JP6135060B2 - Back protection sheet for solar cell module - Google Patents

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 electricity by being incident on the solar cell element.

  For further widespread use of solar cells, further improvement in the power generation rate of solar cell modules is strongly demanded. In order to improve the power generation efficiency, out of the incident light to the solar cell module, the light passing through the periphery of the solar cell element or the gap between the elements without contributing to power generation is made light reflective. It is conceivable that the light is reflected by the back surface protective sheet and is directed again to the solar cell element to contribute to power generation. As such a back surface protection sheet having light reflectivity, a back surface protection sheet in which a white resin film, a resin film coated with a metal oxide, and a hydrolysis resistant resin film are sequentially laminated has been proposed (Patent Document). 1).

  The back surface protection sheet described in Patent Document 1 reflects the passing light by the white resin film. However, in the white resin film, part of the passing light is absorbed and the reflectance is insufficient. Further, in order to direct more passing light toward the surface of the solar cell element, it is effective to increase the diffuse reflectance of the back surface protection sheet. However, in the back surface protection sheet described in Patent Document 1, No consideration is given to increasing the diffuse reflection by reducing the reflection.

  As a back surface protection sheet that can further improve the power generation efficiency of the solar cell module, it is equipped with a light-transmitting layer made of transparent resin and a light reflecting layer made of a metal vapor-deposited film, etc. Document 2), or a back surface protection sheet that has a light-transmitting layer specially processed to form a prism layer (Patent Document 3) has improved the reflectance and diffuse reflectance of transmitted light.

Japanese Patent Laid-Open No. 2002-100788 JP 2006-319250 A JP 2011-129850 A

  However, the back surface protection sheet described in Patent Document 2 requires special light diffusing means such as fine beads and a microlens array. And those coatings require extremely high coating techniques.

  The back surface protection sheet described in Patent Document 3 is also a layer in which a prism layer having a special structure that cannot contribute to the weather resistance and substrate adhesion required for the back surface protection sheet is separately manufactured and additionally laminated It is.

  As described above, the back surface protection sheet having a simple configuration similar to that of a conventional product using only a white resin is insufficient in improving the power generation efficiency. On the other hand, the power generation efficiency is increased by adding special components. All of these have the problem of increasing manufacturing costs.

  The present invention has been made to solve the above-described problems, and its object is to reduce the cost by realizing a back surface protection sheet that can contribute to an improvement in power generation efficiency of a solar cell module with a simple structure. There is to provide in.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, while having the same configuration as the conventional back protection sheet for solar cell modules having a light reflectivity, the white pigment is contained in the adhesive layer or the primer layer instead of the resin layer or the like. As a result, the present inventors have found that the above problems can be solved, and have completed the present invention. More specifically, the present invention provides the following.

  (1) A back surface side resin layer, a metal foil layer or a metal vapor deposition layer, an intermediate resin layer, and a primer layer are sequentially laminated, and the metal foil layer and the intermediate resin layer are light receiving surface side adhesives. The back surface protection sheet for solar cell modules which is laminated | stacked through the layer and contains the white pigment in the said light-receiving surface side adhesive bond layer or the said primer layer.

  (2) The back surface protection sheet according to (1), wherein the metal foil layer or the metal vapor deposition layer is an aluminum foil layer.

(3) The coating amount of the light-receiving surface side adhesive layer is 2.0 g / m ² or more and 20 g / m ² or less in terms of solid content, or the coating amount of the primer layer is 0.1 g in terms of solid content. / M ² or more and 20 g / m ² or less, and the content of the white pigment in the light-receiving surface side adhesive layer or the primer layer is 0.1 to 5.0 in terms of PV ratio, (1) or The back surface protection sheet according to (2).

  (4) The back surface protective sheet according to any one of (1) to (3), wherein the white pigment is titanium oxide having an average particle size of 0.1 μm to 1.0 μm.

  (5) The back surface protective sheet according to any one of (1) to (4), wherein the diffuse reflectance at a wavelength of 750 to 1500 nm when irradiated with light from the primer layer side is 50% or more.

  (6) The back surface protection sheet in any one of (1) to (5) whose light transmittance in wavelength 750 or more and 1500 nm or less of the said intermediate | middle resin layer is 60% or more.

  According to the present invention, the layer to which the white pigment is added is limited to the adhesive layer and the primer layer while maintaining the basic configuration of the conventional back surface protection sheet having light reflectivity, so that only a minimum additional cost is required. And it can be set as the back surface protection sheet which can improve the power generation efficiency of a solar cell module greatly.

It is a schematic diagram of the cross section which illustrates an example of the laminated constitution of the solar cell module using the back surface protection sheet of this invention. It is the partial expansion schematic diagram of the cross section of the solar cell module using the back surface protection sheet of this invention. It is a schematic diagram of the cross section which illustrates an example of the laminated constitution of the back surface protection sheet of this invention. It is a figure which shows the diffuse reflectance (%) of the light with a wavelength of 250 nm to 2600 nm of the back surface protection sheet of an Example, a comparative example, and a reference example. Of the base materials constituting the back surface protective sheets of Examples, Comparative Examples, and Reference Examples, the diffuse reflectance (%) of light having a wavelength of 250 nm to 2600 nm of a laminate composed of a base material other than the metal foil layer or the metal vapor deposition layer. FIG. It is a figure which shows the light transmittance (%) of the laminated body which consists of base materials other than a metal foil layer or a metal vapor deposition layer among the base materials which comprise the back surface protection sheet of an Example, a comparative example, and a reference example. It is a figure which shows the light transmittance (%) of the transparent resin film used as an intermediate resin layer among the base materials which comprise the back surface protection sheet of an Example and a comparative example.

  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 basic structure of the solar cell module using the back surface protection sheet for the solar cell module of the present invention will be described. FIG. 1 is a schematic cross-sectional view showing an example of the layer structure of a solar cell module. As shown in FIG. 1, the solar cell module 1 includes 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 according to the present invention from the light receiving surface side of incident light 7. In this configuration, the sheets 6 are sequentially stacked. These layers are laminated one after another, and then, by using a normal molding method such as a lamination method in which the layers are integrated by vacuum suction or the like and thermocompression-bonded, the above-mentioned layers are thermocompression-molded as an integral molded body, and a solar cell module is obtained. 1 can be manufactured.

  Here, the solar cell element generally has a high spectral sensitivity with respect to light of 300 nm to 1500 nm. More specifically, the amorphous silicon type solar cell element is 300 nm to 1500 nm, the crystalline silicon type solar cell element is 300 nm to 1200 nm, the CdTe type solar cell element is 400 nm to 900 nm, and the CIS type solar cell. The element has a spectral sensitivity to light of 300 nm to 1500 nm, and the GaAs solar cell element has a spectral sensitivity to light of 300 nm to 900 nm.

  FIG. 2 is a schematic diagram showing a part of the cross section of the solar cell module 1 in an enlarged manner. As shown in FIG. 2, in the solar cell module 1 provided with the back surface protection sheet 6, the incident light is used for power generation. The passing light 7 </ b> A that reaches the back surface protection sheet 6 without contributing can be reflected by the back surface protection sheet 6 and reach the light receiving surface of the solar cell element 4. The back surface protective sheet 6 increases the diffuse reflectance of light at a wavelength of 750 or more and 1500 nm or less to a preferable range while maintaining the weather resistance and durability essential for the back surface protection sheet. Therefore, the back surface protection sheet 6 can be preferably used from the viewpoint of improving the weather resistance and durability of the solar cell module, and can contribute to the improvement of the power generation efficiency of the solar cell module.

