JP2012084670A - Back sheet for solar cell module and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a back sheet for a solar cell module which has power generation efficiency accelerated by excellent diffuse reflectivity, and which is excellent in durability, manufacturability, and cost-saving performance.SOLUTION: A back sheet for a solar cell module comprises: a base material sheet; and a reflective layer laminated on the front side of the base material sheet. The reflective layer has white beads and a white binder for the beads. Because the reflective layer has the white beads and the white binder, an uneven surface is formed on the surface, and light can be diffuse-reflected on the uneven surface made of the white beads. This enhances the photoelectric conversion efficiency of the solar cell module to thereby increase power generation efficiency. Further, the invention is excellent in durability, manufacturability, and cost-saving performance because a metal vapor-deposition layer is not required as a reflective layer.

Description

  The present invention relates to a back sheet for a solar cell module, which is a unit constituting a solar cell, and a solar cell module using the back sheet.

  In recent years, solar power generation as a clean energy source has attracted attention due to increasing awareness of environmental problems such as global warming, and solar cells having various forms have been developed. This solar battery is generally composed of a plurality of solar battery modules that are packaged by a plurality of solar battery cells wired in series or in parallel.

  The solar cell module is required to have sufficient durability and weather resistance that can be used outdoors for a long period of time. As shown in FIG. 5, the specific structure of a general solar cell module 61 includes a light-transmitting substrate 62 made of glass or the like, and a filler layer 63 made of a thermoplastic resin such as an ethylene vinyl acetate copolymer. And a plurality of solar cells 64 as photovoltaic elements, a filler layer 65 similar to the filler layer 63, and a solar cell module backsheet 66 are laminated in this order, and a vacuum heating lamination method or the like. Is integrally molded. Since the solar cell module backsheet 66 is required to have weather resistance, durability, gas barrier properties, and the like, conventionally, the front and back surfaces of the inorganic layer 67 that exhibits gas barrier properties are sandwiched between a pair of synthetic resin layers 68. A laminate is adopted.

  Further, as a back sheet for a solar cell module, (a) a back sheet for a solar cell module in which a spherical particle-containing layer is disposed on a white polyethylene terephthalate layer (see JP 2009-302361 A), (b) A back sheet for a solar cell module (see JP 2006-319250 A) or the like has been developed, which includes a bead coating layer in which transparent beads are dispersed in a transparent binder and a metal vapor deposition layer.

JP 2009-302361 A JP 2006-319250 A

  In the conventional solar cell module backsheet 66 described above, although light that passes between the solar cells 64 and enters the synthetic resin layer 68 is partially reflected, the reflectivity is not so high, and the backsheet 66 is synthesized. Since the surface of the resin layer 68 is flat, the incident light is almost regularly reflected, so that the reflected light is unlikely to return to the solar battery cell 64. That is, the conventional solar cell module back sheet 66 cannot efficiently use incident solar rays.

  In addition, the solar cell module backsheet of the above (a) in which the spherical particle-containing layer is disposed on the white polyethylene terephthalate layer is considered in consideration of the reflectivity of the solar rays. Not available for use. This is because when the light incident on the spherical particles from the surface side is refracted and then incident on the white polyethylene terephthalate layer, it is reflected on the polyethylene terephthalate layer, but when the reflected light is incident on the spherical particles again, It is considered that a part of the light is reflected from the spherical particles without being emitted to the surface side and is confined in the back sheet for the solar battery module and cannot be recurred to the solar battery cell. Therefore, even if this solar cell module sheet is used, the rate of recursion to the solar cells is low, and the incident solar rays cannot be fully utilized.

  Furthermore, since the back sheet for solar cell module in (b) above, which has a transparent bead coating layer and a metal vapor deposition layer, has a metal vapor deposition layer, a solar cell in which an ethylene vinyl acetate copolymer is used as a filler layer. When used in a battery module, the vapor deposited metal layer may be corroded by a small amount of gas generated from the ethylene vinyl acetate copolymer.

  The present invention has been made in view of these inconveniences, and the back sheet for a solar cell module, in which power generation efficiency is promoted by excellent diffuse reflectivity, is excellent in durability, and is excellent in manufacturability and low cost, And it aims at provision of the solar cell module using the same.

  The back sheet for a solar cell module of the present invention made to solve the above problems comprises a base sheet and a reflective layer laminated on the surface side of the base sheet, and the reflective layer comprises white beads and its And a white binder.

  In the solar cell module backsheet, since the reflective layer has white beads and a white binder, light incident on the reflective layer is reflected. In particular, since the reflective layer has white beads, an uneven surface is formed on the surface, and light can be diffusely reflected by the uneven surface made of the white beads. For this reason, the solar cell module backsheet can effectively recurs the light transmitted between the solar cells to the solar cells as compared with the conventional transparent spherical resin. The photoelectric conversion efficiency of the battery module can be increased and the power generation efficiency can be increased. Further, since the back sheet for solar cell module does not require a metal vapor deposition layer for reflection, it has excellent durability without being corroded by, for example, gas generated from an ethylene vinyl acetate copolymer, Since metal deposition is not required, it is excellent in manufacturability and low cost.

  The solar reflectance of the surface of the solar cell module backsheet is preferably 80.5% or more. Thereby, since the light which injected into the said solar cell module backsheet can be reflected correctly, the photoelectric conversion efficiency of a solar cell module can be raised, and electric power generation efficiency can be raised.

  Moreover, it is preferable that the whiteness of the surface of the said solar cell module backsheet is 80% or more. Thereby, the light which injected into the said solar cell module backsheet can be reflected accurately, the photoelectric conversion efficiency of a solar cell module can be improved, and electric power generation efficiency can be improved.

  Moreover, it is preferable to employ | adopt the structure in which the said white binder contains titanium dioxide. Thus, by including titanium dioxide, the solar reflectance of the surface of the said solar cell module backsheet can be raised, For this reason, the photoelectric conversion efficiency of a solar cell module can be improved and electric power generation efficiency can be improved.

  Moreover, it is preferable to employ | adopt the structure in which the said white bead contains titanium dioxide. Thus, by including titanium dioxide, the solar reflectance of the surface of the said solar cell module backsheet can be raised, For this reason, the photoelectric conversion efficiency of a solar cell module can be improved and electric power generation efficiency can be improved.

  The reflective layer is preferably formed by coating a coating composition containing white beads on a polymer composition that is a white binder forming material. Such a bead coating layer is easy to form, and the convex portions formed on the outer surface are spherical, and can promote the diffusibility of reflected light.

  Here, it is preferable that the compounding amount of white beads in terms of solid content with respect to 100 parts by mass of the base polymer in the polymer composition which is a material for forming the white binder is 12 parts by mass or more and 500 parts by mass or less. This is because if the blending amount of the beads is less than the above range, the unevenness of the surface of the reflective layer becomes small, and the diffusibility of the reflected light becomes insufficient. On the other hand, if the blending amount of the beads exceeds the above range, This is because the effect of fixing the white beads is reduced.

  The arithmetic average roughness in the three-dimensional surface roughness of the surface of the reflective layer is preferably 3 μm or more and 14 μm or less, and the ten-point average roughness is preferably 10 μm or more and 80 μm or less. Thus, by making the arithmetic average roughness and the ten-point average roughness in the three-dimensional surface roughness of the surface of the reflective layer within the above ranges, it is possible to impart good diffusibility to the reflected light and effectively increase the power generation efficiency. be able to.

