JPS601607B2 - liquid crystal display element - Google Patents

Description

[Detailed description of the invention] The present invention relates to a liquid crystal display element.

Conventionally, liquid crystal cells, especially nematic liquid crystal display elements that utilize electro-optic effects that operate under the action of an electric field,
Inorganic materials such as a deposited film of Si○ have been mainly used as the alignment film.

The reason for this is that these inorganic films do not dissolve into liquid crystals even when they come into contact with liquid crystals, so they do not have any negative effects, and even if glass frit sealing is performed, they have the advantage of being able to uniformly align Schiff-type liquid crystals and biphenyl-type liquid crystals. It's for a reason.
On the other hand, liquid crystal display elements have already been proposed in which various organic polymeric materials are used for the alignment film, and after alignment treatment is performed by rubbing in one direction with a cloth or the like, the rubbing directions are orthogonal to each other.

For example, fluororesin, polyvinyl alcohol, polyester, silicone resin, urea resin, melamine resin, phenolic resin, epoxy resin, alkyd resin, urethane resin,
Resorcinol resin, furan resin, polyvinyl chloride, polyvinyl acetate, polymethyl methacrylate, polystyrene,
Polyvinyl butyrate, polysulfone, polyamide, polycarbonate, polyacetal, polyethylene, cellulose resin, natural rubber, styrene-butadiene rubber,
Acrylonitrile looptadiene rubber, polybutadiene,
Polyisoprene, mercapto silane coupling agent,
Epoxy silane coupling agent, amino silane coupling agent, viscose rayon, polymethyl-Q-
Examples include cyanoacrylate. However, such polymer films cannot be said to have sufficient uniformity in liquid crystal orientation, and due to long-term current tests and deterioration tests, non-uniformity in liquid crystal orientation tends to increase more easily than inorganic insulating films. A drawback is that considerable variation occurs among individual liquid crystal display elements. Further, although the glass frit seal is heated to 400 qo to 45,000 qo, it has insufficient heat resistance, so the alignment film is destroyed and the liquid crystal is not aligned. Next, other heat-resistant polymer materials used for orientation include polyesterimide, polyamideimide, polyimide, and the like.

Compared to the aforementioned polymers with low heat resistance, such polymers have considerably better alignment uniformity and durability in long-term current tests and deterioration tests when an organic seal is used. . However, even with these heat-resistant polymers, after alignment treatment by rubbing in one direction with cloth etc.,
If glass frit sealing is performed at a temperature of 0 qo to 450 pm, alignment defects are likely to occur when liquid crystal is sealed. especially,
Induced domain (regions with different visual angles appear when applying electricity)
occurs, making it difficult to obtain a liquid crystal display element with stable display characteristics. The reason for this is that when measuring the thermogravimetric analysis curve as shown in Figure 1, conventional polyimide has a
The weight loss started around 00, and the weight loss rate was also larger than that of the invention 2. The alignment film used for liquid crystal display elements is usually used at a thickness of about 400A to 2000A, since it is not preferable to form the film thickness (more than a few pulses) used for an insulating film because the electrical response will be poor. It is essential that In this way, it is thought that because the surface of the alignment film is rubbed in one direction with cloth or the like, fine grooves are formed, thereby aligning the liquid crystal. For this reason, it is thought that heating changes the surface properties and changes the alignment state of the liquid crystal. Therefore, in order to maintain stable orientation during heat treatment of 400q0 or more, the heating loss must be 4000q0 or more.
The material must not generate more than 0 or must be as small as possible. In addition, as shown in FIG. 2, polyimide exhibits a large decrease in film thickness when left at high temperatures, making it difficult to maintain uniform orientation and causing induced domains to easily occur.
On the other hand, at a temperature lower than 400 qo, glass frit seals not only fail to achieve the precision of the element gap required for liquid crystal display elements, but also lack sufficient mechanical strength of the elements. At least 40,000 or more, preferably 430oo to 450o0
Should be frit sealed. Therefore, it is essential to improve the heat resistance of the orientation. With conventional polyimide, elements with good orientation could not be obtained. An object of the present invention is to obtain a liquid crystal display element with excellent alignment and a very small activation domain.

