JPH03248129A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To shorten the time for production by making adhere two sheets of substrates having transparent electrodes by an adhesive contg. a monomer, a hardener for UV curing and a hardener for thermal curing and then sealing a liquid crystal therebetween. CONSTITUTION:The substrates 1 are respectively provided with the transparent electrodes 2 and are provided with liquid crystal oriented films 3 on the surfaces formed with these transparent electrodes. Spacers 6 for maintaining the spacing between these substrates 1 are sprayed onto one substrate 1 and two sheets of the substrates 1 with the liquid crystal oriented films 3 disposed to face each other are made to adhere by the adhesive 7 in the peripheral part thereof and the liquid crystal material 4 is sealed into the spacing between the substrates. Namely, two sheets of the substrates 1 having the transparent electrodes 2 are made to adhere by the adhesive 7 contg. at least one kind of the monomer having both of the part to be polymerized and cored by UV rays and the part to be polymerized and cured by heat in the structure, the harder for UV curing and the hardener for thermal curing. The liquid crystal 4 is sealed into the spacing therebetween. The higher reliability to environment and the higher productivity are obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal display device that can be used as a display for many electronic devices.

Conventional Technology However, in order to maintain a high level of environmental resistance and reliability of completed liquid crystal display devices, the thermosetting resin used for adhering substrates requires a long curing process, making it difficult to produce liquid crystal display devices. In order to improve properties, we introduced short-curing resins to replace thermosetting resins. However, although the radical polymerization type acrylate-based ultraviolet curable resin contains few impurity ions, the adhesive strength of the substrate to the substrate is weak and lacks reliability. Although ultraviolet curable epoxy resins belonging to the ionic polymerization type have high adhesive strength, they have had the problem of deteriorating the display quality of liquid crystals due to the influence of cations remaining in the polymer after curing. On the other hand, when the curing agent and curing conditions are changed in order to cure a thermosetting adhesive at high speed, a problem arises in that distortion occurs inside the cured product, resulting in a decrease in adhesive properties.

In consideration of the above points, the present invention improves the ultraviolet curable resin, which has high reliability but poor adhesion to liquid crystals, thereby making it possible to shorten the manufacturing time of liquid crystal display devices and to produce liquid crystals with high reliability. The purpose is to provide a display device.

Means for Solving the Problems In order to achieve the above object, the present invention comprises at least one type of monomer having in its structure both a part that is polymerized and cured by ultraviolet rays and a part that is polymerized and cured by heat; The present invention proposes a liquid crystal display device in which two substrates having transparent electrodes are bonded together using an adhesive containing a hardening agent and a thermosetting hardening agent, and a liquid crystal is sealed inside.

According to the present invention, it is possible to mix a heat-cured part with high adhesive strength and an ultraviolet-cured part with a fast curing speed and good workability in the resin, so it is possible to improve moisture resistance, adhesion, and It becomes possible to design curing conditions. Therefore, it is possible to provide a highly reliable and adhesive adhesive that takes advantage of the features of ultraviolet curable resin, which cures in a short time, has little volumetric shrinkage during curing, and has good workability, making it possible to provide high-performance liquid crystal display devices. can be provided.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

(Example 1) Table 1 is a composition list of an adhesive according to an example of the present invention, and Table 2 is a composition list of commercially available resins A and H for comparison.

Table 1 Table 2 Here, the photopolymerizable polymers shown in Table 1 have either an acrylic group or a methacrylic group that can be crosslinked by at least ultraviolet rays, as shown in the following molecular formula, and
It is a compound that has both thermally crosslinkable Epoquin groups in its structure.

(However, R1 and R2 represent arbitrary alkyl groups.) FIG. 1 is a cross-sectional view of the liquid crystal display device of this embodiment. Each substrate 1 is provided with a transparent electrode 2, and the surface on which the transparent electrode is formed is A liquid crystal alignment film 3 is provided. Spacers 6 for maintaining the gap between the substrates 1 are scattered on one of the substrates 1, and the two substrates 1 are separated with the liquid crystal alignment film 3 facing inside.
The peripheral portion of the substrate is bonded with the adhesive 7 of this embodiment shown in Table 1, and the liquid crystal material 4 is sealed in the gap between the substrates.

