TWI689551B - Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element - Google Patents

Abstract

The present invention is a liquid crystal alignment agent that provides a sealant or forms a liquid crystal alignment film with good adhesion to a substrate.

The liquid crystal alignment agent of the present invention contains a polyimide obtained by imilating the following polyimide precursor and/or the polyimide precursor. The polyimide precursor contains a formula [1] A diamine component and a tetracarboxylic acid component of a diamine having the structure shown.

(R¹、R²為氫原子、碳數1~4的烷基或式(2)的基，該 至少一方為式(2)的基。A為單鍵或由碳數1~4的烴基所成的2價基。)

(R ¹ and R ² are a hydrogen atom, a C 1-4 alkyl group or a group of the formula (2), at least one of which is a group of the formula (2). A is a single bond or a C 1-4 hydrocarbon group The formed bivalent base.)

Description

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

The present invention relates to a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display element obtained by using a diamine having a specific structure.

The liquid crystal alignment film of the liquid crystal display element nowadays mainly uses a liquid crystal alignment agent (also referred to as a liquid crystal alignment treatment agent) containing a polyimide-based polymer applied to a substrate and fired.

The liquid crystal alignment film is used for the purpose of controlling the alignment state of the liquid crystal. With the high definition of the liquid crystal display element, from the perspective of the requirements for the suppression of the contrast reduction of the liquid crystal display element or the reduction of the afterimage image, for the liquid crystal alignment film, The so-called high voltage retention rate or the low residual charge when a DC voltage is input, and/or the rapid relaxation of the accumulated residual charge by the DC voltage are important matters.

In addition, it is known that the liquid crystal display element is a light-weight, thin and low-power consumption display device. In recent years, small, high-definition liquid crystal display devices, such as mobile phones, smart phones, and tablet-type devices, which have rapidly expanded their market share, have also developed significantly to meet the requirements of high display quality.

Especially in these small liquid crystal display elements, To ensure the display surface, it is required to design the width of the sealant used between the substrates following the liquid crystal display element to be narrower than in the past, so-called narrow margin. With the narrow margin of the panel, the application position of the sealant used in the manufacture of liquid crystal display elements can be at the end of the liquid crystal alignment film or on the liquid crystal alignment film, but due to the polyimide There are few or no polar groups, the covalent bond cannot be formed on the surface of the sealant and the liquid crystal alignment film, and there is a problem that the substrates are not sufficiently adhered to each other.

In this case, especially for use under high temperature and high humidity conditions, water is easily mixed between the sealant and the slits of the liquid crystal alignment film, which may cause a problem of uneven display near the front edge of the liquid crystal display element. Therefore, it is a problem to improve the adhesion (adhesion) between the polyimide-based liquid crystal alignment film and the sealant or the substrate. As described above, the improvement of the adhesion between the liquid crystal alignment film and the sealant or the substrate must be achieved without reducing the liquid crystal alignment or electrical characteristics of the liquid crystal alignment film, and these characteristics must also be improved.

[Advanced technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 09-278724

[Patent Document 2] Japanese Patent Laid-Open No. 10-123532

The present invention is obtained in view of the above circumstances, and the object is to provide display liquid crystal alignment for forming a liquid crystal alignment film without causing display unevenness near the front edge of a liquid crystal display element and having good adhesion to a sealant or a substrate Agent, and provide a novel diamine with a specific structure used in the manufacture of the liquid crystal alignment agent.

The inventors of the present invention have carried out repeated detailed examinations to achieve the above object, and found that the liquid crystal alignment agent containing the polyimide obtained from the following polyimide precursor and/or the polyimide precursor has excellent characteristics and completed the present invention. According to the invention, the polyimide precursor is a diamine having a specific structure.

The liquid crystal alignment agent of the present invention contains a polyimide precursor obtained by reacting a diamine component and a tetracarboxylic acid component and/or a polyimide obtained from the polyimide precursor, and is characterized by the aforementioned two The amine component contains a diamine having a structure represented by the following formula (1).

(R¹及R²各獨立為氫原子、碳數1~4的烷基或下述式(2)所示基，該至少一方為式(2)所示基。式(2)中，A為單鍵或碳數1~4的烴基之2價基。)

(R ¹ and R ^{2 are} each independently a hydrogen atom, a C 1-4 alkyl group or a group represented by the following formula (2), at least one of which is a group represented by the formula (2). In the formula (2), A (It is a divalent group of a single bond or a hydrocarbon group having 1 to 4 carbon atoms.)

The liquid crystal alignment film formed by using the liquid crystal alignment agent containing the polyimide obtained by using the polyimide precursor of the novel diamine having a specific structure and/or the polyimide precursor in the present invention is because The liquid crystal display element has high adhesion to the sealant or the substrate, so even under high temperature and high humidity conditions, the occurrence of display unevenness near the front edge can be suppressed, and the area of the front edge around the element can be reduced. Since the display area can be increased, it can be advantageously used in small, high-definition liquid crystal display devices such as mobile phones, smart phones, and tablet-type devices. Moreover, because the residual charge relaxes quickly, it has the advantage that the residual image of the liquid crystal display element can be developed and disappear in a short time.

In addition, the polyimide obtained by using the polyimide precursor of a diamine having a specific structure and/or the polyimide precursor of the present invention has a high solubility in a solvent, so it has high availability Advantages of polymer concentration liquid crystal alignment agent.

[Forms for carrying out the invention] [Diamine]

The present invention contains the diamine component used in the liquid crystal alignment agent Some diamines are those having a structure represented by the following formula (1) in the molecule.

In formulas (1) and (2), R ¹ , R ² and A are as defined above. Among them, it is also preferable that at least one of R ¹ and R ² or both are based on the group represented by formula (2). From the viewpoint of the strength of the alignment film at the time of rubbing, only one of R ¹ and R ² is the formula ( 2) The one shown is better.

A is preferably a single bond. When A is a single bond, the group of formula (2) is t-butoxycarbonyl (also referred to as Boc group in the present invention).

The diamine having the structure represented by the above formula (1) in the molecule may be any diamine if it can satisfy the relevant requirements. As this preferred example, a diamine represented by the following formula [1] may be mentioned.

In formula [1], R ¹ and R ² include the same cases as in formula (1), except for each preferred one. m and n are each independently an integer of 0 to 3. From the viewpoint of ease of obtaining raw materials, it is preferably 0 or 1, more preferably 1.

In addition, in formula [1], the bonding position of the amine group (-NH ₂ ) in each benzene ring to the alkylene group may be any position of ortho, meta, or pair, but the ease of synthesis and From the point of view of polymerization reactivity, the occasional or correct position is preferred, and the preferred position is preferred.

As examples of the diamine represented by formula [1], the following compounds are preferably mentioned. In addition, in the formulas of the compounds exemplified below, Boc is a group shown below.

The synthesis method of the diamine represented by the formula [1] is not particularly limited, and as a general synthesis method, as shown below, it can be produced by reducing the dinitro compound X1 of the diamine X. , And R ^1, R ^2, m, are the same _{and, R 1, R 2, m} , n in each of the above-described formula (1) n.

