JPS5855488B2 - liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having an electrode protective film that is effective in improving the lifespan.

Conventionally, liquid crystal cells, especially nematic liquid crystal display devices that utilize electro-optic effects that operate under the action of an electric field,
In order to prevent deterioration of the electrodes and liquid crystal, an insulating film is provided between the electrodes and the liquid crystal.

For this purpose, inorganic materials such as vapor deposited SiO films, CVD (vapor phase growth) films of SiO2, or spinner coated films are mainly used for this purpose.

The reason for this is that these inorganic films do not have any adverse effects such as dissolving the liquid crystal even when they come into contact with the liquid crystal, and they also have the advantage of being able to withstand heating during glass frit sealing.

On the other hand, liquid crystal display devices have already been proposed in which various organic polymer materials are rubbed in one direction with a cloth or the like for orientation treatment, and then the rubbing directions are perpendicular to each other.

For example, fluororesin, polyvinyl alcohol, polyester, silicone resin, urea resin, melamine resin, phenol resin, epoxy resin, alkyd resin, urethane resin,
Resorcinol resin, furan resin, polyvinyl chloride, polyvinyl acetate, polymethyl methacrylate, polystyrene,
Polyvinyl butyrald, polysulfone, polyamide, polycarbonate, polyacetal, polyethylene, cellulose resin, natural rubber styrene-phtadiene rubber,
Acrylonitrile-butadiene rubber, polybutadiene,
Polyimprene, mercasotho silane coupling agent,
Epoxy-based silane coupling agent, amino-based silane coupling agent, viscose rayon, poly-methyl-α-
Examples include cyanoacrylate.

However, in comparison to inorganic insulating films, the alignment of such polymer solutions is not uniform even after long-term current tests and deterioration tests, and there is considerable variation in individual liquid crystal display devices. arise.

Furthermore, since it is heated to 400° C. during glass frit sealing, there is a drawback that the heat resistance is insufficient and the orientation is destroyed.

Other heat-resistant polymer solutions used for orientation include solutions of polybenzimidazole, polyesterimide, polyamideimide, polyimide, and the like.

Such a polymer solution is better in orientation uniformity and in long-term current tests and deterioration tests than the above-mentioned polymer solutions without heat resistance.

However, conventional heat-resistant polymer solutions are heated to 400°C during glass frit sealing after being rubbed in one direction with cloth, etc., resulting in poor alignment when liquid crystal is sealed. Therefore, it is difficult to obtain a good alignment film with a high yield.

In view of the current situation, the present inventors have investigated the compatibility (whether or not they have a negative effect on the performance of liquid crystals) of various polymer materials.
It was found that the presence of components that dissolve in liquid crystals, such as plasticizers, curing agents, catalysts, or low polymers, in the material impairs compatibility.

Further, the present inventors used a polymer solution having a quinazoline ring in the polymer in order to further improve the heat resistance of the polymer film.

The polymer used in the present invention, for example, polyimide-isoindoroquinazolinedione, is synthesized, and when such a polymer is applied to a substrate and then rubbed in one direction with a cloth or the like for alignment treatment, there is no alignment defect and a high yield is obtained for uniform alignment. It was discovered that a film could be formed.

It has been found that such a polymer has good compatibility, and the cured substrate after coating has good storage stability and can be stably produced.

The present invention has been made from this perspective,
An object of the present invention is to provide a liquid crystal display device having an electrode protective film that has good performance and is effective in extending the lifespan.

The present invention has the following configuration to achieve the above object.

That is, the liquid crystal display device of the present invention comprises two substrates that are sandwiched in parallel and at least one of which is transparent, a liquid crystal layer inserted between the substrates, and a liquid crystal layer provided on the substrates for applying a voltage to the liquid crystal layer. In a liquid crystal display device equipped with an electrode formed of a conductive film, a layer of a polymer having a repeating unit represented by the general formula is provided on at least the surface of the conductive film of the substrate and the conductive film that are in contact with the liquid crystal. It is characterized by having a structure and performing epoxy sealing.

The high molecular weight polymer used in the liquid crystal display device of the present invention can favorably orient azoxy-based, Schiff-based, ester-based, biphenyl-based liquid crystals, etc., is stable without being affected by temperature, humidity, etc., and is suitable for fabrics, etc. Even if an epoxy seal is applied after alignment treatment by rubbing in one direction, there is no alignment defect when the liquid crystal is sealed, and a uniform alignment film can be formed with a high yield.

Examples of the polymer represented by the above general formula used in the present invention include polyimide-isoindoquinazolinedione copolycondensates.

