JP2002100788A - Back sheet for solar battery cover material, and solar battery module using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a back sheet for a solar battery module, which has superior watertightness and voltage resistance and is superior with respect to reflectivity of incident light, lightweight, and inexpensive and a lightweight and inexpensive solar battery module which uses it and has superior durability and high power conversion efficiency. SOLUTION: The back sheet is formed of a two- or three-layered resin film laminate of a hydrolysis-resistant resin film, containing 0.5 to 0.8 wt.% oligomer, a resin film to which metal oxide is adhered, and a white resin film. The resin film is, preferably a PET film, the metal oxide film is formed by using, preferably, aluminum oxide, and titanium oxide is used as white pigment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a back sheet for a solar cell module and a solar cell module using the back sheet. Things.

[0002]

2. Description of the Related Art Solar cells, which can obtain electricity directly from sunlight, are being put to practical use as a semi-permanent and pollution-free new energy source. Recently, solar cells using semiconductor devices such as amorphous silicon have been rapidly spreading, and have been used as power supplies for ordinary houses. When a solar cell is used integrally with a roof member, a plurality of solar cell elements are generally combined and used as a solar cell module whose front and back surfaces are protected by an appropriate cover material. For example, as shown in FIG. 5, the solar cell module cover material is a solar cell element 1
A transparent glass substrate 21 is used as a protective member on the light receiving surface side, a back sheet 22 made of, for example, a highly light-resistant resin film is used as a protective member on the back side, and E is used as a sealing film.
Using a VA (retylene vinyl acetate copolymer) film 23, the solar cell element 1 was sandwiched and sealed by these protective members and used as a solar cell module 20.

[0003] In the above configuration, the transparent glass substrate 21 is excellent in moisture resistance and light resistance, but has disadvantages of low impact resistance and heavy weight. Therefore, there has been a problem in terms of strength and weight reduction when used integrally with a roof material of a general house. Instead of a transparent glass substrate to improve this drawback,
It has been proposed to use a light-resistant transparent resin film and metal foil. For example, Japanese Utility Model Publication No. 2-44995 discloses a back sheet 22 for a solar cell cover material having a structure in which a metal foil 26 as a moisture-proof film is sandwiched between heat-resistant and weather-resistant resin films 24 as shown in FIG. . The back sheet 22 and the EVA film 23 are overlapped to form a back cover material (see FIG. 6B).

Japanese Unexamined Patent Publication No. 2000-174296 discloses a highly moisture-proof base film made of a transparent resin film 25 such as a polyethylene terephthalate (PET) film instead of a metal foil as shown in FIG. And a transparent light-resistant resin film 29
A back sheet 22 for a solar cell cover material having a structure in which a fluororesin film or a resin film kneaded and mixed with an ultraviolet absorber is bonded via an adhesive sheet. The back sheet 22 and the EVA film 23 are overlapped to form a back cover material (see FIG. 7C).

[0005]

In the backsheet for a solar cell cover material having the above-mentioned structure, the use of a metal foil as a moisture-proof film has a low withstand voltage. Is not appropriate. In the backsheet for a solar cell cover material having the above structure,
A weather-resistant resin film or a light-resistant resin film is used on the outermost side of each solar cell module. As these weather-resistant resin films or light-resistant resin films, for example, polytetrafluoroethylene (PT)
FE), 4-fluoroethylene-perchloroalkoxy copolymer (PFA), 4-fluoroethylene-6-propylenepropylene copolymer (FEP), 2-ethylene-4-fluoroethylene copolymer (ETFE) ), Poly3-fluoroethylene (PCTFE), polyvinylidene fluoride (PVDF),
Or, a fluororesin film such as polyfucker vinyl (PVF), or polycarbonate, polymethyl methacrylate, polyacrylate, polyethylene terephthalate (PET), polyethylene naphthalate (PE)
N), a resin composition in which an ultraviolet absorber is kneaded with a resin such as acrylic is used.

