JP6303365B2 - Manufacturing method of sealing material sheet for solar cell module - Google Patents

Description

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

  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 the solar cell element, in addition to a crystalline silicon solar cell manufactured using a single crystal silicon substrate or a polycrystalline silicon substrate, amorphous silicon or microcrystalline silicon is formed on a substrate such as glass and is extremely thin silicon of about 1 μm or less. There is a thin film solar cell element formed by forming a film. As the thin film solar cell element, there is a compound solar cell using a chalcopyrite compound or the like instead of the silicon. Since all solar cell elements are vulnerable to physical impact and are expected to be used outdoors for a long period of time, solar cell modules including those solar cell elements are required to have high weather resistance and durability. It is done.

  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.

  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.

  As in Patent Documents 2 and 3, according to the method for manufacturing a sealing material sheet that is subjected to crosslinking treatment by irradiating with ionizing radiation, it is released to some extent by being released from the temperature conditions of thermal crosslinking treatment at the time of modularization. I can expect an improvement in productivity. However, if an attempt is made to perform a crosslinking treatment of a necessary and sufficient level in order to provide sufficient heat resistance that can withstand use at high temperatures for a long period of time, the ability to follow irregularities of other members when modularized (hereinafter referred to as “ Molding characteristics ”).

  In any cross-linking treatment by heating or irradiation with ionizing radiation, it is extremely difficult to finely adjust the degree of progress of cross-linking, and in order to finely adjust the degree of cross-linking progress to the optimum range, Alternatively, strict adjustment and management of ionizing radiation dose and the like are required, and this burden is an obstacle to increasing productivity.

  Among these, in particular, in the solar cell module using the thin-film solar cell element, which has recently been in a demand increasing trend, the above-mentioned physical properties such as heat resistance and molding characteristics are required at a very high level. However, according to any of the manufacturing methods disclosed in Patent Documents 1 to 3, it has been extremely difficult to produce a sealing material sheet with high productivity while satisfying the required level of physical properties. This problem has been a common problem for all solar cell modules, but has been a serious problem particularly in solar cell modules including the above-described thin-film solar cell elements.

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 is a sealing material sheet having a polyethylene resin having excellent hydrolysis resistance and the like as a base resin and subjected to a crosslinking treatment by irradiation with ionizing radiation. Providing solar cell module sealing material sheets with high levels of properties, such as heat resistance, molding properties, and transparency, required for battery module sealing material sheets, at high levels. Is an issue.

  As a result of intensive studies, the inventors of the present invention have produced two types of low-density polyethylene-based resins having different MFRs in a multilayer encapsulating process in the production of a solar cell encapsulant sheet that involves crosslinking treatment by irradiation with ionizing radiation. By appropriately selecting the dedicated material for each layer of the fixing material sheet, and further, by selecting a means realized by mixing two kinds of polyethylene resins having different MFRs as such a MFR adjusting means, a desired material is simply obtained. The inventors have found that a sealing material sheet having excellent transparency can be obtained as compared with the conventional means for selecting a resin having MFR, and have completed the present invention. More specifically, the present invention provides the following.

(1) an intermediate layer density 0.870 g / cm ³ or more 0.970 g / cm ³ or less is a polyethylene resin for the intermediate layer formed by melting, than polyethylene resin for the intermediate layer, JIS K6922-2 An outermost layer formed by melting and forming a polyethylene resin for outermost layer having a large MFR at 190 ° C. and a load of 2.16 kg measured by a sheet forming step of forming an uncrosslinked multilayer sheet; A cross-linking step of performing cross-linking treatment on the multilayer sheet by irradiation with ionizing radiation, wherein the polyethylene resin for the outermost layer is a mixture of two types of polyethylene resins having different MFRs. The manufacturing method of the sealing material sheet | seat for solar cell modules to perform.

  (2) The manufacturing method of the sealing material sheet as described in (1) whose mixing ratio of the said 2 types of polyethylene resin is the range of 2: 8-8: 2.

  (3) The MFR of the intermediate layer is 0.1 g / 10 min or more and 4 g / 10 min or less, and the MFR of the outermost layer is larger than 100% and not more than 800% of the MFR of the intermediate layer (1) Or the manufacturing method of the sealing material sheet as described in (2).

  (4) The polyethylene resin for the intermediate layer is a resin having a larger number of full double bonds per 2000 carbons by infrared absorption spectrum method than the polyethylene resin for the outermost layer (1) The manufacturing method of the sealing material sheet in any one of (3).

