JP6197531B2 - Encapsulant composition and solar cell module encapsulant sheet using the same - Google Patents

Description

  The present invention relates to a sealing material composition for a solar cell module and a sealing material sheet for a solar cell module using the same.

  In recent years, solar cells as a clean energy source have attracted attention due to the growing awareness of environmental issues. The solar cell module constituting the solar cell includes a solar cell element, and this solar cell element plays a role of converting light energy such as sunlight into electric energy.

  Solar cell elements are often manufactured using a single crystal silicon substrate or a polycrystalline silicon substrate. For this reason, the solar cell element is vulnerable to physical impact, and when the solar cell module is mounted outdoors, it is necessary to protect it from rain or the like. Moreover, since the electrical output generated by one solar cell element is small, it is necessary to connect a plurality of solar cell elements in series and parallel so that a practical electrical output can be taken out. For this reason, it is common practice to connect a plurality of solar cell elements and enclose them with a transparent substrate and a sealing material to produce a solar cell module. Generally, a solar cell module is manufactured by a lamination method or the like in which a transparent front substrate, a sealing material, a solar cell element, a sealing material, a back surface protection sheet, and the like are sequentially stacked, and these are vacuum-sucked and heat-pressed.

  The sealing material used for the solar cell module usually contains an ultraviolet absorber for preventing deterioration of the resin due to ultraviolet rays. For example, Patent Document 1 includes component (A): ethylene / α-olefin copolymer, component (B): high molecular weight hindered amine light stabilizer, and component (C): benzophenone ultraviolet absorber. The resin composition for solar cell sealing materials to contain is disclosed.

JP 2012-44153 A

  In general, in a solar cell module, in order to prevent deterioration of the resin, it is necessary to cut light in the UV region on the lower wavelength side from around 340 to 360 nm. On the other hand, since the effective wavelength of the solar cell element is from the visible region to around 300 nm, it is preferable that ultraviolet rays around 350 nm to 400 nm can be used effectively. Here, the benzophenone-based ultraviolet absorber used in Patent Document 1 is a commonly used UV absorber, but it is inferior in UV resistance, so it is decomposed in a long-time UV resistance test and UV blocking. There was a problem that performance could not be maintained for a long time.

  The present invention has been made in view of the above circumstances, and is a solar cell that can cut light in the UV region on the lower wavelength side from near 340 to 360 nm for a long period of time and that can make maximum use of the effective wavelength of the solar cell element. It is an object to provide a sealing material composition for a module.

  As a result of intensive studies, the present inventors can solve the above problems by using a slight amount of a benzotriazole-based UV absorber and / or a triazine-based UV absorber in addition to a benzophenone-based UV absorber. As a result, the present invention has been completed. More specifically, the present invention provides the following.

(1) containing a resin containing a polyethylene resin having a density of 0.900 g / cm ³ or less, and two or more kinds of ultraviolet absorbers,
A sealing material composition for a solar cell module, wherein A) a benzophenone-based UV absorber and B) a benzotriazole-based UV absorber and / or a triazine-based UV absorber are used in combination as the UV absorber. object.

  (2) The encapsulant composition according to (1), wherein the content of the benzotriazole ultraviolet absorber in the encapsulant composition is 0.02% by mass or more and 0.10% by mass or less.

  (3) The sealing material composition according to (1), wherein the content of the triazine-based ultraviolet absorber in the sealing material composition is 0.05% by mass or more and 0.15% by mass or less.

  (4) A sealing material sheet for a solar cell module, in which the sealing material composition according to any one of (1) to (3) is formed into a sheet.

  (5) A solar cell module including the solar cell module sealing material sheet according to (4).

  ADVANTAGE OF THE INVENTION According to this invention, the sealing material composition for solar cell modules which can cut the light ray of the UV region of the low wavelength side for a long period of time, and can utilize the effective wavelength of a solar cell element to the maximum can be provided.

It is sectional drawing which shows an example of the laminated constitution of the solar cell module of this invention.

<Sealant composition for solar cell module>
The encapsulant composition for producing the encapsulant for solar cell module of the present invention is not particularly limited as long as it contains a polyethylene resin having a density of 0.900 g / cm ³ or less and an ultraviolet absorber. Preferably, it contains a resin composition containing 90% or more of a polyethylene resin having a density of 0.900 g / cm ³ or less, and an ultraviolet absorber.

