JP2017183618A - Backside protection sheet for solar battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backside protection sheet for a solar battery module, which is low in cost and superior in light resistance and hydrolysis resistance.SOLUTION: A backside protection sheet for a solar battery module comprises: an ultraviolet light protection layer (A layer); a white polyester base material (B layer); and an easily adhesive resin layer (C layer) in this order. The B layer includes at least one polyester resin layer with a whitening agent added thereto. The A layer is formed on one face of the B layer through no adhesive layer, and has the function of protecting the B layer against ultraviolet light. The C layer is formed on a face of B layer on a side opposite to the A layer through no adhesive layer, and has the property of adhering to a filler for holding and fixing a solar battery device.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a back surface protective sheet for a solar cell module excellent in light resistance.

  Solar cells have been put into practical use as a semi-permanent and non-polluting clean energy source, and are spreading explosively. Solar cell elements that directly convert solar energy into electricity are manufactured using single crystal silicon substrates, polycrystalline silicon substrates, etc., and connect multiple solar cell elements to generate practical electrical output and receive light. The surface is covered with a transparent substrate or the like, and the gap is processed into a solar cell module having a structure for protecting the solar cell element using a filler or the like. In general, a solar cell module is manufactured using a lamination method or the like in which a transparent front substrate, a surface filler layer, a solar cell element, a back surface filler layer, and a back surface protection sheet are sequentially laminated, and these are vacuum-sucked and thermocompression bonded. Is done. In many cases, a plurality of solar cell modules are arranged side by side and installed outdoors, and therefore, high weather resistance and durability are required for members constituting the solar cell module. Especially, the back surface protection sheet used for the solar cell module mainly protects the back surface side of the solar cell element constituting the solar cell module, and thus has excellent mechanical strength, weather resistance, hydrolysis resistance, durability, etc. It is necessary to prepare (patent document 1).

  Solar cells are often used outdoors. In recent years, solar cells have been installed in areas where the amount of solar radiation that affects the amount of power generation is large (for example, desert areas). Many manufacturers guarantee the amount of power generated at the beginning of installation even after 20 years, and solar cell members with better weather resistance are required. Polyethylene terephthalate film is used for the back surface protection sheet for solar cell modules, and there are various back surface protection sheets for solar cell modules by a method of imparting light resistance and hydrolysis resistance to the polyethylene terephthalate film. . As a method for imparting light resistance, a back surface protective sheet for a solar cell module using a fluorine film containing a white pigment on the outermost layer side, or a back surface protective sheet for a solar cell module using a polyester film containing a white pigment on the outermost layer side There is. In this case, a fluorine film containing a white pigment and a polyethylene terephthalate film having hydrolysis resistance are expensive in terms of price due to the addition of a white pigment that can impart light resistance. There is a need for a back protection sheet for solar cell modules that is cheaper and has light resistance that can be used in a real environment (Patent Document 2).

  As a back surface protection sheet for solar cell modules conventionally used, a white polyvinyl fluoride film (“Tedlar” (registered trademark) manufactured by DuPont) can be exemplified, and a laminated structure in which a polyester film is sandwiched between the films. The back surface protection sheet for solar cell modules is widely used in such applications. The polyvinyl fluoride film is excellent in light resistance but expensive, and becomes an obstacle in terms of reducing the cost of the solar cell module. Moreover, since it contains fluorine, it has a problem of disposal cost.

  In recent years, a back protective sheet for a solar cell module in which an ultraviolet protective layer is laminated on a base film such as polyester has been proposed. It is a configuration that blocks light from entering from the back with an ultraviolet protective layer, and there is a degree of freedom in the selection of a base film, and the cost can be reduced (Patent Document 3).

  Although the back protection sheet for solar cell modules is not directly exposed to sunlight, depending on the installation method, it is exposed to sunlight due to wraparound or reflection, so it is important to give light resistance to the back protection sheet for solar cell modules It is. However, a so-called choking phenomenon in which the surface of the back surface protection sheet is in a state where powder is blown while the solar cell module is installed for a long period of time is a problem.

JP 2000-164907 A JP 2013-16864 A International Publication No. 2010/067780

  The problem to be solved by the present invention is to provide a back protective sheet for a solar cell module in which a white polyester base material having light resistance is provided with an ultraviolet protective layer without an adhesive layer, and the light resistance is further improved. It is.

  In order to solve the above problems, the present invention has the following configuration.

  1st invention has an ultraviolet-ray protective layer (A layer), a white polyester base material (B layer), and an easily-adhesive resin layer (C layer) in this order, The B layer was added with the whitening agent. The layer A includes at least one polyester resin layer, the layer A is formed on one surface of the layer B without an adhesive layer, and has a function of protecting the layer B from ultraviolet rays. A back protective sheet for a solar cell module, which is formed on an opposite surface of the A layer without an adhesive layer and has adhesiveness to a filler for holding and fixing a solar cell element.

  In the second invention, the B layer is formed by laminating a polyester resin layer to which a polyester resin layer and a whitening agent are added, and the A layer is disposed on the polyester resin layer side to which the whitening agent of the B layer is added. Is formed without interposing an adhesive layer.

  3rd invention is characterized by the content rate of the whitening agent in the polyester resin layer to which the whitening agent of the said B layer was added being 10 mass% or more.

  A fourth invention is characterized in that the whitening agent for the B layer is titanium oxide.

  A fifth invention is characterized in that the light transmittance of the A layer at a wavelength of 360 nm is less than 5%.

A sixth invention is characterized in that the amount of thickness reduction after irradiating the layer A with ultraviolet light having an intensity of 1000 W / m ² for 316 hours in an atmosphere of a temperature of 63 ° C. and a relative humidity of 30% is 5 μm or less. To do.

