JP2009218476A - Composition for sealing films of solar cells, sealing film for solar cells, and solar cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell excellent in durability and for ensuring good power generation performance for a long period. <P>SOLUTION: A composition for sealing films of solar cells comprising an ethylene-polar monomer copolymer and an aziridine compound containing at least one aziridine group which may be substituted in the molecule, a sealing film for solar cells, and a solar cell using the same are provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a solar cell encapsulating film composition that is suitably used for forming an encapsulating film mainly composed of an ethylene-polar monomer copolymer in a solar cell.

  In recent years, solar cells that directly convert sunlight into electrical energy have been widely used and further developed in terms of effective use of resources and prevention of environmental pollution.

  As shown in FIG. 1, a solar cell generally has an ethylene-vinyl acetate copolymer (EVA) film between a front surface side transparent protective member 11 made of a glass substrate or the like and a back surface side protective member (back sheet) 12, A plurality of solar battery cells 14 such as silicon power generation elements are sealed through a front side sealing film 13A and a back side sealing film 13B such as an ethylene-ethyl acrylate copolymer (EEA) film. Yes.

  Such a solar cell is obtained by laminating the surface-side transparent protective member 11, the surface-side sealing film 13A, the solar cell 14, the back-side sealing film 13B, and the back-side protecting member 12 in this order, and applying heat and pressure. , EVA is produced by cross-linking and curing and integrating the EVA.

  In a conventional solar cell, moisture or water may permeate into the battery when used for a long period of time in an environment such as outdoors exposed to high temperature and high humidity or wind and rain. Thus, the water | moisture content which entered the inside of a battery reaches | attains the conducting wire and electrode inside a solar cell, and corrodes these, As a result, durability of a solar cell is reduced.

  Therefore, in order to prevent corrosion of the conductive wires and electrodes inside the battery and improve the durability of the solar cell, conventionally, measures such as the use of a glass plate as the surface-side transparent protective member have been taken (for example, Patent Document 1). However, even if the solar cell is sufficiently sealed in this way, rusting is not prevented and the durability is not sufficiently improved.

  On the other hand, in order to improve the power generation characteristics of the solar battery, it is strongly desired to make light enter the battery as efficiently as possible and collect it on the solar battery cell. From such a viewpoint, as a sealing film used for a solar cell, as described above, a film made of an ethylene-polar monomer copolymer such as an EVA film and an EEA film having high transparency is a sealing film in a solar cell. As usual, it is used.

  A film comprising such an ethylene-polar monomer copolymer is produced by forming a film by heating and rolling a composition containing the ethylene-polar monomer copolymer and a crosslinking agent, for example, by extrusion. The

  Among ethylene-polar monomer copolymers, the EVA film is preferably used as a sealing film because it is excellent in transparency and water resistance. However, since EVA films contain vinyl acetate as a constituent component, they tend to be hydrolyzed over time due to permeation of moisture or water at high temperatures to easily generate carboxylic acids such as acetic acid. It became clear that such carboxylic acid promotes the generation of rust by contacting with the lead wires and electrodes inside the battery.

  In order to solve this, an EVA film containing 0.5% by mass or less of an acid acceptor having an average particle diameter of 5 μm or less has been proposed as a transparent film used for a sealing film of a solar cell (Patent Document 2). ). According to the EVA film containing the acid acceptor, it is possible to suppress the generation of carboxylic acid from the film and improve the durability of the solar cell.

JP 2000-174296 A JP 2005-29588 A

  Although a wide range of research and development has been conducted on solar cells, in order to promote the spread of solar cells, it is desired that high power generation characteristics can be exhibited over a longer period even in extremely harsh natural environments outdoors. ing.

  Accordingly, an object of the present invention is to provide a solar cell that is excellent in durability and can exhibit high power generation characteristics over a long period of time.

  Moisture that has entered the solar cell hydrolyzes the ethylene-polar monomer copolymer to generate carboxylic acid such as acetic acid, and further causes the following deterioration factors.

  That is, the moisture that has entered the solar cell may hydrolyze the ethylene-polar monomer copolymer to generate a carboxylic acid such as acetic acid or an alcohol. As described above, the carboxylic acid produced in this manner is brought into contact with the lead wires and electrodes inside the battery to promote the generation of rust. In addition, alcohol easily foams in a portion having weak adhesive force such as a wiring portion inside the solar cell. These cause a decrease in the power generation characteristics of the solar cell and a poor appearance, resulting in a decrease in the durability of the solar cell.

Therefore, in order to further improve the durability of the solar cell, the hydrolysis of the ethylene-polar monomer copolymer in the solar cell sealing film is suppressed, and further, the degradation of carboxylic acid, alcohol, etc. caused by the hydrolysis is suppressed. It is necessary to suppress the generation of factors,
As a result of various studies based on such knowledge, the present inventors have formed a solar cell sealing film using an aziridine compound having at least two aziridine groups in the molecule. It has been found that the durability of can be further improved.

  That is, this invention achieves the said objective by the composition for solar cell sealing films containing the ethylene-polar monomer copolymer and the aziridine compound which has at least 1 the aziridine group which may be substituted in a molecule | numerator.

  The preferable aspect of the composition for solar cell sealing films of this invention is listed below.

