JPH0822009A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To produce a liquid crystal display element having excellent stability under mild conditions compared to conventional conditions by forming an oblique vapor deposition film of inorg. compd. treated with silane as an oriented film. CONSTITUTION:In this element, at least one oriented film is an oblique vapor deposition film of inorg. compd. treated with a silane treating agent. As for the silane treating agent, trimethylchlorosilane, triethylchlorosilane, trichlorophenylsilane, dimethyldichlorosilane, dichloromethylsilane, dichloroethylsilane, dichloromethylphenylsilane, trimethylchlorosilane, trimethyliodosilane, trimethylcyanosilane, dimethylchlorosilane, or the like can be used. An inorg. oxide such as silicon oxide, yttrium oxide, magnesium oxide, and zirconium oxide is treated with the silane treating agent above. The silane treatment is performed by exposing a glass substrate on which the oblique vapor deposition is applied to a heated silylation reagent or the vapor of a silane coupling agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stable and highly reliable liquid crystal display device which can be manufactured under milder conditions than before.

[0002]

2. Description of the Related Art Especially for the last ten years, various technical fields (eg, display parts of watches, calculators, typewriters, etc.) in which liquid crystal electro-optical properties and properties as display elements are required.
At, liquid crystals have been introduced. These display elements utilize the dielectric alignment effect in the nematic, cholesteric or smectic phase of the liquid crystal compound. In these liquid crystal phases, the long axis of the molecule of the compound is the applied electric field due to the dielectric anisotropy. It has a selective orientation. The normal response time of display devices is too long for many other fields where liquid crystal applications are possible. This drawback is especially noticeable when an electric field has to be applied to many pixels. To solve this problem TFT
The active mode using (Thin Film Transistor) is effective, but the production cost of the device having a relatively large screen area is generally too high.

In addition to nematic and cholesteric liquid crystals, optically active smectic liquid crystal phases have also become more important in the last few years.

Clark and Lagavar (L
agerwall) has found that the use of ferroelectric liquid crystal systems in very thin cells can result in electro-optical switching or display devices that exhibit response times 1000 times faster than conventional TN (twisted nematic) cells. Clarified (eg, Ragavar, "Ferroelectoric Liquid Crystal Display
s, SID Symposium, October Meeting, 1985, San D
iego, Ca, USA ”). Due to such a property or other preferable properties such as bistable switching, high viewing angle property, and high contrast, the ferroelectric liquid crystal (FL) is used.
C) is in principle suitable for the fields of application mentioned above, for example the fields of use of matrix addresses.

Conventionally, a rubbing method or an oblique vapor deposition method has been used as a means for forming an alignment film of liquid crystal. The rubbing method is a method in which an organic polymer film is formed on a transparent electrode by spin coating, printing, or the like, and then a roller around which an organic polymer film is wound is rotated to rub the organic polymer film to form liquid crystal molecules. Are aligned in the rubbing direction. This method is excellent in mass productivity, but only a panel in which the tilt angle (pretilt angle) of liquid crystal molecules from the substrate is 0 ° to about 10 ° can be formed.

When a pretilt angle larger than this is required, S
Oblique vapor deposition of inorganic compounds such as iO has been used. In particular, the orientation of the ferroelectric liquid crystal has two "dogleg" layer structures (chevron structure), and the existence of different chevron structures causes zigzag defects, which is not preferable for display quality. Eliminating such zigzag defects,
A sufficiently large pretilt is required to obtain a monodomain alignment, and the oblique vapor deposition method is suitable as an alignment method for ferroelectric liquid crystals.

[0007] Regarding the oblique deposition method, there are many documents to date (eg W. Urbach, M. Boix, and E. Guyon,
Alignment of nematics and smectics on evaporated f
ilms, Applied Physics Letters, Vol. 25, N
o. 9, 1 P479, 1974) and many patent applications have been filed (for example, JP-A-62-161122, JP-A-63-66533, JP-A-63-66537, JP-A-63-97917, JP-A-HEI-1). -198682, JP-A-1-135589, etc.). These patents mainly relate to materials of inorganic compounds and vapor deposition conditions.

However, the oblique vapor deposition layer of an inorganic compound has a large surface area because it forms a fine column structure, and since it has a higher hydrophilicity than an organic film, it has a problem that water is easily adsorbed. Moisture remaining on the alignment film is not preferable because it affects the alignment properties and switching characteristics of liquid crystal molecules. Furthermore, in the ferroelectric liquid crystal display element, even when an organic alignment film is used,
For example, if the cleaning water remains, the adverse effects such as the occurrence of twist and the burning of the memory state will occur. For this reason, in the case of a liquid crystal display device using an obliquely vapor-deposited film, it is necessary to sufficiently dry the cell before injecting the liquid crystal into the cell and preferably sufficiently remove water by heating under reduced pressure. However, since it has a fine column structure, quite severe dehydration conditions are required to sufficiently remove water. Further, when the oblique vapor deposition film is used, when the liquid crystal material is injected and then heat-treated, bubbles are generated in the cell. As a method for preventing the generation of air bubbles, Japanese Patent Application Laid-Open No. 5-803
39, proposes a method of annealing the substrate after the oblique deposition at a temperature of 300 ° C. or higher. However, it is necessary to remove water as described above and to prevent bubbles from occurring.
Pretreatment at high temperature of 0 ° C or more is complicated, and when the annealing temperature becomes high, distortion or deformation of the glass substrate, ITO, etc.
An unfavorable problem such as a change in the resistance value occurs. Moreover, once the water is removed, in order to prevent re-adsorption, it must be carried out in a storage / treatment step under dry conditions, preferably under a nitrogen atmosphere, so that it is not practical.

