JP2003344859A - Liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display element wherein coating properties and adhesion properties of an alignment layer can be improved and which has excellent characteristics of a high pretilt angle and the like. <P>SOLUTION: The twisted nematic type liquid crystal display element wherein a nematic liquid crystal layer is interposed between two substrates each formed by successively disposing a color filter, an electrode and an alignment layer on a transparent substrate and the nematic liquid crystal has 90 to 360° twist angle, is characterized in that the alignment layer is formed by applying varnish consisting of solvent soluble polyimide containing a carboxyl group and an organic group represented by formula (1) and obtained by an imide ring-closure reaction. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twist nematic type and a super twist nematic type liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, a polyamic acid solution has been used as a material used for forming an alignment film of a liquid crystal display device from the viewpoint of process compatibility such as adhesion and printability. The imidation reaction is performed by heating. Since the polyamic acid solution is an unstable component of an intermediate that has not completed imidization, it is inferior in storage stability, and is susceptible to process conditions such as coating work, drying work, and labyrinth treatment, and sensitive to work management. There was a problem in electrical reliability such as voltage stability. In order to improve the storage stability of such a polyamic acid solution, an imide ring-closed polyimide has been proposed.

[0003]

However, although the conventional imide ring-closed polyimide is excellent in storage stability, when it is applied to the formation of an alignment film of a liquid crystal display device, its adhesion with other substrates is not improved. There is a problem that it is inferior and the labyrinth characteristic is inferior.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and by using an imide ring-closed polyimide having excellent storage stability, the coating property and adhesion of the alignment film can be improved. It is an object of the present invention to provide a liquid crystal display device having improved characteristics and excellent characteristics.

[0005]

In order to achieve the above object, the present invention provides a nematic liquid crystal layer sandwiched between two substrates formed by sequentially arranging a color filter, electrodes and an alignment film on a transparent substrate. In the twisted nematic liquid crystal display device in which the twist angle of the nematic liquid crystal is 90 degrees to 360 degrees, the alignment layer is formed of a carboxyl group and a chemical formula.

[Chemical 4] There is provided a liquid crystal display device, which is formed by applying a varnish made of a solvent-soluble polyimide having an imide ring-closed containing an organic group represented by

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a carboxyl group and a chemical formula

[Chemical 5] Examples of the solvent-soluble polyimide having an imide ring-closed containing an organic group represented by:

[Chemical 6] 3,3'-dimethyl-4,4'-diamino-cyclohexylmethane (DMHM) represented by

[Chemical 7] 3,5-diaminobenzoic acid represented by (DABz) is used, to which an acid dianhydride is appropriately added and reacted with a lactone polymerization catalyst in a heated polar solvent to directly imidize Can be mentioned.

The acid dianhydride has the chemical formula

[Chemical 8] 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA) represented by

[Chemical 9] Bicyclo (2,2,2) oct-ene-
2,3,5,6-tetracarboxylic dianhydride (BC
D), chemical formula

[Chemical 10] 4,4'-oxydiphthalic anhydride (BT
DA), chemical formula

[Chemical 11] 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride (6-FDA) represented by

[Chemical 12] 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (BPDA) represented by

[Chemical 13] It is preferable to use at least one selected from 3,3 ′, 4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA) represented by

In the present invention, a polyimide can be obtained by dissolving a diamine and an acid dianhydride in an organic solvent and directly imidizing them, and further dissolving and reacting the diamine and the acid dianhydride in an organic solvent. Then, a polyimide can be obtained by subsequently adding at least one of diamine and acid dianhydride and imidizing. The mixing ratio of the diamine and the acid dianhydride is preferably 0.95 to 1.05 mol% of the total amount of the diamine with respect to 1 mol% of the total amount of the acid dianhydride.

Examples of the organic solvent include N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, sulfolane, anisole, dioxolane, butylcellosolve acetate and lactone series, which can be used alone. You may mix and use 2 or more types. Examples of the lactone catalyst include γ-caprolactone, γ-valerolactone, γ-butyrolactone, γ
-Tetronic acid, γ-phthalide, γ-phthalide acid, γ-coumarin and the like can be mentioned, and a mixture of a lactone type and a basic compound such as pyridine, quinoline or N-methylmorpholine can also be used.