  The average thickness of the reflective layer is preferably 80% to 300% of the average particle diameter of the white beads. In this way, by controlling the average thickness of the reflective layer within the above range in relation to the average particle diameter of the white beads, the concave portions and the convex portions are remarkably formed on the surface of the reflective layer by the white beads that are present, and reflected light is reflected. Good diffusibility can be imparted and power generation efficiency can be effectively increased.

  The base material sheet may include a gas barrier layer. By further laminating the gas barrier layer in this way, the gas barrier property of the solar cell module backsheet can be further improved.

  Therefore, a solar cell module in which a translucent substrate, a filler layer, a solar cell as a photovoltaic element, a filler layer, and the solar cell module backsheet are laminated in this order from the surface side. The solar cell module backsheet has a high diffuse reflectivity, so that the transmitted light is effectively recurred to the solar cells, and the power generation efficiency can be promoted. Further, for example, when an ethylene vinyl acetate copolymer is used for the filler layer, even if gas is generated from the filler layer, the solar cell module backt does not corrode, and the solar cell module Is excellent in durability, and since the back sheet for solar cell module can be manufactured without requiring metal vapor deposition, the solar cell module is excellent in manufacturability and low cost.

また、「白色度」とは、ＪＩＳ−Ｐ８１４８に記載される拡散照明方式によるＩＳＯ白色度であり、完全拡散反射面（反射率が１００％の理想的な完全拡散面）に対する反射量の比率を意味する。
「光学層の平均厚さ」とは、ＪＩＳ−Ｋ−７１３０に規定される５．１．２のＡ−２法により測定した値の平均値である。
「算術平均粗さ」及び「十点平均粗さ」とは、ＪＩＳ−Ｂ−０６０１−１９９４に準じて測定した、カットオフ値λｃ２．５ｍｍ、評価長さ１２．５ｍｍの値である。
「ガスバリア層」とは、水素ガス、酸素ガス等のガスの透過を低減する機能を有する層を意味する。 Here, the “surface” means a light-receiving side surface of the solar cell module and the back sheet constituting the solar cell module.
“Solar radiation reflectance” is a reflectance described in JIS-R3106-1985, and is a numerical value obtained from the following equation based on the reflectance of each wavelength measured by a spectrophotometer.

The “whiteness” is ISO whiteness according to the diffuse illumination method described in JIS-P8148, and the ratio of the amount of reflection with respect to a perfect diffuse reflection surface (an ideal perfect diffusion surface with a reflectance of 100%). means.
The “average thickness of the optical layer” is an average value of values measured by the A-2 method of 5.1.2 defined in JIS-K-7130.
The “arithmetic average roughness” and “ten-point average roughness” are values having a cutoff value λc of 2.5 mm and an evaluation length of 12.5 mm, measured according to JIS-B-0601-1994.
The “gas barrier layer” means a layer having a function of reducing permeation of gas such as hydrogen gas and oxygen gas.

  As described above, the solar cell module backsheet of the present invention has improved power generation efficiency due to excellent diffuse reflectance, excellent durability, and excellent manufacturability and low cost. Moreover, the solar cell module using the back sheet for the solar cell module has improved power generation efficiency, excellent durability, and excellent manufacturability and low cost.

Schematic sectional view showing a back sheet for a solar cell module according to an embodiment of the present invention. Typical sectional drawing which shows the solar cell module using the back seat | sheet for solar cell modules of FIG. Typical sectional drawing which shows the solar cell module backsheet which concerns on the form different from the solar cell module backsheet of FIG. Circuit diagram showing equivalent circuit of solar cell module Schematic sectional view showing a conventional general solar cell module

  A back sheet 1 for a solar cell module in FIG. 1 (hereinafter sometimes referred to as a back sheet) includes a base sheet 2 and a reflective layer laminated on the surface of the base sheet 2. In this embodiment, it is comprised from the bead coating layer 3 formed by coating the coating liquid containing the white bead 4 on the surface of the base material sheet 2.

  It is preferable that the solar reflectance of the surface of the back sheet 1 is 80.5% or more, and thereby, the light incident on the back sheet 1 can be accurately reflected.

  Moreover, it is preferable that the whiteness of the surface of the said backsheet 1 is 80% or more, More preferably, it is 90% or more, More preferably, it is 94% or more. Thereby, the light incident on the back sheet 1 can be accurately reflected.

  The base sheet 2 is composed of a synthetic resin film made of synthetic resin, and is formed by sheet molding. The synthetic resin used for the base sheet 2 is not particularly limited, and for example, a polyethylene resin, a polypropylene resin, a cyclic polyolefin resin, a polystyrene resin, an acrylonitrile-styrene copolymer (AS resin), Acrylonitrile-butadiene-styrene copolymer (ABS resin), polyvinyl chloride resin, fluorine resin, poly (meth) acrylic resin, polycarbonate resin, polyester resin, polyamide resin, polyimide resin, polyamideimide Examples thereof include resins, polyaryl phthalate resins, silicone resins, polysulfone resins, polyphenylene sulfide resins, polyether sulfone resins, polyurethane resins, acetal resins, and cellulose resins. Among the above resins, it has high heat resistance, strength, weather resistance, durability, gas barrier properties against water vapor, etc., withstands the coating conditions of the bead coating layer 3, and tight adhesion to the bead coating layer 3 and the like. Polyester resins, fluorine resins, and cyclic polyolefin resins that are excellent in the above are preferred.

  Examples of the polyester resin include polyethylene terephthalate and polyethylene naphthalate. Among these polyester-based resins, polyethylene terephthalate is particularly preferable because it has a good balance between various functions such as heat resistance and weather resistance, and price.

  Examples of the fluororesin include polytetrafluoroethylene (PTFE), perfluoroalkoxy resin (PFA) made of a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, and a copolymer of tetrafluoroethylene and hexafluoropropylene (FEP). Copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether and hexafluoropropylene (EPE), copolymer of tetrafluoroethylene and ethylene or propylene (ETFE), polychlorotrifluoroethylene resin (PCTFE), ethylene and chlorotrifluoroethylene Copolymer (ECTFE), vinylidene fluoride resin (PVDF), vinyl fluoride resin (PVF), and the like. Among these fluororesins, polyvinyl fluoride resin (PVF) and a copolymer of tetrafluoroethylene and ethylene or propylene (ETFE) which are excellent in strength, heat resistance, weather resistance and the like are particularly preferable.

  As the cyclic polyolefin resin, for example, a) cyclic dienes such as cyclopentadiene (and derivatives thereof), dicyclopentadiene (and derivatives thereof), cyclohexadiene (and derivatives thereof), norbornadiene (and derivatives thereof) are polymerized. And b) a copolymer obtained by copolymerizing the cyclic diene with one or more olefinic monomers such as ethylene, propylene, 4-methyl-1-pentene, styrene, butadiene, and isoprene. . Among these cyclic polyolefin resins, cyclopentadiene (and derivatives thereof), dicyclopentadiene (and derivatives thereof) or norbornadiene (and derivatives thereof) such as polymers having excellent strength, heat resistance, and weather resistance are particularly preferred. preferable.

  In addition, as a forming material of the base material sheet 2, the said synthetic resin can be used 1 type or in mixture of 2 or more types. In addition, various additives and the like can be mixed in the forming material of the base sheet 2 for the purpose of improving and modifying processability, heat resistance, weather resistance, mechanical properties, dimensional stability, and the like. . Examples of the additive include a lubricant, a crosslinking agent, an antioxidant, an ultraviolet absorber, a light stabilizer, a filler, a reinforcing fiber, a reinforcing agent, an antistatic agent, a flame retardant, a flame retardant, a foaming agent, and an antifungal agent. And pigments. The method for forming the base sheet 2 is not particularly limited, and known methods such as an extrusion method, a cast forming method, a T-die method, a cutting method, and an inflation method are employed.

