JPH0222623A - Liquid crystal display element and its production - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display element which is produced with an easy process and causes an uneven electric field in one picture element by adding and dispersing fine particles, whose dielectric constant is different from that of an orienting film, in an orienting film forming coating liquid. CONSTITUTION:At least one of orienting films is coated with the orienting film forming coating liquid where insulating fine particles whose dielectric constant is different from that of the orienting film are added. A pair of transparent electrode substrates 5 and 6 consisting of transparent substrates 1a and 1b, transparent electrodes 2a and 2b, and orienting films 3a and 3b produced in this manner are allowed to face each other with liquid crystal between them so that orienting films 3a and 3b are on the inside. In this case, it is preferable that spacers are dispersed and interposed between both transparent electrode substrates 5 and 6 for the purpose of securing the layer thickness of a liquid crystal layer 7. Thus, orienting films can uniformly orient liquid crystal molecules though silica is included in orienting films, and the liquid crystal display element is obtained which causes an uneven electric field in one picture element because insulating fine particles whose dielectric constant is different from that of the orienting film are included in the orienting film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention 1] The present invention relates to a liquid crystal display element and a method for manufacturing the same. More specifically, the present invention relates to a liquid crystal display element in which the electric field received by a liquid crystal layer is non-uniform within one pixel when a voltage is applied between transparent electrodes, and a method for manufacturing the same.

[Technical Background of the Invention and Prior Art] Conventionally, matrix-type liquid crystal display elements used in liquid crystal television panels and the like include a driving method called a passive matrix display and a driving method called an active matrix display. There are two methods. The former has the advantage that it has a relatively simple structure and can be manufactured at low manufacturing cost, but when the number N of scanning lines is increased to obtain high image quality, the effective electric field at one selected point while scanning the screen is reduced. Since the time during which 17N is applied (that is, the duty ratio) is reduced, crosstalk occurs and high contrast cannot be obtained. Furthermore, as the duty ratio becomes lower, it becomes difficult to control the gradation of each pixel, and as such, liquid crystal television panels have a number of drawbacks.

On the other hand, in the active matrix driving method, an active element such as a transistor or a switch element is provided for each pixel to prevent crosstalk and provide gradation. Specifically, liquid crystal display is performed by the following method. That is, for example, MOS
(metal oxide semiconductor) transistor, M I M (m
A gate-on pulse is applied to the transistor of the selected pixel to conduct between the source and drain, and transfer one image signal from the source to the capacitor. This is a driving method in which the liquid crystal is driven in accordance with the image signal stored in the capacitor, and at the same time grayscale display is performed using the voltage of the video signal. This method has the disadvantage that the structure of the active element used is complex, resulting in a large number of manufacturing steps and high manufacturing costs. Furthermore, since it is difficult to form a film over a wide area of thin film semiconductors, it is difficult to manufacture large-screen display devices.

To overcome the above-mentioned drawbacks, JP-A-62-
Japanese Patent No. 231940 proposes a liquid crystal display element in which the electric field intensity formed when a voltage is applied varies within one pixel. If ferroelectric liquid crystal is used in this liquid crystal display element, even if the same voltage is applied, there will be parts with strong electric field strength and parts with weak electric field strength within one pixel, so the liquid crystal will first be inverted in the parts with strong electric field strength. occurs, and then the reversal spreads to areas where the electric field is weak. For example, by applying an applied pulse that causes inversion only in areas where the electric field is strong and does not occur in areas where the electric field is weak, it is possible to control the gradation within one pixel. Further, if a bistable liquid crystal is used for the liquid crystal display element, this gradation can be memorized. Furthermore, since the reversal in the area where the electric field is strong becomes the nucleus and the reversal spreads, it is possible to obtain a display with better response than the conventional display.

In this way, liquid crystal display elements that generate a non-uniform electric field within a single pixel have excellent features, but how do you actually generate a non-uniform electric field within a single pixel? becomes a problem. The above-mentioned Japanese Unexamined Patent Publication No. 62-231940 discloses a technique for providing distributed irregularities on the electrode surface.

That is, this is a technique in which the electrode surface is roughened by scraping it using a sand glass method, or a conductive substance is partially attached on a uniform conductive film.

However, liquid crystal display elements that create uneven electric fields within one pixel by providing unevenness on the surface of these electrodes,
The process of creating irregularities on the electrode surface during the manufacturing process itself
Since this is a time-consuming process, it cannot be said that the complexity of the process, which was a drawback of conventional active matrix displays, has been sufficiently solved.

In addition, Japanese Patent Laid-Open No. 62-262022 discloses a liquid crystal display in which a non-uniform electric field is produced by providing a dielectric film with varying thickness on the electrode or by stacking the dielectric film non-uniformly. A device is disclosed. However, the manufacturing process of this liquid crystal display element also requires complicated steps such as providing dielectric films with varying thicknesses or non-uniformly stacking dielectric films.

