JP6384162B2 - Solar cell module - Google Patents

Description

  The present invention relates to a solar cell module. More specifically, the present invention relates to an aspect battery module having a wavelength conversion function for improving the efficiency of power generation by sunlight.

  In recent years, solar cells as a clean energy source have attracted attention due to the growing awareness of environmental issues. Currently, various types of solar cell modules have been developed and proposed. Generally, a solar cell module has a configuration in which a transparent front substrate made of glass or the like, a solar cell element, and a back surface protection sheet are laminated via a sealing material sheet.

  As a sealing material sheet for a solar cell module, a sheet based on EVA (ethylene-vinyl acetate copolymer) excellent in transparency, adhesion and the like has been widely used. However, in recent years, development of a sealing material sheet using a polyethylene resin having a transparency equivalent to EVA and excellent in hydrolysis resistance and the like as compared with EVA has been progressing.

  Here, the solar cell element generally has high spectral sensitivity to light in the wavelength region from visible light to near infrared. Therefore, by arranging a wavelength conversion layer containing a wavelength conversion agent that converts ultraviolet light into visible light in the solar cell module on the light receiving surface side of the solar cell element, the use efficiency of sunlight in the solar cell element is improved, and power generation A solar cell module intended to improve the efficiency has been proposed (see Patent Document 1). In addition, in order to exhibit the wavelength conversion function and the original protective function of the sealing material sheet in a well-balanced manner, a multi-layer type sealing in which other functional layers such as a protective layer are laminated on both sides of the wavelength conversion layer. A stopping material sheet has also been proposed (see Patent Document 2).

  Here, in the solar cell module provided with the sealing material sheet provided with the wavelength conversion layer on the light receiving surface side, the back surface side of the solar cell element contains not the sealing material sheet provided with the wavelength conversion layer but an ultraviolet absorber. Conventionally, it has been widely performed to arrange a sealing material sheet to prevent deterioration of the back surface protection sheet disposed on the outermost layer side opposite to the light receiving surface in the solar cell module.

JP 2007-27271 A JP 2012-15205 A

  As described above, by disposing the sealing material sheet containing the ultraviolet absorbent on the back surface side of the solar cell element, it is possible to prevent the back surface protection sheet from being deteriorated by ultraviolet light. However, in the solar cell module having such a layer configuration, for example, after long-term use in a high-temperature and high-humidity environment, a part of the ultraviolet absorber moves to the light-receiving surface side sealing material, and the wavelength conversion function is achieved. It has been recognized as a new problem that there may be a decrease.

  The present invention has been made in view of the above situation, and a sealing material sheet (hereinafter referred to as “wavelength conversion type sealing material”) having a wavelength conversion function using a polyethylene resin having excellent hydrolysis resistance as a base resin. In a solar cell module (hereinafter also referred to as “wavelength conversion type solar cell module”) in which the sheet is also disposed on the light receiving surface side of the solar cell element, it is good even after long-term use in a hot and humid environment. It is an object of the present invention to provide a wavelength conversion type solar cell module that can maintain an excellent wavelength conversion function, that is, has excellent weather resistance and durability.

  As a result of intensive studies, the inventors of the present invention have determined that the sealing material sheet disposed on the back surface side of the solar cell element in the wavelength conversion type solar cell module, in particular, an organic ultraviolet ray that easily migrates between the resin layers. By making a white sheet containing an inorganic white pigment without containing an absorbent, it is possible to prevent deterioration of the wavelength conversion function due to the leaching of the ultraviolet absorbent, and thereby wavelength conversion with excellent long-term weather resistance. The present inventors have found that a solar cell module of a type can be obtained and have completed the present invention. More specifically, the present invention provides the following.

(1) A solar cell element, a light receiving surface side sealing material sheet disposed on the light receiving surface side of the solar cell element, and a back surface side sealing material sheet disposed on the back surface side of the solar cell element. , the light receiving surface side sealing material sheet and the back side sealing material sheet, and a density of 0.870 g / cm ³ or more 0.970 g / cm ³ or less of low density polyethylene base resin, the light-receiving-side sealing member The sheet is a multilayer sheet comprising an intermediate layer and outermost layers disposed on both sides thereof, the organic layer containing an organic wavelength conversion agent in the intermediate layer, and the back side sealing material sheet is organic The solar cell module which is a white sealing material sheet which does not contain a system ultraviolet absorber and contains an inorganic white pigment.

  (2) The solar cell module according to (1), wherein the white pigment is titanium oxide.

  (3) The solar cell module according to (1) or (2), wherein the organic wavelength conversion agent contained in the intermediate layer of the light-receiving surface side sealing material sheet has a number average molecular weight of 100 or more and 1000 or less.

  (4) The content ratio of the wavelength conversion agent in the outermost layer of the light-receiving surface side sealing material sheet is smaller than the content ratio of the organic wavelength conversion agent in the intermediate layer (1) to (3 ) The solar cell module according to any one of the above.

  (5) The content ratio of the wavelength conversion agent in the outermost layer of the light-receiving surface side sealing material sheet is ½ or less of the content ratio of the organic wavelength conversion agent in the intermediate layer (1 The solar cell module according to any one of (4) to (4).

  (6) The solar cell module according to any one of (1) to (5), wherein the organic wavelength conversion agent is any one derivative of pyrazine, pyridine, and triazole or a mixture thereof.

  (7) The solar cell module according to any one of (1) to (6), wherein the outermost layer of the light-receiving surface side sealing material sheet further contains a silane-modified polyethylene resin.

  ADVANTAGE OF THE INVENTION According to this invention, it is a solar cell module provided with the wavelength conversion type sealing material sheet | seat which used polyethylene resin as the base resin, Comprising: The wavelength conversion type solar cell module excellent in long-term weather resistance can be provided.

It is a cross-sectional schematic diagram which shows an example of the laminated constitution of the solar cell module of this invention. It is a cross-sectional schematic diagram which shows an example of the layer structure of the light-receiving surface side sealing material sheet of this invention. It is a cross-sectional schematic diagram which shows an example of the layer structure of the back surface side sealing material sheet of this invention.

  The solar cell module of the present invention has a light receiving surface side sealing material sheet having a wavelength conversion function arranged on the light receiving surface side of the solar cell element, and does not contain an ultraviolet absorber and has a light reflecting function. The main characteristic is that the side sealing material sheet is disposed on the back surface side of the solar cell element. In the present specification, one surface that is mainly a light receiving surface in the solar cell element is referred to as a light receiving surface, and the other surface opposite to the light receiving surface is referred to as a back surface. In the double-sided solar cell element, the arbitrarily selected one light-receiving surface side is referred to as the light-receiving surface side, and the other surface side opposite to the light-receiving surface side is the back surface side. It shall be said. First, the overall configuration of the solar cell module and the method for manufacturing the solar cell module will be described, and then the details of each of the encapsulant sheets separately disposed on both surfaces of the solar cell element will be described later. explain.

