JP6375756B2 - SEALING MATERIAL SHEET FOR SOLAR CELL MODULE AND METHOD FOR PRODUCING THE SAME - Google Patents

Description

  The present invention relates to a sealing material sheet for a solar cell module and a method for producing the same.

  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, EVA resin has a tendency to gradually decompose with long-term use, and deteriorates inside the solar cell module to decrease its strength or generate acetic acid gas that affects the solar cell element. there is a possibility. In recent years, development of a sealing material sheet based on a polyethylene resin having transparency equivalent to EVA and excellent in hydrolysis resistance and the like as compared with EVA has been progressing.

  For example, while the base resin is a polyethylene resin, it can be extruded at a low temperature and can be post-crosslinked. As a result, the solar cell module has excellent transparency, adhesion, and durability. As the encapsulant sheet, an encapsulant composition containing a low-density, low-melting silane-modified polyethylene resin obtained by graft polymerization of an ethylenically unsaturated silane compound on linear low-density polyethylene and a crosslinking agent was used. A sealing material sheet has been proposed (see Patent Document 1).

  However, the above-described encapsulant sheet using a low-density polyethylene-based resin as a base resin still has room for improvement in heat resistance after modularization due to its low density. Therefore, the heat resistance of the encapsulant sheet is improved by crosslinking a low-density polyethylene resin by heat treatment. Such a sealing material sheet comprising a sealing material composition containing a low-density polyethylene-based resin as a base resin and further containing a crosslinking agent must be subjected to a crosslinking treatment by heating in any process until modularization. .

  On the other hand, Patent Documents 2 and 3 disclose a technique for imparting heat resistance by omitting a long-time heat curing step by irradiating a polyethylene resin or the like with ionizing radiation for crosslinking.

  The sealing material sheet described in Patent Document 1 has a problem in that it is difficult to improve the productivity of the solar cell module due to the limitation of the manufacturing conditions accompanying the implementation of the thermal crosslinking treatment.

  According to the manufacturing method of the sealing material sheet which performs the crosslinking process by irradiating with ionizing radiation as in Patent Documents 2 and 3, it is freed from the temperature conditions of the thermal crosslinking process, and a certain degree of productivity improvement can be expected. . However, if a sufficient amount of cross-linking treatment is required to provide sufficient heat resistance to withstand long-term use at high temperatures, the ability to follow the irregularities of other components when modularized (hereinafter referred to as the following) , "Molding characteristics").

  With regard to this molding characteristic, in recent years, especially in the demands for size variations, large modules that are in a growing trend of demand, so-called full-size modules (about 1500 mm x 1000 mm), etc., are not heated when being modularized. It has been recognized that the enormous encapsulant sheet may not be fully distributed. There is a need for a solution to the problem that molding characteristics are more likely to be insufficient, especially in portions where the temperature is relatively low, when there is such a variation in temperature distribution during modularization.

Japanese Patent Laid-Open No. 2002-235048 JP 2009-249556 A JP 2011-77357 A

  The present invention has been made in view of the above situation, and uses a polyethylene-based resin excellent in hydrolysis resistance and the like as a base resin, and has improved heat resistance by performing a crosslinking treatment by irradiation with ionizing radiation. It is an object to provide a sealing material sheet that is a sheet and has extremely excellent adhesion and molding characteristics.

  As a result of intensive studies, the present inventors have determined that the encapsulant sheet is a multilayer sheet having a thickness within a predetermined range, and the loss tangent (hereinafter referred to as “tan δ”) of each layer in the actual resin temperature range when modularized. ) Is optimized by irradiation with ionizing radiation, it is found that a sealing material sheet having more excellent molding characteristics can be obtained while maintaining preferable heat resistance, and the present invention has been completed. It was. More specifically, the present invention provides the following.

(1) A sealing material sheet for a solar cell module that has been subjected to crosslinking treatment by irradiation with ionizing radiation, wherein the sealing material sheet is a multilayer sheet including at least an intermediate layer and an outermost layer. the total thickness of the multilayer sheet is at 100μm or more 1000μm or less, the intermediate layer, the density of 0.870 g / cm ³ or more 0.970 g / cm ³ or less of the polyethylene resin as a base resin, the intermediate layer mean value of the loss tangent (tan [delta) at 80 ° C. to 110 ° C. is in the range of 0.39 to 0.69, the outermost layer, density 0.870 g / cm ³ or more 0.900 g / cm ³ or less of polyethylene-based The sealing material sheet which uses resin as base resin and this outermost layer has the average value of the loss tangent in 80 to 110 degreeC exceeding 1 and 5000 or less.

  (2) The encapsulant sheet according to (1), wherein an average value of loss tangent at 80 ° C. to 110 ° C. of the intermediate layer is in a range of 0.49 to 0.59.

  (3) The encapsulant sheet according to (1) or (2), wherein an average value of loss tangents at 80 ° C. to 110 ° C. of the outermost layer exceeds 100 and is 3000 or less.

  (4) The outermost layer is laminated on both surfaces of the intermediate layer, the total thickness is 200 μm or more and 1000 μm or less, and the thickness ratio of the outermost layer: intermediate layer: outermost layer is 1: 2: The sealing material sheet in any one of (1) to (3) which exists in the range of 1-1: 30: 1.

