JPH06148650A - Liquid crystal oriented film and liquid crystal display element - Google Patents

Abstract

PURPOSE:To provide the org. oriented film which is constant in pretilt angle, exhibits a high pretilt angle in spite of changing of the baking temp. of the oriented film and is further improved in the dependency characteristic of the threshold voltage on frequencies and the liquid crystal display element including this org. oriented film. CONSTITUTION:This org. oriented film 4 for the liquid crystal display element contains the polyimide high-polymer material obtd. by polymerizing the diamine expressed by general formula (where (n) is an integer from 1 to 18; X is 1 to 4C alkyl group; (a), (b) denote 0, 1 or 2) and tetracarboxylic dianhydride. This oriented film 4 may be used by making combination use of other diamine. The oriented films 4 are formed between transparent electrodes 2 and a liquid crystal layer 5 of the liquid crystal display element constituted by clamping a nematic liquid crystal 5 exhibiting positive dielectric anisotropy between a pair of substrates 1 and 1 which have the electrodes 2 and at least one of which are transparent.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an organic alignment film containing a polyimide-based polymer substance obtained by polymerizing a diamine having a basic skeleton of bis-alkyl benzoate type and a tetracarboxylic dianhydride. The present invention relates to a liquid crystal display device including an alignment film.

[0002]

2. Description of the Related Art As an alignment film using a nematic liquid crystal, for example, a super twist liquid crystal display device, an active matrix liquid crystal display device, and a high pretilt angle polyimide alignment film for preventing the generation of various domains have been proposed. (Japanese Patent Laid-Open No. 64-25127, Japanese Patent Laid-Open No. 62-
262829, JP 63-259515, JP 62-127827, and JP 62-1.
No. 74725, No. 2-210328, No. 2-250033).

[0003]

In a liquid crystal display device, as the resolution becomes higher, the pretilt angle varies within the device plane and the stability is deteriorated. There is a problem of uneven brightness that occurs due to the large property. This is because the variation in the pre-tilt angle of the alignment film formed on the substrate, as the screen size of the device progresses,
The main cause is the large frequency dependence of the threshold voltage. The present invention provides an alignment film having a high pretilt angle, in which the fluctuation of the pretilt angle is small and the frequency dependence of the threshold voltage is also compatible, and a liquid crystal display device using the same. This is an issue.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have obtained by polymerizing a diamine having a basic skeleton of a bis-benzoic acid alkyl group and a tetracarboxylic acid dianhydride. By using an organic alignment film containing a polyimide-based or polyimide-siloxane-based substance to be obtained, a stable interface in which the molecular orientation of the alignment film is likely to be constant is obtained, and it has been found that the above problems can be solved and the present invention has been completed. .

That is, the present invention uses the general formula 1

[Chemical 1] (In the formula, n is an integer of 1 to 18, X is an alkyl group having 1 to 4 carbon atoms, and a and b are 0, 1 or 2) and a tetracarboxylic dianhydride. The organic alignment film for a liquid crystal display device contains a polyimide-based polymer substance obtained by polymerization.

The present invention also provides the diamine of the above chemical formula 1,
The following general formula 2,

[Chemical 2]

[Chemical 3] R is an alkyl group, X is an alkyl group having 1 to 4 carbon atoms, and a, b, c, d are 0, 1 or 2) or the general formula 4,

[Chemical 4] (In the formula, n is an integer of 1 to 5 and R is an alkyl group having 1 to 12 carbon atoms) and a diamine of tetracarboxylic acid dianhydride is used to obtain a polyimide polymer substance obtained by copolymerization. It is an organic alignment film for a liquid crystal display device that contains it.

Furthermore, in the present invention, a nematic liquid crystal having a positive dielectric anisotropy added with an optical rotatory substance between a pair of substrates having transparent electrodes, at least one of which is transparent, has a twisted liquid crystal structure. In the sandwiched liquid crystal display element,
A liquid crystal display device is formed by forming an organic alignment film containing the above-mentioned polyimide-based polymer substance between the electrode and the liquid crystal layer.

