JP2010109240A - Solar cell back sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell back sheet that has satisfactory adhesion properties to EVA, namely a filler, or the like, is excellent in characteristics, such as weatherability, moisture resistance, optical reflectivity, and optical diffusion, has superior design nature at low costs, and has high protection capability. <P>SOLUTION: The solar cell back sheet comprising at least two layers including a weather-resistant base film includes an adhesive coating layer colored by a white pigment with a titanium oxide as a main constituent on the innermost surface bonded to a filler for composing a solar cell module of the solar cell back sheet. The adhesive coating layer includes a polyacrylic acid resin as a main resin component. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a solar battery back sheet (back surface protection sheet) constituting a solar battery module used for photovoltaic power generation.

In recent years, depletion of fossil energy sources such as oil and coal has been a problem, and in addition, environmental destruction such as global warming due to an increase in CO ₂ generated during combustion has become an important issue. Under such circumstances, photovoltaic power generation has been put into practical use as a clean alternative energy source that uses inexhaustible solar radiation energy. Solar cells constitute the heart of a photovoltaic power generation system that converts sunlight energy directly into electricity. Photovoltaic elements such as crystalline silicon, polycrystalline silicon, amorphous silicon, copper indium selenide, and compound semiconductors Made from. As its structure, a single photovoltaic element is not used as it is, and generally several to several tens of photovoltaic elements are wired in series and in parallel, and the element is extended over a long period of time. In order to protect the battery, various packaging is performed, and a unit is formed as a solar cell module.

  The basic function of the solar cell module is to efficiently guide the solar radiation energy to the photovoltaic device and to protect the photovoltaic device and the internal wiring so that they can withstand harsh natural environments for a long time. It is in. In general, a solar cell module has an upper transparent material made of glass or transparent plastic on the surface that is exposed to sunlight, and a filler layer made of a thermoplastic resin such as an ethylene vinyl acetate copolymer (hereinafter referred to as EVA). A plurality of solar cells as photovoltaic elements, a filler layer similar to the filler layer, and a solar battery back sheet are laminated in this order, and are integrally formed by a vacuum heating lamination method or the like.

  In order to simplify the manufacturing process of the above-described solar cell module, as an approach from the filler side of the solar cell module, there is an increasing number of cases using EVA, which is said to be a fast cure type that has dramatically improved thermal crosslinking reaction efficiency. . This fast cure type is a combination of heat-sensitive additives to promote the thermal crosslinking reaction. Compared to the standard type used so far, the solar cell back sheet There is a tendency to be inferior to the adhesiveness, and it is easily influenced by the deacetic acid reaction of EVA. That is, there is a need for a solar cell backsheet that is resistant to deacetic acid and excellent in adhesion to the filler, regardless of the type of EVA.

  The solar battery backsheet has excellent mechanical strength and excellent properties such as weather resistance, heat resistance, water resistance, light resistance, and chemical resistance to protect the contents of solar cells and leads. In particular, a high gas barrier property that prevents intrusion of moisture, oxygen and the like is required. In order to maintain the barrier property, not only the barrier performance of the material itself but also the adhesion and adhesion stability with a filling layer such as EVA are important. This is because the permeation of moisture from the interface causes peeling of the filler, discoloration, and corrosion of the wiring, which may affect the output of the module itself. Furthermore, the inner surface is required to be white because of its contribution to improving power generation efficiency.

  Conventionally, as a solar battery back sheet, a fluorine resin having good weather resistance, flame retardancy, EVA, which is often used as a filler, and good adhesiveness, such as polyvinyl fluoride (PVF) and polyvinylidene fluoride (PVDF). Has been used. However, fluororesins have problems such as low mechanical strength, high cost, and lack of easy disposal.

In order to solve these problems, many configurations using a polyester film have been used. For example, Patent Document 1 discloses a back surface sealing film for a solar cell made of a laminate of polybutylene terephthalate (PBT) film containing titanium oxide produced by a chlorine method. However, although the hydrolyzability is improved as compared with PET and exhibits balanced physical properties, adhesion to fillers such as EVA has not been solved.

