JPS58140719A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent the penetration of moisture into a liq. crystal and the deterioration of the display characteristics by providing a multiple structure to a sealing wall of an adhesive for sealing the liq. crystal and by filling a hygroscopic agent into the gap between the sealing walls. CONSTITUTION:A double sealing wall 12A, 12B is formed between substrates 11, 11 at the peripheral part, and a liq. crystal 14A having the same composition as a liq. crystal 14 is filled into the gap between the sealing walls 12A, 12B as a hygroscopic agent. The hygroscopic wall is manufactured by doubly forming a sealing wall of an adhesive and by filling the liq. crystal as the hygroscopic agent. A liq. crystal of a different kind or a hygroscopic substance other than a liq. crystal may be used in place of the liq. crystal 14A to be filled into the gap between the walls 12A, 12B.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal display device, and more particularly to a structure of a liquid crystal display device that prevents deterioration of display characteristics.

A liquid crystal display device consists of two substrates, at least one of which is made of transparent glass, with transparent electrodes provided on the inside, which are placed facing each other with a narrow gap of several microns with a spacer interposed between them, and an adhesive is formed around the periphery of the two substrates. The substrate is bonded with a sealing wall of adhesive, and liquid crystal is filled and sealed between the substrates. When a voltage is applied between the transparent electrodes, the transmittance and reflectance of the liquid crystal's light changes. It provides a visually appealing display.

The structure and manufacturing method of a conventional liquid crystal display device will be explained based on FIG. 11.11 is a glass substrate. First of all,
A conductive transparent thin film of In2O3 or the like is formed on the glass substrate 11 by vacuum evaporation or sputtering, and patterned electrodes 13 are formed from a thin iron film by etching. Furthermore, an organic or inorganic alignment film 15 is integrally formed thereon, and a rubbing process is performed by rubbing in one direction with a fiber material such as cotton cloth to impart alignment. A sealing wall 12 made of adhesive is formed on one of the substrates 11 at its peripheral edge by screen printing or the like. These two substrates 11.11 are bonded with the adhesive sealing wall 12 with the spacer 16 interposed, with the side on which the pattern electrode 13 and alignment film 15 are formed on the inside, and the liquid crystal 14 is placed between the substrates 11.11. A liquid crystal display device is produced by filling and sealing.

The factors that determine the display quality, which is the most important characteristic of such liquid crystal display devices, include alignment agents, alignment treatment conditions, and uniformity of the distance between glass substrates. The quality of the adhesive sealing wall and the sealing structure are also important factors.

In general, liquid crystal materials are hydrolyzable, so they easily undergo chemical reactions and change in quality when exposed to moisture. Even biphenyl liquid crystal materials with good water resistance can suffer from alignment disturbances due to the infiltration of moisture. When this occurs, a decline in display quality cannot be avoided.

However, the adhesives used to seal the liquid crystal of conventional liquid crystal display devices do not necessarily exhibit sufficient sealing properties and water resistance.

Examples of organic adhesives include bisphenol A-based or glue-based epoxy resins with reaction equivalents of aliphatic polyamines added as curing agents; however, when these organic adhesives are used, The disadvantage of this method is that the adhesive itself absorbs moisture, and this moisture gradually permeates and diffuses into the liquid crystal, causing the liquid crystal material to deteriorate over time.

On the other hand, although inorganic glass adhesives are known to have excellent sealing properties and water resistance, these adhesives have the following drawbacks. In other words, when using a glass adhesive, use a glass frit paste instead of the organic adhesive, and do not use the organic adhesive until it is formed on the glass substrate by screen printing, etc. There is no deformity when using the adhesive, but the adhesive substrate must be melted and bonded at a high temperature of 400°C or higher without corrosion afterwards. Therefore, the alignment agent and alignment treatment are limited to oblique vapor deposition of silicon oxide or polyimide methods that can withstand temperatures of 400° C. or higher, resulting in a very expensive manufacturing method. Furthermore, it is extremely difficult to stabilize the clearance between glass substrates, not only for small liquid crystal display devices such as watches and calculators, but also for ultra-large liquid crystal display devices such as those used in automobiles with an area of 100 mm x 200 mm or more. You can say that.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device that can prevent moisture from seeping into the liquid crystal and prevent the display characteristics of the liquid crystal from deteriorating over a long period of time.

