JP2011181637A - Resin sealing sheet, and solar cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin sealing sheet which has superior gap filling properties and creep resistance. <P>SOLUTION: There is provided the resin sealing sheet (5) which has a shrinkage factor of 0 to 40% when suspended at a temperature of 150°C and has been subjected to a crosslinking treatment wherein a gel fraction is 0.1 to 2 mass%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  In recent years, due to the global warming phenomenon, awareness of the environment has increased, and a new energy system that does not generate greenhouse gases such as carbon dioxide has attracted attention. The energy generated by solar cell power generation does not generate carbon dioxide. Therefore, it has been attracting attention as clean energy, and research and development has been carried out as industrial and household energy.

  Representative examples of solar cells include those using single crystal and polycrystalline silicon cells (crystalline silicon cells), those using amorphous silicon, and compound semiconductors (thin film cells). Solar cells are often used outdoors exposed to wind and rain for a long period of time, and the power generation part is modularized by attaching a glass plate, back sheet, etc. to prevent moisture from entering from outside. We are trying to protect the parts and prevent leakage.

  As a member for protecting the power generation portion, transparent glass or transparent resin is used for the light incident side member in order to ensure light transmission necessary for power generation. As the opposite side (back side) member, a laminated sheet on which a barrier coating process such as an aluminum foil called a back sheet, a polyvinyl fluoride resin (PVF), polyethylene terephthalate (PET) or silica is used. The power generation element is sandwiched between resin sealing sheets, the outside is further covered with glass or a back sheet, and heat treatment is performed to melt the resin sealing sheet, and the whole is integrally sealed (modularized).

  The following (1) to (3) are required as characteristics of the resin-encapsulated sheet described above. That is, (1) good adhesion to glass, power generation element and back sheet, (2) flow prevention (creep resistance) of power generation element due to melting of resin-sealed sheet at high temperature, (3) sun Transparency that does not hinder the incidence of light.

  From such a viewpoint, the resin encapsulated sheet is made of an ethylene-vinyl acetate copolymer (EVA), an ultraviolet absorber as a countermeasure for ultraviolet deterioration, a coupling agent for improving adhesion to glass, and an organic material for crosslinking. Additives such as peroxide are blended to form a film by calendar molding or T-die casting. Moreover, in view of being exposed to sunlight for a long time, various additives such as a light-resistant agent are blended in order to prevent a decrease in optical properties due to deterioration of the resin.

  As a method for modularizing the solar cell with the resin-encapsulated sheet as described above, a method using a dedicated solar cell vacuum laminator can be mentioned. Specifically, glass / resin encapsulating sheet / power generation element such as crystalline silicon cell / resin encapsulating sheet / back sheet are stacked in this order, and the melting temperature of the resin or higher (temperature condition of about 150 ° C. in the case of EVA) ) And a step of preheating and a pressing step, and a method of melting and bonding the resin sealing sheet.

  In the above method, first, the resin of the resin sealing sheet is melted in the preheating process, and the member in contact with the molten resin in the pressing process is in close contact with the molten resin and vacuum laminated. In this laminating step, after (i) the crosslinking agent (for example, organic peroxide) contained in the resin sealing sheet is thermally decomposed and EVA crosslinking is promoted, (ii) the resin sealing sheet The coupling agent contained is covalently bonded to the member in contact. Thereby, the mutual adhesiveness is further improved, the flow of the power generation part due to the melting of the resin sealing sheet in a high temperature state is prevented (creep resistance), and the excellent adhesiveness of the glass, the power generation element and the back sheet is obtained. Realized.

  Patent Document 1 discloses a solar cell filling adhesive sheet made of an ethylene copolymer resin containing a coupling agent and an organic peroxide. Patent Document 2 discloses a sheet for sealing a solar cell, which is a sheet made of an ethylene vinyl acetate copolymer blended with a crosslinking agent and a silane coupling agent, and is radiation-crosslinked to a certain gel fraction. Is disclosed.

JP 58-060579 A JP-A-8-283696

  However, in recent years, the viewpoint of responding to the demand for modules with low power loss due to the thickening of metal connections such as tab wires for connecting power generation elements such as crystalline silicon cells due to the demand for higher power output of solar cell modules Therefore, there is still room for improvement with respect to the gap filling property of the power generating element with large unevenness by the resin sealing sheet. Conventionally, in order to improve the above-described creep resistance, the resin-encapsulated sheet has been gelled, and as the gelation proceeds, the thermal fluidity becomes worse when modularizing the solar cell. There arises a problem that a decomposition gas accompanying gelation is generated after the module. Therefore, sufficient gap filling properties may not be obtained. Such a problem becomes conspicuous in the case of a solar cell having a power generation element with large unevenness connected by a thick metal connection.

  This invention is made | formed in view of the said situation, and makes it a main objective to provide the resin sealing sheet which is excellent in gap filling property and creep resistance.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have a shrinkage ratio of 0 to 40% when the sheet is suspended at a temperature of 150 ° C., and a gel fraction of 0.1. It discovered that it could be set as the resin sealing sheet excellent in crevice filling property and creep resistance by giving -2 mass% crosslinking process, and came to complete this invention.