Patent Document 2 discloses a polyester film for solar cells in which a coating layer having adhesiveness with a polyolefin resin typified by EVA is provided at the time of forming a polyester film. This method requires a production lot of a certain degree or more, and it is difficult to deal with a small lot. In particular, whitening has a problem of increasing the price. Furthermore, in applications that require long-term durability, there is a problem with the weather resistance of general PET films, and there is a problem that film hydrolysis occurs during long-term outdoor use. There is a problem that the performance is further deteriorated.
JP 2007-129204 A JP 2006-175664 A

  The present invention has been made in view of the above-described problems, has good adhesiveness with EVA as a filler, and is excellent in various properties such as weather resistance, moisture resistance, light reflectivity, and light diffusibility. It is an object to provide a solar cell back sheet that is low in cost, excellent in design properties, and high in protection ability.

  The invention according to claim 1 of the present invention is the solar cell backsheet composed of at least two layers including the weather resistant substrate film, and is bonded to the filler constituting the solar cell module of the solar cell backsheet. It is a solar cell backsheet characterized by having an adhesive coating layer colored with a white pigment mainly composed of titanium oxide on the inner surface.

  The invention according to claim 2 of the present invention is the solar battery backsheet according to claim 1, wherein the adhesive coating layer contains a polyacrylic acid resin as a main resin component.

  In the invention according to claim 3 of the present invention, rutile titanium dioxide having an average particle diameter of 0.1 μm to 0.5 μm is used as a white pigment for coloring the adhesive coating layer. It is 0.1-30 mass% with respect to the total mass, It is a solar cell backsheet described in Claim 1 or characterized by the above-mentioned.

In the invention according to claim 4 of the present invention, the weather resistant substrate film has a number average molecular weight in the range of 18,000 to 40,000, an oligomer content of 1.5% by mass or less, and an intrinsic viscosity of 5 × 10 ^{−. It} consists of polyester which has the hydrolysis resistance of ⁵ m < ³ > / g or more, It is a solar cell backsheet of any one of Claims 1-3 characterized by the above-mentioned.

  Next, the invention according to claim 5 of the present invention is characterized by comprising a transparent vapor-deposited film in which a gas barrier thin film is formed between the weather-resistant substrate film and the adhesive coating layer. Item 5. A solar cell backsheet according to any one of Items 1 to 4.

The solar cell backsheet of the present invention is composed of at least two layers including a weather-resistant substrate film, an adhesive coating layer is provided on the surface to be bonded to the filler constituting the solar cell module, and the adhesive coating Low-cost solar cell with good adhesion to fillers, excellent weather resistance, heat resistance, workability, and high reflectivity because the layer contains a white pigment mainly composed of titanium oxide It became possible to provide a backsheet. In particular, since a white coating layer with high concealability is used on the innermost surface side, the outer weather-resistant substrate film is a composite of a thin high-weather substrate film and a thick general substrate film. This is advantageous in terms of cost.

  The solar cell backsheet of this invention is demonstrated in detail below based on one Embodiment.

FIG. 1 is a schematic view showing an example of the solar battery backsheet of the present invention in cross section. Moreover, FIG. 2 is the schematic which showed the other example of the solar cell backsheet of this invention in the cross section. FIG. 3 is a schematic view showing in cross section an example of a solar cell module to which the solar cell backsheet of the present invention is applied.
In FIG. 1, the innermost surface to be bonded to the weather-resistant substrate film 10 and the filler constituting the solar cell module is composed of two layers of an adhesive coating layer 20 colored with a white pigment mainly composed of titanium oxide. Has been. The adhesive coating layer 20 is directly coated and laminated on the weather resistant substrate film 10. Moreover, in FIG. 2, it has the structure laminated | stacked as a composite article of the weather resistant base film 10 with the thin high weather resistant base film 11 and the thick general base film 12, and the general base film 12 of an inner surface An adhesive coating layer 20 colored with a white pigment mainly composed of titanium oxide is applied and formed on the side. As shown in FIG. 3, the glass 5 of the upper transparent material, the EVA of the filler 4, the wired solar cells 6 and the solar battery backsheet 1 of the present invention are overlaid and vacuum laminated. As a result, the lead wire 7 is drawn out of the module, and a solar cell module from which power is taken out is obtained.

