JP4992530B2 - Back protection sheet for solar cells - Google Patents

Description

  The present invention relates to a solar cell back surface protective sheet for use in back surface protection in a transparent solar cell module.

  A solar cell used for photovoltaic power generation constitutes the heart of a photovoltaic power generation system that directly converts solar energy into electricity, and is made of a semiconductor. As the structure, a single solar cell element is not used as it is, and generally several to several tens of solar cell elements are wired in series and in parallel to protect the element over a long period of time. Therefore, various packaging is performed and unitized. A unit built in this package is called a solar cell module. Generally, the surface that is exposed to sunlight is covered with glass, the gap is filled with a filler made of thermoplastic, and the back is made of a heat- and weather-resistant plastic material. The structure is protected by a white sheet.

  In recent years, it is possible to incorporate light not only on the roof of the building, but also on the interior of the building to improve daylighting and visibility, in response to the variety of designs required for the building. A solar cell module using a transparent solar cell having translucency is required.

  Since these solar cell modules are used outdoors, sufficient durability and weather resistance are required in the materials used and their configurations. In particular, the back protective sheet is required to have a weather resistance and a low water vapor transmission rate. This is because if the filler in the unit is peeled off or discolored due to the permeation of moisture or the wiring is corroded, the module output itself is adversely affected.

  Conventionally, as a back surface protective sheet for a solar cell (hereinafter sometimes simply referred to as a protective sheet), a sheet having a laminated structure in which an aluminum foil is sandwiched between white polyvinyl fluoride films has been often used. However, this polyvinyl fluoride film has low mechanical strength and is softened by the heat of 140 ° C. to 150 ° C. hot press applied at the time of solar cell module creation, and the protrusions of the solar cell element electrode part penetrate the filler layer. Furthermore, the solar cell element and the aluminum foil are short-circuited to adversely affect the battery performance by penetrating the inner surface of the polyvinyl fluoride film constituting the back surface protection sheet and contacting the aluminum foil in the protection sheet. In order to solve this problem, it has been proposed to use a film in which a water vapor permeability is suppressed by laminating a silicon oxide film or a metal oxide film on a polyester base material as an alternative to an aluminum foil. (For example, refer to Patent Document 1).

However, in transparent solar cells installed on outdoor arcades and wall surfaces, the adhesive strength in the protective sheet due to embrittlement due to hydrolysis of the polyester film by exposure to ultraviolet rays and wind and rain that have passed through transparent solar cells. There are problems such as deterioration in appearance and poor output due to yellowing of the polyester film. The embrittlement of the polyester film has been improved by substituting polyethylene naphthalate from versatile polyethylene terephthalate. Regarding yellowing, there is an effect of suppressing yellowing of a polyester film, for example, by adding an ultraviolet absorber to a glass substrate. However, UV absorbers that are colorless and transparent and can be used for glass substrates are limited and it is difficult to absorb the wavelength of 385 nm, and as a result, yellowing of polyethylene naphthalate in transparent solar cells cannot be suppressed. It was.
JP 2002-134771 A

  The present invention has been made to solve the above-mentioned problems, and the problem is that the back surface protection sheet of the solar cell module has transparency, and the adhesion in the sheet is reduced even when installed outdoors. It is providing the back surface protection sheet for solar cells which suppressed yellowing of a sheet | seat.

The invention according to claim 1 is a solar cell back surface protection sheet in which at least an inorganic oxide layer, an adhesive layer, and an electrical insulating layer are sequentially laminated on at least one surface of a transparent substrate film.
The transparent substrate film is made of polyethylene naphthalate,
The film thickness of the inorganic oxide layer is 50 to 3000 mm,
The electrical insulation layer is made of a fluorine-based resin, and the thickness of the electrical insulation layer is 10 μm or more and 1000 μm or less,
The adhesive layer contains a triazine-based UV absorber in an amount of 0.1 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the resin solid content constituting the adhesive layer.
It is a solar cell back surface protection sheet characterized by this.
The invention according to claim 2 is characterized in that the transmittance of light at a wavelength of 550 nm is 45% or more, and the transmittance of light at a wavelength of 385 nm is 10% or less. It is a protective sheet.
According to a third aspect of the present invention, the adhesive layer contains 0.1 to 10 parts by weight of triazine-based and benzotriazole-based UV absorbers with respect to 100 parts by weight of resin solids constituting the adhesive layer. It is a solar cell back surface protection sheet of Claim 1 or 2 characterized by the above-mentioned.

