JPH01211724A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To improve coatability of an orienting material on a substrate and to form a uniform and smooth orienting film by admixing an organopolysiloxane compd. and/or an F-contg. surface active agent to the orienting material. CONSTITUTION:A liquid crystal display element is provided with an orienting film 4 consisting of a material contg. at least one kind of siloxane compd. and/or a surface active agent selected from a group of organopolysiloxane compds. and a group of F-contg. surface active agents. Thus, a uniform and smooth orienting film 4 is obtd. on a substrate even if the substrate is one considered to be difficult for forming uniform coating, with an orienting material such as those having a color filter 3 or light shielding film, etc., thereon, or those having unevenness on the surface, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides two substrates on which ordinary transparent electrodes coated with an alignment material are formed, facing each other so that their alignment directions are perpendicular to each other.
It is a liquid crystal display element with a liquid crystal sealed between them.
The present invention relates to a liquid crystal display element comprising an alignment film having excellent alignment properties and alignment stability, which is made of an alignment material that has excellent wettability and step coverage on a substrate surface.

[Conventional technology]

Conventionally, liquid crystal display elements, especially nematic liquid crystal display elements that utilize electro-optic effects that are dynamic due to the action of an electric field, have been produced by applying alignment materials made of various organic polymer materials onto a glass substrate provided with transparent electrodes. There is a structure in which the substrates are faced to each other so that the directions of rubbing are perpendicular to each other, and the liquid crystal is sealed between the substrates. Examples of organic polymer materials used for such purposes include fluororesin, polyvinyl alcohol, urea resin, melamine resin, phenol resin, polyester, silicone resin, epoxy resin, polyesterimide, polyamideimide, alkyd resin, and urethane. Resin, redulucin resin, furan resin, polyvinyl chloride, polyvinyl acetate, polymethyl methacrylate, polystyrene, polyvinyl alcohol, polysulfone, polyamide, polycarbonate, polyacetal, polyethylene,
Cellulose resin, natural rubber 11, styrene-butadiene rubber, acrylonitrile-butadiene rubber, polybutadiene, polyisoprene, mercapto-based silane coupling agent, epoxy-based silane coupling agent, amino-based silane coupling agent, viscose, poly- Examples include methyl-α-cyanoacrylate.

However, polymer films made from these materials cannot be said to have sufficient uniformity of liquid crystal alignment, and also cannot be said to have sufficient heat resistance and long-term stability of alignment.

For this reason, when uniformity of these orientations is strictly required, polyimide having excellent physical properties in these respects has been used. The method for manufacturing an alignment film using polyimide is as follows: (1) After applying a solution of polyamic acid, which is a precursor of polyimide, in a solvent using a spin code, printing, etc.
(2) A method in which a soluble polyimide dissolved in a solvent is coated by spin code, printing, etc., and then dried to form a polyimide alignment film. As a solvent, a polar solvent with strong dissolving power, such as NMP (N-methyl-2-pyrrolidone)
, DMAC (dimethylacetamide), DMF (dimethylformamide), DMSO (dimethylsulfoxide), etc. were used.

Problems to be Solved by the Invention] However, in conventional liquid crystal display elements equipped with an alignment film formed by the method described above, if dust, dirt, etc. are present on the substrate, repellency may occur during coating. However, there were manufacturing problems in that unevenness occurred and it was difficult to uniformly apply the alignment material. Furthermore, when applying an alignment material onto a substrate on which color filters, light shielding films, etc. are formed, similar problems arise depending on the materials of the color filters, light shielding films, etc. Furthermore, similar problems occur when the substrate itself has irregularities. For this reason,) the medium contains ethyl cellosolve (official name: ethylene glycol monoethyl ether), butyl cellosolve (official name: ethylene glycol monobutyl ether), ethyl cellosolve acetate (official name: ethylene glycol monoethyl ether acetate), butyl cellosolve acetate. (Ethylene glycol monobutyl ether acetate) and the like have been used to improve the applicability of alignment materials.

However, since there is a problem that the solubility of the alignment material in the solvent decreases when these are added, it is not possible to increase the amount of addition to an extremely large amount, and therefore there is a limit to the improvement of uniform coating properties through such improvements. Ta.

