JPS6161130A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To form easily an orienting film having uniform and high orienting performance at a low temp. by using specified polyamide ester. CONSTITUTION:When a liq. crystal display element is manufactured using electrically conductive transparent substrates each having an orienting film, the orienting film is made of a film contg. polyamide ester having repeating structural units represented by the formula (where X is phenyl which may have a substituent) as the principal component. The polyamide ester has high solubility in a solvent such as dimethylformamide and gives a stable soln. An orienting film formed by applying the soln. has uniform and high orienting performance and high resistance to environment. It also has high heat resistance and enables the manufacture of a liq. crystal display element with high reliability. Since the orienting film can be formed easily at a low temp., high productivity is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a liquid crystal display element using a transparent conductive substrate having a novel alignment film.

[Prior art]

Conventionally, various transparent conductive substrates provided with alignment films have been used in liquid crystal display elements, but in this case, the alignment film has a large effect on the display quality of the liquid crystal display element, Much research has been devoted to the development of

Conventionally, it has been known to use polyimide as an alignment film material, and for example, it has been known to use pyromeliz 1 heimide represented by the following formula.

(In the above formula, n is an integer of 1 or more) However,
Polyimide as mentioned above is insoluble in solvents, so in order to form a film on a substrate, it is coated in the form of a solution of its precursor, polyamic acid (a ring-opened form of polyimide), and then
Heat cyclization is required to form a polyimide structure.

In this case, heating cyclization requires a high temperature of 250 to 300° C. or higher, which causes problems such as deformation of the substrate and the need for special heating equipment. In recent years, active matrix liquid crystal display devices using thin film transistor arrays have been developed in order to increase display capacity. It is difficult to apply it as an alignment film. Further, liquid crystal display elements using plastic substrates have also been developed, but since the heat resistance of plastic substrates is poor, it is similarly difficult to apply the above-mentioned polyimide as an alignment film. Furthermore, in the case of the above-mentioned polyimides, their precursor polyamic acid is unstable, so they have a short pot life.

〔the purpose〕

The present invention aims to provide a liquid crystal display element using a transparent conductive substrate having an alignment film, which uses a novel alignment film that overcomes the above-mentioned drawbacks seen in the use of conventional polyimide alignment films. purpose.

〔composition〕

According to the present invention, in a liquid crystal display element using a transparent conductive substrate having an alignment film, the alignment film is composed of a film mainly composed of polyamide ester having a repeating structural unit represented by the following general formula. A liquid crystal display element having characteristics is provided.

In the general formula (1), X is a phenyl group which may have a substituent. In this case, the substituents include lower alkyl group, lower alkoxy group, aryl group, aralkyl group, aryloxy group, arylthio group, alkylthio group, alkoxycarbonyl group, alkylcarbamoyl group, arylcarbamoyl group, hydroxyl group, alkylcarbonyloxy group, halogen atom, etc. The type of this substituent is not particularly limited, and it may be any inert group that does not adversely affect the reaction when producing a polyamide ester having a repeating structural unit represented by the general formula (1). In addition, the number of substituents is not particularly limited,
It is possible to have 1 to 5 substituents. The degree of polymerization is 2 or more, generally 10-1000, preferably 30-1000.
It is 300.

Among the repeating structural units represented by the general formula (1), the following may be mentioned. The polyamide ester of the present invention may be a copolymer consisting of the above repeating structural units.

41 The polyamide ester in the present invention can be synthesized from a corresponding dicarboxylic acid chloride and a hydroxydiphenylamine derivative according to the following reaction formula.

(In the formula, X is the same as above, and n is a number of 2 or more.) Anisole, O-dichlorobenzene, nitrobenzene, etc. can be used as the reaction solvent, but in order to obtain a high molecular weight In particular, nitrobenzene with a high boiling point (200° C.) is preferred. The reaction temperature depends on the boiling point of the solvent used, but is preferably 140 to 250°C, more preferably 160 to 250°C.

The produced resin can be isolated by pouring the reaction solution into a poor solvent such as methanol and filtering off the precipitate.

The liquid crystal display element of the present invention is produced using a transparent conductive substrate having an alignment film of polyamide ester having a repeating structural unit represented by the general formula (I). In this case, the polyamide used in the present invention, unlike conventional polyimide, has the greatest feature of having high solvent solubility. For example, N,N-dimethylformamide (
DMF), N-methyl-2-pyrrolidone, m-cresol, pyridine, tetrahydrofuran, chloroform, S
Dissolve in ym-tetrachloroethane etc. to give a stable solution.

