JP2011049532A - Encapsulating material for solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an encapsulating material for a solar cell that neither deteriorates nor changes in properties even when used while exposed to light for a long period. <P>SOLUTION: The encapsulating material for the solar cell contains a phosphite ester compound and a thermoplastic polymer that contains a structural unit derived from ethylene. The phosphite ester compound is represented by formula (I) [where R<SP>1</SP>, R<SP>2</SP>, R<SP>4</SP>and R<SP>5</SP>are each independently a hydrogen atom, an alkyl group with C1-8 or the like, R<SP>3</SP>is independently an hydrogen atom or alkyl group with C1-8, X is a single bond, a sulfur atom or the like, A is an alkylene group with C2-8 or the like, and one of Y, Z is a hydroxy group, an alkyl group with C1-8, alkoxy group with C1-8 or aralkyl oxy group with C7-12, the other is a hydrogen atom or alkyl group with C1-8]. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  As a sealing material for solar cells, an ethylene / vinyl acetate copolymer is commercially available and processed into a sheet shape (Non-Patent Documents 1 and 2).

Expansion of solar cell encapsulating sheet manufacturing equipment (June 7, 2005) [Search June 30, 2009] <URL: http://jp.mitsuichem.com/release/2005/pdf/050607.pdf > Fuji Keizai Co., Ltd. “Solar cell-related technologies and market status and future prospects” (July 11, 2008) 169-172

  A solar cell encapsulant is required to have little deterioration and deterioration even when used for a long period of time by exposure to light.

〔式中、Ｒ^１、Ｒ^２、Ｒ^４およびＲ^５は、それぞれ独立に水素原子、炭素数１〜８のアルキル基、炭素数５〜８のシクロアルキル基、炭素数６〜１２のアルキルシクロアルキル基、炭素数７〜１２のアラルキル基またはフェニル基を表し、Ｒ^３はそれぞれ独立に水素原子または炭素数１〜８のアルキル基を表し、Ｘは単結合、硫黄原子または式（Ｉ−１）

（式中、Ｒ^６は水素原子、炭素数１〜８のアルキル基または炭素数５〜８のシクロアルキル基を示す。）で示される２価の基を表し、Ａは炭素数２〜８のアルキレン基または式（Ｉ−２）

（式中、Ｒ^７は単結合または炭素数１〜８のアルキレン基を表し、＊は酸素原子側に結合していることを表す。）で示される２価の基を表し、Ｙ、Ｚはいずれか一方がヒドロキシ基、炭素数１〜８のアルキル基、炭素数１〜８のアルコキシ基または炭素数７〜１２のアラルキルオキシ基を表し、他方が水素原子または炭素数１〜８のアルキル基を表す。〕
で示される亜リン酸エステル化合物とを含有することを特徴とする太陽電池用封止材；
＜２＞ 熱可塑性ポリマー１００重量部に対し、式（Ｉ）で表される亜リン酸エステル化合物を０．００１重量部〜５重量部含有することを特徴とする＜１＞記載の太陽電池用封止材；
＜３＞ 式（Ｉ）で表される亜リン酸エステル化合物が、６−［３−（３−ｔ−ブチル−４−ヒドロキシ−５−メチルフェニル）プロポキシ］−２，４，８，１０−テトラ−ｔ−ブチルジベンズ［ｄ，ｆ］［１，３，２］ジオキサホスフェピンであることを特徴とする＜１＞または＜２＞記載の太陽電池用封止材； Under such circumstances, as a result of intensive studies, the present inventors have reached the inventions described in the following <1> to <14>. That is, the present invention
<1> a thermoplastic polymer containing a structural unit derived from ethylene, and formula (I)

^{Wherein, R 1, R 2, R} 4 and ^{R 5} each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, cycloalkyl group having 5 to 8 carbon atoms, alkylcycloalkyl having 6 to 12 carbon atoms An alkyl group, an aralkyl group having 7 to 12 carbon atoms, or a phenyl group, each R ³ independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and X is a single bond, a sulfur atom, or a formula (I-1 )

(Wherein R ⁶ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms), and A represents a group having 2 to 8 carbon atoms. Alkylene group or formula (I-2)

(Wherein R ⁷ represents a single bond or an alkylene group having 1 to 8 carbon atoms, * represents that it is bonded to the oxygen atom side), and Y and Z represent Either one represents a hydroxy group, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms or an aralkyloxy group having 7 to 12 carbon atoms, and the other is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Represents. ]
And a phosphite compound represented by the formula:
<2> 0.001 part by weight to 5 parts by weight of the phosphite compound represented by the formula (I) is contained with respect to 100 parts by weight of the thermoplastic polymer. Sealing material;
<3> The phosphite compound represented by formula (I) is 6- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10- <1> or <2> solar cell encapsulant according to <1>, which is tetra-t-butyldibenz [d, f] [1,3,2] dioxaphosphine;

（式中、Ｒ^８は、水素原子、炭素数１〜２０のアルキル基または炭素数１〜２０のアルコキシ基を表し、Ｙは酸素原子または窒素原子を表す。）
で示される部分構造を有するピペリジン系化合物を含有することを特徴とする＜１＞〜＜３＞のいずれか記載の太陽電池用封止材；
＜５＞ 前記式（II’）で表される部分構造を有するピペリジン系化合物が、式（II）

〔式中、Ｒ^８は、それぞれ独立に、水素原子、炭素数１〜２０のアルキル基または炭素数１〜２０のアルコキシ基を表し、Ａは、炭素数１〜１０のアルキレン基または式（III）

（式中、Ｒ^８は、それぞれ独立に、水素原子、炭素数１〜２０のアルキル基または炭素数１〜２０のアルコキシ基を表す。）で表される２価の基を表す。〕
で示されるピペリジン系化合物であることを特徴とする＜４＞記載の太陽電池用封止材；
＜６＞ 太陽電池用封止材が、さらに、紫外線吸収剤を含有することを特徴とする＜１＞〜＜５＞のいずれか記載の太陽電池用封止材；
＜７＞ 太陽電池用封止材が、さらに、架橋剤を含有することを特徴とする＜１＞〜＜６＞のいずれか記載の太陽電池用封止材；
＜８＞ 架橋剤が、有機過酸化物であることを特徴とする＜７＞記載の太陽電池用封止材；
＜９＞ 太陽電池用封止材が、さらに、架橋助剤を含有することを特徴とする＜７＞又は＜８＞記載の太陽電池用封止材；
＜１０＞太陽電池用封止材が、さらに、シランカップリング剤を含有することを特徴とする＜１＞〜＜６＞のいずれか記載の太陽電池用封止材；
＜１１＞ 熱可塑性ポリマーが、エチレンに由来する構造単位および酢酸ビニルに由来する構造単位を含有する重合体であることを特徴とする＜１＞〜＜１０＞のいずれか記載の太陽電池用封止材； <4> The solar cell encapsulant further comprises the formula (II ′)

(Wherein R ⁸ represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms, and Y represents an oxygen atom or a nitrogen atom.)
A sealing compound for solar cells according to any one of <1> to <3>, comprising a piperidine-based compound having a partial structure represented by the formula:
<5> A piperidine compound having a partial structure represented by the formula (II ′) is represented by the formula (II)

[Wherein, R ⁸ independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms or an alkoxy group having 1 to 20 carbon atoms, and A represents an alkylene group having 1 to 10 carbon atoms or a compound represented by formula (III )

(In the formula, each R ⁸ independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms). ]
<4> The solar cell encapsulant according to <4>, which is a piperidine compound represented by the formula:
<6> The solar cell sealing material according to any one of <1> to <5>, wherein the solar cell sealing material further contains an ultraviolet absorber;
<7> The solar cell sealing material according to any one of <1> to <6>, wherein the solar cell sealing material further contains a crosslinking agent;
<8> The solar cell encapsulant according to <7>, wherein the crosslinking agent is an organic peroxide;
<9> The solar cell sealing material according to <7> or <8>, wherein the solar cell sealing material further contains a crosslinking aid;
<10> The solar cell sealing material according to any one of <1> to <6>, wherein the solar cell sealing material further contains a silane coupling agent;
<11> The sealing for solar cells according to any one of <1> to <10>, wherein the thermoplastic polymer is a polymer containing a structural unit derived from ethylene and a structural unit derived from vinyl acetate. Stopping material;

