JPS5944604B2 - liquid crystal display element - Google Patents

Description

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

10 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 obliquely deposited films of silicon dioxide have been mainly used as alignment films.

The reason is that these inorganic films are
Since it does not dissolve in 5, it does not have any adverse effects, and it also has the advantage of being able to uniformly align Schiff type liquid crystals, biphenyl type liquid crystals, etc. However, this obliquely deposited film of silicon dioxide also has a problem in that the Nesa pattern is noticeable. Ivy. On the other hand, a liquid crystal display element has been developed in which an organic polymer material is used for an alignment film and alignment treatment is performed by rubbing with a cloth or the like.

However, when most organic polymer materials are used as alignment films, it is difficult to obtain sufficient uniformity of liquid crystal alignment25, and due to long-term deterioration due to electrical current, non-uniformity of alignment occurs. It has the disadvantage that it tends to increase.

Among conventional organic polymer materials, polyimide 30 can be mentioned as a material that forms an alignment film with relatively excellent alignment properties. The polyimide obtained by the condensation of -diaminodiphenyl ether and pyromellitic dianhydride is quite good in terms of uniformity of orientation and durability in a deterioration test.

However, such a polyimide film undergoes significant browning due to the influence of heating during solvent removal and dehydration ring closure, so the liquid crystal display element after encapsulating the liquid crystal becomes brownish, and at the same time, the field of view becomes dark. Furthermore, there was a problem in that the contrast deteriorated and the function as a display element, especially the requirement for high quality display, was not met. Furthermore, in recent years, with the increasing demand for liquid crystal cells having a structure in which two or more liquid crystal layers are laminated via a transparent substrate, coloring has become a problem with conventional polyimide alignment films.

The present invention has been made in view of the current situation, and its purpose is to provide a liquid crystal display element that does not become colored even when the solvent is removed or heated during dehydration and ring closure, has excellent transparency, and has no conspicuous Nesa pattern. There is a particular thing.

The present invention provides 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, in which (a ) General formula H2NHNOC-R-CONHNH2 (in the formula, R represents an aromatic compound or an aliphatic compound)
It is characterized by providing a membrane of a polymer obtained by condensing a dibasic acid hydrazide compound and (t)tetracarboxylic dianhydride represented by:

The inventors of the present invention have repeatedly investigated the causes of coloring and methods for solving the problem in order to reduce coloring, which has been a drawback of conventional polyimide films, and improve transparency.

As a result, they discovered that the cause of coloring of conventional polyimide films was due to the raw materials used in polyimide synthesis, especially diamine compounds, and by using dibasic acid hydrazide without using diamine compounds, they achieved extremely excellent transparency. Furthermore, the present inventors have discovered that it is possible to form an alignment film with an inconspicuous Nesa pattern, and have completed the present invention. The alignment film of the present invention is
Due to its high transparency, it is also excellent for use in multilayer liquid crystal display devices.

The dibasic acid hydrazide compounds used in the synthesis of the polyhydrazide polymer in the present invention include isophthalic acid dihydrazide, terephthalic acid dihydrazide, 4,4'-dihydrazide diphenyl ether, 4,4'-dihydrazide diphenyl sulfone, and 4,4'-dihydrazide diphenyl ether. ′-dihydrazide diphenyl,
4,4'-dihydrazidiphenylmethane, 4,4'-
Dihydrazide diphenyl benzoate, 4,4'-dihydrazide diphenyl sulfide, 3,3'-dihydrazide diphenyl sulfone, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide , suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, etc.
One or more types may be used.

Further, the tetracarboxylic dianhydride compound in the present invention includes pyromellitic dianhydride, 3,3',4,42-benzophenonetetracarboxylic dianhydride, 3,3',4
, 4'-diphenyltetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, 1,2,5,6-
Naphthalenetetracarboxylic dianhydride, 2,3,6,7
-naphthalenetetracarboxylic dianhydride, 2,3,5,
6-pyridinetetracarboxylic dianhydride, 1,4,5,
8-Naphthalenetetracarboxylic dianhydride, 3,49,
10-perylenetetracarboxylic dianhydride, 4,4'-
Examples include disulfonyl diphthalic dianhydride, which may be used alone or in combination of two or more.