That is, the present invention is as follows.
[1]
A resin-encapsulated sheet subjected to a crosslinking treatment in which a shrinkage rate when the sheet is suspended at a temperature of 150 ° C. is 0 to 40% and a gel fraction is 0.1 to 2% by mass.
[2]
The resin sealing sheet according to [1], wherein the crosslinking treatment is performed by ionizing radiation irradiation.
[3]
Ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic acid ester copolymer, saponified ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-acrylic acid The resin-encapsulated sheet according to any one of [1] to [3], comprising at least one resin selected from the group consisting of an ester copolymer saponified product and a polyolefin-based resin.
[4]
Resin sealing sheet as described in any one of [1]-[3] containing resin whose melting | fusing point is 100 degrees C or less.
[5]
The resin sealing sheet according to any one of [1] to [4], which has a multilayer structure.
[6]
A translucent insulating substrate;
A back surface insulating substrate disposed opposite to the translucent insulating substrate;
A power generating element disposed between the translucent insulating substrate and the back insulating substrate;
The resin sealing sheet according to any one of [1] to [5], which seals the power generation element;
A solar cell module comprising:

  ADVANTAGE OF THE INVENTION According to this invention, the resin sealing sheet excellent in crevice filling property and creep resistance can be provided.

It is a section schematic diagram of one mode of a solar cell module of this embodiment.

  Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. The following embodiments are exemplifications for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be implemented with appropriate modifications within the scope of the gist thereof. In the drawings, positional relationships such as up, down, left and right are based on the positional relationships shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

<Resin sealing sheet>
The resin-encapsulated sheet of the present embodiment has a shrinkage rate of 0 to 40% when the sheet is suspended at a temperature of 150 ° C., and undergoes a crosslinking treatment with a gel fraction of 0.1 to 2% by mass. Has been.

  The lower limit of the shrinkage rate when the sheet is suspended at a temperature of 150 ° C. (hereinafter sometimes referred to as “hanging shrinkage rate”) may be 0% or more, and preferably 1% or more. The upper limit may be 40% or less, and preferably 35% or less. The suspension shrinkage rate can be measured by the method described in Examples described later. The suspension shrinkage rate is 0% or more from the viewpoint of creep resistance, and 40% or less from the viewpoint of preventing displacement of the power generating element.

  The resin sealing sheet of the present embodiment is subjected to a crosslinking treatment with a gel fraction of 0.1 to 2% by mass. The lower limit of the gel fraction may be 0.1% by mass or more, preferably 0.2% by mass or more from the viewpoint of creep resistance. The upper limit value may be 2% by mass or less, preferably 1.5% by mass or less from the viewpoint of filling gaps, in particular, filling gaps between power generation elements with large irregularities connected by thick metal connections. In the present embodiment, “crosslinking treatment” refers to a state in which at least a part of the polymer constituting the resin is physically or chemically crosslinked. Even if the resin encapsulating sheet has either a single layer structure or a multi-layer structure to be described later, the gel fraction is the average gel fraction of the entire resin encapsulating sheet (all layers) unless otherwise specified. It means the value of (gel fraction). The gel fraction can be measured by the method described in Examples described later.

  By making the suspension shrinkage rate and gel fraction at 150 ° C. within the above ranges, it has excellent performance (crevice filling property) and creep resistance for sealing the level difference of objects to be sealed such as power generation elements and wiring. It can be set as a resin sealing sheet.

  The crosslinking treatment is preferably performed by ionizing radiation irradiation. Since there is no need to use an organic peroxide for the cross-linking treatment, there is no need for a thermal curing process, less gas is generated due to thermal decomposition of the organic peroxide, etc., corrosion damage such as vacuum pumps, oil stains, etc. Can be suppressed. The gel fraction in the sheet thickness direction can be appropriately controlled by the irradiation intensity (acceleration voltage) and irradiation density of ionizing radiation. The irradiation intensity (acceleration voltage) indicates how deep electrons can reach in the thickness direction of the sheet, and the irradiation density indicates how many electrons are irradiated per unit area. Examples of the ionizing radiation include α rays, β rays, γ rays, neutron rays, and electron beams. The acceleration voltage of ionizing radiation such as an electron beam can be adjusted as appropriate according to the resin to be crosslinked, and the irradiation dose of ionizing radiation varies depending on the resin used, but the entire resin encapsulating sheet is uniform. From the viewpoint of crosslinking, generally 3 kGy or more is preferable.

  Resin encapsulating sheet is made of ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic acid ester copolymer, saponified ethylene-vinyl acetate copolymer, ethylene -It is preferable to include at least one resin selected from the group consisting of saponified vinyl acetate-acrylic acid ester copolymers and polyolefin resins. Among these, a polyolefin resin is more preferable from the viewpoint of high total light transmittance and good sunlight transmittance.

  The resin sealing sheet preferably contains a resin having a melting point of 100 ° C. or lower. The melting point is more preferably 80 ° C. or lower, and further preferably 75 ° C. or lower. Thereby, sufficient heat fluidity | liquidity can be provided to a resin sealing sheet. In the case of a resin-encapsulated sheet obtained using a resin composition containing a plurality of resins, the melting point of the entire resin composition is more preferably 100 ° C. or lower. Melting | fusing point can be measured by the method as described in the Example mentioned later.

  The ethylene-vinyl acetate copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and vinyl acetate. The proportion of vinyl acetate in all monomers constituting the ethylene-vinyl acetate copolymer is preferably 10 to 40% by mass from the viewpoint of optical properties, adhesiveness, and flexibility, and is 13 to 35% by mass. More preferably, it is more preferably 15 to 30% by mass. The melt flow rate (190 ° C., 2.16 kg; hereinafter referred to as “MFR”) measured in accordance with JIS-K-7210 is 0.3 to 30 g / from the viewpoint of workability of the resin-encapsulated sheet. It is preferably 10 minutes, more preferably 0.5 to 30 g / 10 minutes, and further preferably 0.8 to 25 g / 10 minutes. Here, MFR is measured by the measurement method described later.