  (5) The sealing material composition for the intermediate layer and / or the sealing material composition for the outermost layer contains 0.02% by mass or more and less than 0.5% by mass of the crosslinking agent (1). (4) The manufacturing method of the sealing material sheet in any one of.

  (6) The sealing material composition for the intermediate layer and / or the sealing material composition for the outermost layer contains a silane-modified polyethylene resin formed by graft polymerization using an ethylenically unsaturated silane compound as a side chain. The manufacturing method of the sealing material sheet in any one of (1) to (5) to do.

  (7) A solar cell module comprising: a sealing material sheet manufactured by the manufacturing method according to any one of (1) to (6); and a solar cell element, wherein the outermost member of the sealing material sheet is the solar cell module. The solar cell module arrange | positioned so that an outer layer may face the metal electrode of the said solar cell element.

  According to the present invention, a sealing material sheet having a polyethylene resin excellent in hydrolysis resistance and the like as a base resin and subjected to a crosslinking treatment by irradiation with ionizing radiation, which is required for a sealing material sheet for a solar cell module Therefore, it is possible to provide a solar cell module sealing material sheet having high properties such as heat resistance, molding characteristics, and transparency at a high level.

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.

  Hereinafter, first, an encapsulant composition (hereinafter also simply referred to as “encapsulant composition”) that can be preferably used for producing an encapsulant sheet for a solar cell module of the present invention, for a solar cell module. The encapsulant sheet (hereinafter also simply referred to as “encapsulant sheet”) and its manufacturing method will be described, and then the solar cell module using the encapsulant sheet of the present invention and its manufacturing method will be sequentially described.

<Encapsulant composition>
In the manufacturing method of the sealing material sheet of the present invention in which the crosslinking treatment by ionizing radiation is performed, it is suitable as a dedicated material for forming each layer in order to form the intermediate layer and the outermost layer of the multilayer sealing material sheet. Different sealing material compositions having different MFRs can be used. Specifically, as the base resin of the outermost layer sealing material composition, “MFR” at 190 ° C. and a load of 2.16 kg measured according to JIS K6922-2 is the base resin of the intermediate layer sealing material composition. A resin larger than the MFR is used. The base resin of the sealing material composition for the outermost layer is prepared by adjusting the MFR to the above high MFR range, regardless of the selection of a single resin having a high MFR. The present invention is characterized in that it is carried out by mixing the two. Note that “MFR” in this specification refers to “MFR” as defined above.

  In addition to the above MFR conditions, for the encapsulant composition used in the method for producing an encapsulant sheet of the present invention, the number of full double bonds remaining in each resin is in a specific different range. It is more preferable to use a plurality of types of polyethylene-based resins properly as dedicated materials for molding each of the layers.

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.

[Encapsulant composition for intermediate layer]
The sealing material composition for an intermediate layer for forming the intermediate layer is a sealing material composition used for forming the intermediate layer of a multilayer sealant sheet. 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.

  As the base resin of the sealing material composition for the intermediate layer, a polyethylene-based resin having an MFR that is relatively smaller than the MFR of the base resin of the sealing material composition for the outermost layer is used. Thereby, the heat resistance of a sealing material sheet can be hold | maintained in a preferable range.

  As the base resin of the sealing material composition for the intermediate layer, the total number of double bonds remaining at the composition stage is relatively larger than the number of total double bonds of the base resin of the sealing material composition for the outermost layer. It is preferable to use a large amount of polyethylene resin. The number of full double bonds in the base resin of the sealing material composition for the intermediate layer is preferably 0.5 or more and 4.0 or less, and is 1.0 or more and 4.0 or less. It is more preferable.

  By limiting the total number of double bonds of the base resin of the sealing material composition for the intermediate layer to the above range in combination with that of the base resin of the sealing material composition for the outermost layer, ionization is achieved. It is possible to sufficiently improve the heat resistance of the encapsulant sheet by sufficiently proceeding with crosslinking by irradiation with radiation. On the other hand, even if the crosslinking of the intermediate layer is sufficiently advanced in this way, as will be described later, the total double bond number of the base resin of the sealing material composition for the outermost layer is determined as the sealing material composition for the intermediate layer. By limiting to a range different from that of the base resin, the cross-linking progression of the outermost layer is suppressed in a manner different from that of the intermediate layer, and as a result, preferable molding characteristics are maintained as the whole sealing material sheet. You can also. In addition, the heat resistance of a sealing material sheet will not fully improve that the number of full double bonds of the base resin 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.