However, fluororesin films are expensive, and other resin films are not yet satisfactory in terms of weather resistance, especially water resistance. When a solar cell module is installed and used on a roof, rainwater travels along the roof for a long time and comes into contact with a back sheet of the solar cell module. At this time, the resin film, which is a product of the ester reaction, easily undergoes hydrolysis with water, and the material gradually deteriorates. Therefore, it is unsuitable as a building material used for a long time.

Furthermore, in order to effectively utilize the light incident on the solar cell module to increase the power conversion efficiency, a reflective layer having high reflectivity must be disposed on the incident side of the light-shielding moisture-proof film. No. The conventional example discloses that a white pigment is added to a weather-resistant film to form a reflective layer, but a solar cell module having a structure in which the position of the reflective layer is considered is not found.

An object of the present invention is to provide a lightweight and excellent water and voltage resistance, which is useful as a solar cell module integrated with a roofing material, which can be used also for ordinary houses, and has a reflection ability of incident light. It is an object of the present invention to provide a back sheet for a solar cell module which is excellent in cost and is inexpensive. Also,
An object of the present invention is to provide a solar cell module using the back sheet having excellent water resistance.

[0009]

In order to achieve the above object, one of the back sheets for a solar cell module of the present invention comprises a hydrolysis-resistant resin film, a metal oxide-coated resin film, and a white resin film. Of three layers of a resin film. By using a hydrolysis-resistant resin film as the outermost backsheet,
When used integrally with the roofing material, the backsheet withstands hydrolysis by rainwater and has excellent durability and weather resistance. In addition, by using a metal oxide-coated resin film as a moisture-proof layer, a back sheet having high withstand voltage can be obtained without impairing moisture-proof properties. Furthermore, by using a white resin film on the innermost side,
The light incident on the back sheet can be effectively reflected and reused, and the power conversion efficiency of the solar cell can be increased.

In another backsheet for a solar cell module according to the present invention, a hydrolysis-resistant resin film is coated with a metal oxide, and the metal oxide film is coated with the hydrolysis-resistant resin film. And white resin film 2
It was a laminate of layers. Alternatively, a white resin film may be coated with a metal oxide film, and a two-layer laminate of a white resin film coated with the metal oxide film and a hydrolysis-resistant resin film may be used. Hydrolysis resistant resin film on the outermost side, white resin film on the innermost side, if a metal oxide film is applied to any of the resin films, it has hydrolysis resistance and excellent reflectivity A back sheet having a two-layer structure can be obtained.

An ordinary light-fast resin film is a so-called polymer obtained by condensation-polymerizing a monomer, and contains 1.6 to 2% by weight of an oligomer which is an intermediate between the monomer and the polymer. Here, the oligomer is a low polymer having a repeating number of structural units (degree of polymerization) of about 2 to 20. The oligomer content is determined by Nuclear Magnetic Reso
nance: NMR). In contrast, the hydrolysis-resistant resin film used in the present invention is a resin film having a high degree of polymerization reaction and an oligomer content of 0.5 to 0.8 wt%. If the polymerization reaction proceeds and the oligomer content decreases to 0.5 to 0.8 wt%, a stable resin film having excellent hydrolysis resistance can be obtained. As the resin film, a polyethylene terephthalate (PET) resin film can be preferably used. PET resin films are inexpensive and weather-resistant resin films.

The metal oxide film used as the moisture-proof layer in the present invention is at least one selected from the group consisting of silicon oxide, aluminum oxide, titanium oxide, magnesium oxide, zirconium oxide, zinc oxide and tin oxide.
Seeds are available. If these metal oxides are used as a moisture-proof layer, they are inorganic and have high withstand voltage because they are inorganic, and can be used safely even when used integrally with a roofing material. Among these metal oxides, silicon oxide and aluminum oxide are preferably used in combination. The reason is that by embedding small aluminum oxide particles in the gaps between the silicon oxide layers, crack resistance and flexibility of the vapor deposition layer are improved, and a tough and stable vapor deposition layer can be obtained.

