JP6660671B2 - Solar cell encapsulant and solar cell module - Google Patents

Description

  The present invention relates to a solar cell encapsulant for fixing a solar cell element in a solar cell module, and a solar cell module in which a solar cell element is sealed with the solar cell encapsulant.

  BACKGROUND OF THE INVENTION With the recent rise of environmental problems, hydroelectric power, wind power, and solar power have been spotlighted as clean energy. Of these, solar power generation has seen remarkable improvements in performance, such as the power generation efficiency of solar cell modules, while price reductions have progressed and the government and local governments have promoted projects to promote the introduction of residential solar power generation systems. In recent years, its spread has been remarkable.

  In solar power generation, solar energy is directly converted into electric energy using a semiconductor (solar cell element) such as a silicon cell, but the function of the solar cell element used here is reduced when it comes into direct contact with the outside air. Therefore, in general, the solar cell element is sandwiched by a sealing material or a protective film to prevent foreign matter from entering and infiltration of moisture and the like in addition to buffering.

  A solar cell encapsulant for encapsulating a solar cell element is required to have high transparency (light transmittance) so as not to lower the luminous efficiency of the solar cell. In addition, the solar cell encapsulant has an adhesive property with the solar cell element and a resin sheet (back sheet) for protecting the back surface of the solar cell module to prevent the solar cell element from directly contacting the outside air. They need to be excellent.

For example, U.S. Pat. No. 6,059,064 discloses a composition comprising a terionomer derived from an acid terpolymer, or a film or sheet made of a terionomer. The acid terpolymer described above is a constituent unit derived from an α-olefin, about 15 to about 30% by weight, based on the total weight of the acid terpolymer, of an α, β-ethylenically unsaturated unsaturated compound having 3 to 8 carbon atoms. Copolymers comprising structural units derived from carboxylic acids and from about 0.5 to about 40% by weight of α, β-ethylenically unsaturated carboxylic acid esters having 4 to 12 carbons. In the terionomer, about 5% to about 90% of the carboxylic acid contained in the constituent unit derived from the α, β-ethylenically unsaturated carboxylic acid contained in the acid terpolymer is one or more metal ions. It is a summed ionomer.
It is described that the film or sheet described in Patent Document 1 is transparent and has high adhesiveness to another laminate layer.

  Further, for example, Patent Document 2 discloses a material having an ionomer such as an ethylene-based sodium ionomer as a material having excellent transparency (for example, a sealing material for a solar cell).

JP 2011-507278 A International Publication No. 95/22843

As disclosed in Patent Documents 1 and 2, as an encapsulant for a solar cell, an encapsulant having an ionomer as a component and having transparency and adhesiveness has been conventionally known.
However, simply using an ionomer as a component of the solar cell sealing material makes it difficult to further improve transparency and adhesiveness.
Specifically, for example, in a solar cell encapsulant using a general-purpose zinc (Zn) ionomer, although high adhesiveness is obtained, high transparency (high total light transmittance, low haze) is hardly obtained. In the region from the vicinity of 400 nm, which is the center of the visible region, to the vicinity of 600 nm, the transparency is poor.
In addition, a sealing material for a solar cell using a general-purpose Zn ionomer has a medium rigidity as a sealing material, and when the strength is insufficient when a module strength is required (for example, a laminated glass type module). There is. On the other hand, when Na or magnesium (Mg) ionomer is used, transparency is excellent together with rigidity.

  However, the solar cell encapsulant containing the Na or Mg ionomer has relatively weak adhesion to the adherend and deteriorates with time (peeling, etc.) as compared with the solar cell encapsulant containing the Zn ionomer. Therefore, it is necessary to improve adhesion by taking measures such as adding a silane coupling agent or the like and adjusting a base polymer in the ionomer. However, it is difficult to improve the adhesiveness of a Na ionomer or a Mg ionomer even if a silane coupling agent or the like is added, and the tendency of the Na ionomer is particularly remarkable.

The present invention has been made in view of the above, and an object of the present invention is to provide a sealing material for a solar cell which is excellent in rigidity while having both transparency and adhesiveness.
Another object of the present invention is to provide a solar cell module having excellent durability and more stable battery performance.

The present invention that achieves the above object is as follows.
<1> It contains an ionomer of an ethylene / α, β-unsaturated carboxylic acid copolymer and a silane coupling agent, and contains α, β in 100% by mass of the ethylene / α, β-unsaturated carboxylic acid copolymer. A layer (A) in which the content of the structural unit derived from an unsaturated carboxylic acid is 3% by mass or more and 25% by mass or less, and an ethylene / α, β-unsaturated carboxylic acid type having a degree of neutralization of 35% by mol or more. And (B) a layer containing a magnesium ionomer of a copolymer.

<2> The solar cell encapsulant according to <1>, wherein the thickness ratio ((A) / (B)) of the (A) layer and the (B) layer is 以下 or less.

<3> The solar cell sealing material according to <1> or <2>, wherein the degree of neutralization of the ionomer in the layer (A) is 20 mol% or more and 75 mol% or less.

<4> The ethylene / α, β-unsaturated carboxylic acid-based copolymer in the (A) layer is an ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester copolymer And the content ratio of the constituent unit derived from the α, β-unsaturated carboxylic acid ester in 100% by mass of the ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester copolymer is 5%. The sealing material for a solar cell according to any one of <1> to <3>, which is at least 14 mass% and not more than 14 mass%.

<5> The content ratio of the structural unit derived from an unsaturated carboxylic acid in 100% by mass of the ethylene / α, β-unsaturated carboxylic acid-based copolymer in the layer (B) is 5% by mass or more and 25% by mass or less. The sealing material for a solar cell according to any one of <1> to <4>.

<6> The encapsulant for a solar cell according to any one of <1> to <5>, wherein the ionomer contained in the layer (A) is a magnesium ionomer or a zinc ionomer.

<7> A solar cell module comprising the solar cell sealing material according to any one of <1> to <6>.

ADVANTAGE OF THE INVENTION According to this invention, the sealing material for solar cells which is excellent in rigidity while providing both transparency and adhesiveness is provided.
Further, according to the present invention, a solar cell module having excellent durability and more stable battery performance is provided.

It is a schematic structure figure showing an example of a solar cell module concerning the present invention.

[Sealant for solar cell]
The encapsulant for a solar cell of the present invention comprises an ionomer of an ethylene / α, β-unsaturated carboxylic acid-based copolymer and a silane coupling agent, and comprises the ethylene / α, β-unsaturated carboxylic acid-based copolymer. (Hereinafter, also referred to as “base polymer”.) Layer (A) in which the content of the constituent unit derived from α, β-unsaturated carboxylic acid in 100% by mass is 3% by mass or more and 25% by mass or less, and neutralization (B) a layer containing a magnesium ionomer of an ethylene / α, β-unsaturated carboxylic acid copolymer having a degree of 35 mol% or more.
The term "degree of neutralization" refers to the degree of carboxyl groups contained in the ethylene / unsaturated carboxylic acid copolymer, which is the base polymer of the ionomer, which is lost by the reaction with metal ions (the number of moles of carboxyl groups). Is represented by% based on the standard).