  As the polyethylene resin used as the base resin of the sealing material composition for the intermediate layer, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), or metallocene linear low density polyethylene (M-LLDPE) is used. It can be preferably used. Among these, LLDPE, which is a copolymer of ethylene and α-olefin, can provide the encapsulant sheet with good flexibility while maintaining sheet processability.

The density of the polyethylene resin used as the base resin of the sealing material composition for the intermediate layer is 0.870 or more and 0.970 g / cm ³ or less, preferably 0.870 or more and 0.930 g / cm ³ or less. The density of the base resin of the sealing material composition for the intermediate layer is the same as the base resin of the sealing material composition for the outermost layer, or the base resin of the sealing material composition for the outermost layer A higher density is preferable. By keeping the density of the base resin of the sealing material composition for the intermediate layer within the above range, sealing is performed while maintaining the fluidity at the time of lamination and the protection performance of the solar cell element, which are required as a sealing material sheet. Sufficient heat resistance can be imparted to the material.

  The content of the base resin contained in the intermediate layer sealing material composition is preferably 10 parts by mass or more and 99 parts by mass or less, more preferably 100 parts by mass or more, more preferably 100 parts by mass of the total resin components in the composition. It is 50 to 99 mass parts, More preferably, it is 90 to 99 mass parts. Other resins may be included as long as the number of residual double bonds at the composition stage falls 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.

[Encapsulant composition for outermost layer]
The sealing material composition for the outermost layer is used for molding the outermost layer formed on at least one outer surface, preferably both outermost surfaces of the multilayer sealing material sheet of the present invention. It is.

  As the base resin of the sealing material composition for the outermost layer, a polyethylene-based resin having an MFR that is relatively larger than the MFR of the base resin of the sealing material composition for the intermediate layer is used. Thereby, the molding characteristic and adhesiveness of a sealing material sheet can be hold | maintained in a preferable range.

  And the characteristic of this invention exists in the point which adjusts the MFR of the sealing material composition for outermost layers in the said range by mixing of 2 types of polyethylene resin from which MFR differs as above-mentioned. For example, when the MFR of the intermediate layer is 3.0 g / 10 min and it is desired to adjust the MFR of the outer layer to 10.0 g / 10 min which is relatively larger than this, the single MFR is 10.0 g / 10 min. Rather than selecting a resin, by intentionally mixing a low MFR composition with an MFR of 5.0 g / 10 min for an intermediate layer and a high MFR composition with an MFR of 20.0 g / 10 min in an appropriate ratio An example of blending a composition having a desired MFR (10.0 g / 10 min) can be given as a specific example. In addition, as shown in an Example later, it has an equivalent MFR value by using a blend type sealing material composition adjusted to have a predetermined MFR value by mixing two kinds of polyethylene resins. It has been found that the transparency of the encapsulant sheet can be improved as compared with the case where a single-unit encapsulant composition is used.

  The mixing ratio of the two kinds of polyethylene resins constituting the outermost layer sealing material composition is preferably in the range of 2: 8 to 8: 2, more preferably 3: 7 to 7: 3. preferable.

  Further, as the base resin of the sealing material composition for the outermost layer, the total number of double bonds remaining at the composition stage is larger than the number of full double bonds of the base resin of the sealing material composition for the intermediate layer. It is preferable to use a relatively small amount of polyethylene resin. In addition, the total number of double bonds of the polyethylene resin that is the base resin of the sealing material composition for the outermost layer is preferably 0 or more and 1.0 or less, and is 0 or more and 0.5 or less. More preferably.

  By limiting the total number of double bonds of the base resin of the sealing material composition for the outermost layer to the above range in combination with that of the base resin of the sealing material composition for the intermediate layer, ionization is achieved. It is possible to appropriately suppress the crosslinking due to the irradiation of the radiation and maintain the molding property of the encapsulant sheet in a preferable mode. On the other hand, as described in detail above, even if the outermost layer is inhibited from being cross-linked in this way, the total number of double bonds of the base resin of the intermediate layer sealing material composition is determined as the outermost layer sealing material composition. By limiting to a range different from that of the above, it is possible to promote the progress of crosslinking of the intermediate layer in a mode different from that of the outermost layer, and as a result, preferable heat resistance can be maintained as the whole sealing material sheet. In addition, it is not preferable that the number of full double bonds of the sealing material composition for the outermost layer exceeds 0.5 because molding characteristics and adhesiveness deteriorate due to the progress of crosslinking.

