JPH01298317A - Substrate for interposing liquid crystal - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal orientation film having high coatability, high adhesion, stable orientation characteristic, and providing high tilt angle by using a mixture obtd. by adding a specified aminosilane compd. to a reaction product of a specified org. tetacarboxylic acid dianhydride with a specified diamine compd. in a specified proportion. CONSTITUTION:A soln. consisting of a polyimide precursor obtd. by reacting an org. tetracarboxylic acid dianhydride component expressed by the formula I with a diamine component expressed by the formula II, contg. also an aminosilane compd. expressed by the formula III wherein 1-20pts.wt. said aminosilane compd. is added per 100pts.wt. said polyimide precursor, is prepd., and the soln. is coated and then the precursor is dehydrated to cause ring closure to obtain thus a polyimide orientation film to be used as a liquid crystal orientation film. In the formula II, each R1-R4 is a lower alkyl group, etc.; each R5 and R6 is a methyl group, etc. In the formula III, R7 is a linear methylene group, or its branched isomer; X is an alkoxy group, etc.; Y is an alkyl group, etc. Thus, a liquid crystal orientation film having high coatability, high adhesion, stable orientation characteristic, and providing high tilt angle is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a liquid crystal sandwiching substrate that can stably maintain a high pretilt angle of liquid crystal molecules.

(b) Conventional technology Among liquid crystal display elements, those that utilize the supertwisted birefringence effect (hereinafter referred to as SBE) have extremely superior visual characteristics such as contrast compared to conventionally known TN type liquid crystal display elements. It has been attracting attention recently.

The liquid crystal alignment film used in such liquid crystal display elements includes
Even when the twist angle of the liquid crystal molecules is increased to 180 degrees or more, the property of maintaining a high pretilt angle is required so that the alignment of the liquid crystal is not disturbed.

In order to impart such properties, Kuroiso rhombus 7! of silicon oxide, etc. Method using ktJ membrane or JP-A-62-87
As disclosed in Japanese Patent No. 939, a method using a specific polyimide organic polymer film having fluorine atoms between molecules has been proposed.

(c) The problem that the invention seeks to solve, however,
The above-mentioned silicon oxide orthorhombic vaporized X1 film has selectivity to liquid crystals, so it cannot necessarily be said that the alignment of all liquid crystals is good, and the high-temperature heating conditions when assembled as a liquid crystal display element In the lower layer, alignment unevenness occurs, yield decreases, productivity deteriorates, and the film last and visual characteristics required for an alignment control film cannot be satisfied.

On the other hand, when a specific fluorine atom-containing polyimide film disclosed in JP-A-32-87939 is used,
It is a good intermittent crystal alignment film with little selectivity to liquid crystal,
The pretilt angle of the liquid crystal molecules is also slightly higher than that of a polyimide organic polymer film that does not contain fluorine atoms.

However, this device has a pretilt angle of 10 degrees or less, and in this case, stability tends to be impaired at a pretilt angle of 8 degrees or more.

By the way, high-quality SB using the torsional birefringence effect
In order to obtain an E-type liquid crystal display element, the pretilt angle must be at least 8 degrees, preferably at least 10 degrees, and must be stably maintained, which is still insufficient in terms of characteristics.

In addition, the instability of this pretilt angle tends to be exacerbated by high-temperature heat treatment and subsequent rubbing treatment when forming the polyimide film, and liquid crystal alignment films containing highly polar fluorine atoms tend to Since there are problems with coating properties and adhesion, known methods for improving adhesion, such as copolymerization of diaminosiloxane compounds or combined use of silane coupling cutting, have been adopted, but these methods offer high image quality and stable mass production. The reality is that it has not yet been possible to provide a liquid crystal sandwiching substrate that has excellent performance and long-term reliability.

The present invention has been made in view of these circumstances, and provides good coating properties and adhesion, as well as stable liquid crystal alignment, and the pretilt angle can be maintained at a stable high level without any variation. An object of the present invention is to provide a liquid crystal sandwiching substrate formed with a liquid crystal alignment film and having high long-term reliability.

(d) Means for Solving [1] As a result of intensive studies to solve the above eight problems, the present inventors have developed a reaction product 100 of a specific organic tetracarboxylic dianhydride and a specific diamino compound. The inventors have discovered that a composition in which 1 to 20 parts by weight of a specific 7-minosilane compound is added to 1 part by weight can be used as a liquid crystal aligning film, and have completed the present invention.