The above-mentioned reduction reaction includes a hydrogenation reaction in the presence of a catalyst, a reduction reaction performed in the presence of protons, a reduction reaction using formic acid as a hydrogen source, and a reduction reaction using hydrazine as a hydrogen source. These reduction reactions can also be combined. In consideration of the reactivity of the structure of the dinitro compound X1 and the reduction reaction, the hydrogenation reaction is preferred.

The catalyst used in the reduction reaction is loaded with activated carbon available from the sale product The metal is preferably held, and examples thereof include palladium-activated carbon, platinum-activated carbon, rhodium-activated carbon, and the like. In addition, metal catalysts such as palladium hydroxide, platinum dioxide, Raney nickel, etc., which are not necessarily activated carbon supported, may be used. Generally, palladium-activated carbon, which is widely used, is preferable because of good results.

To make the reduction reaction more effective, the reaction can be carried out in the presence of activated carbon. At this time, the amount of activated carbon used is not particularly limited, and the dinitro compound X1 is preferably 1 to 20% by mass, and preferably 5 to 10% by mass.

For the same reason, the reaction may be carried out under pressure. At this time, if you want to avoid the reduction of the benzene nucleus, you can proceed under a pressure range of 20 atmospheres. The reaction is preferably carried out within a range of 10 atmospheres.

For the reduction reaction, it is preferred to use a solvent, which is only a solvent that does not react with each raw material, and can be used without limitation.

For example, an aprotic polar organic solvent (DMF (N, N-dimethylformamide), DMSO (dimethylsulfoxide), DMAc (dimethylacetamide), NMP (N-methyl- 2-pyrrolidone), etc.); ethers (Et ₂ O (diethyl ether), i-Pr ₂ O (diiso-propyl ether), TBME (methyl tert-butyl ether), CPME (cyclic Pentyl methyl ether), THF (tetrahydrofuran), dioxane, etc.); aliphatic hydrocarbons (pentane, hexane, heptane, petroleum ether, etc.); aromatic hydrocarbons (benzene, toluene, xylene, tris Toluene, chlorobenzene, dichlorobenzene, nitrobenzene, tetrahydronaphthalene, etc.); halogenated hydrocarbons (chloroform, methylene chloride, carbon tetrachloride, dichloroethane, etc.); lower fatty acid esters (methyl acetate , Ethyl acetate, butyl acetate, methyl propionate, etc.); nitriles (acetonitrile, propionitrile, butyronitrile, etc.). These solvents may be appropriately selected in consideration of not easily reacting, and may be used alone or in combination of two or more. If necessary, a suitable dehydrating agent or desiccant can be used to dry the solvent, and it can also be used as a non-aqueous solvent.

The use amount (reaction concentration) of the solvent is not particularly limited, and the dinitro compound X1 is 0.1 to 100 times the mass. It is preferably 0.5 to 30 mass times, and more preferably 1 to 10 mass times.

The reaction temperature is not particularly limited, and it is preferably in the range of -100°C to the boiling point of the solvent used, preferably -50 to 150°C. The reaction time is usually 0.05 to 350 hours, preferably 0.5 to 100 hours.

On the other hand, the synthesis method of the dinitro compound X1 is not particularly limited, and it can be synthesized by any method. As a specific example, the compound X2 and di-tert-butyl dicarbonate are reacted in a solvent in the presence of a base as needed.

For the carboxyl group of compound X2, it is better to use 1 to 5 equivalents, preferably 1.3 to 2.5 equivalents of di-tert-butyl dicarbonate. By setting the reaction conditions such as the number of equivalents, the Boc group can be controlled. Import number.

The presence of a base in the reaction is not necessary, but when a base is used, sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium bicarbonate, potassium bicarbonate, potassium phosphate, sodium carbonate, potassium carbonate, lithium carbonate, cesium carbonate can be used And other inorganic bases; trimethylamine, triethylamine, tripropylamine, triisopropylamine, tributylamine, di Isopropylethylamine, pyridine, dimethylaminopyridine, imidazole, quinoline, collidine and other amines; sodium hydride, potassium hydride, tert-butoxy sodium, tert-butoxy potassium and other bases .

For the solvent in this reaction, only a solvent that does not react with each raw material can be used, and the same solvent, aprotic polar organic solvent, ethers, aliphatic hydrocarbons, etc. as described in the synthesis of X1 from the above X can be used. Aromatic hydrocarbons, halogen-based hydrocarbons, lower fatty acid esters, etc. These solvents can be appropriately selected in consideration of factors that easily cause a reaction, and can be used alone or in combination of two or more. If necessary, a suitable dehydrating agent or desiccant can be used as a non-aqueous solvent to dry the solvent.

The amount of the solvent used is not particularly limited. For the dinitro compound X2, a solvent of 0.1 to 100 times the mass can be used. It is preferably 0.5 to 30 mass times, and more preferably 1 to 10 mass times. Although the reaction temperature is not particularly limited, a range from -100°C to the boiling point of the solvent used can be used, preferably a range of -50 to 150°C. The reaction time is usually 0.05 to 200 hours, preferably 0.5 to 100 hours.

Further, the dinitro compound X1 system can be synthesized by reacting the carbonyl compound (α) as described below with the Boc group-providing amine compounds X2 and X2' in a solvent. This specific example is shown in the following flow.

For the nitro compounds X2 and X2', R ¹ and R ² each independently represent hydrogen or a Boc group.

For the carbonyl compound (α), Y and Z are 1- to 2-valent organic groups. Examples of the carbonyl compound (α) include phosgene, triphosgene, diphenyl carbonate, and bis(nitrophenyl) carbonate. , Dimethyl carbonate, diethyl carbonate, ethyl carbonate, 1.1'-carbonylbis-1H-imidazole, methyl chloroformate, benzyl chloroformate, 4-nitrophenyl chloroformate, etc. In addition, carbon oxides can be used in place of the carbonyl compound (α).

In addition, the above compound is an example and is not particularly limited.

For the above procedure, to obtain a compound whose urea has a symmetrical structure based on the center, if the nitro compounds X2 and X2' are the same, an asymmetric compound can be obtained, so the nitro compound X2 is subjected to the carbonyl compound (α) and so on. After the reaction, the nitro compound X2′ having a different structure from the nitro compound X2 may be added for reaction. At this time, the order of introducing the Boc-added amine is not particularly limited.

The addition of alkali is not necessary, but when alkali is used, sodium hydroxide, Inorganic bases such as potassium hydroxide, lithium hydroxide, sodium bicarbonate, potassium bicarbonate, potassium phosphate, sodium carbonate, potassium carbonate, lithium carbonate, cesium carbonate; trimethylamine, triethylamine, tripropylamine, tris Amines such as isopropylamine, tributylamine, diisopropylethylamine, pyridine, imidazole, quinoline, collidine; sodium hydride, potassium hydride, sodium tert-butoxy, tert-butoxy Potassium and other alkalis.

Regarding the solvent in the reaction, only a solvent that does not react with each raw material can be used, and aprotic polar organic solvents, ethers, aliphatic hydrocarbons, etc., which are the same as those described in the synthesis of X1 from the above X, can be used Aromatic hydrocarbons, halogen-based hydrocarbons, lower fatty acid esters, etc. These solvents can be appropriately selected in consideration of factors such as inability to react easily, and they can be used alone or in combination of two or more. If necessary, a suitable dehydrating agent or desiccant can be used as a non-aqueous solvent to dry the solvent.

