JP6255694B2 - Sealing material for solar cell module - Google Patents

Description

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

  In recent years, solar cells as a clean energy source have attracted attention due to the growing awareness of environmental issues. Currently, various types of solar cell modules have been developed. Generally, a solar cell module has a configuration in which a transparent front substrate, a solar cell element, and a back surface protection sheet are laminated via a sealing material for a solar cell module.

  As the solar cell element, in addition to a crystalline silicon solar cell manufactured using a single crystal silicon substrate or a polycrystalline silicon substrate, amorphous silicon or microcrystalline silicon is formed on a substrate such as glass and is extremely thin silicon of about 1 μm or less. There is a thin film solar cell formed by forming a film. As the thin film solar cell, there is a compound solar cell using a chalcopyrite compound or the like instead of the silicon. Since all solar cell elements are vulnerable to physical impact and are expected to be used outdoors for a long period of time, solar cell modules including those solar cell elements are required to have high weather resistance and durability. It is done.

  As a sealing material for a solar cell module, a material using EVA (ethylene-vinyl acetate copolymer), which is excellent in transparency, adhesion, and the like, as a base resin has been widely used. However, in recent years, development of a sealing material using a polyethylene resin having a transparency equivalent to EVA and excellent in hydrolysis resistance as compared with EVA as a base resin has been progressing.

  For example, while the base resin is a polyethylene resin, it can be extruded at a low temperature and can be post-crosslinked. As a result, the solar cell module has excellent transparency, adhesion, and durability. Sealing using a sealing material composition containing, as a sealing material, a low-density, low-melting silane-modified polyethylene resin obtained by graft polymerization of an ethylenically unsaturated silane compound on linear low-density polyethylene, and a crosslinking agent. A stopping material has been proposed (see Patent Document 1).

  In addition, by adding a very small amount of a polymerization initiator to a low-density polyethylene-based resin, a very weak crosslinking reaction that does not increase the gel fraction is allowed to proceed, and the molecular weight is increased. A polyethylene-based sealing material that has extremely high transparency and glass adhesion has also been proposed (see Patent Document 2).

Japanese Patent Laid-Open No. 2002-235048 International Publication 2011/152314

  As described above, in a sealing material for a solar cell module that generally uses a polyethylene-based resin as a base resin, transparency and flexibility can be improved by reducing the density. However, when the density is lowered, the heat durability is lowered and becomes insufficient. For this reason, in a solar cell module in which the environmental temperature under an actual use environment reaches about 85 ° C., when a sealing material based on a low-density polyethylene resin having high transparency and flexibility is used, There has been a problem that the solar cell element may be physically damaged by the thermal contraction stress of the sealing material itself having a low density, that is, a low melting point. This problem has been a common problem for all solar cell modules, but has been a serious problem particularly in solar cell modules including thin-film solar cell elements.

  The present invention has been made in view of the above situation, and is a sealing material for a solar cell module using a polyethylene resin as a base resin, and has sufficient transparency as a sealing material for a solar cell module. It is an object of the present invention to provide a solar cell module sealing material having heat resistance and durability that is practically preferable as a sealing material for a solar cell module that is used in a high temperature environment while being held.

  As a result of intensive studies, the present inventors have determined that a low-density polyethylene-based resin has a core layer that is excellent in transparency and a skin layer that serves as an adhesion surface between a metal part such as an electrode part of a solar electronic element. The inventors have found that the above-mentioned problems can be solved by separately optimizing the melting point of the skin layer and the melting point of the core layer, and have completed the present invention. More specifically, the present invention provides the following.

(1) and also contains a density 0.870 g / cm ³ or more 0.910 g / cm ³ less than the polyethylene-based resin, the plurality including a core layer, and a skin layer disposed on the outermost layer of the sealant, the The core layer has a melting point of 70 ° C. or lower, the skin layer has a melting point of 90 ° C. or higher, and the total thickness of the skin layer The sealing material for solar cell modules whose ratio of the total thickness of a sealing material is 2/10 or more and 1/3 or less.

