WO2004072720A1

WO2004072720A1 - Liquid crystal alignment layer forming method

Info

Publication number: WO2004072720A1
Application number: PCT/JP2004/001388
Authority: WO
Inventors: Hirotsugu Taki; Tetsuya Imamura
Original assignee: Nissan Chemical Industries, Ltd.
Priority date: 2003-02-12
Filing date: 2004-02-10
Publication date: 2004-08-26
Also published as: JP2004264354A; TW200420982A

Abstract

A liquid crystal alignment layer forming method comprises a step of coating a substrate with a liquid crystal aligning agent containing soluble polyimide and polyamic acid and a step of irradiating the substrate with polarized ultraviolet radiation. According to the invention, a liquid crystal alignment layer can be formed with excellent workability and with excellent uniformness and used for a liquid crystal display device with little stored charge. Therefore a liquid crystal display device having this liquid crystal alignment layer can continue to display an image of high contrast without causing image persistence because of the little charge storage. The invention is a high versatility technique leading to improvement of electrical characteristics, and further leading to improvement of the quality of image of any type of liquid crystal device including display devices such as of not only the TFT liquid crystal currently used in the mainstream, but also the VA liquid crystal and the IPS liquid crystal.

Description

Description Method for forming liquid crystal alignment film

The present invention relates to a method for forming a liquid crystal alignment film capable of obtaining a liquid crystal display element with uniform liquid crystal alignment and little image sticking. Background art

Liquid crystal display devices are now widely used in personal computers, televisions, and word processors as thin and lightweight display devices. Regarding the display characteristics of the liquid crystal display element, not only the liquid crystal material used but also a liquid crystal alignment film for uniformly aligning the liquid crystal is important.

In particular, in recent years, as the size of liquid crystal display devices has increased, it has become important to efficiently and uniformly treat liquid crystal alignment films. Also, with the increase in the definition of liquid crystal display elements, the so-called "burn-in phenomenon" in which afterimages remain on the display screen has become an issue. To suppress this, there is a strong demand for a liquid crystal alignment film that does not easily accumulate charges. I have.

At present, liquid crystal alignment films are mainly made of organic resins, applied to the substrate, baked, and then subjected to a so-called "rubbing" treatment in which pressure is applied to the surface with rayon or nylon cloth. Is formed. As for the liquid crystal alignment film formed by rubbing, there is known a method of forming a liquid crystal alignment film by performing a rubbing treatment by forming a coating film using a liquid crystal aligning agent containing a soluble polyimide and a polyamic acid in order to improve characteristics (for example, See Japanese Patent Application Laid-Open No. 08-222,541. However, the rubbing process is a physical process, and it is difficult to uniformly treat a large-area liquid crystal alignment film, and the workability is poor, such as generation of dust and static electricity. I have.

In recent years, various methods of forming a liquid crystal alignment film by irradiating polarized ultraviolet rays, that is, a “photo alignment method” have been proposed (for example, Japanese Patent Application Laid-Open No. 09-297313). The method of forming the alignment film by the photo-alignment method is excellent in uniformity of liquid crystal alignment and workability because polarized ultraviolet light is used, but the characteristics such as image sticking are not satisfactory. Disclosure of the invention

The present invention has been made in view of such circumstances, and has as its object to provide a method for forming a liquid crystal alignment film having excellent uniformity and workability and having less charge accumulation.

As a result of intensive studies, the present inventors have found that polyamic acid is soluble as a liquid crystal aligning agent. An excellent liquid crystal with excellent uniformity and workability and low residual charge accumulation when used as a liquid crystal display device by irradiating polarized ultraviolet light after applying it to a substrate using a resin system containing polyimide. It has been found that an alignment film can be formed.

That is, the present invention has the following features.

(1) A step of applying a liquid crystal aligning agent containing a soluble polyimide and a polyamic acid to a substrate, and a step of irradiating the coating film obtained on the substrate with polarized ultraviolet rays to form a liquid crystal aligning film. Forming a liquid crystal alignment film.

(2) The method for forming a liquid crystal alignment film according to (1), wherein the soluble polyimide comprises a soluble polyimide resin obtained by reacting an acid dianhydride having an alicyclic structure with diamine.

(3) The method for forming a liquid crystal alignment film according to (1) or (2), wherein the soluble polyimide contains a repeating unit represented by the general formula (1).