  According to the present invention, there is provided a back surface protection sheet for a solar cell, which has transparency in a back surface protection sheet of a solar cell module and suppresses a decrease in adhesion in the sheet and yellowing of the sheet even when installed outdoors. be able to.

  Below, the back surface protection sheet for solar cells of this invention is demonstrated in detail based on drawing. In addition, the structure of the protective sheet of this invention is not limited to FIG. In FIG. 1, the structure of the cross section of one Example of the protection sheet of this invention is shown, On the at least one surface of the transparent base film 1, at least the inorganic oxide layer 2, the adhesive layer 4-1, and the electrical insulation layer 3- 1 are sequentially stacked. Further, an adhesive layer 4-2 and an electrical insulating layer 3-2 are sequentially laminated on the other surface of the transparent substrate film 1.

  As the transparent substrate film 1 in the present invention, polyester films such as polyethylene terephthalate and polyethylene naphthalate, polyolefin films such as polyethylene and polypropylene, polystyrene films, polyamide films, polyvinyl chloride films, polycarbonate films, polyacrylonitrile films, polyimides A film or the like is used, which may be stretched or unstretched, and preferably has mechanical strength and dimensional stability. In particular, polyethylene terephthalate arbitrarily stretched in the biaxial direction has been preferably used, but a polyethylene naphthalate film is preferred because of concerns such as embrittlement of the film due to hydrolysis by moisture in the air. Further, various known additives and stabilizers such as an antistatic agent, an ultraviolet ray preventing agent, a plasticizer, and a lubricant may be used on the surface of the transparent base film 1.

  The thickness of the transparent base film 1 is not particularly limited, but it is preferably 6 to 125 μm in consideration of the processability of forming the inorganic oxide layer 2 or laminating an electrically insulating film. .

  The inorganic oxide layer 2 according to the present invention comprises a vapor-deposited film of an inorganic oxide such as aluminum oxide, silicon oxide, tin oxide, magnesium oxide, or a mixture thereof, and has transparency and gas barrier properties such as oxygen and water vapor. What is necessary is just to have. Among them, silicon oxide is particularly preferable. However, the inorganic oxide layer 2 of the present invention is not limited to the inorganic oxide described above, and any material that meets the above conditions can be used.

  The optimum thickness of the inorganic oxide layer 2 varies depending on the type and configuration of the inorganic compound used, but generally it is preferably in the range of 50 to 3000 mm, and the value is appropriately selected. However, if the film thickness is less than 50 mm, a uniform film may not be obtained or the film thickness may not be sufficient, and the function as a gas barrier material may not be sufficiently achieved. In addition, when the film thickness exceeds 3000 mm, the inorganic oxide layer 2 cannot retain flexibility, and there is a possibility that the inorganic oxide layer 2 may crack due to external factors such as bending and pulling after the film formation. . Preferably, it exists in the range of 100-1500cm.

  Various means are possible as means for forming the inorganic oxide layer 2 on the transparent substrate film 1, but it is generally formed by vacuum deposition. Sputtering, ion plating, plasma vapor deposition (CVD), or the like can be used as means other than this vacuum vapor deposition. However, considering productivity, the vacuum deposition method is the best at present. Any one of an electron beam heating method, a resistance heating method, and an induction heating method may be appropriately used as a heating means of the vacuum evaporation apparatus by this vacuum evaporation method. In order to improve the adhesion between the inorganic oxide layer 2 and the transparent base film 1 and the denseness of the inorganic oxide layer 2, a plasma assist method or an ion beam assist method may be used. In addition, in order to increase the transparency of the inorganic oxide layer 2, reactive vapor deposition such as oxygen gas blowing may be performed during vapor deposition.

  In order to improve adhesion between the transparent substrate film 1 and the inorganic oxide layer 2, a primer layer may be provided. In order to achieve the above object, a composite of a silane coupling agent having an organic functional group or a hydrolyzate thereof with a polyol and an isocyanate compound is preferable as the primer layer.

