JP5891836B2 - Sealant for solar cell module - Google Patents

Description

  The present invention relates to a solar cell module sealing material.

In recent years, awareness of environmental issues has increased in various fields, such as countermeasures against global warming and the use of alternative energy instead of fossil fuels. For example, in the power generation field, nuclear power generation always has a risk of radioactive contamination, and thermal power generation using oil has a problem of global warming due to CO ₂ emission. Therefore, photovoltaic power generation is attracting attention as clean energy free of such problems, and its practical application is being promoted with certainty. There are various types of solar cell modules used for photovoltaic power generation. Typical examples include crystalline silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells, copper indium selenide solar cells, and compounds. A semiconductor solar cell etc. are mentioned. Among these, crystalline silicon solar cells, compound semiconductor solar cells, and amorphous silicon solar cells can be increased in area at a relatively low cost, and recently research and development of these solar cells has been actively conducted.

  As shown in FIG. 1, the basic configuration of these various solar cell modules is that a plurality of solar cell cells (solar cell elements) 101 have a weather resistance and a glass plate 102 for protecting the surface (light incident side). Sealing made of thermoplastic transparent resin such as EVA or polyvinyl butyral, which is sandwiched between the sheet 103 and bonded between the glass plate 102 and the back sheet 103 to seal the solar cell 101 A material 104 is interposed.

  By the way, the sealing material used in the solar cell module is required to have physical properties such as weather resistance, adhesiveness, and heat resistance. Therefore, in order to ensure these physical properties, EVA is conventionally crosslinked with an organic peroxide.

  When EVA is crosslinked by being decomposed by the organic peroxide added to EVA, the gel fraction serving as an index of the degree of crosslinking is improved. By improving the gel fraction of EVA, the heat resistance and strength of the solar cell encapsulant can be improved, and the gel fraction is 80% or more for solar cells used outdoors. EVA is required. Therefore, in order to provide a solar cell used outdoors or the like, it is necessary to include EVA in the EVA to crosslink the EVA.

  Therefore, in the crosslinking with the organic peroxide, a step for decomposing the organic peroxide by heating is required. Therefore, in the case of using a dialkyl peroxide type organic peroxide having a one-hour half-life temperature of 130 to 160 ° C., it takes time to perform decomposition and crosslinking reaction. There was a problem of low nature. The half-life temperature is a temperature at which half of the organic peroxide is decomposed.

  However, when organic peroxides such as peroxyester type and peroxyketal type having a low half-life temperature of 100 to 130 ° C. are used, crosslinking in a short time is possible, but organic peroxide is used for the sealing material. There arises a problem that a foaming (swelling) phenomenon which is considered to be caused by a decomposition product of the product occurs. Foaming causes a decrease in the adhesion of the EVA sealing material, resulting in a problem that the sealing performance is lowered and the lifetime and power generation efficiency of the solar cell are lowered.

  Further, when an organic peroxide having a low half-life temperature is used, scorching (early crosslinking) occurs when the organic peroxide is kneaded with EVA, and the workability is significantly reduced.

  Therefore, Patent Document 1 prevents scorch by adding 4 to 50 parts by weight of a chain or alicyclic hydroperoxide to 100 parts by weight of a peroxymonocarbonate type or peroxyketal type organic peroxide. It has been shown that it is possible. However, while scorching can be prevented, there is a problem that the crosslinking time until the gel fraction required for heat resistance is reached is extended.

  Patent Document 2 describes that the addition of t-amyl- (2-ethylhexyl) peroxymonocarbonate to t-butyl- (2-ethylhexyl) peroxymonocarbonate can shorten the crosslinking time while preventing scorch. Is disclosed to be possible. However, there was a problem that the gel fraction required for heat resistance was not reached.

JP 2011-140588 A WO2010 / 007315 publication

  However, it has been found that foaming (blowing) cannot be reliably prevented by blending an organic peroxide as in Patent Document 1. Therefore, as a result of intensive studies by the present inventors, it has been found that the swelling of the solar cell module can be reliably prevented by blending only a specific organic peroxide, and the present invention has been completed.

  That is, this invention solves the said subject, and the place made into the objective is providing the sealing material for solar cell modules which can prevent the swelling resulting from an organic peroxide reliably.

As a means therefor, the present invention is a sealing material for a solar cell module comprising EVA having a structural unit formed from vinyl acetate of 25 to 35% by weight, and an organic peroxide, the organic peroxidation As a product, the weight ratio of the organic peroxide (1) and the organic peroxide (2) represented by the following general formula is (1) / (2) = 100/10 to 100/70. .

  At this time, the content of the organic peroxide is 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the EVA. Moreover, it is preferable that the structural unit formed from the vinyl acetate in EVA is 25 to 35 weight%.

  In the present invention, “OO to XX” indicating a numerical range is a concept including a lower limit (OO) and an upper limit (XX). Therefore, if it is expressed accurately, it will be “XX or more and XX or less”.