〔式中、Ｒ^１、Ｒ^２、Ｒ^４およびＲ^５は、それぞれ独立に水素原子、炭素数１〜８のアルキル基、炭素数５〜８のシクロアルキル基、炭素数６〜１２のアルキルシクロアルキル基、炭素数７〜１２のアラルキル基またはフェニル基を表し、Ｒ^３はそれぞれ独立に水素原子または炭素数１〜８のアルキル基を表し、Ｘは単結合、硫黄原子または式（Ｉ−１）

（式中、Ｒ^６は水素原子、炭素数１〜８のアルキル基または炭素数５〜８のシクロアルキル基を示す。）で示される２価の基を表し、Ａは炭素数２〜８のアルキレン基または式（Ｉ−２）

（式中、Ｒ^７は単結合または炭素数１〜８のアルキレン基を表し、＊は酸素原子側に結合していることを表す。）で示される２価の基を表し、Ｙ、Ｚはいずれか一方がヒドロキシ基、炭素数１〜８のアルキル基、炭素数１〜８のアルコキシ基または炭素数７〜１２のアラルキルオキシ基を表し、他方が水素原子または炭素数１〜８のアルキル基を表す。〕
で示される亜リン酸エステル化合物の使用； <12> Formula (I) for improving the durability of the solar cell encapsulant

^{Wherein, R 1, R 2, R} 4 and ^{R 5} each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, cycloalkyl group having 5 to 8 carbon atoms, alkylcycloalkyl having 6 to 12 carbon atoms An alkyl group, an aralkyl group having 7 to 12 carbon atoms, or a phenyl group, each R ³ independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and X is a single bond, a sulfur atom, or a formula (I-1 )

(Wherein R ⁶ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms), and A represents a group having 2 to 8 carbon atoms. Alkylene group or formula (I-2)

(Wherein R ⁷ represents a single bond or an alkylene group having 1 to 8 carbon atoms, * represents that it is bonded to the oxygen atom side), and Y and Z represent Either one represents a hydroxy group, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms or an aralkyloxy group having 7 to 12 carbon atoms, and the other is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Represents. ]
Use of a phosphite compound represented by:

<13> A step of heat-molding the solar cell encapsulant according to any one of <1> to <11> to obtain a sheet-shaped molded product, and the obtained sheet-shaped molded product as a solar cell. A method for sealing a solar battery cell comprising a step of bonding to both sides or one side of the solar cell;

<14> A molded product obtained by thermoforming the solar cell sealing material according to any one of <1> to <11>;
Etc.

  The solar cell encapsulant of the present invention is less deteriorated and deteriorated even if it is exposed to light over a long period of time.

Hereinafter, the present invention will be described in detail.
In the present invention, the term “durability” means a property that hardly deteriorates or deteriorates even when exposed to light over a long period of time, and “improves the durability” refers to the phosphorous represented by the above formula (I). By using an acid ester compound (hereinafter sometimes referred to as compound (I)), for example, it is possible to suppress a decrease in light transmittance as described later.

  Generally, a solar cell has a configuration in which solar cell cells such as silicon crystals are sealed with a sealing material between a glass substrate as a front surface side protective member and a back sheet as a back surface side protective member. . The sealing material for solar cells of the present invention can be used as a sealing material on the front surface side of this cell or a sealing material on the back surface side. Moreover, it can also be used as a member constituting the back sheet.

  The sealing material for solar cells of the present invention includes a thermoplastic polymer containing a structural unit derived from ethylene (hereinafter sometimes referred to as an ethylene polymer). Examples of the ethylene-based polymer include structural units derived from ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, Structural units derived from α-olefins having 3 or more carbon atoms, such as 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nanodecene, 1-eicocene A copolymer comprising a structural unit derived from ethylene and a structural unit derived from an epoxy group-containing monomer such as glycidyl methacrylate; a structural unit derived from ethylene and an α, β-unsaturated carboxylic acid A copolymer comprising structural units derived from acids; structural units derived from ethylene and / or propylene; and vinyl acetate. , Vinyl propionate, vinyl butyrate, copolymer containing a structural unit derived from vinyl esters of carboxylic acids having 2 to 5 carbon atoms vinyl versatate and the like; and the like.

  Examples of the α, β-unsaturated carboxylic acids include α, β-unsaturated carboxylic acids such as acrylic acid and methacrylic acid; and the sodium salts, potassium salts, and calcium salts of the α, β-unsaturated carboxylic acids. α, β-unsaturated carboxylic acid metal salts; unsaturated carboxylic acid anhydrides such as maleic anhydride, itaconic anhydride, citraconic anhydride, nadic acid anhydride, methyl nadic acid anhydride, and hymic anhydride; methyl acrylate, acrylic acid Ethyl, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-methacrylate Acrylic acid such as butyl, t-butyl methacrylate, isobutyl methacrylate, etc. And esters of tacrylic acid and alkyl having 1 to 12 carbon atoms.

  Specific examples of the ethylene polymer include linear low density polyethylene (including LLDPE, structural units derived from 1-butene), ethylene / propylene rubber (EPR) and other structural units derived from ethylene and 3 or more carbon atoms. A copolymer containing a structural unit derived from an α-olefin; a copolymer comprising a structural unit derived from ethylene such as a copolymer of ethylene and glycidyl methacrylate and a structural unit derived from an epoxy group-containing monomer Combined; including structural units derived from ethylene such as ethylene / methyl methacrylate copolymer (EMA), ethylene / ethyl acrylate copolymer (EEA), and structural units derived from α, β-unsaturated carboxylic acid ester Copolymer; Structural units derived from ethylene such as ethylene vinyl acetate copolymer (EVA) and vinyl carboxylate A copolymer containing a structural unit derived from steal; a copolymer of ethylene and an unsaturated carboxylic anhydride such as an ethylene / maleic anhydride copolymer; an ethylene / acrylic acid copolymer (EAA), an ethylene / maleic anhydride copolymer; A copolymer comprising a structural unit derived from ethylene such as a methacrylic acid copolymer (EMMA) and a structural unit derived from an unsaturated carboxylic acid; a resin in which molecules of the ethylene-methacrylic acid copolymer are crosslinked with metal ions A copolymer containing a structural unit derived from ethylene and a structural unit derived from an unsaturated carboxylic acid, such as an ionomer resin, containing a metal salt;

  Preferred ethylene polymers include copolymers containing structural units derived from ethylene and structural units derived from α, β-unsaturated carboxylic acid esters, structural units derived from ethylene, and vinyl esters of carboxylic acids. And a copolymer containing a structural unit derived from ethylene and a structural unit derived from a vinyl ester of a carboxylic acid, more preferably ethylene. And a copolymer containing a structural unit derived from the above and a structural unit derived from vinyl acetate.

  As content of the structural unit derived from ethylene in an ethylene-type polymer, the range of 50 to 95 weight% is preferable, and the range of 55 to 90 weight% is more preferable.

  The melt flow rate (MFR) of the ethylene-based polymer is preferably in the range of 4 to 100 g / 10 minutes, more preferably in the range of 5 to 50 g / 10 minutes, further preferably in the range of 6 to 20 g / 10 minutes, A range of 10 g / 10 min is particularly preferred. The MFR is measured by the A method according to JIS K7210-1995 under conditions of a temperature of 190 ° C. and a load of 21.18N.

  The ethylene polymer is preferably a block polymer or a random polymer of a structural unit derived from ethylene and a structural unit derived from another monomer, and more preferably a random polymer.

  Examples of the method for producing an ethylene polymer include a method of polymerizing ethylene and another monomer by bringing them into contact with each other in the presence of a catalyst such as a radical polymerization catalyst or an ion polymerization catalyst. Examples of the catalyst include a peroxide catalyst, a Ziegler-Natta catalyst, a metallocene catalyst, and the polymerization method includes, for example, a solution polymerization method, a slurry polymerization method, a high pressure ion polymerization method, a high pressure radical polymerization method, and the like. Examples include gas phase polymerization.

  The sealing material for solar cells of this invention contains compound (I).