  Here, the diffuse reflectance of the back surface protective sheet in the present specification is a value measured with a spectrophotometer (manufactured by Shimadzu Corporation, UV-3100), and is a white plate obtained by solidifying a fine powder of barium sulfate. The relative value of the diffuse reflectance with a diffuse reflectance of 100% shall be said.

<Back protection sheet>
As shown in FIG. 3, the back surface protection sheet 6 has a non-light-receiving surface side adhesive layer 62 on the back-side resin layer 61 and the back-side resin layer 61 from the outermost layer side which is a non-light-receiving surface in the solar cell module 1. And a metal foil layer 63 laminated on the metal foil layer 63, an intermediate resin layer 65 laminated on the metal foil layer 63 via a light-receiving surface side adhesive layer 64, and a primer layer 66 are sequentially laminated. The metal foil layer 63 may be a metal vapor deposition layer. In that case, the non-light-receiving surface side adhesive layer 62 and the light-receiving surface side adhesive layer 64 are not essential constituent elements.

  Here, in general, the metal reflection layer reflects light rays with high reflectivity. Therefore, the back surface protection sheet 6 can improve the power generation efficiency to some extent also by the arrangement of the metal foil layer 63 or the metal vapor deposition layer (these two layers are also referred to as “metal reflective layer” hereinafter). .

  However, since the metal reflection layer totally reflects the passing light 7A, the diffuse reflectance of the metal reflection layer itself is not sufficient for improving the power generation efficiency required for the solar cell module. For example, when the metal reflective layer is an aluminum foil, the diffuse reflectance with respect to light having a wavelength of 500 nm or more and 2000 nm or less is only 30% to 45%.

  Therefore, in the back surface protective sheet 6, the white pigment is contained in either the light receiving surface side adhesive layer 64 or the primer layer 66, or both of them, so that the layer containing the white pigment has high light transmission. And a layer capable of exhibiting an appropriate light diffusion function. Accordingly, the passing light 7A can be efficiently refracted and diffused while minimizing the attenuation thereof. In the present specification, either the light-receiving surface side adhesive layer 64 or the primer layer 66, or both of them have the above-described light transmittance and light diffusion function by making them a white layer. In the case of an enhanced layer, the white layer is also referred to as a “white light diffusion layer”.

  The white light diffusion layer preferably has a high light transmittance. If the light transmittance of the white light diffusing layer is low, the effect of the diffuse reflectance of either the light receiving surface side adhesive layer 64 and / or the primer layer 66 can be obtained, but the effect of light reflection by the metal foil is obtained. Is not preferred because it cannot be obtained.

  For example, in the case of a so-called mirror surface with high smoothness of the metal foil layer 63 itself, light reflection is high but light linearity is strong and diffuse reflectance is low. Even if the light is reflected, it is difficult to receive light on the surface of the cell. Therefore, it can be considered that the metal foil layer 63 itself has a so-called mat surface with poor smoothness.

  However, in the case of a so-called mat surface where the smoothness of the metal foil layer 63 itself is poor, the diffuse reflectance is increased, but the intermediate resin layer 65, which is essential for high insulation, diffuses light due to unevenness on the surface of the metal foil. As a result, the diffuse reflectance is eventually lowered.

  The back surface protective sheet 6 is a sheet in which the light receiving surface side adhesive layer 64 or the primer layer 66, which is a very thin thin film layer, is a white layer to optimize light transmittance and light refraction. Therefore, due to the effects of these white light diffusion layers, even if the metal foil layer 63 is in any of the above embodiments, the diffuse reflectance is sufficiently high, and the power generation efficiency of the solar cell module is improved. Can contribute.

  Hereinafter, the details of each layer constituting the back surface protective sheet 6 will be described. However, the metal foil layer (metal vapor deposition layer) and the light receiving surface which are the constituent requirements contributing to the improvement of the diffuse reflectance which is the main function and effect of the present invention. The side adhesive layer, the intermediate resin layer, and the primer layer will be described in order, and then the other layers will be described.

[Metal foil layer]
The metal foil layer 63 is a metal reflection layer that is arranged as a reflection layer that uses metal foil as a material and reflects the passing light 7A. The metal foil layer 63 is bonded to the back surface side resin layer 61 disposed on the non-light-receiving surface side through the non-light-receiving surface side adhesive layer 62, and also on the light-receiving surface side through the light-receiving surface side adhesive layer 64. The intermediate resin layer 65 is bonded.

  The metal foil layer 63 is a layer arranged to reflect the passing light 7A as a metal reflection layer, and at the same time has high durability and prevents moisture, oxygen, etc. from entering the solar cell module 1. Since it is also excellent in preventing moisture, the long-term weather resistance of the solar cell module 1 is also improved.

  The material of the metal foil layer 63 is aluminum foil, titanium foil, stainless steel foil, nickel foil, Kovar foil, nichrome foil, copper foil, beryllium copper foil, tin foil, lead foil, zinc foil, iron foil, tantalum foil, niobium foil, A metal foil such as a zirconium foil, a gold foil, a silver foil, a platinum foil, or a palladium foil can be used, and an economically inexpensive aluminum foil can be preferably used. Examples of the material of the aluminum foil include aluminum or an aluminum alloy, and an aluminum-iron alloy (soft material) can be preferably used. Moreover, when using aluminum foil, it is preferable that the thickness shall be about 7 micrometers-40 micrometers. If the thickness is less than 7 μm, it is not preferable because it may cause inconveniences such as generation of wrinkles at the time of lamination. On the other hand, if it exceeds 40 μm, the reflection performance and moisture resistance are not improved and the cost is increased. .

  About the surface shape of the metal foil layer 63, what is necessary is just a smooth or substantially smooth plane, and special shape processing is not required with respect to the surface. By arranging such a smooth metal foil surface as a reflective layer, the reflectance of light rays, especially the reflectance of near-infrared light having a wavelength of 750 nm to 1500 nm, is significantly higher than that of a back protective sheet having a conventional white resin layer as a reflective layer. Can be improved. In addition, on the surface of such a smooth metal foil layer 63, almost all of the passing light 7A is specularly reflected. However, the back surface protection sheet 6 causes the light receiving surface side adhesive layer 64, the primer layer 66, or the like to emit white light. By providing as a diffusion layer, the surface of the metal foil layer 63 has a sufficiently high diffuse reflectance even without special shape processing.

  As long as the light reflectance of the metal foil layer 63 can be maintained to a necessary level, the metal foil layer 63 may be subjected to other conventionally known surface treatments. For example, surface treatment such as chromate treatment, phosphate treatment, and lubricating resin coating treatment may be performed from the viewpoint of preventing dissolution and corrosion, and coupling treatment and the like are performed from the viewpoint of promoting adhesion. May be.

[Metal deposition layer]
In the back surface protection sheet 6, instead of the metal foil layer 63 serving as the metal reflection layer as described above, a metal vapor deposition layer having the same surface shape and reflection performance may be formed as the metal reflection layer. The metal vapor-deposited layer is a metal reflective layer formed by forming a metal vapor-deposited film on the back surface side resin layer 61, and exhibits the same effects as the metal foil layer 63 in the back surface protective sheet 6.

