JPH0240623A - Manufacture of liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain the liquid crystal display element which has orienting films capable of orienting ferroelectric liquid crystal excellently by rubbing at least one of two orienting films, then performing ultraviolet-ray irradiation processing, etc. CONSTITUTION:Two transparent substrates are provided with transparent electrodes, on which the orienting films are provided, rubbed, and arranged opposite each other; and liquid crystal is charged between them to manufacture the liquid crystal display element. At such a time, at least one of the orienting films is processed by ultrasonic-wave irradiation, glow discharge, or electron irradiation after being rubbed. Thus, the irradiation or discharge is carried out after the rubbing processing, so a high-temperature heat treatment is required after the film formation to manufacture the liquid crystal element having the orienting films with the uniform ability of orienting the liquid crystal entirely in the short-time process.

Description

[Detailed description of the invention] [Field of invention] The present invention relates to a method for manufacturing a liquid crystal display element.

More specifically, it relates to a method for manufacturing a liquid crystal display element having an alignment film in which ferroelectric liquid crystal can be well aligned [Technical Background of the Invention and Prior Art] Liquid crystals conventionally used in watches, computers, word processors, etc. In the display element, a transparent electrode is provided on each of two transparent substrates, an alignment film is provided on the transparent electrode, and then the two transparent electrode substrates obtained by rubbing the alignment film are subjected to the alignment process. They are usually manufactured by arranging them facing each other with the membranes on the inside and sealing liquid crystal between them.

Generally, in a liquid crystal display element, it is necessary to align the liquid crystals in a certain direction, that is, to align them, so in the above liquid crystal display element, an alignment film is provided to align the liquid crystal molecules. What is the above rubbing process?
The alignment film is rubbed with a cloth, etc., and this rubbing process forms minute grooves on the surface of the alignment film.
It is believed that alignment films will be able to align liquid crystals.

The mainstream of such liquid crystal display elements is display in a leistid nematic (TN) mode in which nematic liquid crystal has a twisted structure. However, this TN type liquid crystal display element has a slow response speed, currently limited to 20 milliseconds, which is a major problem when used in television panels etc. that require high-speed response. It has become.

In contrast, recently, ferroelectric liquid crystals with high-speed response are expected to open up a new field of displays.
being researched. In a display element using this ferroelectric liquid crystal material, it is important to align the liquid crystal molecules in a certain preferred direction parallel to the substrate surface. However, the smectic liquid crystal having a chiral smectic phase used in this ferroelectric liquid crystal display element generally has poor alignment stability compared to the general nematic liquid crystal mentioned above, and the liquid crystal molecules are aligned parallel to the substrate surface. It is difficult to arrange them in a certain preferred direction.

One of the causes of inhibiting the alignment of liquid crystal molecules is that the grooves on the surface of the alignment film formed by the rubbing process are not necessarily formed uniformly.

Even if the rubbing conditions (e.g., rubbing pressure, etc.) are strictly controlled as much as practically possible, the surface of the alignment film that has been subjected to alignment treatment by the rubbing method will suffer from slight variations in the shape of microsteps and grooves.
Because of the formation of particles, the ability to orient the liquid crystal becomes non-uniform on each part of the surface of the alignment film, and this becomes a cause of inhibiting good alignment of the liquid crystal molecules.

As a method to solve such problems, JP-A-63-3
Publication No. 0827 discloses a method for improving the above problem by heat treatment. However, in this method, after the film forming process, it is necessary to heat the film at a temperature of 100°C to 350°C for 30 minutes or more, so this heating process may have an adverse effect on other layers, such as color filters. There are concerns. Furthermore, since this method requires a relatively long heating time of 30 minutes or more, a treatment that can be performed in a shorter time is desired.

[Summary of the Invention] An object of the present invention is to provide a method for manufacturing a liquid crystal display element having an alignment film that allows ferroelectric liquid crystal to be aligned well.

Furthermore, the present invention manufactures a liquid crystal display element having an alignment film that has a uniform ability to align liquid crystal over the entire surface of the alignment film in a shorter time than conventionally and without applying high heat for a long time other than the film forming process. The purpose is also to provide a method.

The above object of the present invention is to provide transparent electrodes on each of two transparent substrates, and after providing an alignment film on the transparent electrodes,
A method for producing a liquid crystal display element, which is produced by arranging two transparent electrode substrates obtained by rubbing the alignment film so as to face each other with the alignment film inside, and filling liquid crystal therebetween. A liquid crystal display element characterized in that at least one of the alignment films is subjected to a rubbing treatment and then subjected to at least one treatment selected from the group consisting of an ultraviolet irradiation treatment, a glow discharge treatment, and an electron beam irradiation treatment. This can be achieved by manufacturing methods.