  (5) A solar cell module comprising the encapsulant sheet according to any one of (1) to (4) and a solar cell element, wherein the outermost layer of the encapsulant sheet is the solar cell element. The solar cell module arrange | positioned so that a metal electrode may be faced.

(6) The method for manufacturing a solar cell module according to (5), wherein the solar cell module constituent members including the sealing material sheet and the solar cell element are integrated and integrated by thermocompression treatment. The manufacturing method of the solar cell module characterized by including a conversion process, and performing the said thermocompression-bonding process on the following heating conditions.
Heating conditions: The resin temperature of the sealing material sheet during the thermocompression bonding process is 50 ° C. or higher and 100 ° C. or lower.

(7) A sealing material sheet manufacturing method for a solar cell module, the intermediate layer for sealing material to a density of 0.870 g / cm ³ or more 0.970 g / cm ³ or less of the polyethylene resin as a base resin composition forming an intermediate layer, and an outermost layer consisting of a density 0.870 g / cm ³ or more 0.900 g / cm ³ or less made of a polyethylene resin outermost layer sealing material composition, a multilayer sheet by laminating consisting thing And a cross-linking step in which the multilayer sheet is subjected to a cross-linking treatment by irradiating with ionizing radiation, and an average value of loss tangents at 80 to 110 ° C. of the intermediate layer after the cross-linking step is 0. The cross-linking process is carried out according to the irradiation conditions in which the average value of the loss tangent at 80 ° C. to 110 ° C. of the outermost layer after the cross-linking step is in the range of 49 to 0.59 and is 5000 or less. Sealing material sheet manufacturing method of performing.

  (8) The polyethylene resin used as the base resin of the intermediate layer sealing material composition is more than 2000 carbon by infrared absorption spectrum method than the polyethylene resin used as the base resin of the outermost layer sealing material composition. The manufacturing method of the sealing material sheet for solar cell modules as described in (7) which is resin with many full double bonds per hit.

  (9) The encapsulant composition for an intermediate layer contains a crosslinking aid that is a polyfunctional monomer having a carbon-carbon double bond and / or an epoxy group, and the encapsulant composition for the outermost layer. The manufacturing method of the sealing material sheet as described in (7) or (8) in which the said crosslinking adjuvant is not contained in the thing.

  (10) The encapsulant according to any one of (7) to (9), wherein the content of the crosslinking aid in the encapsulant composition for intermediate layer is 0.01% by mass to 3% by mass. Sheet manufacturing method.

  According to the present invention, there is provided a sealing material sheet for a solar cell module using a polyethylene-based resin as a base resin and subjected to a crosslinking treatment by irradiation with ionizing radiation, and has a high level of heat resistance and molding characteristics. A stop sheet can be provided.

It is a cross-sectional schematic diagram which shows an example of the laminated constitution of the sealing material sheet of this invention. It is a cross-sectional schematic diagram which shows an example of the laminated constitution of the solar cell module using the sealing material sheet of this invention, and a thin film type solar cell element. It is a graph which shows transition of the loss tangent (tan-delta) in 80 to 110 degreeC of the sealing material sheet of this invention.

  Hereinafter, first, an encapsulant composition (hereinafter also simply referred to as “encapsulant composition”) that can be preferably used for the encapsulant sheet for the solar cell module of the present invention, the solar cell module of the present invention. The solar cell module using the sealing material sheet (hereinafter, also simply referred to as “sealing material sheet”) and the sealing material sheet of the present invention will be sequentially described. Each manufacturing method will also be described together as appropriate. In the present specification, the multilayer encapsulant sheet is an outermost layer that is a layer formed on the outermost surface side of at least one of the encapsulant sheets, and an intermediate layer that is a layer other than the outermost layer. It means a sealing material sheet having a multi-layer structure of two or more layers. 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.

<Encapsulant composition>
The sealing material sheet of this invention is a sealing material sheet for solar cell modules manufactured by performing the crosslinking process by ionizing radiation after melt molding of a sealing material composition. The encapsulant sheet of the present invention is a multilayer encapsulant sheet comprising an intermediate layer and an outermost layer. By optimizing the loss tangent (tan δ) of each of the intermediate layer and the outermost layer, both heat resistance and molding characteristics can be achieved at a high level.

[Sealing material composition for intermediate layer]
The encapsulant composition for intermediate layer is an encapsulant composition used for forming the intermediate layer of the multilayer encapsulant sheet of the present invention. The intermediate layer sealing material composition uses a polyethylene resin as a base resin. Moreover, it is preferable to contain a crosslinking aid.

(Base resin)
The polyethylene resin used as the base resin of the encapsulant composition for the intermediate layer (hereinafter also referred to as “base resin for the intermediate layer”) is low density polyethylene (LDPE), linear low 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, 0.870Cm ³ or 0.970 g / cm ³ or less, or preferably 0.870Cm ³ or more 0.930 g / cm ³ or less. The density of the intermediate layer base resin is preferably higher than the base resin of the outermost layer sealing material composition (hereinafter also referred to as “outermost layer base resin”). By setting the density of the base resin for the intermediate layer within the above range, the heat resistance of the sealing material can be improved while maintaining the molding characteristics and the protection performance of the solar cell element.

