JP2002134771A - Backsheet for solar cell - Google Patents

Abstract

(57) [Summary] [Problem] As a back surface protection sheet for a solar cell, it has heat resistance, weather resistance, moisture resistance and other required functions, and
An object of the present invention is to provide a laminate having a structure in which inexpensive heat-resistant and weather-resistant plastic films made of a polyester resin are laminated. SOLUTION: The intrinsic viscosity is 0.6 (dl / g) or more,
In addition, an inorganic oxide thin film layer is provided on one surface of a heat-resistant, weather-resistant plastic film made of a polyester resin having a cyclic trimer content of 0.5% by weight or less, and another heat-resistant film made of the same resin is provided on the thin film layer surface. And a weather-resistant plastic film is laminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inexpensive backside protective sheet for a solar cell which has excellent heat resistance, weather resistance, moisture proofness and other properties capable of withstanding a severe natural environment for a long period of time. is there.

[0002]

2. Description of the Related Art In recent years, as concerns of global warming have been increasing in various areas both inside and outside the country, to suppress carbon dioxide emissions,
Various efforts are being made. Increased consumption of fossil fuels leads to increased carbon dioxide in the atmosphere, which increases the temperature of the earth due to its greenhouse effect and has a significant impact on the global environment. Various alternatives to fossil fuels have been studied, but expectations for solar power, a clean energy source, are increasing. A solar cell forms the heart of a photovoltaic power generation system that directly converts the energy of sunlight into electricity, and is made of semiconductors. As a structure thereof, a single solar cell element is not used as it is, but generally several to several tens of solar cell elements are wired in series and parallel, and a long time (about 20
For various years, various packagings are performed to protect the elements, and they are unitized. The unit incorporated in this package is called a solar cell module. Generally, the surface exposed to sunlight is covered with glass, the gap is filled with a filler made of thermoplastic plastic, and the back surface is made of a sheet of heat-resistant and weather-resistant plastic material. The configuration is protected by

[0003] Since these solar cell modules are used outdoors, they are required to have sufficient durability and weather resistance in the structure, material structure and the like. In particular, the backside protective sheet is required to have low water vapor transmission rate as well as weather resistance. This is because when the filler is peeled off or discolored due to the permeation of moisture, or when the wiring is corroded, the output of the module itself may be affected.

Hitherto, as this back sheet for solar cells, a back sheet having a laminated structure in which an aluminum foil is sandwiched by a polyvinyl fluoride film (trade name: Tedlar) has been used in many cases. However, this polyvinyl fluoride film has a low mechanical strength, and is softened by the heat of a hot press at 140 ° C. to 150 ° C. which is applied at the time of manufacturing the solar cell module, and the protrusions of the solar cell element electrode penetrate the filler layer. In addition, by penetrating the polyvinyl fluoride film on the inner surface constituting the back protection sheet and coming into contact with the aluminum foil in the back protection sheet, the short circuit between the solar cell element and the aluminum foil adversely affects the battery performance. At the same time, it is expensive and is an obstacle in reducing the price of the solar cell module.

[0005]

In order to improve these drawbacks and obstacles, for example, an acrylic film, a vinyl chloride film, a general-purpose polyester film, a polycarbonate film, a polyvinylidene fluoride film and various other alternative films are laminated. Although a backside protective sheet for a battery has been studied, an inexpensive backside protective sheet for a solar cell having various functions such as heat resistance, weather resistance, and moisture resistance has not been provided.

Accordingly, an object of the present invention is to provide an inexpensive heat-resistant and weather-resistant plastic made of a polyester resin which has heat resistance, weather resistance, moisture resistance and other required functions as a back protective sheet for a solar cell. An object of the present invention is to provide a laminate in which an inorganic oxide thin film layer is provided on one surface of a film, and another heat-resistant and weather-resistant plastic film made of the same resin is laminated on the thin film layer surface.

[0007]

According to a first aspect of the present invention, there is provided an ink jet recording apparatus having an intrinsic viscosity of 0.6 (dl / g) or more and a cyclic trimer content of 0.5% by weight or less. A heat-resistant, weather-resistant plastic film made of a polyester resin is provided with an inorganic oxide thin film layer on one surface, and another heat-resistant, weather-resistant plastic film made of the same resin is laminated on the thin film layer surface. This is a backside protective sheet for a solar cell.

Next, a second aspect of the present invention is the solar cell according to the first aspect, wherein the inorganic oxide thin film layer is formed of either silicon oxide or aluminum oxide. Back protective sheet for use.