The use amount (reaction concentration) of the solvent is not particularly limited, and it is preferable to use a solvent of 0.1 to 100 times the mass of the nitro compound X2. It is preferably 0.5 to 30 mass times, and more preferably 1 to 10 mass times. The reaction temperature is not particularly limited, but it is preferably in the range from -100°C to the boiling point of the solvent used, preferably in the range of -50 to 150°C. The reaction time is usually 0.05 to 200 hours, preferably 0.5 to 100 hours.

In addition, when synthesizing the asymmetric dinitro compound X1 in which n is different, the isocyanate compound X4 and the Boc group-providing amine compound X2 can be synthesized by reacting as follows. This specific example is shown in the following flow.

For the reaction of the isocyanate compound X4 and the amine compound X2, the amount of the amine compound X2 used for the isocyanate compound X4 can only be 0.98 to 1.2 equivalent times. It is preferably 1.0 to 1.02 equivalent times.

The reaction solvent is not particularly limited as long as the reaction is inert, and examples thereof include hydrocarbons such as hexane, cyclohexane, benzene, and toluene; carbon tetrachloride, chloroform, and 1,2-dichloromethane Halogen-based hydrocarbons such as ethane; ethers such as diethyl ether, diisopropyl ether, 1,4-dioxane, and tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; Nitriles such as acetonitrile and propionitrile; carboxylic acid esters such as ethyl acetate and ethyl propionate; N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2 -Nitrogen-containing aprotic polar solvents such as pyrrolidone, 1,3-dimethyl-2-imidazolidinone; sulfur-containing aprotic polar solvents such as dimethyl sulfoxide and cyproterone; pyridine, picoline Such as pyridine. These solvents may be used alone, or two or more of these may be mixed and used. It is preferably toluene, acetonitrile, or ethyl acetate, and more preferably toluene or ethyl acetate.

The use amount (reaction concentration) of the solvent is not particularly limited, and the reaction may be carried out without using a solvent, and when a solvent is used, a solvent of 0.1 to 100 mass times is used for the isocyanate compound X4. It is preferably 0.5 to 30 mass times, and more preferably 1 to 10 mass times.

The reaction temperature is not particularly limited, for example -90 ~ 150 ℃, preferably -30~100℃, more preferably 0~80℃. The reaction time is usually 0.05 to 200 hours, preferably 0.5 to 100 hours.

To shorten the reaction time, a catalyst can be added. Examples of this include dibutyltin dilaurate, dioctyltin bis(isooctylthioglycolate), dibutyltin bis(isooctylthioglycolate), and dibutyltin diacetic acid Organic tin compounds such as esters; triethylamine, trimethylamine, tripropylamine, tributylamine, diisopropylethylamine, N,N-dimethylcyclohexylamine, pyridine, tetramethyl Butanediamine, N-methylmorpholine, 1,4-diazabicyclo-2.2.2-octane, 1,8-diazabicyclo[5.4.0]undecene, 1,5- Diazabicyclo[4.3.0]nonene-5 and other amines; p-toluenesulfonic acid, methanesulfonic acid, fluorosulfuric acid and other organic sulfonic acids; sulfuric acid, phosphoric acid, perchloric acid and other inorganic acids; tetrabutyl titanate Titanium compounds such as salts, tetraethyl titanate, and tetraisopropyl titanate; bismuth compounds such as bismuth ginseng (2-ethylhexanoate); quaternary ammonium salts, etc. These catalysts may be used alone or in combination of two or more. Furthermore, these catalysts may be liquid or dissolved in a reaction solvent.

When the catalyst is added, an amount of 0.005 to 100% by weight of the catalyst is used for the total usage amount (mass) of the isocyanate compound X4. It is preferably 0.05 to 10 wt%, and more preferably 0.1 to 5 wt%. When an organic tin compound, a titanium compound, or a bismuth compound is used as a catalyst, it is preferably 0.005 to 0.1 wt%.

[Liquid crystal alignment agent]

The liquid crystal alignment agent of the present invention contains a polymer obtained by reacting a diamine component containing any of the diamines represented by the above formula [1] with a tetracarboxylic acid component The precursor of amide imine, and/or the polyimide obtained from the precursor of amide imide.

[Tetracarboxylic acid component]

Preferred examples of the tetracarboxylic acid component are shown in any of the following formulas [8] to [10].

Among the above-mentioned tetracarboxylic acid derivatives, polyamic acid is obtained by the tetracarboxylic anhydride and diamine represented by the reaction formula [8]. In addition, a polyamic acid ester can be obtained by reacting the tetracarboxylic acid diester dichloride represented by formula [9] or the tetracarboxylic acid diester represented by formula [10] with a diamine.

The polyimide can be synthesized by subjecting the polyamic acid or polyamic acid ester to imidization.

In formula [9] and formula [10], R ⁶ is a hydrogen atom or a C 1-4 alkyl group. Specific examples of the alkyl group include methyl, ethyl, propyl, 2-propyl, butyl, t-butyl and the like. Generally, as the carbon number of the alkyl group increases, the temperature of the amide imidization increases. Therefore, this alkyl group is preferably a methyl group or an ethyl group, and particularly preferably a methyl group from the viewpoint of easy imidateization by heat.

In formulas [8] to [10], X is preferably a tetravalent hydrocarbon group having a structure of an alicyclic or aromatic ring having 4 to 6 member rings. As a preferred specific example of X Examples include the following (X-1) to (X-46).

[Other diamines]

When the polyimide precursor contained in the liquid crystal alignment agent of the present invention is to be obtained, the following formula [11] can be used in combination as the diamine component in addition to the above-mentioned specific diamine without impairing the effect of the present invention. Other diamines.

[Chem 18]H ₂ NY-NH ₂ [11]

In formula [11], Y is a divalent group made of a hydrocarbon, and it is preferably a group having a structure of an alicyclic or aromatic ring having 6 member rings. To illustrate the preferred specific examples of Y, (Y-1) to (Y-97) can be cited.

[Synthesis of Polyimide Precursor 1 (Polyamide)]

Polyamide (hereinafter also referred to as polymer) can be synthesized by polyaddition reaction of tetracarboxylic dianhydride and diamine (hereinafter also referred to as monomer).

Specifically, tetracarboxylic dianhydride and diamine can be reacted in the presence of an organic solvent at -20 to 150°C, preferably 0 to 50°C, for 30 minutes to 24 hours, preferably 1 to 12 hours. And synthesis.

In view of the solubility of the monomer and the obtained polymer in the organic solvent used in the above reaction, N,N-dimethylformamide, N-methyl-2-pyrrolidone, γ-butyrolactone Preferably, they can be used after mixing one or more of these. The polymer concentration in the reaction system is preferably from 1 to 30% by mass, and preferably from 5 to 20% by mass from the viewpoint of not easily causing precipitation of the polymer and easily obtaining a high molecular weight material.

The polyamic acid obtained as described above can be precipitated and recovered by pouring into a weak solvent while carefully stirring the reaction solution. In addition, after performing several precipitations and washing with a weak solvent, purified polyamide powder can be obtained by drying at normal temperature or by heating. The weak solvent is not particularly limited, and examples thereof include water, methanol, ethanol, hexane, butyl cellosolve, acetone, and toluene.

