JP2013256577A - Resin-sealing sheet for solar cell and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin-sealing sheet for a solar cell, having excellent transparency not available conventionally.SOLUTION: A resin-sealing sheet for a solar cell closely adhering by softening the resin is provided by including, as the resin constituting the resin-sealing sheet for the solar cell, at least one selected from the group consisting of an ethylene-vinyl acetate copolymer, an ethylene-aliphatic unsaturated carboxylic acid copolymer, an ethylene-aliphatic unsaturated carboxylate ester copolymer, an ethylene-α-olefin copolymer and an ethylene homopolymer, and also including a sorbitol-based compound having a specific structure or an alicyclic metal salt by ≥10 mass ppm and ≤5,000 mass ppm range by its total amount.

Description

  The present invention relates to a resin encapsulating sheet for solar cells and a method for producing the same.

  In recent years, the global warming phenomenon has heightened awareness of the environment, and a new energy system that does not generate greenhouse gases such as carbon dioxide is attracting attention. For example, environmentally friendly renewable energy systems such as solar cell power generation systems and wind power generation systems do not emit greenhouse gases such as carbon dioxide, and are therefore actively researched and developed as clean energy systems. In particular, from the viewpoint of safety and ease of handling, the solar cell power generation system is attracting attention as a system that can be used not only as a household energy source but also as an industrial energy source.

  In Japan, where resources are scarce, in each household, installing a solar cell power generation system on the roof to generate electricity, consuming the resulting power as household power, or selling surplus power, In recent years, it has become popular. Above all, in Europe, centered on Germany, not only is it used as household power, but it is also used as industrial power by arranging solar cells on a large site for large-scale power generation. Such solar cells are also attracting attention as a target of investment.

  There are various power generation methods for solar cells that are attracting attention in this way. Typical power generation methods include those using single crystal silicon cells or polycrystalline silicon cells (crystalline silicon cells), those using amorphous silicon, those using compound semiconductors (thin film cells), and the like. . Regardless of which power generation method is used, it is exposed to wind and rain outdoors for a considerably long period of time. Therefore, for the purpose of protecting the power generation part for a long period of time, it is laminated and modularized with a glass plate or a back sheet (solar cell) module). By doing this, the inflow of moisture from the outside is prevented, and measures such as protection of the power generation portion and prevention of leakage are taken. Such a solar cell module is required to protect the power generation portion for a long time and to transmit light necessary for power generation to the power generation surface. Therefore, transparent glass or transparent resin is used as the power generation surface, and barrier coating processing such as aluminum foil, polyvinyl fluoride resin (PVF), polyethylene terephthalate (PET), silica, etc., is used as the non-power generation surface. Use laminated sheets. In addition, modularization means that after the power generation part is sandwiched between resin sealing sheets, the resin sealing sheet is melted by further covering the outside with glass or a back sheet and making the resin sealing sheet high temperature. Integrated sealing (modularization).

  Usually, a resin encapsulating sheet is coupled with an ethylene-vinyl acetate copolymer (hereinafter also referred to as “EVA”) with a light-resistant agent and an ultraviolet absorber for measures against ultraviolet deterioration, and a coupling for improving adhesion to glass. It is manufactured by calendering or T-die casting to form an agent in which various additives such as organic peroxides are blended for crosslinking. In the production of solar cell modules using single-crystal silicon cells or polycrystalline silicon cells, usually the glass / resin encapsulated sheet / crystalline silicon cell or other power generation part / resin encapsulated sheet / back sheet are stacked in this order, The glass surface is placed downward, and a preheating step and a pressing step are performed at a temperature equal to or higher than the melting temperature of the resin (typically 150 ° C. in the case of EVA) using a dedicated solar cell vacuum laminator. Thus, a solar cell module can be manufactured by bonding the molten resin sealing sheet and each member. At this time, the resin of the resin encapsulating sheet is melted in the first preheating step, and a member that adheres to the melted resin in the pressing step is brought into contact and vacuum laminated.

  For example, Patent Document 1 discloses a solar cell module in which at least a light incident side surface of a photovoltaic element is sealed with one or more transparent organic polymer resin layers, and at least of the organic polymer layers. A solar cell module in which one layer is crosslinked by irradiation with an electron beam is disclosed.

  Patent Document 2 discloses a solar cell element sealing material made of an ethylene copolymer subjected to electron beam irradiation. Using a resin selected from EVA, an ethylene / unsaturated carboxylic acid ester copolymer and an ethylene / unsaturated carboxylic acid copolymer as a representative of the ethylene copolymer, with a high degree of cross-linking with a cross-linking gelation rate of 65% or more. A solar cell element sealing material is disclosed.

  Patent Document 3 discloses a technique using a phosphate ester metal salt nucleating agent, a sorbitol nucleating agent, or a carboxylic acid metal salt nucleating agent.

Japanese Patent Laid-Open No. 06-334207 JP 2001-119047 A JP 2012-009773 A

  However, for example, with respect to the techniques described in Patent Documents 1 and 2, the study on the transparency of the resin sealing sheet used is insufficient, and there is room for improvement. Regarding transparency, it is important to balance both total light transmittance and haze in a balanced manner, from the viewpoint of improving the power generation efficiency of solar cells, etc., but these are not fully studied at present. It is.

  Regarding the technique described in Patent Document 3, the nucleating agent used is effective in a propylene polymer, but is insufficient when used in an ethylene polymer.

  This invention is made | formed in view of the said situation, and it aims at providing the resin sealing sheet for solar cells which has the outstanding transparency which is not in the past.

  As a result of intensive studies, the inventors of the present invention are resin encapsulating sheets for solar cells in which a resin is softened and adhered, and the resin constituting the resin encapsulating sheet for solar cells is an ethylene-vinyl acetate copolymer. At least one selected from the group consisting of an ethylene-aliphatic unsaturated carboxylic acid copolymer, an ethylene-aliphatic unsaturated carboxylic acid ester copolymer, an ethylene-α-olefin copolymer, and an ethylene homopolymer. And a sorbitol-based compound having a specific structure or a cycloaliphatic metal salt in a total amount of 10 mass ppm or more and 5000 mass ppm or less in the range of 10 ppm by mass or more and 5000 ppm by mass or less. As a result, the present invention has been completed.