The solar cell module according to the present invention is described in claim 1.
A back sheet for a solar cell cover material according to any one of claims to 7 is used. Such a solar cell module is lightweight, has excellent water resistance, has a high light utilization rate, has good power conversion efficiency, and is inexpensive, so it can be widely used as a building material integrated with a roofing material. it can

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The hydrolysis-resistant resin film used in the present invention has an oligomer content of 0.5 to 0.8 wt%.
Is a resin film. An ordinary light-resistant resin film is a so-called polymer of a condensation compound, and the oligomer is composed of 1.
6 to 2 wt% is contained. If the amount of the oligomer is large, the oligomer lacks in stability and easily undergoes hydrolysis. On the other hand, if a low oligomer resin having an oligomer content of 0.5 to 0.8 wt% is obtained by sufficiently promoting the polymerization reaction, hydrolysis hardly occurs and a resin film having excellent hydrolysis resistance is obtained. be able to. As the resin film, resin films such as polyethylene terephthalate (PET), polycarbonate, polymethyl methacrylate, polyacrylate, and polyethylene naphthalate (PEN) can be used. In particular, polyethylene terephthalate (PE
T) can be preferably used because it has good dimensional stability and workability and is inexpensive. Furthermore, in order to enhance weather resistance and light resistance, these resins are added with 2-hydroxy-4.
-Benzophenones such as octoxybenzophenone and 2-hydroxy-methoxy-5-sulfobenzophenone; benzotriazoles such as 2- (2'-hydroxy-5-methylphenyl) benzotriazole; phenyl salicylate; A mixture obtained by kneading a hindered amine-based ultraviolet absorber such as -butylphenyl salicylate can also be used. It is appropriate that the thickness of the hydrolysis resistant resin film is about 30 to 100 μm.

Next, the metal oxide-coated resin film used as the moisture-proof layer will be described. The metal oxide-deposited resin film is a film in which a metal oxide film is deposited on the surface of a substrate film, and exhibits a moisture-proof effect on a solar cell element. The metal oxide has insulating properties, is chemically stable, and does not react with moisture. Therefore, when used in a solar cell module, there is no danger of current leakage, and a high withstand voltage material can be used as a building material. As described below, the metal oxide film may be adhered to a hydrolysis-resistant resin film or a light-resistant resin film to form a two-layer laminated structure, in which case a resin film as a base material is not particularly required. . A three-layer structure using a metal oxide-coated resin fill has an advantage that a metal oxide film is easily formed. Inexpensive polyethylene terephthalate, polycarbonate,
Resin films such as polymethyl methacrylate, polyacrylate, polyethylene naphthalate, and acrylic can be used. The thickness of the resin film is 10
20 μm is required.

As the metal oxide, at least one selected from silicon oxide, aluminum oxide, titanium oxide, magnesium oxide, zirconium oxide, zinc oxide and tin oxide can be used. These metal oxides may be used alone or as a composite oxide.
To deposit a metal oxide film on the resin film surface,
An evaporation method or a sputtering method may be used. In order to form a composite oxide film, for example, a binary vapor deposition method may be used, or a composite oxide target such as mullite (3Al ₂ O ₃ .2SiO ₂ ) may be used. When the thickness of the metal oxide film is about 3 to 600 °, a sufficient moisture-proof effect is exhibited. If these metal oxides are used as a moisture barrier,
Since it is inorganic, it has insulating properties, high withstand voltage, and excellent moisture resistance, so that it can be used safely even when used integrally with roofing materials. Among these metal oxides, silicon oxide and aluminum oxide are preferably used in combination. The reason is, as described above, that the vapor-deposited particles of aluminum oxide are embedded in the gaps of the silicon oxide layer, thereby improving the crack resistance and flexibility of the vapor-deposited layer.
This is because a tough and stable vapor deposition layer can be obtained.

