JP2014017492A - Resin sheet for sealing and solar cell using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin sheet for sealing that simultaneously achieves excellent gap-sealing, recyclability, resistance to water vapor penetration, and creep resistance while maintaining transparency and adhesion.SOLUTION: A resin sheet for sealing comprises resin components of: at least one kind of resin (A) selected from a copolymer of ethylene and vinyl acetate, a copolymer of ethylene and unsaturated aliphatic carboxylic acid, and a copolymer of ethylene and unsaturated aliphatic carboxylic acid ester; and thermoplastic resin (B) other than the resin (A).

Description

  The present invention relates to a sealing resin sheet and a solar cell using the same.

  In recent years, the global warming phenomenon has heightened awareness of the environment, and a new energy system that does not generate greenhouse gases such as carbon dioxide is attracting attention. Solar cell power generation, wind power generation, and the like are capable of generating electric power without discharging carbon dioxide and other gases that are thought to induce global warming, and are actively researched as renewable clean energy. In particular, solar cell power generation is attracting attention as an energy source for both household energy and industrial energy from the viewpoint of safety and ease of handling.

  In recent years, in Japan, where resources are scarce, it has become increasingly popular to install solar cell power generation systems on the roofs of households and consume the generated electricity as household power or sell it. In Europe, mainly in Germany, it is attracting attention not only for household use but also for securing industrial power sources by large-scale power generation with solar cells on a vast site. It is also.

  There are various power generation methods for solar cells that are attracting attention in this way, and typical ones are those using monocrystalline or polycrystalline silicon cells (crystalline silicon cells), and using amorphous silicon. And those using a compound semiconductor (thin film cell).

  Any of these power generation methods are exposed to wind and rain outdoors for a long time, so it is necessary to protect the power generation portion for a long period of time. Inflow of water, damage to the power generation part, leakage, etc. are prevented. Generally, the power generation portion has a power generation surface that generates light by receiving light and a non-power generation surface, and transparent glass or transparent resin is used to protect the power generation surface. For the non-power generation surface, a laminated sheet of barrier coating such as aluminum foil, polyvinyl fluoride resin (PVF), polyethylene terephthalate (PET) or silica is used as a back sheet.

  In modularization, after the power generation part is sandwiched between sealing resin sheets, the outside is further covered with glass or a back sheet, and the sealing resin sheet is melted at a high temperature. To do.

  For example, in the case of a solar cell module using a single crystal or a polycrystalline silicon cell, the modularization is made up of a power generation part / a resin sheet for sealing / a back sheet (for example, glass / resin sheet for sealing / crystalline silicon cell). Overlap in order, using a dedicated solar cell vacuum laminator with the glass surface down, perform the preheating step and the pressing step above the melting temperature of the resin used (150 ° C for EVA) and seal This is done by melting and laminating the resin sheet for use.

  As such a sealing resin sheet, for example, a module in which an organic polymer sealing resin sheet cross-linked by electron beam irradiation is laminated on an amorphous silicon solar cell is disclosed (Patent Document 1). Examples of the organic polymer sealing resin sheet include ethylene-vinyl acetate copolymer (EVA) and ethylene-methyl acrylate (EMA). These organic polymer resin sheets include an antioxidant, an ultraviolet absorber, A light stabilizer and a silane coupling agent are blended, and a sealing resin sheet is manufactured by extrusion molding from a slit, and this sealing resin sheet is vacuum laminated at 150 ° C. with a power generation part and a back sheet. The module is manufactured. Patent Document 1 discloses that a crosslinking treatment is performed by irradiating an irradiation voltage of 300 kGy with an acceleration voltage of 500 kV from the light receiving surface of the module, or using a sealing resin sheet that has been crosslinked by electron beam irradiation in advance. Describes producing a module by vacuum lamination.

  Patent Document 2 discloses a solar cell element sealing material made of an ethylene copolymer subjected to electron beam irradiation.

JP-A-6-334207 JP 2001-119047 A

  The conventional sealing resin sheet crosslinks the resin by electron beam irradiation treatment or peroxide to give heat resistance, and the sealing resin sheet flows when the solar cell module is in a high temperature state. Attempts to prevent (creep resistance).

  However, the conventional sealing resin sheet still has room for improvement from the viewpoint of achieving both gap filling properties and water vapor permeability in addition to creep resistance. That is, it is desirable that the sealing resin sheet seals unevenness formed on the glass for solar cells, wiring, unevenness resulting from the thickness of the power generation cell, etc. without gaps. If this gap exists, the air remaining in the gap repeatedly expands / contracts due to changes in temperature, etc., and there may be a risk of leakage due to peeling of the sealing resin sheet or inflow of moisture or the like.

  Moreover, it is desired that the sealing resin sheet has a low water vapor transmission rate. When the water vapor transmission rate is high, it may be difficult to protect the metal part used for the power generation unit and the surrounding wiring from water vapor entering from the outside over a long period of time.

  Patent Document 1 describes a method of crosslinking an encapsulating resin sheet by irradiating an electron beam from the light-receiving surface side after vacuum lamination. When crosslinking is performed by such a method, a crystalline silicon cell ( A part that is not sufficiently cross-linked is formed on the back side of the power generation part). As a result, the sealing resin sheet has a partially non-uniform gel fraction, and it becomes difficult to stably hold the crystalline silicon cell in a high temperature environment, and the power generation portion may flow ( May be inferior in creep resistance). In addition, when the sealing resin sheet is subjected to an electron beam irradiation treatment before vacuum lamination, it is possible to reliably seal the unevenness of the glass for solar cells, wiring, unevenness resulting from the thickness of the power generation cell, etc. without gaps. It becomes difficult (it may be inferior to gap filling property). In order to solve this problem, in many cases, vacuum lamination using a resin sheet for sealing after cross-linking is performed by raising the lamination temperature by about 30 ° C. However, the laminating process at a high temperature may cause excessive damage to the power generation portion and cause problems such as a decrease in power generation efficiency.

  Further, Patent Document 2 describes that a higher gelation rate is superior in heat resistance. However, as described above, when the gelation rate is high, the unevenness of the glass for solar cells is sealed without gaps. As a result, the lamination conditions need to be changed. That is, the lamination is performed at a higher temperature than usual, and the power generation portion is excessively damaged, which may cause problems such as a decrease in power generation efficiency. Furthermore, in the invention described in Patent Document 2, the entire sealing resin sheet is cross-linked, and it is difficult to peel off the crystal-based or thin-film power generation portion when discarded, and the recyclability is poor. There are drawbacks.