This solution has high manufacturability and is much easier to coat onto a transparent conductive substrate to form an alignment film than conventionally known polyimide, and the resulting alignment film is uniform.
It has high alignment performance and environmental resistance. On top of that,
This film has a glass transition temperature of 190° C. or higher and a decomposition temperature of 480° C. or higher, and has high heat resistance comparable to conventional polyimide alignment films, and provides an extremely reliable liquid crystal display element.

The polyamide ester used in the present invention thus provides a high-performance alignment film with no selectivity to liquid crystals, but the solubility during preparation of the coating solution differs depending on the resin. ■-Resin having a phenylene skeleton [(■) to (■)] and] ρ
Copolymers with a p-phenylene skeleton (IT) ratio of 90% or less exhibit good solubility, whereas copolymers and homopolymers with a p-phenylene skeleton (IT) ratio of over 90% are limited in the solvents in which they can be dissolved. , the film formability decreases.

Therefore, the content of P-phenylene skeleton in the copolymer is preferably 90% or less.

Unlike ordinary polyimide alignment agents, the polyamide ester used in the present invention has a long pot life, and when stored in powder or solution form, maintains its excellent performance even after storage for 2 months to more than 1 year. do.

To form a polyamide ester alignment film on the transparent conductive substrate-L, first, add this solution to a polyamide ester solution with a concentration of 0.01 to 10% by weight, preferably 0.1 to 5% by weight, and apply it using a spin cord or roller. It is coated by conventionally known methods such as coating, spray coating, and dipping, and then heated to remove the solvent to a film thickness of 100 to 5,000.
After forming a polyamide ester film with a particle size of 500 to 2,000, it is rubbed in one direction with cotton cloth, nylon flocked cloth, polyester flocked cloth, etc. (rubbing treatment). When drying a polyamide ester solution coated on a substrate, the heating temperature depends on the boiling point and vapor pressure of the solvent used. For example, in the case of N-methyl-2-pyrrolidone or m-cresol, the heating temperature is 180 ~200℃, 120~15 in the case of N,N-dimethylformamide or tetrachloroethane
4 for 0°C, chloroform, and tetrahydrofuran
A temperature of 0 to 60°C is sufficient, and by specifying the type of solvent, heating and drying can be performed at extremely low temperatures. Such low-temperature heating and drying can prevent damage and deterioration of the substrate.

The type of liquid crystal substrate used in the present invention is not limited, and it is advantageous to use not only the glass substrate 1 but also plastic films such as polyester, polyethersulfone, polysulfone, and acetyl cellulose, glass substrates on which thin film transistor arrays are formed, silicon wafers, etc. It can be used for.

The alignment film formed on the substrate as described above has excellent homogeneous alignment performance for liquid crystal. In this case, examples of the liquid crystal include Schiff base liquid crystal, azoxy liquid crystal, biphenyl liquid crystal, phenylcyclohexane liquid crystal, ester liquid crystal, pyrimidine liquid crystal, terphenyl liquid crystal, and biphenylcyclohexane liquid crystal. These liquid crystals are used alone or usually as a mixture.

Furthermore, for these liquid crystals, cholesteric liquid crystals such as cholesteryl chloride, cholesteryl nonaate, and cholesteryl carbonate, chiral nematic liquid crystals such as those sold by British Drug House under the trade names C-15 and CB-15, Ionic dopants such as tetraalkylammonium salts, etc. can be added.

When performing etching on the substrate having a polyamide ester alignment film used in the present invention to form required parts such as electrode lead-out parts and seal forming parts, the polyamide ester alignment film is Since it can be eluted using an organic solvent, the required etching can be carried out safely by a simple method such as photolithography.