(Wherein, represents a divalent organic group)

(4) The method for forming a liquid crystal alignment film according to any one of the above (1) to (3), wherein the polyamic acid contains a repeating unit represented by the general formula (2).

(Wherein, R ₂ represents a divalent organic group)

(5) The formation of the liquid crystal alignment film according to any one of the above (1) to (4), wherein the weight ratio of the soluble polyimide / polyamic acid contained in the liquid crystal alignment agent is 0.01 to 99.0 / 1. Method.

(6) The liquid crystal alignment described in any one of (1) to (5) above, wherein the concentration of the soluble polyimide and polyamic acid contained in the liquid crystal alignment agent is 0.1 to 30% by weight. The method of forming the film. (7) The liquid crystal orientation according to any one of (1) to (6) above, wherein the irradiation wavelength of the polarized ultraviolet light is 150 to 400, and the irradiation intensity is 1 to 600 / cm ^2. The method of forming the film.

(8) The method for forming a liquid crystal alignment film according to any one of the above (1) to (7), wherein the thickness of the coating film is 5 to 30 Onm. BEST MODE FOR CARRYING OUT THE INVENTION

The most important point in the present invention is that a so-called photo-alignment method is used, in which a resin containing soluble polyimide and polyamic acid is used as a liquid crystal aligning agent, and this is applied to a substrate and then irradiated with polarized ultraviolet light. Thus, the present inventors formed a liquid crystal alignment film by a photoalignment method having high uniformity and excellent workability, and a liquid crystal display device using the liquid crystal alignment film had excellent electric characteristics, It has been found that since the electric charge is not easily accumulated, the burn-in phenomenon does not easily occur.

The polyamic acid used in the present invention refers to a condensate obtained by reacting diamine with an acid anhydride. Examples of the diamine compound used as a raw material when synthesizing the polyamic acid include the following.

Examples of alicyclic diamines include 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, 4,4,1-diaminodicyclohexylmethane, 4,4'-diamino 3,3'-dimethyl Dicyclohexane, and isophorone diamine. Examples of carbocyclic aromatic diamines include o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, and diaminotoluenes.

(For example, 2,4-diaminotoluene), 1,4-diamino-2-methoxybenzene, 2,5-diaminoxylenes, 1,3-diamino-1-chlorobenzene, 1,4-diamino-2,5-dichlorobenzene, 1,4-diamino-3-isopropylpyrubenzene, 2,2-bis (4-aminophenyl) propane, 4,4,1-diaminodiphenylmethane, 2, 2'-diaminostilbene, 4, 4'-diaminostilbene, 4, 4 'diamino diphenyl ether, 4, 4' diphenyl thioether, 4, 4 'diamino diphenyl sulfone, 3, 3'-diamino diphenyl sulfone, 2, 4- diamino benzoic acid phenyl ester, 2, 2 'jia Minobenzophenone, 4,4 'diaminobenzyl, bis (4-aminophenyl) methylphosphinoxide, bis (3-aminophenyl) sulfone Bis (4-aminophenyl) phenylphosphinoxide, bis (4-aminophenyl) cyclohexylphosphinoxide, N, N-bis (4-aminophenyl) 1 N-phenylamine, N, N-bis (4-aminophenyl) 1) N-methylamine, 4,4'-diaminodiphenylurea, 1,8-diaminonaphthylene, 1,5-diamine Nonaphthalene, 1,5-diaminoanthraquinone, diaminofluorenes (eg, 2,6-diaminofluorene), bis (4-aminophenyl) getylsilane, bis (4-aminophenyl) dimethylsilane, bis (4-aminophenyl) Tetramethyldisiloxane, 4- (3-aminophenyl) aniline, benzidine,

2,2,1-dimethylpendidine, 2,2-bis [4 -— (4-aminophenoxy) phenyl] propane, bis [4-1 (4-aminophenoxy) phenyl] sulfone, 4,4,1-bis (4— Aminophenoxy) biphenylene, 2,2-bis [4-1

(4-aminophenoxy) phenyl] hexafluoropropane, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, and the like.