In the formula (I), examples of the alkyl group having 1 to 8 carbon atoms represented by R ¹ , R ² , R ⁴ and R ⁵ include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, Examples include n-butyl group, i-butyl group, sec-butyl group, t-butyl group, t-pentyl group, i-octyl group, t-octyl group and 2-ethylhexyl group.

  Examples of the cycloalkyl group having 5 to 8 carbon atoms include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. Examples of the alkylcycloalkyl group having 6 to 12 carbon atoms include 1-methylcyclopentyl group, 1-methylcyclohexyl group, and 1-methyl-4-i-propylcyclohexyl group. Examples of the aralkyl group having 7 to 12 carbon atoms include a benzyl group, an α-methylbenzyl group, and an α, α-dimethylbenzyl group.

R ¹ , R ² and R ⁴ are preferably each independently an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms or an alkylcycloalkyl group having 6 to 12 carbon atoms. More preferably, R ¹ and R ⁴ are each independently a t-alkyl group such as a t-butyl group, a t-pentyl group or a t-octyl group, a cyclohexyl group or a 1-methylcyclohexyl group. R ² is independently carbon such as methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, t-butyl group, t-pentyl group, etc. It is preferably a C 1-5 alkyl group, more preferably a methyl group, a t-butyl group or a t-pentyl group. R ⁵ is a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a sec-butyl group, a t-butyl group, a t-pentyl group, etc. 5 is preferably an alkyl group or a hydrogen atom, more preferably a methyl group or a hydrogen atom.

Examples of the alkyl group having 1 to 8 carbon atoms represented by R ³ include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, t -Butyl group, t-pentyl group, i-octyl group, t-octyl group, 2-ethylhexyl group, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i- An alkyl group having 1 to 5 carbon atoms such as a butyl group, a sec-butyl group, a t-butyl group, or a t-pentyl group or a hydrogen atom is preferable, and a methyl group or a hydrogen atom is more preferable.

X represents a single bond, a sulfur atom or a divalent group represented by the formula (I-1). Examples of the alkyl group having 1 to 8 carbon atoms represented by R ⁶ in the formula (I-1) include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, and an i-butyl group. , Sec-butyl group, t-butyl group, t-pentyl group, i-octyl group, t-octyl group and 2-ethylhexyl group. Examples of the cycloalkyl group having 5 to 8 carbon atoms include a cyclopentyl group. , A cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. R ⁶ is preferably a C 1-5 alkyl group such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, or an i-butyl group, or a hydrogen atom. X is preferably a single bond or a divalent group represented by the formula (I-1), and more preferably a single bond.

A represents an alkylene group having 2 to 8 carbon atoms or a divalent group represented by the above formula (I-2), and an alkylene group having 2 to 8 carbon atoms is preferable. Group, propylene group, butylene group, pentamethylene group, hexamethylene group, octamethylene group, 2,2-dimethyl-1,3-propylene group and the like, and propylene group is more preferable. The divalent group represented by the formula (I-2) is bonded to the oxygen atom and the benzene nucleus, but * indicates that it is bonded to the oxygen atom. Examples of the alkylene group having 1 to 8 carbon atoms represented by R ⁷ include methylene group, ethylene group, propylene group, butylene group, pentamethylene group, hexamethylene group, octamethylene group, 2,2-dimethyl-1, A 3-propylene group etc. are mentioned. Such R ⁷ is preferably a single bond or an ethylene group.

  One of Y and Z represents a hydroxy group, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms or an aralkyloxy group having 7 to 12 carbon atoms, and the other is a hydrogen atom or carbon. The alkyl group of number 1-8 is shown. Here, examples of the alkyl group having 1 to 8 carbon atoms include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, and t-butyl. Group, t-pentyl group, i-octyl group, t-octyl group and 2-ethylhexyl group. Examples of the alkoxy group having 1 to 8 carbon atoms include methoxy group, ethoxy group, n-propoxy group, i-propoxy group, n-butoxy group, i-butoxy group, sec-butoxy group, t-butoxy group, t -Pentyloxy group, i-octyloxy group, t-octyloxy group, 2-ethylhexyloxy group may be mentioned. Examples of the aralkyloxy group having 7 to 12 carbon atoms include benzyloxy group, α-methylbenzyloxy group, α, α-dimethylbenzyloxy group.

Among the phosphite compounds represented by the formula (I), R ¹ and R ⁴ are a t-alkyl group, cyclohexyl or 1-methylcyclohexyl group, and R ² is an alkyl group having 1 to 5 carbon atoms. , R ⁵ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ³ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, X is a single bond, and A is 2 to 8 carbon atoms. An alkylene group is particularly preferred.

  In the solar cell encapsulant of the present invention, a single compound may be used as the compound (I), or two or more compounds may be used in combination.

  Examples of the compound (I) include 6- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra-t-butyldibenz [d, f] [1,3,2] Dioxaphosphine [commercially available from Sumitomo Chemical Co., Ltd. as “Sumilyzer (registered trademark) GP”. 2,10-dimethyl-4,8-di-t-butyl-6- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propoxy] -12H-dibenzo [d, g] [1,3,2] dioxaphosphocine, 2,4,8,10-tetra-t-butyl-6- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propoxy] dibenzo [D, f] [1,3,2] dioxaphosphine, 2,4,8,10-tetra-t-pentyl-6- [3- (3,5-di-t-butyl-4- Hydroxyphenyl) propoxy] -12-methyl-12H-dibenzo [d, g] [1,3,2] dioxaphosphocin, 2,10-dimethyl-4,8-di-t-butyl-6- [3 -(3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] -12H Dibenzo [d, g] [1,3,2] dioxaphosphocine, 2,4,8,10-tetra-t-pentyl-6- [3- (3,5-di-t-butyl-4- Hydroxyphenyl) propionyloxy] -12-methyl-12H-dibenzo [d, g] [1,3,2] dioxaphosphocin, 2,4,8,10-tetra-t-butyl-6- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -dibenzo [d, f] [1,3,2] dioxaphosphine, 2,10-dimethyl-4,8-di -T-butyl-6- (3,5-di-t-butyl-4-hydroxybenzoyloxy) -12H-dibenzo [d, g] [1,3,2] dioxaphosphocin, 2,4,8 , 10-Tetra-t-butyl-6- (3,5-di-t-butyl-4- Roxybenzoyloxy] -12-methyl-12H-dibenzo [d, g] [1,3,2] dioxaphosphocin, 2,10-dimethyl-4,8-di-t-butyl-6- [3- (3-Methyl-4-hydroxy-5-t-butylphenyl) propoxy] -12H-dibenzo [d, g] [1,3,2] dioxaphosphocine, 2,4,8,10-tetra-t -Butyl-6- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propoxy] -12H-dibenzo [d, g] [1,3,2] dioxaphosphocine, 2,10 -Diethyl-4,8-di-t-butyl-6- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propoxy] -12H-dibenzo [d, g] [1,3 2] Dioxaphosphocin, 2,4,8,10-tetra-t-butyl Ru-6- [2,2-dimethyl-3- (3-t-butyl-4-hydroxy-5-methylphenyl) propoxy] -dibenzo [d, f] [1,3,2] dioxaphosphine 6- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra-t-butyldibenz [d, f] [1, 3,2] Dioxaphosphepine is most preferred.

  Such compound (I) can be produced, for example, by the method described in JP-A-10-273494.

  The sealing material for solar cells of the present invention is preferably 0.001 to 5 parts by weight, more preferably 0.01 to 3 parts by weight, further preferably 100 parts by weight of the ethylene-based polymer. Contains 0.01 to 2 parts by weight, more preferably 0.03 to 0.5 parts by weight. If content of compound (I) is said range, there exists a tendency for the fall of the light transmittance at the time of transmitting light to the sealing material for solar cells obtained is suppressed.

（式中、Ｒ^８は、水素原子、炭素数１〜２０のアルキル基または炭素数１〜２０のアルコキシ基を表し、Ｙは酸素原子または窒素原子を表す。）
で表される部分構造を有するピペリジン系化合物（以下、単に「ピペリジン系化合物」と記すこともある。）を含有することが好ましい。 The sealing material for solar cells of the present invention further comprises formula (II ′)

(Wherein R ⁸ represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms, and Y represents an oxygen atom or a nitrogen atom.)
It is preferable to contain a piperidine compound having a partial structure represented by the formula (hereinafter, simply referred to as “piperidine compound”).

