JP2010219196A - Back surface protection sheet for solar cell module and solar cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a back surface protection sheet for a solar cell module having excellent steam barrier properties and excellent bending resistance that suppresses reduction in the steam barrier properties when the sheet is bent. <P>SOLUTION: The back surface protection sheet for a solar cell module wherein a gas barrier layer comprised of a silicon nitride is stacked on at least one of the surfaces of a base sheet and a fluorine resin layer is stacked on the other of surfaces of the base sheet or the gas barrier layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a back surface protection sheet for a solar cell module and a solar cell module including the same.

A solar cell module, which is a device that converts solar light energy into electrical energy, has attracted attention as a system that can generate power without discharging carbon dioxide. The solar cell module is required to have high power generation efficiency and durability that can withstand long-term use even when used outdoors.
The main configuration of the solar cell module is a photovoltaic cell that is a photovoltaic element, a sealing material that is an electrical insulator that seals the solar cell, and a light receiving surface side (front surface side) and a back surface side of the sealing material, respectively. It consists of the provided surface protection sheet and back surface protection sheet, and these protection sheets prevent the permeation of water vapor into the solar cell module. Such a protective sheet for a solar cell module is required to have excellent water vapor barrier properties and weather resistance. In particular, with the rapid progress of related technologies such as the development of thin-film solar cells, the back protection sheet for solar cell modules is required to have better water vapor barrier properties.
Conventionally, as a technique for improving water vapor barrier properties and weather resistance as a protective sheet for a solar cell module, for example, a technique disclosed in Patent Document 1 has been proposed.

Patent Document 1, is used as the protective layer of the solar cell module, silicon oxide on the surface (silica) is a sheet containing a fluororesin film layer including a thin film, the oxygen permeability of the sheet is 5 cc / m ² · day · atm or less, water vapor transmission rate of 5 g / m ² · day or less, light transmittance of 80% or more, silica thin film thickness of 150 to 500 mm, and adhesion strength of the film of 200 g / 15 mm or more A protective sheet for a solar cell module is disclosed.

JP-A-10-308521

However, the conventional sheet on which the silica thin film is formed has insufficient water vapor barrier properties, and it is difficult to satisfy the water vapor barrier performance required for future solar cell module back surface protection sheets.
Moreover, the sheet | seat in which the silica thin film was formed has a low bending resistance, and when the sheet | seat is bent, there exists a problem that a silica thin film will be cracked easily and water vapor | steam barrier property will fall.

  The present invention has been made in view of the above circumstances, and can improve the water vapor barrier property as compared with the conventional sheet, and can improve the bending resistance of the sheet, and even when the sheet is bent, the solar cell module has little decrease in the water vapor barrier property. The purpose is to provide a protective sheet for the back of the machine.

  In order to achieve the above object, according to the present invention, a gas barrier layer made of silicon nitride is laminated on at least one surface of a substrate sheet, and a fluororesin layer is laminated on the other surface of the substrate sheet or the gas barrier layer. The back surface protection sheet for solar cell modules characterized by these is provided.

  In the back surface protective sheet for a solar cell module of the present invention, it is preferable that the fluororesin layer contains titanium dioxide.

  In the back surface protective sheet for a solar cell module of the present invention, it is preferable that an adhesive layer made of a heat-adhesive resin is laminated.

  In the back surface protective sheet for a solar cell module of the present invention, the gas barrier layer is formed by reactive sputtering in an inert gas atmosphere containing nitrogen gas or in an inert gas atmosphere containing nitrogen gas and oxygen gas. It is preferable that the film is formed on a material sheet.

  Moreover, this invention provides the solar cell module by which the said back surface protection sheet for solar cell modules is adhere | attached on the back surface.

Since the back surface protective sheet for solar cell module of the present invention is obtained by laminating a gas barrier layer made of silicon nitride on one or both surfaces of a base material sheet, it is a water vapor barrier as compared with a sheet on which a conventional silica thin film is formed. In addition, the bending resistance is improved, the gas barrier layer is hardly deteriorated even when the sheet is bent, and the water vapor barrier property is less deteriorated.
Moreover, the reflectance of a sheet | seat can be improved by making the other surface of a base material sheet or the fluororesin layer laminated | stacked on the said gas barrier layer contain a sheet | seat, and can improve the power generation efficiency of a solar cell module. it can.

