JPH08306947A - Rear protective layer for solar cell module - Google Patents

Abstract

PURPOSE: To improve the high humidity-proof and heat resistance of a rear protective layer by a method wherein the rear protective layer is formed into a laminated mate rial formed by laminating a film which consists of a specified resin and a film which consists of an amorphous cyclic olefin copolymer having a glass transition temperature set in a specified range. CONSTITUTION: A rear protective layer 2 consists of a laminated material formed by laminating a film 21, which consists of a fluorine resin or a polymethyl methacrylate and is used as the outermost layer, and a film 22, which is laminated on this film 21 via a bonding agent and consists of an amorphous cyclic olefin copolymer having a glass transition temperature of 80 deg.C or higher. The film 21, which consists of the fluorine resin or the polymethyl methacrylate, is hardly deteriorated by the sunlight, a rainfall or the like extending over a long period in the layer 2. Moreover, an integral combined structure of the film 21 with the film 22, which consists of the amorphous cyclic olefin copolymer having the glass transition temperature of 80 deg.C or higher, and the layer 2 can be used without hindlance for a long period, can be given. That is, needless to say at a normal temperature the water vapor transmission rate in the vicinity of 80 deg.C is low and a solar cell element can be prevented from being moisturized under severe conditions in the outdoors.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a back surface protective layer for a solar cell module.

[0002]

2. Description of the Related Art A typical structure of a solar cell module is as shown in the sectional view of FIG. That is, the light incident side is referred to as the upper side in the figure and is referred to as the front side. A solar cell made of single crystal silicon or the like connected in series or in parallel between the front surface protective layer 1 and the rear surface protective layer 2. This is a structure in which the element 3 is inserted, and the front surface protective layer 1 and the rear surface protective layer 2 are sealed and fixed by an adhesive resin 4 for the purpose of preventing damage to the element 3 due to a sudden change in the outside air condition and electrical insulation. In the case of amorphous silicon or a compound semiconductor, unlike the above structure, a film of amorphous silicon to be an element is formed or printed by a method such as vapor deposition without interposing an adhesive resin 4 on the back side of the surface protection layer 1. A typical example is a structure in which the solar cell element 3 is formed and the adhesive resin layer 4 is interposed between the back surface protective layers 2. Therefore, the solar cell module has a surface protective layer 1,
The laminated structure includes an adhesive resin layer 4, a solar cell element 3, an adhesive resin layer 4, and a back surface protective layer 2, which are provided as necessary.

Of these, the back surface protective layer 2 has a structure in which a highly moisture-proof film is laminated on the inner surface of a weather resistant resin film. The high moisture-proof film is for preventing the internal parts of the module from deteriorating due to intrusion of moisture from the outside. Conventionally, a metal foil has been used as a highly moisture-proof film, but a short circuit between the solar cell element 3 and the metal foil poses a problem, and a highly moisture-proof film made of a polymer has been proposed. For example, Japanese Patent Publication No. 4-76230
In the issue, vinylidene chloride-vinyl chloride copolymer,
Further, in JP-A-62-40783, ultra high molecular weight polyethylene (water vapor permeability 1-2 g / m ² · day · at
m), polyethylene mixed with 30 to 50% by weight of glass fiber or glass powder (water vapor transmission rate 3 to 5 g / m ² · day · a)
tm) is specifically mentioned.

Certainly, the vinylidene chloride-vinyl chloride copolymer has a water vapor permeability of 0.0 at room temperature to about 40 ° C.
It is as low as about 4g · mm / m ² · day · atm. However, when used outdoors like solar cells, it must be taken into consideration that the temperature can reach up to about 80 ° C depending on the location and season, but this resin has a moisture permeability of 3 at 80 ° C.
It increases to about g · mm / m ² · day · atm. Further, the water vapor transmission rate of polyethylene and ultra-high molecular weight polyethylene is inferior to that of vinylidene chloride-vinyl chloride copolymer by several orders of magnitude.

In addition, there is another problem with these resins. A commonly used adhesive resin in this field is a cross-linked copolymer of ethylene and vinyl acetate. When the crosslinking temperature is 120 ° C., it takes a long time, and at 150 ° C., it takes about 20 minutes. Therefore, the moisture-proof film is required to have heat resistance to a temperature of about 150 ° C. if possible. In contrast, vinylidene chloride
Since the vinyl chloride copolymer is stretched, it is thermally shrunk at such a high temperature and has no heat resistance. Moreover, polyethylene or ultra-high molecular weight polyethylene has a low softening temperature and cannot be used.

