JPS6147777A - Film for protecting solar cell - Google Patents

Abstract

PURPOSE:The titled film capable of standing abrupt change in temperature, eliminating troubles caused by thick coating of protective film and coating of many times, obtained by forming a hot-melt adhesive layer on the surface of a heat-resistant film. CONSTITUTION:For example, a film of polyethylene terephthalate having preferably 20-70mum thickness is used, and at least one side of the film is provided with a layer of a hot-melt adhesive (preferably consisting of especially acrylic acid ester methacrylic ester copolymer resin), to give the aimed film. The layer has preferably 30-60mum thickness. When the surface of protective film is used as a receptor surface, a transparent heat-resistant film having >=60% light transmsittance at 550nm is preferable.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a protective film for solar cells.

[Prior Art] Solar cells have recently been widely used for outdoor power generation, portaple power generation, and the like. Power generation, which is the main function of these solar cells, is possible with the element between the electrodes, but a protective film for solar cells is used to protect the element from the environment and improve its reliability.

Epoxy resin coated protective films have been used as protective films for solar cells, but at present they do not necessarily have sufficient environmental resistance.

Disadvantages of the epoxy resin coated protective film include, for example, that the cured epoxy resin is rigid and may cause peeling due to rapid temperature changes.

On the other hand, in order to improve environmental resistance, it is required that the thickness of the protective film for solar cells be approximately 100 μm.

In order to ensure the thickness of the protective film close to 100 μm, it may be necessary to apply the film several times in the coating process, or it may be necessary to apply the film thickly. Therefore, with the adoption of such a coating process, there are many complex problems such as coating misalignment, repelling, inclusion of air bubbles, inclusion of dust, multi-stage post-curing, complicated viscosity adjustment of the coating material, and reduction in pattern sharpness. The number of process and complicated troubles increases, and as a result, there are cases where the yield decreases in the manufacturing process of a protective film for solar cells.

In addition to these problems, particularly in solar cells of the type in which the surface of the protective film for solar cells is used as the light-receiving surface, more advanced appearance characteristics are being required.

[Problems to be Solved by the Invention] The present invention solves the problem that the conventionally used epoxy resin coating protective film is easily peeled off due to sudden temperature changes, and the need for the thickness of the solar cell protective film to be approximately 100 μm. In such cases, coating misalignment, repelling, air bubbles, dirt, multi-stage post-curing, complicated viscosity adjustment of the coating material, decrease in pattern sharpness, etc. that occur due to multiple coatings or thick coatings. In order to solve problems such as reduced yields caused by complicated processes and complicated troubles, and to meet even higher requirements for the appearance of solar cells of the type that uses the protective film surface as the light-receiving surface. It has been done.

[Means for Solving the Problems] The inventors of the present invention have conducted extensive research in view of the above-mentioned circumstances, and have found that the above-mentioned problems can be solved by using a film with hot melt adhesive. , arrived at the present invention.

That is, the present invention relates to a protective film for solar cells characterized by forming a hot melt adhesive layer on at least one side of a heat-resistant film, and by manufacturing a solar cell using such a protective film for solar cells. , the above-mentioned problems have been solved.

[Example] The heat-resistant film used in the present invention includes, for example, polypropylene film, polyethylene terephthalate film, nylon film, polysulfone film, polyarylate film, FEP film, PCTF film,
100℃ with a film such as polyimide film
It is a film that is not substantially damaged by heating. The thickness of these films is not particularly limited, but is preferably 10 to 200 μm, more preferably 20 to 75 μm.

The film does not need to be a single-layer film, but may be multi-layered if necessary, and may have a coating layer for the purpose of imparting scratch resistance.

Further, surface treatment may be performed to improve adhesion.

The preferred film for use in the present invention is 5°C.
A transparent film having a light transmittance of 60% or more at 50 nm is mentioned, and such a transparent film is suitable when the surface of the thick tilt pond protective film of the present invention is used as the light receiving surface. Further, preferable films from the viewpoint of sufficient environmental resistance include polyethylene terephthalate film, FEP film, and PCTF film.

