JP2012041465A - Spherical phosphor, sealing material for wavelength conversion solar battery, solar battery module and method for producing same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spherical phosphor which increases the efficiency for light utilization in a solar battery module, a sealing material for wavelength conversion solar battery containing the same, a solar battery module and a method for producing these.SOLUTION: In the spherical phosphor including a fluorescent substance and a transparent material, the transparent material is prepared by suspension polymerization of a composition containing a vinyl compound to form a spherical form. Further, the composition containing a vinyl compound contains a di- or higher functional vinyl compound. The sealing material for wavelength conversion solar battery includes a light permeable resin composition layer containing the spherical phosphor and a sealing resin.

Description

  The present invention relates to a spherical phosphor, a wavelength conversion type solar cell encapsulant using the same, a solar cell module using the same, and a method for producing them. More specifically, a solar cell module capable of increasing power generation efficiency by converting light in a wavelength region that does not contribute to power generation into light in a wavelength region that contributes to power generation, a wavelength conversion type solar cell sealing material used therefor, and these It is related with the manufacturing method.

  The conventional silicon crystal solar cell module has the following configuration. The surface protective glass (also called cover glass) is made of tempered glass with respect to impact resistance and is a resin mainly composed of an encapsulant (usually ethylene vinyl acetate copolymer (ethylene-vinyl acetate copolymer)). In order to improve the adhesiveness to the filler, one surface is provided with an uneven pattern by embossing.

Moreover, the uneven | corrugated pattern is formed inside, and the surface of a solar cell module is smooth. Moreover, the sealing material and back film for carrying out protection sealing of the photovoltaic cell and a tab wire are provided under the protective glass (for example, refer nonpatent literature 1).
A layer that emits light in the wavelength region that can contribute to power generation by converting the wavelength of ultraviolet or infrared light that does not contribute to power generation in the sunlight spectrum using a fluorescent substance (also referred to as a light emitting material) Many methods for providing the battery on the light receiving surface side have been proposed (see, for example, Patent Document 1).

In addition, a method for incorporating a rare earth complex, which is a fluorescent substance, in a sealing material has been proposed (see, for example, Patent Document 2).
Conventionally, ethylene-vinyl acetate copolymers imparted with thermosetting properties have been widely used as transparent sealing materials for solar cells (see, for example, Patent Document 3).

JP 2003-218379 A JP 2006-303033 A JP 2003-51605 A

Yasuhiro Sasakawa, “Solar Power Generation”-Latest Technology and System, 2000, CMC Corporation

  Patent Document 1 proposes wavelength conversion of light that does not contribute to power generation into light in a wavelength range that can contribute to power generation. The wavelength conversion layer contains a fluorescent material, but this fluorescent material is generally shaped. When the incident sunlight passes through the wavelength conversion film, the ratio of not reaching the solar cells and contributing to power generation increases. As a result, there is a problem that even if the light in the ultraviolet region is converted into the light in the visible region in the wavelength conversion layer, the ratio of the electric power generated relative to the incident sunlight (power generation efficiency) is not so high.

  Further, in the method described in Patent Document 3, the rare earth complex is easily hydrolyzed together with ethylene vinyl acetate (EVA) widely used as a sealing material and not only deteriorates but also wavelength-converted light. It is difficult to introduce to the solar battery cell. In addition, when the rare earth complex which is a fluorescent substance is dispersed in EVA, the rare earth metal molecules are easily aggregated and subject to hydrolysis, and the aggregate also scatters the excitation wavelength, thereby causing the rare earth as a fluorescent substance. There exists a problem that the utilization efficiency of a metal becomes very bad.

  The present invention is intended to improve the above-described problems, and improves the light utilization efficiency in the solar cell module, and makes it possible to stably improve the power generation efficiency, and a wavelength including the same. It is an object of the present invention to provide a conversion type solar cell sealing material, a solar cell module, and a method for producing them.

As a result of intensive studies to solve the above-mentioned problems, the present inventors converted light that does not contribute to solar power generation into a wavelength that contributes to power generation by using a spherical phosphor containing a fluorescent substance. At the same time, the present inventors have found that moisture resistance and heat resistance are excellent, dispersibility is good, and that incident sunlight can be efficiently introduced into a solar battery cell without scattering the fluorescent material, and the present invention has been completed. . Further, when a rare earth metal organic complex is used as the fluorescent material, the humidity resistance of the fluorescent material can be further improved.
In particular, in the present invention, a technique for obtaining a spherical phosphor having high optical transparency and high light emission efficiency in a spherical phosphor has been found, and the present invention has been completed.

That is, the present invention is as follows.
<1> In a spherical phosphor containing a fluorescent substance and a transparent material, the transparent material is obtained by suspension polymerization of a vinyl compound-containing composition, and the vinyl compound-containing composition is 2 A spherical phosphor containing a vinyl compound that is functional or higher.
<2> The spherical phosphor according to <1>, wherein the phosphor is an organic phosphor or a rare earth metal complex.
<3> The spherical phosphor according to <1> or <2>, wherein the phosphor is a rare earth metal complex.
<4> The spherical phosphor according to any one of <1> to <3>, wherein the fluorescent substance is a europium complex.
<5> The vinyl compound of the vinyl compound-containing composition is a resin obtained by suspension polymerization of a (meth) acrylic acid derivative, and the vinyl compound contains a bifunctional or higher functional (meth) acrylic acid derivative. The spherical phosphor according to any one of <1> to <4>, wherein
<6> The spherical phosphor according to any one of <1> to <5>, wherein a refractive index of the transparent material is lower than that of the phosphor and is 1.4 or more.
<7> The spherical shape according to any one of <1> to <6>, which is a spherical resin particle obtained by emulsion polymerization or suspension polymerization of a vinyl compound-containing composition in which the fluorescent substance is dissolved or dispersed. Phosphor.
<8> The spherical phosphor according to any one of <1> to <7>, which is spherical resin particles obtained by suspension polymerization of a vinyl compound-containing composition in which the fluorescent substance is dissolved or dispersed.

<9> A wavelength conversion type solar cell encapsulant comprising a light-transmitting resin composition layer containing the spherical phosphor according to any one of <1> to <8> and an encapsulating resin.
<10> The wavelength conversion solar cell sealing material according to <9>, wherein the content ratio of the spherical phosphor in the vinyl compound-containing composition layer is 0.0001 to 10 mass percent.
<11> The wavelength conversion solar cell sealing material according to <9> or <10>, further including a light-transmitting layer other than the resin composition layer.
<12> m layers comprising a light-transmitting layer other than the wavelength conversion type solar cell encapsulant layer and the wavelength conversion type solar cell encapsulant layer, and each of the m layers the refractive index _{of, n} 1, _n 2 from the light incident side in this _{order, ···, n (m-1} ), when the _{n m, n 1 ≦ n 2} ≦ ··· ≦ n (m-1) a ≦ n _m, the wavelength conversion-type solar cell encapsulant according to <11>.

A solar cell module provided with a <13> solar cell and the wavelength conversion type solar cell sealing material in any one of said <9>-<12> arrange | positioned on the light-receiving surface of the said solar cell.
<14> A step of obtaining a spherical phosphor by suspension polymerization of a vinyl compound-containing composition in which a fluorescent substance is dissolved or dispersed, and a resin composition obtained by mixing or dispersing the spherical phosphor in a sealing resin A method for producing a wavelength conversion type solar cell encapsulant comprising: a sheet forming step of forming an object into a sheet shape.
<15> A method for producing a solar cell module having a plurality of light transmissive layers and solar cells, wherein the wavelength conversion solar cell encapsulant according to any one of <9> to <12> A method for manufacturing a solar cell module, comprising a step of forming one of the light-transmitting layers by being disposed on a light receiving surface side of a battery cell.

  ADVANTAGE OF THE INVENTION According to this invention, the spherical fluorescent substance which makes it possible to improve the light utilization efficiency in a solar cell module, and to improve a power generation efficiency stably, the wavelength conversion type solar cell sealing material containing this, and a solar cell Modules and methods for manufacturing them can be provided.