  (1) The aziridine compound is represented by the following formula (1)

［ただし、Ｘは、−ＮＨ−ＣＯ−、又は下記式（２）

[Wherein X is —NH—CO— or the following formula (2)

（式中、Ｒ³及びＲ⁴は、置換基を有していてもよい２価の脂肪族炭化水素基である）で示される基であり、
Ｒ²は、下記式（３）又は（４）

(Wherein R ³ and R ⁴ are divalent aliphatic hydrocarbon groups which may have a substituent),
R ² represents the following formula (3) or (4)

（式中、Ｒ⁵〜Ｒ¹¹は、同一であっても異なっていてもよく、水素原子、置換基を有していてもよい１価の脂肪族炭化水素基である）で示される基であり、
ｎは１〜４の整数であり、
ｎが１である場合、Ｒ¹は置換基を有していてもよい１価の脂肪族炭化水素基であり、
ｎが２である場合、Ｒ¹は、それぞれ置換基を有していてもよい、２価の脂肪族炭化水素基、アリーレン基、又はアリーレンアルキレンアリーレン基であり、
ｎが３である場合、Ｒ¹は置換基を有していてもよい３価の脂肪族炭化水素基であり、
ｎが４である場合、Ｒ¹は４価の炭素原子である］で示される。

(Wherein R ^{5 to} R ¹¹ may be the same or different and are a hydrogen atom or a monovalent aliphatic hydrocarbon group which may have a substituent). Yes,
n is an integer of 1 to 4,
when n is 1, R ¹ is a monovalent aliphatic hydrocarbon group which may have a substituent;
When n is 2, R ¹ is a divalent aliphatic hydrocarbon group, an arylene group, or an arylene alkylenearylene group, each of which may have a substituent,
when n is 3, R ¹ is a trivalent aliphatic hydrocarbon group which may have a substituent;
When n is 4, R ¹ is a tetravalent carbon atom].

  (2) The said composition for solar cell sealing films contains 0.1-5 mass parts of said aziridine compounds with respect to 100 mass parts of said ethylene-polar monomer copolymers.

  (3) The ethylene-polar monomer copolymer is an ethylene-vinyl acetate copolymer.

  (4) Content of the polar monomer in the ethylene-polar monomer copolymer is 20 to 35 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer.

  According to the solar cell sealing film formed using the composition of the present invention, the hydrolysis can be suppressed by absorbing the moisture that has penetrated into the battery by the aziridine compound. Furthermore, the solar cell sealing film can reduce components that degrade battery materials such as carboxylic acid and alcohol generated by hydrolysis. Thereby, the durability of the solar cell can be further improved, and the high power generation characteristics of the solar cell can be maintained over a long period from the beginning of power generation.

  The composition for solar cell encapsulating film of the present invention contains, as basic components, an ethylene vinyl acetate copolymer and an aziridine compound having at least one aziridine group which may be substituted in the molecule. The aziridine compound can take water into the aziridine group and has dehydrating properties. Furthermore, even if hydrolysis of the ethylene-polar monomer copolymer occurs due to moisture that could not be removed by dehydration, the carboxylic acid and alcohol produced thereby react with the aziridine compound, and the power generation characteristics of the solar cell A compound having a carboxyl group, an amino group, or the like that does not adversely affect the appearance can be formed. As described above, the aziridine compound can further suppress the generation of the deterioration factor of the solar cell caused by hydrolysis in addition to the moisture that has entered the solar cell. Therefore, components that degrade the battery material such as carboxylic acid, alcohol, and amine can be reduced, and the durability of the solar cell can be further improved.

  Hereinafter, the composition for solar cell sealing film of this invention is demonstrated in detail.

(Aziridine compound)
The aziridine compound used in the composition of the present invention is a compound having at least one aziridine group which may be substituted in the molecule. Such an aziridine compound may be any conventionally known compound and is not particularly limited.

  The aziridine compound has the following formula (1):

［ただし、Ｘは、−ＮＨ−ＣＯ−、又は下記式（２）

[Wherein X is —NH—CO— or the following formula (2)

（式中、Ｒ³及びＲ⁴は、置換基を有していてもよい２価の脂肪族炭化水素基である）で示される基であり、
Ｒ²は、下記式（３）又は（４）

(Wherein R ³ and R ⁴ are divalent aliphatic hydrocarbon groups which may have a substituent),
R ² represents the following formula (3) or (4)

（式中、Ｒ⁵〜Ｒ¹¹は、同一であっても異なっていてもよく、水素原子、置換基を有していてもよい１価の脂肪族炭化水素基である）で示される基であり、
ｎは１〜４の整数であり、
ｎが１である場合、Ｒ¹は置換基を有していてもよい１価の脂肪族炭化水素基であり、
ｎが２である場合、Ｒ¹は、それぞれ置換基を有していてもよい、２価の脂肪族炭化水素基、アリーレン基、又はアリーレンアルキレンアリーレン基であり、
ｎが３である場合、Ｒ¹は置換基を有していてもよい３価の脂肪族炭化水素基であり、
ｎが４である場合、Ｒ¹は４価の炭素原子である］で示されるアジリジン化合物が挙げられる。

(Wherein R ^{5 to} R ¹¹ may be the same or different and are a hydrogen atom or a monovalent aliphatic hydrocarbon group which may have a substituent). Yes,
n is an integer of 1 to 4,
when n is 1, R ¹ is a monovalent aliphatic hydrocarbon group which may have a substituent;
When n is 2, R ¹ is a divalent aliphatic hydrocarbon group, an arylene group, or an arylene alkylenearylene group, each of which may have a substituent,
when n is 3, R ¹ is a trivalent aliphatic hydrocarbon group which may have a substituent;
In the case where n is 4, R ¹ is a tetravalent carbon atom].