  The present invention has been made in view of the above problems, and is a sealing resin sheet that can simultaneously achieve excellent gap sealing properties, recyclability, water vapor permeability resistance and creep resistance while maintaining transparency. The purpose is to provide.

  That is, the present invention comprises at least one resin (A) selected from an ethylene-vinyl acetate copolymer, an ethylene-aliphatic unsaturated carboxylic acid copolymer, and an ethylene-aliphatic unsaturated carboxylic acid ester copolymer, A sealing resin sheet containing a thermoplastic resin (B) other than the resin (A) is provided.

  In the sealing resin sheet, the resin (B) is preferably a polyolefin resin, and the resin (B) is more preferably a polyethylene resin and / or a polypropylene resin.

  Examples of the resin sheet for sealing include a resin sheet for sealing provided with a mixed resin layer composed of a resin (A) and a resin (B).

  The mixed resin layer preferably contains 10 to 45% by mass of the resin (B).

  Moreover, as the said resin sheet for sealing, the resin sheet for sealing provided with the inner layer which consists of resin (B), and the surface layer which consists of resin (A) laminated | stacked on this inner layer is mentioned.

  The inner layer is preferably composed of a laminate of a polyethylene resin layer and a polypropylene resin layer.

  In the sealing resin sheet, the layer adjacent to the surface layer is preferably a polyethylene resin layer.

  When the thickness of the sealing resin sheet is 100%, the thickness ratio of the polypropylene resin layer in the sealing resin sheet is preferably 40% or less.

  The surface layer is preferably a layer subjected to a crosslinking treatment, and the crosslinking treatment is preferably a crosslinking treatment with an organic peroxide and / or ionizing radiation.

  The sealing resin sheet preferably contains a crosslinked product obtained by crosslinking the resin (A) and / or the resin (B) having a melting point of less than 100 ° C.

  It is preferable that the resin (A) and / or resin (B) whose melting | fusing point is less than 100 degreeC are bridge | crosslinked by the organic peroxide and / or ionizing radiation in the said resin sheet for sealing.

The sealing resin sheet is water vapor transmission rate is preferably not less ^40g / m 2 / 24hr.

  The sealing resin sheet preferably has a structure in which one or two or more layers of the same component are laminated on both sides of the central layer so as to be symmetrical with respect to the central layer.

  Moreover, this invention provides a solar cell provided with the resin sheet for sealing.

  ADVANTAGE OF THE INVENTION According to this invention, the resin sheet for sealing which can achieve the outstanding clearance sealing property, water-vapor-permeation resistance, and creep resistance simultaneously can be provided, maintaining transparency.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

  The encapsulating resin sheet of this embodiment is at least one selected from an ethylene-vinyl acetate copolymer, an ethylene-aliphatic unsaturated carboxylic acid copolymer, and an ethylene-aliphatic unsaturated carboxylic ester copolymer. It is the resin sheet for sealing which uses resin (A) and thermoplastic resins (B) other than resin (A) as a resin component.

  The sealing resin sheet softens the resin by a method of directly giving energy such as heat to the resin component or a method of giving vibration inherent to the resin component to cause the resin itself to generate heat. Thus, other substances can be adhered and sealed. As a method for softening the resin, a known method using direct heating to the resin component, indirect heat such as radiant heat, vibrational heat generation such as ultrasonic waves, or the like can be used.

  The sealing resin sheet is preferably excellent in optical properties. Specifically, the haze is preferably 10.0% or less, more preferably 9.5% or less, and even more preferably 9.0% or less. It is preferable that the haze is 10.0% or less because a package can be visually confirmed and a sense of security can be obtained. If the haze exceeds 10.0%, the power generation efficiency of the solar cell may decrease. The sealing resin sheet preferably has a total light transmittance of 85% or more, more preferably 87% or more, and still more preferably 88% or more.

  The sealing resin sheet preferably has a thickness of 50 to 1500 μm, more preferably 100 to 1000 μm, and still more preferably 150 to 800 μm. When the thickness of the sealing resin sheet is less than 50 μm, the cushioning property and workability of the sealing resin sheet may be deteriorated. On the other hand, if it exceeds 1500 μm, productivity and adhesion may be lowered. The sheet thickness is a value measured by a contact thickness gauge.

  The sealing resin sheet can be used as a sealing sheet for solar cells, and can be used for sealing LEDs, interlayer films for laminated glass and crime prevention glass, and the like, for example, plastic and glass, plastics, and glass-to-glass bonding. In addition, when the sealing resin sheet is used as a solar cell sealing sheet, for example, a sealing resin sheet, glass, a back sheet, a silicon-based cell and the like are stacked, and a dedicated vacuum laminator is laminated. It can be installed in a vacuum state to eliminate internal bubbles and the like, heated to soften the resin, and then bonded and sealed.

  Hereinafter, the sealing resin sheet will be described in detail.

<Resin (A)>
The resin (A) refers to at least one resin selected from an ethylene-vinyl acetate copolymer, an ethylene-aliphatic unsaturated carboxylic acid copolymer, and an ethylene-aliphatic unsaturated carboxylic acid ester copolymer. Here, the ethylene-vinyl acetate copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and vinyl acetate. The ethylene-aliphatic unsaturated carboxylic acid copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and at least one monomer selected from aliphatic unsaturated carboxylic acids. Furthermore, the ethylene-aliphatic unsaturated carboxylic acid ester copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and at least one monomer selected from an aliphatic unsaturated carboxylic acid ester.

  The copolymerization can be performed by a known method such as a high pressure method or a melting method, and a multisite catalyst, a single site catalyst, or the like can be used as a catalyst for the polymerization reaction. Moreover, in the said copolymer, the bond shape of each monomer is not specifically limited, The polymer which has bond shapes, such as a random bond and a block bond, can be used. From the viewpoint of optical properties, the copolymer is preferably a copolymer polymerized by random bonding using a high-pressure method.

  In the ethylene-vinyl acetate copolymer, the ratio of vinyl acetate in all monomers constituting the copolymer is preferably 10 to 40% by mass from the viewpoint of optical properties, adhesiveness, and flexibility. More preferably, it is -35 mass%, and it is further more preferable that it is 15-30 mass%. In addition, from the viewpoint of workability of the sealing resin sheet, the value of the melt flow rate measured in accordance with JIS-K-7210 (hereinafter sometimes referred to as “MFR”) (190 ° C., 2. 16 kg) is preferably from 0.3 g to 30 g, more preferably from 0.5 g to 30 g, and even more preferably from 0.8 g to 25 g.