Further, according to the present invention, a nematic liquid crystal having a positive dielectric anisotropy added with an optical rotatory substance between a pair of substrates having transparent electrodes, at least one of which is transparent, has a helical structure twisted by 200 degrees or more. A liquid crystal display element having a liquid crystal sandwiched therein is a super twist liquid crystal display element in which an organic alignment film containing the above-mentioned polyimide-based polymer substance is formed between the electrode and a liquid crystal layer.

Further, according to the present invention, a liquid crystal display in which a nematic liquid crystal having a positive dielectric anisotropy and a twisted nematic liquid crystal having a twisted structure is sandwiched between a pair of substrates having an active matrix type electrode. In the element,
An active matrix liquid crystal display device is formed by forming an organic alignment film containing the above-mentioned polyimide-based polymer substance between the electrode and the liquid crystal layer.

In the present invention, the use of an organic alignment film obtained by polymerizing a diamine having a basic skeleton of a bis-alkyl benzoate type and a tetracarboxylic dianhydride has a high pretilt angle and a variation in the pretilt angle with respect to the firing temperature. It is important for stabilizing the frequency change of the threshold voltage.

Examples of the bis-alkyl benzoate-type diamine of Chemical Formula 1 of the present invention include bis (p-aminobenzoyloxy) propane, bis (m-aminobenzoyloxy) propane and bis (p-aminobenzoyl). (Oxy) pentane, bis (p-aminobenzoyloxy) octane, bis (p-aminobenzoyloxy) ethane, bis (p-aminobenzoyloxy) decane, bis (p-aminobenzoyloxy) tridecane, bis (p-aminobenzoyl) (Oxy) methane, bis (p-aminobenzoyloxy) butane, bis (m-aminobenzoyloxy) butane, bis (p-aminomethylbenzoyloxy) propane, bis (p-aminoethylbenzoyloxy) propane, bis (p- Aminobenzoyloxy) octadecane Can be exemplified bis (p- amino benzoyloxy) heptane, bis (p- amino benzoyloxy) nonane, and the like bis (p- amino benzoyloxy) hexane.

Further, regarding the diamine having an ether group of Chemical formula 2, for example, 2,2-bis [4- (p
-Aminophenoxy) phenyl] propane, 2,2-bis [4- (p-aminophenoxy) phenyl] butane,
2,2-bis [4- (p-aminophenoxy) phenyl] pentane, 2,2-bis [4- (p-aminophenoxy) phenyl] hexane, 2,2-bis [4- (p-
Aminophenoxy) phenyl] octane, 2,2-bis [4- (p-aminophenoxy) phenyl] decane,
2,2-bis [4- (p-aminophenoxy) phenyl] tridecane, 2,2-bis [4- (p-aminophenoxy) phenyl] pentadecane, 2,2-bis [4-
(P-Aminophenoxy) phenyl] methane, 2,2-
Bis [4- (p-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (p-aminophenoxy) phenyl] ketone, 2,2-bis [4- (p-aminophenoxy) phenyl] biphenyl, 2,2-bis [4- (p
-Aminophenoxy) phenyl] propylcyclohexane, 2,2-bis [4- (p-aminophenoxy) phenyl] hexylcyclohexane and the like.

On the other hand, examples of the tetracarboxylic dianhydride include pyromellitic dianhydride, methylpyromellitic dianhydride, and 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride. , 3, 3 ', 4, 4'
-Benzophenone tetracarboxylic dianhydride, 3,
3 ', 4,4'-diphenylmethane tetracarboxylic dianhydride, 3,3', 4,4'-diphenyl ether tetracarboxylic dianhydride, 3,3 ', 4,4'-diphenyl sulfone tetracarboxylic dianhydride Anhydrous, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl]
Propane tetracarboxylic dianhydride, 2,2-bis [4
-(3,4-Dicarboxyphenoxy) phenyl] octyltetracarboxylic dianhydride, 2,2-bis [4-
(3,4-dicarboxybenzoyloxy) phenyl]
Propane tetracarboxylic dianhydride, 2,2-bis [4
-(3,4-dicarboxybenzoyloxy) phenyl] tridecanetetracarboxylic dianhydride, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] tridecanetetracarboxylic dianhydride, Examples include cyclobutanetetracarboxylic dianhydride and butanetetracarboxylic dianhydride.