In the formula (2), R ³ and R ⁴ are divalent aliphatic hydrocarbon groups which may have a substituent.

The divalent aliphatic hydrocarbon group preferably has 1 to 6, particularly 1 to 3 carbon atoms. Specific examples of the divalent aliphatic hydrocarbon group include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, and a hexylene group. Moreover, as a substituent which the said bivalent aliphatic hydrocarbon group has, a C1-C3 alkyl group is mentioned preferably. R ³ and R ⁴ are preferably a methylene group, an ethylene group, a methylmethylene group, a methylethylene group, a methylpropylene group, and a methylbutylene group.

In the above formulas (3) and (4), R ^{5 to} R ¹¹ may be the same or different and are a hydrogen atom or a monovalent aliphatic hydrocarbon group.

The monovalent aliphatic hydrocarbon group of R ^{5 to} R ¹¹ preferably has 1 to 6, particularly 1 to 3 carbon atoms. Examples of the monovalent aliphatic hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. Moreover, as a substituent which the said monovalent | monohydric aliphatic hydrocarbon group has, a C1-C3 alkyl group and a hydroxyl group are mentioned preferably.

R ^{5 to} R ¹¹ are preferably a hydrogen atom, an ethyl group, a propyl group, and a butyl group.

In the formula (1), when n is 1, R ¹ is a monovalent aliphatic hydrocarbon group which may have a substituent.

The monovalent aliphatic hydrocarbon group for R ¹ preferably has 1 to 6, particularly 1 to 3 carbon atoms. Examples of the monovalent aliphatic hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. Preferred examples of the substituent in the monovalent aliphatic hydrocarbon group include an alkyl group having 1 to 3 carbon atoms and a hydroxyl group. Among them, when n in the formula (1) is 1, the R ¹ is preferably a methyl group, an ethyl group and propyl group.

In the formula (1), when n is 2, R ¹ is a divalent aliphatic hydrocarbon group, an arylene group, or an arylene alkylenearylene group, each of which may have a substituent.

Among these, when X in the formula (1) is a group represented by the above formula (2), R ¹ is preferably a divalent aliphatic hydrocarbon group. When X in the formula (1) is a group represented by —NH—CO—, R ¹ is preferably an arylene group or an arylene alkylenearylene group.

Examples of the divalent aliphatic hydrocarbon group which may have a substituent for R ¹ include the following formula (5):

（式中、Ｒ¹²及びＲ¹³は、同一であっても異なっていてもよく、水素原子、１価の脂肪族炭化水素基、又はヒドロキシアルキル基である）で示される基が好ましく挙げられる。

A group represented by the formula (wherein R ¹² and R ¹³ may be the same or different and are a hydrogen atom, a monovalent aliphatic hydrocarbon group, or a hydroxyalkyl group) is preferred.

The monovalent aliphatic hydrocarbon group for R ¹² and R ¹³ preferably has 1 to 6, particularly 1 to 3 carbon atoms. Examples of the monovalent aliphatic hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. Moreover, it is preferable that the hydroxyalkyl group in said R < ¹² > and R < ¹³ > has 1-6, especially 1-3 carbon atoms. Examples of the hydroxyalkyl group include a hydroxymethyl group, a 2-hydroxyethyl group, a 2-hydroxypropyl group, a 3-hydroxypropyl group, and a 4-hydroxybutyl group.

R ¹² and R ¹³ are preferably a methyl group, an ethyl group, and a propyl group.

The arylene group preferably has 4 to 20 carbon atoms. Specific examples include a phenylene group, a biphenylene group, a naphthalenediyl group, an anthracene-9,10-diyl group, a pyridine-2,5-diyl group, and a thienylene group. Moreover, as a substituent in the arylene group of R < ¹ >, a C1-C3 alkyl group is mentioned preferably.

  The arylene alkylene arylene group preferably has 8 to 40 carbon atoms. Specifically, the following formula (6)

（式中、Ｒ¹⁴は、置換基を有していてもよい炭素原子数１〜４のアルキレン基を表す）で示される基などが好ましく挙げられる。Ｒ¹⁴のアルキレン基における置換基としては、炭素原子数１〜３のアルキル基が好ましく挙げられる。前記Ｒ¹⁴として、具体的には、フェニレンメチレンフェニレン基、フェニレンエチレンフェニレン基などが挙げられる。

Preferable examples include a group represented by the formula (wherein R ¹⁴ represents an optionally substituted alkylene group having 1 to 4 carbon atoms). Preferred examples of the substituent for the alkylene group represented by R ¹⁴ include an alkyl group having 1 to 3 carbon atoms. Specific examples of R ¹⁴ include a phenylenemethylenephenylene group and a phenyleneethylenephenylene group.

In the formula (1), when n is 3, R ¹ is a trivalent aliphatic hydrocarbon group which may have a substituent.