The inventor of the present invention has discovered that, after the rubbing treatment, when the alignment film is subjected to at least one treatment selected from the group consisting of ultraviolet irradiation treatment, glow discharge treatment, and electron beam irradiation treatment, the alignment caused by rubbing The present invention was achieved based on the discovery that the decrease in alignment ability caused by fine steps on the film surface, variations in the shape of the grooves, and Paris etc. can be improved.

Although the reason and mechanism by which the alignment ability of the alignment film surface is improved by these treatments are not necessarily clear,
The above treatment generates radicals or highly excited molecules on the surface of the alignment film, which causes a reaction on the surface of the alignment film.
This is thought to be due to the surface being modified.

In the method for manufacturing a liquid crystal display element of the present invention, for the alignment film,
After the rubbing treatment, there is no difference from the manufacturing method of ordinary liquid crystal display elements, except that at least one treatment selected from the group consisting of ultraviolet irradiation treatment, glow discharge treatment, and electron beam irradiation treatment is performed. A liquid crystal display element having an alignment film that has a uniform ability to align liquid crystal over the entire alignment film surface can be manufactured in a short time without the need for subsequent heat treatment at a high temperature for a long time.

[Detailed Description of the Invention] As described above, the method for manufacturing a liquid crystal display element of the present invention includes:
The method differs from the usual manufacturing method for liquid crystal display elements, except that the alignment film is subjected to at least one treatment selected from the group consisting of ultraviolet irradiation treatment, glow discharge treatment, and electron beam irradiation treatment after the rubbing treatment. There isn't. Therefore, the transparent substrate, the transparent electrode, the alignment film, and the liquid crystal used in the method for manufacturing a liquid crystal display element of the present invention can all be the known ones that have been conventionally used in liquid crystal display elements. All methods used in the manufacturing process can also be used.

Examples of the method for manufacturing a liquid crystal display element of the present invention will be described below in order.

First, a transparent electrode is provided on a transparent substrate by a conventional method.

For example, a float glass with good smoothness is used as a transparent substrate, and on this substrate, indium oxide (In20s)-tin oxide (Sn02) and ITO are used as transparent electrodes.
(indium tin oxide) or the like is provided by a known method such as vacuum evaporation, sputtering, or CVD.

An alignment film is provided on the transparent electrode thus provided.

The alignment film material is not particularly limited as long as it is a commonly used resin, but resins such as polyimide resin, polyamide type, polyvinyl acetate type, polyvinyl alcohol type, cellulose type, acrylic type, epoxy type, urethane type, etc. can be used as appropriate. It will be done. The alignment film can also be formed by a conventionally known method. For example, it may be provided by a method of applying an alignment film forming material and heat treatment, a method using vapor deposition such as vacuum deposition, or a lamination method. Further, the alignment film may be placed directly on the transparent electrode, or may be formed on an insulating layer provided on the transparent electrode.

The alignment film provided in this way is subjected to a rubbing treatment using synthetic fibers such as nylon, polyester, and polyacrylonitrile, natural ammonium such as cotton and wool, and then irradiated with ultraviolet rays, which is a feature of the present invention. At least one treatment force selected from the group consisting of treatment, glow discharge treatment, and electron beam irradiation treatment is performed. These treatments themselves can be performed by known methods. For example, the ultraviolet irradiation treatment can be performed using a high-pressure mercury lamp, a rare gas discharge tube such as a xenon lamp, a (heavy) hydrogen discharge tube, or the like as a light source. In addition, when performing glow discharge treatment, the transparent electrode substrate having the alignment film that has been subjected to rubbing treatment is loaded into a vacuum chamber such as a Pel Jar, and the treatment is performed. In glow discharge treatment, conditions such as the degree of reduced pressure in the reactor (chamber), discharge power, and discharge frequency are determined by material molecules,
It is appropriately selected depending on the width of the membrane, the thickness of the membrane, the shape of the reactor (chamber), etc. In the case of ultraviolet irradiation treatment, glow discharge treatment, and electron beam irradiation treatment, the treatment time depends on the material molecules, film conditions such as film width, film thickness, ultraviolet wavelength, and discharge power in the case of glow discharge. , discharge frequency,
Although it is determined based on both processing conditions such as the energy of the electron beam, it is generally several seconds to several tens of minutes.

A pair of transparent electrode substrates each having at least one of the transparent electrode substrates made of a transparent substrate, a transparent electrode, and an alignment film subjected to the above-mentioned treatment, manufactured as described above, are used to form a liquid crystal with the alignment film facing inside. Place them opposite each other.