Such polymers include, for example, N- Methyl-2
-pyrrolidone, N-N'-dimethylformamide, N-
N-dimethylacetamide, dimethyl sulfoxide,
Hexamethylphosphoramide, easily obtained by reaction in a solvent such as cresol, and 4,4'-diaminodiphenyl ether-3-carbonamide, 4,4
It is easily obtained by reacting '-diaminodiphenyl ether and pyromellitic anhydride in the above solvent, and 4,41-diaminodiphenyl ether-3-carbonamide, 4,4'-diaminodiphenyl ether and 3
It can be easily obtained by reacting °3',4,4'-benzophenonetetracarboxylic dianhydride and pyromellitic anhydride in the above-mentioned solvent.

In the present invention, the polymer film needs to cover at least the surface of the conductive film between the substrate and the conductive film, and to cut off direct contact between the conductive film and the liquid crystal.

However, the coating of the polymer is not necessarily limited to only the conductive film, and there is no problem in covering parts other than the conductive film on the substrate.

Rather, it is preferable to cover the entire surface of the substrate in contact with the liquid crystal in order to prevent deterioration of the liquid crystal that would otherwise occur due to the influence of the substrate material such as glass.

Therefore, no special consideration is required when applying the polymer solution of the present invention to the surface of a conductive film, and it can be applied by brush coating, dipping, spin coating, or other conventional means.

Furthermore, a liquid crystal display device (liquid crystal cell) can be formed by applying a rubbing operation using cloth, gauze, absorbent cotton, etc., and enclosing liquid crystal.

The liquid crystal and alignment film in the liquid crystal display device of the present invention are 5o=
No discoloration was observed even when left at CS temperature for a long time, and the compatibility described above (whether or not it adversely affects the performance of the liquid crystal) is good. However, in order to obtain an alignment film with even stronger adhesion, epoxy At least one type of silane coupling agent, amino type, or mercapto type can be used in combination.

As such a silane coupling agent, for example, r
-aminopropyltriethoxysilane, β-(3,4-
epoxycyclohexyl)ethyltrimethoxysilane,
Examples include N-β (aminoethyl)r-aminopropylmethyldimethoxysilane.

Furthermore, in the present invention, a commonly known inorganic compound such as 5iO1SiO2 is used as a base film on the inner surface of the conductive film.
It is also possible to further prevent the effects of dissolution and heating on the liquid crystal by using an insulating inorganic film such as Al2O3.

As is well known, in a liquid crystal display device, two substrates are held in parallel by terminal portions located at the peripheral portions of the two substrates, but the etching of the terminal portions of the alignment film may be performed using commonly used means in the present invention. can be carried out, for example, by means of an oxygen plasma or also by the use of a solvent.

Examples of the solvent that can be used include N-methyl-2-pyrrolidone, N-N'-dimethylacetamide, N-N'-dimethylformamide, dimethyl sulfoxide, and a mixture of hydrazine and ethylenediamine.

In the present invention, the polymer film at the terminal portion is removed by terminal etching, epoxy printing is performed, and after the two substrates are combined, liquid crystal is filled in to form a liquid crystal display device.

In this case, the two substrates are printed with resist except for the terminals, the polymer film on the terminals is removed, the resist is removed with a trichlene solvent, etc., and after rubbing, the liquid crystal is encapsulated. A liquid crystal display device can also be formed by combining two substrates.

Furthermore, although a conventional liquid crystal can be used in the present invention,
In particular, P-methoxy-y-butylazoxybenzene (MB
Azoxy liquid crystals such as AZ) can be effectively used.

The liquid crystal display device of the present invention has excellent durability even when energized for a long time due to the above-mentioned structure even with an epoxy seal, and there is no deterioration such as coloring of the electrode film or generation of bubbles due to voltage application, It can withstand heating and has good compatibility with the above,
Dogs play an important role in this technical field because they have a very high yield and are suitable for mass production.

Next, the present invention will be explained with reference to Examples, but the present invention is not limited to these in any way.

Example 1 A 30011L 40 flask equipped with a thermometer, stirrer, calcium chloride tube, and N2 inlet tube was filled with 4.4 flasks.
'-Diaminodiphenyl ether-3-carbonamide 1.82f (0,0075 mol), 4,41-diaminodiphenyl ether 13.5? (0,0675 mol),
N-Methyl-2-pyrrolidone Ion and N-N-dimethylacetamide 100f? and stir well to dissolve the contents.

After the contents had dissolved, the flask was cooled in a water bath, and pyromellitic anhydride 8.11' (0,0375 mol) and 3.3',4.
4/-benzophenonetetracarboxylic dianhydride 12.
01' (0,0375 mol) was gradually added, and after the addition was completed, the reaction was carried out at 15°C for 6 hours to obtain a solution with a viscosity of 13,000 CP at 25°C.