[Summary of the Invention] The object of the present invention is to produce
An object of the present invention is to provide a liquid crystal display element that generates a non-uniform electric field within one pixel, and a method for manufacturing the same.

The above object is to provide a liquid crystal display element of the present invention in which two transparent electrode substrates each having an alignment film provided on a transparent electrode are arranged with the alignment film inside, and a liquid crystal is sealed between them. A liquid crystal display element characterized in that at least one of the above contains insulating fine particles having a particle size smaller than the gap between the alignment films and a dielectric constant different from that of the alignment films, and In a method for manufacturing a liquid crystal display element, in which two transparent electrode substrates each having an alignment film provided on a transparent electrode are arranged with the alignment film inside, and a liquid crystal is sealed between them, at least one of the alignment films is This can be achieved by a method for manufacturing a liquid crystal display element, which is characterized in that the alignment film is formed by applying an alignment film forming coating liquid to which insulating fine particles having a dielectric constant different from that of the alignment film are added.

In the liquid crystal display element of the present invention, since the alignment film contains fine particles having a dielectric constant different from that of the alignment film,
The fine particles form fine irregularities on the alignment film.

Since the alignment film and the fine particles have different dielectric constants, even if the same voltage is applied, the strength of the electric field generated will be different between the areas where the fine particles are present and the areas where the fine particles are not present. Moreover, the liquid crystal display element of the present invention has a much simpler process than the above-mentioned process of providing unevenness on the electrode surface and the process of providing a dielectric film, that is, it has a dielectric constant different from that of the alignment film. It can be manufactured by the manufacturing method of the present invention, which includes the step of applying an alignment film forming coating liquid to which fine particles are added. Generally, the manufacturing process of a liquid crystal display element includes a step of forming an alignment film, so the manufacturing method of a liquid crystal display element of the present invention is almost different from the conventional manufacturing method of a liquid crystal display element in which an alignment film is formed by coating. do not have. However, a step of adding and dispersing fine particles having a dielectric constant different from that of the alignment film to the alignment film forming coating solution is added.

Preferred embodiments of the present invention are listed below.

(1) The density of the fine particles on the surface of the alignment film is 10
1000 pieces/mm''.

(2) The density of the fine particles on the surface of the alignment film is 10
A liquid crystal display element characterized in that the number of elements is 0 to 500 pieces/mm2.

(3) Thickness n of the alignment film and average particle diameter m of the fine particles
A liquid crystal display element having a ratio m/n of 1.5 to 10.

(4) The dielectric constant of the fine particles is 1.0% of the dielectric constant of the alignment film.
A liquid crystal display element characterized by having a magnification of 3 to 15 times.

(5) The dielectric constant of the fine particles is 1.0% of the dielectric constant of the alignment film.
A liquid crystal display element characterized by having a magnification of 5 to 10 times.

(6) A liquid crystal display element, wherein the fine particles are silica particles.

(7) A liquid crystal display element, wherein the alignment film is at least one organic polymeric substance selected from the group consisting of polyvinyl alcohol, gelatin, polyimide resin, polyamide resin, and polyester resin.

(8) A liquid crystal display element, wherein the liquid crystal is a liquid crystal having ferroelectricity.

(9) A method for manufacturing a liquid crystal display element, characterized in that the amount of the fine particles added is 1 to 20% of the organic polymer substance of the alignment film material in terms of solid content.

(10) The dielectric constant of the fine particles is 1 of the dielectric constant of the alignment film.
．． A method for manufacturing a liquid crystal display element, characterized in that it is 3 to 15 times larger.

(11) The dielectric constant of the fine particles is 1 of the dielectric constant of the alignment film.
．． A method for manufacturing a liquid crystal display element, characterized in that it is 5 to 10 times larger.

(12) A method for manufacturing a liquid crystal display element, wherein the fine particles are colloidal silica particles.

(13) A method for manufacturing a liquid crystal display element, characterized in that the fine particles are surface-modified.

[Configuration of the Invention] The configuration of the liquid crystal display element of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an example of the liquid crystal display element of the present invention. Transparent electrodes 2a, 2b on glass substrates 1a, lb,
Two transparent electrode substrates 5.6 each having alignment films 3a and 3b stacked on top of each other in this order face each other with the liquid crystal layer 7 in between, with the alignment films facing inside. Since the alignment film 3b of the lower transparent electrode substrate 6 contains fine particles 4 having a dielectric constant different from that of the alignment film 3b,
The fine particles 4 form irregularities at the interface between the alignment film 3b and the liquid crystal layer 7. Since the alignment film 3b and the fine particles 4 have different dielectric constants, when a voltage is applied between the transparent electrodes 2a and 2b, electric fields with different strengths are generated in areas where the fine particles 4 are present and where they are not. Become.