That is, the present invention provides a liquid crystal sandwiching substrate in which a liquid crystal alignment film is provided on a substrate on which electrodes are formed, wherein the liquid crystal alignment film is made of an organic tetracarboxylic acid anhydride represented by the following general formula (1) O○. At least one selected component and the following general formula (II) U may also be used. 100 parts by weight of a polyimide precursor obtained by reacting with at least one component selected from diamine compounds represented by the following general formula (III) H2N R, -3i
→ It is something.

That is, in the present invention, the liquid crystal alignment film is obtained by reacting the organic tetracarboxylic anhydride component represented by the above general formula (1) with the diamine compound component represented by the above general formula (II). An aminosilane compound represented by the above general formula (I[) is added to the polyimide surface precursor, and a solution in which 1 to 20 parts by weight of the above specific aminosilane compound is added to 100 parts by weight of the polyimide precursor is applied. It is characterized by the use of a polyimide alignment film obtained by dehydration and ring closure, but if the amide 7 silane compound is less than 1 part by weight, no effect of increasing the pretilt angle to 8 degrees or more is observed; If the amount exceeds 20 parts, the strength and electrical properties of the liquid crystal aligning film are reduced, which is not preferable.

The organic tetracarboxylic anhydride component used in the present invention is represented by the above general 2N), and includes, for example, pyromellitic anhydride, 3,3°,4,4°-nophenyltetracarboxylic anhydride, 2,3,3",4"-nophenyltetracarboxylic anhydride, 3,3°,11,4"-
Examples include benzophenone tetracarboxylic anhydride. These organic tetracarboxylic acid anhydride components may be used alone, or alternatively, two or more types may be used in combination.

Specific examples of the diamine compound represented by the above general formula (II) used in the present invention include 2,2-bis[
4-(4-aminophenoxy)phenyl 110 pan, 2
・2-bis(4-(3-amino7ethoxy)phenyl 1
10pan, 212-bis(4-(2-7minophenoxy)phenyl)propane, 2,2-bis[4-(2-aminophenoxy)-3,5-nomethyl7enyl 1propane, 2,2-bis [4-(4-ami/fairoxy)phenyl 1methane, 2,2-bis[4-(4-ami/fairoxy)phenyl 1hexafluoropropane, 2,2-bis[・L-<3-aminophenoxy] phenyl]hexafluoropropane, 2,2-bis[4-(2-amino7e7xy)phenyl1hexafluoropropane, 2,2-
Bis[4-(2-ami77e/xy)-3.5-tmethylphenyl]hexafluoropropane and the like can be mentioned.

These diamine compounds may be used alone, or in place of this, a mixture of 2 MI or more may be used.

The polyimide precursor used in the present invention is then obtained by reacting the organic tetracarboxylic acid anhydride component and the diamine compound component, but this polyimide precursor can be produced according to a conventionally known method. Generally, it can be obtained by reacting at a predetermined molar ratio in the presence of an organic solvent. Considering that this reaction is usually an exothermic reaction, the temperature is generally 60°C or lower, and particularly preferably, the temperature is 33°C using a water bath or the like.
The reaction may be carried out while controlling the temperature to 0° C. or lower until a high degree of polymerization is obtained.

Examples of the organic solvent include highly polar solvents such as N-methyl-2-pyrrolidone, N-N'-dimethyl 7cetamide, N-N'-dimethylformamide, N-N'-trimethylsulfoxide, and hexamethylphosphoformamide. A basic solvent is used. All of these types of solvents are highly hygroscopic, and absorbed moisture causes a decrease in molecular weight during polymerization and storage stability, so it is recommended to thoroughly dehydrate with a dehydrating agent before use. good. In addition to these solvents, toluene, xylene, benzonitrile, benzene,
A general-purpose solvent such as phenol can also be used in combination.

Further, representative examples of the aminosilane compound represented by the above general formula (III) used in the present invention include γ-7mi/
Propyltrimethoxysilane. There are γ-aminopropyltriethoxysilane, β-aminopropyltrimethoxysilane, β-7minopropyltriethoxysilane, etc.
These can also be used together.

The liquid crystal sandwiching substrate of the present invention has the general formula (
A polyimide alignment film obtained by applying a solution of a polyimide precursor compound containing 1 to 20 parts by weight of an aminosilane compound represented by I [I] and dehydrating and ring-closing is used. Application of the above polyimide precursor formulation to
It is applied once as a weight percent solution by dip method, spinner method, spray method, printing method, brush coating method, etc. After this coating, heat treatment is performed at a temperature of 100 to 400°C, preferably 200 to 350°C to dehydrate and ring-close the polyimide precursor composition, thereby obtaining a polyimide alignment film.