[Synthesis of Polyimide Precursor 2 (Polyamide)]

Polyamide can be synthesized by any of the following methods (A) to (C).

(A) The synthesis of polyamic acid ester from polyamic acid

Polyamidates can be synthesized by esterifying polyamic acids obtained from tetracarboxylic dianhydride and diamine.

Specifically, it is possible to react the polyamic acid and the esterifying agent in the presence of an organic solvent at -20 to 150°C, preferably 0 to 50°C for 30 minutes to 24 hours, preferably 1 to 4 hours. synthesis.

As the esterifying agent, those that can be easily removed by purification are preferred, and examples thereof include N,N-dimethylformamide dimethyl acetal and N,N-dimethylformamide diethyl acetal. Aldehyde, N,N-dimethylformamide dipropyl acetal, N,N-dimethylformamide dineopentylbutyl acetal, N,N-dimethylformamide di-t -Butyl acetal, 1-methyl-3-p-tolyl triazene, 1-ethyl-3-p-tolyl triazene, 1-propyl-3-p-tolyl triazene Wait. The addition amount of the esterifying agent is preferably 2 to 6 molar equivalents for the repeating unit of polyamide, which is 1 molar. The organic solvent used in the above reaction is preferably N,N-dimethylformamide, N-methyl-2-pyrrolidone, γ-butyrolactone, etc. in view of the solubility of the polymer. These are used by mixing 1 type or 2 or more types. The concentration at the time of synthesis is preferably 1 to 30% by mass, and preferably 5 to 20% by mass from the viewpoint of not easily causing polymer precipitation and easily obtaining a high molecular weight material.

(B) Synthesization of polyamide from tetracarboxylic diester dichloride and diamine

Polyamide can be synthesized by the reaction of tetracarboxylic acid diester dichloride and diamine.

Specifically, the tetracarboxylic acid diester dichloride and diamine can be carried out in the presence of an alkali and an organic solvent at -20 to 150°C, preferably 0 to 50°C, for 30 minutes to 24 hours, preferably It is synthesized after 1~4 hours of reaction.

For the base, pyridine, triethylamine, 4-dimethylaminopyridine, etc. can be used. However, when the reaction is to be carried out slowly, pyridine is preferred. The addition amount of the base is preferably 2 to 4 times the molar amount of the tetracarboxylic acid diester dichloride from the viewpoint of easy removal and high molecular weight materials.

The organic solvent used in the above reaction is preferably N-methyl-2-pyrrolidone, γ-butyrolactone, etc. in view of the solubility of the monomer and the polymer, and one or more of these may be mixed. And use. From the viewpoint of not easily causing polymer precipitation and easily obtaining high molecular weight materials, the concentration during synthesis is preferably 1 to 30% by mass, and more preferably 5 to 20% by mass.

In addition, in order to prevent the hydrolysis of the tetracarboxylic acid diester dichloride, the solvent used in the synthesis of the polyamide ester is preferably dehydrated as much as possible. It is preferable to react in a nitrogen environment to prevent the mixing of external air. .

(C) The synthesis of polyamic acid from tetracarboxylic acid diester and diamine

Polyamide can be made by condensing agent of tetracarboxylic acid diester and diamine Synthesized by polycondensation.

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

For the condensing agent, triphenylphosphite, dicyclohexylcarbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N,N' -Carbonyldiimidazole, dimethoxy-1,3,5-triazinylmethylmorpholinium, O-(benzotriazol-1-yl)-N,N,N',N'-tetramethyl Urea tetrafluoroborate, O-(benzotriazol-1-yl)-N,N,N',N'-tetramethylurea hexafluorophosphate, (2,3-dihydro-2- Thio-3-benzoxazolyl)phosphonic acid diphenyl and the like. The addition amount of the condensing agent is preferably 2 to 3 times the molar amount of the tetracarboxylic acid diester.

For the base, tertiary amines such as pyridine and triethylamine can be used. The amount of alkali added is preferably 2 to 4 times the molar amount of the diamine component from the viewpoint of easy removal and high molecular weight materials.

In addition, for the above reaction, by adding Lewis acid as an additive, the reaction can be efficiently performed. As the Lewis acid, lithium halide such as lithium chloride and lithium bromide is preferred. The amount of Lewis acid added is preferably 0 to 1.0 times the molar amount for the diamine component.

Among the above-mentioned methods for synthesizing the polyamide 3, high-molecular-weight polyamide can also be obtained, and the synthesis methods (A) and (B) are particularly preferred.

By pouring the solution of the polyamic acid ester obtained as described above into a weak solvent while carefully stirring, a polymer can be precipitated. After performing several precipitations and washing with a weak solvent, at room temperature or after heating and drying, purified polyamide powder can be obtained. The weak solvent is not particularly limited, and examples thereof include water, methanol, ethanol, hexane, butyl cellosolve, acetone, and toluene.

[Molecular weight of polyimide precursor]

The molecular weight of the polyimide precursor has an influence on the viscosity of the paint or the physical strength of the polyimide film. From the viewpoint of obtaining good coating workability of the paint or good uniformity of the coating film, the weight average molecular weight is preferably 500,000 or less, and from the viewpoint of obtaining a sufficiently strong polyimide film, 2,000 or more. Preferably, it is preferably 2,000 to 300,000, and more preferably 5,000 to 100,000. The molecular weight of the polyimide precursor can be controlled by adjusting the ratio of the diamine component and the tetracarboxylic acid derivative used in the aforementioned polymerization reaction. As this ratio, the molar ratio is 1:0.7 to 1.2. The closer the molar ratio is to 1:1, the greater the molecular weight of the resulting polyimide precursor.

[Synthesis of Polyimide]

The polyimide of the present invention can be synthesized by subjecting the aforementioned polyimide precursor to imidization. As a simple and preferred method for synthesizing polyimide from a polyimide precursor, it is obtained from the reaction of a diamine component and tetracarboxylic dianhydride In the aforementioned solution of polyamic acid, the chemical imidization of the catalyst is added, and the imidization reaction is carried out at a relatively low temperature. It is not easy to cause the molecular weight of the polymer to decrease during the imidization process. good.

The chemical imidization is such that the imidized polymer can be stirred in an organic solvent in the presence of an alkaline catalyst and an acid anhydride. As the organic solvent, the solvent used in the aforementioned polymerization reaction can be used. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, and trioctylamine. Among them, pyridine is preferred to be moderately basic during the reaction. In addition, examples of the acid anhydride include acetic anhydride, trimellitic anhydride, and pyromellitic anhydride. Among them, when acetic anhydride is used, the purification after the end of the reaction is easy and preferable.

The temperature during the amide imidization reaction is -20 to 200°C, preferably 0 to 180°C, and the reaction time is 1 to 100 hours, preferably 1 to 8 hours. The amount of the alkaline catalyst is 0.5 to 30 mole times of the amide acid group, preferably 2 to 20 mole times, and the amount of the acid anhydride is 1 to 50 mole times of the amide acid group, preferably 3 to 30 mole times. The imidate ratio of the resulting polymer can be controlled by adjusting the catalyst amount, temperature, reaction time, and the like. Since the catalyst added in the solution after the imidate reaction remains, the resulting imidate polymer is recovered by the means shown below, and the liquid crystal alignment of the present invention is obtained after re-dissolving in an organic solvent The agent is better.