The liquid crystal display element of the present invention is not limited to the one shown in FIG. 1, and the fine particles may be contained in both the upper and lower alignment films. Furthermore, the liquid crystal display element of the present invention can be adapted to all the aspects that are used for ordinary liquid crystal display elements, such as providing an electrical insulating layer, using a spacer, and depending on the purpose, providing a polarizing plate and a color filter. It is. In particular, it is preferable to use a spacer to ensure a gap between both alignment films (ie, the thickness of the liquid crystal layer). As the spacer, glass fiber, glass beads, plastic beads, alumina fine particles, etc. are used. The thickness of the liquid crystal layer varies depending on the liquid crystal used, but it is 5 to 10 μm for TN liquid crystal and 6 μm for STN liquid crystal.
~Bpm.

For ferroelectric liquid crystals, the thickness is generally about 2 μm.

As the glass substrate, transparent electrode, and liquid crystal used in the liquid crystal display element of the present invention, known materials conventionally used in liquid crystal display elements can be used.

For example, the glass substrate may be float glass with good smoothness, and the transparent electrode may be indium oxide (xn2
o*), tin oxide (SnO2), and ITO (indium tin oxide).

Further, as the liquid crystal used in the present invention, those conventionally used in liquid crystal display elements can be used, but ferroelectric liquid crystal is particularly preferable.

Specifically, liquid crystals having ferroelectric properties include chiral smectic C phase (SmC”), H phase (SmH@), and I phase (SmC”).
ml"), J phase (SmJ"), K phase (SmK')
, G phase (SmG'') or F phase (SmF''). Specific liquid crystal compositions include C5-1011, C5-1013, C5-1015 manufactured by Chisso ■,
ZL l-3488, ZLI-3489 manufactured by Merck & Co., Ltd.
Examples include, but are not limited to, HS-98P and HS-78P (all trade names) manufactured by Teikoku Kagaku Sangyo ■. There is no problem in adding dichroic dyes, viscosity reducers, etc. which are soluble in the liquid crystal to these liquid crystals.

Further, the alignment film material is appropriately selected depending on the liquid crystal used, but is preferably at least one organic polymeric substance selected from the group consisting of polyvinyl alcohol, gelatin, polyimide resin, polyamide resin, and polyester resin. The thickness of the alignment film also varies depending on the liquid crystal used, but is preferably 200 to 2000.

At least one alignment film of the liquid crystal display element of the present invention includes:
Contains fine particles having a particle size smaller than the gap between the alignment films and a dielectric constant different from that of the alignment films. The dielectric constant of these fine particles varies depending on the thickness of the gap between the electrodes of the liquid crystal display element, the type of liquid crystal used, etc.
The dielectric constant is suitably 1.3 to 15 times the dielectric constant of the alignment film used, preferably 1.5 to 10 times. in particular,
Titanium oxide (relative permittivity: 6 or more), oxidized carrier (relative permittivity: 8 to 11), zirconium oxide (relative permittivity = 11)
~13), aluminum oxide (relative permittivity: 9~12)
and silicon oxide (silica) (relative dielectric constant: 4.5-5
．． 5), etc., it is appropriately selected depending on the thickness of the gap between both alignment films, the type of liquid crystal used, and the dispersibility in the alignment film forming material coating liquid in the manufacturing process described later.

The density of the fine particles on the surface of the alignment film is 10 to 1000.
pcs/m m2, more preferably! 00~SOO pieces/mm2.

Naturally, the particle size of the fine particles must be smaller than the gap between the two alignment films (ie, the thickness of the liquid crystal layer) in order to apply an electric field of non-uniform strength to the liquid crystal. The particle size of the fine particles is preferably 1.5 to 10 times the thickness of the alignment film.

Next, a method for manufacturing the liquid crystal display element of the present invention will be described.

The method for manufacturing a liquid crystal display element of the present invention is to form an alignment film by coating, except that insulating fine particles having a dielectric constant different from that of the alignment film used in the element are dispersed and added to the alignment film forming material coating liquid. The manufacturing method is completely the same as the conventional manufacturing method. That is, a transparent electrode is provided on a transparent substrate according to a conventional method, and insulating fine particles having a dielectric constant different from the dielectric constant of the alignment film are added thereon with molecules 11. An alignment film is provided by applying the added alignment film-forming acid coating solution and further heat-treating. At this time, the amount of the fine particles added is 1 to 20% of the organic polymer material as the alignment film material in terms of solid content.
% is preferable. In addition, in the case of the above-mentioned ferroelectric liquid crystal, the fine particles are preferably silica particles, but adding colloidal silica improves dispersibility rather than directly adding silica powder to the alignment film forming coating solution. It is preferable because it improves.