In the liquid crystal display device according to the present invention, 92 substrates each having a transparent electrode inside are bonded together at their peripheral edges with an adhesive sealing wall with a spacer interposed therebetween, and liquid crystal is filled and sealed between the substrates. The liquid crystal display device is characterized in that the adhesive sealing walls are provided in multiple layers, and a moisture absorbent is filled between the multiple adhesive sealing walls.

In a preferred embodiment of the liquid crystal display device according to the present invention,
The same liquid crystal as the liquid crystal filled between the substrates is used as the moisture absorbent.

Embodiments of the liquid crystal display device according to the present invention will be described below with reference to FIG. In the liquid crystal display device of FIG. 2, a double sealing wall 12 is provided at the chest edge between the two substrates 11.
There is no difference from the conventional liquid crystal display device shown in FIG. 1, except that a seal wall 12 and 12B are formed, and a liquid crystal 14A having the same composition as the liquid crystal 14 is filled as a moisture absorbent between the seal walls 12 and 12B. . Further, the manufacturing method is the same as the conventional method except that a double adhesive sealing wall is provided and liquid crystal, which is a moisture absorbent, is filled in between. Although not shown, of course
The liquid crystal 14 is placed inside the adhesive seal wall 12B, and the seal wall 12
Filling ports are provided in the seal walls 12A and 12B for filling the liquid crystal 14 between the liquid crystal 1 and the liquid crystal 12B, respectively.
After filling with 4,14A, it is sealed with the same adhesive.

Instead of the liquid crystal 14 having the same composition as the liquid crystal 14, which is filled between the adhesive seal walls 12A and 12B, it is possible to use a liquid crystal of a different polarity or a hygroscopic substance other than the liquid crystal. It is preferable to use the liquid crystal 14A having the same components as the liquid crystal 14A because there is no need to prepare two materials, the filling operation can be carried out at the same time, and there is no problem even if the two are mixed by mistake. In the liquid crystal display device shown in FIG. 2, the seal wall has a double structure, but it can also have a triple or more multilayer structure.

In the liquid crystal display device of the present invention, the adhesive sealing wall for sealing the liquid crystal has a multilayer structure, so even if an organic adhesive is used, the outer sealing wall absorbs moisture, and gradually both sealing walls Even if moisture is diffused into the liquid crystal as a moisture absorbent between them and deterioration of the liquid crystal occurs, the moisture is captured by the outer seal wall and the liquid crystal between the seal walls, and the amount of moisture absorbed by the inner seal wall is reduced. is extremely small. Therefore, moisture will not diffuse into the display liquid crystal, causing deterioration of the display liquid crystal and deteriorating the display quality.

As an example, adhesives such as those manufactured by Haven Chemical Corporation (Haven Chemical Corporation)
A conventional liquid crystal display device with dimensions of 80 mm x 130 mm and a liquid crystal display device of the present invention were manufactured using the novolac epoxy resin adhesive of n), a silane compound as an alignment agent, and a biphenylcyclohexane liquid crystal as a liquid crystal.

Both were maintained in an atmosphere with a temperature of 70°C and a relative humidity of 95%,
When changes in display quality were observed, display defects were observed in the conventional structure within 400 hours, but the display according to the present invention maintained its initial display quality even after 1000 hours.

[Brief explanation of the drawing]

1 and 2 are longitudinal sectional views of a conventional liquid crystal display device and a liquid crystal display device of the present invention. 11... is a lath substrate, 12, 12A, 12g... adhesive seal wall, 13... transparent electrode, 14... display liquid crystal, 144-... liquid crystal (hygroscopic agent), 15... ...Alignment film, 16...Spacer. Representatives: Asamura and 4 people

Claims (2)

[Claims] (1) Two substrates with transparent electrodes provided on the inside are adhered at their peripheral edges with an adhesive sealing wall with a spacer interposed between them,
The liquid crystal display device in which the liquid crystal is filled and sealed between the substrates is characterized in that the adhesive sealing walls are provided in multiple layers, and a moisture absorbent is filled between the multiple adhesive sealing walls. LCD display device. (2) The liquid crystal display device according to claim 1, wherein the same liquid crystal as the liquid crystal filled between the substrates is used as the moisture absorbent.