  The method for forming the metal vapor deposition film on the back surface side resin layer 61 is not particularly limited, and a known vapor deposition method can be used. Such deposition methods include physical vapor deposition methods such as vacuum deposition methods, sputtering methods, ion plating methods, and ion cluster beam methods, and chemical methods such as plasma chemical vapor deposition methods, thermal chemical vapor deposition methods, and photochemical vapor deposition methods. The vapor phase growth method is mentioned.

  As the metal vapor-deposited layer, a metal that is easily vapor-deposited and exhibits light reflection performance is used. As such a metal, for example, gold, silver, copper, nickel, platinum, zinc, chromium, and aluminum are preferable.

  Although the thickness of a metal vapor deposition layer is not specifically limited, It is preferable that they are 5 nm or more and 1000 nm or less, and it is more preferable that they are 20 nm or more and 70 nm or less. When the thickness of the metal deposition layer is 5 nm or more, sufficient light reflectivity can be imparted, and when the thickness of the metal deposition layer is 1000 nm or less, the metal deposition layer itself is cracked or cracked. Can be suppressed.

[Light-receiving surface side adhesive layer]
The light receiving surface side adhesive layer 64 is a layer that adheres the intermediate resin layer 65 onto the surface of the metal foil layer 63, and the surface of the metal foil layer 63 on the light receiving surface side or the intermediate resin layer 65 facing the surface. The adhesive applied to the surface on the lower surface side is formed by curing after the metal foil layer 63 and the intermediate resin layer 65 are laminated.

  When the light-receiving surface side adhesive layer 64 is a white light diffusion layer, the diffuse reflectance of the back surface protective sheet 6 is obtained by efficiently refracting and diffusing the passing light 7A in the light-receiving surface side adhesive layer 64. Can be increased.

  As an adhesive for forming the light-receiving surface side adhesive layer 64, an adhesive capable of adhering the following metal foil for forming the metal foil layer 63 and a resin sheet or the like for forming the intermediate resin layer 65 is appropriately used. Can do. Specifically, the adhesive exemplified below can be preferably used as an adhesive for forming the light receiving surface side adhesive layer 64. However, when the light receiving surface side adhesive layer 64 is a white light diffusion layer, a white adhesive described later is used.

  Specific examples of the adhesive for forming the light receiving surface side adhesive layer 64 are as follows. An adhesive mainly composed of a curing agent comprising a main component containing a polyester diol compound, a polycarbonate diol compound, or a polyurethane diol compound and a polyisocyanate compound can be preferably used, but is not limited thereto. Specific examples include polyvinyl acetate adhesives, homopolymers such as ethyl acrylate, butyl, and 2-ethylhexyl esters, or copolymers of these with methyl methacrylate, acrylonitrile, styrene, and the like. Polyacrylate adhesives, cyanoacrylate adhesives, ethylene copolymer adhesives composed of copolymers of ethylene and monomers such as vinyl acetate, ethyl acrylate, acrylic acid, methacrylic acid, polyethylene resins, or Is a polyolefin adhesive made of polypropylene resin, cellulose adhesive, polyester adhesive, polyamide adhesive, polyimide adhesive, amino resin adhesive made of urea resin or melamine resin, phenol resin adhesive, etc. Agent, epoxy adhesive, polyurethane adhesive, reactive type ( E) Acrylic adhesives, chloroprene rubber, nitrile rubber, styrene-butadiene rubber, styrene-isoprene rubber, etc., rubber adhesives, silicone adhesives, alkali metal silicates, low melting point glass, etc. An adhesive such as an adhesive or the like (a resin similar to a durable adhesive) can be used.

  In the case of an adhesive containing a polyurethane diol compound as a main component and a polyisocyanate compound as a curing agent component, the blending ratio thereof is (an isocyanate group derived from a polyisocyanate compound) / (a hydroxyl group derived from a polyurethane diol compound). The ratio is preferably in the range of 1.0 to 3.5, and more preferably in the range of 1.2 to 3.0. When the blending ratio is in the above range, the respective base materials constituting the back surface protective sheet 6 can be firmly bonded.

  In addition to the main ingredient component, the main ingredient can be mixed with a tackifier, a stabilizer, a filler, a plasticizer, a softening point improver, a catalyst, and the like as additives. Examples of tackifiers include rosin resins and terpene resins. Examples of the stabilizer include an antioxidant and an ultraviolet ray inhibitor. Examples of the filler include inorganic fillers.

  In addition to the above, the adhesive may be mixed with silane coupling agents, tackifiers, stabilizers, fillers, plasticizers, softening point improvers, catalysts, and the like as necessary. Examples of the silane coupling agent include silane monomers such as methyltrimethoxysilane and methyltriethoxysilane, vinylsilanes such as vinyltriethoxysilane and vinyltrimethoxysilane, 3-methacryloxypropylethoxysilane, and 3-methacryloxypropylmethoxy. Mention may be made of epoxysilanes such as methacrylic silanes such as silane, 3-glycidoxypropyltrimethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane. Examples of tackifiers include rosin resins and terpene resins. Examples of the stabilizer include an antioxidant and an ultraviolet ray inhibitor. Examples of the filler include inorganic fillers.

  In addition, the addition amount of the silane coupling agent is preferably 1 to 3% by mass of the silane coupling agent with respect to 100 parts by mass in total of the main agent and the curing agent of the adhesive. When the amount is 1% by mass or more, the adhesion is good, and when it is 3% by mass or less, the durability is improved.

  As said adhesive composition, in order to acquire favorable applicability | paintability and handling appropriateness, it is preferable to add a solvent component. Examples of such a solvent component include, but are not limited to, carboxylic acid esters such as ethyl acetate, methyl acetate, and methyl propionate. As described above, the adhesive is configured as a two-component agent consisting of a main agent and a curing agent, but the solvent component used in the main agent and the solvent component used in the curing agent are each independently selected and may be the same. May be different.

  The adhesive composition for adjusting the above-mentioned adhesive may be in the form of any composition such as an aqueous type, a solution type, an emulsion type, and a dispersion type. Further, regarding the adhesion mechanism, a chemical reaction type, a solvent volatile type Any form such as a hot melt type and a hot pressure type may be used.

  The above-mentioned adhesive is, for example, a resin sheet or metal foil layer 63 that forms the back-side resin layer 61 by a coating method such as a roll coating method, a gravure roll coating method, a kiss coating method, or the like, or a printing method. It can apply | coat on each surfaces, such as the following aluminum foil to form.

(White adhesive)
When the light receiving surface side adhesive layer 64 is a white light diffusion layer, a white adhesive described below is used. As the white adhesive, an adhesive obtained by adding a white pigment to the adhesive exemplified above can be used. The white adhesive is preferably an adhesive having a property of transmitting light having a wavelength of 750 nm to 1500 nm well in a cured state. The phrase “transmits light having a wavelength of 750 nm to 1500 nm well” means that the light receiving surface side adhesive layer 64 transmits light having a wavelength of 750 nm to 1500 nm by 20% or more, preferably 30% or more, and more preferably 40 It means that more than% is transmitted.

