JP2015016592A - Solar cell sealant and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealant that comprises inorganic filler, and allows the inactivation of silane-modified resin to be inhibited even after long-term storage, and a solar cell module prepared using the same.SOLUTION: A solar cell sealant comprises a resin layer (I) that comprises silane-modified resin, and is free from inorganic filler, and a resin layer (II) that comprises inorganic filler, where a resin layer (III) is provided between the resin layer (I) and the resin layer (II).

Description

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

  In recent years, with increasing awareness of environmental issues such as global warming, expectations are increasing especially for photovoltaic power generation in terms of its cleanliness and non-polluting properties. The solar cell constitutes the central part of a photovoltaic power generation system that directly converts sunlight energy into electricity. In general, a plurality of solar cell elements (cells) are wired in series and in parallel as the structure, and various packaging is performed to protect the cells, thereby forming a unit. The unit incorporated in this package is called a solar cell module, and the surface exposed to sunlight is generally covered with a transparent base material (for example, glass) as an upper (front surface) protective material, and the back surface is covered with a lower (back surface) protective material ( For example, it is configured to be protected by a back sheet including a weather resistant film, and the gap is filled with a sealing material (sealing resin layer) made of a thermoplastic (for example, ethylene-vinyl acetate copolymer). .

Since these solar cell modules are mainly used outdoors, various characteristics are required for the structure and material structure thereof. The above sealing material is mainly required to have flexibility, impact resistance, heat resistance, transparency, durability, dimensional stability, flame retardancy, water vapor barrier properties, and the like.
Furthermore, sealing materials containing various inorganic fillers are used depending on the characteristics required for the solar cell. For example, when the back side sealing material colored in white is used, it is incident between solar cell elements due to reflection of light at the interface between the back side sealing material and the light receiving surface side sealing material or irregular reflection by the pigment. Light or light that has passed through the solar cell element can be diffusely reflected and incident again on the solar cell element. Thereby, the utilization efficiency of the light incident on the solar cell is increased, and the power generation efficiency can be improved. Moreover, since the solar cell element generally has a black appearance, it is possible to improve the design of the solar cell module by coloring the sealing material black. However, the inclusion of the inorganic filler has a concern that the adhesiveness to the front protective material or the back protective material of the sealing material is lowered.

  Patent Document 1 discloses a solar cell sealing film containing ethylene-vinyl acetate (hereinafter sometimes abbreviated as EVA), a crosslinking agent, an inorganic filler (white pigment), and a specific phosphite compound. Is disclosed (see claim 1).

  However, in Patent Document 1, although the dispersibility of the inorganic filler can be improved by the phosphite compound, the inorganic filler exists in the vicinity of the interface (adhesion surface) with the front protective material, the back protective material, and the like. For this reason, there was still concern about a decrease in adhesiveness.

  Thus, for example, Patent Document 2 discloses a back surface filler sheet for a solar cell module that includes a white layer containing a transparent resin and a white pigment, and an adhesive layer containing the white layer and containing a silane-modified resin. (See claim 1).

  Patent Document 3 discloses a back surface filler sheet for a solar cell module having a black layer containing a transparent resin and a black pigment, and an adhesive layer sandwiching the black layer and containing a silane-modified resin. (See claim 1).

JP 2009-239277 A JP 2009-094320 A JP 2010-093120 A

However, in Patent Document 2 or 3, although the inorganic pigment is not present near the interface (adhesive surface) with the front protective material or the back protective material, the adhesive layer containing the silane-modified resin deactivated by water and water Since the layer containing the contained inorganic pigment is adjacent, the silane-modified resin may be deactivated after long-term storage.
Here, the deactivation of the silane-modified resin means that the alkoxysilyl group, which is contained in the silane-modified resin and participates in the adhesion to the solar cell element, etc., is hydrolyzed and condensed in the presence of water to form an alkyloxy group. That is, it refers to a phenomenon in which the alkoxysilyl group decreases and the adhesiveness decreases.

  That is, a sealing material that contains an inorganic filler and has excellent stability during long-term storage has not yet been proposed.

  Therefore, an object of the present invention is to provide a sealing material containing an inorganic filler and suppressing the deactivation of a silane-modified resin even after long-term storage, and a solar cell module produced using the same.

  As a result of intensive studies, the present inventors have found that a resin layer (I) containing a silane-modified resin and not containing an inorganic filler, a resin layer (II) containing an inorganic filler, and the resin layer (I) And it discovered that the subject of this invention could be solved by setting it as the sealing material of the structure which has resin layer (III) between this resin layer (II).

That is, the present invention relates to the following [1] to [10].
[1] A solar cell encapsulant having a resin layer (I) containing a silane-modified resin and not containing an inorganic filler, and a resin layer (II) containing an inorganic filler, the resin layer ( A solar cell encapsulant comprising a resin layer (III) between I) and the resin layer (II).
[2] The solar cell according to [1], wherein a main component of the resin constituting the resin layer (I) is a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms. Sealing material.
[3] The above-mentioned [1], wherein a main component of the resin constituting the resin layer (I) and the resin layer (II) is a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms. ] The sealing material for solar cells as described in.
[4] The solar cell according to [1], wherein the main components of the resin constituting the resin layer (I), the resin layer (II), and the resin layer (III) are the same type of resin. Sealing material.
[5] The main component of the resin constituting the resin layer (I), the resin layer (II), and the resin layer (III) is a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms. The solar cell encapsulant according to [1].
[6] The solar cell encapsulant according to any one of [1] to [5], wherein the resin layer (III) does not contain a silane-modified resin and an inorganic filler.
[7] The solar cell encapsulant according to any one of [1] to [6], wherein the inorganic filler is an inorganic pigment.
[8] The solar cell encapsulant according to [7], wherein the inorganic pigment is a white pigment or a black pigment.
[9] The solar cell encapsulant according to any one of [1] to [8], wherein the resin layer (III) has a water absorption rate (JIS K7209) of 50 ppm or more.
[10] A solar cell module produced using the solar cell encapsulant according to any one of [1] to [9].

  ADVANTAGE OF THE INVENTION According to this invention, the sealing material and solar cell module which contain an inorganic filler and can suppress the deactivation of a silane modified resin even after long-term storage can be provided.

  Hereinafter, a solar cell sealing material as an embodiment of the present invention and a solar cell module produced using the same will be described. However, the scope of the present invention is not limited to the embodiments described below.

In the present specification, the term “main component” is intended to allow other components to be included within a range that does not hinder the action / effect of the constituent resin. Further, this term does not limit the specific content, but it is 50% by mass or more, preferably 65% by mass or more, more preferably 80% by mass or more, and 100% by mass or less of the entire constituent components. It is a component that occupies a range.
“Resin constituting the layer” means all resins contained in the layer. The “resin composition constituting the layer” means all resins, inorganic fillers and other additives contained in the layer. Moreover, ppm which concerns on the water absorption rate and moisture content of this specification means mass ppm.

