JPH05264998A - Oriented film - Google Patents

Abstract

PURPOSE:To obtain the oriented film which has excellent orientability of a liquid crystal, is homogeneous in spite of the thick film, does not crack, has good moisture resistance and power to prevent the elution of alkaline ions, etc., from a substrate and is suitable for mass production. CONSTITUTION:The oriented film consisting of a polysilazane film formed under a non-water condition is constituted. The 'non-water condition' refers to the absence of water and the condition under which water is not formed. The peak of the IR absorption spectra of the polysiloxane film formed in the presence of the water or under the condition under which the water is formed exists in a range from 3200 to 3600cm<-1> wave number where the water exists but the peak of the polysilazane film used as the oriented film does not substantially exist in the range of the wave number. The polysilazane film is obtd. by applying an org. solvent soln. of a silazane compd. on, for example, the solid surface, then subjecting the coating to a heating treatment.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel alignment film, and more specifically, to give excellent alignment properties to liquid crystals,
The present invention relates to an alignment film which does not cause cracks even in a thick film, has a good moisture resistance and an ability to prevent elution of alkali ions from a substrate, is suitable for mass production, and is preferably used for a liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been used for calculators, watches and the like, and their applications have been expanded to information processing as displays for dot matrix display.

This liquid crystal display device generally has an electrode and an alignment film inside a pair of substrates, and has a structure in which a liquid crystal is sealed inside. A liquid crystal display device normally uses electrodes. This is performed based on the principle that a voltage is applied to change the alignment form of the liquid crystal, and as a result, the amount of light transmitted through the substrate is changed. Therefore, the orientation of the liquid crystal plays an extremely important role in the performance of the liquid crystal display device.

Conventionally, it is known that the orientation of liquid crystal is greatly influenced by the orientation film in contact with it, and therefore various orientation films have been developed and put to practical use. This alignment film can be generally classified into an organic alignment film and an inorganic alignment film. As the organic alignment film, an alignment film made of, for example, a polyimide resin or polyvinyl alcohol is known.

However, an alignment film made of a polyimide resin has a drawback that it is necessary to cure at a high temperature of 200 ° C. or higher, and the substrate is necessarily limited to one having good heat resistance. Further, although the alignment film made of polyvinyl alcohol does not require high temperature curing, it has a drawback that the liquid crystal alignment property is poor in sustainability and the transmitted light amount easily changes with time.

On the other hand, as the inorganic alignment film, an alignment film formed by the SiO oblique vapor deposition method is known as a typical one. However, although this alignment film has excellent heat resistance, it has drawbacks such as poor homogeneity and lack of mass productivity.

An alignment film formed by rubbing a polysiloxane film formed from a coating solution obtained by hydrolyzing a halogenosilane or an alkoxysilane is also known. However, although this alignment film is suitable for mass production, it has hygroscopicity, easily absorbs moisture in the atmosphere, and if a thick film is formed, cracks easily occur, and the homogeneity becomes insufficient. It has drawbacks such as inferior effect of preventing elution of alkaline components from the substrate.

[0008]

DISCLOSURE OF THE INVENTION The present invention overcomes the drawbacks of the conventional alignment film for liquid crystal as described above, is excellent in the alignment property of the liquid crystal, is uniform in a thick film, and does not cause cracks. In addition, it is made for the purpose of providing an alignment film for liquid crystal suitable for mass production, which has good moisture resistance and good ability to prevent solutions such as alkali ions from the substrate, does not require high-temperature curing at 200 ° C or higher. Is.

[0009]

The inventors of the present invention have conducted extensive studies to develop an alignment film having excellent properties, and as a result, a polysilazane film formed under non-aqueous conditions can achieve the object. Based on this finding, the present invention has been completed.

That is, the present invention provides an alignment film composed of a polysilazane film formed under non-aqueous conditions.

