JP2014093423A - Back surface protecting sheet for solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a back surface protecting sheet for a solar cell module that can prevent reduction in power generation efficiency by suppressing increase in temperature of a solar cell module, and keep excellent safety even in long-term use.SOLUTION: A back surface protection sheet 6 for a solar cell module 1 has a thermal diffusion layer 61, a weather-resistant 62 and a heat radiation layer 63 which are laminated on a base material layer 60. The thermal diffusion layer 61 has higher thermal conductivity than the base material layer 60. The weather-resistant layer 62 is formed of resin containing at least one material of hydrolysis resistance polyethylene terephthalate, modified polyphenylene ether and polycarbonate which has a mechanical strength maintenance factor of 50% or more after it is kept for 1000 hours in a durability test under 85°C85%RH condition which conforms to JISC8917, and is laminated between the thermal diffusion layer 61 and the heat radiation layer 63. The heat radiation layer 63 has high thermal emissivity and is laminated as an outermost layer of the back surface protection sheet 6.

Description

  The present invention relates to a back surface protection sheet for a solar cell module.

  In recent years, solar cells as a clean energy source have attracted attention due to the growing awareness of environmental issues. In general, a solar cell module constituting a solar cell has a configuration in which a transparent front substrate, a front sealing material, a solar cell element, a back sealing material, and a back surface protection sheet are laminated in order from the light receiving surface side. It has a function of generating power by entering the solar cell element.

  Solar cell modules are used outdoors for a long period of time. For this reason, each member constituting the solar cell module is required to have durability that can withstand outdoor use in a harsh environment for a long period of time.

  In addition, the solar cell module increases the temperature inside the module due to the reception of sunlight, but the power generation amount of the solar cell element is temperature-dependent, and the power generation amount may decrease due to the temperature increase in the module. There is.

  As a heat countermeasure for suppressing such a temperature rise in the module, a back surface protection provided with a barrier layer having a gas barrier property, a heat radiation layer having a higher heat emissivity than the barrier layer, and a heat diffusion layer made of aluminum or the like. A sheet is disclosed (see Patent Document 1).

JP2012-104637A

  However, according to the back surface protective sheet described in Patent Document 1, consideration is not given to the weather resistance and durability of the heat radiation layer that is disposed in the outermost layer and is exposed to harsh conditions for a long period of time. For example, when a part of the heat radiation layer deteriorates or peels off, the metal film forming the heat diffusion layer is exposed to the outermost layer, and the back surface protection necessary for maintaining the safety of the solar cell module There was a possibility that the insulation of the sheet might be impaired.

  The present invention has been made in view of the situation as described above, and is capable of preventing a decrease in power generation efficiency by sufficiently suppressing the temperature rise of the solar cell module and is excellent in weather resistance. By being, it aims at providing the back surface protection sheet for the modules for solar cells which can maintain the outstanding safety | security in the long-term use on severe conditions, such as outdoors.

As a result of intensive studies to solve the above problems, the inventors of the present invention have developed a weather resistant layer made of a resin having excellent hydrolysis resistance in a back surface protection sheet for a solar cell module, and has a high thermal conductivity and thermal diffusion. It has been found that the above-mentioned problems can be solved by arranging between the layer and the thermal radiation layer having a high thermal emissivity, and the present invention has been completed. More specifically, the present invention provides the following.

  (1) A back surface protection sheet for a solar cell module in which a thermal diffusion layer, a weather resistant layer, and a thermal radiation layer are laminated on a base material layer, and the thermal diffusion layer has a thermal conductivity of 150 W. / (M K) or more, and the weather resistant layer is a hydrolysis resistant polyethylene having a mechanical strength maintenance rate of 50% or more after 2000 hours of durability test under 85 ° C. and 85% RH conditions in accordance with JIS C8917. It is made of a resin containing at least one of terephthalate, modified polyphenylene ether, or polycarbonate, and is laminated between the thermal diffusion layer and the thermal radiation layer, and the thermal radiation layer is far infrared radiation. The back surface protection sheet which consists of resin containing a filler, has a heat emissivity higher than the said weather resistance layer, and is laminated | stacked on the outermost layer of the said back surface protection sheet.

  (2) The back surface protective sheet according to (1), wherein the weather-resistant layer is the hydrolysis-resistant polyethylene terephthalate.