  The weather-resistant substrate film is basically a transparent film substrate, but in the solar cell backsheet of the present invention, it is not always necessary to be transparent because a white adhesive coating layer is provided on the innermost surface, For example, white, black or other colors may be used. Specific examples of the substrate include polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polycyclohexanedimethanol-terephthalate (PCT), and perfluoroalkoxy resin (PFA). Ethylene tetrafluoride-6-propylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), chloroethylene trifluoride resin (PCTFE), polyvinylidene fluoride (PVDF), polyfluoride Examples thereof include resin films selected from fluororesins such as vinyl (PVF), polycarbonate resins, or polyacrylonitrile, acrylic resins, methacrylic resins, polyglycolic acid resins, and polylactic acid resins. Moreover, it is not limited to these, It can select suitably considering heat resistance, an intensity | strength physical property, electrical insulation, etc., such as a polysulfone-type resin, a polyimide-type resin, and a polyarylate-type resin.

Among these substrates, polyester resins are preferred because of their strength, heat resistance, transparency, and low cost. Furthermore, in obtaining weather resistance and long-term durability as a solar battery back sheet, the number average molecular weight is in the range of 18,000 to 40,000, the oligomer content is 1.5% by mass or less, and the intrinsic viscosity is 5 × 10 ^−. A polyester base material having a hydrolysis resistance of ⁵ m ³ / g or more is preferred.

In general, a polyester base material is composed of a polymer obtained by condensation polymerization of a monomer, and 1.6 to 2% by mass of an oligomer that is an intermediate between the monomer and the polymer. In addition, when the molecular terminal of the polyester base material is a carboxylic acid, it acts as heat, water, and further as an acid catalyst and is affected by hydrolysis. It is also possible to seal this terminal carboxylic acid group with a carbodiimide compound, an epoxy compound, or an oxazoline compound, but the polymerization reaction is advanced without increasing the terminal carboxylic acid group, that is, the number average molecular weight In order to increase the solid-state polymerization method, the polymerization reaction proceeds and the oligomer content can be reduced to 1.5% by mass or less, preferably 1.0% by mass or less, and it is difficult to hydrolyze and is durable. It can be set as the base material of the laminated body which has the outstanding barrier property. Such a polyester base material is also available as a commercial product, and examples of the commercial product include Lumirror X10S (trade name) manufactured by Toray Industries, Inc. Here, the content of the oligomer can be known by using a method such as nuclear magnetic resonance (NMR).

  In addition, considering the cost, the weather-resistant base film is a film made of a mixture of two or more kinds of resins as described above, and a thin fluororesin film with high weather resistance but excellent weather resistance, for example, as the outermost layer. It is also possible to use a film obtained by laminating and integrating a thick general grade polyester. In addition, known additives, lubricants, plasticizers, stabilizers, ultraviolet absorbers and antistatic agents can be added, and a colorant can be added depending on the application of the laminate. In addition, the weather-resistant substrate film may be either stretched or unstretched, but in consideration of suitability for forming a continuous adhesive coating layer, post-processing suitability such as lamination with a transparent vapor-deposited film, etc., mechanical strength and A film having dimensional stability is good, and a film arbitrarily stretched in a biaxial direction is preferable. The thickness of the substrate is not particularly limited, and is practically preferably in the range of 3 to 300 μm, particularly preferably 20 to 250 μm, as a solar cell backsheet.

  Next, the adhesive coating layer is designed in consideration of the adhesion to the weather-resistant substrate film described above and the adhesion to the filler constituting the solar cell module, particularly EVA. Usually, EVA used as a filler for a solar cell module has a vinyl acetate content of 10 to 40% by mass, and heat or light is used to ensure the heat resistance and physical strength of the solar cell module. EVA is cross-linked by the above. As the resin of the adhesive coating layer having adhesiveness to such EVA, acrylic, epoxy, phenol, polyester, urethane, styrene resin, silicon resin, or modified products thereof are preferably used. It contains polyacrylic acid resin as the main resin component of the adhesive coating layer due to its adhesiveness to both EVA and polyester-based weather resistant substrate film, as well as the retention and dispersibility of white pigments mainly composed of titanium oxide. Is particularly preferred.