<Solar cell module>
FIG. 1 is a cross-sectional view showing an example of the layer configuration of a solar cell module 10 of the present invention in which a light-receiving surface side sealing material sheet 1 having a wavelength conversion function is arranged on the light-receiving surface side of a solar cell element 3. In the solar cell module 10, the transparent front substrate 4, the light receiving surface side sealing material sheet 1, the solar cell element 3, the back surface side sealing material sheet 2, and the back surface protection sheet 5 are laminated in order from the light receiving surface side of incident light. ing.

  In the solar cell module 10, the light-receiving surface side sealing material sheet 1 is disposed on the light-receiving surface side of the solar cell element 3, thereby exhibiting a wavelength conversion function and improving the power generation efficiency of the solar cell module 10. Moreover, the light-receiving surface side sealing material sheet 1 can be firmly adhered to uneven surfaces such as electrodes of the solar cell element 3 due to excellent molding characteristics resulting from the physical properties of the outermost layer. Moreover, in the solar cell module 10, the back surface side sealing material sheet 2 arrange | positioned at the back surface side is white sealing formed by adding inorganic white pigments, such as a titanium oxide, to the polyethylene-type resin used as base resin. A material sheet is used. Such white back surface side sealing material sheet 2 is, for example, the sunlight that has not entered the solar cell element 3 and reaches the non-light-receiving surface side out of the incident light into the solar cell module 10. By leading to the light receiving surface side of the solar cell element 3, the power generation efficiency of the solar cell module 10 can be further improved. The details of each of these sealing material sheets will be described later.

  About the transparent front substrate 4 and the back surface protection sheet 5 which are members other than the light-receiving surface side sealing material sheet 1 and the back surface side sealing material sheet 2, a conventionally well-known material can be especially used without a restriction | limiting. As the transparent front substrate 4, glass or the like, and as the back protective sheet 5, a resin sheet such as ETFE or water-resistant PET can be used. In addition, the solar cell module 10 of this invention may also contain members other than the said member.

  The solar cell element 3 is not particularly limited. Not only a crystalline silicon solar cell manufactured using a single crystal silicon substrate or a polycrystalline silicon substrate, but also a thin film solar cell (CIGS) using amorphous silicon, microcrystalline silicon, a chalcopyrite compound, or the like is preferably used. be able to. Moreover, since the solar cell module 10 uses the back surface side sealing material sheet 2 made of a highly insulating polyethylene-based resin, it is a back contact type in which a plurality of electrodes having different polarities are provided on the non-light receiving surface side. The solar cell element can also be preferably used.

  The layer configuration of the solar cell module of the present invention is not limited to the above embodiment. For example, as dictated, since the light-receiving surface side sealing material sheet 1 has adhesion to both glass and metal, various properties including the glass substrate and the metallic solar cell module are utilized by taking advantage of the characteristics. The solar cell module can be used for general purposes.

  The solar cell module 10 is formed by sequentially stacking the above-described module constituent members including the light-receiving surface side sealing material sheet 1, the back surface side sealing material sheet 2, the solar cell element 3, and the like, and then integrating them by vacuum suction or the like. The above members can be manufactured by thermocompression molding as an integral molded body by a molding method such as a lamination method.

<Light-receiving surface side sealing material sheet>
As illustrated in FIG. 2, the light-receiving surface side sealing material sheet 1 is a multilayer sealing material sheet including an intermediate layer 11 and an outermost layer 12 disposed on both surfaces of the intermediate layer. In this specification, a multilayer encapsulant sheet is an encapsulant having a multilayer structure composed of an outermost layer formed on both surfaces of the encapsulant sheet and an intermediate layer that is a layer other than the outermost layer. Say about the sheet. The intermediate layer refers to a layer other than the outermost layer, and may have a single layer structure, or the intermediate layer itself may have a multilayer structure including a plurality of layers. Hereinafter, the light-receiving surface side sealing material sheet 1 having a three-layer structure in which two outermost layers each including one layer each are laminated on both surfaces of a single intermediate layer will be described.

  The light-receiving surface side sealing material sheet 1 is manufactured by adding an organic wavelength conversion agent only to the intermediate layer 11. As a result, the content ratio of the wavelength conversion agent in the outermost layer 12 after film formation is smaller than the content ratio of the wavelength conversion agent in the intermediate layer 11, and at least immediately after the film formation, It is suppressed to 1/2 or less of the content ratio of the wavelength conversion agent. More specifically, the content of the wavelength conversion agent in the intermediate layer 11 in the light-receiving surface side sealing material sheet 1 after film formation is in the range of 0.05% by mass or more and 0.5% by mass or less. Content of the wavelength conversion agent in an outer layer exists in the range of 0 mass% or more and 0.25 mass% or less.

  The intermediate layer 11 is a layer constituting a main part as a substrate layer in the light-receiving surface side sealing material sheet 1. Furthermore, the intermediate layer 11 is also a wavelength conversion layer that imparts a wavelength conversion function to the light-receiving surface side sealing material sheet 1 by containing a wavelength conversion agent. In addition, it is preferable that the intermediate | middle layer 11 is what the crosslinking process for the purpose of heat resistance improvement, such as the process which combined the appropriate amount addition of the crosslinking adjuvant, and irradiation of ionizing radiation, is performed. Thereby, the weather resistance and durability of the solar cell module can be further improved.

  The outermost layer 12 is a layer that is disposed on the outermost surface of the sealing material sheet in the light-receiving surface side sealing material sheet 1 and constitutes a subordinate portion as a surface material. The outermost layer 12 is a layer that mainly exhibits the effect of improving the adhesion as a solar cell module and the molding characteristics during the integration process.

  The outermost layer 12 also has a low-density polyethylene resin as a base resin. However, unlike the intermediate layer 11, the outermost layer 12 does not contain a wavelength conversion agent or contains a relatively small amount of a wavelength conversion agent of a predetermined amount or less. . The content of the wavelength conversion agent in the outermost layer 12 may be 0%, or a part of the organic wavelength conversion agent leached from the intermediate layer may be included within the above range. . If it is content in the said range, even if the wavelength conversion agent has penetrate | invaded in the outermost layer, the initial optical characteristic and adhesiveness of a sealing material sheet can be fully hold | maintained in the preferable range.

  The light-receiving surface side sealing material sheet 1 is a multilayer sheet obtained by laminating resin sheets for each layer having different advantageous physical properties and special functions in an optimal arrangement. It is a wavelength conversion type sealing material sheet that is made of a polyethylene-based resin having a high water vapor barrier property and has an excellent balance of heat resistance, adhesion, and molding characteristics.

  The total thickness of the light-receiving surface side sealing material sheet 1 including the intermediate layer 11 and the outermost layer 12 is preferably 100 μm or more and 1000 μm or less, and more preferably 200 μm or more and 600 μm or less. If it is less than 100 μm, the impact cannot be sufficiently mitigated, and if it exceeds 1000 μm, no further effect can be obtained and it is uneconomical. In addition, the light-receiving surface side sealing material sheet 1 has flexibility in the outermost layer 12 and heat resistance in the intermediate layer 11, thereby suppressing flow-out and film thickness change during the lamination process. Even when the film thickness is reduced to about 500 μm or less, it is possible to provide sufficiently preferable molding properties, heat resistance, and solar cell element protection performance.