  (3) The back surface protection sheet according to (1) or (2), wherein the heat diffusion layer is an aluminum foil.

  (4) A solar cell module in which the back surface protective sheet according to any one of (1) to (3), a sealing material sheet, and a solar cell element are laminated, A solar cell module in which a heat radiation layer is disposed on one outermost layer of the solar cell module.

  According to the present invention, it is possible to prevent a decrease in power generation efficiency by suppressing an increase in the internal temperature of the solar cell module, and to maintain excellent safety even in long-term use under severe conditions such as outdoors. The back surface protection sheet for solar cells which can be provided can be provided.

It is sectional drawing which shows an example of the laminated constitution of the solar cell module using the back surface protection sheet for solar cell modules of this invention. It is sectional drawing which shows typically the layer structure of the back surface protection sheet for solar cell modules of this invention.

  Hereinafter, the back surface protection sheet for solar cell modules of this invention is demonstrated in detail. The present invention is not limited to the embodiments described below.

<Basic configuration of solar cell module>
First, the structure of the solar cell module in which the back surface protection sheet of this invention is used is demonstrated easily. FIG. 1 is a cross-sectional view showing an example of the layer structure of a solar cell module 1 according to an embodiment of the present invention. As shown in FIG. 1, the solar cell module 1 has a transparent front substrate 2, a front sealing material layer 3, a solar cell element 4, a back sealing material layer 5, and a back surface protection sheet 6 laminated in this order from the light receiving surface side. It is a configuration.

  In the solar cell module having the above-described configuration, it is an essential requirement from the viewpoint of safety that the back surface protection sheet disposed and used in the outermost layer has extremely high weather resistance and insulation. The back surface protection sheet 6 of the present invention sufficiently satisfies this essential requirement, and suppresses an increase in internal temperature when the solar cell module 1 is used outdoors and prevents a decrease in power generation efficiency. It is something that can be done.

<Back protection sheet>
The back surface protection sheet 6 which is one Embodiment of this invention is demonstrated using FIG. The back surface protection sheet 6 is a laminate including a base material layer 60, a heat diffusion layer 61, a weather resistant layer 62, and a heat radiation layer 63. The heat diffusion layer 61 is laminated on one surface of the base material layer 60, and the heat radiation layer 63 is arranged to be the outermost layer when integrated as the solar cell module 1. A weather resistant layer 62 is arranged between the thermal diffusion layer 61 and the thermal radiation layer 63.

[Base material layer]
The base material layer 60 is a resin sheet obtained by molding a resin material into a sheet shape. Examples of the resin sheet used for the base material layer 60 include polyethylene resins, polypropylene resins, cyclic polyolefin resins, polystyrene resins, acrylonitrile-styrene copolymers, acrylonitrile-butadiene-styrene copolymers, polyvinyl chloride resins. Resin, fluorine resin, poly (meth) acrylic resin, polycarbonate resin, polyester resin such as polyethylene terephthalate (PET), polyethylene naphthalate, polyamide resin such as various nylons, polyimide resin, polyamideimide resin Various resins such as polyaryl phthalate resins, silicone resins, polysulfone resins, polyphenylene sulfide resins, polyether sulfone resins, polyurethane resins, acetal resins, and cellulose resins It can be used over door. Among these resin sheets, polyethylene resin, polypropylene resin, polyethylene terephthalate resin, polycarbonate resin, and polyethylene naphthalate are particularly preferably used. Among them, for example, a biaxially stretched polyethylene terephthalate film or sheet is particularly preferable. In this specification, the term “resin sheet” is used as the name of a product obtained by processing these resins into a sheet shape, but this term is used as a concept including a resin film. These may be a single layer, or may be a laminate composed of a plurality of layers laminated with a conventionally known adhesion agent or the like.

  The thickness of the base material layer 60 may be appropriately determined in consideration of the thickness required for the back surface protective sheet 6. Although the range of 30-500 micrometers is given as a general example as thickness of the back surface protection sheet 6, it is not specifically limited. The thickness of the base material layer 60 is not particularly limited, but is preferably 38 to 250 μm. When the thickness of the base material layer 60 is 38 μm or more, preferable durability and weather resistance can be imparted to the back surface protective sheet 6, and when the thickness of the base material layer 60 is 250 μm or less, lamination processing is performed. It is possible to impart film transportability at the time.