  According to the present invention, a white polyester base material having a light-resistant layer is further provided with an ultraviolet protective layer without using an adhesive layer, thereby preventing a choking phenomenon, a low-cost and excellent light resistance for back surface protection for solar cell modules. Sheets can be provided.

It is sectional drawing which showed an example of the back surface protection sheet for solar cell modules of this invention. It is sectional drawing which showed an example of the back surface protection sheet for solar cell modules of this invention. It is sectional drawing which illustrates the solar cell module using the back surface protection sheet for solar cell modules of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, what is shown to a figure is one Embodiment, It is not limited to this.

  In FIG. 1, an ultraviolet protective layer (A layer) is formed on one surface of a single white polyester base material (B layer), and an easily adhesive resin layer (C layer) is formed on the opposite surface of the A layer. It is a back surface protection sheet for solar cell modules.

  FIG. 2 shows a white polyester base material (B layer) obtained by laminating a polyester resin layer and a polyester resin layer to which a whitening agent is added. It is a back surface protection sheet for solar cell modules in which a protective layer (A layer) is formed and an easily adhesive resin layer (C layer) is formed on the opposite surface of the A layer.

  FIG. 3 shows a solar cell module constituted by the surface glass, the filler sheet 1, the solar cell element, the filler sheet 2, and the back surface protective sheet of the present invention. Light from the outside enters from the surface glass, passes through the filler sheet 1, reaches the solar cell element, and a photovoltaic force is generated. Moreover, the light reflected by the back surface protection sheet for solar cell modules reaches a solar cell element, and a photovoltaic power is generated.

  Hereinafter, each component will be described.

(White polyester base material (B layer))
The polyester of the polyester base in the back surface protective sheet for solar cell module of the present invention is an ester bond in the main chain obtained by polycondensation of polycarboxylic acid and polyalcohol, generally dicarboxylic acid and diol. Typical examples thereof include polyethylene terephthalate (PET) composed of terephthalic acid and diethylene glycol, and polyethylene naphthalate (PEN) composed of 2,6-naphthalenedicarboxylic acid and diethylene glycol. The polyester resin may be a copolymer. Examples of the copolymer component include diol components such as propylene glycol, diethylene glycol, neopentyl glycol, and cyclohexanedimethanol, isophthalic acid, adipic acid, azelaic acid, and sebacic acid. And the dicarboxylic acid component of the ester-forming derivative thereof.

  The white polyester base material (B layer) in the present invention needs to be a polyester film having at least one polyester resin layer to which a whitening agent is added, and the polyester to which the polyester resin layer and the whitening agent are added. It is more preferable that the resin layer is laminated by coextrusion molding in order to efficiently use the whitening agent. In this case, it is industrial to add the recovered raw material to the polyester resin layer side and the upper limit of 50% by mass. In this case, a whitening agent is added to the polyester resin layer side.

  The white polyester base material (B layer) is a polyester film having at least one polyester resin layer to which a whitening agent has been added. It is possible to conceal the wiring member such as an interconnector for connecting the photovoltaic elements to each other or a current collecting electrode called a bus bar for connecting cell strings to each other.

  When the white polyester base material (B layer) is formed by coextrusion molding of a polyester resin layer and a polyester resin layer to which a whitening agent is added, whitening in the polyester resin layer to which the whitening agent is added The content of the agent is preferably 10% by mass or more from the viewpoint of ultraviolet resistance of the back surface protective sheet for solar cell module, and more preferably 12% by mass or more. When the content of the whitening agent in the polyester resin layer to which the whitening agent is added is 10% by mass or more, the back surface protection sheet can be prevented from being deteriorated by ultraviolet rays, that is, from the ground or the roof even in long-term outdoor exposure. It is possible to prevent UV deterioration such as a change in the color tone of the resin and strength deterioration due to the reflection of light.

  As such a white polyester base material (B layer), “Lumirror” (registered by Toray Industries, Inc.), which is a hydrolysis-resistant white PET film made of a hydrolysis-resistant polyethylene terephthalate resin to which a whitening agent is added, is registered. (Trademark) manufactured by Toray Industries, Inc., which is a hydrolysis-resistant white PET film in which a hydrolysis-resistant polyethylene terephthalate resin layer to which a hydrolysis-resistant polyethylene terephthalate resin layer and a whitening agent are added is co-extruded. “Lumirror” (registered trademark) MX11 can be preferably used.

  As the whitening agent, titanium oxide, silica, alumina, calcium carbonate, barium sulfate or the like is used, and these whitening agents also have a function as an ultraviolet absorber. The whitening agent is preferably titanium oxide particles that can suppress UV deterioration and reduce yellowing of the film and decrease in mechanical strength when irradiated with light for a long time. Whiteness, dispersibility, concealment, weather resistance From the viewpoint of properties and the like, it is preferable to apply a suitable particle size and addition amount. The average primary particle diameter of the whitening agent such as titanium oxide particles is preferably in the range of 0.1 to 1 μm, and more preferably in the range of 0.15 to 0.5 μm. If the average particle size is outside the above range, it is not preferable because uniform dispersion becomes difficult or the smoothness of the film surface deteriorates. The addition amount of the whitening agent is preferably in the range of 5 to 20% by mass, and more preferably in the range of 7 to 15% by mass. If the addition amount is less than the above range, it is difficult to improve the characteristics such as the optical density and whiteness of the film. Conversely, if the addition amount is more than the above range, the film may be broken during stretching or inconvenience such as powder generation may occur during post-processing. is there.