Further, the heterocyclic diamines include 2,6-diaminopyridine, 2,4-diaminopyridine, 2,4-diamino-s-triazine, 2,5-diaminodibenzofuran, 2,7-diaminocarbazole, 3, 6—diaminocarbazole,

Examples thereof include 3,7-diaminophenothiazine, 2,5-diamino-1,3,4-thiadiazol, and 2,4-diamino-16-phenyl-2-s-triazine. Examples of aliphatic diamines include 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 8-diaminooctane, 1,9 diaminononane, 1,10 diaminodecane, 1,3-diamino-1,2,2-dimethylpropane bread, 1,6-diamino2,5-dimethylhexane, 1,7-diamino-2, 5-dimethylheptane, 1,7-diamino-4,4-dimethylheptane, 1,

7-Diamino-3-methylheptane, 1,9-Diamino 5-methylnonane, 2,11 Diaminododecane, 1,12-Diaminooctadecane, 1,2-Bis (3-aminopropoxy) ethane, etc. In addition, the formula (3)

(In the formula, R ₃ represents a monovalent organic group having 6 or more carbon atoms, including a long-chain alkyl group or a perfluoroalkyl group, and is preferably an alkyl group having 6 to 18 carbon atoms, or It is a monovalent organic group containing a monofluoroalkyl group.)

And an aromatic diamine having a long-chain alkyl or perfluoro group represented by

The above diamines used as a raw material of the polyamic acid can be used alone or in combination, of course, but the long chain represented by the formula (3) can be used. It is preferable to contain at least one of an aromatic diamine having an alkyl or a perfluoro group, since hydrophilicity is reduced and P and water are improved.

The acid dianhydride used as a raw material when synthesizing the polyamic acid is, as an aromatic dianhydride, pyromellitic dianhydride, 3,3 ', 4,4, -biphenyltetracarboxylic dianhydride , 2,3,3 ', 4'-Biphenyltetracarboxylic dianhydride, 3,3', 4,4'-Benzophenonetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ) Ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride Examples thereof include anhydrides. Further, as alicyclic dianhydrides, 1,2,3,4-cyclobutanetetracarbonic anhydride, 1,2,3,4-cyclopentenetetracarboxylic dianhydride, 2,3,3 4,5-tetrahydrofurantetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2-dicarboxy-11- (3,4-dicarboxycyclohexyl) Even dianhydride, 1,2 dicarboxy-11- (3,4-dicarboxy-1,2,3,4-tetrahydronaphthyl) ethane dianhydride and the like are exemplified. Of course, these acid dianhydrides can be used alone or in combination. Among them, boriamic acid having a repeating structure represented by the general formula (2) obtained by reacting an acid anhydride containing an acid dianhydride containing pyromellitic acid with a diamine is preferable from the viewpoint of improving heat resistance.

(Wherein, R ₂ represents a divalent organic group)

The polyamic acid used in the present invention is obtained by mixing the above-described diamine and acid dianhydride in the presence of an organic solvent at a temperature of from 120 to 150 ° C., preferably from 0 to 80 for 30 minutes to 24 hours, preferably from 1 to 80 hours. It can be synthesized by reacting for 10 hours. The molar ratio of the diamine to the acid dianhydride used in the reaction is such that the molecular weight does not increase if the amount of diamine is too large, and that if it is too small, the acid anhydride remains and storage stability deteriorates. It is preferable that the diamine dianhydride = 0.5-3.0 / 1.0 (molar ratio), and that the diamine / acid dianhydride = 0.8-2.0 / 1.0 (molar ratio). It is more preferable, and especially preferred is diamine / acid dianhydride = 1.0 to 1.2Z1.0.

Solvents and concentrations used when synthesizing polyamic acid by polymerization are particularly limited. Not determined. Produced when using N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-12-pyrrolidone, N-methylcaprolactam, dimethylsulfoxide, tetramethylurea, pyridine, or butyrolactones as solvents This is preferred because the solubility of the polymer is high. If the concentration at the time of polymerization is too high, the handleability of the varnish deteriorates, and if it is too low, the molecular weight does not increase. Therefore, the concentration is preferably 1 to 50% by weight, more preferably 5 to 30% by weight, and particularly preferably. Or 8 to 20% by weight. It goes without saying that a poor solvent such as butylcell solvent-toluene and methanol may be added as long as the polymer is dissolved.

Furthermore, since the molecular weight of the polyamic acid tends to increase, it is preferable to keep the inside of the reaction system under a nitrogen atmosphere, and it is more preferable to carry out the reaction while bubbling nitrogen through the solvent in the reaction system. If the final reduced viscosity of the polyamic acid is high, it is difficult to handle the glass, and if it is low, the properties are not stable when the alignment film is formed. Therefore, 0.05 to 3.O dl Zg is preferable. 0.1 to 2.5 dl / g is more preferable (in N-methyl-2-pyrrolidone at a temperature of 30 ° C., a concentration of 0.5 g / d 1).