  The content of the white pigment in the white adhesive is preferably in the range of 0.1 to 5 in terms of PV ratio, which is the mass of the white pigment / the mass of the main agent. When the PV ratio is in the above range, it is possible to form an adhesive layer that sufficiently transmits near-infrared light having a wavelength of 750 nm to 1500 nm and efficiently refracts and diffuses it. When the PV ratio is lower than the above range, the refractive index of light is low and diffuse reflection is not improved. When the PV ratio is higher than the above range, the viscosity of the ink is increased and a uniform coating film is formed when coating is performed. In addition, the adhesion between the metal foil layer 63 and the intermediate resin layer 65 is reduced, and in particular, the adhesion after the hydrolysis resistance test is reduced.

(White pigment)
White pigments added to the white adhesive include titanium oxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc and other inorganic colorants, crosslinked polystyrene resin, crosslinked acrylic resin, urea resin, melamine Organic colorants such as resins can be used.

  As the white pigment, a white pigment having an average particle diameter of 0.1 to 1.0 μm can be preferably used. The average particle size of the white pigment is more preferably 0.2 or more and 0.4 μm μm or less. If the average particle diameter of the white pigment is within the above range, the white layer can transmit near infrared light having a wavelength of 750 nm to 1500 nm well, refract it efficiently, and improve the diffuse reflectance. A typical example of a white pigment having an average particle size of 0.2 μm or more and 0.4 μm or less is titanium oxide. In the present invention, titanium oxide can be particularly preferably used as the white pigment. In the present specification, hereinafter, the particle size of the pigment refers to the average particle size of the pigment unless otherwise specified.

  Regarding the value of the particle size, after taking a photograph of the primary particle size of the white pigment using a transmission electron microscope (JEM-1230) manufactured by JEOL Ltd., the image is analyzed by the image analysis type particle size distribution manufactured by Mountec. A value obtained by performing statistical processing and calculating with software (MAC-View Ver. 3) is adopted. In calculating the particle diameter, a volume-based equivalent circle diameter is adopted.

  In the white adhesive according to the present invention, a white pigment such as titanium oxide having a particle size of 0.1 to 1.0 μm is preferable, and a white pigment such as titanium oxide having a particle size of 0.2 to 0.4 μm is particularly preferable. It can be preferably used. This is because the light transmittance of the white light-receiving surface side adhesive layer 64 can be set within a preferable range, and thus the diffuse reflectance of the back surface protective sheet 6 can be improved. The preferable light transmittance means a function having a light transmittance of 20% or more, preferably 30% or more, and more preferably 40% or more in a wavelength region of about 750 nm to 1500 nm, for example.

The white light-receiving surface side adhesive layer 64 can be formed by applying or laminating the white adhesive described above on the upper surface of the metal foil layer 63 and / or the lower surface of the intermediate resin layer 65 and drying and curing it. As a coating method, it can be applied by a method similar to the adhesive used for the non-light-receiving surface side adhesive layer 62, that is, a coating method such as a gravure roll coating method, or other printing methods. The coating amount is 2.0 g / m ² or more and 20.0 g / m ² or less in terms of solid content, and the coating amount of the white light-receiving surface side adhesive layer 64 is 2.0 g / m ² or more and 20.0 g / m. It is preferable that it is ² or less. If the coating amount and thickness are within this range, the coating amount and thickness may be appropriately changed according to the adhesive strength necessary for the solar cell module sheet laminated member, and the coating amount and thickness are within this range. The near infrared ray having a wavelength of 750 nm to 1500 nm can be sufficiently transmitted, and the near infrared ray can be efficiently refracted and diffused.

  In addition, as long as the content of the white pigment in the white adhesive, the particle diameter, and the coating amount of the white adhesive are within the above ranges, the light receiving surface side adhesive layer is the same as when the light receiving surface side adhesive layer 64 is not colored. 64 can be provided with preferable adhesiveness.

[Intermediate resin layer]
The material constituting the intermediate resin layer 65 is preferably a resin having excellent strength and weather resistance, heat resistance, water resistance, light resistance, and electrical insulation, and particularly has optical transparency and uniformity. Those are preferred. For example, polycarbonate resin, (meth) acrylic resin, cyclic olefin resin, styrene resin, polyester resin, fluorine resin, polyolefin resin, cellulose resin, polyvinyl chloride resin, epoxy resin, polyurethane resin and the like can be mentioned. To these resins, an ultraviolet absorber, a light stabilizer, an antioxidant and the like may be added for the purpose of increasing the weather resistance. In particular, a polyethylene terephthalate resin to which no pigment or the like is added is preferably used, and there are transparent and milky white ones. Milky white has a light transmittance of about 60% to 75% at a wavelength of 750 nm.

  In order to maximize the diffuse reflectance of the back surface protective sheet 6, the intermediate resin layer 65 preferably has a high light transmittance. Specifically, the light transmittance at a wavelength of 750 nm to 2600 nm is preferably 60% or more. By making the light transmittance of the intermediate resin layer 65 within this range, the high light reflectance of the metal foil layer 63 and the light diffusion function of the light receiving surface side adhesive layer 64 and the primer layer 66 are effectively improved. Can be tied to

[Primer layer]
The primer layer 66 is a thin film layer for the purpose of improving adhesiveness with the back sealing material layer 5 formed on the light receiving surface side surface of the intermediate resin layer 65.

  The primer layer 66 may be a thin film layer that can improve the adhesion of the surface of the intermediate resin layer 65 to the back sealing material layer 5 and is not particularly limited, but is a thin film resin formed as a cross-linked resin of a polyisocyanate compound. The layer can be raised as a preferred example. Such a primer layer is composed of a primer / coating liquid composed of a mixture containing a crosslinkable main resin, a curing agent such as a polyisocyanate compound, and other additives such as an adhesion improving component added as necessary. It can be formed by applying to the surface of the intermediate resin layer 65 and forming a film of the applied primer / coating liquid.

(Primer coating solution)
The crosslinkable main resin used in the primer / coating liquid is not particularly limited, and for example, a crosslinkable substituent-containing acrylic resin or a crosslinkable substituent-containing urethane resin can be preferably used. In the case where the cross-linked resin is a cross-linked acrylic resin, for example, the main resin is a cross-linkable substituent-containing acrylic resin, and the cross-linked acrylic resin is obtained by reacting this with a polyisocyanate compound. When the cross-linked resin is a cross-linked urethane resin, for example, the main resin is a polyol, and a cross-linked urethane resin is obtained by a reaction between this and a polyisocyanate compound (conceptually including a urethane prepolymer terminated with an isocyanate group).