The solution of the polyimide obtained by the above method can be precipitated by pouring into a weak solvent while carefully stirring. After performing precipitation several times, washing with a weak solvent, and drying at normal temperature or heating, purified polyimide powder can be obtained. Weak solvents can only precipitate polymers Yes, it 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 alignment agent]

The liquid crystal alignment agent of the present invention is a paint-like solution containing the polyimide precursor and/or polyimide (hereinafter, these are also referred to as polymer components) obtained as described above. The liquid crystal alignment agent of the present invention may contain two or more types of polyimide precursors or two or more types of polyimide, or may contain both a polyimide precursor and a polyimide. In addition, the liquid crystal alignment agent may contain a polymer other than the polyimide precursor of the present invention or the polyimide of the present invention.

As the simplest configuration example of the liquid crystal alignment agent of the present invention, a composition composed of the polymer component of the above-mentioned polyimide precursor and/or polyimide and an organic solvent used for dissolving it may be mentioned. The composition may be the reaction solution itself when synthesizing a polyimide precursor or polyimide, or it may be a dilution of the reaction solution with a solvent described later. In addition, when the polyimide precursor or polyimide is recovered as a powder, it can be dissolved in an organic solvent as a polymer solution.

When the polyimide precursor or the powder of polyimide is dissolved in an organic solvent, the concentration of the polymer component is preferably 10 to 30% by mass, and particularly preferably 10 to 15% by mass. Furthermore, when these are dissolved, they can be heated. The heating temperature is preferably from 20 to 150°C, and particularly preferably from 20 to 80°C.

The organic solvent used when dissolving the polyimide precursor or polyimide is only required to dissolve the polymer component uniformly, and there is no special limited. Specific examples include N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and N- Ethyl-2-pyrrolidone, N-methylcaprolactam, 2-pyrrolidone, N-vinyl-2-pyrrolidone, dimethyl sulfoxide, dimethyl sulfoxide, γ-butyrolidone Ester, 1,3-dimethyl-imidazolidinone, 3-methoxy-N,N-dimethylpropane amide, etc. One kind of these or a mixture of two or more kinds may be used. In addition, even if it is a solvent which cannot dissolve the polymer component uniformly when it is used alone, it can be mixed with the above-mentioned organic solvent only to the extent that the polymer does not precipitate.

The solvent component of the liquid crystal alignment agent of the present invention may contain, in addition to the organic solvent used when the polymer component is dissolved, a solvent used to improve the uniformity of the coating film when the liquid crystal alignment agent is applied to the substrate. Such a solvent generally uses a solvent having a lower surface tension than the above organic solvent. To cite this specific example, 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, 1-phenoxy-2-propanol, propylene glycol monoacetate, propylene glycol diacetic acid Ester, 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, isoamyl lactate, etc. Two or more types of these solvents can be used in combination.

The polymer concentration in the liquid crystal alignment agent of the present invention can be appropriately changed by the thickness of the formed liquid crystal alignment film, but from the viewpoint of forming a uniform and defect-free coating film, it is preferably 1% by mass or more. From the viewpoint of storage stability of the solution, it is preferably 10% by mass or less. The polymer concentration is preferably 2-8% by mass.

The liquid crystal alignment agent of the present invention may contain various additives such as other silane coupling agents or crosslinking agents.

The silane coupling agent is added for the purpose of improving the adhesion between the substrate formed by the liquid crystal alignment agent and the liquid crystal alignment film formed thereon. Specific examples of the silane coupling agent include those described in paragraph 0164, line 1 to last line of International Publication No. WO2010/050523 (International Application PCT/JP2009/068523).

The use amount of the silane coupling agent is not adversely affected by the unreacted liquid crystal alignment, and from the viewpoint of showing the adhesion effect, the polymer component is preferably 0.01 to 5 mass%, 0.1 to 1 mass% Is better. When adding the silane coupling agent, it is preferable to add the silane coupling agent before adding the aforementioned solvent to improve the uniformity of the coating film.

[Liquid crystal alignment film]

The liquid crystal alignment agent of the present invention is applied to a substrate, and the resulting coating film is dried and fired, and if necessary, a known alignment treatment may be performed on the surface of the coating film. The substrate to which the liquid crystal alignment agent is applied is only a substrate with high transparency, and is not particularly limited. A plastic substrate such as a glass substrate, a silicon nitride substrate, an acrylic substrate, or a polycarbonate substrate can be used. In the case of substrates such as ITO electrodes driven by liquid crystal, it is preferable from the viewpoint of simplification of the manufacturing process. In addition, in a reflective liquid crystal display element, if it is a single-sided substrate only, an opaque substance such as a silicon wafer may be used, and an electrode such as aluminum may be used to reflect light.

Examples of the coating method of the liquid crystal alignment agent include a spin coating method, a printing method, and an inkjet method. Any temperature and time can be selected for the drying and firing steps after applying the liquid crystal alignment agent. Generally, in order to sufficiently remove the organic solvent contained, it can be dried at 50 to 120°C for 1 to 10 minutes, and then fired at 150 to 300°C for 5 to 120 minutes.

The thickness of the coating film after firing is not particularly limited. If it is too thin, the reliability of the liquid crystal display element may be reduced. Therefore, it is preferably 5 to 300 nm, preferably 10 to 200 nm. When the liquid crystal is to be aligned horizontally or tilted, the coating film after firing can be subjected to rubbing or optical alignment treatment.

[Liquid crystal display element]

After obtaining a substrate with a liquid crystal alignment film from the liquid crystal alignment agent of the present invention, a liquid crystal cell is manufactured as a liquid crystal display element by a known method.

The manufacturing method of the liquid crystal cell is not particularly limited, but to give an example, generally, a pair of substrates forming a liquid crystal alignment film, with the liquid crystal alignment film surface as the inner side, sandwiching is preferably 1 to 30 μm, more preferably After installing a spacer of 2 to 10 μm, fix the surrounding with a sealant, inject liquid crystal and seal it. The method of sealing the liquid crystal is not particularly limited, and examples thereof include a vacuum method in which the produced liquid crystal cell is decompressed, a liquid crystal is injected into the liquid crystal, and a drop method in which the liquid crystal is dropped and sealed.

As another method for manufacturing a liquid crystal cell, a liquid crystal alignment agent is applied to two substrates to form a liquid crystal alignment layer, two substrates are arranged to face the liquid crystal alignment layer, and the liquid crystal layer is sandwiched between the two substrates. A method of manufacturing by irradiating ultraviolet rays while inputting an electric field to the liquid crystal layer. The substrate to be used is only a substrate with high transparency and is not particularly limited. Usually, a substrate on which a transparent electrode to be driven by liquid crystal is formed on the substrate, or a substrate provided with an electrode pattern or a protrusion pattern can also be used. If a line/slit electrode pattern of 1 to 10 μm is formed on a single-sided substrate of a liquid crystal cell, when a slit pattern or a protrusion pattern electrode structure is not formed on the counter substrate, the manufacturing process can be simplified and Those with high transmittance are better.

The above-mentioned liquid crystal alignment layer is a resin film used for aligning liquid crystals, and a method of forming a liquid crystal alignment layer on a substrate using a liquid crystal alignment agent can be applied to the coating method described in the liquid crystal alignment film and firing after coating成方法。 Cheng method.