Since the solar cell module of the present invention is formed by adhering the back surface protection sheet for solar cell modules according to the present invention to the back surface (back surface) of the module, it has excellent water vapor barrier properties and weather resistance, and can be used outdoors for a long time. It will be durable enough to withstand use.
Moreover, by adhering the sheet having a high reflectance to the back surface, the light generation efficiency is improved by reflecting the light that escapes to the back surface side through the gap between the solar cells in the solar cell module and returning it to the solar cell side. Can be increased.

It is sectional drawing of 1st Embodiment of the back surface protection sheet for solar cell modules of this invention. It is sectional drawing of 2nd Embodiment of the back surface protection sheet for solar cell modules of this invention. It is sectional drawing of 3rd Embodiment of the back surface protection sheet for solar cell modules of this invention. It is sectional drawing of 4th Embodiment of the back surface protection sheet for solar cell modules of this invention. It is a schematic block diagram of the solar cell module of this invention. It is a schematic block diagram for demonstrating the conditions of a bending resistance test. It is a schematic block diagram of the reactive sputtering apparatus used for the film-forming of silicon nitride.

FIG. 5 is a schematic configuration diagram of a solar cell module using the back surface protection sheet for a solar cell module of the present invention (hereinafter abbreviated as a back sheet).
As illustrated in FIG. 5, the configuration of the solar cell module 50 includes a solar cell 40, a sealing material 30 covering the solar cell 40, and a surface fixed to the surface (light-receiving surface) side of the sealing material 30. The protective sheet 10 and the back sheet 20 fixed to the back surface (back surface) side of the sealing material 30 are included. In order to give the solar cell module the weather resistance and durability that can withstand long-term use outdoors and indoors, the solar cell 40 and the sealing material 30 are protected from wind and rain, moisture, dust, mechanical impact, etc. It is necessary to keep the inside of the solar cell module sealed from the outside air. For this reason, the back sheet 20 is required to have a high water vapor barrier property.
Furthermore, the backsheet 20 is provided with a backsheet for reducing light reception loss caused by light incident from the light receiving surface of the solar cell module through the gap between the plurality of solar cells to the back surface side. It is required to provide a function to increase the power generation efficiency by reducing the light receiving loss by reflecting the light that escapes through the gap between the solar cells and returning it to the solar cell side. Yes.

  FIG. 1 is a cross-sectional view of a first embodiment of the backsheet of the present invention. The back sheet 20 </ b> A of the present embodiment has a configuration in which a gas barrier layer 22 made of a silicon nitride thin film is laminated on one surface of a substrate sheet 21 and a fluororesin layer 23 is laminated on the other surface of the substrate sheet 21. ing. Further, the fluororesin layer 23 contains fine particles of titanium dioxide as an inorganic pigment for giving the back sheet high reflectance.

  As the resin sheet that can be used as the base material sheet 21, those generally used as a resin sheet in a protective sheet for a solar cell module can be used. For example, polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polytetrafluoroethylene, polyamide (nylon 6, nylon 66), polyacrylonitrile, polyvinyl chloride, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate Examples thereof include a sheet made of a polymer such as (PEN), polyoxymethylene, polycarbonate, polyphenylene oxide, polyester urethane, poly m-phenylene isophthalamide, poly p-phenylene terephthalamide. Especially, the sheet | seat which consists of polyesters, such as PET, PBT, and PEN, is preferable, and a PET sheet is mentioned as a more preferable thing specifically.

  What is necessary is just to select as thickness of the said base material sheet 21 based on the electrical insulation which a solar cell system requires. For example, when the substrate sheet 21 is a resin sheet, the film thickness is preferably in the range of 10 to 300 μm. More specifically, when the substrate sheet 21 is a PET sheet, the thickness of the PET sheet is preferably in the range of 10 to 300 μm from the viewpoint of lightness and electrical insulation, The range of 200 μm is more preferable, and the range of 50 to 150 μm is more preferable.

The gas barrier layer 22 is a thin film made of silicon nitride (Si 3 _{N 4),} part of the nitrogen (N) may be substituted with oxygen (O). In this embodiment, the gas barrier layer is directly formed on one surface of the base sheet 21.
The film thickness of the gas barrier layer 22 is preferably 20 nm or more, and more preferably 30 nm or more. When the film thickness is less than 20 nm, the water vapor barrier property of the backsheet 20A is lowered.

For example, the gas barrier layer 22 may be formed by sputtering in an inert gas atmosphere using a substance mainly containing silicon nitride (Si ₃ N ₄ ) as a target, or using Si as a target as shown in FIG. A film can be formed on one surface of the substrate sheet 21 by a reactive sputtering method in an inert gas atmosphere containing nitrogen gas and a small amount of oxygen gas.