The present invention has been made in view of the above circumstances, and it is generally common to uniformly apply an alignment material to substrates on which color filters, light-shielding films, etc. are formed, substrates with uneven surfaces, etc. By realizing the formation of an even and flat alignment film using a substrate that is considered difficult,
An object of the present invention is to provide a liquid crystal display element with excellent alignment properties and alignment stability.

[Means to solve the problem]

In order to achieve the above object, the present inventors completed the present invention based on the knowledge that coating properties can be improved by using an alignment material to which an alkaline polysiloxane compound or a fluorosurfactant is added.

That is, the liquid crystal display element according to the present invention includes an alignment film made of a material containing at least one kind of siloxane compound and/or surfactant selected from the group of organopolysiloxane compounds and the group of fluorosurfactants. It is characterized by

This will be explained in detail below.

Examples of the organopolysiloxane compound used in the practice of the present invention include a polysiloxane polymer represented by the following general formula in which dialkylsiloxane units and oxyalkylene units appear alternately in a linear chain.

The organopolysiloxane compound has a weight average molecular weight (hereinafter referred to as "average molecular weight") of 1800 to . +
0000 can be used, and 3500 to 1
6000 is preferred.

In addition, examples of fluorinated surfactants include esters obtained by the reaction of perfluorinated carbonic acid and polyalkylene glycol, and the following esters obtained by the reaction of highly fluorinated alkanols or perfluorinated alkanols and polyalkylene gelylcols. Ether, etc., generally represented by 2, can be used.

General formula: (Co)p(ocyoH2□)+1OR Here, the fluorinated alkyl group Rf is preferably represented by the following general formula.

General formula Ch F zk, +c qII 2q The preferred average molecular weight of the fluorosurfactant is 300 to 350
0, but more preferably 450-2600.

In addition, as other fluorine-based surfactants, the number of carbon atoms containing 40% by weight (hereinafter referred to as "%") or more of fluorine and at least three or more terminal carbon atoms are sufficiently fluorinated. Acrylate or meccrylate containing Rf5 of 3 to 20 and polyoxyalkylene acrylate-1
- or polio; a copolymer with tosialkylene methacrylate-1, which is 25 to 25% depending on the weight of the Ilf group-containing acrylate-I monomer unit or the Rf group-containing methacrylate tomomonomer medium copolymer. 70% can be used. Here, the Rf group is a monovalent saturated aliphatic group, and may have a straight chain or a branched chain structure, and if the molecular weight is sufficiently large, a cyclic structure or a combination thereof. In addition, in order to provide a stable bond between fluorocarbon groups and to exhibit a sufficient effect, the number of carbon atoms in the Rf group is 3 to 20, preferably 6 to 12, and 40% or more, preferably It is desirable that fluorine atoms are bonded to 50% or more of the carbon atoms. If it is less than 40%, the effects of the present invention cannot be sufficiently exhibited. Further, it is preferable that the fluorine atom is localized at the terminal of the Rf group. In addition, R
Even if the number of carbon atoms constituting the f group is 2 or less, it is possible to increase the fluorine content by increasing the ratio of the Rflf-containing monomer to the copolymer, but since the absolute content of fluorine atoms is insufficient, Since fluorine in the polymer is not localized, the effects of the present invention cannot be fully exerted. Further, the terminal carbon atom of the Rf group must be sufficiently fluorinated. That is, the terminal of the Rf group is, for example, CF3CF2CF, -, and the radical is the general formula C7F.
2°. It must be a completely or almost completely fluorinated alkyl group as represented by + (n is an integer of 3 or more).

On the other hand, if the number of carbon atoms in the Rf group is north of 21, the solubility of the resulting copolymer in a solvent will be low if the fluorine content is high, and if the fluorine content is low, it will not bond to carbon atoms. In either case, sufficient effects cannot be achieved because the fluorine atoms are not sufficiently localized.

The soluble portion in the copolymer is a polyoxyalkylene group (OR') x, -011□C1+, -
1-C)■Cl1J)C11□---1-C1l(C1
h) C) 2 to 4 carbon atoms represented by l(C1h)--1, etc.
Preferably. The oxyalkylene units in the polyoxyalkylene group include pomopolymers of polyoxypropylene, polymers in which two or more oxyalkylenes are randomly distributed, linear or branched autodipropylene, and oxoethylene units or linear or branched oxyalkylene units. Branched oxypropylene units or oxoethylene units may exist as blocks. This polyoxyalkylene chain is 1
Alternatively, it may be bonded by two or more chain bonds, such as -S-, or may contain these in the molecule. Here, if a chain bond with a valence of 3 or more is used, a branched oxyalkylene unit can be obtained.