The present inventor developed a diamine compound, a diaminomonoalkoxycarbonylamino compound, and a diamine compound, a diaminomonoalkoxycarbonylamino compound, in order to improve the weight loss starting temperature and reduce heating loss compared to conventional alignment films made of polyesterimide, polyamideimide, polyimide, etc.
An alignment film is formed using a polyimide-penzimidazopyrrolone copolymer resin film having a pyrolone ring structure made from tetracarboxylic dianhydride, that is, a copolymer resin film layer consisting of the following unit structure. , the surrounding area was sealed.

(In the formula, Ar is a diaminomonoalkoxycarbonylamino compound residue, ~2 is a diamine compound residue, and Ar3 is a tetracarboxylic dianhydride residue.) A glass frit seal is used as a seal to seal this element. When evaluated, it is confirmed that even at 450 oo, the orientation and induced domain are very small.

The reason why it is possible to fabricate such a good device is that the thermogravimetric analysis curve shown in FIG. 1 and the result of film thickness reduction when left at high temperatures shown in FIG. This is thought to be due to the excellent heat loss properties. In the polyimide benzimidazopyrrolone copolymer used in the present invention, p-phenylenediamine etc. are used as the diamine compound, and 3,3-diamino-4-ethoxycarbonylamino diphenyl ether, 1,4-diamino- 2-ethoxycarbonylaminobenzene, etc., and as the tetracarboxylic dianhydride compound, pyromellitic dianhydride, 3.3.4.4-benzophenone tetracarboxylic dianhydride, etc. can be used.

In addition, as an organic solvent, N-methyl-2-pyrrolidone,
N.N-dimethylacetamide and the like can be used. The optimal ratio of the diamino compound and the diaminomonoalkoxycarbonylamino compound is 95 to 5 mol% for the former,
The latter may be selected from the range of 5 to 95 mol%.

Also, tetracarboxylic dianhydride pyromellitic acid and 3.3.
The optimum ratio of the former to 4,4'-benzophenonetetracarboxylic dianhydride is 70 to 30 mol%, while the latter is 30 to 30 mol%.
It may be selected from a range of 70 mol%. Note that the mixture of the diamine compound and the diaminomonoalkoxycarbonylamino compound and the tetracarboxylic dianhydride are optimally equimolar. A diamine compound, a diaminomonoalkoxycarponylamino compound, and a tetracarboxylic dianhydride react rapidly even at a low temperature below room temperature. When the present invention is practiced, an even more excellent device can be obtained if the present invention is practiced on a substrate provided with an inorganic insulating film below or above the electrode layer. This is based on an experimental result that a copolymer resin film on a film such as SiQ has a comparatively smaller heat radiation loss than the copolymer resin film on a glass substrate. Examples of insulating films exhibiting such effects include S02 and Si02 single needle 203 mixed films. In forming the alignment film used in the present invention, no special consideration was given to the handling of the polymer solution, and the process was carried out using brush coating, dipping, spin coating, printing, and other conventional methods. Add rubbing with gauze, etc. As a result, a liquid crystal display element can be formed by performing frit sealing at 450 q○. In the present invention, one or more types of epoxy-based and amino-based silane coupling agents can be used in combination in order to obtain an alignment film with even stronger adhesion.

As such a silane coupling agent, for example, y
Examples include -aminopropyltriethoxysilane and y-dalisidoxypropyltrimethoxysilane. As is well known, in a liquid crystal display element, it is necessary to expose the terminal portions on the periphery of the two substrates and connect them to an external conductor. However, the etching of the terminal portions of the cetacean film is carried out by means commonly used in the present invention. For example, this can be carried out by printing a mask resist on the terminal portion and removing it after forming the polymer resin, or by using oxygen plasma.