  As the acrylic acid of the polyacrylic acid resin as the main resin component of the adhesive coating layer, for example, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, Alkyl groups such as t-butyl acrylate, hexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate, palmityl acrylate or cyclohexyl acrylate have 1 to 18 carbon atoms There are alkyl acrylates. Further, there are alkyl esters having a hydroxyl group in the side chain of acrylic acid such as hydroxymethyl acrylate, hydroxypropyl acrylate, and hydroxybutyl acrylate. Further, there are alkyl esters having an alkoxyl group in the side chain of (meth) acrylic acid, such as methoxybutyl acrylate, methoxyethyl acrylate, ethoxybutyl acrylate, and the like. Further, there are alkenyl esters of acrylic acid such as allyl acrylate, and alkyl esters having an epoxy group in the side chain of acrylic acid such as glycidyl acrylate and methyl glycidyl acrylate. There are also mono- or di-alkylaminoalkyl esters of acrylic acid such as diethylaminoethyl acrylate and methylaminoethyl acrylate. Further, it is possible to use a silicon-modified acrylic ester having a silyl group, an alkoxysilyl group or a hydrolyzable alkoxysilyl group as a side chain.

The adhesive coating layer is colored by adding a white pigment mainly composed of titanium oxide. In the solar cell module, the white pigment imparts light reflectivity and light diffusibility to the innermost surface of the back sheet in order to reuse the sunlight transmitted from the surface to the back sheet by light reflection or light diffusion. For the purpose of adding to the adhesive coating layer. As the white pigment, for example, one or more of white pigments such as basic lead carbonate, basic lead sulfate, basic lead silicate, zinc white, zinc sulfide, lithopone, antimony trioxide, and titanium dioxide are used. be able to. The amount added is 0.1 to 30% by mass with respect to the total mass of the adhesive coating layer, although it depends on the hiding power of the pigment. Furthermore, in addition to the white pigment, silica, alumina, calcium carbonate, barium sulfate, zinc sulfide and the like can be used as an inorganic filler, and it is more effective to use a fluorescent whitening agent such as thiophendiyl. .

  From the results of the study by the present inventors, the effect of imparting light reflectivity and light diffusibility to the innermost surface of the backsheet was measured by a method according to JIS P 8123 at 45 degrees in the optical direction of the backsheet inner surface. The whiteness is preferably 80% or more. Among the above-mentioned white pigments, rutile type titanium dioxide having a high refractive index and a large hiding power is most preferable because high whiteness can be obtained with a small addition amount. Rutile-type titanium dioxide generally has low wettability with a resin, and in order to improve dispersibility in the resin, those treated with various surface treatment agents and coated on the surface are used. Among these, those containing two types of alumina hydrate and silicic acid hydrate are preferable because dispersibility of titanium dioxide in the resin used for the adhesive coating layer is improved. It is preferable that the average particle diameter of titanium dioxide is 0.1-0.5 micrometer, More preferably, it is 0.15-0.25 micrometer. When the average particle size is smaller than 0.1 μm, the dispersibility in the resin is deteriorated, not only the light resistance is lowered but also the light shielding property is lowered, and the intended high light reflection performance may not be achieved. On the other hand, if the average particle diameter is larger than 0.25 μm, the appearance of the adhesive coating layer may be poor, and the intended high light reflection performance may not be achieved. The addition amount of titanium dioxide is 0.1 to 30% by mass, more preferably 0.5 to 15% by mass, based on the total mass of the adhesive coating layer, from the concentration that expresses the reflectance.

  By adding a silane coupling agent or an ultraviolet absorber as an additive to the polyacrylic acid resin described above, the adhesive coating layer not only provides adhesion between the weather resistant substrate film and the EVA filler, but also water resistance. Resistance, such as heat resistance, can be raised.