That is, the present invention is as follows.
[1]
A resin encapsulating sheet for solar cells that softens and adheres to a resin,
As the resin constituting the solar cell resin encapsulating sheet, ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic ester copolymer, ethylene-α -Containing at least one selected from the group consisting of an olefin copolymer and an ethylene homopolymer, and
The resin sealing sheet for solar cells containing the sorbitol type compound or cycloaliphatic metal salt represented by following formula (1) in the range of 10 mass ppm or more and 5000 mass ppm or less in total.
(In the formula, when R ₁ is H, R ₂ represents an alkyl group or chloro group having 1 to 3 carbon atoms, and when R ₂ is H, R ₁ represents an alkyl group or chloro group having 1 to 3 carbon atoms. Represents.)
[2]
The resin sealing sheet for solar cells according to [1], further including a silane coupling agent in the range of 0.01% by mass to 5% by mass in the resin sealing sheet for solar cells.
[3]
The resin-encapsulated sheet for solar cells according to [1] or [2], further comprising at least one selected from the group consisting of an antioxidant, a light stabilizer, and an ultraviolet absorber.
[4]
A sorbitol compound represented by the following formula (1) or a cyclic aliphatic metal salt is converted into an ethylene-vinyl acetate copolymer, an ethylene-aliphatic unsaturated carboxylic acid copolymer, an ethylene-aliphatic unsaturated carboxylic acid ester. Adding in a state dispersed in at least one resin selected from the group consisting of a copolymer, an ethylene-α-olefin copolymer, and an ethylene homopolymer, and molding the sheet;
Irradiating the sheet with ionizing radiation to control the gel fraction of the sheet to a range of 2 mass% to 65 mass%;
The manufacturing method of the resin sealing sheet for solar cells which has these.
(In the formula, when R ₁ is H, R ₂ represents an alkyl group or chloro group having 1 to 3 carbon atoms, and when R ₂ is H, R ₁ represents an alkyl group or chloro group having 1 to 3 carbon atoms. Represents.)

  ADVANTAGE OF THE INVENTION According to this invention, the resin sealing sheet for solar cells which has the unprecedented outstanding transparency can be provided.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

≪Resin sealing sheet for solar cell≫
The solar cell resin encapsulating sheet (hereinafter also simply referred to as “resin encapsulating sheet”) of the present embodiment is a solar cell resin encapsulating sheet in which a resin is softened and adhered to the resin encapsulating sheet. As the resin that constitutes, ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic acid ester copolymer, ethylene-α-olefin copolymer, and ethylene It contains at least one resin selected from the group consisting of homopolymers, and contains a sorbitol compound or a cyclic aliphatic metal salt in a total amount of 10 to 5000 ppm by mass.

  The present inventor has intensively studied the reason why sufficient transparency cannot be obtained in the conventional resin-encapsulated sheet, and the size and crystals of spherulites that are present in the resin-encapsulated sheet and cause sunlight to scatter. It was found that the content of has an effect on transparency. And it was found that the smaller the spherulite and the smaller the crystal content, the more the transparency tends to improve because it is less likely to scatter sunlight, and the present invention has been completed. On the other hand, in the conventional resin sealing sheet, sufficient examination was not performed about content of an above-mentioned spherulite or a crystal | crystallization. The resin-encapsulated sheet of the present embodiment includes 10 to 5000 mass ppm of the sorbitol-based compound or cycloaliphatic metal salt as a crystal nucleating agent in a total amount, thereby increasing the nucleation rate in the resin crystallization process. In addition, since the spherulite becomes smaller and the content of crystals can be suppressed, it is considered that excellent transparency which is not conventionally achieved can be achieved (however, the operation of the present embodiment is not limited to this).

  And the resin sealing sheet of this embodiment contains the sorbitol compound or the cyclic aliphatic metal salt as a crystal nucleating agent in a total amount of 10 to 5000 ppm by mass, so that the melting point of the resin constituting the resin sealing sheet Even at these temperatures, the fluidity of the resin is prevented from changing significantly, and at temperatures below the melting point of the resin, it has a high elastic modulus due to being in a solidified state, and the resin sealing having such physical properties. By producing a solar cell module using a stop sheet, the unevenness on the surface of the glass for solar cells and the unevenness caused by the thickness of various parts such as wiring and power generation cells can be sealed without gaps ( Sealability). Furthermore, the obtained solar cell module is expected to be excellent in creep resistance (however, the operation of the present embodiment is not limited to this).

  Resins constituting the resin-encapsulated sheet of the present embodiment are ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic ester copolymer, ethylene-α. -At least one resin selected from the group consisting of an olefin copolymer and an ethylene homopolymer (hereinafter also referred to as "ethylene polymer").

  The resin-encapsulated sheet of this embodiment is preferably in a crosslinked state in order to further improve creep resistance. The resin-encapsulated sheet of the present embodiment is preferably in a cross-linked state before softening the above-described resin and bringing it into intimate contact with each constituent member, or at least after intimate contact. The crosslinking method is not particularly limited, and is a method in which an organic peroxide is blended in a resin sealing sheet, and is crosslinked by radical species generated by decomposing the organic peroxide by heating. A known method such as a method of irradiating ionizing radiation such as β-ray, γ-ray, neutron beam, or electron beam to crosslink the resin constituting the sheet may be used. preferable.

  In the case of crosslinking by irradiating with ionizing radiation, since the resin having a polar group is more easily crosslinked, the ethylene polymer is used as the resin used in this embodiment, and in particular, ethylene-vinyl acetate copolymer. A combination (EVA), an ethylene-α-olefin copolymer, and an ethylene homopolymer are preferred. Hereinafter, each ethylene polymer will be described.

  EVA refers to a copolymer obtained by copolymerization of an ethylene monomer and a vinyl acetate monomer. The ethylene-aliphatic unsaturated carboxylic acid copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and an aliphatic unsaturated carboxylic acid monomer. The ethylene-aliphatic unsaturated carboxylic acid ester copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and an aliphatic unsaturated carboxylic acid ester monomer.

  The polymerization method at the time of copolymerization of the ethylene-based polymer may be any known method such as a high-pressure method or a melting method, and there is no problem even with a method using a multi-site catalyst or a single-site catalyst. Moreover, there is no problem even if the bonding shape at the time of polymerization of each monomer is random bond, block bond or the like. The resin used in the present embodiment is preferably an ethylene polymer polymerized by random bonding using a high-pressure method from the viewpoint of optical characteristics, and more preferably EVA polymerized by random bonding using a high-pressure method.

  In EVA, the ratio of vinyl acetate to the entire copolymer is preferably 2 to 65% by mass, more preferably 5 to 55% by mass, from the viewpoint of optical properties, adhesiveness and flexibility. Preferably it is 5-40 mass%.

  In the ethylene-aliphatic unsaturated carboxylic acid copolymer, the ratio of the aliphatic unsaturated carboxylic acid to the entire copolymer is 3 to 35% by mass from the viewpoint of optical properties, adhesiveness, and flexibility. Preferably, it is 10 to 33% by mass, and more preferably 15 to 30% by mass.

  In the ethylene-aliphatic unsaturated carboxylic acid ester copolymer, the ratio of the aliphatic unsaturated carboxylic acid ester to the whole copolymer is 3 to 35% by mass from the viewpoint of optical properties, adhesiveness, and flexibility. It is preferably 10 to 33% by mass, more preferably 15 to 30% by mass.