It is a conceptual diagram which shows an example of the relationship between the spherical fluorescent substance concerning a present Example, and incident light. It is a conceptual diagram which shows an example of the refraction of the light in the interface where refractive indexes differ. It is a conceptual diagram which shows an example of the wavelength dependence of a refractive index. It is a scanning electron micrograph of the spherical fluorescent substance produced in Example 1 concerning a present Example. 3 is a scanning electron micrograph of a spherical phosphor produced in Comparative Example 1. Excitation spectrum at a fluorescence wavelength of 621 nm measured with a spectrofluorometer.

<Spherical phosphor and production method thereof>
The spherical phosphor of the present invention comprises a fluorescent substance and a spherical transparent material containing the fluorescent substance.
For example, the spherical phosphor is used by being contained in a wavelength-convertible resin composition layer constituting a wavelength-converting solar cell sealing material. For example, in a silicon crystal solar cell, light having a shorter wavelength than 400 nm or longer than 1200 nm is not effectively used in sunlight, and about 56% of solar energy does not contribute to power generation due to this spectrum mismatch. By using phosphors having a specific shape with excellent moisture resistance, heat resistance, good dispersibility, and suppressed concentration quenching, the present invention uses sunlight efficiently and stably by wavelength conversion. , Trying to overcome the spectral mismatch. Furthermore, it is intended to maximize the utilization efficiency of rare earth metal complexes as fluorescent materials and improve the effective luminous efficiency, thereby limiting the amount of expensive rare earth complexes to a very small amount and contributing to power generation. Can do.

  That is, the spherical phosphor of the present invention is a fluorescent material having excellent moisture resistance and heat resistance, good dispersibility, and suppressed concentration quenching. Such a fluorescent material can maximize the utilization efficiency of the rare earth metal complex, which is an expensive fluorescent substance, and can further improve the effective light emission efficiency and improve the power generation efficiency of the solar cell module. In addition, the spherical phosphor of the present invention, and the wavelength conversion type solar cell encapsulant using the same, simultaneously convert light that does not contribute to solar power generation into incident light that contributes to power generation, The scattering of the light can be suppressed and the light can be efficiently introduced into the solar battery cell.

In the present invention, since the fluorescent material is confined in the sphere, the ability of the fluorescent material can be maximized. This will be described with reference to the drawings. As shown in FIG. 2, when light travels from a high refractive medium to a low refractive medium, total reflection occurs at this interface according to its relative refractive index. Typical examples of the positive application of this phenomenon include optical devices such as optical fibers, optical waveguides, and semiconductor lasers. The condition for total reflection occurs when the incident angle is larger than the critical angle θc expressed by the following equation.
θ _c = sin ⁻¹ (n ₁ / n ₂ )

On the other hand, a substance has a specific refractive index, which has a dependency on the wavelength, and the refractive index increases from a long wavelength toward a short wavelength even in a transparent material. In particular, when a substance has absorption at a specific wavelength, the refractive index increases near that wavelength.
Further, in a fluorescent substance, transition from a ground state to an excited state occurs at an absorption wavelength (excitation wavelength), and energy is released as fluorescence (also referred to as light emission) when returning to the ground state. That is, by uniformly mixing a certain fluorescent substance with a transparent material, the refractive index distribution can be enhanced particularly in the excitation wavelength region as compared with the transparent material (for example, a transparent resin) as a base material.
This is conceptually shown in FIG. In the figure, the solid line represents the refractive index distribution of the transparent material as the matrix, and the broken line represents the refractive index distribution when the fluorescent material is contained therein. In particular, regarding the refractive index, by appropriately selecting a transparent material, a fluorescent material, and a medium (encapsulation resin) that are the sphere matrix, the refractive index in the sphere is changed to a medium (encapsulation resin) in the excitation wavelength region as shown in FIG. It is possible to obtain a correlation that is larger than that of the medium (sealing resin) in the emission wavelength region.

  In such a situation, light easily enters the sphere having a high refractive index in the excitation wavelength region. However, in the sphere, the refractive index of the sealing resin outside the sphere is low, so It becomes difficult to go outside the sphere, and total reflection is repeated inside the sphere. For this reason, it can be considered that the fluorescent substance contained in the sphere increases the use efficiency of excitation light. On the other hand, in the emission wavelength region, the difference between the refractive index of the sphere and the refractive index of the medium outside the sphere (for example, sealing resin) is not large, so that light is easily emitted outside the sphere. This state is conceptually shown in FIG.

  However, in the conventional method, if a spherical phosphor is to be obtained, an adhering substance is accompanied on the surface of the sphere. Because of this deposit, it is difficult for light having an excitation wavelength to enter the sphere, making it difficult to obtain the desired effect.

By configuring the particles containing the fluorescent material into a spherical shape as described above, a sufficient amount of wavelength-converted light emission can be obtained even when an expensive fluorescent material is used in a small amount.
In addition, since the fluorescent material absorbs the excitation wavelength, the refractive index in the excitation wavelength region is high and light scattering is likely to occur. Further, when the fluorescent material is aggregated, light scattering is further increased, and the effect of improving the power generation efficiency by the intended wavelength conversion may not be sufficiently obtained. However, since the fluorescent material is encapsulated in a transparent material (preferably a transparent material having a lower refractive index than the fluorescent material), light scattering caused by the difference in refractive index between the fluorescent material and the sealing resin is effectively prevented. Can be suppressed.

Furthermore, when a substance having low moisture resistance such as a rare earth complex is used as the fluorescent substance, the moisture resistance can be further improved by confining the substance in a sphere of a transparent material (preferably a moisture-resistant transparent material).
The spherical phosphor of the present invention can be suitably used for a solar cell module. Besides, wavelength-converted agricultural materials, various optical devices for light emitting diode excitation, display devices, various optical devices for laser excitation, The present invention can be applied to display devices and the like, and the present invention does not limit the application.

The spherical phosphor of the present invention includes at least one fluorescent substance described later and at least one transparent material, and has a spherical shape. Here, the term “spherical” means that the average value of the ratio of the distance between the center of the spherical phosphor and an arbitrary point on the surface to the average radius of the spherical phosphor calculated from the average particle diameter is 0. 8 to 1.2, preferably 0.9 to 1.1, and more preferably 0.95 to 1.05. Here, the average particle diameter of the spherical phosphor is obtained as an arithmetic average value of the particle diameters of 100 spherical phosphor particles measured using a scanning electron microscope.
The main reason for enclosing the fluorescent substance in the particles is to avoid scattering, and for the purpose alone, it is not always necessary to be a sphere.
The particle diameter of the spherical phosphor can be appropriately selected according to the purpose. For example, when used for a wavelength conversion type solar cell encapsulant, it can be 1 to 1000 μm, and 10 to 500 μm. Is preferred.

<Fluorescent substance>
The fluorescent material used in the present invention can be appropriately selected according to the purpose. For example, the fluorescent material is preferably a fluorescent material having an excitation wavelength of 500 nm or less and an emission wavelength longer than that. More preferably, the compound is capable of converting light outside the wavelength range that can be used in the solar cell into a wavelength range that can be used in the solar cell.
Specific examples of the fluorescent substance include organic phosphors, inorganic phosphors, and rare earth metal complexes. Among these, from the viewpoint of wavelength conversion efficiency, at least one of an organic phosphor and a rare earth metal complex is preferable, and a rare earth metal complex is more preferable.

<Inorganic phosphor>
Examples of the inorganic phosphor include, for example, fluorescent particles of Y ₂ O ₂ S: Eu, Mg, Ti, oxyfluoride crystallized glass containing Er ³⁺ ions, compounds composed of strontium oxide and aluminum oxide, and rare earth elements. Inorganic compounds such as SrAl ₂ O ₄ : Eu, Dy, Sr ₄ Al ₁₄ O ₂₅ : Eu, Dy, CaAl ₂ O ₄ : Eu, Dy, ZnS: Cu, etc. to which europium (Eu) and dysprosium (Dy) are added Mention may be made of fluorescent materials.

<Organic phosphor>
Examples of the organic phosphor include organic dyes such as cyanine dyes, pyridine dyes, rhodamine dyes, BASF Lumogen F Violet 570, Yellow083, Orange 240, Red300, and bases manufactured by Taoka Chemical Co., Ltd. And organic phosphors such as sexual dye Rhodamine B, Sumiplast Yellow FL7G manufactured by Sumika Finechem Co., Ltd., MACROLEX Fluorescent Red G manufactured by Bayer, and Yellow 10GN.