  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. Examples of the aliphatic unsaturated carboxylic acid include acrylic acid and methacrylic acid. The copolymer may be a multi-component copolymer obtained by copolymerizing monomers of three or more components.

  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 0.5 to 30 g / 10 minutes, more preferably 0.5 to 30 g / 10 minutes, and 0.8 to 25 g / 10 minutes. More preferably.

  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. Examples of the aliphatic unsaturated carboxylic acid ester include esters of acrylic acid and methacrylic acid with alcohols having 1 to 8 carbon atoms such as methanol and ethanol. The copolymer may be a multi-component copolymer obtained by copolymerizing monomers of three or more components.

  The proportion of the aliphatic unsaturated carboxylic acid ester in all monomers constituting the ethylene-aliphatic unsaturated carboxylic acid ester copolymer is preferably 3 to 35% by mass. MFR (190 ° C., 2.16 kg) is preferably 0.5 to 30 g / 10 min, more preferably 0.8 to 30 g / 10 min, and 1 to 25 g / 10 min. Further preferred.

  Examples of the saponified ethylene-vinyl acetate copolymer include a part of the ethylene-vinyl acetate copolymer or a completely saponified product. Examples of the saponified ethylene-vinyl acetate-acrylic acid ester copolymer include a part of the ethylene-vinyl acetate-acrylic acid ester copolymer or a completely saponified product.

  The ratio of the hydroxyl group in these saponified products is preferably 0.1 to 15% by mass, more preferably 0.1 to 10% by mass in the resin constituting the resin-encapsulated sheet. More preferably, it is 1-7 mass%. By making the ratio of a hydroxyl group into the said range, adhesiveness and compatibility become favorable and the risk of the clouding of the resin sealing sheet obtained can be reduced more.

  The ratio of the hydroxyl group can be calculated from the original olefin polymer resin of the saponified product, VA% (vinyl acetate copolymerization ratio by NMR measurement) of the resin, the degree of saponification, and the blending ratio in the resin. it can.

  The content of vinyl acetate in the ethylene-vinyl acetate copolymer or ethylene-vinyl acetate-acrylic acid ester copolymer before saponification is 10 to 40% by mass from the viewpoints of optical properties, adhesiveness, and flexibility. It is preferable that it is 13 to 35% by mass, more preferably 15 to 30% by mass. The saponification degree of each saponified product is preferably 10 to 70%, more preferably 15 to 65%, and still more preferably 20 to 65% from the viewpoints of transparency and adhesiveness.

  Examples of the saponification method include a method of saponifying an ethylene-vinyl acetate copolymer, an ethylene-vinyl acetate-acrylic ester copolymer pellet or powder using an alkali catalyst in a lower alcohol such as methanol; toluene, Examples thereof include a method in which a copolymer is dissolved in an organic solvent such as xylene and hexane in advance and then saponified using a small amount of alcohol and an alkali catalyst. Moreover, you may graft-polymerize the monomer containing functional groups other than a hydroxyl group to the saponified copolymer.

  Since the saponified product has a hydroxyl group in the side chain, the adhesiveness can be further improved as compared with the copolymer before saponification. By adjusting the degree of saponification, the transparency and adhesiveness can be controlled.

  Copolymerization of each of the above-described copolymers can be performed by a known method such as a high-pressure method or a melting method according to the type of monomer constituting the copolymer, and a multisite catalyst can be used as a polymerization reaction catalyst. A single site catalyst or the like can be used. 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.

  The polyolefin-based resin is preferably at least one selected from the group consisting of a polyethylene-based resin, a polypropylene-based resin, and a polybutene-based resin from the viewpoint of corrosivity and water vapor barrier properties, and from the viewpoint of cost, a polyethylene-based resin A resin is more preferable. Here, the polyethylene resin refers to a homopolymer of ethylene or a copolymer of ethylene and one or more other monomers. The polypropylene resin refers to a homopolymer of propylene or a copolymer of propylene and one or more other monomers. The polybutene resin refers to a homopolymer of butene or a copolymer of butene and one or more other monomers.

The resin sealing sheet preferably contains a polyethylene resin having a density of 0.88 to 0.91 g / cm ³ or less. By using a polyethylene-based resin having a density of 0.91 g / cm ³ or less, the gap filling property and transparency (particularly, the total light transmittance) during thermal lamination can be greatly improved. The lower limit of density, from the viewpoint of improving the ratio of diffuse light transmission, such as the haze value is high, is preferably 0.88 g / cm ³ or more, more not less 0.89 g / cm ³ or more preferable. From the viewpoint of further improving the transparency, different types of resins such as high-density polyethylene resins are used in combination with low-density polyethylene resins so that the density is 0.88 to 0.91 g / cm ^3. More preferably. More specifically, it is more preferable to add the high density polyethylene resin at a ratio of about 1 to 50% by mass with respect to the low density polyethylene resin.

  The polyethylene resin is more preferably linear low density polyethylene. By using linear low density polyethylene, the polarity can be further suppressed, and excellent insulating properties can be obtained. Furthermore, it is excellent in water vapor barrier properties, and the object to be sealed can be reliably sealed even under high temperature and high humidity. In particular, when the crosslinking treatment is performed, these advantages become more remarkable.

