JP2015162498A - Laminate for solar cell sealing material, solar cell sealing material, and solar battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a superior laminate for a solar cell sealing material which is excellent in PID suppressing performance, and achieves good balance among cross-linkability, transparency and electric characteristics; a solar cell sealing material; and a solar battery module.SOLUTION: A laminate for a solar cell sealing material comprises at least two layers including "A" layer having an ethylene α-olefin copolymer resin (a) satisfying the requirements (a-1) to (a-2) below, and "B" layer including a monomer copolymer resin (b) including an ethylene functional group and satisfying the requirement (b-1) below: (a-1) MFR (at 190°C under a load of 21.18 N) is 0.1-50 g/10 min.; (a-2) the density is 0.860-0.920 g/cm; and (b-1) the content of a monomer including a polar group is 10-40 wt.%.

Description

  The present invention relates to a laminate for a solar cell encapsulant, a solar cell encapsulant, and a solar cell module. More specifically, the present invention is excellent in PID suppression performance and excellent in balance in crosslinkability, transparency, and electrical characteristics. It is related with the laminated body for solar cell sealing materials, a solar cell sealing material, and a solar cell module.

As global environmental problems such as an increase in carbon dioxide are being highlighted, solar power generation is gaining attention again along with effective utilization of hydropower, wind power, geothermal heat, and the like.
Photovoltaic power generation generally protects solar cell elements such as silicon, gallium-arsenic, copper-indium-selenium (hereinafter also referred to as “cells”) with an upper transparent protective material and a lower substrate protective material. And a protective material are fixed with a resin sealing material, and a packaged solar cell module is used. Research and development aimed at improving performance such as power generation efficiency and reducing costs are being promoted.

  As a condition of the solar cell encapsulant constituting the solar cell module, it is required to have good transparency in order to secure the incident amount of sunlight so that the power generation efficiency of the solar cell is not lowered. Moreover, since a solar cell module is usually installed outdoors and exposed to sunlight for a long time, the temperature rises. Therefore, in order to avoid troubles in which the resin sealing material flows and the module is deformed, it must have heat resistance. Moreover, in order to reduce the material cost of a solar cell element year by year, the thickness has been reduced, and a sealing material having further excellent flexibility has been demanded.

At present, as a solar cell sealing material in a solar cell module, an ethylene / vinyl acetate copolymer is widely used as a resin component, and an organic peroxide or a silane coupling agent is used in combination as an additive (for example, , See Patent Document 1). In addition, a polyethylene resin such as an ethylene / α-olefin copolymer can also be used as a solar cell sealing material (see, for example, Patent Document 2).
And in the sealing operation of the solar cell element, after the solar cell element is covered with a resin sealing material, the solar cell element is heated for several minutes to tens of minutes and temporarily bonded, and the organic peroxide is decomposed in the oven. Then, heat treatment, adhesion, and the like are imparted to the sealing material by performing heat treatment for several minutes to one hour for adhesion (see, for example, Patent Document 3).

  On the other hand, in recent years, it has been reported that PID (abbreviation of Potato Induced Degradation) phenomenon in which the power generation capacity is greatly reduced due to the increase in the system voltage accompanying the enlargement of the power generation system such as mega solar, which is a big problem. ing. The PID phenomenon is caused by the leakage current generated by a large potential difference generated between the outer frame of the solar cell module and the cell inside the module, and the movement of sodium ions due to moisture adhesion to the glass surface as the upper transparent protective material. This is considered to be a cause of the occurrence, and it is considered that there is a PID suppressing effect by increasing the volume resistivity of the sealing material for fixing the cell and enhancing the insulation.

  However, a sealing material using an ethylene / vinyl acetate copolymer can provide a solar cell sealing material excellent in transparency, flexibility, crosslinkability, etc., but has a low volume resistivity and thus a high power generation voltage. In a large-scale power generation system, there is a high possibility that a PID problem will occur.

  On the other hand, it has been reported that a sealing material using an ethylene / α-olefin copolymer has a high volume resistivity and thus has an effect of suppressing the PID phenomenon (for example, see Patent Document 4).

  Moreover, although the solar cell sealing material which blended the ethylene-vinyl acetate copolymer and the ethylene-alpha-olefin copolymer is also reported (for example, refer patent document 5 and patent document 6), the effect of PID suppression is reported. There is no description about.

JP-A-9-116182 International Publication No. 2010/114028 JP 2003-204073 A International Publication No. 2012/046456 JP 2011-153286 A JP 2013-155238 A

  According to the inventors' investigation, the sealing material using the ethylene / α-olefin copolymer disclosed in Patent Document 4 has a high PID deterrent effect, but when compared with the ethylene / vinyl acetate copolymer, Because the crosslinking rate is inferior, and it is necessary to increase the amount of crosslinking agent and crosslinking aid in order to maintain the crosslinking rate, it is inferior in economic efficiency and used as a sealing material to add a large amount of crosslinking agent and crosslinking agent. In some cases, there was a problem of foaming inside. Moreover, in the sealing material which blended the ethylene / vinyl acetate copolymer and the ethylene / α-olefin copolymer disclosed in Patent Documents 5 and 6 and the like, although PID generation can be prevented, Further, combinations having excellent quality such as transparency and crosslinkability are limited, and further improvement has been demanded.

  In view of the above problems, an object of the present invention is to provide a laminate for a solar cell encapsulant that is not only excellent in PID suppression performance but also excellent in crosslinkability, transparency, and electrical characteristics.

  As a result of intensive studies to solve the above problems, the present inventors have an A layer containing a specific polyethylene resin and a B layer containing a specific ethylene-functional group-containing monomer copolymer resin, and at least two layers. It has been found that a laminate for solar cell encapsulant comprising the above can solve the above problems, and has completed the present invention.

That is, according to the first invention of the present invention, the A layer containing the ethylene / α-olefin copolymer resin (a) satisfying the following requirements (a-1) to (a-2), and the following ( A laminate for a solar cell encapsulant comprising at least two layers having a B layer containing an ethylene-functional group-containing monomer copolymer resin (b) that satisfies the requirement of b-1) is provided.
(A-1) MFR (190 ° C., 21.18 N load): 0.1 to 50 g / 10 min (a-2) Density: 0.860 to 0.920 g / cm ³
(B-1) Content of polar group-containing monomer: 10 to 40 wt%

According to the second invention of the present invention, in the first invention, the ethylene / α-olefin copolymer resin (a) further satisfies the following requirements (a-3) and (a-4): The laminated body for solar cell sealing materials which fills is provided.
(A-3) The total number of double bonds of vinyl and vinylidene is 0.5 (total / total 1000C) or more (provided that the number of vinyl and vinylidene is a total of 1000 main chains and side chains measured by NMR) Per carbon number)
(A4) The total number of double bonds of vinyl and vinylidene is 55% or more of the total number of all double bonds (vinyl, vinylidene, cis-vinylene, trans-vinylene, trisubstituted olefin) (however, vinyl, (The number of vinylidene, cis-vinylene, trans-vinylene, and tri-substituted olefin is the number per 1000 carbon atoms in total of main chain and side chain measured by NMR)

  According to the third invention of the present invention, in the first or second invention, the solar cell comprises three layers of the outermost layer, the intermediate layer and the outermost layer, and has the B layer as the outermost layer and the A layer as the intermediate layer. A laminate for an encapsulant is provided.