  As the crosslinkable substituent-containing acrylic resin, one or two or more kinds of acrylic acid compound and a monomer having a crosslinkable substituent are copolymerized, or one or two or more kinds of acrylic acid compound and a crosslinkable substituent. And a monomer obtained by copolymerizing one or two or more ethylenic monomers. Examples of such crosslinkable substituent-containing acrylic resins include (meth) acrylic acid-2-hydroxyethyl, (meth) acrylic acid-2-hydroxypropyl, (meth) acrylic acid-2-hydroxy-3-phenoxypropyl, (Meth) acrylic compounds having hydroxyl groups such as ethylene glycol mono (meth) acrylate and propylene glycol mono (meth) acrylate, and (meth) acrylic acid or alkyl groups as methyl, ethyl, n-propyl, i- Examples include those obtained by copolymerizing an alkyl (meth) acrylate monomer having a propyl group, an n-butyl group, an i-butyl group, a t-butyl group, a 2-ethylhexyl group, a cyclohexyl group, or the like. Further, as a monomer used for copolymerization, (meth) acrylamide, N-alkyl (meth) acrylamide, N, N-dialkyl (meth) acrylamide (alkyl groups include methyl group, ethyl group, n -Propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group and the like), N-alkoxy (meth) acrylamide, N, N-di Alkoxy (meth) acrylamide (alkoxy groups include methoxy group, ethoxy group, butoxy group, isobutoxy group, etc.), amide group-containing monomers such as N-methylol (meth) acrylamide, N-phenyl (meth) acrylamide, Contains glycidyl groups such as glycidyl (meth) acrylate and allyl glycidyl ether Monomer, styrene, α-methylstyrene, vinyl methyl ether, vinyl ethyl ether, maleic acid, alkyl maleic acid monoester, fumaric acid, alkyl fumaric acid monoester, itaconic acid, alkyl itaconic acid monoester, (meth) acrylonitrile, chloride Various compounds having an ethylenically unsaturated bond such as vinylidene, ethylene, propylene, vinyl chloride, vinyl acetate, and butadiene may be used. Among these, a copolymer of methyl (meth) acrylate and 2-ethylhexyl acrylate, a copolymer of at least methyl (meth) acrylate, 2-ethylhexyl acrylate, and a hydroxyl group-containing (meth) acrylate is preferably used. Is done. Moreover, 1000-300,000 is mentioned as a preferable mass mean molecular weight of such resin.

  The crosslinkable substituent-containing urethane resin used in the primer / coating solution has a plurality of hydroxyl groups to react with the polyisocyanate compound, and reacts with the polyisocyanate compound to crosslink to form a firm film. To do. The main resin is selected from a solvent-soluble resin or a resin dispersible in a solvent. A conventional polyol compound can be used as the main resin. For example, polyether type polyol, polyester type polyol, polycarbonate type polyol, etc. are mentioned, and it is used individually or in multiple types. Of these, polycarbonate polyols are preferably used, and polycarbonate polyols that are liquid at room temperature are particularly preferred. Since it has an active hydrogen group as a reactive group in the urethane bond, it can be crosslinked with a lower hydroxyl value compared to other resins. A preferred hydroxyl value range is from 0 to 50. Furthermore, polyamines, polyamine alkylene oxide adducts, amide group-containing polyols, polycarboxylic acids, and the like may be contained within a range not departing from the spirit of the present invention. Examples of the polyamine include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, ethanolamine, propanolamine and other aliphatic polyamines, 1,3- or 1,4-bis (aminomethyl) cyclohexane, Alicyclic polyamines such as 4,4′-, 2,4′- or 2,2′-dicyclohexylmethanediamine, isophoronediamine, norbornanediamine, m- or p-xylylenediamine, 1,3- or 1,4 -Aromatic polyamines such as tetramethylxylylenediamine, aromatic polyamines such as 2,4- or 2,6-tolylenediamine, 4,4'-, 2,4'- or 2,2'-diaminodiphenylmethane Can be illustrated. Examples of the amide group-containing polyol include hydroxyalkylamides. Examples of the polycarboxylic acid include isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, paraphenylene dicarboxylic acid, trimellitic acid, pyromellitic acid and other aromatic polycarboxylic acids, 1,3-cyclohexanedicarboxylic acid, 1 Aliphatic polycarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, and aliphatic polycarboxylic acids such as malonic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid.

  A polyisocyanate compound is a compound having two or more isocyanate groups in one molecule. As described above, the polyisocyanate compound crosslinks and cures (high molecular weight) the main resin to form the resin contained in the primer layer 66. At this time, the polyisocyanate compound becomes part of the resin contained in the primer layer 66 together with the main resin. Examples of the polyisocyanate compound include aliphatic, alicyclic, aromatic, and aromatic-aliphatic compounds. The easy-adhesion layer is exposed to the external environment for a long period of time. From the viewpoint of suppressing the accompanying coloring, an aliphatic or alicyclic polyisocyanate compound is preferably used.

  Specific examples of the polyisocyanate compound include aliphatic isocyanates having 3 to 12 carbon atoms such as hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexane diisocyanate, and lysine diisocyanate; 1,4-cyclohexane diisocyanate, isophorone diisocyanate ( Alicyclic diisocyanates having 5 to 18 carbon atoms such as IPDI); modified products of these diisocyanates (burettes, isocyanurate modified products, etc.). These can be used alone or in combination of two or more. Further, when the crosslinked resin is a crosslinked urethane resin, it may be a urethane prepolymer having an isocyanate group at the terminal.

  Other additives are added as necessary to impart to the primer layer 66 weather resistance, light resistance, heat resistance, moisture resistance, flame resistance, and the like. Further, the additive is added as necessary to improve the stability, coating property, drying property, blocking resistance and the like of the coating solution. Other additives include, specifically, silane coupling agents such as isocyanate silane coupling agents, epoxy silane coupling agents, mercapto silane coupling agents, and methyl / phenyl silane coupling agents, and aluminum tris. Examples include organometallic coordination compounds such as acetylacetonate, and other dispersants, antifoaming agents, light stabilizers, ultraviolet absorbers, heat stabilizers, antioxidants, and the like. Any known one can be used without particular limitation, and is appropriately selected according to the performance required for the primer / coating solution and the primer layer 66.

  As a method for applying the primer / coating liquid to the surface of the back surface protective sheet substrate, a conventionally known method can be used without any particular limitation. Examples of such a coating method include a printing method, a coating method using a gravure coater, a roll coating method, a spray coating method, a dip coating method, a solid coating method, and a brush coating method.

  As a method for evaporating the solvent contained in the coating film applied by the above method, a conventionally known method can be used without any particular limitation. Examples of such an evaporation method include a heating method, a reduced pressure drying method, a hot air drying method, and a natural drying method, but are not particularly limited. The conditions for evaporating the solvent contained in the coating film may be appropriately set according to the solvent used, but the heating time and heating temperature are 15 seconds to 5 minutes when using a gear oven. It is preferable that it is the range of ° C-200 ° C, and it is still more preferable that it is 70 ° C-120 ° C for 30 seconds-2 minutes. By heating in this way, preferable blocking resistance and adhesiveness are exhibited. The coating film obtained by evaporating the solvent is preferably subjected to curing for sufficiently carrying out the crosslinking reaction. Curing conditions may be set as appropriate according to the types of the main resin and the curing agent used. Examples of the curing conditions include leaving at 40 ° C. to 60 ° C. for 3 to 7 days.

  When the solvent is removed by evaporation from the coating film, the main resin, the curing agent, and other additives added to the coating solution remain on the surface of the substrate to form a thin film. This thin film is cured to become the primer layer 66.

(White primer / coating solution)
Similarly to the light receiving surface side adhesive layer 64, the primer layer 66 can also contribute to an improvement in the diffuse reflectance of the back surface protective sheet 6 by being a white light diffusion layer. In particular, when a metal vapor deposition film is disposed as a metal reflection layer instead of the metal foil layer 63, the light receiving surface side adhesive layer 64 is not formed or the light receiving surface side adhesive layer 64 is diffused with white light. When it is not a layer, it is essential that the primer layer 66 be a white light diffusion layer. In order to make the primer layer 66 a white light diffusing layer, a white primer / coating liquid obtained by adding a white pigment to the above primer / coating liquid may be used.