  About the ratio of the thickness of each layer in the light-receiving surface side sealing material sheet 1, thickness ratio with outermost layer 12: intermediate layer 11: outermost layer 12 is in the range of 1: 2: 1 to 1: 30: 1. Preferably there is. By setting the thickness ratio of each layer within this range, the heat resistance and molding characteristics of the light-receiving surface side sealing material sheet 1 can be maintained within a favorable range.

<Encapsulant composition for light-receiving surface side encapsulant sheet>
Hereinafter, the sealing material composition for the light-receiving surface side sealing material sheet used for manufacture of the light-receiving surface side sealing material sheet 1 will be described.

[Encapsulant composition for intermediate layer]
The intermediate layer sealing material composition used for forming the intermediate layer 11 of the light-receiving surface side sealing material sheet 1 includes a base resin made of a polyethylene resin and an organic wavelength conversion agent as essential components. contains.

(Base resin)
The polyethylene resin used as the base resin of the sealing material composition for the intermediate layer of the light-receiving surface side sealing material sheet (hereinafter also referred to as “base resin for the intermediate layer”) includes low density polyethylene (LDPE), linear low High density polyethylene (LLDPE) or metallocene linear low density polyethylene (M-LLDPE) can be preferably used.

Density polyethylene resin used as the intermediate layer base resin, 0.870 g / cm ³ or more 0.970 g / cm ³ or less, or preferably 0.870 g / cm ³ or more 0.930 g / cm ³ or less. The density of the intermediate layer base resin is preferably higher than the outermost layer base resin described in detail later. By setting the density of the base resin for the intermediate layer within the above range, it is possible to sufficiently improve the heat resistance of the encapsulant sheet while maintaining the molding characteristics and the protection performance of the solar cell element.

  The intermediate layer base resin is preferably a polyethylene-based resin in which the number of full double bonds remaining in the composition stage is relatively larger than the number of full double bonds of the outermost layer base resin. Further, the number of full double bonds in the base resin for the intermediate layer is preferably 0.5 or more and 4.0 or less, and more preferably 1.0 or more and 4.0 or less. By setting the total number of double bonds of the encapsulant composition for the intermediate layer within the above range, when crosslinking is performed by irradiation with ionizing radiation, the crosslinking is sufficiently advanced to increase the heat resistance of the encapsulant sheet. It can be improved sufficiently. On the other hand, even if the crosslinking of the intermediate layer by irradiation with ionizing radiation is sufficiently advanced, the total number of double bonds of the sealing material composition for the outermost layer is different from that of the sealing material composition for the intermediate layer By limiting to, the progress of crosslinking of the outermost layer is suppressed in a mode different from that of the intermediate layer, and as a result, preferable molding characteristics can be maintained as the whole sealing material sheet. In addition, the heat resistance of a sealing material sheet is not fully improved as the number of full double bonds of the sealing material composition for intermediate | middle layers is less than 0.5 piece. On the other hand, when the number exceeds 4.0, molding characteristics and adhesion are deteriorated due to excessive progress of crosslinking, which is not preferable.

Here, “the number of full double bonds” in the present specification means the sheet density d (g / cm ³ ) and sheet thickness t (cm) of the encapsulant composition in the sheet state and the absorption band of the infrared absorption spectrum. It is the value calculated | required by the following formula from the absorbance A of. In addition, about the measurement of the light absorbency A of the absorption band of an infrared absorption spectrum, it carried out by NICOLET6700 made from Thermo Scientific.
Number of terminal vinyl groups = 0.231 / (d × t) × A (910 cm ⁻¹ )
Vinylidene base = 0.271 / (d × t) × A (888 cm ⁻¹ )
Number of trans vinylene groups = 0.328 / (d × t) × A (965 cm ⁻¹ )
Total number of double bonds = number of terminal vinyl groups + number of vinylidene groups + number of transvinylene groups The total number of double bonds per 2000 carbons by the above method.

  The content of the intermediate layer base resin contained in the intermediate layer sealing material composition of the light receiving surface side sealing material sheet is 100 parts by mass in total of all resin components in the intermediate layer sealing material composition. Is preferably 10 parts by mass or more and 99 parts by mass or less, more preferably 50 parts by mass or more and 99 parts by mass or less, and still more preferably 90 parts by mass or more and 99 parts by mass or less. The sealing material composition for the intermediate layer may contain another resin within the above range. These may be used, for example, as an additive resin, or may be used for masterbatching other components described later. In the present specification, the term “all resin components” includes the other resins described above.

(Organic wavelength conversion agent)
A wavelength conversion agent contributes to the improvement of the power generation efficiency of a solar cell module by converting light in a wavelength region with low absorption sensitivity into a wavelength region with high absorption sensitivity and making it incident on a solar pond device in a solar cell element. Say things. Various wavelength conversion agents of inorganic type, organic type, or hybrid type thereof are known.

  Among these, an organic wavelength conversion agent can be preferably used for the sealing material composition for the intermediate layer of the sealing material sheet of the present invention. Among these organic wavelength conversion agents, those having a number average molecular weight of 100 or more and 1000 or less can be particularly preferably used. The organic wavelength conversion agent excellent in compatibility with the polyethylene-based dendritic used as the base resin is limited to such an organic agent having a relatively large molecular weight and a number average molecular weight of 100 or more, and only the intermediate layer By adding to, the optical characteristics at the initial stage of production of the encapsulant sheet can be made extremely favorable. In addition to this, even after a long period of use under high temperature and high humidity conditions, the leaching out of the wavelength converting agent to the outermost layer side of the sealing sheet of the organic wavelength converting agent is sufficiently suppressed. It is possible to sufficiently avoid the deterioration of the optical characteristics and adhesion of the encapsulant sheet due to the above. In addition, by setting the number average molecular weight of the wavelength conversion agent to 1000 or less, compatibility of the wavelength conversion agent in the sealing material composition is ensured, and preferable optical characteristics and adhesion of the light-receiving surface side sealing material sheet 1 are ensured. Can be held.

  The organic wavelength conversion agent is preferably in the above molecular weight range, but not limited thereto, and conventionally known agents can be used without any particular limitation. Specifically, pyrazine derivatives, pyridine derivatives, triazole derivatives, benzoxazoyl derivatives, coumarin derivatives, styrene biphenyl derivatives, pyrazolone derivatives, bis (triazinylamino) stilbene disulfonic acid derivatives, bisstyryl biphenyl derivatives, bisbenzoxazolylthiophenes Derivatives, perylene derivatives, pyrene derivatives, pentacene derivatives, fluorescene derivatives, rhodamine derivatives, acridine derivatives, benzimidazole derivatives, flavone derivatives, and the like. Among these, in particular, any one derivative of pyrazine, pyridine, and triazole or a mixture thereof can be preferably used.