〔effect〕

In the liquid crystal display element of the present invention, the alignment film is 1'l
Since it is formed using polyamide ester with good thermal stability, such as Special 5311, like Jl'R2, it is uniform and has excellent alignment performance. Therefore, the liquid crystal display element of the present invention has not only excellent display quality but also remarkable high-temperature durability. In addition, the formation of the alignment film is
Since the process can be carried out easily and at low temperatures, the product of the present invention also has excellent productivity.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Synthesis Example 1 ], 45 g (7.85 mmol) of m-anilinophenol and 1.60 g (7.85 mmol) of isophthalic acid chloride were dissolved in 10 mfl of nitrobenzene, and while removing the generated hydrogen chloride gas, The reaction was carried out at ℃ for 7 hours. The reaction solution was diluted with 30 mm of N,N-dimethylformamide and then poured into a large amount of methanol. The resulting yellow precipitate was filtered off, washed with methanol, and then dried to give 2.15 g of polyamide ester (
V) was obtained. The intrinsic viscosity of the produced resin is 0.40αl,/g
(0.5 g/dL, DMF, 30°C), and the infrared absorption spectrum shows 1660 cm ” and 1740 cm
-” Absorption due to amide and ester groups was confirmed.

Elemental analysis value: HN Calculated value (%) 76, +9 4.13 4.14 Actual value (%) 75.33 3.86 4.29 Glass transition point: 164°C, decomposition point = 495°C Synthesis example 2 A resin (TV) was synthesized from m-anilinophenol and terephthalic acid chloride in the same manner as in Synthesis Example 1.

Intrinsic viscosity: 0.58 dL/g (0.5 g/di4, r
) MF, 30°C) Glass transition temperature: 180°C, decomposition point:
500°C Synthesis Example 3 Resin (m) was synthesized from P-anilinophenol and isophthalic acid chloride in the same manner as in Synthesis Example 1.

Intrinsic viscosity: 0.3]dL/g (0.5g/dL, l1
14F, 30°C) Glass transition temperature: 191°C1 Decomposition point: 505°C Synthesis example 4 1.45g (7,85mmo]) p-anilinophenol, 0.80g (3,413mn1ol) isophthalic acid chloride , 0.80g (3,93nono I)
Copolymer hair was synthesized from terephthalic acid chloride in the same manner as in Example 1.

Intrinsic viscosity: 0.32dL/g (0.5g/dL, DM
F, 30°C) Glass transition point: 217°C, decomposition point: 48
5°C Example 1 The polyamide ester obtained in Synthesis Example 1 was heated to N,N
- A polyimide solution having a concentration of 0.5% by weight was obtained by dissolving in dimethylformamide. These solutions were coated on a glass substrate having a transparent conductive film of indium oxide-tin oxide by a spin code method, and then heated at 120°C for 15 minutes to
By heating for 30 minutes at °C to evaporate the solvent,
A uniform polyimide coating was obtained.

Next, this polyimide coating was subjected to a rubbing treatment to form an alignment film, and then subjected to a heat resistance test at 150°C for 24 hours and a heat resistance test at 60°C.
A moisture resistance test was conducted at 90% RH for 1100 hours. The two substrates obtained in this way were placed in a 10μ
They were stacked with a spacer of m in size in between and bonded together using an epoxy adhesive as a sealant, and a biphenyl liquid crystal (manufactured by BD11, E-8) was encapsulated to create a twisted nematic type liquid crystal encapsulated cell. The liquid crystal-filled cell obtained in this way showed good orientation, and even when compared with a liquid crystal-filled cell similarly prepared without performing these tests, no difference was observed in the orientation. It was confirmed that the material showed excellent high-temperature durability. Furthermore, it was confirmed that there was no change in orientation at all in a high temperature storage test of a cell filled with liquid crystal at 80° C. for 100 hours and a high temperature storage test of 60° C. and 90% RIL for 1000 hours.

Example 2 When the polyamide esters obtained in Synthesis Examples 2 to 4 were evaluated in the same manner as in Example 1, it was found that all of them had excellent initial orientation, high temperature storage stability, and high humidity storage stability. was confirmed.

Example 3 A liquid crystal-filled cell was produced in the same manner as in Example 1, except that phenylcyclohexane liquid crystal (manufactured by E-Merck, ZLI-1285) was used as the liquid crystal.

This product also showed excellent orientation and reliability similar to Example 1.2.

Example 4 A liquid crystal-filled cell was produced in the same manner as in Examples 1 to 3, except that a polyester (PET) film with a transparent conductive film was used as the substrate. This cell also showed excellent orientation similar to Examples 1-3.

Claims (1)

[Claims] (1) A liquid crystal display element using a transparent conductive substrate having an alignment film, characterized in that the alignment film consists of a film mainly composed of polyamide ester having a repeating structural unit represented by the following general formula. Liquid crystal display element. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, X represents a phenyl group that may have a substituent.)