  As the trivalent aliphatic hydrocarbon group, the following formula (7)

（式中、Ｒ¹⁵は、上記式（３）又は（４）で示される基、水素原子、１価の脂肪族炭化水素基、ヒドロキシアルキル基である）で示される基が好ましく挙げられる。

(Wherein, R ¹⁵ is preferably a group represented by the above formula (3) or (4), a hydrogen atom, a monovalent aliphatic hydrocarbon group, or a hydroxyalkyl group).

The monovalent aliphatic hydrocarbon group for R ¹⁵ preferably has 1 to 6, particularly 1 to 3 carbon atoms. Examples of the monovalent aliphatic hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. The hydroxyalkyl group in R ¹⁵ preferably has 1 to 6, particularly 1 to 3 carbon atoms. Examples of the hydroxyalkyl group include a hydroxymethyl group, a 2-hydroxyethyl group, a 2-hydroxypropyl group, a 3-hydroxypropyl group, and a 4-hydroxybutyl group.

  Further, as the aziridine compound, in addition to the compound represented by the above formula (1), the following formula (8)

（式中、Ｒ¹⁶〜Ｒ²¹は、それぞれ同一であっても異なっていてもよく、水素原子、塩素原子、アルキル基、ハロゲン化アルキル基、アルキルアルコール基、アクリル酸アルキル基、アルキルフェノール基、又は式（３）若しくは式（４）で示される基であり、
Ｒ¹⁶〜Ｒ²¹のうち、少なくとも１個が式（３）又は式（４）で示される基である）で示されるものも好ましく挙げられる。

(Wherein R ^{16 to} R ²¹ may be the same as or different from each other, and each represents a hydrogen atom, a chlorine atom, an alkyl group, a halogenated alkyl group, an alkyl alcohol group, an alkyl acrylate group, an alkylphenol group, or A group represented by formula (3) or formula (4);
Of those, at least one of R ^{16 to} R ²¹ is a group represented by the formula (3) or the formula (4)).

As an aziridine compound, specifically, trimethylolmethane-tris- (β- (1-aziridinylpropionate)), trimethylolethane-tris- (β- (1-aziridinylpropionate)) , Trimethylolpropane-tris- (β- (1-aziridinylpropionate)), trimethylolbutane-tris- (β- (1-aziridinylpropionate)), monochlorotrimethylolethane-tris- (Β- (1-aziridinylpropionate)), monophenyltrimethylolethane-tris- (β- (1-aziridinylpropionate)), monoethoxytrimethylolmethane-tris- (β- ( 1-aziridinylpropionate)), trimethylolethane-tris- (β- (2-methyl-1-aziridinylpropionate)), Limethylolethane-tris- (β- (2-hydroxyethyl-1-aziridinylpropionate)), trimethylolpropane-tris- (β- (2-methyl-1-aziridinylpropionate)) , Trimethylolpropane-tris- (β- (2,2-dimethyl-1-aziridinylpropionate)), trimethylolpropane-tris- (β- (2-aziridinylpropionate)), tri Methylolpropane-tris- (β- (1-methyl-2-aziridinylpropionate), trimethylolpropane-tris- (α-methyl-β- (1-aziridinylpropionate), trimethylolpropane -Tris- (β-methyl-β- (1-aziridinylpropionate), tetramethylolmethane-tri-β-aziridinylpropionate, Tramethylolmethane-tris- (α-methyl-α-aziridinyl acetate), tetramethylolmethane-tris- (β- (1-aziridinylpropionate), tetramethylolethane-tris- (β- (1 -Aziridinylpropionate)), tetramethylolmethane-tris- (β- (2-propyl-1-aziridinylpropionate)), tetramethylolmethane-tris- (β- (2-methyl-1 -Aziridinylpropionate)), tetramethylolmethane-tris- (β- (2,2-dimethylaziridinylpropionate), tetramethylolmethane-tris- (β- (2,2-diethyl-1) -Aziridinylpropionate) tetramethylolmethane-tetrakis-β- (1-aziridinylpropionate), tetramethylol Tan-tetrakis-β-methyl-β- (1-aziridinylpropionate), tetramethylolmethane-tetrakis-β- (2-methyl-1-aziridinylpropionate), ditrimethylolpropane-hexakis- (Β-aziridinylpropionate), ditrimethylolpropane-pentakis- (β- (2-methylaziridinylpropionate), N, N′-toluene-2,4-bis (1-aziridinecarboxamide) ), N, N′-hexamethylene-1,6-bis (1-aziridinecarboxamide), N, N′-diphenylmethane-4,4′-bis (1-aridiridinecarboxamide), and the like.
Of the above-mentioned aziridine compounds, those shown below are particularly preferred.

  Each of the aziridine compounds described above may be used alone or in combination of two or more.

  In the composition of the present invention, the content of the aziridine compound is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer. It is good to do. If the content of the aziridine compound is less than 0.1 parts by mass, a sufficient effect of the aziridine compound may not be obtained. There is a risk of deteriorating properties.

(Ethylene-polar monomer copolymer)
Examples of the polar monomer of the ethylene-polar monomer copolymer used in the composition of the present invention include unsaturated carboxylic acid, its salt, its ester, its amide, vinyl ester, carbon monoxide and the like. More specifically, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, fumaric acid, itaconic acid, monomethyl maleate, monoethyl maleate, maleic anhydride, itaconic anhydride, lithium, sodium of these unsaturated carboxylic acids, Monovalent metal salts such as potassium, polyvalent metal salts such as magnesium, calcium and zinc, methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, nbutyl acrylate, isooctyl acrylate, methyl methacrylate Illustrative examples of unsaturated carboxylic acid esters such as ethyl methacrylate, isobutyl methacrylate and dimethyl maleate, vinyl esters such as vinyl acetate and vinyl propionate, carbon monoxide, sulfur dioxide, etc. Can do.