The solar cell encapsulant of the present invention having the above-described configuration has excellent rigidity while achieving both transparency and adhesiveness, which tend to conflict with each other.
It is presumed that the reason is as follows.

First, in the solar cell encapsulant of the present invention, in the (A) layer, the content ratio of the structural unit derived from the unsaturated carboxylic acid (hereinafter, may be referred to as “acid content”) is 100% by mass of the base polymer. An ionomer of an ethylene / α, β-unsaturated carboxylic acid-based copolymer (hereinafter sometimes referred to as “specific ionomer”) in an amount of 3% by mass or more and 25% by mass or less, and a silane coupling agent. As a result, high adhesiveness to an object to be bonded (for example, a glass substrate or a resin sheet (back sheet) for protecting the back surface of the solar cell module) is realized.
In the solar cell encapsulant of the present invention, the (B) layer is a magnesium ionomer of an ethylene / α, β-unsaturated carboxylic acid-based copolymer having a degree of neutralization of 35 mol% or more (hereinafter, referred to as “ Layer which may be referred to as “specific Mg ionomer”), realizes high transparency and is excellent in rigidity.

  As described above, the solar cell encapsulant of the present invention is a solar cell encapsulant having both excellent transparency and adhesiveness and excellent rigidity.

  Hereinafter, the solar cell sealing material of the present invention will be described in detail.

<(A) layer>
The (A) layer is composed of an ethylene / α, β-unsaturated carboxylic acid-based copolymer in which the content of the structural unit derived from the unsaturated carboxylic acid is 3% by mass or more and 25% by mass or less in 100% by mass of the base polymer. Includes ionomer and silane coupling agent.

(Specific ionomer)
The (A) layer is composed of an ethylene / α, β-unsaturated carboxylic acid-based copolymer in which the content of the structural unit derived from the unsaturated carboxylic acid is 3% by mass or more and 25% by mass or less in 100% by mass of the base polymer. Includes ionomers (specific ionomers).
The ethylene / α, β-unsaturated carboxylic acid-based copolymer may be a binary system or a ternary system.

-Metal in specific ionomer-
Examples of the metal in the specific ionomer include Zn, Mg, Li (lithium), and Na (sodium), and Zn and Mg are more preferable.
When the metal in the specific ionomer is Mg, it is considered that the transparency of the layer (A) is enhanced and the rigidity is excellent.
When the metal in the specific ionomer is Zn, it is considered that the adhesion between the layer (A) and the adherend is enhanced.

  In addition, the metal in the specific ionomer contained in the layer (A) may be any one of the above metals, or may be a combination of a plurality of the above metals.

-Base polymer of specific ionomer-
The specific ionomer contains an ethylene / α, β-unsaturated carboxylic acid copolymer as a base polymer.
Examples of the ethylene / α, β-unsaturated carboxylic acid copolymer include a binary copolymer having a structural unit derived from ethylene and a structural unit derived from an unsaturated carboxylic acid, and a structural unit derived from ethylene. And terpolymers having a structural unit derived from an unsaturated carboxylic acid and a structural unit derived from an α, β-unsaturated carboxylic acid ester.
Among these, as the base polymer of the specific ionomer contained in the layer (A), the binary copolymer of ethylene / α, β-unsaturated carboxylic acid is used from the viewpoint of playing an important role in the adhesion to the adherend. And a terpolymer of ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester, preferably ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated Carboxylic acid ester terpolymers are particularly preferred.
The terpolymer of ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester is considered to mainly provide adhesiveness. And a structural unit derived from an α, β-unsaturated carboxylic acid ester.

  Examples of the α, β-unsaturated carboxylic acid in the ethylene / α, β-unsaturated carboxylic acid-based copolymer include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, and maleic anhydride monoester. Among these, acrylic acid or methacrylic acid is preferred.

  In the ethylene / α, β-unsaturated carboxylic acid-based copolymer, examples of the type of the ester in the unsaturated carboxylic acid ester include methyl ester, ethyl ester, n-propyl ester, isopropyl ester, n-butyl ester, and the like. Isobutyl ester, 2-ethylhexyl ester and the like.

  Specific examples of the ethylene / α, β-unsaturated carboxylic acid copolymer include ethylene / methacrylic acid copolymer, ethylene / methacrylic acid / acrylic acid methyl ester copolymer, and ethylene / methacrylic acid / acrylic acid. Acid ethyl ester copolymer, ethylene / methacrylic acid / acrylic acid n-butyl ester copolymer, and ethylene / methacrylic acid / acrylic acid isobutyl ester copolymer are preferred. Among them, ethylene / methacrylic acid copolymer, ethylene / methacrylic acid / methyl acrylate copolymer, and ethylene / methacrylic acid / isobutyl acrylate copolymer are more preferable.

The specific ionomer contained in the layer (A) is, for example, an ethylene ionomer when the base polymer is a Mg ionomer of an ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester copolymer. Mg ionomer of acrylic acid / acrylic acid ester copolymer, Mg ionomer of ethylene / acrylic acid / methacrylic acid ester copolymer, Mg ionomer of ethylene / methacrylic acid / acrylic acid ester copolymer (for example, ethylene / methacrylic acid / Mg ionomer of isobutyl acrylate copolymer) and Mg ionomer of ethylene / methacrylic acid / methacrylic acid ester copolymer.
On the other hand, when the base polymer is a Na ionomer of an ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester copolymer, the specific ionomer contained in the layer (A) is, for example, ethylene / ion. Na ionomer of acrylic acid / acrylic acid ester copolymer, Na ionomer of ethylene / acrylic acid / methacrylic acid ester copolymer, Na ionomer of ethylene / methacrylic acid / acrylic acid ester copolymer (for example, ethylene / methacrylic acid / Na ionomer of acrylic acid isobutyl ester copolymer), and Na ionomer of ethylene / methacrylic acid / methacrylic acid ester copolymer.

In the case where the base polymer is an ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester copolymer, the specific ionomer contained in the (A) layer is ethylene / α from the viewpoint of adhesiveness. The structural units derived from α, β-unsaturated carboxylic acid and the structural units derived from α, β-unsaturated carboxylic acid ester, based on the total mass of the α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester copolymer It is preferable that the total content of the constituent units is 3% by mass or more.
When the content ratio is 3% by mass or more, transparency and flexibility are improved.
On the other hand, from the viewpoints of suppressing stickiness and improving processability, the α, β-unsaturated carboxylic acid is used in a proportion to the total mass of the ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester copolymer. The total content of the structural units derived and the structural units derived from the α, β-unsaturated carboxylic acid ester is preferably 30% by mass or less.