  The base resin for the intermediate layer is a resin whose MFR after the crosslinking treatment by irradiation with ionizing radiation can be 0.1 g / 10 min or more and 4 g / 10 min or less. The intermediate layer base resin preferably has a smaller MFR than the outermost layer base resin. Thereby, the heat resistance of a sealing material sheet can be hold | maintained in a preferable range. Note that “MFR” in this specification means all MFR at 190 ° C. and a load of 2.16 kg measured according to JIS K6922-2, unless otherwise specified.

  The polyethylene resin used as the base resin for the intermediate layer is preferably one having a melting point of about 90 ° C. or less, but as will be described later, such as the number of double bonds and the illuminance of the radiation during the crosslinking treatment with ionizing radiation. By appropriately adjusting the production conditions, for example, even a relatively high-density and inexpensive polyethylene-based resin having a melting point of about 120 ° C. can be used.

(Crosslinking aid)
The intermediate layer sealing material composition preferably contains a crosslinking assistant in addition to the intermediate layer base resin. In the present invention, a polyfunctional monomer having a carbon-carbon double bond and / or an epoxy group can be preferably used as a crosslinking aid. More preferably, the cross-linking aid is one in which the functional group of the polyfunctional monomer is an allyl group, a (meth) acrylate group, or a vinyl group. By adding such a crosslinking aid, the crystallinity of the low density polyethylene can be reduced, and a crosslinked encapsulant 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 crosslinking effect with an electron beam, 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 in the intermediate layer sealing material composition. .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 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 sealing material composition which concerns on this invention, it is preferable not to add the said crosslinking adjuvant to the sealing material composition for outermost layers. In the production method of the present invention in which crosslinking treatment is performed by irradiation with ionizing radiation, the addition of a crosslinking aid only to the intermediate layer can provide a sealing material sheet having an excellent balance between adhesion and heat resistance, This is because, when a crosslinking aid is added to the outermost layer sealing material composition, there is a high risk of lowering adhesion due to lowering of fluidity or so-called bleeding out of the crosslinking aid.

  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.

  The content of the base resin for the intermediate layer contained in the intermediate layer sealing material composition is preferably 10 parts by mass or more and 99 parts by mass with respect to a total of 100 parts by mass of all the resin components in the intermediate layer sealing material composition. It is 50 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. Within the said range, other resin may be included. 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.

  By setting the number of full double bonds of the encapsulant composition for the intermediate layer within the above range, the heat resistance of the encapsulant sheet can be sufficiently improved by sufficiently proceeding with crosslinking by irradiation with ionizing radiation. . On the other hand, even if the intermediate layer is sufficiently cross-linked by irradiation with ionizing radiation, the number of full double bonds of the outermost layer sealing material composition is limited to a range different from that of the intermediate layer sealing material composition. By doing so, the progress of cross-linking 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 may not fully improve that 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 may be 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 sealing material composition in the sheet state and the absorption of the infrared absorption spectrum. It is a value obtained from the following formula from the absorbance A of the band. 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.

[Sealant composition for outermost layer]
The outermost layer sealing material composition is a sealing material composition used to form the outermost layer disposed on at least one outermost surface, preferably both outermost surfaces of the multilayer sealing material sheet of the present invention. is there. The sealing material composition for the outermost layer uses a polyethylene resin as a base resin, and preferably contains an adhesive copolymer resin such as a silane-modified polyethylene resin.

(Base resin)
As the polyethylene resin used as the base resin of the sealing material composition for the outermost layer, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), or metallocene linear low density polyethylene (M-LLDPE) is appropriately used. It can be preferably used.

Density of the polyethylene resin used as the outermost layer for the base resin is preferably 0.870Cm ³ or more 0.900 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. 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.

  The outermost layer base resin is a resin whose MFR after the crosslinking treatment by irradiation with ionizing radiation can be 0.6 g / 10 min or more and 5.0 g / 10 min or less. The outermost layer base resin is preferably a resin having a larger MFR than the intermediate layer base resin. Thereby, the adhesiveness and molding characteristic of a sealing material sheet can be hold | maintained in a preferable range.

  On the other hand, as the base resin for the outermost layer, it is preferable to use a polyethylene-based resin in which the number of full double bonds remaining in the composition stage is relatively smaller than the number of full 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)
The outermost layer sealing material composition preferably contains a silane-modified polyethylene resin in addition to the outermost layer 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. reactions using the container, for example, a pressure 500~4000Kg / cm ^2-position, preferably, 1000~4000Kg / cm ^2-position, temperature, 100 to 400 ° C.-position, preferably under the conditions of 150 to 350 ° C.-position, Part of the silane compound constituting the random copolymer which is produced by random copolymerization simultaneously or stepwise in the presence of a radical polymerization initiator and, if necessary, a chain transfer agent. Can be modified or condensed to produce a silane-modified polyethylene resin.

  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 to 15% by mass, preferably 0.01 to 5% by mass in the base resin of the silane-modified polyethylene resin. %, Particularly preferably 0.05 to 2% by mass. 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.