  FIG. 7 is a schematic configuration diagram of a reactive sputtering apparatus for performing the reactive sputtering. Reactive sputtering using this reactive sputtering apparatus is performed as follows. First, the Si target 77 is placed on the cathode 74 in the vacuum chamber 71, and the base material 76 (base material sheet 21) is placed on the anode 75 provided to face the cathode 74. Next, the inside of the vacuum chamber 71 is evacuated by the vacuum pump 72, and the supply gas 80 may contain a mixed gas of inert gas (mainly argon gas) and nitrogen gas (or nitrogen gas together with a trace amount of oxygen gas). ) Is introduced into the vacuum chamber 71 between the electrodes 74 and 75 by applying a voltage from the DC high-voltage power source 73 to the target 77 by using the glow discharge obtained by applying glow discharge to the plasma 77. , The target 77 is decomposed into molecular or atomic level fragments 81 which are blown off and condensed on the substrate 76 to form a film 79. At this time, by using the mixed gas as the supply gas 80, the blown Si reacts with nitrogen, and the generated silicon nitride is deposited as a film 79.

Here, the silicon nitride of the formed film 79 does not become a stoichiometric composition component (Si ₃ N ₄ ), but may have a non-stoichiometric composition component (SixNy). Furthermore, when a small amount of oxygen gas is mixed in the mixed gas of inert gas and nitrogen gas as the mixed gas, a film having a composition in which a part of nitrogen of silicon nitride is replaced by oxygen is obtained. Can do.

  As mentioned above, although the case where the gas barrier layer 22 was formed by reactive sputtering was described, the film formation method of the gas barrier layer 22 is not limited only to reactive sputtering, such as PVD method, CVD method, laser vapor deposition method, etc. Other film formation methods can also be used.

  The fluororesin layer 23 laminated on the other surface of the base sheet 21 is not particularly limited as long as it does not impair the effects of the present invention and contains fluorine. For example, the sheet | seat which has a fluorine-containing polymer may be sufficient, and the coating film which apply | coated the coating material (coat liquid) which has a fluorine-containing polymer may be sufficient. From the viewpoint of making the fluororesin layer 23 thinner in order to reduce the weight of the protective sheet, a coating film coated with a paint having a fluorine-containing polymer is preferable.

As the sheet having the fluorine-containing polymer, for example, a sheet obtained by processing a polymer mainly composed of polyvinyl fluoride (PVF), ethylene chlorotrifluoroethylene (ECTFE), or ethylene tetrafluoroethylene (ETFE) into a sheet shape is preferable. As mentioned. Examples of the polymer mainly composed of PVF include E.I. I. Tedlar (trade name) manufactured by du Pont de Nemours and Company can be used. Moreover, as a polymer having ECTFE as a main component, Halar (trade name) manufactured by Solvay Solexis can be used. As the polymer containing ETFE as a main component, Fluon (trade name) manufactured by Asahi Glass Co., Ltd. can be used.
The thickness of the sheet having a fluorine-containing polymer is generally preferably in the range of 5 to 200 μm, more preferably in the range of 10 to 100 μm, and most preferably in the range of 10 to 50 μm from the viewpoint of weather resistance and weight reduction.

The paint having a fluorine-containing polymer is not particularly limited as long as it can be applied by being dissolved in a solvent or dispersed in water.
The fluorine-containing polymer contained in the paint is not particularly limited as long as it is a polymer containing fluorine without impairing the effects of the present invention, but is soluble in the solvent (organic solvent or water) of the paint and can be crosslinked. Those are preferred.
The fluorine-containing polymer is a polymer of a fluorine-containing monomer and other monomers copolymerizable with a fluorine-containing monomer that is optionally used. Examples of the fluorine-containing monomer include vinyl fluoride (VF) and vinylidene fluoride ( VdF), chlorotrifluoroethylene (CTFE), tetrafluoroethylene (TFE), hexafluoropropylene, fluorinated vinyl ether and the like. These fluorine-containing monomers can be used alone or in combination of two or more.
Examples of other monomers include vinyl acetate, vinyl propionate, butyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caproate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl cyclohexylcarboxylate, and benzoic acid. Examples thereof include vinyl esters of carboxylic acids such as vinyl, alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether and cyclohexyl vinyl ether, hydroxybutyl vinyl ether, and isobutylene. These monomers can be used alone or in combination of two or more.
Examples of fluorine-containing polymers include polymers of fluoroolefins having a curable functional group such as a hydroxyl group, and specific examples thereof include copolymers comprising TFE, isobutylene, VdF, hydroxybutyl vinyl ether and other monomers, and Preferred examples include copolymers comprising TFE, VdF, hydroxybutyl vinyl ether and other monomers.