  The amount of these organic wavelength conversion agents added to the sealing material composition for the intermediate layer is 0.05% by mass or more and 0.5% by mass or less, preferably 0.1% by mass or more and 0.4% by mass. It is as follows. Within this range, an optimal amount may be added as appropriate depending on the light emission intensity and quantum yield of each material, the thickness of each layer of the encapsulant sheet, and the like. When the addition amount of the organic wavelength conversion agent is less than 0.05% by mass, the wavelength conversion cannot be sufficiently performed, so that the power generation efficiency of the solar cell module cannot be sufficiently increased. On the other hand, when the addition amount of the organic wavelength conversion agent is more than 0.5% by mass, the deterioration of the optical properties of the encapsulant sheet due to the leaching of the wavelength conversion agent to the outermost layer and bleed out can be sufficiently avoided. Since it may become impossible, it is not preferable.

  As described above, the organic wavelength conversion agent added to the encapsulant composition for the intermediate layer is added to the composition for the intermediate layer only in an appropriate amount range, thereby forming the encapsulant sheet after film formation. The leaching of the wavelength conversion agent from the intermediate layer to the outermost layer side can be sufficiently suppressed. And a wavelength conversion type sealing material sheet that can exhibit a sufficient wavelength conversion function while preventing deterioration of adhesion due to lowering of the fluidity of the outermost layer and deterioration of optical properties due to bleeding out of the wavelength conversion agent It can be.

(Crosslinking aid)
The encapsulant composition for the intermediate layer preferably further contains a crosslinking aid. As a crosslinking aid, a polyfunctional monomer having a carbon-carbon double bond and / or an epoxy group can be preferably used. More preferably, a crosslinking functional agent having a polyfunctional monomer whose functional group is an allyl group, a (meth) acrylate group or a vinyl group can be used. By adding such a crosslinking aid, the crystallinity of the low-density polyethylene can be reduced, and a sealing material sheet excellent in low-temperature flexibility can be obtained.

  Specifically, polyallyl compounds such as triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fumarate, diallyl maleate, trimethylolpropane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA) , Ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, etc. ) An acryloxy compound, a glycidyl methacrylate containing a double bond and an epoxy group, 4-hydroxybutyl acrylate glycidyl ether and 1, containing two or more epoxy groups - hexanediol diglycidyl ether, and 1,4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, an epoxy-based compounds such as trimethylolpropane polyglycidyl ether. These may be used alone or in combination of two or more.

  Among these, tricyclodecane dimethanol diacrylate, which has a particularly high effect of improving adhesion to the glass surface, has good compatibility with low density polyethylene, and can be expected to improve heat resistance, can be particularly preferably used. The content of the crosslinking aid is preferably 0.01 parts by mass or more and 3 parts by mass or less, more preferably 0 with respect to 100 parts by mass in total of all resin components of the sealing material composition for the outer layer. .05 parts by mass or more and 2.0 parts by mass or less. By providing a multilayer sheet structure in which the crosslinking aid is contained only in the intermediate layer, sufficient heat resistance is simultaneously imparted to the encapsulant sheet while maintaining the adhesion and molding characteristics of the encapsulant sheet within a preferable range. be able to.

  In addition, in the manufacturing method of this invention, it is preferable not to add the said crosslinking adjuvant to the sealing material composition for outermost layers. This is because when a crosslinking aid is added to the sealing material composition for the outermost layer, there is a high risk of lowering adhesion due to lowering of fluidity or so-called bleeding out of the crosslinking aid.

[Encapsulant composition for outermost layer]
The encapsulant composition for the outermost layer used for forming the outermost layer 12 of the light-receiving surface side encapsulant sheet 1 has a polyethylene resin as a base resin, and preferably has an adhesive property such as a silane-modified polyethylene resin. Contains a polymer resin.

(Base resin)
As the polyethylene resin used as the base resin of the sealing material composition for the outermost layer (hereinafter also referred to as “base resin for the outermost layer”), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or Metallocene linear low density polyethylene (M-LLDPE) can be suitably used as appropriate.

Density of the polyethylene resin used as the base resin for the outermost layer, 0.870 g / cm ³ or more 0.970 g / cm ³ or less, preferably 0.870 g / cm ³ or more 0.930 g / cm ³ or less. And it is preferable that the density of base resin for outermost layers is a lower density than the base resin of the sealing material composition for intermediate | middle layers. More specifically, the density of the outermost layer base resin is preferably 93% or more and 99% or less of the density of the intermediate layer base resin. By setting the density of the base resin for the outermost layer within the above range, sufficient adhesion and molding characteristics can be imparted while maintaining the protection performance of the solar cell element. From the viewpoint of imparting molding characteristics, the density of the outermost layer is preferably as low as possible. However, by maintaining the density at 93% or more of the density of the intermediate layer, excess organic wavelength conversion agent from the intermediate layer to the outermost layer Leaching can be suppressed.

  As the base resin for the outermost layer, it is preferable to use a polyethylene-based resin in which the total number of double bonds remaining in the composition stage is relatively smaller than the number of total double bonds of the base resin for the intermediate layer. The number of full double bonds of the polyethylene resin that is the base resin for the outermost layer is preferably 0 or more and 1.0 or less, and more preferably 0 or more and 0.5 or less.

(Silane-modified polyethylene resin)
It is preferable that the sealing material composition for the outermost layer contains a silane-modified polyethylene resin in addition to the base resin. The silane-modified polyethylene resin is a resin obtained by graft polymerizing low-density polyethylene as a main chain, preferably linear low-density polyethylene, with an ethylenically unsaturated silane compound as a side chain. Since such a graft copolymer has a high degree of freedom of silanol groups that contribute to the adhesive force, it can improve the adhesion of the sealing material sheet to other members in the solar cell module. The silane-modified polyethylene resin in the present specification refers to, for example, a silane-modified polyethylene resin that can be produced by the following production method, and at least a part of a linear low-density polyethylene resin that becomes a main chain. Is a concept indicating a resin obtained by graft polymerization with an ethylenically unsaturated silane compound. The resin as a main chain of the above, as with the base resin, it is preferred that the density 0.870 g / cm ³ or more 0.900 g / cm ³ or less of the polyethylene resin.

The silane-modified polyethylene resin can be produced by the following method, for example, as described in JP-A-2003-46105. For example, one or more α-olefins, one or more ethylenically unsaturated silane compounds, and, if necessary, one or more other unsaturated monomers are desired. For example, the pressure is 500 kg / cm ² or more and 4000 kg / cm ² or less, preferably 1000 kg / cm ² or more and 4000 kg / cm ² or less, temperature, 100 ° C. or more and 400 ° C. or less, preferably Random copolymerization is performed simultaneously or stepwise in the presence of a radical polymerization initiator and, if necessary, a chain transfer agent under conditions of 150 ° C. or higher and 350 ° C. or lower, and further generated by the copolymerization. A silane-modified polyethylene resin can be produced by modifying or condensing the silane compound portion constituting the random copolymer.

  As the polyethylene-based resin of the main chain, it is preferable to use linear low-density polyethylene that is an ethylene-α-olefin copolymer, and it is more preferable to use metallocene-based linear low-density polyethylene. Metallocene linear low density polyethylene is synthesized using a metallocene catalyst which is a single site catalyst. Such polyethylene has few side chain branches and a uniform comonomer distribution. For this reason, molecular weight distribution is narrow, it is possible to make it the above ultra-low density, and a softness | flexibility can be provided with respect to a sealing material sheet. As a result of the flexibility imparted to the sealing material sheet, the adhesion between the sealing material sheet and a transparent front substrate such as glass can be enhanced.