Even if such an adhesive resin that does not require heat resistance is used, as described above, when it is used outdoors, heat resistance of about 80 ° C. is required depending on the season, whereas vinylidene chloride- The vinyl chloride copolymer does not have heat resistance because it shrinks even at 80 ° C. In addition, polyethylene and ultra-high molecular weight polyethylene have low moisture permeability at 80 ° C, and when laminated with other adhesives such as hot melt type adhesives, these highly moisture-proof films are usually softened. It does not work as well.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a back surface protective layer for a solar cell module which has high moisture resistance and heat resistance at a temperature of room temperature to 80 ° C.

[0008]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a solar comprising a surface protective layer, an adhesive resin layer optionally provided, a solar cell element, an adhesive resin layer and a back surface protective layer laminated structure. In a battery module, the back surface protective layer is a film made of a fluororesin or polymethylmethacrylate, and a glass transition temperature of 8 is laminated on the inner surface of the film.
It is a back surface protective layer for a solar cell module, which is a laminate with a film made of an amorphous cyclic olefin copolymer at 0 ° C. or higher.

Hereinafter, the present invention will be described in detail with reference to the drawings based on specific examples of the present invention. FIG. 1 is a schematic cross-sectional view showing the structure of one embodiment of a solar cell module using the back surface protection layer of the present invention, and FIG. 2 is a cross-sectional view of the back surface protection layer. As the structure of the solar cell module according to the present invention, when the element 3 is single crystal silicon, the structure between the front surface protective layer 1 and the back surface protective layer 2 is similar to that of the conventional art.
A typical structure is one in which the element 3 is inserted and the space between the front surface protective layer 1 and the back surface protective layer 2 is sealed and fixed by an adhesive resin 4. When the element 3 is amorphous silicon or a compound semiconductor, the element 3 is formed into a thin film on the back side of the surface protective layer 1 by a method such as vapor deposition or printed, and the adhesive resin layer 4 is provided between the back surface protective layers 2. The structure in which is intervened is typical. Therefore, the solar cell module comprises a laminated structure of the surface protective layer 1, the adhesive resin layer 4 provided as necessary, the solar cell element 3, the adhesive resin layer 4, and the back surface protective layer 2.

Of these, the back surface protective layer 2 has a film 21 made of a fluororesin or polymethylmethacrylate as an outermost layer as shown in FIG. 2, and is laminated with an adhesive agent, and has a glass transition temperature of 80 ° C. or more. And a film 22 made of the amorphous cyclic olefin copolymer.

A film made of a fluororesin or polymethylmethacrylate is a resin which is not easily deteriorated in the back surface protective layer for solar cell modules by sunlight, rainfall, etc. for a long period of time, and an amorphous cyclic olefin having a glass transition temperature of 80 ° C. or higher. By combining with a film made of a copolymer, it is possible to take an integral structure that can be used for a long time without trouble. Examples of the fluororesin include vinylidene fluoride resin, vinyl fluoride resin, perfluoroalkoxy resin, tetrafluoroethylene-hexafluoropropylene copolymer, perfluoroethylene-perfluoropropylene-perfluorovinyl ether terpolymer. , Ethylene-tetrafluoroethylene copolymer,
Chlorine-trifluoroethylene copolymer and the like are preferable.

The film 21 made of a fluororesin or polymethylmethacrylate in the present invention may be only such a resin, but one or more compositions of such a resin or a composition mainly containing any of the above. It consists of things. As the other components constituting the composition, fillers used in this field, for example, titanium oxide, ultraviolet absorber, calcium carbonate, silicon dioxide, mica, aluminum oxide, etc. are typically mentioned as typical examples. . Further, by adding a polymer lubricant, metal soap or the like as a processing aid, uneven thickness, surface roughness, etc. can be prevented. The thickness of the film 21 made of a fluororesin or polymethylmethacrylate is appropriately selected in consideration of the use environment and the weather resistance of the resin, but usually about 15 to 75 μm is adopted.

In the present invention, the film 21 made of such a fluororesin or polymethylmethacrylate is laminated via an adhesive agent because the glass transition temperature is 8%.
The film 22 is an amorphous cyclic olefin copolymer having a temperature of 0 ° C. or higher. Here, the amorphous cyclic olefin copolymer is a copolymer of α-olefin such as ethylene, propylene, butene, and 1,4-methylpentene 1 and at least one cyclic olefin. Specific examples of the cyclic olefin copolymer include bicyclo [2.2.1] hept-2.
Ene derivatives, tetracyclo [4.4.0.1 ^2,5 . 1
^7,10 ] -3-decene derivative, hexacyclo [6.6.
1.1 ^3,6 . 1 ^10,13 . 0 ^2,7 . 0 ^9,14] -4-heptadecene derivatives, octacyclo [8.8.0.1 ^2,9.
1 ^4,7 . 1 ^11,18 . 1 ^{1 3,16} . 0 ^3,8 . 0 ^12,17 ] -5 docosene derivative, pentacyclo [6.6.1.1 ^3,6 . 0
^2,7 . 0 ^9,14] -4-hexadecene derivative, Heputajishikuro 5 Ikosen derivatives, Heputashikuro 5 Hen'eikosen derivatives, tricyclo [4.3.0.1 ^{2, 5]} -3 Desen derivatives, tricyclo [4.3.0.1 ^{2, 5} ]
-3-undecene derivative, pentacyclo [6.5.1.
1 ^3,6 . 0 ^2,7 . 0 ^9,14] -4 Pentadesen derivatives, penta cyclopentadiene decadiene derivative, pentacyclo [4.7.0.1 ^2,5. 0 ^{8, 13.} 1 ^9,12 ] -3-Pentadecene derivative and nonacyclo [9.10.1.
1 ^{4 , 7} . 1 ^13,20 . 1 ^15,18 . 0 ^2,10 . 0 ^12,21 .
0 ^14,19] -5-pentacosene derivatives, and the like.