  As the base resin of the sealing material composition for the outermost layer, the low density polyethylene (LDPE) and the linear low density polyethylene (LLDPE) are used as the base resin of the sealing material composition for the intermediate layer. Alternatively, metallocene linear low density polyethylene (M-LLDPE) can be preferably used as appropriate. However, as described above, a resin in which the number of full double bonds remaining in the resin is limited to a range different from the encapsulant composition for the intermediate layer is used for the total double bond number of the resin. Among them, M-LLDPE, which is synthesized using a metallocene catalyst that is a single-site catalyst, has few side chain branches and a uniform comonomer distribution, so the molecular weight distribution is narrow and the ultra-low level as described above. The density can be easily set, and preferable flexibility can be imparted to the outermost layer of the encapsulant sheet. As a result, adhesion between the solar cell module and the other member laminated with the sealing material sheet can be enhanced.

The density of the polyethylene resin used as the base resin of the sealing material composition for the outermost layer is 0.870 or more and 0.900 g / cm ³ or less, preferably 0.870 or more and 0.900 g / cm ³ or less. The resin is a base resin. The density of the base resin of the sealing material composition for the outermost layer is the same as the base resin of the sealing material composition for the intermediate layer, or the base resin of the sealing material composition for the intermediate layer It is preferable that the density is lower than that. By keeping the density of the base resin of the sealing material composition for the outermost layer in the above range, sealing is performed while maintaining the fluidity at the time of lamination and the protection performance of the solar cell element, which are required as a sealing material sheet. Sufficient molding characteristics can be imparted to the material. In addition, by setting the density to 0.900 g / cm ³ or less, even when used with a thin-film solar cell element having a thickness of about 150 μm or less and a high risk of cell cracking, Sufficient protection performance can be exhibited and the risk of cell cracking can be sufficiently reduced.

  Content of the said base resin contained in the sealing material composition for outermost layers is the same amount ratio as the case of the sealing material composition for intermediate | middle layers mentioned above. And other resin may be included in the condition range that MFR of the sealing material composition for outermost layers becomes larger than MFR of the sealing material composition for intermediate | middle layers.

(Silane-modified polyethylene resin)
In each of the sealing material compositions for the intermediate layer and the outermost layer, a silane-modified polyethylene resin can be appropriately contained. The silane-modified polyethylene resin is obtained by graft-polymerizing an ethylenically unsaturated silane compound as a side chain to linear low-density polyethylene (LLDPE) or the like as a main 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 can be produced, for example, by the method described in JP-A-2003-46105. By using the resin as a component of the sealing material composition of the solar cell module, strength and durability can be obtained. In addition, it has excellent weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, yield resistance, and other characteristics, and is also affected by manufacturing conditions such as thermocompression bonding for manufacturing solar cell modules. Therefore, it is possible to manufacture solar cell modules having extremely excellent heat-fusibility, stably and at low cost, and suitable for various applications.

  Examples of ethylenically unsaturated silane compounds to be graft polymerized with LLDPE etc. include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinyltripentyloxysilane, vinyltri One or more selected from phenoxysilane, vinyltribenzyloxysilane, vinyltrimethylenedioxysilane, vinyltriethylenedioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, and vinyltricarboxysilane can be used. .

  The graft amount, which is the content of the ethylenically unsaturated silane compound, is, for example, 0.001 to 15 parts by mass, preferably 0.01 to 100 parts by mass with respect to a total of 100 parts by mass of all resin components in the sealing material composition. What is necessary is just to adjust suitably so that it may become 5 mass parts, Especially preferably, it is 0.05-2 mass parts. 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.

(Crosslinking agent)
Each of the encapsulant compositions for the intermediate layer and the outermost layer can contain a crosslinking agent as appropriate. A well-known thing can be used for a crosslinking agent, It does not specifically limit, For example, a well-known radical polymerization initiator can be used. Examples of radical polymerization initiators include hydroperoxides such as diisopropylbenzene hydroperoxide and 2,5-dimethyl-2,5-di (hydroperoxy) hexane; di-t-butyl peroxide, t-butyl Cumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-peroxy) hexyne-3, etc. Dialkyl peroxides; diacyl peroxides such as bis-3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, benzoyl peroxide, o-methylbenzoyl peroxide, 2,4-dichlorobenzoyl peroxide; t-butyl peroxyacetate, t-butyl pero Ci-2-ethylhexanoate, t-butyl peroxypivalate, t-butyl peroxyoctoate, t-butyl peroxyisopropyl carbonate, t-butyl peroxybenzoate, di-t-butyl peroxyphthalate, 2 , 5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexyne-3, t-butylperoxy-2-ethylhexyl carbonate Oxyesters; organic peroxides such as methyl peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide, or azo compounds such as azobisisobutyronitrile and azobis (2,4-dimethylvaleronitrile), dibutyltin Diacetate, dibutyltin dilaurate It can be mentioned dibutyltin dioctoate, dioctyltin dilaurate, dicumyl peroxide, such a silanol condensation catalyst.