  Furthermore, additives such as an antistatic agent, an ultraviolet absorber, a stabilizer, an antioxidant, a plasticizer, a lubricant, and a filler are added to the white polyester base material (B layer) as necessary. You may add in the range which does not impair the effect.

  In addition, the thickness of the white polyester base material (B layer) in the present invention is not particularly limited, but is preferably in the range of 25 to 300 μm in view of the withstand voltage characteristics and cost of the back protective sheet.

(UV protective layer (A layer))
The ultraviolet protective layer (A layer) in the back surface protective sheet for solar cell module of the present invention is a layer disposed in the outermost layer of the back surface protective sheet, and is a back surface protective sheet laminated on the back surface side of the solar cell module. It has a function for protecting from ultraviolet irradiation, and is applied onto a polyester base material and introduced into a back surface protective sheet.

  The UV protective layer (A layer) is selected in consideration of the weather resistance, heat resistance, UV resistance, adhesion to the polyester base material, etc. in addition to the UV absorptivity for performing the original function. In order to impart the properties, a colorant depending on the purpose may be added.

  The ultraviolet protection layer (A layer) includes an ultraviolet absorber and a binder resin for fixing the ultraviolet absorber. The binder resin is preferably an acrylic resin, a fluorine resin, or a polyester resin, and is preferably used in combination with a light stabilizer for preventing its own photodegradation because weather resistance can be maintained for a long time. In order to stably hold the light stabilizer in the resin, it is preferable to introduce a group having a light stabilizing function into the binder resin, and it is preferable to copolymerize a monomer having a light stabilizing group with the binder resin. The binder resin preferably has a cross-linked structure from the viewpoint of long-term weather resistance, and a polymer structure is obtained by reacting a composition comprising a polyol-based binder resin having a hydroxyl group serving as a base point of cross-linking with a polyisocyanate cross-linking agent in the coating process. It is preferable to form a crosslinked structure therein. Furthermore, the binder resin is copolymerized and fixed with a monomer having an ultraviolet absorbing ability, but when added alone, its function is reduced due to volatilization, etc. Preferred for exhibiting ultraviolet absorbing ability, for example, “Hals Hybrid” (registered trademark) manufactured by Nippon Shokubai Co., Ltd., “Adekastab” (registered trademark) LA-82, LA-87 manufactured by Asahi Denka Co., Ltd. Monotypes such as “Hostabin” (registered trademark) N-20 manufactured by Hoechst Japan, “Tomithorpe” (registered trademark) 77 manufactured by Yoshitomi Fine Chemical Co., and oligomer types such as Uvinal 5050H manufactured by BASF Japan Can be used.

  In addition, the coating liquid for forming the ultraviolet protective layer (A layer) according to the present invention includes a crosslink having a functional group capable of reacting with a hydroxyl group in the polyol binder resin for the purpose of improving the properties of the ultraviolet protective layer (A layer). It is preferable to mix an agent as a curing agent, and among them, a prescription using a polyisocyanate curing agent to form a crosslinked structure of urethane bonds is preferable.

  In the ultraviolet protective layer (A layer), a colorant may be used to color the ultraviolet protective layer and maintain the color tone for a long period of time. As for the back surface protection sheet for a solar cell module, white is mainly used from the viewpoint of light reflectivity and design, and by coloring it, the effect of protecting the binder resin of the ultraviolet protection layer from light can be obtained.

  The whitening agent used in the UV protective layer (A layer) is weather-resistant, such as inorganic fine particles such as calcium carbonate, silica, alumina, magnesium hydroxide, zinc oxide, talc, kaolin clay, titanium oxide, and barium sulfate. Among them, titanium oxide particles are most preferable from the viewpoint of availability, price, color development performance, and UV absorption of the pigment itself, and the rutile type, anatase type, brookite type, etc. are known as crystal types, but are excellent. The rutile type is preferred from the standpoints of whiteness, weather resistance and light reflectivity. In order to further increase the whiteness, it is effective to use a fluorescent whitening agent such as thiophenediyl. In particular, from the viewpoint of color development, regarding titanium oxide, the number average particle diameter is preferably 0.1 to 1.0 μm, and more preferably 0.2 to 0.5 μm from the viewpoint of dispersibility with respect to the binder resin and cost.

  What is necessary is just to adjust suitably about the compounding quantity of the said coloring agent according to the design of the color tone to develop. However, if the amount of pigment is too small, a color appearance with excellent design cannot be obtained. Conversely, if the amount is too large, the cost will be high, and the hardness of the resin layer will be greatly improved. The range of 1 to 200 parts by mass with respect to 100 parts by mass of the binder resin is preferable because it tends to cause poor adhesion with the substrate due to the above.

  In addition, a hydrocarbon wax may be added to the ultraviolet protective layer (A layer) in the present invention for the purpose of improving the slipperiness and making it difficult to be scratched by nails or metal (scratch resistance). The addition amount of the hydrocarbon wax is preferably 0.5 to 10% by mass in the solid content of the ultraviolet protective layer, and the average particle size of the hydrocarbon wax is preferably 2 to 20 μm. More preferably, it is 10-10 micrometers.

  In the present invention, it is important that the ultraviolet protective layer (A layer) is formed on the white polyester base material (B layer) without an adhesive layer. By providing an ultraviolet protective layer (A layer) directly on the white polyester base material (B layer) without using an adhesive layer, it is possible to prevent peeling / dropping of an ultraviolet protective film or the like due to deterioration of the adhesive layer. it can. In order to provide an ultraviolet protective layer (A layer) directly on the white polyester base material (B layer), methods such as an extrusion laminating method and a coating method can be used. An ultraviolet protective layer having a stable appearance can be formed with high productivity. As a coating method, for example, a roll coating method, a dip coating method, a bar coating method, a die coating method, a gravure roll coating method, or a combination of these methods can be used. This is a preferred method capable of forming an ultraviolet protective layer having excellent thickness uniformity and small coating appearance unevenness.

