JPS5817418A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain the titled element having a superior contrast and maintaining the transparency without causing coloring in yellowish brown even if the ring closure of a polymer by heating is carried out. CONSTITUTION:A liq. crystal orienting film is made of polyimide having repeating units represented by general formulaI(where R1 is a group represented by formula II or III, n is 0 or 1, R2 is an org. residue of tetracarboxylic acid, and R3 is a bonding radical or a bivalent group). Diamine corresponding to said general formula includes 1,3-bisaminomethylcyclohexane, 1,4-bisaminomethylcyclohexane and 1,4-diaminocyclohexane. By substituting a siloxane group represented by formula IV (where R2 is a bivalent org. group, R3 is a univalent hydrocarbon group and n is an integer of >=1) for a part of a diphenylsulfone group which is each diamine residue of polyimide, the transparency is enhanced, and the exfoliation and blurring of the orienting film can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal display element, and more particularly, to a liquid crystal display element with <Ic, excellent transparency.

In general, it has a structure as shown in Figure 1 of Liquid Crystal Display Elements Co., Ltd., and indium oxide (rs, o,
) are provided with segment electrodes 2 and 2' made of transparent conductive films such as 3 and 2', and alignment films (or insulating films) 3 and 3' are provided thereon.
With this, the peripheral area of the liquid crystal 4 is sealed with a seal 5. Furthermore, polarizing plates 6,6' are arranged on both sides thereof.

BACKGROUND ART Conventionally, in liquid crystal display elements, particularly in nematic liquid crystal display elements that operate under the action of an electric field and utilize an electro-optic effect, inorganic materials such as SiOf)M deposited films have been mainly used as alignment films. The reason is that these inorganic films do not have any factors that adversely affect liquid crystals even when they come into contact with liquid crystals.
In addition, the ninth type has the advantage that the liquid crystal can be aligned uniformly even if glass 7-lit sealing is performed.

On the other hand, liquid crystal display elements using various organic polymer materials as alignment films have also been proposed. In this case, the polymer film is generally rubbed in one direction with a cloth or the like for orientation treatment, and then used so that the rubbing directions are perpendicular to each other. fluororesin,
Films made of polyvinyl alcohol, polyester, silicone resin, polyamide, polyesterimide, polycarbonate, and many other organic polymer compounds have been proposed as alignment films for liquid crystal display devices. However, these conventionally known polymer films cannot be said to have sufficient uniformity in liquid crystal alignment, and due to long-term electrical current tests and deterioration tests, non-uniformity in alignment tends to increase compared to inorganic insulating films. However, there is a drawback that variations occur in the number of individual liquid crystal display elements. Further, the glass 7-lit seal is heated to about 400° C., but many conventionally known polymer films have insufficient heat resistance, resulting in the disadvantage that the alignment film is destroyed and the liquid crystal is not aligned.

Among conventional organic polymer materials, polyimide can be cited as a material that forms an alignment film with relatively excellent alignment properties. For example, polyamic acid, which is a polyimide precursor obtained by condensation of beemeridic dianhydride and 4,4'-diaminodiphenyl ether, described in JP-A No. 51-65960, is coated and then ring-closed by heating. It is quite good in terms of uniformity of bolioidite orientation and durability in deterioration tests.

However, many polyindo materials, such as polyimides obtained from pyromellitic dianhydride and diaminodiphenyl ether, become noticeably discolored when heated at the imide ring-closing temperature of 300°C to 350°C + the temperature of the gun frit seal of about 400°C. do. For this reason, there is a problem that the liquid crystal display element becomes colored after the liquid crystal is sealed, and at the same time, the field of view becomes dark and wide, and the contrast deteriorates, so that the function as a display element, especially the requirement for high-quality display, is not met. Ta.

In addition, when polyimide is used as an alignment film, since polyimide is highly adhesive to the substrate, moisture that has permeated into the liquid crystal display element due to peeling of the alignment film and poor alignment can be absorbed onto the substrate. Problems such as agglomeration and water droplets that cause smearing on letters, etc. are likely to occur.

