JPH08328027A - Sealing material composition for liquid crystal display element and liquid crystal display element using the same - Google Patents

Abstract

PURPOSE: To improve adhesive property and resistance to moist/heat by using an epoxy resin having dicyclopentadiene skeleton and >=2 glycidyl groups in the molecule as the essential component. CONSTITUTION: In an one-pack type adhesive composition consisting essentially of the epoxy resin, a hardening agent, an inorganic filler and a solvent, the epoxy resin having dicyclopentadiene skeleton and >=2 glycidyl groups in the molecule is used as the essential component. The content of the epoxy resin per total epoxy resin is preferably >=20wt.%. One or more kind thereof can be jointly used. Further, the epoxy resin is preferably solid or semisolid to prevent the slippage between two substrates in a state before heating and hardening in an assembly process of the liquid crystal display element. As the inorganic filler, a carbonate, a sulfate of various metals, alumina and silica are exemplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing material composition for liquid crystal display devices and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art In recent years, liquid crystal display elements have become widespread due to their features such as light weight, thin shape and low power consumption. The liquid crystal display element has a structure in which the liquid crystal is sandwiched between glass or plastic substrates, and the periphery is sealed with an adhesive so that the liquid crystal does not leak outside. Generally, this is used for liquid crystal display elements. It is called sealing material (liquid crystal sealing material for short).

At present, epoxy resin is widely used as the liquid crystal sealing material, but a more excellent liquid crystal sealing material is required to improve the reliability of the liquid crystal display element, for example, the resistance to moisture and heat. As epoxy resin used as a sealing material for liquid crystal display elements, Japanese Patent Publication No. Sho 64-5630 and Japanese Examined Patent Publication 3-3
There are 4787 publications and the like, but when the epoxy resin described therein is used as a sealing material for a liquid crystal display element, the cured product has insufficient heat resistance and moisture resistance, so that the reliability as a liquid crystal display element is low. Is insufficient. Specifically, during long-term use, display defects may occur due to moisture permeation from the seal portion.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a sealing material for a liquid crystal display element which improves the reliability of the liquid crystal display element as compared with the conventional liquid crystal sealing material, and a liquid crystal display element using the same. .

[0005]

The present invention provides a one-pack type adhesive composition containing an epoxy resin, a curing agent, an inorganic filler, and a solvent as main components, and the dicyclopentadiene skeleton in the molecule as the epoxy resin. And has 2 glycidyl groups
A sealant composition for a liquid crystal display device, which comprises an epoxy resin having at least one epoxy resin as an essential component.

The epoxy resin having a dicyclopentadiene skeleton in the molecule used as an essential component in the present invention is
It is well known that it has been conventionally used as a semiconductor sealing material, but it is also excellent when used as a sealing material for a liquid crystal display device in which two glass substrates are bonded together with a gap of about 1 to 10 μm. The inventors have found that the characteristics can be obtained and have completed the present invention.

That is, the characteristics required for the sealing material of the liquid crystal display element are that the liquid crystal sandwiched between the two glass substrates does not leak out under various conditions.
Secondly, it is possible that, for example, moisture or the like does not enter from the outside to cause display abnormality. With respect to any of the required characteristics, the sealing material is required to have good adhesiveness to glass under various conditions. In particular, since the gap between two glass substrates is as narrow as about 1 to 10 μm, the stress caused by the difference in the coefficient of thermal expansion from the glass base material due to temperature changes in the sealing material and the adhesive part is peeled off and cracks are generated. It is important to absorb without causing.
From such a point of view, conventional sealing materials for liquid crystal display elements have been exclusively added with a component such as a silicone component that lowers the elastic modulus (for example, Japanese Patent Publication No. 4-5063).
No. 6-73164, 6-75231). However, the addition of such a component that lowers the elastic modulus lowers the heat resistance of the sealing material itself and also lowers the adhesiveness, and thus is not a fundamental solution. That is, the best measure is to impart toughness against stress while maintaining heat resistance.

From the above points, the inventors of the present invention have made earnest studies, and as a result, by using an epoxy resin having a dicyclopentadiene skeleton in the molecule and having two or more glycidyl groups as an essential component, It has sufficiently high heat resistance as a sealing material for liquid crystal display elements, and temperature conditions that can be considered in the manufacturing process and use conditions of liquid crystal display elements,
It has been found that the material has sufficient toughness to withstand the stress generated by temperature changes and the like.