Further, when this copolymer is added to an alignment material, the molecular weight of the polyoxyalkylene group is preferably 250 to 2,500 in order to obtain the desired solubility.

The above-mentioned copolymer used in the present invention includes, for example, a fluoroaliphatic group-containing acrylate or a fluoroaliphatic group-containing methacrylate and a polyoxyalkylene acrylate or a polyoxyalkylene methacrylate, such as monoacrylate, diacrylate, or a mixture thereof. It can be produced by initial polymerization.

The molecular weight of the copolymer (polyacrylate oligomer) can be adjusted by adjusting the concentration and activity of the initiator, the monomer concentration, the polymerization reaction temperature, and the amount of a chain transfer agent such as a thiol compound such as n-octyl mercaptan. can be adjusted.

As an example of the copolymer, fluoroaliphatic group-containing acrylate Rf-R"
When COCII•CI+□ is copolymerized with polyoxyalkylene monoacrylate CH2=Cl1CO(OR')XOCH3, a copolymer having repeating units represented by the following general formula is obtained.

-(CH2-C)l-)-1-(CH2-CH-)-c
=oc=.

(OR’) x .

OR# l CH3Rf The above fluoroaliphatic group-containing acrylate is disclosed in U.S. Pat.
No. 803615, No. 2642416, No. 2826
No. 564, No. 3102103, No. 3282905
No. 33042'78. Commercially available hydroxypolyoxyalkylene materials can be used as the polyoxyalkylene acrylate and other useful acrylates used in the production of the above copolymer, and for example, the following are commercially available.

Product name “Pluronic” (manufactured by Asahi Denka Kogyo ■), “ADEKA Polyether” (manufactured by Asahi Denka Kogyo ■), “Carbowax” (manufactured by Glico Products) (
Glyc.

ProductsCo)], “Triton” (
Triton (Rohm & Haas)
and Haas Co.

(manufactured by Daiichi Kogyo Seiyaku)], "P, E, G" (manufactured by Daiichi Kogyo Seiyaku ■) These can be produced by reacting them with acrylic acid, methacrylic acid, acrylic chloride, or acrylic anhydride by a known method. Separately, polyochine alkylene diacrylate CH2=CHCOO(R'O)x C0C) produced by a known method
l=c)lzFor example C)+2 =C11COz(C2H
40)to(CJ60)zz(CzllJ)+.

When CHCl-1=C)12 is copolymerized with the above fluoroaliphatic group-containing acrylate, a polyacrylate copolymer having the following repeating units is obtained.

-(CH2-CH-)-1-(CI-12-CH-)-
c=o c=.

(OR') U.S. Patent No. 2,592,069, U.S. Patent No. 2,995
542, same No. 3078245, same No. 3081274
No. 3,291,843 and No. 3,325,163, and U.S. Pat. It is described in the specification of No. 3574791.

The copolymer used in the practice of the present invention is a copolymer of fluoroaliphatic group-containing acrylate or fluoroaliphatic group-containing meacrylate and polyoxyalkylene acrylate-1. ~70%
fluoroaliphatic group-containing monomer units.

If the fluoroaliphatic group-containing monomer unit is less than 25%, the effect will not be sufficient, and if it exceeds 70%, the solubility in the solvent will decrease, which is not preferable.

The average molecular weight of the copolymer used in the present invention is 2500~
100,000 is preferable; exceeding 100,000 is not preferable because the solubility in solvents decreases.

The copolymer used in the present invention contains 50 to 100% of the fluoroaliphatic group-containing acrylate to the fluoroaliphatic group-containing monomer units, and copolymerizes polyoxoalkylene acrylate monomer units that do not contain Rf groups. It is preferable that the amount is 15% or more based on the total weight of the polymer, and a copolymer of a fluoroaliphatic group-containing acrylate and polyoxyalkylene acrylate-1 is particularly preferable. When the fluoroaliphatic group-containing methacrylate-1. accounts for 50% or more of the fluoroaliphatic group-containing monomer unit, the solubility in the solvent decreases. In addition, polyoxyalkylene acrylate monomer units account for 15% of the total weight of the copolymer.
If it is less than that, pinholes are likely to occur in the alignment film.