<Rare earth metal complex>
The metal constituting the rare earth metal complex is preferably at least one of europium and samarium, and more preferably europium, from the viewpoint of luminous efficiency.
The ligand constituting the rare earth metal complex is not particularly limited as long as it can coordinate to the rare earth metal, and can be appropriately selected according to the metal to be used. Among these, from the viewpoint of luminous efficiency, an organic ligand is preferable, and an organic ligand capable of forming a complex with at least one of europium and samarium is preferable.

In the present invention, although the ligand is not limited, the neutral ligand is selected from carboxylic acid, nitrogen-containing organic compound, nitrogen-containing aromatic heterocyclic compound, β-diketone, and phosphine oxide. It is preferable that it is at least one kind.
In addition, as a ligand of the rare earth complex, a general formula R ¹ COCHR ² COR ³ (wherein R ¹ represents an aryl group, an alkyl group, a cycloalkyl group, a cycloalkylalkyl group, an aralkyl group, or a substituent thereof, R ² Represents a hydrogen atom, an alkyl group, a cycloalkyl group, a cycloalkylalkyl group, an aralkyl group or an aryl group, and R ³ represents an aryl group, an alkyl group, a cycloalkyl group, a cycloalkylalkyl group, an aralkyl group or a substituent thereof. (Beta) -diketone represented by this may be contained.

  Specific examples of β-diketones include acetylacetone, perfluoroacetylacetone, benzoyl-2-furanoylmethane, 1,3-di (3-pyridyl) -1,3-propanedione, benzoyltrifluoroacetone, and benzoylacetone. , 5-chlorosulfonyl-2-thenoyltrifluoroacetone, bis (4-bromobenzoyl) methane, dibenzoylmethane, d, d-dicamphorylmethane, 1,3-dicyano-1,3-propanedione, p- Bis (4,4,5,5,6,6,6-heptafluoro-1,3-hexanedinoyl) benzene, 4,4'-dimethoxydibenzoylmethane, 2,6-dimethyl-3,5-heptane Dione, dinaphthoylmethane, dipivaloylmethane, bis (perfluoro-2-propoxypropionyl) Tan, 1,3-di (2-thienyl) -1,3-propanedione, 3- (trifluoroacetyl) -d-camphor, 6,6,6-trifluoro-2,2-dimethyl-3,5 -Hexanedione, 1,1,1,2,2,6,6,7,7,7-decafluoro-3,5-heptanedione, 6,6,7,7,8,8,8-heptafluoro -2,2-dimethyl-3,5-octanedione, 2-furyltrifluoroacetone, hexafluoroacetylacetone, 3- (heptafluorobutyryl) -d-camphor, 4,4,5,5,6,6 6-heptafluoro-1- (2-thienyl) -1,3-hexanedione, 4-methoxydibenzoylmethane, 4-methoxybenzoyl-2-furanoylmethane, 6-methyl-2,4-heptanedione, 2 -Naftoil Fluoroacetone, 2- (2-pyridyl) benzimidazole, 5,6-dihydroxy-1,10-phenanthroline, 1-phenyl-3-methyl-4-benzoyl-5-pyrazole, 1-phenyl-3-methyl-4 -(4-butylbenzoyl) -5-pyrazole, 1-phenyl-3-methyl-4-isobutyryl-5-pyrazole, 1-phenyl-3-methyl-4-trifluoroacetyl-5-pyrazole, 3- (5 -Phenyl-1,3,4-oxadiazol-2-yl) -2,4-pentanedione, 3-phenyl-2,4-pentanedione, 3- [3 ', 5'-bis (phenylmethoxy) Phenyl] -1- (9-phenanthyl) -1-propane-1,3-dione, 5,5-dimethyl-1,1,1-trifluoro-2,4-hexanedione, 1-phenyl-3- (2-thienyl) -1,3-propanedione, 3- (t-butylhydroxymethylene) -d-camphor, 1,1,1-trifluoro-2,4-pentanedione, 1,1,2,2,3,3,7,7,8,8,9,9,9-tetradecafluoro-4,6-nonanedione, 2,2,6,6-tetramethyl-3, 5-heptanedione, 4,4,4-trifluoro-1- (2-naphthyl) -1,3-butanedione, 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione, 2,2,6,6-tetramethyl-3,5-heptanedione, 2,2,6,6-tetramethyl-3,5-octanedione, 2,2,6-trimethyl-3,5-heptanedione 2,2,7-trimethyl-3,5-octanedione, 4,4, -Trifluoro-1- (thienyl) -1,3-butanedione (TTA), 1- (pt-butylphenyl) -3- (N-methyl-3-pyrrole) -1,3-propanedione (BMPP) ), 1- (pt-butylphenyl) -3- (p-methoxyphenyl) -1,3-propanedione (BMDBM), 1,3-diphenyl-1,3-propanedione, benzoylacetone, Dibenzoylacetone, diisobutyroylmethane, dibiparoylmethane, 3-methylpentane-2,4-dione, 2,2-dimethylpentane-3,5-dione, 2-methyl-1,3-butanedione, 1,3-butanedione, 3-phenyl-2,4-pentanedione, 1,1,1-trifluoro-2,4-pentanedione, 1,1,1-trifluoro-5,5-dimethyl-2, -Hexanedione, 2,2,6,6-tetramethyl-3,5-heptanedione, 3-methyl-2,4-pentanedione, 2-acetylcyclopentanone, 2-acetylcyclohexanone, 1-heptafluoropropyl -3-t-butyl-1,3-propanedione, 1,3-diphenyl-2-methyl-1,3-propanedione, 1-ethoxy-1,3-butanedione, and the like can be given.

  Nitrogen-containing organic compounds, nitrogen-containing aromatic heterocyclic compounds, and phosphine oxides of neutral ligands of rare earth complexes include, for example, 1,10-phenanthroline, 2-2'-bipyridyl, 2-2'-6, 2 "-terpyridyl, 4,7-diphenyl-1,10-phenanthroline, 2- (2-pyridyl) benzimidazole, triphenylphosphine oxide, tri-n-butylphosphine oxide, tri-n-octylphosphine oxide, tri- Examples include n-butyl phosphate.

As the rare earth complex having the above-described ligand, for example, Eu (TTA) ₃ phen, Eu (BMPP) ₃ phen, Eu (BMDBM) ₃ phen or the like can be preferably used from the viewpoint of wavelength conversion efficiency.
A method for producing Eu (TTA) ₃ Phen is described, for example, in Masa Mitsui, Shinji Kikuchi, Tokuji Miyashita, Yutaka Amano, J. et al. Mater. Chem. Reference may be made to the method disclosed in 2003, 13, 285-2879.

  In the present invention, a solar cell module having high power generation efficiency can be configured by using a europium complex as the fluorescent material. The europium complex converts light in the ultraviolet region into light in the red wavelength region with high wavelength conversion efficiency, and the converted light contributes to power generation in the solar battery cell.

  There is no restriction | limiting in particular as content of the fluorescent substance in the spherical fluorescent substance of this invention, Although it can select suitably according to the objective and the kind of fluorescent substance, it is 0.001-1 mass% from a viewpoint of electric power generation efficiency. Is preferable, and it is more preferable that it is 0.01-0.5 mass%.

<Transparent material>
In the present invention, the fluorescent substance is contained in a transparent material. In the present invention, “transparent” means that the transmittance of light having a wavelength of 400 to 800 nm at an optical path length of 1 cm is 90% or more.
The transparent material is not particularly limited as long as it is transparent, and is formed by suspension polymerization of a vinyl compound-containing composition into a spherical shape. Further, the vinyl compound-containing composition has a spherical fluorescence containing a bifunctional or higher functional vinyl compound. Is the body. For example, resins such as acrylic resin and methacrylic resin can be mentioned. Although there is no restriction | limiting in particular as a monomer compound which comprises the said resin, From a viewpoint of light-scattering suppression, it is preferable to contain at least a vinyl compound.
In the present invention, some of these vinyl compounds include bifunctional or higher functional vinyl compounds. The blending ratio is preferably 0.1 to 50% by mass and more preferably 0.5 to 10% by mass in the mass ratio of all vinyl compounds.