The method for manufacturing a liquid crystal display element of the present invention includes TN liquid crystal, STN
Of course, devices using liquid crystals are also effective in obtaining good liquid crystal alignment, but the effects of the present invention are most effectively exhibited in liquid crystal display devices using ferroelectric liquid crystals. As the ferroelectric liquid crystal, conventionally known ones can be used.

Below, liquid crystals having ferroelectricity are specifically chiral smectic C phase (SmC"), H phase (SmH"), I phase (S
mI'), J phase (SmJ''), K phase (SmK'),
It is a liquid crystal having a G phase (SmG") or an F phase (SmF').

For example, the following molecules are used as ferroelectric liquid crystals.

IL R Or, CN (:H3 As a specific liquid crystal composition, C5-10 manufactured by Chisso ■
11, C3-1013, C3-1015, ZLI-3488, ZLI-3489 manufactured by Merck, Teikoku Kagaku Sangyo ■
H5-9BP, H3-78P (all product names)
Examples include, but are not limited to, the following. There is no problem in adding dichroic dyes, viscosity reducers, etc. which are soluble in the liquid crystal to these liquid crystals.

Of course, the liquid crystal display element manufactured according to the present invention is
All the embodiments used in ordinary liquid crystal display elements, such as providing an electrical insulating layer, using a spacer, providing a polarizing plate, and a color filter, are possible.

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).

Glass fibers, glass beads, plastic beads, metal oxide particles such as alumina and silica are used as spacers. The particle size of the spacer varies depending on the liquid crystal used, alignment film material, cell gap setting, metal oxide used, etc., but it ranges from 1.2 μm to 6 μm.
m is common.

Next, Examples and Comparative Examples of the present invention will be described.

However, the present invention is not limited to this example.

[Example 1] A transparent electrode of indium tin oxide was provided on a 5 cm square glass substrate (thickness 1.1 mm), and a polyimide alignment agent (LX-5400 manufactured by Hitachi Chemical Co., Ltd.) was applied thereon. , heat treatment was performed at 110° C. for 1 hour to form a film with a thickness of 0.1 μm. The polyimide film thus obtained was rubbed 10 times with a polyester cloth. Next, this transparent electrode substrate was irradiated with ultraviolet rays for 3 minutes using a 2 kW high-pressure mercury lamp (length: 25 cm, output per length 80 W/cm) as a light source to form a transparent electrode having an alignment film that had been irradiated with ultra violet rays. I got the board. The same process was repeated to obtain another transparent electrode substrate similar to the above. These two transparent electrode substrates were bonded together with a spacer interposed so that the rubbing directions were parallel to each other, to create a liquid crystal cell with a cell gap of 2 μm. A ferroelectric liquid crystal ZLI-3775 (manufactured by Merck & Co., Ltd.) was injected into this cell, heated once to 100°C, and then slowly cooled to 40°C to obtain a liquid crystal display element.

[Comparative Example 1] A liquid crystal display element was manufactured in exactly the same manner as in Example 1 except that ultraviolet irradiation was not performed.

[Evaluation of Liquid Crystal Display Elements] The liquid crystal display element of Example 1 and the liquid crystal display element of Comparative Example 1 were observed under crossed Nicols, and the number of linear alignment defects was measured.

The results are shown in Table 1.

Number of first surface linear defects (pieces) Example 1 Comparative Example 1 As is clear from the above results, the liquid crystal display element manufactured by the method for manufacturing a liquid crystal display element of the present invention has a good ferroelectric liquid crystal. This is a liquid crystal display element having an alignment film that can be oriented in a direction.

Furthermore, as is clear from the above, according to the method for manufacturing a liquid crystal display element of the present invention, the ability to orient liquid crystal uniformly over the entire surface of the alignment film is achieved without applying high heat for a long time other than the film formation process. It is possible to manufacture a liquid crystal display element having a film 45.

Patent applicant: Fuji Photo Film Co., Ltd. Representative: Yasuo Yanagawa, patent attorney

Claims (1)

[Claims] 1. A transparent electrode is provided on each of the two transparent substrates, and an alignment film is provided on the transparent electrode, and then the alignment film is rubbed and the resulting two transparent electrode substrates are placed with the alignment film on the inside. A method for manufacturing a liquid crystal display element, which is manufactured by arranging the alignment films to face each other and sealing a liquid crystal therebetween; at least one of the alignment films is subjected to a rubbing treatment, and then subjected to an ultraviolet irradiation treatment and a glow discharge. 1. A method for manufacturing a liquid crystal display element, comprising performing at least one treatment selected from the group consisting of treatment and electron beam irradiation treatment.