The liquid crystal compound sealed in the display element of the present invention includes {1
1 Schiff-type liquid crystal (mixture of e.g.), {2} biphenyl-type liquid crystal (mixture of e.g.), '3} azoxy-type liquid crystal (mixture of e.g.), [4} ester-type liquid crystal (mixture of e.g.), [5-cyclohexane type liquid crystal (mixture of e.g.)
etc. can be used.

All are mixtures of two or more components. The liquid crystal display element of the present invention does not generate induced domains even when frit-sealed, and has excellent durability even when energized for a long time.

Example 1 3,3-diamino-4-ethoxycarbonylaminodiphenyl ether (5 mol%), paraphenyl diamine (95 mol%), and pyromellitic dianhydride (50 mol%)
), 3,3,4,4'-penzophenonetetracarboxylic dianhydride (50 mol %), and N-methyl-2-pyrrolidone were placed in a flask and heated at 15 to 20 oo for 7 to 8 hours.

A 15% copolymer solution with a viscosity of 1700 p at 25 oo was obtained.

This solution was diluted to 3%, and an inorganic film of Si02 was prepared in advance at 12%.
The polymer solution was applied by spin coating onto a substrate having a thickness of 00A, a transparent electrode containing 1 to 03 as main components, and a mask material printed on the terminal portion. After removing the mask material,
The ring was closed by heating at 250°C for 1 hour to form an alignment film of polyimide-benzimidazopyrrolone copolymer resin with a thickness of 800A. Thereafter, a rubbing operation was performed with a cotton cloth in a certain direction to print a glass frit around the substrate, and the two substrates were combined and fired at 450° C. for 30 minutes to form an element.
Schiff-type liquid crystal [1}, biphenyl-type liquid crystal 2}, azoxy-type liquid crystal '3', Estel-type liquid crystal 4-, and cyclohexane-type liquid crystal [5} are separately injected into these elements, and then each injection port is opened. Sealed with epoxy resin,
A liquid crystal element was manufactured. The alignment performance of these devices was investigated by inducing domains. The results are shown in the table, and a good device with no alignment defects and a very small induced domain width was obtained. Further, even when the display element was left at 70° C. and RH 95% for 100 hours, there was no change in orientation, and a display element with excellent orientation was obtained.
Example 2 3,3-diamino-4-ethoxycarbonylaminodiphenyl ether (50 mol%), paraphenyl diamine (50 mol%), and pyromellitic dianhydride (70 mol%), 3・3,4,4-benzophenonetetracarboxylic dianhydride (30 mol%) was reacted in N-methyl-2-pyrrolidone for 7 hours at 25°C, viscosity 22
A 15% copolymer solution with a 00 ratio p was obtained.

This solution was diluted to 4%, a mask material was printed on the terminal part of the transparent electrode of ln203, and the polymer solution was applied by spin coating.
After removing the mask material, ring closure was performed by heating at 25,000 ℃ to form an alignment film having a polyimide-benzimidazopyrrolone copolymer resin to a thickness of 1,200 Å. Hereinafter, a device was prepared in the same manner as in Example 1, and the orientation was investigated by measuring the induced domain width.

The results are shown in the table above. Example 3 A device was formed by further adding 0.05% y-amino/propyltriethoxysilane to the copolymer solution of Example 1,
Each liquid crystal was injected.

The results are shown in the table. Example 4 0.1% of y-glycidoxypropyltrimethoxysilane was further added to the copolymer solution of Example 2 to form devices, and each liquid crystal was injected.

The results are shown in the table. Example 5 3,3-diamino-4-ethoxycarbonylamino diphenyl ether (95 mol%), paraphenylene diamine (5 mol%), and pyromellitic dianhydride (50 mol%)
), 3,3',4,4-benzophenonetetracarboxylic dianhydride (50 mol%) was reacted in N-N-dimethylacetamide at 15°C for 7 hours to obtain a viscosity of 25,000.
A 15% copolymer solution with a ratio p of 400 was obtained.

