Patent Application
20120012165
The present invention relates to a protective sheet for a solar battery module, a solar battery module equipped with the same, and a method for producing a solar battery module.
This application claims priority on Japanese Patent Application No. 2009-082018 filed on Mar. 30, 2009, the disclosure of which is incorporated by reference herein
A solar battery module, which is a device capable of converting solar light energy into electric energy, has attracted special interest as a system capable of generating electricity without emitting carbon dioxide. It is necessary that the solar battery module have high generating efficiency and have durability that enables long-term use even when used outdoors.
The solar battery module is mainly constituted of solar battery cells as photovoltaic elements, an encapsulant including solar battery cells therein in a sealed state, and a protective sheet. A front protective sheet and a back protective sheet are adhered on the light receiving surface side (front side) of the solar battery module and the back side thereof, thereby preventing steam from penetrating into the solar battery module. It is required for such a protective sheet for a solar battery module to have excellent steam barrier properties and weatherability, and to have excellent adhesion with an encapsulant of the solar battery module.
Heretofore, there have been proposed, as methods for improving steam barrier properties, weatherability, adhesion to an encapsulant of a protective sheet for a solar battery module, for example, technologies disclosed in Patent Literatures 1 to 3.
Patent Literature 1 discloses a protective layer for a solar battery module having a laminate structure of an ultraviolet-shielding film made of a transparent weatherable resin, and a film made of an amorphous cyclic olefin copolymer having a glass transition temperature of 80° C. or higher, laminated on the inside surface of the film. Patent Literature 2 discloses a surface protective sheet using a cyclic olefin copolymer, and a surface protective sheet in which a resin film such as a PET film is laminated on the inside surface of a cyclic olefin copolymer film through an adhesive layer.
Patent Literature 3 discloses a protective sheet for a solar battery module including a layer made of a cyclic olefin copolymer formed on both surfaces of a layer made of an ethylene-vinyl acetate copolymer.
Conventional protective sheets disclosed in Patent Literatures 1 to 3 have a problem in that, in the step of tightly adhering a protective sheet to an encapsulant by lamination, ambient air remains as bubbles between the encapsulant and the protective sheet as a result of air entrainment. When the air remains, the encapsulant gradually peels away from the protective sheet and thus the function of the entire solar battery module may sometimes deteriorate.
Under the above circumstances, the present invention has been made, and an object of the present invention is to provide a protective sheet for a solar battery module which can prevent bubbles remaining and enable use over a long period of time.
In order to achieve the above object, the present invention provides a protective sheet for a solar battery module, including a base material sheet and a heat-fusible sheet made of a heat-fusible resin having a melting point measured by differential scanning calorimetry (a DSC method) of 80° C. or higher and lower than 130° C., laminated on one surface of the base material sheet, and including an air-flow path on a surface of the heat-fusible sheet.
In the protective sheet for a solar battery module of the present invention, it is preferred that the heat-fusible sheet contains an ethylene vinyl acetate copolymer (EVA) and the content of vinyl acetate (VA) in the heat-fusible sheet is 20% by mass or less.
In the protective sheet for a solar battery module of the present invention, a fluorine-containing resin layer may be further laminated on a surface opposite to the surface, on which the heat-fusible sheet is laminated, of the base material sheet.
In the protective sheet for a solar battery module of the present invention, the base material sheet may be a resin sheet.
The present invention also provides a solar battery module in which the protective sheet for a solar battery module according to the present invention is adhered on either or both of the front side and the back side.
The present invention further provides a method for producing a solar battery module, which includes the step of laminating the protective sheet for a solar battery module according to the present invention on a surface of an encapsulant including a solar battery cell therein, using a vacuum thermocompression bonding method.
In the present invention, since the protective sheet for a solar battery module includes a base material sheet and a heat-fusible sheet made of a heat-fusible resin having a melting point measured by differential scanning calorimetry (a DSC method) of 80° C. or higher and lower than 130° C., laminated on one surface of the base material sheet, and includes an air-flow path on a surface of the heat-fusible sheet, it is possible to provide a protective sheet for a solar battery module which can prevent bubbles remaining between the encapsulant and the protective sheet and enable use over a long period of time; and a solar battery module.