In the present invention, compounds other than those mentioned above, for example, phenylenediamine in each of the para and meta positions, diaminodiphenyl ether, diaminodiphenylmethane,
It is also possible to copolymerize diaminodiphenylpropane, diaminodiphenylsulfone, diaminonaphthalene, diaminohexane, diaminooctane and the like.

The precursor varnish is generally synthesized by N-methyl-2-pyrrolidone (hereinafter referred to as NMP),
In a solvent such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, sulfolane, butyl lactone, cresol, phenol, cyclohexanone, dioxane, tetrahydrofuran, butyl cellosolve, butyl cellosolve acetate, acetophenone,
It can be carried out at -20 to 200 ° C.

The precursor varnish may be a polyamic acid or its derivative other than a complete polyamic acid, and may be one that has undergone imidization to some extent. Also, silane coupling agents, titanate coupling agents, aluminum alcoholates,
Surface treatment agents such as aluminum chelate and zirconium chelate can be mixed and reacted in the precursor varnish.

In order to adjust the fluidity of the precursor varnish, the thermal expansion coefficient of the cured product, the elastic modulus, the dielectric constant, the refractive index, etc.,
Inorganic or organic powders, fibers and the like may be mixed and used as long as the object of the present invention is not lost. The precursor film can be formed by general spin coating, printing, brush coating, spraying, or the like.

[0018]

The polyimide and polyimidesiloxane of the present invention are polymerized with a tetracarboxylic dianhydride using a bis-alkyl benzoate type diamine to increase flexibility in the main chain direction and further imidize at low temperature. It is considered that the improvement is achieved by reducing the fluctuation of the pretilt angle with respect to the firing temperature and the frequency dependence ΔF of the threshold voltage shown in FIG. 2 at a high pretilt angle.

[0019]

EXAMPLES The present invention will be specifically described below with reference to examples. However, the technical scope of the present invention is not limited by these examples. Example 1 Bis (p-aminobenzoyloxy) propane 1 mol%
And pyromellitic dianhydride 0.5 mol% and 3,3 ′,
4,4'-biphenyltetracarboxylic dianhydride 0.3
Mol% and 3,3 ', 4,4'-benzophenone tetracarboxylic acid dianhydride 0.2 mol% were polymerized in N-methyl-2-pyrrolidone at 5 ° C for 12 hours to obtain a polyimide precursor varnish. . After diluting this varnish to a concentration of 5%, spin coating is performed on the surface of the transparent electrode on which the SiO ₂ —TiO ₂ inorganic film is formed, and heat treatment is performed at 220 to 270 ° C./10 min to form a polyimide film of about 500 Å. Rubbing was performed under a cutting condition of 0.3 mm, and ZLI-113 manufactured by Merck & Co., Inc.
A liquid crystal material such as No. 2 was sealed to produce a liquid crystal display element. The sectional view is shown in FIG. In FIG. 1, a transparent electrode 2, a SiO ₂ film 3, and an alignment film 4 made of a polyimide film are formed between glass substrates 1 and a liquid crystal material 5 is enclosed. The pretilt angle of this liquid crystal display device was measured by a general crystal rotation method, and as a result, it showed an almost constant value at a high pretilt angle of 4.1 to 4.2 degrees.

Next, the above-mentioned polyimide precursor is spin-coated on the surface of the substrate on which the SiO ₂ --TiO ₂ inorganic film is formed on the transparent electrode, and heat treated at 250 ° C./10 min to about 5
A 00Å polyimide film was formed. In order to set the twist angle of the liquid crystal molecules sandwiched by the substrates to 240 degrees, the upper and lower substrates were rubbed at respective angles, and seal printing was performed between the substrates to assemble a liquid crystal cell having a gap of 6 μm. A nematic liquid crystal containing a biphenyl liquid crystal, a phenylcyclohexane liquid crystal, or an ester cyclohexane liquid crystal as a main component is added to the cell, and an optical rotatory substance (Merck: S
The liquid crystal material containing 0.5% by weight of 811) was vacuum-sealed. Frequency dependence of threshold voltage of the liquid crystal cell: ΔF
When (30 Hz / 1 kHz) was measured, it showed a value of 0.99 or more, and liquid crystal display elements in which various domains and uneven brightness were reduced were obtained.