  The method for forming the adhesive coating layer includes a method of laminating the resin of the adhesive coating layer by coextrusion when the above-mentioned weather resistant substrate film is formed, and before stretching the film forming step of the weather resistant substrate film. Alternatively, a method of laminating a heat-melted adhesive coating layer resin on the stretched film, or a coating solution using water or an organic solvent as a coating solution for the adhesive coating layer resin is applied to a weather resistant substrate film. Any of the techniques for processing is possible. In particular, the adhesive coating layer that is flexible and has low substrate selectivity can be produced with high productivity by using a wet coating method that can be processed with existing equipment. When the adhesive coating layer is applied as a coating solution, it is applied to a weather-resistant substrate film, heated and dried, and in some cases, cured by ultraviolet irradiation or the like. As a coating method, known coating methods such as gravure coating and roll coating can be applied. It is also effective to generate coating stripes of about 0.5 to 2.0 μm in order to prevent blocking of the coating layer.

  The thickness of the adhesive coating layer is 0.1 μm to 10 μm, more preferably 3 μm to 7 μm. When the thickness of the adhesive coating layer is less than 0.1 μm, coating omission occurs, adhesion with the weather-resistant substrate film is insufficient, and the light reflectivity of the film that plays an important role in the present invention is present. Not expressed. Moreover, when thickness exceeds 10 micrometers, the adhesiveness with a weather-resistant base film and the whiteness improvement effect will reach a peak, and it will become economically disadvantageous. The thickness of the adhesive coating layer can be measured by using a transmission electron microscope, a scanning electron microscope, a micrometer, or the like.

Next, the transparent vapor deposition film in which the gas barrier thin film formed between the weather resistant substrate film and the adhesive coating layer is formed will be described. In the solar battery backsheet of the present invention, a weather-resistant substrate film and a transparent vapor-deposited film are laminated in advance with an adhesive or the like, and then a white adhesive coating layer is formed on a gas barrier thin film that is usually disposed on the inner surface side. However, the method for stacking is not particularly limited. The barrier thin film layer made of an inorganic compound prevents permeation of gases such as water vapor and oxygen. The material for forming the barrier thin film layer is not particularly limited, and is transparent and has a gas barrier property such as oxygen, water vapor, etc., such as oxides, nitrides and fluorides of metals such as silicon, aluminum, chromium and magnesium. Things can be used. Of these, metal oxides and mixtures thereof can be preferably used. Among these, for example, silicon oxide, aluminum oxide, and magnesium oxide are preferable because high gas barrier properties are obtained. As the vapor deposition substrate, a biaxially stretched polyethylene terephthalate film can be preferably used because of its strength, heat resistance, transparency, and low cost, but is not limited thereto.

The barrier property of the transparent vapor-deposited film is preferably such that the water vapor permeability is 0 to 50 g / m ² · day · 40 ° C. 90% RH. In the solar cell backsheet, its effectiveness is exhibited particularly in a low region where the water vapor permeability is 1.0 g / m ² · day · 40 ° C. and 90% RH or less, that is, high barrier properties. Such a transparent barrier film with a high barrier is also available as a commercial product, and examples of the commercially available product include an aluminum oxide transparent vapor deposition film GX-PF (trade name) 12 μm manufactured by Toppan Printing Co., Ltd. It is done. In addition, according to the catalog value, the vapor barrier property of a single substance of GX-PF is 0.05 g / m ² / day · 40 ° C. 90% RH. The water vapor transmission rate used here can be measured under the conditions of a temperature of 40 ° C. and a humidity of 90% RH using a water vapor transmission rate measuring device (PERMATRAN 3/31 manufactured by Modern Control Co., Ltd.) according to JIS K7129B method.

  There are various methods for forming a barrier thin film layer made of a metal oxide such as silicon oxide, aluminum oxide, and magnesium oxide on a plastic substrate, and it can be formed by a normal vacuum deposition method. In addition, other thin film forming methods such as sputtering, ion plating, and plasma vapor deposition (CVD) can also be used. However, considering productivity, the vacuum deposition method is the best at present. As a heating means of the vacuum evaporation method, it is preferable to use any one of an electron beam heating method, a resistance heating method, and an induction heating method. Further, in order to further improve the adhesion between the deposited thin film layer and the substrate and the denseness of the deposited thin film layer, it is also possible to perform deposition using a plasma assist method or an ion beam assist method. In order to increase the transparency of the deposited film, it is possible to use reactive deposition in which various gases such as oxygen are blown during the deposition.

