JPS6256494B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a liquid crystal display element, and more particularly to a liquid crystal display element having an alignment film that can also serve as an electrode protective film, which is effective in improving lifespan. Conventionally, in liquid crystal cells, especially nematic liquid crystal display devices that utilize electro-optical effects that operate under the action of an electric field, an insulating film is provided between the electrodes and the liquid crystal to prevent deterioration of the electrodes and the liquid crystal. . Typically used for this purpose is SiO
The main materials used were inorganic materials such as SiO 2 films obtained by firing vapor-deposited films of SiO ₂ , CVD (vapor phase growth) films of SiO ₂ , or spinner-coated films such as silanol solutions. On the other hand, a liquid crystal display device uses various polymeric materials for the alignment film, and after alignment treatment is performed by rubbing in one direction with a cloth or the like, the liquid crystal is sandwiched between two electrodes whose rubbing directions are perpendicular to each other. Already developed. Examples of such polymeric materials include fluorine resin, polyvinyl alcohol, polyester, silicone resin, urea resin, melamine resin, phenolic resin, epoxy resin, alkyd resin, urethane resin, resorcinol resin, furan resin, and polyvinyl chloride. , polyvinyl acetate, polymethyl methacrylate, poly-methyl-α-cyanoacrylate, polystyrene, polyvinyl butyral, polysulfone, polyamide, polycarbonate, polyacetal, polyethylene, cellulose resin,
Examples include natural rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, polybutadiene, polyisoprene, etc. Other alignment film materials include mercapto-based silane coupling agents, epoxy-based silane coupling agents, amino-based silane coupling agents, and Examples include viscose rayon. However, when such polymeric materials are used as an alignment film, the uniformity of alignment and film forming properties are not sufficient, and in long-term current tests and deterioration tests, the inorganic alignment film shows In comparison, non-uniformity in alignment tends to increase, and there is a drawback that considerable variation occurs in individual liquid crystal display elements. Furthermore, after alignment treatment of the electrode substrates, a pair of electrode substrates are bonded together when liquid crystal is sealed and a liquid crystal display element is manufactured. However, if an organic material with a high curing temperature is used as a sealing material, the heating temperature during sealing may There is also the drawback that orientational destruction occurs. Next, other heat-resistant organic polymer materials used for orientation include polyesterimide, polyamideimide, polyimide, and the like. Such materials are considerably superior in terms of alignment uniformity, contrast, etc., compared to the aforementioned materials with low heat resistance. On the other hand, regarding the seal structure, there are organic and inorganic sealing materials.Among these, organic sealing materials have poor water resistance and airtightness compared to inorganic sealing materials. Regarding the alignment film, as mentioned above, there are difficulties in obtaining a highly reliable liquid crystal element. The present invention has been made in view of the current situation, and an object thereof is to provide a liquid crystal display element having an alignment film that is excellent in water resistance and can also serve as an electrode protective film that is effective in improving lifespan. To summarize the present invention, the liquid crystal display element of the present invention has a liquid crystal alignment film on a substrate on which electrodes are formed, and the alignment film contains 1 mole of dibasic acid and about 0.5 to 1.5 moles of a diamine compound. An epoxy-modified amide polymer compound obtained by reacting a reaction product obtained by condensing with about 0.3 to 1.5 moles of an epoxy compound having two or more epoxies in one molecule. It is. The present inventors have discovered that when a film formed from a reaction product formed by the condensation of a dibasic acid, such as an aliphatic or aromatic dicarboxylic acid, and a diamine compound is applied as an alignment film of a liquid crystal display element, and in particular, an inorganic film is used to protect electrodes. Various studies have been conducted on the characteristics of liquid crystal display elements when no protective film is applied. As a result, it was found that a liquid crystal display element in which an organic sealant is applied around the electrodes does not have sufficient water resistance, and it is not possible to prevent the adverse effects caused by the water resistance on the properties of the liquid crystal. As a result of further research, the present inventors found that the reaction product produced by condensing the predetermined amount of dibasic acid and the diamine compound,
