JPS5917808B2 - LCD cell - Google Patents

Description

[Detailed description of the invention] The present invention relates to a liquid crystal cell.

More specifically, the present invention relates to a liquid crystal cell with improved performance obtained by sealing a pair of substrates with an epoxy adhesive. BACKGROUND ART Conventionally, as a liquid crystal cell used for a display, a light control device, a decorative plate, etc., it is known that two substrates are sealed with an adhesive with a spacer interposed therebetween to maintain a predetermined distance between them.

As a method of sealing these liquid crystal cells, there are a method of sealing with an inorganic adhesive such as a low melting point glass frit, a method of sealing with an organic adhesive such as an epoxy adhesive, a thermoplastic resin, etc. be. However, when inorganic adhesives are used in conventional sealing methods, they have significantly lower moisture permeability than organic adhesives and are known to have less negative impact on the lifespan of LCDs; however, the sealing temperature To create a twisted cell in which the arrangement structure of liquid crystal molecules is twisted due to the high
For example, oblique evaporation must be used, which complicates the cell fabrication process, resulting in difficulties in workability. On the other hand, when an organic adhesive is used, since the sealing temperature is low, the surface treatment of the substrate for making the twisted cell can be done by a simple method, such as a rubbing method, which has the advantage of being easy to operate. However, in order to make a highly reliable liquid crystal cell using an organic adhesive, strict performance is required of the organic adhesive. In other words, even when the liquid crystal cell is exposed to high temperatures, the organic adhesive does not release contaminants that have a negative effect on the liquid crystal, and the organic adhesive is used to prevent the liquid crystal from deteriorating due to moisture entering through the sealant during moisture resistance tests. It is required that the moisture permeability of the agent be sufficiently low. Conventionally proposed liquid crystal cells bonded with thermocompression films made of thermoplastic resins such as nylon, epoxy-based butyral, and polyethylene have a problem with the moisture permeability of the sealant, and water permeates through the film when used for a long time. Because of the water, there is a lot of moisture in the liquid crystal, causing bubbles and deterioration of the liquid crystal.

On the other hand, epoxy adhesives have excellent workability when creating cells, but in order to provide highly reliable liquid crystal cells, strict selection must be made of the main agent and curing agent of the epoxy adhesive. At present, no commercially available epoxy adhesive has yet been found that meets this purpose. That is, the epoxy equivalent of the main component of the epoxy adhesive is 182 to 1.
94 is most commonly used, but when this type of base resin is used, the resin itself becomes hard during curing, which causes stress to accumulate at the interface between the adhesive and the substrate, so durability tests were conducted. In this case, seal peeling is likely to occur, and even if a resin with low moisture permeability is used, moisture cannot be avoided from entering through the peeled surface, causing deterioration of the liquid crystal.

As described above, none of the adhesives for liquid crystal cells that have been proposed so far satisfy the required properties in a well-balanced manner, and various adhesives are still being tried.

Based on the recognition of the above-mentioned problems, the present inventor has conducted various studies and examinations, and as a result has come to the interesting knowledge that the main ingredient of the epoxy adhesive is related to the peeling resistance of the sealing material. .

The present invention was made based on the above study results, and is characterized by using an epoxy adhesive containing urethane bonds as a sealing material for a liquid crystal cell. Generally, in order to impart flexibility to a cured epoxy resin, there are two methods: modification with urethane, silicone resin, etc., methods using flexible epoxy resin and hardening agents, methods using flexible agents and non-reactive agents such as polyethylene glycol. Methods such as adding a diluent are known, but many of them have drawbacks such as workability in forming cells, moisture permeability, and adverse effects on liquid crystal.

As a result of studying these, the inventors have found that epoxy resins containing urethane bonds are particularly excellent for the above purpose. Since the liquid crystal cell of the present invention uses an epoxy adhesive containing urethane bonds as a sealing material, the resin retains flexibility after curing, reducing stress generated at the interface between the adhesive and the substrate. In addition, since there is little reactivity with the liquid crystal, seal peeling phenomenon can be avoided even after long-term moisture resistance tests, and changes in the characteristics of the liquid crystal cell are extremely small, resulting in excellent reliability. It can be held. In the present invention, epoxy adhesives containing urethane bonds include urethane-modified epoxy resins made by reacting isocyanate compounds and epoxy resins, mixtures of this and epoxy adhesives, and epoxy-modified urethane resins and epoxy adhesives. These include adhesives made by mixing urethane resin and epoxy resin, and broadly include epoxy adhesives containing urethane bonds.

Further, in the present invention, the epoxy resin includes conventionally known epoxy resins such as aromatic, alicyclic, aliphatic, etc., and one or more types of epoxy resins may be used depending on the workability of the known epoxy resins. The mixture is selected accordingly. Furthermore, by adding a filler such as Aerosil in an amount of about 0.1 to 30% to adjust the viscosity to a value suitable for workability, a liquid crystal cell with high commercial value can be obtained without disturbing the seal edges when the sealing material is cured.

The curing agent for the epoxy resin of the present invention is not particularly limited, and known curing agents such as amine compounds, acid anhydrides, polyamide compounds, dicyandiamide compounds, and imidazole compounds can be used.

In manufacturing the liquid crystal cell of the present invention, an epoxy adhesive containing a urethane bond containing the above-mentioned curing agent is applied to a desired portion of the electrode plate, usually the peripheral portion, by, for example, a screen printing method. The thickness and shape are printed, another electrode plate is placed on top of this, and the adhesive is fixed by applying the curing conditions for the sealing material.

In order to obtain a liquid crystal cell in which the distance between the adhesively fixed electrode plates is uniform to a predetermined thickness, the sealing material may contain additives such as alumina powder, glass beads, etc. of a predetermined thickness or diameter. It is possible. As explained above, by using the above-described sealing material, the liquid crystal cell of the present invention significantly improves the peeling resistance of the sealing material and, in turn, significantly improves the reliability of the liquid crystal cell.

Example epoxy resin with 10% Aerosil as a filler, 3% imidazole curing agent, and 15% as an additive for spacing control.
00 mesh A sealing material mixed with 3% Al2O is referred to as A, and a urethane-modified epoxy resin is added to the epoxy resin at a weight ratio of 10% to be used as a main ingredient, and a filler, curing agent, and spacing are mixed in the sealing material A. The control agent was added in the same amount as the seal material A and mixed to form a seal material B.

Claims (1)

[Claims] 1. In a liquid crystal cell formed by sealing a pair of electrode plates with an adhesive at a predetermined distance and sealing a liquid crystal between them, the adhesive is an epoxy adhesive containing a urethane bond. A liquid crystal cell characterized by: 2. The liquid crystal cell according to claim 1, wherein the adhesive is an epoxy adhesive prepared by mixing a urethane-modified epoxy resin and an epoxy resin.