  The linear low-density polyethylene preferably has a melting point of 110 ° C. or lower from the viewpoint of processability of the resin-encapsulated sheet and suitability for thermal lamination, and in addition, MFR (190 ° C., 2.16 kg) is 0.5 to 30 g. / 10 minutes is more preferable, 0.8 to 30 g / 10 minutes is still more preferable, and 1.0 to 25 g / 10 minutes is still more preferable.

  Linear low-density polyethylene can be polymerized using known catalysts such as single-site catalysts and multi-site catalysts, but the content of low-molecular components can be suppressed, and low-density resins can be efficiently used. From the viewpoint of synthesis, etc., it is preferable to perform polymerization using a single site catalyst. The single-site catalyst is not particularly limited, and a known one can be used. Examples thereof include metal complexes having a cyclopentacene ring. A commercial item can also be used for these.

  It is preferable that the resin sealing sheet of this Embodiment does not contain an organic peroxide substantially. Accordingly, since there is no restriction on the temperature at the time of manufacturing the sheet, the sheet temperature at the time of forming the sheet or at the time of embossing described later can be increased. As a result, the film forming speed, the embossing speed, etc. can be improved, and the productivity is excellent. Here, the organic peroxide refers to one that can chemically crosslink the resin used in the resin sealing sheet of the present embodiment. For example, 1,1-bis (t-butylperoxy) 3, 3,5 -Trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) valerate, 2,2-bis (t-butylperoxy) butane, etc. Is mentioned.

  The resin sealing sheet may further contain an ionizing radiation-disintegrating resin. The ionizing radiation decay type resin refers to a resin having a property of decaying by irradiation with ionizing radiation such as α rays, β rays, γ rays, neutron rays, and electron beams.

  Examples of the ionizing radiation disintegrating resin include disintegrating resins in which a functional group is bonded to the α-position of the C—C bond of the main chain. Examples of the functional group include a halogen atom, a hydroxy group, a nitro group, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted amino group, and an optionally substituted carboxyl. And at least one selected from the group consisting of a group, an optionally substituted amide group, and an optionally substituted aryl group.

  Here, the alkyl group, alkoxy group, amino group, carboxyl group, amide group, and aryl group may be substituted with one or more substituents at substitutable positions. Examples of the substituent include a halogen atom (eg, fluorine atom, chlorine atom, bromine atom), an alkyl group having 1 to 6 carbon atoms (eg, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl). Group, sec-butyl group, tert-butyl group, pentyl group, hexyl group), aryl group (for example, phenyl group, naphthyl group), aralkyl group (for example, benzyl group, phenethyl group), alkoxy group (for example, methoxy group) Ethoxy group) and the like.

  Specifically, the ionizing radiation decay type resin is selected from the group consisting of polypropylene, polyisobutylene, poly α-methylstyrene, tetrafluoroethylene, polymethyl methacrylate, polyacrylamide, polymethyl glycidyl methacrylate, and cellulose. There is at least one kind.

  The resin constituting the resin sealing sheet may contain an ionizing radiation cross-linking resin having both a crosslinkable portion and a disintegratable portion. Examples of such a resin include an ethylene copolymer containing glycidyl methacrylate, an ethylene copolymer containing polypropylene, an ethylene copolymer containing methyl methacrylate, an ethylene copolymer containing glycidyl methacrylate, and an ethylene copolymer containing isoprene rubber. , Ethylene copolymers containing butadiene rubber, ethylene copolymers containing styrene-butadiene copolymer rubber, and the like.

  The ethylene copolymer containing glycidyl methacrylate indicates an ethylene copolymer, an ethylene terpolymer, or the like with glycidyl methacrylate having an epoxy group as a reaction site, and may be a multi-component copolymer. Examples thereof include an ethylene-glycidyl methacrylate copolymer, an ethylene-glycidyl methacrylate-vinyl acetate copolymer, and an ethylene-glycidyl methacrylate-methyl acrylate copolymer. Since these have high reactivity of glycidyl methacrylate, they can exhibit stable adhesiveness, tend to have a low glass transition temperature and good flexibility.

  The resin sealing sheet of the present embodiment may have either a single layer structure or a multilayer structure. Hereinafter, each structure will be described. Here, when the resin sealing sheet has a multilayer structure, the surface layer of the resin sealing sheet is referred to as a “surface layer”, and the other layers are referred to as “inner layers” (in the case of three or more layers). That is, two layers forming both surfaces of the resin sealing sheet are “surface layers”. For example, in the case of a multilayer structure consisting of two layers, the structure is composed of two surface layers, but one surface layer and the other surface layer may be the same component or different components. Also good.

[Single layer structure]
When the resin-encapsulated sheet has a single-layer structure, from the viewpoint of ensuring good transparency, flexibility, adhesion of the adherend and handleability, ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid From the group consisting of acid copolymers, ethylene-aliphatic unsaturated carboxylic acid ester copolymers, saponified ethylene-vinyl acetate copolymers, saponified ethylene-vinyl acetate-acrylic acid ester copolymers, and polyolefin resins. A layer containing at least one selected from the above is preferable.

[Multilayer structure]
The resin sealing sheet of the present embodiment preferably has a multilayer structure. By setting it as a multilayer structure, the physical property of a resin sealing sheet can be improved by providing a different function for every layer (resin layer). When the resin-encapsulated sheet has a multilayer structure, the suspension shrinkage rate of the entire sheet may be 0 to 35%, and the gel fraction of the entire sheet may be 0.1 to 2% by mass.