Example 2 0.5 mol% of bis (p-aminobenzoyloxy) propane, 0.5 mol% of 2,2-bis [4- (p-aminophenoxy) phenyl] propane and pyromellitic dianhydride. 0.5 mol% and 0.5 mol% of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride were polymerized in dimethylacetamide at 10 ° C. for 10 hours to obtain a polyimide precursor varnish. After diluting this varnish to 4% concentration,
The surface of the transparent electrode on which the SiO ₂ —TiO ₂ inorganic film is formed is spin-coated and heat treated at 220 to 270 ° C./10 min to form a polyimide film of about 600 Å, and then 0.3 mm.
Rubbing was performed under the following cutting conditions, and ZLI- from Merck
A liquid crystal material such as 1132 was sealed to produce a liquid crystal display element. As a result of measuring the pretilt angle by a general crystal rotation method, the value was 4.5 to 4.6 degrees, which was almost constant at a high pretilt angle.

Next, the above-mentioned polyimide precursor was spin-coated on the surface of the transparent electrode of the substrate on which the SiO ₂ —TiO ₂ inorganic film was formed, and heat-treated at 250 ° C./10 min for about 6 minutes.
A 00Å polyimide film was formed. In order to set the twist angle of the liquid crystal molecules sandwiched by the substrates to 260 degrees, the upper and lower substrates were rubbed at each angle, and seal printing was performed between the substrates to assemble a liquid crystal cell with a gap of 5.5 μm. . A liquid crystal material obtained by adding 0.5% by weight of an optical rotatory substance (S811 manufactured by Merck & Co., Inc.) to a nematic liquid crystal containing a biphenyl liquid crystal, a phenylcyclohexane liquid crystal, and an ester cyclohexane liquid crystal as a main component was vacuum-sealed in the cell. Frequency dependence of threshold voltage of the liquid crystal cell:
When ΔF (30 Hz / 1 kHz) is measured, it is 0.99
The above values are shown, various domains and luminance unevenness are reduced, and a phase plate is attached to obtain a monochrome display liquid crystal display device.

Example 3 0.8 mol% of bis (p-aminobenzoyloxy) pentane, 0.2 mol% of 2,2-bis [4- (p-aminophenoxy) phenyl] octane and pyromellitic dianhydride. 0.9 mol% and 1,1-bis [4- (3,4-dicarboxyphenoxy) phenyl] cyclohexanetetracarboxylic acid dianhydride 0.1 mol% were added to N-methyl-2-
Polymerization was carried out in pyrrolidone at 20 ° C. for 12 hours to obtain a polyimide precursor varnish. After diluting this varnish to a concentration of 5%, spin coating it on a transparent electrode, 220-270 ° C / 10m
In heat treatment to form a polyimide film of about 550Å,
Rubbing was performed under a cutting condition of 0.3 mm, and a liquid crystal material such as ZLI-1132 manufactured by Merck Ltd. was sealed to manufacture a liquid crystal display element. As a result of measuring the pretilt angle by a general crystal rotation method, the value was 4.4 to 4.5 degrees, which was almost constant at a high pretilt angle.

Next, the above polyimide precursor was spin-coated on the surface of the transparent electrode of the substrate on which the SiO ₂ —TiO ₂ inorganic film was formed, and heat-treated at 240 ° C./10 min for about 5 minutes.
A 50Å polyimide film was formed. In order to set the twist angle of liquid crystal molecules sandwiched by the substrates to 270 degrees, the upper and lower substrates were rubbed at respective angles, and seal printing was performed between the substrates to assemble a liquid crystal cell with a gap of 6.5 μm. . A liquid crystal material obtained by adding 0.5% by weight of an optical rotatory substance (S811 manufactured by Merck & Co., Inc.) to a nematic liquid crystal containing a biphenyl liquid crystal, a phenylcyclohexane liquid crystal, and an ester cyclohexane liquid crystal as a main component was vacuum-sealed in the cell. Frequency dependence of threshold voltage of the liquid crystal cell:
When ΔF (30 Hz / 1 kHz) is measured, it is 0.99
Liquid crystal display devices having the above values and having reduced various domains and uneven brightness were obtained.