  Moreover, according to the 4th invention of this invention, in 1st or 2nd invention, the laminated body for solar cell sealing materials which consists of two layers of A layer and B layer is provided.

According to the fifth invention of the present invention, in any one of the first to fourth inventions, the solar cell is sealed with a volume resistivity of 1.0 × 10 ^{13 to} 1.0 × 10 ¹⁶ Ω · cm. A laminate for a material is provided.

  According to a sixth invention of the present invention, in any one of the first to fifth inventions, the ethylene / α-olefin copolymer resin (a) is a laminate for a solar cell encapsulant obtained from a metallocene catalyst. Is provided.

  According to the seventh invention of the present invention, in any one of the first to sixth inventions, the solar cell encapsulant wherein the ethylene / α-olefin copolymer resin (a) contains 10 to 30 mol% of propylene as a comonomer. A resin laminate for a stopping material is provided.

  According to the eighth invention of the present invention, in any one of the first to seventh inventions, the ethylene-functional group-containing monomer copolymer resin (b) is an ethylene-vinyl acetate copolymer, ethylene- ( Selected from the group consisting of a (meth) acrylic acid ester copolymer, an ethylene- (meth) acrylic acid copolymer, an ethylene- (meth) acrylic acid ester multi-component copolymer, and an ethylene- (meth) acrylic acid multi-component copolymer There is provided a resin laminate for a solar cell encapsulant which is one or more ethylene-functional group-containing monomer copolymers.

  Moreover, according to the ninth invention of the present invention, in any one of the first to eighth inventions, there is provided a laminate for a solar cell encapsulant obtained by a co-pressing multilayer molding method.

According to a tenth aspect of the present invention, in any one of the first to ninth aspects, the A layer and / or the B layer further contains the following component (c), and the content of the component (c): However, the laminated body for solar cell sealing materials which is 0.2-5 weight part with respect to 100 weight part of resin contained in the layer in which a component (c) is contained is provided.
Component (c): Organic peroxide

  Moreover, according to the eleventh invention of the present invention, in any one of the first to tenth inventions, there is provided a resin laminate for a solar cell encapsulant containing the following component (d).

  Moreover, according to 12th invention of this invention, the solar cell sealing material solar cell sealing material using the resin laminated body for solar cell sealing materials which concerns on any one of 1st-11th invention is provided. .

  Furthermore, according to the thirteenth aspect of the present invention, a solar cell module is provided although the solar cell sealing material solar cell sealing material according to the twelfth aspect is used.

  The laminated body for solar cell sealing materials of this invention is excellent in PID suppression performance, and is excellent also in crosslinkability, transparency, and an electrical property (volume resistivity) with sufficient balance. Moreover, the solar cell module using the solar cell encapsulating material of the present invention can be expected to maintain stable conversion efficiency for a long period of time because the generation of PID is greatly suppressed even in a large-scale solar cell power generation system.

FIG. 1 is a cross-sectional view schematically showing one embodiment of a solar cell module.

The present invention comprises an A layer containing a specific ethylene / α-olefin copolymer resin (a) and a B layer containing a specific ethylene-functional group-containing monomer copolymer resin (b). The new laminated body for solar cell sealing materials which concerns, and a solar cell sealing material and solar cell module using the same are related.
Hereinafter, each component used in the present invention, the resulting laminate for a solar cell encapsulant (hereinafter also simply referred to as “laminate”), a solar cell encapsulant, a solar cell module, and the like will be described in detail.

1. Laminate for Solar Cell Sealant The laminate of the present invention comprises an A layer containing an ethylene / α-olefin copolymer resin (a) (hereinafter also referred to as “component (a)”) and a specific ethylene- It consists of at least 2 layers which have B layer containing functional group containing monomer copolymer resin (b) (henceforth "component (b)").

(1) Ethylene / α-olefin copolymer resin (a)
Component (a) used in the present invention satisfies the following requirements (a-1) to (a-2), and more preferably satisfies the following requirements (a-3) to (a-4).
(A-1) MFR (190 ° C., 21.18 N load): 0.1 to 50 g / 10 min (a-2) Density: 0.860 to 0.920 g / cm ³
(A-3) The total number of double bonds of vinyl and vinylidene is 0.5 (unit / total 1000C) or more (however, the number of vinyl and vinylidene is a total of 1000 main chains and side chains measured by NMR) Is the number per carbon number.)
(A-4) The total number of vinyl and vinylidene double bonds is 55% or more of the total number of all double bonds (vinyl, vinylidene, cis-vinylene, trans-vinylene, trisubstituted olefin) (however, (The number of vinyl, vinylidene, cis-vinylene, trans-vinylene, and tri-substituted olefin is the number per 1000 carbon atoms in total of the main chain and side chain measured by NMR)

In the laminated body of the present invention, by having the A layer containing the component (a), the volume resistivity is higher than that of a conventional sealing material made of EVA or EVA and an ethylene / α-olefin resin. Obtained and exhibits excellent PID suppression performance. One of the reasons for exhibiting excellent PID suppression performance is considered to be that the movement of sodium ions is inhibited by the presence of a continuous nonpolar resin layer.
Further, by blending component (c): organic peroxide with component (a) having specific density, number of unsaturated bonds, etc., layer A containing component (a) is crosslinked in a relatively short time. Therefore, when the laminated body of this invention is used as a solar cell sealing material, module formation is easy and manufacturing cost can be reduced. Moreover, the obtained solar cell module becomes excellent in heat resistance, transparency, and weather resistance, and it can be expected to maintain stable conversion efficiency for a long period of time.

(I) Each requirement (a-1) MFR
The component (a) used in the present invention has an MFR (190 ° C., 21.18 N load) of 0.1 to 50 g / 10 minutes, preferably 1 to 50 g / 10 minutes, more preferably 2 to 40 g / 10. Minutes. When the MFR is less than 0.1 g / 10 min, the molecular weight is too high, the melt viscosity becomes high, and sheet formation becomes difficult. On the other hand, if the MFR exceeds 50 g / 10 min, the melt viscosity becomes too low and the handleability is lacking. MFR can be controlled, for example, by appropriately adjusting the temperature and pressure during polymerization, the amount of chain transfer agent added, and the like.
In addition, MFR is the value measured based on JIS-K6922-2: 1997 appendix (190 degreeC, 21.18N load).