  The electrically insulating layers 3-1 and 3-2 in the present invention are transparent, heat resistant, weather resistant, and flame retardant fluorine-based resins such as vinylidene fluoride resin, vinyl fluoride resin, perfluoroalkoxy resin, and four fluorocarbon resins. An ethylene-hexafluoropropylene copolymer, a perfluoroethylene-perfluoropropylene-perfluorovinyl ether terpolymer, and an ethylene-tetrafluoroethylene copolymer are preferably used. As the polyester film, a polyethylene terephthalate film or a polybutylene terephthalate film can be used. The fluorine-based film and the polyester film used as the electrical insulating layers 3-1 and 3-2 can be manufactured according to a conventionally known manufacturing method.

  The thickness of the electrical insulating layers 3-1 and 3-2 is not particularly limited, and the electrical insulation can be improved by increasing the total thickness, but if the total thickness is too thick, the solar cell module Since workability at the time of manufacture deteriorates, it may be arbitrarily selected in consideration of electrical insulation required between 10 and 1000 μm.

  As a method for laminating the electrical insulating layers 3-1 and 3-2, it can be laminated by a known laminating method such as a dry laminating method using an adhesive.

The material used for the adhesive layers 4-1 and 4-2 includes delamination due to deterioration due to long-term outdoor use where the adhesive strength between the electrical insulating layers 3-1 and 3-2 and the transparent base film 1 is long-term. It is necessary that the adhesive does not occur and the adhesive does not turn yellow. For example, an adhesive such as a polyurethane adhesive and an organic ultraviolet absorber can be used. The adhesive layers 4-1 and 4-2 are applied by, for example, a roll coating method, a gravure roll coating method, a kiss coating method, a coating method or the like, or a printing method. The coating amount is preferably about 0.1 to 10 g / m ² (dry state).

  Examples of the triazine-based ultraviolet absorber that can be added to the adhesive layers 4-1 and 4-2 in the present invention include 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl). ) Oxy] -phenol, 2- [4-[(2-hydroxy-3-dodecyloxypropyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1,3 5-triazine, 2- [4-[(2-hydroxy-3-tridecyloxypropyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4dimethylphenyl) -1,3,5- Triazine, 2,4-bis (2,4-dimethylphenyl) -6- (2-hydroxy-4-iso-octyloxyphenyl) -s-triazine can be used as a benzotriazole UV absorber 2- (2H-benzotriazol-2-yl) -p-cresol, 2- (2H-benzotriazol-2-yl) -4-6-bis (1-methyl-1-phenylethyl) phenol, 2- [5-Chloro (2H) -benzotriazol-2-yl] -4-methyl-6- (tert-butyl) phenol, 2- (2H-benzotriazol-yl) -4,6-di-tert-pentylphenol , 2- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol, etc., and these can be used alone or in combination to mix ultraviolet absorption ability and wavelength to be absorbed. It may be arbitrarily selected in consideration.

  The addition amount of the ultraviolet absorber to the adhesive layers 4-1 and 4-2 in the present invention is 0.1 to 10 parts by weight, preferably 1 part by weight with respect to 100 parts by weight of the resin solid content constituting the adhesive layer. Part to 5 parts by weight. If the amount is less than 0.1 parts by weight, the amount of ultraviolet rays absorbed by the transparent base film (PEN) cannot be absorbed and the transparent base film (PEN) is yellowed. If it exceeds 10 parts by weight, bleeding out occurs. The adhesion of the adhesive layer and the inorganic oxide layer, and the adhesive layer and the electrical insulating layer is inferior due to the deposition of the ultraviolet absorber by bleeding out.

  The protective sheet of the present invention preferably has a light transmittance of 45% or more at a wavelength of 550 nm and a light transmittance of 10% or less at a wavelength of 385 nm. If the light transmittance at a wavelength of 550 nm is less than 45%, the transparency is inferior, and when it is installed in a window or the like as a transparent solar cell module, light cannot be taken into the building. Moreover, when the transmittance | permeability in wavelength 385nm of light is larger than 10%, yellowing of a transparent base film (PEN) cannot be suppressed. In addition, the transmittance | permeability as used in the field of this invention is measured by JISK7361.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not restrict | limited to the following example.