The step of irradiating ultraviolet rays while inputting an electric field to the liquid crystal layer may include, for example, a method of applying a voltage between the electrodes provided on the substrate, applying an electric field to the liquid crystal layer, and maintaining the electric field and irradiating ultraviolet rays. Among them, the voltage applied between the electrodes is, for example, 5 to 30 Vp-p, preferably 5 to 20 Vp-p. The irradiation amount of ultraviolet rays is, for example, preferably 1 to 60J, preferably 40J or less. When there are relatively few ultraviolet rays, it is possible to suppress the decrease in reliability that causes damage to the members constituting the liquid crystal display element, and by selecting the irradiation time of ultraviolet rays, it is preferable to increase manufacturing efficiency.

[Example]

The following examples illustrate the invention in more detail, but the invention is not limited to these interpreters. The abbreviations, analysis methods, analysis conditions, and property evaluation methods of the compounds used are shown below.

NMP: N-methyl-2-pyrrolidone BCS: butyl cellosolve

DMAP: dimethylaminopyridine

Boc2O: di-tert-butyl dicarbonate

DMAP: dimethylaminopyridine Pd/C: palladium carbon

DIEPA: diisopropylethylamine

DMF: dimethylformamide

THF: tetrahydrofuran

(Measurement of ¹ H-NMR)

Device: Varian NMR system 400NB (400MHz) (manufactured by Varian), and JMTC-500/54/SS (500MHz) (manufactured by JEOL)

Determination solvent: CDCl ₃ (hydrogenated chloroform), DMSO-d ₆ (hydrogenated dimethyl sulfoxide)

Reference materials: TMS (tetramethylsilane) (δ: 0.0 ppm, ¹ H) and CDCl ₃ (δ: 77.0 ppm, ¹³ C)

(Determination of molecular weight of polyimide precursor and imide polymer)

Using a room temperature gel permeation chromatography (GPC) device (GPC-101) (manufactured by Showa Denko) and a column (KD-803, KD-805) (manufactured by Shodex), the measurement was performed as follows.

Column temperature: 50℃

Dissolution solution: N,N'-dimethylformamide (as additives: lithium bromide-hydrate (LiBr‧H ₂ O) 30mmol/L (liter), phosphoric acid‧ anhydrous crystal (o-phosphoric acid) 30mmol/L, tetrahydrofuran (THF) 10ml/L)

Flow rate: 1.0ml/min

Standard samples for standard curve creation: TSK standard polyethylene oxide (molecular weight; approximately 900,000, 150,000, 100,000, and 30,000) (manufactured by Tosoh Corporation) and polyethylene glycol (molecular weight; approximately 12,000, 4,000, and 1,000) ( Manufactured by Polymer Laboratory).

<Synthesis of Diamine (A1)>

In a 1 L (liter) four-necked flask, dinitro compound B (100 g, 279 mmol) and 1,2-dichloroethane (700 g) were charged, and the temperature was raised to 85°C with stirring blades, and DMAP (0.3 g, 2.8 mmol), Boc 2 O (103 g, 474 mmol), and 1,2-dichloroethane (300 g) were added dropwise over 30 minutes and stirred for 2 hours. After confirming the completion of the reaction by HPLC (high-speed liquid chromatography), the solution was concentrated under reduced pressure to 350 g, followed by addition of 2-propanol (600 g), cooled to 5°C, and stirred for 1 hour. The precipitated crystals were filtered under reduced pressure, washed with 2-propanol (200 g), and dried to obtain powder crystal A1-1 (yield 120 g, yield 94%).

1H-NMR (500MHz, CDCl3); 8.76 (1H, s), 8.17 (4H, m), 7.39 (4H, m), 3.93 (2H, t), 3.57 (2H, t), 2.97 (4H, m) , 1.49 (9H, s)

A mixture of A1-1 (100 g, 218 mmol), 5 mass% Pd/C (50% aqueous type), and toluene (1200 ml) was stirred at 60° C. for 5 hours in the presence of hydrogen. After the reaction was completed, the catalyst was filtered, and the solution was cooled to 5°C and stirred for another hour. The precipitated crystals were filtered under reduced pressure, washed with toluene (200g) and dried to obtain powder crystal A1 (yield 70g, yield 80%).

1H-NMR (500MHz, CDCl3); 8.70 (1H, s), 7.00 (4H, m), 6.64 (4H, m), 3.82 (2H, t), 3.57 (1H, br), 3.45 (4H, m) , 2.74 (4H, m), 1.47 (9H, s)

<Synthesis of Diamine (A2)>

In a four-necked flask of 1 L (liter), add DIEPA (21.3 g, 165 mmol) and DMAP (1.83 g, 15 mmol) to the DMF solution (269 g) of the dinitro derivative B (53.8 g, 150 mmol) in DMF solution (269 g). Boc2O (32.7g, 150mmol) was added dropwise at room temperature for 30 minutes. After stirring at room temperature for 2 hours, DIEPA (21.3 g, 165 mmol) and Boc 2 O (32.7 g, 165 mol) were added, and the mixture was stirred at room temperature for 24 hours. Thereafter, DIEPA (21.3 g, 165 mmol) and Boc 2 O (32.7 g, 150 mmol) were added, and the mixture was stirred at room temperature for 18 hours. After the obtained reaction liquid was diluted with ethyl acetate (1078 g), it was washed three times with a 10% by mass NaCl aqueous solution (1000 g). Thereafter, the organic layer was dried over magnesium sulfate and concentrated, and the resulting crude product was subjected to column chromatography using ethyl acetate and hexane (volume ratio is 1:3, the same applies hereinafter) to obtain dinitro body A2-1 (Yield 17.7g, yield 21%).

¹ H-NMR (CDCl ₃ , δppm): 8.19-8.15 (m, 2H), 7.42-7.27 (m, 2H), 3.86 (br, 4H), 3,07 (br, 4H), 1.50 (s, 18H )

In dinitro body A2-1 (17.7g, 31.7mmol) To the THF solution (88.5 g), 5 mass% Pd/C (50% aqueous type) (1.71 g, 10 wt%) was added, followed by hydrogen substitution, and stirring at room temperature for 24 hours. Next, it is filtered through a membrane filter to remove Pd/C, and then concentrated to obtain a crude product. The obtained crude product was subjected to column chromatography using ethyl acetate and hexane (volume ratio 2:3) to obtain diamine A2 (yield 12.2 g, yield 77%).

¹ H-NMR (CDCl ₃ , δppm): 7.06-7.02 (m, 2H), 6.65-6.62 (m, 2H), 3.78 (br, 4H), 3.56 (s, 4H), 2.86 (br, 4H), 1.48(s, 18H)

[Synthesis Example 1]

In a 50ml four-necked flask equipped with a stirring device and a nitrogen introduction tube, put the weighed DA-1 (0.42g, 2.8mmol) and DA-3 (1.67g, 4.2mmol), then add NMP21.7g, Stir and dissolve while feeding nitrogen. While stirring this diamine solution, CA-1 (0.534 g, 2.45 mmol) and CA-2 (0.837 g, 4.27 mmol) were added, and 5.4 g of NMP was further added. Thereafter, stirring was performed for 3 hours to obtain a polyamic acid solution having a resin solid content concentration of 12% by mass. After confirming the viscosity of the polyamide solution at 25°C with an E-type viscometer (manufactured by Toki Industries Co., Ltd.), it was 320 mPa‧s. The molecular weight of the polyamide is Mn=10,550 and Mw=32,000.