The sealing material for solar cell modules of this invention is a single layer film which consists of this sealing material composition, or a multilayer film formed by laminating | stacking this sealing material composition. When the solar cell module encapsulant is a multilayer film, each encapsulant composition laminated as a multilayer film contains 90% or more of a polyethylene resin having a density of 0.900 g / cm ³ or less. As long as it is a resin composition to be used, those having different compositions and component ratios can be used for each layer.

[Polyethylene resin]
As the base resin, low density polyethylene (LDPE) having a density of 0.900 g / cm ³ or less, preferably linear low density polyethylene (LLDPE) is used in the present invention. The linear low density polyethylene is a copolymer of ethylene and α-olefin, and in the present invention, the density is 0.900 g / cm ³ or less, preferably 0.870 to 0.890 g / cm ³ . is there. If it is this range, favorable transparency and heat resistance can be provided, maintaining sheet workability.

  In the present invention, it is preferable to use a metallocene linear low density polyethylene. Metallocene linear low density polyethylene is synthesized using a metallocene catalyst which is a single site catalyst. Such polyethylene has few side chain branches and a uniform distribution of comonomer. For this reason, molecular weight distribution is narrow and it is possible to make it the above ultra-low density. In addition, since the crystallinity distribution is narrow and the crystal sizes are uniform, not only a large crystal size does not exist, but also the crystallinity itself is low due to the low density. For this reason, it is excellent in transparency when processed into a sheet shape. Therefore, even if the sealing material for solar cell modules comprising the sealing material composition of the present invention is disposed between the transparent front substrate and the solar cell element, the power generation efficiency hardly decreases.

  As the α-olefin of the linear low density polyethylene, an α-olefin having no branch is preferably used. Among these, 1-hexene and 1-heptene which are α-olefins having 6 to 8 carbon atoms are preferable. Or 1-octene is particularly preferably used. When the α-olefin has 6 to 8 carbon atoms, the solar cell module sealing material can be provided with good flexibility and good strength. As a result, the adhesiveness between the solar cell module sealing material and the base material is increased, and moisture can be prevented from entering between the solar cell module sealing material and the base material.

  The melt mass flow rate (MFR) of the polyethylene resin is preferably 1.0 g / 10 min or more and 40 g / 10 min or less at 190 ° C. and a load of 2.16 kg, preferably 2 g / 10 min or more and 40 g / 10 min or less. More preferably it is. When the MFR is in the above range, the processability during film formation is excellent.

Unless otherwise specified, MFR in the present specification is a value obtained by the following method.
MFR (g / 10 min): Measured according to JIS K7210. Specifically, the synthetic resin was heated and pressurized at 190 ° C. in a cylindrical container heated by a heater, and the amount of resin extruded per 10 minutes from an opening (nozzle) provided at the bottom of the container was measured. . The test machine used was an extrusion plastometer, and the extrusion load was 2.16 kg.
In addition, about the sealing material sheet which is a multilayer film, it measured by the said process with the multilayer state by which all the layers were laminated | stacked integrally, and the obtained measured value was made into the MFR value of the said multilayer sealing material sheet. .

  The “polyethylene resin” in the present invention includes not only ordinary polyethylene obtained by polymerizing ethylene, but also a resin obtained by polymerizing a compound having an ethylenically unsaturated bond such as α-olefin. Examples include resins obtained by copolymerizing a plurality of different compounds having an ethylenically unsaturated bond, and modified resins obtained by grafting different chemical species to these resins.

  Among these, a silane copolymer obtained by copolymerizing at least an α-olefin and an ethylenically unsaturated silane compound as a comonomer can be preferably used. By using such a resin, adhesiveness between a member such as a transparent front substrate or a solar cell element and a solar cell module sealing material can be obtained.

  The silane copolymer is described in, for example, JP-A-2003-46105. By using the copolymer as a component of the solar cell module sealing material composition, it is excellent in strength, durability, etc., and weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, yield resistance In addition, it has excellent other characteristics, and has extremely excellent heat-sealability without being affected by manufacturing conditions such as thermocompression bonding for manufacturing solar cell modules. A solar cell module suitable for the above can be manufactured.

  The silane copolymer is a copolymer obtained by copolymerizing at least an α-olefin and an ethylenically unsaturated silane compound as a comonomer and, if necessary, further using another unsaturated monomer as a comonomer. The modified product or condensate is also included.

Specifically, for example, one or more of α-olefins, one or more of ethylenically unsaturated silane compounds, and, if necessary, one or more of other unsaturated monomers. Using a desired reaction vessel, for example, pressure 500-4000 Kg / cm ² position, preferably, 1000-4000 Kg / cm ² position, temperature 100-400 ° C., preferably 150-350 ° C. In the presence of a radical polymerization initiator and, if necessary, a chain transfer agent, random copolymerization is performed simultaneously or stepwise, and if necessary, a random copolymer formed by the copolymerization is formed. A silane compound portion can be modified or condensed to produce a copolymer of an α-olefin and an ethylenically unsaturated silane compound, or a modified or condensed product thereof.