  From the viewpoint of resin encapsulating sheet processability, the melt flow rate (MFR; 190 ° C., 2.16 kg) of the resin used in the present embodiment is preferably 0.3 to 40 g / 10 min, more preferably 0. 0.5 to 35 g / 10 min, and more preferably 0.8 to 30 g / 10 min. The resin here is a resin constituting a resin encapsulating sheet for a solar cell, for example, ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic acid. It contains at least one selected from the group consisting of an acid ester copolymer, an ethylene-α-olefin copolymer, and an ethylene homopolymer, and not only one type of resin but also two or more types of resins What is a resin composition containing is also included.

  An ethylene-aliphatic unsaturated carboxylic acid copolymer and an ethylene-aliphatic unsaturated carboxylic acid ester copolymer can be used in the same manner as EVA, and specific examples thereof include an ethylene-acrylic acid copolymer (hereinafter referred to as “ethylene-acrylic acid copolymer”). , “EAA”), ethylene-methacrylic acid copolymer (hereinafter also referred to as “EMAA”), ethylene-acrylic acid ester (usually having 1 to 8 carbon atoms such as methyl, ethyl, propyl, butyl, etc.) Selected from alcohol components.) Copolymers, ethylene-methacrylic acid esters (usually selected from components of alcohols having 1 to 8 carbon atoms such as methyl, ethyl, propyl, butyl) copolymers. . These are multi-component copolymers of three or more components to which other components are further added (for example, terpolymers of three or more components including ethylene, aliphatic unsaturated carboxylic acid, and aliphatic unsaturated carboxylic acid ester, etc. ).

  The ethylene-α-olefin copolymer refers to a copolymer obtained by copolymerization of ethylene and propylene or an α-olefin having 4 to 20 carbon atoms. The total content of propylene and the α-olefin having 4 to 20 carbon atoms with respect to the entire copolymer is preferably 2 to 30% by mass. Examples of the ethylene-α-olefin copolymer include linear low density polyethylene (LLDPE), linear ultra-low density polyethylene (usually called VLDPE and ULDPE), and the like.

  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, 1-decene, Examples include 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosane and the like.

  The ethylene-α-olefin copolymer may be polymerized using a multisite catalyst, a single site catalyst, or any other catalyst. Furthermore, a copolymer in which the crystal / amorphous structure (morphology) of the polymer is controlled in nano order can also be used. In addition to the above resins, there is no problem even if a known resin such as an ionomer is introduced alone or in combination.

  The ethylene-α-olefin copolymers include those containing a commercially available ethylene homopolymer or a copolymer with a small amount of α-olefin. The ethylene-α-olefin copolymer is generally polymerized using a catalyst called a single-site catalyst or a multi-site catalyst, but among them, it is polymerized by a single-site catalyst. Those are preferred. Specifically, from the viewpoint of availability, a copolymer of ethylene and any one comonomer selected from ethylene comonomer, butene comonomer, hexene comonomer, and octene comonomer is more preferable.

From the viewpoint of transparency, the ethylene-α-olefin copolymer preferably has a density in the range of 0.860 to 0.950 g / cm ³ , more preferably 0.863 to 0.930 g / cm ³ . More preferably 0.863 to 0.910 g / cm ³ . When the density is lower, the cushioning property tends to be improved, and when the density is 0.950 g / cm ³ or less, the transparency tends to be better. When using a high-density resin from the viewpoint of transparency, the transparency is further improved by adding low-density polyethylene in a proportion of 30 to 70% by mass with respect to the total amount of the resin. The density here is measured by a method based on ASTM D1505.

  From the viewpoint of processability of the resin-encapsulated sheet, the melt flow rate (MFR; 190 ° C., 2.16 kg) of the ethylene-α-olefin copolymer is preferably 0.5 to 30 g / 10 minutes, more Preferably it is 0.8-30 g / 10min, More preferably, it is 1.0-25 g / 10min.

  Examples of the ethylene homopolymer include high density polyethylene (HDPE); medium density polyethylene; high pressure method low density polyethylene. Among these, low density polyethylene obtained by polymerization by a so-called high pressure method is preferable.

From the viewpoint of transparency, the ethylene homopolymer preferably has a density in the range of 0.910 to 0.950 g / cm ³ , more preferably 0.913 to 0.940 g / cm ³ , and still more preferably. Is 0.915 to 0.930 g / cm ³ . The low density in the above range tends to improve not only the transparency but also the cushioning property. The density here is measured by a method based on ASTM D1505.

  From the viewpoint of processability of the resin-encapsulated sheet, the melt flow rate (MFR; 190 ° C., 2.16 kg) of the ethylene homopolymer is preferably 0.5 to 30 g / 10 minutes, more preferably 0.00. It is 8-30 g / 10 minutes, More preferably, it is 1.0-25 g / 10 minutes.

  When the resin sealing sheet of this embodiment has a single-layer structure, the resin sealing sheet may be composed of a single resin based on an ethylene polymer, or a resin composition containing two or more types of ethylene polymers. It may be comprised from the resin composition containing the said ethylene-type polymer and other resin.

  The resin sealing sheet of this embodiment may have a multilayer structure. As the multilayer structure, for example, a two-layer structure composed of a first surface layer and a second surface layer; a three-layer structure in which an inner layer is disposed between the first surface layer and the second surface layer; It may be a multilayer structure of four or more layers in which two or more inner layers are disposed between one surface layer and the second surface layer.

  When the resin-encapsulated sheet of the present embodiment has a multilayer structure, the surface layer preferably contains the ethylene polymer from the viewpoint of adhesion to an adherend, not only the ethylene polymer, It is more preferable that a sorbitol compound or a cyclic aliphatic metal salt is included. Furthermore, by the polarization due to the polar group of the comonomer contained in the ethylene-based polymer, an adhesive function with an adherend such as glass can be exhibited, the transparency of the resin-sealed sheet can be ensured, From the viewpoint that it becomes easy to contain additives and the like when a resin having a group is contained, the resin used for the surface layer is only from an ethylene polymer other than an ethylene homopolymer (so-called ethylene copolymer). More preferably, the resin is

  When the resin sealing sheet of this embodiment has a multilayer structure, the inner layer may be a resin layer containing the ethylene polymer or a resin layer containing a resin other than the ethylene polymer. May be. A new resin layer or a resin layer containing a mixture of resins or a resin layer containing a mixture of a resin and an additive may be introduced as a new layer in the inner layer.

  As a new resin layer to be introduced for the purpose of improving cushioning properties, a layer containing a thermoplastic resin may be mentioned. A thermoplastic resin here shows rubber elasticity at normal temperature, and has thermoplasticity.

  Examples of such thermoplastic resins include olefin resins, styrene resins, vinyl chloride resins, polyester resins, urethane resins, chlorinated ethylene resins, polyamide resins, and the like. Also included are biodegradable thermoplastic resins, plant-derived thermoplastic resins, and the like.

  The thermoplastic resin is preferably a hydrogenated block copolymer, a propylene copolymer, or an ethylene copolymer, more preferably a hydrogenated block copolymer or an ethylene copolymer, from the viewpoint of good transparency. It is a polymer.