  As a minimum of the thickness (average thickness) of substrate sheet 2, 10 micrometers is preferred and 20 micrometers is especially preferred. On the other hand, as an upper limit of the thickness of the base material sheet 2, 250 micrometers is preferable and 188 micrometers is especially preferable. When the thickness of the base material sheet 2 is less than the above lower limit, inconveniences such as curling easily occur during handling of the bead coating layer 3 and handling become difficult. On the contrary, if the thickness of the base sheet 2 exceeds the above upper limit, it is against the request for thinning and light weight of the solar cell module 11.

  The bead coating layer 3 includes white beads 4 and a white binder 5 that are disposed substantially uniformly on the surface of the base sheet 2. Such white beads 4 are coated with a white binder 5. The white beads 4 are substantially spherical particles, and fine convex portions or concave portions are formed substantially uniformly on the surface of the bead coating layer 3 by being contained in the bead coating layer 3.

  Specifically, the bead coating layer 3 (reflection layer) is prepared by adjusting a coating solution in which the white beads 4 are dissolved or dispersed in a polymer composition that is a material for forming the white binder 5. Is applied to the surface of the substrate sheet 2 by a coating method such as dipping, flow coating, spraying, bar coating, gravure coating, roll coating, blade coating, air knife coating, etc. Can be formed. The reflective layer is formed by forming a mixture of the white beads 4 and the polymer composition into a film or sheet using methods such as photocuring, injection molding, T-die molding, calendar molding, compression molding, and casting. And the method etc. which adhere | attach on the surface of the base material sheet 2 are employable. However, by forming the bead coating layer 3 by coating as described above to form the reflective layer, the formation is easy, and the convex portion formed on the outer surface becomes spherical, and the diffusibility of the reflected light Can be promoted.

  The lower limit of the arithmetic average roughness (Ra) in the three-dimensional surface roughness of the surface of the bead coating layer 3 is preferably 3 μm or more, more preferably 5 μm, and particularly preferably 7 μm. On the other hand, the upper limit of the arithmetic average roughness (Ra) is preferably 14 μm, more preferably 12 μm, and particularly preferably 10 μm. By controlling the average particle diameter, blending amount, coating amount and the like of the beads 4 and setting the three-dimensional surface arithmetic average roughness (Ra) of the bead coating layer 3 within the above range, the diffusibility of reflected light can be enhanced. .

  Similarly, the lower limit of the ten-point average roughness (Rz) in the three-dimensional surface roughness of the surface of the bead coating layer 3 is preferably 10 μm, more preferably 15 μm, and particularly preferably 50 μm. On the other hand, the upper limit of the ten-point average roughness (Rz) is preferably 80 μm, more preferably 70 μm, and particularly preferably 60 μm.

  The lower limit of the average thickness of the bead coating layer 3 is preferably 80%, particularly 85%, and more particularly 90% of the average particle diameter of the white beads 45. On the other hand, the upper limit of the average thickness of the bead coating layer 3 is preferably 300%, particularly 290%, more particularly 280% of the average particle diameter of the white beads 45. By setting the thickness of the bead coating layer 3 to this level, fine irregularities are conspicuously formed on the surface of the bead coating layer 3, and the light diffusion function can be effectively achieved.

  The lower limit of the average particle diameter of the white beads 4 is preferably 1 μm, particularly 2 μm, and more particularly 5 μm. On the other hand, the upper limit of the average particle diameter of the white beads 4 is preferably 50 μm, particularly 20 μm, and more particularly 15 μm. When the average particle diameter of the white beads 4 is less than the above range, the irregularities on the surface of the bead coating layer 3 formed by the white beads 4 become small, and the diffusibility of reflected light may be reduced. Conversely, if the average particle size of the white beads 4 exceeds the above range, the thickness of the back sheet 1 may increase.

  The lower limit of the coefficient of variation of the particle size distribution of the white beads 4 is preferably 30%, particularly 32%, more particularly 34%, and the upper limit of this coefficient of variation is preferably 40%, particularly 38%, more particularly 36%. This is because if the coefficient of variation of the white beads 4 exceeds the above upper limit, the white beads 4 buried inside that do not contribute to the formation of fine irregularities on the surface of the bead coating layer 3 will increase. If the variation coefficient of the white beads 4 is smaller than the above lower limit, the diffusibility of the reflected light does not increase so much, and if the particle diameter is random to some extent, it contributes to the optical function and the diffusive quality of the reflected light is improved. Because it becomes high.

  In addition, the variation coefficient of the average particle diameter and particle diameter distribution of the white beads 4 is a value measured by a Coulter counter method. The Coulter counter method is a method for electrically measuring the number and size of particles dispersed in a solution, in which particles are dispersed in an electrolyte solution and electricity flows using suction force. This is a method of measuring a voltage pulse in proportion to the volume of the particle by replacing the electrolyte by the volume of the particle when passing the particle through the pores, increasing the resistance. Therefore, the number and individual particle volume are measured by electrically measuring the height and number of the voltage pulses, and the particle size and particle size distribution are obtained from the measurement results. A coefficient of variation is determined.

  The blending amount of the white beads 4 (the blending amount in terms of solid content of the white beads 4 with respect to 100 parts by mass of the base polymer in the polymer composition that is the forming material of the white binder 5) is preferably 12 parts by mass or more, More preferably, it is 82 parts by mass or more, preferably 500 parts by mass or less, more preferably 300 parts by mass or less, and still more preferably 200 parts by mass or less. This is because, if the blending amount of the white beads 4 is less than the above range, the unevenness of the surface of the white bead coating layer 3 becomes small, and the diffusibility of the reflected light becomes insufficient. This is because if the amount exceeds the above range, the effect of fixing the white beads 4 decreases.

  The white beads 4 can be composed of a synthetic resin containing a white pigment. Examples of the synthetic resin include acrylic resin, acrylonitrile resin, polyurethane, polyvinyl chloride, polystyrene, polyacrylonitrile, polyamide, and the like.

  As the white pigment contained in the synthetic resin, titanium oxide (titanium white) is used in the present embodiment. The material of the white pigment is not particularly limited, and for example, zinc oxide (zinc white), lead carbonate (lead white), barium sulfate, calcium carbonate (chalk), or the like can be used. However, it is preferable to use titanium oxide from the viewpoint of increasing whiteness and solar reflectance.

  The average particle diameter of the white pigment is preferably from 100 nm to 30 μm, particularly preferably from 200 nm to 20 μm. If the average particle diameter of the white pigment is less than the above range, the whiteness and solar reflectance of the backsheet 1 may be too low. Conversely, the average particle diameter of the white pigment exceeds the above range. This is because it is difficult to control the particle diameter of the white beads 4.

  The content of the white pigment (concentration in the whole white beads 4) is preferably 15% by mass or more, more preferably 20% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass. It is as follows. If the white pigment content is less than the above range, the whiteness and solar reflectance may be too low. On the other hand, if the white pigment content exceeds the above range, the strength of the white beads 4 is insufficient. This is because it may be difficult to handle.

  The white binder 5 is formed by curing a polymer composition including a base polymer in which a white pigment is blended. The beads 4 are arranged and fixed on the surface of the base film 2 by the white binder 5 at substantially equal density. In the polymer composition for forming the white binder 5, in addition to the base polymer, for example, a fine inorganic filler, a curing agent, a plasticizer, a dispersant, various leveling agents, an ultraviolet absorber, and an antioxidant. , Viscosity modifiers, lubricants, light stabilizers and the like may be appropriately blended.