  Examples of the copolymer of an α-olefin and an ethylenically unsaturated silane compound or a modified or condensed product thereof include, for example, one or more α-olefins and, if necessary, other unsaturated monomers. One or two or more kinds are polymerized simultaneously or stepwise in the presence of a radical polymerization initiator and, if necessary, a chain transfer agent, using a desired reaction vessel, and then the polymerization. 1 to 2 or more types of ethylenically unsaturated silane compounds are graft-copolymerized to the polyolefin-based polymer produced by the above, and further, if necessary, a graft copolymer produced by the copolymer is constituted. A silane compound portion can be modified or condensed to produce a copolymer of an α-olefin and an ethylenically unsaturated silane compound or a modified or condensed product thereof. That.

  Examples of the α-olefin include ethylene, propylene, 1-butene, isobutylene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 1-heptene, 1-octene, One or more selected from 1-nonene and 1-decene can be used.

  Examples of the ethylenically unsaturated silane compound include vinyl trimethoxy silane, vinyl triethoxy silane, vinyl tripropoxy silane, vinyl triisopropoxy silane, vinyl tributoxy silane, vinyl tripentyloxy silane, vinyl triphenoxy silane, vinyl tri One or more selected from benzyloxysilane, vinyltrimethylenedioxysilane, vinyltriethylenedioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, and vinyltricarboxysilane can be used.

  As the other unsaturated monomer, for example, one or more selected from vinyl acetate, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, and vinyl alcohol can be used.

  Examples of radical polymerization initiators include organic peroxides such as lauroyl peroxide, dipropionyl peroxide, benzoyl peroxide, di-t-butyl peroxide, t-butyl hydroperoxide, and t-butyl peroxyisobutyrate. Products, molecular oxygen, azo compounds such as azobisisobutyronitrile azoisobutylvaleronitrile, and the like can be used.

  Examples of the chain transfer agent include paraffinic hydrocarbons such as methane, ethane, propane, butane and pentane, α-olefins such as propylene, 1-butene and 1-hexene, and aldehydes such as formaldehyde, acetaldehyde and n-butyraldehyde. Further, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, aromatic hydrocarbons, chlorinated hydrocarbons, and the like can be used.

  Examples of the method of modifying or condensing the silane compound portion constituting the random copolymer, or the method of modifying or condensing the silane compound portion constituting the graft copolymer include, for example, tin, zinc, iron, lead, Using α-olefin and ethylenically unsaturated silane using metal carboxylate such as cobalt, organometallic compound such as titanate and chelate, organic base, inorganic acid, silanol condensation catalyst such as organic acid, etc. Modification of copolymer of α-olefin and ethylenically unsaturated silane compound by performing dehydration condensation reaction between silanols of the silane compound part constituting the random copolymer or graft copolymer with the compound The method of manufacturing a condensate is mentioned.

  As the silane copolymer, any of a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer can be preferably used. However, the silane copolymer is more preferably a graft copolymer. A graft copolymer obtained by polymerizing polyethylene for polymerization as a main chain and an ethylenically unsaturated silane compound as a side chain is more preferable. Since such a graft copolymer has a high degree of freedom of silanol groups that contribute to the adhesive force, the adhesion of the solar cell module sealing material to other members in the solar cell module can be improved.

  The content of the ethylenically unsaturated silane compound when constituting the copolymer of the α-olefin and the ethylenically unsaturated silane compound is, for example, about 0.001 to 15% by mass relative to the total copolymer mass. Preferably, about 0.01 to 5 mass%, particularly preferably about 0.05 to 2 mass% is desirable. In the present invention, when the content of the ethylenically unsaturated silane compound constituting the copolymer of the α-olefin and the ethylenically unsaturated silane compound is large, the mechanical strength and heat resistance are excellent, but the content is excessive. When it becomes, it exists in the tendency which is inferior to tensile elongation, heat-fusibility, etc.

The content of the polyethylene resin having a density of 0.900 g / cm ³ or less contained in the sealing material composition may be 90% by mass or more in the sealing material composition, and is 99.9% or more. It is preferable. Within that range, other resins may be included. Examples of other resins include other polyethylene resins exceeding 0.900 g / cm ³ , for example. These may be used, for example, as an additive resin, and can be used for masterbatching other components described later.