  More specific examples of the ethylene-polar monomer copolymer include ethylene-acrylic acid copolymers, ethylene-unsaturated carboxylic acid copolymers such as ethylene-methacrylic acid copolymers, and ethylene-unsaturated carboxylic acid copolymers. Ionomer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-acrylic, wherein some or all of the carboxyl groups of the polymer are neutralized with the above metals Acid isobutyl copolymer, ethylene-unsaturated carboxylic acid ester copolymer such as ethylene-n-butyl acrylate copolymer, ethylene-isobutyl acrylate-methacrylic acid copolymer, ethylene-n-butyl acrylate-methacrylic acid Ethylene-unsaturated carboxylic acid ester-unsaturated carboxylic acid copolymer such as copolymer It can be exemplified vinyl ester copolymers and the like as a typical example - some or all of the body and its carboxyl group ionomer neutralized with the metal, ethylene - ethylene such as vinyl acetate copolymer.

  Among these, the ethylene-polar monomer copolymer is most preferably an ethylene-vinyl acetate copolymer (EVA). Since the ethylene-vinyl acetate copolymer tends to generate a carboxylic acid which is a deterioration factor by hydrolysis, the effect of the above-mentioned aziridine compound can be exhibited highly.

  The content of the polar monomer in the ethylene-polar monomer copolymer is 20 to 35 parts by mass, more preferably 22 to 30 parts by mass, especially 24 to 28 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer. Is preferred. If the content of the polar monomer is less than 20 parts by mass, the transparency of the sealing film obtained in the case of crosslinking and curing at a high temperature may not be sufficient, and if it exceeds 35 parts by mass, carboxylic acid, alcohol, amine, etc. May be more likely to occur.

(Crosslinking agent)
Furthermore, the composition of the present invention preferably contains a crosslinking agent in addition to the ethylene-polar monomer copolymer and the aziridine compound. Thereby, the crosslinked cured film of ethylene-polar monomer copolymer can be obtained, and the sealing performance of a solar cell can be improved.

  As the crosslinking agent used in the composition, an organic peroxide or a photopolymerization initiator is preferably used. Among them, it is preferable to use an organic peroxide because a sealing film having improved temperature dependency of adhesive strength, transparency, moisture resistance, and penetration resistance can be obtained.

  Any organic peroxide may be used as long as it decomposes at a temperature of 100 ° C. or higher to generate radicals. The organic peroxide is generally selected in consideration of the film formation temperature, the adjustment conditions of the composition, the curing temperature, the heat resistance of the adherend, and the storage stability. In particular, the one having a decomposition temperature of 70 ° C. or more with a half-life of 10 hours is preferable.

  Examples of the organic peroxide include 2,5-dimethylhexane; 2,5-dihydroperoxide; 2,5-dimethyl-2,5-di (tert) from the viewpoint of processing temperature and storage stability of the resin. 3-butyl-peroxy) hexane; 3-di-tert-butyl peroxide; tert-dicumyl peroxide; 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane; Dimethyl-2,5-bis (tert-butylperoxy) hexane; 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne; dicumyl peroxide; tert-butylcumyl peroxide; α, α′-bis (tert-butylperoxyisopropyl) benzene; α, α′-bis (tert-butylperoxy) diisopropyl N-butyl-4,4-bis (tert-butylperoxy) butane; 2,2-bis (tert-butylperoxy) butane; 1,1-bis (tert-butylperoxy) cyclohexane; 1-bis (tert-butylperoxy) 3,3,5-trimethylcyclohexane; 1,1-bis (tert-hexylperoxy) -3,3,5-trimethylcyclohexane; tert-butylperoxybenzoate; benzoylper Preferable examples include oxide. These may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  As the organic peroxide, 1,1-bis (tert-hexylperoxy) -3,3,5-trimethylcyclohexane is particularly preferable. If it is this organic peroxide, the sealing film for solar cells which has the outstanding sealing property and transparency will be obtained, without reducing the characteristic of an aziridine compound.

  As the photopolymerization initiator, any known photopolymerization initiator can be used, but a photopolymerization initiator having good storage stability after blending is desirable. Examples of such a photopolymerization initiator include 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, and 2-methyl-1- (4- (methylthio) phenyl). Acetophenones such as 2-morpholinopropane-1, benzoins such as benzyldimethylketal, benzophenones such as benzophenone, 4-phenylbenzophenone and hydroxybenzophenone, thioxanthones such as isopropylthioxanthone and 2-4-diethylthioxanthone, As other special ones, methylphenylglyoxylate can be used. Particularly preferably, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- (4- (methylthio) phenyl) -2-morpholinopropane-1, Examples include benzophenone. These photopolymerization initiators may contain one or two or more kinds of known and commonly used photopolymerization accelerators such as benzoic acid-based or tertiary amine-based compounds such as 4-dimethylaminobenzoic acid as required. Can be mixed and used. Moreover, it can be used individually by 1 type of only a photoinitiator, or 2 or more types of mixture.