  In the resin-encapsulated sheet of the present embodiment, the saponified ethylene-vinyl acetate copolymer, the saponified ethylene-vinyl acetate-acrylic ester copolymer, and the saponified ethylene-glycidyl methacrylate copolymer are used as the adhesive resin. It is preferable that the resin layer containing at least one selected from the group consisting of is formed as a layer (at least one surface layer) in contact with the object to be sealed.

  The surface layer may be a layer composed only of the above-described saponified material. However, from the viewpoint of ensuring good transparency, flexibility, adhesion and handling properties of the adherend, saponified material and ethylene-vinyl acetate copolymer are used. A layer composed of a mixed resin of at least one resin selected from the group consisting of a coalescence, an ethylene-aliphatic unsaturated carboxylic acid copolymer, an ethylene-aliphatic unsaturated carboxylic acid ester copolymer, and a polyolefin resin. Preferably there is. As these resins, those described above can be used. For example, as the ethylene-aliphatic unsaturated carboxylic acid copolymer, the above-described ethylene-aliphatic unsaturated carboxylic acid copolymer can be used, and specifically, an ethylene-acrylic acid copolymer, an ethylene- A methacrylic acid copolymer etc. are mentioned. As the polyolefin-based resin, the above-described polyolefin-based resin can be used, and specific examples include a polyethylene-based resin, a polypropylene-based resin, and a polybutene-based resin.

  Although content of adhesive resin in a surface layer is not specifically limited, From an adhesive viewpoint, 5-50 mass% is preferable, 5-40 mass% is more preferable, 5-35 mass% is further more preferable.

  When the resin sealing sheet has a multilayer structure, the ionizing radiation-disintegrating resin is preferably contained in a layer (at least one of the surface layers) in contact with the object to be sealed. If the layer of the resin sealing sheet that comes into contact with the object to be sealed contains an ionizing radiation-disintegrating resin, the ability to seal a step such as a power generation element or wiring without gaps (gap filling property) is improved. There is a tendency.

  When the ionizing radiation-disintegrating resin is contained in the layer in contact with the object to be sealed, the content of the ionizing radiation-disintegrating resin in the layer in contact with the object to be sealed is preferably 5 to 80% by mass. 7 to 70% by mass is more preferable, and 8 to 60% by mass is more preferable.

  When the layer in contact with the object to be sealed contains an ionizing radiation decay type resin, the gel fraction of the layer in contact with the object to be sealed (surface layer) is preferably less than 3% by mass, more preferably 0.1%. It is not less than 2% by mass and more preferably not less than 0.1% by mass and not more than 1% by mass. When the gel fraction of the layer in contact with the object to be sealed is less than 3% by mass, the gap filling property tends to be good, and when it is 0.1% by mass or more, the resin is used even in a high temperature state such as summer. However, the material to be sealed tends to be stable without flowing.

The density of the surface layer in contact with the object to be sealed is preferably 0.87 g / cm ³ or more from the viewpoint of blocking, and 0.96 g / cm ³ or less from the viewpoint of cushioning and transparency. preferable. It is also effective to reduce the surface contact area by a known embossing method as a method for preventing blocking. The layer ratio of the surface layer in contact with the object to be sealed preferably has a thickness of at least 5% with respect to the total thickness of the resin sealing sheet from the viewpoint of ensuring good adhesiveness. When the thickness is 5% or more, the same adhesiveness as in the case of the single layer structure described above tends to be obtained.

  The resin constituting the inner layer is not particularly limited, and any other resin may be used in addition to the resin suitably used for the surface layer described above. For the purpose of imparting other functions to the inner layer, resin materials, mixtures, additives, and the like can be appropriately selected. For example, for the purpose of newly imparting cushioning properties, a layer containing a thermoplastic resin may be provided as the inner layer.

  Examples of the thermoplastic resin used as the inner layer include polyolefin resins, styrene resins, vinyl chloride resins, polyester resins, polyurethane resins, chlorinated ethylene polymer resins, polyamide resins, and the like. It includes those possessed and plant-derived raw materials. Among the above, a hydrogenated block copolymer resin, a propylene copolymer resin, and an ethylene copolymer resin that have good compatibility with the crystalline polypropylene resin and good transparency are preferable, and a hydrogenated block copolymer. A resin and a propylene-based copolymer resin are more preferable.

  As the hydrogenated block copolymer resin, a block copolymer of vinyl aromatic hydrocarbon and conjugated diene is preferable. Examples of vinyl aromatic hydrocarbons include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, and 1,1-diphenyl. Examples thereof include ethylene, 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 is 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- Examples include butadiene, 1,3-pentadiene, and 1,3-hexadiene. These may be used alone or in combination of two or more.

  As the propylene-based copolymer resin, a copolymer obtained from propylene and ethylene or an α-olefin having 4 to 20 carbon atoms is preferable. The content of the ethylene or α-olefin having 4 to 20 carbon atoms is preferably 6 to 30% by mass. Examples of the α-olefin having 4 to 20 carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-pentene and 1-decene. 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosane and the like.

  The propylene-based copolymer resin may be polymerized using a multi-site catalyst, a single-site catalyst, or any other catalyst. Further, a propylene copolymer in which the crystal / amorphous structure (morphology) of the polymer is controlled in nano order can also be used.

  The ethylene copolymer resin may be polymerized with any of a multisite catalyst, a single site catalyst, and other catalysts. Further, an ethylene copolymer in which the crystal / amorphous structure (morphology) of the polymer is controlled in nano order can be used.