  The hydrogenated block copolymer is preferably a hydrogenated block copolymer of vinyl aromatic hydrocarbon and conjugated diene. 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. Conjugated dienes are diolefins having at least one pair of conjugated double bonds, such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3. -Butadiene, 1,3-pentadiene, 1,3-hexadiene and the like. These may be used alone or in combination of two or more.

  As the propylene-based copolymer, a copolymer of propylene and ethylene or an α-olefin having 4 to 20 carbon atoms is preferable. The total content of ethylene and the α-olefin having 4 to 20 carbon atoms in the copolymer is preferably 6 to 30% by mass.

  Here, 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, 1- Examples include decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosane and the like.

  Examples of the ethylene copolymer include the above-described ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic acid ester copolymer, ethylene-α-olefin copolymer. Polymers are preferred.

  The propylene copolymer may be polymerized using any catalyst such as a multi-site catalyst, a single-site catalyst, and the like. Furthermore, a propylene-based copolymer in which the crystal / amorphous structure (morphology) of the polymer is controlled in nano order can also be used. The ethylene copolymer may be polymerized with any one of a multi-site catalyst, a single-site catalyst, and other catalysts. Further, an ethylene-α-olefin copolymer in which the crystal / amorphous structure (morphology) of the polymer is controlled in nano order can also be used. In addition to the above resins, there is no problem even if a known resin such as an ionomer is introduced alone or in combination.

<Sorbitol compounds, cycloaliphatic metal salts>
The resin-encapsulated sheet of the present embodiment contains at least a sorbitol-based compound or a cyclic aliphatic metal salt component represented by the following formula (1) in the range of 10 to 5000 ppm by mass in the resin-encapsulated sheet. .

(In the formula, R ₁ represents an alkyl group or chloro group R ₂ is a 1 to 3 carbon atoms when the H, R ₁ is when R ₂ is H, an alkyl group or chloro group having 1 to 3 carbon atoms Represents.)

  As the alkyl group, a methyl group, an ethyl group, and an isopropyl group are preferable.

  As specific examples of the sorbitol-based compound represented by the formula (1), 1,3,2,4-dibenzylidene sorbitol and derivatives thereof are preferable. Since this is a structure suitable for promoting crystallization of the ethylene-based polymer, a more excellent addition effect can be exhibited.

  Preferable specific examples of the compound represented by the formula (1) include 1,3-benzylidene-2,4-p-methylbenzylidene sorbitol, 1,3-p-methylbenzylidene-2,4-benzylidene sorbitol and the like. It is done. One of the characteristics of these compounds is a nuclear substitution product in which any one hydrogen group of the phenyl nucleus is substituted with a methyl group. These compounds are produced, for example, according to the method described in Japanese Patent Publication No. 02-059832.

Examples of the cycloaliphatic metal salt include metal salts of cycloaliphatic carboxylic acid compounds. More specifically, a compound represented by the following formula (2) is exemplified.

Here, M ₁ and M ₂ each independently represent one selected from the group consisting of calcium, strontium, lithium, zinc, magnesium, and monobasic aluminum, and M ₁ and M ₂ are It is a divalent metal ion in total. R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , and R ₁₂ each independently comprise hydrogen and a hydrocarbon group having 1 to 9 carbon atoms. Any two of the R _{5 to} R ₁₂ hydrocarbon groups which represent one kind selected from the group and are adjacent to each other may be optionally bonded to form a ring.

M ₁ and M ₂ are divalent in total. For example, M ₁ and M ₂ may each be lithium (Li ⁺ ), but are preferably a single divalent metal ion. That is, when M ₁ ²⁺ (a divalent metal ion), M ₂ does not exist. When the metal salt of the cycloaliphatic carboxylic acid compound represented by the above formula (2) is compounded with the resin component, the crystallization starts when crystallization starts, and the crystal grows starting from that. It is estimated that it acts as a crystal nucleating agent. From this viewpoint, from the viewpoint of ease of crystallization, M ₁ is more preferably a divalent calcium ion (Ca ²⁺ ) (however, the action of the present embodiment is not limited to this). Furthermore, as the cycloaliphatic metal salt, from the viewpoint that the crystallized structure is a structure suitable for promoting the crystallization of the ethylene-based polymer, a compound represented by the following formula (3) (cis-hexa More preferred is calcium hydridophthalate.

  The total content of the sorbitol-based compound and the cyclic aliphatic metal salt in the resin-encapsulated sheet is in the range of 10 mass ppm to 5000 mass ppm, and preferably 10 mass ppm to 3000 mass ppm. 50 mass ppm or more and 2000 mass ppm or less is more preferable. When the content of the sorbitol compound and the cyclic aliphatic metal salt with respect to the resin sealing sheet exceeds 5000 mass ppm in total, the elastic modulus of the resin sealing sheet becomes too high, and the adhesiveness is greatly reduced. The gap filling property necessary for the resin sealing sheet is insufficient, and further, the tensile breaking strength and elongation of the sheet are lowered, and the sealing property is lowered. Further, if the total content is less than 10 ppm by mass, the resin crystallization speed is too slow and the spherulite size becomes large, so that sufficient transparency cannot be obtained. Usually, the size of the spherulite of the ethylene polymer is larger than the wavelength of visible light (about 0.38 to 0.75 μm) and is about several μm to several hundred μm. For this reason, it is considered that the transparency is lowered by the scattering of visible light at the spherulite interface. However, in this embodiment, by adding the above-described sorbitol compound or cycloaliphatic metal salt at a specific ratio to these ethylene polymers, the spherulites are less than or equal to the visible light wavelength. Therefore, transparency can be increased by suppressing the scattering of visible light at the spherulite interface. Thereby, even if it does not change the kind of resin component or increases content, transparency can be improved (however, the effect of this embodiment is not limited to this).

<Additive>
The resin-encapsulated sheet of this embodiment has a coupling agent, an antifogging agent, a plasticizer, an antioxidant, a surfactant, a colorant, a light stabilizer, and an ultraviolet absorber as long as the original properties are not impaired. Other additives such as antistatic agents, lubricants, antiblocking agents, inorganic fillers, crosslinking aids, crosslinking modifiers and the like may be added. These additives can be added to the molten resin as a solution containing the additive, directly kneaded into the resin layer, added after film formation, etc. Any known method can be used as long as it is a method.

  A coupling agent may be added to the resin sealing sheet of this embodiment for the purpose of ensuring stable adhesiveness. In the resin-encapsulated sheet of the present embodiment, the content of the coupling agent is preferably 0.01 to 5% by mass, although it depends on the desired degree of adhesion and the material of the adherend. Preferably it is 0.03-4 mass%, More preferably, it is 0.05-3 mass%. The coupling agent is preferably a substance that imparts good adhesion to solar cells or glass to the ethylene-based polymer. From this viewpoint, as the coupling agent, for example, a silane coupling agent such as an organic silane compound or an organic silane peroxide, or a titanate coupling agent such as an organic titanate compound is preferable, and a silane coupling agent is more preferable. When the resin sealing sheet has a multilayer structure, the coupling agent is preferably included in the surface layer that comes into contact with the object to be sealed.