  The optimum conditions for the thickness of the gas barrier thin film layer vary depending on the type and configuration of the inorganic compound used. In general, the thickness is preferably in the range of 1.0 nm to 300 nm, and the value is appropriately selected. However, if the film thickness is less than 1.0 nm, a uniform film may not be obtained or the film thickness may not be sufficient, and the function as a gas barrier material may not be sufficiently achieved. Also, if the film thickness exceeds 300 nm, the thin film cannot retain flexibility, and there is a risk that the thin film may be cracked due to external factors such as bending, pulling, or expansion / contraction due to temperature changes. There is. More preferably, it exists in the range of 10-150 nm, and a high barrier property is obtained at this time.

  Specific examples of the present invention will be described below.

<Example 1>
Two-component curable urethane adhesive (AD76P1 / CAT10 manufactured by Toyo Morton Co., Ltd.) with a solid content of 4 g / m ² was applied to 25 μm of a fluorine film (PVF tedlar manufactured by DuPont), and PET film (Lumirror S10 manufactured by Toray Industries Inc. ) 250 μm was laminated by the dry lamination method. Next, on the PET film surface of this laminate, a coating solution in which an acrylic resin (thermo rack manufactured by Soken Chemical Industry Co., Ltd.) having a polyester skeleton introduced therein and an acrylic resin (Acto Flow manufactured by Soken Chemical Industry Co., Ltd.) is blended, , Rutile-type titanium oxide (CR-90 manufactured by Ishihara Sangyo Co., Ltd.) was added and mixed with 10% by mass of the resin solid content to obtain a white coating solution, which was applied by gravure coating and dried. Then, an adhesive coating layer having a solid content coating amount of 4 g / m ² was provided. This was used as a solar cell back sheet having a white adhesive coating layer on the inner surface side (EVA adhesion side).

<Comparative Example 1>
Two-component curable urethane adhesive (AD76P1 / CAT10 manufactured by Toyo Morton Co., Ltd.) solid content 4 g / m ² is applied to 25 μm of a fluorine film (DuPont PVF Tedlar), and a white PET film (Toray Co., Ltd. Lumirror) E20) 250 μm was laminated by a dry lamination method. The white PET film was used as a solar cell back sheet on the inner surface side (EVA adhesion side).

<Comparative example 2>
Two-component curable urethane adhesive (AD76P1 / CAT10 manufactured by Toyo Morton Co., Ltd.) with a solid content of 4 g / m ² was applied to 25 μm of a fluorine film (PVF tedlar manufactured by DuPont), and PET film (Lumirror S10 manufactured by Toray Industries Inc. ) 250 μm was laminated by the dry lamination method. Next, a gravure coat is applied to the PET film surface of this laminate, which is a mixture of an acrylic resin (thermo rack manufactured by Soken Chemical Industry Co., Ltd.) with an introduced polyester skeleton and an acrylic resin (Act Flow manufactured by Soken Chemical Industry Co., Ltd.). It was coated by the method and dried to provide an adhesive coating layer having a solid content coating amount of 4 g / m ² . This was used as a solar battery back sheet having a transparent adhesive coating layer on the inner surface side (EVA adhesion side).

Using the solar cell backsheets prepared in Example 1 and Comparative Examples 1 and 2 above, tempered glass of the upper transparent material, EVA sheet of filler (RCO2B type manufactured by Mitsui Chemicals Fabro), Example 1 And the solar cell backsheet of Comparative Examples 1 and 2 was superposed and vacuum heated and laminated under the conditions of 150 ° C./vacuum 3 minutes / crimping 10 minutes / 1.33 × 10 ² Pa to obtain a test solar cell module. . After the solar cell module for this test was subjected to a storage test for 2000 hours in an environment of 85 ° C. to 85% RH, the light reflectivity of the backsheet and the adhesion to EVA as a filler were observed as weather resistance and durability. evaluated. Appearance characteristics were evaluated by whiteness measured by a method according to JIS P 8123 at 45 degrees in the optical direction of the inner surface of the backsheet after the storage test, with less than 70% x, 70% to less than 80% Δ, 80% or more was rated as ◯. Before the storage test, the whiteness was 80% or more. Moreover, the adhesiveness with EVA was measured according to the test method prescribed | regulated by Japanese Industrial Standard JISK6854-3: 1999 "adhesive-peeling adhesive strength test method-part 3: T-type peeling". An orientec Tensilon universal testing machine RTC-1250 was used for the test. The evaluation results and measurement results are summarized in Table 1.