  (2) The skin layer is laminated on both surfaces of the core layer and disposed on both outermost layers of the sealing material. The thickness of the core layer (S1) and the thickness of the skin layer (S2) The ratio of the thickness of the sealing material according to (1) is in the range of S2: S1: S2 = 1: 4: 1 to S2: S1: S2 = 1: 8: 1.

(3) The sealing material according to (1) or (2), wherein the density of the core layer is less than 0.900 g / cm ³ and the density of the skin layer is 0.900 g / cm ³ or more.

  (4) The sealing material according to any one of (1) to (3), wherein the polyethylene resin is a metallocene linear low-density polyethylene.

  (5) The sealing material according to any one of (1) to (4), wherein the polyethylene-based resin contains a copolymer obtained by copolymerizing an α-olefin and an ethylenically unsaturated silane compound as a comonomer.

  (6) A solar cell module comprising: the sealing material according to any one of (1) to (5); and a solar cell element, wherein the skin layer is formed of the solar cell element. The solar cell module arrange | positioned so that a metal electrode may be faced.

  (7) The solar cell module according to (7), wherein the solar cell element is a thin-film solar cell element.

  According to the present invention, a sealing material for a solar cell module using a polyethylene-based resin as a base resin is used in a high-temperature environment while maintaining sufficient transparency as a sealing material for a solar cell module. As a sealing material for a solar cell module, a sealing material for a solar cell module having practically preferable heat resistance and durability can be provided.

It is a cross-sectional schematic diagram which shows an example of the laminated constitution of the sealing material of this invention. It is a cross-sectional schematic diagram which shows an example of the laminated constitution of the thin film type solar cell module using the sealing material of this invention.

  Hereinafter, first, the encapsulant composition for producing the encapsulant for the solar cell module of the present invention will be described, and thereafter the encapsulant for the solar cell module of the present invention and the solar cell of the present invention. Details will be described in the order of modules.

<Encapsulant composition>
The encapsulant composition for producing the encapsulant for the solar cell module of the present invention (hereinafter also simply referred to as “encapsulant composition”) has a density of 0.870 g / cm ³ or more and 0.910 g. A polyethylene-based resin of less than / cm ³ and a polymerization initiator are contained as essential components.

[Polyethylene resin]
As the base resin, low density polyethylene (LDPE) having a density within the above range, preferably linear low density polyethylene (LLDPE) is used in the present invention. Linear low density polyethylene is a copolymer of ethylene and α-olefin.

  As the base resin, it is more 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 the solar cell module of the present invention is disposed between the transparent front substrate and the solar cell element, the power generation efficiency is hardly lowered.

  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 “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 condensate 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. .

  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.

[Polymerization initiator]
In the present invention, the content of the polymerization initiator with respect to the solar cell module sealing material composition is different from the case where the conventional crosslinking treatment of the solar cell module sealing material composition is conventionally performed. It is preferable to use a polymerization initiator so that the content in a specific range is smaller than in the case of general crosslinking treatment. The content of the polymerization initiator is preferably 0.02% by mass or more and less than 0.5% by mass in the encapsulant composition for solar cell modules, and the upper limit is more preferably 0.2% by mass or less. Most preferably, it is 0.1 mass% or less. If it is less than this range, the weak crosslinking of the polyethylene resin does not proceed and the heat resistance is insufficient. On the other hand, if this range is exceeded, gel formation will occur during molding, resulting in a decrease in film forming properties and a decrease in transparency.

  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. These have a high amount of active oxygen as high as 5% or more, and the one-minute half-life temperature of the polymerization initiator is 160 to 190 ° C., which is consumed at the time of molding and can remain after molding to suppress the progress of excessive post-crosslinking. Therefore, it is 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, unlike a general crosslinking treatment, it is preferable not to use a crosslinking aid. However, this is not the case when a trace amount that does not show a crosslinking effect is contained. Specifically, the trace amount that does not show the crosslinking effect is less than 0.01% by mass in the composition. 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.

[Other ingredients]
The solar cell module sealing material 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 light stabilizer, an ultraviolet absorber, Components such as heat stabilizers 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, an ultraviolet absorber, a heat stabilizer and the above-mentioned antioxidant in a resin such as polyethylene, and adding this to a sealing material composition. Thereby, 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, ultraviolet absorbers, 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.