  The coupling agent can be added by injecting and mixing into an ethylene polymer in an extruder, mixing into an extruder hopper and introducing it into the ethylene polymer, adding a masterbatch in advance and mixing Any known addition method can be used as long as the effect of the coupling agent can be exhibited.

  Further, the type of the coupling agent may be appropriately selected from the viewpoints of transparency and dispersion of the ethylene polymer, corrosiveness to the extruder, and extrusion stability when mixed with the ethylene polymer. From this point of view, preferred coupling agents include those having an unsaturated group or an epoxy group, and specifically, vinyltrichlorosilane, vinyltris (β-methoxyethoxy) silane, vinyltriethoxysilane, vinyltrimethoxy. Silane, γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxy Silane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltri Methoxysilane And the like.

  These coupling agents may be used individually by 1 type, and may use 2 or more types together.

  The crosslinking aid is preferably a compound having a plurality of vinyl groups in the molecule, and examples thereof include triallyl isocyanurate and trimethallyl isocyanurate.

  The resin-encapsulated sheet of this embodiment preferably contains at least one selected from the group consisting of an antioxidant, a light stabilizer, and an ultraviolet absorber in order to increase stability.

  It is preferable to add an antioxidant to the resin-encapsulated sheet of this embodiment in order to impart stability at high temperatures. In the resin-encapsulated sheet of this embodiment, it is preferable that the addition amount of the antioxidant is 0.1 to 1 part by mass with respect to 100 parts by mass of the ethylene polymer. As the antioxidant, for example, monophenol-based antioxidants, bisphenol-based antioxidants, polymer-type phenol-based antioxidants, sulfur-based antioxidants, and phosphoric acid-based antioxidants are preferable.

  Examples of the monophenol antioxidant include 2,6-di-tert-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-tert-butyl-4-ethylphenol, n-octadecyl- (4-hydroxy-3,5-di-tert-butylphenyl) propionate.

  Examples of the bisphenol antioxidant include 2,2'-methylene-bis- (4-methyl-6-tert-butylphenol) and 2,2'-methylene-bis- (4-ethyl-6-tert-butylphenol). ), 4,4'-thiobis- (3-methyl-6-tert-butylphenol), 4,4'-butylidene-bis- (3-methyl-6-tert-butylphenol), 3,9-bis [{1 , 1-dimethyl-2- {β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} ethyl} 2,4,8,10-tetraoxaspiro] 5,5-undecane. It is done.

  Examples of the polymeric phenolic antioxidant include 1,1,3-tris- (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4. , 6-Tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, tetrakis- {methylene-3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate } Methane, bis {(3,3'-bis-4'-hydroxy-3'-tert-butylphenyl) butyric acid} glycol ester, 1,3,5-tris (3 ', 5'-di- tert-butyl-4'-hydroxybenzyl) -s-triazine-2,4,6- (1H, 3H, 5H) trione, triphenol (vitamin E).

  Examples of the sulfur-based antioxidant include dilauryl thiodipropionate, dimyristyl thiodipropionate, and distearyl thiopropionate.

  Examples of phosphoric acid antioxidants include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, 4,4'-butylidene-bis- (3-methyl-6-tert-butylphenyl-di-tridecyl). ) Phosphite, cyclic neopentanetetraylbis (octadecyl phosphite), tris (mono and / or di) phenyl phosphite, diisodecyl pentaerythritol diphosphite, 9,10-dihydro-9-oxa-10-phospha Phenanthrene-10-oxide, 10- (3,5-di-tert-butyl-4-hydroxybenzyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10- Decyloxy-9,10-dihydro-9-oxa 10-phosphaphenanthrene, cyclic neopentanetetraylbis (2,4-di-tert-butylphenyl) phosphite, cyclic neopentanetetraylbis (2,6-di-tert-methylphenyl) phos Phyto, 2,2-methylenebis (4,6-tert-butylphenyl) octyl phosphite.

  These antioxidants may be used alone or in combination of two or more.

  It is preferable to add a light stabilizer as an additive capable of imparting weather resistance to the resin-encapsulated sheet of the present embodiment, in addition to the ultraviolet absorbent described below. The light stabilizer does not absorb ultraviolet rays like the ultraviolet absorber, but exhibits a remarkable synergistic effect when used in combination with the ultraviolet absorber. The addition amount of the light stabilizer is preferably 0.1 to 0.3 part by mass with respect to 100 parts by mass of the ethylene polymer. As the light stabilizer, a hindered amine light stabilizer is preferable from the viewpoint of ensuring further excellent transparency in the resin-encapsulated sheet of the present embodiment.

  Examples of the hindered amine light stabilizer include dimethyl succinate-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, poly [{6- (1, 1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {{2 , 2,6,6-tetramethyl-4-piperidyl) imino}], N, N′-bis (3-aminopropyl) ethylenediamine-2,4-bis [N-butyl-N- (1,2,2 , 6,6-pentamethyl-4-piperidyl) amino] -6-chloro-1,3,5-triazine condensate, bis (2,2,6,6-tetramethyl-4-piperidyl) separate, 2- ( 3,5-di-tert 4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl), bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate Etc.

  Further, the resin-encapsulated sheet of the present embodiment is disposed in the lower layer of the layer containing the ethylene polymer or inside the solar cell module in order to suppress the light deterioration of the ethylene polymer and improve the weather resistance. In order to protect the power generation member and the like, it is preferable to add an ultraviolet absorber. It is preferable that the addition amount of a ultraviolet absorber is 0.1-0.5 mass part with respect to 100 mass parts of said ethylene-type polymers. Examples of the UV absorber include salicylic acid UV absorbers, benzophenone UV absorbers, benzotriazole UV absorbers, and cyanoacrylate UV absorbers.

  Examples of the salicylic acid ultraviolet absorber include phenyl salicylate, p-tert-butylphenyl salicylate, and p-octylphenyl salicylate.

  Examples of the benzophenone ultraviolet absorber include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2 ′. -Dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy-5-benzophenone) Methane is mentioned.

  Examples of the benzotriazole ultraviolet absorber include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-5′-tert-butylphenyl) benzotriazole, 2- ( 2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3', 5'-di-tert-amylphenyl) benzotriazole, 2- {2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methyl Sulfonyl} benzotriazole, 2,2- methylenebis {4- (1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl) phenol}, and the like.

  Examples of the cyanoacrylate ultraviolet absorber include 2-ethylhexyl-2-cyano-3,3′-diphenyl acrylate, ethyl-2-cyano-3,3′-diphenyl acrylate, and the like.

  It is preferable to add at least one of these ultraviolet absorbers.