  The solar cell encapsulant of the present invention (hereinafter sometimes referred to as encapsulant) contains at least a resin layer (I) containing a silane-modified resin and no inorganic filler, and an inorganic filler. It has resin layer (II) and resin layer (III) distribute | arranged between this resin layer (I) and this resin layer (II).

[Resin layer (I)]
The resin layer (I) used in the present invention contains a silane-modified resin and does not contain an inorganic filler. The resin constituting the resin layer (I) is not particularly limited, but from the viewpoint of productivity at the time of film formation of a sealing material for solar cells, in addition to adhesiveness, long-term stability of adhesive strength and heat resistance. Preferably, the main component is an olefin resin.

<Olefin resin>
Although it does not specifically limit as an olefin resin, Specifically, the olefin resin shown by each of following (A)-(C) is used suitably. Olefin resins can be used alone or in combination of two or more. Shown in (A) and (B) from the viewpoints of flexibility of the sealing material obtained, water vapor barrier properties, less fish eye (gel), less corrosive substances (such as acetic acid) in the circuit and economy. Among them, those shown in (A) are particularly preferably used because they are excellent in low temperature characteristics and weather resistance.

Olefin resin (A)
The olefin resin (A) is a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms. Here, the α-olefin copolymerized with ethylene includes propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 3-methyl. -Butene-1,4-methyl-pentene-1 and the like are exemplified.
In the present invention, propylene, 1-butene, 1-hexene, and 1-octene are preferably used as the α-olefin copolymerized with ethylene from the viewpoint of industrial availability, various characteristics, and economical efficiency. Used. From the viewpoint of flexibility, an ethylene-α-olefin random copolymer is preferably used. The α-olefin copolymerized with ethylene can be used alone or in combination of two or more.

  Further, the content of the α-olefin copolymerized with ethylene is not particularly limited, but with respect to all monomer units in the copolymer of ethylene and the α-olefin having 3 to 20 carbon atoms. The monomer based on an α-olefin having 3 to 20 carbon atoms is usually 2 mol% or more, preferably 40 mol% or less, more preferably 3 to 30 mol%, still more preferably 5 to 25 mol%. . Within this range, the crystallinity is reduced by the copolymerization component, so that flexibility is improved and problems such as blocking of raw material pellets are less likely to occur. In addition, the kind and content of the monomer copolymerized with ethylene can be qualitatively quantitatively analyzed by a well-known method, for example, a nuclear magnetic resonance (NMR) measuring apparatus or other instrumental analyzers.

The copolymer of ethylene and a C3-C20 alpha olefin may contain the monomer unit based on monomers other than an alpha olefin. Examples of the monomer include cyclic olefins, vinyl aromatic compounds (such as styrene), polyene compounds, and the like. The content of the monomer units is preferably 20 mol% or less when the total monomer units in the copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms is 100 mol%. More preferably, it is 15 mol% or less.
In addition, the three-dimensional structure, branching, branching degree distribution, molecular weight distribution and copolymerization form (random, block, etc.) of the copolymer of ethylene and C3-C20 α-olefin are not particularly limited. For example, a copolymer having a long chain branch generally has good mechanical properties, and has an advantage that the melt tension (melt tension) at the time of molding a sheet is increased and the calendar moldability is improved.

The melt flow rate (MFR) of the copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms used in the present invention is not particularly limited, but usually MFR (JIS K7210, temperature: 190 ° C.). , Load: 21.18 N) is about 0.5 to 100 g / 10 min, preferably 1 to 50 g / 10 min, more preferably 2 to 50 g / 10 min, and further preferably 3 to 30 g / 10 min.
Here, the MFR may be selected in consideration of molding processability when molding a sheet, adhesion when sealing a solar cell element (cell), a wraparound condition, and the like. For example, when calendering a sheet, the MFR is preferably a relatively low value, specifically about 0.5 to 5 g / 10 min from the handling property when the sheet is peeled off from the molding roll. In the case of extruding using a mold, the MFR is preferably 1 to 50 g / 10 min, more preferably 2 to 50 g / 10 min, and further preferably 3 to 30 g / 10 min from the viewpoint of reducing the extrusion load and increasing the amount of extrusion. It is. Furthermore, MFR is preferably 2 to 50 g / 10 min, more preferably 3 to 30 g / 10 min, from the viewpoint of adhesion and ease of wraparound when sealing a solar cell element (cell).

  The method for producing a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms used in the present invention is not particularly limited, and a known polymerization method using a known olefin polymerization catalyst can be employed. . For example, a slurry polymerization method, a solution polymerization method, a gas phase polymerization method, etc. using a multi-site catalyst typified by a Ziegler-Natta type catalyst, a single site catalyst typified by a metallocene catalyst or a post metallocene catalyst, etc. And a bulk polymerization method using a radical initiator. In the present invention, a polymerization method using a single-site catalyst capable of polymerizing a raw material having a low molecular weight component and a narrow molecular weight distribution is preferable from the viewpoints of easy granulation after pelletization and prevention of blocking of raw material pellets. is there.

  As a specific example of a copolymer (olefin-based resin (A)) of ethylene and an α-olefin having 3 to 20 carbon atoms used in the present invention, a trade name “Engage” manufactured by Dow Chemical Co., Ltd. ”,“ Affinity ”,“ Infuse ”, trade name“ Exact ”manufactured by ExxonMobil Co., Ltd., trade name“ TAFMER H ”manufactured by Mitsui Chemicals, Inc. , “TAFMER A”, “TAFMER P”, LG Chemical's trade name “LUCENE”, Nippon Polyethylene's trade name “Kernel”, etc. be able to.

Olefin resin (B)
The olefin resin (B) is a copolymer of propylene and another monomer copolymerizable with the propylene, or a homopolymer of propylene. However, these copolymerization forms (random, block, etc.), branching, branching degree distribution and three-dimensional structure are not particularly limited, and can be a polymer having an isotactic, atactic, syndiotactic or mixed structure. .
Examples of other copolymerizable monomers include α-olefins having 4 to 12 carbon atoms such as ethylene, 1-butene, 1-hexene, 4-methyl-pentene-1, 1-octene, and divinylbenzene, Examples include dienes such as 4-cyclohexadiene, dicyclopentadiene, cyclooctadiene, and ethylidene norbornene.
In the present invention, ethylene or 1-butene is preferably used as the α-olefin copolymerized with propylene from the viewpoints of industrial availability, various characteristics, and economical efficiency. In addition, a propylene-α-olefin random copolymer is preferably used from the viewpoint of flexibility and the like. The monomer copolymerized with propylene can be used alone or in combination of two or more.

  The content of other monomers copolymerizable with propylene is not particularly limited, but can be copolymerized with propylene with respect to all monomer units in the olefin resin (B). The monomer units based on other monomers are usually 2 mol% or more, preferably 40 mol% or less, more preferably 3 to 30 mol%, and further preferably 5 to 25 mol%. Within this range, the crystallinity is reduced by the copolymerization component, so that flexibility is improved and problems such as blocking of raw material pellets are less likely to occur. In addition, the kind and content of the other monomer copolymerizable with propylene can be qualitatively and quantitatively analyzed by a known method, for example, a nuclear magnetic resonance (NMR) measuring device or other instrumental analyzer.