[0009]

According to the present invention, as a backside protective sheet for a solar cell, a polyester resin having an intrinsic viscosity of 0.6 (dl / g) or more and a cyclic trimer content of 0.5% by weight or less is used. A heat-resistant, weather-resistant plastic film is provided with an inorganic oxide thin film layer on one side, and another heat-resistant, weather-resistant plastic film made of the same resin is laminated on the thin film layer surface, so that it is excellent in moisture resistance, inexpensive, and It has various functions that can withstand long-term outdoor use.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A backsheet for a solar cell according to the present invention will be described in detail below along with embodiments.

FIG. 1 is a side sectional view showing an embodiment of a back protective sheet 10 for a solar cell according to the present invention, in which a heat-resistant and weather-resistant plastic film 1, an inorganic oxide thin film layer 2, An adhesive layer 3 and a heat-resistant and weather-resistant plastic film 4 are laminated.

The backsheet 10 for a solar cell according to the present invention.
Has a structure in which an inorganic oxide thin film layer 2 is provided on one side of a heat-resistant and weather-resistant plastic film 1 and another heat-resistant and weather-resistant plastic film 4 made of the same resin is laminated via an adhesive layer 3. Because of external mechanical pressure,
It can withstand impacts, etc. and does not melt or deteriorate due to the heat applied during the heat pressing process during the manufacture of solar cell modules. It does not deteriorate due to sunlight, rain, etc., even when exposed. The heat-resistant and weather-resistant plastic films 1 and 4 used for the back protective sheet 10 for a solar cell of the present invention are usually heated at about 150 ° C., especially at the time of hot pressing. The resin film must not be used. Further, it is necessary to have higher heat resistance and strength than a conventionally used white polyvinyl fluoride film, have weather resistance to withstand outdoor use for a long period of time, and be more inexpensive.

The film used for the backsheet 10 for a solar cell of the present invention is a film polymerized by a solid phase polymerization method.
The heat-resistant and weather-resistant plastic film must be made of a polyester resin having an intrinsic viscosity of 0.6 (dl / g) or more and a cyclic trimer content of 0.5% by weight or less. Polymers containing a large amount of cyclic trimers are liable to promote hydrolysis under high temperature and high humidity. By setting the content of the cyclic trimer to 0.5% by weight or less, hydrolysis under high temperature and high humidity can be suppressed, so that a film excellent in heat resistance and weather resistance can be obtained. Generally used polyester resin films have a cyclic trimer content of more than 0.5% by weight, so their mechanical strength deteriorates due to long-term exposure outdoors and hydrolysis, cracks, etc. This is undesirable.

As the polyester resin, polyethylene terephthalate, polybutylene terephthalate,
Any of polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and a copolyester composed of two or more of these may be used.

The content of the cyclic trimer is determined by dissolving 100 mg of the polymer in 2 ml of orthochlorophenol, measuring the content by liquid chromatography, and measuring the weight% of the polymer.

The backsheet for solar cell 10
Heat and weather resistant plastic films 1 and 4
May be transparent, but titanium oxide or the like is added to 100 parts by weight of the polyester resin so as to diffusely reflect ultraviolet rays on the film surface, prevent transmission of the ultraviolet rays into the inside of the film, and increase the power generation capability of the element. 5 to 2 white pigments
It is preferable to use a white polyester film kneaded at a ratio of 0 parts by weight. Its thickness is 20μm ~ 20
The range is 0 μm. More preferably, 30 μm to 50 μm
m.

Also, the backsheet 10 for solar cells
Heat and weather resistant plastic films 1 and 4
May contain a flame retardant, an antioxidant, an ultraviolet absorber, an antistatic agent, and the like, if necessary.

Further, the above-mentioned heat-resistant and weather-resistant plastic films 1 and 4 are provided so that the back protective sheet 10 for solar cells does not warp during the hot pressing in the solar cell module manufacturing process, so that the workability is not adversely affected. It is more preferable to use the same type of heat-resistant and weather-resistant plastic film.

The inorganic oxide thin film layer 2 is made of aluminum oxide, silicon oxide, tin oxide, magnesium oxide, or the like, and may be any material as long as it is transparent and has a gas barrier property against oxygen, water vapor and the like. Among them, aluminum oxide and silicon oxide are particularly preferable. The optimum conditions vary depending on the type and composition of the inorganic oxide used,
Generally, it is desirable to be within the range of 5 × 10 ⁻³ μm to 300 × 10 ⁻³ μm, and the value is appropriately selected. However, if the film thickness is less than 5 × 10 ⁻³ μm, 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. On the other hand, if the film thickness exceeds 300 × 10 ⁻³ μm, the flexibility of the thin film cannot be maintained, and the thin film may be cracked due to external factors such as bending and pulling after film formation. Preferably, 10 × 10 ⁻³ μm or more
It is in the range of 150 × 10 ⁻³ μm. As a method for forming the inorganic oxide thin film layer 2, it can be formed by a normal vacuum deposition method, but other thin film forming methods such as a sputtering method, an ion plating method, and a plasma vapor deposition method (CVD). Etc. can also be used. However, considering productivity, the vacuum deposition method is currently the most excellent.