[Polymerization initiator]
In the present invention, the polymerization initiator is used so that the content of the polymerization initiator with respect to the encapsulant composition for solar cell modules is in a specific range less than that in the case of general crosslinking treatment. Also good. Content of a polymerization initiator is 0.02 mass% or more and less than 0.5 mass% in the sealing material composition for solar cell modules, Preferably an upper limit is 0.2 mass% or less, More preferably, it is 0.00. 1% by mass or less. If it is less than this range, crosslinking of the polyethylene resin does not proceed and heat resistance is insufficient. Moreover, when this range is exceeded, film forming property will fall, for example, gel will generate | occur | produce during shaping | molding, and transparency will also fall.

  A well-known thing can be used for a polymerization initiator and it does not specifically limit, For example, a well-known radical polymerization initiator can be used. Examples of radical polymerization initiators include hydroperoxides such as diisopropylbenzene hydroperoxide and 2,5-dimethyl-2,5-di (hydroperoxy) hexane; di-t-butyl peroxide, t-butyl Cumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-peroxy) hexyne-3, etc. Dialkyl peroxides; diacyl peroxides such as bis-3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, benzoyl peroxide, o-methylbenzoyl peroxide, 2,4-dichlorobenzoyl peroxide; t-butyl peroxyacetate, t-butyl t-- Tylhexanoate, t-butyl peroxypivalate, t-butyl peroxyoctoate, t-butyl peroxyisopropyl carbonate, t-butyl peroxybenzoate, di-t-butyl peroxyphthalate, 2,5-dimethyl Peroxyesters such as -2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexyne-3, t-butylperoxy-2-ethylhexyl carbonate; Ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide; organic peroxides such as t-amyl-peroxy-2-ethylhexyl carbonate, peroxycarbonates such as t-butylperoxy 2-ethylhexyl carbonate, or Azo Examples include azo compounds such as sisobutyronitrile and azobis (2,4-dimethylvaleronitrile), silanol condensation catalysts such as dibutyltin diacetate, dibutyltin dilaurate, dibutyltin dioctate, dioctyltin dilaurate, and dicumyl peroxide. Can do.

  Of the above, t-butylperoxy 2-ethylhexyl carbonate, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, and the like can be preferably used. Since the active oxygen content is as high as 5% or more, and the one-minute half-life temperature of the polymerization initiator is 160 to 190 ° C., it is consumed at the time of molding and can remain after molding to suppress the progress of excessive post-crosslinking. preferable. A one-minute half-life temperature of less than 160 ° C. is not preferable because it is difficult to allow the crosslinking reaction to proceed after sufficiently dispersing the polymerization initiator during molding.

[Crosslinking aid]
In the present invention, a crosslinking aid may be used as necessary. Here, the crosslinking assistant is, for example, a polyfunctional vinyl monomer and / or a polyfunctional epoxy monomer, and specifically, triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fuma. Polyallyl compounds such as rate and diallyl maleate, trimethylolpropane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6 -Poly (meth) acryloxy compounds such as hexanediol diacrylate and 1,9-nonanediol diacrylate, glycidyl methacrylate containing double bond and epoxy group, 4-hydroxybutyl acrylate glycol Epoxy compounds such as 1,6-hexanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexane dimethanol diglycidyl ether, trimethylolpropane polyglycidyl ether and the like containing two or more diyl ethers and epoxy groups Can be mentioned.

[Light stabilizer (HALS)]
In the present invention, a light stabilizer may be contained. As such a light stabilizer, a conventionally known radical absorber can be used and is not particularly limited. For example, high molecular weight type hindered amine light stabilizers represented by Chimassorb 2020, Chimassorb 944, Uvinul 5050 (both manufactured by BASF) can be exemplified. On the other hand, in the present invention, a low molecular weight type hindered amine light stabilizer represented by Tinuvin 770 is easy to bleed out due to its low molecular weight, and the amount necessary for the present invention can be kneaded into the resin. Since it is difficult, it is not preferable. The content of the light stabilizer is preferably 0.01% by mass or more from the viewpoint of exhibiting the effect of HALS in the composition, and 1.0% by mass or less from the viewpoint of preventing bleeding.

[Ultraviolet absorber]
In the present invention, as the ultraviolet absorber, A) a benzophenone ultraviolet absorber and B) a benzotriazole ultraviolet absorber and / or a triazine ultraviolet absorber are used in combination.

