JP2016004895A - Sealing film for solar battery and solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing film for a solar battery and a solar battery in which resin particles formed of acrylic resin containing organic rare earth complex are contained as wavelength conversion material and an effect of enhancing the power generation efficiency of the solar battery can be kept for a long term.SOLUTION: A sealing film contains resin material containing olefin (co-)polymer and wavelength conversion material. The wavelength conversion material contains resin particles formed of acrylic resin including organic rare earth complex. The acrylic resin is polymer obtained by reacting components for acrylic resin containing (meta) acrylate monomer, crosslinking agent and azo-type polymerization initiator. The crosslinking agent contains azo-type polymerization initiator, and does not substantially contain organic peroxide having a group represented by R-C(=O)O- (R represents a carbon hydrocarbon group which may be arbitrarily substituted), but contains organic peroxide whose half-life temperature per minute is not more than 145°C.

Description

  The present invention relates to a solar cell sealing film that includes a wavelength conversion material to increase light rays contributing to power generation of a solar cell element and improve power generation efficiency.

  In recent years, solar cells that directly convert sunlight into electrical energy have been widely used from the viewpoints of effective use of resources and prevention of environmental pollution, and further development has been promoted in terms of power generation efficiency and weather resistance.

  As shown in FIG. 1, a solar cell generally includes a surface-side transparent protective member 11 made of a glass substrate, a surface-side sealing film 13A made of a resin material such as an ethylene-vinyl acetate copolymer (EVA), and a silicon crystal. A solar battery cell 14 such as a system power generation element, a back surface side sealing film 13B, and a back surface side protective member (back cover) 12 are laminated in this order, deaerated under reduced pressure, and heated and pressurized to seal the surface side. It is manufactured by cross-linking and hardening the stop film 13A and the back surface side sealing film 13B.

  On the other hand, in general, any type of solar cell element such as a silicon crystal power generation element has a low spectral sensitivity to light in the ultraviolet region, and the problem that solar energy cannot be effectively utilized is known. It has been. In order to solve this problem, a layer containing a material (wavelength conversion material) that converts light in the ultraviolet region into light in the visible region or near-infrared region is provided on the light receiving surface side of the solar battery cell. There has been proposed a technique for improving the power generation efficiency of a solar cell by emitting light having a wavelength that greatly contributes to the power generation of the solar cell. However, a fluorescent substance such as an organic rare earth complex used as a wavelength conversion material has a problem that it is low in dispersibility or easily deteriorated in a resin material for a sealing film such as EVA. In order to solve the problem, in Patent Document 1, a fluorescent substance such as an organic rare earth complex having an absorption peak at 300 to 450 nm and a fluorescence peak at 500 to 900 nm is included in a resin particle composed of a vinyl compound or the like. There has been proposed a solar cell sealing film in which the particles thus dispersed are dispersed in a sealing film.

JP 2012-33605 A

  However, when the present inventors examined the resin material of the resin particles encapsulating the organic rare earth complex, for example, when an acrylic resin mainly composed of poly (methyl methacrylate) (PMMA) is used as the resin material, It has been found that the effect of improving the power generation efficiency may decrease due to the deterioration of the organic rare earth complex.

  Accordingly, an object of the present invention is a solar cell encapsulating film containing resin particles in which an organic rare earth complex is encapsulated in an acrylic resin as a wavelength conversion material, which prevents deterioration of the organic rare earth complex and improves power generation efficiency. It is providing the sealing film for solar cells which can maintain an effect for a long period of time.

  Moreover, the objective of this invention is providing the solar cell which can maintain high electric power generation efficiency for a long period of time using the sealing film for solar cells.

  The object is a sealing film for a solar cell containing a resin material containing an olefin (co) polymer and a wavelength conversion material, wherein the wavelength conversion material is a resin particle made of an acrylic resin encapsulating an organic rare earth complex. And the acrylic resin is a polymer obtained by reacting an acrylic resin composition containing a (meth) acrylate monomer, a crosslinking agent, and an azo polymerization initiator, and the acrylic resin composition is polymerized. As an agent, an organic peroxide having a group represented by R—C (═O) O— (R represents an optionally substituted hydrocarbon group) is substantially free, and As another polymerization initiator, it is achieved by a sealing film for a solar cell comprising an organic peroxide having a 1 minute half-life temperature of 145 ° C. or lower.

  When the present inventors examined the factor which the organic rare earth complex in an acrylic resin deteriorates, R-C (= O), such as a benzoyl peroxide which is a polymerization initiator generally used for the preparation of an acrylic resin. When an organic peroxide having a group represented by O- (R represents an optionally substituted hydrocarbon group) is blended in the acrylic resin composition, benzoa It was considered that carboxylic acids such as acids were generated, and that the organic rare earth complexes were deteriorated by this acid. Therefore, in the present invention, an azo polymerization initiator is employed as the polymerization initiator in the acrylic resin composition, and an organic peroxide having a group represented by R—C (═O) O— is substantially included. Therefore, the organic rare earth complex encapsulated in the acrylic resin is prevented from being deteriorated. On the other hand, it is preferable to use an organic peroxide that does not generate an acid in addition to the azo polymerization initiator as the polymerization initiator because a sufficient degree of crosslinking can be secured in the resulting acrylic resin. However, since the polymerization reaction for preparing the acrylic resin is preferably performed by suspension polymerization as described later, an organic peroxide that starts the reaction at a relatively low temperature is required. Therefore, the present invention stipulates that an organic peroxide having a one-minute half-life temperature of 145 ° C. or lower is included as another polymerization initiator. In addition, this organic peroxide naturally has no group represented by R—C (═O) O— (R represents an optionally substituted hydrocarbon group). It is a peroxide. Thereby, in an acrylic resin, generation | occurrence | production of an acid can be prevented and sufficient bridge | crosslinking degree can be ensured, Therefore The deterioration of the organic rare earth complex in an acrylic resin can fully be prevented. Therefore, as a wavelength conversion material, a solar cell sealing film containing resin particles in which an organic rare earth complex is encapsulated in an acrylic resin can maintain the effect of improving power generation efficiency for a long period of time. It is.

  Preferred embodiments of the solar cell sealing film according to the present invention are as follows.

  (1) The organic peroxide having a 1-minute half-life temperature of 145 ° C. or lower is 1,1-di (t-butylperoxy) -2-methylcyclohexane.

  (2) The (meth) acrylate monomer is methyl methacrylate.