  The base material layer 60 may contain other resins other than those described above as long as the effects of the present invention are not impaired. Also, for example, workability, heat resistance, light resistance, weather resistance, mechanical properties, dimensional stability, antioxidant properties, slipperiness, mold release properties, flame retardancy, antifungal properties, electrical properties, etc. Various plastic compounding agents and additives, other resins, and the like can be added for the purpose of improvement and modification. The addition amount of these additives and the like is not particularly limited, and can be arbitrarily added according to the purpose. Common additives include, for example, lubricants, crosslinking agents, antioxidants, UV absorbers, light stabilizers, fillers, lubricants, reinforcing fibers, reinforcing agents, antistatic agents, flame retardants, flame retardants, foaming Agents, fungicides, coloring additives, pigments, modifying resins and the like.

[Heat diffusion layer]
The heat diffusion layer 61 diffuses the heat accumulated in the solar cell module 1 in the horizontal direction mainly along the surface of the back surface protection sheet 6 in this layer, so that the heat diffusion layer 61 has an internal structure. It is a layer having a function of increasing the thermal radiation efficiency of heat, and is a layer made of a material having high thermal conductivity. The thermal conductivity of the thermal diffusion layer 61 is 150 W / (m K) or more.

  Specific examples of the material with high thermal conductivity used for the thermal diffusion layer 61 include metals such as aluminum and copper, and other minerals with high thermal conductivity such as graphite. Among these, aluminum foil or copper foil that is excellent in gas barrier properties as well as thermal conductivity can be preferably used. Among these metal foils, an aluminum foil having a sufficient balance of sufficient thermal conductivity, processability and economy can be particularly preferably used.

  The thickness of the heat diffusion layer 61 may be appropriately determined in consideration of the thickness required for the back surface protection sheet 6 and is not particularly limited. For example, when the heat diffusion layer 61 is an aluminum foil, the thickness thereof is not limited. The thickness is preferably 4 to 100 μm. When the thickness of the aluminum foil is 4 μm or more, it can be rolled as a foil and the thermal diffusibility is good, and when the thickness of the thermal diffusion layer 61 is 100 μm or less, it is excellent in roll processability. Moreover, it can be manufactured at low cost.

[Weatherproof layer]
As the weather resistant layer 62, a resin sheet obtained by molding a resin material that can exhibit sufficient weather resistance and durability in the solar cell module 1 used in a severe environment such as outdoors can be used. Examples of the resin sheet used for the weather resistant layer 62 include a resin sheet containing at least one of hydrolysis-resistant polyethylene terephthalate (hydrolysis-resistant PET), polyphenylene ether (PPE), or polycarbonate (PC). be able to.

  Here, hydrolysis resistant PET shall mean the polyethylene terephthalate which was excellent in hydrolysis resistance of Unexamined-Japanese-Patent No. 2012-62380. The hydrolysis-resistant PET is polyethylene terephthalate containing 2 to 100 ppm of an alkali metal element and 10 to 250 ppm of a phosphorus element, and further polyoxyalkylene with respect to 100 parts by weight of the polyethylene terephthalate resin composition. This resin contains 2 to 20 parts by weight of glycol.

  Hydrolysis-resistant PET is excellent in hydrolysis resistance and also in heat resistance and durability required for a back surface protection sheet for solar cell modules. Moreover, since it is excellent in processability and is relatively inexpensive, it can be used very preferably as a material for forming the weather resistant layer 62 of the back surface protective sheet 6. In addition, the hydrolysis resistance in this invention means that the mechanical strength maintenance rate in the method of an Example is 50% or more after 2000 hours of durability tests on 85 degreeC85% RH conditions based on JISC8917. Means.

  The modified polyphenylene ether is a general term for a synthetic resin polymer alloy belonging to a thermoplastic resin mainly composed of polyphenylene ether (PPE) having an aromatic polyether structure. The thermoplastic resin to be mixed with the polyphenylene ether is not particularly limited, but it is preferable to use a polystyrene resin. Modification by mixing polyphenylene ether and a thermoplastic resin is preferable from the viewpoint of easy production, but may be modification by copolymerizing a phenolic monomer with another monomer.