(Benzophenone UV absorber)
Benzophenone-based UV absorbers effectively cut light in the UV region of 340 to 360 nm and have high transmittance at wavelengths of 360 nm and higher, so that the effective wavelength of solar cell elements can be used effectively while absorbing UV rays. In the present invention, it is an essential ultraviolet absorber.

  Examples of benzophenone-based ultraviolet absorbers include 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2′-carboxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, and 2-hydroxy-4. -N-dodecyloxybenzophenone, 2-hydroxy-4-n-octadecyloxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2-hydroxy-5-chlorobenzophenone 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, etc. It can be shown.

  The content of the benzophenone-based ultraviolet absorber is preferably 0.3% by mass or more and 0.4% by mass or less in the composition or the sealing material. If it is less than 0.3% by mass, the ultraviolet absorption effect is insufficient, and if it exceeds 0.4% by mass, the absorption from 360 nm to 370 nm increases and the power generation efficiency decreases, which is not preferable.

  However, when a benzophenone ultraviolet absorber is used alone, it is inferior in UV resistance and is not suitable for long-term use. For this reason, in this invention, the ultraviolet absorber of following B) is used together.

(Benzotriazole UV absorber and / or triazine UV absorber)
According to the study by the present inventors, the UV resistance could be greatly improved by adding a slight amount of the ultraviolet absorber of B) to A). The reason for this is not clear, but it is presumed that the UV resistance of the ultraviolet absorber B) is high, and as a result, the UV resistance of the UV absorber A) is effectively increased.

  In addition, since benzotriazole type ultraviolet absorbers and triazine type ultraviolet absorbers have an absorption peak on the longer wavelength side than 350 nm originally, they may overlap with the power generation effective wavelength of the solar cell element, which may reduce power generation efficiency. However, in the present invention, since the amount of addition is extremely small, there is little decrease in power generation efficiency. As described above, the present invention is characterized by the fact that it is not used for direct UV absorption by adding a small amount of a benzotriazole UV absorber or a triazine UV absorber but is used as an anti-degradation agent for other UV absorbers. There is.

  The benzotriazole ultraviolet absorber is a hydroxyphenyl-substituted benzotriazole compound, for example, 2- (2-hydroxy-5-methylphenyl) benzotriazole, 2- (2-hydroxy-5-t-butylphenyl) Benzotriazole, 2- (2-hydroxy-3,5-dimethylphenyl) benzotriazole, 2- (2-methyl-4-hydroxyphenyl) benzotriazole, 2- (2-hydroxy-3-methyl-5-t- Butylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-t-amylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-t-butylphenyl) benzotriazole, and the like. It can be illustrated.

  The content of the benzotriazole-based ultraviolet absorber is preferably 0.02% by mass or more and 0.10% by mass or less in the composition or the sealing material. If it is less than 0.02% by mass, the ultraviolet absorption effect is insufficient, and if it exceeds 0.10% by mass, the absorption from 360 nm to 370 nm increases and the power generation efficiency decreases, which is not preferable.

  Examples of the triazine ultraviolet absorber include 2- [4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl] -5- (octyloxy) phenol, 2- (4 , 6-diphenyl-1,3,5-triazin-2-yl) -5- (hexyloxy) phenol and the like.

  The content of the triazine-based ultraviolet absorber is preferably 0.05% by mass or more and 0.15% by mass or less in the composition or the sealing material. If it is less than 0.05% by mass, the ultraviolet absorption effect is insufficient, and if it exceeds 0.15% by mass, the absorption from 360 nm to 370 nm increases and the power generation efficiency decreases, which is not preferable.

[Other ingredients]
In addition to the above HALS and ultraviolet absorber, the solar cell module encapsulant composition may further contain other components. For example, a weather resistance masterbatch for imparting weather resistance to a solar cell module sealing material produced from the solar cell module sealing material composition of the present invention, various fillers, a thermal stabilizer, an antioxidant, etc. Ingredients are exemplified. These contents vary depending on the particle shape, density, and the like, but are preferably in the range of 0.001 to 5 mass% in the solar cell module encapsulant composition. By including these additives, it is possible to impart a long-term stable mechanical strength, an effect of preventing yellowing, cracking, and the like to the encapsulant composition for solar cell modules.

  A weatherproof masterbatch is obtained by dispersing a light stabilizer such as HALS, an ultraviolet absorber, a heat stabilizer and the above-mentioned antioxidant in a resin such as polyethylene, and this is used as a sealing material composition. By adding, favorable weather resistance can be provided to the sealing material for solar cell modules. The weatherproof masterbatch may be prepared and used as appropriate, or a commercially available product may be used. The resin used in the weatherproof masterbatch may be a linear low density polyethylene used in the present invention, or other resins described above.