The term "non-aqueous conditions" as used in the present invention means the absence of water and the conditions without water formation. In the infrared absorption spectrum of the polysiloxane film formed in the presence of water or under the condition that water is produced, a peak exists in the wave number range of 3200 to 3600 cm ⁻¹ due to the presence of water. The polysilazane film used as the alignment film of the present invention has substantially no peak in the wave number range.

A polysilazane film having such characteristics is
For example, it can be obtained by applying a solution of a silazane compound in an organic solvent to a solid surface and then heat-treating the solution. This silazane compound is a general term for compounds having a Si—N bond in the molecule, but in the present invention, it is preferable to use a silazane compound containing no oxygen atom in the molecule.

Such silazane compounds can be obtained by reacting halogenosilane or organohalogenosilane with ammonia or amines in an organic solvent. Examples of the halogenosilane used at this time include SiCl ₄ , HSiCl ₃ , H ₂ SiCl ₂ , and H ₃ SiC.
1 and the like, and examples of the organohalogenosilane include CH ₃ SiHCl ₂ and CH ₃ S.
iH ₂ Cl, CH ₃ SiCl ₃ , (CH ₃ ) ₂ SiCl
₂ , (CH ₃ ) ₃ SiCl, C ₂ H ₅ SiCl ₃ , (C
_{2 H 5) 3 SiCl, (} C 2 H 5) (C 6 H 5) SiCl 2,
_{(C 2 H 5) (C} 6 H 5) 2 SiCl, (CH 3) 3 CSiH
Cl ₂ , (CH ₃ ) ₂ CHSiHCl ₂ , (C ₆ H ₅ ) SiH
_{Cl 2, (C 6 H 5} ) SiCl 3, (C 6 H 5) 2 SiC
_{l 2, (C 6 H 5} ) 3 SiCl, C 6 H 5 CH 2 SiC
_{l 3, (C 6 H 5} CH 2) 2 SiCl 2, (C 6 H 5 CH
₂ ) ₃ SiCl and the like.

On the other hand, examples of amines to be reacted with these halogenosilanes and organohalogenosilanes include lower alkylamines such as monomethylamine, ethylamine, propylamine and butylamine, polyamines such as ethylenediamine, aralkylamines such as benzylamine and phenethylamine. And so on.

Examples of the organic solvent used in these reactions include toluene, xylene, diethyl ether,
Examples include dichloromethane.

A particularly suitable silazane compound is obtained by dissolving a halogenosilane such as HSiCl ₃ , H ₂ SiCl ₂ or H ₃ SiCl in the above organic solvent and blowing ammonia gas into the solution.

In the present invention, the reaction mixture of the halogenosilane or organohalogenosilane thus obtained and ammonia or amines may be used as it is as a coating solution, or the reaction mixture may be distilled under reduced pressure. The solvent can be removed by to recover the desired silazane compound as an oily substance or a solid substance, and this can be dissolved in an appropriate organic solvent to obtain a coating liquid.

Examples of the organic solvent in this case include methanol, ethanol, propanol, butanol, cyclohexanol, benzyl alcohol, dimethylolbenzene, furfuryl alcohol, tetrahydrofurfuryl alcohol, diacetone alcohol, ethylene glycol monoalkyl ether, and diethylene glycol. Alcohols such as monoalkyl ether, triethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, acetic acid alkyl ester, diethylene glycol monoalkyl ether acetate, triethylene glycol monoalkyl ether acetate,
Propylene glycol monoalkyl ether acetate, acetoacetic acid ethyl ester, lactic acid alkyl ester, benzoic acid alkyl ester, benzyl acetate,
Esters such as glycerin diacetate, acetone,
Ketones such as methyl ethyl ketone, cyclohexanone, acetylacetone, isophorone, diethyl ketone, methyl isobutyl ketone, methyl n-butyl ketone, acetonyl acetone, n-pentane, n-hexane, isohexane, n-heptane, n-octane, isooctane,
Hydrocarbons such as benzene, tonene, xylene, ethylbenzene, diethylbenzene, isopropylbenzene, and tetralin are included. These organic solvents may be used alone or in combination of two or more.

