JP2011176261A - Solar-cell sealing sheet and solar-cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar-cell sealing sheet that can improve energy efficiency when a solar-cell module is adopted and is superior in steam barrier properties, corrosion resistance in metals, such as a power generation cell, and producibility, and to provide a solar cell module which uses the sheet. <P>SOLUTION: The solar-cell sealing sheet contains a resin layer, including at least one kind of resin selected from a group consisting of ethylene-aliphatic carboxylic acid ester copolymer, ethylene copolymer containing glycidyl methacrylate, and polyolefin resin, and a coloring agent, and moreover, it substantially does not contain organic peroxides. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solar cell encapsulating sheet and a solar cell module using the solar cell encapsulating sheet.

  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. Since the energy generated by solar cell power generation does not emit carbon dioxide and other gases that cause global warming, research and development has been conducted as clean energy, and has attracted attention as industrial 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 for a long period of time by being exposed to wind and rain, and the power generation part is modularized by laminating a glass plate or back sheet to prevent moisture from entering from outside. It was intended to protect and prevent leakage. The member that protects the power generation portion uses transparent glass or transparent resin on the light incident side in order to ensure light transmission necessary for power generation. For the member on the opposite side, an aluminum foil called a back sheet, a polyvinyl fluoride resin (PVF), polyethylene terephthalate (PET), or a laminated sheet of a barrier coating such as silica is used. The power generation element is sandwiched between resin sealing sheets, the outside is further covered with glass or a back sheet, 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. (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) Transparency that does not hinder the incidence of sunlight. From this point of view, the resin-encapsulated sheet is made of an ethylene-vinyl acetate copolymer (hereinafter also abbreviated as “EVA”) with a UV absorber and a cup for improving adhesion to glass as a countermeasure against UV degradation. Additives such as organic peroxides for ring agents and cross-linking are blended to form a film by calendar molding or T-die casting. In view of being exposed to sunlight over a long period of 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. Thereby, transparency is maintained over a long period of time.

  As a method of modularizing solar cells with the above-mentioned resin sealing sheet, a power generation element such as glass / resin sealing sheet / crystalline silicon cell / resin sealing sheet / back sheet is stacked in this order, and a dedicated vacuum laminator is used. A method of using a molten resin encapsulated sheet as a module by performing a preheating step or a pressing step at a temperature equal to or higher than the melting temperature of the resin (for example, a temperature condition of about 150 ° C. in the case of EVA). In this method, first, the resin of the resin encapsulating sheet is melted in the preheating step, and in the subsequent pressing step, the molten resin is in close contact with the member in contact with itself and vacuum laminated. In this laminate, the crosslinking agent contained in the resin sealing sheet is thermally decomposed to promote EVA crosslinking. And it couple | bonds with the member which the coupling agent contained in the resin sealing sheet is contacting. Thereby, the outstanding adhesiveness with respect to glass, an electric power generation element, and a back sheet can be expressed.

  Patent Document 1 discloses a solar battery in which a cell for solar battery is sealed between an upper surface side transparent protective member and a rear surface side protective member via an adhesive film, and the adhesive film contains ethylene containing a colorant. A solar cell, which is a colored film formed by forming a vinyl acetate copolymer composition, is disclosed.

JP 2003-258283 A

  However, the conventional solar cell encapsulating sheet using EVA or the like has a problem that it is vulnerable to moisture because of its high water vapor permeability. In particular, when the solar cell module is used in a humid environment, water vapor flows from the end of the solar cell module and adheres to a power generation part such as a power generation element, resulting in a malfunction.

  In addition, when an organic peroxide is included for the purpose of improving the heat resistance of the solar cell encapsulating sheet, in order to prevent decomposition (cleavage) of the organic peroxide when the sheet is heated, There is a problem that the sheet temperature cannot be sufficiently raised during embossing, and the productivity of the sheet is lowered. And it is necessary to perform a long-time heat curing process. Furthermore, there is a problem that gas is generated by thermal decomposition of the organic peroxide, resulting in corrosion damage of the vacuum pump and oil contamination.

  In addition, by using a colored EVA film, even if it is intended to enhance the light reflectance improvement effect and improve the power generation efficiency, there is an inflow of moisture due to the high water vapor permeability, resulting in a decrease in the power generation rate of the cell and functional failure There is a problem of inviting.

  The present invention has been made in view of the above circumstances, can improve the energy efficiency of a solar cell module, is excellent in water vapor barrier properties, corrosion resistance of metals such as power generation cells, and further produced. The main object is to provide a solar cell encapsulating sheet excellent in performance and a solar cell module using the same.

  As a result of intensive studies to solve the above problems, the present inventors are selected from the group consisting of an ethylene-aliphatic carboxylic acid ester copolymer, an ethylene copolymer containing glycidyl methacrylate, and a polyolefin resin. It has been found that the above problem can be solved by providing a solar cell encapsulating sheet having at least a resin layer containing at least one resin and a colorant and substantially not containing an organic peroxide. The present invention has been completed.