The melt flow rate (MFR) of the olefin resin (B) used in the present invention is not particularly limited, but usually MFR (JIS K7210, temperature: 230 ° C., load: 21.18 N) is 0. About 5 to 100 g / 10 min, preferably 2 to 50 g / 10 min, more preferably 3 to 30 g / 10 min.
Here, the MFR may be selected in consideration of molding processability when molding a sheet, adhesion when sealing a solar cell element (cell), a wraparound condition, and the like. For example, when calendering a sheet, the MFR is preferably relatively low, specifically about 0.5 to 5 g / 10 min from the handling property when the sheet is peeled off from the forming roll, In the case of performing extrusion molding using M, MFR is preferably 2 to 50 g / 10 min, more preferably 3 to 30 g / 10 min from the viewpoint of reducing the extrusion load and increasing the extrusion amount. Furthermore, MFR is preferably 2 to 50 g / 10 min, more preferably 3 to 30 g / 10 min, from the viewpoint of adhesion and ease of wraparound when sealing a solar cell element (cell).

  The method for producing a copolymer of propylene and another monomer copolymerizable with the propylene or a homopolymer of propylene (olefin resin (B)) used in the present invention is not particularly limited. Alternatively, a known polymerization method using a known olefin polymerization catalyst can be employed. For example, a slurry polymerization method, a solution polymerization method, a gas phase polymerization method, etc. using a multi-site catalyst represented by a Ziegler-Natta type catalyst, a single site catalyst represented by a metallocene catalyst or a post metallocene catalyst, Examples thereof include a bulk polymerization method using a radical initiator. In the present invention, a polymerization method using a single-site catalyst capable of polymerizing a raw material having a low molecular weight component and a narrow molecular weight distribution is preferable from the viewpoints of easy granulation after pelletization and prevention of blocking of raw material pellets. is there.

  Specific examples of the olefin resin (B) used in the present invention include a propylene-butene random copolymer, a propylene-ethylene random copolymer, and a propylene-ethylene-butene-1 copolymer. Products include “Tuffmer XM”, “NOTIO”, Sumitomo Chemical Co., Ltd. “TAFFCELLEN”, and Prime Polymer Co., Ltd. The product name “PRIME TPO”, the product name “VERSIFY” manufactured by Dow Chemical Co., the product name “VistaMAX” manufactured by ExxonMobil Co., Ltd., etc. Can do.

Olefin resin (C)
The olefin resin (C) is a modified olefin.
Although the kind of modified olefin is not particularly limited, ethylene-vinyl acetate copolymer (EVA), ethylene-vinyl alcohol copolymer (EVOH), ethylene-methyl methacrylate copolymer (E-MMA), Ethylene-ethyl acrylate copolymer (E-EAA), ethylene-glycidyl methacrylate copolymer (E-GMA), ionomer resin (ionic crosslinkable ethylene-methacrylic acid copolymer, ionic crosslinkable ethylene-acrylic acid copolymer) And at least one resin selected from the group consisting of maleic anhydride graft copolymers.

  Further, the content of various monomers for modifying the modified olefin is not particularly limited, but is usually 0.5 mol% or more, preferably 1 mol% or more, more preferably 2 mol% or more, and Usually, it is 40 mol% or less, preferably 30 mol% or less, more preferably 25 mol% or less. Within this range, transparency is improved by reducing crystallinity due to the copolymerization component, and problems such as blocking of raw material pellets are less likely to occur. In addition, the kind and content of various monomers which modify | denature a modified olefin can be qualitatively quantitatively analyzed by a well-known method, for example, a nuclear magnetic resonance (NMR) measuring apparatus, and another instrumental analyzer.

  The production method of the modified olefin fat used in the present invention is not particularly limited, and a known polymerization method using a known olefin polymerization catalyst other than the ionomer resin and maleic anhydride graft copolymer shown below, For example, slurry polymerization method, solution polymerization method, gas phase polymerization method, etc. using multi-site catalyst typified by Ziegler-Natta type catalyst and single site catalyst typified by metallocene catalyst, and bulk using radical initiator Examples thereof include a polymerization method.

  The ionomer resin contains at least a part of an unsaturated carboxylic acid component of a copolymer comprising ethylene, an unsaturated carboxylic acid, and other unsaturated compounds as optional components, at least one of a metal ion and an organic amine. It can be obtained by summing. The ionomer resin can also be obtained by saponifying at least a part of an unsaturated carboxylic acid ester component of a copolymer comprising ethylene, an unsaturated carboxylic acid ester, and other unsaturated compounds as optional components. .

  Although the maleic anhydride graft copolymer is not limited, it can be obtained by melt-mixing a polyolefin-based resin and maleic anhydride in the presence of a radical generator at a high temperature and graft polymerization.

  As specific examples of the modified olefin used in the present invention, as EVA, trade name “NOVATECH-EVA” manufactured by Nippon Polyethylene Co., Ltd., trade name “EVA” manufactured by Mitsui DuPont Polychemical Co., Ltd. “FLEX”, “NUC” series manufactured by Nihon Unicar Co., Ltd., and EVOH as trade name “SOARNOL” manufactured by Nippon Synthetic Chemical Co., Ltd., product name “EVAL” manufactured by Kuraray Co., Ltd. ) ", Trade name" ACRIFFT "manufactured by Sumitomo Chemical Co., Ltd. as E-MMA, and trade name" REXPEARL EEA "manufactured by Nippon Polyethylene Co., Ltd., E-GMA as E-EAA As a product name "BONDFAST" manufactured by Sumitomo Chemical Co., Ltd. as an ionomer , Mitsui Du Pont Polychemical Co., Ltd. under the trade name "Himilan (binary copolymerized ionomer)", as the maleic anhydride-grafted copolymer can be exemplified by Mitsui Chemicals Co., Ltd., "Admer (ADMER)" and the like.

<Silane modified resin>
The silane-modified resin used in the present invention is not particularly limited, and examples thereof include those obtained by polymerization of a resin such as an olefin resin and a urethane resin and a silane coupling agent. From the viewpoint of industrial availability and economic efficiency, a silane-modified olefin resin is preferably used.
The method for producing the silane-modified resin is not particularly limited. For example, the olefin-based resin shown in each of the above-described olefin-based resin (A) to olefin-based resin (C) (in which, reactivity or In view of weather resistance, the olefin resin (A) is particularly preferable) and a silane coupling agent described later can be obtained by melt-mixing at a high temperature in the presence of a radical generator and graft polymerization.