In the synthesis of the polyhydrazide polymer in the present invention, the above-mentioned dibasic acid hydrazide and tetracarboxylic dianhydride,
Condensation is carried out by stirring in a conventional organic solvent at a temperature of about 10° C. for several hours. The produced polymer solution was diluted to a concentration of about 5 to 10% by weight, and the concentration was about 150 to 300%.
A polymer film can be formed by heating to a temperature of .degree. C. to remove the solvent and close the ring. Organic solvents used in this reaction include N-methyl-2-pyrrolidone, N-methyl-2-pyrrolidone,
, N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide hexamethylphosphoramide, and the like are suitable. In forming the alignment film, no special consideration is required when handling the polymer solution prepared as described above, and it can be carried out by brush coating, dipping, spin coating, printing, or other conventional means. The alignment film of the present invention can be formed directly on a substrate provided with a conductive layer, but an even more excellent liquid crystal display element can be obtained by using one in which an inorganic insulating film is provided below or above the conductive layer. be able to.

This is because it has been confirmed through experiments that the force formed on the inorganic insulating film can prevent thermal deterioration during curing due to sodium ions in soda glass, rather than forming it directly on a glass substrate with a conductive layer. Films of SiO2, Al2O3, and TiO2 are suitable as inorganic insulating films exhibiting such effects. Furthermore, in the present invention, one or more of epoxy-based and amino-based silane coupling agents may be used in order to obtain a stronger alignment film.
Examples of the silane coupling agent include γ-aminopropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane. In application, it may be added dropwise into the above polymer solution, or an alignment film may be further formed on top of the silane coupling agent film. Examples of the liquid crystal sealed in the liquid crystal display element of the present invention include the following.

These are usually applied as a mixture of two or more components. For example, (1) a mixture of -1Zite)1-1(δ)-1CN as a biphenyl type liquid crystal, (2) a mixture of B-<○>-CN as an ester type liquid crystal, and (3) a cyclohexane type liquid crystal. There is an I mixture.

Next, the present invention will be explained by examples.

Example 1 0.1 mol of isophthalic acid dihydrazide, 0.1 mol of pyromellitic dianhydride and N-methyl-2-pyrrolidone were placed in a flask and stirred at 5°C for 3 hours to give a solution with a viscosity of 8500 cp1 and a concentration of 12 at 25°C. A wt % polymer solution was obtained.

This solution was diluted to 7% by weight, an oriented film of the polymer solution was formed using an offset printing machine, and heated for 1 hour to remove the solvent and close the ring.
A film with a thickness of 1500 was obtained.

After that, rub in a certain direction with a cotton cloth, and
The device was fabricated using an epoxy resin seal. Elements are formed in this way, and the liquid crystal (1) is applied to these elements.
After separately injecting each of the biphenyl type liquid crystal, (2) ester type liquid crystal, and (3) cyclohexane type liquid crystal, each injection port was sealed with an epoxy resin to produce a liquid crystal display element. The transmittance of these elements was measured using a spectrometer.

The obtained results are shown in the figure, and in all cases it was possible to produce high-quality elements with excellent transparency and inconspicuous Nesa patterns. Example 2 To the same polymer solution as in Example 1, γ-aminopropyltriethoxysilane (% by weight) was further added, an alignment film was formed in the same manner as in Example 1, and a liquid crystal display element was manufactured using a frit seal. The transparency and presence or absence of the Nesa pattern were investigated.

The results obtained are shown in FIG. Example 3 0.1 mol of isophthalic dihydrazide, 0.05 mol of pyromellitic dianhydride, 0.05 mol of 3,3',4,4'-benzophenonetetracarboxylic dianhydride and N,
Pour N-dimethylacetamide into a flask container and add 10
After reacting at ℃ for 5 hours, the viscosity at 25℃ was 10,000.
A polymer solution with a CP1 concentration of 14% by weight was obtained.