<Encapsulant>
The encapsulant of the present invention is obtained by a step of molding the above encapsulant composition by a conventionally known method, and is disposed in one core layer and one of the outermost layers. It is a multilayer sealing material constituted by a plurality of layers including one skin layer or a total of two skin layers respectively disposed on the outermost layer of both skin layers. Hereinafter, as a preferred embodiment of the present invention, a sealing material 1 having a three-layer structure including two skin layers will be described with reference to FIG. However, the present invention is not limited to this embodiment.

  The sealing material 1 has a single core layer 11 as an inner layer, and skin layers 12 are disposed on both surfaces of the core layer 11 as outermost layers. However, for example, a sealing material having a two-layer structure in which one skin layer is disposed on one side of one core layer, or another intermediate layer is disposed between the core layer 11 and the skin layer 12. Even if it is the sealing material of the multilayered structure which is provided with the core layer used as a board | substrate layer and the skin layer arrange | positioned at the outermost layer of a sealing material, it is a sealing material provided with the other structural requirements of this invention. As long as it is within the scope of the present invention.

  The core layer 11 is a layer constituting a main part as a substrate layer in the sealing material 1. The core layer 11 is extremely excellent in transparency that has a great influence on the power generation efficiency of the solar cell module, particularly due to its low melting point, low density, and low molecular weight.

  The skin layer 12 is a layer that is disposed in the outermost layer of the sealing material in the sealing material 1 and constitutes a subordinate portion as a surface material. In particular, the skin layer 12 has higher heat resistance and weather resistance than the core layer 11 by having a relatively high melting point, high density, and high molecular weight as compared with the core layer.

  In this way, the sealing material 1 is formed by laminating resin sheets having different advantageous physical properties as described above to form a multilayer sheet, and at this time, particularly focusing on the difference in melting point of each resin sheet, the thickness ratio of each layer is optimized at the same time. As a result, the sealing material for the solar cell module is extremely excellent in the balance between transparency and heat resistance.

  The total thickness of the sealing material 1 including the core layer 11 and the outermost skin layers 12 is preferably 200 μm or more and 800 μm or less. If it is less than 200 μm, the impact cannot be sufficiently mitigated, and if it exceeds 800 μm, no further effect can be obtained, which is uneconomical.

  About the ratio of the thickness of each layer in the sealing material 1, the total thickness of the skin layer 12, that is, the total thickness of the two outermost skin layers 12 and the total thickness of the sealing material 1. The thickness ratio (total thickness of skin layer / total thickness of sealing material) is 2/10 or more and 1/3 or less, and preferably 2/9 or more and 2/7 or less. As the thickness ratio of each of the three layers, the ratio of skin layer thickness (S2): core layer thickness (S1): skin layer thickness (S2) is S2: S1: S2 = 1: 4: 1. To S2: S1: S2 = 1: 8: 1. This ratio is more preferably in the range of 1: 5: 1 to 1: 7: 1. If the ratio of the total thickness of the skin layer 12 is less than 2/10, the effect of improving the heat resistance described above is insufficient, and if it exceeds 1/3, the core layer has excellent transparency. Regardless, the transparency of the sealing material 1 is not always sufficient.

  The correlation between the thickness ratio of each of the above layers and the above effect is the same even when the sealing material of the present invention is a sealing material having a two-layer structure having a skin layer only on the outermost surface on one side. . Specifically, if the ratio of the thickness of the skin layer to the total thickness of the sealing material is at least 1/8 or more, preferably 2/10 or more, and 1/3 or less, the same heat resistance as described above. And a sealing material having transparency.

  The thickness of each of the core layer 11 and the skin layer 12 may be in a range that satisfies the conditions of the total thickness of the sealing material 1 and the thickness ratio of each layer. Specifically, the thickness of the core layer 11 is preferably 150 μm or more and 600 μm or less, and the thickness of the skin layer 12 is preferably 20 μm or more and 100 μm or less.