  Examples of the ethylene-aliphatic unsaturated carboxylic acid copolymer include an ethylene-acrylic acid copolymer (hereinafter sometimes referred to as “EAA”), an ethylene-methacrylic acid copolymer (hereinafter referred to as “ May be described as “EMAA”). Examples of the ethylene-aliphatic unsaturated carboxylic acid ester copolymer include an ethylene-acrylic acid ester copolymer and an ethylene-methacrylic acid ester copolymer. Here, as acrylic acid ester and methacrylic acid ester, ester with C1-C8 alcohol, such as methanol and ethanol, is used suitably.

  These copolymers may be multi-component copolymers obtained by copolymerizing three or more monomers. Examples of the multi-component copolymer include a copolymer obtained by copolymerizing at least three types of monomers selected from ethylene, aliphatic unsaturated carboxylic acid, and aliphatic unsaturated carboxylic acid ester.

  In the ethylene-aliphatic unsaturated carboxylic acid copolymer, the proportion of the aliphatic unsaturated carboxylic acid in all monomers constituting the copolymer is preferably 3 to 35% by mass. MFR (190 ° C., 2.16 kg) is preferably 0.3 g to 30 g, more preferably 0.5 g to 30 g, and further preferably 0.8 g to 25 g.

  In the ethylene-aliphatic unsaturated carboxylic acid ester copolymer, the proportion of the aliphatic unsaturated carboxylic acid ester in all monomers constituting the copolymer is preferably 3 to 35% by mass. Moreover, it is preferable that MFR (190 degreeC, 2.16 kg) is 0.3g-30g, It is more preferable that it is 0.5g-30g, It is further more preferable that it is 0.8g-25g.

<Resin (B)>
Examples of the resin (B) include polyolefin resins, styrene resins, hydrogenated vinyl aromatic resins, vinyl chloride resins, polyester resins, polyurethane resins, chlorinated ethylene polymer resins, polyamide resins, and the like. Also, biodegradable resins, plant-derived raw material resins, and the like are included. Among these, from the viewpoint of compatibility and transparency when a crystalline polypropylene resin is used as the material for the sealing resin sheet, a hydrogenated vinyl aromatic resin, a polyolefin resin, a polyamide resin, and a polyester resin are used. Resins can be suitably used.

  The hydrogenated vinyl aromatic resin is a resin obtained by hydrogenating a polymer containing vinyl aromatic hydrocarbon as a monomer unit. Specifically, for example, a resin obtained by hydrogenating a copolymer of styrene and 1,3-butadiene can be used. The hydrogenated vinyl aromatic resin is preferably a resin obtained by hydrogenating a vinyl aromatic hydrocarbon and a conjugated diene block copolymer.

  Examples of the vinyl aromatic hydrocarbon include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, 1,1- Examples thereof include diphenylethylene, N, N-dimethyl-p-aminoethylstyrene, N, N-diethyl-p-aminoethylstyrene, and styrene is particularly preferable. These may be used alone or in combination of two or more.

  The conjugated diene refers to a diolefin having a pair of conjugated double bonds, such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3. -Butadiene, 1,3-pentadiene, 1,3-hexadiene and the like. These may be used alone or in combination of two or more.

  As the polyolefin resin, polyethylene resin, polypropylene resin, and polybutene resin are preferable. Here, the polyethylene resin refers to a polymer of ethylene or a copolymer of ethylene and one or more other monomers. The polypropylene resin refers to a propylene polymer or a copolymer of propylene and one or more other monomers.

  Examples of the polyethylene resin include polyethylene, ethylene-aliphatic unsaturated carboxylic acid polymer, ethylene-aliphatic unsaturated carboxylic acid ester copolymer, ethylene-α-olefin copolymer, and the like.

  Examples of the polyethylene include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and linear very low density polyethylene (referred to as “VLDPE” and “ULDPE”).

  The ethylene-α-olefin copolymer is preferably a copolymer consisting of ethylene and at least one selected from α-olefins having 3 to 20 carbon atoms, and ethylene and α having 3 to 12 carbon atoms. It is more preferable that it is a copolymer comprising at least one selected from olefins. Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-decene, and 1-decene. Examples include dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosane and the like, and these can be used alone or in combination. The proportion of α-olefin in all monomers constituting the copolymer (based on charged monomers) is preferably 6 to 30% by mass. Further, the ethylene-α-olefin copolymer is preferably a soft copolymer, and preferably has a crystallinity of 30% or less by an X-ray method.

  In addition, as the ethylene-α-olefin copolymer, a copolymer of ethylene and at least one comonomer selected from propylene comonomer, butene comonomer, hexene comonomer, and octene comonomer is generally easily available. It can be used suitably.

The polyethylene resin can be polymerized using a known catalyst such as a single site catalyst or a multisite catalyst, and is preferably polymerized using a single site catalyst. The polyethylene resin preferably has a density of 0.860 to 0.920 g / cm ² , more preferably 0.870 to 0.915 g / cm ² from the viewpoint of cushioning properties, and 0.870 to 0.915 g / cm ^2. More preferably, it is 0.910 g / cm ² . As the density of the polyethylene resin is lower, the cushioning property tends to be improved, and when the density is larger than 0.920 g / cm ² , the transparency tends to be deteriorated. When a high-density resin is used, transparency can be improved by adding low-density polyethylene, for example, at a ratio of about 30% by mass.

  From the viewpoint of processability of the sealing resin sheet, the polyethylene resin preferably has an MFR (190 ° C., 2.16 kg) of 0.5 g to 30 g, more preferably 0.8 g to 30 g. 1.0 g to 25 g is more preferable.

  As said polyethylene-type resin, the polyethylene-type copolymer which controlled crystal / amorphous structure (morphology) by nano order can also be used.

  As the polypropylene resin, polypropylene, propylene-α-olefin copolymer, terpolymer of propylene, ethylene, and α-olefin can be preferably used.

  The propylene-α-olefin copolymer refers to a copolymer composed of at least one selected from propylene and α-olefin. The propylene-α-olefin copolymer is preferably a copolymer composed of propylene and at least one selected from ethylene and an α-olefin having 4 to 20 carbon atoms, preferably propylene, ethylene and 4 to 8 carbon atoms. A copolymer composed of at least one selected from α-olefins is more preferable. Examples of the α-olefin having 4 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, and 3-methyl-1-pentene. , 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosane and the like, and these can be used alone or in combination. Moreover, it is preferable in the content rate (charge monomer reference | standard) of ethylene and / or alpha-olefin in all the monomers which comprise the said propylene-alpha-olefin copolymer being 6-30 mass%. Furthermore, the propylene-α-olefin copolymer is preferably a soft copolymer, and preferably has a crystallinity of 30% or less by an X-ray method.

