JPH0635575B2 - Sealing composition and sealing method using the composition - Google Patents

Description

The present invention relates to an encapsulating composition for encapsulating an electronic material such as a liquid crystal, a solar cell, electroluminescence, plasma display, etc., and a method for encapsulating the electronic material with the composition. Is.

That is, the present invention is a liquid crystal, solar cell, electroluminescence, plasma display, etc. module is firmly sealed between glass, metal, plastics, etc., various environmental conditions, especially shock, fluctuation cycle of temperature. Protects the above elements from thermal expansion and contraction due to
It enables its stable use.

Further, the present invention is transparent and strong, and provides an inexpensive encapsulating composition that adheres well to glass, metal, plastics, etc., and liquid crystals, solar cells, and electroluminescence. This makes it possible to create a large-scale module such as a plasma display.

Heretofore, silicone resins, epoxy resins, polyvinyl butyral resins, cellulose acetate, etc. have been used as these encapsulating compositions, and ethylene-vinyl acetate copolymers have also been used in some cases. The encapsulating resin generally prevents external (eg water, atmosphere, etc.) from contacting the element and wiring to suppress its deterioration, and also has a buffer function to protect the element from mechanical impact such as hitting or hail drop. Is also very important. Further, it is required that the element, another substrate, and the window material are well and stably bonded and that the sealing process is simple. In addition, for example, when it is used for adhesion and sealing with a dense material (transparent glass, polymer film, etc.), high transparency is required.

Silicone resins conventionally used for these purposes have advantages such as flexibility and impact absorption capacity and good transparency, but they are liquid and difficult to handle, and it takes several hours to heat cure. However, there are drawbacks such as that the resin is expensive and the economy is low, and the moisture permeability is high.

Further, the epoxy resin is also liquid and inconvenient to handle, and has low impact resistance. Furthermore, it is necessary to pay attention to damage to the element due to shrinkage during curing.

The polyvinyl butyral resin can be handled in the form of a sheet, and since it is a thermoplastic type, sealing can be performed relatively easily. It also has excellent optical properties. However, this resin is inconvenient to handle, for example, by spraying or cooling a water-soluble powder to prevent blocking of the sheet, and it exhibits adhesive strength, so that water content adjustment is required. Furthermore, this resin foams above 100 ° C, making it difficult to use at high temperatures. Since polyvinyl butyral resin contains a large amount of plasticizer, its electrical resistance is down to the order of 10 ″ Ω-cm, which is a big problem as a sealant for electronic materials. Furthermore, its adhesive strength under high temperature and high humidity is high. In addition to the drastic decrease, the water absorption rate is high and the change due to the water content of the metal part of the sealed element remains an issue that cannot be overlooked.In view of these circumstances, ethylene-vinyl acetate copolymer has recently been sealed. This resin (hereinafter abbreviated as EVA) is a thermoplastic type similar to polyvinyl butyral, and the element can be encapsulated by thermocompression bonding, but the conventional one is (1) glass and so on. Since it is a type that applies a silane coupling agent to the surface of EVA film or glass to obtain adhesion, there is a limit to the time until it adheres to the adherend. Then Significantly adhesive force decreases by boiling test, (2) as it in insufficient transparency, the optical applications there is a disadvantage that those unsuitable.

The present invention has greatly improved these drawbacks of the EVA system, and is made from a composition obtained by adding a proper amount of a crosslinking agent or a photosensitizer to EVA, a polyfunctional crosslinking aid, a silane coupling agent, and the like. Become. The composition according to the present invention has excellent transparency and high mechanical strength by being heat-crosslinked at a temperature higher than the melting point of EVA. Also, a film formed by a film forming method such as a calendar, extrusion, or inflation method,
The sheet has a high storage stability, and has extremely excellent properties such as a decrease in the adhesive strength with the adherend when stored at ordinary room temperature and humidity after production, and a liquid crystal element,
Encapsulation of various plasma day spray electronic materials such as solar cells and electroluminescence, glass, metal,
It is useful for adhesion between plastics.

The EVA resin used in the present invention has a vinyl acetate content of 5 to 50%, preferably 15 to 40%. If the vinyl acetate content is less than 5%, the weather resistance and transparency of the resin will be problematic, and if it exceeds 40%, the mechanical properties of the resin will be significantly deteriorated, and film formation will be difficult, and film,
Blocking of sheets occurs. However, when it is used as a sealing material on the back surface, transparency is not essentially important, and 15% or less of resin may be used for this purpose.