In the present invention, the varnish made of a solvent-soluble polyimide having an imide ring closed has a solid content concentration of 1 to 20.
%, Preferably 3 to 10%. When the solid content concentration is less than 1%, the film forming property is poor, and when it exceeds 20%, problems occur in film thickness control and the like. Also, the viscosity is 1
It is preferably 400 mPa · s, preferably 1
It is 0 to 200 mPa · s. If the viscosity is less than 1 mPa · s, the film-forming property is poor, and if it exceeds 400 mPa · s, problems occur in film thickness control and the like.

[0011]

EXAMPLES Examples of the present invention will be described below together with comparative examples. FIG. 1 is a cross-sectional explanatory view of an embodiment of a liquid crystal display device of the present invention, in which 1a and 1b are transparent substrates, 2a and 2b.
Is a color filter, 3a and 3b are light-shielding films, 4a and 4b
Is a protective film, 5a and 5b are XY electrodes, 6a and 6b are alignment films, and 7 is a liquid crystal. Alignment films 6a and 6b
Are transparent substrates 1a and 1b on which XY electrodes 5a and 5b are formed.
It is formed by applying a varnish made of a solvent-soluble polyimide having an imide ring closed thereon and curing it. The coating method includes spin coating, printing, dipping, brush coating, spraying, and roll coater. Law etc.

Example 1 Bicyclo (2,2,2) octa-2,3,5,6-tetracarboxylic dianhydride (BC
D) 0.33 mol% and diaminobenzoic acid (DABz)
0.5 mol% of N-methyl-2-pyrrolidone (NMP)
It was dissolved in the mixture, γ-caprolactone, pyridine and toluene were further added, and the mixture was stirred at 180 ° C. for 1 hour in a nitrogen atmosphere. Next, 0.58 mol% of 3,3 ', 4,4'-biphenyl-tetracarboxylic dianhydride (BPDA),
0.5 mol% of 3'-dimethyl-4,4'-diamino-dicyclohexylmethane (DMHM), NMP and toluene were added, and the mixture was reacted at 170 ° C for 3.5 hours to obtain a reddish brown transparent high viscosity varnish. Furthermore, varnish at 200 ° C,
When the solid content concentration was examined by heating for 2 hours, it was 16.0%. This varnish was diluted and adjusted with NMP, N-vinyl-2-pyrrolidone and butyl cellosolve acetate so as to have a solid content concentration of 5.0% and a viscosity of 50 mPa · s.

[Preparation of Super Twisted Liquid Crystal Element] This adjusting varnish was applied on a transparent electrode glass substrate with a color filter by printing using a spin coating device, and then 8
After preheating at 0 ° C. for 2 minutes, it was heated at 250 ° C. for 1 hour to be cured to form a polyimide film (alignment film) having a thickness of 800 Å (angstrom). In addition, push in 0.4mm so that the twist angle is 240 degrees.
A rubbing treatment was performed at a rotation speed of 0 rpm and a stage speed of 2 m / min, pre-cleaning was performed in ultrasonic pure water, and heating and drying were performed at 80 ° C. for 10 minutes. Epoxy sealant is printed between the substrates, and the liquid crystal element with a gap of 6.3 μm is made by the DIC liquid crystal D
LC-430002E075 was injected to produce a super twist type liquid crystal element.

The electro-optical characteristics of this element were observed by a microscope using a voltage-light transmittance measuring device to avoid the dispersed bead position at the center of the cell, and the spot diameter was 100 μm and the frequency was 32.
Hz, white light source used, boost rate 0.02V / sec,
The applied voltages V ₁₀ and V ₉₀ and the ratio thereof were measured for relative light transmittances of 10% and 90% at the time of vertical incidence.