As a more specific content ratio, a composition derived from α, β-unsaturated carboxylic acid in an ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester copolymer (base polymer) The content of the unit is preferably from 3% by mass to 25% by mass, more preferably from 3% by mass to 20% by mass, and particularly preferably from 5% by mass to 15% by mass.
The amount of α, β-unsaturated carboxylic acid can be determined by the IR method.
The content ratio of the structural unit derived from the α, β-unsaturated carboxylic acid ester in the ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester copolymer (base polymer) is as follows: It is preferably from 1.5% by mass to 20% by mass, more preferably from 3% by mass to 20% by mass, still more preferably from 5% by mass to 20% by mass, and more preferably from 5% by mass to 14% by mass. It is particularly preferred that the content is not more than mass%.

  When the base polymer is an ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester copolymer, the content of the structural unit derived from ethylene is 60% by mass to 97% by mass. The content is preferably not more than 60% by mass and not more than 95% by mass, more preferably not less than 60% by mass and not more than 94% by mass, particularly preferably not less than 60% by mass and not more than 90% by mass.

When the base polymer is an ethylene / α, β-unsaturated carboxylic acid copolymer (binary copolymer), the specific ionomer contained in the layer (A) is ethylene / α from the viewpoint of adhesiveness. The content ratio of the structural unit derived from the α, β-unsaturated carboxylic acid is preferably 3% by mass or more and 25% by mass or less with respect to the total mass of the α, β-unsaturated carboxylic acid copolymer. The content is more preferably 15% by mass or less, particularly preferably 5% by mass or more and 15% by mass or less.
When the content ratio of the structural unit derived from the α, β-unsaturated carboxylic acid is 3% by mass or more, transparency and flexibility are improved.

  When the base polymer is an ethylene / α, β-unsaturated carboxylic acid copolymer, the content ratio of the structural unit derived from ethylene is preferably from 75% by mass to 97% by mass, more preferably 85% by mass. Or more and 97% by mass or less, more preferably 85% by mass or more and 95% by mass or less.

The ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester copolymer and the ethylene / α, β-unsaturated carboxylic acid copolymer include, for example, It can be obtained by radical copolymerization under high temperature and high pressure.
Further, ionomers of these copolymers include, for example, an ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester copolymer, a metal hydroxide, a metal oxide, and a metal acetate. It can be obtained by reacting any one or more of salts and the like.

-Characteristics of specific ionomer-
The acid content of the specific ionomer contained in the (A) layer in the base polymer is from 3% by mass to 25% by mass in 100% by mass of the base polymer. The content of the structural unit derived from the α, β-unsaturated carboxylic acid is more preferably 3% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less in 100% by mass of the base polymer. Is particularly preferred.
When the acid content of the specific ionomer is 3% by mass or more, the sealing material for a solar cell of the present invention can provide a material having both adhesiveness and transparency.
Further, in the encapsulant for a solar cell of the present invention, since the acid content in the base polymer is 25% by mass or less, the processability when a silane coupling agent described later is blended is not impaired.

The degree of neutralization of the specific ionomer contained in the layer (A) is preferably from 10 mol% to 75 mol%, more preferably from 20 mol% to 65 mol%.
The degree of neutralization can be determined by a neutralization titration method.

  In consideration of workability and mechanical strength, the specific ionomer preferably has a melt flow rate (MFR; in accordance with JIS K7210-1999) at 190 ° C. and a load of 2160 g of 0.1 g / 10 min or more and 150 g / 10 min or less. In particular, it is more preferably from 0.1 g / 10 min to 50 g / 10 min.

The total amount of the specific ionomer contained in the (A) layer is preferably 60% by mass or more, more preferably 70% by mass or more, and more preferably 80% by mass or more of the solid content of the (A) layer. Particularly preferred.
When the total amount of the specific ionomer is 60% by mass or more, good adhesiveness and durability can be obtained while maintaining high transparency, and sound insulation properties are excellent.

(Silane coupling agent)
The (A) layer contains at least one silane coupling agent.
When the layer (A) contains the silane coupling agent, the adhesiveness (including the adhesiveness over time) between the solar cell sealing material and the adherend tends to be improved.

Examples of the silane coupling agent include γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropylmethyldimethoxysilane, N- (β- Examples include (aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, and γ-glycidoxypropyltrimethoxysilane. can do.
Among these, a silane coupling agent having an amino group and an alkoxy group (for example, a silane coupling agent having an amino group and an alkoxy group) in terms of enhancing adhesiveness and stably performing adhesion processing with a substrate such as glass or a back sheet. Preferred is an alkoxysilane having an amino group).

Specific examples of the silane coupling agent having an amino group and an alkoxy group include, for example, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyl Amino-trialkoxysilanes such as trimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldiethoxysilane, N- ( 2-aminoethyl) -3-aminopropyldimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-phenyl-3-aminopropylmethyldimethoxysilane, N-phenyl-3-aminopropyl Methyldiethoxysilane, 3-methyldi Tokishishiriru-N-(1,3-dimethyl - butylidene) propylamine, 3-methyldimethoxysilyl-N-(1,3-dimethyl - butylidene) amino, such as propylamine - and the like dialkoxy silanes.
Among these, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldiethoxysilane, N- (2-aminoethyl) -3- Preferred are aminopropylethyldimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane and the like. Particularly, a silane coupling agent containing an amino group and two alkoxy groups, such as N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, is preferable.
When such a silane coupling agent containing an amino group and two alkoxy groups (sometimes abbreviated as dialkoxysilane) is used, the processing stability during sheet molding can be further maintained. More preferred.

  In the layer (A), the amount of the silane coupling agent (the total amount in the case of two or more types) is 0% with respect to 100 parts by mass of the specific ionomer from the viewpoint of improving the adhesiveness and processing stability during sheet molding. It is preferably more than 3 parts by mass, more preferably from 0.03 part by mass to 3 parts by mass, and particularly preferably from 0.05 part by mass to 1.5 parts by mass. When the silane coupling agent is within the above range, the adhesiveness between the solar cell sealing material and the adherend can be improved.

(Other additives)
The layer (A) may contain various other additives as long as the object of the present invention is not impaired. From the viewpoint of preventing deterioration due to exposure to ultraviolet light, for example, it is preferable to include, for example, an ultraviolet absorber, a light stabilizer, and an antioxidant.

  Examples of the ultraviolet absorber include 2-hydroxy-4-methoxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2-carboxybenzophenone and 2-hydroxy-4-n- Benzophenones such as octoxybenzophenone; 2- (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) benzotriazole, 2- (2′-hydroxy-5-methylphenyl) benzotriazole and 2- ( Benzotriazoles such as 2'-hydroxy-5-t-octylphenyl) benzotriazole; and salicylic acid esters such as phenyl salicylate and p-octylphenyl salicylate are used.