The soluble polyimide in the present invention refers to a condensate obtained by synthesizing a polyamic acid in the same manner as the above-mentioned polyamic acid and then completely or partially cyclizing (imidizing) them. Here, the soluble polyimide used in the present invention preferably contains an alicyclic structure in the polymer from the viewpoint of improving transparency. Among them, 1,2-dicarboxy-1- (3,4-dicarboxy-1,2,3,4-tetrahydronaphthyl) ethane dianhydride including dianhydride is reacted with diamine to synthesize polyamic acid, Further, it is particularly preferable to include a soluble polyimide having a repeating structure represented by the general formula (1) obtained by imidizing the same, since the liquid crystal display element has excellent electric characteristics.

(Wherein represents a divalent organic group)

In the present invention, a method for synthesizing a soluble polyimide, that is, a method for obtaining a soluble polyimide by ring-closing (imidizing) a polyamic acid is not particularly limited, and a method of promoting imidization by heating or a method of chemically using a catalyst. For example, a method of imidizing the compound can be exemplified. Among them, the reaction proceeds easily and side reactions are unlikely to occur Therefore, it is preferable to use a soluble polyimide obtained by chemically imidizing with a catalyst. That is, after synthesizing the polyamic acid, the reaction is carried out at a temperature of 120 to 300 ° C. in the presence of a base catalyst of 2 to 20 mol times of the acid of the acid and an acid anhydride of 3 to 30 times of the acid of the acid of the acid. The reaction is preferably conducted at a temperature of 0 to 250 ° C. for 1 to 100 hours. If the amount of the base catalyst or the acid anhydride is small, the reaction does not proceed sufficiently. If the amount is too large, it is difficult to completely remove the reaction after the reaction is completed. Examples of the base catalyst used at this time include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine and the like. Among them, pyridine is preferable because it has an appropriate basicity for causing the reaction to proceed. Examples of the acid anhydride include acetic anhydride, anhydrous trimellitic acid, and pyromellitic anhydride. Among them, acetic anhydride is preferred because purification after the reaction is easy.

Also, if the reaction rate (imidization rate) of the amic acid at the time of imidizing the polyamic acid is too low, the electrical characteristics of the liquid crystal display will be poor, and if it is too high, the synthesis will take a long time. 9% is preferred, 20 to 99.5% is more preferred, and 50 to 99% is particularly preferred. The soluble polyimide thus obtained can be purified by injecting it into a poor solvent while stirring well and reprecipitating it. The poor solvent used at this time is not particularly limited, but examples thereof include methanol, acetone, hexane, butylcellosolve, heptane, methylethylketone, methylisobutylketone, ethanol, toluene, and benzene. The polyimide resin obtained by reprecipitation can be recovered by filtration and then dried at normal temperature or under reduced pressure at normal temperature or under heat to form a powder. Repeating the operation of dissolving the powder in a good solvent and reprecipitating 2 to L 0 times is preferable because the impurities in the polymer are reduced and the electrical characteristics of the liquid crystal alignment film are excellent. In this case, it is preferable to use three or more kinds of poor solvents such as alcohols, ketones, and hydrocarbons as the poor solvent, because the purification efficiency is further improved. The polyimide resin thus obtained can be used by re-dissolving it in a solvent containing a good solvent used in the synthesis.