In addition, as a method of making the transparent material contain the fluorescent material and making the shape spherical, for example, a vinyl compound-containing composition is prepared by dissolving or dispersing the fluorescent material in a monomer compound and polymerizing ( (Emulsion polymerization or suspension polymerization). Specifically, for example, a mixture containing a fluorescent substance and a vinyl compound is prepared, and this is emulsified or dispersed in a medium (for example, an aqueous medium) to obtain an emulsion or suspension. For example, by using a radical polymerization initiator to polymerize a vinyl compound contained in an emulsion or suspension (emulsion polymerization or suspension polymerization), a spherical phosphor is obtained as a spherical resin particle containing a fluorescent substance. Can be configured.
In the present invention, from the viewpoint of power generation efficiency, a mixture containing a fluorescent substance and a vinyl compound is prepared, and this is dispersed in a medium (for example, an aqueous medium) to obtain a suspension. It is preferable to form a spherical phosphor as spherical resin particles containing a fluorescent substance by polymerizing (suspension polymerization) a vinyl compound contained in the suspension using an initiator.

<Vinyl compound>
In the present invention, the vinyl compound is not particularly limited as long as it is a compound having at least one ethylenically unsaturated bond, and an acrylic monomer, a methacrylic monomer, which can be converted into a vinyl resin, particularly an acrylic resin or a methacrylic resin when polymerized. (Meth) acrylic acid derivatives such as acrylic oligomers and methacrylic oligomers can be used without particular limitation. In the present invention, an acrylic monomer, a methacryl monomer, and the like are preferable.

  Preferred acrylic monomers and methacrylic monomers as (meth) acrylic acid derivatives include, for example, acrylic acid, methacrylic acid, and alkyl esters thereof, and may be used in combination with other vinyl compounds that can be copolymerized therewith. It can be used alone or in combination of two or more. Here, (meth) acrylic acid means acrylic acid, methacrylic acid or a mixture thereof.

  Examples of the alkyl acrylate ester and the alkyl methacrylate ester include, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate. Acrylic acid unsubstituted alkyl ester and methacrylic acid unsubstituted alkyl ester; dicyclopentenyl (meth) acrylate; tetrahydrofurfuryl (meth) acrylate; benzyl (meth) acrylate; urethane (meth) acrylate (for example, tolylene diisocyanate and Reaction product with 2-hydroxyethyl (meth) acrylic ester, trimethylhexamethylene diisocyanate, cyclohexanedimethanol and 2-hydroxyethyl (meth) Reaction products of acrylic acid ester, etc.); a hydroxyl group in these alkyl groups, an epoxy group, an acrylic acid and a halogen group is substituted substituted alkyl esters or methacrylic acid-substituted alkyl ester; and the like.

  Examples of other vinyl compounds that can be copolymerized with acrylic acid, methacrylic acid, alkyl acrylate ester, or alkyl methacrylate ester include acrylamide, acrylonitrile, diacetone acrylamide, styrene, vinyl toluene, and the like. These vinyl monomers can be used alone or in combination of two or more.

The bifunctional or higher functional vinyl compound in the present invention is, for example, a compound obtained by reacting a polyhydric alcohol with an α, β-unsaturated carboxylic acid (for example, polyethylene glycol di (meth) acrylate (the number of ethylene groups is 2 ~ 14), ethylene glycol dimethacrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane ethoxytri (meth) acrylate, trimethylolpropane propoxytri (meth) acrylate, tetra Methylol methane tri (meth) acrylate, tetramethylol methane tetra (meth) acrylate, polypropylene glycol di (meth) acrylate (having 2 to 14 propylene groups), dipentaerythritol penta (meth) ) Acrylate, dipentaerythritol hexa (meth) acrylate, bisphenol A polyoxyethylene di (meth) acrylate, bisphenol A dioxyethylene di (meth) acrylate, bisphenol A trioxyethylene di (meth) acrylate, bisphenol A decaoxyethylene Di (meth) acrylate, etc.);
Compounds obtained by adding an α, β-unsaturated carboxylic acid to a polyvalent glycidyl group-containing compound (for example, trimethylolpropane triglycidyl ether triacrylate, bisphenol A diglycidyl ether diacrylate, etc.);
And an esterified product of a polyvalent carboxylic acid (for example, phthalic anhydride) and a substance having a hydroxyl group and an ethylenically unsaturated group (for example, β-hydroxyethyl (meth) acrylate).

  The vinyl compound in the present invention can be appropriately selected so that the refractive index of the resin particles to be formed has a desired value, and at least one selected from an alkyl acrylate ester and an alkyl methacrylate ester is used. preferable.

<Radical polymerization initiator>
In the present invention, it is preferable to use a radical polymerization initiator in order to polymerize the vinyl compound. As the radical polymerization initiator, a commonly used radical polymerization initiator can be used without particular limitation. For example, a peroxide etc. are mentioned preferably. Specifically, organic peroxides or azo radical initiators that generate free radicals by heat are preferred.
Examples of the organic oxide include isobutyl peroxide, α, α′-bis (neodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecanoate, di-n-propylperoxydicarbonate, and bis-s-. Butyl peroxydicarbonate, 1,1,3,3-tetramethylbutyl neodecanoate, bis (4-t-butylcyclohexyl) peroxydicarbonate, 1-cyclohexyl-1-methylethyl peroxyneodecanoate Bis-2-ethoxyethylperoxydicarbonate, bis (ethylhexylperoxy) dicarbonate, t-hexylneodecanoate, bismethoxybutylperoxydicarbonate, bis (3-methyl-3-methoxybutylperoxy) Dicarbonate, t-butyl pero Cineodecanoate, t-hexylperoxypivalate, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, 1,1,3,3-tetramethylbutylper Oxy-2-ethylhexanoate, succinic peroxide, 2,5-dimethyl-2,5-bis (2-ethylhexanoyl) hexane, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexano Ate, t-hexylperoxy-2-ethylhexanoate, 4-methylbenzoyl peroxide, t-butylperoxy-2-ethylhexanoate, m-toluonoylbenzoyl peroxide, benzoyl peroxide, t-butyl Peroxyisobutyrate, 1 , 1-bis (t-butylperoxy) 2-methylcyclohexane, 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-hexylperoxy) Cyclohexane, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexanone, 2,2-bis (4,4-dibutylper Oxycyclohexyl) propane, 1,1-bis (t-butylperoxy) cyclododecane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylperoxy-3,5,5-trimethyl Hexanoate, t-butyl peroxylaurate, 2,5-dimethyl-2,5-bis (m-toluoyl par Xyl) hexane, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-bis (benzoylperoxy) hexane, t-butyl peroxyacetate, 2,2-bis (t-butylperoxy) butane, t-butylperoxybenzoate, n-butyl-4,4-bis (t-butylperoxy) valerate, di-t- Butyl peroxyisophthalate, α, α′-bis (t-butylperoxy) diisopropylbenzene, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, t-butyl Cumyl peroxide, p-menthane hydroperoxide, 2,5-dimethyl- 2,5-bis (t-butylperoxy) hexyne, diisopropylbenzene hydroperoxide, t-butyltrimethylsilyl peroxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-hexyl Hydroperoxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane and the like can be used.

  Examples of the azo radical initiator include azobisisobutyronitrile (AIBN, trade name V-60, manufactured by Wako Pure Chemical Industries, Ltd.), 2,2′-azobis (2-methylisobutyronitrile) ( Trade name V-59, manufactured by Wako Pure Chemical Industries, Ltd.), 2,2′-azobis (2,4-dimethylvaleronitrile) (trade name V-65, manufactured by Wako Pure Chemical Industries, Ltd.), dimethyl-2, 2′-azobis (isobutyrate) (trade name V-601, manufactured by Wako Pure Chemical Industries, Ltd.), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) (trade name V-70, Japanese Kosei Pharmaceutical Co., Ltd.).

  The usage-amount of a radical polymerization initiator can be suitably selected according to the kind of said vinyl compound, the refractive index of the resin particle formed, etc., and is used by the usage-amount normally used. Specifically, for example, it can be used at 0.01 to 2% by weight, preferably 0.1 to 1% by weight, based on the vinyl compound.