  In consideration of the usage environment of the solar cell module, the above-described antioxidant, light stabilizer and ultraviolet absorber are preferably low-volatile.

  When the resin sealing sheet of the present embodiment has a multilayer structure including other resin layers other than the layer including the ethylene polymer, the additives such as the ultraviolet absorber, the antioxidant, and the light stabilizer described above are In addition to the layer containing the ethylene polymer, it may be added to other resin layers. In this case, in the resin sealing sheet of this embodiment, the total amount of the additive is preferably 0 to 10% by mass, more preferably 0 to 5% with respect to the resin constituting the other resin layer. % By mass.

≪Characteristics of resin sealing sheet≫
The optical characteristics of the resin sealing sheet will be described. The resin-encapsulated sheet of the present embodiment is configured to be able to suppress the haze value without excessively impairing the total light transmittance. Specifically, the total light transmittance is preferably 80% or more, and the haze value is preferably 60% or less.

  The haze of the resin-encapsulated sheet is a value measured in accordance with JIS K7136, and when the haze is 60% or less, a decrease in power generation efficiency of the solar cell can be suppressed. From this viewpoint, the haze of the resin-encapsulated sheet of the present embodiment is preferably 60% or less, and more preferably 55% or less.

  The total light transmittance of the resin-encapsulated sheet is a value measured in accordance with JIS K7361-1, preferably 75% or more, more preferably 80% or more, and still more preferably 83% or more. Yes, and more preferably 85% or more. In the resin sealing sheet of this embodiment, it has the physical property balance that the haze value can be made low by making a total light transmittance 80% or more. It should be noted that, for a resin having a haze of 20% or more, the effect of lowering the haze value is particularly exerted, and there is a more excellent effect for a resin having a haze of 30% or more. It exhibits even better effects.

  The haze value of this type of sealing sheet of this embodiment can be adjusted by the density of the resin used and the amount of the crystal nucleating agent such as the sorbitol-based compound and cyclic aliphatic metal salt described above. For example, the haze value tends to increase by using a resin having a higher density or by reducing the amount of the crystal nucleating agent added. For example, the haze value tends to decrease by using a resin having a lower density or increasing the amount of the crystal nucleating agent added.

  The total light transmittance of this type of encapsulating sheet can be adjusted by the density of the resin used and the amount of crystal nucleating agent such as the sorbitol-based compound and cyclic aliphatic metal salt described above. For example, the total light transmittance tends to increase by using a resin having a lower density or by reducing the amount of the crystal nucleating agent added. For example, the total light transmittance tends to decrease by using a resin having a higher density or increasing the amount of the crystal nucleating agent added.

  It is preferable that the thickness of the resin sealing sheet of this embodiment is 50-1500 micrometers, More preferably, it is 100-1000 micrometers, More preferably, it is 150-800 micrometers. By making the thickness of the resin encapsulating sheet of the present embodiment a thin sheet in the above range, the cushioning property of the resin encapsulating sheet, workability, the productivity of the solar cell module, and the adhesion to the object to be encapsulated The physical property balance is further improved.

≪Method for producing resin-encapsulated sheet≫
Next, the manufacturing method of the resin sealing sheet of this embodiment is described. The manufacturing method of the resin sealing sheet of this embodiment is
A sorbitol compound represented by the above formula (1) or a cyclic aliphatic metal salt is converted into an ethylene-vinyl acetate copolymer, an ethylene-aliphatic unsaturated carboxylic acid copolymer, an ethylene-aliphatic unsaturated carboxylic acid ester. Adding in a state dispersed in at least one resin selected from the group consisting of a copolymer, an ethylene-α-olefin copolymer, and an ethylene homopolymer, and molding the sheet;
Irradiating the sheet with ionizing radiation to control the gel fraction of the sheet to a range of 2 mass% to 65 mass%;
Have More specific description will be given below.

<Sheet molding>
In the method for producing the resin-encapsulated sheet of the present embodiment, the sheet molding method includes ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic acid ester copolymer. Examples thereof include a method in which at least one resin (raw material resin) selected from the group consisting of a coalescence, an ethylene-α-olefin copolymer, and an ethylene homopolymer is melt-extruded into a sheet shape with an extruder.

  The sheet forming temperature can be appropriately set, but is preferably 90 to 170 ° C. from the viewpoint of the thermal shrinkage rate of the obtained sheet. When the raw material resin does not contain an organic peroxide, the sheet molding temperature can be increased, which is preferable.

  It is preferable that the manufacturing method of the resin sealing sheet of this embodiment includes the process of melt | dissolving raw material resin with an extruder, co-extruding from a die | dye, rapidly solidifying, and obtaining a raw material, for example. At this time, as the extrusion, a T-die method, a circular die (annular die) method or the like can be used, and the T-die method is preferable from the viewpoint of increasing the thickness accuracy of the resin-encapsulated sheet.

  When the resin sealing sheet has a multilayer structure, a multilayer T die method or a multilayer circular die (annular die) method may be used, or a multilayer structure may be obtained by a laminating method. Among these, the multilayer T-die method is preferable.

  The resin sealing sheet of this embodiment contains a sorbitol compound or a cyclic aliphatic metal salt. In addition, various additives may be included as long as the original characteristics are not impaired. In general, as a method of adding an additive to an ethylene polymer, a method of directly adding the additive to the ethylene polymer, or adding the additive in a state of being dispersed in the resin in advance, that is, in advance A method of preparing a so-called master batch and adding the master batch is known.

  As a method of adding the sorbitol compound or cycloaliphatic metal salt to the raw material resin, a master batch of the sorbitol compound or cycloaliphatic metal salt and a part of the raw resin is prepared in advance, A method of adding to the remaining raw resin is preferable. By this method, the dispersibility of the sorbitol-based compound and the cycloaliphatic metal salt becomes better, the crystallization time can be further shortened, and the spherulites can be made smaller, so that the transparency of the resin-encapsulated sheet is further enhanced.

  In a state where the sorbitol compound or the cycloaliphatic metal salt is dispersed in the resin in advance by using a master batch or the like, the concentration of the sorbitol compound or the cycloaliphatic metal salt is 1% by mass or more and 50% by mass or less. Preferably, it is 3 mass% or more and 30 mass% or less, More preferably, it is 5 mass% or more and 20 mass% or less. If it is 1 mass% or more, the efficiency by dispersing in the resin in advance is sufficiently high and industrially useful. If it is 50% by mass or less, the sorbitol-based compound or the cyclic aliphatic metal salt is sufficiently kneaded with the resin and is easy to handle as pellets.

  The resin used when the sorbitol-based compound or the cyclic aliphatic metal salt is dispersed in the resin in advance is preferably one containing an ethylene-based polymer, which is a resin constituting the resin-encapsulated sheet. It is more preferable that it is the same kind as resin which comprises, and it is still more preferable that it is exactly the same as resin which comprises the resin sealing sheet for solar cells.