  As the α-olefin of the linear low density polyethylene, an α-olefin having no branch is preferably used. Among these, 1-hexene and 1-heptene which are α-olefins having 6 to 8 carbon atoms are preferable. Or 1-octene is particularly preferably used. When the number of carbon atoms of the α-olefin is 6 or more and 8 or less, the sealing material sheet can be given good flexibility and good strength. As a result, the adhesion between the encapsulant sheet and a transparent front substrate such as glass is further enhanced.

  Examples of ethylenically unsaturated silane compounds to be graft polymerized with linear low density polyethylene include, for example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinyltripentyloxysilane , One or more selected from vinyltriphenoxysilane, vinyltribenzyloxysilane, vinyltrimethylenedioxysilane, vinyltriethylenedioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, and vinyltricarboxysilane be able to.

  The graft amount, which is the content of the ethylenically unsaturated silane compound in the silane-modified polyethylene resin, is 0.001% by mass or more and 15% by mass or less, preferably 0.01% by content in the base resin of the silane-modified polyethylene resin. What is necessary is just to adjust suitably so that it may become 0.05 mass% or more and 2 mass% or less especially preferably 5 mass% or more. In the present invention, when the content of the ethylenically unsaturated silane compound is large, the mechanical strength and heat resistance are excellent. However, when the content is excessive, the tensile elongation and heat-fusibility tend to be inferior.

  It is preferable that content in the sealing material composition for outermost layers of the silane modified polyethylene resin used for the sealing material composition for outermost layers is 8 mass% or more and 45 mass% or less. In the present invention, if the content of the silane-modified polyethylene resin is 8% by mass or more, the mechanical strength and heat resistance are excellent, but if the content is excessive, the tensile elongation and heat-fusibility are poor. There is a tendency.

  By using the silane-modified polyethylene resin described above as a component of the encapsulant composition for the outermost layer among the encapsulant composition for the solar cell module, it has excellent adhesion, strength, durability, etc. And it can be set as the sealing material sheet which is excellent in a weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, yield resistance, and other various characteristics. Various effects can be obtained in this way by using a silane-modified polyethylene-based resin, but in particular, it is extremely effective for a sealing material sheet without being affected by manufacturing conditions such as thermocompression bonding for manufacturing a solar cell module. As a general advantage, excellent heat-fusibility, that is, excellent adhesion to a glass substrate constituting a solar cell module can be given.

  Moreover, according to the addition of the silane-modified polyethylene resin to the outermost layer of the sealing material sheet of the present invention, not only the above general advantages, but also (bleed out) of the wavelength conversion agent is further suppressed. The effects specific to the present invention are also exhibited. This suppression of bleed-out is not caused by the silane-modified polyethylene resin staying inside the outermost layer but aggregating at the interface with the glass or solar cell element constituting the transparent front substrate to form Si—O—Si bonds. Thus, it is presumed that the wavelength conversion agent is an effect due to the delay of shifting to the surface of the encapsulant sheet. Also from the viewpoint of the effect specific to the present invention, addition of the silane-modified polyethylene resin to the outermost layer is preferable.

[Other additives]
Any of the encapsulant compositions for the intermediate layer and the outermost layer may contain the following additives as necessary, as necessary.

(Crosslinking agent)
Each sealing material composition for the intermediate layer and the outermost layer may contain a necessary minimum amount of a crosslinking agent, but it is more preferable that the crosslinking agent is not added to any layer. While addition of a crosslinking aid to the intermediate layer described above allows adequate crosslinking to proceed sufficiently, a separate addition of a crosslinking agent such as an organic peroxide would result in integration with the solar cell module. This is because there is an increased risk of problems such as foaming due to degas during the heat laminating process. When adding a crosslinking agent, a well-known thing can be used and it does not specifically limit, For example, a well-known radical polymerization initiator can be used.

  When the crosslinking agent is added, the content thereof is preferably 0 to 0.5% by mass, more preferably 0 to the sealing material composition for the intermediate layer and the outermost layer. The range is 0.02 mass% or more and 0.5 mass% or less. When the addition amount of the crosslinking agent exceeds 0.5% by mass, the progress of crosslinking in the crosslinking process becomes excessive, and molding characteristics are insufficient, which is not preferable.

(Adhesion improver)
In each of the encapsulant compositions for the intermediate layer and the outermost layer, the adhesion durability with other base materials can be further enhanced by appropriately adding an adhesion improver. As the adhesion improver, a known silane coupling agent can be used. The silane coupling agent is not particularly limited. For example, vinyl-based silane coupling agents such as vinyltrichlorosilane, vinyltrimethoxysilane, and vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-methacryloxypropyldiethoxy. A methacryloxy-based silane coupling agent such as silane or 3-methacryloxypropyltriethoxysilane can be preferably used. In addition, these can also be used individually or in mixture of 2 or more types.

  When a silane coupling agent is added as an adhesion improver, the content thereof is 0.1% by mass or more and 10.0% by mass or less in the sealing material composition, and the upper limit is preferably 5.0% by mass. It is as follows. When the content of the silane coupling agent is in the above range, and the polyolefin resin constituting the encapsulant composition contains an appropriate amount of the ethylenically unsaturated silane compound, the adhesion is more preferable. And improve. In addition, when this range is exceeded, the film-forming property is lowered, and the silane coupling agent may bleed out, which is not preferable.

(Other ingredients)
Each sealing material composition for intermediate layer and outermost layer may further contain other components. For example, a weather-resistant masterbatch for imparting weather resistance to a sealing material sheet produced using the combination set of the sealing material composition of the present invention, various fillers, a light stabilizer, an ultraviolet absorber, and heat stability Ingredients such as agents are exemplified. These contents vary depending on the particle shape, density, and the like, but are preferably in the range of 0.001% by mass to 5% by mass with respect to each sealing material composition. By including these additives, it is possible to impart a mechanical strength that is stable over a long period of time, an effect of preventing yellowing, cracking, and the like to the encapsulant sheet.

  A weatherproof masterbatch is obtained by dispersing a light stabilizer, an ultraviolet absorber, a heat stabilizer and the above-mentioned antioxidant in a resin such as polyethylene, and adding this to a sealing material composition. Thus, good weather resistance can be imparted to the encapsulant sheet. The weatherproof masterbatch may be prepared and used as appropriate, or a commercially available product may be used. As resin used for a weatherproof masterbatch, the polyethylene-type resin used as a base resin for this invention may be sufficient, and said other resin may be sufficient.

<Back side sealing material sheet>
The back surface side sealing material sheet may be a single layer white sealing material sheet, but as shown in FIG. 3, either the white intermediate layer 21 or the white intermediate layer, preferably both outermost layers. It is preferable that it is a multilayer sealing material sheet | seat comprised by the several layer containing transparent outermost layer 22 arrange | positioned. Hereinafter, the back side sealing material sheet 2 which is a white sealing material sheet having a three-layer structure in which a total of two transparent outermost layers 22 are laminated on both surfaces of a single white intermediate layer 21 will be described. However, the present invention is not limited to this embodiment.