［式中、Ｒ１及びＲ２は、それぞれ独立して水素原子又はメチル基を表し、ｎは、２〜１４の整数である。］で表される化合物である。アクリル樹脂用組成物に、架橋剤（本発明において、複数個の重合性二重結合を有するモノマーのことをいう）を配合することで、十分な架橋度を確保し、樹脂粒子の膨潤を防止することができ、気泡の発生、ヘイズ値の上昇及び透過率の低下を抑制することができるが、一般的に使用される架橋剤であるポリエチレングリコールジ（メタ）アクリレート（エチレン基の数が２以上）を用いた場合、エチレンオキサイド基の親水性が高いため、得られるアクリル樹脂が吸湿し易くなる傾向があり、樹脂用組成物の構成成分の加水分解による酸の発生を引き起こす場合がある。架橋剤として、上記式（Ｉ）の直鎖アルキレン基を有するジ（メタ）アクリレート化合物を選定することで、親水性成分を低減することができ、得られるアクリル樹脂において、より酸が発生し難くなり、アクリル樹脂に内包された有機希土類錯体の劣化をさらに防止することができる。 (3) The crosslinking agent is represented by the following formula (I):

[Wherein, R 1 and R 2 each independently represent a hydrogen atom or a methyl group, and n is an integer of 2 to 14. It is a compound represented by this. By adding a crosslinking agent (referred to as a monomer having a plurality of polymerizable double bonds in the present invention) to the acrylic resin composition, a sufficient degree of crosslinking is secured and swelling of the resin particles is prevented. Although it is possible to suppress the generation of bubbles, increase in haze value and decrease in transmittance, polyethylene glycol di (meth) acrylate, which is a commonly used crosslinking agent (the number of ethylene groups is 2). When the above is used, since the ethylene oxide group has high hydrophilicity, the resulting acrylic resin tends to absorb moisture, which may cause acid generation due to hydrolysis of the constituent components of the resin composition. By selecting a di (meth) acrylate compound having a linear alkylene group of the above formula (I) as the crosslinking agent, the hydrophilic component can be reduced, and the resulting acrylic resin is less likely to generate an acid. Thus, the deterioration of the organic rare earth complex encapsulated in the acrylic resin can be further prevented.

  (4) The acrylic resin composition further comprises a hydrophobic monomer having a higher n-octanol / water partition coefficient than methyl methacrylate. As a result, the water resistance of the resulting acrylic resin is further improved and the hygroscopicity is suppressed, so that it is more difficult for acid to be generated, and deterioration of the organic rare earth complex included in the acrylic resin can be further prevented.

  (5) In (4), the hydrophobic monomer is styrene.

［式中、Ｒは、それぞれ独立して水素原子又は任意に置換されていても良い炭素原子数１〜２０の炭化水素基を表し、ｎは、１〜４の整数である。］で表されるユウロピウム錯体である。上記ユウロピウム錯体は、耐紫外線性に優れているので太陽電池用封止膜に含有させる有機金属錯体として好ましいが、酸による劣化が生じる場合がある。本発明において、上記アクリル樹脂に内包させることで、酸による劣化を防止することで、より耐候性の高い波長変換材料とすることができる。 (6) The organic rare earth complex has the following formula (II):

[Wherein, R independently represents a hydrogen atom or an optionally substituted hydrocarbon group having 1 to 20 carbon atoms, and n is an integer of 1 to 4. It is a europium complex represented by this. The europium complex is preferable as an organometallic complex to be contained in the solar cell sealing film because it has excellent ultraviolet resistance, but it may be deteriorated by acid. In this invention, it can be set as the wavelength conversion material with higher weather resistance by preventing degradation by an acid by making it include in the said acrylic resin.

  (7) In (6), the organic rare earth complex is a europium complex in which R is a hydrogen atom and n is 1 in the formula (II).

  (8) An ethylene / α-olefin copolymer (m-LLDPE), a low density polyethylene (LDPE), a linear low density polyethylene (LLDPE), wherein the olefin (co) polymer is polymerized using a metallocene catalyst, One or more polymers selected from the group consisting of polypropylene, polybutene, and ethylene-polar monomer copolymers.

  (9) The olefin (co) polymer is an ethylene / α-olefin copolymer (m-LLDPE) and / or an ethylene-polar monomer copolymer polymerized using a metallocene catalyst. It is excellent in processability, can form a crosslinked structure with a crosslinking agent, and can be a sealing film with high adhesiveness.

  (10) The ethylene-polar monomer copolymer is an ethylene-vinyl acetate copolymer or an ethylene-methyl (meth) acrylate copolymer (EMMA). It can be set as the sealing film which was more excellent in transparency and excellent in the softness | flexibility.

  Moreover, the said objective is achieved by the solar cell characterized by sealing a solar cell element with the sealing film for solar cells of this invention. Since the solar cell sealing film of the present invention is used in the solar cell of the present invention, the power generation efficiency of the solar cell element is improved by the wavelength conversion material, and the high power generation efficiency is maintained for a long time. It can be said that it is a battery.

  The wavelength conversion material contained in the solar cell sealing film of the present invention includes an organic peroxide having an azo polymerization initiator as a polymerization initiator and having a group represented by R—C (═O) O—. Resin particles containing an organic rare earth complex in an acrylic resin obtained from a resin composition containing an organic peroxide having a predetermined half-life temperature, and preventing deterioration of the organic rare earth complex in the resin. Has been. Therefore, the solar cell sealing film containing the resin particles as a wavelength conversion material is a solar cell sealing film capable of maintaining the effect of improving the power generation efficiency of the solar cell element for a long period of time. And it can be said that the solar cell of this invention is a solar cell by which high electric power generation efficiency is maintained for a long period of time.

It is a schematic sectional drawing of a common solar cell.

  The encapsulating film for solar cell of the present invention includes at least a resin material containing an olefin (co) polymer and resin particles made of an acrylic resin including an organic rare earth complex as a wavelength conversion material. The acrylic resin is a polymer obtained by reacting an acrylic resin composition containing a (meth) acrylate monomer, a crosslinking agent, and an azo polymerization initiator, and the acrylic resin composition is a polymerization initiator. As an organic peroxide having a group represented by R—C (═O) O— (R represents an optionally substituted hydrocarbon group), and As the polymerization initiator, an organic peroxide having a 1 minute half-life temperature of 145 ° C. or lower is included.