  In the composition, the content of the crosslinking agent is preferably 0.1 to 5.0 parts by mass, more preferably 0.2 to 1.5 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer. It is preferable that If the content of the organic peroxide is small, the transparency of the resulting sealing film may be lowered, and if it is increased, the compatibility with the copolymer may be deteriorated.

(Crosslinking aid)
Furthermore, the composition of this invention may contain the crosslinking adjuvant as needed. The crosslinking aid can be added to the composition in order to improve the gel fraction of EVA and improve durability. As a crosslinking aid (compound having a radical polymerizable group as a functional group) provided for this purpose, in addition to a trifunctional crosslinking aid such as triallyl cyanurate and triallyl isocyanurate, (meth) acrylic ester ( Examples thereof include monofunctional or bifunctional crosslinking aids such as NK ester. Of these, triallyl cyanurate and triallyl isocyanurate are preferable, and triallyl isocyanurate is particularly preferable. These crosslinking aids are generally used in an amount of 10 parts by mass or less, preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer.

(Other)
The composition is used for improving or adjusting various physical properties of the film (optical properties such as mechanical strength, adhesiveness, transparency, heat resistance, light resistance, crosslinking speed, etc.), particularly for improving mechanical strength. If necessary, various additives such as an acid acceptor, a plasticizer, an adhesion improver, an acryloxy group-containing compound, a methacryloxy group-containing compound and / or an epoxy group-containing compound may further be included.

  As the acid acceptor, a metal oxide, a metal hydroxide, a metal carbonate or a composite metal hydroxide is used, and can be appropriately selected according to the amount of acetic acid generated and the application. Specific examples of the acid acceptor include magnesium oxide, calcium oxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, magnesium carbonate, barium carbonate, calcium carbonate, calcium borate, zinc stearate, calcium phthalate, Periodic table Group 2 metal oxides such as calcium phosphate, zinc oxide, calcium silicate, magnesium silicate, magnesium borate, magnesium metaborate, calcium metaborate, barium metaborate, hydroxide, carbonate, carvone Acid salt, silicate, borate, phosphite, metaborate, etc .; tin oxide, basic tin carbonate, tin stearate, basic tin phosphite, basic tin sulfite, trilead tetraoxide, silicon oxide, stearin Group 14 metal oxides such as silicon acid, basic carbonate, basic carboxylate, base Phosphites, and basic sulfite salt; zinc oxide, aluminum oxide, aluminum hydroxide, iron hydroxide; composite metal hydroxide such as hydrotalcite; aluminum hydroxide gel compound; and the like. These may be used individually by 1 type, and may mix and use 2 or more types.

  In the composition, the content of the acid acceptor is preferably 0.01 to 0.15 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer.

  The plasticizer is not particularly limited, but polybasic acid esters and polyhydric alcohol esters are generally used. Examples thereof include dioctyl phthalate, dihexyl adipate, triethylene glycol-di-2-ethylbutyrate, butyl sebacate, tetraethylene glycol diheptanoate, and triethylene glycol dipelargonate. One type of plasticizer may be used, or two or more types may be used in combination. The content of the plasticizer is preferably in the range of 5 parts by mass or less with respect to 100 parts by mass of the ethylene-polar monomer copolymer.

  As the adhesion improver, a silane coupling agent can be used. Thereby, it becomes possible to form the sealing film for solar cells which has the outstanding adhesive force. Examples of the silane coupling agent include γ-chloropropylmethoxysilane, vinylethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, and γ-glycidoxypropyltrimethoxy. Silane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β Mention may be made of-(aminoethyl) -γ-aminopropyltrimethoxysilane. These silane coupling agents may be used alone or in combination of two or more. Moreover, it is preferable that content of the said adhesive improvement agent is 5 mass parts or less with respect to 100 mass parts of ethylene-polar monomer copolymers.

  The acryloxy group-containing compound and the methacryloxy group-containing compound are generally acrylic acid or methacrylic acid derivatives, and examples thereof include acrylic acid or methacrylic acid esters and amides. Examples of ester residues include linear alkyl groups such as methyl, ethyl, dodecyl, stearyl, lauryl, cyclohexyl group, tetrahydrofurfuryl group, aminoethyl group, 2-hydroxyethyl group, 3-hydroxypropyl group. Group, 3-chloro-2-hydroxypropyl group. Examples of amides include diacetone acrylamide. In addition, polyhydric alcohols such as ethylene glycol, triethylene glycol, polypropylene glycol, polyethylene glycol, trimethylolpropane, and pentaerythritol, and esters of acrylic acid or methacrylic acid can also be used.

Examples of the epoxy-containing compound include triglycidyl tris (2-hydroxyethyl) isocyanurate, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, Examples include phenol (ethyleneoxy) ₅ glycidyl ether, pt-butylphenyl glycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, glycidyl methacrylate, and butyl glycidyl ether.

  The acryloxy group-containing compound, the methacryloxy group-containing compound, or the epoxy group-containing compound is generally 0.5 to 5.0 parts by weight, particularly 1.0, respectively, with respect to 100 parts by weight of the ethylene-polar monomer copolymer. It is preferable that -4.0 mass part is contained.

  Further, the composition may contain an ultraviolet absorber, a light stabilizer, and / or an anti-aging agent.