EXAMPLE 4 0.8 mol% of bis (p-aminobenzoyloxy) octane

[Chemical 5] 0.2 mol% of a diamine having a siloxane group, 0.8 mol% of pyromellitic dianhydride, and 2,2-bis [4
-(3,4-Dicarboxybenzoyloxy) phenyl] tridecanetetracarboxylic acid dianhydride 0.2 mol%
Was polymerized in N-methyl-2-pyrrolidone at 5 ° C. for 8 hours to obtain a polyimide precursor varnish. 5% of this varnish
After diluting to a concentration, a SiO ₂ —TiO ₂ inorganic film is spin-coated on the transparent electrode and heat-treated at 220 to 270 ° C./10 min to form a polyimide siloxane film of about 700 Å,
Rubbing was performed under a cutting condition of 0.3 mm, and a liquid crystal material such as ZLI-1132 manufactured by Merck Ltd. was sealed to manufacture a liquid crystal display element. As a result of measuring the pretilt angle by a general crystal rotation method, the value was 4.0 to 4.1 degrees, which was almost constant at a high pretilt angle.

Next, the above-mentioned polyimide precursor was spin-coated on the transparent electrode of the substrate on the surface on which the SiO ₂ —TiO ₂ inorganic film was formed, and heat treated at 250 ° C./10 min for about 7 minutes.
A 00Å polyimide film was formed. In order to set the twist angle of the liquid crystal molecules sandwiched by the substrates to 240 degrees, the upper and lower substrates were rubbed at respective angles, and seal printing was performed between the substrates to assemble a liquid crystal cell with a gap of 6.0 μm. . A liquid crystal material obtained by adding 0.5% by weight of an optical rotatory substance (S811 manufactured by Merck & Co., Inc.) to a nematic liquid crystal containing a biphenyl liquid crystal, a phenylcyclohexane liquid crystal, and an ester cyclohexane liquid crystal as a main component was vacuum-sealed in the cell. Frequency dependence of threshold voltage of the liquid crystal cell:
When ΔF (30 Hz / 1 kHz) is measured, it is 0.99
The above values are shown, various domains and brightness unevenness are reduced, and a phase plate is additionally provided to obtain a monochrome display liquid crystal display device.

Example 5 0.7 mol% of bis (m-aminobenzoyloxy) propane, 0.3 mol% of 2,2-bis [4- (p-aminophenoxy) phenyl] methane and pyromellitic dianhydride. 0.8 mol% and 0.2 mol% of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride were polymerized in N-methyl-2-pyrrolidone at 10 ° C. for 8 hours to obtain a polyimide precursor varnish. Got This varnish was diluted to a concentration of 5%, spin-coated on a transparent electrode, and then 220-270 ° C /
After heat treatment for 10 minutes to form a polyimide film having a thickness of about 800 Å, rubbing was performed under a cutting condition of 0.3 mm, and a liquid crystal material such as ZLI-1132 manufactured by Merck Ltd. was sealed to manufacture a liquid crystal display element. As a result of measuring the pretilt angle by a general crystal rotation method, an almost constant value of 3.9 to 4.0 degrees was shown.

Next, the above-mentioned polyimide precursor varnish was spin-coated on a transparent electrode provided with a color filter, and 23
A heat treatment was performed at 0 ° C. for 10 minutes to form a polyimide film of about 800 Å. In order to set the twist angle of the liquid crystal molecules sandwiched by the substrates to 220 degrees, the upper and lower substrates were rubbed at respective angles, and seal printing was performed between the substrates to assemble a liquid crystal cell with a gap of 6.5 μm. . A liquid crystal material was vacuum-sealed in the cell in the same manner as in Example 1. Frequency dependence of threshold voltage of the liquid crystal: ΔF (30 Hz / 1 kHz
When z) was measured, it showed a value of 0.99 or more, and various domains and uneven brightness were reduced.