The above-mentioned adverse effects can be prevented by applying a solution of an epoxy-modified amide-based polymer compound obtained by adding and reacting an epoxy compound having 1 or more epoxy groups onto an electrode substrate and heating it to form a film. The present invention was achieved by discovering that it is possible to obtain a liquid crystal display element which has good water resistance and durability and extremely excellent optical properties. Examples of dibasic acids in the present invention include maleic acid, maleic anhydride, fumaric acid, chloromaleic acid, citraconic acid, citraconic anhydride, mesaconic acid, itaconic acid, tetrahydrophthalic acid,
unsaturated acids such as carbicic anhydride, hettsic acid and hettsic anhydride; and unsaturated acids such as succinic acid, adipic acid,
Methylglutaric anhydride, azelaic acid, pimelic acid, sebacic acid, azelaic acid, phthalic anhydride,
Saturated acids such as isophthalic acid, terephthalic acid and tetrachlorophthalic acid may be mentioned. In addition, as the diamine compound in the present invention,
For example, 4,4'-diaminodiphenyl ether,
4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfide, m-phenylenediamine,
p-phenylenediamine, m-xylenediamine, p-xylenediamine, 3,3'-dimethyl-
4,4'-diaminodiphenylmethane, 3,3',
5,5'-tetramethyl-4,4'-diaminodiphenylmethane, 2,2'-bis(4-aminophenyl)propane, 4,4'-methylene dianiline, penzidine, 2,4-bis(β- amino-tertiary butyl) toluene and bis(4-β-amino-tertiary)
butyl phenyl) ether and the like. In addition, examples of the epoxy compound having two or more epoxy groups in one molecule in the present invention include bisphenol A type epoxy resin, resorcinol type epoxy resin, tetrahydroxyphenylethane type epoxy resin, Novock type epoxy resin,
Examples include polyglycol type epoxy resins and glycerin triether type epoxy resins. The condensation reaction between the dibasic acid and the diamine compound is usually carried out at about 50°C under anhydrous conditions using a solvent such as N-methyl-2-pyrrolidone (NMP).
This is carried out by reacting for several hours at the following temperature. In this case, it is appropriate to react the diamine compound in an amount of about 0.5 to 1.5 moles per mole of the dibasic acid, and the reaction between the above reactant and the above epoxy compound can be carried out under almost the same conditions as above. In this case, the amount of epoxy resin is suitably about 0.3 to 1.5 mol per 1 mol of dibasic acid. The reason for limiting it to the above range is 70
When moisture is absorbed for 100 hours under the conditions of ℃ and 95% RH, the creeping resistance value becomes 10 ¹¹ Ω or more within this range and serves to protect the electrode without causing bleeding, but outside this range the electrode substrate and alignment This is because bleeding occurs between the membranes due to moisture absorption, and the membrane no longer serves its role of protecting the electrodes. When applying the obtained solution of the epoxy-modified amide polymer compound onto an electrode substrate such as glass, it is diluted to an appropriate concentration with a solvent such as N-methyl-2-pyrrolidone, and this solution is generally It can be applied by known methods, such as dipping, spinning, spraying and printing. After application, 100
A coating is provided on the electrode by heating and curing at ~250°C, preferably 150-230°C. After the film has hardened, a liquid crystal can be sealed by rubbing the film with cloth or gauze, thereby producing a liquid crystal display element. Note that various silane compounds (coupling agents) can also be used in combination to improve the adhesion of the film onto the substrate. The liquid crystal compound in the present invention includes Schiff type, biphenyl type, azoxy type, ester type, cyclohexane type, etc., and a mixture of two or more of them is usually used. The liquid crystal display element of the present invention does not cause moisture absorption and bleeding in the display portion, and has excellent durability against long-term energization and high-temperature and high-humidity tests. Next, the present invention will be explained with reference to Examples, but the present invention is not limited to these in any way. Furthermore, in the following examples, the moisture absorption and bleeding characteristics were expressed by creepage resistance between segments. The creeping resistance value was calculated from the leakage current 1 minute after applying a DC voltage of 13.5 V to the terminal portion of the transparent electrode. Moisture absorption conditions were 70°C and 95%RH, and the values were taken after being left for 100 hours. Furthermore, the moisture absorption and bleed characteristic test for liquid crystal display elements was conducted by leaving the liquid crystal display element at 70°C and 95% RH for 500 hours, and then driving it with a 100Hz, 4.5V rectangular wave alternating current. This was done by observing. Example 1 1 mole of maleic anhydride and 1 mole of 4,4'-diaminodiphenylsulfone were added to N-methylpyrrolidone to make a 50% by weight solution, and condensation was carried out at 30°C or lower for 2 hours. This reaction product (solution) was added with 1 bisphenol A type epoxy resin (epoxy equivalent: 172 to 178).
mol was added thereto, and the mixture was further reacted at 30°C for 5 hours. The concentration of the obtained solution of the epoxy-modified amide polymer compound was adjusted to 4% by weight with N-methyl-2-pyrrolidone, and the solution was applied onto a glass substrate with an indium oxide electrode by a rotation method. Then in a drying oven
A film was formed by heating and curing at 210°C for 1 hour.