  When the composition of the present invention contains an ultraviolet absorber, it is possible to suppress deterioration of the ethylene-polar monomer copolymer due to the influence of irradiated light and the like, and the yellowing of the solar cell sealing film. . The ultraviolet absorber is not particularly limited, but 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4- Preferred examples include benzophenone-based ultraviolet absorbers such as methoxybenzophenone and 2-hydroxy-4-n-octoxybenzophenone. In addition, it is preferable that the compounding quantity of the said benzophenone series ultraviolet absorber is 0.01-5 mass parts with respect to 100 mass parts of ethylene-polar monomer copolymers.

  Even when the composition of the present invention contains a light stabilizer, it is possible to suppress deterioration of the ethylene-polar monomer copolymer due to the influence of irradiated light and the like, and the solar cell sealing film from being yellowed. it can. As the light stabilizer, a light stabilizer called a hindered amine type is preferably used. For example, LA-52, LA-57, LA-62, LA-63LA-63p, LA-67, LA-68 (all ( ADEKA), Tinuvin 744, Tinuvin 770, Tinuvin 765, Tinuvin 144, Tinuvin 622LD, CHIMASORB 944LD (all manufactured by Ciba Specialty Chemicals), UV-3034 (BF Goodrich) Can be mentioned. In addition, the said light stabilizer may be used individually or may be used in combination of 2 or more types, and the compounding quantity is 0.01-5 mass parts with respect to 100 mass parts of ethylene-polar monomer copolymers. It is preferable that

  Examples of the antioxidant include hindered phenol antioxidants such as N, N′-hexane-1,6-diylbis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide]. , Phosphorus heat stabilizers, lactone heat stabilizers, vitamin E heat stabilizers, sulfur heat stabilizers, and the like.

  According to the solar cell sealing film using the above-described solar cell sealing film composition, in addition to hydrolysis by moisture inside the solar cell, degradation of carboxylic acid, alcohol, amine, etc. caused by hydrolysis Generation of factors can be suppressed. Therefore, it is possible to provide a solar cell with excellent durability.

  What is necessary is just to perform according to a well-known method in order to form the sealing film for solar cells using the composition of this invention mentioned above. For example, it can be produced by a method for obtaining a sheet-like material by molding by ordinary extrusion molding, calendar molding (calendering) or the like. Alternatively, a sheet-like material can be obtained by dissolving the composition in a solvent and coating the solution on a suitable support with a suitable coating machine (coater) and drying to form a coating film. When a film is formed by heat rolling using extrusion molding or the like, heating is generally in the range of 50 to 90 ° C.

  Although the thickness in particular of the sealing film for solar cells is not restrict | limited, What is necessary is just the range of 50 micrometers-2 mm.

  The structure of the solar cell using the solar cell sealing film according to the present invention is not particularly limited. However, the solar cell sealing film is interposed between the front surface side transparent protective member and the back surface side protective member to crosslink. Examples include a structure in which cells for solar cells are sealed by integration. In the present invention, the light receiving surface side with respect to the solar cell is referred to as “front surface side”, and the surface opposite to the light receiving surface of the solar cell is referred to as “back surface side”.

  In the solar cell, in order to sufficiently seal the solar cell, as shown in FIG. 1, the surface side transparent protective member 11, the surface side sealing film 13A, the solar cell 14 and the back surface side sealing film 13B. And the back surface side protection member 12 may be laminated | stacked, and the sealing film should just be bridge | crosslinked and hardened | cured according to conventional methods, such as heating and pressurization.

In order to heat and pressurize, for example, the laminate is heated with a vacuum laminator at a temperature of 135 to 180 ° C., further 140 to 180 ° C., particularly 155 to 180 ° C., a degassing time of 0.1 to 5 minutes, and a press pressure of 0.1. What is necessary is just to heat-press in about 1.5 kg / cm < ² > and press time 5-15 minutes. By crosslinking the ethylene-polar monomer copolymer contained in the front side sealing film 13A and the back side sealing film 13B during this heating and pressurization, the front side sealing film 13A and the back side sealing film 13B are interposed. And the surface side transparent protection member 11, the back surface side transparent member 12, and the cell 14 for solar cells can be integrated, and the cell 14 for solar cells can be sealed.

  The surface side transparent protective member used for the solar cell of the present invention is usually a glass substrate such as silicate glass. As for the thickness of a glass substrate, 0.1-10 mm is common, and 0.3-5 mm is preferable. The glass substrate may generally be chemically or thermally strengthened.

  The back surface side protective member used in the present invention is a plastic film such as PET. In consideration of heat resistance and moist heat resistance, a fluorinated polyethylene film, particularly a fluorinated polyethylene film / Al / fluorinated polyethylene film, in this order. A film laminated with is preferable.

  In addition, the solar cell of this invention has the characteristics in the sealing film used for the surface side and a back surface side as above-mentioned. Therefore, the members other than the sealing film such as the front-side transparent protective member, the back-side protective member, and the solar cell need only have the same configuration as the conventionally known solar cell, and are not particularly limited. .

  Hereinafter, the present invention will be described with reference to examples. The present invention is not limited by the following examples.