R ⁸ in the formula (II ′) is, for example, a hydrogen atom, methyl group, ethyl group, isopropyl group, n-propyl group, t-butyl group, isobutyl group, n-butyl group, methoxy group, ethoxy group, iso Examples thereof include a propoxy group, an n-propoxy group, a t-butoxy group, an isobutoxy group, and an n-butoxy group. A hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an alkoxy group having 1 to 10 carbon atoms is preferable, and a hydrogen atom is more preferable.

〔式中、Ｒ^８は、それぞれ独立に、水素原子、炭素数１〜２０のアルキル基または炭素数１〜２０のアルコキシ基を表し、Ａは、炭素数１〜１０のアルキレン基または式（III）

（式中、Ｒ^８は、それぞれ独立に、水素原子、炭素数１〜２０のアルキル基または炭素数１〜２０のアルコキシ基を表す。）で表される２価の基を表す。〕
で示されるピペリジン系化合物（以下、化合物（II）と記すこともある。）； Examples of piperidine compounds include the formula (II)

[Wherein, R ⁸ independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms or an alkoxy group having 1 to 20 carbon atoms, and A represents an alkylene group having 1 to 10 carbon atoms or a compound represented by formula (III )

(In the formula, each R ⁸ independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms). ]
A piperidine-based compound represented by formula (hereinafter also referred to as compound (II));

Bis (1,2,2,6,6-pentamethyl-4-piperidinyl) 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-butylmalonate, bis (1-acryloyl-2) , 2,6,6-tetramethyl-4-piperidinyl) 2,2-bis (3,5-di-t-butyl-4-hydroxybenzyl) -2-butylmalonate;
For example, 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, 4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -1- [2- (3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy) ethyl] -2,2,6,6-tetramethylpiperidine, 2-methyl-2- (2,2,6,6- Tetramethyl-4-piperidinyl) amino-N- (2,2,6,6-tetramethyl-4-piperidinyl) propionamide;

Tetrakis (1,2,2,6,6-pentamethyl-4-piperidinyl) -1,2,3,4-butanetetracarboxylate, 1,2,3,4-butanetetracarboxylic acid and 1,2,2 , 6,6-pentamethyl-4-piperidinol and 1-tridecanol esterified products, 1,2,3,4-butanetetracarboxylic acid and 2,2,6,6-tetramethyl-4-piperidinol and 1- Mixed esterified product with tridecanol, 1,2,3,4-butanetetracarboxylic acid and 1,2,2,6,6-pentamethyl-4-piperidinol and 3,9-bis (2-hydroxy-1,1- Dimethylethyl) -2,4,8,10-tetraoxaspiro [5 · 5] undecane, 1,2,3,4-butanetetracarboxylic acid and 2,2,6 Mixed esterified product of 6-tetramethyl-4-piperidinol and 3,9-bis (2-hydroxy-1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane, Polycondensate of dimethyl succinate and 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine, poly [(6-morpholino-1,3,5-triazine-2, 4-diyl) ((2,2,6,6-tetramethyl-4-piperidinyl) imino) hexamethylene ((2,2,6,6-tetramethyl-4-piperidinyl) imino)], poly [(6 -(1,1,3,3-tetramethylbutyl) -1,3,5-triazine-2,4-diyl) ((2,2,6,6-tetramethyl-4-piperidinyl) imino) hexamethylene ((2,2,6,6-tetramethyl-4-piperidinyl) imino)];

Poly [{6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidinyl) ) Imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidinyl) imino}], dimethyl-1- (2-hydroxyethyl) succinate-4-hydroxy-2,2,6,6- Tetramethylpiperidine polycondensate;
Etc.

  A single compound may be used as the piperidine-based compound, or two or more compounds may be used in combination. As the piperidine compound, compound (II) is preferable.

  Examples of the compound (II) include bis (2,2,6,6-tetramethyl-4-piperidinyl sebacate, bis (N-octoxy-2,2,6,6-tetramethyl-4-piperidinyl sebacate) ), Bis (N-benzyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis (N-cyclohexyloxy-2,2,6,6-tetramethyl-4-piperidinyl sebacate) ), Bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis (1-ethyl-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis sebacate (1-n-butyl-2,2,6,6-tetramethyl-4-piperidinyl), bis (1-octyl-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, Bis (1-ethoxy-2,2,6,6-tetramethyl-4-piperidinyl) succinate, bis (1-n-butoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, Piperidine compounds containing sebacic acid such as bis (1- (octyloxy) -2,2,6,6-tetramethyl-4-piperidinyl) sebacate;

Bis (1,2,2,6,6-pentamethyl-4-piperidinyl) adipate, bis (1-ethyl-2,2,6,6-tetramethyl-4-piperidinyl) adipate, bis (1 -N-butyl-2,2,6,6-tetramethyl-4-piperidinyl), bis (1-octyl-2,2,6,6-tetramethyl-4-piperidinyl), bis (1) adipate (1 -Ethoxy-2,2,6,6-tetramethyl-4-piperidinyl), bis (1-n-butoxy-2,2,6,6-tetramethyl-4-piperidinyl), bis (1) adipate Piperidine compounds containing adipic acid such as-(octyloxy) -2,2,6,6-tetramethyl-4-piperidinyl);
Bis succinate (1,2,2,6,6-pentamethyl-4-piperidinyl), bis succinate (1-ethyl-2,2,6,6-tetramethyl-4-piperidinyl), bis succinate (1 -N-butyl-2,2,6,6-tetramethyl-4-piperidinyl), bis succinate (1-octyl-2,2,6,6-tetramethyl-4-piperidinyl), bis succinate (1 -Succinic acid such as ethoxy-2,2,6,6-tetramethyl-4-piperidinyl) and bis (1-n-butoxy-2,2,6,6-tetramethyl-4-piperidinyl) succinate Piperidine compounds;
1,2,3,4-butanetetracarboxylic acid tetrakis (1,2,2,6,6-pentamethyl-4-piperidinyl), 1,2,3,4-butanetetracarboxylic acid tetrakis (1-ethyl-2) , 2,6,6-tetramethyl-4-piperidinyl), 1,2,3,4-butanetetracarboxylic acid tetrakis (1-n-butyl-2,2,6,6-tetramethyl-4-piperidinyl) 1,2,3,4-butanetetracarboxylic acid tetrakis (1-octyl-2,2,6,6-tetramethyl-4-piperidinyl), 1,2,3,4-butanetetracarboxylic acid tetrakis (1 -Methoxy-2,2,6,6-tetramethyl-4-piperidinyl), 1,2,3,4-butanetetracarboxylic acid tetrakis (1-ethoxy-2,2,6,6-tetramethyl-4- Piperidi L), 1,2,3,4-butanetetracarboxylic acid tetrakis (1-n-butoxy-2,2,6,6-tetramethyl-4-piperidinyl), 1,2,3,4-butanetetracarboxylic Piperidine compounds containing 1,2,3,4-butanetetracarboxylic acid such as tetrakis acid (1- (octyloxy) -2,2,6,6-tetramethyl-4-piperidinyl);
Etc.

  Piperidine compounds containing sebacic acid, piperidine compounds containing succinic acid and piperidine compounds containing 1,2,3,4-butanetetracarboxylic acid are preferred, and bis (1,2,2,6,6-sebacate) is preferred. Pentamethyl-4-piperidinyl), bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and sebacic acid (methyl-1,2,2,6,6-pentamethyl-4-piperidinyl) , Sebacate (methyl-4-piperidinyl), bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis [1- (octyloxy) -2,2,6, sebacate 6-tetramethyl-4-piperidinyl] and bis (1,2,2,6,6-pentamethyl-4-piperidinyl) succinate are more preferable, and sebacic acid (1,2,2,6,6-pentamethyl-4-piperidinyl), bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and sebacic acid (methyl-1,2,2) , 6,6-pentamethyl-4-piperidinyl), bis (1,2,2,6,6-pentamethyl-4-piperidinyl) succinate, and bis (2,2,6,6-tetra sebacate) More preferred is methyl-4-piperidinyl). Bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and sebacic acid (methyl-1,2) , 2,6,6-pentamethyl-4-piperidinyl), bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate is even more preferred.