  The content of the silane-modified polyethylene resin used in the sealing material composition for the outermost layer of the sealing material sheet of the present invention in the sealing material composition for the outermost layer is the same as that of the base resin of the sealing material composition. It is preferable that content in 100 mass parts of resin components which consist of united resin is 8 mass parts or more and 45 mass parts or less. In the present invention, if the content of the silane-modified polyethylene resin is 8 parts by mass or more, it is excellent in mechanical strength and heat resistance, but if the content is excessive, it tends to be inferior in tensile elongation and heat-fusibility. It is in.

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

[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 cross-linking agent is added, the content thereof is 0 part by mass or more and 0.5 part by mass or less with respect to a total of 100 parts by mass of all the resin components in the intermediate layer and outermost layer sealing material compositions. The content is preferably 0.02 parts by mass or more and 0.5 parts by mass or less. When the addition amount of the cross-linking agent exceeds 0.5 parts by mass, the progress of cross-linking in the cross-linking step becomes excessive, and molding characteristics become 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 adding a silane coupling agent as an adhesion improver, the content is 0.1 parts by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass in total of all resin components of the sealing material composition. Yes, the upper limit is preferably 5.0 parts by mass or less. 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 it exceeds this range, the film-forming property is deteriorated, or so-called bleed-out in which the silane coupling agent aggregates and solidifies with time and is pulverized on the surface of the sealing material sheet is not preferable.

(Radical absorbent)
In each encapsulant composition for the intermediate layer and the outermost layer, the degree of cross-linking is further refined by using the above-mentioned cross-linking auxiliary agent that serves as a radical polymerization initiator and the radical absorbent that quenches it. Can be adjusted. Examples of such radical absorbents include hindered phenol-based antioxidants, hindered amine-based weather resistance stabilization, and the like. A hindered phenol-based radical absorbent having a high radical absorbing ability near the crosslinking temperature is preferred. The amount of the radical absorbent used is preferably 0.01 parts by mass or more and 3 parts by mass or less, more preferably 0.05 parts by mass or more, with respect to 100 parts by mass in total of all resin components of the encapsulant composition. It is the range of -2.0 mass parts or less.

(Other ingredients)
Each sealing material composition for intermediate layer and outermost layer may further contain other components. For example, components such as a weather resistance masterbatch for imparting weather resistance to the sealing material sheet of the present invention, various fillers, a light stabilizer, an ultraviolet absorber, and a heat stabilizer are exemplified. These contents vary depending on the particle shape, density, and the like, but are 0.001 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass in total of all resin components of each sealing material composition. It is preferable to be within the range. 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.

<Sealing material sheet>
The sealing material sheet of the present invention is a multilayer sealing material constituted by a plurality of layers including an intermediate layer and either one of the intermediate layers, preferably the outermost layer disposed on the outermost surface of both. . A multilayer encapsulant sheet produced through a crosslinking treatment by irradiation with ionizing radiation, wherein the average value of loss tangent (tan δ) of each of the intermediate layer and the outermost layer at 80 ° C. to 110 ° C. is within a predetermined range. It is characterized by being controlled to become.

  Hereinafter, as a preferred embodiment of the present invention, referring to FIG. 1, a three-layer encapsulant sheet 1 including two outermost layers 12 in total, one layer above and below a single intermediate layer 11. explain. However, the present invention is not limited to this embodiment. In addition, the average value of the loss tangent (tan δ) of each layer in this specification is the resin temperature that the sealing material sheet actually reaches in the thermal lamination process of a general solar cell module with respect to tan δ of the resin forming each layer. A transition in a range of 80 ° C. to 110 ° C., which is a typical temperature range, is measured as a value, and an average value in the temperature range is calculated. Specifically, as a measuring method, it can be measured by the method shown in the following examples. The resin temperature of the encapsulant sheet can be measured using a temperature / humidity data logger by attaching a temperature sensor thermocouple to the upper surface of the encapsulant sheet during heating. The temperature refers to, for example, the resin temperature of the sealing material sheet measured as described above.

  The total thickness of the sealing material sheet 1 including the intermediate layer 11 and the outermost layer 12 is 200 μm or more and 1000 μm or less, and preferably 300 μm or more and 600 μm or less. If it is less than 200 μm, the impact cannot be sufficiently mitigated, and if it exceeds 1000 μm, no further effect can be obtained, which is uneconomical. In addition, since the sealing material sheet of the present invention has adhesiveness in the outermost layer and heat resistance and molding characteristics in the intermediate layer, it suppresses flow-out and film thickness change during the lamination process. Even when it is thinned to the following extent, it can be provided with sufficiently preferable molding properties and heat resistance, and protection performance of the solar cell element.

  About the ratio of the thickness of each layer in a sealing material sheet, the thickness of an intermediate | middle layer should just be in the range of 1 / 2-30 / 32 of the total thickness of a sealing material sheet more than 100 micrometers. In the case of the sealing material sheet 1 having a three-layer structure, the thickness ratio of the outermost layer 12: intermediate layer 11: outermost layer 12 is preferably in the range of 1: 2: 1 to 1: 30: 1. 1: 2: 1 to 1: 10: 1 are more preferable. By setting the thickness ratio of each layer within this range, the heat resistance and molding characteristics of the sealing material sheet 1 can be maintained within a favorable range.