[0009]

Therefore, the present invention provides a liquid crystal display device having a stable and excellent inorganic oblique vapor deposition film, which can be manufactured under milder conditions than conventional ones.
The purpose is to solve the above problems.

[0010]

The present invention is characterized in that at least one of the alignment films is a silane-treated oblique vapor deposition film of an inorganic compound. One or both of the inner surfaces are provided with a transparent electrode and an alignment film. Provided is a liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of substrates that are sequentially formed. The liquid crystal display device of the present invention is characterized in that the hydroxyl groups and the adsorbed water present on the surface of the inorganic vapor deposition film are subjected to the hydrophobic treatment with the silane treating agent, so that the adsorption of the water is prevented and the film is more easily dried. .

Examples of the inorganic compound for the vapor deposition film used in the present invention include inorganic oxides such as silicon oxide, yttrium oxide, magnesium oxide and zirconium oxide.
The oblique vapor deposition film can be formed by means known to those skilled in the art, such as those described in the documents and publications listed in the section of the prior art.

As the silane treating agent used in the present invention, trimethylchlorosilane, triethylchlorosilane, trichlorophenylsilane, dimethyldichlorosilane, dichloromethylsilane, dichloroethylsilane, dichloromethylphenylsilane, trimethylchlorosilane, trimethyliodosilane, Trimethylcyanosilane, dimethylchlorosilane, t-butyldimethylchlorosilane, triethylchlorosilane, tri-n-propylchlorosilane, tri-n-butylchlorosilane, triphenylchlorosilane, trimethylsilylimidazole,
Trimethylsilylacetamide, N, N-dimethylaminotrimethylsilane, N, N-diethylaminotrimethylsilane, hexamethyldisilazane, tetramethyldisilazane, N, N'-bis (trimethylsilyl) urea,
Silylating agents such as N, N'-bis (triethylsilyl) urea, N, N-dimethylaminotrimethylsilane and N-trimethylsilylphenylurea, trimethoxymethylsilane, triethoxymethylsilane, trimethoxyphenylsilane, tri Examples thereof include silane coupling agents such as ethoxyphenylsilane, dimethoxydimethylsilane, diethoxydimethylsilane, dimethoxymethylsilane, diethoxymethylsilane, dimethoxydiphenylsilane, and diethoxydiphenylsilane.

The silane treatment can be easily carried out by exposing the obliquely vapor-deposited glass substrate to the vapor of the heated silylating agent or silane coupling agent. Also, a small amount of water and a catalyst for hydrolysis (eg hydrochloric acid, acetic acid, etc.)
There is also a method in which silane is dissolved in a solvent containing and the substrate is immersed in this solution for reaction, or a method in which a chlorosilane-based silane treating agent is mixed with a tertiary amine and the substrate is immersed therein. Examples of the solvent used in these methods include alcohols, benzene and halogenated hydrocarbons. After the reaction, it is preferable to wash away excess silane compounds and by-products with toluene, hexane, etc., and then dry at, for example, about 100 ° C. to remove the solvent.
Further, in order to suppress a side reaction between water and the silane treating agent and reduce the amount of the silane treating agent used, it is preferable to dry the substrate as much as possible before the silane treatment.

The liquid crystal display device of the present invention can be manufactured by a method well known to those skilled in the art using an oblique vapor deposition substrate of a silane-treated inorganic compound. The silane-treated oblique vapor deposition film of an inorganic compound may be formed on only one inner surface of the substrate of the liquid crystal display element of the present invention, or may be formed on both inner surfaces. When it is formed on only one inner surface, the alignment film may not be formed on the other inner surface, or any alignment film known to those skilled in the art may be formed. Examples of other alignment films include organic alignment films, for example, rubbing polyamide, polyimide, polyvinyl alcohol-based polymer alignment films, silane coupling agents, etc., which are generally used as alignment films for nematic or ferroelectric liquid crystals. Can be used. Although various kinds of liquid crystals can be used in the liquid crystal display element of the present invention, it is preferable to use the ferroelectric liquid crystal among them.

[0015]

EXAMPLES The features and effects of the present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(Example 1) SiO powder was put in a tantalum boat with a lid and a pinhole opened, and resistance heating was performed on the glass substrate provided with ITO to obliquely vapor-deposit SiO film having a thickness of 400 Å. A film was formed. The vacuum degree, vapor deposition rate and vapor deposition angle during vapor deposition were respectively 10 ⁻⁵ Torr, 7 Å / sec and 85 °.