That is, the present invention is as follows.
[1]
At least one resin selected from the group consisting of an ethylene-aliphatic carboxylic acid ester copolymer, an ethylene copolymer containing glycidyl methacrylate, and a polyolefin resin;
A colorant;
A solar cell encapsulating sheet that has at least a resin layer that contains no organic peroxide.
[2]
The solar cell encapsulating sheet according to [1], wherein the resin layer contains at least a polyethylene resin.
[3]
The solar cell encapsulating sheet according to [1] or [2], wherein the resin layer contains a polyethylene resin having a density of 0.92 g / cm ³ or less.
[4]
The colorant is blended in a master batch using at least one resin selected from the group consisting of an ethylene-aliphatic carboxylic acid ester copolymer, an ethylene copolymer containing glycidyl methacrylate, and a polyolefin resin as a carrier resin. The solar cell encapsulating sheet according to any one of [1] to [3].
[5]
The solar cell encapsulating sheet according to [4], wherein the carrier resin has a melt tension (MT) at 160 ° C. of 50 g or less.
[6]
The solar cell encapsulating sheet according to any one of [1] to [5], wherein the resin layer is subjected to a crosslinking treatment by ionizing radiation irradiation.
[7]
The solar cell encapsulating sheet according to any one of [1] to [6], wherein embossing is performed on at least a part of the surface of the resin layer.
[8]
The solar cell encapsulating sheet according to [7], wherein a depth of the embossed shape formed in the resin layer is 30 μm or more.
[9]
The solar cell module containing the solar cell sealing sheet as described in any one of [1]-[8].

  According to the present invention, a solar cell encapsulating sheet that can improve energy efficiency when used as a solar cell module, is excellent in water vapor barrier properties, corrosion resistance of metals such as power generation cells, etc., and is also excellent in productivity. And a solar cell module using the same.

It is the schematic which shows an example of the apparatus used for manufacture of the solar cell sealing sheet in this Embodiment. It is the schematic which shows an example of the emboss shape of the solar cell sealing sheet of this Embodiment. FIG. 3 is a cross-sectional view taken along line A-A ′ of FIG. 2. It is the schematic which shows another example of the embossed shape of the solar cell sealing sheet of this Embodiment. It is sectional drawing which follows the B-B 'line of FIG.

  Hereinafter, modes for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail with reference to the drawings as necessary. The following embodiments are exemplifications for explaining the present invention, and are not intended to limit the present invention to the following contents. And this invention can be deform | transformed suitably and implemented within the range of the summary. 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.

  The solar cell encapsulating sheet of the present embodiment is an ethylene-aliphatic carboxylic acid ester copolymer, an ethylene copolymer containing glycidyl methacrylate, and at least one resin selected from the group consisting of polyolefin resins, A solar cell encapsulating sheet having at least a resin layer containing a colorant and substantially not containing an organic peroxide.

  The resin layer is made of an ethylene-aliphatic carboxylic acid ester copolymer, an ethylene copolymer containing glycidyl methacrylate, and a polyolefin-based polymer, from the viewpoint of ensuring good transparency, flexibility, adhesion and handling properties of the adherend. It contains at least one resin selected from the group consisting of resins.

  Conventionally used resin-encapsulated sheets using EVA or the like use a resin having a carboxylic acid group as a terminal group, and therefore have a problem that water vapor permeability is large and water vapor easily flows in and is weak against moisture. In EVA or the like, the side chain portion is easily decomposed and detached. Further, since the side chain portion tends to be an acidic group or a polar group, it tends to easily retain moisture. As a result, when it is set as the solar cell sealing sheet using EVA, it becomes easy to cause a withstand voltage property or a fall of insulation. On the other hand, the solar cell encapsulating sheet of the present embodiment is at least one resin selected from the group consisting of an ethylene-aliphatic carboxylic acid ester copolymer, an ethylene copolymer containing glycidyl methacrylate, and a polyolefin resin. Therefore, polarity can be suppressed and excellent insulation can be obtained. And it is excellent in water vapor | steam barrier property, and to-be-sealed things (power generation cell etc.) can be reliably sealed even under high temperature, high humidity. In particular, when the crosslinking treatment is performed, these advantages become more remarkable. From this point of view, polyolefin resins are preferable among the above-described resins. By using the polyolefin-based resin, the effect of the present embodiment becomes more remarkable.

  The ethylene-aliphatic carboxylic acid ester copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and at least one monomer selected from an aliphatic 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.

  As said aliphatic carboxylic acid ester, the ester bond of C1-C8 alcohol, such as acrylic acid and methacrylic acid, methanol, ethanol, etc. is used suitably, for example, and copolymerization with these is mentioned. These copolymers may be multi-component copolymers obtained by copolymerizing three or more monomers.

  The ethylene copolymer containing glycidyl methacrylate refers to an ethylene copolymer and an ethylene terpolymer with glycidyl methacrylate having an epoxy group as a reaction site. For example, ethylene-glycidyl methacrylate copolymer, ethylene-glycidyl methacrylate-vinyl acetate copolymer And an ethylene-glycidyl methacrylate-methyl acrylate copolymer. Since the above compounds have high reactivity of glycidyl methacrylate, they can exhibit stable adhesion, and have a low glass transition temperature and tend to have good flexibility.

  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 viewpoints of corrosiveness and water vapor barrier properties. 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 layer preferably contains a polyethylene resin having a density of 0.92 g / cm ³ or less. By using a polyethylene resin having a density of 0.92 g / cm ³ or less, the transparency can be greatly improved. The lower limit of the density is preferably 0.86 g / cm ³ or more, and more preferably 0.87 g / cm ³ or more, from the viewpoint of the productivity of the polyethylene resin. When a high-density polyethylene resin is used in combination, the transparency can be further improved by adding a low-density polyethylene resin at a ratio of, for example, about 30% by mass.

Furthermore, it is more preferable to use linear low density polyethylene having a density of 0.92 g / cm ³ or less. By using linear low density polyethylene, the polarity can be further suppressed, and excellent insulating properties can be obtained. And it is excellent in water vapor | steam barrier property, and can seal a to-be-sealed object reliably under high temperature and high humidity. In particular, when the crosslinking treatment is performed, these advantages become more remarkable.

  From the viewpoint of workability of the solar cell encapsulating sheet, the linear low density polyethylene preferably has an MFR (190 ° C., 2.16 kg) of 0.5 to 30 g / 10 minutes, and 0.8 to 30 g / 10. It is more preferable that it is a minute, and it is still more preferable that it is 1.0-25 g / 10min.