  According to the sealing material of the present invention, by blending only a specific organic peroxide with EVA, EVA ensures good weather resistance, adhesiveness, heat resistance and the like of the sealing material. Can be crosslinked in a short time, and foaming (swelling) at each interface of the solar cell module can be further suppressed.

It is sectional drawing which shows the basic structure of a common solar cell module.

  Hereinafter, the present invention will be described in detail. In the solar cell module, the sealing material of the present invention adheres a glass plate disposed on the light incident side surface and a back sheet disposed on the substrate side, and has a solar cell (element) disposed therebetween. It is for sealing and contains EVA and only a predetermined organic peroxide. The solar cell module to be applied is not particularly limited as long as it has the above basic configuration. For example, a crystalline silicon solar cell, a polycrystalline silicon solar cell, an amorphous silicon solar cell, a copper indium selenide solar cell, and a compound A semiconductor solar cell etc. are mentioned.

(Ethylene-vinyl acetate copolymer)
Ethylene-vinyl acetate copolymer (EVA) is a component that constitutes the main component of the sealing material. The content of vinyl acetate in EVA, that is, the structural unit formed from vinyl acetate is preferably 25 to 35% by weight. When the vinyl acetate content exceeds 35% by weight, the tackiness increases and handling becomes difficult. On the other hand, when the content of vinyl acetate is less than 25% by weight, the sealing material becomes hard, so that the workability is lowered. Also, the sealing material has a function as a cushioning material as it is cured. Since the solar cell protected by is easily broken by impact, it is not preferable.

(Organic peroxide)
In the sealing material of the present invention, as an organic peroxide, t-butyl- (2-ethylhexyl) monoperoxycarbonate represented by the following general formula ( 2 ) and 1,1 represented by the following general formula ( 1 ) are used. -Di (t-amylperoxy) cyclohexane is blended at a weight ratio of (1) / (2) of 100/10 to 100/70. By blending the organic peroxide (1) and the organic peroxide (2) at a ratio of 100/10 to 100/70, while ensuring the good weather resistance, adhesiveness, heat resistance, etc. of the sealing material EVA can be crosslinked in a short time, and foaming (blowing) at each interface of the solar cell module can be further suppressed.

  Content of the organic peroxide in a sealing material shall be 0.1-3.0 weight part with respect to 100 weight part of EVA, More preferably, you may be 0.3-2.5 weight part. If the content of the organic peroxide is less than 0.1 parts by weight with respect to 100 parts by weight of EVA, the gel fraction (crosslinking degree) of EVA after the crosslinking reaction is low or the crosslinking time is long. Absent. On the other hand, when the content of the organic peroxide exceeds 5.0 parts by weight with respect to 100 parts by weight of EVA, the crosslinking of EVA is fast, and the usability at the time of manufacturing the solar cell module is remarkably deteriorated. Cause the survival of. The remaining of the mixed organic peroxide causes coloring of the sealing material and the like, and decreases the light transmittance of the sealing material, so that the amount of received light of the solar battery cell disposed between the sealing materials is reduced, As a result, the photoelectric conversion efficiency in the solar cell module is lowered.

(Other additives)
Various other additives can be blended in the sealing material of the present invention as necessary. For example, a coupling agent can be blended in order to improve adhesiveness. Examples of the coupling agent include organic silicon compounds and organic titanium compounds. Examples of organosilicon compounds include compounds having reactive organic groups such as vinyl groups, methacryloxyalkyl groups, acryloxyalkyl groups, and epoxy groups, and hydrolyzable groups such as halogens, alkoxy groups, and acetoxy groups. it can. Specifically, one or more of compounds having an unsaturated group such as vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropylmethoxysilane, and vinyltriacetoxysilane can be used. . The coupling agent may be blended in an amount of about 0.1 to 10 parts by weight, preferably about 0.5 to 5 parts by weight with respect to 100 parts by weight of EVA.

  Moreover, in order to improve a crosslinking speed and crosslinking efficiency, a crosslinking adjuvant can be mix | blended. Examples of the crosslinking aid include polyunsaturated compounds such as polyallyl compounds and poly (meth) acryloxy compounds. Specifically, polyallyl compounds such as triallyl isocyanurate, triallyl cyanate, diallyl phthalate, diallyl fumarate, diallyl maleate, poly (meth) acryloxy compounds such as ethylene glycol diacrylate, ethylene glycol dimethacrylate 1 type (s) or 2 or more types can be used.

  Furthermore, antioxidants, light stabilizers, ultraviolet absorbers, colorants, and the like can be blended within a range that does not impair the effects of the present invention. Examples of the antioxidant include a phenol stabilizer, a sulfur stabilizer, and a phosphoric acid stabilizer. Examples of the light stabilizer include hindered amine light stabilizers. Examples of the ultraviolet absorber include benzophenone and benzotriazole. Examples of the colorant include titanium oxide. When a polymer compound is added as an additive, a low volatility compound having a relatively large molecular weight is preferable.