  These light stabilizers, heat stabilizers and antioxidants can be used alone or in combination of two or more.

  In addition to the above, the other components used in the solar cell module encapsulant composition of the present invention include an adhesion improver such as a silane coupling agent, a nucleating agent, a dispersant, a leveling agent, a plasticizer, A foaming agent, a flame retardant, etc. can be mentioned.

<Sealant for solar cell module>
A solar cell module encapsulant (hereinafter also simply referred to as “encapsulant sheet”) is obtained by molding and processing the above encapsulant composition by a conventionally known method. It is a sheet or film. In addition, the sheet form in this invention means the film form, and there is no difference in both.

  The sealing material sheet is formed into a sheet by various molding methods such as injection molding, extrusion molding, hollow molding, compression molding, and rotational molding, which are usually used in ordinary thermoplastic resins. In addition, as an example of the sheet forming method when the encapsulant sheet is a multilayer film, a method of forming by co-extrusion using two or more types of melt-kneading extruders can be given. However, in any method, in order to promote a crosslinking reaction during molding, the molding temperature is preferably the melting point of the polyethylene resin + 50 ° C. or more. Specifically, a high temperature of 150 to 250 ° C. is preferable, and a range of 190 to 230 ° C. is more preferable.

  The gel fraction of the sealing material for solar cell modules is 25% or less, preferably 10% or less, more preferably 1% or less including zero. From this, the technical idea of imparting flame retardancy by crosslinking treatment so as to have a gel fraction of 30% or more as in Patent Document 2 of the above prior art and the crosslinking treatment of the present invention are fundamentally Is different. In addition, the gel fraction here is a value obtained by the following method.

  Gel fraction (%): After crosslinking, 1 g of the sealing material is weighed and placed in an 80 mesh wire mesh bag. Next, a sample with the wire mesh is put into a Soxhlet extractor, and xylene is refluxed at the boiling point. After 10 hours of continuous extraction, the sample was taken out together with the wire mesh, weighed after drying, and compared with the mass before and after extraction to measure the mass% of the remaining insoluble matter, which was taken as the gel fraction. In addition, about the gel fraction of the sealing material sheet | seat which is a multilayer film, the said process is performed with the multilayer state in which all the layers were laminated | stacked, and the obtained measured value is the said multilayer sealing material sheet. The gel fraction was used.

  The polystyrene equivalent weight average molecular weight of the encapsulant for solar cell module of the present invention is 120,000 to 300,000, and the ratio of the weight average molecular weight of the encapsulant after crosslinking / polyethylene resin before crosslinking is 1.5. It is the range of 3.0 or more and below. In addition, the weight average molecular weight in this invention melt | dissolves so that it may become 6 wt% of xylene, a viscosity is measured, and the weight average molecular weight is calculated | required from conversion with the polystyrene sample from the viscosity. As for the molecular weight of the encapsulant sheet, which is a multilayer film, the above-mentioned treatment was carried out with all the layers being laminated, and the obtained measurement value was determined based on the gel content of the multilayer encapsulant sheet. Rate.

  In the sealing material sheet which is a multilayer film, it is more preferable to set it as the sealing material sheet from which MFR for every layer differs. As will be described later, in the solar cell module, the sealing material sheet is generally used with one surface being in close contact with the electrode surface of the solar cell element. In that case, the encapsulant sheet is required to have high adhesion regardless of the unevenness of the electrode surface. Even when the encapsulant sheet of the present invention is a single-layer encapsulant sheet, the encapsulant sheet has preferable transparency, flexibility and heat resistance, but the surface which is in close contact with the electrode surface of the solar cell element. Furthermore, it is more preferable that such molding characteristics are excellent. The encapsulant sheet of the present invention, which is a multilayer film having a different MFR for each layer, can be used as an encapsulant sheet by arranging a layer having a high MFR in close contact with the electrode surface of the solar cell element and using it on the outermost layer. While maintaining the above-described preferable transparency and heat resistance, it is possible to further improve the molding characteristics on the contact surface with the solar cell element.

  For example, in the encapsulant sheet which is a multilayer film composed of three or more layers, the thickness of the outermost layer is 30 μm or more and 120 μm or less, and the intermediate layer and the outermost layer composed of all layers other than the outermost layer The thickness ratio is preferably in the range of outermost layer: intermediate layer: outermost layer = 1: 3: 1 to 1: 8: 1. By doing in this way, while maintaining the preferable heat resistance as a sealing material, the preferable molding characteristic in an outermost layer can be provided, and also manufacturing cost can be suppressed low.