  A hindered amine-based light stabilizer is used. Examples of hindered amine light stabilizers include 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4-stearoyloxy-2,2,6,6-tetramethylpiperidine, and 4-acryloyloxy-2. , 2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 4-cyclohexanoyloxy-2,2,6,6-tetramethylpiperidine, 4- ( o-chlorobenzoyloxy) -2,2,6,6-tetramethylpiperidine, 4- (phenoxyacetoxy) -2,2,6,6-tetramethylpiperidine, 1,3,8-triaza-7,7, 9,9-tetramethyl-2,4-dioxo-3-noctyl-spiro [4,5] decane, bis (2,2,6,6-tetramethyl-4-piperidi ) Sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) terephthalate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, tris (2,2,6, 6-tetramethyl-4-piperidyl) benzene-1,3,5-tricarboxylate, tris (2,2,6,6-tetramethyl-4-piperidyl) -2-acetoxypropane-1,2,3- Tricarboxylate, tris (2,2,6,6-tetramethyl-4-piperidyl) -2-hydroxypropane-1,2,3-tricarboxylate, tris (2,2,6,6-tetramethyl- 4-piperidyl) triazine-2,4,6-tricarboxylate, tris (2,2,6,6-tetramethyl-4-piperidine) phosphite, tris (2,2,6 -Tetramethyl-4-piperidyl) butane-1,2,3-tricarboxylate, tetrakis (2,2,6,6-tetramethyl-4-piperidyl) propane-1,1,2,3-tetracarboxylate And tetrakis (2,2,6,6-tetramethyl-4-piperidyl) butane-1,2,3,4-tetracarboxylate.

As the antioxidant, various hindered phenols and phosphites are used. Specific examples of the hindered phenol-based antioxidant include 2,6-di-t-butyl-p-cresol, 2-t-butyl-4-methoxyphenol, 3-t-butyl-4-methoxyphenol, 2,6-di-t-butyl-4-ethylphenol, 2,2′-methylenebis (4-methyl-6-t-butylphenol), 2,2′-methylenebis (4-ethyl-6-t-butylphenol), 4,4′-methylenebis (2,6-di-t-butylphenol), 2,2′-methylenebis [6- (1-methylcyclohexyl) -p-cresol], bis [3,3-bis (4-hydroxy -3-tert-butylphenyl) butylic acid] glycol ester, 4,4'-butylidenebis (6-t-butyl-m-cresol), 2,2'-ethylidenebis (4-se -Butyl-6-t-butylphenol), 2,2′-ethylidenebis (4,6-di-t-butylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-t-butyl) Phenyl) butane, 1,3,5-tris (3,5-di-t-butyl-4-hydroxybenzyl) -2,4,6-trimethylbenzene, 2,6-diphenyl-4-octadecyloxyphenol, Tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 4,4′-thiobis (6-t-butyl-m-cresol), tocopherol, 3,9-bis [1,1-dimethyl-2- [β- (3-t-butyl-4-hydroxy- -Methylphenyl) propionyloxy] ethyl] 2,4,8,10-tetraoxaspiro [5,5] undecane, 2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzylthio) ) -1,3,5-triazine and the like.
Specific examples of the phosphite-based antioxidant include 3,5-di-t-butyl-4-hydroxybenzylphosphonate dimethyl ester, bis (3,5-di-t-butyl-4-hydroxy). Examples include ethyl benzylphosphonate and tris (2,4-di-t-butylphenyl) phosphanate.

The antioxidant, the light stabilizer, and the ultraviolet absorber are each preferably contained in an amount of 5 parts by mass or less, more preferably 0.1 part by mass to 3 parts by mass, based on 100 parts by mass of the specific ionomer. Parts.
In addition, any combination of an antioxidant, a light stabilizer, and an ultraviolet absorber can be used in any combination and in an arbitrary amount in view of taking in sunlight to the solar cell to the maximum.

In addition, the layer (A) may contain additives such as a colorant, a light diffusing agent, a flame retardant, and a metal deactivator, if necessary, in addition to the additives described above.
Examples of the coloring agent include pigments (inorganic pigments and organic pigments), dyes, and the like. Various known coloring agents can be used.

  As inorganic pigments, for example, titanium oxide, zinc white, lead white, lithopone, barite, precipitated inorganic barium sulfate, calcium carbonate, gypsum, precipitated inorganic silica and other white inorganic pigments, carbon black, lamp black, titanium black, synthetic iron Black inorganic pigments such as black, gray inorganic pigments such as zinc dust, lead suboxide, and slate powder; red inorganic pigments such as cadmium red, cadmium mercury red, silver vermilion, red iron, molybdenum red, and lead red; amber; iron oxide tea; Brown inorganic pigments, cadmium yellow, zinc yellow, orca, siena, synthetic orca, graphite, yellow inorganic pigments such as titanium yellow, green inorganic pigments such as chromium oxide green, cobalt green, chrome green, etc., ultramarine, navy blue, iron blue And blue inorganic pigments such as cobalt blue, and metal powder inorganic pigments.

Examples of the organic pigment include permanent red 4R, para red, first yellow G, first yellow 10G, disazo yellow G, disazo yellow GR, disazo orange, pyrazolone orange, brilliant carmine 3B, and brilliant carmine. Carmin 6B, Brilliant Scarlet G, Brilliant Bordeaux 10B, Bordeaux 5B, Permanent Red F5R, Permanent Carmin FB, Resor Red R, Resor Red B, Rake Red C, Rake Red D, Brilliant Fast Azo pigments such as scarlet, pyrazolone red, bon maroon light, bon maroon medium and fire red; nitroso pigments such as naphthol green B; nitro pigments such as naphthol yellow S Dyes, basic dye lakes such as rhodamine B lake, rhodamine 6G lake, mordant dye lakes such as alizarin lake, vat dye pigments such as indanthrene blue, phthalocyanine blue, phthalocyanine green, fast dye Phthalocyanine pigments such as sky blue and dioxazine pigments such as dioxazine violet can be presented.
In addition, organic fluorescent pigments, pearl pigments, and the like can be used.

  Examples of the light diffusing agent include, as inorganic spherical substances, glass beads, silica beads, silicon alkoxide beads, and hollow glass beads. Examples of the organic spherical substance include acrylic or vinylbenzene-based plastic beads.

  Examples of the flame retardant include halogen-based flame retardants such as bromide, phosphorus-based flame retardants, silicone-based flame retardants, and metal hydrates such as magnesium hydroxide and aluminum hydroxide.

  As the metal deactivator, a well-known compound that suppresses metal damage of the thermoplastic resin can be used. Two or more metal deactivators may be used in combination. Preferred examples of the metal deactivator include a hydrazide derivative and a triazole derivative. Specifically, as a hydrazide derivative, decamethylene dicarboxyl-disalicyloyl hydrazide, 2 ′, 3-bis [3- [3,5-ditert-butyl-4-hydroxyphenyl] propionyl] propionohydrazide, Bis (2-phenoxypropionyl-hydrazide) isophthalate is preferably exemplified, and 3- (N-salicyloyl) amino-1,2,4-triazole is preferably exemplified as a triazole derivative. In addition to the hydrazide derivative and the triazole derivative, 2,2′-dihydroxy-3,3′-di- (α-methylcyclohexyl) -5,5′-dimethyldiphenylmethane, tris (2-methyl-4-hydroxy-5) -Tert-butylphenyl) butane, a mixture of 2-mercaptobenzimidazole and a phenol condensate, and the like.

