JPH0117132B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electro-optical device, and particularly to a liquid crystal display device using a nematic liquid crystal having positive dielectric anisotropy.

It is known that nematic liquid crystals (abbreviated as N-liquid crystals) can be used for optical modulation, etc. by making use of changes in optical properties caused by the application of electric fields, magnetic fields, ultrasonic waves, etc. This usually consists of an N-liquid crystal sandwiched between two substrates, at least one of which is transparent, which are placed facing each other with an interval of about 50μ or less.
It utilizes changes in molecular arrangement due to the application of electric fields, magnetic fields, ultrasonic waves, etc. for optical modulation. When applying an electric field, an electrode plate is used as the substrate, which is a support plate such as a glass plate with a thin conductive coating applied on one side.

The compounds forming the above-mentioned N-liquid crystals can be divided into two types depending on the relationship between molecular structure and dielectric properties. One is a type where the molecular axis and the electric dipole are almost perpendicular (this is called Nn), and the other is a type where they are almost parallel (this is called Np). Nn means N-liquid crystal with negative dielectric anisotropy, and Np
means an N-liquid crystal with positive dielectric anisotropy. A conventional Np-liquid crystal electro-optical device generally used has a structure in which an Np-liquid crystal is sandwiched between two opposing electrode plates. In this case, the molecular axes of the Np-liquid crystal are parallel to the electrode plates, and the molecular axes are aligned in almost the same direction on the same plane parallel to the electrode plates, and the electrode plates are perpendicular to each other between adjacent surfaces. Arrange in a continuous twisted direction. Such orientation of the molecular axes can be achieved by polishing the electrode surface in one direction with cloth, paper, etc., and injecting liquid crystal between the two sheets stacked so that the polishing directions cross each other. It is known that near the electrode surface, the molecular axes are aligned in the polishing direction, but within the liquid crystal layer, the molecular axes are continuously twisted.

However, this method has the disadvantage that the orientation is not uniform and that the orientation is lost within a short time. Furthermore, it is known that orientation destruction occurs under heating.

As a method to solve these problems, it is known to use a certain kind of surfactant in combination to rub the electrode plate in one direction, but surfactant causes deterioration of the liquid crystal and makes it difficult to apply voltage. If this continues, the surfactant may be decomposed or altered by the electric field, and its orientation may be destroyed. As another method, it is known to coat the surface of an electrode plate with a certain type of polymer such as polyimide or polyamideimide, and to orient the coated polymer layer.
However, when aligning using this method, a strong polar solvent is used, and the heat treatment temperature is also high.
The temperature is as high as 300-350℃, which poses problems in terms of manufacturing safety and health.

An object of the present invention is to provide a liquid crystal display device that has improved the above-mentioned points, and particularly to provide a liquid crystal display device that has improved alignment stability against heat and stability over time.

It is an object of the present invention to provide an electro-optical device using an electrode plate in which the surface of a base provided with a conductive film is covered with a film of a water-soluble resin cured in the presence of a water-resistant insolubilizer, and the display thereof is oriented. In particular, this can be achieved by using it as an electrode plate constituting a liquid crystal display device.

The water-soluble resin used in the electro-optical device of the present invention can be selected from a wide variety of resins.
In particular, polyvinyl alcohol is one of the preferred ones. In addition, for example, polyvinylpyrrolidone, methylcellulose, hydroxyethylcellulose, sodium alginate, sodium polyacrylate, etc. can be used. These water-soluble resins can be used alone or in combination of two or more.

These water-soluble resins are, for example, dissolved in water or alcohols (methanol, ethanol, isopropyl alcohol, etc.), and in this solution, ammonium dichromate, magnesium chloride, dimethylolated melamine, dialdehydes, etc. are added as water-insolubilizing agents. After adding the compound with two or more active groups, it can be cured under predetermined curing conditions. The dialdehydes mentioned above include glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, maleic dialdehyde, phthalaldehyde, isophthalaldehyde,
Examples include terephthalaldehyde, but glyoxal and glutardialdehyde are preferred, and glyoxal is particularly preferred.