Example 6 0.8 mol% of bis (p-aminobenzoyloxy) hexane, 0.2 mol% of 2,2-bis [4- (p-aminophenoxy) phenyl] sulfone and pyromellitic dianhydride 0.8 mol% and 0.2 mol% of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride were added to N-methyl-
Polymerization was performed in 2-pyrrolidone at 10 ° C. for 8 hours to obtain a polyimide precursor varnish. After diluting this varnish to 5% concentration,
Spin coating on a transparent electrode, 220-270 ° C / 10
After heat treatment for min to form a polyimide film of about 800Å,
Rubbing was performed under a cutting condition of 0.3 mm, and a liquid crystal material such as ZLI-1132 manufactured by Merck Ltd. was sealed to manufacture a liquid crystal display element. As a result of measuring the pretilt angle by a general crystal rotation method, it showed an almost constant value of 3.7 to 3.8 degrees.

Next, the above polyimide precursor varnish was spin-coated on the active matrix type electrode and the color filter and heat-treated at 220 ° C./10 min to form a polyimide film of about 700 Å. Rubbing is performed so that the twist angle of liquid crystal molecules sandwiched by the substrates is 90 degrees, and seal printing is performed between the substrates to form a gap of 6.0 μm.
As a result of assembling the liquid crystal cell of m and enclosing the liquid crystal material in a vacuum and evaluating it, uneven brightness was reduced.

Comparative Example 1 2,2-bis [4- (p-aminophenoxy) phenyl] propane 0.5 mol% and 1,1,1,3,3,3-
Hexafluoro-2,2-bis [4- (p-aminophenoxy) phenyl] propane 0.5 mol% and pyromellitic dianhydride 0.5 mol% and 3,3 ', 4,4'-
Biphenyl tetracarboxylic dianhydride 0.5 mol% N
Polymerized in methyl-2-pyrrolidone at 10 ° C. for 8 hours,
A polyimide precursor varnish was obtained. After diluting this varnish to a concentration of 5%, spin coating it on a transparent electrode,
After heat treatment at 0 ° C./10 min to form a polyimide film having a thickness of about 800 Å, rubbing was performed under a cutting condition of 0.3 mm, and a liquid crystal material such as ZLI-1132 manufactured by Merck Ltd. was sealed to manufacture a liquid crystal display element. As a result of measuring the pretilt angle by a general crystal rotation method, it is 3.5 to 4.5.
The temperature and the baking temperature of the alignment film greatly changed.

Next, the above-mentioned polyimide precursor is spin-coated on the surface of the substrate on which the SiO ₂ --TiO ₂ inorganic film is formed on the transparent electrode, and heat treated at 250 ° C./10 min to about 5
A 00Å polyimide film was formed. In order to set the twist angle of the liquid crystal molecules sandwiched by the substrates to 260 degrees, the upper and lower substrates were rubbed at respective angles, and seal printing was performed between the substrates to assemble a liquid crystal cell with a gap of 6.5 μm. . A liquid crystal material obtained by adding 0.5% by weight of an optical rotatory substance (S811 manufactured by Merck & Co., Inc.) to a nematic liquid crystal containing a biphenyl liquid crystal, a phenylcyclohexane liquid crystal, and an ester cyclohexane liquid crystal as a main component was vacuum-sealed in the cell. Frequency dependence of threshold voltage of the liquid crystal cell:
When ΔF (30 Hz / 1 kHz) is measured, it is 0.96.
Value, indicating that various domains and uneven brightness occurred.

Comparative Example 2 2,2-bis [4- (p-aminophenoxy) phenyl] propane 0.5 mol% and 2,2-bis [4- (p-
Aminophenoxy) phenyl] octane 0.5 mol% and pyromellitic dianhydride 0.5 mol% and 3,3 ′,
0.5 mol% of 4,4'-benzophenone tetracarboxylic acid dianhydride in N-methyl-2-pyrrolidone at 10 ° C.
Polymerization was carried out for 8 hours to obtain a polyimide precursor varnish. This varnish was diluted to a concentration of 5%, spin-coated on a transparent electrode, and heat-treated at 220 to 270 ° C./10 min to about 800.
After forming the polyimide film of Å, rubbing was performed under a cutting condition of 0.3 mm, and a liquid crystal material such as ZLI-1132 manufactured by Merck Co., Ltd. was sealed to manufacture a liquid crystal display element. As a result of measuring the pretilt angle by a general crystal rotation method,
The temperature largely changed from 3.2 to 3.9 degrees depending on the firing temperature of the alignment film.