Further, the layer (A) may contain another resin material together with the specific ionomer contained in the layer (A).
As other resin materials, any resin material can be used as long as it has good compatibility with the specific ionomer and does not impair the transparency and mechanical properties of the (A) layer. Acid copolymers and ethylene / unsaturated carboxylic acid ester / unsaturated carboxylic acid copolymers are preferred.
Further, if the other resin material is a resin material having a higher melting point than the specific ionomer, it is possible to improve the heat resistance and durability of the (A) layer.

<(B) layer>
The (B) layer contains a magnesium ionomer of an ethylene / α, β-unsaturated carboxylic acid-based copolymer having a degree of neutralization of 35 mol% or more.
The solar cell sealing material of the present invention has at least one (B) layer.

(Specific Mg ionomer)
When the ionomer contained in the layer (B) is a specific Mg ionomer, the transparency and rigidity of the entire solar cell sealing material are improved.

-Specific Mg ionomer base polymer-
The specific Mg ionomer contained in the (B) layer preferably contains, for example, an ethylene / α, β-unsaturated carboxylic acid-based copolymer as a base polymer.
Examples of the ethylene / α, β-unsaturated carboxylic acid copolymer include a binary copolymer having a structural unit derived from ethylene and a structural unit derived from an unsaturated carboxylic acid, and a structural unit derived from ethylene. And terpolymers having a structural unit derived from an unsaturated carboxylic acid and a structural unit derived from an α, β-unsaturated carboxylic acid ester.
Among these, the base polymer of the specific Mg ionomer is preferably an ethylene / α, β-unsaturated carboxylic acid binary copolymer from the viewpoint of transparency and rigidity.

  Specific examples of the base polymer of the specific Mg ionomer include, for example, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid-acrylic acid methyl ester copolymer, ethylene-methacrylic acid-acrylic acid ethyl ester copolymer, ethylene Methacrylic acid / acrylic acid n-butyl ester copolymer, ethylene / methacrylic acid / acrylic acid isobutyl ester copolymer, and among them, ethylene / methacrylic acid copolymer, ethylene / methacrylic acid copolymer, ethylene -Methacrylic acid-acrylic acid methyl ester copolymer, ethylene-methacrylic acid-acrylic acid isobutyl ester is preferable, and ethylene-methacrylic acid copolymer is more preferable.

The content ratio of the structural unit derived from ethylene in the base polymer of the specific Mg ionomer is preferably from 75% by mass to 97% by mass, and more preferably from 75% by mass to 95% by mass.
When the base polymer of the specific Mg ionomer is an ethylene / α, β-unsaturated carboxylic acid copolymer, the content ratio of the structural unit derived from the α, β-unsaturated carboxylic acid in the copolymer is as follows: The content is preferably from 3% by mass to 25% by mass, more preferably from 5% by mass to 25% by mass.

  When the content ratio of the structural unit derived from ethylene is 75% by mass or more, the heat resistance and mechanical strength of the copolymer (base polymer) are good. On the other hand, when the content ratio of the structural unit derived from ethylene is 97% by mass or less, the adhesiveness and the like are good.

Structural units derived from α, β-unsaturated carboxylic acid contained in the ethylene / α, β-unsaturated carboxylic acid copolymer (base polymer) are important for adhesion to a substrate such as an adherend. It plays a role. The ionomer in the layer (B) which comes into contact with the wiring material and may not adhere to the substrate such as the adherend may have relatively low adhesiveness, but also contributes to the improvement of the adhesiveness.
From the viewpoint of such adhesiveness, the content ratio of the structural unit derived from the unsaturated carboxylic acid to the total mass of the ethylene / α, β-unsaturated carboxylic acid copolymer is preferably 3% by mass or more. Further, when the content ratio is 3% by mass or more, transparency and flexibility are good.
On the other hand, from the viewpoint of suppressing stickiness and improving processability, the content ratio of the structural unit derived from the unsaturated carboxylic acid with respect to the total mass of the ethylene / α, β-unsaturated carboxylic acid copolymer is 25% by mass. The following is preferred. The encapsulant for solar cells of the present invention has high optical properties and rigidity when the acid content of the specific Mg ionomer is 3% by mass or more in the base polymer.
Further, when the acid content in the base polymer in the specific Mg ionomer is 25% by mass or less, the solar cell encapsulant of the present invention has more excellent moisture permeability and heat resistance.

  The ethylene / α, β-unsaturated carboxylic acid copolymer can be obtained, for example, by subjecting each polymerization component to radical copolymerization at high temperature and high pressure. The ionomer can be obtained by reacting an ethylene / α, β-unsaturated carboxylic acid copolymer with a metal hydroxide, a metal oxide, a metal acetate, or the like.

The ethylene / α, β-unsaturated carboxylic acid copolymer contains more than 0 to 30 parts by mass, preferably more than 0 to 25 parts by mass, based on 100 parts by mass of the total of ethylene and α, β-unsaturated carboxylic acid. Structural units derived from other copolymerizable monomers of not more than parts by mass may be contained.
Other copolymerizable monomers include unsaturated esters, for example, vinyl esters such as vinyl acetate and vinyl propionate; methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, (Meth) acrylic acid esters such as methyl methacrylate and isobutyl methacrylate. It is preferable that the constitutional unit derived from the other copolymer monomer be contained in the above range, since the flexibility of the ethylene / unsaturated carboxylic acid copolymer is improved.

-Properties of specific Mg ionomer-
The degree of neutralization of the specific Mg ionomer contained in the layer (B) is 35 mol% or more, preferably 35 mol% or more and 70 mol% or less, particularly preferably 40 mol% or more and 60 mol% or less.
When the degree of neutralization of the specific Mg ionomer is 35 mol% or more, the sealing material for a solar cell of the present invention has more excellent transparency and rigidity.
The degree of neutralization is preferably 45 mol% or more from the viewpoint of processability and flexibility.
The degree of neutralization is preferably 60 mol% or less, particularly from the viewpoint of processability.
The measurement of the degree of neutralization of the specific Mg ionomer in the layer (B) is performed by the method described above for the specific ionomer.

In consideration of workability and mechanical strength, the specific Mg ionomer has a melt flow rate (MFR; in accordance with JIS K7210-1999) at 190 ° C and a load of 2160 g of 0.1 g / 10 min or more and 150 g / 10 min or less. Is particularly preferable, and it is more preferable that it is 0.1 g / 10 min or more and 50 g / 10 min or less.
From the viewpoint of workability and mechanical strength, the layer (B) has a melt flow rate of both the specific ionomer contained in the layer (A) and the specific Mg ionomer contained in the layer (B) of 0.1 g / 10 min or more. It is preferably 150 g / 10 min or less, and more preferably 0.1 g / 10 min or more and 50 g / 10 min or less.