  The intermediate layer 11 is a layer constituting a main part as a substrate layer in the encapsulant sheet 1. The intermediate layer 11 is given sufficient heat resistance by sufficiently proceeding with cross-linking, whereby the durability of the solar cell module can be improved. In addition, by giving the intermediate layer 11 a thickness greater than or equal to a predetermined value, tan δ is optimally adjusted within a predetermined range with respect to an average value within a temperature range assuming a heating temperature at the time of modularization. The sealing material sheet as a whole can exhibit a preferable molding. This optimum adjustment of tan δ can be performed, for example, by optimizing the irradiation conditions during the crosslinking treatment with ionizing radiation.

  In the intermediate layer 11, the average value of tan δ at 80 ° C. to 110 ° C. is in the range of 0.39 to 0.69. The average value is more preferably in the range of 0.49 to 0.59. When the average value of tan δ at 80 ° C. to 110 ° C. of the intermediate layer 11 is less than 0.39, molding characteristics are insufficient. On the other hand, if it exceeds 0.59, the heat resistance becomes insufficient.

  The outermost layer 12 is a layer that is disposed on the outermost surface of the sealing material sheet in the 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.

  The outermost layer 12 has an average value of tan δ in the range from 80 ° C. to 110 ° C. exceeding 1 and not more than 5000. The average value is more preferably in the range of more than 100 and 3000 or less. When the average value of tan δ at 80 ° C. to 110 ° C. of the outermost layer 12 is less than 1, the adhesion with other laminated base materials at the time of modularization becomes insufficient. On the other hand, if it exceeds 5000, the adhesion layer becomes excessively fluid and the adhesion component flows out, resulting in insufficient adhesion.

  The sealing material sheet 1 is a multilayer sheet formed by laminating resin sheets each having superior physical properties. This is a cross-linked polyethylene resin having an extremely high water vapor barrier property, and is a sealing material sheet for a solar cell module that is extremely excellent in the balance between heat resistance, adhesion and molding characteristics.

<Method for producing sealing material sheet>
As described above, the manufacturing method of the sealing material sheet of the present invention focuses on the difference in the double bond amount for each layer of the intermediate layer and the outermost layer, as described above. It is preferred to limit the dedicated compositions used respectively and optimize their combinations. Thereby, the degree of progress of the degree of crosslinking by irradiation with ionizing radiation performed after melt formation can be promoted or suppressed to an optimum degree individually for each of the above layers.
[Sheet making process]
The melt molding of each composition for the intermediate layer and the outermost layer is performed by molding methods usually used in ordinary thermoplastic resins, that is, by various molding methods such as injection molding, extrusion molding, hollow molding, compression molding, and rotational molding. Done. 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 during molding may be any temperature that exceeds the melting point of the encapsulant composition. The upper limit of the molding temperature is the temperature at which crosslinking does not start during film formation, that is, the temperature at which the gel fraction of the encapsulant composition can be maintained at 0%, depending on the 1 minute half-life temperature of the crosslinking agent used. Good. 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, the content is 0.5 parts by mass or less. Is preferable. By limiting the addition amount of the cross-linking agent in this way, the gel fraction does not change under the normal low-density polyethylene resin molding temperature, for example, about 120 ° C., and the physical properties of the resin are substantially reduced. Cross-linking that has a negative effect does not proceed. In addition, as described above, it is possible to use a cross-linking agent having a half-life temperature higher than that of the conventional one by solving from the limitation of the heating conditions in the modularization process. Therefore, even if the molding temperature is set higher than before, the gel fraction of the encapsulant composition can be maintained at 0%. According to the production method of the present invention that maintains the gel fraction of the encapsulant composition during film formation at 0%, the load on the extruder and the like during film formation is reduced, and the productivity of the encapsulant sheet is increased. It is possible.

  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.

[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. 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. The cross-linking treatment may be performed continuously in-line following the sheet forming step, or may be performed off-line.

  Regarding the crosslinking treatment by irradiation with ionizing radiation, the individual crosslinking conditions are not particularly limited. What is necessary is just to set suitably so that tan (delta) of the intermediate | middle layer after a crosslinking process may become the optimal range demonstrated above. Examples of preferable specific irradiation conditions are, for example, the irradiation conditions described in the examples. Specifically, the crosslinking treatment by the irradiation of ionizing radiation can be performed by ionizing radiation such as electron beam (EB), α-ray, β-ray, γ-ray, neutron beam, etc. Among them, electron beam (EB) is used. It is preferable to use it. Further, the ionizing radiation may be irradiated from either one side or both sides.

  When ionizing radiation is applied by double-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 a 0.6 mm thick sheet, irradiation is performed at 200 kV or more and 1000 kV or less, preferably 250 kV or more and 1000 kV or less. When the acceleration voltage is less than 200 kV, electrons do not reach the intermediate layer even when irradiated from both sides, and the heat resistance of the encapsulant sheet 1 becomes insufficient. On the other hand, if the acceleration voltage exceeds 1000 kV, the cross-linking progress on the irradiated surface side becomes excessive, and the molding characteristics of the surface are lowered. In this case, the irradiation dose is in the range of 25 kGy to 75 kGy, preferably 30 kGy to 50 kGy, and more preferably 30 kGy to 40 kGy.

  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.