As the cross-linking agent used in the present invention, an organic peroxide is suitable when heat-crosslinking, film forming processing temperature, cross-linking temperature,
It is selected taking into consideration the stability of savings. Examples of usable peroxides include 2,5-dimethylhexane-2,5-dihydroperoxide; 2,5-dimethyl-2,5-
Di (t-butylperoxy) hexane-3; di-t-butylperoxide; t-butylcumylperoxide; 2,5-dimethyl-2,5-di (t-butylperoxy) hexane; dicumylper Oxide; α, α'-
Bis (t-butylperoxyisopropyl) benzene;
n-Butyl-4,4-bis (t-butylperoxy) valerate; 2,2-bis (t-butylperoxy) butane; 1,1-bis (t-butylperoxy) cyclohexane; 1,1- Bis (t-butylperoxy) -3,3,5
-Trimethylcyclohexane; t-butylperoxybenzade; benzoyl peroxide; tert-butylperoxyacetate; 2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane-3; 1,1-bis (Tert-Butylperoxy) -3,3,5-trimethylcyclohexane; 1,1-bis (tert-butylperoxy) cyclohexane; methyl ethyl ketone peroxide; 2,
5-Dimethylhexyl-2,5-bisperoxybenzate; tert-butyl hydroperoxide; p-menthane hydroperoxide; p-chlorobenzoyl peroxide; tert-butyl peroxyisobutyrate;
Hydroxyheptyl peroxide; chlorohexanone peroxide and the like.

At least one of these peroxides may be used alone or as a mixture, and 5 parts by weight or less per 100 parts by weight of EVA is usually sufficient. An organic peroxide is usually kneaded with an extruder by an extruder or a roll mill, but an organic solvent, a plasticizer,
You may melt | dissolve in a vinyl monomer etc. and may add it to the film or sheet | seat of ethylene-vinyl acetate copolymer by the impregnation method.

EVA physical properties (mechanical strength, optical properties, adhesion, weather resistance,
In the present invention, various acryloxy group- or methacryloxy group- and allyl group-containing compounds may be added for the purpose of improving whitening resistance, crosslinking rate, etc.). Acrylic acid or methacrylic acid derivatives, such as esters and amides thereof, are the most common compounds to be used for this purpose, and the ester residue is in addition to alkyl groups such as methyl, ethyl, dodecyl, stearyl, and lauryl. Examples thereof include a cyclohexyl group, a tetrahydrofurfuryl group, an aminoethyl group, a 2-hydroethyl group, a 3-hydroxypropyl group and a 3-chloro-2-hydroxypropyl group. Further, esters with polyfunctional alcohols such as ethylene glycol, triethylene glycol, polyethylene glycol, trimethylolpropane and pentaerythritol can also be used. Diacetone acrylamide is a typical amide.

Polyfunctional crosslinking aids such as trimethylolpropane, pentaerythritol, glycerin, and other acrylic and methacrylic acid esters, and allyl group-containing compounds such as triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl isophthalate, and maleic acid. One or a mixture of two or more kinds such as diallyl is used in an amount of 0.1 to 10 parts, preferably 0.5 to 5 parts. If it is less than 0.1 part, the effect is insignificant, and if more than 10 parts is added, the physical properties are rather deteriorated (embrittlement).

When the encapsulating material according to the present invention is cross-linked by light, a photosensitizer may be used in place of peroxide in an amount of 5 parts by weight or less per 100 parts by weight of EVA, or a mixture thereof. Examples of usable photosensitizers include benzoin, benzophenone, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, dibenzyl, 5-nitroacenaphthene, hexachlorocyclopentadiene, paranitrodiphenyl, paranitro. Aniline, 2,4,6-trinitroaniline, 1,2
-Benzanthraquinone, 3-methyl-1,3-diaza-1,9-benzanthrone and the like.

Examples of silane coupling agents added as adhesion promoters include vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, and γ.
-Glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-
Epoxycyclohexyl) ethyltrimethoxysilane,
γ-chloropropylmethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane,
Examples include γ-aminopropyltriethoxysilane and N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane.

Usually, 0.01 to 10 parts, preferably 5 parts or less, of at least one kind or a mixture thereof is added to EVA.

In addition to these, the composition of the present invention may contain a small amount of an ultraviolet absorber, an antiaging agent, a dye processing aid and the like. For applications where transparency is not required, a filler such as carbon black, hydrophobic silica, or charcoal may be included.

Further, as a means for improving the adhesiveness, a sheet, corona discharge treatment on the film surface, low temperature plasma treatment, electron beam irradiation,
Means such as irradiation with ultraviolet light is also effective.

The encapsulating composition of the present invention is prepared by mixing EVA resin and the above-mentioned additives and kneading the mixture with an extruder, a roll, etc., and then by a film-forming method such as calendering, roll, T-die extrusion, inflation. The film is formed into a shape. During film formation, embossing is applied to prevent blocking and to facilitate deaeration during pressure bonding with glass or an element.

Hereinafter, the present invention will be specifically described with reference to examples.