  Examples of the polyphenylene ether include poly (2,6-dimethylphenylene-1,4-ether), poly (2-methyl-6-ethylphenylene-1,4-ether), and poly (2,6-diethylphenylene). 1,4-ether), poly (2-methyl-6-n-propylphenylene-1,4-ether), poly (2-methyl-6-n-butylphenylene-1,4-ether), poly (2 -Methyl-6-chlorophenylene-1,4-ether), poly (2-methyl-6-bromophenylene-1,4-ether), poly (2-ethyl-6-chlorophenylene-1,4-ether) Etc. These may be used alone or in combination of two or more.

  Polycarbonate is a linear polymer having a carbonate bond in the main chain, and is generally produced from bisphenol A as a raw material. Polycarbonate is excellent in heat resistance, dimensional stability and impact resistance, and has excellent transparency. Further, the glass transition point (Tg) is as high as about 150 ° C., and there is little thermal deformation during heating. However, there is a problem of yellowing due to ultraviolet rays, and it is necessary to take measures to prevent this. However, the back surface protective sheet 6 can solve this problem by providing the heat radiation layer 63 with an ultraviolet blocking effect as described later. Therefore, polycarbonate having excellent heat resistance and the like as described above can be preferably used as the weather resistant layer 62.

  The thickness of the weather resistant layer 62 may be appropriately determined in consideration of the thickness required for the back surface protective sheet 6 and is not particularly limited, but is preferably 30 to 100 μm. When the thickness of the weathering layer 62 is 30 μm or more, weather resistance can be exhibited, and when the thickness of the weathering layer 62 is 100 μm or less, the heat radiation layer can be thermally conducted without delay and can be manufactured at low cost. it can.

  It should be noted that the weather resistant layer 62 can be added with other resins or various plastic compounding agents, additives, and the like within the range that does not impair the effects of the present invention, similarly to the base material layer 60.

[Thermal radiation layer]
The heat radiation layer 63 is formed by laminating a resin sheet obtained by molding a resin material having heat radiation capable of efficiently releasing the internal heat of the solar cell module 1 into a sheet shape, or a resin having such heat radiation. It can be formed by coating the material on the outermost layer of the back protective sheet 6. As such a material used for the heat radiation layer 63, a material in which a far infrared radiation filler is mixed with various binder resins can be used.

  The binder resin is not particularly limited, but is a resin having a hydroxyl group for reacting with a polyisocyanate compound. Specific examples include a crosslinkable substituent-containing acrylic resin, a crosslinkable substituent-containing fluororesin, and a crosslinkable substituent group. A vinyl resin, a crosslinkable substituent-containing olefin resin, or the like can be preferably used. The far-infrared radiation filler includes alumina, silicon oxide, zirconium oxide, titanium oxide, magnesium oxide, calcium fluoride, aluminum nitride, silicon nitride, calcium carbonate, iron oxide, barium sulfate, aluminum powder, mica, barium carbonate. , Talc and the like can be used.

  Among the far infrared radiation fillers, titanium oxide, silicon oxide, aluminum oxide, magnesium oxide, and barium sulfate are preferably used from the viewpoint of heat dissipation.

  The thickness of the heat radiation layer 63 may be appropriately determined in consideration of the thickness required for the back surface protective sheet 6 and is not particularly limited, but is preferably 5 to 100 μm. When the thickness of the heat radiation layer 63 is 5 μm or more, heat dissipation can be expressed, and when the thickness of the heat radiation layer 63 is 100 μm or less, heat conduction is performed without delay to the outermost layer of the heat radiation. Moreover, it can be manufactured at low cost.

  In addition, the resin other than the above or various plastic compounding agents and additives can be added to the heat radiation layer 63 within the range that does not impair the effects of the present invention, similarly to the base material layer 60. .

  The heat radiation layer 63 described above has a heat emissivity higher than that of the weather resistant layer 62. Moreover, it is preferable that the thermal emissivity of the thermal radiation layer 63 is 0.9 or more. By making the thermal emissivity of the thermal radiation layer 63 higher than the thermal emissivity of the weather resistant layer 62, the temperature rise of the solar cell module 1 can be significantly suppressed by the thermal radiation from the thermal radiation layer 63. it can. Moreover, the said thermal radiation can be performed more efficiently by making the thermal emissivity of the thermal radiation layer 63 or more into 0.9, and the temperature rise of the solar cell module 1 can be suppressed in a very preferable aspect.