(Production method)
The sealing material is a single screw extruder, a twin screw extruder, a Banbury mixer, a kneader, an open roll containing a composition containing EVA, a predetermined organic peroxide, and other additives appropriately blended as necessary. Is kneaded at a temperature at which the organic peroxide is not substantially decomposed, specifically about 50 to 110 ° C., and is generally formed into a sheet by extrusion molding, calendar molding, or the like. Is done. In the case of a sheet shape, the thickness may be about 0.1 to 1.0 mm. In addition, the shape of a sealing material can be suitably changed according to the shape of a solar cell module, etc., and is not limited to a sheet form.

  Thereafter, the solar cell module may be manufactured by a conventionally known method. That is, sandwiching the solar cell between at least two encapsulants, with the glass plate and the back sheet superimposed on both outer sides, the organic peroxide decomposition temperature or higher, specifically 115 ° C. or higher, Preferably, a solar cell module can be manufactured by bonding and sealing by heating and pressurizing at a temperature of 120 ° C. or higher. In addition, in order to improve adhesiveness, it is preferable that the glass plate or the back sheet is previously primed. Moreover, the sealing material can also be laminated on the solar cell.

  Heating is preferably performed until the organic peroxide is almost completely decomposed. By this heat treatment, EVA is crosslinked, and the sealing material and other components are firmly bonded. The heat treatment can also be performed in two stages. For example, it can be temporarily bonded by heating for about 1 to 5 minutes under vacuum conditions, and then further bonded for about 5 to 30 minutes under normal pressure for complete bonding. In the sealing material of the solar cell module manufactured as described above, it is preferable that the gel fraction serving as an index of the crosslinking density of EVA is 80% or more, preferably 90% or more.

  Various sealing material compositions containing organic peroxides shown in Tables 1 and 2 in proportions shown in Tables 1 and 2 are extruded at 80 ° C. with respect to 100 parts by weight of EVA (vinyl acetate content 28% by weight). A sheet-like sealing material having a thickness of 0.5 mm was formed by heating and rolling by molding.

In addition, the organic peroxide used as a comparative example is represented by the following general formula (3).
t-Amyl- (2-ethylhexyl) peroxymonocarbonate:

  A foaming test (determination of swellability) and measurement of a gel fraction serving as an index of the degree of crosslinking were performed on the obtained sealing materials of Examples and Comparative Examples. The results are also shown in Tables 1 and 2. The foaming test and the measurement of the gel fraction were performed as follows.

<Foaming test>
The sealing materials of each Example and Comparative Example were cut into a length of 3 cm × width of 6 cm, sandwiched between MS pouch films (manufactured by Meiko Shokai Co., Ltd.), heated and laminated, and heated at 135 ° C. for 2 minutes. The swelling of the film due to the gas generated at the time was visually observed and evaluated.
The case of foaming below the same level as in Comparative Example 2 was evaluated as x, and the case of foaming more remarkable than Comparative Example 2 was evaluated as x.

<Measurement of gel fraction>
Using the encapsulant of each example and comparative example, crosslinking was performed at 135 ° C. for 2 minutes using a curast meter V type manufactured by JSR Trading Co., Ltd. The EVA sealing material after cross-linking is weighed (Xg), immersed in xylene at 110 ° C. for 12 hours, and the insoluble matter is filtered through a 200 mesh wire net washed and dried in xylene at 110 ° C. The residue on the wire net was vacuum dried, the weight of the dried residue was measured (Yg), and the gel fraction was calculated (gel fraction (% by weight) = (Y / X) × 100).

  As is clear from the results in Table 1, the predetermined organic peroxide represented by the general formulas (1) and (2) with respect to EVA has a weight ratio of (1) / (2) of 100/10 to 100 / If it was the sealing material mix | blended by 70, scorch and foaming could be suppressed and the sealing material for solar cells from which a gel fraction will be 80% or more was obtained. On the other hand, in Comparative Example 1, since 5.0 parts by weight of the organic peroxide was contained, the amount of gas generated by thermal decomposition was large and foaming occurred. In Comparative Examples 2 and 3, since the weight ratio of the organic peroxide (1) was small, the gel fraction at a crosslinking time of 2 minutes did not reach 80%. In Comparative Example 4, gas was generated due to thermal decomposition of the organic peroxide, foaming occurred, and it was difficult to shorten the crosslinking time.

101 Solar Cell 102 Glass Plate 103 Back Sheet 104 Sealing Material

Claims (2)

A sealing material for a solar cell module, comprising an ethylene-vinyl acetate copolymer (EVA) having a structural unit formed from vinyl acetate of 25 to 35% by weight, and an organic peroxide,
As the organic peroxide, the weight ratio of the organic peroxide (1) and the organic peroxide (2) represented by the following general formula is (1) / (2) = 100/10 to 100/70. The sealing material for solar cell modules characterized by the above-mentioned.

The sealing material for solar cell modules according to claim 1, wherein the content of the organic peroxide is 0.3 to 3.0 parts by weight with respect to 100 parts by weight of the EVA.

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