(A-2) Density The component (a) used in the present invention has a density of 0.860 to 0.920 g / cm ³ , preferably 0.865 to 0.915 g / cm ³ , more preferably 0.870. ˜0.910 g / cm ³ . Particularly preferred is an ultra-low density ethylene / α-olefin copolymer of 0.870 to 0.900 g / cm ³ . When the density is less than 0.860 g / cm ³ , the crystallization speed is slow and the sheet is sticky, and thus the processed sheet is blocked. On the other hand, if the density exceeds 0.920 g / cm ³ , the crystallinity becomes high, so that the transparency is lowered, and the rigidity of the sheet after processing is too high and the handling property is lacking. The density can be controlled, for example, by appropriately adjusting the α-olefin content, the polymerization temperature, the catalyst amount, and the like.
In addition, a density is the value measured based on JIS-K6922-2: 1997 annex (in the case of a low density polyethylene, 23 degreeC).

(A-3) Total number of vinyl and vinylidene The component (a) used in the present invention has a total number of vinyl and vinylidene double bonds per 1000 carbon atoms in total of main chain and side chain measured by NMR. It is preferably 0.50 (pieces / total 1000C) or more, more preferably 0.50 to 5.0 (pieces / total 1000C), more preferably 0.60 to 4.5 (pieces / total 1000C). More preferably 0.70 to 4.0 (pieces / total 1000C), and most preferably 0.80 to 4.0 (pieces / total 1000C).
When the total number of vinyl and vinylidene is in the above range, a sealing material having an excellent crosslinking rate is obtained, and when it is less than 0.5, the crosslinking rate is not sufficient. The total number of vinyl and vinylidene can be controlled within the above range by appropriately selecting the appropriate metallocene catalyst, the polymerization temperature, and the type of comonomer.
In addition, the number of these double bonds is the number per 1000 carbon atoms in total of the main chain and the side chain, and was calculated using the integrated intensity of the characteristic peaks of the ¹ H-NMR spectrum and ¹³ C-NMR spectrum. Value.

(A-4) Type of double bond and ratio thereof Component (a) used in the present invention has a total number of vinyl and vinylidene in the ethylene / α-olefin copolymer in the ethylene / α-olefin copolymer. It is preferably 55% or more of the total number of all the double bonds (vinyl, vinylidene, cis-vinylene, trans-vinylene, trisubstituted olefin), more preferably 60% or more, still more preferably 65% or more, Most preferably, it is 70% or more. When the total number of vinyl and vinylidene is 55% or more of the total number of double bonds, a sealing material having an excellent crosslinking rate is obtained. When the total number is small, the crosslinking rate is not sufficient.

In addition, the component (a) used in the present invention is composed of a double bond (vinyl, vinylidene, cis-vinylene, trans-) per 1000 carbon atoms in total of main chain and side chain measured by NMR from the viewpoint of crosslinking rate. The number of vinylene or trisubstituted olefin) is preferably 1.0 (total / total 1000C) or more, more preferably 1.0 to 5.0 (total / 1000C), and more preferably 1.1. It is -4.5 (piece / total 1000C), More preferably, it is 1.2-4.0 (piece / total 1000C).
Examples of a method for adjusting the total number of double bonds include selection of an appropriate metallocene catalyst, a method for appropriately adjusting the polymerization temperature, and the type of comonomer.
In addition, the number of these double bonds was computed using the integrated intensity | strength of the characteristic peak of a < ¹ > H-NMR spectrum and a < ¹³ > C-NMR spectrum similarly to said (a3).

(Ii) Monomer structure of ethylene / α-olefin copolymer resin (a) The component (a) used in the present invention is a random copolymer of ethylene and α-olefin, whose main component is a structural unit derived from ethylene. It is a polymer.
The α-olefin used as a comonomer is preferably an α-olefin having 3 to 12 carbon atoms. Specifically, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-heptene, 4-methyl-pentene-1, 4-methyl-hexene-1, 4,4-dimethylpentene- 1 etc. can be mentioned. Specific examples of such ethylene / α-olefin copolymers include ethylene / propylene copolymers, ethylene / 1-butene copolymers, ethylene / 1-hexene copolymers, ethylene / 1-octene copolymers, ethylene -4-methyl-pentene-1 copolymer etc. are mentioned.

In the component (a) used in the present invention, the α-olefin content in the component (a) is preferably 5 to 40 mol%, more preferably 10 to 35 mol%, particularly 10 to 30 mol. % Is preferred. If it is this range, the softness | flexibility and transparency, such as a film, will be favorable, and a crosslinking rate will also become favorable. If the α-olefin content is less than 10 mol%, the transparency and flexibility of the resin may deteriorate. On the other hand, when it exceeds 40 mol%, since the softening point of the ethylene / α-olefin copolymer is too low, blocking of the obtained encapsulant sheet becomes worse and handling becomes insufficient.
Here, the content of α-olefin is a value measured by ¹³ C-NMR method under the following conditions.
Device: JEOL-GSX270 manufactured by JEOL
Concentration: 300 mg / 2 mL
Solvent: Orthodichlorobenzene

  In the present invention, the α-olefin used as a comonomer of the ethylene / α-olefin copolymer is particularly preferably propylene. This is because, when propylene is used as a comonomer and polymerization is performed using a metallocene catalyst described later, an ethylene / α-olefin copolymer having a large total number of vinyl and vinylidene can be obtained. When an α-olefin such as 1-hexene or 1-octene is polymerized as a comonomer main component, this effect cannot be obtained.

  Although the detailed cause of the ethylene / α-olefin copolymer having a large total number of vinyl and vinylidene when propylene is used is not known, the possible mechanism for the increase in vinylidene is shown below.

In the upper side of the above formula, an α-olefin such as 1-hexene or 1-octene is inserted into the polymer chain (P) in the polymerization reaction, and subsequently the hydrogen at the β position of the complex metal (M) is withdrawn. Body 1 is produced. In this intermediate 1, the elimination reaction of (a) or (b) from hydrogen can be considered. However, due to steric and electronic factors, the hydrogen of (a) is preferentially eliminated and intermediate 2 becomes Arise. Further, a trisubstituted olefin or vinylidene is generated from the intermediate 2 depending on the insertion position of the next monomer, but the route in which the vinylidene is generated is sterically inserted between the complex metal (M) and the secondary carbon. Is difficult. Therefore, the intermediate 2 preferentially produces a trisubstituted olefin body through insertion of the complex metal (M) and primary carbon.
On the other hand, on the lower side of the above formula, when propylene is inserted into the polymer chain (P) during the polymerization reaction and hydrogen at the β-position of the complex metal (M) is subsequently extracted, intermediate 3 is formed. In this intermediate 1 as well, the elimination reaction of (a) or (b) from hydrogen can be considered, but the hydrogen of (b) is preferentially eliminated due to steric and electronic factors, and the intermediate 4 is produced. Furthermore, vinylidene is generated regardless of which of the following monomers is inserted into intermediate 4.
For the above reason, it is considered that vinylidene is preferentially produced after propylene insertion, compared to after insertion of α-olefin such as 1-hexene and 1-octene. In the present invention, the mechanism of occurrence of double bonds such as vinylidene is not limited to the above mechanism.

