JPS60253253A - Back protective sheet for solar cell module - Google Patents

Abstract

PURPOSE:To enable to hold the heat shrinkage factors of the front and the back of the titled sheet in the same on and to prevent the generation of curling in the sheet by a method wherein the sheet is made into a front-to-back symmetrical three-layer constitution, which is formed by evaporating an electrically insulative glassy dampproof coated film on both faces of a heat- resistant film, or the sheet is cnstituted by further forming a filler layer on the inside face side thereof. CONSTITUTION:This back protective sheet 10 consists of an inside face glassy dampproof coated film 1, a heat-resistant film 2 and an outside face side glassy dampproof coated film 4, or this back protective sheet is constituted by further forming a filler layer 7 on the inside face side glassy dampproof coated film 1. The heat-resistant film 2 functions as a supporting member at the evaporating time of the glassy dampproof coated film 1 and 4, and at the same time, functions as a supporting member to shoulder the strength of the back protective sheet 10. It is needful that this film 2 has little heat resistance and heat shrinkage, and the film 2 is selected judging from the suitability to the glassy dampproof coated films as well. A polyester film, however, which is represented by a biaxially oriented polyethylene terephthalate film, is desirable for the film 2 in aspect of cost. An inorganic matter coated film containing silicon oxide as its main component is suitable to the electrically insulative glassy dampproof coated films 1 and 4 in points of a suitability for evaporation, a continuous coated film forming property, a dampproof property and cost. Moreover, stabilization of the efficiency of the sheet is contrived by providing forming the filler layer 7 in advance on the inside face of the dampproof coated film 1.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an improved back protection sheet that serves as a lower substrate of a solar cell module.

Technical Background In recent years, it has been pointed out that the existing energy sources, mainly oil, have been depleted, and it has become necessary to develop alternative energy sources. Moreover, as it utilizes inexhaustible solar radiant energy, it is desired to put it into practical use as soon as possible. Solar power generation uses solar cells to directly convert the sun's radiant energy into electrical energy, and this function is generally obtained by utilizing the quantum effect of silicon semiconductors, selenium semiconductors, etc.

Its function deteriorates when exposed directly to the outside air.

The basic function of a solar cell module is to efficiently guide the sun's radiant energy to the solar cell elements, and to protect the solar cell elements and internal wiring so that they can withstand harsh natural environments for a long period of time, for example, 20 years. be. Conventionally, solar cell modules generally have an upper transparent protective material (5) that serves as a structural support for the entire module, as shown in the cross-sectional view of Fig. 1. Examples include glass, acrylic resin,
Upper transparent protective material made of polycarbonate resin etc.
5) and the lower substrate material (back protection sheet) (10) made by laminating a stainless steel plate or aluminum foil with a light-resistant and weather-resistant polymer film such as polyvinyl fluoride (10) on the paint surface. Solar cell elements (6
), and furthermore, due to sudden changes in outside air conditions, the element (6
) for damage prevention and electrical insulation, the upper transparent material (5)
A transparent filler (7) having elastomeric properties such as silicone resin is filled between the and lower substrate material (10), heated and hardened, and the entire frame (8) is made of aluminum, stainless steel, etc. It was sealed and fixed using wo.

In addition, in response to recent demands for lower costs and improved suitability for mass production, we have omitted the complicated process of filling and curing silicone resin, and instead use a sheet of butyral resin or ethylene-vinyl resin on top of the upper transparent protective material (51). Acetate resin (E
VA), and then the solar cell element (6), a sheet-shaped filler sheet of butyral resin or EVA, and a back protection sheet aO) were placed on top of this in order, and after hot pressing under reduced pressure, the frame was A method of enclosing and fixing with a body (8) (heat press method) is also being studied at a rapid pace. The module obtained by this heat pressing method also has the same cross-sectional shape as shown in Figure 1, but the filler is not silicone resin but two butyral resin or EVA filler sheets fused together. (71f
It is 71'. In addition, in this heat press method, the back protective sheet (10) has a 20 to 60
A laminated sheet made by sandwiching μ aluminum foil with polyvinyl fluoride film is usually used.
The mechanical strength of the polyvinyl fluoride film is low, and
Because it is softened by the heat during pressing, such as 40 to 150 degrees Celsius,
Soldering of the solar cell element electrodes can cause pinholes due to protrusions on the electrodes or the edges of the amorphous silicon element on the stainless steel substrate, which can cause electrical problems such as short circuits or poor insulation.