This film is subjected to a rubbing treatment to obtain a liquid crystal alignment film.

When the polyimide alignment film of the present invention is used as a liquid crystal sandwiching substrate, the pretilt angle of the liquid crystal molecules is 8 to 15 degrees,
This pretilt angle hardly changed even depending on the heat treatment and rubbing conditions during film formation. It also has excellent 'fi adhesion to glass substrates and the like, making it possible to maintain a good alignment state with high reliability.

Therefore, the polyimide alignment film of the present invention is particularly suitable as a liquid crystal sandwiching substrate used in an SBE type liquid crystal display element that requires stably maintaining a high pretilt angle of liquid crystal molecules.

(e) Function The liquid crystal sandwiching substrate of the present invention has the above structure, that is, as a liquid crystal alignment film, an organic tetracarboxylic acid anhydride component represented by the above general formula (1) and the above -general formula (II ) to 100 parts by weight of the polyimide precursor obtained by reacting the diamine compound component represented by the general formula (I[l
) A polyimide alignment film obtained by applying a solution containing 1 to 20 parts by weight of an amide/silane compound represented by the formula (2) and dehydrating and ring-closing is used.In this way, a specific polyimide precursor is first produced. By adding a specific aminosilane compound in a predetermined range to this specific polyimide precursor, the adhesion or adhesion to each 111y glass plate for liquid crystal cells is significantly improved, resulting in an effect with excellent long-term reliability. In other words, by using a specific 7-minosilane compound, a high degree of silane modification can be achieved with the minimum amount of silane modification without impairing various properties such as polyimide's original excellent heat resistance, electrical insulation, and mechanical properties. A liquid crystal alignment film is formed that can stabilize the pretilt angle, have good coating properties and adhesion, and provide stable liquid crystal alignment, as well as maintain a stable and high pretilt angle. 9(f) has the effect of providing a liquid crystal sandwiching substrate with high long-term reliability.
EXAMPLES Hereinafter, the present invention will be explained in detail based on Examples, but the present invention is not limited thereto.

In the following, the measurement of the tilt angle is based on the gloss
Applied Finosox (Jpn, J.

A ppi, P hys, ) Vol. 19, p. 2013 (1
The method described in 1980) was used.

Example 1 Using N-methyl-2-pyrrolidone as a solvent, 1 mol of pyronolitic anhydride and 1 mol of 2,2-bis[. Polyimide precursor 1 obtained by reaction
To 00 parts by weight, 5 parts of γ-amino/p-a-pyrtriethquine silane were added and diluted with N-methyl-2-pyrrolidone to prepare a 5 parts by 1% polyimide precursor complex solution. I got it. Using this solution and using a spinner, a glass substrate (vertical 15 cm
Ω, width 15cm, thickness 1111111)! Two coats were applied.

After this coating, it was heated at a temperature of 250° C. for 1 hour to cause dehydration and ring closure, thereby forming a polyimide film (Ua crystal oriented film) with a thickness of 1000 mm. This polyimide film (liquid crystal alignment film) was rubbed with a nylon thread cloth to obtain a liquid crystal sandwiching substrate. The pair of liquid crystal sandwiching substrates are separated and the liquid crystal [ZLI-229
3, (manufactured by Merck & Co.), right-handed chiral n1lcB15 (
I3DH M) was added to ZLI-2293 at 3.07% by weight and left-handed chiral agent 5811 (manufactured by Merck & Co., Ltd.) was added to ZLI-2293.
A liquid crystal display element (cell thickness: 6.3μ+#) was prepared by filling LI-2293 with 3°33 weight of Mixture 1.

When a voltage was applied to this liquid crystal display element and the orientation and contrast were observed, it was found to be extremely good, and there was no variation within the display panel. Also, when we measured the pretilt angle, it was 11.7 degrees over the entire display panel.
There was very little variation.

In addition, this element was heated to 100% at a temperature of 70"
When the alignment characteristics were observed after being left for 0 hours, no defects such as bleeding occurred, and the leakage current value was almost the same as the initial value.

Examples 2 to 4 In Example 1, only the heat treatment conditions and rubbing conditions were changed as shown in Table 1, and the characteristics of the ponds were evaluated in the same manner as in Example 1.