  As the propylene-α-olefin copolymer, a copolymer of propylene and at least one comonomer selected from ethylene comonomer, butene comonomer, hexene comonomer, and octene comonomer is generally easily available, and preferably Can be used.

The polypropylene resin can be polymerized using a known catalyst such as a single-site catalyst or a multi-site catalyst, and is preferably polymerized using a single-site catalyst. The polypropylene resin preferably has a density of 0.860 to 0.920 g / cm ² , more preferably 0.870 to 0.915 g / cm ² from the viewpoint of cushioning properties, and 0.870 to 0.920 g / cm ^2. More preferably, it is 0.910 g / cm ² . As the density of the polypropylene resin is lower, the cushioning property tends to be improved, and when the density is larger than 0.920 g / cm ² , the transparency tends to be deteriorated.

  From the viewpoint of the processability of the sealing resin sheet, the polypropylene resin preferably has an MFR (230 ° C., 2.16 kgf) of 0.3 g to 15.0 g, and preferably 0.5 g to 12 g. More preferably, it is 0.8 to 10 g.

  As the polypropylene resin, a polypropylene copolymer in which the crystal / amorphous structure (morphology) is controlled in nano order can also be used.

  Examples of the polypropylene resin include copolymers of propylene and α-olefins such as ethylene, butene, hexene, and octene, or ternary compounds of propylene, ethylene and α-olefins such as butene, hexene, and octene. A copolymer etc. can be used conveniently. These copolymers may be in any form such as a block copolymer, a random copolymer, etc., preferably a random copolymer of propylene and ethylene, or a random copolymer of propylene, ethylene and butene. is there.

  The polypropylene resin may be not only a resin polymerized with a catalyst such as a Ziegler-Natta catalyst, but also a resin polymerized with a metallocene catalyst, for example, syndiotactic polypropylene, isotactic polypropylene, etc. it can. Further, the proportion of propylene in all monomers constituting the polypropylene resin (based on the charged monomers) is preferably 60 to 80% by mass. Further, from the viewpoint of excellent heat shrinkability, the propylene content ratio (based on the charged monomer) in all monomers constituting the polypropylene resin is 60 to 80% by mass, and the ethylene content ratio (based on the charged monomer) is 10 to 10%. A terpolymer having 30% by mass and a butene content ratio (based on charged monomers) of 5 to 20% by mass is preferred.

  The polypropylene resin may be a resin obtained by uniformly finely dispersing a rubber component having a high concentration of 50% by mass or less with respect to the total amount of the polypropylene resin.

  By containing the polypropylene resin, the sealing resin sheet tends to further improve properties such as hardness and heat resistance.

  Since the polybutene-based resin is particularly excellent in compatibility with the polypropylene-based resin, it is preferably used in combination with the polypropylene-based resin for the purpose of adjusting the hardness and waist of the sealing resin sheet. The polybutene resin is crystalline and is a copolymer of butene and at least one selected from ethylene, propylene and an olefin compound having 5 to 8 carbon atoms, and constitutes a polybutene resin. A high molecular weight polybutene resin having a butene content of 70 mol% or more in all monomers can be suitably used.

  The polybutene resin preferably has an MFR (190 ° C., 2.16 kg) of 0.1 g to 10 g. Moreover, it is preferable that a Vicat softening point is 40-100 degreeC. Here, the Vicat softening point is a value measured according to JIS K7206-1982.

  Examples of the polyamide-based resin include a polyamide resin obtained by polymerizing lauryl lactam (hereinafter sometimes referred to as “nylon 12”). Moreover, as said polyester-type resin, an amorphous polyester etc. are mentioned, for example. These resins can be suitably used from the viewpoint of further improving the transparency and cushioning properties of the sealing resin sheet.

  In addition, when resin (B) comprises the layer which adjoins the layer which consists of resin (A), it is preferable from a viewpoint of the workability of the resin sheet for sealing that MFR is lower than resin (A).

<Mixed resin layer>
Examples of the sealing resin sheet include a sealing resin sheet including a mixed resin layer composed of a resin (A) and a resin (B). As such a sealing resin sheet, for example, a sealing resin sheet having a single-layer structure composed of only the mixed resin layer may be mentioned.

  The mixed resin layer has a feature that generation of volatile substances such as organic acids due to deterioration of an ethylene-vinyl acetate copolymer or the like is suppressed as compared with a resin layer made of only the resin (A). The mixed resin layer preferably contains the resin (B) in an amount of 10 to 45% by mass based on the total mass of the mixed resin layer, more preferably 12 to 40% by mass, and 15 to 35% by mass. More preferably. If content of resin (B) is said range, it exists in the tendency for the transparency and adhesiveness of the said mixed resin layer to be further excellent.

  The resin (B) contained in the mixed resin layer is preferably a polyolefin-based resin, more preferably a polyethylene-based resin or a polypropylene-based resin, from the viewpoint of preventing a decrease in transparency due to resin phase separation or the like.

<Surface layer / Inner layer>
The sealing resin sheet may have a multilayer structure formed by laminating a plurality of resin layers. At this time, two layers forming both surfaces of the sealing resin sheet are referred to as surface layers, and the other layers are referred to as inner layers. For example, such a sealing resin sheet includes a sealing resin sheet including an inner layer made of resin (B) and a surface layer made of resin (A) laminated on the inner layer.

  As said surface layer, the layer which consists of resin (A) is preferable. When the surface layer is a layer made of the resin (A), the adhesion with the adherend such as glass and the compatibility with various additives is improved by the polarization due to the polar group in the resin (A). To do. Further, in the case of crosslinking by irradiating with an organic peroxide or ionizing radiation, a resin having a polar group is more easily crosslinked. Also in this respect, the surface layer is preferably a layer made of the resin (A).

  When the surface layer is cross-linked, the thickness of the surface layer is preferably 10 to 150 μm, more preferably 15 to 140 μm, and further preferably 20 to 120 μm in order to seal the steps such as the power generation unit and wiring without gaps. preferable.

  As said inner layer, if it is a layer which consists of resin (B), it can use without a restriction | limiting in particular. From the viewpoint of improving the cushioning property of the sealing resin sheet, the inner layer preferably exhibits a rubber elasticity at room temperature, and is preferably a layer made of a thermoplastic resin in which a copolymer rubber and a polymer are blended at an arbitrary mass ratio. Can be used for The copolymer rubber can be present in the thermoplastic resin in a state such as uncrosslinked, partially crosslinked, or totally crosslinked.