Silane coupling agents are useful for improving adhesion to protective materials for sealing materials (glass, resin front sheets, back sheets, etc.) and solar cell elements, such as vinyl groups, acryloxy groups, Examples thereof include compounds having a hydrolyzable group such as an alkoxy group together with an unsaturated group such as a methacryloxy group, an amino group, an epoxy group and the like. Specific examples of the silane coupling agent include N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, and γ-aminopropyltriethoxy. Examples include silane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and the like. In the present invention, γ-glycidoxypropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane are preferably used because of good adhesiveness and little discoloration such as yellowing. These silane coupling agents can be used alone or in combination of two or more.
The addition amount of the silane coupling agent is usually about 0.1 to 5 parts by mass, preferably 0.2 to 3 parts by mass with respect to 100 parts by mass of the silane-modified resin before silane modification.

The radical generator is useful for graft polymerization of the silane coupling agent onto the silane-modified resin before silane modification. The radical generator is not particularly limited, and examples thereof include organic peroxides, azo compounds such as azobisisobutyronitrile (AIBN) and polymer azo compounds, and organometallic compounds such as allyl tin and triethylborane. . Among them, organic peroxides that generate radicals at 100 ° C. or higher and have a decomposition temperature of 70 ° C. or higher at a half-life of 10 hours are preferably used from the viewpoint of reaction rate and safety during compounding. The Examples of such radical generators include 2,5-dimethylhexane; 2,5-dihydroperoxide; 2,5-dimethyl-2,5-di (t-butylperoxy) hexane; 3-di- t-butyl peroxide; t-dicumyl peroxide; 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne; dicumyl peroxide; α, α'-bis (t-butylperoxy) Isopropyl) benzene; n-butyl-4,4-bis (t-butylperoxy) butane; 2,2-bis (t-butylperoxy) butane; 1,1-bis (t-butylperoxy) cyclohexane; 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane; t-butylperoxybenzoate; benzoyl peroxide, etc. are preferably used Rukoto can.
The addition amount of the radical generator is usually about 0.001 to 0.1 parts by mass, preferably 0.005 to 0.05 parts by mass with respect to 100 parts by mass of the silane-modified resin before silane modification. It is.

  As a specific example of the silane-modified resin used in the present invention, trade name “LINKLON” manufactured by Mitsubishi Chemical Corporation can be exemplified.

  Although content of silane modified resin is not specifically limited, It is preferable that it is 1-50 mass parts in 100 mass parts of resin which comprises resin layer (I), Preferably it is 5-30 mass parts. Is more preferable. Within such a range, the function as the resin layer (I) can be exhibited, and characteristics such as flexibility, sealing properties, and heat resistance as a sealing material can be adjusted. In addition, an increase in resin pressure and generation of foreign matters such as gels and fish eyes can be suppressed in the molding process.

<Resin composition constituting resin layer (I)>
The resin composition constituting the resin layer (I) of the present invention has various physical properties (flexibility, heat resistance, transparency, adhesiveness, etc.), molding processability, economic efficiency, etc. within a range not departing from the gist of the present invention. For the purpose of further improving the above, resins other than those mentioned above can be included. Examples of other resins include tackifier resins (petroleum resins, terpene resins, coumarone-indene resins, rosin resins, etc.), various elastomers (styrene elastomers, etc.), and the like.

  It is important that the resin composition constituting the resin layer (I) of the present invention does not contain an inorganic filler described later. “Does not contain inorganic filler” means that the amount of the silane-modified resin is not deactivated by the inorganic filler, and is usually 1 part by mass with respect to 100 parts by mass of the resin constituting the resin layer (I). Hereinafter, it is preferably 0.5 parts by mass or less, particularly preferably 0.1 parts by mass or less.

  Various additives can be added to the resin composition constituting the resin layer (I) of the present invention as necessary without departing from the gist of the present invention. Examples of the additive include the silane coupling agent, the antioxidant, the ultraviolet absorber, the weather resistance stabilizer, the light diffusing agent, the nucleating agent, the flame retardant, and the discoloration preventing agent described above.

The antioxidant is not particularly limited, and various commercially available products can be applied. Examples of the antioxidant include various types such as phenol, sulfur, phosphite, such as monophenol, bisphenol, and high-molecular phenol. From the viewpoints of the effect of the antioxidant, thermal stability, economy, etc., phenolic and phosphite antioxidants are preferably used, and using both in combination provides an effect as an antioxidant with respect to the amount added. Since it can raise, it is still more preferable.
The addition amount of the antioxidant is not limited, but it is preferably 0.1 to 1 part by mass with respect to 100 parts by mass of the resin constituting the resin layer (I). A range of 2 parts by mass or more and 0.5 parts by mass or less is more preferable.

As the ultraviolet absorber, various commercially available products can be applied, and various types such as benzophenone-based, benzotriazole-based, triazine-based, and salicylic acid ester-based materials can be exemplified.
The addition amount of the ultraviolet absorber is not limited, but is preferably 0.01 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the resin constituting the resin layer (I). More preferably, it is 0.05 mass part or more and 0.5 mass part or less.

A hindered amine light stabilizer is suitably used as a weather stabilizer that imparts weather resistance in addition to the above ultraviolet absorber. The hindered amine light stabilizer does not absorb ultraviolet rays like the ultraviolet absorber, but has a remarkable synergistic effect when used in combination with the ultraviolet absorber.
The addition amount of the hindered amine light stabilizer is not limited, but is usually 0.01 parts by mass or more and 0.5 parts by mass or less with respect to 100 parts by mass of the resin constituting the resin layer (I). Is preferable, and the range of 0.05 parts by mass or more and 0.3 parts by mass or less is more preferable.

  Said antioxidant, ultraviolet absorber and weathering stabilizer may be used alone or in combination of two or more.

  The resin layer (I) may be a single layer or a multilayer. When the sealing material has multiple resin layers (I), the resin composition constituting each layer of the resin layer (I) may be the same or different, and the thickness of each layer of the resin layer (I) is the same or different. It may be.

  The thickness of the resin layer (I) of the encapsulant of the present invention (meaning the total thickness of each layer in the case of multiple layers) is not particularly limited, but fills the uneven surface of the cell and the gap between the wirings. From the viewpoints of sealing performance, adhesiveness, economy, etc., it is usually 0.01 mm or more, preferably 0.03 mm or more, more preferably 0.05 mm or more, and about 0.3 mm or less, preferably 0. .2 mm or less, more preferably 0.1 mm or less.

[Resin layer (II)]
The resin layer (II) used in the present invention contains an inorganic filler. The resin constituting the resin layer (II) is not particularly limited, but the ease of regenerative addition during the production of the sealing material of the present invention, thereby improving the productivity such as yield, further flexibility, From the viewpoint of heat resistance and the like, specifically, it is preferable that the olefin-based resin shown in each of the aforementioned (A) to (C) is a main component, and the main component of the resin constituting the resin layer (I). It is more preferable to use the same type of resin as the component. The “same kind of resin” as used herein refers to, for example, a resin constituting the resin layer (II) when the main component of the resin constituting the resin layer (I) is the olefin resin (A). This means that the main component is a resin classified as the olefin resin (A).
Moreover, it is more preferable that the main component of the resin constituting the resin layer (II) and the resin layer (I) is a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms.