[Other layers]
The back surface protective sheet 6 may be provided with other layers as long as the effects of the present invention are not impaired. For example, on the surface of the base material layer 60 where the heat diffusion layer 61 is not formed, an adhesion reinforcing layer made of a polyolefin resin such as polyethylene resin or polypropylene resin, polyethylene terephthalate (PET), or the like, if necessary, A primer layer made of a resin mixture containing an adhesion improver such as a coupling agent may be provided.

  Further, the back protective sheet 6 may be provided with a reflective layer using a mixture of rutile type titanium oxide, aluminum oxide, zinc oxide, manganese dioxide, etc. and an acrylic resin. According to this reflective layer, it is possible to reflect the sunlight irradiated to the solar cell module 1 but passing through the solar cell elements 4 and reaching the back surface protective sheet 6 to be directed to the solar cell elements. The power generation efficiency of the module 1 can be improved.

<Production method of back surface protection sheet>
The manufacturing method of the back surface protection sheet of this invention is demonstrated. The back surface protection sheet 6 can be manufactured by sequentially forming the heat diffusion layer 61, the weather resistant layer 62, and the heat radiation layer 63 on one surface of the base material layer 60 so as to be arranged in this order. .

  As the resin sheet for forming the base material layer 60 and the weather resistant layer 62, the resin materials suitable for the respective layers described above are formed by an extrusion method, a cast molding method, a T-die method, a cutting method, an inflation method, and other components. A resin sheet formed by a film forming method or the like can be used.

  For the heat diffusion layer 61, a metal foil such as an aluminum foil can be preferably used.

  The resin sheet forming the base material layer 60 described above, the metal foil forming the heat diffusion layer 61, and the resin sheet forming the weathering layer 62 are laminated and integrated in this order, and further integrated as such. By forming the heat radiation layer 63 on the surface of the weathered layer 62 of the laminated body, the back surface protective sheet 6 of the present invention can be obtained.

  Integration of the resin sheet forming the base layer 60, the metal foil forming the heat diffusion layer 61, and the resin sheet forming the weathering layer 62 can be performed by a conventionally known dry laminating method. A conventionally known laminate adhesive can be used and is not particularly limited. Specifically, a two-component curable dry laminate adhesive composed of a polyurethane-based or epoxy-based main agent and a curing agent can be appropriately used.

  In addition to the far-infrared radiation filler, the heat radiation layer 63 may further contain a resin binder using an acrylic polyol resin as a main ingredient and a polyisocyanate compound as a curing agent. Titanium oxide, aluminum oxide as a colorant or an antiblocking agent, Inorganic fillers such as silicon oxide may be included, and organic fillers such as phthalocyanine and acrylic resin beads may be included. These include hydrocarbon solvents such as toluene and xylene and ketone solvents such as methyl ethyl ketone (MEK). The heat radiation ink which is a mixed coating liquid can be formed, and this can be formed by coating the surface of the weather resistant layer 62 by a conventionally known coating method.

  In addition, the back surface protection sheet of the present invention has improved heat resistance and the like by performing a crosslinking treatment by irradiating a predetermined amount of ionizing radiation to each of the material resin sheets described above or a laminate obtained by laminating them. It may be. The crosslinking step is carried out by ionizing radiation such as electron beam (EB), α-ray, β-ray, γ-ray, neutron beam, etc. Among them, it is preferable to use an electron beam. The acceleration voltage in electron beam irradiation is determined by the thickness of a resin sheet or the like that is an object to be irradiated, and a thicker sheet requires a larger acceleration voltage. For example, a 0.5 mm-thick sheet is irradiated with 100 kV or more, preferably 200 kV or more. The irradiation dose is in the range of 51 to 500 kGy, preferably 80 to 300 kGy.

<Method for manufacturing solar cell module>
The solar cell module 1 is, for example, vacuum suction after sequentially laminating members composed of the transparent front substrate 2, the front sealing material layer 3, the solar cell element 4, the back sealing material layer 5, and the back surface protection sheet 6. Then, the above-mentioned members can be manufactured by thermocompression molding as an integrally molded body by a molding method such as a lamination method. For example, in the case of vacuum heat laminating, the laminating temperature is preferably in the range of 130 ° C to 180 ° C. The laminating time is preferably in the range of 5 to 20 minutes, particularly preferably in the range of 8 to 15 minutes. In this way, the solar cell module 1 can be manufactured by thermocompression-bonding each of the above layers as an integral molded body.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example at all.