[Preparation of Liquid Crystal Cell for Pretilt Angle Measurement] The adjustment varnish was spin-coated on a glass substrate with a transparent electrode, preheated at 80 ° C. for 2 minutes, and then heated at 250 ° C. for 1 hour to be cured to a thickness. 800Å (Angstrom)
Of polyimide film was formed. Further, a pushing amount of 0.4 mm, a rotation speed of 1300 rpm, and a rubbing treatment at a stage speed of 2 m / min.
After being heated and dried for a minute and printed with an epoxy sealant, a liquid crystal ZLI-1132 manufactured by Merck Ltd. was vacuum-injected to prepare a pretilt angle measurement liquid crystal cell.

This liquid crystal cell was replaced with a He-Ne laser, 1/4.
Wave plate, pinhole, polarizer, sample cell with drive rotation,
Using a pretilt angle measuring device by a crystal rotation method composed of an analyzer and a power meter, the measurement was performed under the conditions of a wavelength of 633 nm and a rotation range of −45 ° to 45 °.

Table 1 shows the measurement results of the applied voltages V ₁₀ and V ₉₀ , their ratio, the measurement result of the pretilt angle, and the evaluation results of the coating property of the varnish, the adhesion and the storage stability. As is apparent from the table, V ₁₀ is 2.40 V and V ₉₀ is 2.33.
With respect to V, V ₁₀ / V ₉₀ is 1.03, which is excellent in steepness, the pretilt angle is 3.5 degrees, and it is clear that the coating property, adhesion, and storage stability are also excellent.

The coatability was determined by applying a varnish onto a glass substrate with a transparent electrode that had been thoroughly washed using a spin coating apparatus at 25 ° C. and 55% humidity at 2000 rpm / 40 seconds, and visually observing. The uniformity and the whitening property were evaluated.

Regarding the adhesiveness, the sample coated under the above conditions was treated under predetermined curing conditions, and the adhesiveness after rubbing, pre-cleaning and drying was evaluated by a cross-cut test.

The storage stability was evaluated by measuring the initial viscosity of the varnish and the viscosity after standing at room temperature for 3 months. Viscosity measurement is
Using a TVE-20HT viscometer manufactured by Tokimec, the rotor 0.8 × R24 was used to measure the rotor rotation 30 rpm and the sample amount 0.5 ml, and the average value of 5 times was calculated.

(Example 2) A super twist type liquid crystal element and a liquid crystal cell were produced in the same manner as in Example 1 except that the same adjusting varnish as in Example 1 was used and the heating temperature at the time of curing the polyimide film was 200 ° C. Then, the same evaluation as in Example 1 was performed, and the results are shown in Table 1. V ₁₀ is 2.44V, V ₉₀ is 2.35V, V ₁₀ / V ₉₀ is 1.04, which is excellent in steepness, pretilt angle is 3.0 degrees, coating property, adhesiveness, storage It can be seen that the stability is also excellent.

(Example 3) A super twist type liquid crystal element and a liquid crystal cell were prepared in the same manner as in Example 1 except that the same adjusting varnish as in Example 1 was used and the heating temperature during curing of the polyimide film was 220 ° C. Then, the same evaluation as in Example 1 was performed, and the results are shown in Table 1. V ₁₀ is 2.43V, V ₉₀ is 2.35V, V ₁₀ / V ₉₀ is 1.04, which is excellent in steepness, and the pretilt angle is 3.6 degrees. It can be seen that the stability is excellent.

Example 4 A super twist type liquid crystal element and a liquid crystal were prepared in the same manner as in Example 1 except that the same adjusting varnish as in Example 1 was used and preheating for curing the polyimide film was performed at 60 ° C. for 2 minutes. A cell was prepared and evaluated in the same manner as in Example 1, and the results are shown in Table 1. V ₁₀ is 2.40V,
V ₉₀ is 2.33 V, V ₁₀ / V ₉₀ is 1.03, which is excellent in steepness, the pretilt angle is 3.3 degrees, and the coating property is
It can be seen that the adhesiveness and storage stability are excellent.

(Example 5) A super twist type liquid crystal element and a liquid crystal cell were produced in the same manner as in Example 1 except that the same adjusting varnish as in Example 1 was used and the pushing amount of the rubbing treatment was 0.2 mm. . V ₁₀ is 2.40V, V ₉₀ is 2.33V, V ₁₀ / V ₉₀ is 1.03, which is excellent in steepness, and the pretilt angle is 3.8 degrees. It can be seen that the stability is excellent.