  The refractive index of the transparent material in the present invention is not particularly limited, but is preferably lower than the refractive index of the fluorescent material, lower than the refractive index of the fluorescent material, and sealed later, from the viewpoint of suppressing light scattering. More preferably, the ratio of the refractive index of the stop resin is close to 1. Generally, the refractive index of the fluorescent material is larger than 1.5, and the refractive index of the sealing resin is about 1.4 to 1.5. Therefore, the refractive index of the transparent material is 1.4 to 1.5. Preferably there is.

  The spherical phosphor preferably has a refractive index higher than that of the sealing resin serving as a dispersion medium at the excitation wavelength of the fluorescent material and lower than that of the sealing resin at the emission wavelength. By being this mode, the light utilization efficiency in the excitation wavelength region is further improved.

<Wavelength conversion solar cell encapsulant>
The wavelength conversion type solar cell encapsulant of the present invention is a light transmissive resin having wavelength conversion ability used as one of the light transmissive layers of a solar cell module having a plurality of light transmissive layers and solar cells. At least one layer of the composition is provided. The resin composition layer includes at least one of the spherical phosphors and at least one of a sealing resin (preferably a transparent sealing resin), and the spherical phosphor is dispersed in the sealing resin. Yes.
When the wavelength conversion type solar cell encapsulant includes the resin composition layer containing the spherical phosphor, when used as one of the light transmissive layers in the solar cell module, the light utilization efficiency is improved, The power generation efficiency can be improved stably.

  Light scattering correlates with the ratio between the refractive index of the spherical phosphor and the refractive index of the sealing resin. Specifically, the light scattering is less affected by the particle size of the spherical phosphor if the ratio of the refractive index of the spherical phosphor to the refractive index of the transparent sealing resin is close to “1”. Light scattering is also small. In particular, when the present invention is applied to a wavelength conversion type light transmission layer of a solar cell module, it is preferable that the refractive index ratio in a wavelength region sensitive to solar cells, that is, 400 to 1200 nm is close to “1”. On the other hand, in order to efficiently cause total reflection of light in the excitation wavelength region in the spherical phosphor, the refractive index of the spherical phosphor is higher than that of the sealing resin that is a medium in the excitation wavelength region. It is preferable.

From the above requirements, for example, a sphere obtained by suspension polymerization of Eu (TTA) ₃ phene as a fluorescent substance and 95% by mass of methyl methacrylate and 5% by mass of ethylene glycol dimethacrylate as a transparent material (spherical matrix material). By using ethylene-vinyl acetate copolymer (EVA) as the sealing resin, a particularly favorable refractive index correlation can be given from the viewpoints of excitation wavelength and emission wavelength, and also from the viewpoint of solar cell sensitivity. .
However, in the present invention, it is preferable to appropriately select each so that the mutual relationship in the respective refractive indexes of the fluorescent material, the transparent material, and the sealing resin satisfies the above conditions, and only in the above combinations. It is not limited.

  The preferred blending amount of the spherical phosphor in the wavelength-converting resin composition layer provided in the wavelength-converting solar cell encapsulating material of the present invention is 0.0001 to 10% by mass with respect to the total nonvolatile content. preferable. Luminous efficiency improves by setting it as 0.0001 mass% or more. Moreover, by setting it as 10 mass% or less, scattering of incident light is suppressed more effectively, and a power generation effect improves more.

(Sealing resin)
The wavelength-convertible resin composition layer in the present invention contains a sealing resin (transparent sealing resin). As the transparent sealing resin, a photocurable resin, a thermosetting resin, a thermoplastic resin, or the like is preferably used.
Conventionally, as a resin used as a transparent sealing material for solar cells, an ethylene-vinyl acetate copolymer (EVA) imparted with thermosetting properties is widely used as described in Patent Document 3 described above. However, the present invention is not limited to this.

  When a photocurable resin is used for the dispersion medium resin (transparent sealing resin) of the resin composition for wavelength conversion type solar cell encapsulant, the resin configuration and photocuring method of the photocurable resin are not particularly limited. For example, in the photocuring method using a photoradical initiator, the wavelength-converting solar cell sealing material resin composition includes (A) a photocurable resin, (B) a crosslinkable monomer, and (C ) A dispersion medium resin containing a photoinitiator that generates free radicals by light.

  Here, as the photocurable resin (A), a copolymer obtained by copolymerizing acrylic acid or methacrylic acid and alkyl esters thereof and other vinyl monomers copolymerizable therewith as constituent monomers is used. These copolymers can be used alone or in combination of two or more. Examples of the alkyl acrylate or alkyl methacrylate include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, and the like. Acrylic acid unsubstituted alkyl ester or methacrylic acid unsubstituted alkyl ester, acrylic acid substituted alkyl ester or methacrylic acid substituted alkyl ester in which a hydroxyl group, an epoxy group, a halogen group or the like is substituted on these alkyl groups.

  Examples of other vinyl monomers that can be copolymerized with acrylic acid, methacrylic acid, alkyl acrylate ester, or alkyl methacrylate ester include acrylamide, acrylonitrile, diacetone acrylamide, styrene, vinyl toluene, and the like. These vinyl monomers can be used alone or in combination of two or more. Moreover, it is preferable that the weight average molecular weight of the dispersion medium resin of (A) component is 10,000-300,000 from the point of coating-film property and coating-film intensity | strength.

  (B) As the crosslinkable monomer, for example, a compound obtained by reacting a polyhydric alcohol with an α, β-unsaturated carboxylic acid (for example, polyethylene glycol di (meth) acrylate (the number of ethylene groups is 2-14) ), Ethylene glycol dimethacrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane ethoxytri (meth) acrylate, trimethylolpropane propoxytri (meth) acrylate, tetramethylolmethanetri (Meth) acrylate, tetramethylolmethane tetra (meth) acrylate, polypropylene glycol di (meth) acrylate (having 2 to 14 propylene groups), dipentaerythritol penta (meth) acrylate , Dipentaerythritol hexa (meth) acrylate, bisphenol A polyoxyethylene di (meth) acrylate, bisphenol A dioxyethylene di (meth) acrylate, bisphenol A trioxyethylene di (meth) acrylate, bisphenol A deoxyoxyethylene di ( A compound obtained by adding an α, β-unsaturated carboxylic acid to a glycidyl group-containing compound (for example, trimethylolpropane triglycidyl ether triacrylate, bisphenol A diglycidyl ether diacrylate, etc.); Esterified product of carboxylic acid (for example, phthalic anhydride) and substance having hydroxyl group and ethylenically unsaturated group (for example, β-hydroxyethyl (meth) acrylate); acrylic acid or methacrylic acid Alkyl ester (eg, (meth) acrylic acid methyl ester, (meth) acrylic acid ethyl ester, (meth) acrylic acid butyl ester, (meth) acrylic acid 2-ethylhexyl ester); urethane (meth) acrylate (eg, tolylene diene) A reaction product of isocyanate and 2-hydroxyethyl (meth) acrylic acid ester, a reaction product of trimethylhexamethylene diisocyanate, cyclohexanedimethanol and 2-hydroxyethyl (meth) acrylic acid ester, and the like.

  Particularly preferred (B) crosslinkable monomers are trimethylolpropane tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate in the sense that the crosslinking density and reactivity can be easily controlled. Bisphenol A polyoxyethylene dimethacrylate. In addition, the said compound is used individually or in combination of 2 or more types.

  As will be described later, in particular, when the refractive index of the wavelength conversion type solar cell encapsulant or its lower layer (the side in contact with the solar cell) is increased, (A) a photocurable resin and / or (B) cross-linking It is advantageous that the functional monomer contains bromine and sulfur atoms. Examples of the bromine-containing monomer include New Frontier BR-31, New Frontier BR-30, and New Frontier BR-42M manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Examples of the sulfur-containing monomer composition include IU-L2000, IU-L3000, and IU-MS1010 manufactured by Mitsubishi Gas Chemical Company, Inc. However, the bromine and sulfur atom-containing monomers (polymers containing them) used in the present invention are not limited to those listed here.