Embodiments of a protective sheet for a solar battery module of the present invention will be described below.
This mode is specifically described for more satisfactory understanding of the sprit of the invention and is in no way to be construed as limiting of the present invention unless otherwise specified.
Protective sheets for a solar battery module 10A, 20A of the first embodiment shown in
In the protective sheets for a solar battery module 10A, 20A of the present invention, the heat-fusible sheet 22 is made of a heat-fusible resin whose melting point measured by a DSC method is 80° C. or higher and lower than 130° C., and the heat-fusible sheet 22 includes an air-flow path 22a on the surface. When the heat-fusible sheet 22, the melting point of which, measured by a DSC method, is 80° C. or higher and lower than 130° C. is melted during thermocompression bonding, the air-flow path 22a formed on the surface of the heat-fusible sheet 22 after thermocompression bonding disappears and bubbles satisfactorily decrease, and thus adhesion can be improved.
The heat-fusible resin is preferably a resin containing an ethylene vinyl acetate copolymer (EVA), polyethylene, an ethylene-methacrylic acid copolymer (EMMA), an ethylene-acrylic acid copolymer (EMAA), an ethylene-glycidyl methacrylate copolymer (EGMA) and the like, and more preferably a resin containing EVA. Commonly, an encapsulant 30 constituting the solar battery module is often a resin composed of EVA. In that case, when the heat-fusible sheet 22 is made of a resin containing EVA, it is possible to improve compatibility and adhesion between the encapsulant 30 and the heat-fusible sheet 22.
When the heat-fusible sheet 22 contains EVA, the content of vinyl acetate (VA) in the heat-fusible sheet 22 is preferably 20% by mass or less, and more preferably 10% by mass or less.
As the encapsulant 30 constituting the solar battery module, an encapsulating resin composed of EVA is mainly used. The content of VA in the encapsulant is commonly from 25 to 40% by mass, and a melting point measured by a DSC method is often from 40 to 75° C. In an EVA-containing resin, as the content of VA in the resin increases, heat resistance deteriorates.
Accordingly, by decreasing the content of VA in the heat-fusible sheet 22 in the present invention when compared with the content of VA in a common encapsulant 30, a melting point of the heat-fusible sheet 22 is set at a temperature higher than a melting point of the common encapsulant 30. Therefore, in case the temperature is gradually raised using a laminate and a protective sheet for a solar battery module is laminated on the encapsulant 30, the encapsulant 30 is melted first and, after further raising the temperature, the heat-fusible sheet 22 is melted and thus the encapsulant 30 is adhered on the heat-fusible sheet 22. In the present invention, it is possible to efficiently decrease bubbles by providing the heat-fusible sheet 22, which has a higher melting point and exhibits late timing of melting when compared with the encapsulant 30, with the air-flow path 22a. The heat-fusible resin preferably has a melting point measured by a DSC method of lower than 130° C., and more preferably lower than 120° C., from the view point of heat fusibility. From the viewpoint of efficiency of a decrease in bubbles, the melting point measured by a DSC method is preferably 80° C. or higher, and more preferably 90° C. or higher.
The thickness of the heat-fusible sheet 22 may be appropriately adjusted according to the kind of the heat-fusible resin constituting the heat-fusible sheet 22. Usually, the thickness of the sheet 22 is preferably within a range from 1 to 200 μm. More specifically, when the heat-fusible sheet 22 is a sheet containing EVA, the thickness of the EVA sheet is preferably within a range from 10 to 200 μm, more preferably from 50 to 150 μm, and still more preferably from 80 to 120 μm from the viewpoint of lightweight properties and electrical insulation properties.
The air-flow path 22a is constituted by forming grooves on a surface (a surface opposite to the surface, on which a base material sheet is laminated) of the heat-fusible sheet 22.