The total amount of the specific Mg ionomer is preferably 60% by mass or more, more preferably 70% by mass or more, and particularly preferably 80% by mass or more of the solid content of the layer (B).
When the total amount of the specific Mg ionomer is 60% by mass or more, the transparency can be improved.

The (B) layer may include another resin material together with the specific Mg ionomer.
As the other resin material, any resin material can be used as long as it has good compatibility with the specific Mg ionomer and does not impair the transparency and mechanical properties of the (B) layer.
As another resin material, for example, an ethylene / unsaturated carboxylic acid copolymer or an ethylene / unsaturated carboxylic acid ester / unsaturated carboxylic acid copolymer is preferable.
Further, if the other resin material is a resin material having a higher melting point than the specific Mg ionomer, the heat resistance and durability of the layer (B) can be improved.

  Various additives and coloring agents can be contained in the layer (B) within a range that does not impair the object of the present invention. Examples of such additives include all those described above as additives that can be contained in the layer (A). When the additive is contained in the layer (B), the same amount of the additive as when the additive is contained in the layer (A) can be contained.

In the present invention, the silane coupling agent is contained in the layer (A), but the silane coupling agent may be contained in the layer (B) as long as the effect of the present invention is not impaired.
Specifically, from the viewpoint of production stability, when the silane coupling agent in the (B) layer is included, the content of the silane coupling agent is 0.1% by mass or less of the solid content of the (B) layer. It is preferable that the silane coupling agent is not contained in the layer (B) (0% by mass).

<Form of sealing material for solar cell>
The thickness ratio ((A) / (B)) of the layers (A) and (B) of the solar cell sealing material is preferably 以下 or less, more preferably １ ／ or less.
When the thickness ratio ((A) / (B)) is 以下 or less, the strength of the solar cell module is improved due to the effect of the rigidity of the sealing material of the (B) layer.

The thickness of the layer (A) is preferably from 1 μm to 500 μm, more preferably from 10 μm to 500 μm, and particularly preferably from 20 μm to 300 μm.
When the layer (A) has a thickness of 1 μm or more, the adhesiveness is improved. Further, when the layer (A) has a thickness of 500 μm or less, the transparency becomes more excellent.

The layer (B) preferably has a thickness of 50 μm or more and 1000 μm or less, and more preferably 50 μm or more and 700 μm or less.
When the layer (B) has a thickness of 100 μm or more, module strength can be imparted. When the layer (B) has a thickness of 1000 μm or less, the transparency is excellent.

The total thickness of the solar cell sealing material of the present invention is not particularly limited, but the total thickness is preferably in the range of 5 μm to 2000 μm (0.005 mm to 2 mm), and 100 μm to 2000 μm (0 .1 mm to 2 mm), more preferably 100 μm or more and 1500 μm or less (0.1 mm to 1.5 mm).
When the total thickness is 5 μm or more and 2000 μm or less, it is excellent in economy (that is, at an appropriate cost as a product), and has excellent adhesiveness and transparency.

  The form of the layer (A) in the present invention is preferably a single layer. However, the form of the (A) layer is not limited to the form of a single layer, but includes, for example, the type of ionomer contained (eg, copolymerization ratio of base polymer, degree of neutralization, metal type, etc.). May be composed of a plurality of different layers.

The (B) layer of the solar cell sealing material of the present invention is preferably in a form in which the (A) layer is provided on the surface of the (B) layer opposite to the surface in contact with the wiring material.
Further, the solar cell sealing material of the present invention may include two or more layers (A) and two or more layers (B). In this case, the layer that contacts the wiring material is (B). ) Layer, and the layer in contact with the adherend preferably has a layer structure of the (A) layer.
With such a layer structure, excellent optical properties and strength can be imparted to the solar cell module of the present invention.
The layer (B) is preferably a single layer, like the layer (A). However, the form of the (B) layer is not limited to the form of a single layer, but includes, for example, the type of ionomer contained (eg, copolymerization ratio of base polymer, degree of neutralization, metal type, etc.). May be composed of a plurality of different layers.

The molding of the sealing material for a solar cell of the present invention is performed by a known method using a single-layer T-die extruder, a multilayer T-die extruder, a calendar molding machine, a single-layer inflation molding machine, a multilayer inflation molding machine, or the like. Can do it.
For example, the encapsulant for a solar cell of the present invention is obtained by dry blending an ionomer as a raw material, if necessary, with additives such as a silane coupling agent, an antioxidant, a light stabilizer, and an ultraviolet absorber. Then, it is supplied from a hopper of a main extruder and a sub-extruder of a T-die extruder and is extruded into a sheet.

The solar cell encapsulant of the present invention is laminated with a double vacuum chamber laminating machine while sandwiching the solar cell encapsulant between two 3.2 mm thick blue plate float glasses ( (Conditions: 150 ° C., 8 minutes), and then, after cooling (that is, slow cooling) in the air at 23 ° C., the total light transmittance according to JIS-K7105 can be 83% by mass or more. That is, in general, the transparency tends to deteriorate when gradually cooled after laminating. Therefore, it is customary to rapidly quench after laminating and evaluated by the total light transmittance after quenching. In the present invention, the total light transmittance after slow cooling is 83% by mass or more, showing extremely good transparency.
Further, the total light transmittance is more preferably 85% by mass or more.
The total light transmittance is a value measured using a haze meter (manufactured by Suga Test Instruments Co., Ltd.) according to JIS-K7105. Note that cooling (gradual cooling) refers to cooling at a cooling rate of 15 ° C./min or less (calculated from the temperature 5 minutes after the start of cooling).

  The solar cell sealing material of the present invention realizes transparency, adhesiveness, and high rigidity, and thus can be used, for example, for an interlayer film for laminated glass.

[Solar cell module]
The solar cell module of the present invention includes the above-described solar cell sealing material of the present invention.
The solar cell module of the present invention is excellent in durability and has more stable battery performance by providing a solar cell encapsulant having excellent rigidity while achieving both transparency and adhesiveness.
One embodiment of a solar cell module will be described with reference to FIG.
In addition, the solar cell module 10 of the present invention is not limited to the one shown in FIG.