  (C) The photoinitiator is preferably a photoinitiator that generates free radicals by ultraviolet light or visible light. For example, benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isobutyl ether, and benzoin phenyl ether Benzophenones such as benzophenone, N, N′-tetramethyl-4,4′-diaminobenzophenone (Michler's ketone), N, N′-tetraethyl-4,4′-diaminobenzophenone, benzyldimethyl ketal (Ciba Japan) IRGACURE (Irgacure) 651), benzyl ketals such as benzyl diethyl ketal, 2,2-dimethoxy-2-phenylacetophenone, p-tert-butyldichloroacetophenone, p-di Acetophenones such as tilaminoacetophenone, xanthones such as 2,4-dimethylthioxanthone and 2,4-diisopropylthioxanthone, or hydroxycyclohexyl phenyl ketone (manufactured by Ciba Japan, IRGACURE (Irgacure) 184), 1- (4- Isopropylphenyl) -2-vitroxy-2-methylpropan-1-one (Ciba Japan, Darocur 1116), 2-hydroxy-2-methyl-1-phenylpropan-1-one (Ciba Japan) Darocur 1173) and the like, and these may be used alone or in combination of two or more.

  Examples of (C) photoinitiators that can be used as photoinitiators include 2,4,5-triallylimidazole dimer, 2-mercaptobenzoxazole, leucocrystal violet, and tris (4-diethylamino-2). Combinations with -methylphenyl) methane and the like are also mentioned. In addition, although it does not itself have photoinitiating properties, it can be used in combination with the above-mentioned substances to provide a sensitizer system with better photoinitiating performance as a whole, such as triethanolamine for benzophenone. Secondary amines can be used.

Moreover, what is necessary is just to change the said (C) photoinitiator into a thermal initiator in order to make sealing resin thermosetting.
(C) The thermal initiator is preferably an organic peroxide that generates free radicals by heat. For example, isobutyl peroxide, α, α′bis (neodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecano Bis-n-propyl peroxydicarbonate, bis-s-butyl peroxydicarbonate, 1,1,3,3-tetramethylbutyl neodecanoate, bis (4-t-butylcyclohexyl) peroxydi Carbonate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, di-2-ethoxyethylperoxydicarbonate, bis (ethylhexylperoxy) dicarbonate, t-hexylneodecanoate, bismethoxybutylperoxy Dicarbonate, bis (3-methyl-3 Methoxybutylperoxy) dicarbonate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, succinic peroxide, 2,5-dimethyl-2,5-di (2-ethylhexanoyl) hexane, 1-cyclohexyl -1-methylethylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, 4-methylbenzoyl peroxide, t-butylperoxy-2-ethylhexanoate, m- Toluonoyl benzoyl peroxide, benzo Ile peroxide, t-butylperoxyisobutyrate, 1,1-bis (t-butylperoxy) 2-methylcyclohexane, 1,1-bis (t-hexylperoxy) -3,3,5-trimethyl Cyclohexane, 1,1-bis (t-hexylperoxy) cyclohexane, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) Cyclohexanone, 2,2-bis (4,4-dibutylperoxycyclohexyl) propane, 1,1-bis (t-butylperoxy) cyclododecane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid , T-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaur 2,5-dimethyl-2,5-di (m-toluoylperoxy) hexane, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxy Benzoate, 2,5-dimethyl-2,5-bis (benzoylperoxy) hexane, t-butylperoxyacetate, 2,2-bis (t-butylperoxy) butane, t-butylperoxybenzoate, n- Butyl-4,4-bis (t-butylperoxy) valerate, di-t-butylperoxyisophthalate, α, α′bis (t-butylperoxy) diisopropylbenzene, dicumyl peroxide, 2,5- Dimethyl-2,5-bis (t-butylperoxy) hexane, t-butylcumyl peroxide P-menthane hydroperoxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexyne, diisopropylbenzene hydroperoxide, t-butyltrimethylsilyl peroxide, 1,1,3,3-tetra Methylbutyl hydroperoxide, cumene hydroperoxide, t-hexyl hydroperoxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, and the like can be used.

  The above is an example of the acrylic photocurable resin and the thermosetting resin, but the epoxy photocurable resin and the thermosetting resin that are usually used are also included in the wavelength conversion type solar cell encapsulant of the present invention. It can be used as a dispersion medium resin. However, since the curing of the epoxy is ionic, the coated phosphor or the rare earth metal complex that is a fluorescent substance may be affected and may cause deterioration or the like. Therefore, an acrylic type is more preferable.

  When a thermoplastic resin that flows by heating or pressurization is used for the dispersion medium resin of the resin composition for wavelength conversion type solar cell encapsulant, for example, natural rubber, polyethylene, polypropylene, polyvinyl acetate, polyisoprene, poly- (Di) enes such as 1,2-butadiene, polyisobutene, polybutene, poly-2-heptyl-1,3-butadiene, poly-2-t-butyl-1,3-butadiene, poly-1,3-butadiene , Polyethers such as polyoxyethylene, polyoxypropylene, polyvinyl ethyl ether, polyvinyl hexyl ether, and polyvinyl butyl ether, polyesters such as polyvinyl acetate and polyvinyl propionate, polyurethane, ethyl cellulose, polyvinyl chloride, polyacrylonitrile, polymethacrylate Ronitrile, poly Sulfone, phenoxy resin, polyethyl acrylate, polybutyl acrylate, poly-2-ethylhexyl acrylate, poly-t-butyl acrylate, poly-3-ethoxypropyl acrylate, polyoxycarbonyl tetramethacrylate, polymethyl acrylate, polyisopropyl methacrylate, poly Dodecyl methacrylate, polytetradecyl methacrylate, poly-n-propyl methacrylate, poly-3,3,5-trimethylcyclohexyl methacrylate, polyethyl methacrylate, poly-2-nitro-2-methylpropyl methacrylate, poly-1,1-diethyl Poly (meth) acrylic acid esters such as propyl methacrylate and polymethyl methacrylate can be used as the dispersion medium resin.

  Two or more kinds of these thermoplastic resins may be copolymerized as required, or two or more kinds may be blended and used.

  Furthermore, epoxy acrylate, urethane acrylate, polyether acrylate, polyester acrylate, or the like can be used as a copolymer resin with the above resin. In particular, urethane acrylate, epoxy acrylate, and polyether acrylate are excellent from the viewpoint of adhesiveness.

  As epoxy acrylate, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, allyl alcohol diglycidyl ether, resorcinol diglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, polyethylene glycol diglycidyl ether And (meth) acrylic acid adducts such as trimethylolpropane triglycidyl ether, glycerin triglycidyl ether, pentaerythritol tetraglycidyl ether, and sorbitol tetraglycidyl ether.

  A polymer having a hydroxyl group in the molecule, such as epoxy acrylate, is effective in improving adhesion. These copolymer resins can be used in combination of two or more as required. The softening temperature of these resins is preferably 200 ° C. or less, and more preferably 150 ° C. or less from the viewpoint of handleability. Considering that the use environment temperature of the solar cell unit is usually 80 ° C. or lower and workability, the softening temperature of the resin is particularly preferably 80 to 120 ° C.

When the thermoplastic resin is used as a dispersion medium resin, the composition of the other resin composition is not particularly limited as long as the spherical phosphor is contained, but usually used components such as a plasticizer, a flame retardant, It is possible to contain a stabilizer and the like.
As the dispersion medium resin of the wavelength conversion type solar cell encapsulant of the present invention, as described above, photocurability, thermosetting, thermoplasticity, and the resin is not particularly limited, but as a particularly preferable resin, The composition which mix | blended the thermal radical initiator with the ethylene-vinyl acetate copolymer widely utilized as the sealing material for conventional solar cells is mentioned.

The wavelength conversion type solar cell encapsulant of the present invention may be composed only of a wavelength convertible resin composition layer containing a spherical phosphor and an encapsulating resin, but in addition to this, the resin composition layer It is preferable to further have a light transmission layer other than the above.
Examples of the light-transmitting layer other than the resin composition layer include a light-transmitting layer obtained by removing the spherical phosphor from the wavelength-converting resin composition layer.
When the wavelength conversion type solar cell encapsulating material of the present invention is composed of a plurality of light transmissive layers, it is preferable that the wavelength conversion type solar cell encapsulating material has at least the same or higher refraction than the layer on the incident side.
In detail, m light-transmitting layers are layer 1, layer 2,..., Layer (m−1), layer m in order from the light incident side, and the refractive indices of the respective layers are sequentially n _{1. , n 2, ···, n (} m-1), when the _{n m,} it is preferable _{that n 1 ≦ n 2 ≦ ··· ≦} n (m-1) ≦ n m holds.