  Examples of the solvent of the coating liquid for forming the ultraviolet protective layer (A layer) of the present invention by a coating method without using an adhesive layer include, for example, toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl Examples thereof include isobutyl ketone, methanol, ethanol and water. The properties of the coating liquid may be either an emulsion type or a dissolution type.

  The thickness of the ultraviolet protective layer (A layer) is preferably 0.5 to 10 μm, more preferably 1 to 8 μm, and particularly preferably 1 to 4 μm. When this ultraviolet protective layer (A layer) is formed by a coating method without an adhesive layer, if the thickness is less than 0.5 μm, a phenomenon such as repellency or film breakage is likely to occur during coating, and it is uniform. Since it is difficult to form a coating film, adhesion to the white polyester base material (B layer), ultraviolet ray cutting property, peeling resistance, and scratch resistance may not be sufficiently exhibited. On the other hand, if the thickness of the UV protective layer (A layer) exceeds 10 μm, the UV-cutting performance is fully expressed, but the coating method is limited (specific process capable of thick film coating, device limitations), production cost There is a concern that the film is likely to be high, the film sticks to the transport roll, and the film peels easily.

The ultraviolet protective layer (A layer) in the present invention is disposed on the outdoor layer side of the solar cell module, and changes in color tone due to reflection from the ground or the roof even during long-term outdoor exposure and the breaking elongation of the entire solar cell back surface protective sheet. It is responsible for preventing UV degradation such as degradation, and the UV transmittance of the UV protective layer (A layer) at a wavelength of 360 nm is preferably less than 5%, more preferably less than 1%. It is possible to reduce the change in color tone as viewed from the ultraviolet protective layer (A layer) side of the protective sheet and the deterioration in elongation at break of the entire solar cell back surface protective sheet. Specifically, the color difference (ΔE ^* ) after irradiating the polyester resin layer with the whitening agent added with 1000 W / m ² of ultraviolet light for 316 hours in an atmosphere of a temperature of 63 ° C. and a relative humidity of 30% is 3 or less. And the elongation at break can be 70% or more.

Further, in the present invention, by providing the white polyester base material (B layer) with an ultraviolet protective layer (A layer), the so-called choking phenomenon in which the surface of the white polyester base material (B layer) is in a powdered state is prevented. be able to. As an indicator of the choking phenomenon, the UV protective layer (A layer) side of the back protective sheet was irradiated with UV light having an intensity of 1000 W / m ² on the A layer side for 316 hours in an atmosphere of a temperature of 63 ° C. and a relative humidity of 30%. This is a subsequent thickness reduction amount, which is preferably 5 μm or less, and more preferably 3 μm or less.

  In particular, in the case where the white polyester base material (B layer) is obtained by laminating a polyester resin layer and a polyester resin layer to which a whitening agent is added by coextrusion molding, in the polyester resin layer to which the whitening agent is added. While the concentration of the whitening agent can be increased to effectively suppress yellowing of the back surface protection sheet due to ultraviolet rays and the decrease in elongation at break, the choking phenomenon tends to worsen. By providing an ultraviolet protective layer (A layer) on the side of the polyester resin layer to which the whitening agent of the material (B layer) is added, it is possible to suppress the yellowing of the back protective sheet due to ultraviolet rays and the reduction in elongation at break and the choking phenomenon. Both prevention can be achieved.

(Easily adhesive resin layer (C layer))
The easy-adhesive resin layer (C layer) in the present invention is obtained by laminating a surface protective sheet, a sealing material sheet 1, a solar power generation element provided with wiring, a sealing material sheet 2, and a back surface protective sheet in this order, In the manufacturing process of the solar cell module integrated by thermocompression molding, the adhesive force between the back surface protection sheet and the sealing material sheet is determined. The sealing material sheet in the present invention is a sheet made of an ethylene / vinyl acetate copolymer resin (EVA). In the present invention, it is preferable that the adhesion strength after thermocompression-molding with the easily adhesive resin layer (C layer) surface and the sealing material sheet is 50 N / cm or more.

  Furthermore, of the light incident from the front surface of the solar cell module, a resin is selected that exhibits resistance to light that does not cause a photodegradation reaction with respect to light that passes through the cells and passes through the sealing material sheet layer and reaches the back surface protection sheet. It is preferable to maintain the adhesion performance stably over a long period of time. Therefore, the resin forming the easily adhesive resin layer (C layer) is preferably a resin having light resistance, and it is preferable to use an acrylic resin or a fluorine resin having further excellent light resistance.

  As the acrylic resin, an acrylic resin, an acrylic polyol copolymer, an acrylic / urethane copolymer, or the like is used. For example, “Acrynal” (registered trademark) (manufactured by Toei Kasei Co., Ltd.), “Acryt” (registered trademark) (manufactured by Taisei Fine Chemical Co., Ltd.), “Hitaroid” (registered trademark) (manufactured by Hitachi Chemical Co., Ltd.) , “Acridic” (registered trademark) (manufactured by DIC Corporation), “Udable” (registered trademark) (manufactured by Nippon Shokubai Co., Ltd.), “Dianar” (registered trademark) (Mitsubishi Rayon Co., Ltd.), etc. Can be mentioned. Examples of polyurethane resins include “Samprene” (registered trademark) (manufactured by Sanyo Chemical Industries), “Takelac” (registered trademark) (manufactured by Mitsui Chemicals), and TA (manufactured by Hitachi Chemical Polymer Co., Ltd.). ), “Seika Bond” (registered trademark) (manufactured by Dainichi Seika Kogyo Co., Ltd.)