<Inorganic filler>
As the inorganic filler, an inorganic filler for imparting rigidity, heat resistance and the like, an inorganic filler for enhancing reflectivity, concealing property and designability (hereinafter sometimes referred to as an inorganic pigment) and the like are used.

  Inorganic fillers for imparting rigidity and heat resistance include silica, glass beads, silicon oxide such as glass fiber, magnesium silicate such as talc, kaolin, montmorillonite, layered aluminum silicate such as mica, feldspar, zeolite A silicon compound such as reticulated aluminum silicate such as synthetic zeolite is used.

Various pigments such as a white pigment, a black pigment, and a blue pigment are used as the inorganic filler (inorganic pigment) for improving the reflectivity, concealability and design.
By adding a white pigment, sunlight can be reflected, and light passing through the solar cell can be reused to improve power generation efficiency. Moreover, the designability and decoration of a solar cell module can be improved by adding various pigments, such as a black pigment and a blue pigment.

White pigments include calcium carbonate, anatase titanium oxide, rutile titanium oxide, zinc oxide, lead carbonate, barium sulfate, basic lead carbonate, basic lead sulfate, basic lead silicate, zinc white, zinc sulfide, lithopone, etc. Can be used. As the titanium oxide, the rutile type is preferable because it causes less yellowing after irradiation with light for a longer time than the anatase type, and is suitable for suppressing changes in color difference. Among the white pigments, at least one kind of inorganic fine particles selected from the group consisting of rutile type titanium oxide, barium sulfate, calcium carbonate and silicon dioxide is preferable from the viewpoint of stability and non-heavy metal compound.
As the black pigment, carbon black, acetylene black, black iron oxide, graphite or the like is used. From the viewpoint of long-term stability, carbon black is preferably used.
As other pigments, ultramarine, bitumen, cobalt blue and the like are used as blue pigments, yellow iron oxide, titanium yellow, yellow lead and the like are used as yellow pigments, and bengara, cadmium red and red lead are used as red pigments.

  The inorganic filler may be added alone, or may be subjected to an inorganic surface treatment with an inorganic substance or a hydroxide thereof, or an organic surface treatment with a polyhydric alcohol, an organic silane compound, or the like.

Although the addition amount of an inorganic filler changes with kinds of used inorganic filler, normally, it is about 0.1-30 mass parts with respect to 100 mass parts of resin which comprises resin layer (II), Preferably it is 1- 20 parts by mass.
For example, when the inorganic filler is a white pigment, it is about 1 to 30 parts by mass, preferably 3 to 20 parts by mass, and more preferably 5 to 15 parts by mass from the viewpoint of reflectivity.
For example, when the inorganic filler is a black pigment, it is about 0.1 to 15 parts by mass, preferably 0.5 to 10 parts by mass, and more preferably 1 to 5 parts by mass from the viewpoint of concealability.

  The resin composition constituting the resin layer (II) of the present invention contains the above-described silane-modified resin, various other resins, and various additives as necessary without departing from the gist of the present invention. be able to.

When preparing the resin layer (II), the inorganic filler and various additives added as necessary (hereinafter sometimes referred to as inorganic filler) are dry-blended with the resin in advance and then supplied to the hopper. Alternatively, it may be supplied after melting and mixing all materials in advance to produce pellets, or a master batch in which only an inorganic filler or the like is previously concentrated in a resin may be produced and supplied. From the viewpoint of productivity during film formation, it is preferable to prepare a master batch in which an inorganic filler or the like is previously concentrated in a resin.
In the case of a master batch in which an inorganic filler or the like is previously concentrated in a resin, the content of the inorganic filler or the like is preferably 30% by mass to 70% by mass.

The water content of the inorganic filler is usually 1000 ppm or less, preferably 800 ppm or less, more preferably 600 ppm or less, and still more preferably 400 ppm or less.
The water content of the master batch in which the inorganic filler or the like is previously concentrated in the resin is usually 1000 ppm or less, preferably 800 ppm or less, more preferably 600 ppm or less, and further preferably 400 ppm or less.
The water content can be measured according to the method B of JIS K7251.

  The resin layer (II) may be a single layer or a multilayer. When the sealing material has a multilayer resin layer (II), the resin composition constituting each layer may be the same or different, and the thickness of each layer of the resin layer (II) may be the same or different.

  The thickness of the resin layer (II) of the sealing material of the present invention (when the resin layer (II) is a multilayer, it means the total thickness of each layer) is not particularly limited, but is rigid or heat resistant. Or, from the viewpoint of concealability when containing an inorganic pigment, it is usually 0.01 mm or more, preferably 0.05 mm or more, more preferably 0.1 mm or more, and about 0.5 mm or less, preferably Is 0.4 mm or less, more preferably 0.3 mm or less.

[Resin layer (III)]
It is important to install the resin layer (III) used in the present invention between the resin layer (I) and the resin layer (II). The resin constituting the resin layer (III) is not particularly limited, but it is possible to prevent moisture contained in the inorganic filler added to the resin layer (II) from moving to the resin layer (I). From the viewpoints of ease of regenerative addition during the production of the sealing material and improvement of productivity such as yield, specifically, the olefinic compounds shown in each of the aforementioned (A) to (C) It is preferable that the resin is a main component, and it is more preferable to use the same type of resin as the main component of the resin constituting the resin layer (I). Moreover, it is more preferable that the main components of the resin constituting the resin layer (I), the resin layer (II), and the resin layer (III) are the same type of resin, and ethylene and an α- Most preferred is a copolymer with an olefin.

It is preferable that the resin layer (III) can absorb moisture transferred from the resin layer (II). If moisture cannot be absorbed and moves to the resin layer (I), it reacts with the silane-modified resin and the silane-modified resin may be deactivated by water. From the above viewpoint, the water absorption rate of the main component of the resin constituting the resin layer (III) is preferably 50 ppm or more, more preferably 80 ppm or more, still more preferably 100 ppm or more, and most preferably 150 ppm or more. It is. The upper limit of the water absorption rate is not particularly limited, but is preferably 500 ppm, more preferably 300 ppm.
If the water absorption is within this range, it is difficult to cause problems such as excessive absorption of moisture during use as a solar cell module in an outdoor environment, and rusting of the wiring, and moisture generated from the inorganic filler is the resin layer (I). Therefore, it is difficult to cause problems such as deactivation by reacting with the silane-modified resin.
The water absorption rate can be measured according to method A of JIS K7209.

Considering the role of water absorption of the resin layer (III), the resin composition constituting the resin layer (III) preferably does not contain an inorganic filler. However, the addition of an inorganic filler is not excluded. If necessary, an inorganic filler and the various additives described above can be contained without departing from the gist of the present invention.
In addition, the resin composition constituting the resin layer (III) does not contain a silane-modified resin from the viewpoints that the adhesiveness of the sealing material is already imparted by the resin layer (I) and economical. May be.
It is preferable that the resin composition which comprises resin layer (III) does not contain an inorganic filler and a silane modified resin from a viewpoint of the role of resin layer (III), such as economical efficiency and water absorption.