  As content of a crosslinking agent, it is preferable that it is content of 0 mass part or more and 0.5 mass part or less with respect to a total of 100 mass parts of all the resin components of a sealing material composition, More preferably, it is 0.02. The range is not less than 0.5 parts by mass. By adding 0.02 parts by mass or more of a crosslinking agent, more preferable heat resistance can be imparted to the polyethylene resin used in the sealing material sheet of the present invention. On the other hand, when the addition amount of the cross-linking agent exceeds 2.0 parts by mass, the progress of cross-linking in the cross-linking step becomes excessive, and molding characteristics become insufficient, which is not preferable.

(Crosslinking aid)
In the present invention, a polyfunctional monomer having a carbon-carbon double bond and / or an epoxy group can be 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 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 0.05 parts by mass with respect to 100 parts by mass in total of all resin components of the sealing material composition. It is the range below 2.0 parts by mass.

(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, and 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 this range is exceeded, the film-forming property is deteriorated, or the 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, etc., but in the range of 0.001 to 5 parts by mass with respect to 100 parts by mass in total of all resin components of each sealing material composition. Preferably there is. 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.

  These light stabilizers, ultraviolet absorbers, heat stabilizers and antioxidants can be used alone or in combination of two or more.

<Sealing material sheet>
The sealing material sheet of the present invention uses the above-described sealing material composition for the intermediate layer and the sealing material composition for the outermost layer, which are optimized for the combination, focusing on MFR, and particularly for the outermost layer. The MFR of the sealing material composition is obtained by a production method characterized by performing blending of two kinds of polyethylene resins having different MFRs. The structure includes a plurality of layers including a relatively low MFR intermediate layer and a relatively high MFR outermost layer disposed on either one of the intermediate layers, preferably both outermost surfaces. It is a multilayer sealing material. Hereinafter, as a preferred embodiment of the present invention, a sealing material sheet 1 having a three-layer structure including two outermost layers in total, one layer above and below a single intermediate layer, will be described with reference to FIG. . However, the present invention is not limited to this embodiment.

  The sealing material sheet 1 has an intermediate layer 11, and the outermost layer 12 is disposed on both surfaces of the intermediate layer 11. However, for example, a sealing material sheet having a two-layer structure in which the outermost layer is disposed only on one side of the intermediate layer, or a seal in which the intermediate layer has a multilayer structure and other functional layers are disposed in the intermediate layer. Even if it is a sealing material sheet, it is within the scope of the present invention as long as it is an encapsulant sheet having an intermediate layer and an outermost layer having the constituent elements of the present invention and having other constituent elements of the present invention.

  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.

  The outermost layer 12 is a layer that is disposed on the outermost surface of the encapsulant sheet 1 and constitutes a subordinate portion as a surface material. The outermost layer 12 is imparted with preferable flexibility by appropriately suppressing cross-linking, thereby improving molding characteristics and substrate adhesion during an integration process as a solar cell module.

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

  The total thickness of the sealing material sheet 1 in which the outermost layer 12 is laminated on both surfaces of the intermediate layer 11 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, since the sealing material sheet of the present invention has flexibility in the outer layer and heat resistance in the inner layer, it suppresses flow out and film thickness change during the laminating process, so the thickness is reduced to about 500 μm or less. Even in this case, 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 sealing material sheet 1, the outermost layer 12: the intermediate layer 11: the outermost layer 12 and the n thickness ratio may be in the range of 1: 2: 1 to 1: 30: 1. 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.

<Method for producing sealing material sheet>
[Sheet making process]
The melt molding of each composition for the intermediate layer and the outermost layer, each of which has been described in detail above, is a molding method usually used in ordinary thermoplastic resins, that is, injection molding, extrusion molding, hollow molding, compression molding, It is performed by various molding methods such as rotational molding. 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, 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, 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.

[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. Unlike the conventional method, the method for producing a sealing material sheet of the present invention basically optimizes the degree of crosslinking by limiting the physical properties on the composition side, without fine adjustment of irradiation conditions. This is because it is a method. 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. The acceleration voltage in electron beam irradiation is determined by the thickness of the sheet that is the object to be irradiated, and the thicker the sheet, the larger the acceleration voltage is required. For example, a 0.5 mm-thick sheet is irradiated with 100 kV or more, preferably 200 kV or more. If the accelerating voltage is lower than this, crosslinking of the intermediate layer does not proceed sufficiently. The irradiation dose is in the range of 5 kGy to 500 kGy, preferably 5 to 200 kGy. When the irradiation dose is less than 5 kGy, the crosslinking of the intermediate layer does not proceed sufficiently, and when it exceeds 500 kGy, there is a concern about deformation or coloring of the sealing material sheet due to the generated heat. Irradiation with ionizing radiation may be performed from one side or from both sides as long as the crosslinking of the intermediate layer can sufficiently proceed to the above-described level. 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.