  As the white pigment used in the white primer / coating liquid, a white pigment having the same type and the same particle size as the white pigment used when the light receiving surface side adhesive layer 64 described above is used as the white light diffusion layer is used in the same manner. be able to. Specifically, a white pigment such as titanium oxide having a particle size of 0.1 μm to 1.0 μm is preferable, and a white pigment such as titanium oxide having a particle size of 0.2 μm to 0.4 μm can be particularly preferably used. . The content of the white pigment in the primer / coating liquid is preferably 0.1 to 5.0 in terms of PV ratio, as in the case of the white adhesive.

Using the white primer / coating solution described above, the primer layer 66 is formed as a white light diffusion layer on the light receiving surface side surface of the intermediate resin layer 65 in the same manner as the primer layer 66 not colored as described above. Can do. The coating amount is preferably 0.1 g / m ² or more and 20 g / m ² or less in terms of solid content. If the coating amount and thickness are within this range, the coating amount and thickness may be appropriately changed according to the adhesive strength necessary for the solar cell module sheet laminated member, and the coating amount and thickness are within this range. The near infrared ray having a wavelength of 750 nm or more and 1500 nm or less can be sufficiently transmitted, and the near infrared ray can be efficiently refracted and diffused.

  As long as the white pigment content, the particle size, and the white adhesive coating amount in the white primer / coating liquid are within the above ranges, the primer layer 66 is not coated with the white light diffusion layer. Sufficient adhesion can be imparted, processability with good blocking resistance can be imparted, and cost can be reduced.

[Back side resin layer]
Various resin sheets having excellent weather resistance can be used for the back surface side resin layer 61. Examples thereof include polyester resins, polyolefin resins, cyclic polyolefin resins, polystyrene resins, poly (meth) acrylic resins, polycarbonate resins, and fluorine resins. Among these, it is particularly preferable to use a fluorine-based resin excellent in hydrolysis resistance, water vapor barrier properties, and the like, and polyethylene terephthalate (PET) that has substantially the same physical properties and can suppress the manufacturing cost.

  As the back surface side resin layer 61, a colored resin sheet may be used. By using the colored weather-resistant resin sheet, it is possible to meet various requests on the design according to the use purpose and use mode of the colored back sheet and further the colored solar cell module.

[Non-light-receiving surface side adhesive layer]
The non-light-receiving surface side adhesive layer 62 is a layer that adheres the metal foil layer 63 on the surface of the back surface side resin layer 61, and the top surface of the back surface side resin layer 61 or the metal foil layer 63 facing the top surface. The adhesive applied to the lower surface is formed by curing after the backside resin layer 61 and the metal foil layer 63 are laminated.

  As an adhesive for forming the non-light-receiving surface side adhesive layer 62, an adhesive capable of adhering a resin sheet or the like that forms the back surface side resin layer 61 and the following metal foil that forms the metal foil layer 63 is appropriately used. Can do. As a specific example, urethane adhesives (not containing a white pigment) exemplified as the adhesive for forming the light receiving surface side adhesive layer 64 can be preferably used. The bonding method can be performed in the same manner as described above.

  As described above, the back surface protective sheet 6 includes a metal reflection layer that can reflect near infrared rays having a wavelength of 750 nm to 1500 nm with high light reflectance, and a white light diffusion layer that can efficiently diffuse passing light. By combining these, the power generation efficiency of the solar cell module 1 can be significantly improved while having a simple configuration. In the case of providing a white layer in the sheet for the purpose of improving the power generation efficiency or improving the designability in the conventional back surface protection sheet, the back surface side resin layer 61 and the intermediate resin layer in the back surface protection sheet 6 of the present invention. The base material resin layer corresponding to 65 or the sealing material adhesive layer corresponding to the primer layer 66 was highly filled with a white pigment or provided with a cavity. When these base resin layers having a certain thickness are highly filled with white pigments or provided with cavities, they have a high light diffusion function, but it is necessary to increase the film thickness, which is not economical. And there exists a problem that there exists a fall of tensile strength by highly filling a pigment or providing a cavity. The back surface protective sheet 6 is a light-receiving surface side adhesive layer 64 or primer layer 66 that is a very thin thin film layer, and is a white layer that optimizes light transmittance and light refraction. The diffuse reflectance of the protective sheet is improved.

[Other layers]
The back surface protective sheet 6 of the present invention may be provided with other layers as long as the effects of the present invention are not impaired. For example, another reinforcing layer (not shown) for increasing the strength of the back surface protection sheet 6 may be provided closer to the non-light-receiving surface side than the metal foil layer 63. Further, another transparent reinforcing layer (not shown) may be provided between the metal foil layer 63 and the intermediate resin layer 65.

<Method for manufacturing back surface protection sheet for solar cell module>
Finally, the manufacturing method of the back surface protection sheet for solar cell modules of this invention is demonstrated. The manufacturing method of the back surface protection sheet for solar cell modules of this invention is not specifically limited, For example, an adhesive bond layer is provided between each layer, and it can manufacture by dry lamination processing. In addition, the said white adhesive bond layer also has a function of the adhesive bond layer for manufacturing a back surface protection sheet.

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

<Examples 1-5>
With the composition shown in Table 1 below and the method described below, the back surface protective sheet having a multilayer structure shown in FIG. 3 was produced as the back surface protective sheet of the example.

The following weather-resistant resin film was used as the resin film constituting the back side resin layer, the following aluminum foil was used as the metal foil constituting the metal foil layer, and the following transparent resin film was used as the resin film constituting the intermediate resin layer. As the adhesive that forms the non-light-receiving surface side adhesive layer, the following transparent adhesive, as the adhesive that forms the light-receiving surface side adhesive layer, using either the following transparent adhesive or white adhesive, Each was coated at an application amount of 5.0 g / m ² (dry state) to form an adhesive layer, and the above film members were laminated by a conventionally known dry laminating method. Then, on the surface of the intermediate resin layer after lamination, any of the following primer / coating liquids is applied by a Myer bar method at a coating amount of 2.0 to 8.0 g / m ² (dry state) by the method described below. The primer layer was formed by evaporating the solvent component from the applied primer / coating solution by drying with a dryer at 70 ° C. for 1 minute. After the formation, the film was further allowed to stand at 45 ° C. for 3 days to obtain a back protective sheet of Examples 1 to 5.

The following films and metal foils were used as the base material for each layer.
Weather-resistant resin film: White ETFE sheet, trade name “Aflex” (manufactured by Asahi Glass Co., Ltd.), transparent resin film 1 (indicated as “transparent PET” in Table 1) containing 20% by mass of titanium oxide having a thickness of 25 μm and a particle size of 300 nm : Polyethylene terephthalate (PET) sheet, trade name “Lumirror S10” (manufactured by Toray Industries, Inc.), thickness 250 μm. The light transmittance of this transparent resin film 1 (according to the light transmittance measurement method in Evaluation Example 1 below) is 85% or more (see FIG. 7) in the wavelength range of 400 nm to 1500 nm.
Aluminum foil: trade name “Nippaku # 30” (manufactured by Nippon Foil Co., Ltd.), thickness 30 μm

The following solvents were added to the following adhesive materials to prepare transparent adhesives and white adhesives, respectively.
Transparent adhesive (indicated as “Transparent AD” in Table 1)
Main agent: “A1143” curing agent “A50” (both manufactured by Mitsui Chemicals)
Solvent: Toluene: Methyl ethyl ketone = 1: 1 mixed solution White adhesive (indicated as “White AD” in Table 1)
Main agent: Same as transparent adhesive Curing agent: Same as transparent adhesive Solvent :: Same as transparent adhesive White pigment: Titanium oxide, “D918” (manufactured by Sakai Chemical Co., Ltd.), particle size 0.26 μm, main agent and curing agent So that the mass ratio with respect to the total solid content is 100 mass%.