<Manufacture of backside protection sheet>
The back surface protection sheet of an Example and a comparative example was manufactured by the following method using the following material.

Example 1
As a weather-resistant layer, a 50 μm-thick hydrolysis-resistant polyethylene terephthalate film (hydrolysis-resistant PET, manufactured by Toray Industries, Inc .: X10-S) was used, and a polyurethane adhesive with a solid content of 30% by weight was applied on one side thereof. A laminated body (hereinafter referred to as “laminated body a”) obtained by applying an aluminum foil having a thickness of 20 μm as a thermal diffusion layer was applied so that the coating amount in a dry state was 5.0 g / m ^2. Obtained.
As a base material layer, a polyethylene terephthalate film (PET, manufactured by Teijin DuPont Films Co., Ltd .: Melinex S) having a thickness of 250 μm is used, and the same amount of polyurethane adhesive as described above is applied on one side thereof in a dry state of 5 0.0 g / m ^2, and the laminate a was laminated with the aluminum foil surface facing the base layer (hereinafter referred to as “laminate b”). In order to cure, curing was performed at 56 ° C. for 5 days.
Further, after the corona treatment is applied to the surface of the weather resistant layer side of the laminate b, a thermal radiation ink having a thermal emissivity of 0.95 at a wavelength of 4 to 15 μm containing titanium oxide, aluminum oxide, and silicon oxide is obtained. It apply | coated so that it might become a dry film thickness of 15 micrometers, and the heat radiation layer was formed by making it dry at 80 degreeC and 20 minutes, and obtained the back surface protection sheet of the Example.

(Example 2)
The back surface protective sheet manufactured by the same material, configuration, and manufacturing method as in Example 1 was used as the back surface protective sheet of Example 2 except that the thickness of the aluminum foil used as the heat diffusion layer was 7 μm.

(Example 3)
The back surface protective sheet manufactured by the same material, configuration, and manufacturing method as in Example 1 was used as the back surface protective sheet of Example 3 except that the thickness of the aluminum foil used as the heat diffusion layer was 50 μm.

(Example 4)
The back surface protection sheet manufactured by the same material, composition, and manufacturing method as Example 1 is implemented except that the weather-resistant layer is a polyethylene terephthalate film (PET, manufactured by Teijin DuPont Films Co., Ltd .: EP) having a thickness of 50 μm. The back protective sheet of Example 4 was obtained.

(Comparative Example 1)
The laminated body b subjected to the curing was directly used as a back surface protective sheet of Comparative Example 1 without forming the heat radiation layer.

(Comparative Example 2)
After a laminate (weatherproof layer not formed) in which only the same aluminum foil as described above was bonded to the base material layer by the same method as described above was cured in the same manner as described above, the laminate was then formed on the aluminum foil of the laminate. The same heat radiation layer as described above was formed to provide a back surface protective sheet of Comparative Example 2.

(Comparative Example 3)
A backside protective sheet manufactured by the same material, configuration, and manufacturing method as in Example 1 except that the weatherproof layer was a polyethylene terephthalate film (PET, manufactured by Toray Industries, Inc .: Lumirror S10) having a thickness of 50 μm was a comparative example. No. 3 back protective sheet.

(Comparative Example 4)
Manufactured by the same material, configuration and production method as in Example 1 except that the weathering layer was a tetrafluoroethylene / ethylene copolymer film (ETFE, manufactured by Asahi Glass Co., Ltd .: 25 PW) having a thickness of 50 μm. The back surface protective sheet was used as the back surface protective sheet of Comparative Example 4.

<Manufacture of solar cell modules>
180mm □ white plate semi-tempered glass (manufactured by AGC Fabricec Co., Ltd .: 3KWE33), front sealing material sheet, 5 inch single crystal solar cell element connected by wiring, tape-type temperature sensor (manufactured by Anritsu Keiki Co., Ltd .: ST- 14K-060-GW1-ANP), the back surface sealing material sheet, and the back surface protection sheet of the above example or each comparative example, and each of the above sealing material sheets while heating under reduced pressure using a vacuum laminator. Crosslinking and fusion integration were performed, and solar cell module samples for evaluation of examples and comparative examples were produced.