In order to prevent these problems, measures are taken such as making the filler sheet (7) thicker than necessary, lowering the pressing temperature and slowing down the module compounding speed. Also, currently the filler sheet (7) and the back protection sheet (kawa) are separate.
Problems include the fact that the press pressure cannot be increased because the elements are usually easily damaged, and the process of manufacturing solar cell modules cannot be made continuous or automated, such as pressing in a vacuum chamber due to the difficulty of removing air. The reality is that there are points.

Therefore, the present inventors proposed the use of a heat-resistant film in which an electrically insulating glassy moisture-proof film such as silicon oxide was deposited on one or both sides of the aluminum foil instead of this aluminum foil, and filed a patent application No. 59-20510. No., patent application No. 59-5799
A patent application was filed as No. 2. This is as shown in the cross-sectional views of Figures 2 and 6, where (2) is a heat-resistant film;
fil (41 is a vapor-deposited layer of glassy moisture-proof film, (3) is a weather-resistant and heat-resistant film. This back protective sheet is
It has excellent moisture resistance and electrical insulation properties, and has a silicon oxide surface with a similar composition to the solar cell element (61) and the upper transparent material (5), so it has good adhesion to the filler (7). It was excellent.

By the way, when creating a module, as mentioned above, 1
Heat press at a temperature of 40-150°C.

If the press plate is peeled off without cooling after heat pressing, the heat shrinkage rate of the glassy moisture-proof film and that of the weather-resistant and heat-resistant film will be significantly different, so the back protective sheet will tend to curl as it cools ( .

Phenomena of peeling and deterioration of adhesive strength tended to occur.

For this reason, there is a method of heat pressing the next module without cooling the press plate after heat pressing (hot-hot method).
The problem was that after hot pressing, the only method that could be applied was to cool the pressed module, remove the press plate, and then heat it again when pressing the next module (hot-cold method). .

<Object of the Invention> The present invention is a solar cell module back protection sheet using a sheet on which an electrically insulating glassy moisture-proof film is vapor-deposited as a moisture-proof material. The purpose of the present invention is to provide a sheet that does not curl even when

<Summary of the Invention> That is, the present invention provides a sheet with a symmetrical three-layer structure on the front and back surfaces, which is formed by depositing an electrically insulating glassy moisture-proof film on both sides of a heat-resistant film, or a filler layer is formed on the inner surface of the sheet. Since the sheet is made up of two sides and is symmetrical, the front and back sides have the same heat shrinkage rate and do not curl. Further, the filler layer formed on the inner surface side is the same as the filler (7) in FIG.
This layer does not affect the curl.

<Detailed description of the invention) The present invention will be explained below with reference to the drawings.

FIGS. 4 and 5 are cross-sectional views of the back protection sheet for solar cell modules of the present invention.

That is, in FIG. 4, this back protection sheet includes, from above, an inner glass moisture-proof film (1), a heat-resistant film (
2) Consists of an outer glassy moisture-proof coating (4).

In FIG. 5, a filler layer (3) is further formed on this inner glass moisture-proof coating (1).

Here, the heat-resistant film (21) serves as a support during vapor deposition of the glassy moisture-proof coatings (1) and (4).