  The acrylic resin is generally a resin obtained by polymerizing a (meth) acrylic monomer such as methyl (meth) acrylate as a main component. Generally, R—C (═O) O— such as benzoyl peroxide, 4-methylbenzoyl peroxide, isobutyryl peroxide, and dilauryl peroxide, which are polymerization initiators used for the polymerization of (meth) acrylic monomers. In the case where an organic peroxide having a group represented by formula (2) is blended in an acrylic resin composition, a carboxylic acid such as benzoic acid is generated in the resulting acrylic resin, and this acid may cause deterioration of the organic rare earth complex. is there. In the present invention, an azo polymerization initiator is employed as the polymerization initiator, and the acrylic resin is substantially free of an organic peroxide having a group represented by R—C (═O) O—. Degradation of the organic rare earth complex encapsulated in is prevented. In the present invention, “substantially free” means 0.01 mass part or less, preferably 0.005 mass part or less, with respect to 100 mass parts of the (meth) acrylate monomer in the acrylic resin composition. In particular, it means 0 parts by mass. On the other hand, by using an organic peroxide that does not generate an acid in addition to the azo polymerization initiator as the polymerization initiator, it is possible to ensure a more sufficient degree of crosslinking in the resulting acrylic resin. However, since the polymerization reaction for preparing the acrylic resin is preferably performed by suspension polymerization as described later, an organic peroxide that starts the reaction at a relatively low temperature is required. Therefore, the present invention stipulates that an organic peroxide having a one-minute half-life temperature of 145 ° C. or lower is included as another polymerization initiator. In addition, this organic peroxide naturally has no group represented by R—C (═O) O— (R represents an optionally substituted hydrocarbon group). It is a peroxide. Thereby, in an acrylic resin, generation | occurrence | production of an acid can be prevented and sufficient bridge | crosslinking degree can be ensured, Therefore The deterioration of the organic rare earth complex in an acrylic resin can fully be prevented.

  Since the sealing film for solar cells of the present invention contains the resin particles made of the acrylic resin encapsulating an organic rare earth complex as a wavelength conversion material, the effect of improving the power generation efficiency can be maintained for a long period of time. It is a sealing film for solar cells.

  In the present invention, the azo polymerization initiator used as a polymerization initiator is optimal for a polymerization reaction by suspension polymerization because the reaction starts at a relatively low temperature. The azo polymerization initiator is not particularly limited. For example, 2,2′-azobis (isobutyronitrile) (AIBN), 2,2′-azobis (2,4-dimethylvaleronitrile), 2, Examples include 2′-azobis (2-methylbutyronitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), dimethyl-2,2′-azobisisobutyrate, and the like. Although there is no restriction | limiting in particular in content of the azo polymerization initiator in the composition for acrylic resins, 0.01-5 mass parts is preferable with respect to 100 mass parts of (meth) acrylate monomers, 0.01-1 mass part Is preferable, and 0.05 to 0.5 part by mass is particularly preferable.

  On the other hand, as another polymerization initiator, the one-minute half-life temperature contained in the acrylic resin composition is 145 ° C. or lower, and a group represented by R—C (═O) O— (R is optionally substituted) The organic peroxide having no hydrocarbon group is not particularly limited, but for example, 1,1-di (t-butylperoxy) -2-methylcyclohexane is preferable. Can be mentioned. Although there is no restriction | limiting in particular in content of the said organic peroxide in the composition for acrylic resins, 0.01-2 mass parts is preferable with respect to 100 mass parts of (meth) acrylate monomers, 0.05-1 mass part Is preferable, and 0.1-0.5 mass part is especially preferable.

  Below, the other material which comprises the sealing film for solar cells of this invention is demonstrated.

[Resin particles (wavelength conversion material)]
In the present invention, the resin particles are made of an acrylic resin containing an organic rare earth complex. And as above-mentioned, an acrylic resin is a polymer obtained by making the composition for acrylic resins which contains a (meth) acrylate monomer and a crosslinking agent as a main component other than the said polymerization initiator react. The (meth) acrylate monomer is not particularly limited. For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) ) Acrylate, 2-ethylhexyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, and the like. These (meth) acrylate monomers may be used alone or in combination of two or more. In order to make the refractive index of the obtained acrylic resin closer to the resin material of the sealing film for solar cells, it is preferable to use methyl (meth) acrylate, and particularly preferably methyl methacrylate as the (meth) acrylate monomer. As a result, even if resin particles are contained in the solar cell sealing film, a decrease in transparency caused by a difference in refractive index is unlikely to occur, and a solar cell sealing film with higher transparency can be obtained.

  In the present invention, by adding a crosslinking agent to the acrylic resin composition, a sufficient degree of crosslinking can be ensured, and the resin particles can prevent swelling due to the influence of coexisting additives and solvents, and appearance due to void generation Defects, generation of bubbles, increase in haze value, and decrease in transmittance can be suppressed. However, when polyethylene glycol di (meth) acrylate (the number of ethylene groups is 2 or more), which is a commonly used crosslinking agent, is used, the acrylic resin obtained absorbs moisture because the hydrophilicity of ethylene oxide groups is high. It tends to be easy, and may cause the generation of acid by hydrolysis of the constituent components of the resin composition. Therefore, in the present invention, the crosslinking agent has the following formula (I):

［式中、Ｒ１及びＲ２は、それぞれ独立して水素原子又はメチル基を表し、ｎは、２〜１４の整数である。］で表される化合物であることが好ましい。架橋剤として、式（Ｉ）で表される直鎖アルキレン基を有するジ（メタ）アクリレート化合物を選定することで、親水性成分を低減することができ、得られるアクリル樹脂において、より酸が発生し難くなり、アクリル樹脂に内包された有機希土類錯体の劣化をさらに防止することができる。

[Wherein, R 1 and R 2 each independently represent a hydrogen atom or a methyl group, and n is an integer of 2 to 14. It is preferable that it is a compound represented by this. By selecting a di (meth) acrylate compound having a linear alkylene group represented by the formula (I) as a crosslinking agent, hydrophilic components can be reduced, and more acid is generated in the resulting acrylic resin. This makes it possible to further prevent deterioration of the organic rare earth complex encapsulated in the acrylic resin.

  Specific examples of the di (meth) acrylate compound include ethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and 1,9- Nonanediol di (meth) acrylate, 1,14-tetradecanediol di (meth) acrylate, and the like can be given. “(Meth) acrylate” means “acrylate or methacrylate”.

  In the acrylic resin composition, the content of the di (meth) acrylate compound represented by the formula (I) is not particularly limited, and can be appropriately set within a range not impairing the effects of the present invention. For example, in the formula (I), when n is 2, since one highly hydrophilic ethylene oxide group is contained, in order to suppress the hygroscopicity of the resulting acrylic resin, It is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, and particularly preferably 1 to 5 parts by mass. In addition, when n is 3 to 14, since the influence of a linear alkylene group having high hydrophobicity is increased, the amount is preferably 0.1 to 50 parts by mass with respect to 100 parts by mass of methyl methacrylate. More preferably, it is 50 mass parts, and it is especially preferable that it is 5-50 mass parts. Thereby, since the raise of the hygroscopic property of the acrylic resin by further mix | blending a crosslinking agent can be suppressed and it becomes difficult to generate | occur | produce an acid, deterioration of the organic rare earth complex in an acrylic resin can further be prevented.