  Preferable examples of the fluorine-containing polymer include chlorotrifluoroethylene 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 based on (CTFE), polymers based on tetrafluoroethylene (TFE) such as ZEFFLE (trade name) manufactured by Daikin Industries, Ltd .; I. Examples thereof include polymers having a fluoroalkyl group such as Zonyl (trade name) manufactured by du Pont de Nemours and Company, Unidyne (trade name) manufactured by Daikin Industries, Ltd., and polymers having a fluoroalkyl unit as a main component. Among these, from the viewpoint of weather resistance, pigment dispersibility, and the like, a polymer containing CTFE as a main component and a polymer containing TFE as a main component are more preferable. Among them, the LUMIFLON (trade name) and the ZEFFLE (trade name) are preferable. Most preferred.

The LUMIFLON (trade name) is an amorphous polymer containing CTFE, several kinds of specific alkyl vinyl ethers (VE), and hydroxyalkyl vinyl ethers as main structural units. A polymer having a monomer unit of hydroxyalkyl vinyl ether, such as LUMIFLON (trade name), is preferable because it is excellent in solvent solubility, crosslinking reactivity, substrate adhesion, pigment dispersibility, hardness, and flexibility.
The ZEFFLE (trade name) is a copolymer of TFE and an organic solvent-soluble hydrocarbon monomer (which may contain oxygen), and in particular, the copolymer has a highly reactive hydroxyl group. Is preferable because it is excellent in solvent solubility, cross-linking reactivity, substrate adhesion, and pigment dispersibility.

  Examples of the fluorine-containing polymer comprising a plurality of fluorine-containing monomers include Dyneon THV (trade name; manufactured by 3M Company), which is a terpolymer of VdF, TFE, and hexafluoropropylene. Such a multi-polymer is preferable because it can impart the properties of each monomer to the polymer. For example, the Dyneon THV (trade name) is preferable because it can be produced at a relatively low temperature, can be bonded to an elastomer or a hydrocarbon-based plastic, and is excellent in flexibility and optical transparency.

  The paint preferably contains fine particles of titanium dioxide as an inorganic pigment in addition to the fluorine-containing polymer. Further, if necessary, a crosslinking agent, a crosslinking accelerator, a solvent, other pigments, an inorganic filler, and the like. It can also be included.

  The titanium dioxide contained in the paint is not particularly limited as long as it does not impair the effects of the present invention, but the dispersion in the fluororesin layer 23 is good, a high reflectance is obtained, and the durability is excellent. What can form the layer 23 is preferable, and specific examples include Ti-Pure R105 (trade name; manufactured by EI du Pont de Nemours and Company), which is a rutile type titanium dioxide that has been coated and surface-treated. It is done.

The crosslinking agent contained in the paint is not particularly limited as long as it does not impair the effects of the present invention, and metal chelates, silanes, isocyanates, and melamines are preferably used. By blending a crosslinking agent, the resulting coating film is cured, and weather resistance and scratch resistance can be improved. However, when it is assumed that the protective sheet is used outdoors for 30 years or more, the weather resistance is improved. From the viewpoint, aliphatic isocyanates are preferable as the crosslinking agent.
Examples of the crosslinking accelerator contained in the paint include tin dibutyl dilaurate and tin dioctyl dilaurate, which are used to promote the crosslinking reaction between the fluorine-containing polymer and isocyanate.

  The solvent contained in the paint is not particularly limited as long as it does not impair the effect of the present invention. For example, methyl ethyl ketone (MEK), cyclohexanone, acetone, methyl isobutyl ketone (MIBK), toluene, xylene, methanol, isopropanol, ethanol , Heptane, ethyl acetate, isopropyl acetate, n-butyl acetate, or n-butyl alcohol can be preferably used. Among these, from the viewpoint of solubility of the components contained in the paint and low persistence in the coating film (low boiling point temperature), the solvent has at least one of xylene, cyclohexanone, and MEK. More preferably.

