JPH0412325A - Liquid crystal display element and production thereof - Google Patents

Abstract

PURPOSE:To form an oriented film with which a high pretilt angle is obtd. at a low treating temp. and which has excellent stability by using a polyimide or polyamide polymer contg. specific metals as the oriented film. CONSTITUTION:The high-polymer film contg. at least one kind of the group IIIb, IVa, IVb, and Va metals in the film essentially consisting of the polymide, polyamide or polyamideimide polymer obtd. from polyamic acid, polyimide high polymer or polyamide high polymer is used as the oriented film for liquid crystals. The film oriented with the high pretilt angle is formed in this way and the stable film oriented with the high pretilt angle is formed on a polymer film substrate as well. The supertwisted liquid crystal display element having a large number of scanning lines is thus obtd.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a liquid crystal display element and a method for manufacturing the same.

[Conventional technology]

In recent years, liquid crystal display devices have become popular as terminal displays for personal computers, word processors, etc., and video displays for flat-screen TVs, etc., because they can be made lighter and thinner, consume less power, and can be easily converted to color. It is used in

The LCD display is of twisted nematic (TN) type.
Super twisted nematic (STN) types, guest-host types, phase transition types, birefringence control types, etc. are known, but recently, among these, TN liquid crystal displays have been used to increase the twist angle of liquid crystal molecules from 180 to 360°. Twisted ST
N-type liquid crystal display devices are attracting attention.

Normally, a twist angle of 200 to 270° is becoming commonly used, but in this case, increasing the twist angle requires making the angle at which the liquid crystal molecules are aligned on the substrate (pretilt angle) larger than in conventional liquid crystal systems. There is. Therefore,
No. 4-24226, No. 64-79725, No. 64-7
No. 9726, No. 64-79727, No. 64-8422
No. 1 publications and the like propose means for forming an alignment film (orientation layer) for increasing the pretilt angle.

Polyimide polymer compounds are generally used as alignment materials for liquid crystals. This polyimide film is rubbed to form a pretilt angle that aligns the liquid crystal molecules.

The pretilt angle of the polyimide film formed by this method is a small value of 2 to 3 degrees or less. When displaying using the STN method, if the number of scanning lines on the liquid crystal display is 200 or less,
The twist angle of the liquid crystal molecules may be 200 degrees or less, and a pretilt angle of 2 to 3 degrees can also be used. However, when the number of scanning lines increases to around 400, the twist angle is reduced to 240°.
With this, the pretilt angle is also required to be 4 to 5'' or more.

[Problems to be Solved by the Invention] However, in order to increase the pretilt angle with a normal polyimide compound, the polyimide film forming treatment temperature must be raised to a high temperature of around 200° C. or higher. However, when high temperature treatment is applied to form a polyimide film, it is difficult to form an alignment film on a substrate on which active elements (thin film transistors, two-terminal elements, etc.) or color filters are formed as a liquid crystal display element, or on a substrate of a liquid crystal display element. When a polymer film is used as a material, damage is often caused to the device, color filter, or polymer film substrate. Furthermore, productivity is poor due to high temperature processing.

Furthermore, there is a high possibility that the alignment layer will be non-uniform.

Therefore, an object of the present invention is to overcome the problems of the prior art, obtain a high pretilt angle at a low processing temperature, and
An object of the present invention is to provide a liquid crystal display element using a stable alignment film and a method for manufacturing the same.

[Means to solve the problem]

As a result of extensive research, the present inventors found that a liquid crystal display element using a polyimide or polyamide polymer containing a specific metal as an alignment film is suitable for the above purpose, and thus completed the present invention. Ta.

That is, according to the present invention, II
At least one of metals from groups Ib, IVa, IVb and Va
Provided is a liquid crystal display element characterized in that a polymer film containing seeds is used as an alignment film for liquid crystal.

Further, according to the present invention, at least one organic compound of metals of the mb, rVa, IVb, and Va groups is added to a solution of a polymer material whose main component is polyamic acid, polyimide polymer, or polyamide polymer. The method includes a step of mixing and dissolving, applying the resulting mixed solution onto an electrode substrate having a transparent electrode, heating it, forming a polyimide or polyamide polymer coating on the substrate, and further subjecting the coating to an orientation treatment. A method for manufacturing a liquid crystal display element is provided.

The liquid crystal display element of the present invention is characterized in that an alignment film made of a polyimide or polyamide polymer containing an organic compound of a specific metal is formed on a substrate. Since the polyimide reaction of the body is promoted, a film of the polymer can be formed at a low temperature and in a short time, and a stable alignment film with a high pretilt angle can be formed by the alignment treatment.

Hereinafter, the liquid crystal display element of the present invention and its manufacturing method will be explained in detail.