  In the present invention, the composition for acrylic resin may further contain (meth) acrylate monomer, particularly other monomer copolymerizable with methyl methacrylate, as long as the object of the present invention is not impaired. In particular, in order to further improve the water resistance of the resulting acrylic resin and suppress hygroscopicity, it is preferable to include a hydrophobic monomer having a higher n-octanol / water partition coefficient than methyl methacrylate (partition coefficient of methyl methacrylate: 1 .38). Suppressing the hygroscopicity of the acrylic resin makes it more difficult for an acid to be generated in the acrylic resin, and further prevents deterioration of the organic rare earth complex encapsulated in the acrylic resin. In the present invention, the hydrophobic monomer refers to a polymerizable monomer having a property of phase separation when mixed with water, and has no polar group in the structure or has no polarity even if it has a polar group in the structure. It is. Specifically, for example, a (meth) acrylate monomer having a hydroxyalkyl group having 4 or more carbon atoms, preferably 4 to 20 carbon atoms as an alcohol residue, a styrene monomer, a fluorine-containing monomer, and the like are preferable. Examples of the hydrophobic (meth) acrylate monomer include n-butyl (meth) acrylate (partition coefficient: 2.88), isobutyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (exemplified as (meth) acrylate monomers. (Meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like. The styrene monomer is a polymerizable monomer containing a styrene structure, and includes styrene (distribution coefficient: 2.95), o-methylstyrene, m-methyl. Styrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc., and fluorine-containing As a monomer, trifluoromethyl (meth) Methacrylate, trifluoroethyl (meth) acrylate (partition coefficient: 1.51), trifluoroacetic isobutyl (meth) acrylate, perfluorohexylethyl (meth) acrylate, perfluorooctyl ethyl (meth) acrylate. These (meth) acrylate monomers may be used alone or in combination of two or more. The hydrophobic monomer preferably includes a styrene monomer and a fluorine-containing monomer in that the water resistance of the resulting acrylic resin can be further improved. Among them, styrene, n-butyl methacrylate, isobutyl methacrylate, trifluoromethyl methacrylate are preferable. , Trifluoroethyl acrylate, trifluoroethyl methacrylate and trifluoroisobutyl methacrylate, trifluoroisobutyl acrylate, perfluorohexyl ethyl methacrylate, perfluorohexyl ethyl acrylate, perfluorooctyl ethyl methacrylate, perfluoro octyl ethyl acrylate It is preferable that one or more monomers are included, and it is particularly preferable that styrene is included. Although there is no restriction | limiting in particular in content of the hydrophobic monomer in the composition for acrylic resins, 1-125 mass parts is preferable with respect to 100 mass parts of (meth) acrylate monomers, 5-80 mass parts is preferable, 40 parts by mass is particularly preferred.

  In the present invention, the method for polymerizing the above monomer to obtain an acrylic resin is not particularly limited, and can be performed by a conventionally known method such as suspension polymerization or emulsion polymerization. Among these, suspension polymerization is preferable because it has advantages such as easy reaction control. In suspension polymerization, the monomer is polymerized in a solvent such as water in the presence of the polymerization initiator. The solvent can include an organic solvent in addition to water. Examples of the organic solvent include alcohols such as methanol, ethanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, pentanol, ethylene glycol, propylene glycol, 1,4-butanediol; acetone, Examples thereof include ketones such as methyl ethyl ketone; astels such as ethyl acetate; (cyclo) paraffins such as isooctane and cyclohexane; aromatic hydrocarbons such as benzene and toluene. These may be used alone or in combination of two or more. The temperature of the polymerization reaction can be appropriately adjusted according to the polymerization initiator used. When two or more kinds of polymerization initiators are used, the polymerization may be carried out by changing the temperature in several stages.

  In the present invention, the method of encapsulating the organic rare earth complex in the acrylic resin is, for example, a method of encapsulating the resin composition obtained by dissolving or dispersing the organic rare earth complex in the acrylic resin composition by suspension polymerization or the like. Etc.

  In the present invention, the shape of the resin particles is not particularly limited, but a spherical shape is preferable in terms of low dispersibility and light scattering properties. In addition, the average particle diameter of the resin particles is not particularly limited, but if it is too large, the surface area per mass of the fine particles becomes small, so that the light emission efficiency may be reduced. Resin particles may be easily bonded to each other and dispersibility may be reduced. Therefore, the average particle diameter of the resin particles is preferably 0.1 to 300 μm, more preferably 1 to 200 μm, and particularly preferably 10 to 150 μm. The average particle diameter of the resin particles can be determined by a laser diffraction method, an image image obtained by an optical microscope or an electron microscope.

[Organic rare earth complex]
In the present invention, the organic rare earth complex can be used without any particular limitation. Examples thereof include lanthanoid complexes such as europium, samarium and terbium. Europium complexes are particularly preferred in that the fluorescence is strong, the Stokes shift (difference between excitation maximum wavelength and emission maximum wavelength) is large, and the fluorescence lifetime is long. The europium complex is composed of Eu ions (Eu3 +) and an organic ligand, and examples thereof include Eu (hfa) 3 (TPPO) 2, Eu (hfa) 3 (BIPHEPO), Eu (TTA) 3Phen, and the like. In particular, in terms of weather resistance, the following formula (II):

［式中、Ｒは、それぞれ独立して、水素原子又は任意に置換されていても良い炭素原子数１〜２０の炭化水素基を表し、ｎは、１〜４の整数、好ましくは１である。］で表されるユウロピウム錯体が好ましい。炭素原子数１〜２０の炭化水素基は、脂肪族でも芳香族でも良く、不飽和結合やヘテロ原子を含んでいても良く、直鎖状でも分枝を有していても良い。例えば、アルキル基（メチル基、エチル基、プロピル基等）、アルケニル基（ビニル基、アリル基、ブテニル基等）、アルキニル基（エチニル基、プロピニル基、ブチニル基等）、シクロアルキル基、シクロアルケニル基、フェニル基、ナフチル基、ビフェニル基等が挙げられる。上記炭化水素基は任意に置換されていても良く、置換基としては、ハロゲン原子、ヒドロキシル基、アミノ基、ニトロ基、スルホ基等が挙げられる。式（Ｉ）におけるＲは全て水素原子であることが好ましい。

[Wherein, each R independently represents a hydrogen atom or an optionally substituted hydrocarbon group having 1 to 20 carbon atoms, and n is an integer of 1 to 4, preferably 1. . ] The europium complex represented by this is preferable. The hydrocarbon group having 1 to 20 carbon atoms may be aliphatic or aromatic, may contain an unsaturated bond or a hetero atom, and may be linear or branched. For example, alkyl group (methyl group, ethyl group, propyl group etc.), alkenyl group (vinyl group, allyl group, butenyl group etc.), alkynyl group (ethynyl group, propynyl group, butynyl group etc.), cycloalkyl group, cycloalkenyl group Group, phenyl group, naphthyl group, biphenyl group and the like. The hydrocarbon group may be optionally substituted, and examples of the substituent include a halogen atom, a hydroxyl group, an amino group, a nitro group, and a sulfo group. R in formula (I) is preferably all hydrogen atoms.