  The manufacturing method of the resin sealing sheet of this embodiment may further have the process of carrying out an embossing process on the resin sealing sheet surface using the raw material obtained as mentioned above. For example, when performing a double-sided embossing process, the method of passing the shape | molded sheet | seat between two heating embossing rolls is employable. Moreover, when performing a single-sided embossing process, it is possible to adopt a method in which only one of the two embossing rolls is used as a heating embossing roll, and a molded sheet is passed between them. Thereby, the embossing process can be performed on at least one surface of the resin sealing sheet.

  The manufacturing method of the resin sealing sheet of this embodiment may include the post-processing process. Examples of the post-treatment process include a corona treatment process, a plasma treatment process, a lamination process with other resin sealing sheets, and the like.

  Although it does not specifically limit as a crosslinking method of the resin sealing sheet of this embodiment, The method of irradiating ionizing radiations, such as an alpha ray, a beta ray, a gamma ray, a neutron beam, an electron beam, is preferable. For example, by irradiating ionizing radiation to crosslink the ethylene polymer, unreacted components such as organic acids and peroxides due to elimination of side chain portions of the ethylene polymer remain in the resin. This can prevent the adverse effect of the unreacted components on the solar battery cell, the conductive functional layer, or the wiring.

  The acceleration voltage of ionizing radiation such as an electron beam may be appropriately selected depending on the thickness of the resin sealing sheet to be subjected to crosslinking treatment. For example, when the resin sealing sheet has a thickness of 500 μm, the entire layer is crosslinked. Is preferably 300 kV or higher.

  The irradiation dose of ionizing radiation such as an electron beam is preferably 3 to 500 kGy. By setting the irradiation dose of ionizing radiation within the above range, a resin encapsulating sheet with a uniform degree of crosslinking is obtained, and the gel fraction of the resin encapsulating sheet does not become too large, and solar cells are arranged. It is possible to fill a level difference between a location where the image is placed and a location where it is not placed.

  The accelerating voltage and irradiation dose of ionizing radiation may be changed as appropriate in order to achieve a desired gel fraction and gel distribution. The degree of crosslinking generated by the accelerating voltage and irradiation dose of ionizing radiation is indicated by the gel fraction. The upper limit of the gel fraction of the resin-encapsulated sheet of this embodiment is preferably 65% by mass or less, more preferably 60% by mass or less, and still more preferably 57% by mass or less. The lower limit of the gel fraction is preferably 2% by mass or more, and more preferably 3% by mass or more. Moreover, even at the same irradiation dose, the gel fraction can be determined by utilizing the difference in the degree of crosslinking depending on the type of ethylene polymer and the difference in the degree of crosslinking due to the promotion of crosslinking with a crosslinking aid or the like and the inhibition of crosslinking due to an antioxidant. Can be adjusted as appropriate.

  As a method of obtaining a resin encapsulating sheet having a gel fraction in the above range, a method of utilizing the difference in crosslinking due to the type of ethylene polymer, or the difference in crosslinking due to crosslinking promotion or crosslinking inhibition by additives, This will be described in detail. For example, a resin having an ethylene monomer and a polar group such as vinyl acetate, aliphatic unsaturated carboxylic acid or aliphatic unsaturated carboxylic acid ester is disposed on the surface layer, and linear low density polyethylene (LLDPE), When low-density polyethylene (usually called “VLDPE” or “ULDPE”) is placed in the inner layer, the gel fraction of the surface layer is even if the acceleration voltage is sufficient to pass through the entire layer. High and the inner layer can have a low gel fraction. Furthermore, by adjusting the acceleration voltage, the inner layer of linear low density density polyethylene (LLDPE) or linear ultra low density polyethylene (usually called “VLDPE” or “ULDPE”) is cross-linked. While being constructed as an uncrosslinked layer that does not undergo crosslinking, crosslinking treatment by electron beam irradiation can be performed. Further, when a polypropylene resin is used as the inner layer, the polypropylene resin tends to be hard to be cross-linked by ionizing radiation irradiation and the like, so that an uncrosslinked layer can be constructed. In addition, in this embodiment, a gel fraction can be measured by the method as described in the Example mentioned later.

  It is preferable that the resin sealing sheet of this embodiment does not contain an organic peroxide that induces a crosslinking reaction. By not containing the organic peroxide, there is no risk of decomposition of the organic peroxide at the distribution stage of the resin-encapsulated sheet, and the temperature conditions during sheet molding can be set in a wide range. In addition, the resin-encapsulated sheet containing no organic peroxide is an organic peroxide that induces a crosslinking reaction while maintaining transparency, adhesiveness, and creep resistance, and other members such as solar cells by decomposition thereof. This eliminates the adverse effects on the product and speeds up the process by eliminating the crosslinking process, which was difficult in the past, and reliably seals irregularities such as glass for solar cells, wiring, and thickness of power generation cells with a resin sealing sheet. can do.

  When the resin sealing sheet is composed of two or more layers, it may include a layer crosslinked by a conventionally known method such as use of peroxide in addition to the layer irradiated with ionizing radiation (electron beam, γ-ray, ultraviolet ray, etc.). Good. The crosslinking treatment process may be performed before or after the embossing treatment process described above.

<Sealing method>
The resin-encapsulated sheet of the present embodiment is a resin-encapsulated sheet used for solar cells. For example, when producing a solar cell module composed of glass, a power generation portion, and a back sheet, each component is sealed. Used. Examples of the sealing method include a method in which the resin of the resin sealing sheet is softened and closely adhered to each constituent member.

  The term “softening” as used herein means giving energy such as heat to the resin to make the resin softened. Since the energy at that time is simple, heat is preferable, but it is not limited thereto. Also, how to give energy such as heat to the resin is a method of heating directly with heating wire, an indirect heating method such as radiant heat, a method of generating heat by causing molecular motion of the resin itself by vibrating the molecular chain of the resin Any method may be used. Specific examples of the sealing method used in the present embodiment include a method in which a softened resin is adhered to a material to be sealed and fixed by solidifying the resin. When long-term durability is required, it is fixed stably so that there is no gap between the resin and the material to be sealed. Although used, it is not limited to this.

  When the resin encapsulating sheet of this embodiment does not contain an organic peroxide, when used as a resin encapsulating sheet constituting a module of a solar cell, the transparency, adhesiveness, which are the characteristics of a conventional resin encapsulating sheet, While maintaining the creep resistance, it is possible to eliminate the adverse effects on the organic peroxide that induces the crosslinking reaction and other members such as solar cells due to the decomposition thereof.

  When manufacturing the resin-encapsulated sheet of the present embodiment, when crosslinking treatment is performed by irradiating ionizing radiation in advance without using an organic peroxide, crosslinking in a solar cell modularization process that has been difficult in the past Since the processing can be omitted or simplified, the manufacturing process of the solar cell can be simplified and speeded up. Furthermore, the resin sealing sheet of the present embodiment can seal the unevenness on the surface of the glass for solar cells and the unevenness caused by the thickness of various parts such as wiring and power generation cells without gaps, and is discarded. In this case, it is excellent in recyclability that can separate and separate glass and silicon cells.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example and a comparative example, this invention is not limited to the following content. Further, “parts” and “%” in the examples are based on mass unless otherwise specified.