The mixing ratio of the water-resistant insolubilizer to the water-soluble resin can be 0.1 to 100 parts by weight, preferably 1 part to 50 parts by weight, per 100 parts by weight of the water-soluble resin.

Water-soluble resins containing ammonium dichromate can be cured by appropriate light irradiation, especially ultraviolet irradiation, and water-soluble resins containing dimethylolated melamines and dialdehydes can be cured at a suitable temperature (e.g. It can be cured by heating at 100-300°C.

Methods for providing the water-soluble resin used in the present invention on the electrode plate include, for example, a method in which a solution prepared by adding ammonium dichromate and glyoxal as water-resistant insolubilizers to an aqueous polyvinyl alcohol solution is applied by brush coating, dip coating, spinner coating, etc. After being applied to an electrode plate by a spray coating method or a bar coating method, it is dried to form a water-soluble resin film that is cured under predetermined curing conditions.

The water-soluble resin film treated with this water-resistant insolubilizer is homogeneously aligned in one direction with cloth, etc.
For example, rubbing processing is performed. This alignment-treated water-soluble resin coating can improve stability and stabilize the alignment over time.

The electrode plate used in the liquid crystal display device of the present invention is a substrate on which at least one side is provided with a transparent conductive film (for example, indium oxide, tin oxide, indium oxide-tin oxide (tin oxide: 0.1 to 40% by weight), etc.) (glass, plastic, etc.) is preferably used. Furthermore, examples of the opaque conductive film used in the present invention include aluminum, gold, silver, copper, and lead.

The liquid crystal sealed in the display device of the present invention is not particularly limited, and various types can be used as appropriate. In particular, nematic liquid crystals with positive dielectric anisotropy, such as "ZLI-1216", "ZLI-1253", "ZLI-" manufactured by Merck & Co., Ltd.
1285”, “ZLI−1414”, “ZLI−1565” and “ZLI−
1694" etc. can be used. These liquid crystals can be used alone or in combination.

Hereinafter, a liquid crystal display device will be described as an example of the electro-optical device of the present invention, but the present invention is not limited thereto.

FIG. 1 is a sectional view of a display device of the present invention.
In FIG. 1, reference numerals 11 and 12 indicate substrates such as glass plates and plastic plates. Segment electrodes 13 patterned into a predetermined shape are formed on the inner surface of the substrate 11, and are further covered with a water-soluble resin film 15 cured with a water-resistant insolubilizer. At this time, the segment electrodes 13 can be formed from a transparent conductive film such as indium oxide or tin oxide.

The portion 17 of the coating 15 that covers the segment electrodes 13 is dyed by an appropriate method so that it can be identified by displaying half of it. The coating 15 is
When alignment treatment is performed by rubbing in the mutually intersecting directions with one of the insulating films 14 provided on the opposing common electrodes 16, the liquid crystal 18 disposed between them becomes
Twisted orientation at a 90° angle. As the liquid crystal 18 used in this case, a nematic liquid crystal (hereinafter referred to as Np liquid crystal) having positive dielectric anisotropy is used.

Polarizing plates 10 and 19 in a crossed nicol state are arranged outside the liquid crystal cell having such a structure.

In this liquid crystal display device, when a voltage is applied between the segment electrode 13 and the common electrode 16 shown in FIG. 1, for example, the molecular axis of the Np liquid crystal 18 is aligned in the direction of the electric field, so that incident light is blocked between crossed nicols. This can be seen as a black display 22 in a liquid crystal display device 21 as shown in FIG. 2, and this black display 22 can be distinguished from a half display 23 that looks like a dyed color.

In the liquid crystal display device shown in FIGS. 1 and 2,
By using polarizing plates colored blue, gray, red, etc. as the polarizing plates 10 and 19, the color tone effect in this device can be enhanced. or,
A reflecting plate (not shown) having light diffusing properties can be placed behind the polarizing plate 10.

As a method for dyeing the portion 17 covering the segment electrode 13, for example, a coating 15 is formed on a substrate having a transparent conductive coating patterned into a predetermined shape, and a coating of photoresist material is further formed on this coating 15. After that, the area other than the aforementioned electrode area is subjected to prescribed exposure and development so as to serve as a mask, and then immersed in a staining solution (for example, 2% ammonia solution of "Sumix Super Brilliant Red3BF" manufactured by Sumitomo Chemical Co., Ltd.). By doing so, a method can be mentioned in which the mask is removed after dyeing the portion of the coating 15 covering the electrodes.