The preferred blending ratio of the organopolysiloxane compound or fluorosurfactant used in the present invention is in the range of 0.0002 to 5%, and 0.001 to 5% relative to the alignment material (coating component excluding solvent). A range of 3% is more preferred. If the blending ratio of the organopolysiloxane compound or fluorosurfactant is less than 0.0002%, the effect will be insufficient, and if it exceeds 5%, the orientation will deteriorate.

[Effect]

In the present invention, since an organopolysiloxane compound and/or a fluorine-based surfactant are added to the alignment material, the wettability of the alignment material to the substrate and the step coverage are improved.
The alignment properties and alignment stability of an alignment film included in a liquid crystal display element are improved.

〔Example〕

SiO
An ITO film, which is a transparent electrode, is formed on a 1.1m+n thick soda glass substrate formed to a thickness of 130mm by a conventional method.
Form to a thickness of 0 people. This ITO film was etched using a conventional method, with a width of 0.2mm and a gap of 20μ between the electrodes.
A stripe electrode of m is formed.

Patent application No. 62-239777 (P87-2) is placed on the transparent electrode.
A striped color filter pattern is formed using an organic photosensitive composition containing the pigment described in 620). The shape of the color filter pattern is 0.2mm wide and 1.5mm thick.
It is μm.

On this color filter pattern, "PIX" (manufactured by Hitachi Chemical Co., Ltd.), which is a polyamic acid solution type alignment material, is applied by a conventional method. For PIX, the concentration of coating components in the solution is adjusted to 6% so that the film thickness after drying is 1000%. Further, the solvent is NMP.

Immediately after coating, the coating was uniform, but due to insufficient wettability of the alignment material to the color filter, repelling occurred from the edges of the color filter pattern, making it difficult to coat evenly and flatly. FIG. 2 shows a cross-sectional view of a liquid crystal display element obtained by such a conventional method. In the figure, 1 is a soda glass substrate on which SiO2 is formed, and a striped transparent electrode 2 is formed on the substrate 1.
A color filter 3 is formed on the transparent electrode 2, and an alignment film 4 is formed on the transparent electrode 2 and the color filter 3. As is clear from the figure, it can be seen that an uneven alignment film is formed.

On the other hand, when an alignment material containing 0.5% of a fluorine-based surfactant added to the coating components was used, it had sufficient wettability and could be easily coated without causing repellency. FIG. 1 shows a cross-sectional view of a liquid crystal display element obtained by the thin film forming method according to the present invention. In the drawings, parts designated by the same numbers as in FIG. 2 are the same as or corresponding to those in FIG. 2.

As is clear from the figure, it can be seen that an alignment film with no unevenness is formed.

Similarly, stripe electrodes with a width of 0.5 mm were formed on the opposing substrate, and an alignment film was formed.

Both substrates were rubbed using a conventional method and bonded together via a spacer so that the gap between the alignment films was 8 μm.
Enclosed with liquid crystal. Note that although a glass substrate is used as the substrate, other materials such as a plastic board, a plastic film, etc. can be used.

As a result, when applying the alignment material without adding surfactant, poor alignment occurred at the repellent part of the alignment film and it was not possible to obtain uniform alignment, but when the surfactant according to the present invention was added. Uniform alignment can be obtained by applying alignment material,
Furthermore, the long-term stability of orientation was also sufficient.

〔Effect of the invention〕

As detailed above, in the liquid crystal display element of the present invention, since the organopolysiloxane compound and/or the fluorine-based surfactant are blended in the alignment material, the applicability of the alignment material to the substrate is improved and uniformity is achieved. Moreover, since it becomes possible to form a flat alignment film, the alignment property and alignment stability are excellent.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a liquid crystal display element according to the present invention, and FIG. 2 is a sectional view of a conventional liquid crystal display element. 1... Soda glass substrate on which SiO□ is formed 2...
Transparent electrode 3...Color filter 4...Alignment film 4' of the liquid crystal display element of the present invention...Alignment film of conventional liquid crystal display element Applicant: Sanyo Electric Co., Ltd. and one other representative Patent attorney Kono Noboru 1 figure ¥-2 mouth

Claims (1)

[Claims] 1. A liquid crystal display element comprising an alignment film made of a material containing at least one siloxane compound and/or surfactant selected from the group of organopolysiloxane compounds and the group of fluorine-based surfactants.