(Evaluation method)
<Density of ethylene polymer>
The measurement was performed according to JIS K7112.

<Haze and total light transmittance>
The haze was measured according to JIS K7136, and the total light transmittance was measured according to JIS K7361-1, using a haze meter “NDH2000” (manufactured by Nippon Denshoku Industries Co., Ltd.). Glass plate for solar cell (manufactured by AGC, white plate glass 5 cm × 10 cm square: thickness 3 mm) / resin sealing sheet / glass plate for solar cell (manufactured by AGC, white plate glass 5 cm × 10 cm square: thickness 3 mm) Using a LM50 type vacuum laminating apparatus (NPC), the sample was preheated and degassed at 150 ° C. for 5 minutes and then vacuum laminated for 5 minutes to obtain a sample, which was used for measurement.

(Preparation of raw materials)
<Ethylene Polymer-1 (a-1)>
A low density polyethylene resin (ethylene homopolymer; “Suntech-LD M6525” manufactured by Asahi Kasei Chemicals Corporation) was used as the ethylene polymer. The density of this low density polyethylene was 0.916 g / cm ³ .

<Ethylene polymer-2 (a-2)>
A linear low-density polyethylene resin (ethylene-1-hexene copolymer; “Evolue SP2040” manufactured by Prime Polymer Co., Ltd.) was used as the ethylene polymer. The density of this linear low density polyethylene was 0.918 g / cm ³ .

<Cyclic aliphatic metal salt (b)>
As the cycloaliphatic metal salt, calcium cis-hexahydrophthalate (manufactured by Milliken Chemical Co., “Hyperform HPN-20E”) was used.

(Production of master batch)
<Masterbatch-1 (c-1)>
To 100 parts by mass of low density polyethylene resin (ethylene homopolymer; manufactured by Asahi Kasei Chemicals Corporation, “Suntech-LD M6525”) using a twin screw extruder (“KZW15TW-45MG type”) manufactured by Technobel Co., Ltd. On the other hand, a mixture of 2 parts by mass of cycloaliphatic metal salt (b) was extruded at a resin temperature of 130 ° C. to prepare a master batch.

<Masterbatch-2 (c-2)>
Linear low density polyethylene resin (ethylene-1-hexene copolymer; manufactured by Prime Polymer Co., Ltd., “Evolue SP2040”) using a twin screw extruder (“KZW15TW-45MG type”) manufactured by Technobel Co., Ltd. What mixed 2 mass parts of cycloaliphatic metal salt (b) with respect to 100 mass parts was extruded at the resin temperature of 200 degreeC, and the masterbatch was produced.

<Masterbatch-3 (c-3)>
Instead of the cycloaliphatic metal salt (b), 1,3-p-methylbenzylidene corresponding to the compound represented by the above formula (1) synthesized according to the method described in Japanese Patent Publication No. 02-059832 Except having used -2, 4- benzylidene sorbitol, it extruded on the conditions similar to the masterbatch 1, and produced the masterbatch.

<Masterbatch-4 (c-4)>
A master batch except that 1,2,3,4-di-p-methylbenzylidene sorbitol synthesized in accordance with the method described in Japanese Patent Publication No. 02-059832 is used instead of the cyclic aliphatic metal salt (b). A master batch was prepared by extrusion under the same conditions as in 1.

<Masterbatch-5 (c-5)>
Extruded under the same conditions as in Masterbatch 1 except that sodium p-tert-butylbenzoate (manufactured by Sakai Chemical Industry Co., Ltd.) was used instead of cycloaliphatic metal salt (b) to produce a masterbatch did.

(Examples 1-4, Comparative Examples 1-4)
<Preparation of resin encapsulated sheet>
With the composition shown in Table 1, the temperature of the resin was adjusted using a T-die-equipped twin screw extruder ("KZW15TW-45MG type" / width 150 mm T-die attachment / lip thickness 0.8 mm) manufactured by Technobel Co., Ltd. By extrusion molding, a resin-sealed sheet having a thickness of 600 μm was obtained.
<Electron beam irradiation treatment>
The obtained resin-encapsulated sheet was irradiated with an electron beam under the conditions of an acceleration voltage of 500 kV and an irradiation density of 60 kGy using “EPS-800” (manufactured by Nissin High Voltage Co., Ltd.).

  The measurement results are shown in Table 1. In any of the examples, the haze was 60% or less, and the haze improvement effect was clear even when compared with the comparative example. Moreover, in all the Examples, the total light transmittance was 75% or more. In particular, in Examples 1 to 3 using the master batch dispersed in the resin in advance, the total light transmittance was 85% or more.

  The solar cell resin-encapsulated sheet according to the present invention can be suitably used as a solar cell member.

Claims (4)

A resin encapsulating sheet for solar cells that softens and adheres to a resin,
As the resin constituting the solar cell resin encapsulating sheet, ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic ester copolymer, ethylene-α -Containing at least one selected from the group consisting of an olefin copolymer and an ethylene homopolymer, and
The resin sealing sheet for solar cells containing the sorbitol type compound or cycloaliphatic metal salt represented by following formula (1) in the range of 10 mass ppm or more and 5000 mass ppm or less in total.
(In the formula, when R ₁ is H, R ₂ represents an alkyl group or chloro group having 1 to 3 carbon atoms, and when R ₂ is H, R ₁ represents an alkyl group or chloro group having 1 to 3 carbon atoms. Represents.)   The resin sealing sheet for solar cells according to claim 1, further comprising a silane coupling agent in the range of 0.01% by mass to 5% by mass in the resin sealing sheet for solar cells.   The resin-encapsulated sheet for a solar cell according to claim 1 or 2, further comprising at least one selected from the group consisting of an antioxidant, a light stabilizer, and an ultraviolet absorber. A sorbitol compound represented by the following formula (1) or a cyclic aliphatic metal salt is converted into an ethylene-vinyl acetate copolymer, an ethylene-aliphatic unsaturated carboxylic acid copolymer, an ethylene-aliphatic unsaturated carboxylic acid ester. Adding in a state dispersed in at least one resin selected from the group consisting of a copolymer, an ethylene-α-olefin copolymer, and an ethylene homopolymer, and molding the sheet;
Irradiating the sheet with ionizing radiation to control the gel fraction of the sheet to a range of 2 mass% to 65 mass%;
The manufacturing method of the resin sealing sheet for solar cells which has these.
(In the formula, when R ₁ is H, R ₂ represents an alkyl group or chloro group having 1 to 3 carbon atoms, and when R ₂ is H, R ₁ represents an alkyl group or chloro group having 1 to 3 carbon atoms. Represents.)