<Solar cell module>
Next, a preferred embodiment of the solar cell module of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view illustrating an example of the layer configuration of the solar cell module 10 including the solar cell element according to the embodiment of the present invention. In the solar cell module 10, the transparent front substrate 2, the solar cell element 3 formed on the transparent front substrate 2, the encapsulant sheet 1, and the back surface protection sheet 4 are sequentially laminated from the light receiving surface side of incident light. .

  By using the encapsulant sheet 1, the solar cell module 10 maintains high water vapor barrier properties, and has a heat resistance as a solar cell module particularly when used in a high temperature environment and molding characteristics when modularized. It is a well-balanced improvement. For example, the solar cell element 3 generally has a shape in which the metal electrode 31 protrudes as shown in FIG. 2, but according to the excellent molding characteristics of the sealing material sheet 1 of the present invention, The encapsulant sheet 1, the thin-film solar cell element 3, and the transparent front substrate 2 can be integrated with high adhesion by following such unevenness sufficiently.

  The layer configuration of the solar cell module of the present invention is not limited to that according to the above embodiment. Since the sealing material sheet 1 of the present invention has adhesiveness to both glass and metal, taking advantage of its characteristics, the solar cell module of various configurations including a glass substrate and a metallic solar cell module can be used. Can be used for general purposes. For example, in a solar cell module, the encapsulant sheet of the present invention is preferably used even when one surface of the encapsulant sheet faces the metal surface and the other surface opposes the glass layer. be able to.

  Moreover, the structure by which a sealing material sheet | seat is arrange | positioned on the upper and lower surfaces of the solar cell element which has spread widely conventionally, for example may be sufficient as the solar cell module of this invention. In this case, the sealing material sheet of this invention can be laminated | stacked and used for any of the said both surfaces.

  Furthermore, as another preferred embodiment of the solar cell module of the present invention, a solar cell module including a configuration in which the current collector sheet and the sealing material sheet of the present invention are integrated can be exemplified. A current collector sheet is a component of a solar cell module that is generally arranged for the purpose of collecting current from a back contact solar cell element, and a conductive circuit for current collection is formed on the surface of a resin base material. It is what has been. Since the sealing material sheet laminated on the circuit of the current collecting sheet and the solar cell element is required to have an impact buffering function and further an insulating function, the molding characteristics for the uneven shape on the current collecting sheet are specially selected. A high level of physical properties is required. As described above, since the encapsulant sheet of the present invention has extremely good molding characteristics, it can be preferably used also in a solar cell module including the above configuration.

  For example, the solar cell module 10 is formed by sequentially laminating members composed of the transparent front substrate 2 on which the solar cell elements 3 are formed, the sealing material sheet 1 and the back surface protective sheet 4 and then integrating them by vacuum suction or the like. According to a molding method such as the above method, the above-described member can be manufactured by thermocompression molding as an integral molded body.

  In the solar cell module 10 of the present invention, the transparent front substrate 2, the solar cell element 3, and the back surface protective sheet 4, which are members other than the sealing material sheet 1, can use conventionally known materials without particular limitation. . Moreover, the solar cell module 10 of this invention may also contain members other than the said member. In addition, the sealing material sheet | seat of this invention is preferably applicable not only to the solar cell module 10 provided with a thin film type solar cell element but to all other solar cell modules.

  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 encapsulant sheet for solar cell module>
The encapsulant composition raw materials described below are mixed in the proportions (parts by mass) shown in Table 1 below, and the encapsulant composition for the intermediate layer and the encapsulant for the outermost layer of the encapsulant sheets of Examples and Comparative Examples, respectively. A material composition was obtained.

(Examples 1-2 and Comparative Examples 1-2)
As the sealing material composition raw material for each sealing material sheet of Examples 1-2 and Comparative Examples 1-2, the following raw materials were used.
Base resin for intermediate layer: Metallocene linear low density polyethylene (M-LLDPE) having a density of 0.880 g / cm ³ , a melting point of 60 ° C., and an MFR at 190 ° C. of 3.5 g / 10 min.
Base resin for outermost layer: Metallocene linear low density polyethylene (M-LLDPE) having a density of 0.880 g / cm ³ , a melting point of 60 ° C., and an MFR at 190 ° C. of 19.0 g / 10 min.
Weatherproof masterbatch 1: Base resin: 100 parts by mass. KEMISTAB62 (HALS): 0.6 parts by mass. KEMISORB 12 (UV absorber): 3.5 parts by mass. KEMISORB 79 (UA absorbent): 0.6 parts by mass. CHIMASORB 202 (UV absorber): 0.07 parts by mass. Tricyclodecane dimethanol diacrylate (crosslinking aid): 2.14 parts by mass.
Weatherproof masterbatch 2: Base resin: 100 parts by weight. Tricyclodecane dimethanol diacrylate (crosslinking aid): 2.04 parts by mass.
Weatherproof master batch 3: Base resin: 100 parts by mass. KEMISTAB62 (HALS): 0.6 parts by mass. KEMISORB 12 (UV absorber): 3.5 parts by mass. KEMISORB 79 (UV absorber): 0.6 parts by mass. CHIMASORB 202 (UV absorber): 0.07 parts by mass.
The weathering master batches 1 and 2 containing a crosslinking aid were added in an amount of 10 parts by mass to 100 parts by mass of the base resin, respectively, only in the intermediate layer sealing material compositions of all Examples and Comparative Examples. Moreover, the weatherproof masterbatch 3 which does not contain a crosslinking aid was added in an amount of 10 parts by mass with respect to 100 parts by mass of the base resin, respectively, only in the outer layer sealing material compositions of all Examples and Comparative Examples.
Silane-modified polyethylene-based resin 1: 2 parts by mass of vinyltrimethoxysilane with respect to 100 parts by mass of a metallocene linear low-density polyethylene having a density of 0.880 g / cm ³ and an MFR of 30.0 g / 10 min, a radical A silane-modified polyethylene resin obtained by mixing 0.15 parts by mass of dicumyl peroxide as a generator (reaction catalyst), melting and kneading at 200 ° C. Density 0.880 g / cm ³ , MFR 13.0 g / 10 min. Melting point 60 ° C.
The silane-modified polyethylene resin 1 was added in an amount of 15 parts by mass to 100 parts by mass of the base resin only in the compositions for the outermost layers of Examples 1-2 and Comparative Examples 1-2.