Example 1
The materials shown in Table 1 were supplied to a roll mill and kneaded at 70 ° C. to prepare a solar cell sealing film composition. The solar cell sealing film composition was calendered at 70 ° C., allowed to cool, and then a solar cell sealing film (thickness 0.6 mm) was produced.

(Example 2 and Comparative Example 1)
A solar cell encapsulating film composition was prepared in the same manner as in Example 1 except that the materials and blending were as shown in Table 1, and a solar cell encapsulating film was prepared using the composition.

(Evaluation)
Evaluation was performed according to the following procedure using the solar cell sealing film prepared above.

(1) Production of Acetic Acid Generation Amount Quantitative Test Module Each of the solar cell sealing films produced above was used as an acetic acid generation amount quantification sealing film 26, and as shown in FIG. ) And a back side protective member 22 (thickness 120 μm) in which a front surface transparent protective member 21 and a fluorinated polyethylene film / Al / fluorinated polyethylene film are laminated in this order, sealed, and acetic acid A generation quantitative test module was produced.

  The sealing is performed by temporarily pressing a laminated body of the front side transparent protective member, the sealing film for determining the amount of acetic acid generated, and the back side protective member with a vacuum laminator at 90 ° C. for 8 minutes, followed by temporary pressure bonding. This was carried out by heating and crosslinking until the gel fraction (crosslinking degree) of the generation amount sealing film reached 90%.

(2) Acetic acid generation amount quantitative test The acetic acid generation amount quantitative test module prepared above was allowed to stand in an environment of a temperature of 121 ° C and a humidity of 100% RH for 240 hours. The sample was immersed in 2.0 ml of acetone for 48 hours, and the amount of acetic acid (ppm) contained in the acetone extract was quantified using a gas chromatograph. The results are shown in Table 1. In Table 1, “◎”, “◯”, and “X” are as follows.

A: The amount of acetic acid is less than 500 ppm. A: The amount of acetic acid is 500 ppm or more and less than 2000 ppm. X: The amount of acetic acid is 2000 ppm or more.

  From the results of Table 1, it can be seen that the sealing film containing the aziridine compound can highly suppress the generation of acetic acid due to the hydrolysis of EVA.

It is sectional drawing of a common solar cell. It is sectional drawing of the acetic acid generation amount fixed quantity test module produced in the Example.

Explanation of symbols

11, 21 Surface side transparent protective member,
12, 22 Back side protection member,
13A surface side sealing film,
13B Back side sealing film,
14 solar cells,
26 Sealing film for determining the amount of acetic acid generated.

Claims (14)

  A composition for a solar cell encapsulating film comprising an ethylene-polar monomer copolymer and an aziridine compound having at least one aziridine group which may be substituted in the molecule. The aziridine compound is represented by the following formula (1):

[Wherein X is —NH—CO— or the following formula (2)

(Wherein R ³ and R ⁴ are divalent aliphatic hydrocarbon groups which may have a substituent),
R ² represents the following formula (3) or (4)

(Wherein R ^{5 to} R ¹¹ may be the same or different and are a hydrogen atom or a monovalent aliphatic hydrocarbon group which may have a substituent). Yes,
n is an integer of 1 to 4,
when n is 1, R ¹ is a monovalent aliphatic hydrocarbon group which may have a substituent;
When n is 2, R ¹ is a divalent aliphatic hydrocarbon group, an arylene group, or an arylene alkylenearylene group, each of which may have a substituent,
when n is 3, R ¹ is a trivalent aliphatic hydrocarbon group which may have a substituent;
The composition for solar cell encapsulating film according to claim 1, wherein when n is 4, R ¹ is a tetravalent carbon atom.   The aziridine compound is trimethylolpropane-tris- (β- (1-aziridinylpropionate)), N, N′-toluene-2,4-bis (1-aziridinecarboxamide), N, N ′. -At least one selected from the group consisting of hexamethylene-1,6-bis (1-aziridinecarboxamide) and N, N'-diphenylmethane-4,4'-bis (1-aridiridinecarboxamide) The composition for solar cell sealing films of Claim 1 or 2.   The composition for solar cell sealing film of any one of Claims 1-3 which contains 0.1-5 mass parts of said aziridine compounds with respect to 100 mass parts of said ethylene-polar monomer copolymers. .   The composition for solar cell sealing film according to any one of claims 1 to 4, wherein the ethylene-polar monomer copolymer is an ethylene-vinyl acetate copolymer.   The content of the polar monomer in the ethylene-polar monomer copolymer is 20 to 35 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer. Composition for solar cell sealing film.   The composition for solar cell sealing films of any one of Claims 1-6 which further contain a crosslinking agent.   The composition for solar cell sealing film according to claim 7, wherein the content of the crosslinking agent is 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer.   The composition for solar cell sealing film of any one of Claims 1-8 which further contain a crosslinking adjuvant.   The composition for solar cell sealing films of any one of Claims 1-9 which further contains a silane coupling agent.   The composition for solar cell sealing films of any one of Claims 1-10 which further contains a ultraviolet absorber.   The composition for solar cell sealing film of any one of Claims 1-11 which further contains a light stabilizer.   The solar cell sealing film which uses the composition for solar cell sealing films of any one of Claims 1-12. In a solar cell formed by sealing a solar cell by interposing a sealing film between the front surface side transparent protective member and the back surface side protective member and integrating them with each other,
The solar cell, wherein the sealing film is the solar cell sealing film according to claim 13.

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