  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.

  The resin layer contains substantially no organic peroxide. Therefore, 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, “substantially free of organic peroxide” means a content in a range that does not hinder the effects of the present embodiment, specifically, the content in the resin layer is 0.5% by mass or less. The content is preferably 0.2% by mass or less, more preferably 0.1% by mass, and still more preferably 0% by mass. When the content of the organic peroxide is large, the back sheet may swell due to a gas generated from the organic peroxide. Examples of such organic peroxides include 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, and n-butyl. Examples include -4,4-bis (t-butylperoxy) valerate, 2,2-bis (t-butylperoxy) butane, and the like.

  The resin layer of the solar cell encapsulating sheet is preferably subjected to a crosslinking treatment. Thereby, good heat resistance can be imparted to the sheet without separately performing a long-time heat curing step. Furthermore, the crosslinking treatment is preferably performed by irradiating with ionizing radiation. In this embodiment, since it is not necessary to use an organic peroxide for the crosslinking treatment, gas generation due to thermal decomposition of the organic peroxide is small, and corrosion damage such as a vacuum pump and oil stains are suppressed. be able to. In the present embodiment, “crosslinking treatment” refers to a resin layer in a state where the gel fraction is preferably 3% by mass or more as a result of physical or chemical crosslinking of the polymer constituting the resin.

  In the solar cell encapsulating sheet in the present embodiment, the gel fraction in the thickness direction of the sheet is appropriately controlled by the irradiation intensity (acceleration voltage) of ionizing radiation and the irradiation density. The irradiation intensity (acceleration voltage) indicates how deeply 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 method of crosslinking by irradiating with ionizing radiation include a method of irradiating with ionizing radiation such as α ray, β ray, γ ray, neutron beam, electron beam and the like. The accelerating voltage of ionizing radiation can be appropriately adjusted according to the resin layer subjected to the crosslinking treatment, and the irradiation dose of ionizing radiation varies depending on the resin used, but is generally less than 3 kGy, It tends to be difficult to uniformly crosslink the entire stop sheet.

  A gel fraction becomes like this. Preferably it is 3-70 mass%, More preferably, it is 3-60 mass%, More preferably, it is 3-50 mass%. By setting the gel fraction within the above range, it is possible to further improve the performance of sealing the level difference of the objects to be sealed such as solar cells and wiring (gap filling property), and to improve creep resistance. It can be demonstrated. In addition, even if it is a case where a solar cell sealing sheet has any structure of the single layer structure or multilayer structure mentioned later, the said gel fraction is the average gel fraction (all layer gel of the whole solar cell sealing sheet). Value).

The gel fraction of the solar cell encapsulating sheet can be obtained from the following formula by extracting the solar cell encapsulating sheet in boiling p-xylene for 12 hours and from the proportion of the insoluble portion.

Gel fraction (mass%) = (sample weight after extraction / sample weight before extraction) × 100

  The resin layer constituting the solar cell encapsulating sheet in the present embodiment may further include an ionizing radiation decay type resin. Here, the ionizing radiation decay type resin refers to a resin having a property of decaying by irradiating 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 group. Examples include at least one selected from the group consisting of a carboxyl 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.

  The ionizing radiation decay type resin is not particularly limited, and is selected from the group consisting of, for example, polypropylene, polyisobutylene, poly α-methylstyrene, tetrafluoroethylene, polymethyl methacrylate, polyacrylamide, polymethyl glycidyl methacrylate, and cellulose. And at least one of them.

  The resin constituting the solar cell encapsulating sheet may contain an ionizing radiation cross-linking collapsing resin having both a crosslinkable site and a disintegrating site. 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 refers to an ethylene copolymer and an ethylene terpolymer with glycidyl methacrylate having an epoxy group as a reaction site. For example, ethylene-glycidyl methacrylate copolymer, ethylene-glycidyl methacrylate-vinyl acetate copolymer And an ethylene-glycidyl methacrylate-methyl acrylate copolymer. Since the above-mentioned compound has high reactivity of glycidyl methacrylate, it can exhibit stable adhesiveness, tends to have a low glass transition temperature and good flexibility.

  The solar cell encapsulating 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 solar cell encapsulating sheet has a multilayer structure, the surface layer of the solar cell encapsulating sheet is referred to as a “surface layer”, and the others are referred to as “inner layers” (in the case of three or more layers). That is, the layers forming both surfaces of the solar cell encapsulating 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 solar cell encapsulating sheet has a single layer structure, ethylene-aliphatic carboxylic acid ester copolymer and glycidyl methacrylate are used from the viewpoint of ensuring good transparency, flexibility, adhesion and handling properties of the adherend. The resin layer includes at least one resin selected from the group consisting of an ethylene copolymer and a polyolefin-based resin, and a colorant.

  If the resin layer constituting the solar cell encapsulating sheet contains saponified ethylene-vinyl acetate copolymer or saponified ethylene-vinyl acetate-acrylate copolymer as an adhesive resin, the saponification The degree and the content can be adjusted as appropriate, whereby the adhesiveness with the object to be sealed can be controlled. From the viewpoint of adhesiveness and optical properties, the content of the saponified ethylene-vinyl acetate copolymer and saponified ethylene-vinyl acetate-acrylate copolymer in the resin layer is 3 to 60% by mass. Preferably, it is 3-55 mass%, More preferably, it is 5-50 mass%.

(Multilayer structure)
When the resin layer of the solar cell encapsulating sheet has a multilayer structure, any layer is selected from the group consisting of an ethylene-aliphatic carboxylic acid ester copolymer, an ethylene copolymer containing glycidyl methacrylate, and a polyolefin resin. Any resin layer containing at least one selected resin and a colorant may be used.