Example 5 In Example 1, 1-3,3'-4,4'-nophenyltetracarboxylic anhydride was used instead of pyromellitic anhydride, and 2,2-bis[4-(4- Ami/7e/
quin) phenyl 1 instead of hexafluoropropane 2
・2-bis[4-(4-7my77eth7xy)phenyl 1
The same procedure as in Example 1 was carried out except that Bropaci was used.

The results of each of the above examples are shown in Table 1.

Comparative Example I Using N-methyl-2-pyrrolidone as a solvent, 1 mol of pyronolitic anhydride and 1 mol of 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane were heated in a water bath at a temperature of 30 Keep the temperature below 5°C.
A polyimide precursor was obtained by reacting for several hours.

Table 1 below shows the results of characteristic evaluation conducted in the same manner as in Example 1.

Comparative Examples 2 to 4 In Comparative Example 1, only the heat treatment conditions and rubbing conditions were changed as shown in Table 1, and the characteristics of the pond were evaluated in the same manner as in Example 1.

The results are shown in Table 1.

Comparative Example 5 Characteristics were evaluated in the same manner as in Example 1, except that γ-ureidopropyl Y-ethoxysilane was used instead of γ-amino/propyltriethoxysilane, and the results are shown in Table 1. Shown below.

Comparative Example 6 A polyimide precursor was obtained in the same manner as in Example 1, except that N-phenyl-γ-7minobrobyltrimethoxysilane was used instead of γ-ami7propyltrie)oxysilane. .

Table 1 below shows the results of characteristic evaluation conducted in the same manner as in Example 1.

From the results shown in Table 1, it can be seen that each Example was superior to the Comparative Example in terms of adhesion to the substrate, uniformity of the funilast, and pretilt angle.

Furthermore, it is recognized that the variations in the pretilt angle are smaller (and the reliability is higher) in each example than in the comparative example.

(8) Effects of the Invention The liquid crystal sandwiching substrate made of the polyimide film of the present invention as a liquid crystal alignment film can maintain a high pretilt angle of liquid crystal molecules, and the pretilt angle is determined by the heat treatment conditions and rubbing conditions during film formation. In addition, it has excellent adhesion to glass substrates, etc., and can stably maintain a good orientation state for a long time.
A high pretilt angle can be stabilized with a specific amount of silane modification that does not impair various properties such as mechanical properties, and stable liquid crystal orientation can be obtained, resulting in high reliability in the VC period. It has an effect.

In addition, because it has such excellent characteristics, it is ideal as a liquid crystal sandwiching substrate for a high-quality SBE type liquid crystal display element, which requires uniform high-tilt alignment of liquid crystal molecules over a large area. be.

Patent applicant: Nitto Electric Industry Co., Ltd.

Claims (1)

[Claims] (1) In a liquid crystal sandwiching substrate in which a liquid crystal alignment film is provided on a substrate on which electrodes are formed, the liquid crystal alignment film has the following general formula (I) ▲Mathematical formula, chemical formula, table, etc.▼……………… ...(
I) [However, Ar in the formula indicates ▲There are mathematical formulas, chemical formulas, tables, etc.▼ and ▲There are mathematical formulas, chemical formulas, tables, etc.▼. ] At least one component selected from organic tetracarboxylic acid anhydrides represented by the following general formula (II) ▲There are mathematical formulas, chemical formulas, tables, etc.▼……………………(I
I) [However, in the formula, R_1 to R_4 are hydrogen, lower alkyl group,
It represents a lower alkoxy group, chlorine or bromine, and may be the same or different. Further, R_5 and R_6 are hydrogen, a methyl group, an ethyl group, a trifluoromethyl group, or a trichloromethyl group, and may be the same or different. ] At least one selected from the diamine compounds represented by
Polyimide precursor 100 obtained by reacting with seed components
For parts by weight, the following general formula (III) ▲There are mathematical formulas, chemical formulas, tables, etc.▼…………………………(I
II) [In the formula, R_7 is a linear methylene group represented by ■CH_2■n (n=1 to 10 integer) or a branched isomer thereof, and X is a hydrate selected from an alkoxy group, an acetoxy group, a phenoxy group, or a halogen. The decomposable group Y is a group selected from an alkyl group, an alkoxy group or an acetoxy group. 1. A liquid crystal sandwiching substrate characterized in that it is formed of a polyimide alignment film obtained by applying a solution containing 1 to 20 parts by weight of an aminosilane compound represented by the formula and then dehydrating and ring-closing the solution.