In the present invention, the thus obtained soluble polyimide and polyamic acid can be blended to form a liquid crystal aligning agent. At this time, the order and method of blending are not particularly limited, but as a result of intensive studies by the present inventors, the blending ratio is preferably the weight ratio of soluble polyimide Z polyamic acid, preferably from 0.01 to 9%. When the ratio is 9.0, preferably 0.3 to 1.0 Z1, and particularly preferably 0.05 to 0.8 Z1, an orientation having excellent electric characteristics when a liquid crystal display element is formed. It has been found that a film is obtained. In addition, in order to improve the uniformity of the film thickness when forming the liquid crystal alignment film, N, N-dimethylformamide, N, N-dimethylacetate may be used as a solvent when compounding. Good solvents such as amide, N-methyl-2-pyrrolidone, N-methylcaprolactam, dimethyl sulfoxide, tetramethylurea, pyridine, and butyrolactone: 30 to 99.9% by weight, and butylcellosolve toluene, methanol And the like. It is preferable to use a mixed solvent containing 0.1 to 70% by weight. If the concentration of the soluble polyimide and the polyamic acid in the liquid crystal aligning agent of the present invention is too low, the liquid crystal alignment film becomes too thin and the reliability of the liquid crystal display device may be deteriorated. The thickness is preferably 0.1 to 30% by weight, more preferably 1 to 10% by weight, since the film thickness uniformity is impaired. In the present invention, the liquid crystal aligning agent thus obtained can be used as it is, but it is preferable to further add a force coupling agent since the adhesion between the liquid crystal aligning film and the substrate is improved. Here, the coupling agent means a covalent bond between an oxygen atom and at least one element selected from the group consisting of silicon and all typical metal elements belonging to groups 1 to 3 of the periodic table and all transition metal elements. Shown are compounds having. In particular, a coupling agent having an alkoxysilane, alkoxyaluminum, alkoxyzirconium, or alkoxytitanium structure is preferable because it is easily available and is excellent in cost. It is particularly preferable because the electrical characteristics in the above case are improved. Further, if the content of the force coupling agent is large, the strength of the alignment film is weakened, and if the content is small, the effect of improving the adhesiveness is reduced, so that the solid content in the liquid crystal alignment agent is preferably 0.01 to 30% by weight. It is more preferably 0.1 to 20% by weight, particularly preferably 0.5 to 10% by weight.

When compounding the above-mentioned coupling agents, dilute the coupling agents in advance with a solvent, then inject them little by little into the liquid crystal alignment agent at a temperature of -5 to 80 ° C to increase the viscosity and insolubilize the resin. This is preferable because a uniform liquid crystal aligning agent hardly occurs. At this time, the solvent and the concentration for diluting the coupling agent are not particularly limited, but include, for example, N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, toluene, hexane, and r-butylamine. The solvent can be used after diluting to a concentration of preferably 1 to 50% by weight, more preferably 3 to 30% by weight.

It goes without saying that various additives such as a cross-linking agent may be added to the liquid crystal aligning agent thus obtained and used. Moreover, it is preferable to use the obtained liquid crystal aligning agent after filtering.

The method for forming a liquid crystal alignment film of the present invention comprises the steps of: applying a liquid crystal alignment agent containing a soluble polyimide and a polyamic acid obtained as described above to a substrate; and irradiating the substrate with polarized ultraviolet light. This is a method for forming a liquid crystal alignment film formed through the above steps. The process of applying the liquid crystal aligning agent to the substrate includes spin coating, printing, ink jet A method such as the G method can be used. In this case, the substrate to be used is not particularly limited as long as it is a substrate having high transparency, and a glass substrate, an acrylic substrate, a plastic substrate such as a poly-carbon substrate, or the like can be used. It is preferable to use a substrate on which the IT0 electrode for driving the liquid crystal is formed from the viewpoint of simplifying the process. The liquid crystal aligning agent applied to these substrates is dried at a temperature of 50 to 300 ° C., preferably 80 to 200 ° C. for 1 to 200 minutes to form a coating of the liquid crystal aligning agent. Is formed. If the thickness of the coating film to be formed is too thick, it is disadvantageous in terms of cost, and if it is too thin, the reliability of the liquid crystal display element is reduced. Therefore, it is preferably 5 to 30 nm, more preferably 7 to L 0. O nm, particularly preferably 10 to 8 O nm. The step of irradiating the substrate with polarized ultraviolet light includes a step of irradiating polarized ultraviolet light to the surface of the coating film of the substrate obtained as described above to thereby perform an alignment treatment, thereby forming the coating film as a liquid crystal alignment film. is there. The irradiation wavelength of the polarized ultraviolet light to be applied is preferably 150 to 40 nm, more preferably 190 to 380 nm, and particularly preferably 220 to 350 nm. It is preferably 1 to 60 J / cm ² , more preferably 20 to 50 J / cm ² , and particularly preferably 25 to 40 J / cm ² . If the irradiation wavelength of the polarized ultraviolet light is too short, the liquid crystal alignment ability of the formed liquid crystal alignment film is deteriorated, and if it is too long, the light resistance is deteriorated. In addition, if the irradiation intensity is low, the liquid crystal alignment ability deteriorates, and if it is too high, the electric characteristics deteriorate. The alignment direction of the obtained liquid crystal alignment film is determined by the polarization direction of the irradiated ultraviolet light.