  A resin layer containing at least one of ethylene-vinyl acetate copolymer saponified product, ethylene-vinyl acetate-acrylic acid ester copolymer saponified product, and ethylene-glycidyl methacrylate copolymer saponified product as an adhesive resin It is preferably 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 saponified product described above. However, from the viewpoint of ensuring good transparency, flexibility, adhesion and handling properties of the adherend, the saponified product and the ethylene-vinyl acetate copolymer are used. A layer comprising a mixed resin of at least one resin selected from the group consisting of a polymer, an ethylene-aliphatic unsaturated carboxylic acid copolymer, an ethylene-aliphatic unsaturated carboxylic acid ester copolymer, and a polyolefin resin It is preferable that 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 still more preferable.

  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 ethylene-aliphatic unsaturated carboxylic acid copolymer include an ethylene-acrylic acid copolymer (hereinafter abbreviated as “EAA”) and an ethylene-methacrylic acid copolymer (hereinafter, “EMAA”). Abbreviated).

  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 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 alcohols, 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.

  As the polyolefin resin, the above-described polyolefin resin can be used, and examples thereof include a polyethylene resin, a polypropylene resin, and a polybutene resin.

  When the solar cell encapsulating sheet has a multi-layer structure, the ionizing radiation-disintegrating resin is preferably contained in a layer (at least one surface layer) that comes into contact with an object to be encapsulated. The ability to seal steps such as solar cells and wiring without gaps (gap filling property) by including ionizing radiation-disintegrating resin in the layer of the solar cell sealing sheet that comes into contact with the object to be sealed It tends to be good.

  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. More preferably, it is 7-70 mass%, More preferably, it is 8-60 mass%.

  When the layer in contact with the object to be sealed contains an ionizing radiation-disintegrating resin, the gel fraction of the layer (surface layer) in contact with the object to be sealed is preferably less than 3% by mass, more preferably 2% by mass. The content is 0.1% by mass or more, more preferably 1% by mass or less and 0.1% by mass or more. If 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 if it is 0.1% by mass or more, the resin can be used even in a high temperature state such as summer. It tends to be stable without melting and the material to be sealed flowing.

In the case of multiple layers, the density of the layer in contact with the object to be sealed is preferably 0.880 g / cm ³ or more from the viewpoint of blocking. From the viewpoint, it is preferably 0.925 g / cm ³ or less. 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 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 solar cell encapsulating sheet from the viewpoint of ensuring good adhesion. 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 contained in 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 these, hydrogenated block copolymer resins, propylene copolymer resins, and ethylene copolymer resins are preferable from the viewpoint of good compatibility with crystalline polypropylene resins and good transparency. An added block copolymer 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-based copolymer in which the crystal / amorphous structure (morphology) of the polymer is controlled in nano order can 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 0.860 to 0.925 g / cm ³ . From the viewpoint of transparency, 0.925 g / cm ³ or less is preferable, and from the viewpoint of manufacturability of the polyethylene resin, 0.860 g / cm ³ or more is preferable.

  The solar cell encapsulating sheet may have 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. As such a solar cell encapsulating sheet, for example, it is a solar cell encapsulating sheet composed of two surface layers (hereinafter sometimes referred to as “skin layer”) and three inner layers. Examples include a solar cell encapsulating sheet in which the surface layer of the layers 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 solar cell encapsulating sheet having the above structure, the thickness of the surface layer is preferably 5 to 40% with respect to the total thickness of the solar cell encapsulating sheet, and the thickness of the base layer is the solar cell. It is preferable that it is 50 to 90% with respect to the film thickness of the whole sealing sheet, and the film thickness of the inner layer (hereinafter sometimes referred to as “core layer”) sandwiched between the base layers is solar cell sealing. It is preferable that it is 5 to 40% with respect to the film thickness of the entire stop sheet.

  The MFR (190 ° C., 2.16 kg) of the resin constituting the solar cell encapsulating sheet is preferably 0.5 to 30 g / 10 minutes from the viewpoint of ensuring good workability, and 0.8 to 30 g. / 10 min is more preferable, and 1.0 to 25 g / 10 min is still more preferable. When the solar cell encapsulating sheet has a multilayer structure of two or more layers, the MFR of the resin constituting the inner layer (base layer or core layer) may be lower than the MFR of the surface layer from the viewpoint of workability of the solar cell encapsulating sheet. preferable. Thereby, the workability of a solar cell sealing sheet can be improved more.

  The resin layer further contains a colorant. Thereby, the light reflectance of a solar cell sealing sheet can be improved. It does not specifically limit as a coloring agent, The coloring agent which can be used together with resin used as a material of a resin layer can be used. The colorant is not particularly limited as long as it can color the resin, and known ones can also be used. Preferable specific examples include at least one selected from the group consisting of titanium oxide, calcium carbonate, carbon black, glass beads, ultramarine, phthalocyanine, and an azo compound. Among these, titanium oxide is preferable from the viewpoint of cost and kneading with a master batch.

  When the additive including the colorant contains a porous substance, a corrosive gas (for example, a decomposition product of the resin in the porous portion, for example, if the resin-encapsulated sheet mainly composed of EVA or the like that is conventionally used) , Acetic acid gas, etc.) are trapped and tend to stay in the solar cell encapsulating sheet. As a result, corrosion is more advanced. However, since the solar cell encapsulating sheet of the present embodiment uses an ethylene-aliphatic carboxylic acid ester copolymer, an ethylene copolymer containing glycidyl methacrylate, or a polyolefin resin, the colorant used is porous. It also has the advantage that no corrosive gas is generated even if it contains substances. From this viewpoint, the colorant preferably contains a porous material. This advantage becomes more remarkable when the additive including the colorant contains a porous material.