Examples of colloidal silica include Aerosol, Snotex (manufactured by Nissan Chemical Industries, Ltd.), Organosol (manufactured by Catalyst Kasei Corporation), and Ludox (manufactured by DuPont).

In addition, in order to ensure that the above-mentioned fine particles are uniformly dispersed in the alignment film and to prevent cracks from occurring at the interface between the fine particles and the material that forms the alignment film, when using colloidal silica, the surface is coated with amine, epoxy, etc. Preference is given to using modified colloidal silica. Also, when using other fine particles, it is preferable to use fine particles treated with a surface modifier such as a silane coupling agent.

The alignment film may be provided directly on the transparent electrode, or a film having other functions such as an electrically insulating layer may be provided on the transparent electrode and provided on this layer. In addition, depending on the purpose of use, polarizing plates,
As described above, functions provided in conventional liquid crystal display elements, such as color filters, can be provided.

The alignment film thus provided is preferably rubbed with synthetic fibers such as nylon, polyester, and polyacrylonitrile, and natural fibers such as cotton and wool.

A pair of transparent electrode substrates manufactured as described above, each consisting of a transparent substrate, a transparent electrode, and an alignment film, are placed facing each other with the liquid crystal sandwiched therebetween, with the alignment film facing inside. As mentioned above, in this case, in order to ensure the thickness of the liquid crystal layer, spacers are preferably dispersed and interposed between both transparent electrode substrates.

Next, examples of the present invention will be described. However, the present invention is not limited to this.

[Example 1] An indium-tin oxide (ITO) film was formed on each of two 0.7 mm thick glass plates. This IT
A coating solution having the following composition was applied to both of the glass plates with the O film using a spinner.

Coating liquid: Polycarbonate: 1.5% (parts by weight) (Niepilon S-2000 manufactured by Mitsubishi Gas Chemical ■) (relative permittivity of polycarbonate = 3) Demethylformamide: 50% (parts by weight) 2-Methylpyrrolidone...48.5% (parts by weight) Amine-modified colloidal silica...0.2% (parts by weight) (solid component 30%; manufactured by Catalyst Kasei ■) (Relative permittivity of silica: Approximately 5) The spinner conditions were: rotation speed 2000 r, p, m, and time 30 seconds. After coating, heat treatment was performed at 150°C for about 1 hour. The thickness of this coating film is approximately 500 people (0
, 05 μm). In both cases, the membrane surface was rubbed with a nylon flocked cloth and washed with a fluorocarbon solution. next,
Plastic beads with an average particle size of 2 μm were sprinkled onto one glass plate. A cell was created by stacking two glass plates with their respective rubbed surfaces facing inside.

The thickness of this cell was 1.8 μm. This cell uses C31 manufactured by Chisso, which is a phenyl ester ferroelectric liquid crystal.
013 was injected, heated to 95°C, and then slowly cooled at a rate of 3°C/min.

When the liquid crystal display element thus obtained by the manufacturing method of the present invention was observed under cross Nicolization, the liquid crystal showed uniform alignment.

As is clear from this Example 1, even if the alignment film contains silica, the alignment film can align liquid crystals uniformly, and therefore, insulating fine particles having a dielectric constant different from that of the alignment film can be formed. By including it in the alignment film, it is possible to obtain a liquid crystal display element that generates a non-uniform electric field within one pixel. Furthermore, from Example 1, it was confirmed that the method for manufacturing a liquid crystal display element of the present invention is a simpler process than the conventional method for manufacturing a liquid crystal display element that generates a non-uniform electric field within one pixel. Ta.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically showing a configuration example of a liquid crystal display element of the present invention. 1a, 1b = Glass substrates 2a, 2b = Transparent electrodes 3a, 3b: Alignment film 4: Fine particles 5.6: Transparent electrode substrate 7: Liquid crystal patent applicant Fuji Photo Film Co., Ltd. Agent Patent attorney Hatao Yanagawa

Claims (1)

[Claims] 1. In a liquid crystal display element in which two transparent electrode substrates each having an alignment film provided on a transparent electrode are arranged with the alignment film inside, and a liquid crystal is sealed between them, the alignment film is A liquid crystal display element characterized in that at least one of the layers contains insulating fine particles having a particle size smaller than the gap between the alignment films and a dielectric constant different from that of the alignment films. 2. In a method for manufacturing a liquid crystal display element, in which two transparent electrode substrates each having an alignment film provided on a transparent electrode are arranged with the alignment film inside, and a liquid crystal is sealed between them, at least one of the alignment films is . A method for manufacturing a liquid crystal display element, characterized in that the liquid crystal display element is formed by applying an alignment film forming coating liquid to which insulating fine particles having a dielectric constant different from that of the alignment film are added.