[Synthesis Example 2]

In a 50ml four-necked flask with a stirring device and a nitrogen introduction tube, put After DA-1 (0.42 g, 2.8 mmol) and DA-4 (2.09 g, 4.2 mmol) were weighed, 21.7 g of NMP was added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring the diamine solution, CA-1 (0.534 g, 2.45 mmol) and CA-2 (0.837 g, 4.27 mmol) were added, and then 5.4 g of NMP was added. After stirring for 3 hours, a polyamic acid solution with a resin solid content concentration of 12% by mass was obtained. The viscosity of the polyamic acid solution at 25°C was 370 mPa‧s after confirmation with an E-type viscometer (manufactured by Toki Industries Co., Ltd.). The polyamide has an Mn of 19,000 and an Mw of 50,500.

[Comparative Synthesis Example 1]

In a 50ml four-necked flask equipped with a stirring device and a nitrogen introduction tube, put the weighed DA-1 (0.42g, 2.8mmol) and DA-2 (1.25g, 4.2mmol), then add NMP21.7g, Stir and dissolve while feeding nitrogen. While stirring this diamine solution, CA-1 (0.534 g, 2.45 mmol) and CA-2 (0.837 g, 4.27 mmol) were added, and 5.4 g of NMP was further added. After stirring for 3 hours, a polyamide acid solution having a resin solid content concentration of 12% by mass was obtained. The viscosity of the polyamide solution at 25°C was 330 mPa‧s after confirmation with an E-type viscometer (manufactured by Toki Industries Co., Ltd.). The molecular weight of the polyamide is Mn=9,900 and Mw=21,800.

[Example 1]

To 10.0 g of the polyamic acid solution obtained in Synthesis Example 1, add NMP5.65g, 1.0g of NMP solution containing 3-glycidoxypropyltriethoxysilane 1.0% by mass, and BCS5.55g, to obtain a liquid crystal alignment agent (A-1) with a concentration of 4.5% by mass. The liquid crystal alignment agent (A-1) was confirmed to be a uniform solution in which no abnormal phenomena such as turbidity or precipitation were observed.

[Example 2]

To 10.0 g of the polyamic acid solution obtained in Synthesis Example 2, NMP 5.65 g, NMP solution 1.0 g containing 3-glycidoxypropyltriethoxysilane 1.0% by mass, and BCS 5.55 g were added, A liquid crystal alignment agent (A-2) with a concentration of 4.5% by mass was obtained. As for the liquid crystal alignment agent (A-2), it was confirmed that it was a uniform solution in which abnormal phenomena such as turbidity or precipitation were not observed.

[Comparative Example 1]

To 10.0 g of the polyamic acid solution obtained in Comparative Synthesis Example 1, NMP 5.65 g, NMP solution 1.0 g containing 3-glycidoxypropyltriethoxysilane 1.0% by mass, and BCS5.55 g were added To obtain a liquid crystal alignment agent (B-1) with a concentration of 4.5% by mass. The liquid crystal alignment agent (B-1) was confirmed to be a homogeneous solution in which no abnormal phenomena such as turbidity or precipitation were observed.

<Solubility to γ-butyl lactone>

In 5.0g of the obtained stirring solution of liquid crystal alignment agent, while adding γ-butyl lactone (GBL), the amount of solvent was recorded until the solid was precipitated as However, the solubility assessment was carried out.

For the liquid crystal alignment agents A-1, A-2, and B-1, the results of the amount of GBL added are shown in Table 1.

<Production of Adhesion Evaluation Sample>

After filtering the liquid crystal alignment agent with a 1.0 μm filter, spin-coating on a glass substrate with a transparent electrode, drying on a hot plate at 80°C for 2 minutes, and firing at 230°C for 20 minutes to obtain a film thickness It is a 100nm coating film. Two substrates thus obtained were prepared, and a bead spacer with a diameter of 4 μm was spread on the liquid crystal alignment film surface of one substrate, and then a sealant (XN-1500T manufactured by Kyoritsu Chemical Co., Ltd.) was applied in dots. Next, using the liquid crystal alignment film surface of the other substrate as the inner side, the overlap width of the substrate is to be 1 cm, and the sealant is placed at the center of the overlapped portion of the substrate for bonding. At this time, the amount of the sealant to be dropped was adjusted so that the diameter of the sealant after bonding was about 3 mm. After fixing the two bonded substrates with a jig, heat curing was performed at 120°C for 1 hour until a test sample for evaluation of adhesion was made.

<Measurement of adhesion>

Use the table-top precision universal testing machine (AGS-X 500N) manufactured by Shimadzu Corporation to fix the test sample, and press the upper part of the overlapping part of the substrate to fix the pressure of the peeling (N ).

The normalized value calculated by dividing the area (mm ² ) estimated from the measured diameter of the sealant by the pressure (N) is used as an index of the adhesive force.

The adhesion results of the liquid crystal alignment agents A-1 and B-1 are shown in Table 1.

<Fabrication of liquid crystal cell>

After filtering the liquid crystal alignment agent with a 1.0 μm filter, spin-coating on a glass substrate with a transparent electrode, drying on a hot plate at 80°C for 2 minutes, and firing at 230°C for 20 minutes to obtain a film thickness 100nm coating film. After rubbing the imimidized polymer film with a rayon cloth (roller diameter 120 mm, rotation number 1000 rpm, moving speed 20 mm/sec, pressing amount 0.4 mm), ultrasonic irradiation was performed in pure water for 1 minute. Dry at 80°C for 10 minutes. Two substrates with a liquid crystal alignment film obtained in this way were prepared. After a 4 μm spacer was provided on the surface of the liquid crystal alignment film of one substrate, the rubbing directions of the two substrates combined were antiparallel, and the periphery of the liquid crystal injection port was sealed to produce a cell. Empty cells with a gap of 4 μm. The unit cell will Liquid crystal (MLC-2041, manufactured by Merck) was vacuum injected at normal temperature, and the injection port was sealed to serve as an anti-parallel liquid crystal cell.

<Liquid crystal alignment>

The alignment state of the liquid crystal cell was observed with a polarizing microscope, and those without alignment defects were judged as "good", and those with alignment defects were judged as "bad". The evaluation results of the alignment of the liquid crystal alignment agents A-1, A-2 and B-1 are shown in Table 3.

<Fabrication of liquid crystal cell for evaluation of electrical characteristics>

A liquid crystal cell equipped with a liquid crystal display element of FFS (Fringe Field Switching) method was produced.

First prepare a substrate with electrodes. The substrate is a glass substrate with a size of 30 mm×35 mm and a thickness of 0.7 mm. The counter electrode is used as the first layer on the substrate to form a solid pattern IZO (Indium Tin Oxide) electrode. As the second layer on the counter electrode of the first layer, a SiN (silicon nitride) film formed by CVD (Chemical Vapor Deposition) method is formed. The SiN film of the second layer has a thickness of 500 nm, and is used as a function of the interlayer insulating film. Placed on the second layer of SiN film There is a comb-shaped pixel electrode formed by patterning the IZO film as the third layer, and two types of pixels of the first pixel and the second pixel are formed. The size of each pixel is 10 mm long and about 5 mm wide. At this time, the counter electrode of the first layer and the pixel electrode of the third layer are electrically insulated by the action of the SiN film of the second layer.