<Solar cell module>
Next, an example of the solar cell module of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of the layer structure of the solar cell module of the present invention. In the solar cell module 1 of the present invention, a transparent front substrate 2, a front sealing material layer 3, a solar cell element 4, a back sealing material layer 5, and a back surface protection sheet 6 are sequentially laminated from the incident light receiving surface side. ing. The solar cell module 1 of the present invention uses the solar cell module sealing material described above for at least one of the front sealing material layer 3 and the back sealing material layer 5.

  The solar cell module 1 is, for example, vacuum suction after sequentially laminating members composed of the transparent front substrate 2, the front sealing material layer 3, the solar cell element 4, the back sealing material layer 5, and the back surface protection sheet 6. Then, the above-mentioned members can be manufactured by thermocompression molding as an integrally molded body by a molding method such as a lamination method.

  Moreover, the solar cell module 1 is formed on the front side and the back side of the solar cell element 4 by a molding method usually used in ordinary thermoplastic resins, for example, T-die extrusion molding. The back sealing material layer 5 is melt-laminated, the solar cell element 4 is sanded with the front sealing material layer 3 and the back sealing material layer 5, and then the transparent front substrate 2 and the back surface protection sheet 6 are sequentially laminated, Then, they may be manufactured by a method in which these are integrated by vacuum suction or the like and heat-pressed.

  In the solar cell module 1 of the present invention, the transparent front substrate 2, the solar cell element 4, and the back surface protective sheet 6 that are members other than the front sealing material layer 3 and the back sealing material layer 5 are made of conventionally known materials. It can be used without particular limitation. Moreover, the solar cell module 1 of this invention may also contain members other than the said member. In addition, the sealing material sheet | seat of this invention is applicable not only to a single crystal type but to all other solar cell modules.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.

<Manufacture of sealing material sheet>
MB (masterbatch) was blended so that the content in the encapsulant composition was the following ratio, and encapsulant sheets of Examples and Comparative Examples were prepared. The layer thickness ratio of the sealing material sheet was 2 layers / 3 layers of outer layer / inner layer / outer layer = 1: 5: 1, and the sheet thickness was 400 μm in total. The encapsulant composition was formed into a film at an extrusion temperature of 210 ° C. and a take-off speed of 1.1 m / min using a φ30 mm extruder and a film molding machine having a 200 mm wide T die.

  The composition of the inner layer is 89 parts by mass of the base resin, 3 parts by mass of the Si-modified resin, 8 parts by mass of the crosslinking agent MB, and 5 parts by mass of the weathering agent MB. The composition of the outer layer is 75 parts by mass of the base resin, 20 parts by mass of the Si-modified resin. The crosslinking agent MB is 5 parts by mass and the weathering agent MB is 5 parts by mass.

[Base resin]
Metallocene linear low density polyethylene (M-LLDPE) having a density of 0.880 g / cm ³ and MFR at 190 ° C. of 3.5 g / 10 min.

[Si-modified resin]
Silane crosslinkable resin: Vinyl is used for 98 parts by mass of metallocene linear low density polyethylene (M-LLDPE) having a density of 0.881 g / cm ³ and an MFR at 190 ° C. of 1.5 g / 10 min. Silane copolymer in which base resin is mixed with silane crosslinkable resin (silane-modified polyethylene resin) composed of 2 parts by mass of trimethoxysilane and 0.1 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) Containing resin. The density of this resin was 0.884 g / cm ³ and the MFR at 190 ° C. was 1.5 g / 10 min.

[Crosslinking agent MB]
2,5-dimethyl-2,5-di (t-butylperoxy) with respect to 100 parts by mass of M-LLDPE pellets having a density of 0.880 g / cm ³ and MFR at 190 ° C. of 3.1 g / 10 min. Compound pellets impregnated with 0.5 part by mass of hexane were used as a crosslinking agent master batch (MB).

[Weatherproof MB]
As a weathering agent, a hindered amine light stabilizer (light stabilizer, trade name Tinuvin 622, manufactured by BASF) with respect to 100 parts by mass of powder obtained by pulverizing Ziegler linear low density polyethylene having a density of 0.880 g / cm ^3. 0.25 parts by mass (0.24% by mass in the composition), 0.5 parts by mass of the phosphorous heat stabilizer, and the following ultraviolet absorber in the composition (in the encapsulant sheet) The master batch (MB) was mixed, melted, processed, and pelletized.