  The base polymer is not particularly limited, and examples thereof include acrylic resins, polyurethanes, polyesters, fluorine resins, silicone resins, polyamideimides, epoxy resins, ultraviolet curable resins, and the like. Can be used singly or in combination of two or more. In particular, the base polymer is preferably a polyol having excellent processability and the like.

  Examples of the polyol include a polyol obtained by polymerizing a monomer component containing a hydroxyl group-containing unsaturated monomer, a polyester polyol obtained under the condition of excess hydroxyl group, and the like alone or in combination of two or more. Can be used as a mixture.

  Examples of the hydroxyl group-containing unsaturated monomer include (a) 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, allyl alcohol, homoallyl alcohol, Keihi Hydroxyl group-containing unsaturated monomers such as alcohol and crotonyl alcohol, (b) for example ethylene glycol, ethylene oxide, propylene glycol, propylene oxide, butylene glycol, butylene oxide, 1,4-bis (hydroxymethyl) cyclohexane, phenylglycidyl Dihydric alcohols or epoxy compounds such as ether, glycidyl decanoate, Plaxel 14FM-1 (manufactured by Daicel 14 Chemical Industry Co., Ltd.) and, for example, acrylic acid, methacrylic acid, maleic acid, fumar Acid, crotonic acid, and the like hydroxyl group-containing unsaturated monomers obtained by reaction of an unsaturated carboxylic acid such as itaconic acid. One or more selected from these hydroxyl group-containing unsaturated monomers can be polymerized to produce a polyol.

  The above polyols are ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl acrylate, ethyl hexyl acrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, methacrylic acid. N-butyl acid, tert-butyl methacrylate, ethyl hexyl methacrylate, glycidyl methacrylate, cyclohexyl methacrylate, styrene, vinyl toluene, 1-methylstyrene, acrylic acid, methacrylic acid, acrylonitrile, vinyl acetate, vinyl propionate, stearic acid Vinyl, allyl acetate, diallyl adipate, diallyl itaconate, diethyl maleate, vinyl chloride, vinylidene chloride, acrylamide, N-methylolacrylamide, N-but One or more ethylenically unsaturated monomers selected from dimethyl acrylamide, diacetone acrylamide, ethylene, propylene, isoprene and the like, and hydroxyl group-containing unsaturated selected from the above (a) and (b) It can also be produced by polymerizing a monomer.

  The number average molecular weight of a polyol obtained by polymerizing a monomer component containing a hydroxyl group-containing unsaturated monomer is from 1,000 to 500,000, preferably from 5,000 to 100,000. The hydroxyl value is 5 or more and 300 or less, preferably 10 or more and 200 or less, more preferably 20 or more and 150 or less.

  The polyester polyol obtained under the condition of excess hydroxyl group is (c), for example, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl. Glycol, hexamethylene glycol, decamethylene glycol, 2,2,4-trimethyl-1,3-pentanediol, trimethylolpropane, hexanetriol, glycerin, pentaerythritol, cyclohexanediol, hydrogenated bisphenol A, bis (hydroxymethyl) Polyhydric alcohols such as cyclohexane, hydroquinone bis (hydroxyethyl ether), tris (hydroxyethyl) isosinurate, xylylene glycol, and (d) for example malee , Fumaric acid, succinic acid, adipic acid, sebacic acid, azelaic acid, trimetic acid, terephthalic acid, phthalic acid, isophthalic acid and other polybasic acids, and propanediol, hexanediol, polyethylene glycol, trimethylolpropane It can be produced by reacting under the condition that the number of hydroxyl groups in the monohydric alcohol is larger than the number of carboxyl groups of the polybasic acid.

  The number average molecular weight of the polyester polyol obtained under such an excessive hydroxyl group condition is 500 or more and 300,000 or less, and preferably 2000 or more and 100,000 or less. The hydroxyl value is 5 or more and 300 or less, preferably 10 or more and 200 or less, more preferably 20 or more and 150 or less.

  The polyol used as the base polymer of the polymer composition is obtained by polymerizing a monomer component containing the polyester polyol and the hydroxyl group-containing unsaturated monomer, and is a (meth) acryl unit or the like. An acrylic polyol having The white binder 5 having such a polyester polyol or acrylic polyol as a base polymer has high weather resistance. In addition, any one of this polyester polyol and acrylic polyol may be used, and both may be used.

  The number of hydroxyl groups in the polyester polyol and acrylic polyol is not particularly limited as long as it is 2 or more per molecule, but if the hydroxyl value in the solid content is 10 or less, the number of crosslinking points decreases, and the solvent resistance , Film properties such as water resistance, heat resistance and surface hardness tend to decrease.

  As the white pigment contained in the white binder 5, titanium oxide (titanium white) is used in the present embodiment. The material of the white pigment is not particularly limited, and for example, zinc oxide (zinc white), lead carbonate (lead white), barium sulfate, calcium carbonate (chalk), or the like can be used. However, it is preferable to use titanium oxide from the viewpoint of increasing whiteness and solar reflectance.

  The average particle diameter of the white pigment is preferably from 100 nm to 30 μm, particularly preferably from 200 nm to 20 μm. If the average particle diameter of the white pigment is less than the above range, the backsheet 1 may lack whiteness and solar reflectance, and conversely, if the average particle diameter of the white pigment exceeds the above range, This is because the reflectivity of the bead coating layer 3 may be uneven.

  The blending amount of the white pigment (the blending amount in terms of solid content of the white pigment with respect to 100 parts by weight of the base polymer in the polymer composition that is the forming material of the white binder 5) is preferably 100 parts by weight or more. Preferably it is 130 mass parts or more, and 200 mass parts or less are preferable, More preferably, it is 150 mass parts or less. This is because if the white pigment content is less than the above range, the whiteness and solar reflectance may be lowered. On the other hand, if the white pigment content exceeds the above range, the effect of fixing the white beads 4 is obtained. It is because it falls.

  A fine inorganic filler may be contained in the polymer composition forming the binder 5. By containing the fine inorganic filler in the binder 5, the heat resistance of the bead coating layer 3 and thus the back sheet 1 is improved. The inorganic material constituting the fine inorganic filler is not particularly limited, and an inorganic oxide is preferable. This inorganic oxide is defined as various oxygen-containing metal compounds in which a metal element mainly forms a three-dimensional network through bonds with oxygen atoms. In addition, as the metal element constituting the inorganic oxide, for example, an element selected from Groups 2 to 6 of the Periodic Table of Elements is preferable, and an element selected from Groups 3 to 5 of the Periodic Table of Elements is more preferable. In particular, an element selected from Si, Al, Ti, and Zr is preferable, and colloidal silica in which the metal element is Si is most preferable as a fine inorganic filler in terms of heat resistance improvement effect and uniform dispersibility. The shape of the fine inorganic filler may be any particle shape such as a spherical shape, a needle shape, a plate shape, a scale shape, and a crushed shape, and is not particularly limited.

  The lower limit of the average particle size of the fine inorganic filler is preferably 5 nm, and particularly preferably 10 nm. On the other hand, the upper limit of the average particle size of the fine inorganic filler is preferably 50 nm, particularly preferably 25 nm. This is because when the average particle size of the fine inorganic filler is less than the above range, the surface energy of the fine inorganic filler becomes high and aggregation or the like is likely to occur.

