing a stirrer, 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, 3-glycidoxypropylmethyldi. 0.81 g of ethoxysilane solution and 6.84 g of NMP were added. Then, 3.60 g of DAA was added and stirred with a magnetic stirrer for 30 minutes to obtain a liquid crystal alignment agent (A-1). When the liquid crystal alignment agent A-1 was stored at −20 ° C. for 1 week, no precipitation of solid matter was observed, and the solution was a uniform solution.

(Examples 2 to 5, Comparative Examples 1 to 6)
Same as Example 1 except that the polyamic acid-soluble polyimide resin powder solution (SPI-1) was used instead of the polyamic acid (PAA-1), or the solvent shown in the table below was used instead of DAA as the solvent. The liquid crystal alignment agents (A-2) to (A-5) and (B-1) to (B-6) were obtained, respectively. When all the liquid crystal alignment agents obtained as described above were stored at −20 ° C. for 1 week, no solid matter was observed and the solution was uniform. The results of each 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 has a stripe pattern of 40 mm in length and 10 mm in width.

Next, the liquid crystal alignment 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, it was fired in an IR oven at 230 ° C. for 20 minutes to form a coating film having a film thickness of 100 nm to obtain a substrate with a liquid crystal alignment film. After rubbing this liquid crystal alignment film with a rayon cloth (roller diameter: 120 mm, roller rotation speed: 1000 rpm, moving speed: 20 mm / sec, pushing length: 0.4 mm), ultrasonic irradiation is performed in pure water for 1 minute. After washing with air blow to remove water droplets, the substrate was dried at 80 ° C. for 15 minutes to obtain a substrate with a liquid crystal alignment film. Two substrates with this liquid crystal alignment film are prepared, a spacer of 4 μm is sprayed on the surface of one liquid crystal alignment film, a sealant is printed on the substrate, and the other substrate is rubbed in the opposite direction. And, after laminating so that the film surfaces face each other, the sealing agent was cured to prepare an empty cell. A liquid crystal ML-7026-100 (manufactured by Merck Japan) was injected into this empty cell by a vacuum injection method, and the injection port was sealed to obtain a liquid crystal cell. Then, the obtained liquid crystal cell was heated at 120 ° C. for 60 minutes, then cooled to room temperature, and the cell was observed. As a result, the orientation was good.

<Measurement of voltage retention rate>
(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 could be maintained was calculated as the voltage retention rate.

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

(Examples 7 to 10, 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 measuring method described in Example 6. The results of each are shown in Table 2 below.

It is widely useful for TN elements, STN elements, TFT liquid crystal elements, and vertically oriented liquid crystal display elements.

Claims (8)

A liquid crystal alignment agent comprising at least one polymer selected from the group consisting of polyimide and a polyimide precursor, and an organic solvent containing 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 Group (B): 4-methoxy-4-methyl-2-pentanone, 4 -At least one solvent selected from hydroxy-2-butanone and 2-methyl-2-hexanol The liquid crystal alignment 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. The liquid crystal alignment agent according to claim 1 or 2, 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 alignment agent according to any one of claims 1 to 3, wherein the solvent of the group (B) is 5% by weight to 50% by weight with respect to the total amount of the solvent. The liquid crystal alignment 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 alignment agent according to any one of claims 1 to 5, wherein the solvent is contained in an amount of 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.