As the method for polymerizing the above α-olefin and at least one cyclic olefin, hexane, heptane, octane, cyclohexane, benzene, toluene,
A preferable example is a method of using a catalyst such as a vanadium compound or an organoaluminum compound in a hydrocarbon solvent such as xylene.

Of the amorphous cyclic olefin copolymers thus obtained, those used in the present invention are those having a glass transition temperature of 80 ° C. or higher, and preferably 12
Those having a temperature of 0 ° C. or higher, and more preferably 130 ° C. or higher are used. Of these, the trade name "Apel" for manufacturing by Mitsui Petrochemical Industry Co., Ltd. and the trade name "ZONEX" for manufacturing by Nippon Zeon Co., Ltd. are preferable. This water vapor transmission rate varies slightly depending on the grade of "Apel" or "Zonex". For example, "Apel 6013" is 0.0 at 40 ° C.
7 g · mm / m ² · day · atm, 1 g · mm / m ² · day · atm at 80 ° C., and the glass transition temperature is 80 ° C. In addition, "Zeonex 25
0 "is 0.2 g · mm / m ² · day · at 40 ° C.
atm, 2 g · mm / m ² · da at 80 ° C.
y • atm, and the glass transition temperature is 141 ° C.

The film made of the amorphous cyclic olefin copolymer may be only the amorphous cyclic olefin copolymer, but may be a composition mainly composed of the amorphous cyclic olefin copolymer. Crystalline cyclic olefin copolymer 7
0-98% by mass and elastomer or polyethylene 2-3
A composition containing 0% by mass is slightly inferior to the amorphous cyclic olefin copolymer alone in terms of moisture resistance, but it is improved in impact strength and is preferably used. The thickness of the film 22 made of the amorphous cyclic olefin copolymer is used, the environment in which it is used, the type of resin used for the film made of fluororesin or polymethylmethacrylate, and the film made of the amorphous cyclic olefin copolymer. It depends on the type of resin used. Further, although it depends on the structure of the back surface protective layer as described later, about 25 to 300 μm is usually adopted.

The film 21 made of the above-mentioned fluororesin or polymethylmethacrylate and the film 22 made of the amorphous cyclic olefin copolymer are laminated by a dry laminating method or a heat laminating method using an appropriate adhesive. can do. As an adhesive, usually 120
A material having a heat resistance of 0.degree. C., preferably about 150.degree. C. is used, and a polyester or polyurethane adhesive for dry laminating, polymethylmethacrylate or the like is exemplified as a preferable example. Further, in order to improve the adhesiveness between the film made of an amorphous cyclic olefin copolymer and the film made of a fluororesin or polymethylmethacrylate, for example, a silane coupling treatment, a titanium coupling treatment, a corona treatment, a plasma treatment. Such a process is preferably adopted.

In the case of the structure shown in FIG. 2, a film 21 made of fluororesin or polymethylmethacrylate.
And a film of amorphous cycloolefin copolymer 22
There is a concern that curling may occur due to the difference in the coefficient of thermal expansion from the above. Such a curl is too soft in a thin film such as a conventional metal foil and easily curls if there is a difference in thermal expansion coefficient. However, the amorphous cyclic olefin copolymer used in the present invention is used. In this case, since it has a considerable thickness and has a high glass transition temperature as described above,
If these conditions are appropriately selected, curling will not occur easily, but in order to eliminate the concern of curling at all, FIG.
2 is a film 21 made of another fluororesin or polymethacrylate having the same shape and the same shape as the film 21 made of fluororesin or polymethacrylate on the side further contacting the adhesive resin 4 in the structure of FIG. '
It is even more preferable to employ a structure having a symmetric structure, which is provided via an adhesive.