Polyamic acids, polyimide-based polymers, and polyamide-based polymers, particularly polyamic acids that are precursors of polyimide, undergo heat treatment to complete imidization through a dehydration reaction in the compounds.

Generally, when the heat treatment temperature is high, the polyimidization progresses and at the same time, the pretilt angle of the film subjected to the alignment treatment (rubbing) increases. On the other hand, if the heat treatment temperature is low, the pretilt angle will not become large even if the simultaneous alignment treatment is performed, and stability will be lacking. Therefore, it is absolutely necessary to fully complete polyimidation.

Organic compounds of metals used in the present invention (organometallic compounds)
is very reactive, particularly in hydrolytic reactivity.

Since the imidization reaction of polyamic acid is a dehydration reaction by heating, the addition of the organometallic compound accelerates the imidization reaction.

Further, the metal of the organometallic compound is an element generally called a transition metal, and may form a bond with an active group in the film through coordination bonds, thereby forming a thermally stable film. Moreover, since it exists in the film in combination, it does not have any adverse effect on the liquid crystal. In addition, the main reaction of imidization of polyamic acid is shown by the following formula.

(In the formula, Ro represents a tetravalent organic group constituting a tetracarboxylic acid or a derivative thereof containing an alicyclic structure, and R2 represents a divalent organic group constituting a diamine containing an alicyclic structure. ) On the other hand, the organometallic compound coating also has the effect of lowering surface tension. In particular, the critical surface tension of a film of a Ti compound is around 20, and generally causes liquid crystal to be vertically aligned. Therefore, when these compounds exist in a polyimide film or a polyamide film, it is possible to change the orientation from vertical to horizontal, and the pretilt angle can be changed over a wide range (several degrees to 90 degrees).
) can be controlled.

As the metal of the organometallic compound, IIIb, IVa
, IVb and Va groups can be used, and specific examples include Ti, Zr, Cr, V,
Examples include No, AQ, Sn, and Zn, and these types of organic alcoholade compounds are easy to handle as organometallic compounds. Of course, it is not limited to the Alcorado type. Among these, T is particularly important as a metal.
i and Zr are effective, and organometallic compounds such as tetrabutoxytitanate, titanium acetylacetate, zirconium acetylacetate and the like are preferred. The amount of organometallic compound added to polyamic acid, polyimide, polyamide, etc. varies depending on the case, but it is 0 to 0 for the polymer compound.
．． A range of 0.05 to 30% by weight is preferred. When the amount of the organometallic compound added exceeds 30% by weight, the properties of the organometallic compound become dominant. Conversely, if it is less than 0.05% by weight, the imidization reaction rate is low. However, in the case of an alignment treatment agent that may require a low imidization rate, it may be less than 0.05% by weight.

Examples of the polyamic acid, polyimide polymer, and polyamide polymer used in the present invention include compounds represented by the following general formula (1).

(In the formula, Ro is a tetravalent organic group constituting a tetracarboxylic acid or its derivative containing an alicyclic structure, R2 is a divalent organic group constituting a diamine containing an alicyclic structure, and R3
represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, respectively. ) In the above formula, specific examples of R1 include 4 derived from cyclobutane, cyclopentane, cyclohexane, benzene, etc.
Specific examples of the valent group R2 include divalent groups derived from cyclohexane, dicyclohexylmethane, dicyclohexylsulfone, dicyclohexyl ether, diphenyl ether, diphenylmethane, diphenylsulfone, long-chain alkyl compounds, etc. Specific examples of the alkyl group include methyl, ethyl, and propyl groups.

Next, a method for manufacturing a liquid crystal display element according to the present invention will be explained.

The method for manufacturing a liquid crystal display element of the present invention includes mixing and dissolving the organometallic compound in a solution of the polymer material, applying the resulting mixed solution onto an electrode substrate having a transparent electrode, and heat-treating the resulting substrate. The method is characterized in that it includes a step of forming a polyimide or polyamide polymer film thereon and further subjecting the film to an orientation treatment.

That is, in the production method of the present invention, first, an appropriate amount of at least one of the organometallic compounds is added and dissolved in a solution of a polymer material whose main component is polyamic acid, polyimide polymer, or polyamide polymer, and Prepare the solution for application. The solvent for dissolving the polymer material is preferably a polar solvent, and specific examples thereof include N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methylcaprolactam, tetramethylurea, and pyridine. , dimethylsulfolane, hexamethylphosphoramide, butyrolactone, and the like. These polar solvents may be used alone or in combination of two or more. This solvent is selected depending on the solubility of the polyamic acid, polyimide polymer, and polyamide polymer used, and may be other than those mentioned above.

The concentration of the polymeric material in the solution is usually preferably in the range of 0.1 to 10% by weight. If the concentration exceeds 10% by weight, coating properties will deteriorate.