  The white intermediate layer 21 is a layer constituting a main part as a substrate layer in the back surface side sealing material sheet 2. Moreover, in this layer, the white pigment for making a white external appearance appear in the external appearance of the back surface side sealing material sheet 2 contains. The back surface side sealing material sheet 2 can further improve the power generation efficiency of the solar cell module 10 by reflecting sunlight in the white intermediate layer 21 as described above.

  In addition, the inorganic white pigment contained in the white intermediate layer 21 not only has excellent light reflection performance in the visible light region, but also has an action of absorbing ultraviolet rays. Even if the ultraviolet absorber is not contained, it is possible to block the ultraviolet rays and prevent the back surface protection sheet from being deteriorated by ultraviolet rays. In addition, the wavelength conversion function is not deteriorated because the transfer to the light-receiving surface side sealing material such as an organic ultraviolet absorber hardly occurs.

  The white intermediate layer 21 is preferably subjected to a crosslinking treatment for the purpose of improving heat resistance, such as a treatment in which an appropriate amount of a crosslinking aid is added and irradiation with ionizing radiation is combined. Thereby, the weather resistance and durability of the solar cell module can be further improved.

  The transparent outermost layer 22 is a layer that is disposed on the outermost surface of the sealing material sheet in the light-receiving surface side sealing material sheet 1 and constitutes a subordinate portion as a surface material. The transparent outermost layer 22 is a layer that mainly exhibits the effect of improving the adhesion as a solar cell module and the molding characteristics during the integration process. Note that the white intermediate layer 21 mainly contributes to ultraviolet cut and light reflection, but the back surface side sealing material sheet 2 is required to have high adhesion to the solar cell element 3 and the back surface protection sheet 5. Therefore, as described above, the provision of the transparent outermost layer 22 that exhibits the effect of improving the adhesion and molding characteristics as a layer separate from the white intermediate layer 21 is a highly necessary component.

  The back surface side sealing material sheet 2 is also a multi-layer sheet obtained by laminating resin sheets for each layer having different advantageous physical properties and special functions in an optimal arrangement. It is a wavelength conversion type sealing material sheet that is made of a polyethylene-based resin having a high water vapor barrier property and has an excellent balance of heat resistance, adhesion, and molding characteristics.

  The total thickness of the back surface side sealing material sheet 2 including the white intermediate layer 21 and the transparent outermost layer 22 is preferably 100 μm or more and 1000 μm or less, and more preferably 200 μm or more and 600 μm or less. If it is less than 100 μm, the impact cannot be sufficiently mitigated, and if it exceeds 1000 μm, no further effect can be obtained and it is uneconomical. Moreover, the back surface side sealing material sheet 2 suppresses the flow-out and film thickness change in a lamination process by giving a softness | flexibility to the transparent outermost layer 22, and giving heat resistance to the white intermediate | middle layer 21. Even when the film thickness is reduced to about 500 μm or less, it is possible to provide sufficiently preferable molding properties, heat resistance, and solar cell element protection performance.

  About the ratio of the thickness of each layer in the back surface side sealing material sheet 2, thickness ratio with transparent outermost layer 22: white intermediate | middle layer 21: transparent outermost layer 22 is 1: 2: 1-1: 30: 1. A range is preferable. By setting the thickness ratio of each layer within this range, the heat resistance and molding characteristics of the back surface side sealing material sheet 2 can be maintained in a favorable range.

<Sealing material composition for back side sealing material sheet>
Hereinafter, the sealing material composition for back surface side sealing material sheets used for manufacture of the back surface side sealing material sheet 2 is demonstrated.

[Sealant composition for white intermediate layer]
The white intermediate layer sealing material composition used for forming the white intermediate layer 21 of the back surface side sealing material sheet 2 uses a low density polyethylene resin in a predetermined density range as a base resin, and is made of an inorganic material such as titanium oxide. System white pigment as an essential component.

(Base resin)
As the base resin of the sealing material composition for the white intermediate layer (hereinafter also referred to as “white intermediate layer base resin”), the sealing material composition for the intermediate layer of the light-receiving surface side sealing material sheet (for the intermediate layer) The same low density polyethylene (LDPE), linear low density polyethylene (LLDPE), or metallocene linear low density polyethylene (M-LLDPE) as the base resin can be preferably used. As for the number of double bonds of the material resin, the same resin as the intermediate layer base resin can be preferably used.

(White pigment)
The sealing material composition for a white intermediate layer contains a coloring material for expressing a preferable appearance and light reflection performance as a white sealing material sheet. As such a coloring material, an inorganic white pigment made of an inorganic compound can be used. By including such a white pigment, when the white sealing material sheet of the present invention is disposed on the non-light-receiving surface side of the solar cell module, the incident light into the solar cell module is reflected, and the solar cell The power generation efficiency of the module can be improved.

  As the inorganic white pigment, for example, calcium carbonate, barium sulfate, zinc oxide, titanium oxide and the like can be preferably used. Among these, titanium oxide can be particularly preferably used from the viewpoint of versatility.

  The white pigment preferably has a particle size of 0.2 μm or more and 1.5 μm or less. If the particle size of the white pigment is in the above range, the white layer formed from it effectively reflects near infrared rays in addition to the visible light region, so that the particles that can further contribute to the power generation efficiency improvement of the solar cell module. A typical example of a white pigment having a diameter of 0.3 μm or more and 1.5 μm or less is titanium oxide, and it is preferable to use titanium oxide as the white pigment in order to improve the reflection performance of sunlight. This inorganic white pigment is contained only in the white intermediate layer 21, and the content in the white intermediate layer 21 is preferably 5% by mass or more and 30% by mass or less. Moreover, a white sealing material sheet can suppress that the adhesiveness of the transparent outermost layer 22 falls by the influence of a white pigment by setting it as the structure in which a white pigment contains only in the white intermediate | middle layer 21. FIG.

[Encapsulant composition for transparent outermost layer]
The sealing material composition for the transparent outermost layer uses a polyethylene-based resin in a predetermined low density range relatively lower than that used for the sealing material composition for the white intermediate layer as a base resin, It is more preferable to contain an adhesive copolymer resin made of a silane-modified polyethylene resin or the like.

(Base resin)
As the base resin of the sealing material composition for transparent outermost layer (hereinafter also referred to as “base resin for transparent outermost layer”), the sealing material composition for outermost layer of the light-receiving surface side sealing material sheet (for outermost layer) The same low density polyethylene (LDPE), linear low density polyethylene (LLDPE), or metallocene linear low density polyethylene (M-LLDPE) as the base resin can be preferably used. As for the number of double bonds of the material resin, the same resin as the outermost base resin can be preferably used.

(Silane-modified polyethylene resin)
It is preferable that the sealing material composition for transparent outermost layers contains the same silane modified polyethylene resin as the sealing material composition for outermost layers.