The white resin film reflects the light incident on the back sheet and returns the light to the solar cell element, thereby improving the power conversion efficiency. The white resin film is obtained by mixing a white pigment with a resin. Inexpensive polyethylene terephthalate as a resin film,
Resin films such as polycarbonate, polymethyl methacrylate, polyacrylate, polyethylene naphthalate, and acrylic can be used. As the white pigment, titanium oxide or zinc oxide can be used. A white pigment is added to the resin to form a white resin film having a whiteness of 80% or more and an opacity of 80% or more. The thickness of the white resin film is 4
It is suitable to be about 0 to 100 μm. Since the metal oxide film has a light-shielding property, the white resin film is arranged at a position closest to the light incident side of the back sheet.

The hydrolysis-resistant resin film, the metal oxide-coated resin film, and the white resin film are separated from each other by sandwiching the metal oxide-coated resin film. Is the innermost side (solar cell element side). For lamination of the resin films, it is preferable to use a urethane-based adhesive layer having a thickness of 3 to 5 μm. The above three resin films are overlapped with each other via a bonding agent layer, and heated to 60 to 120 ° C. to obtain 5 to 10 g / m 2.
A pressure of about ^{2 is} applied to form a three-layer backsheet.

When a back sheet having a two-layer structure is used,
After applying the metal oxide film to either the hydrolysis-resistant resin film or the white resin film, the hydrolysis-resistant resin film and the white resin film become the outermost, and the metal oxide film becomes the inner side. And press-bond.

Next, a solar cell module using the thus obtained back sheet will be described. The solar cell module of the present invention has a structure in which a solar cell element is sandwiched between two cover materials, a conventionally known transparent sheet is used as a front sheet on which sunlight is incident, and the sunlight is incident on the front sheet. As the back sheet on the opposite side, a back sheet using the hydrolysis-resistant resin film according to the present invention is used to increase the water resistance. In order to form a solar cell module, two cover sheets are joined to a solar cell element using an adhesive resin layer for sealing. As the adhesive resin layer, an ethylene-vinyl acetate copolymer (Ethylene-Vin
ylacetate Copolymer (EVA) film can be used. Although the thickness of the EVA film depends on the thickness of the solar cell element, a thickness of about 0.3 to 0.6 mm is appropriate.

The EVA film may have a crosslinked structure by blending a crosslinking agent in order to improve weather resistance. As the cross-linking agent, an organic peroxide that generally generates a radical at 100 ° C. or higher can be used.
2,5-dimethylhexane, 2,5-dihydroperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 3-di-t-butyl peroxide, t-dicumyl Peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne, dicumyl peroxide, α, α′-bis (t-butylperoxyisopropyl) benzene, n-butyl-4, 4-
Bis (t-butylperoxy) butane, 2,2- (t-
Butylperoxy) butane, 1,1-bis (t-butylperoxy) 3,3,5-trimethycycloxane, t-
Butyl-oxybenzoate or benzoyl peroxide can be used.

A silane coupling agent can be added to the EVA film for the purpose of improving the adhesive strength between the solar cell element and various resin films. Examples of silane coupling agents used in such applications include γ-chloropropyltrimethyxylane,
Vinyltrichlorosilane, vinyltriethoxysilane, vinyl-tris- (β-methoxyethoxy) silane, γ-
Methacryloxy-propyltrimethoxysilane, β-
(3,4-ethoxycyclohexyl) ethyltrimethoxylan, γ-glycidoxypropyltrimethoxylan,
Examples thereof include vinyltriacetoxysilane, γ-mercaptopropyltrimethoxylan, γ-aminopropyltrimethoxylan, and N-β- (aminoethyl) -γ-aminopropyltrimethoxylan. further,
Examples of the crosslinking aid for improving the gel fraction and improving the durability include triallyl isocyanurate and triallyl isocyanate. In addition, hydroquinone or hydroquinone monoethyl ether may be added for the purpose of improving stability. In addition, various colorants, discoloration inhibitors, antioxidants, and the like can also be added.