When a polyethylene resin is used as the material for the inner layer, the density of the polyethylene resin is preferably 0.88 to 0.91 g / cm ³ . From the viewpoint of transparency with a high total light transmittance, it is preferably 0.91 g / cm ³ or less, and from the viewpoint of a high ratio of haze value or diffused light transmittance, 0.88 g / cm ³ or more is preferable.

  In addition, the resin sealing sheet has a structure in which one or more layers of the same component are laminated on both sides of a central layer (layer located at the center of the multilayer structure) so as to be symmetrical with respect to the central layer. You may have. As such a resin sealing sheet, for example, a resin sealing sheet composed of two surface layers (hereinafter sometimes referred to as “skin layer”) and three inner layers, Examples thereof include a resin-encapsulated sheet in which the surface layer is composed of the same component, and two inner layers adjacent to the surface layer (hereinafter sometimes referred to as “base layer”) are composed of the same component.

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

  In the resin-encapsulated sheet of the present embodiment, it is preferable that at least a part of the surface is embossed. By embossing, blocking can be prevented (blocking resistance). It does not specifically limit as a method of performing embossing, A well-known method can also be used. For example, an emboss shape can be formed by pressing an emboss roll on the surface of the softened resin sheet. From the viewpoint of emboss transfer accuracy, it is more preferable that the resin is formed into a sheet and then cooled and solidified, and the cooled and solidified resin sheet is heated to soften and then embossed. Here, “softening” (sometimes referred to as “softening”) refers to a state where the embossing roll can be pressed to form and is usually heated at a temperature about 10 ° C. higher than the melting point of the resin. Can be softened.

  The shape and size of the emboss are not particularly limited, and suitable conditions can be selected based on the use of the resin sealing sheet. There are no particular restrictions on the shape (pattern) of the emboss, but for example, stripes, textures, satin, leather, diamond lattices, synthetic leather-like, wrinkled patterns, quadrangular pyramid shapes (so-called pyramid patterns), quadrilateral frustum shapes (so-called trapezoidal shapes) Cup pattern) and the like. The embossed portion preferably has a small number of flat portions, and the ratio of the area of the convex portion due to embossing in the entire area of the embossed portion is more preferably 5 to 50%.

  The embossing may be performed on at least a part of one surface of the resin sealing sheet, but the embossing may be performed on both surfaces of the resin sealing sheet. From the viewpoint of blocking resistance of the resin-encapsulated sheet, the emboss depth is preferably 5 to 300 μm. Here, the emboss depth refers to the depth from the embossed convex portion to the concave portion.

  The resin sealing sheet may contain various additives as required. As additives, for example, antifogging agents, plasticizers, antioxidants, surfactants, ultraviolet absorbers, antistatic agents, crystal nucleating agents, lubricants, antiblocking agents, inorganic fillers, crosslinking modifiers, etc. are added. May be. For example, when it is necessary to maintain transparency and adhesiveness for a long period of time, it is preferable to use an ultraviolet absorber, an antioxidant, a discoloration inhibitor, or the like. When these additives are blended, the addition amount is not particularly limited, but is preferably 10% by mass or less, and more preferably 5% by mass or less, based on the total amount of resin to be added.

  Although the resin sealing sheet of this Embodiment can be used as a sealing material which seals various members, it is especially suitable as a resin sealing sheet for solar cells. Since the resin sealing sheet of this Embodiment is excellent in gap sealing property and creep resistance, it is suitable as a sealing material for sealing the power generation element of the solar cell.

<Solar cell module>
It can be set as a solar cell module using the resin sealing sheet of this Embodiment. FIG. 1 is a schematic cross-sectional view of one aspect of the solar cell module of the present embodiment. That is, the solar cell module 1 of the present embodiment includes a translucent insulating substrate 2, a back insulating substrate 3, and a power generation element 4 disposed between the translucent insulating substrate 2 and the back insulating substrate 3. And a resin sealing sheet 5 for sealing the power generating element 4.

(Translucent insulating substrate)
There are no particular restrictions on the light-transmitting insulating substrate, but because it is located on the outermost layer of the solar cell module, long-term reliability in outdoor exposure of the solar cell module, including weather resistance, water repellency, contamination resistance, mechanical strength, etc. It is preferable to provide performance for ensuring the performance. Moreover, in order to utilize sunlight effectively, it is preferable that it is a highly transparent member with a small optical loss.

  Examples of the material of the translucent insulating substrate include a resin film made of polyester resin, fluororesin, acrylic resin, cyclic olefin (co) polymer, ethylene-vinyl acetate copolymer, and a glass substrate. A glass substrate is preferable from the viewpoint of a balance between weather resistance, impact resistance, and cost.

  Particularly suitable as the resin film is a polyester resin excellent in transparency, strength, cost and the like, particularly a polyethylene terephthalate resin.

  A fluororesin having particularly good weather resistance is also preferably used. Specifically, tetrafluoroethylene-ethylene copolymer (ETFE), polyvinyl fluoride resin (PVF), polyvinylidene fluoride resin (PVDF), polytetrafluoroethylene resin (TFE), tetrafluoroethylene-6 Examples thereof include a fluorinated propylene copolymer (FEP) and a poly (trifluorotrifluoroethylene resin) (CTFE). Polyvinylidene fluoride resin is preferable from the viewpoint of weather resistance, but tetrafluoroethylene-ethylene copolymer is preferable from the viewpoint of achieving both weather resistance and mechanical strength. Moreover, it is preferable to perform a corona treatment and a plasma treatment to a translucent insulated substrate for the improvement of adhesiveness with the material which comprises other layers, such as a resin sealing sheet. In order to improve mechanical strength, it is also possible to use a sheet that has been subjected to stretching treatment, for example, a biaxially stretched polypropylene sheet.

