JPS5821245B2 - 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 SiO vapor deposited films have been mainly used as alignment films.

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 they also have the advantage of being able to uniformly align thick-type liquid crystals and biphenyl-type liquid crystals even when glass frit sealing is applied. 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, phenol resin, epoxy resin, alkyd resin, urethane resin,
Resorcinol resin, furan resin, polyvinyl chloride, polyvinyl acetate, polymethyl methacrylate, polystyrene,
Polyvinyl butylade, polysulfone, polyamide, polycarbonate, polyacetal, polyethylene, cellulose resin, natural rubber, styrene-butadiene rubber,
Acrylonitrile-butadiene rubber, polybutadiene,
Polyisoprene, mercapto silane coupling agent,
Epoxy silane coupling agent, amine silane cassoplating agent, viscose rayon, poly-methyl-α-
Examples include cyanoacrylate.

However, such polymer films cannot be said to have sufficient uniformity in liquid crystal alignment, and the non-uniformity in alignment tends to increase more easily than inorganic insulating films due to long-term current tests and deterioration tests. A drawback is that considerable variation occurs among individual liquid crystal display elements.

Further, although the glass frit seal is heated to 400° C. to 450° C., it has insufficient heat resistance, so the alignment film is destroyed and the liquid crystal is not aligned.

. Next, other heat-resistant polymeric 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 orientation uniformity and durability in long-term current tests and deterioration tests when organic seals are used. be.

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 0°C, alignment defects are likely to occur when liquid crystal is sealed.

In particular, it is difficult to obtain a liquid crystal display element with stable display characteristics due to the occurrence of induced domains (areas with different viewing angles appear when electricity is applied).

The reason for this is that when the thermogravimetric analysis curve is measured as shown in FIG. 1, conventional polyimide 1 begins to lose weight at around 400°C, and its weight loss rate is larger than that of polyimide 11 of the present invention.

The alignment film used for liquid crystal display elements is usually 400λ to 400λ, because it is not preferable to form the film thickness (several μm or more) used for an insulating film because the electrical response will be poor.
It is essential to use it at around 2000λ.

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 at 400°C or higher, heating loss must not occur at temperatures above 400°C.
The material must be as small as possible.

Further, as shown in FIG. 2, the film thickness of polyimide 111 decreases greatly when left at high temperatures, so it is difficult to maintain uniform orientation and induced domains are likely to occur.

On the other hand, at temperatures lower than 400° C., glass frit seals not only fail to achieve the precision of the element gap required for liquid crystal elements, but also lack sufficient mechanical strength of the elements.

At least 400°C or higher, preferably 430°C to 450°C
The frit should be sealed at °C.

Therefore, it is essential to improve the heat resistance of the alignment film.

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 properties and a very small induced domain.

The present inventor developed diamine compounds, diaminodialkoxycarbonylamino compounds, and tetracarboxylic dianhydrides in order to improve the weight loss initiation temperature and reduce heat loss compared to conventional alignment films made of polyesterimide, polyamideimide, polyimide, etc. An alignment film is formed using a polyimide-benzoylimidazopyrrolone copolymer resin film having a pyrrolone ring structure made from a polyimide resin, that is, a copolymer resin film layer consisting of the following unit structure A and unit structure B, and the surrounding area is I sealed it.

A; (In the formula of each unit structure, Ar, is a diaminodialkoxycarbonylamino compound residue, Ar2 is a diamine residue, and Ar3 is a tetracarboxylic dianhydride residue.

) A good liquid crystal display element with very small orientation and induced domains was produced even at 450°C.

The reason why such a good device can be manufactured is that the thermogravimetric analysis curve shown in FIG. 1 and the result of film thickness reduction when left at high temperature shown in FIG. This is thought to be due to the excellent heat loss properties.

The polyimide-benzimidazopyrrolone copolymer used in the present invention includes p-phenylenediamine and the like as a diamine compound, 3,3'-diamino-4,4'-')ethoxycarbonylamino diphenyl ether, and 1 as a diaminodialkoxycarbonylamino compound.・4-diamino-
2,5-jethoxycarbonylaminobenzene, etc. can be used, and as the tetracarboxylic dianhydride compound, pyromellitic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, etc. can be used. be.