  When the solar cell encapsulant of the present invention contains a piperidine compound, the content thereof is preferably 0.001 to 5 parts by weight, and 0.05 to 3 parts by weight with respect to 100 parts by weight of the ethylene polymer. Is more preferable, and 0.01 to 2 parts by weight is even more preferable. In addition to the compound (I), if a piperidine compound is further contained in the ethylene polymer within the above range, a decrease in light transmittance when light is transmitted through the resulting solar cell encapsulant is further suppressed. Tend to be.

（式中、Ｒ^９〜Ｒ^１４は、それぞれ独立に水素原子、ハロゲン原子、ヒドロキシ基、炭素数１〜１０のアルキル基または炭素数１〜１０のアルコキシ基を表す。Ｒ^１５は、水素原子、メチル基またはエチル基を表す。）
で示されるシュウ酸ジアニリド系紫外線吸収剤； The solar cell sealing material may further contain an ultraviolet absorber.
As an ultraviolet absorber, for example, the formula (IV)

(Wherein R ^{9 to} R ¹⁴ each independently represents a hydrogen atom, a halogen atom, a hydroxy group, an alkyl group having 1 to 10 carbon atoms or an alkoxy group having 1 to 10 carbon atoms. R ¹⁵ represents a hydrogen atom, Represents a methyl group or an ethyl group.)
An oxalic acid dianilide ultraviolet absorber represented by:

（式中、Ｒ_１６、Ｒ_１７及びＲ_１８は、それぞれ独立に、水素原子、ハロゲン原子、水酸基、炭素数１〜１０のアルキル基、フェニル基、ベンジル基、カルボキシ基、炭素数１〜１０のアルコキシ基、炭素数１〜１０のヒドロキシアルキル基等を表す。これらアルキル基、フェニル基、ベンジル基、アルコキシ基及びヒドロキシアルキル基の水素原子は、それぞれ炭素数１〜１０のアルキル基で置換されていてもよい。）
で表される化合物（以下、化合物（Ｖ）と記すことがある）等のベンゾフェノン系紫外線吸収剤； Formula (V)

(Wherein R _16, R ₁₇ and R ₁₈ are each independently a hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group having 1 to 10 carbon atoms, a phenyl group, a benzyl group, a carboxy group, or an alkyl group having 1 to 10 carbon atoms. Represents an alkoxy group, a hydroxyalkyl group having 1 to 10 carbon atoms, etc. The hydrogen atoms of these alkyl group, phenyl group, benzyl group, alkoxy group and hydroxyalkyl group are each substituted with an alkyl group having 1 to 10 carbon atoms. May be.)
A benzophenone-based ultraviolet absorber, such as a compound represented by formula (hereinafter sometimes referred to as compound (V));

（式中、Ｒ^１９は、水素原子またはハロゲン原子を表す。）
で示される部分構造を有するベンゾトリアゾール系紫外線吸収剤； Formula (VI)

(In the formula, R ¹⁹ represents a hydrogen atom or a halogen atom.)
A benzotriazole ultraviolet absorber having a partial structure represented by:

（式中、Ｒ_２０は、水酸基を表し、Ｒ_２１は、水酸基、炭素数１〜１０のアルコキシ基又は炭素数１〜１０のヒドロキシアルキル基を表し、Ｒ_２２〜Ｒ_２３は、それぞれ独立に、水素原子、ハロゲン原子、水酸基、炭素数１〜１０のアルキル基、フェニル基、ベンジル基、炭素数１〜１０のアルコキシ基、炭素数１〜１０のヒドロキシアルキル基等を表す。アルキル基、フェニル基、ベンジル基、アルコキシ基及びヒドロキシアルキル基の水素原子は炭素数１〜１０のアルキル基で置換されていてもよい。）
で表される化合物（以下、化合物（VII）と記すことがある）等のトリアジン系紫外線吸収剤；
で示されるトリアジン系紫外線吸収剤； Formula (VII)

(In the formula, R ₂₀ represents a hydroxyl group, R ₂₁ represents a hydroxyl group, an alkoxy group having 1 to 10 carbon atoms, or a hydroxyalkyl group having 1 to 10 carbon atoms, and R _{22 to} R ₂₃ each independently represents: A hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group having 1 to 10 carbon atoms, a phenyl group, a benzyl group, an alkoxy group having 1 to 10 carbon atoms, a hydroxyalkyl group having 1 to 10 carbon atoms, etc. An alkyl group and a phenyl group , A hydrogen atom of a benzyl group, an alkoxy group and a hydroxyalkyl group may be substituted with an alkyl group having 1 to 10 carbon atoms.)
A triazine-based ultraviolet absorber such as a compound represented by formula (hereinafter sometimes referred to as compound (VII));
A triazine-based ultraviolet absorber represented by:

Salicylic acid ultraviolet absorbers; cyanoacrylate ultraviolet absorbers; and the like.

  Specific examples of the oxalic acid dianilide ultraviolet absorber include N- (2-methylphenyl) -N ′-(2-methoxyphenyl) oxalic acid diamide, N- (2-ethylphenyl) -N ′-(2- Ethoxyphenyl) oxalic acid diamide, N- (2-t-butylphenyl) -N ′-(2-t-butoxyphenyl) oxalic acid diamide, N- (5-t-butyl-2-methoxyphenyl) -N ′ -(4-t-butyl-2-methylphenyl) oxalic acid diamide, N- (5-t-butyl-2-ethoxyphenyl) -N '-(4-t-butyl-2-ethylphenyl) oxalic acid diamide N- (5-t-butyl-2-t-butoxyphenyl) -N ′-(2,4-di-t-butylphenyl) oxalic acid diamide, N, N′-bis (2-methylphenyl) sulfur Acid diamide, N N′-bis (2-ethylphenyl) oxalic acid diamide, N, N′-bis (2-tert-butyltylphenyl) oxalic acid diamide, N, N′-bis (2-methoxyphenyl) oxalic acid diamide, N , N′-bis (2-ethoxyphenyl) oxalic acid diamide, N, N′-bis (2-t-butoxyphenyl) oxalic acid diamide, and the like, and N- (2-ethylphenyl) -N ′-( 2-Ethoxyphenyl) oxalic acid diamide and N- (5-t-butyl-2-ethoxyphenyl) -N ′-(4-t-butyl-2-ethylphenyl) oxalic acid diamide are preferred.

  Specific examples of the benzophenone ultraviolet absorber include 2,2′-dihydroxy-4,4′-di (hydroxymethyl) benzophenone and 2,2′-dihydroxy-4,4′-di (2-hydroxyethyl) benzophenone. 2,2′-dihydroxy-3,3′-dimethoxy-5,5′-di (hydroxymethyl) benzophenone, 2,2′-dihydroxy-3,3′-dimethoxy-5,5′-di (2- Hydroxyethyl) benzophenone, 2,2′-dihydroxy-3,3′-di (hydroxymethyl) -5,5′-dimethoxybenzophenone, 2,2′-dihydroxy-3,3′-di (2-hydroxyethyl) -5,5'-dimethoxybenzophenone, 2,2-dihydroxy-4,4-dimethoxybenzophenone, 2-hydroxy-4-n-octyl Xylbenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2′-carboxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2-hydroxy-4-n-octadecyloxybenzophenone, Examples include 2-hydroxy-4-benzyloxybenzophenone and 2-hydroxy-5-chlorobenzophenone.