The treated electrode surfaces of the two substrates obtained in this way are polished in one direction with a cloth, and the two electrode substrates are placed on top of each other with an organic sealant in between so that the polishing directions intersect at right angles, and then sealed by heating. The parts were cured and made into cells. Next, liquid crystal p-methoxy-p'-butylazoxybenzene (hereinafter referred to as MBAZ) was injected through the injection hole prepared in advance, and the injection hole was then sealed with an epoxy adhesive to produce a liquid crystal display element. did. Example 2 Condensation was carried out in the same manner as in Example 1 using 1 mol of maleic anhydride and 1.5 mol of 4,4'-diaminodiphenyl ether, and the reaction product (solution) was
1 mole of bisphenol A type epoxy resin (epoxy equivalent: 450 to 500) was added to carry out a reaction. N-methyl-2-pyrrolidone was added to the obtained solution to adjust the concentration to 4% by weight, and this solution was spin-coated with a spinner onto an electrode of a Nesa electrode glass substrate having a conductive film of indium oxide, and then dried in a drying oven.
It was heat cured at 210°C for 1 hour. The treated electrode surfaces of the two substrates thus obtained were treated in the same manner as in Example 1 to form cells, and a liquid crystal injection operation was performed to produce a liquid crystal display element. Example 3 0.1% by weight of γ was added to the same solution of the epoxy-modified amide polymer compound as in Example 1.
- After dropping and stirring aminopropyltriethoxysilane, spin coating was performed on the same glass substrate as in Example 1 to obtain an alignment film with even stronger adhesion. A display element was manufactured. Example 4 A liquid crystal display element was produced in exactly the same manner as in Example 1, except that 1.5 mol of a cresol novolak type epoxy resin (epoxy equivalent: 230) was used as the epoxy compound. Example 5 The same procedure was carried out, except that 2 moles of hestic anhydride and 1 mole of 4,4'-diaminodiphenylsulfone were condensed, and 1 mole of a cycloaliphatic epoxy resin (epoxy equivalent weight 131 to 137) was used as the epoxy compound. Example 1
A liquid crystal display element was produced in the same manner as above. Example 6 Example 1 except that 1 mole of tetrahydrophthalic acid and 1 mole of 4,4'-diaminodiphenylmethane were condensed and 1 mole of cycloaliphatic epoxy resin (epoxy equivalent weight 133) was used as the epoxy resin.
A liquid crystal display element was produced in the same manner as above. Example 7 The same procedure was carried out except that 1 mole of phthalic anhydride and 1 mole of 4,4'-diaminodiphenylmethane were condensed, and 1 mole of cresol novolak type epoxy resin (epoxy equivalent: 176 to 187) was used as the epoxy compound. A liquid crystal display element was produced in the same manner as in Example 1. Comparative Example 1 A liquid crystal display element was produced in the same manner as in Example 1, except that 0.2 mol of bisphenol A type epoxy resin (epoxy equivalent: 450 to 500) was used. Comparative Example 2 A liquid crystal display element was produced in the same manner as in Example 1 except that 1.7 mol of bisphenol type epoxy resin was used. Comparative Example 3 The same procedure was carried out except that 1 mol of maleic anhydride and 0.3 mol of 4,4'-diaminodiphenylsulfone were condensed, and 1 mol of bisphenol A type epoxy resin (epoxy equivalent 450 to 500) was used as the epoxy compound. A liquid crystal display element was produced in the same manner as in Example 1. Comparative Example 4 Example 1 except that 1 mol of maleic anhydride and 1.7 mol of 4,4'-diaminodiphenylsulfone were condensed and 1 mol of bisphenol A type epoxy resin (epoxy equivalent: 500) was used as the epoxy compound. A liquid crystal display element was produced in the same manner as above. The creeping resistance value and bleeding characteristics after moisture absorption were investigated for the liquid crystal display elements produced in the above Examples and Comparative Examples. The results obtained are shown in the table below. The numerical values in the table are the average values of six.

[Table] As is clear from the table, the liquid crystal display element of the present invention has a higher creepage resistance value than that of the comparative example, and
It also has good bleeding properties and is excellent in water resistance and durability. As described above, according to the present invention, it is possible to provide a liquid crystal display element having an electrode protective film that is excellent in water resistance and effective in improving lifespan.

Claims (1)

[Claims] 1 In a liquid crystal display element having a liquid crystal alignment film on a substrate on which an electrode is formed, the alignment film is a dibasic acid 1
An epoxy-modified amide polymer obtained by reacting a reaction product obtained by condensing about 0.5 to 1.5 moles of a diamine compound with about 0.3 to 1.5 moles of an epoxy compound having two or more epoxy groups in one molecule. A liquid crystal display element characterized by being composed of a compound.