  As a minimum of the compounding quantity (compounding quantity of only an inorganic ingredient) with respect to 100 mass parts of base polymer of a fine inorganic filler, 5 mass parts are preferred in terms of solid content, and 50 mass parts is especially preferred. On the other hand, the upper limit of the amount of the fine inorganic filler is preferably 500 parts by mass, more preferably 200 parts by mass, and particularly preferably 100 parts by mass. This is because if the blending amount of the fine inorganic filler is less than the above range, the heat resistance of the bead coating layer 3 may not be sufficiently expressed. Conversely, the blending amount is within the above range. This is because if it exceeds, blending into the polymer composition may be difficult.

  As the fine inorganic filler, one having an organic polymer fixed on its surface may be used. Thus, by using the organic polymer-fixed fine inorganic filler, the dispersibility in the binder 5 and the affinity with the binder 5 can be improved. The organic polymer is not particularly limited with respect to its molecular weight, shape, composition, presence or absence of a functional group, and any organic polymer can be used. Moreover, about the shape of an organic polymer, the thing of arbitrary shapes, such as a linear form, a branched form, and a crosslinked structure, can be used.

  Specific resins constituting the organic polymer include, for example, (meth) acrylic resins, polystyrene, polyvinyl acetate, polyolefins such as polyethylene and polypropylene, polyesters such as polyvinyl chloride, polyvinylidene chloride, polyethylene terephthalate, and the like. Examples thereof include a resin partially modified with a functional group such as a copolymer, an amino group, an epoxy group, a hydroxyl group, or a carboxyl group. Among them, those having an organic polymer containing a (meth) acryl unit such as a (meth) acrylic resin, a (meth) acrylic-styrene resin, and a (meth) acrylic-polyester resin have a film forming ability. Is preferred. On the other hand, a resin having compatibility with the base polymer of the polymer composition is preferred, and therefore, the resin having the same composition as the base polymer contained in the polymer composition is most preferred.

  The fine inorganic filler may contain an organic polymer in the fine particles. As a result, moderate softness and toughness can be imparted to the inorganic material that is the core of the fine inorganic filler.

  As the organic polymer, one containing an alkoxy group may be used, and the content is preferably 0.01 mmol or more and 50 mmol or less per 1 g of the fine inorganic filler on which the organic polymer is fixed. Such an alkoxy group can improve the affinity with the matrix resin constituting the binder 5 and the dispersibility in the binder 5.

  The alkoxy group represents an RO group bonded to a metal element that forms a fine particle skeleton. R is an alkyl group which may be substituted, and the RO groups in the fine particles may be the same or different. Specific examples of R include methyl, ethyl, n-propyl, isopropyl, n-butyl and the like. It is preferable to use the same metal alkoxy group as the metal constituting the fine inorganic filler. When the fine inorganic filler is colloidal silica, it is preferable to use an alkoxy group having silicon as a metal.

  The content of the organic polymer in the fine inorganic filler to which the organic polymer is fixed is not particularly limited, but is preferably 0.5% by mass or more and 50% by mass or less based on the fine inorganic filler.

  A polyfunctional isocyanate compound, melamine compound and amino having at least two functional groups capable of reacting with a hydroxyl group in the polymer composition constituting the binder 5 are used as the organic polymer fixed to the fine inorganic filler. It is good to contain the at least 1 sort (s) chosen from plast resin. Thereby, the fine inorganic filler and the matrix resin of the binder 5 are bonded in a crosslinked structure, and the storage stability, stain resistance, flexibility, weather resistance, storage stability, etc. are improved, and the resulting coating film is further obtained. It becomes glossy.

  Examples of the polyfunctional isocyanate compound include aliphatic, alicyclic, aromatic and other polyfunctional isocyanate compounds and modified compounds thereof. Specific examples of this polyfunctional isocyanate compound include, for example, tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, lysine diisocyanate, 2,2,4-trimethylhexylmethane diisocyanate, methylcyclohexane diisocyanate, 1, Trimers such as biuret and isocyanurate of 6-hexamethylene diisocyanate; produced by reaction of these polyfunctional isocyanates with polyhydric alcohols such as propanediol, hexanediol, polyethylene glycol and trimethylolpropane Compounds in which two or more isocyanate groups remain; these polyfunctional isocyanate compounds are ethanol, hexanol, etc. Blocked polyfunctional isocyanate compounds blocked with blocking agents such as alcohols, compounds having a phenolic hydroxyl group such as phenol and cresol, oximes such as acetooxime and methylethylketoxime, and lactams such as ε-caprolactam and γ-caprolactam Can be mentioned. In addition, the said polyfunctional isocyanate compound can be used 1 type or in mixture of 2 or more types. Among these, a non-yellowing polyfunctional isocyanate compound having no isocyanate group directly bonded to an aromatic ring is preferable.

  Examples of the melamine compound include dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, hexamethylol melamine, isobutyl ether type melamine, n-butyl ether type melamine, butylated benzoguanamine and the like.

  Examples of the aminoplast resin include alkyl etherified melamine resins, urea resins, and benzoguanamine resins. These aminoplast resins can be used alone or as a mixture or cocondensate of two or more. The alkyl etherified melamine resin is obtained by methylolating aminotriazine and alkyl etherifying with cyclohexanol or alkanol having 1 to 6 carbon atoms. The butyl etherified melamine resin, methyl etherified melamine resin, methylbutyl mixed melamine Resin is representative. In addition, a sulfonic acid-based catalyst for promoting curing, such as paratoluenesulfonic acid and its amine salt, can be used.

  The base polymer is preferably a polyol having a cycloalkyl group. Thus, by introducing a cycloalkyl group into the polyol as the base polymer constituting the binder 5, the hydrophobicity of the binder 5 such as water repellency and water resistance becomes high, and beads under high temperature and high humidity conditions. The coating layer 3 and thus the back sheet 1 has improved bending resistance, dimensional stability, and the like. Further, the basic properties of the coating film such as weather resistance, hardness, feeling of holding, and solvent resistance of the bead coating layer 3 are improved. Furthermore, the affinity with the fine inorganic filler having the organic polymer fixed on the surface and the uniform dispersibility of the fine inorganic filler are further improved.

  The cycloalkyl group is not particularly limited, and examples thereof include a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, a cycloundecyl group, a cyclododecyl group, a cyclotridecyl group, Examples thereof include a cyclotetradecyl group, a cyclopentadecyl group, a cyclohexadecyl group, a cycloheptadecyl group, and a cyclooctadecyl group.

  The polyol having a cycloalkyl group can be obtained by copolymerizing a polymerizable unsaturated monomer having a cycloalkyl group. The polymerizable unsaturated monomer having a cycloalkyl group is a polymerizable unsaturated monomer having at least one cycloalkyl group in the molecule. The polymerizable unsaturated monomer is not particularly limited, and examples thereof include cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, and cyclododecyl (meth) acrylate.

  Moreover, it is good to contain isocyanate as a hardening | curing agent in a polymer composition. Thus, by containing an isocyanate hardening | curing agent in a polymer composition, it becomes a much stronger crosslinked structure and the film physical property of the bead coating layer 3 further improves. As this isocyanate, the same substance as the polyfunctional isocyanate compound is used. Of these, aliphatic isocyanates that prevent yellowing of the coating are preferred.