The pixel electrode of the third layer has the following comb-tooth shape, and the comb-tooth shape is formed by arranging a plurality of electrode elements having a curved “ㄑ” shape at the center. The width of each electrode element in the lateral direction is 3 μm, and the interval between the electrode elements is 6 μm. The pixel electrodes forming each pixel are composed of electrode elements with a curved "ㄑ" shape in the center part arranged in plural, so the shape of each pixel is not rectangular, and is in the center part like the electrode element In order to bend, those who have the shape of "ㄑ" similar to bold characters. Each pixel divides each central curved portion as a boundary into upper and lower portions, and has a first area on the upper side and a second area on the lower side of the curved portion.

When comparing the first region and the second region of each pixel, the formation direction of the electrode elements constituting these pixel electrodes becomes different. That is, when the rubbing direction of the liquid crystal alignment film described later is used as a reference, the electrode element of the pixel electrode is formed at an angle of +10° (clockwise direction) in the first area of the pixel, and drawn in the second area of the pixel The electrode element of the plain electrode is formed at an angle of -10° (clockwise direction). That is, the first area and the second area of each pixel are configured such that the rotation of the liquid crystal in the surface of the substrate due to the voltage application between the pixel electrode and the counter electrode (plane‧switch) Reverse each other.

Next, after filtering the obtained liquid crystal alignment agent with a 1.0 μm filter, spin coating is performed on the prepared substrate with electrodes The cloth is coated. After drying on a hot plate at 80°C for 120 seconds, it was fired in a far infrared oven at 230°C for 20 minutes to obtain a polyimide film with a thickness of 60 nm. The polyimide film was rubbed with a rayon cloth (roller diameter: 120 mm, roller rotation number: 500 rpm, moving speed: 30 mm/sec, pressing length: 0.3 mm, rubbing direction: the third layer IZO comb After the tooth electrode was tilted by 10°), it was irradiated with pure water for 1 minute and irradiated with ultrasonic waves. After removing water drops by blowing, the substrate was attached with a liquid crystal alignment film after drying at 80°C for 15 minutes. As a counter substrate, a glass substrate having a column spacer with a height of 4 μm on which an ITO electrode is formed is also formed with a polyimide film in the same manner as above, and the alignment treatment is performed by the same procedure as above. Substrate with liquid crystal alignment film. Take these two substrates with liquid crystal alignment film as a group, print the sealant on the substrate in the shape of the liquid crystal injection port, and put the other substrate facing the liquid crystal alignment film surface, and paste it against the rubbing direction After paralleling, the sealant was hardened to produce empty cells with a cell gap of 4 μm. Liquid crystal MLC-2041 (manufactured by Merck) was injected into the air cell by a reduced pressure injection method, and the injection port was sealed to obtain a liquid crystal cell of the FFS method. Thereafter, the resulting liquid crystal cell was heated at 110° C. for 30 minutes, and left overnight at 23° C. for use in each evaluation.

<Relief characteristics of accumulated residual charge>

The liquid crystal cell (usually using liquid crystal) is provided between two polarizing plates arranged with the polarizing axis perpendicular, and the pixel electrode and the counter electrode are short-circuited to the same potential, from the bottom of the two polarizing plates Illuminated LED Backlight, adjust the angle of the liquid crystal cell to minimize the brightness of the LED backlight transmitted light measured above the two polarizers.

Next, while applying a rectangular wave with a frequency of 30 Hz to the liquid crystal cell, the V-T characteristic (voltage-transmittance characteristic) was measured at a temperature of 23° C., and an AC voltage with a relative transmittance of 23% was calculated. Since this AC voltage is equivalent to a region where the brightness of the voltage changes greatly, it is suitable for evaluating the residual charge through the brightness.

Secondly, after applying an alternating voltage with a relative transmittance of 23% and applying a rectangular wave with a frequency of 30 Hz for 5 minutes, a DC voltage of +1.0 V is superimposed and driven for 30 minutes. After that, the DC voltage was cut off, and again an AC voltage with a relative transmittance of 23%, and only a rectangular wave with a frequency of 30 Hz was applied for 30 minutes.

The faster the accumulated charge is relaxed, the faster the charge accumulation of the liquid crystal cell when the DC voltage is superimposed, so the relaxation characteristic of the accumulated charge is required to be reduced to 35% in a state where the relative transmittance after superimposing the DC voltage is more than 40% Time to evaluate. The shorter the time, the better the relaxation characteristics of the accumulated charge and evaluation. The relaxation characteristics of the liquid crystal alignment agents A-1 and B-1 are shown in Table 4.

[Industry availability]

The liquid crystal alignment agent of the present invention is a liquid crystal alignment film that can form a good adhesion to the sealant or the substrate for the device, the display unevenness near the front edge is less, and a large display area can be ensured, so it can be used in mobile phones, Smart phones, tablet-type terminals, etc., can be especially used for small high-definition liquid crystal display components.

In addition, the entire contents of the specification, patent application scope, and abstract of Japanese Patent Application No. 2014-190292 filed on September 18, 2014 are incorporated herein by reference as the disclosure content of the specification of the present invention.

Claims (10)

A liquid crystal alignment agent containing polyimide obtained from the following polyimide precursor and/or the polyimide precursor, the polyimide precursor is composed of a diamine component and a tetracarboxylic acid A person obtained by reacting an acid component, characterized in that the diamine component contains a diamine represented by the following formula [1];

(R ¹ and R ^{2 are} each independently a hydrogen atom, a C 1-4 alkyl group or a group represented by the following formula (2), at least one of which is a group represented by the formula (2); m and n are each independently 0 ~3; in formula (2), A is a single bond or a divalent group of a hydrocarbon group having 1 to 4 carbon atoms)

The liquid crystal alignment agent according to claim 1, wherein the diamine component contains 5 to 100 mol% of the diamine represented by the foregoing formula [1]. The liquid crystal alignment agent according to claim 1 or 2, wherein the total content of the polyimide precursor and the polyimide is 1 to 20% by weight. The liquid crystal alignment agent according to claim 1, wherein the substitution position of the amine group in the benzene ring of the diamine represented by formula [1] is meta or para to the bonding position of the alkylene group. A diamine represented by the following formula [1], characterized by

(R ¹ and R ^{2 are} each independently a hydrogen atom, a C 1-4 alkyl group or a group of the following formula (2), at least one of which is a group of the formula (2); m and n are each independently 0 to 3 ; In formula (2), A is a single bond or a bivalent group of a C 1-4 hydrocarbon group);

The diamine as claimed in claim 5, wherein the NH ₂ group in the benzene ring is meta or para to the bonding position of the alkylene group. If the diamine of claim 5 is any of the following diamines;

(However, Boc is a group represented by the following formula)

A liquid crystal alignment film characterized by being formed of the liquid crystal alignment agent according to any one of claims 1 to 4. The liquid crystal alignment film according to claim 8, wherein the film thickness is 5 to 500 nm. A liquid crystal display element, characterized in that the substrate having the liquid crystal alignment film according to claim 8 or 9 is a glass substrate or a plastic substrate.