The following primer / coating liquid materials were prepared according to the formulation described below, and the following solvent was added to adjust the transparent coating liquid and the white coating liquid at a solid content concentration of 60% by mass, respectively.
Transparent primer / coating solution (indicated as “Transparent Pr” in Table 1)
Main agent: Crosslinkable substituent-containing acrylic resin (solid content 40%, Tg 41 ° C., acid value 5.9, hydroxyl value 19, weight average molecular weight 25000), 100 parts by mass Curing agent: polyisocyanate compound, product name “Coronate HX” (Solid content 80%, manufactured by Nippon Polyurethane Industry Co., Ltd.), 2.29 parts by mass Organometallic coordination compound: aluminum trisacetylacetonate, product name “aluminum chelate A (W)” (manufactured by Kawaken Fine Chemical Co., Ltd.), main agent And the curing agent were blended so that the mass ratio with respect to the total amount was 1.0 mass%.
Silane coupling agent: Mercapto group-containing methoxy / ethoxysilane oligomer, product name “X-41-1805” (manufactured by Shin-Etsu Silicone Co., Ltd.). It mix | blended so that the mass ratio with respect to the total amount of a main ingredient and a hardening | curing agent might be 1.5 mass%.
Solvent: Toluene: Methyl ethyl ketone = 1: 1 mixture White primer / coating solution (indicated as “White Pr” in Table 1)
Main agent: Same as transparent primer / coating solution.
Hardener: Same as transparent primer / coating solution.
Organometallic coordination compound: Same as transparent primer / coating solution.
Silane coupling agent: Same as transparent primer / coating solution.
White pigment: Titanium oxide, “D918” (manufactured by Sakai Chemical Co., Ltd.), particle size 0.26 μm, blended so that the mass ratio with respect to the total solid content of the main agent and curing agent is 100 mass% Solvent: Toluene: Transparent Same as primer coating solution.

<Comparative example, reference example>
The composition shown in Table 1 below and the method shown below are the same as the layer structure shown in FIG. 3, and the transparent layer is replaced with a white layer, or the white layer is replaced with a transparent layer. The back protective sheet was produced by the dry laminating method as in the example. As shown in Table 1, as the resin film constituting the intermediate resin layer, either the same transparent resin film 1 as in the example or the following white resin film 1 is used, and an adhesive that forms the light-receiving surface side adhesive layer As a substitute for the white adhesive, except that the transparent adhesive used in the examples was used, back protective sheets of comparative examples and reference examples were produced using the same materials and the same manufacturing conditions as the examples.

The following films were used as base materials for the intermediate resin layer.
Transparent resin film 1: Same as in Example White resin film 1 (indicated as “white cavity PET” in Table 1): White cavity-containing polyethylene terephthalate (PET) sheet having a thickness of 250 μm (trade name “Crisper” manufactured by Toyobo Co., Ltd.) K1212 ")
In addition, as described above, the light transmittance of the transparent resin film 1 (according to the light transmittance measurement method in Evaluation Example 1 below) is the light transmittance of the white resin film in a wavelength range of 400 nm to 1500 nm. And less than 6%.

<Evaluation example 1 (diffuse reflectance and transmittance)>
About the back surface protection sheet of Examples 1-5, a comparative example, and a reference example, the diffuse reflectance and transmittance | permeability for every wavelength range were evaluated. Evaluation was performed based on the numerical value measured by the following method.

  Using a spectrophotometer (manufactured by Shimadzu Corporation, UV-3100), the wavelength of 250 nm to 2600 nm when light is incident from the primer layer side of the back surface protective sheet of Examples 1 to 5 and Comparative Examples and Reference Examples. The diffuse reflectance of light is a value measured with a spectrophotometer (manufactured by Shimadzu Corporation, UV-3100), and the diffuse reflectance of a white plate obtained by solidifying fine barium sulfate powder is 100%. The relative value of reflectance was used. The evaluation results are shown in FIG.

  Moreover, in the back surface protection sheet of Examples 1-5 and a comparative example and a reference example, except for aluminum foil and a weather resistant resin film, a base material laminate (hereinafter referred to as a light receiving surface side adhesive layer, an intermediate resin layer, and a primer layer) In FIG. 5, the diffuse reflectance (%) of light having a wavelength of 250 nm to 2600 nm when light is incident on the base material layer from the primer layer side was measured. The evaluation results are shown in FIG.

  In addition, using a spectrophotometer (manufactured by Shimadzu Corporation, UV-3100), light is incident on the above-mentioned base material laminate of the back surface protective sheets of Examples 1 to 5 and Comparative Examples and Reference Examples from the primer layer side. The light transmittance (%) of light having a wavelength of 250 nm to 2600 nm was measured. The evaluation results are shown in FIG.

  From the results shown in FIG. 4, it was confirmed that the back surface protective sheet of the present invention has high diffuse reflectance of near infrared rays having a wavelength of 750 nm to 1500 nm. This result shows that when a solar cell module is manufactured using the back surface protective sheet of the present invention, the reflection of the light beam having a wavelength of 750 nm or more and 1500 nm or less by the metal reflection layer and the diffusion in the white light diffusion layer This means that power generation efficiency is improved.

  Further, from FIGS. 5 and 6, the white primer layer and the adhesive layer constituting the back protective sheet of the present invention are not high in diffuse reflectance (see FIG. 5), but are white layers. It was confirmed that the diffuse reflectance for near infrared rays having a wavelength of 750 nm or more and 1500 nm or less of the back surface protection sheet can be sufficiently increased by sufficiently transmitting the light and utilizing the reflected light of the aluminum foil. .

<Evaluation Example 2 (Durability)>
Durability was evaluated about the back surface protection sheet of Examples 1-5, a comparative example, and a reference example. Evaluation was performed based on the numerical value measured by the following method. The results are shown in Table 2.

(Break strength test)
As the intermediate resin layer, the breaking strength of each of transparent PET used in Examples 1 to 5 and Comparative Example and white hollow PET used in Reference Example was measured according to ISO 527-3. Each resin was cut into a length of 130 mm and a width of 10 mm to give a test piece, and measured with a Tensilon at a pulling speed of 100 mm / min and a distance between chucks of 100 mm. The results are shown in Table 2. With respect to the breaking strength, a material having a strength of 120 MPa or higher was evaluated as “A”, and a material having a strength of less than 120 MPa was evaluated as “C”. The results are shown in Table 2.