  Further, the resin layer (III) provided between the resin layer (I) and the resin layer (II) may be a single layer or a multilayer. When the sealing material has a multilayer resin layer (III), the resin composition constituting each layer may be the same or different, and the thickness of each layer of the resin layer (III) may be the same or different.

  The thickness of the resin layer (III) (when the resin layer (III) is a multilayer, it means the total thickness of each layer) is not particularly limited, but water absorption, economy, production during film formation From the viewpoint of properties, it is usually 0.01 mm or more, preferably 0.05 mm or more, preferably 0.1 mm or more and about 0.3 mm or less, preferably 0.25 mm or less, preferably 0.2 mm or less. is there.

[Sealant for solar cell]
The encapsulant for solar cell of the present invention includes at least a resin layer (I) containing a silane-modified resin and no inorganic filler, a resin layer (II) containing an inorganic filler, and a resin layer (I). And a resin layer (III) disposed between the resin layer (II).
The layer structure of the sealing material of the present invention is not particularly limited. For example, a three-layer / three-layer structure including resin layer (I) / resin layer (III) / (resin layer (II), resin Examples of the layer (I) / resin layer (III) / resin layer (II) / resin layer (III) / resin layer (I) include 5 types of layers, among others, resin layer (I) / resin A three-layer five-layer configuration of layer (III) / resin layer (II) / resin layer (III) / resin layer (I) is a front / back symmetrical configuration, which is preferable from the viewpoint of handling properties.

Moreover, it is more preferable that the sealing material of this invention satisfy | fills the following physical properties.
<Adhesiveness>
Since the sealing material of this invention has resin layer (I), it is excellent in the adhesiveness with respect to a solar cell element, an upper protection material, a lower protection material, etc.
The sealing material of the present invention contains an inorganic filler and is a sealing material that suppresses the deactivation of the silane-modified resin even after long-term storage. As for the sealing material (patent documents 2 and 3) containing the conventional inorganic filler (for example, inorganic pigment), the moisture contained in an inorganic pigment is absorbed according to the water absorption rate of the resin of the layer containing an inorganic pigment. However, the water | moisture content exceeding the quantity which can absorb water transfers to the adjacent layer (layer containing silane modified resin). At this time, the silane-modified resin may be deactivated by water. In the sealing material of the present invention, by forming the resin layer (III), moisture that has not been absorbed by the resin layer (II) can be absorbed, and the silane-modified resin and water contained in the resin layer (I) Reaction with can be suppressed. Therefore, it is possible to have excellent adhesiveness even after long-term storage.
For example, the evaluation of adhesion to glass used as an upper protective material or a lower protective material can be evaluated by the peel strength when the sealing material and glass are laminated and then the interface is peeled off by a tensile tester. I can do it.

<Flexibility>
The flexibility at normal temperature of the sealing material of the present invention is not particularly limited, and can be appropriately adjusted in consideration of the shape and thickness of the applied solar cell, the installation location, and the like.
For example, the storage elastic modulus (E ′) at a vibration frequency of 10 Hz and a temperature of 20 ° C. in the dynamic viscoelasticity measurement of the sealing material is preferably 1 to 2000 MPa. In consideration of protection and flexibility of the solar cell element, the pressure is preferably 1 to 100 MPa, more preferably 5 to 50 MPa, and further preferably 5 to 30 MPa. In addition, handling properties when the sealing material is collected in the form of a sheet, prevention of blocking between sheet surfaces, or weight reduction in a solar cell module (usually about 3 mm, thin film glass (about 1 mm) is applicable, Alternatively, it is preferably 100 to 800 MPa, and more preferably 200 to 600 MPa in consideration of a glassless configuration). The storage elastic modulus (E ′) is obtained by measuring a predetermined temperature range at a vibration frequency of 10 Hz using a viscoelasticity measuring device and obtaining a value at a temperature of 20 ° C.

<Heat resistance>
The heat resistance of the encapsulant used in the present invention is affected by various properties of the resin constituting the encapsulant (crystal melting peak temperature, crystal melting heat, MFR, molecular weight, etc.). Temperature has a strong influence. Generally, a solar cell module is heated to about 85 to 90 ° C. due to heat generated during power generation or radiant heat of sunlight, etc. If the crystal melting peak temperature is 100 ° C. or higher, the heat resistance of the sealing material should be ensured. Is preferable. The evaluation of the heat resistance is, for example, a sheet-like seal having a thickness of 0.5 mm between a white plate glass (size: 75 mm length, 25 mm width) and a 5 mm thickness aluminum plate (size: length 120 mm, width 60 mm). A sample obtained by laminating a stop material and laminating and pressing at 150 ° C. for 15 minutes using a vacuum press machine is installed at an inclination of 60 ° in a 100 ° C. constant temperature bath, and after 500 hours have elapsed. By observing the state, it is possible to evaluate the superiority or inferiority by ◯ when the glass did not deviate from the initial reference position, and x when the glass deviated from the initial reference position or when the sheet melted.

<Manufacturing method>
Next, the manufacturing method of the sealing material of this invention is demonstrated.
The shape of the sealing material is not limited, but is preferably a sheet from the viewpoint of handleability.

A method for forming a sheet-like sealing material will be described. The thickness of the sealing material is not particularly limited, but is usually 0.03 mm or more, preferably 0.05 mm or more, more preferably 0.1 mm or more, and about 1 mm or less, preferably 0.7 mm or less. More preferably, it may be 0.5 mm or less.
As a film forming method, a known method, for example, a single-screw extruder, a multi-screw extruder, a Banbury mixer, a kneader or the like may be used, and an extrusion casting method using a T die or a calendar method may be employed. Although not particularly limited, in the present invention, a co-extrusion casting method using a plurality of extruders and a T die is preferably used from the viewpoints of handling properties and productivity.
The molding temperature in the coextrusion casting method using a T-die is appropriately adjusted depending on the flow characteristics and film forming properties of the resin composition used, but is generally 80 ° C. or higher, preferably 100 ° C. or higher, more preferably 120 ° C. or higher. More preferably, the temperature is 140 ° C. or higher, and is generally 300 ° C. or lower, preferably 250 ° C. or lower, more preferably 200 ° C. or lower, still more preferably 180 ° C. or lower. When a silane coupling agent or the like is added, crosslinking is performed. It is preferable to lower the molding temperature in order to suppress an increase in the resin pressure accompanying the reaction and an increase in fish eyes.
Various additives such as silane coupling agents, antioxidants, UV absorbers and weathering stabilizers may be dry blended with the resin in advance and then supplied to the hopper. It may be possible to supply after preparing, or it may be possible to prepare and supply a master batch in which only the additive is previously concentrated in the resin.
In addition, if necessary, embossing and various irregularities for the purpose of preventing sheet blocking when the sheet is used as a scroll and improving the ease of air removal and handling in the sealing process of solar cell elements. (Cone, pyramid shape, hemispherical shape, etc.) can be processed. Furthermore, when a sheet is formed, another base film (such as an expanded polyester film (OPET) or an expanded polypropylene film (OPP)) and an extrusion laminate are used for the purpose of improving the handleability when forming the sheet. It can be laminated by a method such as a sand laminating method.