[0023]

According to the present invention, the oligomer content is 0.5 to 0.8.
The water resistance of the back sheet is improved by using a resin film as little as wt%. In the present invention, the voltage resistance and corrosion resistance of the back sheet are improved by using a metal oxide film as a moisture-proof layer.

[0024]

Hereinafter, the present invention will be described in more detail with reference to examples. (Embodiment 1) FIG. 1 is a sectional view for explaining the structure of a solar cell module according to the present invention. In FIG. 1, a solar cell element 1 made of amorphous silicon is laminated and sandwiched between a front cover material 2 and a back cover material 3 and is integrated by bonding. The front cover member 2 includes a front sheet 4 made of a transparent weather-resistant resin film and an adhesive resin layer 11a also serving as a sealing material. The back cover member 3 includes the back sheet 5 of the present invention and an adhesive resin layer 11b also serving as a sealing material. Light enters from the direction of the front cover member 2 and is converted into electric power by the solar cell element 1. In addition, a part of the incident light is reflected by the back sheet 5, enters the solar cell element 1, and is converted into electric power. In this embodiment, as the front cover material 2, polyethylene terephthalate (PE) kneaded with benzotriazole as an ultraviolet absorber is used.
A resin film having a thickness of 120 μm manufactured by T) was used. For the adhesive resin layers 11a and 11b, an EVA film containing a crosslinking agent and a silane coupling agent was used.

FIG. 2 shows the back sheet 5 of this embodiment.
(B) a white resin film 6, a metal oxide-coated resin film 9, and a hydrolysis-resistant resin film 10 as shown in FIG.
A sheet having a three-layer laminated structure was adopted. As the white resin film 6, a PET film having a transparency of 87% and titanium oxide added as a white pigment was prepared. The thickness of the white resin film 6 was 50 μm. As the metal oxide-coated resin film 9, a PET film 7 having a thickness of 15 μm is used.
Aluminum oxide (Al ₂ O ₃ ) film 8 to a thickness of about 3 to 5
What was deposited by ion beam evaporation at 00 ° was prepared. As the hydrolysis-resistant resin film 10, a PET film (manufactured by Toray; X10S) having a thickness of 50 μm and an oligomer content of 0.5 wt% was prepared. As shown in FIG. 2A, these three resin films are overlapped so that the Al ₂ O ₃ film 8 is in contact with the hydrolysis-resistant resin film 10, and the urethane-based two-component reactive adhesive 12 is used for 3 to 3 times. 4g / m
^{2 was} applied and joined at 8 kg / cm at 100 ° C. as shown in FIG.

In the solar cell module thus obtained, since the white resin film is disposed immediately below the solar cell element, the solar cell element effectively captures the reflected light, so that the power conversion efficiency is high, and Since a resin film having excellent hydrolysis resistance was used for the cover, no deterioration of the back sheet was observed even in a 2000-hour weather resistance test exposed to running water.

(Embodiment 2) In this embodiment, a silicon oxide (SiO ₂ ) film is deposited on the surface of a white resin film.
A two-layer back sheet laminated with a hydrolysis-resistant resin film was employed. Other configurations of the solar cell module are the same as those in the first embodiment. As shown in FIG.
A film was prepared in which a silicon oxide film 8 ′ having a thickness of about 500 ° was formed by vapor deposition on the surface of a white resin film 6 similar to that in Example 1. As shown in FIG. 3 (b), the silicon oxide film 8 'is formed of the hydrolysis-resistant resin film 1 as shown in FIG.
Then, they were overlapped so as to be in contact with 0, and joined using a urethane-based adhesive in the same manner as in Example 1. The hydrolysis-resistant resin film used was the same as in Example 1.

The solar cell module thus configured also has high power conversion efficiency and excellent water resistance and weather resistance. In particular, since a silicon oxide film is used, it has excellent insulation properties and is safe even if it is integrally formed as a roof material.

