JPH10268329A - Manufacture of liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce stress applied to a seal part and to prevent peeling by overheating the plastic substrate of the liquid crystal display element up to glass transition point (Tg) at which seal resin show elasticity. SOLUTION: A couple of plastic substrates having transparent electrodes formed are put one over the other face to face across the seal resin, and the plastic substrates are cut along the cell surrounded with the seal resin to form an injection hole. At this time, the temperature of the seal resin is held within a range of Tg of the seal resin -30 to +50 deg.C and the plastic substrates are cut. As a cutting method, a scribe cutting method is applicable for the plastic substrates without causing any problem of seal material peeling. When the temperature of the seal part is lower than the Tg of the seal resin -30 deg.C at the time of the cutting of the substrates, the seal part is easy to peel, but when higher than Tg +50 deg.C, there is the possibility of thermal deformation of the substrate, inconvenience regarding facilities, and trouble in operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal display device, and more particularly to a technique for cutting a liquid crystal display device using a transparent electrode substrate as a plastic substrate.

[0002]

2. Description of the Related Art A manufacturing process of a liquid crystal display device is roughly as follows. First, a pair of large transparent substrates as a motherboard is prepared, a plurality of display screens are allocated on one surface of each of them, for example, in a matrix, and a transparent electrode is formed for each display screen. Then, one transparent substrate
Print the seal resin around the display screen unit,
The other transparent substrate is positioned so that the transparent electrodes face each other, and the sealing resin is cured by heating or light irradiation to bond the two transparent substrates together.

Next, this motherboard is cut into a plurality of stick substrates along rows or columns in a matrix arrangement, and an injection port for injecting liquid crystal into each cell is formed. Then, after injecting the liquid crystal from the injection port, the injection port is sealed with an adhesive, and if necessary, the cell is cut, washed, and a polarizing film is attached. Thus, a liquid crystal display element as a product is finally obtained.

[0004]

However, liquid crystal display elements using plastic as a transparent substrate have the characteristics of being lightweight and hard to break, and in recent years, their use has been expanded particularly to portable information terminals and the like. However, on the other hand, there is a problem that reliability is low.

One of the reasons is that when a dense sealing resin having a high Tg, which is advantageous from the viewpoint of reliability, is used, for example, when a motherboard is cut into a plurality of stick substrates, the sealing portion is likely to peel off due to the stress. It is mentioned. This is because the plastic substrate is flexible and the sealing resin cannot follow the substrate even when the substrate is deformed during cutting.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. It is an object of the present invention to provide a transparent substrate made of a plastic substrate, even if a high Tg resin is used as a sealing resin. It is an object of the present invention to provide a method of manufacturing a liquid crystal display element in which a sealing resin does not peel off when a substrate is cut after bonding.

[0007]

According to the present invention, a pair of plastic substrates having transparent electrodes formed thereon are opposed to each other via a sealing resin, and are surrounded by the sealing resin. When cutting the plastic substrate along the cell and performing injection porting, the temperature of the sealing resin is set to Tg (glass transition point) of the sealing resin.
The method is characterized in that the plastic substrate is cut within the range of -30 to + 50 ° C.

[0008] The substrate cutting method is roughly divided into a dicing cutting method in which a dicing blade is rotated at a high speed to cut the substrate, and a half cut by pressing a carbide wheel on the substrate, and then applying a pressing force to remove the remaining portion. Although there is a scribe cutting method that breaks, in the case of a plastic substrate, since the resin is melted and adheres to the dicing blade in the dicing cutting method, it is necessary to frequently clean the blade.

In this regard, according to the scribe cutting method, the molten resin does not adhere to the carbide wheel, which is preferable for maintenance. However, it has been considered that a large external force is applied to the substrate at the time of cutting, so that the sealing material may be peeled off. Can be applied to the scribe cutting method.

In the present invention, a material having high light transmittance, optical uniformity and good heat resistance is used for the plastic substrate. Examples of such a resin include thermoplastics such as polyacrylate, polycarbonate, and polyethylene terephthalate, or alloys, blends, and composites thereof. It is also possible to use a curable resin such as an epoxy resin or a photocrosslinking resin.

As the sealing resin, the same one as the conventional one, such as a heat-curable epoxy resin, a photo-curable epoxy resin, or a photo-curable acrylic resin, which is dense and highly reliable when cured, is used. The thermosetting epoxy resin-based sealing material contains, as basic components, an epoxy agent, a curing agent, a coupling agent, rubber particles, a filler, a solvent, and the like. The Tg (glass transition point) of the cured resin is usually measured by DSC (differential scanning calorimeter) or the like.

In the present invention, at the time of cutting the substrate, the temperature of the sealing portion is set to Tg−30 ° C. or more of the sealing resin and Tg + 50.
It should be in the range of ℃ or less. If the temperature is lower than that, peeling is likely to occur in the seal portion, and if the temperature is higher than that, there is a possibility that thermal deformation of the substrate, inconvenience in equipment, and trouble in work may occur.

[0013]

【Example】

Example 1 A gas barrier layer, a hard coat, and a transparent conductive film were laminated on a polycarbonate substrate having a thickness of 0.4 mm and patterned to prepare a laminate. An alignment film was attached to the substrate according to a conventional method, and alignment processing was performed. One-part epoxy-type sealing resin DSA-7236 (manufactured by Shikoku Chemicals) was printed at a predetermined position on the substrate, superposed on the counter substrate, and heated at 110 ° C. for 30 minutes with a crimping machine to form a display cell.

Next, when the display cells were cut one by one with a scriber, the temperature of the scriber table was raised to adjust the temperature of the seal portion to 120 ° C. The cutting did not peel off the sealing resin. Thereafter, liquid crystal was injected into the cell, and thereafter, a liquid crystal display device was completed according to a standard method.

A sample of the seal resin after pressure bonding was partially scraped off, and Tg (glass transition point) was measured by using a DSC (differential scanning calorimeter). This liquid crystal display device was exposed to a high-temperature and high-humidity test at 60 ° C. and a relative humidity of 90% for a long time.
There was no peeling of the sealing resin and the display characteristics did not change at all.

Comparative Example 1 A display cell was prepared in the same manner as in Example 1, except that the temperature of the seal portion at the time of cutting was kept at the working atmosphere temperature, and no particular heating was performed. In this case, peeling of the sealing resin was observed at a rate of about 16% in the cell after cutting.

[0017]

As described above, according to the present invention,
When the plastic substrate of the liquid crystal display element is cut, the sealing resin is heated to around the Tg temperature at which the elasticity of the sealing resin is exhibited.

Even if a stress is applied to the seal portion at the time of cutting, since the sealing resin has elasticity, the stress is relieved and the separation does not occur. As a result, it becomes possible to use a dense resin having a high Tg that cannot be used conventionally as a sealing material,
An extremely reliable plastic liquid crystal display element can be manufactured. Since the plastic substrate can be cut without any trouble, productivity can be improved.

Claims (2)

[Claims] 1. A pair of plastic substrates having a transparent electrode formed thereon are opposed to each other with a sealing resin interposed therebetween, and the plastic substrate is cut along cells surrounded by the sealing resin to form an injection port. In this case, the temperature of the above sealing resin is set to Tg (glass transition point) of the sealing resin.
A method for manufacturing a liquid crystal display element, comprising cutting the plastic substrate at a temperature within the range of -30 to + 50 ° C. 2. The method according to claim 1, wherein the cutting method of the plastic substrate is a scribe cutting method.