  In particular, when a polyol is used as the base polymer, one or more of hexamethylene diisocyanate, isofurone diisocyanate and xylene diisocyanate may be mixed and used as a curing agent to be blended in the polymer composition. When these curing agents are used, the curing reaction rate of the polymer composition is increased. Therefore, even if a cationic agent that contributes to the dispersion stability of the fine inorganic filler is used as the antistatic agent, the cationic antistatic agent is used. Can sufficiently compensate for a decrease in the curing reaction rate. Further, the improvement in the curing reaction rate of the polymer composition contributes to the uniform dispersibility of the fine inorganic filler in the binder 5. As a result, bending of the bead coating layer 3 due to heat, ultraviolet rays or the like can be remarkably suppressed.

  In the solar cell module 11 of FIG. 2, the translucent substrate 12, the filler layer 13, the plurality of solar cells 14, the filler layer 15, and the solar cell module backsheet 1 are from the surface side. They are stacked in this order.

  The translucent substrate 12 is laminated on the outermost surface, and has (a) transparency to sunlight and electrical insulation, (b) mechanical, chemical and physical strength, specifically Has excellent weather resistance, heat resistance, durability, water resistance, gas barrier properties against water vapor, wind pressure resistance, chemical resistance, fastness, (c) high surface hardness, and accumulation of dirt, dust, etc. on the surface It is required to have excellent antifouling properties.

  As a material for forming the translucent substrate 12, glass and synthetic resin are used. Examples of the synthetic resin used for the translucent substrate 12 include polyethylene resin, polypropylene resin, cyclic polyolefin resin, fluorine resin, polystyrene resin, acrylonitrile-styrene copolymer (AS resin), and acrylonitrile rubber. Butadiene-styrene copolymer (ABS resin), polyvinyl chloride resin, fluorine resin, poly (meth) acrylic resin, polycarbonate resin, polyester resin such as polyethylene terephthalate, polyethylene naphthalate, various nylons, etc. Polyamide resin, polyimide resin, polyamideimide resin, polyaryl phthalate resin, silicone resin, polyphenylene sulfide resin, polysulfone resin, acetal resin, polyethersulfone resin, polyurethane resin Fat, and cellulosic resins. Among these resins, fluorine resins, cyclic polyolefin resins, polycarbonate resins, poly (meth) acrylic resins, or polyester resins are particularly preferable.

  In the case of the translucent substrate 12 made of a synthetic resin, (a) transparent deposition of an inorganic oxide such as silicon oxide or aluminum oxide on one surface by the PVD method or the CVD method for the purpose of improving gas barrier properties and the like. (B) For the purpose of improving and modifying processability, heat resistance, weather resistance, mechanical properties, dimensional stability, etc., for example, lubricants, crosslinking agents, antioxidants, ultraviolet absorbers, charging It is also possible to contain various additives such as an inhibitor, a light stabilizer, a filler, a reinforcing fiber, a reinforcing agent, a flame retardant, a flame retardant, a foaming agent, a fungicide, and a pigment.

  The thickness (average thickness) of the translucent substrate 12 is not particularly limited, and is appropriately selected depending on the material to be used so as to have required strength, gas barrier properties, and the like. The thickness of the synthetic resin translucent substrate 12 is preferably 6 μm or more and 300 μm or less, and particularly preferably 9 μm or more and 150 μm or less. The thickness of the glass translucent substrate 12 is generally about 3 mm.

  The filler layer 13 and the filler layer 15 are filled around the solar cells 14 between the translucent substrate 12 and the solar cell module backsheet 1, and the translucent substrate 12 and the solar cell module back. It has adhesiveness with the sheet 1, scratch resistance for protecting the solar battery cell 14, shock absorption, and the like. Furthermore, the filler layer 13 and the filler layer 15 have transparency to transmit sunlight in addition to the above functions.

  Examples of the material for forming the filler layer 13 and the filler layer 15 include a fluorine resin, an ethylene-vinyl acetate copolymer, an ionomer resin, an ethylene-acrylic acid or methacrylic acid copolymer, a polyethylene resin, a polypropylene resin, and polyethylene. Examples thereof include acid-modified polyolene fin-based resins, polyvinyl butyral resins, silicone-based resins, epoxy-based resins, (meth) acrylic resins, and the like obtained by modifying the above polyolefin-based resins with unsaturated carboxylic acids such as acrylic acid. Among these synthetic resins, fluorine resins, silicone resins, or ethylene-vinyl acetate resins that are excellent in weather resistance, heat resistance, gas barrier properties, and the like are preferable.

  Moreover, as a forming material of the filler layer 13 and the filler layer 15, the thermoreversible crosslinkable olefin polymer composition shown by Unexamined-Japanese-Patent No. 2000-34376, specifically, (a) Unsaturated carboxylic acid anhydride Modified olefin polymer modified with an unsaturated carboxylic acid ester, the average number of bonds of carboxylic anhydride groups per molecule is one or more, and the carboxylic acid in the modified olefin polymer A modified olefin polymer in which the ratio of the number of carboxylic acid ester groups to the number of anhydride groups is 0.5 to 20, and (b) a hydroxyl group-containing polymer having an average number of hydroxyl groups per molecule of 1 or more, Those having a ratio of the number of hydroxyl groups of component (b) to the number of carboxylic anhydride groups of component (a) of 0.1 to 5 are also used.

  The forming material of the filler layer 13 and the filler layer 15 is, for example, a crosslinking agent, a thermal antioxidant, a light stabilizer, an ultraviolet absorber, a photo-oxidant for the purpose of improving weather resistance, heat resistance, gas barrier properties, and the like. Various additives such as an inhibitor can be appropriately contained. Further, the thickness (average thickness) of the filler layer 13 and the filler layer 15 is not particularly limited, but is preferably 200 μm or more and 1000 μm or less, and particularly preferably 350 μm or more and 600 μm or less.

The solar battery cell 14 is a photovoltaic element that converts light energy into electrical energy, and is disposed between the filler layer 13 and the filler layer 15. The plurality of solar cells 14 are laid in substantially the same plane and slightly apart from each other, and are wired in series or in parallel, although not shown. Examples of the solar battery cell 14 include a crystalline silicon solar electronic element such as a single crystal silicon type solar cell element and a polycrystalline silicon type solar cell element, an amorphous silicon solar cell element composed of a single junction type or a tandem structure type, and gallium arsenide. Group 3 to 5 compound semiconductor solar electronic devices such as (GaAs) and indium phosphorus (InP), and Group 2 to 6 compound semiconductor solar electronic devices such as cadmium tellurium (CdTe) and copper indium selenide (CuInSe ₂ ) Etc., and those hybrid elements can also be used. In addition, the filler layer 13 or the filler layer 15 is filled between the plurality of solar battery cells 14 without any gap.

  Although it does not specifically limit as a manufacturing method of the said solar cell module 11, Generally, (1) The translucent board | substrate 12, the filler layer 13, the several photovoltaic cell 14, the filler layer 15 And a step of laminating the solar cell module backsheet 1 in this order, and (2) a laminating step of integrally forming them by a vacuum heating lamination method or the like in which they are integrated by vacuum suction and thermocompression bonded. In the manufacturing method of the solar cell module 11, for the purpose of adhesiveness between the respective layers, (a) applying a heat-melt adhesive, solvent-type adhesive, photo-curing adhesive, etc., (b) each lamination The opposing surface can be subjected to corona discharge treatment, ozone treatment, low temperature plasma treatment, glow discharge treatment, oxidation treatment, primer coating treatment, undercoat treatment, anchor coating treatment, and the like.