The back protection sheet 1- (10) serves as a support that increases the strength of the film and does not lose its supporting function for the moisture-proof films (1) and (4) even when subjected to heat and pressure during module creation using heat press. It needs to be heat resistant and have little heat shrinkage, which can cause distortion that can lead to element damage. In addition, unlike conventional aluminum foil, the moisture-proof layers (11 and (4)) are transparent, so the whiteness can be improved to utilize reflected and scattered light, which affects the light/current conversion efficiency of solar cells. So (J
It is necessary that the opacity (measured based on IS-P-8123) is 60% or more, preferably 80% or more, and the opacity (measured based on JIS-P-8138) is 60% or more, preferably 80 or more. In addition, since solar cells are usually used for a long period of time, the heat-resistant film (2) is either made of a weather-resistant material itself or is made of a white filler such as titanium oxide along with an ultraviolet absorber such as benzophenone or benzotriazole. It is something that has been soaked or impregnated. Although it is possible to apply a similar function in the form of a coating, in consideration of long-term durability and suitability for glass vapor deposition, it is preferable to have the entire film weather-resistant or whitened rather than just the surface treatment.

The material base of the heat-resistant film (2) is perfluoroalkoxy tree IIW (pFA)-tetrafluorinated ethylene-hexafluorinated propylene copolymer resin (FEP).

Perfluoroethylene-perfluoropropylene-per70
Robinyl ether ternary copolymer tree IIW (E P E)
, ethylene-tetrafluoroethylene copolymer resin (gT
Fg) - fluororesin film selected from polyvinylidene fluoride resin (pvDF), polyvinyl fluoride resin (PVF), polychloride fluorinated ethylene resin (PCTFE), polycarbonate film, polymethyl methacrylate film, polyarylate film, polyethylene terephthalate film, polyamide film,
Polyvinyl chloride film etc. can be used.

The heat-resistant film (2) is selected from the above properties as well as the glassy moisture-proof film fil (41) vapor deposition suitability 1 mechanical strength, electrical insulation, low moisture absorption, etc., but it is currently the biggest bottleneck in the spread of solar cells. Considering the cost aspect,
A polyester film typified by biaxially oriented polyethylene terephthalate is preferred. By the way, at the maximum excitation wavelength of 325 nm, which has a decomposition effect on polyester,
The glass vapor-deposited layer, which is a moisture-proof layer, is more effective in the present invention because it can block ultraviolet rays of 50 coefficients or higher.

The electrically insulating glassy moisture-proof coatings (11 and (4)) are preferably inorganic coatings containing silicon oxide as a main component in terms of vapor deposition suitability, continuous film formation, moisture resistance, and cost.

Usually, silicon oxide has a composition of 5i02, but the composition of the vapor deposited film is close to that of SiO. The thickness of the vapor-deposited film must be at least 200 mm or more from the viewpoint of moisture resistance, and if it exceeds 1000 A, the film is likely to crack, which will actually impair the moisture resistance.
1oooX is preferred.

Particularly preferred is 500 to 800.

In the present invention, the reason for vapor deposition on both sides is to improve the weather resistance of the heat-resistant film, and because of the difference in thermal shrinkage rate at high temperatures when creating a module between the glassy film and the heat-resistant film. This is because there is a problem of curling on the heat-resistant film side, and it is difficult to automate the solar cell module integration process.

The innermost surface of this back protection sheet is a glass-like moisture-proof film (1)
However, the filler such as polyvinyl butyral-EVA that is commonly used at present is a conductive film of a metal oxide such as indium oxide or tin oxide on the surface of a silicon wafer, or silicon itself, or a glass plate that is the upper transparent material. It has thermal adhesion properties and can be easily bonded and composited.

However, in order to maintain a high degree of moisture resistance before the module composite process using heat and pressure, it is desirable to protect the glassy moisture-proof coating (1) surface, which is prone to cranking, in advance. It is desirable to further form a filler layer (7) on the inner surface of the moisture-proof coating (11) in advance as shown in FIG.

By forming the filler layer (7) on the inner surface of the moisture-proof film 111 in advance, it is possible to stabilize the performance of this back protection sheet 00), and when combining modules, it is not necessary to fill the filler layer outside the back protection sheet 00). This has the advantage of simplifying the module assembly process, such as not requiring any agents. The filler layer (7) used here is 02 to 10.
) is preferable, but depending on the case, it may be coated with several tens of microns of EVA resin. In this case, the filler layer may be transparent, but it is more preferable if it is milky white in terms of improving the light/current conversion efficiency.