There is no particular limitation on the method of forming an air-flow path 22a and it is possible to use a method of directly forming by embossing using an embossing roll, a method of forming a film on a casting sheet having an uneven shape imparted on a surface using a casting method and the like.
There is no particular limitation on the shape of the groove (recessed portion) of the air-flow path 22a, as long as it is a shape which is preferred to decrease bubbles, and the shape may be a lattice shape, a inclined lattice shape, a honeycomb shape, a shape of a plurality of linear or curved bands or lattices arranged in parallel, or a protean shape, when viewed as a planar view.
The size of the groove of the air-flow path 22a may be appropriately adjusted according to the shape of the groove to be formed or the like. When a lattice-shaped groove is formed as shown in
There is no particular limitation on the cross-sectional shape of the groove of the air-flow path 22a, as long as it is a shape which is preferred to decrease bubbles and includes, in addition to an inverted trapezoid shape shown in
The depth of the groove of the air-flow path 22a may be appropriately adjusted according to the thickness or the like of the heat-fusible sheet 22 on which the groove is formed and the depth indicated by the sign “i” is preferably within a range from 1 to 100 μm, and more preferably from 10 to 60 μm. The gap (protruding portion) between the groove and the groove of the air-flow path 22a may be appropriately adjusted according to the shape, size and the like of the groove to be formed. When the lattice-shaped groove is formed as shown in
The base material sheet 24 in the protective sheet for a solar battery module 10A, 20A of the present invention may be a resin sheet or not, and is preferably a resin sheet from the viewpoint of flexibility, lightweight properties and the like.
When materials having no light transmittability are used as the base material sheet 24, the protective sheets for a solar battery module 10A, 20A are not used as a front protective sheet 10A which protects a front side of a solar battery module, but as a back protective sheet 20A which protects a back side of a solar battery module.
As the resin sheet, materials used commonly as a resin sheet in the protective sheet for a solar battery module are selected. Examples of the resin sheet include sheets made of polymers such as polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polytetrafluoroethylene, polyamide (nylon 6, nylon 66), polyacrylonitrile, polyvinyl chloride, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyoxymethylene, polycarbonate, polyphenylene oxide, polyesterurethane, poly m-phenyleneisophthalamide, poly p-phenyleneterephthalamide and the like. Among these sheets, sheets made of polyesters such as PET, PBT and PEN are preferred, and a PET sheet is more preferred because of satisfactory electrical insulation properties, heat resistance, chemical resistance, dimensional stability and moldability.
The thickness of the resin sheet may be appropriately adjusted based on electrical insulation properties which are required to the solar battery module. Usually, the thickness is preferably within a range from 10 μm to 300 μm. More specifically, when the resin sheet is a PET sheet, the thickness is preferably within a range from 10 μm to 300 μm, and more preferably from 30 μm to 200 μm, from the viewpoint of lightweight properties and electrical insulation properties.
As long as the effects of the present invention are not adversely affected, the resin sheet may be subjected to a surface modification treatment so as to enhance weatherability, moisture resistance and the like. For example, it is possible to enhance weatherability, moisture resistance and the like of the protective sheet for a solar battery module by vapor deposition of silica (SiO2) and/or alumina (Al2O3) on the PET sheet. Both surfaces of the resin sheet, or only any one of surfaces may be subjected to the vapor deposition treatment of silica and/or alumina.
There is no particular limitation on the method of laminating the base material sheet 24 on a the surface opposite to the surface (back surface), on which the air-flow path 22a is formed, of the heat-fusible sheet 22, as long as it does not adversely affect the effects of the present invention. It is possible to further provide an adhesive layer 23 between a base material sheet 24 and a heat-fusible sheet 22, and to laminate the base material sheet 24 and the heat-fusible sheet 22 through the adhesive layer 23.
It is preferred that the adhesive layer 23 contains an adhesive which has adhesion to the base material sheet 24 and the heat-fusible sheet 22.
There is no particular limitation on the adhesive, and examples thereof include an acrylic adhesive, an urethane-based adhesive, an epoxy-based adhesive, a polyester-based adhesive and the like. In order to improve adhesion, the heat-fusible sheet 22, and the surface of the adhesive layer side of the base material sheet 24 may be subjected to a corona treatment and/or a chemical treatment.