Example 1: In the encapsulant composition, benzosonone ultraviolet absorber (trade name Chimassorb 81, manufactured by BASF) 0.3 mass% and benzotriazole ultraviolet absorber (trade name Tinuvin 329, manufactured by BASF) Combined use with 0.02% by mass.
Example 2: In the encapsulant composition, 0.3 mass% of a benzophenone ultraviolet absorber (trade name Chimassorb 81, manufactured by BASF) and a benzotriazole ultraviolet absorber (trade name Tinuvin 329, manufactured by BASF) Combined use with 0.10% by mass.
Example 3 In the encapsulant composition, 0.3 mass% of benzophenone ultraviolet absorber (trade name Chimassorb 81, manufactured by BASF) and triazine ultraviolet absorber (trade name Tinuvin 1577, manufactured by BASF) 0 Combined use with 05 mass%.
Example 4: In the encapsulant composition, 0.3 mass% of a benzophenone ultraviolet absorber (trade name Chimassorb 81, manufactured by BASF) and a triazine ultraviolet absorber (trade name Tinuvin 1577, manufactured by BASF) 0 Combined use with 15% by mass.
Comparative Example 1: Single use of 0.35% by mass of a benzophenone ultraviolet absorber (trade name Chimassorb 81, manufactured by BASF) in the encapsulant composition.
Test Example 1: In encapsulant composition, benzosophenone ultraviolet absorber (trade name Chimassorb 81, manufactured by BASF) 0.3 mass% and benzotriazole ultraviolet absorber (trade name Tinuvin 329, manufactured by BASF) Combined use with 0.01% by mass.
Test Example 2: In the encapsulant composition, benzosophenone ultraviolet absorber (trade name Chimassorb 81, manufactured by BASF) 0.3 mass% and benzotriazole ultraviolet absorber (trade name Tinuvin 329, manufactured by BASF) Combined use with 0.15% by mass.
use.
Test Example 3: In the encapsulant composition, 0.3 mass% of benzophenone ultraviolet absorber (trade name Chimassorb 81, manufactured by BASF) and triazine ultraviolet absorber (trade name Tinuvin 1577, manufactured by BASF) 0 Combined use with 0.03 mass%.
Test Example 4: In the encapsulant composition, 0.3 mass% of a benzophenone ultraviolet absorber (trade name Chimassorb 81, manufactured by BASF) and a triazine ultraviolet absorber (trade name Tinuvin 1577, manufactured by BASF) 0 Combined use with 20% by mass.

<Evaluation example>
Table 3 shows the results of performing an irradiation test for 300 hours using a metal halide lamp manufactured by Iwasaki Electric Co., Ltd., SUV-W151, and measuring the spectral transmittance (%) before and after irradiation on the sealing material sheets of Examples and Comparative Examples. It is shown in 1. In Table 1, the numerical values represent before / after irradiation.

  As can be seen from Table 1, in Examples 1 to 4 of the present invention, the change before and after the UV irradiation test is as small as 10%, and it is understood that the deterioration with time of the UV blocking performance is suppressed as compared with the comparative example. it can. In Test Example 2 and Test Example 4, since the amount of B) UV absorber used in combination is too large, the transmittance at 360 nm or 370 nm, which is the effective wavelength of the solar cell element, is 2% or less. Therefore, it can be understood that the power generation efficiency is reduced accordingly.

DESCRIPTION OF SYMBOLS 1 Solar cell module 2 Transparent front substrate 3 Front sealing material layer 4 Solar cell element 5 Back sealing material layer 6 Back surface protection sheet

Claims (4)

A resin containing a polyethylene resin having a density of 0.900 g / cm ³ or less, and two or more kinds of ultraviolet absorbers,
As the ultraviolet absorber, A) and a benzophenone-based ultraviolet absorbent, B) a sealing material composition for a solar cell module which is characterized by a combination of benzotriazole-based UV absorber or a triazine-based UV absorber ,
In the sealing agent composition, the content of the benzophenone-based ultraviolet absorber is 0.3 mass% or more and 0.4 mass% or less,
The content of the benzotriazole-based ultraviolet absorber in the encapsulant composition is 0.02% by mass or more and 0.10% by mass or less, or in the encapsulant composition The sealing material composition whose content of a triazine type ultraviolet absorber is 0.05 mass% or more and 0.15 mass% or less. Sheeted the sealing material sheet for a solar cell module encapsulant composition of claim 1. The solar cell module sealing material sheet according to claim 2, wherein the spectral transmittance at wavelengths of 360 nm and 370 nm is 2% or more. A solar cell module provided with the sealing material sheet for solar cell modules of Claim 2 or 3 .

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