  By using the silane-modified polyethylene-based resin described above as a component of the sealing material composition for the outer layer among the sealing material composition for the solar cell module, it has excellent adhesion, strength, durability, etc., and In addition, a white sealing material sheet excellent in weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, yield resistance, and other characteristics can be obtained. Various effects can be obtained in this way by using a silane-modified polyethylene-based resin, but in particular, the white sealing material sheet is extremely effective without being affected by manufacturing conditions such as thermocompression bonding for manufacturing a solar cell module. The point which can provide the outstanding heat-fusion property, ie, the outstanding adhesiveness with the glass base material etc. which comprise a solar cell module, can be mention | raise | lifted as a biggest advantage.

[Other additives]
For each encapsulant composition for the white intermediate layer and the transparent outermost layer, the same cross-linking agent, cross-linking aid, and adhesion as those of the additive to the light-receiving surface side encapsulant sheet composition are used as appropriate. A property improver and other additives may be added as necessary.

[Ultraviolet absorber]
In addition, the back surface side sealing material sheet 2 used for the solar cell module 10 of this invention is characterized by not containing an organic type ultraviolet absorber in any layer.

  Here, the ultraviolet absorber absorbs harmful ultraviolet rays in sunlight, converts them into innocuous heat energy in the molecule, and initiates photodegradation of the resin for filler used in the filler for solar cell modules. It prevents the active species from being excited. Specific examples of organic ultraviolet absorbers include benzophenone-based, benzotriazole-based, salicylate-based, and acrylonitrile-based ultraviolet absorbers.

<Method for producing sealing material sheet>
[Sheet making process]
Each of the light receiving surface side and back surface side sealing material sheets, the details of which are described above, is a molding method usually used in ordinary thermoplastic resins, that is, injection molding, extrusion molding, hollow molding, compression molding, rotational molding, etc. The various molding methods are used. As an example of the forming method as the multilayer sheet, a method of forming by co-extrusion with two or more melt-kneading extruders can be given.

  The lower limit of the molding temperature at the time of molding may be a temperature exceeding the melting point of each sealing material composition. The upper limit of the molding temperature is, when a crosslinking agent is used, the temperature at which crosslinking does not start during film formation, that is, the gel fraction of the encapsulant composition, depending on the 1 minute half-life temperature of the crosslinking agent used. The temperature may be any temperature that can be maintained at 0%. Here, in the method for producing a sealing material sheet of the present invention, a crosslinking agent is not essential in the sealing material composition, and even when a crosslinking agent is added, its content is less than 0.5% by mass. It is limited to. For this reason, under a normal low density polyethylene resin molding temperature, for example, a heating condition of about 120 ° C., the gel fraction does not change, and the crosslinking that substantially affects the physical properties of the resin does not proceed. In addition, when the crosslinking treatment is performed by irradiation with ionizing radiation, a crosslinking agent having a half-life temperature higher than that of the conventional one can be used, which is freed from the restriction of heating conditions in the modularization process. In this case, the gel fraction of the encapsulant composition can be maintained at 0% even when the molding temperature is set higher than before. According to the manufacturing method that maintains the gel fraction of the encapsulant composition during film formation at 0%, it is possible to reduce the load on the extruder during film formation and increase the productivity of the encapsulant sheet. It is.

[Crosslinking process]
A cross-linking step of performing a cross-linking process by ionizing radiation on the uncross-linked encapsulant sheet after the sheet forming step is integrated with the other members after the completion of the sheet forming step. It is preferably performed before the start of the solar cell module integration step. By this crosslinking treatment, a sealing material sheet having a gel fraction of 2% to 80% is obtained.

  Regarding the crosslinking treatment by irradiation with ionizing radiation, the individual crosslinking conditions are not particularly limited. As a rough standard of specific irradiation amount, it may be appropriately set so that the gel fraction of the intermediate layer after the crosslinking treatment is in a range of about 10% or more. Specifically, it can be performed by ionizing radiation such as electron beam (EB), α-ray, β-ray, γ-ray, neutron beam, etc. Among them, it is preferable to use an electron beam. Further, the ionizing radiation may be irradiated from either one side or both sides. From the viewpoint of improving productivity, single-sided irradiation that is irradiation only from one outermost layer side is preferable.

  When ionizing radiation is applied by single-sided irradiation, the acceleration voltage is determined by the thickness of the sheet that is the object to be irradiated, and a thicker sheet requires a larger acceleration voltage. For example, in the case of a sheet having a thickness of 0.6 mm, irradiation is performed at 200 kV to 1000 kV, preferably 250 kV to 1000 kV. When the acceleration voltage is less than 200 kV, electrons do not pass to the outermost layer on the non-irradiation surface side, and the heat resistance of the light-receiving surface side sealing material sheet 1 becomes insufficient. On the other hand, when the acceleration voltage exceeds 1000 kV, electrons are uniformly transmitted through all the layers of the multilayer sheet, and it becomes impossible to form a storage elastic gradient structure which is a characteristic structure of the present invention. The irradiation dose is in the range of 5 kGy to 800 kGy, preferably 100 kGy to 500 kGy. Irradiation may be in an air atmosphere or a nitrogen atmosphere.

  Here, the gel fraction (%) means that 0.1 g of a sealing material sheet is put in a resin mesh, extracted with 60 ° C. toluene for 4 hours, taken out together with the resin mesh, weighed after drying, and mass before and after extraction. Comparison is made and the mass% of the remaining insoluble matter is measured, and this is used as the gel fraction.

  This crosslinking treatment may be performed continuously in-line following the sheet forming step, or may be performed off-line. Further, when the crosslinking treatment is a general heat treatment, generally, the content of the crosslinking agent is 0.5 parts by mass or more and 1.5 parts by mass or less with respect to 100 parts by mass of all components of the sealing material sheet. However, in the sealing material sheet of the present invention, the content of the crosslinking agent may be 0, and even if it is contained, it is preferably less than 0.5 parts by mass. Thereby, the risk of the productivity fall by gelatinization of the sealing material composition in the sheeting process of a sealing material composition can be reduced.

  While the present invention has been specifically described with reference to the embodiment, the present invention is not limited to the above embodiment, and can be implemented with appropriate modifications within the scope of the present invention.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.

<Manufacture of sealing material sheet for solar cell module>
The raw materials of the encapsulant composition described below are mixed so that the contents in the encapsulant composition are in the ratios shown in Table 1 below, and the encapsulants of Examples, Comparative Examples, and Reference Examples, respectively. It was set as the sealing material composition for producing the sealing material sheet for inner layers and outer layers of a sheet | seat. Each sealing material composition is produced by using a φ30 mm extruder and a film forming machine having a 200 mm wide T die at an extrusion temperature of 210 ° C. and a take-off speed of 1.1 m / min to produce an inner layer and an outer layer sealing material sheet. These inner layer and outer layer encapsulant sheets were laminated to form a single or three-layer encapsulant sheet for solar cell modules (Examples, Comparative Examples and Reference Examples). Each of these encapsulant sheets had a thickness of 600 μm, and the outer layer: inner layer: outer layer thickness ratio was 1: 5: 1. In addition, as a raw material of a sealing material composition, the following raw materials were used.