Next, the prepared coating solution is applied onto an electrode substrate having a transparent electrode, but the application method is not particularly limited, and for example, a conventional method such as a spin coating method, a print coating method, a dip coating method, etc. is adopted. be able to. The thickness of the coating film is 5.
The number is preferably in the range of 00 to 2,000 people.

Subsequently, when the obtained coating film is dried and heat-treated, the solvent is removed and the polyamic acid is imidized to form a polyimide or polyamide polymer film. The drying heat treatment conditions vary depending on the type of solvent, etc., and therefore cannot be unconditionally defined, but numerically, they are at a temperature of about 60 to about 200° C. and for about 30 minutes to about 2 hours.

An alignment film is formed by subjecting the polymer film formed as described above to an alignment treatment. The means for orientation treatment is not particularly limited, and any conventional method can be used.

For example, this can be easily achieved by rubbing with a sponge, nylon flocked cloth, or the like.

The magnitude of the pretilt angle obtained by the alignment film thus formed can be controlled in the range from several degrees to 90 degrees depending on the temperature of the heat treatment and the degree of the alignment treatment.

11 - As the substrate of the liquid crystal display element, various materials can be used, such as - axially stretched polyester film,
Examples include polymer films such as polyether sulfone film, polyarylate film, and surface-treated polycarbonate film, glass, and quartz glass.

Particularly in the present invention, it is advantageous to use a glass substrate provided with a polymer film or a color filter because low-temperature processing is possible.

The liquid crystal is not particularly limited, and materials conventionally used in liquid crystal display elements, such as nematic liquid crystal, cholesteric liquid crystal, smectic liquid crystal, and ferroelectric liquid crystal, can be used.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 Polyamic acid [In the general formula (1), R1
A 3% solution of N-methyl-2-pyrrolidone is prepared, and tetra-n-butoxytitanate (TOT) is added to this solution. was added at a solid content ratio of 0.2%, and after applying it to an l-axis stretched polyester film using a spinner, it was heated at 100°C.
A dry heat treatment was carried out for 1 hour to form a film of 800 people.

The resulting coating was rubbed with a sponge, and a liquid crystal (ZL)
I2293; manufactured by Merck & Co., Ltd.) to prepare a 2400 twist liquid crystal cell and measure the pretilt angle, a value of approximately 5'' was obtained, which is larger than the case without TOT (pretilt angle of approximately 2°). value was obtained.

Example 2 A liquid crystal display element was manufactured in the same manner as in Example 1 except that 0.5% of zirconium acetylacetate was added instead of TOT in Example 1, and the pretilt angle was measured and found to be approximately 7'' The value of was obtained.

Example 3 A liquid crystal display element was produced in the same manner as in Example 1 except that the amount of TOT added in Example 1 was changed to about 2%, and when evaluated, a vertical alignment state was obtained.

〔Effect of the invention〕

=14- The liquid crystal display element according to claim (1) has a structure in which a polymer film containing the specific metal mixed in a film mainly composed of polyimide or polyamide polymer is used as an alignment film for the liquid crystal. Therefore, it produces the following outstanding effects.

(a) A high pretilt angle alignment treatment film is formed.

(b) A stable high pretilt angle alignment film is formed on the polymer film substrate, and a super twist liquid crystal display element with a large number of scanning lines can be obtained.

In addition, in the method for manufacturing a liquid crystal display element according to claim (2), an organic compound of the specific metal is mixed and dissolved in a solution of a polymer material whose main component is polyamic acid, polyimide polymer, or polyamide polymer. The mixed solution was coated onto a substrate with transparent electrodes and then heated to form a polyimide or polyamide polymer coating, and the coating was further subjected to an orientation treatment, resulting in the following outstanding results. be effective.

(c) A polyimide or polyamide polymer coating can be formed at low temperatures and in a short time.

(d) Productivity can be improved without damaging active elements and color filters.

Patent applicant Rico Co., Ltd. Representative patent attorney: Toshiaki Ikeura (and one other person)

Claims (2)

[Claims] (1) In a film mainly composed of polyimide, polyamide, or polyamideimide polymer obtained from polyamic acid, polyimide polymer, or polyamide polymer, IIIb
, IVa, IVb and Va group metals is used as a liquid crystal alignment film. (2) Add III to a solution of a polymer material whose main component is polyamic acid, polyimide polymer, or polyamide polymer.
At least one organic compound of group metals IVa, IVb, and Va is mixed and dissolved, and the resulting mixed solution is coated on an electrode substrate having a transparent electrode and then heat-treated to form polyimide, polyamide, etc. on the substrate. Or, a method for producing a liquid crystal display element, comprising the steps of forming a polyamide-imide polymer film and further subjecting the film to an alignment treatment.