  The europium complex of the formula (II) is preferable as an organometallic complex to be contained in the sealing film for solar cells because it is excellent in ultraviolet resistance, but may be deteriorated by an acid. In this invention, it can be set as the wavelength conversion material with higher weather resistance by preventing degradation by an acid by making it include in the said acrylic resin.

  The above europium complex is preferably Eu (hfa) 3 (TPPO) 2 in which n in the formula (II) is 1 and all R are hydrogen atoms from the viewpoint of particularly excellent ultraviolet resistance. Eu (hfa) 3 (TPPO) 2 is a europium complex in which two ligands of triphenylphosphine oxide and hexafluoroacetylacetone are coordinated to a rare earth metal europium which is a central element.

  The content of the organic rare earth complex in the resin particles is not particularly limited as long as the effect of improving the power generation efficiency of the solar cell element can be obtained when it is contained in the solar cell sealing film. The higher the organic rare earth complex content in the resin particles, the higher the emission intensity, which is advantageous. On the other hand, if the content is too high, the transparency may be affected, which is disadvantageous in terms of cost. Therefore, the content of the organic rare earth complex in the resin particles is preferably 0.01 to 10% by mass, more preferably 0.05 to 5% by mass, and particularly preferably 0.1 to 1% by mass.

[Resin material]
In this invention, the resin material of the sealing film for solar cells contains an olefin (co) polymer as a main component. Here, the olefin (co) polymer means an ethylene / α-olefin copolymer (for example, an ethylene / α-olefin copolymer (m-LLDPE) polymerized using a metallocene catalyst), polyethylene (for example, Olefin polymers such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polypropylene, polybutene, and the like, and copolymers of olefins and polar monomers such as ethylene-polar monomer copolymers. It means a copolymer and has adhesiveness and transparency required for a sealing film for solar cells. As the olefin (co) polymer, one of these may be used, or two or more may be mixed and used. In the present invention, as the olefin (co) polymer, an ethylene / α-olefin copolymer (m-LLDPE) polymerized using a metallocene catalyst, a low density polyethylene (LDPE), a linear low density polyethylene (LLDPE). ), At least one polymer selected from the group consisting of polypropylene, polybutene and ethylene-polar monomer copolymers. In particular, an olefin (co) polymer can be formed using a metallocene catalyst because it is excellent in processability, can form a crosslinked structure with a crosslinking agent, and can form a solar cell sealing film with high adhesion. A polymerized ethylene / α-olefin copolymer (m-LLDPE) and / or an ethylene-polar monomer copolymer is preferred.

(Ethylene / α-olefin copolymer (m-LLDPE) polymerized using metallocene catalyst)
m-LLDPE is composed mainly of a structural unit derived from ethylene and further has an α-olefin having 3 to 12 carbon atoms, such as propylene, 1-butene, 1-hexene, 1-octene, 4-methylpentene-1, An ethylene / α-olefin copolymer (including a terpolymer and the like) having one or more structural units derived from 4-methyl-hexene-1, 4,4-dimethyl-pentene-1, and the like. Specific examples of the ethylene / α-olefin copolymer include an ethylene / 1-butene copolymer, an ethylene / 1-octene copolymer, an ethylene-4-methyl-pentene-1 copolymer, an ethylene / butene / hexene copolymer. Center polymers, ethylene / propylene / octene terpolymers, ethylene / butene / octene terpolymers, and the like. The content of the α-olefin in the ethylene / α-olefin copolymer is preferably 5 to 40% by mass, more preferably 10 to 35% by mass, and still more preferably 15 to 30% by mass. When the content of α-olefin is small, the flexibility and impact resistance of the solar cell sealing film may not be sufficient, and when it is too large, the heat resistance may be low.

  A known metallocene catalyst may be used as the metallocene catalyst for polymerizing m-LLPDE, and is not particularly limited. The metallocene catalyst is generally a compound having a structure in which a transition metal such as titanium, zirconium or hafnium is sandwiched between unsaturated cyclic compounds containing a π-electron cyclopentadienyl group or a substituted cyclopentadienyl group. And a promoter such as an aluminum compound such as alkylaluminoxane, alkylaluminum, aluminum halide, and alkylaluminum halide. Metallocene catalysts are characterized by a uniform active site (single site catalyst), and usually a polymer having a narrow molecular weight distribution and an approximately equal comonomer content of each molecule is obtained.

  In the present invention, the density of m-LLDPE (according to JIS K 7112; the same applies hereinafter) is not particularly limited, but is preferably 0.860 to 0.930 g / cm 3. The melt flow rate (MFR) of m-LLDPE (according to JIS-K7210) is not particularly limited, but is preferably 1.0 g / 10 min or more, more preferably 1.0 to 50.0 g / 10 min. 3.0 to 30.0 g / 10 min is more preferable. In addition, MFR is measured on condition of 190 degreeC and load 21.18N.

  In the present invention, commercially available m-LLDPE may be used. For example, Harmolex series, Kernel series manufactured by Nippon Polyethylene Co., Ltd., Evolution series manufactured by Prime Polymer Co., Ltd., Excellen GMH series, Excellen FX series manufactured by Sumitomo Chemical Co., Ltd. and the like can be mentioned.

(Ethylene-polar monomer copolymer)
Examples of the polar monomer of the ethylene-polar monomer copolymer include vinyl esters, unsaturated carboxylic acids, salts thereof, esters thereof, amides thereof, and carbon monoxide. More specifically, vinyl esters such as vinyl acetate and vinyl propionate, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, fumaric acid, itaconic acid, monomethyl maleate, monoethyl maleate, maleic anhydride, and itaconic anhydride. Acids, salts of monovalent metals such as lithium, sodium and potassium of these unsaturated carboxylic acids and salts of polyvalent metals such as magnesium, calcium and zinc, methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, Illustrative examples include n-butyl acrylate, isooctyl acrylate, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, dimethyl maleate and other unsaturated carboxylic acid esters, carbon monoxide, sulfur dioxide and the like. be able to.