Example 1
As a transparent substrate film, a 12 μm thick polyethylene naphthalate (Teijin DuPont Co., Ltd., trade name: Teonex) film is an inorganic film composed of a 400-nm-thick silicon oxide film using an electron beam heating vacuum deposition apparatus. An oxide layer was formed.
A polyvinyl fluoride film (DuPont Co., Ltd., trade name: Tedlar) having a thickness of 50 μm was used as an electrical insulating film constituting the electrical insulating layer. In addition, as an adhesive layer, triazine-based ultraviolet absorber (Ciba Specialty Chemicals Co., Ltd.) with respect to 100 parts by weight of the solid content of the two-component curable polyurethane adhesive (Mitsui Chemical Polyurethane Co., Ltd., trade name: Takelac) , Trade name: Tinuvin) and 2 parts by weight of benzotriazole ultraviolet absorber (BASF Japan Ltd., trade name: Uvinul) were added.
It laminated | stacked by the dry laminating method on the front and back of a transparent base film in order of the said contact bonding layer and an electrically insulating layer, and the said contact bonding layer might contact | connect a transparent base film. The application amount of the adhesive layer was 5 g / m ² (dry state). The protection sheet of the present invention was prepared as described above.

Comparative Example 1
A protective sheet was produced in the same manner as in Example 1 except that no ultraviolet absorber was added to the adhesive in Example 1.

Comparative Example 2
A protective sheet was produced in the same manner as in Example 1 except that polyethylene terephthalate (Toray Co., Ltd., trade name: Lumirror) having a thickness of 12 μm was used as the transparent substrate film in Example 1.

<Performance comparison 1>
The protective sheets of Examples and Comparative Examples 1 and 2 prepared as described above were subjected to a weather resistance acceleration test (metal halide lamp type tester JTM G 01 2000 Japan Testing Machine Industry Association Standard) in order to evaluate the weather resistance. As a tester, a die plastic metal weather (KU-R5CI-A: manufactured by Daipura Wintes Co., Ltd.) was used.

The weathering acceleration test conditions were: light source lamp: MW-60W, filter: KF-1 (irradiation range 295 nm to 780 nm) illuminance 65 ± 3 mW / cm ² (measurement range 330 nm to 390 nm), LIGHT mode (53 ° C., 50% RH) Then, irradiation was performed for 24 hours from the side with the inorganic oxide layer. The yellowing degree of the sample after irradiation was visually evaluated (after 12 hours and 24 hours). ○: No change, Δ: Slightly yellow, ×: Yellowish.

<Performance comparison 2>
The protective sheets of Example 1 and Comparative Examples 1 and 2 thus prepared were allowed to stand for 500 hours in an environment of 85 ° C. and 85%, after which the width between the transparent substrate film and the electrical insulating layer was 15 mm, the peeling angle was 180 degrees, and the peeling speed was The laminate was peeled off at 300 mm / min, and the laminate strength before and after standing in a high temperature and high humidity environment was measured.
The results of performance comparison 1 and performance comparison 2 are shown in Table 1.

[Table 1]

  As described above, according to the present invention, the solar cell back surface protection sheet for use in back surface protection in a transparent solar cell module is particularly excellent in yellowing resistance, electrical insulation and heat resistance, and weather resistance and water resistance. In addition, it has become possible to provide a back surface protection sheet for a solar cell module that is excellent in various properties such as moisture resistance, extremely durable, and excellent in protection ability.

It is explanatory drawing which shows the structure of the cross section of one Example of the back surface protection sheet for solar cells of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base film 2 ... Inorganic oxide layer 3 ... Electrical insulation layer 4 ... Adhesive layer

Claims (3)

In at least one surface of the transparent substrate film, at least an inorganic oxide layer, an adhesive layer, and an electrically insulating layer are sequentially laminated on the back surface protective sheet for solar cell,
The transparent substrate film is made of polyethylene naphthalate,
The film thickness of the inorganic oxide layer is 50 to 3000 mm,
The electrical insulation layer is made of a fluorine-based resin, and the thickness of the electrical insulation layer is 10 μm or more and 1000 μm or less,
The adhesive layer contains a triazine-based UV absorber in an amount of 0.1 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the resin solid content constituting the adhesive layer.
The solar cell back surface protection sheet characterized by the above-mentioned.   The back protective sheet for a solar cell according to claim 1, wherein the transmittance of light at a wavelength of 550 nm is 45% or more, and the transmittance of light at a wavelength of 385 nm is 10% or less. 2. The adhesive layer contains 0.1 to 10 parts by weight of triazine-based and benzotriazole-based UV absorbers with respect to 100 parts by weight of resin solids constituting the adhesive layer. Or the solar cell back surface protection sheet of 2.

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