  Various surface treatments such as corona treatment, plasma treatment and primer treatment can be performed on the surface for the purpose of improving the adhesion to various adherends. Here, as a standard of the surface treatment amount, the wet index is preferably 50 mN / m or more, and more preferably 52 mN / m or more. The upper limit of the wetting index is generally about 70 mN / m.

[Solar cell module]
In the solar cell module, the solar cell element is provided between the upper and lower protective materials. Examples of solar cell modules include various configurations, for example: (i) upper protective material (glass) / sealing material used on the glass side (light-receiving surface side sealing material) / solar cell element / back sheet Such as a sealing material (back side sealing material) / lower protective material (back sheet) used on the side, sandwiched between both sides of the solar cell element, (ii) upper protective material / The sealing material / upper protective material is arranged on the solar cell element provided on the inner peripheral surface of the lower protective material, like the lower protective material provided with the solar cell element on the inner surface of the sealing material. (Iii) Under the solar cell element provided under the inner peripheral surface of the upper protective material, such as an upper protective material / sealing material / lower protective material provided with the solar cell element under the inner peripheral surface Examples thereof include those configured to provide a sealing material and a lower protective material. The symbol “/” indicates that layers sandwiching the symbol “/” are stacked adjacent to each other.

<Solar cell element>
Examples of solar cell elements include single crystal silicon type, polycrystalline silicon type, amorphous silicon type, III-V group and II-VI group compound semiconductor types such as gallium-arsenic, copper-indium-selenium, cadmium-tellurium, Examples include a dye sensitizing type and an organic thin film type.

<Upper protective material, lower protective material>
About each member which comprises a solar cell module, although it does not specifically limit, As an upper protective material, it is a single layer or multilayer sheets, such as an inorganic material and various thermoplastic resin films, for example, glass etc. Mention may be made of a single-layer or multilayer protective material made of a thermoplastic resin such as an inorganic material, polyester, inorganic vapor-deposited polyester, fluorine-containing resin or polyolefin. The lower protective material is a single-layer or multilayer sheet such as an inorganic material or various thermoplastic resin films, for example, metal (tin, aluminum, stainless steel, etc.), inorganic materials such as glass, polyester, inorganic vapor-deposited polyester, fluorine Examples thereof include a single layer or multilayer protective material made of a thermoplastic resin such as a containing resin and polyolefin. The surface of the upper and / or lower protective material can be subjected to a known surface treatment such as a primer treatment or a corona treatment in order to improve the adhesion to the sealing material or other members.

The solar cell module produced using the sealing material of the present invention is the above-described upper protective material (glass) / sealing material (light-receiving surface side sealing material) used on the glass side / solar cell element / backsheet side. As an example, a structure such as a sealing material (back side sealing material) / lower protective material (back sheet) used in the above will be described. Glass, light-receiving surface side sealing material, solar cell element, back side sealing material and back sheet are laminated in order from the sunlight receiving side, and further, a junction box (power is generated from the solar cell element) on the lower surface of the back sheet. A terminal box for connecting wiring for taking out electricity to the outside is bonded. The solar cell elements are connected by wiring in order to conduct the generated current to the outside. The wiring is taken out through a through hole provided in the backsheet and connected to the junction box.
Among the sealing materials of the present invention, those containing an inorganic pigment and having reflectivity and concealability are preferably used as the back side sealing material.

As a manufacturing method of the solar cell module, a known manufacturing method can be applied, and it is not particularly limited, but in general, an upper protective material, a light receiving surface side sealing material, a solar cell element, a back surface side sealing. A step of stacking the material and the lower protective material in this order, and a step of vacuum-sucking them and thermocompression bonding them. Also, batch type manufacturing equipment, roll-to-roll type manufacturing equipment, and the like can be applied.
In the solar cell module of the present invention, the upper protective material, the light-receiving surface side sealing material, the solar cell element, the sealing material of the present invention, and the lower protective material are vacuum laminators according to a conventional method, preferably 100 to 180 ° C., More preferably, pressurization with heat and pressure is performed at a temperature of 130 to 150 ° C., a degassing time of 2 to 15 minutes, a pressing pressure of 0.5 to 1 atm, preferably 2 to 45 minutes, more preferably 4 to 20 minutes. Can be manufactured.

  The solar cell module manufactured using the sealing material of the present invention is a small solar cell represented by a mobile device, a large solar cell installed on a roof or a roof, etc., depending on the type and module shape of the applied solar cell. It can be applied to various uses regardless of indoors or outdoors.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited by these examples and comparative examples. Various measurements and evaluations in this example were performed as follows.

[Measurement and evaluation method]
<Water absorption rate>
The water absorption was measured according to A method of JIS K7209.

<Moisture content>
The moisture content was measured in accordance with JIS K7251 method B.

<Adhesiveness>
The adhesiveness of the sealing material in the present invention was evaluated as follows.
White plate glass (product name “Solite”) having a thickness of 3.2 mm, length 150 mm, width 150 mm, and a back sheet (product name “Solmate VTPE1”, made by Taiflex Co., Ltd.) having a thickness of 0.33 mm, length 150 mm, width 150 mm. ) And a sealing material (150 mm long, 150 mm wide) described later and a release PET film having a thickness of 0.1 mm, 90 mm long and 150 mm wide, and a vacuum laminator is used to set a temperature of 150 ° C. and a vacuum of 5 minutes. After preparing a sample that was laminated and pressed under the condition of 6 minutes of press, the release film was removed, and a laminate of glass and sealing material was sandwiched between chucks of a universal tensile testing machine (product name “200X” manufactured by INTESCO). The back sheet and the sealing material are attached to the other chuck, and the peel test is performed at an angle of 180 degrees and a tensile speed of 50 mm / min. The maximum value in the chart (maximum delamination strength) was read from the measurement results and evaluated according to the following criteria. In the case of 200 N / 10 mm width or more,> 200 was described.
○: Maximum delamination strength is 100 N / 10 mm width or more Δ: Maximum delamination strength is smaller than 100 N / 10 mm width and 50 N / 10 mm width or more ×: Maximum delamination strength is smaller than 50 N / 10 mm width