  Although there is no restriction | limiting in particular as a refractive index of the wavelength conversion type solar cell sealing material of this invention, Preferably it is 1.5-2.1, More preferably, you may be 1.5-1.9. Moreover, when the wavelength conversion type solar cell sealing material of this invention consists of a some light transmissive layer, it is preferable that the whole refractive index of the wavelength conversion type solar cell sealing material is in the said range.

  It is preferable that the wavelength conversion type solar cell sealing material of this invention is arrange | positioned on the light-receiving surface of a photovoltaic cell. By doing so, it is possible to follow the uneven structure including the texture structure of the solar cell light receiving surface, the cell electrode, the tab line and the like without a gap.

<Method for Producing Wavelength Conversion Type Solar Cell Sealant>
The method for producing a wavelength-converting solar cell encapsulant of the present invention comprises: (1) a spherical phosphor obtained by suspension polymerization of a vinyl compound-containing composition containing a bifunctional or higher functional vinyl compound in which a fluorescent substance is dissolved or dispersed; And (2) a sheet forming step of forming a resin composition obtained by mixing or dispersing the spherical phosphor in a sealing resin (transparent sealing resin) into a sheet shape.
The details of the step of obtaining the spherical phosphor are as described above. Moreover, the sheet | seat formation process can use the method normally used as a method of forming a resin composition in a sheet form without a restriction | limiting in particular.
The wavelength conversion type solar cell encapsulant of the present invention is preferably formed in a sheet shape from the viewpoint of ease of use.

  In the present invention, a step of obtaining a spherical phosphor by suspension polymerization of a vinyl compound-containing composition containing a bifunctional or higher functional vinyl compound in which a fluorescent substance (preferably, a europium complex) is dissolved or dispersed; And a sheet forming step of forming a resin composition obtained by dispersing the spherical phosphor in a sealing resin (transparent sealing resin) into a sheet shape.

<Solar cell module>
The present invention also includes a solar module including the wavelength conversion type solar cell encapsulant. The solar cell module of this invention is equipped with the photovoltaic cell and the said wavelength conversion type solar cell sealing material arrange | positioned on the light-receiving surface of the said photovoltaic cell. This improves power generation efficiency.
The wavelength conversion type solar cell encapsulant of the present invention is used as one of light transmissive layers of a solar cell module having a plurality of light transmissive layers and solar cells, for example.

  In this invention, a solar cell module is comprised from required members, such as an antireflection film, protective glass, a wavelength conversion type solar cell sealing material, a photovoltaic cell, a back film, a cell electrode, a tab wire, for example. Among these members, the light-transmitting layer having light transmittance includes an antireflection film, a protective glass, the wavelength conversion type solar cell sealing material of the present invention, a SiNx: H layer and a Si layer of the solar cell, and the like. Can be mentioned.

  In the present invention, the order of lamination of the light-transmitting layers mentioned above is usually an antireflection film, protective glass, and the wavelength conversion type solar cell sealing of the present invention, which are formed in order from the light receiving surface of the solar cell module. The material is a SiNx: H layer or Si layer of the solar battery cell.

  That is, in the wavelength conversion type solar cell encapsulant of the present invention, the external light entering from any angle has little reflection loss, and the refractive index of the wavelength conversion type solar cell encapsulant is efficiently introduced into the solar cell. The light-transmitting layer disposed on the light incident side from the wavelength conversion type solar cell encapsulant, that is, higher than the refractive index of the antireflection film, protective glass, etc., and the reflection of the wavelength conversion type solar cell encapsulant The refractive index of the light transmissive layer disposed on the incident side, that is, the SiNx: H layer (also referred to as “cell antireflection film”) and the Si layer of the solar battery cell is preferably lower.

  Specifically, the light transmitting layer disposed on the light incident side from the wavelength conversion type solar cell encapsulant, that is, the refractive index of the antireflection film is 1.25 to 1.45, and the refractive index of the protective glass is Usually, about 1.45 to 1.55 is used. The refractive index of the light transmissive layer disposed on the light incident side of the wavelength conversion type solar cell encapsulant, that is, the SiNx: H layer (cell antireflection film) of the solar cell is usually 1.9 to 2. The refractive index of about 1 and the Si layer or the like is usually about 3.3 to 3.4. From the above, the refractive index of the wavelength conversion type solar cell encapsulant of the present invention is preferably 1.5 to 2.1, more preferably 1.5 to 1.9.

  By using a europium complex as the fluorescent material used for the wavelength conversion type solar cell sealing material of the present invention, a solar cell module having high power generation efficiency can be realized. The europium complex converts light in the ultraviolet region into light in the red wavelength region with high wavelength conversion efficiency, and the converted light contributes to power generation in the solar battery cell.

<Method for manufacturing solar cell module>
Using the sheet-shaped resin composition that becomes the wavelength conversion type solar cell encapsulant of the present invention, the wavelength conversion type solar cell encapsulant is formed on the solar cell to produce a solar cell module.
Specifically, it is the same as the manufacturing method of a normal silicon crystal solar cell module, and instead of the normal sealing material sheet, the wavelength conversion type solar cell sealing material (particularly preferably in the form of a sheet) of the present invention is used. .

  Generally, a silicon crystal solar cell module is first made into a sheet-like sealing material (mostly an ethylene-vinyl acetate copolymer with a thermal radical initiator on a cover glass which is a light receiving surface, and a thermosetting type. ). In this invention, the wavelength conversion type solar cell sealing material of this invention is used for the sealing material used here. Next, the cells connected by tab wires are placed, and a sheet-shaped sealing material (in the present invention, a wavelength conversion type solar cell sealing material may be used only on the light receiving surface side. And a back sheet, and a module using a vacuum press laminator dedicated to the solar cell module.

  At this time, the hot plate temperature of the laminator is a temperature necessary for the sealing material to soften and melt, wrap the cell, and further harden, and is usually 120 to 180 ° C., most of which is 140 to 160 ° C. Designed to cause these physical and chemical changes.

The wavelength conversion type solar cell encapsulant of the present invention is in a state before being made into a solar cell module, specifically, a semi-cured state when a curable resin is used. In addition, the refractive index of the wavelength conversion type solar cell sealing material in a semi-cured state and the wavelength conversion type solar cell sealing material after being cured (after being formed into a solar cell module) is not greatly changed.
Although there is no restriction | limiting in particular in the form of the wavelength conversion type solar cell sealing material of this invention, It is preferable that it is a sheet form from the ease of manufacture of a solar cell module.

  Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to these examples. Unless otherwise specified, “%” and “part” are based on mass.

Example 1
<Synthesis of fluorescent substances>
200 mg of 4,4,4-trifluoro-1- (thienyl) -1,3-butanedione (TTA) was dissolved in 7 ml of ethanol, and 1.1 ml of 1M sodium hydroxide was added thereto and mixed. 6.2 mg of 1,10-phenanthroline dissolved in 7 ml of ethanol is added to the above mixed solution and stirred for 1 hour, and then a solution of 103 ml of EuCl ₃ · 6H ₂ O in 3.5 ml is added to obtain a precipitate. This was separated by filtration, washed with ethanol, and dried to obtain a fluorescent substance Eu (TTA) ₃ Phen (phenanthroline-based europium complex).

<Production of spherical phosphor>
0.05 g of the fluorescent substance Eu (TTA) 3Phen obtained above, 95 g of methyl methacrylate, 5 g of ethylene glycol dimethacrylate, 2,2′-azobis (2,4-dimethylvaleronitrile, which is a thermal radical initiator ) Was weighed out and placed in a 200 ml screw tube, and stirred and mixed using an ultrasonic cleaner and a mix rotor. In a separable flask equipped with a condenser, 500 g of ion exchange water and 59.1 g of a 1.69% polyvinyl alcohol solution as a surfactant were added and stirred. The mixed liquid of methyl methacrylate and ethylene glycol dimethacrylate prepared previously was added thereto, and this was heated to 50 ° C. while stirring at 350 rpm, and reacted for 4 hours. The particle diameter of this suspension was measured using a Beckman Coulter LS13320 (high resolution laser diffraction scattering method / particle size distribution analyzer, Beckman Coulter, Inc.), and the volume average diameter was 104 μm. The precipitate was separated by filtration, washed with ion exchange water, and dried at 60 ° C. to obtain a spherical phosphor A by suspension polymerization.