The content of the epoxy resin having a dicyclopentadiene skeleton in the molecule and having two or more glycidyl groups with respect to the total epoxy resin is not particularly limited, but 20% by weight from the viewpoint of the reliability of the liquid crystal display device. % Or more is preferable. Further, they can be used alone or in combination of two or more. Furthermore, in order to prevent the displacement of the two substrates before heat curing in the process of assembling the liquid crystal display element, the epoxy resin having a dicyclopentadiene skeleton in the molecule and having two or more glycidyl groups is solid. Alternatively, it is preferably in a semi-solid state.

Further, in addition to the epoxy resin having a dicyclopentadiene skeleton in the molecule and having two or more glycidyl groups, other epoxy resins may be used in combination, but they are not particularly limited, and examples thereof include bisphenol A type epoxy. Resin, alkyl-substituted bisphenol A type epoxy resin,
Bisphenol F type epoxy resin, alkyl-substituted bisphenol F type epoxy resin, bisphenol S type epoxy resin, glycidyl amine type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, glycidyl ester Type epoxy resin, alicyclic epoxy resin, urethane modified epoxy resin and the like.

There is no particular limitation on what is used as a curing agent, and amine curing agents, imidazole curing agents, dicyandiamide, hydrazide curing agents, acid anhydride curing agents commonly used as epoxy resin curing agents are used. , A phenolic curing agent or the like can be used, and further, these microencapsulating curing agents for improving storage stability,
An adduct type curing agent or the like can be used, and a curing accelerator can also be used in combination therewith. As the curing accelerator, phosphorus compounds, imidazole compounds, urea compounds and the like are generally used.

Examples of the inorganic filler include carbonates, sulfates, alumina, silica, titanium oxide of various metals,
Examples thereof include potassium titanate, and among these, it is preferable to use one kind or two or more kinds of alumina and silica in combination from various points. Furthermore, the addition amount of the inorganic filler is 3 out of the total composition from the viewpoint of workability such as printability.
It is preferably set to 50% by weight.

Further, the solvent used for the purpose of adjusting the viscosity of the sealant composition and uniformly mixing the respective components is not particularly limited. For example, hydrocarbon solvents such as n-hexane, n-decane, cyclohexane and the like. , Benzene, toluene, aromatic hydrocarbon solvents such as xylene, butyl acetate, ester solvents such as benzyl acetate, methyl cellosolve, butyl cellosolve, methyl carbitol, ethyl carbitol, butyl carbitol, methyl cellosolve acetate, ethylene glycol, Polyhydric alcohols such as diethylene glycol and diglyme and derivatives thereof are used alone or in combination of two or more. The amount of solvent added is 2 to 50% by weight of the total composition in terms of printability.
It is preferable that

Further, a coupling agent, a defoaming agent, a leveling agent and the like may be added in addition to the above-mentioned epoxy resin, curing agent, inorganic filler and solvent which are essential components in the present invention.
When preparing the sealant composition for a liquid crystal display device of the present invention, it is preferable to knead using a triple roll or the like in order to uniformly mix the respective components.

As a method for producing a liquid crystal display element using the sealant composition for a liquid crystal display element of the present invention, the following method is generally used. First, a sealing material pattern is formed on one side of the glass substrate on which the liquid crystal alignment layer is formed by a process such as screen printing, preliminarily dried in a drying oven or the like, and then the other substrate is bonded and added as necessary. Pressurize and heat cure in a drying oven or the like. Pre-drying is usually at 50 to 120 ° C for 5 to 60 minutes, and heat curing is usually at 100 to 200 ° C for 15 minutes.
About 180 minutes is appropriate. Further, in order to maintain the gap between the two substrates, the sealing material may contain a spherical or rod-shaped spacer having a predetermined diameter. Liquid crystal is injected into this bonded substrate, and the injection port is sealed with UV curable resin or the like to form a liquid crystal display element.

[0016]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Example 1) 50 parts by weight of a dicyclopentadiene type epoxy resin (manufactured by Dainippon Ink and Chemicals, HP-7200) as an epoxy resin, a bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy, Epicoat 828) 50 parts by weight, dicyandiamide as a curing agent 15 parts by weight, fine silica as an inorganic filler (manufactured by Nippon Aerosil Co., Ltd., Aerosil
R972) 5 parts by weight, spherical silica (Admatex, SO-
15 parts by weight of C4) and 10 parts by weight of methyl carbitol as a solvent were mixed by stirring and further kneaded with a three-roll to obtain an adhesive composition.