<Amount of water reached>
In the sealing material shown in Table 1 of unit area (1 m ² ), the amount of water reaching the resin layer (I) was calculated from the following (Formula 1), and evaluated according to the following criteria.
Calculation Formula (Formula 1) Amount of Water Reached = (Water Content of Inorganic Filler or Masterbatch x Mass per Unit Area of Inorganic Filler or Masterbatch)-[{Water Absorption Rate of Resin Layer (II) x Resin Layer (II) Mass per unit area} + {water absorption rate of resin layer (III) × mass per unit area of resin layer (III)}]
Evaluation criteria ○: Achieving water content is less than 1.0 mg Δ: Achieving water content is 1.0 mg or more and less than 10 mg ×: Achieving water content is 10 mg or more

<Raw material>
The raw material which comprises a sealing material is shown below.
(PE)
Ethylene-octene random copolymer (manufactured by Prime Polymer Co., Ltd., trade name: Evolue P SP00108, density: 0.90 g / cm ³ , MFR: 10 g / 10 min, Tm: 95 ° C.) and ethylene-hexene random copolymer 2: 1 mixed composition with a coalescence (manufactured by Prime Polymer Co., Ltd., trade name: Neozex 0234N, density: 0.92 g / cm ³ , 2 g / 10 min, Tm: 125 ° C.). (Water absorption rate: 160ppm)
(S-PE)
Silane-modified ethylene-butene random copolymer (manufactured by Mitsubishi Chemical Corporation, trade name: Linkron XLE815N, density: 0.915 g / cm ³ , Tm: 122 ° C., MFR: 0.5 g / 10 min)
(W-MB)
White masterbatch (Tokyo Ink Co., Ltd., trade name: PEX6800 White, titanium oxide 60% by mass, density: 1.7 g / cm ³ , resin used: low density polyethylene, moisture content 550 ppm)
(B-MB)
Black masterbatch (Tokyo Ink Co., Ltd., trade name: PEX9999017 Black, carbon black 50% by mass, density: 1.2 g / cm ³ , resin used: linear low density polyethylene, moisture content 250 ppm)

<Resin composition constituting resin layer (I)>
(I-1): PE / S-PE = 90/10 (mass ratio)
(I-2): PE / S-PE / W-MB = 60/10/30 (mass ratio)
(I-3): PE / S-PE / B-MB = 85/10/5 (mass ratio)

<Resin composition constituting resin layer (III)>
(III-1): PE only

<Resin composition constituting resin layer (II)>
(II-1): PE / W-MB = 70/30 (mass ratio)
(II-2): PE / W-MB = 75/25 (mass ratio)
(II-3): PE / B-MB = 95/5 (mass ratio)

<Example 1>
(I-1) as the resin composition constituting the resin layer (I), (III-1) as the resin composition constituting the resin layer (III), and (II) as the resin composition constituting the resin layer (II) -1), biaxially in the same direction so as to have a laminated structure of resin layer (I) / resin layer (III) / resin layer (II) / resin layer (III) / resin layer (I) After co-extrusion molding at a resin temperature of 180 to 200 ° C. by a T-die method using an extruder, the film was rapidly cooled with a cast embossing roll at 25 ° C. to obtain a sealing material. The thickness of each layer and various evaluation results are shown in Table 1.

<Examples 2 to 4>
A sealing material was obtained in the same manner as in Example 1 except that the resin composition used in each layer and the thickness of each layer were changed as shown in Table 1. The thickness of each layer and various evaluation results are shown in Table 1.

<Comparative Example 1>
Using (I-1) as the resin composition constituting the resin layer (I) and (II-1) as the resin composition constituting the resin layer (II), the resin layer (I) / resin layer ( II) / Co-extrusion molding at a resin temperature of 180 to 200 ° C. by a T-die method using a same-direction twin screw extruder so as to have a laminated structure of resin layer (I), and then a cast embossing roll at 25 ° C. The film was rapidly cooled to obtain a sealing material. The thickness of each layer and various evaluation results are shown in Table 1.

<Comparative example 2>
Using (I-2) as a resin composition constituting the resin layer (I), co-extrusion molding at a resin temperature of 180 to 200 ° C. by a T-die method using a same-direction twin-screw extruder, 25 The film was rapidly cooled with a cast embossing roll at 0 ° C. to obtain a single-layer sealing material. Table 1 shows the thickness and various evaluation results.

<Comparative Example 3>
A sealing material was obtained in the same manner as in Comparative Example 2 except that the resin composition constituting the resin layer (I) was changed to (I-3). Table 1 shows the thickness and various evaluation results.

As is clear from the results in Table 1, the sealing material of the present invention includes a resin layer (I) containing a silane-modified resin and no inorganic filler, and a resin layer (II) containing an inorganic filler. By including the resin layer (III) in between, the amount of water reaching the resin layer (I) (the amount of water reached) can be suppressed to 0.9 mg or less. Among them, it is possible to reduce the amount of moisture reached to 0 by increasing the thickness of the resin layer (III) (Examples 1 to 3).
On the other hand, in the case of a sealing material that does not have the resin layer (III) that satisfies the characteristics defined in the present invention, the amount of water reaching the resin layer (I) (the amount of water reached) is 14 mg (Comparative Example). 1). At this time, the silane-modified resin contained in the resin layer (I) may be deactivated by water.
In order to prove by using a simple method that the silane-modified resin contained in the resin layer (I) is deactivated by moisture contained in the inorganic filler, the resin layers (I) of Comparative Examples 2 and 3 are configured. The resin composition to be contained contains an inorganic filler (titanium oxide, carbon black). As shown in the results of Table 1, the resin layers (I) of Comparative Examples 2 and 3 have the same silane-modified resin content (10% by mass) as the resin layers (I) of Examples 1 to 4. Even so, the adhesion was greatly reduced.

Claims (10)

  A solar cell encapsulant having a resin layer (I) containing a silane-modified resin and not containing an inorganic filler, and a resin layer (II) containing an inorganic filler, the resin layer (I) A sealing material for solar cells, comprising a resin layer (III) between the resin layer (II).   2. The solar cell encapsulant according to claim 1, wherein a main component of the resin constituting the resin layer (I) is a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms. .   The main component of the resin constituting the resin layer (I) and the resin layer (II) is a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms. Solar cell encapsulant.   The solar cell encapsulant according to claim 1, wherein the main components of the resin constituting the resin layer (I), the resin layer (II), and the resin layer (III) are the same type of resin. .   The main component of the resin constituting the resin layer (I), the resin layer (II) and the resin layer (III) is a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms. Item 2. A solar cell encapsulant according to Item 1.   The said resin layer (III) does not contain a silane modified resin and an inorganic filler, The sealing material for solar cells of any one of Claims 1-5 characterized by the above-mentioned.   The said inorganic filler is an inorganic pigment, The sealing material for solar cells of any one of Claims 1-6 characterized by the above-mentioned.   The solar cell encapsulant according to claim 7, wherein the inorganic pigment is a white pigment or a black pigment.   The solar cell encapsulant according to any one of claims 1 to 8, wherein the resin layer (III) has a water absorption rate (JIS K7209) of 50 ppm or more.   The solar cell module produced using the sealing material for solar cells of any one of Claims 1-9.