  Specific examples of the benzotriazole ultraviolet absorber include 2- [2′-hydroxy-5 ′-(hydroxymethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′-(2-hydroxy). Ethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′-(3-hydroxypropyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-3′-methyl-5 ′ -(Hydroxymethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-methyl-5 '-(2-hydroxyethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy -3'-methyl-5 '-(3-hydroxypropyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3 -T-butyl-5 '-(hydroxymethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-t-butyl-5'-(2-hydroxyethyl) phenyl] -2H-benzo Triazole, 2- [2′-hydroxy-3′-t-butyl-5 ′-(2-hydroxyethyl) phenyl] -5-chloro-2H-benzotriazole, 2- [2′-hydroxy-3′-t -Butyl-5 '-(3-hydroxypropyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-t-octyl-5'-(hydroxymethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-3′-t-octyl-5 ′-(2-hydroxyethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy 3′-t-octyl-5 ′-(3-hydroxypropyl) phenyl] -2H-benzotriazole or the like, or 2,2′-methylenebis [6- (2H-benzotriazoly-2-yl) -4- (hydroxymethyl) ) Phenol], 2,2'-methylenebis [6- (2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol], 2,2'-methylenebis [6- (5-chloro-2H- Benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol], 2,2′-methylenebis [6- (5-bromo-2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol 2,2′-methylenebis [6- (2H-benzotriazoly-2-yl) -4- (3-hydroxypropyl) phenol], 2, 2'-methylenebis [6- (5-chloro-2H-benzotriazoly-2-yl) -4- (3-hydroxypropyl) phenol], 2,2'-methylenebis [6- (5-bromo-2H-benzotriazoly- 2-yl) -4- (3-hydroxypropyl) phenol], 2,2′-methylenebis [6- (2H-benzotriazoly-2-yl) -4- (4-hydroxybutyl) phenol], 2,2 ′ -Methylenebis [6- (5-chloro-2H-benzotriazoly-2-yl) -4- (4-hydroxybutyl) phenol], 2,2'-methylenebis [6- (5-bromo-2H-benzotriazoly-2- Yl) -4- (4-hydroxybutyl) phenol], 3,3- {2,2′-bis [6- (2H-benzotriazoly-2-yl) -1-hydro Ci-4- (2-hydroxyethyl) phenyl]} propane, 2,2- {2,2′-bis [6- (2H-benzotriazoly-2-yl) -1-hydroxy-4- (2-hydroxyethyl) ) Phenyl]} butane, 2,2′-oxybis [6- (2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol], 2,2′-bis [6- (2H-benzotriazolyl) 2-yl) -4- (2-hydroxyethyl) phenol] sulfide, 2,2′-bis [6- (2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol] sulfoxide, 2, 2′-bis [6- (2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol] sulfone, 2,2′-bis [6- (2H-benzotriazo 2-yl) -4- (2-hydroxyethyl) phenol] amine.

  Specific examples of the triazine ultraviolet absorber include 2- (2-hydroxy-4-hydroxymethylphenyl) -4,6-diphenyl-s-triazine, 2- (2-hydroxy-4-hydroxymethylphenyl) -4. , 6-Bis (2,4-dimethylphenyl) -s-triazine, 2- [2-hydroxy-4- (2-hydroxyethyl) phenyl] -4,6-diphenyl-s-triazine, 2- [2- Hydroxy-4- (2-hydroxyethyl) phenyl] -4,6-bis (2,4-dimethylphenyl) -s-triazine, 2- [2-hydroxy-4- (2-hydroxyethoxy) phenyl] -4 , 6-Diphenyl-s-triazine, 2- [2-hydroxy-4- (2-hydroxyethoxy) phenyl] -4,6-bis (2,4-dimethylphenyl) s-triazine, 2- [2-hydroxy-4- (3-hydroxypropyl) phenyl] -4,6-diphenyl-s-triazine, 2- [2-hydroxy-4- (3-hydroxypropyl) phenyl]- 4,6-bis (2,4-dimethylphenyl) -s-triazine, 2- [2-hydroxy-4- (3-hydroxypropoxy) phenyl] -4,6-diphenyl-s-triazine, 2- [2 -Hydroxy-4- (3-hydroxypropoxy) phenyl] -4,6-bis (2,4-dimethylphenyl) -s-triazine, 2- [2-hydroxy-4- (4-hydroxybutyl) phenyl]- 4,6-diphenyl-s-triazine, 2- [2-hydroxy-4- (4-hydroxybutyl) phenyl] -4,6-bis (2,4-dimethylphenyl) s-triazine, 2- [2-hydroxy-4- (4-hydroxybutoxy) phenyl] -4,6-diphenyl-s-triazine, 2- [2-hydroxy-4- (4-hydroxybutoxy) phenyl]- 4,6-bis (2,4-dimethylphenyl) -s-triazine, 2- (2-hydroxy-4-hydroxymethylphenyl) -4,6-bis (2-hydroxy-4-methylphenyl) -s- Triazine, 2- [2-hydroxy-4- (2-hydroxyethyl) phenyl] -4,6-bis (2-hydroxy-4-methylphenyl) -s-triazine, 2- [2-hydroxy-4- ( 2-hydroxyethoxy) phenyl] -4,6-bis (2-hydroxy-4-methylphenyl) -s-triazine, 2- [2-hydroxy-4- (3-hydroxyl) (Lopyl) phenyl] -4,6-bis (2-hydroxy-4-methylphenyl) -s-triazine, 2- [2-hydroxy-4- (3-hydroxypropoxy) phenyl] -4,6-bis (2 -Hydroxy-4-methylphenyl) -s-triazine, 2- [4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl] -5- (octyloxy) phenol, 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] -phenol and the like.

  Specific examples of the salicylic acid ultraviolet absorber include phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate, and the like. Specific examples of the cyanoacrylate ultraviolet absorber include 2-ethylhexyl-2-cyano-3,3'-diphenyl acrylate, ethyl-2-cyano-3,3'-diphenyl acrylate, and the like.

  A single compound may be used as the ultraviolet absorber, or two or more compounds may be used in combination. As the ultraviolet absorber, 2-hydroxy-4-n-octyloxybenzophenone and 2- (3-tert-butyl-2-hydroxy-5-methidylphenyl) -5-chlorobenzotriazole are preferable, and 2-hydroxy- 4-n-octyloxybenzophenone is more preferred.

  The solar cell encapsulant of the present invention is preferably 0 to 5 parts by weight, more preferably 0.005 to 3 parts by weight, still more preferably 0.005 parts by weight, based on 100 parts by weight of the ethylene polymer. Contains from 0.5 to 3 parts by weight.

  The solar cell sealing material of the present invention may contain a crosslinking agent. Examples of the crosslinking agent include those that decompose at a temperature of 100 ° C. or higher to generate radicals. It is preferable that the crosslinking agent has a decomposition temperature of 70 ° C. or more at a half life of 10 hours. When producing a solar cell, a crosslinking agent bridge | crosslinks and can seal the cell in a solar cell.

  Such a crosslinking agent is preferably an organic peroxide, such as 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-bis (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne 3,5-dimethyl-2,5- (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di- (t-butyl-peroxy) hexane-3,4,4'-bis ( t-butylperoxy) diisopropylbenzene, dicumyl peroxide, t-butylcumyl peroxide, α, α′-bis (t-butylperoxyisopropyl) benzene, α, α′-bis (t-butyl) Luperoxy) diisopropylbenzene, 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, t-butylperoxy-2-ethylhexyl carbonate. These may be used alone or in combination of two or more. 1,1-bis (t-butylperoxy) cyclohexane, 3,5-dimethyl-2,5- (t-butylperoxy) hexane, 2,5-dimethyl-2,5-bis (t-butylperoxy) ) Hexane, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexyne, α, α'-bis (t-butylperoxy) diisopropylbenzene, dicumyl peroxide, t-butylcumyl peroxide And 3-di-t-butyl peroxide and t-butylperoxy-2-ethylhexyl carbonate are preferred, and 1,1-bis (t-butylperoxy) cyclohexane, 2,5-dimethyl-2,5-di ( t-Butylperoxy) hexane and t-butylperoxy-2-ethylhexyl carbonate are more preferred.

  When the solar cell sealing material of the present invention contains a crosslinking agent, the content thereof is preferably 0.1 to 5 parts by weight, and 0.3 to 3 parts by weight with respect to 100 parts by weight of the ethylene-based polymer. More preferred.

  The solar cell encapsulant of the present invention may further contain a crosslinking aid. Examples of the crosslinking aid include ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, polyhydric alcohol methacrylate and acrylate, N, Nm-phenylene dimaleimide, triallyl isocyanurate, triallyl cyanurate, methacrylic acid. Examples include zinc, magnesium dimethacrylate, trimethylolpropane triacrylate, and trimethylolpropane trimethacrylate. These crosslinking aids may be used alone or in combination of two or more, and triallyl isocyanurate, trimethylolpropane triacrylate, and trimethylolpropane trimethacrylate are preferable. Triallyl isocyanurate is even more preferred.