  More specific examples of the ethylene-polar monomer copolymer include an ethylene-vinyl ester copolymer such as an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, and an ethylene-methacrylic acid copolymer. An ethylene-unsaturated carboxylic acid copolymer, an ionomer in which some or all of the carboxyl groups of the ethylene-unsaturated carboxylic acid copolymer are neutralized with the above metal, an ethylene-methyl acrylate copolymer, an ethylene- Ethylene-unsaturated carboxylic acid ester copolymer such as ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer (EMMA), ethylene-isobutyl acrylate copolymer, ethylene-n-butyl acrylate copolymer Polymer, ethylene-isobutyl acrylate-methacrylic acid copolymer, ethylene-acrylic acid n-buty -Representative examples of an ethylene-unsaturated carboxylic acid ester-unsaturated carboxylic acid copolymer such as a methacrylic acid copolymer, and an ionomer in which a part or all of the carboxyl groups thereof are neutralized with the above-described metal. Can do.

  As the ethylene-polar monomer copolymer, it is preferable to use a copolymer having a melt flow rate defined by JIS K7210 of 35 g / 10 min or less, particularly 3 to 6 g / 10 min. By using such an ethylene-polar monomer copolymer having a melt flow rate, a sealing film for a solar cell excellent in processability can be obtained. In the present invention, the value of the melt flow rate (MFR) is measured based on conditions of 190 ° C. and a load of 21.18 N according to JIS K7210.

  Examples of the ethylene-polar monomer copolymer include ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl methacrylate copolymer, and ethylene-methyl acrylate copolymer. Ethylene-ethyl acrylate copolymer is preferable, and EVA and EMMA are particularly preferable. Thereby, it can be set as the sealing film for solar cells which is cheap and excellent in transparency and a softness | flexibility. By using such a solar cell sealing film, it is possible to manufacture a solar cell that is more durable and has higher power generation efficiency.

  The content of vinyl acetate in EVA is preferably 20 to 35% by mass, more preferably 22 to 30% by mass, and particularly preferably 24 to 28% by mass with respect to EVA. The lower the content of EVA vinyl acetate units, the harder the sheet obtained. If the content of vinyl acetate is too low, the resulting sheet may not have sufficient transparency when crosslinked and cured at high temperatures. Further, if the vinyl acetate content is too high, the hardness of the sheet may be insufficient.

  The content of methyl methacrylate in EMMA is preferably 20 to 30% by mass, and more preferably 22 to 28% by mass. If it is this range, a highly transparent sealing film will be obtained and it can be set as a solar cell with high electric power generation efficiency.

  In addition, in this invention, in addition to the above-mentioned olefin (co) polymer, resin such as polyvinyl acetal resin (for example, polyvinyl formal, polyvinyl butyral (PVB resin), modified PVB) is used as a resin material. You may mix.

[Organic peroxide or photopolymerization initiator]
In the solar cell sealing film of this invention, it is preferable to contain an organic peroxide or a photoinitiator and to form the crosslinked structure of an ethylene-polar monomer copolymer. Among these, it is preferable to use an organic peroxide because a sealing film with improved temperature dependency of adhesive strength, moisture resistance, and penetration resistance can be obtained.

  Any organic peroxide may be used as long as it decomposes at a temperature of 100 ° C. or higher and generates radicals. The organic peroxide is generally selected in consideration of the film formation temperature, the adjustment conditions of the composition, the curing temperature, the heat resistance of the adherend, and the storage stability. In particular, those having a decomposition temperature of 70 hours or more with a half-life of 10 hours are preferred.

  Examples of the organic peroxide include 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, 2,5-dimethylhexane-2,5-dihydroperoxide, 3-di-t- Butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexyne, α, α'-bis (t-butylperoxyisopropyl) benzene, n-butyl-4 , 4-bis (t-butylperoxy) butane, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxyisopropyl monocarbonate, 2,2-bis (t-butylperoxy) butane, 1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) -3,3 -Trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, 1,1-bis (t-butylperoxy) ) Cyclododecane, 1,1-bis (t-butylperoxy) cyclohexane, benzoyl peroxide curing agents (t-butylperoxybenzoate, etc.) and the like.

  As the organic peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane or t-butylperoxy-2-ethylhexyl monocarbonate is particularly preferable. Thereby, the sealing film for solar cells which is bridge | crosslinked favorably and has the outstanding transparency is obtained.

  The content of the organic peroxide used for the solar cell sealing film is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 3 parts by mass with respect to 100 parts by mass of the resin material. Is preferred. If the content of the organic peroxide is small, the crosslinking speed may be lowered during the crosslinking and curing, and if the content is large, the compatibility with the copolymer may be deteriorated.

  As the photopolymerization initiator, any known photopolymerization initiator can be used, but a photopolymerization initiator having good storage stability after blending is desirable. Examples of such a photopolymerization initiator include 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, and 2-methyl-1- (4- (methylthio) phenyl). Acetophenones such as 2-morpholinopropane-1, benzoins such as benzyldimethylketal, benzophenones such as benzophenone, 4-phenylbenzophenone and hydroxybenzophenone, thioxanthones such as isopropylthioxanthone and 2-4-diethylthioxanthone, As other special ones, methylphenylglyoxylate can be used. Particularly preferably, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- (4- (methylthio) phenyl) -2-morpholinopropane-1, Examples include benzophenone. These photopolymerization initiators may be optionally selected from one or more known photopolymerization accelerators such as a benzoic acid type such as 4-dimethylaminobenzoic acid or a tertiary amine type. It can be used by mixing at a ratio. Moreover, it can be used individually by 1 type of only a photoinitiator, or 2 or more types of mixture.

  Content of the said photoinitiator is 0.1-5 mass parts with respect to 100 mass parts of resin materials, Preferably it is 0.2-3 mass parts.

[Crosslinking aid]
In the sealing film for solar cells of this invention, the crosslinking adjuvant may be included as needed. The crosslinking assistant can improve the gel fraction of the ethylene-polar monomer copolymer and improve the adhesion and durability of the sealing film.

  The content of the crosslinking aid is generally 10 parts by mass or less, preferably 0.1 to 5 parts by mass, and more preferably 0.1 to 2.5 parts by mass with respect to 100 parts by mass of the resin material. Thereby, the sealing film for solar cells which is further excellent in adhesiveness is obtained.