  In the solar cell module 11 configured as described above, light that has passed between the solar cells 14 and entered the back sheet 1 is diffusely reflected by the bead coating layer 3 having the white beads 4 and the white binder 5. . Then, the reflected light again passes between the solar cells 14, and the light incident on the translucent substrate 12 is reflected on the back surface of the translucent substrate 12 to be incident on the solar cells 14. The For this reason, since the backsheet 1 can effectively recurs the light transmitted between the solar cells 14 to the solar cells 14, the photoelectric conversion efficiency of the solar cell module 11 is increased and the power generation efficiency is increased. be able to. Further, since the backsheet 1 does not require a metal vapor deposition layer for reflection, for example, even if the filler layer 13 is made of an ethylene vinyl acetate copolymer, it is corroded by the gas generated from the charging material layer 13 or the like. It is excellent in durability and has excellent manufacturability and low cost because metal deposition is not required.

  Thereby, the said solar cell module 11 can be used conveniently for the roof stationary type solar cell, the solar cell for small electrical devices, such as a wristwatch and a calculator.

  In addition, the solar cell module backsheet 1 and the solar cell module 11 of the present invention are not limited to the above embodiment. Specifically, for example, as shown in FIG. 3, it is possible to employ a configuration in which the base sheet 2 has a gas barrier layer. The substrate sheet 2 shown in FIG. 3 includes a pair of substrate films 8 and a gas barrier layer 9 laminated between the pair of substrate films 8. The gas barrier layer 9 is not particularly limited as long as it has gas barrier properties. For example, a metal foil, a vapor deposition layer, or the like is used. As a material constituting the vapor deposition layer, a metal such as aluminum, or an inorganic compound such as aluminum oxide, silicon oxide, or titanium oxide is used. By providing the gas barrier layer 9 in this way, the gas barrier property can be improved.

  It is also possible to adopt an inorganic material as the white beads 4. Examples of the inorganic material include titanium oxide, silica, aluminum hydroxide, aluminum oxide, zinc oxide, barium sulfide, magnesium silicate, or a mixture thereof.

  Furthermore, the base material sheet 2 or the bead coating layer 3 (white beads 4 or / and white binder 5) can contain an ultraviolet absorber. Thus, the weather resistance and durability of the said solar cell module backsheet 1 can be improved by containing a ultraviolet absorber. The ultraviolet absorber is not particularly limited as long as it is a compound that absorbs ultraviolet rays and can be efficiently converted into heat energy, and is stable to light, and a known one can be used. . Among them, salicylic acid-based UV absorbers, benzophenone-based UV absorbers, benzotriazole-based UV absorbers, and cyano have a high UV-absorbing function, good compatibility with the above-mentioned base polymer, and exist stably in the base polymer. An acrylate ultraviolet absorber is preferable, and one or more selected from these groups may be used. Further, as the ultraviolet absorber, a polymer having an ultraviolet absorbing group in a molecular chain (for example, “Udable UV” series of Nippon Shokubai Co., Ltd.) is also preferably used. By using a polymer having an ultraviolet absorbing group in such a molecular chain, the compatibility with the polymer constituting the base film 2 and the like is high, and deterioration of the ultraviolet absorbing function due to bleeding out of the ultraviolet absorber can be prevented. .

  The lower limit of the content of the ultraviolet absorber (the content of the ultraviolet absorber relative to the whole substrate sheet 2 or bead coating layer 3 (white beads 4 and / or white binder 5) containing the ultraviolet absorber) is 0. 0.1% by mass, particularly 1% by mass, more preferably 3% by mass, and the upper limit of the content of the ultraviolet absorber is preferably 10% by mass, particularly 8% by mass, more preferably 5% by mass. If the blending amount of the UV absorber is smaller than the lower limit, the UV absorbing function of the solar cell module backsheet 1 may not be effectively achieved. Conversely, the content of the UV absorber exceeds the upper limit. If it exceeds, the matrix polymer will be adversely affected, and the strength, durability, etc. of the substrate sheet 2 may be lowered.

  Further, the base sheet 2 or the bead coating layer 3 (white beads 4 or / and white binder 5) can contain an ultraviolet stabilizer or a polymer having an ultraviolet stabilizing group bonded to a molecular chain. By this ultraviolet stabilizer or ultraviolet stabilizer, radicals generated by ultraviolet rays, active oxygen, and the like are inactivated, and the ultraviolet stability, weather resistance, and the like of the solar cell module backsheet 1 can be improved. As the UV stabilizer or UV stabilizer, a hindered amine UV stabilizer or a hindered amine UV stabilizer having high stability to UV is preferably used.

  Furthermore, it is good to contain an antistatic agent in the base material sheet 2 or the bead coating layer 3 (white bead 4 or / and white binder 5). By containing the antistatic agent in this manner, the backsheet 1 exhibits an antistatic effect, and as a result, it is attracted by static electricity such as sucking up dust and making it difficult to overlap with the solar battery cell 14 or the like. The inconvenience which generate | occur | produces can be prevented. Further, when the antistatic agent is coated on the surface, the surface becomes sticky or contaminated. However, such an adverse effect is reduced by containing the antistatic agent in the base sheet 2 or the like. The antistatic agent is not particularly limited. For example, anionic antistatic agents such as alkyl sulfates and alkyl phosphates, cationic antistatic agents such as quaternary ammonium salts and imidazoline compounds, polyethylene glycol type Nonionic antistatic agents such as polyoxyethylene sorbitan monostearic acid ester and ethanolamides, and high molecular antistatic agents such as polyacrylic acid are used. Among these, a cationic antistatic agent having a relatively large antistatic effect is preferable, and an antistatic effect is exhibited by addition of a small amount.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

[Example 1]
As the white beads, the product name Love Color 010 (X) White (manufactured by Dainichi Seika Kogyo Co., Ltd.) is used. ) Was used. A white bead was included in the white binder polymer composition to form a coating solution. The blending amount of white beads in terms of solid content with respect to 100 parts by mass of the base polymer in the polymer composition was 100 parts by mass. This coating solution was applied to a base sheet made of polyethylene terephthalate and dried to form a bead coating layer. The arithmetic average roughness (Ra) and ten-point average roughness (Rz) in the three-dimensional surface roughness were measured at several places on the surface of the bead coating layer. As a result of this measurement, the arithmetic average roughness (Ra) is in the range of 5.7 to 7.2 μm, the average is 6.5 μm, and the ten-point average roughness (Rz) is in the range of 18.2 to 26.6 μm. The average was 22.4 μm.

[Examples 2 to 6]
Example 2 is the same as Example 1 except that the amount of the white beads in terms of solid content in Example 1 is 200 parts by mass, 82 parts by mass, 63 parts by mass, 38 parts by mass, and 12 parts by mass. 3, 4, 5 and 6 backsheets were obtained.

[Comparative Example 1]
As in Patent Document 1, a back sheet was prepared in which a spherical particle-containing transparent layer including spherical particles made of a transparent resin, a white polyethylene terephthalate layer, and a silicon oxide vapor deposition layer were laminated in this order from the surface side. The spherical particle-containing transparent layer was formed by dispersing acrylic beads (spherical particles) in a polymer composition containing cellulose, coating the white polyethylene terephthalate layer, and drying.

[Comparative Example 2]
Like patent document 2, the base sheet, the bead coating layer, the metal vapor deposition layer, the contact bonding layer, and the base sheet produced the back sheet laminated | stacked in this order from the surface side. A transparent resin sheet made of polyethylene terephthalate was used as the base sheet, acrylic beads were dispersed in a polymer composition made of acrylic polyol, applied to the base sheet, and dried to form a bead coating layer. The metal vapor deposition layer was formed by metal vapor-depositing aluminum on the bead coating layer.