In addition, as an organic solvent, N-methyl-2-pyrrolidone,
N.N-dimethylacetamide and the like can be used.

The ratio of the diamine compound to the diaminodialkoxycarbonylamino compound may be selected from the range of 95 to 5 mol% for the former and 5 to 95 mol% for the latter.

In addition, the optimal ratio of the tetracarboxylic dianhydride pyromellitic anhydride and 3,3',4,4'-benzophenone tetracarboxylic dianhydride is 70 to 30 mol%,
The latter may be selected from the range of 30 to 70 mol%.

In addition, the mixture of the diamine compound, the diaminodialkoxycarbonylamino compound, and the mixture of the tetracarboxylic dianhydride is optimally equimolar.

A diamine compound, a diaminodialkoxycarbonylamino 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 it is practiced on a substrate with an inorganic insulating film provided below or above the electrode layer □.

This is more than 5i02 than the copolymer resin film on the glass substrate.
This is based on the experimental results that the loss on heating is comparatively smaller when using a copolymer resin film on a film such as .

Insulating films that exhibit this effect include SiO□, 5i0
Examples include a 2-Al2O2 mixed film.

In order to form the alignment film used in the present invention, there is no need for special consideration in handling the polymer solution, and it can be applied by brush coating, dipping, spin coating, etc.
This is done by printing or other conventional means, and after the film has hardened, it is rubbed with cloth, gauze, etc.

This allows frit sealing to be performed at 450° C. to form a liquid crystal display element.

In the present invention, in order to obtain an alignment film with even stronger adhesion, one or more types of epoxy-based and amine-based silane coupling agents can be used in combination.

As such a silane cassilling agent, for example, γ
Examples include -aminopropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane.

As is well known, in a liquid crystal display element, it is necessary to expose the terminal parts at the periphery of the two substrates and connect them to the external conductor, but the present invention also uses the commonly used means for etching the terminal parts of the alignment film. For example, this can be carried out by printing a mask resist on the terminal portion and removing it after forming the polymer resin film, or by using oxygen plasma.

The liquid crystal compound sealed in the display element of the present invention includes (1
) Schiff type liquid crystal (for example, a compound), (2) biphenyl type liquid crystal (for example, (3) azoxy type liquid crystal (for example, (4) ester type liquid crystal (for example, (5) cyclohexane type liquid crystal (for example, a compound), 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 13,3'-diamino-4,4'-jethoxycarbonylamino diphenyl ether (5 mol%), paraphenylene diamine (95 mol%), pyromellitic dianhydride (50 mol%), and 3.3 ',4,4'-benzophenonetetracarboxylic dianhydride (50 mol%) and N-methyl-2-pyrrolidone were placed in a flask, and the
Stirred at <0>C for 7-8 hours.

A 15% copolymer solution with a viscosity of tsooocp at 25°C was obtained.

This solution was diluted to 3% and a 5i02 inorganic film was coated with 12%
A polymer solution was applied by spin coating onto a substrate on which a transparent electrode containing In2O3 as a main component was formed and a mask material was printed on the terminal portion.

After removing the mask material, ring closure was performed by heating at 250° C. for 1 hour to form an alignment film of polyimide-benzimidazopyrrolone copolymer resin to a thickness of 800 mm.

After that, a rubbing operation is performed with a cotton cloth in a certain direction, a glass frit is printed around the substrate, and the two substrates are combined.
A device was formed by firing at 50° C. for 30 minutes.

These elements include Schiff type liquid crystal (1), biphenyl type liquid crystal (2), azoxy type liquid crystal (3), and ester type liquid crystal (4).
, cyclohexane type liquid crystal (5) were injected separately, and then each injection port was sealed with an epoxy resin to produce a liquid crystal element.

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.

Also, even if left at 70℃RH95% for 1000 hours,
A display element with excellent orientation without any change in orientation could be produced.

Example 2 3,3'-diamino-4,47-jethoxycarbonylaminodiphenyl ether (50 mol%), paraphenylenediamine (50 mol%), and pyromellitic dianhydride (70 mol%), 3,3'・4,4'-benzophenonetetracarboxylic dianhydride (30 mol%) was reacted in N-methyl-2-pyrrolidone at 15°C for 7 hours to give 25
A 15% copolymer solution having a temperature of 21,000 cp and a viscosity of 21,000 cp was obtained.