  When the solar cell encapsulant of the present invention contains a crosslinking aid, the content thereof is preferably 10 parts by weight or less, more preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the ethylene-based polymer. Preferably, 0.5 to 3.5 parts by weight are more preferable, and 0.5 to 2 parts by weight are even more preferable.

  The solar cell sealing material of the present invention may further contain a silane coupling agent. Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and vinyl. Trimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, 3-methacryloxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, N- (2-aminoethyl) Examples include -3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and 3-aminopropyltrimethoxysilane. These silane coupling agents may be used alone or in combination of two or more, and 3-methacryloxypropylmethyldiethoxysilane is particularly preferable.

  When the solar cell encapsulant of the present invention contains a silane coupling agent, the content is preferably 5 parts by weight or less, and 0.1 to 2 parts by weight with respect to 100 parts by weight of the ethylene-based polymer. More preferred is 0.1 to 1 part by weight.

  The sealing material for solar cells of the present invention may further contain a polyvinyl acetal resin (for example, polyvinyl formal, polyvinyl butyral (PVB resin), modified PVB), or a vinyl chloride resin. Preferably, PVB resin is illustrated.

The solar cell encapsulant of the present invention can further contain additives described in the following additive group as long as the properties of the solar cell encapsulant are not affected.
[Additives group: neutralizer, phenolic antioxidant, phosphorus antioxidant, metal soap, higher fatty acid, antiblocking agent, pigment, flame retardant, nucleating agent, filler, foaming agent and foaming aid]

  Examples of the additive include the following additives.

  Examples of the neutralizing agent include synthetic hydrotalcite, natural hydrotalcite, and calcium hydroxide. These neutralizing agents may be used alone or in combination of two or more.

  Examples of the phenol-based antioxidant include pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, octadecyl-3- (3,5-di-tert-butyl-4). -Hydroxyphenyl) propionate, 3,9-bis [2- {3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] -2,4,8 , 10-tetraoxaspiro [5 · 5] undecane. These phenolic antioxidants may be used alone or in combination of two or more.

  Examples of phosphorus antioxidants include tris (2,4-di-t-butylphenyl) phosphite, bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite, and bis (2,6-diphenyl). -T-butyl-4-methylphenyl) pentaerythritol diphosphite, bis (2,4-di-cumylphenyl) pentaerythritol diphosphite, tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylene diphosphonite Can be mentioned. These phosphorus antioxidants may be used alone or in combination of two or more.

  Examples of metal soaps include stearic acid Li salt, stearic acid Na salt, stearic acid Mg salt, stearic acid K salt, stearic acid Ca salt, stearic acid Ba salt, stearic acid Al salt, stearic acid Zn salt of acid, Fe salt of stearic acid, Ca salt of lauric acid, Ba salt of lauric acid, Zn salt of lauric acid, Ca salt of behenic acid, Ba salt of behenic acid, Zn salt of behenic acid, 12-hydroxy Examples include Ca salt of stearic acid, Mg salt of 12-hydroxystearic acid, and Zn salt of 12-hydroxystearic acid. These metal soaps may be used alone or in combination of two or more.

  Examples of higher fatty acids include lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid, and behenic acid. These higher fatty acids may be used alone or in combination of two or more.

  Examples of the antiblocking agent include inorganic or organic antiblocking agents such as aluminum silicate, synthetic silica, natural silica, zeolite, kaolin and diatomaceous earth. These antiblocking agents may be used alone or in combination of two or more.

  Examples of pigments include carbon black, titanium oxide, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, perylene or perine pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, dioxazine pigments, disazo condensation pigments. And pigments and benzimidazolone pigments. These pigments may be used alone or in combination of two or more.

  Examples of the flame retardant include decabromobiphenyl, antimony trioxide, a phosphorus flame retardant, and aluminum hydroxide. These flame retardants may be used alone or in combination of two or more.

  Examples of the nucleating agent include sodium benzoate, 2,2′-methylenebis (4,6-di-t-butylphenyl) sodium phosphate, and bis (p-methylbenzylidene) sorbitol. These nucleating agents may be used alone or in combination of two or more.

  Examples of the filler include calcium carbonate, silicate, glass fiber, talc, kaolin, mica, barium sulfate, carbon black, carbon fiber, zeolite, metal powder, and metal oxide. These fillers may be used alone or in combination of two or more.

  Examples of the foaming agent and foaming aid include azocarboxylic acid derivatives such as azodicarboxylic acid amide; Nitroso compounds such as N'-dinitrosopentamethylenetetramine; sulfonyl hydrazide compounds such as p, p'-oxybisbenzenesulfonyl hydrazide; and the like. These foaming agents and foaming assistants may be used alone or in combination of two or more.

  The sealing material for solar cells of this invention contains an ethylene-type polymer and compound (I). As the production method, for example, using a batch mixer such as a Henschel mixer or a super mixer, the ethylene polymer and the compound (I), and further, if necessary, the compound (II), an ultraviolet absorber, a crosslinking agent, A method of dry blending a crosslinking aid and an additive can be mentioned.

  Next, the solar cell sealing method using the solar cell sealing material of the present invention will be described. Such a sealing method includes a step of heat-molding a solar cell sealing material to obtain a sheet-shaped molded product, and a step of bonding the obtained sheet-shaped molded product to both surfaces or one surface of a solar cell. Including. An example of such a solar cell is a silicon crystal.

  As the thermoforming method, for example, the solar cell encapsulant of the present invention is used in a temperature range from 60 ° C. to a level where the cross-linking agent does not cross-link using a single-screw or multi-screw extruder, preferably 60 ° C. to 200 ° C. Preferably a method of melt extrusion at 70 ° C. to 180 ° C. to form a pellet; the pellet-shaped product is further in a temperature range from 60 ° C. to the extent that the crosslinking agent is not crosslinked, preferably 60 ° C. to 200 ° C., more preferably A method of injection molding while heating at 70 ° C. to 180 ° C .; a temperature range in which the pellet-shaped molded article is not further crosslinked from 60 ° C. to a crosslinking agent, preferably 60 ° C. to 200 ° C., more preferably 70 ° C. to A method of extrusion molding from a T-die or the like while heating at 180 ° C .; after the solar cell sealing material of the present invention is dissolved in an organic solvent, it is applied to a substrate and the crosslinking agent is not crosslinked from 60 ° C. And the like can be given; temperature range of degrees, preferably 60 ° C. to 200 DEG ° C., more preferably by distilling off the organic solvent at 70 ° C. to 180 ° C., a method of obtaining a sheet-like molded article.

  A molded product obtained by thermoforming the solar cell encapsulant of the present invention tends to be less deteriorated and deteriorated even if it is exposed to light over a long period of time.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
The following components were mixed and kneaded at 90 ° C. and a screw rotation speed of 50 rpm with a 30 mm diameter single screw extruder (VS30-28 type extruder manufactured by Tanabe Plastics Co., Ltd.). The material was obtained.
Next, the solar cell encapsulant was pressed at 155 ° C. for 15 minutes to obtain a sheet-like molded product having a thickness of 0.5 mm.

<Ingredients>
Ethylene-based polymer: ethylene / vinyl acetate copolymer (190 ° C., MFR at 2.16 kg: about 40, The Polyolefin Company (Singapore) Pte. Ltd. MA-10) 100 parts by weight Crosslinker: 2,5-dimethyl -2,5-bis (t-butylperoxy) hexane 0.4 parts by weight Crosslinking aid: triallyl isocyanurate 0.6 parts by weight Compound (I): 6- [3- (3-t-butyl-4 -Hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra-t-butyldibenz [d, f] [1,3,2] dioxaphosphine 0.2 parts by weight of compound (II) : Bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate 0.1 part by weight

<Evaluation test>
About the molded article obtained in Example 1, the transmittance | permeability (%) in wavelength 380nm and 600 nm was calculated | required with the spectrophotometer (the JASCO make, V560). Next, the molded product was irradiated with xenon using a xenon weatherometer (black panel temperature: 63 ° C., no rain), and the sheet after irradiation for 1000 hours was determined with a spectrophotometer for transmittance (%) at a wavelength of 380 nm and 600 nm. It was.

(Example 2)
Except having changed the usage-amount of compound (I) into 0.1 weight part, it implemented similarly to Example 1 and obtained the molded article of the solar cell sheet material and this solar cell sheet material. The obtained molded product was evaluated in the same manner as in Example 1, and the results are shown in Table 1 together with Example 1.