<Evaluation of heat dissipation of back protection sheet>
[Heat dissipation test]
About the back surface protection sheet of an Example and a comparative example, heat dissipation was evaluated based on JISC8912. A SUS mask that irradiates pseudo-sunlight with an illuminance of 100 mW / cm ² equivalent to AM1.5G with a solar simulator (manufactured by Mitsunaga Electric Co., Ltd .: XES-155S1) and defines an effective area as 11 cm □, The back surface protective sheet of the comparative example was placed on the light receiving part side of the solar cell module sample for evaluation, and the cell temperature and photoelectric conversion efficiency were measured over time for 90 minutes at 1 minute intervals. The cell temperature and photoelectric conversion efficiency in each sample were evaluated according to the following criteria. About a result, it shows in following Table 1 as "heat dissipation."
A: 3 ° C or higher B: 1 ° C or higher C: Less than 1 ° C

<Evaluation of adhesion of backside protection sheet>
[Adhesion test]
About the back surface protection sheet of the Example produced as mentioned above and a comparative example, the adhesive test according to ASTM D3359 was done, and the adhesiveness between a heat radiation layer and a weather-resistant layer was evaluated on the following references | standards. The results are shown in Table 1 below as “adhesiveness”.
A: Less than 15% coating peeling C: 15% or more coating peeling

[Wet heat durability (dump heat) test of weather-resistant layer]
For the weathering layers of the above examples and comparative examples, the mechanical strength maintenance ratio (breaking strength from the initial value by Tensilon) after conducting a durability test under the conditions of 85 ° C. temperature and 85% humidity in accordance with JIS C8917 The test time at which the maintenance ratio was 50% or more was investigated. Here, the distance between chucks was 80 mm, the test piece width was 10 mm, and the tensile speed was 100 mm / min. The results are shown in Table 1 below as “durability”.
A: 3000 hours or more B: 2000 hours or more C: Less than 2000 hours

<Insulation evaluation of back surface protection sheet>
[Surface resistivity]
In accordance with JIS-K6911, a constant voltage of 1000 V was applied to the outermost surface of the back surface protective sheet of the above examples and comparative examples using a resistivity meter (manufactured by Mitsubishi Chemical Analytech Co., Ltd .: Hiresta UP MCP-HT450 type). The surface resistivity was measured. Here, the outermost surface is the hydrolysis resistant PET in Comparative Example 1 and the heat radiation layer in the other cases. The results are shown in Table 1 as “surface resistivity”.
A: 10 ^ 13Ω / □ or more C: Less than 10 ^ 13Ω / □

  From Table 1, the back surface protection sheet of this invention is excellent in heat dissipation, adhesiveness, durability, and insulation, and gives preferable power generation efficiency and weather resistance to the back surface protection sheet for solar cell modules. It can be seen that

DESCRIPTION OF SYMBOLS 1 Solar cell module 2 Transparent front substrate 3 Front sealing material layer 4 Solar cell element 5 Back sealing material layer 6 Back surface protection sheet 60 Base material layer 61 Thermal diffusion layer 62 Weather resistance layer 63 Thermal radiation layer

Claims (4)

A back surface protection sheet for a solar cell module in which a heat diffusion layer, a weather resistant layer, and a heat radiation layer are laminated on a base material layer,
The thermal diffusion layer has a thermal conductivity of 150 W / (m K) or more,
The weather-resistant layer is a hydrolysis-resistant polyethylene terephthalate, modified polyphenylene ether, or polycarbonate having a mechanical strength maintenance rate of 50% or more after 2000 hours of durability test under 85 ° C. and 85% RH conditions according to JIS C8917. Are made of a resin containing at least one of them, and are laminated between the thermal diffusion layer and the thermal radiation layer,
The said heat radiation layer consists of resin containing a far-infrared radiation filler, and has a heat emissivity higher than the said weathering layer, The back surface protection sheet laminated | stacked on the outermost layer of the said back surface protection sheet.   The back surface protection sheet according to claim 1, wherein the weather resistant layer is the hydrolysis resistant polyethylene terephthalate.   The back surface protection sheet according to claim 1 or 2, wherein the heat diffusion layer is an aluminum foil. The back surface protection sheet according to any one of claims 1 to 3,
An encapsulant sheet;
A solar cell module in which a solar cell element is laminated,
The solar cell module in which the heat radiation layer of the back surface protection sheet is disposed in one outermost layer of the solar cell module.

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