Further, as shown in FIG. 4, it is more preferable that the film 21 'made of fluororesin or polymethylmethacrylate is replaced by a resin film 23 having a similar coefficient of thermal expansion and heat resistance, instead of the film 21'. Adopted by. Because this layer is not directly affected by UV light, it does not need weathering. Therefore, it consists of expensive fluororesin or polymethylmethacrylate. 2
If it is not necessary to use 1'and there is no concern about curling, it is a much desired place to substitute a cheaper resin. Moreover, as described above, the thickness of the film made of the amorphous cyclic olefin copolymer is considerably thicker and more rigid than the aluminum foil. It is possible to use many low-priced general-purpose resins. Examples thereof include polypropylene, polyethylene, polyethylene terephthalate, polybutylene phthalate, polyvinyl chloride, and polyamide. Among them, polypropylene has a thermal expansion coefficient close to that of a fluororesin, and is preferably used.

The adhesive resin that is in direct contact with the back surface protective layer or via an adhesive is made of a resin that has adhesiveness to the solar cell element and that melts and softens at the temperature during lamination. The lamination temperature is usually lower than 150 ° C, preferably 120 ° C or lower. Specifically, a modified resin of ethylene-vinyl acetate copolymer such as ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-glycidyl methacrylate terpolymer, ethylene-vinyl acetate partial saponification product-organic acid graft quaternary copolymer, etc. Examples include carboxyl group-containing polyolefins such as polyvinyl butyral and maleic anhydride grafted polyethylene, and polyester modified resins such as ethylene terephthalate-modified alkylene ether terephthalate block copolymers.

In the case of an ethylene-vinyl acetate copolymer for solar cells or a similar product, the film 22 made of an amorphous cyclic olefin copolymer and the adhesive resin 4 are laminated simply by heating. However, treatment such as corona treatment or silane coupling treatment is preferable from the viewpoint of improving the adhesiveness. Depending on the type of adhesive resin, a dry lamination method using an adhesive, a method of heat-melting the adhesive resin and directly extrusion coating it onto a moisture-proof resin film, etc. Can be created.

Known techniques can be used for the surface protective layer,
Among them, a laminated body of a UV shielding film made of a transparent weather resistant resin and a film made of an amorphous cyclic olefin copolymer, glass or the like is preferably used.

[0023]

The film made of an amorphous cyclic olefin copolymer having a glass transition temperature of 80 ° C. or higher used in the present invention has a low water vapor transmission rate at around 80 ° C. at room temperature, but has a low outdoor humidity. The solar cell element can be protected from moisture under various severe conditions. At the same time, it has sufficient heat resistance under the molding conditions of the solar cell module and is useful as a back surface protective layer for the solar cell module.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of one embodiment of a solar cell module using a back surface protective layer of the present invention.

FIG. 2 is a cross-sectional view of one aspect of the back surface protective layer in FIG.

3 is a cross-sectional view of another aspect of the back surface protective layer in FIG.

FIG. 4 is a cross-sectional view of yet another aspect of the back surface protective layer in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Surface protective layer 2 Back surface protective layer 3 Solar cell element 4 Adhesive resin 21, 21 'Film made of fluororesin or polymethylmethacrylate 22 Film made of amorphous cyclic olefin copolymer 23 Made of fluororesin or polymethylmethacrylate Instead of the film 21 ', a resin film having the same thermal expansion coefficient and heat resistance

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masamichi Akatsu Inventor 18-13 Kamamitamari, Tamari-mura, Shinji-gun, Ibaraki Prefecture, Kureha Chemical Industry Co., Ltd. (72) Inventor Satoru Matsunaga Tamarikami, Tamari-mura, Shinji-gun, Ibaraki Prefecture 18-13 Kureha Chemical Industry Co., Ltd., Resin Processing Technology Center

Claims (4)

[Claims] 1. A solar cell module comprising a laminated structure of a surface protective layer, an adhesive resin layer optionally provided, a solar cell element, an adhesive resin layer and a back surface protective layer, wherein the back surface protective layer is a fluororesin or A back surface protective layer for a solar cell module, which is a laminate of a film made of polymethylmethacrylate and a film made of an amorphous cyclic olefin copolymer having a glass transition temperature of 80 ° C. or higher and laminated on the inner surface thereof. 2. The back surface protective layer for a solar cell module according to claim 1, wherein the amorphous cyclic olefin copolymer has a glass transition temperature of 120 ° C. or higher. 3. The back surface protective layer for a solar cell module according to claim 1, wherein the amorphous cyclic olefin copolymer has a glass transition temperature of 130 ° C. or higher. 4. The solar cell module according to claim 1, wherein the film made of an amorphous cyclic olefin copolymer comprises 70 to 98% by mass of an amorphous cyclic olefin copolymer and 2 to 30% by mass of an elastomer or polyethylene. Back protective layer for.