The protective sheets for a solar battery module 10B, 20B of the second embodiment shown in
In
In protective sheets for a solar battery module 10B, 20B of the present invention, a fluorine-containing resin layer 25 can be formed by applying a coating material containing a fluorine-containing resin on a surface opposite to the surface, on which a heat-fusible sheet 22 is laminated, of a base material sheet 24 so as to form a coating film having a desired thickness, followed by curing with drying.
There is no particular limitation on the coating material containing a fluorine-containing resin, as long as it does not adversely affect the effects of the present invention and forms the fluorine-containing resin layer 25 after curing with drying. The coating material may be a coating material, which is prepared by dissolving in a solvent or dispersed in water and can be applied on one surface of the base material sheet 24.
There is no particular limitation on the fluorine-containing resin contained in the coating material, as long as it does not adversely affect the effects of the present invention and is a resin containing fluorine. The fluorine-containing resin is preferably a resin which is dissolved in a solvent (an organic solvent or water) of the above coating material and is crosslinkable.
Preferred examples of the fluorine-containing resin include polymers containing chlorotrifluoroethylene (CTFE) as a main component, such as LUMIFLON (trade name) manufactured by ASAHI GLASS CO., LTD., CEFRAL COAT (trade name) manufactured by Central Glass Co., Ltd. and FLUONATE (trade name) manufactured by DIC Corporation; polymers containing tetrafluoroethylene (TFE) as a main component, such as ZEFFLE (trade name) manufactured by DAIKIN INDUSTRIES, Ltd.; polymers having a fluoroalkyl group, such as Zonyl (trade name) manufactured by E.I. duPont de Nemours and Company and Unidyne (trade name) manufactured by DAIKIN INDUSTRIES, Ltd.; and polymers including a fluoroalkyl unit as a main component. Among these, polymers containing CTFE as a main component and polymers containing TFE as a main component are preferred, and LUMIFLON (trade name) and ZEFFLE (trade name) are most preferred from the viewpoint of weatherability, pigment dispersibility or the like.
The coating material may contain, in addition to the fluorine-containing resin, a crosslinking agent (curing agent), a catalyst (crosslinking accelerator) and a solvent and, if necessary, it may contain inorganic and organic compounds such as a pigment, a dye and a filler.
There is no particular limitation on the composition of the coating material, as long as it does not adversely affect the effects of the present invention, and examples thereof include a coating material composition containing LUMIFLON (trade name) as a base, which is mixed with LUMIFLON (trade name), a pigment, a crosslinking agent, a solvent and a catalyst. With respect to a composition ratio, the content of LUMIFLON (trade name) is preferably from 3 to 80% by mass, and more preferably from 25 to 50% by mass; the content of the pigment is preferably from 5 to 60% by mass, and more preferably from 10 to 30% by mass; and the content of the organic solvent is preferably from 20 to 80% by mass, and more preferably from 30 to 70% by mass; based on 100% by mass of the entire coating material.
As shown in a schematic view of
The protective sheet for a solar battery module of the present invention can be preferably used not only as a front protective sheet 10, but also as a back protective sheet 20, and is more preferably used as a back protective sheet 20 from the viewpoint of light transmittability.
The method for producing a solar battery module of the present invention includes the step of laminating protective sheets for a solar battery module 10, 20 according to the present invention on a surface of an encapsulant 30 including solar battery cells therein, using a vacuum thermocompression bonding method.
When the protective sheets for a solar battery module 10, of the present invention are laminated on the surface of the encapsulant 30, a surface of a heat-fusible sheet in the protective sheets for a solar battery module 10, 20 is laminated on the surface of the encapsulant 30.
It is preferred that the temperature in the case of employing the vacuum thermocompression bonding method is gradually raised within a range from 120° C. to 150° C. as a maximum temperature.
The present invention will be described in more detail below by way of Examples, but the present invention is not limited to the following Examples.