[Comparative Example 3]
A back sheet of Comparative Example 3 was obtained in the same manner as in Example 1 except that transparent acrylic beads were used instead of the white beads in Example 1.

[Comparative Example 4]
A back sheet of Comparative Example 4 was obtained in the same manner as in Example 1 except that a transparent acrylic resin binder was used instead of the white binder in Example 1.

[Comparative Example 5]
A back sheet of Comparative Example 5 was obtained in the same manner as in Example 1 except that the beads of Comparative Example 3 and the binder of Comparative Example 4 were used in place of the white beads and white binder in Example 1.

[Comparative Example 6]
A backsheet of Comparative Example 6 was obtained in the same manner as in Example 1 except that the white binder not containing the white beads in Example 1 was used.

[Comparative Example 7]
The back sheet of Comparative Example 7 was composed of a sheet made of white polyethylene terephthalate.

<Evaluation 1>
About the manufactured back sheet | seat, the solar radiation reflectance of Example 1 and Comparative Examples 1 and 2 was evaluated. The evaluation results are shown in Table 1 below. Moreover, about the solar cell module using this back sheet, the short circuit current, the open circuit voltage, the fill factor, and the photoelectric conversion efficiency were evaluated. The evaluation results are shown in Table 2 below.

ここで、ＦＦは曲線因子であり、Ｐｍａｘは最大出力電力であり、Ｉｓｃは短絡電流であり、Ｖｏｃは開放電圧である。 In addition, the said solar reflectance is a reflectance described in JIS-R3106-1985. Moreover, a short circuit current is an electric current which flows when a positive electrode and a negative electrode are short-circuited in the state which is irradiating light to a solar cell module. The open circuit voltage is a potential difference between the two electrodes when the positive electrode and the negative electrode are insulated when the solar cell module is irradiated with light. The fill factor is a numerical value obtained by the following equation based on the short-circuit current, the open-circuit voltage, and the maximum output power, and ideally becomes 1. Note that the maximum output power is the power at which the maximum output power is obtained when the solar cell module is irradiated with light.

Here, FF is a fill factor, Pmax is the maximum output power, Isc is a short circuit current, and Voc is an open circuit voltage.

<Discussion 1>
As shown in Table 1 above, the back sheet of Example 1 was higher in solar reflectance than the back sheets of Comparative Examples 1 and 2. Further, as shown in Table 2, the back sheet of Example 1 had a curve factor close to 1 and higher photoelectric conversion efficiency than the back sheets of Comparative Examples 1 and 2.

<Evaluation 2>
About the manufactured back sheet | seat, the solar radiation reflectance of Example 1 and Comparative Examples 3-5 was evaluated. The evaluation results are shown in Table 3 below.

<Discussion 2>
As shown in Table 3 above, the back sheet of Example 1 was higher in solar reflectance than the back sheets of Comparative Examples 3-5.

<Evaluation 3>
About the solar cell module using the manufactured said back sheet, the photoelectric conversion efficiency of Examples 1-6 and Comparative Examples 6 and 7 was evaluated. The evaluation results are shown in Table 4 below.

<Discussion 3>
As shown in Table 4 above, the back sheets of Examples 1 to 6 were higher in photoelectric conversion efficiency than the back sheets of Comparative Examples 6 and 7. In particular, higher photoelectric conversion efficiencies were obtained in the backsheets of Examples 1 to 3 in which the amount of white beads in terms of solid content was 82 parts by mass or more.

<Evaluation 4>
In order to compare Example 1 and Comparative Example 7 about the solar cell module using the manufactured back sheet, the following experiment was performed and the following evaluation items were evaluated.

  The surface of the solar cell module was masked in a partially opened state, and 960 mW light was applied to the mask to measure each evaluation item. The evaluation results are shown in Table 5 below. Here, a part of the opening of the mask has a square shape with a side of 31 mm matched to the region of the solar battery cell (a square shape with a side of 31 mm), a square shape with a side of 36 mm including the entire region of the solar battery cell, and a solar battery. A square shape with a side of 41 mm including the entire cell region was formed. As evaluation items, short-circuit current, open-circuit voltage, maximum output power, maximum output voltage, maximum output current, curve factor, series resistance, parallel resistance, photoelectric conversion efficiency, and photoelectric conversion efficiency increase rate were used.

  The short-circuit current, open-circuit voltage, maximum output power, fill factor, and photoelectric conversion efficiency are the same as described above. The maximum output voltage and the maximum output current are the voltage and current at the maximum output power. The series resistance and the parallel resistance mean the series resistance Rs and the parallel resistance Rsh in the solar cell equivalent circuit shown in FIG. The rate of increase in photoelectric conversion efficiency means the ratio of the photoelectric conversion efficiency in the case where one side of the opening is 36 mm and in the case of 41 mm with respect to the photoelectric conversion efficiency when one side of the square opening is 31 mm. To do.

<Discussion 4>
As shown in Table 5 above, the back sheet of Example 1 had higher photoelectric conversion efficiency than the back sheet of Comparative Example 7. Moreover, the back sheet of Example 1 has a higher rate of increase in photoelectric conversion efficiency than the back sheet of Comparative Example 7, and light that has passed through the solar cells and entered the back sheet is recursed to the solar cells. Therefore, it can be used effectively for power generation.

  As described above, the solar cell module backsheet of the present invention and the solar cell module using the backsheet are useful as a component of the solar cell, and are particularly popular in today's residential rooftop solar cells and calculators. It is suitably used for solar cells for small electric devices.

1 Back sheet for solar cell module 2 Base material sheet 3 Bead coating layer (reflection layer)
4 Bead 5 Binder 8 Base film 9 Gas barrier layer 11 Solar cell module 12 Translucent substrate 13 Filler layer 14 Solar cell 15 Filler layer

Claims (11)

A base sheet and a reflective layer laminated on the surface side of the base sheet;
The solar cell module backsheet, wherein the reflective layer has white beads and a white binder thereof.   The solar cell module backsheet according to claim 1, wherein the solar reflectance of the surface is 80.5% or more.   The solar cell module backsheet according to claim 1 or 2, wherein the surface whiteness is 80% or more.   The back sheet for solar cell module according to claim 1, wherein the white binder contains titanium dioxide.   The back sheet for a solar cell module according to any one of claims 1 to 4, wherein the white beads contain titanium dioxide.   The solar cell module according to any one of claims 1 to 5, wherein the reflective layer is formed by coating a coating composition containing white beads on a polymer composition that is a white binder forming material. Back sheet.   7. The solar cell module according to claim 6, wherein a blending amount of white beads in terms of solid content with respect to 100 parts by mass of the base polymer in the polymer composition which is a forming material of the white binder is 12 parts by mass or more and 500 parts by mass or less. Back sheet.   The arithmetic average roughness in the three-dimensional surface roughness of the surface of the reflective layer is 3 μm or more and 14 μm or less, and the ten-point average roughness is 10 μm or more and 80 μm or less. Back sheet for solar cell module.   The solar cell module backsheet according to any one of claims 1 to 8, wherein an average thickness of the reflective layer is 80% or more and 300% or less of an average particle diameter of the white beads.   The back sheet for a solar cell module according to any one of claims 1 to 9, wherein the base sheet has a gas barrier layer. A translucent substrate, a filler layer, a solar battery cell as a photovoltaic element, a filler layer, and the solar cell module backsheet according to any one of claims 1 to 10. A solar cell module stacked in this order from the surface side.

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