This solution was diluted, 0.1% of N-β-(aminoethyl)γ-aminoflobilmethylmethoxysilane was added dropwise, stirred, and spin-coated onto a glass substrate with a transparent In2O3 electrode that had been cleaned in advance. 200℃~
The ring was closed by heating at 350 DEG C. to obtain a stable polyimide-isoindoquinazolinedione film that is hardly affected by temperature and humidity.

The two substrates thus obtained were rubbed with gauze to obtain an alignment film with strong adhesion.

In addition, the polymer film on the terminal portion in the peripheral area was removed using oxygen plasma, epoxy resin was printed, and the two substrates were assembled.

After that, liquid crystal P-methoxyy-butylazoxybenzene (hereinafter referred to as MBAZ) is injected through the injection hole made in advance, and then the injection hole is sealed with epoxy resin to form a liquid crystal display device (hereinafter referred to as liquid crystal cell). Created.

A DC voltage of 30V was applied to this liquid crystal cell from the outside through a transparent conductive film, but there was no deterioration that normally occurs such as coloration of the electrode film, generation of bubbles, or poor alignment, and the cell withstood the electricity supply for over 1000 hours. .

Further, the substrate with the polymer film obtained in the same process as above was cut into strips, and equal amounts of the strips and liquid crystal MBAZ were placed in a glass ampoule, which was degassed and sealed.

Even after this ampoule was left in an electric furnace at 80° C. for 2400 hours, no discoloration was observed in the liquid crystal and polymer film, indicating that they were compatible.

Example 2 4.4 flasks of 300rr Ll equipped with a thermometer, stirrer, calcium chloride tube and N2 inlet tube
'-Diaminodiphenyl ether-3 carbonamide 1
．． 82'iI (0,0075 mol), 4,4'-diaminodiphenyl ether 13.5f (0,0675 mol)
, 100P of N-methyl-2-pyrrolidone and 1001P of N-N-dimethylacetamide were added, and the contents were stirred well to dissolve.

After the contents have dissolved, cool the flask in a water bath, and
・4'-benzophenone tetracarboxylic dianhydride 24
．． 15f (0,075 mol) was gradually added, and after the addition was completed, the reaction was carried out at 15°C for 6 hours, and the viscosity at 25°C was 12000C.
A solution of P was obtained.

This solution was diluted, 0.1% of N-β-(aminoethyl)γ-aminoflobilmethylmethoxysilane was added dropwise, stirred, and rotated onto a glass substrate with an In2O3 transparent electrode that had been cleaned beforehand. After coating, remove the terminals and print a resist, remove the terminals with N-methyl-2-pyrrolidone, further ultrasonically clean the resist with trichlene, close the tube by heating at 200°C to 350°C, and adjust the temperature and temperature. A stable polyimide-isoindoroquinazolinedione film that is very little affected by humidity was obtained.

The two substrates thus obtained were rubbed with gauze, then printed with epoxy resin, and the two substrates were combined to form a cell.

Then, from the injection hole made in advance, liquid crystal P methoxy
'-Butylazoxybenzene (MBAZ) was injected, and the injection port was then sealed with epoxy resin to produce a liquid crystal display device (liquid crystal cell).

A DC voltage of 30V was applied to this liquid crystal cell from the outside through a transparent conductive film, but there was no deterioration that normally occurs such as coloration of the electrode film, generation of bubbles, or poor alignment, and the cell withstood the electricity supply for over 1000 hours. .

Further, the substrate with the polymer film obtained in the same process as above was cut into strips, and equal amounts of the strips and liquid crystal MBAZ were placed in a glass ampoule, which was degassed and sealed.

Even after this ampoule was left in an electric furnace at 80° C. for 2400 hours, no discoloration was observed in the liquid crystal and polymer film, indicating that they were compatible.

As is clear from the results of the above examples, the liquid crystal display device of the present invention is particularly excellent in heat resistance and stability, and is extremely useful from the viewpoint of improving lifespan and manufacturing liquid crystal cells with high yield with epoxy seal. It is.

Claims (1)

[Claims] 1. Two substrates, at least one of which is transparent, sandwiched in parallel through a seal, a liquid crystal layer inserted between the substrates, and a liquid crystal layer on the substrate for applying a voltage to the liquid crystal layer. In a liquid crystal display device comprising an electrode formed of a conductive film provided on the substrate, a layer of a polymer having a repeating unit represented by the general formula is provided on at least the surface of the conductive film and the substrate in contact with the liquid crystal. 1. A liquid crystal display device having a structure in which the seal is an epoxy seal.