Example 3 In this example, a mixed film of silicon oxide and aluminum oxide was applied to the surface of a hydrolysis-resistant resin film and laminated with a white resin film.
A backsheet with a layer structure was adopted. Other configurations of the solar cell module are the same as those in the first embodiment. FIG. 4 (a)
As shown in FIG. 5, a film was prepared by forming a mixed film 8 ″ of silicon oxide and aluminum oxide with a thickness of about 500 ° on the surface of the hydrolysis-resistant resin film 10 as in Example 1 by a binary vapor deposition method. This film was overlapped so that the mixed film 8 ″ was in contact with the white resin film 6 as shown in FIG. 4B, and joined using a urethane-based adhesive as in Example 1. The used white resin film and hydrolysis-resistant resin film are the same as in Example 1.

The solar cell module thus configured also had high power conversion efficiency and excellent water and weather resistance. In particular, since a mixed film of silicon oxide and aluminum oxide is used, the solar cell module has excellent withstand voltage, and is suitable as a tough and stable roof material having crack resistance and flexibility.

[0031]

According to the present invention, it is possible to obtain an inexpensive back sheet for a solar cell module which is lightweight, has excellent water resistance and voltage resistance, has excellent incident light reflectivity, and is inexpensive.
Therefore, the solar cell module using the back sheet of the present invention is lightweight, has excellent durability, has high power conversion efficiency, and is inexpensive when the solar cell module is integrated with a roof material for a general house. It can be a solar cell module.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a cross-sectional structure of a solar cell module of the present invention.

FIG. 2 is a diagram illustrating a back sheet according to a first embodiment of the present invention.

FIG. 3 is a diagram illustrating a back sheet according to a second embodiment of the present invention.

FIG. 4 is a diagram illustrating a back sheet according to a third embodiment of the present invention.

FIG. 5 is a diagram illustrating a cross-sectional structure of a conventional solar cell module.

FIG. 6 is a diagram illustrating an example of a conventional back sheet.

FIG. 7 is a diagram illustrating another example of a conventional back sheet.

[Explanation of symbols]

1 ····· Solar cell element 2 ····· Front cover material 3 ···
... back cover material, 4 ... front seat, 5 ...
Back sheet, 6... White resin film, 7... PE
T film, 8... Aluminum oxide film, 9... Metal oxide-coated resin film, 10... Hydrolysis-resistant resin film, 12... Adhesive, 20 ······ Solar cell module, 21 ···· Transparent glass substrate, 22 ···· Backsheet, 24 ··· Heat and weather resistant resin film, 25 ····
Transparent resin film, 26 ... metal foil, 28 ... inorganic oxide film, 29 ... transparent light-resistant resin film

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Michio Takemoto 520 Imazato, Susono-shi, Shizuoka F-term in M-PA Packaging Susono Factory (reference) 5F051 EA18

Claims (8)

[Claims] 1. A back sheet for a solar cell cover material comprising a three-layer laminate of a hydrolysis-resistant resin film, a metal oxide-coated resin film, and a white resin film. 2. A back sheet for a solar cell cover material, comprising a two-layer laminate of a hydrolysis-resistant resin film coated with a metal oxide and a white resin film. 3. A back sheet for a solar cell cover material, comprising a two-layer laminate of a hydrolysis-resistant resin film and a white resin film coated with a metal oxide. 4. The solar cell according to claim 1, wherein the hydrolysis-resistant resin film is a resin film having an oligomer content of 0.5 to 0.8 wt%. Back sheet for battery cover material. 5. The back sheet for a solar cell cover material according to claim 1, wherein the resin film is a polyethylene terephthalate resin film. 6. The method according to claim 1, wherein the metal oxide is at least one selected from silicon oxide, aluminum oxide, titanium oxide, magnesium oxide, zirconium oxide, zinc oxide, and tin oxide. The backsheet for a solar cell cover material according to any one of claims 1 to 3. 7. The back sheet for a solar cell cover material according to claim 6, wherein the metal oxide comprises silicon oxide and aluminum oxide. 8. A solar cell module using the back sheet for a solar cell cover material according to any one of claims 1 to 7.