  The sealing material 1 is characterized in that, in the core layer 11 and the skin layer 12 that is the outermost layer, the melting point of each layer is separately optimized. Specifically, the melting point of the core layer 11 is 70 ° C. or lower, and the melting point of the skin layer is 90 ° C. or higher. By setting the melting point of the core layer 11 to 70 ° C. or less, the transparency of the sealing material 1 can be kept in a very preferable range. However, such a low-melting core layer 11 itself does not necessarily have sufficient heat resistance as a sealing material for a solar cell module that is assumed to be used in a severe thermal environment. For example, when the sealing material of the solar cell module is a sealing material having only a layer equivalent to the core layer 11, the solar cell resulting from the heat shrinkage stress of the sealing material under an environment exceeding 85 ° C. In some cases, problems such as damage to the element may occur. The sealing material 1 has a multi-layered structure composed of layers having different melting points, and the skin layer 12 laminated on the outermost surface as a surface material has a melting point of 90 ° C. or more, whereby the core layer 11 having excellent transparency. Thus, the heat resistance of the sealing material 1 can be sufficiently enhanced.

Further, the sealing material 1 is a resin sheet comprising a density 0.870 g / cm ³ or more 0.910 g / cm ³ less than the polyethylene-based resin, the core layer 11 and skin layer 12, the layers density It is characterized in that is separately optimized separately. Specifically, in the sealing material 1, the density of the core layer 11 is less than 0.900 g / cm ^3, and the density of the skin layer is 0.900 g / cm ³ or more.

By setting the density of the core layer 11 that is the substrate material to 0.900 g / cm ³ or less, the transparency and flexibility of the sealing material 1 can be maintained within a preferable range. However, such a core layer 11 itself still has insufficient heat resistance as described above. Similarly to the above, the sealing material 1 has a multilayer structure composed of layers having different densities, and the density of the skin layer 12 is 0.900 g / cm ³ or more. Covering can sufficiently increase the heat resistance of the sealing material 1.

  The sealing material 1 is molded 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 a shaping | molding method as a multilayer film, the method of shape | molding by the co-extrusion by 2 or more types of melt-kneading extruders is mentioned as an example.

  In addition, the sealing material of the present invention has a sufficient film-forming property while maintaining a low density by performing the weak crosslinking treatment described in Patent Document 2 during the above molding, while maintaining a low density. The characteristic of having can be made more remarkable. Thereby, it can be set as the sealing material extremely excellent in balance of transparency, a softness | flexibility, and heat resistance further.

<Solar cell module>
Next, a preferred embodiment of the solar cell module of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view showing an example of the layer structure of a solar cell module 10 including a thin-film solar cell element according to an embodiment of the present invention. In the solar cell module 10, a glass substrate 2, a thin-film solar cell element 3 formed on the glass substrate 2, a sealing material 1, and a back surface protection sheet 4 are sequentially laminated from the light receiving surface side of incident light. .

  In addition, when the sealing material of this invention is a sealing material which consists of two layers of the core layer 11 and the one-layer skin layer 12 arrange | positioned at the outermost layer of one side, the said skin layer 12 is exposed. The surfaces are laminated in the same manner as described above, with the surface being in close contact with the solar cell element 3.

  The solar cell module 10 having the above configuration uses a sealing material to maintain high transparency that contributes to power generation efficiency, while maintaining heat resistance and weather resistance as a solar cell module particularly when used in a high temperature environment. The property is remarkably improved.

  The layer configuration of the solar cell module of the present invention is not limited to that according to the above embodiment. Since the sealing material of the present invention has adhesion to both glass and metal, taking advantage of its properties, it is versatile for solar cell modules of various configurations including glass substrates and metallic solar cell modules. Can be used for For example, in a solar cell module, the sealing material of the present invention is preferably used even when one surface of the sealing material faces the metal surface and the other surface faces the glass layer. it can.

  The solar cell module 10 is, for example, laminated by sequentially laminating a member composed of the glass substrate 2, the sealing material 3, and the back surface protection sheet 4 on which the thin film solar cell element 3 is formed, and then integrated by vacuum suction or the like, By the molding method such as the lamination method, the above-mentioned member can be manufactured by thermocompression molding as an integral molded body.