  The inner layer is preferably a layer made of a polyolefin resin, and more preferably a layer made of a polyethylene resin and / or a polypropylene resin.

  The inner layer is preferably a multilayer structure including a plurality of layers, and more preferably a laminate of a polyethylene resin layer and a polypropylene resin layer. By providing a polypropylene resin layer in the inner layer, the water vapor permeability of the sealing resin sheet is improved, and by providing the inner resin layer with a polyethylene resin layer, the cushioning property of the sealing resin sheet is improved. Moreover, it is preferable in the resin layer which comprises the said inner layer that the layer adjacent to the said surface layer is a polyethylene-type resin layer. When the polyethylene resin layer is adjacent to the surface layer, the cushioning property of the sealing resin sheet is further improved. For the inner layer, the composition ratio of these resin layers can be appropriately selected depending on the purpose. For example, an inner layer having many polyethylene resin layers is used for the purpose of obtaining a sealing resin sheet that is particularly excellent in cushioning properties. can do. Since the sealing resin sheet is excellent in cushioning properties, a power generation unit such as a silicon cell can be more stably held.

  The inner layer is composed of a polyethylene-based resin layer and a polypropylene-based resin layer, and the layer adjacent to the surface layer is a polyethylene-based resin, so that cushioning properties and / or recyclability can be more efficiently exhibited. Therefore, it is preferable. Such a sealing resin sheet is easy to adjust the thickness of the polypropylene layer that is difficult to form a cross-linked layer, and when peeling the sealing resin sheet, it is easy to specify the peeling layer and can be easily peeled off.

<Layer structure>
The sealing resin sheet preferably has a structure in which one or more layers of the same component are laminated on both sides of the central layer so as to be symmetrically arranged with respect to the central layer. As such a sealing resin sheet, for example, it is a sealing resin sheet composed of two surface layers and three inner layers, and the two surface layers are made of the same component and are adjacent to the surface layer. An encapsulating resin sheet in which two inner layers (hereinafter sometimes referred to as “base layer”) are composed of the same component is exemplified.

  In such a sealing resin sheet, the film thickness of the surface layer is preferably 5 to 40% with respect to the entire film thickness of the sealing resin sheet, and the film thickness of the base layer is The film thickness of the entire resin sheet is preferably 50 to 90%, and the film thickness of the inner layer (hereinafter sometimes referred to as “core layer”) sandwiched between the base layers is for sealing. It is preferable that it is 5 to 40% with respect to the film thickness of the whole resin sheet.

<Crosslinking treatment>
The sealing resin sheet is preferably cross-linked. As the crosslinking treatment, known methods can be used without limitation, and examples thereof include crosslinking treatment with an organic peroxide and crosslinking treatment by irradiation with ionizing radiation (electron beam, γ-ray, ultraviolet ray, etc.). The sealing resin sheet is cross-linked so that the power generation unit such as a silicon cell can be more stably held even when the usage environment is a high-temperature environment.

  In the sealing resin sheet, the surface layer is preferably crosslinked. Moreover, it is preferable that the layer containing resin whose melting | fusing point is less than 100 degreeC is bridge | crosslinked. These sealing resin sheets can hold the power generation unit such as a silicon cell more stably.

  The surface layer is preferably crosslinked and has a gel fraction of 3% by mass or more. When the gel fraction is 3% by mass or more, the resin of the surface layer is in a sufficiently crosslinked state, and it is possible to further prevent the sealed material from flowing due to melting of the resin in a high temperature state such as summer. it can. In addition, when a power generation part such as a silicon cell is laminated after the crosslinking resin sheet is subjected to a crosslinking treatment, if the gel fraction of the surface layer is too high, a step such as a power generation part such as a silicon cell or a wiring is formed. It may be impossible to seal without a gap. For this reason, as a gel fraction of a surface layer, 3-90 mass% is preferable, 5-85 mass% is more preferable, and 8-80 mass% is further more preferable.

  The crosslinking treatment with the organic peroxide can be carried out, for example, by heating after blending or impregnating the organic peroxide with the resin layer used for the sealing resin sheet or the sealing resin sheet. As an organic peroxide used here, the organic peroxide whose half life in 100-130 degreeC is less than 1 hour is mentioned, for example. Examples of the organic peroxide include 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane from the viewpoint of compatibility with the resin (A) and the resin (B) and from the viewpoint of half-life. 1,1-bis (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) valerate, 2,2-bis (t-butylperoxy) butane and the like are preferable. Can be used. The encapsulating resin sheet using these organic oxides has a relatively short cross-linking time and can greatly shorten the curing process. These organic peroxides are preferably used in an amount of 10% by mass or less, and in an amount of 5% by mass or less, based on the resin layer used for the sealing resin sheet or the sealing resin sheet. Is more preferable.

  The crosslinking treatment by irradiation with ionizing radiation is performed by, for example, applying ionizing radiation such as α rays, β rays, γ rays, neutron rays, electron beams to the resin layer used for the sealing resin sheet or the sealing resin sheet. Irradiation can be performed. The cross-linking treatment by irradiation with ionizing radiation suppresses the generation of organic acids and peroxides generated by decomposition and elimination of the side chain portion (ester group, etc.) of the resin (A), and the organic acids and peroxides described above. From the viewpoint of suppressing the influence on the solar battery cell, the conductive functional layer, or the wiring due to the above.

  The acceleration voltage of the ionizing radiation can be appropriately selected depending on the thickness of the sealing resin sheet to be irradiated. For example, when the thickness of the sealing resin sheet is 500 μm, the acceleration voltage is set to 300 kV or more. Thus, the entire sealing resin sheet can be crosslinked.

  The irradiation dose of the ionizing radiation can be appropriately selected depending on the resin to be crosslinked, but is preferably 3 kGy to 500 kGy. In general, when it is less than 3 kGy, it tends to be difficult to obtain a uniform resin sheet for crosslinking and sealing. Moreover, when the irradiation amount of ionizing radiation exceeds 500 kGy, the gel fraction of the sealing resin sheet becomes too large, and the ability to fill the step where there is a solar battery cell may be poor.