  Each of the above-mentioned sealing material compositions is used for an intermediate layer and an outermost layer at an extrusion temperature of 210 ° C. and a take-off speed of 1.1 m / min using a φ30 mm extruder and a film molding machine having a 200-mm width T-die. Each resin sheet was prepared, and each of these resin sheets was laminated to produce a three-layer encapsulant sheet of Examples and Comparative Examples 1 and 2 having an intermediate layer and both outermost layers. The thickness of each sealing material sheet of an Example and a comparative example was all made into the total thickness of 600 micrometers. About ratio of the thickness of each layer of the sealing material of the 3 layer structure of Examples 1-2 and Comparative Examples 1-2, about any sealing material sheet, the thickness ratio of outermost layer: intermediate layer: outermost layer is 1: 4: 1.

  Next, an electron beam irradiation device (product name: EC250 / 15 / 180L, manufactured by Iwasaki Electric Co., Ltd.) is applied to each of the uncrosslinked sealing material sheets after the molding of Examples 1-2 and Comparative Examples 1-2. The accelerating voltage is 250 kV and the illuminance is irradiated on both sides with the illuminance described in Table 1 below (described as “EB illuminance” in Table 1) to produce a cross-linked encapsulant sheet. It was set as the sealing material sheet of an example and a comparative example.

(Comparative Example 3)
As the sealing material composition raw material for the sealing material sheet of Comparative Example 3, the following raw materials were used. In addition, the sealing material sheet of this comparative example 3 assumes the thermoplastic sealing material sheet which does not perform the crosslinking process after film forming using a polyethylene-type resin.

Weatherproof masterbatch 4: 3.8 parts by mass of a benzophenol UV absorber and a hindered amine light stabilizer 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 5 parts by mass and 0.5 parts by mass of a phosphorous heat stabilizer were mixed and melted and processed to obtain a pelletized master batch.
The weatherproof masterbatch 4 was added to the encapsulant composition for intermediate layer and the encapsulant composition for outermost layer in Comparative Example 3 both by 5 parts by mass.
Polymerization initiator compound resin for intermediate layer 1: 2,5-dimethyl-2 with respect to 100 parts by mass of M-LLDPE pellets having a density of 0.880 g / cm ³ and an MFR at 190 ° C. of 3.5 g / 10 min. Impregnated with 0.032 parts by mass of 5-di (t-butylperoxy) hexane, an intermediate layer compound pellet was obtained.
The intermediate layer polymerization initiator compound resin 1 was added to the intermediate layer sealing material composition of Comparative Example 97 in an amount of 97 parts by mass.
Polymerization initiator compound resin 2 for outermost layer: 2,5-dimethyl-2 with respect to 100 parts by mass of M-LLDPE pellets having a density of 0.880 g / cm ³ and MFR at 190 ° C. of 3.5 g / 10 min. Compound pellets for the outermost layer were obtained by impregnating 0.041 parts by mass of 5-di (t-butylperoxy) hexane.
80 parts by mass of the intermediate layer polymerization initiator compound resin 2 was added to the outermost layer sealing material composition of Comparative Example 3.
Silane-modified polyethylene-based resin 2: 98 parts by mass of a metallocene linear low-density polyethylene having a density of 0.881 g / cm ³ and an MFR of 2 g / 10 minutes, 2 parts by mass of vinyltrimethoxysilane, and a radical 0.1 parts by mass of dicumyl peroxide as a generator (reaction catalyst) is mixed, melted and kneaded at 200 ° C., density 0.884 g / cm ³ , and MFR at 190 ° C. is 1.8 g / 10 min. A silane-modified polyethylene resin was obtained.
The silane-modified polyethylene resin 2 was added in an amount of 3 parts by mass to the encapsulant composition for the intermediate layer of Comparative Example 3, and 20 parts by mass to the encapsulant composition for the outermost layer.

  Each said sealing material composition was shape | molded on the same molding conditions as said Examples 1-2 and Comparative Examples 1-2, and the sealing material sheet of the 3 layer structure of the comparative example 3 was manufactured. The thickness of the sealing material sheet of Comparative Example 3 and the thickness ratio of each layer were the same as those of Examples 1-2 and Comparative Examples 1-2.