As described above, the liquid crystal alignment film formed by using the method of the present invention can uniformly align the liquid crystal and has a small accumulated charge. Therefore, by using this liquid crystal alignment film, the alignment of the liquid crystal is uniform. Thus, a liquid crystal display element with less image sticking can be obtained. As a method for obtaining a liquid crystal display element using the liquid crystal alignment film formed by using the method of the present invention, a known method can be used. As an example, a pair of substrates with a liquid crystal alignment film is preferably sandwiched by a spacer of 1 to 30 °, more preferably 2 to 10 m, and the alignment direction is preferably 0 to 270 °. There is a method in which a liquid crystal display element is formed by installing the liquid crystal at an angle, injecting liquid crystal, and sealing the liquid crystal. The method of sealing the liquid crystal is not particularly limited, and examples thereof include a vacuum method in which the pressure in the manufactured liquid crystal cell is reduced and then the liquid crystal is injected, and a dropping method in which the liquid crystal is dropped and then sealed. Thus, the liquid crystal display device manufactured by using the present invention can be a liquid crystal display device in which liquid crystal orientation is uniform and image sticking is unlikely.

Hereinafter, the present invention will be described in more detail with reference to Examples, but it should be understood that the present invention is not construed as being limited thereto. Example (Synthesis example 1)

Connect a nitrogen inlet tube and a calcium chloride tube to a 500 ml three-necked flask, and add 9.73 g (0.09 mol) of P-phenylenediamine, 1-hexadecyloxy 2,4 diaminobenzene. 49 g (0.01 mol) was thoroughly dissolved in 245 g of N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) by thoroughly stirring. Thereafter, 30.03 g (0.1 mol) of 1,2-dicarboxy-l- (3,4-dicarboxy-1,2,3,4-tetrahydronaphthyl) dianhydride was added, and the mixture was added at room temperature for 10 hours. The reaction was performed to synthesize a polyamic acid. To 100 g of this polyamic acid solution, 21.6 g (0.212 mol) of acetic anhydride and 9.97 g (0.126 mol) of pyridine were added as imidation catalysts and reacted at 50 ^ for 3 hours to obtain a polyimide resin solution. Was prepared. This solution was poured into 1000 ml of methanol, and the obtained white precipitate was separated by filtration and dried to obtain a white polyimide resin. After dissolving this resin again in NMP, it was poured into acetone, and the white precipitate obtained in the same manner was separated by filtration and dried to obtain a white polyimide resin. The reduced viscosity of the obtained polyimide was 0.64 dl / g (0.5% by weight NMP solution, 30 V). 7.2 g of this powder was dissolved in 11.2 g of Lactone mouth lactone to obtain a solvent-soluble polyimide resin solution having a solid content of 6%.

(Synthesis example 2)

A 500 ml three-necked flask was connected to a nitrogen inlet tube and a chloride tube, and under nitrogen atmosphere, 4,9.8 g of diaminodiphenylmethane (0.1 mol) was added to 226 g of NMP. Then, 10.687 g (0.049 mol) of pyromellitic dianhydride and 9.609 g (0.049 mol) of 1,2,3,4-tetracarboxycyclobutane dianhydride were added. The reaction was carried out at room temperature for 10 hours to synthesize a polyamic acid. The reduced viscosity of the obtained boramic acid was 1.18 dl / g (0.5% by weight NMP solution, 3.) This solution was diluted to a solution concentration of 6% with arctyrolactone to obtain a polyamic acid solution. Was.

(Formulation Example 1)

After stirring 20 g of the soluble polyimide solution having a concentration of 6% obtained in Synthesis Example 1 and 80 g of the polyamic acid solution having a concentration of 6% obtained in Synthesis Example 2 in a 30 Oml Erlenmeyer flask at room temperature for 12 hours, the concentration was changed to 4%. It was diluted with NMP to%. To this solution, 0.12 g of a cutting agent LS-3450 (manufactured by Shin-Etsu Chemical Co., Ltd.) was diluted with 2 g of NMP, and the mixture was further stirred for 12 hours. The obtained varnish was used as a liquid crystal aligning agent. (Formulation Example 2)

10 Og of the 6% concentration soluble polyimide solution obtained in Synthesis Example 1 was diluted with NMP to a concentration of 4%. 0.12 g of coupling agent LS-3450 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) was diluted with 2 g of NMP and added to this solution, followed by stirring for further 12 hours. The obtained varnish was used as a liquid crystal aligning agent.