  According to the production method of the present invention, by setting the irradiation condition that optimizes the progress of crosslinking of the intermediate layer as described above, it is possible to appropriately suppress the progress of the crosslinking of the outermost layer under the irradiation condition. It can be realized at the same time. For this reason, management of crosslinking conditions is easy, and productivity can be improved by releasing from complicated and complicated management of crosslinking conditions. Further, the setting of the irradiation condition is not necessarily limited to the gel fraction. For example, the thermal shrinkage rate after crosslinking of the sample sealing material sheet may be measured at an initial stage, the result may be fed back to the initial irradiation conditions, and thereafter irradiation may be continued under the same conditions. .

  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. In addition, since the sealing material sheet | seat of this invention obtained by doing in this way has been bridge | crosslinked, the annealing process etc. again are unnecessary and can be used in a modularization process as it is.

<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 showing an example of the layer structure of the solar cell module 10 including the thin-film solar cell element according to the embodiment of the present invention. The solar cell module 10 includes a transparent front substrate 2 made of glass or the like, a thin film solar cell element 3 formed on the transparent front substrate 2, a sealing material sheet 1, and a back surface protection sheet 4 from the light receiving surface side of incident light. Are sequentially stacked.

  In addition, when the sealing material sheet of this invention is a sealing material sheet which consists of two layers of the intermediate | middle layer 11 and the outermost layer 12 of one layer arrange | positioned at the outermost layer of one side, The exposed surface is laminated in the same manner as described above as a layer in close contact with the thin film solar cell element 3.

  In the solar cell module 10, by using the sealing material sheet 1, the heat resistance as the solar cell module and the molding characteristics at the time of modularization are improved in a balanced manner. For example, the thin-film solar cell element 3 generally has a shape in which a metal electrode 31 protrudes as shown in FIG. 2, but the thin molding solar cell element 3 has an excellent molding characteristic of the sealing material sheet 1 of the present invention. For example, 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 the solar cell module, the encapsulant sheet of the present invention is suitably used even when one surface of the encapsulant sheet 1 is opposed to the metal surface and the other surface is opposed to the glass layer. Can be used.

  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. However, since the encapsulant sheet of the present invention is an encapsulant sheet that is particularly excellent in molding characteristics, that is, the ability to follow the unevenness of the opposing substrate, the lower surface (non- The arrangement on the light receiving surface side is particularly effective.

  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 used very preferably even in a solar cell module including the above-described configuration.

  For example, the solar cell module 10 is formed by sequentially laminating a member composed of the transparent front substrate 2, the sealing material sheet 1 and the back surface protection sheet 4 on which the thin film solar cell element 3 is formed, 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.

  The thermocompression treatment at the time of manufacturing the solar cell module 10 of the present invention is performed under such heating conditions that the resin temperature of the encapsulant sheet 1 during the thermocompression treatment is 50 ° C. or more and 100 ° C. or less. It can be carried out. For example, when a conventional EVA sealing material sheet is used, heating exceeding 140 ° C. is generally essential. In addition, since a general polyethylene-based sealing material sheet has a low crosslinking rate, when it is used, for example, when laminating is performed at a temperature of 140 ° C. or lower, heating for a long time is required. There are disadvantages such as a large change in film thickness, or the need for a second heat cure after integration. In the solar cell module 10 of the present invention, the solar cell module can be manufactured in a preferable aspect even within the range of the heating conditions. By making the heating condition in the integration process at the time of modularization into such a low temperature range, the productivity and quality stability of the solar cell module can be enhanced.

  In the solar cell module 10 of the present invention, the transparent front substrate 2, the thin film solar cell element 3, and the back surface protection sheet 4 which are members other than the sealing material sheet 1 use conventionally known materials without particular limitation. Can do. 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.

  The resin temperature of the encapsulant sheet can be measured by attaching a temperature sensor thermocouple to the upper surface of the encapsulant sheet during heating and using a temperature / humidity data logger. The resin temperature refers to, for example, the resin temperature of the sealing material sheet measured as described above.