The coating liquid used for forming the alignment film of the present invention contains the silazane compound in an amount of 1 to 60% by weight, preferably 10 to 30% by weight, and has a viscosity at room temperature of 0.5 to 50%. Centipoise, preferably 1-20
Those in the range of centipoise are practically suitable. The viscosity can be adjusted by appropriately selecting the type and amount of the organic solvent according to the desired film thickness and the like.

For the alignment film of the present invention, the coating solution prepared as described above is applied onto a substrate provided with electrodes by a spinner method,
After being applied by a conventionally used means such as a spray method or a dipping method, a polysilazane film is formed by heat treatment at a temperature of about 100 to 200 ° C., and then a rubbing treatment is applied by an ordinary method to form the film. can do. The alignment film thus formed is a continuous film made of polysilazane having a film thickness of 0.2 to 3.0 μm, which is uniform and has a low hygroscopic property without cracks.

A gap agent is usually sprinkled on the substrate on which the alignment film is formed in this manner so as to maintain a constant distance when the two substrates are stacked. A liquid crystal cell is obtained by stacking two substrates so that the alignment films face each other, sealing the periphery with an epoxy resin or the like, and then injecting a liquid crystal.

Polarizing plates are provided above and below this liquid crystal cell so that light does not pass when no voltage is applied, and when a constant voltage is applied, light is transmitted by the alignment of the liquid crystal to produce a liquid crystal display. ..

[0023]

EFFECT OF THE INVENTION The alignment film of the present invention is excellent in the alignment property of liquid crystal, is homogeneous in a thick film, does not generate cracks, and has a good moisture resistance and an ability to prevent the elution of alkali ions from the substrate. Has characteristics such as suitable for mass production,
It is preferably used for liquid crystal display devices.

[0024]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

EXAMPLE A 20% by weight xylene solution of a reaction product of a halogenosilane and ammonia on a transparent electrode of a substrate provided with a patterned transparent electrode on a soda glass substrate, which is 20% by weight.
EFP [trade name, manufactured by Tonen Corporation] was uniformly applied at 3500 rpm using a spinner and heat-treated at 150 ° C. for 30 minutes to form a polysilazane film having a thickness of 0.3 μm. No cracks were observed on the surface of the polysilazane film thus obtained, and the film had a very high degree of homogeneity, and the effect of preventing the elution of the alkaline component from the substrate was confirmed. The presence of water could not be confirmed from the infrared absorption spectrum of the obtained polysilazane film.

Next, this polysilazane film was rubbed with a felt in a certain direction to prepare a substrate having an alignment film having an orientation property.

Alignment films of the two substrates thus prepared were arranged so as to face each other, and these substrates were provided at a predetermined interval and adhered with an adhesive to prepare a liquid crystal display element. Phenylcyclohexane-based liquid crystal was injected between the alignment films of this device, and the orientation of the liquid crystal was examined between the two orthogonal polarizing plates. As a result, extremely good orientation was exhibited.

Comparative Example In the examples, instead of TEFP, 152 g of tetraethoxysilane, 240 g of glacial acetic acid and 24 of methyl alcohol were used.
Except for using the solution obtained by adding 10 g of oxalic acid to a mixture with 0 g while stirring at room temperature and reacting with isopropyl alcohol to adjust the concentration to 5.9% by weight. Similarly, a polysiloxane film having a film thickness of 0.3 μm was formed on the transparent electrode of the substrate and subjected to rubbing treatment to prepare a substrate having an alignment film.

The orientation film thus obtained had poor homogeneity and was inferior in the effect of preventing the elution of alkaline components from the substrate.

Then, when a liquid crystal element was prepared in the same manner as in the example and the orientation was examined, the orientation was inferior to that in the example.

Claims (1)

[Claims] 1. An alignment film comprising a polysilazane film formed under non-aqueous conditions.