実施例１で作成した本発明の太陽電池バックシートは、外観的にも劣化が見られず高い白色度を保持し、ＥＶＡとの接着強度は２０００時間の高温多湿条件下での保存後も、太陽電池バックシートで実用上必要とされる２０Ｎ／１０ｍｍ以上の値が保持され、耐久性にすぐれた結果が明らかとなった。それに対して、比較例１では、白色ＰＥＴフィルムにやや黄変が発生し、ＥＶＡとの接着性は元々やや弱いものであったが、部分的に層間での剥離が発生して不十分なものとなった。また、接着性塗布層に酸化チタンを入れていない比較例２では、ＥＶＡとの接着性は保たれていたが、ＰＥＴフィルムに細かいクラックが入り黄変が激しく光反射性は大幅に低下する結果となった。なお、コストの比較は、白色ＰＥＴと一般ＰＥＴの価格差が影響する結果となり、本発明の太陽電池バックシートは、最外層に薄いフッ素樹脂を内側に厚い一般ＰＥＴフィルムを使うことが可能なため大幅なコストダウンが実現できる結果となった。

The solar cell backsheet of the present invention prepared in Example 1 maintains high whiteness with no deterioration in appearance, and the adhesive strength with EVA is 2000 hours after storage under high temperature and high humidity conditions. The value of 20 N / 10 mm or more required for practical use in the solar battery back sheet was maintained, and the results of excellent durability were revealed. On the other hand, in Comparative Example 1, the white PET film was slightly yellowed and the adhesiveness with EVA was originally slightly weak, but it was insufficient due to partial peeling between layers. It became. Further, in Comparative Example 2 in which titanium oxide was not added to the adhesive coating layer, the adhesiveness with EVA was maintained, but the PET film was finely cracked and yellowed rapidly, resulting in a significant decrease in light reflectivity. It became. In addition, the comparison of the cost results in the influence of the price difference between white PET and general PET, and the solar battery backsheet of the present invention can use a thin general PET film with a thin fluororesin on the innermost layer. As a result, a significant cost reduction was achieved.

Schematic which showed the example of the solar cell backsheet of this invention in the cross section. Schematic which showed the other example of the solar cell backsheet of this invention in the cross section. The partial cross section schematic of an example of the solar cell module in which the solar cell backsheet of this invention is used.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Solar cell back sheet 10 ... Weather-resistant film base material 11 ... Weather-resistant film base material (outer layer) 12 ... Weather-resistant film base material (inner layer)
DESCRIPTION OF SYMBOLS 20 ... Adhesive coating layer 4 ... Filler (EVA) 5 ... Glass 6 ... Solar cell 7 ... Lead wire

Claims (5)

A white pigment mainly composed of titanium oxide on the innermost surface of a solar cell backsheet composed of at least two layers including a weather-resistant base film and bonded to a filler constituting the solar cell module of the solar cell backsheet A solar battery backsheet, characterized by having an adhesive coating layer colored with.   The solar cell backsheet according to claim 1, wherein the adhesive coating layer contains a polyacrylic acid resin as a main resin component.   As a white pigment for coloring the adhesive coating layer, 0.1-30% by mass of rutile type titanium dioxide having an average particle size of 0.1 μm to 0.5 μm is included with respect to the total mass of the adhesive coating layer. The solar cell backsheet according to claim 1 or 2, wherein The weather-resistant substrate film has hydrolysis resistance such that the number average molecular weight is in the range of 18,000 to 40,000, the oligomer content is 1.5% by mass or less, and the intrinsic viscosity is 5 × 10 ⁻⁵ m ³ / g or more. It consists of polyester, The solar cell backsheet described in any one of Claims 1-3 characterized by the above-mentioned.   5. The solar battery back according to claim 1, comprising a transparent vapor-deposited film in which a gas barrier thin film is formed between the weather-resistant substrate film and the adhesive coating layer. Sheet.

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