Therefore, it is difficult to obtain a liquid crystal display element with excellent transparency using conventional polyimide. Therefore, it is desired to develop an alignment film that is less colored and has excellent transparency even when heated during ring closure and sealing with a glass frit.

The present invention was made in view of the current situation.
The purpose is to provide a liquid crystal display element that does not become colored by heating and has excellent transparency.

That is, in the liquid crystal display element of the present invention, the liquid crystal alignment film has the general formula:

It is characterized by being made of a polyimide having repeating units represented by R, Fi, which represents an organic residue of a tetracarboxylic acid, and LAR, which represents a bond or a divalent group.

Examples of diamines corresponding to the above general formula include 1,3-bisaminomethylcyclohexane, 1,4-bisaminomethylcyclohexane, 1,4-diaminocyclohexane, toco-diaminocyclohexane, and 4,4'-diaminodicyclohexylmethane. Examples include, but are not limited to, -4,4'-diaminodicyclohexylisopropane and 3,3'-diaminodicyclohexylisopropane.

Examples of tetracarboxylic dianhydride include pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride, benzophenonetetracarboxylic dianhydride, biphenyltetracarboxylic dianhydride, naphthalenetetracarboxylic dianhydride, etc. Examples include aromatic tetracarbo/acid dianhydrides.

The polyimide used as the alignment film in the present invention has the general formula H, N
-CCH, ), -R(CH,), -M2 are obtained by polycondensation reaction of the diamine represented by the formula and the tetracarboxylic dianhydride represented by the general formula. By preparing a polyamic acid solution, which is a polyimide precursor, and then applying it to a glass substrate for a liquid crystal display element and subjecting it to soft sail heat treatment, an alignment film having the desired upper repeating unit can be formed.

Synthesis of the polyimide precursor in the present invention is carried out favorably by stirring the above diamine and tetracarboxylic dianhydride in an organic solvent at a temperature of about 15° C. to 50° C. for several hours. The solution of the produced polymer was kept at a concentration of 5s.
Dilute to about 1000/1 (usually about 500A to 200A)
After coating to a desired film thickness (preferably within the range of about 0 A), a desired polyimide film can be formed. Examples of organic solvents used in this reaction include L N-methyl-2-pyrrolidone, N, N
-Polar organic solvents such as dimeteramide and the like. Examples of methods for applying the polyimide precursor include spin coating, dip coating, roll coating, printing, and brush coating.

Although the alignment film made of polyimide according to the present invention can be directly formed on a substrate provided with a conductive layer, it is possible to form an even more excellent alignment film by using a substrate provided with an inorganic insulating film below or above the conductive layer. A liquid crystal display element can be obtained. This is done by placing a! on a glass substrate with a conductive layer. i-
This is because thermal deterioration caused by sodium ions in soda glass is less likely to be accelerated in the formed alignment film. SIO is suitable as an inorganic insulating film that exhibits this better effect.

Further, in the present invention, in order to obtain a stronger alignment film, one or more types of epoxy-based and anno-based coupling agents can be used in combination. Examples of Sila 7 coupling agents include r-aminopropyltriethoxysilane and T-glycidoxyprepyltrimethoxysilane. In application, it may be added to the polyimide precursor solution, or an alignment film may be formed on a silane coupling agent film formed on a glass substrate.

As the liquid crystal sealed in the liquid crystal display element, any known liquid crystal may be appropriately selected and used.

The liquid crystal display element of the present invention has the advantage that it does not turn yellowish brown even when the polymer is subjected to thermal ring closure, maintains transparency, and has excellent contrast.

Furthermore, membrane transparency is improved by replacing the diamine residues of the polyimide used in the present invention with siloxane groups represented by 7 diphenylsulfonyl groups (0-St, ``false'' represents an integer greater than or equal to 1, respectively). Not only this, but also the problem of bleeding during spreading of the alignment film can be avoided. As a siloxane group, CHCH.