(Comparative Example 1)
Except not using compound (I), it carried out similarly to Example 1, and obtained the molded product of the solar cell sheet material and this solar cell sheet material. The obtained molded product was evaluated in the same manner as in Example 1, and the results are shown in Table 1 together with Example 1.

(Example 3)
The following components were mixed and kneaded at 90 ° C. and a screw rotation speed of 50 rpm with a 30 mm diameter single screw extruder (VS30-28 type extruder manufactured by Tanabe Plastics Co., Ltd.). The material was obtained.
Next, the solar cell encapsulant was pressed at 155 ° C. for 15 minutes to obtain a sheet-like molded product having a thickness of 0.5 mm.

<Ingredients>
Ethylene-based polymer: ethylene / vinyl acetate copolymer (190 ° C., MFR at 2.16 kg: about 40, The Polyolefin Company (Singapore) Pte. Ltd. MA-10) 100 parts by weight Crosslinker: 2,5-dimethyl -2,5-bis (t-butylperoxy) hexane 0.4 parts by weight Crosslinking aid: triallyl isocyanurate 0.6 parts by weight Compound (I): 6- [3- (3-t-butyl-4 -Hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra-t-butyldibenz [d, f] [1,3,2] dioxaphosphine 0.2 parts by weight of compound (III) : 2-hydroxy-4-n-octyloxybenzophenone 0.1 parts by weight Compound (IV): bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, methyl 1,2 sebacate 2, 6, 6 -A mixture of pentamethyl-4-piperidinyl (Tinuvin 292 (registered trademark of Ciba Holding Incorporated)) 0.25 parts by weight

<Evaluation test>
Both sides of the molded product obtained in Example 3 were sandwiched between 1.0 mm thick glass, and the obtained cell was measured for transmittance (%) at a wavelength of 380 nm and 600 nm with a spectrophotometer (JASCO Corp., V560). Asked. Next, the cell was irradiated with xenon with a xenon weatherometer (black panel temperature: 63 ° C., no rain), and the transmittance (%) at a wavelength of 380 nm and 600 nm was determined with a spectrophotometer for the cell after irradiation for 500 hours. .

(Comparative Example 2)
Except not using compound (I), it carried out similarly to Example 3, and obtained the solar cell sheet material and the molded article of this solar cell sheet material. The obtained molded product was evaluated in the same manner as in Example 3, and the results are shown in Table 2 together with Example 3.

(Example 4)
Instead of 100 parts by weight of the ethylene / vinyl acetate copolymer as the component used in Example 2, 100 parts by weight of linear low-density polyethylene Sumikasen L (registered trademark of Sumitomo Chemical Co., Ltd., FS240, MFR = 2.2) is used. Except for the above, a solar cell sealing material of the present invention was obtained in the same manner as Example 2.

(Example 5)
Instead of using 100 parts by weight of the ethylene / vinyl acetate copolymer as the component used in Example 2, 100 parts by weight of a special ethylene copolymer ACLIFT (registered trademark of WH202 MFR = 2) was used. The solar cell sealing material of the present invention was obtained in the same manner as Example 2.

(Example 6)
Instead of 100 parts by weight of the ethylene / vinyl acetate copolymer of the component used in Example 2, 100 parts by weight of ethylene / methacrylic acid copolymer nuclel (registered trademark of AN DuPont, AN42115C MFR = 35) is used. Except for the above, a solar cell sealing material of the present invention was obtained in the same manner as Example 2.

(Example 7)
The procedure was carried out except that 100 parts by weight of the ionomer resin Himiran (registered trademark of Mitsui DuPont Chemical Co., Ltd., 1555 MFR = 10) was used instead of 100 parts by weight of the ethylene / vinyl acetate copolymer used in Example 2. The solar cell sealing material of the present invention was obtained in the same manner as Example 2.

(Reference example)
Glass substrate and back sheet (the back sheet is obtained by laminating polyethylene, adhesive and polyethylene terephthalate, and the polyethylene constituting the back sheet contains compound (I) described in Example 1 )), The solar battery cell of silicon crystal is sealed with the solar battery sealing material of the present invention obtained in Example 2 to obtain a solar battery.

The solar cell encapsulant of the present invention is less deteriorated and deteriorated even if it is exposed to light over a long period of time.

Claims (14)

A thermoplastic polymer containing structural units derived from ethylene and a compound of formula (I)

^{Wherein, R 1, R 2, R} 4 and ^{R 5} each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, cycloalkyl group having 5 to 8 carbon atoms, alkylcycloalkyl having 6 to 12 carbon atoms An alkyl group, an aralkyl group having 7 to 12 carbon atoms, or a phenyl group, each R ³ independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and X is a single bond, a sulfur atom, or a formula (I-1 )

(Wherein R ⁶ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms), and A represents a group having 2 to 8 carbon atoms. Alkylene group or formula (I-2)

(Wherein R ⁷ represents a single bond or an alkylene group having 1 to 8 carbon atoms, * represents that it is bonded to the oxygen atom side), and Y and Z represent Either one represents a hydroxy group, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms or an aralkyloxy group having 7 to 12 carbon atoms, and the other is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Represents. ]
A phosphite compound represented by the formula:   2. The solar cell encapsulant according to claim 1, comprising 0.001 to 5 parts by weight of the phosphite compound represented by the formula (I) with respect to 100 parts by weight of the thermoplastic polymer. .   The phosphite compound represented by formula (I) is 6- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra-t. The sealing material for solar cells according to <1> or 2, wherein the encapsulant is -butyldibenz [d, f] [1,3,2] dioxaphosphine. The solar cell encapsulant further has the formula (II ′)

(Wherein R ⁸ represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms, and Y represents an oxygen atom or a nitrogen atom.)
The solar cell encapsulant according to claim 1, comprising a piperidine compound having a partial structure represented by the formula: A piperidine compound having a partial structure represented by the formula (II ′) is represented by the formula (II)

[Wherein, R ⁸ independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms or an alkoxy group having 1 to 20 carbon atoms, and A represents an alkylene group having 1 to 10 carbon atoms or a compound represented by formula (III )

(In the formula, each R ⁸ independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms). ]
The solar cell encapsulant according to claim 4, which is a piperidine-based compound represented by the formula:   The solar cell sealing material according to any one of claims 1 to 5, wherein the solar cell sealing material further contains an ultraviolet absorber.   The solar cell sealing material according to any one of claims 1 to 6, wherein the solar cell sealing material further contains a crosslinking agent.   The solar cell encapsulant according to claim 7, wherein the crosslinking agent is an organic peroxide.   The solar cell sealing material according to claim 7 or 8, wherein the solar cell sealing material further contains a crosslinking aid. The sealing material for solar cells according to claim 1, wherein the sealing material for solar cells further contains a silane coupling agent.   The sealing material for solar cells according to any one of claims 1 to 10, wherein the thermoplastic polymer is a polymer containing a structural unit derived from ethylene and a structural unit derived from vinyl acetate. Formula (I) for improving the durability of a solar cell encapsulant

^{Wherein, R 1, R 2, R} 4 and ^{R 5} each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, cycloalkyl group having 5 to 8 carbon atoms, alkylcycloalkyl having 6 to 12 carbon atoms An alkyl group, an aralkyl group having 7 to 12 carbon atoms, or a phenyl group, each R ³ independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and X is a single bond, a sulfur atom, or a formula (I-1 )

(Wherein R ⁶ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms), and A represents a group having 2 to 8 carbon atoms. Alkylene group or formula (I-2)

(Wherein R ⁷ represents a single bond or an alkylene group having 1 to 8 carbon atoms, * represents that it is bonded to the oxygen atom side), and Y and Z represent Either one represents a hydroxy group, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms or an aralkyloxy group having 7 to 12 carbon atoms, and the other is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Represents. ]
Use of a phosphite compound represented by   A step of thermoforming the solar cell encapsulant according to any one of claims 1 to 11 to obtain a sheet-shaped molded product, and the obtained sheet-shaped molded product on both surfaces or one surface of a solar cell. The sealing method of the cell for solar cells including the process to paste.   The molded article obtained by heat-molding the solar cell sealing material according to claim 1.