JPS581765B2 - liquid crystal display element - Google Patents

Description

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

Conventionally, in liquid crystal cells, particularly in nematic liquid crystal display elements that operate under the action of an electric field and utilize electro-optic effects, inorganic materials such as vapor deposited SiO 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 Schiff-type liquid crystals and biphenyl-type liquid crystals even when glass frit sealing is performed. 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,
Resorcin resin, furan resin, polyvinyl chloride, polyvinyl acetate, polymethyl methacrylate, polystyrene,
Polyvinyl butyrate, polysulfone, polyamide, polycarbonate, polyacetal, polyethylene, cellulose resin, natural rubber, styrene-butadiene rubber
Acrylic nitrile-butadiene rubber, polybutadiene,
Polyisoprene, mercapto silane coupling agent,
Epoxy silane coupling agent, amine silane coupling agent, viscose rayon, polymethyl α-
Examples include cyanoacrylate.

However, such polymer films cannot be said to have sufficient uniformity in melt crystal orientation, and long-term current tests and deterioration tests have shown that the orientation is more non-uniform than inorganic insulating films. The problem is that the number of liquid crystal display elements tends to increase, and that there is considerable variation 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 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 0° C., alignment defects are likely to occur when liquid crystal is sealed.

In particular, induced domains (areas with different viewing angles appear when electricity is applied) are generated, 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 i starts to lose weight at around 400°C, and the weight loss rate is also greater than that of the present invention 11. .

The alignment film used for liquid crystal display elements is normally not preferable to be formed to the thickness used for an insulating film (several μm or more) because the electrical response will be poor;
It is essential to use the film at a thickness of about 2000 Å.

In this way, it is thought that because the surface of the alignment film is rubbed in one direction with a 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, it is necessary to ensure that heating loss does not occur above 400°C.
The material must be as small as possible.

Furthermore, as shown in FIG. 2, the film thickness of conventional polyimide III is greatly reduced by being left at high temperatures, making it 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 molten crystal elements, but also lack sufficient mechanical strength of the elements.

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

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 liquid crystal display element of the present invention uses diaminomonoamide compounds and tetracarboxylic dianhydrides as raw materials in order to improve the weight loss starting temperature and reduce heating loss compared to conventional alignment films made of polyesterimide, polyamideimide, polyimide, etc. A polyimidoisoindo-quinazolinedione polymer resin having a quinazoline term structure, general formula (wherein, Ar1 is a diaminomonoamide compound residue, Ar
2 is a tetracarboxylic dianhydride residue.

) is formed by forming an alignment film of a polymer layer.

The polyimide isoindo-quinazolinedione polymer used in the present invention contains 1,
4-diaminobenzene-2-carbonamide, 4,4'
-diaminodiphenyl ether-3-carbonamide, etc., and as tetracarboxylic dianhydride compounds, romellitic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, etc. Can be used.

In addition, as organic solvents, N-methyl-2-pyrrolidone, N-methyl-2-pyrrolidone,
, N-dimethylacetamide, etc. can be used.

The diaminomonoamide compound and the tetracarboxylic dianhydride react rapidly even at low temperatures 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 the experimental result that a polymer resin film on a film such as SiO2 has a comparatively smaller loss on heating than the polymer resin film on a glass substrate.

Insulating films that exhibit this effect include SiO2 and SiO2.
Examples include a 2-Al2O3 mixed film.

In forming the alignment film used in the present invention, no special consideration is required in handling the polymer solution; brush coating, dipping, spin coating, etc.
This is done by printing or other conventional means, and after the film has hardened, it is further rubbed with cloth, gauze, etc.

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

Examples of such silane coupling agents include γ-aminopropyltriethoxysilane, γ-glycidoxypyltrimethoxysilane, and the like.

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.

As the liquid crystal compound sealed in the display element of the present invention, a mixture of --CN), (3) an azoxy type liquid crystal (for example, a compound), etc. can be used.

All are mixtures of two or less components.

The liquid crystal display element of the present invention does not generate induced domains even when used with a frit seal, and has excellent durability even when energized for a long time.

Example 1 4,4'-cyamino diphenyl ether-3-carbonamide (100 mol%) and pyromellitic dianhydride (5
0 mol%) and 3,3',4,4'-benzophenonetetracarboxylic dianhydride (50 mol%) and N-methyl-
2-pyrrolidone was placed in a flask and stirred at 15-20°C for 7-8 hours.

A 15% copolymer solution with a viscosity of 15000 cp at 25°C was obtained.