  When propylene is used as a comonomer, the content of the comonomer derived from propylene in the component (a) is preferably 10 mol% or more, more preferably 10 to 30 mol%, still more preferably 15 to 25 mol%. When the content of propylene is less than 10 mol%, the crosslinking rate may decrease due to a decrease in the number of branches.

Moreover, the alpha olefin used as a comonomer is a range which satisfies (a-1)-(a-2), Preferably (a-3)-(a-4), or even 1 type or a combination of 2 or more types Good. When combining two kinds of α-olefins to form a terpolymer, ethylene / propylene / 1-butene terpolymer, ethylene / propylene / 1-hexene terpolymer, ethylene / propylene / 1 -Octene terpolymers and the like.
As a comonomer, a small amount of a diene compound such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, 1,8-nonadiene, and 1,9-decadiene may be added to the α-olefin. When these diene compounds are added, long-chain branching can be performed, so that the crystallinity of the ethylene / α-olefin copolymer is lowered, transparency, flexibility, adhesiveness, etc. are improved, and long-chain branch end groups are added. Since it becomes an unsaturated group, a crosslinking reaction with an organic peroxide, a copolymerization reaction with an acid anhydride group-containing compound or an epoxy group-containing compound, and a graft reaction can be easily performed. Further, cyclic dienes such as 5-vinyl-2-norbornene and 5-ethylidene-2-norbornene can be used as a diene compound blended in a small amount in the ethylene / α-olefin copolymer.
The content of the diene compound as such a comonomer is preferably 0.01 to 5.00 mol%, more preferably 0.02 to 1.00 mol%, and still more preferably 0, from the viewpoints of flexibility and crosslinking properties. 0.05 to 0.50 mol%.

(Iii) Polymerization catalyst and polymerization method of ethylene / α-olefin copolymer resin (a) The catalyst used in the production of component (a) used in the present invention is not particularly limited, and is a conventionally known Ziegler catalyst. A vanadium catalyst or a metallocene catalyst can be used, but a vanadium catalyst or a metallocene catalyst is preferably used, and a metallocene catalyst is more preferably used.
Although it does not necessarily limit as a metallocene catalyst, The catalyst which uses a metallocene compound, such as a zirconium compound coordinated with the group which has a cyclopentadienyl skeleton, etc., and a promoter as a catalyst component is mentioned. In particular, it is preferable to use a metallocene compound such as a zirconium compound coordinated with a group having a cyclopentadienyl skeleton.
The production method is not particularly limited, and a high-pressure ion polymerization method, a gas phase method, a solution method, a slurry method, or the like can be used, and an ethylene / olefin copolymer with adjusted double bonds according to the present invention is obtained. Therefore, since it is desirable to carry out the polymerization at a high temperature of 150 to 330 ° C., it is preferable to use a high-pressure ion polymerization method (“Polyethylene Technology Reader”, Chapter 4, edited by Kazuo Matsuura and Naotaka Mikami, 2001).

(2) Ethylene-functional group-containing monomer copolymer resin (b)
The component (b) used in the present invention satisfies the following requirement (b-1).
(B-1) Content of polar group-containing monomer: 10 to 40% by weight
By having the B layer containing the component (b), the laminate of the present invention is particularly excellent in cross-linking properties and additive retention as compared with a conventional sealing material made of ethylene / α-olefin.

(I) Monomer structure Component (b) used in the present invention is a copolymer of ethylene and a polar group-containing monomer, the main component of which is a structural unit derived from ethylene.
Specific examples of the component (b) include ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid ester copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester multielement. A copolymer, an ethylene- (meth) acrylic acid multi-component copolymer, etc. can be mentioned, It can use 1 type or in mixture of 2 or more types. Among these, an ethylene-vinyl acetate copolymer is preferable from the viewpoints of flexibility, transparency, and crosslinking rate.
Examples of commercially available ethylene-vinyl acetate include EVAFLEX (registered trademark): EV150, EV250 manufactured by Mitsui DuPont Polychemical Co., Ltd. and Novatec (registered trademark) EVA: LV670, LV780 manufactured by Nippon Polyethylene Co., Ltd. Can be mentioned.

(Ii) Each requirement (b-1) Content of polar group-containing monomer Component (b) used in the present invention has a polar group-containing monomer content of 10 to 40% by weight, preferably 12 to 38% by weight. %, More preferably 14 to 36% by weight. When the content is less than 10% by weight, the transparency and flexibility are insufficient, and when it exceeds 40% by weight, the sealing material is too soft to be attached, resulting in poor handling.

(Iii) Other properties The component (b) used in the present invention preferably has an MFR of 0.1 to 100 g / min, and more preferably 2 to 40 g / min. When the MFR is less than 0.1 g / 10 min, the molecular weight is too high, the melt viscosity becomes high, and sheet formation becomes difficult. On the other hand, if the MFR exceeds 100 g / 10 min, the melt viscosity becomes too low and the handleability is lacking. MFR can be controlled, for example, by appropriately adjusting the temperature and pressure during polymerization, the amount of chain transfer agent added, and the like.
In addition, MFR is a value measured by JIS-K6922-2: 1997 appendix (190 degreeC, 21.18N load).

(3) Layer structure of laminate for solar cell encapsulant The laminate of the present invention comprises at least two layers having an A layer containing component (a) and a B layer containing component (b). A resin layer other than the B layer may be included. Of these, a laminate comprising three layers of outermost layer / intermediate layer / outermost layer, with the outermost layer being B layer and the intermediate layer being A layer, and a laminate comprising two layers of A layer and B layer are preferred.
When the laminate of the present invention is used for a solar cell module as a solar cell encapsulant, the component (a) contained in the A layer contributes to the improvement of insulation, and the component (b) contained in the B layer In particular, it contributes to the improvement of crosslinkability, and as a whole layer, it has an excellent balance of physical properties and exhibits a PID suppression effect.

  When the outermost layer is composed of the outermost layer / intermediate layer / outermost layer, and the outermost layer is the B layer and the intermediate layer is the A layer, both outer layers are polar, so volatile additives (especially organic peroxidation) ), The additive retention performance (bleed resistance) is improved, and the degree of crosslinking is improved during use after transportation and storage. Further, since the additive does not bleed, the surface of the sealing material is not sticky, and the handleability is excellent.