Next, the above polyimide precursor varnish was spin-coated on the active matrix type electrode and the color filter and heat-treated at 220 ° C./10 min to form a polyimide film of about 800 Å. Rubbing is performed so that the twist angle of liquid crystal molecules sandwiched by the substrates is 90 degrees, and seal printing is performed between the substrates to form a gap of 6.5 μm.
As a result of assembling the liquid crystal cell of m and enclosing the liquid crystal material in a vacuum and evaluating it, uneven brightness occurred.

[0035]

The organic alignment film of the present invention provides an alignment film having a new characteristic that the pretilt angle is substantially constant even when the firing temperature is changed, and the frequency change of the threshold voltage is stable. As a result of producing a super twist liquid crystal display element and an active matrix liquid crystal display element from them, domains and luminance unevenness do not occur, and finally the display quality of the product can be greatly improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a liquid crystal display element.

FIG. 2 is a graph showing frequency characteristics of threshold voltage.

[Explanation of symbols]

1 ... Glass substrate, 2 ... Transparent electrode, 3 ... SiO ₂ film, 4 ...
Alignment film, 5 ... Liquid crystal

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Keiko Inoue Keiko Inoue 7-1, 1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Katsumi Kondo 7-chome, Omika-cho, Hitachi-shi, Ibaraki No. 1 Incorporated company Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Shuichi Ohara 7-1 1-1 Omika-cho, Hitachi City, Ibaraki Prefecture Incorporated Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Shinji Hasegawa Mobara City, Chiba Prefecture 3300 Hayano Hitachi Ltd. Mobara factory

Claims (6)

[Claims] 1. A general formula 1, (In the formula, n is an integer of 1 to 18, X is an alkyl group having 1 to 4 carbon atoms, and a and b are 0, 1 or 2) and a tetracarboxylic dianhydride. An organic alignment film for a liquid crystal display device containing a polyimide-based polymer obtained by polymerization. 2. A general formula 1, (In the formula, n is an integer of 1 to 18, X is an alkyl group having 1 to 4 carbon atoms, a and b are 0, 1 or 2) and a diamine represented by the general formula 2, [Chemical 3] R represents an alkyl group, X represents an alkyl group having 1 to 4 carbon atoms, and a, b, c, d represent 0, 1 or 2, and a diamine represented by the formula An organic alignment film for a liquid crystal display device containing a polyimide-based polymer obtained by polymerization. 3. A general formula 1, (In the formula, n is an integer of 1 to 18, X is an alkyl group having 1 to 4 carbon atoms, a and b are 0, 1 or 2) and a diamine represented by the general formula 4, (In the formula, n is an integer of 1 to 5 and R is an alkyl group having 1 to 12 carbon atoms) and a polyimide siloxane-based polymer obtained by copolymerizing a dicarboxylic acid and a tetracarboxylic dianhydride. An organic alignment film for a liquid crystal display device containing a molecular substance. 4. A liquid crystal display in which a liquid crystal having a spiral structure is sandwiched between a pair of substrates each having a transparent electrode and at least one of which is transparent, and a nematic liquid crystal having a positive dielectric anisotropy added with an optical rotatory substance is twisted. A liquid crystal display device, wherein an organic alignment film containing the polyimide-based polymer substance according to claim 1 is formed between the electrode and the liquid crystal layer. 5. A nematic liquid crystal having a positive dielectric anisotropy added with an optical rotatory substance and sandwiching a liquid crystal having a helical structure twisted by 200 degrees or more between a pair of substrates having transparent electrodes and at least one of which is transparent. In the above liquid crystal display element, a super twist liquid crystal display element is characterized in that an organic alignment film containing the polyimide polymer material according to claim 1, 2 or 3 is formed between the electrode and the liquid crystal layer. 6. A liquid crystal display device in which a nematic liquid crystal having a positive dielectric anisotropy and twisted nematic liquid crystal having a twisted structure is sandwiched between a pair of substrates having an active matrix type electrode. An active matrix liquid crystal display device, characterized in that an organic alignment film containing the polyimide polymer material according to claim 1, 2 or 3 is formed between an electrode and a liquid crystal layer.