  The degree of crosslinking by irradiation with the ionizing radiation is represented by the gel fraction. A desired gel fraction and gel distribution can be achieved by changing the acceleration voltage and irradiation dose of the ionizing radiation. Moreover, a desired gel fraction and gel distribution can also be achieved by utilizing the difference in the degree of crosslinking depending on the type of resin and the difference in the degree of crosslinking due to the promotion of crosslinking and the suppression of crosslinking due to additives. For example, it is composed of a surface layer made of resin (A) and an inner layer made of linear low density polyethylene (LLDPE) or linear ultra-low density polyethylene (called “VLDPE” or “ULDPE”). When the sealing resin sheet is irradiated with ionizing radiation at an acceleration voltage sufficient to permeate through all layers, the gel fraction of the inner layer is lower than the gel fraction of the surface layer. If the acceleration voltage is further adjusted, the surface layer can be subjected to a crosslinking treatment while the inner layer is kept in an almost uncrosslinked state.

  The sealing resin sheet has a low degree of crosslinking of at least one of the inner layers and has a gel fraction of less than 3% by mass (hereinafter referred to as “uncrosslinked” that the gel fraction is less than 3% by mass). It is sometimes possible to do this.) Such a sealing resin sheet can be easily peeled off from the power generation unit or the like by melting an uncrosslinked layer by heating or the like, and is further excellent in recyclability. For example, in the case of a solar cell using the above-described sealing resin sheet, the sealing resin sheet can be easily peeled off by melting an uncrosslinked layer at the time of disposal. The member can be easily separated into glass, a power generation unit, a wiring unit, a back sheet, and the like. Specifically, for example, in the case of a solar cell using a sealing resin sheet having a polypropylene resin layer as an inner layer, when separating and discarding, the used solar cell is set to a temperature higher than the melting point of the polypropylene resin. This layer melts and easily peels off from other layers. The peeling method may be any method, and after being brought to a high temperature state, the laminated part may be peeled off by applying a shearing force, or may be peeled by inserting a wire or the like into the molten uncrosslinked resin layer . Such an uncrosslinked layer preferably has a thickness of 15 μm or more, more preferably 20 μm or more, and further preferably 30 μm or more from the viewpoint of peelability.

  The main resin forming the uncrosslinked layer preferably has a low melting point from the viewpoint of recyclability, and preferably has a high melting point from the viewpoint of creep resistance. Therefore, the melting point of the main resin forming the uncrosslinked layer is preferably 100 to 300 ° C, more preferably 110 to 260 ° C, and still more preferably 115 to 250 ° C.

<Other additives>
The sealing resin sheet includes a coupling agent, an antifogging agent, a plasticizer, an antioxidant, a surfactant, a colorant, an ultraviolet absorber, an antistatic agent, a crystal nucleating agent, a lubricant, an antiblocking agent, and an inorganic material. Fillers, cross-linking regulators, etc. may be added, and the effect of the additive is that the liquid can be added to the molten resin, added directly into the target resin layer, or applied after film formation May be introduced into the resin by a known method.

  For example, a coupling agent may be added to the sealing resin sheet for the purpose of ensuring stable adhesion. The addition amount and type of the coupling agent can be appropriately selected depending on the desired degree of adhesion and the type of adherend. The addition amount of the coupling agent is preferably 0.01 to 5 mass%, more preferably 0.03 to 4 mass%, more preferably 0.05 to 3 based on the total mass of the resin layer to which the coupling agent is added. More preferred is mass%. As the kind of the coupling agent, a substance that gives the resin (A) good adhesion to the solar battery cell or glass is preferable, and examples thereof include an organic silane compound, an organic silane peroxide, and an organic titanate compound. Can be mentioned. In addition, these coupling agents are added to the resin in the extruder, mixed and introduced into the extruder hopper, added as a master batch, mixed and added, etc. can do. However, when passing through an extruder, the function of the coupling agent may be marginalized due to heat, pressure, etc. in the extruder, so the amount of addition needs to be adjusted appropriately depending on the type of coupling agent. Further, the type of the coupling agent may be appropriately selected in consideration of the transparency and dispersion state of the sealing resin sheet, the corrosion to the extruder and the viewpoint of extrusion stability. Preferred coupling agents include γ-chloropropylmethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyl-tris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, β- (3,4- Ethoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ- Examples thereof include those having an unsaturated group or an epoxy group such as aminopropyltrimethoxysilane glycidoxypropyltriethoxysilane.

  Further, an ultraviolet absorber, an antioxidant, a discoloration preventing agent, and the like can be added to the sealing resin sheet. In particular, when it is necessary to maintain transparency and adhesiveness over a long period of time, it is preferable to add an ultraviolet absorber, an antioxidant, a discoloration inhibitor and the like. When these additives are added to the resin (A) or the resin (B), the addition amount is preferably 10% by mass or less, and more preferably 5% by mass or less based on the total amount of the resin to be added. Examples of the ultraviolet absorber include 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-n-5-sulfobenzophenone, 2-hydroxy-4-methoxybenzophenone, and 2,2′-dihydroxy-4. , 4'-dimethoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, etc. And antioxidants such as those based on sulfur, sulfur, phosphorus, amine, hindered phenol, hindered amine, and hydrazine.

  Furthermore, a crosslinking aid may be added to the sealing resin sheet in order to increase the degree of crosslinking of the resin (A). Examples of the crosslinking aid include triallyl isocyanurate, triallyl sialate, diallyl phthalate, diallyl fumarate, diallyl maleate, acrylic acid derivatives, methacrylic acid derivatives, or esters thereof. As these crosslinking adjuvants, 10 mass% or less is preferable with respect to the total amount of resin (A), and 5 mass% or less is more preferable.

<Manufacture of resin sheet for sealing>
Although there is no restriction | limiting in particular in the manufacturing method of the said resin sheet for sealing, For example, the following method is mentioned. First, the resin forming the sealing resin sheet is melted with an extruder, the melted resin is extruded from a die, and rapidly cooled and solidified to obtain an original fabric. At this time, for extrusion, a T die, an annular die, or the like can be used. In the case of multiple layers, it is preferable to use an annular die. In the case of double-sided embossing treatment, the raw material thus obtained passes between two heated embossing rolls, and in the case of single-sided embossing treatment, it passes between the embossing rolls heated only on one side to the sealing resin sheet surface. An embossing process may be performed. When the sealing resin sheet has a multilayer structure, a multilayer T-die method or a multilayer circular die method may be used, or a multilayer structure may be formed by a known laminating method. More preferably, the multilayer circular die method is preferable from the viewpoint of easily controlling the thickness of each layer of the multilayer structure.