(Formulation 3)

100 g of the 6% polyamic acid solution obtained in Synthesis Example 2 was diluted with NMP to a concentration of 4%. To this solution, 0.12 g of coupling agent LS-3450 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) was diluted with 2 g of NMP, and the mixture was further stirred for 12 hours. The obtained varnish was used as a liquid crystal aligning agent.

(Example 1)

The liquid crystal aligning agent obtained in Formulation Example 1 was spin-coated on a glass substrate with a transparent electrode, and baked at 210 ° C for 1 hour in a hot air circulating dryer to obtain a 5 um thick polyimide film. Was. The coating film was irradiated with polarized ultraviolet light of 30 J / cm ² to obtain a substrate having a liquid crystal alignment film. When the surface of the alignment film of the substrate with a liquid crystal alignment film was observed with a microscope, it was found that a uniform liquid crystal alignment film was formed without any scratches or unevenness on the surface. In order to measure the electrical characteristics of the liquid crystal cell, two of these substrates were prepared, a 6-meter spacer was sprayed, and a sealant was printed on one of the two substrates. The two substrates were sealed with the polyimide films facing inward. After decompressing the inside of the cell, a liquid crystal MLC-2003 (trade name, manufactured by Merck Japan) was injected to prepare a liquid crystal cell. When polarizing plates are placed above and below this liquid crystal cell, and a backlight is placed below, and the liquid crystal cell is rotated 90 degrees, the light transmittance changes, and a bright and dark appearance appears, and the liquid crystal is aligned properly. Was confirmed.

A 30 Hz / soil 3 V rectangular wave superimposed with a 3 V DC voltage is applied to this liquid crystal cell at 60 for 20 minutes.After 20 minutes, the residual voltage remaining in the liquid crystal cell immediately after the 3 V DC is cut off. Was measured by an optical flicker elimination method, and the residual DC voltage immediately after was 0 V, and the residual DC voltage after 20 minutes was 0.05 V. Also, using a liquid crystal cell and ion density measurement system (manufactured by Toyo Corp., model name: MTR-1), a voltage of 0.01 Hz and an amplitude of 10 V was applied to this liquid crystal cell, and the liquid crystal cell was mounted. When the liquid crystal cell resistance was measured from the flowing current and the voltage applied to the liquid crystal cell, it was 46.6 × 10 ⁹ Ω. (Comparative Example 1)

Using the liquid crystal aligning agent obtained in Formulation Example 2, a substrate with a liquid crystal alignment film was produced in the same manner as in Example 1. When the surface of the alignment film of the substrate with a liquid crystal alignment film was observed with a microscope, it was found that a uniform liquid crystal alignment film was formed without any scratches or unevenness on the surface. Further, a liquid crystal cell was produced in the same manner as in Example 1. When a polarizing plate is placed above and below this liquid crystal cell, and a backlight is placed below, and the liquid crystal cell is rotated 90 degrees, the light transmittance changes, clear light and dark appear, and the liquid crystal is properly aligned. This was confirmed.

A 30 Hz / soil 3 V rectangular wave superimposed with a 3 V DC voltage was applied to this liquid crystal cell at 60 ° C for 20 minutes, and 20 minutes later, the liquid crystal cell immediately after the 3 V DC was cut off When the residual voltage remaining inside was measured by an optical flicker elimination method, the residual DC voltage value immediately after was 0.12 V, and the residual DC voltage after 20 minutes was 0.30 V. Using a liquid crystal cell / ion density measurement system (manufactured by Toyo Corp., model name: MTR-1), a voltage of 0.01 Hz and an amplitude of 10 V was applied to this liquid crystal cell. measurement of the liquid crystal cell resistance from current and voltage applied to the liquid crystal cell through the liquid crystal cell, the thickness is ^{2 1 0 X 1 0 9 Ω} .

(Comparative Example 2)

Using the liquid crystal aligning agent obtained in Formulation Example 3, a substrate with a liquid crystal alignment film was produced in the same manner as in Example 1. When the surface of the alignment film of the substrate with the liquid crystal alignment film was observed with a microscope, it was found that a uniform liquid crystal alignment film was formed without any scratches or unevenness on the surface. Further, a liquid crystal cell was fabricated in the same manner as in Example 1, but the liquid crystal was not uniformly aligned, and a clear change in transmittance did not appear even when the liquid crystal cell was rotated 90 °.