In the case of polyvinyl butyral, it has the disadvantage of high hygroscopicity, as well as high blocking properties.1 Normally, in order to use it in sheet form, starch, etc. used as an anti-blocking agent must be removed, making lamination work difficult. However, in the case of EVA-based sheets, it is also possible to laminate them as sheets using an adhesive, and more preferably, the film can be formed by melt-extruding directly onto the glassy moisture-proof film (1) surface, resulting in a total This makes it possible to significantly shorten the process and reduce costs.

Here, the EVA resin is not particularly limited as long as it melts and softens at 150°C or lower, preferably 120°C or lower, and has adhesive properties to glass, but EVA, partially saponified EVA, and It is possible to use a material grafted with an organic acid, or a material whose surface is coated or impregnated with a silane-based, titanium-based, or aluminum-based coupling agent.

The back protection sheet 00) of the present invention is used in the form of a laminated sheet shown in FIG. 4 or 5, and in the state shown in FIG. Thickness 643X on both sides) Maximum 3.0/, /'24Hr, 4
It has a moisture permeability value of 0°C-954RH or less, and has better moisture resistance than sealants such as butyl rubber that are normally used for sealing the ends of modules, preventing devitrification due to moisture absorption of the filler, corrosion of wiring, etc. It is possible to prevent this.

Back protection sheet of the present invention) (When creating a solar cell module using 101, the solar cell element (6) that has been wired in advance is attached to the upper protective filler sheet (an upper transparent material (glass plate, etc.) 5)), and cover the bottom protective filler sheet (7) from above, or directly without covering it with the back protection sheet Q (fi) of the present invention.

Cover with the moisture-proof film (1) side or the filler sheet (3) layered thereon as the inner surface, heat press the whole thing under reduced pressure to fuse and integrate the back protection sheet, and seal the edges with aluminum, etc. Enclose and fix with the frame (8).

<Effects of the Invention> As described in detail above, the solar cell module back surface purulent preservation sheet of the present invention has many advantages compared to conventional protective sheets. Therefore, there is no risk of electrical troubles such as short circuits with the element electrodes, and the yield is improved. Therefore, it is possible to select pressing pressure, time, temperature, etc. more freely, increasing work efficiency, and there is no risk of short circuits. Since there is no filler sheet, the thickness of the filler sheet can be reduced to the minimum necessary.

This saves on materials, and ■Since the filler is integrated into the back protection sheet itself or can be easily fused with the filler, it can be used in multiple stages under different conditions, such as back protection sheet - filler, then filler - element. Instead of requiring pressing, it is now possible to create a module with just one pressing process, and damage to the elements is also greatly reduced.

Furthermore, the protective sheet does not curl, so it has good hot adhesion, and can be adapted from the hot-cold process to the hot-hot process, which was required to automate and speed up the conventional module manufacturing process. The point is that it is possible.

As described above, according to the present invention, quality stabilization of solar cell modules,
Benefits include stabilization of production and material savings,
It is expected to make a significant contribution to the practical application and spread of solar power generation.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing the structure of a solar cell module to which the conventional protection sheet and the present invention are applied, and FIGS. 2 and 6 are schematic sectional views of the conventional protection sheet. 4 and 5 are schematic sectional views of embodiments of the protective sheet of the present invention. +1 l +4)... Glassy moisture-proof film (2)...
Heat-resistant film (3) Weather-resistant heat-resistant sheet Patent applicant Toppan Printing Co., Ltd. Representative Kazuo Suzuki 15- Figure 1 Figure 3 Figure 4 Figure 0 Figure 5

Claims (1)

[Claims] 1) A back protection sheet for a solar cell module, which is symmetrical on the front and back, and is formed by depositing an electrically insulating glassy moisture-proof film on both sides of a heat-resistant film. 2) A back protection sheet for solar cell modules, which is made by forming a filler layer on the inner surface of a symmetrical three-layer sheet made by depositing an electrically insulating glassy moisture-proof film on both sides of a heat-resistant film.