  When a glass substrate is used as the translucent insulating substrate, the total light transmittance of light having a wavelength of 350 to 1400 nm is preferably 80% or more, and more preferably 90% or more. As such a glass substrate, it is common to use white plate glass with little absorption in the infrared part, but even blue plate glass has little influence on the output characteristics of the solar cell module if the thickness is 3 mm or less. Further, tempered glass can be obtained by heat treatment to increase the mechanical strength of the glass substrate, but float plate glass without heat treatment may be used. In order to suppress reflection on the light receiving surface side of the glass substrate, an antireflection coating may be applied.

(Back insulation substrate)
Although there is no restriction | limiting in particular as a back surface insulating substrate, Since it is located in the outermost layer of a solar cell module, various characteristics, such as a weather resistance and mechanical strength, are calculated | required similarly to the above-mentioned translucent insulating substrate. Therefore, you may comprise a back surface insulating board | substrate with the material similar to a translucent insulating board | substrate. That is, the above-described various materials that can be used in the light-transmitting insulating substrate can also be used in the back insulating substrate. In particular, a polyester resin and a glass substrate can be preferably used, and among these, a polyethylene terephthalate resin (PET) is more preferable from the viewpoint of weather resistance and cost.

  Since the back insulating substrate is not premised on the passage of sunlight, the transparency (translucency) required for the translucent insulating substrate is not necessarily required. Therefore, a reinforcing plate may be attached to increase the mechanical strength of the solar cell module or to prevent distortion and warpage due to temperature change. For example, a steel plate, a plastic plate, an FRP (glass fiber reinforced plastic) plate or the like can be preferably used.

  The back insulating substrate may have a multilayer structure composed of two or more layers. Examples of the multilayer structure include 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 what has such a structure, PET / alumina vapor deposition PET / PET, PVF (brand name: Tedlar) / PET / PVF, PET / AL foil / PET etc. are mentioned, for example.

(Power generation element)
The power generation element is not particularly limited as long as it can generate power using the photovoltaic effect of the semiconductor. For example, silicon (single crystal system, polycrystalline system, amorphous system), compound semiconductor (3- Group 5, 2-6, etc.) can be used, and among these, polycrystalline silicon is preferred from the viewpoint of balance between power generation performance and cost.

(Method for manufacturing solar cell module)
There is no restriction | limiting in particular as a manufacturing method of the solar cell module in this Embodiment, For example, it overlaps in order of a translucent insulated substrate / resin sealing sheet a / electric power generation element / resin sealing sheet b / back surface insulating substrate, and vacuum It can be produced by vacuum lamination using a laminator at 150 ° C. for 15 minutes. In particular, the resin sealing sheet of the present embodiment is preferably used at least as the resin sealing sheet a that fills the gap between the power generation element and the translucent insulating substrate. Since sunlight reaches the power generation element through the resin sealing sheet of the present embodiment, it can contribute to the improvement of power generation efficiency effectively.

  The thickness of each member in the solar cell module is not particularly limited, but the thickness of the translucent insulating substrate is preferably 3 mm or more from the viewpoint of weather resistance and impact resistance, and the thickness of the back insulating substrate is insulating. Preferably from the viewpoint of 75 μm or more, the thickness of the power generation element is preferably 140 to 250 μm from the viewpoint of balance between power generation performance and cost, and the thickness of the resin sealing sheet is preferably from the viewpoint of cushioning and sealing properties 250 μm or more.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples.

The resins used in this example are as follows.
(1) Ethylene-vinyl acetate copolymer Trade name “Ultrasen 751”, manufactured by Tosoh Corporation (VA (vinyl acetate content) = 28 mass%, MFR = 6.0 g / 10 min, melting point = 72 ° C.)
(2) Linear low density polyethylene Product name “Affinity EG8200G”, manufactured by Dow Chemical Company (density = 0.870 g / cm ³ , MFR = 5.0 g / 10 min, melting point = 63 ° C.)
(3) Linear low density polyethylene Product name “Affinity PF1140G”, manufactured by Dow Chemical Co., Ltd. (density = 0.897 g / cm ³ , MFR = 1.6 g / 10 min, melting point = 96 ° C.)

The melting point of the resin was measured according to JIS-K-7121.
The density of the resin was measured according to JIS-K-7112.
The melt flow rate (MFR; 190 ° C., 2.16 kg) of the resin was measured according to JIS-K-7210.

<Preparation of resin encapsulated sheet>
Using the resins shown in the table, the resin was melted using three extruders, the resin was melt-extruded into a tube shape from an annular die connected to the extruder, and the tube formed by melt extrusion was directed upward Thus, a melted resin sheet was obtained by the direct inflation method. This was cooled and solidified by blowing cold air to obtain a resin sheet. Next, the resin sheet that has been cooled and solidified is heated by an infrared heater, and the softened resin sheet is passed between a backup roll and an embossing roll to emboss (embossed shape: square frustum shape, embossed depth: 50 μm). ). The obtained resin-encapsulated sheet (embossed sheet) was subjected to a crosslinking treatment by irradiating it with an electron beam using an EPS-800 electron beam irradiation apparatus (manufactured by Nisshin High Voltage).