Next, 1% of a spherical silica spacer having a diameter of 5 μm was mixed with this adhesive composition to prepare a liquid crystal cell in the following manner. (Screen printing) A square pattern having a line width of 0.3 mm was screen-printed on a glass substrate with ITO (square having a side of 3 cm) on which an alignment film was formed using a 250 mesh plate. (Preliminary drying) Preliminary drying was performed in a hot air dryer at 90 ° C for 30 minutes. (Laminating and heat curing) A glass substrate with ITO on which an orientation film is formed is attached so that the orientation direction is 90 degrees with respect to the orientation treatment direction of the substrate on which the sealing material is printed, and 1 kg
It was heat-cured in a hot air dryer at 170 ° C. for 120 minutes while applying a pressure of / cm ² . (Liquid crystal injection, sealing) Fluorine-based liquid crystal (Merck, ZLI-47
92) was injected, and the injection port was sealed with an acrylic UV curing resin.

The following items were evaluated. (1) Adhesive strength after heat curing (peeling the glass substrate with a knife). (2) Pressure cooker test (LCD cell at 125 ° C /
After processing at 100% RH / 2.3 atm for 24 hours, a ± 3 V rectangular wave was applied to evaluate display unevenness.) The evaluation results are shown in Table 1.

(Example 2) 30 parts by weight of a dicyclopentadiene type epoxy resin (manufactured by Dainippon Ink and Chemicals, HP-7200H) as an epoxy resin, a bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy Co., Epicoat 828) 50 parts by weight, glycidyl amine type epoxy resin (Okaka Shell Epoxy Co., Epicoat 604) 20 parts by weight, adipic acid dihydrazide 15 parts by weight as a curing agent, fine silica as an inorganic filler (Nippon Aerosil Co., Ltd. Aerosil R972) 5
By weight, 15 parts by weight of alumina (UA-5105 manufactured by Showa Denko KK) and 10 parts by weight of methyl carbitol as a solvent were mixed by stirring, and further kneaded with a three-roll to obtain an adhesive composition. Next, 1% of a spherical silica spacer having a diameter of 5 μm was mixed with this adhesive composition to prepare a liquid crystal cell in the same manner as in Example 1. The evaluation results are as shown in Table 1.

(Comparative Example 1) 30 parts by weight of bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy Co., Epicoat 828) as epoxy resin, 70 parts by weight of bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy Co., Epicoat 1001) , 15 parts by weight of adipic acid dihydrazide as a curing agent,
As an inorganic filler, 5 parts by weight of fine silica (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.), 15 parts by weight of spherical silica (SO-C4 manufactured by Admatechs Co., Ltd.), and 10 parts by weight of methyl carbitol as a solvent are stirred and mixed, and further 3 The mixture was kneaded with this roll to obtain an adhesive composition. Then add the diameter to this adhesive composition
A 5% spherical silica spacer was mixed with 1%, and a liquid crystal cell was produced in the same manner as in Example 1. The evaluation results are as shown in Table 1.

(Comparative Example 2) 50 parts by weight of a bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy Co., Epicoat 828) as an epoxy resin, 50 parts by weight of an o-cresol novolak type epoxy resin (ESCN195LB manufactured by Sumitomo Chemical Co., Ltd.), 20 parts by weight of dicyandiamide as a curing agent, silica having a specific surface area of 5 m ² / g as an inorganic filler (manufactured by Admatechs,
25 parts by weight of SO-C4) and 10 parts by weight of methyl carbitol as a solvent were mixed by stirring and further kneaded with a three-roll to obtain an adhesive composition. Next, 1% of a spherical silica spacer having a diameter of 5 μm was mixed with this adhesive composition, and a liquid crystal cell was produced in the same manner as in Example 1. The evaluation results are as shown in Table 1.

[0023]

[Table 1]

[0024]

EFFECT OF THE INVENTION The sealing material for liquid crystal display device of the present invention exhibits good adhesiveness and excellent heat and humidity resistance.
When applied to a liquid crystal display element, a liquid crystal display element having excellent reliability can be provided.

Claims (4)

[Claims] 1. A one-pack type adhesive composition comprising an epoxy resin, a curing agent, an inorganic filler and a solvent as main components, wherein the epoxy resin has a dicyclopentadiene skeleton in the molecule and a glycidyl group of 2 A sealant composition for a liquid crystal display device, which comprises an epoxy resin having one or more as an essential component. 2. The epoxy resin having a dicyclopentadiene skeleton in the molecule and having two or more glycidyl groups is contained in an amount of 20% by weight or more based on all epoxy resins.
A sealing material composition for a liquid crystal display device as described above. 3. The sealant composition for a liquid crystal display device according to claim 1, wherein the epoxy resin having a dicyclopentadiene skeleton in the molecule and having two or more glycidyl groups is solid or semisolid. 4. A liquid crystal display device using the sealant composition for liquid crystal display device according to claim 1.