This solution was diluted to 4%, a mask material was printed on the terminal part of the In2O3 transparent electrode, and the polymer solution was applied by spin coating.
After removing the mask material, ring closure was performed by heating at 250° C. to form an alignment film having a thickness of 1,200 wafers having a polyimide-benzimidazopyrrolone copolymer resin.

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 above.

Example 3 0.05% of γ-aminopropyltriethoxysilane was further added to the copolymer solution of Example 1 to form an element,
Each liquid crystal was injected.

The results are shown in the table.

Example 4 0.1% of γ-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-4,4'-jethoxycarbonylaminodiphenyl ether (95 mol%), paraphenylene diamine (5 mol%), and pyromellitic dianhydride (
50 mol%) and 3,3',4,4'-benzophenonetetracarboxylic dianhydride (50 mol%) were reacted in N-N-dimethylacetamide at 15°C for 7 hours to obtain 25
A 15% copolymer solution with a viscosity of 24000 cp at °C was obtained.

This solution was diluted to 3% and an alignment film having a thickness of 1000 mm was formed using the same process as in Example 1.

The results are shown in the table.

Example 6 1,4-diamino-2,5-jethoxycarbonylaminobenzene (50 mol%) and paraphenylenediamine (
50 mol%) and pyromellitic dianhydride (30 mol%)
, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (70 mol%) was reacted in N-methyl-2-pyrrolidone at 15°C for 7 hours to obtain a viscosity of 230°C at 25°C.
A 15% copolymer solution of 00 cp was obtained.

This solution was diluted to 3% and a 5i02 inorganic film was diluted to 1000%.
A mask material is printed on the terminals of a substrate formed to a human thickness and a transparent electrode mainly composed of In2O3 is formed, a polymer solution is applied by spin coating, and after removing the mask material,
The alignment film containing the polyimide-benzimidazopyrrolone copolymer resin was heated to 1000λ by heating at 250°C for 1 hour to close the ring.
It was formed to a thickness of .

The results are shown in the table.

Example 7 1,4-diamino-2,5-jethoxycarbonylaminobenzene (10 mol%) Tohalaphenylenediamine (
90 mol%) and pyromellitic dianhydride (50 mol%)
, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (50 mol%) was reacted with N-methyl-2-pyrrolidone in N-N-dimethylacetamide at 15°C for 7 hours to obtain 25 A 15% copolymer solution with a viscosity of 25000 cp at °C was obtained.

This solution was diluted to 4% and an alignment film having a thickness of 1500 mm was formed using the same process as in Example 6.

Thereafter, a rubbing operation was performed in a certain direction, a glass frit was printed, 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 element 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 stirred in N-methyl-2-pyrrolidone and N-N-dimethylacetamide at 15°C for 7 hours, and the viscosity at 25°C was 20,000.
A 15% polymer solution of cp was obtained.

This solution was diluted to 3%, and an inorganic film of SiO2 was diluted to 1000%.
A substrate with a transparent electrode made of I'n203 as the main component (printed with a mask material on the terminal part) to a human thickness.
The polymer solution was applied by spin coating.

After removing the mask material, ring closure was performed by heating at 250° C. for 1 hour to form an alignment film having a polyimide resin with a thickness of 800 mm.

Thereafter, a rubbing operation was performed in a certain direction, a glass frit was printed around the substrate, and an element was formed by baking at 450° C. for 30 minutes.

The results are shown in the table, and poor orientation and induced domains were observed.

[Brief explanation of drawings]

FIG. 1 is a graph showing a thermogravimetric analysis curve of a polymer used for the alignment film at a temperature of 0.degree. i, iii... Conventional example, ii, iv・
...This invention.

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, there is a polyimide-benzimidazopyrrolone copolymer resin film layer which is a reaction product of (a) a diaminodialkoxycarbonylamino compound, (b) a diamine compound, and (e) a tetracarboxylic dianhydride compound, A liquid crystal display element characterized by a sealed periphery.