(Peel test)
It measured according to ISO11339. A cut was made into a width of 15 mm, and a T-shaped peel test between an aluminum foil and a daytime resin layer was performed with Tensilon at a pulling speed of 50 mm / min. When any of the resin base materials for the back surface protection sheet broke, it was indicated as base material breakage (* 1) in the table. In addition, it was noted in the table which layer was peeled off. The peeling test was a wet heat durability (85 ° C., 85% RH 1000 h) test, and after the test was left at 25 ° C. and 50% RH for 48 hours, the adhesion durability was evaluated. When the peel strength was 70% or more compared to before the wet heat endurance test, it was determined as “A”, and when it was less than 70%, it was determined as “C”. The results are shown in Table 3.

  From Table 2 and Table 3, it was confirmed that the back surface protective sheet of the present invention has durability preferable as a back surface protective sheet for solar cell modules.

<Evaluation Example 3 (Sealant Adhesiveness)>
The above Examples 1-5, Comparative Example and Reference Example, the surface on the primer layer side of the back surface protective sheet, the back surface sealing material sheet and the tempered glass made of the following sealing material are vacuum-pressed at 150 ° C. for 15 minutes and laminated. The adhesive strength between the back surface protective sheet and the back surface sealing sheet after the measurement was measured in accordance with ISO 8510-2, and a 180 ° C. peel test was performed with a substrate width of 15 mm and a peel speed of 50 mm / min as N / 15 mm width. The initial value and the endurance value after a wet heat endurance (85 ° C., 85% RH) test (1000 hours) are measured, the peel strength is 30 N / 15 mm or more, and the peel strength after the endurance test is 70 compared with the initial value. % Or more was shown as “A” as pass, and less than 70% was shown as “C” as fail. The results are shown in Table 4.

Sealing material 1 (polyethylene resin without cross-linking agent)
Silane-modified transparent resin: 98 parts by mass of a metallocene linear low density polyethylene (hereinafter referred to as M-LLDPE) having a density of 0.898 g / cm 3 and a melt mass flow rate at 190 ° C. of 2 g / 10 min. On the other hand, 2 parts by mass of vinyltrimethoxysilane and 0.1 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) were mixed and melted and kneaded at 200 ° C. to obtain a silane-modified transparent resin. .
Weatherproof masterbatch: 3.8 parts by mass of benzophenol UV absorber and 5 parts by mass of hindered amine light stabilizer with respect to 100 parts by mass of powder obtained by pulverizing Ziegler linear low density polyethylene with a density of 0.920 g / cm3 Part and 0.5 parts by mass of a phosphorous heat stabilizer were mixed, melted, processed, and pelletized to obtain a master batch.
20 parts by mass of the above silane-modified transparent resin, 5 parts by mass of a weather-resistant masterbatch, and 80 parts by mass of a metallocene linear low density polyethylene having a density of 0.905 g / cm 3 as an additive polyethylene are mixed, φ150 mm extruder, 1000 mm Using a film forming machine having a T-die having a width, a sealing material sheet having a thickness of 400 μm was produced at an extrusion temperature of 230 ° C. and a take-off speed of 2.3 m / min.

Sealing material 2 (polyethylene resin with a crosslinking agent)
Silane modified transparent resin: vinyl trimethoxy with respect to 98 parts by mass of metallocene linear low density polyethylene (M-LLDPE) having a density of 0.881 g / cm ³ and an MFR at 190 ° C. of 2 g / 10 min. and silane 2 parts by mass were mixed and dicumyl peroxide 0.1 part by weight of a radical generator (catalyst), melted at 200 ° C., kneaded, MFR at a density 0.884g ^/ cm 3, 190 ℃ A silane-modified transparent resin having a weight of 1.8 g / 10 min was obtained.
Weatherproof masterbatch: 3.8 parts by mass of benzophenol UV absorber and hindered amine light stabilizer 5 with respect to 100 parts by mass of powder obtained by pulverizing Ziegler linear low density polyethylene having a density of 0.880 g / cm ³ Mass parts and 0.5 parts by mass of a phosphorous heat stabilizer were mixed, melted, processed, and pelletized to obtain a master batch.
Crosslinking agent compound resin 1: 2,5-dimethyl-2,5 as a crosslinking agent with respect to 100 parts by mass of M-LLDPE pellets having a density of 0.880 g / cm ³ and MFR at 190 ° C. of 3.1 g / 10 min. -Compound pellets were obtained by impregnating 0.1 part by weight of di (t-butylperoxy) hexane.
20 parts by mass of the above silane-modified transparent resin, 5 parts by mass of weatherproof masterbatch, and 80 parts by mass of the crosslinker compound resin 1 are mixed and extruded using a film forming machine having a φ30 mm extruder and a 200 mm wide T die. A sealing material sheet having a thickness of 400 μm was produced at a temperature of 210 ° C. and a take-off speed of 1.1 m / min.

Sealing material 3 (polyethylene resin with a crosslinking agent)
100 parts by mass of EVA (vinyl acetate content 28%, manufactured by Mitsui DuPont Polychemical, trade name EVAFLEX / EV250 grade), 1.5 parts by mass of cross-linking agent (Lupersol 101), antioxidant (NAUGARD-P) 0. 2 parts by mass and a UV absorber (0.1 part by mass of Tinuvin 7709 and 0.3 part by mass of Cyasorb UV-531) were used. A 400 μm-thick sealing material sheet was prepared by a T-die method at a film forming temperature of 90 ° C. to 100 ° C.

  From Table 4, it was confirmed that the back surface protection sheet of this invention is equipped with sealing material adhesiveness preferable as a back surface protection sheet for solar cell modules.

  From the above test results, the back surface protective sheet of the present invention has sufficient durability and sealing material adhesion essential for the back surface protective sheet for solar cell modules, and a conventional back surface protective sheet. It can be understood that the diffuse reflectance of near infrared rays having a wavelength of 750 nm or more and 1500 nm or less contributing to the power generation efficiency of the solar cell module is sufficiently improved without greatly changing the layer configuration. That is, it turns out that the back surface protection sheet of this invention can contribute to the improvement of the power generation efficiency of a solar cell module at low cost.

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 61 Back surface side resin layer 62 Non-light receiving surface side adhesive layer 63 Metal foil layer 64 Light receiving surface side adhesion Agent layer 65 Intermediate resin layer 66 Primer layer 7 Incident light 7A Passing light

Claims (4)

A back side resin layer, a metal foil layer, an intermediate resin layer, and a primer layer are sequentially laminated,
The metal foil layer and the intermediate resin layer are laminated via a light receiving surface side adhesive layer,
The light-receiving surface side adhesive layer does not contain a white pigment,
The primer layer contains a white pigment ,
The application amount of the primer layer is 0.1 g / m ² or more and 2 g / m ² or less in terms of solid content ,
The white pigment content in the primer layer is 0.1 to 5 in terms of PV ratio,
The back surface protection sheet for solar cell modules whose white pigment contained in the said primer layer is a titanium oxide with an average particle diameter of 0.2 micrometer or more and 1.0 micrometer or less . The back surface protection sheet according to claim 1, wherein the metal foil layer is an aluminum foil layer. The back surface protection sheet of Claim 1 or 2 whose diffuse reflectance in the wavelength of 750 nm or more and 1500 nm or less when irradiated from the said primer layer side is 50% or more. The back surface protection sheet in any one of Claim 1 to 3 whose light transmittance in the wavelength of 750 nm or more and 1500 nm or less of the said intermediate | middle resin layer is 60% or more.

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