  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 compositions for the intermediate layer and the outermost layer of the encapsulant sheets of Examples and Comparative Examples are respectively used. It was set as the sealing material composition. Using each sealing material composition 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 forming machine having a 200-mm wide T-die Each resin sheet was produced, each of these resin sheets was laminated, and the sealing material sheet of the three-layer structure of the Example provided with an intermediate | middle layer and both outermost layers and Comparative Examples 1-2 was manufactured. 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 the ratio of the thickness of each layer of the sealing material sheet of the three-layer structure of the example and the comparative example, the thickness ratio of the outermost layer: intermediate layer: outermost layer is 1: 4 in any sealing material sheet. It was set to 1.

The following raw materials were used as a sealing material composition raw material for molding each resin sheet for a sealing material.
Base resin for intermediate layer (denoted as “intermediate” in the table, the same applies hereinafter): Metallocene system 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. Linear low density polyethylene (M-LLDPE).
Base resin 1 for outermost layer (denoted as “outer layer A” in the table, the same applies hereinafter): density is 0.880 g / cm ³ , melting point is 60 ° C., and MFR at 190 ° C. is 3.5 g / 10 min. Metallocene linear low density polyethylene (M-LLDPE).
Base resin 2 for outermost layer (“outer layer B”): metallocene linear low-density polyethylene having a density of 0.885 g / cm ³ , a melting point of 66 ° C., and an MFR at 190 ° C. of 19.0 g / 10 min ( M-LLDPE).
Base resin 3 for outermost layer (“outer layer C”): a metallocene linear low-density polyethylene having a density of 0.885 g / cm ³ , a melting point of 66 ° C., and an MFR at 190 ° C. of 11.1 g / 10 minutes ( M-LLDPE).
Silane-modified polyethylene resin (“S”): 2 parts by mass of vinyltrimethoxysilane with respect to 100 parts by mass of metallocene linear low density polyethylene having a density of 0.880 g / cm ³ and an MFR of 20 g / 10 min. A silane-modified polyethylene resin obtained by mixing 0.15 parts by mass of dicumyl peroxide as a radical 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.
Weathering agent master batch 1 (“MB1 for intermediate layer”): 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. )
Weathering agent master batch 2 ([MB2 for intermediate layer]): Base resin: 100 parts by weight. Tricyclodecane dimethanol diacrylate (crosslinking aid): 2.04 parts by mass.
Weathering agent master batch 3 (“MB for outermost layer”): 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. )
In addition, 10 mass parts of weatherproofing agent master batches 1 and 2 were added to each of the compositions for inner layers of all Examples and Comparative Examples. In addition, 10 parts by mass of the weathering agent master batch 3 was added to each of the compositions for outer layers of all Examples and Comparative Examples.

  For the outermost base resin, Table 1 shows the MFR after mixing when A and B are mixed and the MFR of each base resin.

  The compositions of the intermediate layers of Examples 2-3 and Comparative Examples 1-3 were all the same as those of Example 1.

The number of full double bonds and the number of terminal vinyl groups per 2000 carbon derived from the base resin of each sealing material composition of Example 3 and Comparative Example 1 were determined by the following formula. The total number of double bonds per 2000 carbons was determined from the density d (g / cm ³ ), the sheet thickness t (μm), and the absorbance A of the absorption band of the infrared absorption spectrum. Measurement of the absorbance A of the absorption band of the infrared absorption spectrum was performed by NICOLET6700 manufactured by Thermo Scientific. The results are shown in Table 2.
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)
Number of full double bonds = number of terminal vinyl groups + number of vinylidene groups + number of transvinylene groups

  Next, with respect to all the uncrosslinked sealing material sheets after the above-described molding of Examples and Comparative Examples, respectively, using an electron beam irradiation device (Iwasaki Electric Co., Ltd., product name EC250 / 15 / 180L), Both surfaces were irradiated with an acceleration voltage of 250 kV and an irradiation intensity of 65 kGy to irradiate a total of 130 kGy to produce a crosslinked encapsulant sheet, which was used as the encapsulant sheets of Examples and Comparative Examples.

<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. Thereafter, the large-sized glass was placed vertically and allowed to stand at 150 ° 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 3 as “heat resistance”.