  Furthermore, examples of other pigments and inorganic fillers contained in the paint include silica, mica, boron nitride, zinc oxide, and aluminum oxide. As a specific example of silica, CAB-O-SIL TS 720 (trade name; manufactured by Cabot Specialty Chemicals, Inc.), which is a hydrophobic silica in which the hydroxyl group on the silica surface is modified by the surface treatment of dimethyl silicone, is preferable. It can be illustrated.

The composition of the coating is not particularly limited as long as the effects of the present invention are not impaired. However, the composition preferably includes 3 to 120 parts by mass of titanium dioxide, and 10 to 100 parts by mass with respect to 100 parts by mass of the fluoropolymer. Is more preferable. The solid content concentration of the paint is not particularly limited, but is usually about 10 to 80% by mass.

As a method for applying the coating material on the other surface side of the base sheet 21 or on the gas barrier layer, a known method can be used. For example, the coating material may be applied with a bar coater so as to have a desired film thickness.
The film thickness of the fluororesin layer 23 formed by curing the paint is not particularly limited, and may be, for example, a film thickness of 5 μm or more. From the viewpoint of water vapor barrier properties, weather resistance, and lightness, the thickness of the fluororesin layer 23 is preferably 5 to 100 μm, more preferably 10 to 50 μm, and even more preferably 10 to 30 μm.
The temperature in the drying process of the applied paint may be any temperature that does not impair the effects of the present invention, and is preferably in the range of about 50 to 130 ° C. from the viewpoint of reducing the influence on the base material sheet 21. .

Since the back sheet 20A of this embodiment is formed by laminating a gas barrier layer 22 made of silicon nitride on one surface of a base sheet 21, a conventional silica thin film is formed as demonstrated in the examples described later. Compared with the sheet, the water vapor barrier property can be improved, the bending resistance is further improved, and even when the sheet is bent, the gas barrier layer 22 is less deteriorated and the vapor barrier property is less deteriorated.
Moreover, the reflectance of this back sheet 20A can be improved by containing titanium dioxide in the fluororesin layer 23 laminated on the other surface of the base sheet 21, but silicon nitride is used as the barrier layer. Thus, a higher reflectance than that of a conventional back sheet using a silicon oxide compound thin film can be obtained, and the power generation efficiency of the solar cell module can be increased.

FIG. 2 is a cross-sectional view showing a second embodiment of the backsheet of the present invention.
The back sheet 20 </ b> B of the present embodiment has a configuration in which a gas barrier layer 22 and a fluororesin layer 23 are laminated in that order on one surface of a base sheet 21.
The details of the base sheet 21, the gas barrier layer 22, and the fluororesin layer 23 can be the same as those of the base sheet 21, gas barrier layer 22, and fluororesin layer 23 in the first embodiment described above.

The back sheet 20B of the present embodiment is the same as that of the first embodiment described above by providing the gas barrier layer 22 made of silicon nitride and the fluororesin layer 23 containing titanium dioxide on one surface of the base sheet 21. Almost the same effect can be obtained.
In the present embodiment, since the fluororesin layer 23 is laminated on the surface of the gas barrier layer 22, even if the base sheet 21 that does not easily adhere to the fluororesin layer 23 is used, the adhesion of the fluororesin layer 23 by the gas barrier layer is used. Therefore, the degree of freedom in selecting the material of the base material sheet 21 can be expanded, and the peeling of the fluororesin layer 23 can be prevented over a long period of time.

FIG. 3 is a cross-sectional view showing a third embodiment of the backsheet of the present invention.
In the backsheet 20C of the present embodiment, a gas barrier layer 22 made of a silicon nitride thin film is laminated on one surface of the base sheet 21, a fluororesin layer 23 is laminated on the other surface of the base sheet 21, and the gas barrier The adhesive layer 24 is laminated on the surface of the layer 22.
The details of the base sheet 21, the gas barrier layer 22, and the fluororesin layer 23 can be the same as those of the base sheet 21, gas barrier layer 22, and fluororesin layer 23 in the first embodiment described above.