  In addition, in order to further impart flexibility and the like to the A layer and the B layer used in the present invention, ethylene such as EBR and EPR polymerized by a Ziegler-based or metallocene-based catalyst within a range that does not impair the purpose of the present invention. A rubber compound such as an α-olefin elastomer or SEBS, a styrene elastomer such as a hydrogenated styrene block copolymer can be added in an amount of about 3 to 75% by weight. Furthermore, in order to give melt tension etc., about 3 to 75 weight% of high pressure method low density polyethylene can also be mix | blended.

The thickness of the A layer is preferably 1 to 99%, more preferably 10 to 90%, and still more preferably 15 to 80%, and the thickness of the B layer is preferably relative to the thickness of the entire laminate of the present invention. Is 1 to 99%, more preferably 10 to 90%, and still more preferably 20 to 85%. When the thickness of each layer is within the above range, PID suppression performance and crosslinkability (effect) are obtained.
Furthermore, when the outermost layer / intermediate layer / outermost layer is composed of three layers and the outermost layer is the B layer and the intermediate layer is the A layer, the ratio of the thickness of the B layer: A layer: B layer is not particularly limited. , Preferably 0.1-3.0: 1.0: 0.1-3.0, more preferably 0.3-2.0: 1.0: 0.3-2.0, and even more preferably 0 .3 to 0.8: 1.0: 0.3 to 0.8.

(4) Other additive components (i) Component (c): Organic peroxide The layer A and / or layer B constituting the laminate of the present invention further contains an organic peroxide as the component (c). Can do. The organic peroxide is mainly used for crosslinking the resin component in the laminate.
As the organic peroxide, an organic peroxide having a decomposition temperature (temperature at which the half-life is 1 hour) is 70 to 180 ° C., particularly 90 to 160 ° C. can be used. Examples of such organic peroxides include t-butyl peroxyisopropyl carbonate, t-butyl peroxy-2-ethylhexyl carbonate, t-butyl peroxyacetate, t-butyl peroxybenzoate, dicumyl peroxide, 2 , 5-dimethyl-2,5-di (t-butylperoxy) hexane, di-t-butylperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, 1 , 1-di (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-butylperoxy) cyclohexane, methyl ethyl ketone peroxide, 2,5-dimethylhexyl-2,5- Diperoxybenzoate, t-butyl hydroperoxide, p-menthane hydroperoxy Id, benzoyl peroxide, p- chlorobenzoyl peroxide, t- butyl peroxy isobutyrate, hydroxyheptyl peroxide, and di cyclohexanone peroxide.

  The blending ratio of the component (c) is preferably 0.2 to 5 parts by weight, more preferably 100 parts by weight of the resin component in the layer (A layer / B layer) containing the component (c). Is 0.5 to 3 parts by weight, more preferably 1 to 2 parts by weight. When the blending ratio of component (c) is less than the above range, crosslinking is not performed or it takes time for crosslinking. Moreover, when larger than the said range, dispersion | distribution will become inadequate and it will be easy to become non-uniform | crosslinked.

(Ii) Component (d): Silane Coupling Agent The laminate of the present invention preferably further contains a silane coupling agent as component (d). A silane coupling agent mainly improves the adhesive force with the upper protection material and solar cell element of a solar cell.
Examples of the silane coupling agent in the present invention include γ-chloropropyltrimethoxysilane; vinyltrichlorosilane; vinyltriethoxysilane; vinyltrimethoxysilane; vinyl-tris- (β-methoxyethoxy) silane; γ-methacryloxypropyl. Β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane; γ-glycidoxypropyltrimethoxysilane; vinyltriacetoxysilane; γ-mercaptopropyltrimethoxysilane; γ-aminopropyltrimethoxysilane; N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane and the like can be mentioned. Vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and 3-acryloxypropyltrimethoxysilane are preferable.
These silane coupling agents are preferably used in an amount of 0 to 5 parts by weight, more preferably 0.005 parts by weight with respect to 100 parts by weight of the resin component in the layer (A layer / B layer) containing the component (d). It is used in an amount of 01 to 5 parts by weight, more preferably 0.01 to 2 parts by weight, and still more preferably 0.05 to 1 part by weight.

(Iii) Other components In the laminated body of this invention, another additional arbitrary component can be mix | blended in the range which does not impair the objective of this invention remarkably. Examples of such optional components include an antioxidant, a crystal nucleating agent, a clarifying agent, and a lubricant used in ordinary polyolefin-based resin materials, in addition to the light stabilizer, crosslinking aid, and ultraviolet absorber described below. , Colorants, dispersants, fillers, fluorescent brighteners and the like.

(Light stabilizer)
The laminate of the present invention preferably contains a hindered amine light stabilizer. The hindered amine light stabilizer captures radical species harmful to the polymer and prevents generation of new radicals. There are many types of hindered amine light stabilizers ranging from low molecular weight compounds to high molecular weight compounds, but any conventionally known compounds can be used without particular limitation.

  Low molecular weight hindered amine light stabilizers include decanedioic acid bis (2,2,6,6-tetramethyl-1 (octyloxy) -4-piperidinyl) ester, 1,1-dimethylethyl hydroperoxide and Consists of 70% by weight of a reaction product of octane (molecular weight 737) and 30% by weight of polypropylene; bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis (1,1 -Dimethylethyl) -4-hydroxyphenyl] methyl] butyl malonate (molecular weight 685); bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl-1,2,2,6 6-pentamethyl-4-piperidyl sebacate mixture (molecular weight 509); bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate ( 481); tetrakis (2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate (molecular weight 791); tetrakis (1,2,2,6, 6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate (molecular weight 847); 2,2,6,6-tetramethyl-4-piperidyl-1,2,3,4-butane Mixture of tetracarboxylate and tridecyl-1,2,3,4-butanetetracarboxylate (molecular weight 900); 1,2,2,6,6-pentamethyl-4-piperidyl-1,2,3,4-butane Examples thereof include a mixture (molecular weight 900) of tetracarboxylate and tridecyl-1,2,3,4-butanetetracarboxylate.

  As the high molecular weight hindered amine light stabilizer, poly [{6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2, 2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino}] (molecular weight 2,000-3,100); succinic acid Polymer of dimethyl and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (molecular weight 3,100 to 4,000); N, N ′, N ″, N ″ ′-tetrakis- ( 4,6-bis- (butyl- (N-methyl-2,2,6,6-tetramethylpiperidin-4-yl) amino) -triazin-2-yl) -4,7-diazadecane-1,10- Diamine (molecular weight 2,286) and above A mixture of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol; dibutylamine, 1,3,5-triazine, N, N′-bis (2,2 , 6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine polycondensate (molecular weight 2,600-3) 400) and 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4-acryloyloxy-1-ethyl -2,2,6,6-tetramethylpiperidine, 4-acryloyloxy-1-propyl-2,2,6,6-tetramethylpiperidine, 4-acryloyloxy 1-butyl-2,2,6,6-tetramethylpiperidine, 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine, 4-methacryloyloxy-1,2,2,6,6-pentamethyl Peridine, 4-methacryloyloxy-1-ethyl-2,2,6,6-tetramethylpiperidine, 4-methacryloyloxy-1-butyl-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy Examples include copolymers of cyclic aminovinyl compounds such as -2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-1-propyl-2,2,6,6-tetramethylpiperidine and ethylene. The above-mentioned hindered amine light stabilizers may be used alone or in combination of two or more.