In this liquid crystal display device, conventional acrylate-based ultraviolet curable resin (herein referred to as Comparative Example 1) and thermosetting resin (herein referred to as Comparative Example 2) shown in Table 2 were used in place of the adhesive 7. Three types of liquid crystal display devices obtained by bonding the periphery of the substrate 1 were heated at 90°C and 85°C and at a humidity of 85°C.
Table 3 summarizes the results of the visual inspection after approximately 1000 hours of being left in the environmental test tank. The curing conditions for the resin were: Comparative Example 1: UV irradiation time of 3 minutes, Comparative Example 2: 100°C.
In this example, after 3 minutes of UV irradiation, 1
Heat treatment was performed at 40° C. for 10 minutes.

Table 3: ○, Good ×: Orientation disorder △, bubbles M: Gap change Reliability equivalent to resin can be obtained. This is thought to be because the adhesive of the present invention has a resin structure that combines the flexibility of an ultraviolet curable resin and the high adhesiveness of a thermosetting resin, which alleviates internal strain during curing. A liquid crystal display device made using this material can simultaneously achieve improved environmental reliability and high productivity.

In addition, in this practical example, a monomer with an acrylic group at one end and one epoxy group introduced into the structure was used as a photopolymerizable monomer, or the terminal group may be a monomer with an epoxy group introduced into the structure as long as it can be crosslinked by ultraviolet rays. The number of epoxy groups introduced can also be changed arbitrarily. Furthermore, the structure of the alkyl group forming the main chain of the heptadome can be selected in accordance with the properties required for the cured product.

Also, in this example, it was found that it was difficult to obtain effects such as improving adhesive strength and reliability depending on the blending ratio of the curing agent in the thermosetting part and the ultraviolet curing part, so depending on the structure of each resin. It is desirable to consider the optimal blending amount.

(Example 2) A second embodiment of the present invention will be described below.

Table 4 shows the composition of the adhesive according to the present invention, and Table 5 shows the peel strength of soda glass cut into strips, glued together in a cross shape using the adhesives of Examples 1, 2 and 3 of the present invention. This is the result of measuring.

At this time, the curing conditions for each resin were as follows: For Examples 1 and 2, UV irradiation was performed for 3 minutes, then 140°C, 10°C.
Although the heat treatment was carried out for 1 minute, in Example 3, heat treatment was also performed at 80°C for 10 minutes before UV irradiation.

Table 4 (blank below) Table 5 As is clear from the results in Table 5, the surface of the glass plate as the adherend is like the γ-methacryloxypropyltrimethoxysilane of Example 2.3 in the resin. The adhesive strength is further improved by treatment with an alkoxysilane, and this effect is further promoted by adding an organotin compound to the adhesive component and heat treating it before UV irradiation.

Therefore, liquid crystal display devices made using these adhesives have even higher performance.

Note that in this example, quaternary alkoxysilane was used as the alkoxysilane.
There is no problem as long as the γ-methacrylatetrimethoxysilane shown in the table is used or a compound that has a cambling effect is used, and the effect was also observed with the organotin compound dibutyltin acetate in Example 3. There is.

Effects of the Invention As described above, according to the present invention, an adhesive having higher moisture resistance than conventional ultraviolet curable resins can be obtained, so that an adhesive with good workability and high reliability can be obtained. Therefore, it has become possible to use UV-curable resins in liquid crystal display devices, which previously used two-component thermosetting epoxy resins to achieve high reliability against humidity, greatly improving workability and productivity. Its industrial value is enormous, as improvements can be made.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a liquid crystal display element according to an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional liquid crystal display element. 1...Substrate, 2...Transparent electrode, 3...
...Liquid crystal alignment film, 4...Liquid crystal material, 5...
...Thermosetting adhesive, 6... Spacer 7... Adhesive.

Claims (5)

[Claims] (1) An adhesive containing at least one type of monomer having in its structure both a part that polymerizes and hardens with ultraviolet rays and a part that polymerizes and hardens with heat, a curing agent for UV curing, and a curing agent for thermosetting. A liquid crystal display device in which two substrates with transparent electrodes are glued together and liquid crystal is sealed inside. (2) The liquid crystal display device according to claim 1, using an adhesive mixed with alkoxysilane. (3) The liquid crystal display device according to claim 1, using an adhesive containing a mixture of alkoxysilane and an organic tin compound. (4) The liquid crystal display device according to claim 1, wherein the portion that is cured by ultraviolet rays is an acrylic group or a methacrylic group. (5) The liquid crystal display device according to claim 1, wherein the portion is a ■■■■■ group that hardens by heat.