  As the adhesive layer 24, an acrylic urethane resin, an ethylene-vinyl acetate copolymer (EVA) is used from the viewpoint of improving the adhesion with the sealing material 30 when the back sheet is laminated on the back surface of the solar cell module 50. Polyvinyl butyral (PVB), an ethylene-methacrylic acid copolymer, an ionomer resin in which molecules of an ethylene-methacrylic acid copolymer are crosslinked with metal ions, and the like can be used. Furthermore, it is preferable to have thermal adhesiveness so that it can be thermally bonded to the sealant 30. Here, thermal adhesiveness is a property that develops adhesiveness by heat treatment. As temperature in this heat processing, it is the range of 50-200 degreeC normally. From the viewpoint of having thermal adhesiveness, the adhesive layer 24 is selected from the group consisting of ethylene-vinyl acetate copolymer (EVA), ethylene-methacrylic acid copolymer (EMAA), ionomer resin, and mixtures thereof. One resin is preferable. Generally, the sealing material 30 is often a sealing resin made of EVA, and in this case, the sealing material 30 and the adhesive layer are formed by the adhesive layer 24 being a resin made of a polymer mainly composed of EVA. Adhesion with 24 can be improved.

  The thickness of the adhesive layer 24 is not particularly limited as long as the effects of the present invention are not impaired. More specifically, when the base resin of the adhesive layer 24 is EVA, from the viewpoint of light weight and electrical insulation. The thickness is preferably in the range of 10 to 200 μm, and more preferably in the range of 20 to 150 μm.

Other polymers and various compounding agents may be added to the adhesive layer 24 as necessary.
Moreover, as various compounding agents, any of an organic compound and an inorganic compound may be sufficient, and the compounding agent normally used in the resin industry is used. For example, anti-aging agents, stabilizers, pigments such as titanium dioxide, flame retardants, plasticizers, crystal nucleating agents, hydrochloric acid absorbers, antistatic agents, inorganic fillers, lubricants, antiblocking agents, and ultraviolet absorbers are used.

  In this embodiment, when the adhesion between the gas barrier layer 22 and the adhesive layer 24 is inferior, a laminating adhesive layer is provided between these layers, and the gas barrier layer 22 is bonded to the gas barrier layer 22 via the adhesive layer. The layer 24 may be bonded. Examples of the adhesive used for the laminate adhesive layer include acrylic adhesives, urethane adhesives, silicone adhesives, epoxy adhesives, ester adhesives, and the like. These adhesives may be used individually by 1 type, and may be used in combination of 2 or more type.

The back sheet 20 </ b> C of the present embodiment has a configuration in which a gas barrier layer 22 made of a silicon nitride thin film is laminated on one surface of a substrate sheet 21 and a fluororesin layer 23 is laminated on the other surface of the substrate sheet 21. Since it is a thing, the effect similar to the back seat | sheet of 1st Embodiment mentioned above can be acquired.
Further, the back sheet 20C of the present embodiment has good thermal adhesiveness with the sealing material 30 on the back surface of the solar cell module 50 by providing the adhesive layer 24 made of EVA or the like on the surface of the gas barrier layer 22. Since the back sheet 20C can be firmly bonded and fixed, a solar cell module having excellent durability can be configured.

FIG. 4 is a cross-sectional view showing a fourth embodiment of the backsheet of the present invention.
The back sheet 20D of the present embodiment has a gas barrier layer 22, a laminating adhesive layer 26, an aluminum (Al) layer 25, a laminating adhesive layer 26, and an adhesive layer 24 in that order on one surface of the base sheet 21. While being laminated, the fluororesin layer 23 is laminated on the other surface of the base sheet 21.
The details of the base sheet 21, the gas barrier layer 22, and the fluororesin layer 23 can be the same as those of the base sheet 21, gas barrier layer 22, and fluororesin layer 23 in the first embodiment described above. Examples of the adhesive used for the laminating adhesive layer 26 include acrylic adhesives, urethane adhesives, silicone adhesives, epoxy adhesives, and ester adhesives. These adhesives may be used individually by 1 type, and may be used in combination of 2 or more type.

The Al layer 25 is formed in order to further improve the water vapor barrier property of the backsheet 20D, and the thickness thereof is not particularly limited as long as the moisture-proof improvement effect can be exhibited, but usually in the range of 1 μm to 100 μm. is there.
The method of forming the Al layer 25 is not particularly limited. For example, the Al layer 25 can be formed by bonding an aluminum foil to the surface of the gas barrier layer 22 via a laminating adhesive layer 26, or on the surface of the gas barrier layer 22. It is also possible to form a film directly without the adhesive layer 26 for laminating by a method such as vacuum deposition.

  The back sheet 20D of the present embodiment can obtain substantially the same effect as the back sheet 20C of the third embodiment described above, and can further improve moisture resistance by laminating the Al layer 25.

  In the back sheet of the present invention, a gas barrier layer made of silicon nitride may be provided on both surfaces of the base sheet. By providing the gas barrier layer on both surfaces of the base sheet, the gas barrier property is further improved.