  The content of the colorant in the resin layer is not particularly limited, and can be appropriately selected in consideration of the light transmittance and light reflectance of the resin layer, etc., from the viewpoint of the dispersion condition and the color condition at the time of kneading, It is preferable that it is 0.1-10 mass%.

  The method for adding the colorant is not particularly limited, and a known method can be adopted. However, it is preferable to use a colorant that has been previously masterbatched with a resin. More specifically, the colorant contains at least one resin selected from the group consisting of an ethylene-aliphatic carboxylic acid ester copolymer, an ethylene copolymer containing glycidyl methacrylate, and a polyolefin resin as a carrier resin ( It is preferable to be blended in a master batch that may be called “carrier resin” or the like. By using the colorant thus masterbatched, the dispersibility of the colorant can be further improved.

  It is more preferable that the melt tension at 160 ° C. of the carrier resin is 50 g or less. By using a resin having such a melt tension, the kneadability between the colorant and the resin can be further improved.

  In the solar cell encapsulating sheet in the present embodiment, various additives such as an antifogging agent, a plasticizer, an antioxidant, a surfactant, an ultraviolet absorber, an antistatic agent, as long as the characteristics are not impaired. A crystal nucleating agent, a lubricant, an antiblocking agent, an inorganic filler, a crosslinking regulator and the like may be added.

  A coupling agent may be further added to the solar cell encapsulating sheet for the purpose of ensuring stable adhesiveness. 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% by mass, more preferably 0.03 to 4% by mass, based on the total mass of the resin layer to which the coupling agent is added. More preferably, the content is 0.05 to 3% by mass.

  As a kind of coupling agent, the substance which provides the resin layer with the favorable adhesiveness to a photovoltaic cell or glass is preferable, for example, an organic silane compound, an organic silane peroxide, an organic titanate compound etc. are mentioned. These coupling agents may be added by a known addition method such as injection and mixing into a resin in an extruder, mixing and introducing into an extruder hopper, masterbatching, mixing and adding. it can. However, when passing through an extruder, the function of the coupling agent may be hindered by heat, pressure, etc. in the extruder, so the amount of addition needs to be adjusted appropriately depending on the type of coupling agent.

  The type of the coupling agent may be appropriately selected in consideration of the transparency and dispersion state of the solar cell encapsulating 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.

  An ultraviolet absorber, an antioxidant, a discoloration preventing agent, or the like can be added to the solar cell encapsulating 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, or the like. When these additives are added to the resin, the amount added is preferably 10% by mass or less, 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, and the like. Examples of the antioxidant include phenol-based, sulfur-based, phosphorus-based, amine-based, hindered phenol-based, hindered amine-based, and hydrazine-based antioxidants.

  These ultraviolet absorbers, antioxidants, discoloration inhibitors and the like are preferably added in an amount of 0 to 10% by mass, more preferably 0 to 5% by mass, in the resin constituting the solar cell encapsulating sheet. When added to an ethylene-based resin, adhesiveness can be further imparted by mixing a resin having a silanol group into a master batch. The addition method is not particularly limited, and examples thereof include a method of adding to a molten resin in a liquid state, directly kneading and adding to a target resin layer, and applying after sheeting.

  The solar cell encapsulating 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 is less than 50 μm, there is a tendency for problems in durability and strength from the viewpoint of structurally poor cushioning properties or workability. On the other hand, when the thickness exceeds 1500 μm, there is a tendency that a problem of reducing productivity and adhesion is caused.

  The resin layer is preferably embossed. Blocking can be prevented by embossing.

  The embossing method is not particularly limited, and a known method can be used. After forming the resin into a sheet shape, the resin sheet is once cooled and solidified, and the cooled and solidified resin sheet is heated and softened. Later, it can be embossed.

  The method for forming the resin into a sheet is not particularly limited, and examples thereof include a T-die method, a circular die method, and a calendar method. The T-die method is suitable for forming a resin film having high fluidity (high melt flow). The circular die method is excellent in that a resin having a relatively low melt flow can be formed. Among these, the T die method and the circular die method are preferable from the viewpoint of stably forming a multilayered sheet, and the circular die method is more preferable from the viewpoint of equipment cost.

  As an example of a specific film forming method, first, a resin used as a raw material for a solar cell encapsulating sheet, and other additives as necessary, are mixed with a known mixing apparatus (eg, Henschel mixer, ribbon blender, tumbler blender). Etc.) in advance. Subsequently, after melt-kneading with a screw extruder such as a single-screw extruder or a twin-screw extruder, a kneader, or a mixer, the kneaded product is extruded into a sheet form from a T-die, a circular die, a calendar die, or the like. At this time, single-layer extrusion or lamination extrusion may be used.

  Next, the melt extruded into the sheet is once cooled and solidified. Examples of the cooling method include a method of directly contacting a cooling medium such as cold air or cooling water, a method of contacting a roll or press machine cooled with a refrigerant, and a method of contacting a roll or press machine cooled with a refrigerant. , Which is preferable in terms of excellent film thickness control.

  Although there is no restriction | limiting in particular as temperature at the time of cooling solidification, It is preferable that it is below melting | fusing point-5 degreeC of resin used as a material of a sheet | seat, More preferably, it is room temperature-melting | fusing point-5 degreeC, More preferably, room temperature-melting | fusing point- 10 ° C. At this time, in order to suppress the shrinkage rate of the sheet, it is preferable to slowly cool (slow cooling) in order to relax the flow orientation during film formation. As a cooling method, a method of cooling by directly immersing in a coolant such as water may be used, but from the viewpoint of reducing the shrinkage of the sheet, a method of gradually cooling with a temperature-controlled roll or a method of gradually cooling with air cooling is preferable. Even when a refrigerant is used, a method of spraying a mist-like mist and gradually cooling it is preferable. Here, the “melting point” in the case where a plurality of resins are used as the material of the sheet, such as when the sheet has a multilayer structure, means the melting point of the resin component contained most in the resin constituting the sheet. The melting point of the resin can be measured using a differential scanning calorimeter.