  Among these, as the hindered amine light stabilizer, poly [{6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2 , 2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino}] (molecular weight 2,000-3,100); Polymer of dimethyl acid and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (molecular weight 3,100 to 4,000); N, N ′, N ″, N ″ ′-tetrakis- (4,6-Bis- (butyl- (N-methyl-2,2,6,6-tetramethylpiperidin-4-yl) amino) -triazin-2-yl) -4,7-diazadecane-1,10 -Diamine (molecular weight 2,286) A mixture of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol; dibutylamine, 1,3,5-triazine, N, N′-bis (2 , 2,6,6-Tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine polycondensate (molecular weight 2,600) ~ 3,400) It is preferable to use a copolymer of a cyclic aminovinyl compound and ethylene, because the hindered amine light stabilizer bleeds out over time when the product is used, and the hindered amine light stabilizer is also used. It is preferable to use a material having a melting point of 60 ° C. or higher from the viewpoint of easy preparation of the composition.

In the present invention, the content of the hindered amine light stabilizer is 0.01 to 2.5 parts by weight with respect to 100 parts by weight of the resin component in the layer (A layer / B layer) containing this component. More preferably, 0.01 to 1.0 part by weight, more preferably 0.01 to 0.5 part by weight, still more preferably 0.01 to 0.2 part by weight, and most preferably 0.03 to 1.0 part by weight. 0.1 parts by weight.
When the content is 0.01 parts by weight or more, a sufficient stabilizing effect is obtained, and when the content is 2.5 parts by weight or less, the resin is discolored due to excessive addition of a hindered amine light stabilizer. In the present invention, the weight ratio of the organic peroxide to the hindered amine light stabilizer (organic oxide: light stabilizer) is 1: 0.01 to 1:10, preferably 1: 0.02 to 1: 6.5. Thereby, it becomes possible to remarkably suppress yellowing of the resin.

(Crosslinking aid)
Moreover, a crosslinking aid can be mix | blended with the laminated body of this invention. The crosslinking aid is effective in promoting the crosslinking reaction and increasing the degree of crosslinking of the ethylene / α-olefin / nonconjugated polyene copolymer. Specific examples thereof include polyallyl compounds and poly (meth) acryloxy compounds. Such polyunsaturated compounds can be exemplified.
More specifically, polyallyl compounds such as triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, diallyl fumarate, diallyl maleate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, etc. Examples include poly (meth) acryloxy compounds and divinylbenzene. The crosslinking aid can be blended at a ratio of about 0 to 5 parts by weight with respect to 100 parts by weight of the resin component in the layer containing this component (A layer / B layer).

(UV absorber)
An ultraviolet absorber can be blended in the laminate of the present invention. Examples of the ultraviolet absorber include various types such as benzophenone, benzotriazole, triazine, and salicylic acid ester.
Examples of benzophenone-based ultraviolet absorbers include 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2′-carboxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, and 2-hydroxy-4. -N-dodecyloxybenzophenone, 2-hydroxy-4-n-octadecyloxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2-hydroxy-5-chlorobenzophenone 2,2-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, etc. To mention Can.

Examples of the benzotriazole-based ultraviolet absorber include hydroxyphenyl-substituted benzotriazole compounds such as 2- (2-hydroxy-5-methylphenyl) benzotriazole, 2- (2-hydroxy-5-t-butylphenyl) benzotriazole, 2- (2-hydroxy-3,5-dimethylphenyl) benzotriazole, 2- (2-methyl-4-hydroxyphenyl) benzotriazole, 2- (2-hydroxy-3-methyl-5-t-butylphenyl) Benzotriazole, 2- (2-hydroxy-3,5-di-t-amylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-t-butylphenyl) benzotriazole, and the like. it can. Examples of triazine ultraviolet absorbers include 2- [4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl] -5- (octyloxy) phenol, 2- ( And 4,6-diphenyl-1,3,5-triazin-2-yl) -5- (hexyloxy) phenol. Examples of salicylic acid esters include phenyl salicylate and p-octylphenyl salicylate.
These ultraviolet absorbers can be blended in an amount of 0 to 2.0 parts by weight with respect to 100 parts by weight with respect to 100 parts by weight of the resin component in the layer (A layer / B layer) containing this component. The preferred amount is 0.05 to 2.0 parts by weight, more preferably 0.1 to 1.0 parts by weight, still more preferably 0.1 to 0.5 parts by weight, and most preferably 0.2 to 0 parts by weight. It is recommended to add 4 parts by weight.

(5) Method for Producing Laminate for Solar Cell Encapsulant The method for producing the laminate of the present invention is not particularly limited, and a conventionally known method for producing a laminate can be used. A co-extrusion multilayer molding method such as a (circular) die method can be particularly preferably used. For example, component (c) and component (d) are added to component (a) and / or component (b) as necessary, hindered amine light stabilizers, further crosslinking aids, ultraviolet rays Additives such as absorbers, antioxidants, and light stabilizers are dry blended in advance and supplied from each hopper of the multilayer T-die extruder, and extruded into a sheet at an extrusion temperature of 80 to 130 ° C. Can be obtained.
Further, lamination with other types of resin sealing sheets or the like may be performed, and the surface of the laminate may be embossed on both sides or one side depending on the purpose. Further, as post-treatment, for example, heat setting for dimensional stabilization, corona treatment, or plasma treatment may be performed.

(6) Characteristics of laminated body for solar cell encapsulant The laminated body of the present invention preferably has a volume resistivity of 1.0 × 10 ^{13 to} 1.0 × 10 ¹⁶ Ω · cm, more preferably 5.0 ×. 10 ^{13 to} 7.5 × 10 ¹⁵ Ω · cm, more preferably 1.0 × 10 ^{14 to} 5.0 × 10 ¹⁵ Ω · cm. It is considered that when the volume resistivity is in the above range, an excellent insulating property is obtained and contributes to the PID suppression performance.
Moreover, the laminated body of this invention becomes higher in volume resistivity than the blend resin which has the same composition ratio. Therefore, according to the present invention, a high volume resistivity can be obtained even if the ratio including the component (a) is reduced by using a laminate having the A layer and the B layer. Therefore, as one embodiment of the present invention, ethylene / vinyl acetate is obtained by a laminate structure containing a small amount of component (a) with component (b) such as ethylene / vinyl acetate copolymer as the main material (B layer). While maintaining the excellent properties of the copolymer as a sealing material, the copolymer can have excellent insulating properties and excellent PID suppression performance.