  Further, as post-processing, for example, heat setting for dimensional stabilization, corona processing, plasma processing, lamination with other types of sealing resin sheets, or the like may be performed. The sealing resin sheet preferably has a sufficiently cross-linked surface layer, and the crosslinking treatment is conventionally known such as irradiation with ionizing radiation (electron beam, γ-ray, ultraviolet ray, etc.) or use of peroxide. The crosslinking process may be performed before or after embossing.

  When the sealing resin sheet is used as a sealing resin sheet constituting a module of a solar cell, the power generation is stable with respect to an external temperature change while maintaining transparency, adhesion, and creep resistance. A silicon cell or the like as a part can be held. In addition, the multilayer structure can reduce the amount of volatile substances such as organic acids induced from the resin used in the sealing resin sheet. Furthermore, when ionizing radiation is used as a crosslinking reaction, the generation of organic peroxides and decomposition products thereof can be further suppressed, and adverse effects on members such as solar cells can be further reduced. That is, the sealing resin sheet can simplify the process by eliminating the cross-linking process, which has been difficult in the past, reduce the complicated work associated therewith, and increase the production speed. In addition, it is possible to securely seal the unevenness such as the thickness of the silicon cell, which is the power generation part, with the sealing resin sheet without gaps, and to have recyclability so that it can be separated into glass or silicon cell members when discarded , Etc. Furthermore, since the sealing resin sheet has a low water vapor transmission rate, it is possible to prevent a metal part used for a silicon cell or the like as a power generation unit or a peripheral wiring from water vapor entering from the outside for a long period of time than water vapor exposure. it can.

Hereinafter, specific examples and comparative examples will be described. In Examples 1 to 22 and Comparative Examples 1 to 3, as shown in Tables 1 to 7 below, a predetermined core layer is sandwiched from above and below by a base layer and a surface layer to produce a sealing resin sheet having a laminate structure. did. In Example 23, a predetermined base layer was sandwiched between two types of surface layers to produce a sealing resin sheet having a laminate structure. In the table, the column of the layer configuration is a description focusing on the number of types of raw material resins. If the same raw material resin is used for the surface layer, the base layer, and the core layer, it is a “single layer”. Further, for example, in Example 3, two types and three layers are described, which means that two surface layers are formed so as to sandwich the core layer.
First, evaluation and processing for a predetermined measurement object are shown below.

<Gel fraction>
About the total-layer gel fraction, the said resin sheet for sealing was extracted in boiling p-xylene for 12 hours, and the ratio of the insoluble part was calculated | required by the following formula. Evaluation was made as a measure of the degree of crosslinking of the sealing resin sheet.
Gel fraction (mass%) = (sample weight after extraction / sample weight before extraction) × 100
Regarding the gel fraction of the surface layer, a sheet having the same resin and the same thickness as the surface layer was prepared, and the sheet was subjected to an electric wire irradiation treatment, and the gel fraction was calculated by the above method.

<Ionizing radiation irradiation>
The sealing resin sheet was subjected to electron beam treatment using an EPS-300 or EPS-800 electron beam irradiation apparatus (manufactured by Nissin High Voltage) at a predetermined acceleration voltage and irradiation density.

<Density (ρ)>
It measured based on JIS-K-7112.

<MFR>
It measured based on JIS-K-7210. In addition, the unit of MFR shown in the following Tables 1-7 is g / 10min.

<Melting point (mp)>
Using a differential scanning calorimeter “MDSC 2920 type” manufactured by TA Instruments Inc., heat about 8-12 mg of resin from 0 ° C. to 200 ° C. at a rate of 10 ° C./min, and melt at 200 ° C. for 5 minutes. After being held, it was rapidly cooled to −50 ° C. or lower, and then the temperature of the endothermic peak accompanying melting obtained when the temperature was raised from 0 ° C. to 200 ° C. at 10 ° C./min was taken as the melting point.

<Haze and total light transmittance>
Measured according to ASTM D-1003.
As a sample for evaluation, a glass plate for solar cells (white glass 5 cm × 10 cm square manufactured by AGC Co., Ltd .: thickness 3 mm) / resin sheet for sealing / glass plate for solar cells is laminated in this order, and an LM50 type vacuum laminator (NPC) And vacuum laminated at 150 ° C. for 15 minutes.

<Water vapor transmission rate>
It measured based on JIS-K7129.
As a sample for evaluation, a 150 μm film was prepared using the same resin as the core layer of the sealing resin sheet, and evaluation was performed. However, in Example 23, a 150 μm film was prepared and evaluated using the same resin as the base layer of the sealing resin sheet as an evaluation sample.

<Power generation partial gap evaluation>
Glass plate for solar cell (white glass made by AGC, 5 cm × 10 cm square: thickness 3 mm) / resin sheet for sealing / power generation part (single crystal silicon cell (thickness 250 μm) / resin sheet for sealing / glass for solar cell) Stacked in the order of the plates, vacuum laminated using a LM50 type vacuum laminator (NPC) at 150 ° C. for 15 minutes, and visually checked the contact state with the sealing resin sheet of the single crystal silicon cell of the power generation part confirmed.
A: All contact portions between the single crystal silicon cell and the sealing resin sheet are good. (No gap)
◯: Good contact between the single crystal silicon cell and the sealing resin sheet. (No gap)
X: A gap occurred at the contact portion between the single crystal silicon cell and the sealing resin sheet.

<Creep resistance evaluation>
Glass plate for solar cell (white glass made by AGC, 5 cm × 10 cm square: thickness 3 mm) / resin sheet for sealing / power generation part (single crystal silicon cell (thickness 250 μm) / resin sheet for sealing / glass for solar cell) Laminate in the order of the plates, vacuum laminate using an LM50 type vacuum laminator (NPC), fix one glass plate of the laminated solar cells to the wall of a thermostat set at 85 ° C., leave for 24 hours, The deviation from the glass plate was measured.
A: There is no displacement of the glass plate.
○: There is almost no displacement of the glass plate.
X: The shift | offset | difference of a glass plate is 3 mm or more.

<Recyclability evaluation>
Glass plate for solar cell (white glass made by AGC, 5 cm × 10 cm square: thickness 3 mm) / resin sheet for sealing / power generation part (single crystal silicon cell (thickness 250 μm) / resin sheet for sealing / glass for solar cell) Laminate in the order of the plates, vacuum laminate using LM50 type vacuum laminator (NPC) at 150 ° C. for 15 minutes, and fix one glass plate of the laminated solar cells on the wall of the thermostat and let stand for 24 hours The deviation from the other glass plate was measured.
The set temperature of the thermostatic bath was set to a temperature 30 ° C. higher than the highest melting point among the resins used for the sealing resin sheet.
A: The deviation of the glass plate is 5 mm or more.
A: The deviation of the glass plate is 3 mm or more.
X: There is almost no shift of the glass plate.