This solution was diluted to 5% by weight, an inorganic insulating film of SiO2 was formed in advance to a thickness of 1200λ, and a transparent electrode mainly composed of N2O3 was formed. , 1000, and 1500 were prepared. Thereafter, the same operations as in Example 1 were carried out to produce a device and its transparency was examined. The results obtained are shown in the figure.
Example 4 0.15% by weight of γ-glycidoxypropyltrimethoxysilane was further added to the same polymer solution as in Example 3, and an alignment film was formed in the same manner as in Example 3.

Afterwards, a liquid crystal display element was created using the organic seal and its transparency was examined. The obtained results are shown in the figure Example 5 0.05 mol of unsophthalic dihydrazide, 0.05 mol of terephthalic acid dihydrazide, 0.07 mol of pyromellitic dianhydride
0.03 mol of 3,3',4,4'-benzophenonetetracarboxylic dianhydride and N,N-dimethylformamide were placed in a flask and reacted at 5°C for 6 hours. Viscosity 9000CP1 concentration 12% by weight
A polymer solution was obtained.

This solution was diluted to 10% by weight, and an alignment film of the polymer solution was formed using an offset printing machine.
Heating for 500,100 hours to remove the solvent and close the ring.
A film with a thickness of 0.1500λ was obtained. Thereafter, a device was fabricated using an organic seal by rubbing in a certain direction with a cotton cloth, and its transparency was examined. The results obtained are shown in the figure.
Example 6 0.07% by weight of γ-glycidoxypropyltrimethoxysilane was further added to the same polymer solution as in Example 5, and the same operation as in Example 5 was performed to produce a device using a frit seal. We investigated its transparency.

The results obtained are shown in the figure. Example 7 A multilayer purchased liquid crystal display element was produced by stacking two sets of the liquid crystal display elements produced in Example 1, and its transparency was examined.

The results obtained are shown in the figure. Example 8 A multilayer structure liquid crystal display element was produced by stacking two sets of the liquid crystal display elements produced in Example 2, and its transparency was examined.

The results obtained are shown in the figure. Comparative Example 1 0.1 mol of 4,4'-diaminodiphenyl ether, 0.1 mol of pyromellitic dianhydride, and N,N-dimethylacetamide were placed in a flask and reacted with stirring at 10 to 15°C for 7 hours. , viscosity 15000c at 25°C
A polymer solution with a p1 concentration of 15% by weight was obtained.

This solution was diluted to 7 parts by weight and ring-closed by heating at 280°C to form alignment films with thicknesses of 500, 1000, and 1500λ. Hereinafter, an organic sealing element was prepared in the same manner as in Example 1, and its transparency was examined. The results obtained are shown in the figure. Comparative Example 2 A multilayer structure liquid crystal display element was produced by stacking two sets of the liquid crystal display elements produced in Comparative Example 1, and its transparency was examined.

The results obtained are shown in the figure. As is clear from the figure, all of the liquid crystal display elements having the alignment film of the present invention did not change color to yellowish brown, had excellent transparency, and were able to obtain high-quality liquid crystal display elements with no conspicuous Nesa pattern. .

Furthermore, it has become possible to maintain high transparency even in multilayer purchased liquid crystal display elements.

[Brief explanation of the drawing]

The figure is a curve diagram showing film thickness spectral transmittance characteristics. 1 to 8...Example 1 to Example 8, 9 and 10
...Comparative example 1 and comparative example 2.

Claims (1)

[Claims] 1. In a liquid crystal display element having a liquid crystal alignment film on a substrate on which electrodes are formed, the alignment film has the following structure: (a) general formula H_2N
A liquid crystal display comprising a polymer of a dibasic acid hydrazide compound represented by HNOC-R-CONHNH_2 (in the formula, R represents an aromatic compound or an aliphatic compound) and (b) tetracarboxylic dianhydride. element. 2. A liquid crystal display according to claim 1, characterized in that (a) the dibasic acid hydrazide compound is phthalic acid dihydrazide and (b) the tetracarboxylic dianhydride is aromatic tetracarboxylic dianhydride. element.