  Examples of the fluorine-based resin include perfluoroolefin-based resins mainly composed of perfluoroolefin units from the viewpoint of structural units. Specific examples include a tetrafluoroethylene homopolymer (PTFE), a copolymer of tetrafluoroethylene with hexafluoropropylene, perfluoro (alkyl vinyl ether) or the like, and other monomers copolymerizable therewith. And a copolymer with the body. Of these, a fluororesin mainly composed of tetrafluoroethylene is preferable in terms of excellent pigment dispersibility, weather resistance, copolymerization, and chemical resistance. For example, “Zeffle” (manufactured by Daikin Industries, Ltd.) (Registered trademark) GK series and the like. Since these fluororesins are also excellent in flame retardancy, they also have an effect of improving the flame retardancy of the film for the back surface protection sheet for solar cell modules.

  Moreover, in order to improve adhesiveness with a polyester base material or the back surface protection sheet for solar cell modules of this invention is exposed to a high temperature process in a solar cell module manufacturing process, it improves the heat resistance of a coating film. For this purpose, it is preferable to form a crosslinked structure in these weather resistant resins.

  In the present invention, it is important that the easily adhesive resin layer (C layer) is formed on the opposite surface of the white polyester base material (B layer) to the ultraviolet protective layer (A layer) without an adhesive layer. By providing an easy-adhesive resin layer (C layer) directly on the white polyester base material (B layer) without using an adhesive layer, it is possible to remove and drop off an easy-adhesive resin film due to deterioration of the adhesive layer. Can be prevented. In order to provide an easy-adhesive resin layer (C layer) directly on the white polyester base material (B layer), a method such as an extrusion laminating method or a coating method can be used. An easily adhesive resin layer having a stable coating appearance can be formed with high productivity. As a coating method, for example, a roll coating method, a dip coating method, a bar coating method, a die coating method, a gravure roll coating method, or a combination of these methods can be used. This is a preferable method capable of forming an easy-adhesive resin layer having excellent thickness uniformity and small coating appearance unevenness.

  The thickness of the easily adhesive resin layer (C layer) is preferably 0.2 to 10 μm, more preferably 1 to 5 μm. When the thickness of the easy-adhesive resin layer (C layer) is less than 0.2 μm, a phenomenon such as repellency or film breakage tends to occur during coating, and it is difficult to form a uniform coating film. In some cases, the adhesion strength to the B layer) and the sealing material sheet is not sufficiently developed. On the other hand, when the thickness of the easy-adhesive resin layer (C layer) exceeds 10 μm, the adhesion strength is sufficiently developed, but the coating method is restricted, the production cost becomes high, the coating film adhesion to the transport roll, There is a concern that the coating film is liable to be peeled off.

  Examples of the solvent of the coating liquid for forming the easily adhesive resin layer (C layer) in the present invention by a coating method include, for example, toluene, xylene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dimethylformamide, Examples thereof include dimethylacetamide, methanol, ethanol and water. The properties of the coating liquid may be either an emulsion type or a dissolution type.

  An inorganic colorant is preferably added to the easily adhesive resin layer (C layer) of the present invention for the purpose of imparting light resistance. At present, the appearance of the back surface protection sheet for solar cells is mainly white, and for the purpose of the present invention, the addition of an inorganic whitening agent is intended to impart light resistance to the easy-adhesion coat layer C. Therefore, it is preferable.

  As the whitening agent used for the easily adhesive resin layer (C layer), titanium oxide having excellent light resistance is preferable. From the viewpoint of color development, the number average particle diameter is preferably from 0.1 to 1.0 μm, and more preferably from 0.2 to 0.5 μm from the viewpoint of dispersibility and cost.

  What is necessary is just to adjust suitably about the compounding quantity of the whitening agent used for an easily-adhesive resin layer (C layer) according to the design of the color tone to develop. However, if the blending amount of the whitening agent is too small, a color appearance with an excellent design property cannot be obtained, the light resistance performance becomes insufficient, and conversely, if the blending amount is too large, the cost becomes high. That the hardness of the easy-adhesive resin layer (C layer) is greatly improved, that the adhesion to the sealing material sheet is liable to be insufficient or reduced, and that the pigment bleeds out to the coating surface. There are concerns.

  For the above reason, the blending amount of the whitening agent is preferably 20 to 80 parts by mass, more preferably 30 to 70 parts by mass with respect to 100 parts by mass of the easily adhesive resin. If the whitening agent is less than 20 parts by weight, suitable light resistance cannot be obtained, and if it is more than 80 parts by weight, the resin layer becomes brittle and appropriate strength is difficult to obtain. Will occur and the light resistance tends to decrease.

(Back protection sheet)
As the back surface protection sheet for the solar cell module of the present invention, an ultraviolet protective layer (A layer) and an easily adhesive resin layer (C layer) may be formed on both sides of the white polyester base material (B layer), If necessary, a white film, metal oxide, on the opposite side of the UV protective layer (A layer) exposed to sunlight, that is, between the white polyester base material (B layer) and the easy-adhesive resin layer (C layer) For solar cell modules satisfying various required characteristics by laminating at least one of a barrier film having a material vapor deposition layer and an insulating film for preventing discharge from the solar cell element to the outside using a known dry laminating technique You may obtain a back surface protection sheet.