This solution was diluted to 30%, and an inorganic film of SiO2 was coated with 120% in advance.
The polymer solution was applied by spin coating onto a substrate formed to a thickness of 0.00 Å, on which a transparent electrode mainly composed of In 2 O 3 was formed, and a mask material was printed on the terminal portion.

After removing the mask material, ring closure was carried out by heating at 250° C. for 1 hour to form an alignment film of polyimide-isoindo-quinazolinedione polymer resin to a thickness of 800 Å.

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.
An element was formed by firing at 450° 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 epoxy resin to produce a liquid crystal element.

The alignment performance of these devices was investigated using induced 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 for 1000 hours at 70℃RH95%,
A display element with excellent alignment characteristics without any change in alignment was obtained.

450°C Frit Seal Example 2 4,4'-diaminodiphenyl ether-3-carbonamide (100 mol%) and pyromellitic dianhydride (7
0 mol%), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (30 mol%) and N-methyl-2-pyrrolidone were reacted at 15°C for 7 hours to give a 25°C viscosity of 20%. ,000 cp of a 15% polymer solution was obtained.

This solution was diluted to 4%, a mask material was printed on the terminal part of the In203 transparent electrode, the polymer solution was applied by spin coating, and after the mask material was removed, the ring was closed by heating at 250°C, and the polyimide-isoindo An alignment film containing a quinazolinedione polymer resin was formed to a thickness of 1200 Å.

Hereinafter, a device was prepared in the same manner as in Example 1, and the orientation was examined by measuring the induced domain width.

The results are shown in the table above.

Example 3 0.05% of γ-aminopyrtriethoxysilane was further added to the polymer solution of Example 1 to form devices, and each liquid crystal was injected.

The results are shown in the table.

Example 4 0.1% of γ-glycidoxypropyltrimentoxysilane was further added to the polymer solution of Example 2 to form devices, and each liquid crystal was injected.

The results are shown in the table.

Example 5 4,4'-diaminodiphenyl ether-3-carbonamide (70 mol%) and 1,4-diaminobenzene-2
-Carbonamide (30 mol%), topyromellitic dianhydride (50 mol%), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (50 mol%) with N,N
-Dimethylacetamide at 15°C for 7 hours to obtain a 15% polymer solution with a viscosity of 25000 cp at 25°C.

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-diaminobenzene-2-carbonamide (50
mol%) and 4,4'-diaminodiphenyl ether-3
-Carboxamide (50 mol%), pyromellitic dianhydride (30 mol%), 3.3',4,4'-benzophenonetetracarboxylic dianhydride (70 mol%) with N-methyl- React in 2-pyrrolidone at 15°C for 7 hours,
A 15% copolymer solution with a viscosity of 22,000 cp at 25°C was obtained.

This solution was diluted to 3%, and an inorganic film of S1O2 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, and a polymer solution is applied using a spin coating method. After removing the mask material, The ring was closed by heating at 250°C for 1 hour to form an alignment film of polyimide-isoindo-quinazolinedione polymer resin with a thickness of 1000 Å.
It was formed to a thickness of .

The results are shown in the table.

Example 7 1,4-diaminobenzene-2-carbonamide (10
0 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. , a 15% polymer solution with a viscosity of 24,000 cp at 25°C was obtained.

This solution was diluted to 4%, and an alignment film having a thickness of 1500 Å was formed using the same steps 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-isoindo-quinazolinedione polymer resin of the present invention does not generate induced domains and has extremely excellent display characteristics.

Comparative Example 4,4'-diaminodiphenyl ether (1.00 mol%), pyromellitic dianhydride (100 mol%) and N
-Methyl-2-pyrrolidone and N,N-dimethylacetamide were stirred at 15°C for 7 hours, and the viscosity at 25°C was 200.
A 15% polymer solution of 00 cp was obtained.

This solution was diluted to 3%, and an inorganic film of SiO2 was diluted to 1000%.
A polymer solution was applied by a spin coating method to a substrate (with a mask material printed on the terminal portion) formed to a thickness of 1.5 Å, and on which a transparent electrode mainly composed of In2O3 was formed.

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 Å.

Thereafter, a rubbing operation was performed in a certain direction to print a glass frit around the substrate, and it was baked at 450° C. for 30 minutes to form an element.

The results are shown in the table, and poor orientation 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. i, iii... conventional example, ii, iv... present 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, the general formula (where Arl is a diaminomonoamide compound residue, Ar
2 is a tetracarboxylic dianhydride residue. 1. A liquid crystal display element characterized in that it has a polyimide-iso-indo-quinazolinedione polymer resin film layer shown in ) and is sealed around the periphery.