<Observation with a scanning electron microscope>
The obtained spherical phosphor A was observed using a scanning electron microscope, and it was confirmed that the obtained spherical phosphor A was spherical. This scanning electron micrograph is shown in FIG.

<Measurement of fluorescence excitation spectrum>
For this spherical phosphor A, an excitation spectrum at a fluorescence wavelength of 621 nm was measured with a spectrofluorometer manufactured by Hitachi, Ltd. This excitation spectrum is shown in FIG. 6 together with a comparative example.

<Preparation of resin composition for wavelength conversion type solar cell encapsulant>
100 g of ethylene-vinyl acetate resin manufactured by Tosoh Corporation as a transparent sealing resin (dispersion medium resin), Ultracene 634 (MFR = 4.0, vinyl acetate content = 26%), peroxide manufactured by Arkema Yoshitomi Corporation Using a thermal radical initiator, 1.5 g of Luperox 101 (2,5-dimethyl-2,5-di (t-butylperoxy) hexane), a silane coupling agent manufactured by Toray Dow Corning Co., Ltd., SZ6030 ( A mixture of 0.5 g of 3-methacryloxypropyltrimethoxysilane) and 1.0 g of the spherical phosphor A was kneaded with a roll mixer adjusted to 100 ° C., and wavelength conversion type solar cell sealing material resin A composition was obtained.

<Preparation of wavelength conversion type solar cell encapsulant sheet>
About 30 g of the resin composition for wavelength conversion type solar cell encapsulant obtained above was sandwiched between release sheets, a 0.6 mm thick stainless steel spacer was used, and a hot plate adjusted to 80 ° C. was used. Made into a sheet. The refractive index of the obtained sheet-form wavelength conversion type solar cell encapsulant was 1.5.

<Preparation of solar cell encapsulant sheet for back surface>
In the preparation of the wavelength conversion type solar cell encapsulant sheet, instead of the wavelength conversion type solar cell encapsulant resin composition, a resin composition prepared in the same manner as described above except that it does not contain a spherical phosphor. The solar cell encapsulant sheet for back surface was produced by the same method as above.

<Production of wavelength conversion type solar cell module>
A solar cell in which the wavelength conversion type solar cell encapsulant sheet is placed on a tempered glass (manufactured by Asahi Glass Co., Ltd., refractive index 1.5) as a protective glass, and an electromotive force can be taken out thereon. Place the cell so that the light-receiving surface is facing down, further place the back surface solar cell sealing material sheet, PET film as a back film (trade name: A-4300, manufactured by Toyobo Co., Ltd.), using a vacuum laminator, Lamination was performed to produce a wavelength conversion type solar cell module.
Note that a cell antireflection film having a refractive index of 1.9 is formed on the used solar battery cell.

<Evaluation of solar cell characteristics>
As a simulated solar ray, a solar simulator (manufactured by Wacom Denso Co., Ltd., WXS-155S-10, AM1.5G) is used, and current-voltage characteristics are measured using an IV curve tracer (manufactured by Eiko Seiki Co., Ltd., MP-160). According to JIS-C8914, the short-circuit current density Jsc in the state of the cell before module sealing and the short-circuit current density Jsc after module sealing were measured and evaluated by taking the difference (ΔJsc). . As a result, ΔJsc was 0.478 mA / cm ² .

(Comparative Example 1)
In <Production of spherical phosphor> in Example 1, spherical phosphor B was obtained in the same manner except that 100 g of methyl methacrylate was used without using a bifunctional or higher vinyl compound (ethylene glycol dimethacrylate). Hereinafter, in the same manner, <observation with scanning electron microscope><measurement of fluorescence excitation spectrum><preparation of resin composition for wavelength conversion type solar cell encapsulant><production of wavelength conversion type solar cell encapsulant sheet>< Production of back surface solar cell encapsulant sheet><Production of wavelength conversion type solar cell module><Evaluation of solar cell characteristics>
The scanning electron micrograph is shown in FIG. 5, and the fluorescence excitation spectrum is shown in FIG. ΔJsc was 0.212 mA / cm ² .

By constructing a solar cell module using the wavelength conversion type solar cell encapsulant containing the spherical phosphor of the present invention, it is possible to improve the light utilization efficiency in the solar cell module and to stably improve the power generation efficiency. It became.
Furthermore, the utilization efficiency of the rare earth metal complex as a fluorescent substance can be maximized and the effective light emission efficiency can be improved, thereby suppressing the amount of expensive rare earth complex to a very small amount and contributing to power generation. . The spherical phosphor of the present invention is a fluorescent material having excellent moisture resistance and heat resistance, good dispersibility, and suppressed concentration quenching. Such a fluorescent material can maximize the utilization efficiency of the rare earth metal complex, which is an expensive fluorescent substance, and can further improve the effective light emission efficiency and improve the power generation efficiency of the solar cell module. In addition, the spherical phosphor of the present invention, and the wavelength conversion type solar cell encapsulant using the same, simultaneously convert light that does not contribute to solar power generation into incident light that contributes to power generation, The scattering of the light can be suppressed and the light can be efficiently introduced into the solar battery cell.

Claims (15)

  In a spherical phosphor containing a fluorescent substance and a transparent material, the transparent material is a spherical compound obtained by suspension polymerization of a vinyl compound-containing composition, and the vinyl compound-containing composition is bifunctional or more functional. A spherical phosphor containing a vinyl compound.   The spherical phosphor according to claim 1, wherein the phosphor is an organic phosphor or a rare earth metal complex.   The spherical phosphor according to claim 1 or 2, wherein the phosphor is a rare earth metal complex.   The spherical phosphor according to any one of claims 1 to 3, wherein the fluorescent substance is a europium complex.   The vinyl compound of the vinyl compound-containing composition is a resin obtained by suspension polymerization of a (meth) acrylic acid derivative, and the vinyl compound contains a bifunctional or higher functional (meth) acrylic acid derivative. The spherical phosphor according to any one of claims 1 to 4, wherein the spherical phosphor is characterized.   The spherical phosphor according to any one of claims 1 to 5, wherein a refractive index of the transparent material is lower than that of the fluorescent material and is 1.4 or more.   The spherical phosphor according to any one of claims 1 to 6, which is spherical resin particles obtained by emulsion polymerization or suspension polymerization of a vinyl compound-containing composition in which the fluorescent substance is dissolved or dispersed.   The spherical phosphor according to any one of claims 1 to 7, which is spherical resin particles obtained by suspension polymerization of the vinyl compound-containing composition in which the fluorescent substance is dissolved or dispersed.   A wavelength conversion type solar cell sealing material provided with the light-transmitting resin composition layer containing the spherical fluorescent substance in any one of Claims 1-8, and sealing resin.   The wavelength conversion type solar cell sealing material according to claim 9, wherein a content of the spherical phosphor in the resin composition layer is 0.0001 to 10 mass percent.   The wavelength conversion type solar cell sealing material according to claim 9 or 10, further comprising a light transmissive layer other than the layer of the wavelength conversion type solar cell sealing material. Each of the m layers includes a layer of the wavelength conversion type solar cell encapsulant and a light transmissive layer other than the layer of the wavelength conversion type solar cell encapsulant, and each of the m layers has a refractive index. , N ₁ , n ₂ ,..., N _(m−1) , n _m in this order from the light incident side, n ₁ ≦ n ₂ ≦ ... ≦ n _(m−1) ≦ n _m The wavelength conversion type solar cell sealing material according to claim 11, wherein   A solar cell module provided with a photovoltaic cell and the wavelength conversion type solar cell sealing material in any one of Claims 9-12 arrange | positioned on the light-receiving surface of the said photovoltaic cell. A step of suspension polymerization of a vinyl compound-containing composition in which a fluorescent substance is dissolved or dispersed to obtain a spherical phosphor;
A sheet forming step of forming a resin composition obtained by mixing or dispersing the spherical phosphor in a sealing resin into a sheet; and
The manufacturing method of the wavelength conversion type solar cell sealing material which has this.   It is a manufacturing method of the solar cell module which has a some light transmissive layer and a photovoltaic cell, Comprising: The light reception of a photovoltaic cell by using the wavelength conversion type solar cell sealing material in any one of Claims 9-12. A method for manufacturing a solar cell module, comprising a step of forming one of the light transmissive layers on a surface side.

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