2. Solar cell sealing material and solar cell module The laminate of the present invention is used as a solar cell sealing material. If the solar cell sealing material of this invention is used, a solar cell module can be manufactured by fixing a solar cell element with an upper and lower protective material. The structure of such a solar cell module is not particularly limited, and various known types can be exemplified. FIG. 1 shows an example of the configuration of the solar cell module. For example, an upper transparent protective material 11 / encapsulant 12a / solar cell element 10 / encapsulant 12b / lower protective material 14 having a structure sandwiched between both sides of the solar cell element by the encapsulant, A solar cell element formed on the inner peripheral surface of the upper transparent protective material, such as one having a configuration in which a sealing material and an upper transparent protective material are formed on the solar cell element formed on the peripheral surface, such as a fluororesin system The thing of the structure which forms a sealing material and a lower protective material on what formed the amorphous solar cell element by sputtering etc. on the transparent protective material can be mentioned.

  The solar cell element is not particularly limited, and is based on silicon such as single crystal silicon, polycrystalline silicon, amorphous silicon, III-V group or II-VI group such as gallium-arsenic, copper-indium-selenium, cadmium-tellurium. Various solar cell elements such as compound semiconductor solar cell elements can be used.

Examples of the upper transparent protective material constituting the solar cell module include glass, acrylic resin, polycarbonate, polyester, and fluorine-containing resin.
The lower protective material is a single or multilayer sheet such as a metal or various thermoplastic resin films, for example, a metal such as tin, aluminum or stainless steel, an inorganic material such as glass, polyester, an inorganic vapor-deposited polyester, or fluorine. Examples of the protective material include a single layer or a multilayer such as a containing resin and polyolefin. Such an upper and / or lower protective material can be subjected to a primer treatment in order to enhance the adhesion to the sealing material. In the present invention, glass is preferred as the upper protective material.

  The solar cell encapsulant of the present invention is usually used after being formed into a sheet having a thickness of about 0.1 to 1 mm. If the thickness is less than 0.1 mm, the strength is small and the adhesion is insufficient. If the thickness is more than 1 mm, the transparency may be lowered, which may be a problem. A preferred thickness is 0.1 to 0.8 mm.

  In manufacturing the solar cell module, the solar cell sealing material (sheet) of the present invention is prepared in advance, and the resin composition of the sealing material is melt-bonded at a temperature, for example, 120 to 200 ° C. A module having the above-described configuration can be formed.

  On the other hand, when the solar cell module is manufactured, the sealing material is temporarily applied to the solar cell element or the protective material at a temperature at which the organic peroxide is not substantially decomposed and the sealing material of the present invention is melted. Adhesion is then performed, and then the temperature can be raised to achieve sufficient adhesion and crosslinking of the resin component constituting the solar cell encapsulant. In this case, the solar cell encapsulant layer of the present invention is used in order to obtain a solar cell module with good heat resistance having a melting point (DSC method) of the encapsulant of 85 ° C. or higher and a storage elastic modulus of 150 ° C. of 103 Pa or higher. Gel fraction (0.5 g of sample was placed in a 200-mesh wire mesh and Soxhlet extracted for 12 hours with a xylene solvent, and then the mass fraction of the unmelted portion in the wire mesh was measured) was 50 to 98%, preferably 70 to 95 It is good to crosslink so that it may become about%.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The evaluation methods and resins used in the examples and comparative examples are as follows.

1. Evaluation method of resin component (1) Melt flow rate (MFR): Measured according to JIS-K6922-2: 1997 appendix (190 ° C., 21.18 N load).
(2) Density: Measured according to JIS-K6922-2: 1997 appendix (23 ° C., in the case of low density polyethylene).
(3) mol% of each component
The content of ethylene and α-olefin in the polymer was determined by ¹³ C-NMR with reference to Seger et al. (M. R. Seger and GE Maciel, Anal. Chem., 76, 5734 (2004)). It was calculated by assigning a characteristic peak. The content of non-conjugated polyenes, Pakkanen et al (H. Lasarov and T. T. Pakkanen, Macromol. Chem. Phys., 201, 1780 (2000)) the characteristic peaks in ¹ H-NMR spectrum in Reference Calculated by attribution.
(4) Number of double bonds in polymer The number of double bonds in the polymer was calculated using the integrated intensity of the characteristic peak of the ¹ H-NMR spectrum.

2. Laminate Evaluation Method (1) PID Evaluation A light-receiving surface protection member, a sealing material, a solar cell element, a sealing material, and a back surface protection member were set in this order, and a solar cell module was produced using a vacuum laminator. As a light-receiving surface protection member, 3.2 mm-thick white plate float glass manufactured by Asahi Glass Fabrictech Co., Ltd., the laminate of the present invention as a sealing material, a single crystal silicon type as a solar cell element, and a product made by Toyo Aluminum Co., Ltd. as a back surface protection member A PET backsheet was used. Water was applied to the surface of the surface protection member of the produced module, and the module was held for 96 hours in a constant temperature and humidity chamber at a bath temperature of 60 ° C. and a relative humidity of 85% while DC −1000 V was applied to the internal circuit.
In accordance with IEC61215, the IV characteristics were evaluated, and when the maximum output power Pmax of the IV characteristics after the test was less than 3% compared to the initial value, it was judged as ◯, and when the decline was 5% or more, it was judged as x.
(2) Light transmittance Based on JIS-K7136: 2000, using a HM-150 made by Murakami Color Research Laboratory Co., Ltd., a glass cell containing a 0.5 mm thick laminate with special grade liquid paraffin made by Kanto Chemical. The measurement was carried out by setting.
(3) HAZE
Based on JIS-K7136: 2000, using Murakami Color Research Laboratory Co., Ltd. HM-150, a 0.5 mm thick laminate was set in a glass cell containing special liquid paraffin manufactured by Kanto Chemical and measured. It was.
(4) Gel fraction (crosslinking rate)
The laminate was pressurized by a hot press machine under conditions of 150 ° C.-10 kg / cm ² for 4, 7, 10, 30 minutes, and then cooled for 5 minutes to crosslink the resin. Thereafter, in order to deactivate the cross-linking agent remaining in the resin, the resin was immersed in a sufficient amount of methanol for 24 hours, and then vacuum-dried at 40 ° C. for 24 hours. Was packed in a bag and extracted with xylene using a Soxhlet extractor for 7 hours. Then, it vacuum-dried at 40 degreeC for 24 hours, and calculated the gel fraction from the weight of resin before and behind extraction according to the following formula | equation.
(Weight of the resin after extraction) / (Weight of the resin before extraction) × 100 = Gel fraction (5) Volume resistivity JIS-K6911: 1995, with reference to digital super high resistance / miniature made by ADC Co., Ltd. Using an ammeter 8340A and a resiliency chamber 12704A manufactured by the same company, a volume resistivity of a laminate having a thickness of 0.5 mm was measured by applying 500 V in an atmosphere of 23 ° C. and 50% relative humidity.