Hereinafter, the present invention will be explained according to examples.

Example 1 Ammonium dichromate and glyoxal (ammonium dichromate: glyoxal = 1:1) were added to the solid content of polyvinyl alcohol in a 5% aqueous solution of polyvinyl alcohol ("NL-05" from Nippon Gosei Kagaku Kogyo Co., Ltd.). It was added at a rate of 5% by weight. This solution was applied onto the electrode plate for 10 seconds using a spinner coating machine rotating at 2000 rpm, and then heated and dried at a temperature of 180°C for 10 minutes.

Next, the pair of electrode plates provided with the polyvinyl alcohol coating were rubbed in one direction with a cloth to align them.
After that, the cells are assembled so that the rubbing directions are perpendicular to each other, and a nematic liquid crystal with positive dielectric anisotropy ("ZLI-1253" manufactured by Merck & Co., Ltd. in West Germany) is sealed, and then a polarizing film is applied to both outside surfaces of the cell. A display device was prepared by laminating the polarizing films so that the polarization directions of the polarizing films were parallel to the rubbing direction of the adjacent substrates (this will be referred to as sample No. 1).

On the other hand, as a comparative sample, instead of the polyvinyl alcohol treated with a water-resistant insolubilizer that was used when creating the display device of sample No. 1 described above, polyvinyl alcohol without the use of the water-resistant insolubilizer was used. A display device was created in the same manner as described above.

These samples were heated to a temperature of 90°C and a relative humidity of 65%.
100 hours, 200 hours, 300 hours under the conditions, respectively.
A forced aging test was performed on each sample by storing it every 400 and 500 hours;
The liquid crystal display ability was observed at each elapsed time. As a result, sufficient liquid crystal display ability was observed for sample No. 1 of the present invention even after 500 hours, but the comparative sample completely lost its alignment uniformity after 300 hours.
It turned out that the LCD display was not possible.

Example 2 A display device was prepared in the same manner as in Example 1, except that dimethylolated melamine was used as the water-resistant insolubilizing agent used when preparing Sample No. 1 of Example 1 (Sample No. 2).

When sample No. 2 was subjected to a forced aging test in the same manner as in Example 1, sufficient liquid crystal display ability was observed even after 500 hours.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a liquid crystal display device of the present invention, and FIG. 2 is a plan view thereof. 11, 12...Substrate, 13...Segment electrode, 16...Common electrode, 14...Insulating film, 15...
...A water-soluble resin coating cured with a water-resistant insolubilizer,
17... Part of the insulating film covering the segment electrode 13 (dyed part), 18... Liquid crystal, 10, 19...
...Polarizing plate, 21...Liquid crystal display device, 22...Display by driving, 23...Half display.

Claims (1)

[Scope of Claims] 1. In an electro-optical device in which a liquid crystal layer is sandwiched between two substrates each having a transparent conductive coating on at least one of the substrates, at least one of the electrode plates has at least one layer on its surface. An electro-optical device comprising a coating of a water-soluble resin cured by a water-insolubilizing agent that is a compound having two active groups, and the coating is subjected to an orientation treatment. 2. The electro-optical device according to claim 1, wherein the liquid crystal is a nematic liquid crystal having positive dielectric anisotropy. 3. The electro-optical device according to claim 1, wherein the water-soluble resin is polyvinyl alcohol. 4. The electro-optical device according to claim 1, wherein the water-resistant insolubilizer is at least one compound selected from the group of compounds consisting of ammonium dichromate, magnesium chloride, dialdehydes, and dimethylolated melamine. 5. The electro-optical device according to claim 4, wherein the water-resistant insolubilizer is glyoxal. 6. The electro-optical device according to claim 1, wherein the alignment treatment is a rubbing treatment. 7. The electro-optical device according to claim 1, wherein the water-soluble resin coating is colored at a portion of the conductive coating forming the segment electrode.