The hot melt adhesive used in the present invention includes, for example, copolymerized polyamide, copolymerized polyester, copolymerized acrylic resin such as ethylene-vinyl acetate copolymer, acrylic ester-methacrylic ester copolymer resin, epoxy-modified polyethylene, and ionomer. Commonly known hot melt adhesives manufactured from

Among these hot melt adhesives, hot melt adhesives manufactured from copolymerized acrylic resins such as acrylic acid ester-methacrylic acid ester copolymer resins and epoxy-modified polyethylene are preferred from the viewpoint of fully satisfying severe environmental resistance. It is preferable that These adhesive-rich methods may be employed.

Preferably, it is 100 μm.

The solar cell manufactured in this way has −j[11i! I
Epoxy-modified PE using a copolymer of 50% 2-ethylhexyl I acid; Bonded Fast Ionomer manufactured by Sumitomo Chemical ■ Himiran 16 manufactured by Nimitsui Polychemical ■
52 Lamination conditions were adjusted as appropriate based on 140° C. x 500 mm/min.

(Thermal shock resistance) After leaving the solar cell at -20°C for 30 minutes, it was heated to 8°C for 30 minutes.
After repeating the heat cycle of leaving it for 0 minutes 5 times, the appearance was judged with the naked eye.

0: No abnormality at all Δ: Slight abnormality X: Significant abnormality (heat resistance) After the solar cell was treated at 100°C for 100 hours, the appearance was judged with the naked eye.

○: No abnormality Δ: Slight abnormality X: Significant abnormality (water resistance) After immersing the solar cell in fresh water at 100°C for 5 minutes, the appearance was judged with the naked eye.

○: No abnormality at all △: Slight abnormality ×: Significant abnormality (Protective film formation process yield) After forming a protective film on 100 elements in the following process, pass when the appearance is judged with the naked eye. The number of elements is displayed as a percentage.

In the case of the example: Lamination process - External punching process In the case of Comparative example: Coating process - Cure process - Coating process - Cure process - External punching process From the results in Table 1, 11 When the protective film of the present invention is used, It can be seen that solar cells with excellent environmental resistance can be manufactured with an excellent yield.

[Effects of the Invention] A feature of the present invention is that a hot melt adhesive is used as the adhesive, and that the adhesive is used as a film with an adhesive.

By using such a protective film of the present invention,
Surprisingly, researchers have discovered scales using thermoplastic films as protective coatings for solar cells.

Additionally, protective coatings using thermoplastic films can withstand rapid temperature changes, which are problematic for conventional solar cell protective coatings. Further, as an additional effect when using the protective film of the present invention, it is possible to omit the post-curing process, it is possible to overcome the problem of dust adhering to the protective film during the curing process, and the protective film The effect of this method is that the thickness of the coating can be easily adjusted to the required thickness, thereby eliminating all the problems caused by thick coating or multiple coatings. It is particularly useful to manufacture a solar cell in which the surface provided with the protective film is the light-receiving surface by using the protective film of the present invention which produces these effects, since it can meet higher requirements for appearance.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are both explanatory diagrams regarding solar cells manufactured using the protective film for solar cells of the present invention. (Main symbols in drawings) (1): Heat resistant film (2): Hot melt adhesive layer

Claims (1)

[Scope of Claims] 1. A protective film for solar cells, characterized in that a hot melt adhesive layer is formed on at least one side of a heat-resistant film. 2. The protective film for solar cells according to claim 1, wherein the hot melt adhesive is an adhesive using a copolymerized acrylic resin or epoxy-modified polyethylene. 3. The protective film for solar cells according to claim 2, wherein the copolymerized acrylic resin is an acrylic ester-methacrylic ester copolymerized resin. 4. The protective film for solar cells according to claim 1, wherein the heat-resistant film is transparent, and the protective film surface made of the heat-resistant film is used as a light-receiving surface.