  Moreover, the solar cell module 10 is obtained by melting and laminating the sealing material 1 on the glass substrate 2 on which the solar cell element 3 is formed by a molding method usually used in a normal thermoplastic resin, for example, T-die extrusion molding or the like. Subsequently, the back surface protection sheets 4 may be sequentially laminated, and then these may be manufactured by a method in which these are integrated by vacuum suction or the like and thermocompression bonded.

  In addition, in the solar cell module 10 of this invention, conventionally well-known material can be especially used for the glass substrate 2, the solar cell element 3, and the back surface protection sheet 4 which are members other than the sealing material 1 without a restriction | limiting. Moreover, the solar cell module 10 of this invention may also contain members other than the said member. In addition, the sealing material of this invention is preferably applicable not only to the solar cell module 10 provided with a thin film type solar cell element 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 for solar cell module>
The raw materials for the sealing material composition described below are mixed in the proportions (parts by mass) shown in Table 1 below to produce resin sheets for the core layer and skin layer of the sealing materials of Examples and Comparative Examples, respectively. It was set as the sealing material composition. Each of the encapsulant compositions was formed into a core layer and a skin layer 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 forming machine having a 200 mm wide T-die. A resin sheet was prepared, and each of these resin sheets was laminated to obtain a sealing material having a three-layer structure of Example 1 and Comparative Examples 1 and 2 including a core layer and skin layers disposed on both outermost layers. Moreover, about the sealing material of the comparative example 3, it was set as the single layer sealing material using the said sealing material composition for core layers. Moreover, about the sealing material of the comparative example 4, it was set as the single layer sealing material using said sealing material composition for skin layers. The thicknesses of the sealing materials in Examples and Comparative Examples were all set to a total thickness of 600 μm. About the ratio of the thickness of each layer of the sealing material of the three-layer structure of Example 1 and Comparative Examples 1-2, it was set as the ratio as described in the following Table 1, respectively.

The following raw materials were used as the sealing material composition raw material for forming each resin sheet for the sealing material.
Transparent resin A (PA): Metallocene linear low density polyethylene (M-) having a density of 0.880 g / cm ³ , a melting point of 57.55 ° C., and an MFR at 190 ° C. of 3.5 g / 10 min. LLDPE).
Transparent resin B (P-B): metallocene linear low density polyethylene (M-) having a density of 0.905 g / cm ³ , a melting point of 97.0 ° C., and an MFR at 190 ° C. of 3.5 g / 10 min. LLDPE).
Weatherproof masterbatch (weatherproof): 3.8 parts by weight of benzophenol UV absorber and hindered amine light stabilizer for 100 parts by weight of powder obtained by pulverizing Ziegler linear low density polyethylene with a density of 0.880 g / cm ³ Master batch obtained by mixing, melting, processing and pelletizing 5 parts by mass of an agent and 0.5 parts by mass of a phosphorus-based heat stabilizer.
Polymerization initiator compound resin 1 (M1): Triallyl isocyanurate (TAIC) with respect to 100 parts by mass of M-LLDPE pellets having a density of 0.905 g / cm ³ and an MFR at 190 ° C. of 3.5 g / 10 min. Compound pellets obtained by impregnating 1 part by mass of the product “SR533” manufactured by Statomer.
Polymerization initiator compound resin 2 (M2): glycidyl methacrylate (GMA), (Mitsubishi) with respect to 100 parts by mass of M-LLDPE pellets having a density of 0.905 g / cm ³ and MFR at 190 ° C. of 3.5 g / 10 min. Compound pellets obtained by impregnating 1 part by mass of Gas Chemical Co., Ltd., trade name “glycidyl methacrylate”.
Silane-modified polyethylene resin (S): 2 parts by mass of vinyltrimethoxysilane with respect to 100 parts by mass of metallocene linear low density polyethylene having a density of 0.880 g / cm ³ and an MFR of 3.5 g / 10 min. A silane-modified polyethylene resin obtained by mixing 0.15 parts by mass of dicumyl peroxide as a radical generator (reaction catalyst), melting and kneading at 200 ° C. Density 0.880 g / cm ³ , MFR 3.5 g / 10 min. Melting point 58 ° C.
Cross-linking agent (cross-linking): 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (manufactured by Arkema Yoshitomi Co., Ltd., trade name Luperox 101)

  In addition, it measured also about melting | fusing point and the density of each layer of the sealing material of Example 1 produced by the said method, and Comparative Examples 1-4. The melting point was measured according to JISK7121, and the density was measured according to JISK7112. The results are shown in Table 2.