Using a T-die extrusion film forming machine, EVA (EVAFLEX V5961, manufactured by DuPont-Mitsui Polychemicals Co., Ltd., ethylene/vinyl acetate=91:9 (mass ratio), melting point measured by a DSC method: 97° C.) was melt-extruded to form a film having a thickness of 100 μm. On the EVA film thus formed, an air-flow path with an uneven portion having a predetermined lattice shape shown in
In the same manner as in Example 1, except that an air-flow path with an uneven portion having a predetermined inclined lattice shape shown in
As a coating material containing a fluorine-containing resin, a mixture of 100 parts by mass of LUMIFLON LF-200 (trade name, manufactured by ASAHI GLASS CO., LTD.), 10 parts by mass of SUMIDUR N3300 (trade name, manufactured by Sumika Bayer Urethane Co., Ltd.) and 30 parts by mass of Ti-Pure R105 (trade name, manufactured by E.I. duPont de Nemours and Company) was prepared. On one surface of an annealed polyester film (Melinex SA, manufactured by Teijin DuPont Films Japan Limited, 125 μm in thickness), this coating material containing a fluorine-containing resin was applied using a bar coater and then cured by drying at 130° C. for 1 minute to obtain 15 μm thick fluorine-containing resin layer.
Then, on a surface opposite to the surface, on which the fluorine-containing resin layer of the annealed polyester film was formed, an adhesive layer was formed in the same manner as in Example 1. In the same manner as in Example 1, the adhesive layer thus formed and the EVA film with an air-flow path formed thereon were laminated so that the adhesive surface of the layer thus formed faces the non-embossed surface of the EVA film to produce a protective sheet for a solar battery module.
In the same manner as in Example 1, except that an EVA film with no air-flow path formed thereon was used, a protective sheet for a solar battery module was produced.
A protective sheet for a solar battery module (measuring 100 mm×100 mm) and an EVA for an encapsulant (Ultra Pearl, manufactured by SANVIC INC., melting point measured by a DSC method: 72° C., measuring 400 μm×100 mm×100 mm) were laminated, and glass plate (measuring 1 mm×125 mm×125 mm) subjected to a release treatment was laminated on the side of EVA for an encapsulant. This protective sheet for a solar battery module/EVA for an encapsulant/glass plate laminate was placed in an oven at 23° C. and 100 g of a balance weight was further placed on the glass plate and, after raising the temperature to 140° C., a heat treatment was carried out as it is for 20 minutes. After the heat treatment, the protective sheet was left to stand under the conditions of 23° C. and 50% RH for 24 hours and then cooled to normal temperature. The glass plate was removed from the protective sheet for a solar battery module/EVA for an encapsulant/glass plate laminate to obtain a protective sheet for a solar battery module/EVA for an encapsulant. The side surface of EVA for an encapsulant of the obtained protective sheet for a solar battery module/EVA for an encapsulant was imaged at 50 times magnification using a microscope (KH-7700, manufactured by HIROX Co., Ltd.). Imaged file was analyzed by binarization using an image analyzing software Image Pro-plus (trade name, manufactured by Media Cybernetics) and an area of bubbles entered into a space between the protective sheet for a solar battery module and EVA for an encapsulant was calculated. The results are shown in Table 1.
The above results revealed that the groove of protective sheets for a solar battery module of Examples 1 to 3 according to the present invention disappeared and prevented bubbles from remaining.
According to the present invention, since the protective sheet for a solar battery module includes a base material sheet and a heat-fusible sheet made of a heat-fusible resin having a melting point measured by differential scanning calorimetry (a DSC method) of 80° C. or higher and lower than 130° C., laminated on one surface of the base material sheet, and includes an air-flow path on a surface of the heat-fusible sheet, it is possible to provide a protective sheet for a solar battery module which can prevent bubbles remaining between the encapsulant and the protective sheet and enable use over a long period of time; and a solar battery module.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-082018 | Mar 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/001982 | 3/19/2010 | WO | 00 | 9/29/2011 |