Example 6 A super twist type liquid crystal element and a liquid crystal cell were produced in the same manner as in Example 1 except that the same adjusting varnish as in Example 1 was used and the indentation amount in the rubbing treatment was set to 0.6 mm. . V ₁₀ is 2.40V, V ₉₀ is 2.33V, V ₁₀ / V ₉₀ is 1.03, which is excellent in steepness, and the pretilt angle is 3.6 degrees. It can be seen that the stability is excellent.

Example 7 A super twist type liquid crystal element and a liquid crystal cell were prepared in the same manner as in Example 1 except that the same adjusting varnish as in Example 1 was used and the stage speed of the rubbing treatment was 4.2 m / min. It was made. V ₁₀ is 2.40V, V
₉₀ is 2.33V, V ₁₀ / V ₉₀ is 1.03, which is excellent in steepness, the pretilt angle is 3.3 degrees, and it is excellent in coating property, adhesion, and storage stability. Recognize.

Example 8 The reddish brown and transparent high viscosity varnish obtained in Example 1 was used with NMP, N-vinyl-2-pyrrolidone and butyl cellosolve acetate to obtain a solid content concentration of 3.0% and a viscosity of 20 mPa · s. It was diluted and adjusted to be s. Using this adjusting varnish, a super twist type liquid crystal element and a liquid crystal cell having a polyimide film thickness of 400 L were prepared in the same manner as in Example 1. V ₁₀ is 2.40V, V ₉₀ is 2.33V, V ₁₀ / V ₉₀ is 1.03, which is excellent in steepness, and the pretilt angle is 3.5 degrees. It can be seen that the stability is excellent.

(Example 9) The reddish brown and transparent high viscosity varnish obtained in Example 1 was mixed with NMP, N-vinyl-2-pyrrolidone and butylcellosolve acetate to obtain a solid content of 1
It was diluted and adjusted to have a viscosity of 5.0% and a viscosity of 300 mPa · s. Using this adjusting varnish, a super twist type liquid crystal element and a liquid crystal cell having a polyimide film having a thickness of 4000 Å were prepared in the same manner as in Example 1. V ₁₀ is 2.40V,
V ₉₀ is 2.33 V, V ₁₀ / V ₉₀ is 1.03, which is excellent in steepness, the pretilt angle is 3.5 degrees, and the coating property is
It can be seen that the adhesiveness and storage stability are excellent.

(Comparative Example 1) Varnish for liquid crystal alignment film material (manufactured by Japan Synthetic Rubber Co., Ltd., trade name: Optoma, imide complete ring closure type, solid content concentration 5.2%, viscosity 55 mPa · s)
Is applied by printing on a transparent electrode glass substrate with a color filter using a spin coating device, preheated at 80 ° C. for 2 minutes, and then heated at 250 ° C. for 1 hour to cure,
A polyimide film (alignment film) having a thickness of 830 Å (angstrom) was formed. Furthermore, when the pushing angle was 0.4 mm, the rotational speed was 1300 rpm, and the stage speed was 2 m / min so that the twist angle was 240 degrees, the film was rubbed and pre-cleaned in ultrasonic pure water. Therefore, the super twist type liquid crystal element could not be manufactured.

Comparative Example 2 A varnish for liquid crystal alignment film (manufactured by Nissan Chemical Industries, Ltd., trade name: SAN EVER, solid content concentration 4.0%, viscosity 42 mPa · s) is a transparent electrode glass substrate with a color filter. After printing by using a spin coating device, preheat at 80 ℃ for 2 minutes, then
The polyimide film having a thickness of 700 Å (angstrom) was formed by heating at 0 ° C. for 1 hour for curing. Further, a rubbing treatment is performed at a pushing amount of 0.2 mm, a rotation speed of 1300 rpm, and a stage speed of 2 m / min so that the twist angle becomes 240 degrees, and after pre-cleaning in ultrasonic pure water, at 10 ° C. for 10 minutes.
Heated for minutes to dry. Epoxy sealant is printed between the substrates, and DIC is applied to the liquid crystal element with a gap of 6.3 μm.
Liquid crystal DLC-430002E075 manufactured by the same company was injected to prepare a super twist type liquid crystal element.