(Comparative Example 3)

The liquid crystal aligning agent obtained in Formulation Example 1 was spin-coated on a glass substrate with a transparent electrode, and baked in a hot-air circulating drier at 210 for 1 hour to obtain a 50-nm-thick polyimide film. . This coating film was rubbed using rayon cloth at a roll rotation speed of 500 rpm, a roll advance speed of 20 mm / sec, and a pushing amount of 0.6 mm to obtain a substrate with a liquid crystal alignment film. When the surface of the alignment film of the substrate with a liquid crystal alignment film was observed with a microscope, streak-like scratches due to rubbing were confirmed on the surface. Further, in order to measure the electrical characteristics of the liquid crystal cell, two of these substrates were prepared, and a liquid crystal cell was prepared in the same manner as in Example 1.

Place the polarizers above and below this liquid crystal cell, place the backlight below, and remove the liquid crystal cell. When rotated 90 degrees, the transmittance of light changed, and clear light and dark appeared, confirming that the liquid crystal was properly aligned. A 30 Hz / 3 V square wave obtained by superimposing a 3 V DC voltage was applied to this liquid crystal cell at 60 ° C for 20 minutes.After 20 minutes, the liquid crystal immediately after the 3 V DC was cut off was applied. When the residual voltage remaining in the cell was measured by the optical flicker elimination method, the residual DC voltage immediately after was 0 V, and the residual DC voltage after 20 minutes was 0.000 V. Using a liquid crystal cell / ion density measurement system (manufactured by Toyo Corp., model name: MTR-1), a voltage of 0.01 Hz and an amplitude of 10 V was applied to this liquid crystal cell, measurement of the liquid crystal cell resistance from the voltage applied to the current and the liquid crystal cell through the cell was ^{1 0 6 X 1 0 9 Ω} . Industrial applicability

ADVANTAGE OF THE INVENTION According to this invention, the liquid crystal alignment film with little accumulation | storage of a liquid crystal display element can be formed by the method excellent in workability and uniformity. In addition, since the liquid crystal display element using the liquid crystal orientation film formed according to the present invention has little charge accumulation, it can continue to display an image with a high contrast without causing burn-in. Furthermore, the present invention is a highly versatile technology for improving electrical characteristics, and not only the TF (Liquid Crystal Display) currently used in the mainstream, but also the latest display resolutions such as VA and IPS LCD displays. Therefore, the image quality of all liquid crystal devices can be improved.

Claims

The scope of the claims

1. A step of applying a liquid crystal aligning agent containing a soluble polyimide and a polyamic acid to a substrate, and a step of irradiating the coating film obtained on the substrate with polarized ultraviolet rays to form a liquid crystal aligning film. A method for forming a liquid crystal alignment film, comprising:

2. The method for forming a liquid crystal alignment film according to claim 1, wherein the soluble polyimide contains a soluble polyimide resin obtained by reacting an acid dianhydride having an alicyclic structure with diamine.

3. The method for forming a liquid crystal alignment film according to claim 1, wherein the soluble polyimide contains a repeating unit represented by the general formula (1).

(Wherein, represents a divalent organic group)

4. The method for forming a liquid "alignment film according to any one of claims 1 to 3, wherein the polyamic acid includes a repeating unit represented by the general formula (2).

(Wherein, R, represents a divalent organic group)

5. The liquid crystal alignment according to any one of claims 1 to 4, wherein the weight ratio of the soluble polyimide / polyamic acid contained in the liquid crystal alignment agent is 0.01 to 99.0 Z1. Method of forming a film.

6. The method for forming a liquid crystal alignment film according to any one of claims 1 to 5, wherein the concentration of the soluble polyimide and polyamic acid contained in the liquid crystal alignment agent is 0.1 to 30% by weight. .

7. A radiation wavelength of 1 5 0~ 4 0 0 mn of polarized ultraviolet, and liquid crystal alignment according to any one of claims 1 to 6, wherein the irradiation intensity is 1-6 0 JI cm ² film Formation method.

8. The method for forming a liquid crystal alignment film according to any one of claims 1 to 7, wherein the thickness of the coating film is 5 to 300 dishes.