The SiO oblique deposition substrate was immersed in a solution of 10 parts by weight of trimethylchlorosilane, 10 parts by weight of triethylamine and 80 parts by weight of toluene. The by-product salt on the surface of the substrate was washed away with water, ultrasonically washed in hexane, and hexane was dried under reduced pressure at 120 ° C.

A cell was produced using the silane-treated SiO diagonal vapor deposition substrate as described above so that the vapor deposition directions were parallel to each other with a cell gap of 1.5 μm. Meanwhile, a ferroelectric liquid crystal (manufactured by Hoechst) having the following characteristics was injected in a nematic phase in a vacuum oven.

[0019]

[Table 1] The liquid crystal cell manufactured in this manner formed a defect-free monodomain. 70 μs at room temperature for ±
Switching was performed when a voltage pulse of 20 V was applied.
The effective cone angle in this cell was 43 °, and the contrast in memory was 200 or more. Also, this cell
After being stored at 10 ° C. for 24 hours, there was no change in orientation, switching characteristics and the like.

Example 2 In Example 1, hexamethyldisilazane was used instead of trimethylchlorosilane. Hexamethyldisilazane and an SiO vapor deposition substrate were placed in a reactor equipped with a cooling tube, heated to 120 ° C., boiled, and the substrate surface was treated with the vapor. After reacting for 30 minutes, the same post-treatment as in Example 1 was performed to prepare a cell, and the liquid crystal was evaluated. The orientation and other characteristics were the same as those in Example 1.

(Example 3) In Example 2, N, N'-bis (trimethylsilyl) acetamide was used in place of hexamethyldisilazane. N, N′-bis (trimethylsilyl) acetamide and a SiO oblique deposition substrate were charged in a reactor equipped with a cooling tube, heated to 100 ° C. and boiled to treat the substrate surface with the vapor. After reacting for 30 minutes, the same post-treatment as in Example 1 was performed to prepare a cell, and the liquid crystal was evaluated. The orientation and other characteristics were the same as those in Example 1.

Example 4 In Example 2, dimethyldimethoxysilane was used instead of hexamethyldisilazane. In a reactor equipped with a cooling tube, dimethyldimethoxysilane and a SiO vapor deposition substrate were charged, heated to 100 ° C. and boiled, and the substrate surface was treated with the vapor. After reacting for 30 minutes, the same post-treatment as in Example 1 was performed to prepare a cell, and the liquid crystal was evaluated. The orientation and other characteristics were the same as those in Example 1.

Comparative Example 1 S before the silane treatment of Example 1
The iO orthorhombic vapor deposition substrate was dehydrated and dried at 120 ° C. for 2 hours under reduced pressure, and then a cell was prepared and evaluated in the same manner as in Example 1. Performance immediately after injection was similar to Example 1, but 1
The orientation was disturbed after storage at 10 ° C. for 24 hours. In addition, bubbles were observed in the cell. In addition, smectic C
The transition temperature from the phase to the smectic A phase was lowered by 2 ° C. and the threshold voltage was also increased by 10%.

Comparative Example 2 S before the silane treatment of Comparative Example 1
The dehydration and drying conditions of the iO oblique vapor deposition substrate were set to 200 ° C. under reduced pressure for 2 hours, a cell was prepared, and the same evaluation as in Comparative Example 1 was performed. The performance immediately after injection was similar to that of Example 1, but the orientation was slightly disturbed after storage at 110 ° C. for 24 hours. The number of air bubbles in the cell was smaller than that of Comparative Example 1, but was generated, which was not acceptable. Also,
The transition temperature from the smectic C phase to the smectic A phase was lowered by 1 ° C., and the threshold voltage was increased by 10%. As described above, the stability of the cell was slightly improved by heating and drying the SiO oblique deposition substrate before the cell was manufactured.
Even at ℃ was insufficient.

[0025]

The liquid crystal display device of the present invention is characterized in that at least one of the inorganic compound oblique vapor deposition films is treated with silane. Since the hydroxyl groups, which are the active groups of the oblique vapor deposition film, are hydrophobized by the silane treatment, the vapor deposition film is less likely to adsorb moisture, and the substrate is easier to manage. Further, the liquid crystal display device of the present invention can be manufactured under milder conditions than those of the conventional liquid crystal display device having an oblique vapor deposition film of an inorganic compound.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Haruhiko Ito 1-3-2 Minamidai, Kawagoe City, Saitama Hoechst Japan Co., Ltd., Institute for Advanced Materials Technology (72) Inventor Jaffia Manello 65931 Federal Republic of Germany Frankfurt, Gintlinger Bernstrasse 163

Claims (3)

[Claims] 1. A liquid crystal display device having a liquid crystal layer sandwiched between a pair of substrates having a transparent electrode and an alignment film sequentially formed on one or both inner surfaces, and at least one of the alignment films is a silane-treated inorganic material. A liquid crystal display device, which is an oblique vapor deposition film of a compound. 2. The liquid crystal display device according to claim 1, wherein the inorganic compound is silicon oxide. 3. The liquid crystal display device according to claim 1, wherein the liquid crystal layer is made of a ferroelectric liquid crystal.