<Production of solar cell module>
Using the obtained resin encapsulating sheet, white glass with solar cell embossing manufactured by AGC Co., Ltd. (thickness: 3.2 mm × width 700 mm × length 1000 mm, sealing material surface has 150 μm emboss) as a transparent protective material, power generation A polycrystalline Si cell (6 inch square × thickness 200 μm) manufactured by E-TON as an element, and PVF (40 μm thickness) / PET (250 μm thickness) / PVF manufactured by Mitsubishi Aluminum Packaging as a back surface protective material (back sheet). A solar cell module was fabricated using (40 μm thickness). Six 6-inch polycrystalline cells are arranged in 16 sheets (4 rows x 4 sheets), transparent substrate (transparent protective material) / resin sealing sheet (a) / power generation element (200 μm) / resin sealing sheet (b) / back Sheets (back surface protective materials) are stacked in this order, and a solar cell module is manufactured by using a LM type vacuum laminating apparatus (manufactured by NPC) and vacuum laminating under a laminating condition of 150 ° C. residual heat for 5 minutes and pressing for 10 minutes. An evaluation test was conducted.

<Gel fraction>
In accordance with JIS-K-6696, the sample was boiled and extracted in p-xylene for 8 hours ± 5 minutes, and the ratio of the insoluble portion, which is the sample after extraction, to the sample before extraction was expressed by the following formula. The product was used as a measure of the gel fraction and the degree of crosslinking of the resin encapsulated sheet.
Gel fraction (mass%) = (mass of sample after extraction / mass of sample before extraction) × 100

<150 ° C hanging shrinkage>
The obtained resin sealing sheet was cut into a width of 20 mm and a length of 130 mm, and the thickness was 0.5 to 1.0 mm on the length of 100 mm in the central portion leaving both ends at 10 mm and 20 mm in the length direction. The front line was entered with an oil pen. Next, the end with 20 mm in the length direction is sandwiched between clips and suspended in an oven at 150 ° C., taken out 10 minutes after the oven temperature reading returns to 150 ° C., and the dimensional change from 100 mm between the surface lines Was measured, and the shrinkage rate was determined by the following equation.
Shrinkage rate (%) = 100-Length between front lines after test (mm)

<Evaluation for gap filling in power generation part>
LM50 type, laminated in the order of glass plate for solar cell (white glass 5cm x 10cm square: thickness 3mm) / resin sealing sheet (thickness 600μm) / power generation part / resin sealing sheet / solar glass plate by AGC Using a vacuum laminator (NPC), vacuum lamination was performed at 150 ° C., and the contact state of the power generation portion with the resin-encapsulated sheet of the single crystal silicon cell was visually confirmed.
Two tab wires (thickness 300 μm) were wired on each side of the single crystal silicon cell (thickness 200 μm) in the power generation portion. The power generation portion has a shape in which convex portions of 300 μm exist on a part of both surfaces of a cell having a thickness of 200 μm, and the entire power generation portion has a thickness of 200 μm to 800 μm.
Judgment of the contact state of the power generation part was made visually according to the following criteria.
◯: All contact portions of the single crystal silicon cell, the tab wire, and the resin encapsulating sheet as the power generation portion are good. (No gap)
X: A gap occurred in the contact portion between the single crystal silicon cell, which is a power generation portion, the tab wire, and the resin sealing sheet. Alternatively, the sealing sheet protruded from the edge of the glass plate by making it heat flow during lamination. (Poor appearance)

<Creep resistance evaluation>
Glass plate for solar cell (white glass 5 cm × 10 cm square manufactured by AGC, thickness 3 mm) / resin sealing sheet / power generation part (single crystal silicon cell (thickness 250 μm) / resin sealing sheet / solar cell glass plate Laminate one after another, vacuum laminate using LM50 type vacuum laminator (NPC), fix one glass plate of the laminated solar cell on the wall of the thermostat set at 85 ° C, let stand for 24 hours, and the other glass The deviation from the plate was measured.
A: The deviation of the glass plate is less than 3 mm.
X: The shift | offset | difference of a glass plate is 3 mm or more.

  Table 1 shows the production conditions and evaluation results of each Example and each Comparative Example.

  As shown in Table 1, it was confirmed that both the gap filling property and the creep resistance of the resin sealing sheet of each example were excellent. On the other hand, it was confirmed that at least one of the gap filling property and the creep resistance of the resin sealing sheet of each comparative example was defective.

  The resin sealing sheet according to the present invention has industrial applicability as a sealing material or the like for sealing various members such as a power generation element constituting a solar cell.

DESCRIPTION OF SYMBOLS 1 Solar cell module 2 Translucent insulating substrate 3 Back surface insulating substrate 4 Power generation element 5 Resin sealing sheet

Claims (6)

  A resin-encapsulated sheet subjected to a crosslinking treatment in which a shrinkage rate is 0 to 40% when the sheet is suspended at a temperature of 150 ° C. and a gel fraction is 0.1 to 2% by mass.   The resin sealing sheet according to claim 1, wherein the crosslinking treatment is performed by ionizing radiation irradiation.   Ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic acid ester copolymer, saponified ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-acrylic acid The resin-encapsulated sheet according to claim 1 or 2, comprising at least one resin selected from the group consisting of saponified ester copolymers and polyolefin resins.   The resin sealing sheet as described in any one of Claims 1-3 containing resin whose melting | fusing point is 100 degrees C or less.   It is a multilayer structure, The resin sealing sheet as described in any one of Claims 1-4. A translucent insulating substrate;
A back surface insulating substrate disposed opposite to the translucent insulating substrate;
A power generating element disposed between the translucent insulating substrate and the back insulating substrate;
The resin sealing sheet according to any one of claims 1 to 5, which seals the power generation element,
A solar cell module comprising:

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