Example 1 Ethylene-vinyl acetate copolymer (Toray Soda Ultrasen 634; vinyl acetate content 26%, melt index 4)
100 parts, 1 part of dicumyl peroxide and 0.5 part of γ-methacryloxypropyltrimethoxysilane were blended and a 0.4 m / m thick double-sided embossed sheet (width 900 m / m) was prepared by an extruder or calendering method. . Clean and dry the white plate glass and stainless (SUS 430) plate in advance, place the solar cell module sandwiched between the two embossed sheets between these white plate glass and the stainless plate, and attach it at 100 ℃ with a vacuum laminator. I matched it.
Furthermore, for the purpose of improving transparency and heat resistance, crosslinking was carried out at 150 ° C for 30 minutes to obtain a module that was transparent and firmly adhered to the white plate glass and stainless plate. 40 modules obtained
0 W high pressure mercury lamp (with water filter) 1900 at a distance of 15 cm
After time exposure, there was almost no change in appearance and optical properties. In addition, there was no change even after exposure in a 100 ° C oven for 1500 hours and a weatherometer for 1500 hours. Further, in order to check the adhesiveness to the white plate glass and the stainless plate, the sheets were separately bonded to the glass and the stainless under the above bonding conditions and heated at 150 ° C. for 30 minutes. A sheet / white plate glass or sheet / stainless plate laminate thus obtained is cut at a width of 25 m / m from the sheet side, and white plate glass or a stainless plate (SUS 43
The peeling test was carried out by grasping the end surface that had been treated so as not to adhere to (0) (tensile speed 100 mm / min, 180 ° peeling method). The adhesive force to glass was 6 kg / 25 mm on average, and to stainless steel was 5 to 7 kg / 25 mm.

As a comparative control, the adhesive strength was almost 0 even though the film was not heat-treated after bonding at 100 ° C.

Further, the sheet made of the composition according to the present invention contains a silane coupling agent, and retains good adhesive strength even after 90 days from the production, and has reduced adhesive strength even after being immersed in boiling water for 2 hours. Was scarce. On the other hand, in the type in which the silane coupling agent was applied to the sheet as a primer, the adhesive strength drastically decreased in the above boiling test when used after being left in the air for 4 to 5 days. Furthermore, the conventionally used polyvinyl butyral resin was peeled off in this test.

Example 2 A composition containing 1 part by weight of benzoin isopropyl ether in place of dicumyl peroxide in the composition of Example 1 was prepared, and the same method as in Example 1 was used. A sheet having a thickness of 4 m / m was prepared. A solar cell module is sandwiched between two sheets, and this sheet is inserted between white glass sheets having a thickness of 3 m / m, and air degassing is performed under vacuum at 100 ° C. as in Example 1 to perform heat treatment. Instead, it was irradiated under a 4 KW high-pressure mercury lamp with a water cooling jacket at a distance of 15 cm for 30 minutes on each side for a total of 1 minute. The haze (cloudiness value) of the irradiated product including glass was measured using an integral turbidimeter TC-SP (manufactured by Tokyo Denshoku Co., Ltd.). The UV-treated product was 0.8, and the untreated product was 3.1, which was a great improvement and was found to be an excellent transparent resin for sealing.

Example 3 A composition was prepared by mixing 5 parts of trimethylolpropane trimethacrylate with the composition of Example 2, and a double-sided embossed sheet having a thickness of 0.3 m / m was prepared in exactly the same manner as in Example 1.

Insert a sandwiched liquid crystal module between two sheets of white sheet glass (40 cm × 40 cm) having a thickness of 2 m / m, which was washed in the same manner as in Example 2, and deaerated under vacuum at 100 ° C. A large module was obtained by irradiating ultraviolet rays under the same conditions as in Example 2.
The temperature at this time was 110 ° C at most, and did not cause any thermal damage to the liquid crystal module.

This plate was left for 1000 hours at 60 ° C and 90% RHF, but no change in appearance was observed. Also, the operation of the liquid crystal did not change at all.

A 235-g steel ball was dropped from the top 5 m of this panel, but only cracks were found and no glass peeling was observed. Not only the haze value was high in the panel that was not irradiated with ultraviolet rays, but also the sinking was observed due to the falling of the steel balls. Also, in the system in which the sheet did not contain trimethylolpropane, the haze was inferior and the strength was also insufficient, although it was not as high as that without UV irradiation.

Claims (4)

[Claims] 1. An ethylene-vinyl acetate copolymer,
A sealing composition for sealing an electronic material containing a silane coupling agent and an organic peroxide or a photosensitizer. 2. The encapsulating composition according to claim 1, further comprising an encapsulating electronic material containing a (meth) acrylic acid ester and / or an allyl group-containing compound. Composition. 3. An ethylene-vinyl acetate copolymer,
An electronic material is sandwiched between molding materials mixed with a silane coupling agent and an organic peroxide or a photosensitizer, and this is placed between plates or sheets of glass, metal, plastic, rubber, etc. to reduce the pressure. A method for encapsulating an electronic material, which comprises degassing under heating, cross-linking the molding material by heating or light irradiation to make it transparent, and encapsulating without air bubbles or air bubbles. 4. The sealing method according to claim 3, further comprising (meth) acrylic acid ester and / or
Alternatively, a method for sealing an electronic material, in which an allyl group-containing compound is added.