The solar cell module 10 shown in FIG. 1 includes an upper transparent protective material 1 (for example, glass), a cell (solar cell element) 3 disposed on a side where sunlight enters, and a side opposite to the side where sunlight enters. A lower protective material (for example, a back sheet) 5 for protecting the back surface is laminated in this order.
The space between the upper transparent protective material 1 and the lower protective material 5 is sealed with a solar cell sealing material 2 having a (A) layer 2A and a (B) layer 2B.
Specifically, the sealing material 2 for solar cells has a laminated structure in which an (A) layer 2A, a (B) layer 2B, and an (A) layer 2A are laminated in this order. Here, the (B) layer 2B has a two-layer structure in which the (B) layer 2b is laminated.
The solar cell sealing material 2 is formed by using two sealing sheets each including an (A) layer 2A and a (B) layer 2b, and overlapping the (B) layers 2b so as to be in contact with each other.
That is, the space sandwiched between the upper transparent protective material 1 and the lower protective material 5 is used for the solar cell sealing material 2, the upper transparent protective material 1 side of the cell 3 and the lower protective material 5 side of the cell 3, respectively. , (B) by being arranged so as to be sandwiched by the layer 2b.
In the solar cell module 10 of FIG. 1, one sealing is performed by applying the solar cell sealing material 2 including two sealing sheets each including the (B) layer 2 b and the (A) layer 2 A. The (A) layer of the sheet is in contact with the upper transparent protective material 1, and the (A) layer of the other sealing sheet is in contact with the lower protective material 5.
The cell 3 is a stacked body of the n-type silicon 12 and the p-type silicon 14. The first electrode 16 is provided on the n-type silicon 12, and the second electrode 18 is provided on the p-type silicon 14. I have.
A plurality of cells 3 are provided in the solar cell module 10, and the first electrode 16 of the n-type silicon 12 and the second electrode 18 of the p-type silicon 14 in another adjacent cell 3 are formed of the wiring material 4. The second electrodes 18 of the p-type silicon 14 in the cells 3 at both ends are connected to, for example, terminals by the wiring material 4.
Here, since the solar cell module 10 includes a plurality of cells 3 arranged side by side, the solar cell sealing material 2 covers not only the cells 3 but also the gap between the cells 3 and the lower protective material 5. It will be. Therefore, the surface of the solar cell sealing material 2 opposite to the surface in contact with the upper transparent protective material 1 also contacts the wiring material 4 exposed from the gap between the cells 3 and the lower protective material 5. It will be.
Further, in the solar cell module, the end face of the laminated structure may be protected by an end face sealing material 6 or a metal frame 7 (for example, an aluminum frame).

  The wiring material 4 is a wiring material containing copper, for example, a wiring board on which copper wiring is formed.

  The cell 3 may be, for example, a group IV semiconductor such as monocrystalline silicon, polycrystalline silicon, and amorphous silicon; and a group III-V semiconductor such as gallium-arsenic, copper-indium-selenium, copper-indium-gallium-selenium, and cadmium-tellurium. And Group II-VI compound semiconductors are preferably used.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless departing from the gist of the present invention. Unless otherwise specified, “parts” and “ppm” are based on mass.
In addition, "ethylene content", "methacrylic acid content", and "isobutyl acrylate content" are the content ratio of the structural unit derived from ethylene and the content ratio of the structural unit derived from methacrylic acid in the resin, respectively. And the content ratio of the structural unit derived from isobutyl acrylate in the resin.

  The materials used in this example, the composition of each layer, the base material, and the evaluation method are as follows.

<1. Ionomer>
(Ionomer 1)
・ Type: Magnesium ionomer ・ Base polymer: ethylene / methacrylic acid / isobutyl acrylate copolymer (ethylene content = 80% by mass, methacrylic acid content = 10% by mass, isobutyl acrylate content = 10% by mass)
-Characteristics: neutralization degree 45 mol%, MFR 2.5 g / 10 min

(Ionomer 2)
・ Type: zinc ionomer ・ Base polymer: ethylene / methacrylic acid copolymer (ethylene content = 85% by mass, methacrylic acid content = 15% by mass)
-Characteristics: neutralization degree 23 mol%, MFR 5.0 g / 10 min

(Ionomer 3)
-Type: magnesium ionomer-Base polymer: ethylene-methacrylic acid copolymer (ethylene content 85% by mass, methacrylic acid content = 15% by mass)
-Characteristics: neutralization degree 54 mol%, MFR 0.7 g / 10 min

(Ionomer 4)
・ Type: zinc ionomer ・ Base polymer: ethylene / methacrylic acid copolymer (ethylene content = 85% by mass, methacrylic acid content = 15% by mass)
-Characteristics: neutralization degree 23 mol%, MFR 5.0 g / 10 min

(Ionomer 5)
・ Type: zinc ionomer ・ Base polymer: ethylene / methacrylic acid copolymer (ethylene content = 91% by mass, methacrylic acid content = 9% by mass)
-Characteristics: neutralization degree 18 mol%, MFR 14.0 g / 10 min

(Ionomer 6)
・ Type: zinc ionomer ・ Base polymer: ethylene / methacrylic acid / isobutyl acrylate copolymer (ethylene content = 80% by mass, methacrylic acid content = 10% by mass, isobutyl acrylate content = 10% by mass)
-Characteristics: neutralization degree 56 mol%, MFR 2.1 g / 10 min

(Ionomer 7)
・ Type: zinc ionomer ・ Base polymer: ethylene / methacrylic acid / isobutyl acrylate copolymer (ethylene content = 75% by mass, methacrylic acid content = 8% by mass, isobutyl acrylate content = 17% by mass)
-Characteristics: neutralization degree 65 mol%, MFR 2.5 g / 10 min (ionomer 8)
・ Type: magnesium ionomer ・ Base polymer: ethylene / methacrylic acid copolymer (ethylene content = 85% by mass, methacrylic acid content = 15% by mass)
-Characteristics: neutralization degree 20 mol%, MFR 10.0 g / 10 min

(Polymer 1)
・ Type: Ethylene / methacrylic acid copolymer ・ Polymer composition: Ethylene / methacrylic acid copolymer (ethylene content = 96% by mass, methacrylic acid content = 4% by mass)
-Characteristics: MFR 7.0 g / 10 min

(Polymer 2)
・ Type: Ethylene / methacrylic acid / isobutyl acrylate copolymer ・ Polymer composition: Ethylene / methacrylic acid / isobutyl acrylate copolymer (ethylene content = 75% by mass, methacrylic acid content = 8% by mass, isobutyl acrylate) (Ester content = 17% by mass)
・ Characteristics: MFR2.5g / 10min

<2. Silane coupling agent>
-N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane: "KBM602" manufactured by Shin-Etsu Chemical Co., Ltd.

-(3) Formulation-
The compounding of the silane coupling agent into the layer (A) was performed by mixing the ionomer and the silane coupling agent at a predetermined ratio before molding.

-(4) Substrate-
・ 3.2mm thick blue plate tempered glass (made by Asahi Glass Co., Ltd.)