  Hereinafter, the manufacturing method of the resin sheet for sealing of Examples 1-23 and Comparative Examples 1-3 is shown.

<Examples 1 to 23>
Using the resins shown in Tables 1 to 6, the resin was melted using three extruders (surface layer extruder, base layer extruder, core layer extruder), and an annular die connected to the extruder The resin was melt extruded in a tube shape, and the tube formed by melt extrusion was rapidly cooled using a water-cooled ring to obtain resin sheets for sealing of Examples 1 to 23. In introducing the organic peroxide or the silane coupling agent, the resin to be introduced was kneaded in advance at a concentration of about 5% by mass to form a master batch, which was diluted to the desired amount. In the table, the thickness ratio indicates the ratio of the thickness of each layer when the thickness of the entire sealing resin sheet is 100.

  The sealing resin sheets of Examples 1 to 21 were subjected to an electron beam crosslinking treatment in accordance with “irradiation conditions” shown in Tables 1 to 6 below. For the sealing resin sheets of Examples 22 and 23, an organic peroxide was used as a crosslinking agent. The gel fraction, optical characteristics, and water vapor transmission rate were evaluated for each sealing resin sheet. Moreover, the solar cell glass was used as a power generation surface member, a solar cell module was produced, and solar cell power generation partial gap filling evaluation and creep resistance evaluation were performed. The evaluation results are shown in Tables 1-6. Moreover, the solar cell module was created using the resin sheet for sealing of Examples 8, 13, 20, and 21, and recyclability evaluation was performed. The evaluation results are shown in Table 8.

<Comparative Examples 1-3>
Using the resin material shown in Table 7, a sealing resin sheet was produced according to the same conditions as in the examples.
The sealing resin sheet was subjected to an electron beam crosslinking treatment in accordance with the “irradiation conditions” shown in Table 7.
The gel fraction and optical properties were evaluated for each sealing resin sheet.
Moreover, the solar cell glass was used as a power generation surface member, a solar cell module was produced, and solar cell power generation partial gap filling evaluation, creep resistance evaluation, and recyclability evaluation were performed. Table 7 shows the evaluation results.

  As shown in Tables 1 to 7, the resin sheets for sealing of Examples 1 to 23 have obtained practically good evaluations on optical characteristics and water vapor transmission rate, and solar cell power generation by producing solar cell modules. When partial gap filling evaluation and creep resistance evaluation were performed, good evaluation results were obtained in both cases. That is, it was confirmed that the sealing resin sheet has a low water vapor transmission rate while maintaining transparency and creep resistance.

  In Example 20 and Example 21, the creep resistance test was slightly inferior to that of the other examples. Although these are crosslinked by ionizing radiation, it is considered that the intermediate layer is made an uncrosslinked layer by adjusting the acceleration voltage.

  Further, as shown in Table 8, Examples 8, 13, 20, and 21 were confirmed to have recyclability while maintaining transparency, creep resistance, and low water vapor permeability.

  About Example 20 and Example 21, since it has an uncrosslinked layer in the middle layer as described above, separation of separation was confirmed at a temperature equal to or higher than the melting point. In Example 8 and Example 13, since the core layer of the inner layer was a polypropylene resin, it was not crosslinked by an electron beam or the like, and peeling separation was confirmed at a temperature equal to or higher than the melting point.

  As shown in Table 7, the sealing resin sheet of Comparative Example 1 produced from the ethylene-vinyl acetate copolymer produced a deviation from the other glass plate in the thermostat set at 85 ° C. Further, in Comparative Example 2 in which the ethylene-vinyl acetate copolymer was subjected to a crosslinking treatment to obtain a gel fraction of 80% or more, a gap was generated in the periphery of the single crystal silicon cell. In Comparative Example 3, the water vapor permeability was high, and it was not possible to prevent peripheral members including silicon cells as a power generation unit from water vapor that entered from the outside in the solar cell module over a longer period than water vapor exposure.

  The resin sheet for sealing of the present invention has industrial applicability as a sealing material for protecting various elements such as semiconductor elements of solar cells.

Claims (15)

  At least one resin (A) selected from an ethylene-vinyl acetate copolymer, an ethylene-aliphatic unsaturated carboxylic acid copolymer and an ethylene-aliphatic unsaturated carboxylic acid ester copolymer, and other than the resin (A) A resin sheet for sealing containing the thermoplastic resin (B).   The resin sheet for sealing according to claim 1, wherein the resin (B) is a polyolefin-based resin.   The resin sheet for sealing according to claim 1 or 2, wherein the resin (B) is a polyethylene resin and / or a polypropylene resin.   The resin sheet for sealing of any one of Claims 1-3 provided with the mixed resin layer which consists of resin (A) and resin (B).   The encapsulating resin sheet according to claim 4, wherein the mixed resin layer contains 10 to 45 mass% of the resin (B).   The resin sheet for sealing of any one of Claims 1-3 provided with the inner layer which consists of resin (B), and the surface layer which consists of resin (A) laminated | stacked on this inner layer.   The encapsulating resin sheet according to claim 6, wherein the inner layer is a laminate of a polyethylene resin layer and a polypropylene resin layer.   The sealing resin sheet according to claim 7, wherein the layer adjacent to the surface layer is a polyethylene resin layer.   The resin sheet for sealing according to claim 7 or 8, wherein the thickness ratio of the polypropylene resin layer is 40% or less when the thickness of the resin sheet for sealing is 100%.   The resin sheet for sealing according to any one of claims 6 to 9, wherein the surface layer is a layer subjected to a crosslinking treatment.   The resin sheet for sealing according to claim 10, wherein the crosslinking treatment is a crosslinking treatment with an organic peroxide and / or ionizing radiation.   The resin sheet for sealing of any one of Claims 1-11 containing the crosslinked material which bridge | crosslinked resin (A) and / or resin (B) whose melting | fusing point is less than 100 degreeC.   The resin sheet for sealing according to claim 12, wherein the resin (A) and / or the resin (B) having a melting point of less than 100 ° C are crosslinked by an organic peroxide and / or ionizing radiation.   14. The structure according to claim 1, wherein one or more layers of the same component are laminated on both sides of the central layer so as to be symmetrically arranged with respect to the central layer. Resin sheet for sealing.   A solar cell provided with the resin sheet for sealing of any one of Claims 1-14.