  Next, after the cooled and solidified resin sheet is heated and softened, the sheet surface is embossed. Here, “softening” (hereinafter, also referred to as “softening”) refers to a state in which an 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.

  It does not specifically limit as a heating method for softening a resin sheet, For example, infrared heating, a heating roll, hot air heating etc. are mentioned. Among these, infrared heating is excellent in that it can efficiently heat the sheet to the center and it is easy to add deep embossing. Further, the heating roll and hot air heating are advantageous in that the temperature of the surface to be embossed can be increased at a stretch, and the embossed shape can be shaped while preventing the sheet from stretching and suppressing the shrinkage rate. Examples of infrared heating include far infrared and near infrared, and an optimum infrared wavelength for achieving a desired temperature may be selected. The said heating method may be used independently and may use 2 or more types together.

  The heating temperature when the resin sheet is softened by heating is not particularly limited, but when deep embossing is used, it is preferably near the melting point of the resin used. When shallow embossing is added, it is preferably about 3 ° C. lower than the melting point. From the viewpoint of reducing the residual stress in order to suppress the shrinkage rate, it is important not to stretch the sheet in the machine flow direction when softening, but if the heating temperature is higher than the melting point + 20 ° C., the sheet It tends to be stretched in the flow direction. Accordingly, the heating temperature at the time of softening is preferably from melting point -5 ° C to melting point + 20 ° C, more preferably from melting point -3 ° C to melting point + 20 ° C.

  As a heating method, first, after pre-heating by being in close contact with a heating roll or the like, main heating may be performed by infrared heating or the like. After preheating, the main heating at a higher temperature has the advantage that a softened state that can sufficiently shape embossing can be achieved quickly. If it is not preheated, the temperature does not rise easily, so that shaping may be difficult, or the temperature may not be uniform and may become uneven. In addition, preheating has an advantage of preventing the sheet from being stretched and the shrinkage rate from being increased because the viscosity of the sheet does not drop extremely. As a heating method, after preheating with a heating roll having a temperature relatively lower than the melting point, immediately before the embossing roll, the surface is softened by heating with hot air or a specific infrared wavelength, and embossing is performed by pressing with an embossing roll. It is preferable to shape the shape. The preheating temperature is preferably a melting point of the resin from −20 ° C. to a melting point, more preferably from a melting point of −20 ° C. to a melting point of −3 ° C.

  It is preferable that the preheating roll has a non-adhesive surface because it tends not to stretch when the softened sheet is peeled off and tends to have a low shrinkage rate. Non-adhesive processing can be performed by fluorine-based, silicon-based or glass-based coating or surface coating.

  A shorter length of the preheating roll and the embossing roll is preferable because the shrinkage rate of the sheet tends to be reduced. Furthermore, when a softened sheet is peeled off from the preheating roll, a thin rotating roll (separating roll) is installed so that the sheet can be peeled off from the preheating roll without stretching the sheet, so that the shrinkage rate is further reduced. There is a tendency. At this time, it is preferable that the separating roll is also non-adhesive processed like the preheating roll.

  The surface of the resin sheet softened by heating can be embossed according to the form of the final solar cell encapsulating sheet. For example, when embossing treatment is performed on both sides, at least one pair of two embossing rolls is used. When embossing treatment is performed on one surface, at least one pair of embossing rolls and backup rolls are used. By passing the formed resin sheet in a pressurized state, the shape of the embossing roll can be transferred to the sheet surface.

  The shape and size of the embossed portion of the embossed part are not particularly limited, and suitable conditions can be selected based on the use of the solar cell encapsulating sheet. The shape (pattern) of the embossing is not particularly limited, but for example, stripes, textures, pearskin, crests, diamond lattices, synthetic leather-like, wrinkled patterns, so-called pyramid shapes (so-called pyramid patterns; see FIGS. 2 and 3), Examples include a quadrangular frustum shape (so-called trapezoidal cup pattern; see FIGS. 4 and 5). 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%.

  Although the embossing should just be given to a part of at least one side of the solar cell sealing sheet, the embossing may be given to both sides of the solar cell sealing sheet. From the viewpoint of blocking resistance of the solar cell encapsulating sheet, the emboss depth is preferably 5 μm or more and 300 μm or less, and more preferably 30 μm or more and 300 μm or less. Here, the emboss depth refers to the depth from the embossed convex portion to the concave portion. For example, in the case of the square pyramid-shaped embossing shown in FIGS. 2 and 3, D1 is the embossing depth, and in the case of the square frustum-shaped embossing shown in FIGS. 4 and 5, D2 is the embossing depth. .

  Before and after the step of heating and softening the cooled and solidified resin sheet, tension control may be performed so that the softened resin sheet does not stretch. By performing tension control, stretching of the softened sheet is suppressed and the shrinkage rate tends to be lowered. The tension at the time of tension control is not particularly limited, but is usually 0.1 to 80 N, more preferably 0.1 to 70 N, and still more preferably 0.1 to 60 N with respect to 1 m of the sheet width.

  As a tension control method, for example, before and after the process of heating and softening the cooled and solidified resin sheet, it is restrained by pinching with at least one pair of pinch rolls, at least one pair of backup rolls and embossing rolls. And the like.