  As the white film, “Lumirror” (registered trademark) E20F manufactured by Toray, which is a polyethylene terephthalate film, “Tedlar” (registered trademark) PV2001, manufactured by DuPont, which is a polyvinyl fluoride film, and “Kiner” manufactured by Arkema, which is a polyvinylidene fluoride film. "(Registered trademark) 302-PGM-TR" can be exemplified. An example of a film having an inorganic oxide vapor deposition layer is “Barrier Rocks” (registered trademark) 1011HG manufactured by Toray Film Processing Co., Ltd., in which a metal oxide vapor deposition layer made of aluminum oxide is formed on a polyethylene terephthalate film substrate. it can. An example of the insulating film is “Lumirror” (registered trademark) S10 manufactured by Toray Industries, Inc., which is a polyethylene terephthalate film. When a white film is laminated, light reflectivity is imparted, when a film having a metal oxide vapor deposition layer is laminated, water vapor barrier property is imparted, or when an insulating film is laminated, The thickness can be increased and electrical characteristics such as dielectric breakdown voltage and partial discharge voltage can be improved. Moreover, the film laminated | stacked on the back surface protection sheet for solar cell modules of this invention does not necessarily need to be 1 sheet, According to the characteristic to give, combine each member film suitably and design the back surface protection sheet for solar cell modules. It ’s fine.

A known dry laminating method can be used as a method of laminating films and processing into sheets. For the lamination of resin films using the dry laminating method, a known dry laminating composition comprising a main component such as polyether polyurethane, polyester polyurethane, polyester or polyepoxy resin and a polyisocyanate curing agent as components. It is preferable that the total thickness of the back surface protection sheet for solar cell modules in this invention is 100-300 micrometers, More preferably, it is 130-250 micrometers from a viewpoint of economical efficiency. If the thickness exceeds 300 μm, the electrical insulation is improved, but the cutting property may be deteriorated when cutting into single sheets in the solar cell module manufacturing process, and further, the solar cell is affected by the curling effect in the processing process. The thermocompression workability with the element may deteriorate. On the other hand, when the thickness of the film is less than 100 μm, it is not preferable because the wiring connecting the solar cell elements is easily seen through, the appearance may be deteriorated and the partial discharge voltage is lowered.

  Moreover, the back surface protection sheet for solar cell modules of the present invention has a shrinkage ratio in heat treatment of 150 ° C. for 30 minutes from the wrinkle-suppressing surface at the time of processing in both the vertical direction and the horizontal direction of 1.0% or less, more preferably Both direction and lateral direction are 0.5% or less. As a method of suppressing the shrinkage rate in the heat treatment at 150 ° C. for 30 minutes of the solar cell module back surface protection sheet to 0.5% or less in both the vertical direction and the horizontal direction, for example, by giving a thermal history in advance by annealing treatment A technique is known in which contraction is prevented in a process such as thermocompression bonding in which heat is applied in a subsequent process.

(Solar cell module)
The solar cell module is laminated in the order of a filler layer for holding and fixing solar cell elements such as surface glass and crystalline silicon, a solar cell element, a filler layer, and a back surface protection sheet from the side irradiated with sunlight. . The filler layer in this configuration covers the unevenness of the solar cell element, protects the element from temperature change, humidity, impact, etc., and secures adhesion to the surface glass, surface protection sheet, and back surface protection sheet Used in. As the filler layer of the solar cell module, a known adhesive film can be used. For example, in addition to ethylene / vinyl acetate copolymer resin (EVA), ethylene / methyl acrylate copolymer, ethylene / acrylic acid Examples thereof include ethyl copolymers, polyurethane resins, polyvinyl butyral, partially saponified ethylene / vinyl acetate, silicone resins, and polyester resins. As the filler layer of the solar cell module, EVA is particularly preferably used from the viewpoint of light resistance, transparency, moisture resistance and economy, and the vinyl acetate content is 15 to 40 with respect to all resin components constituting the filler layer. Particularly preferred is mol%. When the vinyl acetate content of the filler layer of the solar cell module is 15 to 40 mol%, the transparency is not lowered, the resin is not sticky, and the workability and handleability are good.

  Next, an Example is given and the back surface protection sheet for solar cell modules of this invention is demonstrated concretely.

[Characteristic evaluation method]
The characteristic evaluation method used in the present invention is as follows.

(1) Light transmittance at 360 nm In order to measure the light transmittance at a wavelength of 360 nm of the ultraviolet protective layer (A layer), UV3100-PC manufactured by Shimadzu Corporation was used and measured using a 5 cm square test piece.

  UV protection by the ratio of the transmittance of a UFFE film “Toyoflon” (registered trademark) 50E manufactured by Toray Film Processing Co., Ltd. with a thickness of 50 μm to the light transmittance at 360 nm of the film coated with the UV protective layer (A layer). The light transmittance at 360 nm of the layer (A layer) was determined.

  It was judged that the light transmittance at 360 nm was less than 5% as a practical range.

(2) Thickness reduction due to ultraviolet irradiation Iwasaki Electric Co., Ltd. Eye Super UV Tester SUV-W161, an accelerated weathering tester, using an illuminometer, in an atmosphere at a temperature of 63 ° C. and a relative humidity of 30% It was adjusted to UV intensity 1000W / ^{m 2} at. Under the conditions of the present apparatus, ultraviolet irradiation was performed for 316 hours on the ultraviolet protective layer (A layer) side of the back surface protective sheet for solar cell module of the present invention. The cross section of the back surface protection sheet before and after the ultraviolet irradiation was cut, the thickness was measured using an optical microscope (UDM ECLIPSE LV100D-U manufactured by Nikon Corporation), and the average value of three points in the width direction was used. The thickness reduction amount of the back surface protection sheet by ultraviolet irradiation was calculated by the following formula, and if the thickness reduction amount was 5 μm or less, it was judged as a practical range.