  As a crosslinking aid (generally, a compound having a radical polymerizable group as a functional group), a trifunctional crosslinking aid such as triallyl cyanurate and triallyl isocyanurate, and a (meth) acrylic ester (eg, NK ester) Etc.) of monofunctional or bifunctional crosslinking aids. Of these, triallyl cyanurate and triallyl isocyanurate are preferable, and triallyl isocyanurate is particularly preferable.

[Adhesion improver]
The solar cell sealing film of the present invention may further contain an adhesion improver. As the adhesion improver, a silane coupling agent can be used. Thereby, it can be set as the sealing film for solar cells which has the further outstanding adhesive force. Examples of the silane coupling agent include γ-chloropropyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, and γ-glycidoxypropyl. Trimethoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N Mention may be made of -β- (aminoethyl) -γ-aminopropyltrimethoxysilane. These silane coupling agents may be used alone or in combination of two or more. Of these, γ-methacryloxypropyltrimethoxysilane is particularly preferred.

  It is preferable that content of the said silane coupling agent is 0.1-0.7 mass part with respect to 100 mass parts of resin materials, especially 0.3-0.65 mass part.

[Others]
In the sealing film for solar cell of the present invention, various properties (optical properties such as mechanical strength and transparency, heat resistance, light resistance, etc.) of the sealing film are improved or adjusted as necessary. In addition, various additives such as a plasticizer, an acryloxy group-containing compound, a methacryloxy group-containing compound and / or an epoxy group-containing compound may be further included.

[Seal film for solar cell]
What is necessary is just to perform according to a well-known method in order to form the sealing film for solar cells of this invention mentioned above. For example, as described above, after preparing resin particles encapsulating an organic rare earth complex as a wavelength conversion material, together with the other materials described above, a super mixer (high-speed fluid mixer), a roll mill, or the like can be used. The mixed composition can be produced by a method of obtaining a sheet-like product by molding by ordinary extrusion molding, calendar molding (calendering) or the like. Further, the composition is dissolved in a solvent (fine particles are dispersed), and this dispersion is coated on a suitable support with a suitable coating machine (coater) and dried to form a coating film to form a sheet-like material. You can also get In addition, when using an organic peroxide, it is preferable that the heating temperature at the time of film formation is a temperature at which the organic peroxide does not react or hardly reacts. For example, it is preferably 50 to 90 ° C, particularly 40 to 80 ° C. The thickness of the solar cell sealing film is not particularly limited, and can be appropriately set depending on the application. Generally, it is in the range of 50 μm to 2 mm.

  The content of the wavelength conversion material (resin particles) in the solar cell sealing film is not particularly limited as long as the effect of improving the power generation efficiency of the solar cell element is obtained, and the content of the organic rare earth complex in the resin particles is not limited. Can be adjusted accordingly. As an organic rare earth complex, it is preferable to mix | blend within 0.000001-1 mass part with respect to 100 mass parts of resin materials of the sealing film for solar cells. If the amount is less than 0.000001 parts by mass, a sufficient effect of improving the power generation efficiency may not be obtained, and it is preferable to add 0.00001 parts by mass or more, and particularly preferably 0.0001 parts by mass or more. On the other hand, if it exceeds 1 part by mass, it may be difficult to ensure the transparency required to allow sunlight to be sufficiently incident on the power generation element, and there is a tendency that it is disadvantageous in terms of cost. It is preferable to mix | blend below mass part, and it is preferable to mix | blend below 0.01 mass part especially.

[Solar cell]
The structure of the solar cell of the present invention is not particularly limited as long as it includes a structure in which the solar cell element is sealed with the solar cell sealing film of the present invention. For example, the structure etc. which sealed the cell for solar cells by interposing the sealing film for solar cells of this invention between the surface side transparent protection member and the back surface side protection member, and making it bridge-integrate are mentioned. . In addition, in this invention, the side (light-receiving surface side) where the light of the solar cell is irradiated is referred to as “front surface side”, and the surface opposite to the light-receiving surface of the solar cell is referred to as “back surface side”.

  Since the solar cell sealing film of the present invention is used in the solar cell of the present invention, the power generation efficiency of the solar cell element is improved by the wavelength conversion material, and the high power generation efficiency is maintained for a long time. It is a solar cell.

  In the solar cell, in order to sufficiently seal the solar cell, for example, as shown in FIG. 1, the front surface side transparent protective member 11, the front surface side sealing film 13A, the solar cell cell 14, the back surface side sealing. The film 13B and the back surface side protection member 12 may be laminated, and the sealing film may be cross-linked and cured according to a conventional method such as heat and pressure.

  In order to heat and pressurize, for example, a laminated body in which each member is laminated is heated by a vacuum laminator at a temperature of 135 to 180 ° C., further 140 to 180 ° C., particularly 155 to 180 ° C., a degassing time of 0.1 to 5 minutes, and a press pressure. What is necessary is just to heat-press in 0.1-1.5 kg / cm <2> and press time for 5-15 minutes. By crosslinking the olefin (co) polymer contained in the front side sealing film 13A and the back side sealing film 13B during this heating and pressurization, the front side sealing film 13A and the back side sealing film 13B are interposed. The solar cell 14 can be sealed by integrating the front surface side transparent protective member 11, the back surface side transparent member 12, and the solar cell 14.

  Since the solar cell sealing film of the present invention can improve the power generation efficiency of the solar cell element by including the wavelength conversion material as described above, it is disposed on the light receiving surface side of the solar cell element in the solar cell. It is preferable to use as the sealing film 13A, that is, the sealing film 13A disposed between the surface-side transparent protective member 12 and the solar battery cell 14 in FIG.

  The solar cell sealing film of the present invention is not limited to a solar cell using a single crystal or polycrystalline silicon crystal solar cell as shown in FIG. It can also be used for a sealing film of a thin film solar cell such as a solar cell and a copper indium selenide (CIS) solar cell. In this case, for example, the solar cell of the present invention is formed on a thin film solar cell element layer formed by a chemical vapor deposition method or the like on the surface of a surface side transparent protective member such as a glass substrate, a polyimide substrate, or a fluororesin transparent substrate. On the solar cell element formed on the surface of the back surface side protective member, the structure for laminating the battery sealing film and the back surface side protective member and adhering and integrating them, the front surface side Laminated transparent protective member, bonded and integrated structure, or front side transparent protective member, front side sealing film, thin film solar cell element, back side sealing film, and back side protective member are laminated in this order, For example, a structure that is bonded and integrated. In addition, in this invention, the cell for solar cells and a thin film solar cell element are named generically, and are called a solar cell element.