As shown in FIG. 5, the solar cell module of the present invention has the back sheets 20 </ b> A, 20 </ b> B, 20 </ b> C described above on the sealing material 30 on the back surface (back surface) of the solar cell module 50 so that the fluororesin layer is outside. 20D is bonded.
The type and structure of the solar cell module 50 are not particularly limited, and examples thereof include amorphous silicon (a-Si) solar cells, single crystal silicon (c-Si) solar cells, microcrystalline silicon (μc-Si) solar cells, and GaAs. It can be set as a compound semiconductor type solar cell and a dye-sensitized solar cell.

Since the solar cell module of the present invention is formed by adhering the back sheets 20A, 20B, 20C, and 20D according to the present invention to the back surface (back surface) of the module, it has excellent water vapor barrier properties and weather resistance, and has a long outdoor period. It will be durable enough to withstand use.
In addition, by adhering the sheet having high reflectivity to the back surface, the light that escapes to the back surface side through the gap between the solar cells in the solar cell module is reflected and returned to the solar cell side to increase the power generation efficiency. be able to.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to a following example at all. In addition, the thickness (film thickness) of the gas barrier layer (silicon nitride, silica) of an Example and a comparative example was measured using the stylus type | formula step surface and shape measuring apparatus (Ambios TECHNOLOGY company "XP-1").

[Example 1]
(Preparation of coating solution)
120 parts by mass of methyl ethyl ketone, 18.2 parts by mass of hydrophobic silica (manufactured by Cabot Specialty Chemicals, Inc., trade name “CAB-O-SIL TS-720”), titanium dioxide (EI du Pont de Nemours and Company, trade name “Ti-Pure R105”) is blended at a ratio of 100 parts by mass, and dispersed using a pigment disperser (special machine industry Co., Ltd., device name “TK Homo Disper”). A pigment dispersion was prepared.
Subsequently, to 87 parts by mass of the obtained pigment dispersion, 100 parts by mass of a chlorotrifluoroethylene copolymer (manufactured by Asahi Glass Co., Ltd., trade name “LUMIFLON LF200”, solid content concentration 60% by mass), aliphatic isocyanate -Based crosslinking agent (curing agent) (manufactured by Sumika Bayer Urethane Co., Ltd., trade name “Sumijour N3300”) 10.7 parts by mass, crosslinking accelerator (manufactured by Toyo Ink Manufacturing Co., Ltd., trade name “BXX3778-10”), (Dioctyl dilaurate tin) 0.004 parts by mass and methyl ethyl ketone 110 parts by mass were mixed to prepare a coating agent containing titanium dioxide and a fluororesin.

(Gas barrier layer deposition)
Reactive sputtering film formation was performed on one side of a 125 μm-thick polyethylene terephthalate film (trade name “Melinex-S” manufactured by Teijin DuPont Films Ltd.) using the reactive sputtering apparatus shown in FIG. A gas barrier layer made of 30 nm silicon nitride was formed.
Deposition conditions:
Plasma generation gas: Argon, nitrogen Gas flow rate: Argon 100 sccm, Nitrogen 60 sccm
Target material: Si
Power value: 2500W
Vacuum chamber internal pressure: 0.2Pa

(Formation of fluororesin layer)
Next, on the surface of the polyethylene terephthalate film opposite to the surface on which the gas barrier layer is formed, apply the coating agent and a bar coater so that the thickness of the dried coating film is 15 μm (coating amount 30 g / m ² ). The film was applied and dried at 120 ° C. for 2 minutes to form a fluororesin layer, and the back sheet of Example 1 was produced.

[Example 2]
A back sheet of Example 2 was obtained in the same manner as Example 1 except that the thickness of the gas barrier layer was 60 nm.

[Example 3]
A back sheet of Example 3 was obtained in the same manner as Example 1 except that the thickness of the gas barrier layer was 20 nm.

[Comparative Example 1]
In the reactive sputtering film formation, a silicon oxide (silica) with a thickness of 30 nm is formed by performing the same operation as in Example 1 except that oxygen gas is used instead of nitrogen gas in the plasma generation gas. Thus, a back sheet of Comparative Example 1 was produced.

For each of the backsheets of Examples 1 to 3 and Comparative Example 1 produced as described above, the water vapor transmission rate, the water vapor transmission rate after bending test (flexibility test), and the reflectance were measured.
These measurements were performed as follows. The measurement results are summarized in Table 1.