  FIG. 1 is a schematic view showing an example of an apparatus used for manufacturing a solar cell encapsulating sheet in the present embodiment. An example of the apparatus in the process of heating and softening the resin sheet which solidified by cooling, and the process of embossing is shown conceptually. In the apparatus shown in FIG. 1, the cooled and solidified resin sheet 1 is preheated in close contact with a steam heating type preheating roll 2 and further heated by an infrared heater 3 to be softened. Next, the softened resin sheet is embossed on the surface of the sheet by a metal embossing roll 6 in a state where the softened resin sheet is pressed by a backup roll 5 made of silicon rubber. Before and after the step of softening the resin sheet by heating, tension control is performed by the pinch roll 4, the backup roll 5, and the embossing roll 6 so that the softened resin sheet does not stretch.

  Furthermore, the solar cell encapsulating sheet that has been subjected to embossing can be subjected to post-treatments such as heat setting for dimensional stabilization, corona treatment, plasma treatment, lamination with other types of solar cell encapsulating sheets, etc. May be performed.

  Moreover, it can select whether the crosslinking process (irradiation of ionizing radiation etc.) with respect to a resin layer is performed as a pre-process or a post-process of an embossing process according to each case.

  The solar cell encapsulating sheet of the present embodiment has a feature that the residual stress is small and shrinkage hardly occurs as compared with the solar cell encapsulating sheet obtained by the conventional method. The shrinkage ratio of the solar cell encapsulating sheet is preferably 30% or less, more preferably 25%, still more preferably 5% or less, and particularly preferably substantially 0%. Here, the shrinkage rate is a value obtained by immersing the solar cell encapsulating sheet in warm water at 70 ° C. for 5 minutes and then measuring the change in the length of the sheet in the machine flow direction with a ruler.

[Use of solar cell encapsulating sheet]
The solar cell encapsulating sheet in the present embodiment is useful as a solar cell encapsulant for protecting members such as elements constituting the solar cell, and is a glass plate, acrylic or polycarbonate constituting the solar cell. Stable and strong adhesion to resin plates such as By using the solar cell encapsulating sheet in the present embodiment, various members having irregularities such as the solar cell glass itself, various wirings, and power generation elements can be reliably sealed without gaps. In particular, since the solar cell encapsulating sheet in the present embodiment contains a colorant, it is suitable as the encapsulating sheet on the back sheet side. Thereby, since a light reflectance can be improved more, the energy efficiency of a solar cell module can be improved.

  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 materials used in the examples and comparative examples are as follows.

<Resin>
(1) Ethylene-vinyl acetate copolymer (EVA)
2805 made by ARUKEMA
751 manufactured by Tosoh Corporation
(2) Ethylene-vinyl acetate-glycidyl methacrylate copolymer (EVA-GMA copolymer)
Bond First 7B manufactured by Sumitomo Chemical Co., Ltd.
(3) Linear very low density polyethylene (VL)
Engage EG8100 manufactured by Dow Chemical
Dow Chemical Engagement EG8200
Affinity PL1880G manufactured by Dow Chemical
Affinity PF1140G manufactured by Dow Chemical
Affinity KC8852 manufactured by Dow Chemical
VL200 made by Sumitomo Chemical
Ultra Zex 1020 manufactured by Mitsui Chemicals, Inc.
(4) Linear low density polyethylene (LL)
FZ201 manufactured by Sumitomo Chemical Co., Ltd.
F208-3 manufactured by Sumitomo Chemical Co., Ltd.

<Colorant>
Titanium oxide Ishihara Sangyo R-855 (sulfuric acid method titanium oxide (rutile type), average particle size 0.26 μm)

<Organic peroxide>
Lupazole 101 from Arkema Yoshitomi

<Transparent substrate>
(1) Glass AGC company solar cell glass White plate with glass embossed thickness 3.2mm

<Back sheet>
Mitsubishi Aluminum Packaging Back Sheet Polyvinyl Fluoride (Trade Name: Tedlar) / PET / Polyvinyl Fluoride Back Sheet

<Power generation element>
E-TON manufactured crystalline silicon cell thickness 250μm

<Gel fraction>
Regarding the gel fraction, a sample was extracted for 12 hours in boiling p-xylene, and the proportion of the insoluble portion was determined by the following formula.
Gel fraction (mass%) = (sample weight after extraction / sample weight before extraction) × 100
In the case of multiple layers, a sheet having the same thickness and resin composition was collected in advance by the same method, and the sheet subjected to crosslinking treatment under the same conditions was used as a gel fraction measurement sample.

<Resin density>
It measured based on JIS-K-7112.

<Melt flow rate (MFR) and melt tension (MT) of resin>
MFR (190 degreeC, 2.16 kg) was measured based on JIS-K-7210. The melt tension was measured using a Toyo Seiki Seisakusho Capillograph 1D (nozzle temperature 160 ° C.).

<Preparation of master batch>
The resin (carrier resin) and the colorant were blended at a predetermined mixing ratio, and extruded into a spun shape (spinning hole 4 mm) at an extrusion temperature of 160 ° C. using an extruder, which was cooled with cold water to produce a strand. The obtained strand was cut into a length of about 3 mm using a strand cutter to obtain a master batch. When the strand was formed, the case where the strand was able to be formed stably was regarded as good. Otherwise, it was judged that the master batch could not be produced.

<Preparation of resin encapsulated sheet>
It shows about the manufacturing method of the sealing material of each Example. Resin encapsulated sheets were produced with the materials and composition ratios (units are parts by mass) shown in each table. Using three extruders (surface layer extruder, inner layer extruder, surface layer extruder), the resin is melted, and the resin is melt extruded into a tube from a circular die connected to the extruder. The formed tube was formed into a film by an upward direct inflation method, and the molten resin sheet was cooled and solidified using cold air at 20 ° C. to obtain a resin sheet. In Examples 18 to 20, the route of the polymer pipe to be connected to the die of three extruders was changed to be used as a surface layer extruder, an inner layer extruder, and an innermost layer extruder. A sheet of layers was obtained.