[Polyethylene resin]
Metallocene linear low density polyethylene (M-LLDPE): Metallocene linear low density polyethylene having a density of 0.880 g / cm ³ and MFR at 190 ° C. of 3.5 g / 10 min was used as a base resin (Table 1 and described as “PE”).

[Silane-modified polyethylene resin]
Silane crosslinkable resin: vinyl trimethoxy with respect to 98 parts by mass of metallocene linear low density polyethylene (M-LLDPE) having a density of 0.881 g / cm ³ and an MFR at 190 ° C. of 2 g / 10 min. A silane crosslinkable resin composed of 2 parts by mass of silane and 0.1 parts by mass of dicumyl peroxide as a radical generator (reaction catalyst) was used as a silane-modified polyethylene resin mixed with the base resin. The density of this resin is 0.884 g / cm ³ and the MFR at 190 ° C. is 1.8 g / 10 minutes (described as “S-PE” in Table 1).

[Light stabilizer]
As a light stabilizer, hindered amine light stabilizer (Kemipro Kasei Co., Ltd .: KEMISTAB62) 2.28 mass with respect to 100 mass parts of powder obtained by pulverizing Ziegler linear low density polyethylene having a density of 0.880 g / cm ^3. The parts were mixed, melted, processed, and pelletized master batch (MB) was prepared (described as “HALS” in Table 1).

[Ultraviolet absorber]
As a UV absorber, benzophenone UV absorber (Kemipro Kabushiki Kaisha: KEMISORB12) 3.32 parts by mass with respect to 100 parts by mass of powder obtained by pulverizing Ziegler linear low density polyethylene having a density of 0.880 g / cm ^3. And a benzophenone ultraviolet absorber (Kemipro Kasei Co., Ltd .: KEMISORB 79) 0.6 parts by mass were mixed, melted, processed, and pelletized master batch (MB) was prepared (described as “UVA” in Table 1). ).

[Organic wavelength conversion agent]
As an organic wavelength converting agent, 100 parts by mass of powder obtained by pulverizing Ziegler linear low density polyethylene having a density of 0.880 g / cm ³ is mixed with 1 part by mass of a triazole derivative (number average molecular weight: 323) and melted. The master batch (MB) which was processed and pelletized was created.

[White pigment]
As a white pigment, with respect to 100 parts by mass of powder obtained by pulverizing Ziegler linear low density polyethylene having a density of 0.880 g / cm ³ , 60 parts by mass of titanium oxide (manufactured by DuPont: R105, particle size 0.3 μm) A master batch (MB) was prepared by mixing, melting, processing, and pelletizing.

<Evaluation Example 1>
About the sealing material 1 (Test Example 1) and the sealing material 2 (Test Example 2), a storage stability test (temperature 40 ° C., humidity 90% RH, for 3 months) is performed, and optical characteristics before and after the storage stability test (HAZE) (Measured with JIS K7136, Murakami Color Research Co., Ltd., haze / transmittance system HM150) and glass adhesion were evaluated. Regarding the optical characteristics, a haze of 5.0% or less was “◯”, and a haze of over 5.0% was “x”. The glass adhesion was 23 ° C. at a peeling condition of 50 mm / min at 180 ° peel using a peeling test apparatus (trade name “TENSILON RTA-1150-H” manufactured by A & D Co., Ltd.). In the peeling, 20 N / 15 mm or more was set as “◯”, and less than 20 N / 15 mm was set as “X”. The results are shown in Table 2.

<Evaluation Example 2>
The solar cell module of an Example and a comparative example was created using sealing material sheet AD (refer Table 1), and PV characteristic before and behind a dump heat test was evaluated. Specifically, the sealing material is laminated on the cell in a state in which the other than the cell portion of the T-SEC single crystal cell (TSS63TN) is sealed with aluminum to prevent light from entering, and a solar cell module is created. In accordance with JIS C8917, the durability test of the sample module for evaluation was performed for 1000 hours under the conditions of a test chamber temperature of 85 ° C. and a humidity of 85%. Using a solar simulator (EWXS-300S-50 manufactured by Eiko Seiki Co., Ltd.), the conditions were such that the cell back surface temperature was 25 ° C. and the illuminance was 100 mW / cm ² . The evaluation results are shown in Table 3.

  From Table 3, it can also be confirmed that the Isc value (short circuit current, unit A) is higher than that of the solar cell module of Comparative Example 2 in which the back side sealing material sheet does not contain a white pigment or an organic wavelength conversion agent. Moreover, it turns out that the solar cell module of an Example has the deterioration of the power generation efficiency after a dump heat test clearly less than the solar cell module of the comparative example 1 which contains a ultraviolet absorber in a back surface side sealing material. From the results of Evaluation Examples 1 and 2, it can be seen that the solar cell module of the present invention is a solar cell module that can maintain good power generation efficiency even after long-term use in a high-temperature and high-humidity environment.

DESCRIPTION OF SYMBOLS 1 Light-receiving surface side sealing material sheet 11 Intermediate layer 12 Outermost layer 2 Back surface side sealing material sheet 21 White intermediate layer 22 Transparent outermost layer 3 Solar cell element 4 Transparent front substrate 5 Back surface protection sheet 10 Solar cell module

Claims (7)

A solar cell element;
A light-receiving surface side sealing material sheet disposed on the light-receiving surface side of the solar cell element;
A back side sealing material sheet disposed on the back side of the solar cell element,
The light receiving side sealing material sheet and the back side sealing material sheet, and a density of 0.870 g / cm ³ or more 0.970 g / cm ³ or less of low density polyethylene-based resin,
The light-receiving surface side sealing material sheet is a multilayer sheet comprising an intermediate layer and outermost layers disposed on both sides thereof, and contains an organic wavelength conversion agent in the intermediate layer,
The back surface side sealing material sheet is a multilayer sheet comprising a white intermediate layer containing an inorganic white pigment and a transparent outermost layer disposed on both surfaces thereof, and both layers are organic. The solar cell module which does not contain a ultraviolet absorber and the content of the white pigment in the intermediate layer is more than 8% by mass and 30% by mass or less .   The solar cell module according to claim 1, wherein the white pigment is titanium oxide.   The solar cell module according to claim 1 or 2, wherein the number average molecular weight of the organic wavelength conversion agent contained in the intermediate layer of the light-receiving surface side sealing material sheet is 100 or more and 1000 or less.   The content ratio of the wavelength conversion agent in the outermost layer of the light-receiving surface side sealing material sheet is smaller than the content ratio of the organic wavelength conversion agent in the intermediate layer. The solar cell module described.   The content ratio of the wavelength conversion agent in the outermost layer of the light-receiving surface side sealing material sheet is ½ or less of the content ratio of the organic wavelength conversion agent in the intermediate layer. The solar cell module according to any one of the above.   The solar cell module according to any one of claims 1 to 5, wherein the organic wavelength conversion agent is any one derivative of pyrazine, pyridine, and triazole or a mixture thereof.   The solar cell module according to any one of claims 1 to 6, wherein the outermost layer of the light-receiving surface side sealing material sheet further contains a silane-modified polyethylene resin.

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