Next, the above-mentioned polyimide varnish was spin-coated on a glass substrate with a transparent electrode, preheated at 80 ° C. for 2 minutes, and then heated at 250 ° C. for 1 hour to be cured, and a polyimide having a thickness of 700 Å (angstrom). A film was formed. Furthermore, the pushing amount of 0.2 mm, the number of revolutions of 1300 rpm, the stage speed of 2 m / min, the rubbing treatment, the pre-cleaning in the ultrasonic pure water, after heating at 80 ℃ for 10 minutes and drying, the epoxy sealant After printing, the liquid crystal ZLI-1 manufactured by Merck
132 was vacuum-injected to prepare a pretilt angle measurement liquid crystal cell.

V ₁₀ is 2.37V, V ₉₀ is 2.27V,
V ₁₀ / V ₉₀ is 1.04, which is excellent in steepness, but the pretilt angle is 5.0 degrees, which is greatly affected by the pressing during rubbing, and the pretilt angle, V ₁₀ , and V ₉₀ vary greatly.

[0033]

[Table 1]

[0034]

According to the present invention, it is possible to realize a liquid crystal display device which can improve the coating property and adhesiveness of an alignment film and has excellent characteristics such as a high pretilt angle.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a liquid crystal display element of the present invention.

[Explanation of symbols]

1a, 1b transparent substrate 2a, 2b color filter 3a, 3b Light-shielding film 4a, 4b protective film 5a, 5b XY electrodes 6a, 6b Alignment film 7 liquid crystal

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsumoto Hosokawa             1-6-1, Otemachi, Chiyoda-ku, Tokyo             Standing Wire Co., Ltd. (72) Inventor Yuki Honda             1-6-1, Otemachi, Chiyoda-ku, Tokyo             Standing Wire Co., Ltd. (72) Inventor Yoshiyuki Ando             1-6-1, Otemachi, Chiyoda-ku, Tokyo             Standing Wire Co., Ltd. (72) Inventor Yuzo Ito             1-6-1, Otemachi, Chiyoda-ku, Tokyo             Standing Wire Co., Ltd. (72) Inventor Yasushi Tomioka             7-1-1, Omika-cho, Hitachi-shi, Ibaraki Prefecture             Inside the Hitachi Research Laboratory, Hitachi Ltd. (72) Inventor Hidetoshi Abe             Hitachi, 3-10-3 Bentencho, Hitachi City, Ibaraki Prefecture             Kyowa Engineering Co., Ltd. F term (reference) 2H090 HB08Y HC05 HC08 KA08                       LA01 LA15 MB01                 4J043 PA04 PC066 QB31 RA35                       SB03 TB01 UA032 UA041                       UA082 UA121 UA132 UB062                       UB152 UB402 VA022 VA062                       YA06 ZB23

Claims (3)

[Claims] 1. A nematic liquid crystal layer is sandwiched between two substrates formed by sequentially arranging a color filter, an electrode and an alignment film on a transparent substrate, and the twist angle of the nematic liquid crystal is 90 ° to 360 °. In a twisted nematic liquid crystal display device, the former alignment film has a carboxyl group and a chemical formula: A liquid crystal display device, which is formed by applying a varnish made of a solvent-soluble polyimide having an imide ring-closed containing an organic group represented by 2. The solvent-soluble polyimide having an imide ring closed is represented by the following chemical formula: And the chemical formula The liquid crystal display device according to claim 1, wherein the compound represented by the formula (1) is used, and an acid dianhydride is added to the compound to cause a reaction in a lactone-based polymerization catalyst and a polar solvent for direct imidization. 3. The varnish has a solid content concentration of 1 to 20%,
The liquid crystal display device according to claim 1, which has a viscosity of 1 to 400 mPa · s.