A typical example is C6H5C@Hs, but it goes without saying that it is not limited to these. The ratio of siloxane groups to &3'-diphenylsulfone groups is 1 to 10 moles for the former and 99 for the latter.
It is desirable to select from the range of ~90 molti.

The present invention will be explained below based on Examples.

Example L 4.4'-diaminodicyclohexylmethane (100 mol), benzophenone dicarboxylic dianhydride (1
00 mol%) and N-methyl-2-pyrrolidone were placed in a flask and stirred at 50°C for 3 hours. The viscosity at 30℃ is 1
A 17% solution of 1.0 poise was obtained. This solution was diluted with N-methyl-2-pyrrolidone to obtain a third coating solution.

A coating film of r-7 minoprobyltriethoxysilane was formed on a glass substrate with an In, O, and transparent electrode in advance, and then the coating solution was applied using a spinner and heated at 300C for 1 hour to obtain a film thickness of about 100OA. A polyimide film was formed. An alignment film was formed by rubbing in a certain direction with a cotton cloth. After removing the polyimide in the sealed portions of the two glass substrates thus obtained by plasma etching, they were sealed using epoxy resin to create a cell. Next, a ship-type nematic liquid crystal was injected to complete the liquid crystal display element.

The 4DOrnp transmittance of the liquid crystal display element was 79 inches.

In addition, after being left in an atmosphere of 70° C. and 95% RH (D) for 100 days, a light was turned on to check for bleeding, but no bleeding was observed.

Example 2 Meta-xylylene diamine (95 mol), compound represented by formula 0 (5 mol %), 3・3′・4・4′-
Biphenylnato 2-carboxylic dianhydride (100 7 L buns)
and N-methyl-2-pyrrolidone into a flask, and S
Stirred on OC for 3 hours.

A 17-solution having a viscosity of 10.2 poise at 30°C was obtained.

This solution was diluted with N-methyl-2-pyrrolidone to 3%
A coating solution was obtained.

lK2O without forming a coating film of silane coupling agent
3 A liquid crystal display element was formed in the same manner as in Example 1 using a glass substrate with transparent electrodes.

When the same evaluation as in Example 1 was performed, the transmittance of 40 ψ was 5 ots, and no bleeding was observed after the moisture resistance test.

Comparative Example 1゜Diaminodiphenyl ether (100 ml), pyromellitic dianhydride (100 mol ts) and N-methyl-
2-Pyrrolide/ was placed in a flask and stirred at 50°C for 3 hours. A 17% solution with a viscosity of 10 poise at 30°C was obtained. This solution was diluted with N-methyl-2-pyrrolidone to give 2
．． A coating solution of No. 5- was obtained.

rfi2 without forming a coating film of silane coupling agent
o. A liquid crystal display element was formed in the same manner as in Example 1 using a glass substrate with transparent electrodes.

The same evaluation as in Example 1 was performed and ζro%40011L
The transmittance of F was 65-, and bleeding was observed after the humidity test.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a liquid crystal display element. 1.1'-...Glass substrate, 2.2'...
...Transparent conductive film, 3.3'...Orientation &
4-----1 liquid crystal, 5.--1. sealant,
6.6′-・・・Polarizing plate. Offense 1 Amendment to figure procedure August 28, 1980 Commissioner of the Japan Patent Office Shima 1) Indication of the Haruki Tonori case 1982 Patent Application No. 115244 ゛λ Name of the invention Liquid crystal display element 5, subject of amendment Description of the description Column 6 for detailed description of the invention
, Contents of correction (1) F! 0 (2) Specification No. 1 O: [Part of polyimide...--1...] t-[Part of the diamine component of polyimide] in lines 2 to 1 from the bottom of page 9 of Specification A From the second line from the bottom of the page to the first line of page 11, "7 siloxa groups are desirable." It is desirable.”

Claims (1)

[Claims] A liquid crystal having a liquid crystal alignment film on a substrate on which a transparent electrode is formed. A liquid crystal display element characterized by being made of polyimide having reverse orientation.