<Loss tangent of each layer (tan δ)>
The loss tangent (tan δ) of each layer of Examples and Comparative Examples is measured in the range of 80 ° C. to 110 ° C. by the following measurement method using a single film, and the average value of tan δ of each layer in the same temperature range is calculated. did. The transition of tan δ of the intermediate layer of each sealing material sheet in the above temperature range is shown in the graph of FIG. Moreover, it shows in Table 1 about the average value of tan-delta of each layer of each sealing material sheet in the said temperature range. In addition, the tan δ of the outermost layer of each sealing material sheet in the above temperature range transitioned between a value clearly exceeding 100 to about 3000.
(Measurement method) Measurement was carried out using a rhogel E-4000 manufactured by UBM, using samples obtained by cutting out the sealing material sheets of Examples and Comparative Examples into 5 × 20 mm. Measurement was performed in the pull mode under the following conditions. Initial load 100 g, continuous excitation mode, waveform: sine wave, frequency 10 hz, temperature increase rate 3 ° C./min

<Evaluation Example 1: Heat resistance>
A heat-resistant creep test was conducted. Two sheets of the sealing material sheets of Examples and Comparative Examples cut out to 5 × 7.5 cm on a large-sized glass plate that has been subjected to grain processing, and 5 × 7.5 grain glass are placed on top of each other, 150 ° C. A sample for evaluation was prepared by performing a vacuum heating laminator treatment in 10 minutes. The resin temperature (final temperature) of the sealing material sheet in the laminate during the heat treatment was 100 ° C. Thereafter, the large format glass was placed vertically and allowed to stand at 140 ° C. for 12 hours, and the moving distance (mm) of the 5 × 7.5 grain glass after the standing was measured and evaluated. Evaluation was performed according to the following criteria.
(Evaluation criteria) A: 0.00 mm
B: More than 0.00mm and less than 1.0mm
C: 1.0 mm or more The evaluation results are shown in Table 1 as “heat resistance”.

<Evaluation Example 2: Molding characteristics>
On the same glass substrate as that used in the heat-resistant creep test, an aluminum plate having a thickness of 200 μm and 150 mm × 150 mm assuming a pseudo solar cell element is allowed to stand, and a lead wire is further provided on the aluminum plate. (250 μm diameter) is placed, and from above, each of the sealing material sheets of Examples and Comparative Examples cut to 150 mm × 150 mm is laminated on the non-irradiated surface side of the ionizing radiation of each sealing material sheet. In the arrangement facing the above-mentioned aluminum plate or the like, vacuum heating laminator treatment was performed under the same heat laminating conditions as in the above heat-resistant creep test, and solar cell module evaluation samples were obtained for the respective examples and comparative examples. About these solar cell module evaluation samples, molding characteristics were evaluated by visual observation according to the following evaluation criteria.
(Evaluation criteria) A: Completely follows the unevenness of the substrate surface facing the encapsulant sheet.
B: Generally follows the unevenness of the substrate surface facing the encapsulant sheet. There is a fine adhesion failure.
C: A part of the sealing material sheet does not completely follow the unevenness of the substrate surface facing, and a defective laminate portion occurs.
The evaluation results are shown in Table 1 as “molding characteristics”.

  From Table 1 and FIG. 3, it turns out that the sealing material sheet | seat of the Example manufactured by the manufacturing method of this invention has heat resistance and a molding characteristic on a high level.

DESCRIPTION OF SYMBOLS 1 Sealant sheet 11 Intermediate layer 12 Outermost layer 2 Transparent front substrate 3 Solar cell element 4 Back surface protection sheet 10 Solar cell module

Claims (4)

A method for producing a sealing material sheet for a solar cell module,
An intermediate layer consisting of the intermediate layer sealing material composition and density 0.870 g / cm ³ or more 0.970 g / cm ³ or less of the polyethylene resin as a base resin, density 0.870 g / cm ³ or more 0.900 g / a sheet forming step of forming a multilayer sheet by laminating an outermost layer composed of a sealing material composition for an outermost layer composed of a polyethylene-based resin of cm ³ or less;
A cross-linking step of performing cross-linking treatment by irradiation of ionizing radiation to the multilayer sheet,
Wherein in the crosslinking step, the average value of the loss tangent at 80 ° C. to 110 ° C. of the intermediate layer after the crosslinking step is in the range of from .39 to .69, 80 ° C. ~ of the outermost layer after the crosslinking step The manufacturing method of the sealing material sheet which optimizes irradiation conditions so that the average value of loss tangent in 110 degreeC may exceed 1 and is 5000 or less. The polyethylene resin used as the base resin of the intermediate layer sealing material composition is more than the polyethylene resin used as the base resin of the outermost layer sealing material composition. The method for producing a sealing material sheet for a solar cell module according to claim 1 , wherein the resin is a resin having a large number of double bonds. The encapsulant composition for an intermediate layer contains a crosslinking aid that is a polyfunctional monomer having a carbon-carbon double bond and / or an epoxy group,
The method for producing a sealing material sheet according to claim 1 or 2 , wherein the outermost layer sealing material composition does not contain the crosslinking aid. The method for producing a sealing material sheet according to any one of claims 1 to 3 , wherein a content of the crosslinking aid in the sealing material composition for intermediate layer is 0.01 mass% or more and 3 mass% or less.

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