3. Raw materials used (1) Ethylene / α-olefin copolymer resin (a)
The following ethylene / α-olefin copolymer resins (α1) to (α7), Engage (registered trademark) “EG8407” manufactured by Dow Chemical Company, and Tuffmer (registered trademark) “A35070S” manufactured by Mitsui Chemicals, Inc. were used. The respective physical properties are shown in Table 1.

(2) Ethylene-functional group-containing monomer copolymer resin (b)
Novatec (registered trademark) EVA “LV670” (β1) manufactured by Nippon Polyethylene and Novatec (registered trademark) EVA “LV780” (β2) manufactured by Nippon Polyethylene were used as ethylene-vinyl acetate (VA) copolymers. The respective physical properties are shown in Table 2.

(3) Component (c): Organic peroxide As the component (c), 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (manufactured by Arkema Yoshitomi, Luperox 101) was used.
(4) Component (d): Silane coupling agent γ-methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM503) was used as the component (d).
(5) Other A polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (TINSFIN 622LD, manufactured by BASF) as a light stabilizer, and 2-hydroxy as an ultraviolet absorber. -4-n-octoxybenzophenone (manufactured by Sun Chemical Co., Ltd., CYTEC UV531), stearyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate as an antioxidant (manufactured by BASF, IRGANOX 1076) Was used.

4). Examples and Comparative Examples (Examples 1 to 12 and Comparative Examples 1 and 2)
Resin compositions for the A layer and the B layer were prepared at the blending ratios shown in Table 3. Specifically, each resin pellet of components (a) and (b) and each additive containing components (d) and (d) were kneaded at 90 ° C. using a 40 mm single screw extruder. Resin compositions (pellets) for A layer and B layer were obtained.
The laminated body shown in Table 3 was produced using a 3 type 3 layer multilayer T-die molding machine. Out of three 30 mm single-screw extruders set at 100 ° C., two B-layer pellets and one A-layer pellet are put into one, and the total thickness is 500 μm, and the A and B layers have a predetermined thickness. The screw rotation speed was adjusted so as to achieve a ratio, and the mixture was extruded from a 300 mm wide die and taken up with a rubber nip roll and a mat roll to obtain a laminate.
In Comparative Examples 1 and 2, laminates were similarly obtained using a single-layer T-die molding machine equipped with a 40 mm single-screw extruder.
The evaluation results of the obtained laminate are shown in Table 3.

5. Evaluation Examples 1-12 differ from EVA single layer comparative example 5 in that no PID phenomenon occurs and have excellent long-term performance.
Moreover, Examples 1-12 are excellent in balance about PID inhibitory performance, crosslinkability, transparency, and electrical properties, and among them, the component (a) satisfies the requirements (a-3) and (a-4). Examples 1 to 8 differ from Comparative Example 2 in which an ethylene / α-olefin copolymer resin single layer was used, and the gel fraction after 30 minutes exceeded 70%, and had excellent heat resistance. .

  The laminate for a solar cell encapsulant of the present invention is preferably used as a solar cell encapsulant because it has excellent PID suppression performance and is well balanced in crosslinkability, transparency, and electrical characteristics. In particular, it is useful as a sealing material for thin film solar cells and a solar cell module.

10: Solar cell element 11: Upper transparent protective material 12a: Sealing material a
12b: Sealing material b
13: Wiring 14: Lower transparent protective material

Claims (13)

Layer A containing an ethylene / α-olefin copolymer resin (a) that satisfies the following requirements (a-1) to (a-2), and an ethylene-functional group that satisfies the requirements (b-1) below A laminate for a solar cell encapsulant comprising at least two layers having a B layer containing the monomer copolymer resin (b).
(A-1) MFR (190 ° C., 21.18 N load): 0.1 to 50 g / 10 min (a-2) Density: 0.860 to 0.920 g / cm ³
(B-1) Content of polar group-containing monomer: 10 to 40 wt% The laminate for a solar cell encapsulant according to claim 1, wherein the ethylene / α-olefin copolymer resin (a) further satisfies the following requirements (a-3) and (a-4): body.
(A-3) The total number of double bonds of vinyl and vinylidene is 0.5 (total / total 1000C) or more (provided that the number of vinyl and vinylidene is a total of 1000 main chains and side chains measured by NMR) Per carbon number)
(A4) The total number of double bonds of vinyl and vinylidene is 55% or more of the total number of all double bonds (vinyl, vinylidene, cis-vinylene, trans-vinylene, trisubstituted olefin) (however, vinyl, (The number of vinylidene, cis-vinylene, trans-vinylene, and tri-substituted olefin is the number per 1000 carbon atoms in total of main chain and side chain measured by NMR)   The laminate for a solar cell encapsulant according to claim 1 or 2, comprising an outermost layer, an intermediate layer, and an outermost layer, wherein the outermost layer has a B layer and the intermediate layer has an A layer.   The laminate for a solar cell encapsulant according to claim 1 or 2, comprising an A layer and a B layer. The volume resistivity is 1.0 * 10 < ¹³ > -1.0 * 10 < ¹⁶ > ohm * cm, The laminated body for solar cell sealing materials in any one of Claims 1-4 characterized by the above-mentioned.   The laminate for a solar cell encapsulant according to claim 1, wherein the ethylene / α-olefin copolymer resin (a) is obtained from a metallocene catalyst.   The laminate for a solar cell sealing material according to any one of claims 1 to 6, wherein the ethylene / α-olefin copolymer resin (a) contains 10 to 30 mol% of propylene as a comonomer.   The ethylene-functional group-containing monomer copolymer resin (b) is an ethylene-vinyl acetate copolymer, an ethylene- (meth) acrylic acid ester copolymer, an ethylene- (meth) acrylic acid copolymer, an ethylene- (meta 2. An ethylene / functional group-containing monomer copolymer selected from the group consisting of: acrylate multipolymers and ethylene- (meth) acrylic multipolymers. The resin laminated body for solar cell sealing materials in any one of 1-7.   The laminate for a solar cell encapsulant according to claim 1, wherein the laminate is obtained by a co-pressing multilayer molding method. The A layer and / or B layer further contains the following component (c), and the content of the component (c) is 0. 0 parts by weight relative to 100 parts by weight of the resin contained in the layer containing the component (c). It is 2-5 weight part, The resin laminated body for solar cell sealing materials in any one of Claims 1-11 characterized by the above-mentioned.
Component (c): Organic peroxide The laminated body for solar cell sealing materials according to any one of claims 1 to 10, comprising the following component (d).
Component (d): Silane coupling agent   The solar cell sealing material using the resin laminated body for solar cell sealing materials in any one of Claims 1-11.   A solar cell module using the solar cell encapsulant of claim 12.

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