This solution was diluted to 3% and an alignment film having a thickness of 1000 Å was formed using the same steps as in Example 1. The results are shown in the table.
Example 6 1,4-diamino-2-ethoxycarbonylaminobenzene (50 mol%), paraphenylenediamine (50 mol%), pyromellitic dianhydride (30 mol%), 3.
3',4,4-benzophenonetetracarboxylic dianhydride (70 mol%) in N-methyl-2-pyrrolidone
A 15% copolymer solution with a viscosity of 2500 and a ratio p of 2300 was obtained by reacting at 5qo for 7 hours.

This solution was diluted to 3%, and an inorganic film of Si02 was diluted to 1000%.
A mask material was printed on the terminals of a substrate formed to a thickness of A, and a transparent electrode mainly composed of ln203 was formed, a polymer solution was applied by spin coating, and after removing the mask material,
The orientation stiffness of the polyimide benzimidazopyrrolone copolymer resin was 1000 by heating and ring-closing at 250 CO for 1 hour.
It was formed to a thickness of A. The results are shown in the table. Example 7 1,4-diamino-2-ethoxycarbonylaminobenzene (10 mol%), paraphenylenediamine (90 mol%), pyromellitic dianhydride (50 mol%), 3.
3',4,4'-benzophenonetetracarboxylic dianhydride (50 mol%) with N-methyl-2-pyrrolidone and N
lyo was reacted in N-dimethylacetamide for 7 hours to obtain a 15% copolymer solution with a viscosity of 2500 p.

This solution was diluted to 4% and an alignment film having a thickness of 1500 Δ was formed using the same process as in Example 6. Thereafter, a rubbing operation was performed in a certain direction to print a glass frit, and the two substrates were combined and fired at 450° C. for 30 minutes to form a device. From the above results, the liquid crystal display device using the polyimide-benzimidazopyrrolone copolymer resin of the present invention does not generate induced domains and has extremely excellent display properties.

Comparative Example 4 4-diaminodiphenyl ether (100 mol%)
, pyromellitic dianhydride (100 mol%) was heated in N-methyl-2-pyrrolidone and N·N-dimethylacetamide for 15 q○ for 7 hours, and the viscosity at 25 qo was 2000.
A polymer solution with a ratio p of 15% was obtained.

This solution was diluted to 3%, and an inorganic film of Si02 was diluted to 1000%.
A polymer solution was applied by spin coating to a substrate formed to a thickness of Δ and further formed with a transparent electrode containing ln203 as a main component (with a mask material printed on the terminal portion). After removing the mask material, 2
The ring was closed by heating at 50 qo for 1 hour to form an alignment film having a thickness of 800 A having a polyimide resin. Thereafter, a rubbing operation was performed in a certain direction to print a glass frit around the substrate, and it was baked at 4500° for 30 minutes to form an element. The results are shown in the table, and alignment defects and induced domains occurred.

[Brief explanation of drawings]

Figure 1 is a thermogravimetric analysis curve diagram of the polymer used for the alignment film.
FIG. 2 is a film thickness reduction curve diagram due to the alignment film being left at high temperatures. 1... Conventional example, 2... Present invention. Tsutomu diagram *Z diagram

Claims (1)

[Claims] 1. A liquid crystal display element in which a liquid crystal layer is interposed between two glass substrates arranged in parallel, at least one of which has a transparent conductive film, wherein the conductive film and the liquid crystal layer are arranged in parallel. In between, the unit structure which is a reactant of (a) diamine compound, (b) diaminomonoalkoxycarbonylamino compound, and (c) tetracarboxylic dianhydride compound has the following general formula ▲ Numerical formula, chemical formula, table, etc. Yes▼ (In the formula, Ar_1 is a diaminomonoalkoxycarbonylamino compound residue, Ar_2 is a diamine compound residue, A
r_3 is a tetracarboxylic dianhydride residue. 1.) A liquid crystal display element comprising a polyimide-benzimidazopyrrolone copolymer resin film layer shown in ) and whose periphery is sealed.