  About the sealing material of Example 1 and Comparative Examples 1 to 4 produced by the above method, total light transmittance (JIS K7361, Murakami Color Research Laboratory), HAZE (JIS K7136, Murakami Color Research Laboratory, Haze The value of the transmittance system HM150) and the heat resistance were measured and evaluated. The heat resistance was measured and evaluated by the following heat resistance creep test. The results are shown in Table 3.

[Test method for heat-resistant creep test (mm)]
Two sheets of encapsulant sheets after film formation of Examples and Comparative Examples cut to 7.5 × 5.0 cm are stacked on a glass substrate (white plate float semi-tempered glass JPT3.2 150 mm × 150 mm × 3.2 mm). A glass substrate (white plate float semi-tempered glass JPT3.2 75 mm × 50 mm × 3.2 mm) is placed on top of each other, and vacuum heating laminator treatment is performed according to the following heat laminating conditions (a) to (d), respectively. Samples for solar cell module evaluation were obtained for the examples and comparative examples. These solar cell module evaluation samples were subjected to a heat-resistant creep test under the following test conditions to evaluate heat resistance.
The solar cell module evaluation sample was placed vertically and allowed to stand at 100 ° C. for 12 hours, and the moving distance of the glass substrate after being left (white plate float semi-tempered glass JPT3.2 75 mm × 50 mm × 3.2 mm) was measured and evaluated. . About the sealing material sheet after film forming of each Example and a comparative example, the measurement result was evaluated by the following evaluation criteria AC.
(Thermal lamination conditions) (a) Vacuum drawing: 5.0 minutes
(B) Pressurization (0 kPa to 100 kPa): 1.5 minutes
(C) Pressure holding (100 kPa): 8.0 minutes
(D) Temperature 165 ° C
(Evaluation criteria) A: Less than 2.0 mm
B: 2.0 mm or more and less than 6.0 mm
C: 6.0 mm or more

  From Table 3, the sealing material of Example 1 has both high transparency essential for maintaining a high level of power generation efficiency and high heat resistance that can withstand long-term use in a high-temperature environment. I understand.

DESCRIPTION OF SYMBOLS 1 Sealing material 11 Core layer 12 Skin layer 2 Glass substrate 3 Solar cell element 4 Back surface protection sheet

Claims (6)

And also contains a density 0.870 g / cm ³ or more 0.910 g / cm ³ less than the polyethylene-based resin, constituted by a plurality of layers including a core layer, and a skin layer disposed on the outermost layer of the sealant, the A multi-layer encapsulant,
The core layer has a melting point of 70 ° C. or less,
The skin layer has a melting point of 90 ° C. or higher,
The skin layer is laminated on both surfaces of the core layer and disposed on both outermost layers of the sealing material,
The ratio of the thickness of the core layer (S1) to the thickness of the skin layer (S2) is from S2: S1: S2 = 1: 4: 1 to S2: S1: S2 = 1: 5: The sealing material for solar cell modules which is the range of 1 . The density of the core layer is less than 0.900 g / cm ³ ;
The sealing material according to claim 1 , wherein the density of the skin layer is 0.900 g / cm ³ or more. The encapsulant according to claim 1 or 2 , wherein the polyethylene resin is a metallocene linear low-density polyethylene. The sealing material according to any one of claims 1 to 3 , wherein the polyethylene resin contains a copolymer obtained by copolymerizing an α-olefin and an ethylenically unsaturated silane compound as a comonomer. A solar cell module comprising the sealing material according to any one of claims 1 to 4 and a solar cell element,
The said sealing material is a solar cell module arrange | positioned so that the said skin layer may face the metal electrode of the said solar cell element. The solar cell module according to claim 5 , wherein the solar cell element is a thin-film solar cell element.

Images