[Example 1]
A resin composition obtained by adding 0.05 parts by mass (500 ppm) of a silane coupling agent (KBM602) to 100 parts by mass of the ionomer 1 is molded by a sheet molding machine, and is used for a layer (A). A single-layer sheet (100 μm thickness) was prepared.
Also, using a sheet molding machine in the same manner as above using 100 parts by mass of the ionomer 3, a single layer sheet (thickness: 300 μm) for the layer (B) was prepared.
As each of the sheet forming machines, a 40 mmφ single screw extruder (manufactured by Nakatani Machine Co., Ltd.) equipped with a die having a die width of 40 mm was used.

<Evaluation>
Using each of the above single-layer sheets, evaluation was performed as follows. The evaluation results are shown in Table 1 below.

(Measurement of neutralization degree and acid content)
The neutralization degree and the acid content of the specific ionomer contained in the layer (A) and the specific Mg ionomer contained in the layer (B) were measured by the methods described above.

(transparency)
3.2 mm thick blue sheet tempered glass (75 mm × 120 mm), the single layer sheet for the (A) layer, the single layer sheet for the (B) layer, and the 3.2 mm thick blue sheet tempered glass ( 75 mm x 120 mm) using a vacuum heating bonding machine (LM-50x50S, a double vacuum tank bonding machine manufactured by NPC) at 170 ° C for 8 minutes in this order, and then bonding the short side. With one end fixed and placed in a glass stand, it was left in the air at a temperature of 23 ° C. to be gradually cooled (temperature drop rate: 13 ° C./min, surface temperature of the center of the glass 5 minutes after cooling started, 85 ° C.), A sample having a structure of blue sheet tempered glass / (A) layer / (B) layer / blue sheet tempered glass was produced.
Using this sample, total light transmittance (%) and haze (%) were measured with a haze meter (manufactured by Suga Test Instruments Co., Ltd.) according to JIS-K7105.
This evaluation of transparency is an evaluation assuming a multilayer sheet of “(A) layer / (B) layer”.

(Adhesiveness)
A 3.2 mm thick blue-plated tempered glass (75 mm x 120 mm), a single layer sheet for the (A) layer, and a single layer sheet for the (B) layer are vacuum-heated and bonded to each other (LM-50x50S, NPC). Under the conditions of 170 ° C. for 8 minutes to produce an adhesion evaluation sample having a structure composed of a blue sheet reinforced glass / (A) layer / (B) layer.
Using the obtained adhesive evaluation sample, the initial adhesive strength and the moisture-resistant adhesive strength were measured at a width of 15 mm and a tensile speed of 100 mm / min.
The initial adhesive strength was measured using the above-mentioned sample after preparation, and the moisture-resistant adhesive strength was similarly measured on the sample after aging for 1000 hours in an environment of 85 ° C. and 90% RH. .
The evaluation of the adhesiveness is based on the assumption that the adhesiveness between the layer (A) and the glass in the case of using “(A) layer / (B) layer sheet” (solar material for solar cell). It is.

(rigidity)
−Measurement of bending stiffness−
The (A) layer / (B) layer two-layer sheet was subjected to multi-layer sheet molding using a 40 mmφ single screw extruder (manufactured by Nakatani Machine Co., Ltd.) equipped with a die having a die width of 40 mm, and this sample was further used. A sample for evaluating bending stiffness was prepared.
A test piece was prepared from the sample for evaluating bending stiffness in accordance with JIS-K7106, and the bending stiffness (MPa) was determined.

[Examples 2 to 4, Comparative Examples 1 to 4]
Single layer sheets for the (A) layer and the (B) layer were prepared in the same manner as in Example 1 except that the ionomer or polymer in the layer (A) in Example 1 was changed according to Tables 1 and 2. After preparing samples for evaluation, various evaluations were performed. Tables 1 and 2 show the evaluation results.

As is clear from Tables 1 and 2, the solar cell encapsulants of Examples have both transparency (high total light transmittance, low haze) and adhesiveness as compared with the solar cell encapsulants of Comparative Examples. While having excellent strength.
In addition, if such a sheet for a solar cell encapsulant having both transparency and heat shrink resistance is applied to the production of a solar cell module, a solar cell module with excellent durability and more stable cell performance can be obtained. Is expected.

DESCRIPTION OF SYMBOLS 1 Upper transparent protective material 2 Solar cell sealing material 2A (A) layer 2B, 2b (B) layer 3 Cell 4 Wiring material 5 Lower protective material 6 End face sealing material 7 Metal frame 10 Solar cell module 12 n-type silicon 14 p-type silicon 16 first electrode 18 second electrode

Claims (4)

Including an ionomer of an ethylene / α, β-unsaturated carboxylic acid copolymer and a silane coupling agent, α, β-unsaturation in 100% by mass of the ethylene / α, β-unsaturated carboxylic acid copolymer the content of constituent units derived from a carboxylic acid is 3 or less mass% to 25 mass% (a) layer and, et styrene · alpha, including magnesium ionomer β- unsaturated carboxylic acid copolymer (B) layer And having
The ionomer contained in the (A) layer, Ri magnesium ionomer der,
The ethylene / α, β-unsaturated carboxylic acid copolymer of the layer (A) is a terpolymer of ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester. Yes,
The content ratio of the structural unit derived from ethylene in 100% by mass of the terpolymer of the ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester in the layer (A) is 60%. At least 94% by mass,
Structure derived from α, β-unsaturated carboxylic acid in 100% by mass of terpolymer of ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester in layer (A) The content ratio of the unit is 3% by mass or more and 25% by mass or less,
It is derived from the α, β-unsaturated carboxylic acid ester in 100% by mass of the terpolymer of the ethylene / α, β-unsaturated carboxylic acid / α, β-unsaturated carboxylic acid ester in the layer (A). The content ratio of the constituent unit to be used is 3% by mass or more and 20% by mass or less,
The degree of neutralization of the magnesium ionomer in the layer (A) is 20 mol% or more and 65 mol% or less;
The content ratio of the structural unit derived from ethylene in 100% by mass of the ethylene / α, β-unsaturated carboxylic acid-based copolymer in the layer (B) is 75% by mass or more and 95% by mass or less,
In the (B) layer, the content of the structural unit derived from the α, β-unsaturated carboxylic acid in 100% by mass of the ethylene / α, β-unsaturated carboxylic acid-based copolymer is from 5% by mass to 25% by mass. % Or less,
The degree of neutralization of the magnesium ionomer in the layer (B) is 40 mol% or more and 60 mol% or less;
The sealing material for solar cells , wherein the layer (B) does not contain a silane coupling agent .   The encapsulant for solar cells according to claim 1, wherein the ratio of the thickness ((A) / (B)) in the (A) layer and the (B) layer is 1/2 or less. The front Symbol ethylene · alpha in the layer (A), beta-unsaturated carboxylic acid · alpha, beta-unsaturated carboxylic acid ester copolymer 100 wt% alpha, beta-unsaturated carboxylic acid ester derived constituent units of 3. The encapsulant for a solar cell according to claim 1, wherein the content ratio is 5% by mass to 14% by mass. Solar cell module with a sealing material for a solar cell according to any one of claims 1 to 3.