Back surface protection sheet thickness before UV irradiation: a (μm)
Back surface protection sheet thickness after UV irradiation: b (μm)
Thickness reduction due to UV irradiation: ab (μm)
(3) Interconnector transparency (concealment)
The concealability of the back surface protection sheet for solar cell modules is confirmed by the see-through of the interconnector. Solar cell module back surface protection sheet / EVA sheet (manufactured by Sunvic Co., Ltd., PV-45FR000 thickness 450 μm) / in the direction where the easily adhesive resin layer (C layer) side of the back surface protection sheet for solar cell modules faces the EVA sheet An interconnector (2 mm width × thickness 0.6 mm) / EVA sheet (thickness 450 μm) / glass plate is laminated in this order, and a solar cell module laminator (LM-50X50-S) manufactured by NPC Corporation. After the installation, heat pressure bonding was performed under the conditions of a vacuum time of 5 minutes, a control time of 1 minute, a press time of 9 minutes, and a temperature of 142 ° C. After crimping, the module was cooled to room temperature to produce a pseudo module.

  Ten sheets of each level were prepared by the above method, and visually observed from the side of the solar cell module back surface protection sheet under a fluorescent lamp and reflected. As a judgment of the sheer, the “◯” was determined to be acceptable according to the following criteria.

○: Slight sheer of the interconnector is 4 sheets or less. X: There is clear sheer of the interconnector in any of 10 sheets. Alternatively, there are 5 or more slightly transparent connectors.

(Preparation of paint for forming UV protective layer (A layer))
“HALS HYBRIT POLYMER” (registered trademark) UV-G301 (solid content concentration: 40% by mass) manufactured by Nippon Shokubai Co., Ltd. is a coating agent in which an ultraviolet absorber and a light stabilizer (HALS) are cross-linked to an acrylic polyol resin. 42.5 parts by mass, 30.0 parts by mass of Titanic Co., Ltd. titanium oxide particles JR-709 as a whitening agent and 23.5 parts by mass of ethyl acetate as a diluent were dispersed using a bead mill. . Then, 4.0 parts by mass of a polyester plasticizer “Polysizer” (registered trademark) W-220EL manufactured by DIC Corporation as a plasticizer is added, and the main component (solid content concentration) of the ultraviolet protective layer (A layer) coating material is added. : 51% by mass).

  In 100 parts by mass of the above main agent, 4 parts by mass of “Desmodur” (registered trademark) N3300 (solid content concentration: 100% by mass) manufactured by Sumika Bayer Urethane Co., Ltd., which is a nurate type hexamethylene diisocyanate resin, and a diluent 171 parts by mass of n-propyl acetate was blended and stirred for 15 minutes using a bead mill to obtain an ultraviolet protective layer (A layer) -forming coating material (solid content concentration: 20% by mass).

(Preparation of paint for forming an easily adhesive resin layer (C layer))
A four-necked flask equipped with a cooling tube, a stirrer, a thermometer, and a nitrogen inlet tube is charged with 18 parts by mass of methyl methacrylate, 80 parts by mass of n-butyl methacrylate, 2 parts by mass of 2-hydroxyethyl methacrylate, and 100 parts by mass of toluene. The temperature was raised to 100 ° C. with stirring in a nitrogen atmosphere. Next, 0.15 parts by mass of azobisisobutyronitrile was added to carry out a polymerization reaction for 2 hours. Subsequently, 0.07 parts by mass of azobisisobutyronitrile was added to conduct a polymerization reaction for another 2 hours, and further 0.07 parts by mass of azobisisobutyronitrile was added to conduct a polymerization reaction for another 2 hours. An acrylic copolymer solution was obtained.

  Next, with respect to 100 parts by mass of the acrylic copolymer solution, 50 masses of ethyl acetate with a trimer of isophorone diisocyanate blocked with MEK oxime and a trimer of hexamethylene diisocyanate blocked with MEK oxime. An acrylic polymer solution was obtained by blending 10 parts by mass of a polyisocyanate compound solution diluted to%.

  Next, a titanium oxide pigment having an average particle diameter of 100 nm is blended in the acrylic polymer solution so that the mass ratio with respect to the resin solid content is 30% by mass, and ethyl acetate and methyl isobutyl ketone are added as diluent solvents to completely add The concentration was adjusted so that the solid mass was 50% by mass of the solution to obtain a titanium oxide-containing acrylic polymer solution.

  Next, 1 mass of hexamethylene polyisocyanate (HDI) -containing curing agent solution “N-3200” manufactured by Sumika Bayer Urethane Co., Ltd. is used as a polyisocyanate curing agent with respect to 100 parts by mass of the titanium oxide-containing acrylic polymer solution. After partly blending, methyl isobutyl ketone was further blended, and the concentration was adjusted so that the total solid content was 20% by mass, to obtain a paint for forming an easily adhesive resin layer (C layer).

Example 1
A single-layer hydrolysis-resistant white polyethylene terephthalate film “Lumirror” (registered trademark) MG13 (125 μm, titanium oxide concentration: 4 mass%) manufactured by Toray Industries, Inc. was prepared as a white plastic substrate (B layer). After applying corona treatment to both sides of this white plastic substrate in sequence, using a wire bar, the UV protective layer (A layer) forming coating is applied on one side so that the coating thickness is 2 μm after drying. Then, it is dried at 150 ° C. for 30 seconds, and further coated with an easy-adhesion resin layer (C layer) forming coating on the other surface so that the coating thickness becomes 2 μm after drying, and dried at 150 ° C. for 30 seconds. Thereafter, aging was performed at a temperature of 40 ° C. for 72 hours to promote the curing reaction of the ultraviolet protective layer (A layer) and the easy-adhesive resin layer (C layer) to obtain a back surface protective sheet for a solar cell module.