<Measurement of water vapor transmission rate>
The amount of water vapor permeating from the fluororesin layer side of the back sheet was measured by A method (moisture sensitive sensor method) of JIS K7129. The measuring apparatus used was “L80-5000” manufactured by LYSSY, under the conditions of a permeation cell temperature of 40 ° C. and a relative humidity difference of 90%.

<Measurement of water vapor permeability after bending resistance test>
The bending resistance test was performed as shown in FIG. A back sheet (size 15 cm × 35 cm) 60 is wound around a stainless steel rod 61 having a diameter of 8 mm and a length of 20 cm so that the surface not provided with the gas barrier layer is in contact therewith. As shown in FIG. 6, the back sheet 60 was reciprocated 500 times (10 reciprocations per minute) using “IMC-15AE”). The moving distance of the back sheet 60 was 20 cm per reciprocation. Further, the bending resistance test was performed in an environment of 23 ° C. and a relative humidity of 50%.
With respect to the back sheet subjected to this bending resistance test, the water vapor transmission rate was measured in the same manner as in the above <Measurement of water vapor transmission rate>.

<Measurement of reflectance>
According to JIS K7105, the reflectance at 300 to 1200 nm was measured at a wavelength interval of 1 nm, and the average value was taken as the reflectance of the protective sheet. As a measuring apparatus, “UV-3600” manufactured by Shimadzu Corporation was used.

From the results of Table 1, the back sheets of Examples 1 and 2 having 30 nm and 60 nm thick silicon nitride thin films as the gas barrier layer are the back of Comparative Example 1 having a gas barrier layer made of silica (SiO ₂ ) having a thickness of 30 nm. It can be seen that the water vapor permeability is lower than half of the sheet, and an excellent water vapor barrier property can be obtained. Furthermore, in the back sheet of Comparative Example 1, the water vapor transmission rate after the bending resistance test was significantly increased, whereas in the back sheets of Examples 1 and 2, the water vapor transmission rate after the bending resistance test was increased. It can be seen that the back sheets of Examples 1 and 2 are excellent in bending resistance. Further, it can be seen that the back sheets of Examples 1 and 2 have a higher reflectance than the back sheet of Comparative Example 1.
Further, the back sheet of Example 3 having a silicon nitride thin film having a thickness of 20 nm as a gas barrier layer had a water vapor permeability equivalent to that of Comparative Example 1. However, the back sheet of Example 3 has less increase in water vapor permeability after the flex resistance test than Comparative Example 1, and the back sheet of Example 3 is superior in flex resistance compared to Comparative Example 1. I understand that. Furthermore, it can be seen that the back sheet of Example 3 has a higher reflectance than the back sheet of Comparative Example 1.
As described above, the backsheets of Examples 1 to 3 have high water vapor barrier properties, and even when the sheets are bent, the water vapor barrier properties are hardly reduced and the film is excellent in bending resistance. It has excellent performance as a back sheet for modules.

  The back sheet of the present invention has a high water vapor barrier property, and even when the sheet is bent, the water vapor barrier property does not decrease and is excellent in bending resistance. Further, since the reflectance can be increased, the back sheet for solar cell modules can be used. Useful as a sheet.

DESCRIPTION OF SYMBOLS 10 ... Surface protection sheet 20 ... Back sheet 20A, 20B, 20C, 20D ... Back sheet 21 ... Base material sheet 22 ... Gas barrier layer 23 ... Fluororesin layer 24 ... Adhesive layer 25 ... Al layer 26 ... Adhesive layer 30 for lamination ... Sealing material 40 ... solar battery cell 50 ... solar battery module

Claims (5)

  A back protective sheet for a solar cell module, wherein a gas barrier layer made of silicon nitride is laminated on at least one surface of a base sheet, and a fluororesin layer is laminated on the other side of the base sheet or the gas barrier layer .   The back protective sheet for a solar cell module according to claim 1, wherein the fluororesin layer contains titanium dioxide.   The back surface protection sheet for solar cell modules according to claim 1 or 2, wherein an adhesive layer made of a heat-adhesive resin is laminated.   The gas barrier layer is formed on the base sheet by a reactive sputtering method in an inert gas atmosphere containing nitrogen gas or in an inert gas atmosphere containing nitrogen gas and oxygen gas. The back surface protection sheet for solar cell modules in any one of Claims 1-3 characterized by these.   The solar cell module by which the back surface protection sheet for solar cell modules of any one of Claims 1-4 is adhere | attached on the back surface.

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