  Subsequently, the resin sealing sheet was produced from the obtained resin sheet by the method shown in FIG. That is, it preheated by making it contact | adhere to the preheating roll 2 set to 50 degreeC, and also heated by the infrared heater 3 by which sheet | seat temperature was set to 70 degreeC, and softened. Next, embossing was performed by passing the softened resin sheet between the backup roll 5 and the embossing roll 6 (see FIG. 1). As the embossing, embossing of a pyramid pattern (quadrangular pyramid shape) shown in FIGS. 2 and 3 was performed to obtain a resin-encapsulated sheet (embossed sheet) subjected to embossing. Before and after the step of softening the resin sheet by heating, tension control was performed so that the softened resin sheet was not stretched by the pinch roll, the backup roll, and the embossing roll. In the table, the thickness ratio of the surface layer / inner layer / surface layer indicates the ratio of the thickness of each layer when the thickness of the entire resin sealing sheet is 100. In addition, Examples 18-20 are the thickness ratio of surface layer / inner layer / innermost layer / inner layer / surface layer, and the ratio of the thickness of each layer when the thickness of the entire resin-encapsulated sheet is 100 is used. Show. Using the EPS-300 or EPS-800 electron beam irradiation apparatus (manufactured by Nissin High Voltage), the obtained resin-encapsulated sheet (embossed sheet) is an electron beam at the acceleration voltage and irradiation density shown in each table. Processed.

<Production of solar cell module>
Using the obtained resin sealing sheet, a solar cell module was produced using the materials shown in each table. 6-inch polycrystalline cells are arranged in 6 sheets (2 rows × 3 sheets), and are laminated in the order of transparent substrate / resin sealing sheet (a) / power generation element (250 μm) / resin sealing sheet (b) / back sheet, Using a LM50 type vacuum laminator (NPC), a solar cell module was manufactured by vacuum lamination under the conditions described in each table, and each evaluation test was performed. Production conditions and evaluation results are shown in Tables 2 to 5. The output when all the sealing materials were transparent was 20.5 W, which was the standard output value. The output when using a colored sealing material (colored sealing material) from this value is measured, and when an improvement from the standard 20.5W is observed, it is displayed as a plus, and the difference (increased efficiency) Rate) in%. The output value was measured by Nisshinbo Solar Simulator PVS1116i, and the efficiency increase rate (%) was calculated based on the following formula.

Efficiency increase rate (%) = (output value when using colored sealing material−standard output value) / standard output value × 100

<Appearance after lamination>
The appearance immediately after lamination of the produced solar cell module was visually observed.
Then, the solar cell module was installed vertically in a test tank maintained at a test temperature of 85 ° C. and a relative humidity of 85%, and the appearance of the solar cell module after two weeks was visually observed. Those in which the displacement of the members such as the power generation elements were observed were judged as abnormal appearance, and those in which the displacement of the members such as the power generation elements were not observed were judged as good appearance.

<Discoloration test of copper plate>
In each example, a copper sheet (250 μm) was laminated under the same conditions in place of the power generation element to obtain a laminate sheet. This laminate sheet was placed vertically in a test tank maintained at a test temperature of 85 ° C. and a relative humidity of 85%, and the presence or absence of discoloration of the copper plate after 2 weeks was observed. Those in which rust and discoloration due to moisture were confirmed were judged as corrosion levels (discoloration), and those in which rust and discoloration were not confirmed were judged good.

<Water vapor transmission rate of sealing material (WVTR)>
It measured based on JIS-K7129.

  The conditions of the master batch are shown in Table 1, and the production conditions and physical property evaluation results of each Example and each Comparative Example are shown in Tables 2-7.

  As shown in Tables 2 to 7, it is confirmed that the solar cell encapsulating sheet of this example can improve the energy efficiency when it is a solar cell module, and is excellent in water vapor barrier properties and corrosion resistance. It was done. Furthermore, since the solar cell sealing sheet of the present Example did not contain an organic peroxide, it was confirmed that the productivity was also excellent.

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

DESCRIPTION OF SYMBOLS 1 ... Resin sheet, 2 ... Preheating roll, 3 ... Infrared heater, 4 ... Pinch roll, 5 ... Backup roll, 6 ... Embossing roll

Claims (9)

At least one resin selected from the group consisting of an ethylene-aliphatic carboxylic acid ester copolymer, an ethylene copolymer containing glycidyl methacrylate, and a polyolefin resin;
A colorant;
A solar cell encapsulating sheet that has at least a resin layer that contains no organic peroxide.   The solar cell encapsulating sheet according to claim 1, wherein the resin layer contains at least a polyethylene-based resin. The solar cell encapsulating sheet according to claim 1, wherein the resin layer contains a polyethylene-based resin having a density of 0.92 g / cm ³ or less.   The colorant is blended in a master batch using at least one resin selected from the group consisting of an ethylene-aliphatic carboxylic acid ester copolymer, an ethylene copolymer containing glycidyl methacrylate, and a polyolefin resin as a carrier resin. The solar cell sealing sheet according to claim 1, wherein the solar cell encapsulating sheet is used.   The solar cell sealing sheet according to claim 4, wherein the carrier resin has a melt tension (MT) at 160 ° C. of 50 g or less.   The solar cell encapsulating sheet according to any one of claims 1 to 5, wherein the resin layer is subjected to a crosslinking treatment by ionizing radiation irradiation.   The solar cell sealing sheet according to any one of claims 1 to 6, wherein at least a part of the surface of the resin layer is embossed.   The solar cell sealing sheet of Claim 7 whose depth of the embossed shape formed in the said resin layer is 30 micrometers or more.   The solar cell module containing the solar cell sealing sheet as described in any one of Claims 1-8.