(Example 2)
Hydrolysis-resistant white polyethylene terephthalate film “Lumirror” (registered trademark) MX12, in which a polyester resin layer manufactured by Toray Industries, Inc. and a polyester resin layer to which a whitening agent is added are laminated as a white plastic base material (B layer) (250 μm, titanium oxide concentration of polyester resin layer to which whitening agent was added: 12% by mass) was prepared. After applying corona treatment to both sides of this white plastic substrate sequentially, using a wire bar, the coating material for drying the UV protective layer (A layer) is dried on the polyester resin layer side to which the whitening agent has been added. Is applied at a temperature of 150 ° C. for 30 seconds, and then the easy-adhesive resin layer (C layer) forming coating is applied to the polyester resin layer side so that the coating thickness is 2 μm after drying. Dry at 150 ° C. for 30 seconds, and then perform aging at 40 ° C. for 72 hours to promote the curing reaction of the UV protection layer (A layer) and the easy-adhesion resin layer (C layer), and protect the back surface for solar cell modules A sheet was used.

(Example 3)
Hydrolysis-resistant white polyethylene terephthalate film “Lumirror” (registered trademark) MX12, in which a polyester resin layer manufactured by Toray Industries, Inc. and a polyester resin layer to which a whitening agent is added are laminated as a white plastic base material (B layer) (160 μm, titanium oxide concentration of polyester resin layer added with whitening agent: 12% by mass) and drying UV protective layer (A layer) coating on the polyester resin layer side added with whitening agent A back protective sheet for a solar cell module was obtained in the same procedure as in Example 1 except that the post-coating thickness was 0.5 μm.

(Comparative Example 1)
Hydrolysis-resistant white polyethylene terephthalate film “Lumirror” (registered trademark) MX12, in which a polyester resin layer manufactured by Toray Industries, Inc. and a polyester resin layer to which a whitening agent is added are laminated as a white plastic base material (B layer) (250 μm, titanium oxide concentration of polyester resin layer to which whitening agent was added: 12% by mass) was prepared. After the corona treatment on the polyester resin layer side of this white plastic substrate, using a wire bar, the coating material for forming an easily adhesive resin layer (C layer) is applied so that the coating thickness is 2 μm after drying, The film was dried at 150 ° C. for 30 seconds, and thereafter aged at a temperature of 40 ° C. for 72 hours to promote the curing reaction of the easily adhesive resin layer (C layer), thereby obtaining a back surface protective sheet for a solar cell module.

  The white plastic base material (B layer) is not provided with an ultraviolet protective layer (A layer), so that the white plastic base material (B layer) is choked by UV irradiation and the sheet thickness is reduced. It was a thing.

(Comparative Example 2)
Example 1 except that a hydrolysis-resistant polyethylene terephthalate film “Lumirror” (registered trademark) X10S (125 μm, containing no whitening agent) manufactured by Toray Industries, Inc. was used instead of the white plastic substrate (B layer). The back surface protection sheet for solar cell modules was obtained in the same procedure.

  The white polyester base material (B layer) is not used, so when the solar cell module is manufactured, the concealing property of the back surface protection sheet is poor, and the interconnector see-through occurs on the back surface of the solar cell module, which cannot be put into practical use. Met.

  Table 1 shows the configuration requirements and characteristics of the back surface protective sheet for solar cell module of each example and comparative example.

  The back surface protection sheet for solar cell modules of this invention can provide the back surface protection sheet for solar cell modules excellent in light resistance, and can connect with a solar cell market expansion.

1: Easy-adhesive resin layer (C layer)
2: White polyester base material (B layer)
21: Polyester resin layer 22: Polyester resin layer with whitening agent added 3: UV protection layer (A layer)
4: Surface glass 5: Filler sheet 1
6: Solar cell element 7: Filler sheet 2
8: Back protection sheet

Claims (6)

  It has an ultraviolet protective layer (A layer), a white polyester base material (B layer) and an easily adhesive resin layer (C layer) in this order, and the B layer has at least one polyester resin layer to which a whitening agent is added. The A layer is formed on one surface of the B layer without an adhesive layer, and has a function of protecting the B layer from ultraviolet rays. The C layer is on the opposite surface of the B layer to the A layer. A back surface protective sheet for a solar cell module, which is formed without an adhesive layer and has adhesiveness with a filler for holding and fixing a solar cell element.   The B layer is formed by laminating a polyester resin layer and a polyester resin layer to which a whitening agent is added, and the A layer is interposed through an adhesive layer on the polyester resin layer side of the B layer to which the whitening agent is added. The back surface protection sheet for solar cell modules according to claim 1, wherein the back surface protection sheet is formed.   The back protective sheet for a solar cell module according to claim 2, wherein the content of the whitening agent in the polyester resin layer to which the whitening agent of the B layer is added is 10% by mass or more.   The back surface protective sheet for a solar cell module according to any one of claims 1 to 3, wherein the whitening agent for the B layer is titanium oxide.   The back surface protection sheet for solar cell modules according to any one of claims 1 to 4, wherein the light transmittance of the A layer at a wavelength of 360 nm is less than 5%. The thickness reduction amount after irradiating the layer A side with ultraviolet rays having an intensity of 1000 W / m ² for 316 hours in an atmosphere of a temperature of 63 ° C. and a relative humidity of 30% is 5 μm or less. The back surface protection sheet for solar cell modules in any one of.