  The surface side transparent protective member 11 is usually a glass substrate such as silicate glass. As for the thickness of a glass substrate, 0.1-10 mm is common, and 0.3-5 mm is preferable. The glass substrate may generally be chemically or thermally strengthened.

  The back surface side protection member 12 is preferably a plastic film such as polyethylene terephthalate (PET) or polyamide. Further, a film obtained by laminating a fluorinated polyethylene film, particularly a fluorinated polyethylene film / Al / fluorinated polyethylene film in this order in consideration of heat resistance and wet heat resistance.

  In addition, the sealing film for solar cells of this invention has the characteristics in the sealing film used for the surface side and / or back surface side of a solar cell (a thin film solar cell is included). Therefore, the members other than the sealing film such as the front surface side transparent protective member, the back surface side protective member, and the solar battery cell are not particularly limited as long as they have the same configuration as a conventionally known solar battery.

  Hereinafter, the present invention will be described in detail with reference to examples.

(1) Preparation of wavelength conversion material (resin particles encapsulating organic rare earth complex) Using each of the materials shown in Table 1, suspension polymerization is performed by a conventional method to obtain spherical resin particles (average particle size 100 μm). It was.

(2) Preparation of Solar Cell Sealing Film Each material was supplied to a roll mill with the formulation shown in Table 2, and kneaded at 70 ° C. to prepare a solar cell sealing film composition. This solar cell sealing film composition was calendered at 70 ° C., allowed to cool, and then a solar cell sealing film (thickness 0.46 mm) was produced.

(3) Preparation of cross-linked cured sample The solar cell sealing film was sandwiched between two pieces of white plate glass (thickness: 3.2 mm), and the resulting laminate was vacuum-treated for 2 minutes at 90 ° C. using a vacuum laminator. After press-bonding with a press time of 8 minutes, a sample was prepared by heating in an oven at 155 ° C. for 30 minutes for crosslinking and curing.

(4) Evaluation method (i) Light transmittance (%)
About the said sample, the spectrum measurement of 400-1000 nm was implemented using the spectrophotometer (the Hitachi Ltd. make, U-4100), and the average value was made into light transmittance (%).

(Ii) Wet heat degradation test About the said sample, the fluorescence intensity was measured using the spectrophotometer (the Hitachi High-Technologies company make, F-7000). Measurement conditions: Photomultiplier voltage 400 V, excitation side slit 20 nm, fluorescence side slit 10 nm, scan speed 240 nm / min. The irradiation wavelength was 325 nm. The function f (x) with the wavelength on the X-axis and the light emission amount on the Y-axis represents a curve from the start wavelength to the end wavelength of the emission peak and a straight line connecting two points X = X0 and X1 on the function f (x). The area of the enclosed region was calculated and used as the fluorescence intensity. Next, the sample was left in an environment of 85 ° C. and 85% RH for 250 hours, the fluorescence intensity was measured again, and the residual ratio of fluorescence intensity from the initial state was calculated.

(5) Evaluation result Each evaluation result is shown in the table.

  As shown in the table, resin fine particles comprising an acrylic resin encapsulating an organic rare earth complex, the acrylic resin contains methyl methacrylate as a (meth) acrylate monomer, a crosslinking agent, and an azo polymerization initiator as a polymerization initiator And 1,1-di (t-butylperoxy) as an organic peroxide having a 1-minute half-life temperature of 145 ° C. or lower and having no group represented by R—C (═O) O— Resin particles which are polymers obtained by reacting a composition containing 2-methylcyclohexane and substantially free of an organic peroxide having a group represented by R—C (═O) O— In the wet heat degradation test, the fluorescence intensity of the solar cell sealing film included as the wavelength conversion material is unlikely to decrease. Therefore, it was shown that the sealing film for solar cells of this invention can maintain the effect which improves electric power generation efficiency for a long period of time.

  In addition, this invention is not limited to the structure and Example of said embodiment, A various deformation | transformation is possible within the range of the summary of invention.

  According to the present invention, it is possible to provide a solar cell in which the power generation efficiency of the solar cell element is improved by the wavelength conversion material and the high power generation efficiency is maintained for a long time.

DESCRIPTION OF SYMBOLS 11 Surface side transparent protective member 12 Back surface side protective member 13A Surface side sealing film 13B Back surface side sealing film 14 Cell for solar cells

Claims (10)

A resin material containing an olefin (co) polymer, and a solar cell sealing film containing a wavelength conversion material,
The wavelength conversion material is a resin particle made of an acrylic resin encapsulating an organic rare earth complex,
The acrylic resin is a polymer obtained by reacting a composition for acrylic resin containing a (meth) acrylate monomer, a crosslinking agent, and an azo polymerization initiator,
The acrylic resin composition has an organic peroxide having a group represented by R—C (═O) O— (R represents a hydrocarbon group which may be optionally substituted) as a polymerization initiator. A sealing film for solar cells, characterized by containing an organic peroxide substantially free of oxide and having a 1 minute half-life temperature of 145 ° C. or lower as another polymerization initiator.   The solar cell sealing film according to claim 1, wherein the organic peroxide having a one-minute half-life temperature of 145 ° C. or lower is 1,1-di (t-butylperoxy) -2-methylcyclohexane.   The solar cell sealing film according to claim 1, wherein the (meth) acrylate monomer is methyl methacrylate. The crosslinking agent is represented by the following formula (I):

[Wherein, R 1 and R 2 each independently represent a hydrogen atom or a methyl group, and n is an integer of 2 to 14. ]
The solar cell sealing film of any one of Claims 1-3 which is a compound represented by these.   The solar cell sealing film according to claim 1, wherein the acrylic resin composition further comprises a hydrophobic monomer having a higher n-octanol / water partition coefficient than methyl methacrylate.   The solar cell sealing film according to claim 5, wherein the hydrophobic monomer is styrene. The organic rare earth complex has the following formula (II):

[Wherein, R independently represents a hydrogen atom or an optionally substituted hydrocarbon group having 1 to 20 carbon atoms, and n is an integer of 1 to 4. ]
It is a europium complex represented by any one of Claims 1-6.   The solar cell sealing film according to claim 7, wherein the organic rare earth complex is a europium complex in which R is all hydrogen atoms and n is 1 in the formula (II).   The olefin (co) polymer is an ethylene / α-olefin copolymer (m-LLDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), polypropylene, polybutene polymerized using a metallocene catalyst. And at least one polymer selected from the group consisting of ethylene-polar monomer copolymers. 9. The solar cell sealing film according to claim 1.   A solar cell, wherein a solar cell element is sealed with the solar cell sealing film according to claim 1.

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