<Evaluation Example 2: Initial adhesion>
Each sealing material sheet of Examples and Comparative Examples is adhered to a glass substrate (white plate float semi-tempered glass JPT3.2 75 mm × 50 mm × 3.2 mm) and subjected to vacuum heating laminator treatment at 150 ° C. for 12 minutes for evaluation. A sample was prepared. And in said sample for evaluation, the sealing material sheet | seat closely_contact | adhered on a glass substrate is cut into 15 mm width, and vertical peeling (50 mm / min) with a peeling tester (Tensilon universal testing machine RTF-1150-H). ) A test was conducted to measure and evaluate the glass adhesion strength. Evaluation was performed according to the following criteria.
A: 30 N / 15 mm or more B: 25 N / 15 mm or more and less than 30 N / 15 mm C: 20 N / 15 mm or more and less than 25 N / 15 mm D: Less than 20 N / 15 mm The evaluation results are shown in Table 3 as “adhesiveness”.

<Evaluation Example 3: 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 and vacuum heated under the same heat laminating conditions as in the heat-resistant creep test. Laminator processing was performed, 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.
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 3 as “molding characteristics”.

<Evaluation Example 4: Film production>
About the sealing material sheet | seat of an Example and a comparative example, each sheet cross section was observed with the microscope, the layer ratio was measured, and film forming property was evaluated based on the result. Evaluation was performed according to the following criteria.
(Evaluation criteria)
A: Area where the layer ratio is 1: 4: 1 as intended at the design stage is 90% or more of the total width of the film-forming sheet B: Area where the layer ratio is 1: 4: 1 Is 80% or more and less than 90% of the entire width of the film-forming sheet.

<Evaluation Example 5: Transparency>
About the sealing material sheet | seat of an Example and a comparative example, the HAZE value was measured in "Murakami Color Research Institute haze and transmittance | permeability system HM150" along JISK7136. The value when the sealing material sheet heated to 150 ° C. was cooled under the condition of −3 ° C./min was defined as the haze value.
(Evaluation criteria) A: 3.0 or less
C: 3.0 or more
The evaluation results are shown in Table 3 as “transparency”.

  From Tables 1-3, the sealing material sheet of the Example manufactured by the manufacturing method of this invention has heat resistance, adhesiveness, a molding characteristic, film formation, and transparency on a high level. I understand. Further, from the result of Comparative Example 2, even when the MFR of the outermost layer is the same, the case where a composition in which two kinds of resins having different MFR are mixed is used rather than the case where a composition made of a single resin is used. It can be seen that the method can have an advantageous effect on the transparency of the encapsulant sheet.

DESCRIPTION OF SYMBOLS 1 Sealant sheet 11 Intermediate layer 12 Outermost layer 2 Transparent front substrate 3 Thin film solar cell element 31 Metal electrode 4 Back surface protection sheet 10 Solar cell module

Claims (6)

Is density of 0.870 g / cm ³ or more 0.970 g / cm ³ or less and an intermediate layer of polyethylene resin for the intermediate layer formed by melting, than polyethylene resin for the intermediate layer, MFR is greater for the outermost layer A sheet forming step of forming an uncrosslinked multilayer sheet by laminating an outermost layer formed by melting and forming a polyethylene resin;
A crosslinking step of performing crosslinking treatment by irradiation of ionizing radiation to the uncrosslinked multilayer sheet,
The polyethylene resin for outermost layers, der a mixture of MFR of two different types of polyethylene resins with each other,
The sealing resin for a solar cell module , wherein the polyethylene resin for the intermediate layer is a resin having a larger number of full double bonds per 2000 carbon by infrared absorption spectrum method than the polyethylene resin for the outermost layer. A method for manufacturing a stop sheet.   The method for producing a sealing material sheet according to claim 1, wherein a mixing ratio of the two kinds of polyethylene resins is in a range of 2: 8 to 8: 2. The MFR of the intermediate layer is 0.1 g / 10 min or more and 4 g / 10 min or less,
The manufacturing method of the sealing material sheet according to claim 1 or 2, wherein the MFR of the outermost layer is greater than 100% and not more than 800% of the MFR of the intermediate layer. The sealing material composition for the intermediate layer and / or the sealing material composition for outermost layers, one of claims 1 contains a crosslinking agent of less than 0.02 mass% to 0.5 mass% 3 The manufacturing method of the sealing material sheet of crab. The encapsulant composition for the intermediate layer and / or the encapsulant composition for the outermost layer contains a silane-modified polyethylene resin formed by graft polymerization using an ethylenically unsaturated silane compound as a side chain. The manufacturing method of the sealing material sheet in any one of 1-4 . It is a manufacturing method of a solar cell module provided with the sealing material sheet manufactured with the manufacturing method in any one of Claims 1-5 , and a solar cell element,
Method of manufacturing a solar cell module wherein the outermost layer of the sealing material sheet is arranged so as to face the metal electrodes of the solar cell element.

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