The lamination can be performed by a known method such as a dry lamination method. The adhesive used for the adhesive layer 3 is a heat-resistant and weather-resistant plastic film 1 and 4.
It is necessary that the adhesive strength between the inorganic oxide thin film layer 2 and the inorganic oxide thin film layer 2 deteriorates during long-term outdoor use, does not cause delamination and the like, and further that the adhesive does not yellow, and a polyurethane-based adhesive can be used. .

Next, FIG. 2 shows a schematic side sectional view of an example in which a solar cell module is manufactured by using the solar cell back surface protection sheet 10 of the present invention. In order in the thickness direction, the upper transparent material 40, the filler 30, the solar cell element 20, the wiring 21,
The back protection sheet 10 for a solar cell and the frame body 50 are formed.

The upper transparent material 40 has good light transmittance, has excellent weather resistance over a long period of time (about 20 years), has a small decrease in light transmittance, does not easily adhere to dust and the like, and has scratches. It is necessary to have various functions such as hardly sticking and extremely low water vapor transmission rate.
An acrylic resin, a polycarbonate resin, a silicone resin, a fluorine resin, or the like is used.

The filler 30 has a high transmittance of sunlight, has no change in physical properties such as a decrease in light transmittance due to being left outdoors for a long period of time, has a high insulation resistance, and does not corrode other materials. It is necessary to have various functions such as resin cracking, interface peeling, etc. due to sudden changes in outside air conditions, etc., polyvinyl butyral resin, silicone resin, vinyl chloride resin, polyurethane resin, ethylene-vinyl acetate copolymer Resin can be used.

As the back surface protection sheet 10 for a solar cell,
Generally, it has various functions such as insulation, heat resistance in the module manufacturing process (150 ° C. or higher), extremely low water vapor permeability, and weather resistance to withstand long-term outdoor exposure. At the same time, it is required that the price be low.

As the frame, an aluminum mold is generally used.

[0026]

Next, a backside protective sheet 1 for a solar cell according to the present invention.
The solar cell module 60 manufactured using the protective sheet 0 and this protective sheet will be described below with reference to specific examples, but the present invention is not limited to these examples.

Example 1 A heat-resistant and weather-resistant plastic film layer 1 having the structure shown in FIG. 1 has an intrinsic viscosity of 0.67.
(Dl / g) and a thickness of 50% produced from a polyester resin having a cyclic trimer content of 0.5% by weight or less.
Aluminum oxide is vapor-deposited on one side of a heat-resistant, weather-resistant polyester resin film having a thickness of μm as an inorganic oxide thin film layer 2 by a vacuum vapor deposition method, and a solid content of 30% by weight of Takeda Pharmaceutical Co., Ltd. Polyurethane-based adhesive (base agent Takelac A515 / hardener Takenate A50 = 10/1 solution) was applied in an amount of 5 g / m ² (dry state), dried, and then heat-resistant and weather-resistant plastic film 4 of the same resin Another heat-resistant and weather-resistant polyester resin film having a thickness of 50 μm was bonded to form a backsheet 10 for a solar cell of the present invention. Subsequently, the previously connected solar cell element 20 is placed on an upper transparent material 40 (glass plate) on which a filler sheet 30 (100 μm ethylene-vinyl acetate sheet) is laid, and another sheet of the same material is placed thereon. Of the backing sheet for solar cells of the present invention
0, and the whole is hot-pressed at 150 ° C. for 20 minutes under reduced pressure to fuse and integrate the back surface protection sheet 10 for a solar cell, and the ends are fixed with a frame of aluminum or the like. The battery module 60 was created.

<Example 2> In Example 1, a heat-resistant and weather-resistant plastic film layer 1 having the structure shown in FIG. 1 was used as the inorganic oxide thin film layer 2 with silicon oxide deposited by a vacuum deposition method. Similarly, the back protective sheet 10 for a solar cell of the present invention was prepared, and a solar cell module 60 using the sheet was prepared.

<Comparative Example 1> In Example 1, the heat-resistant and weather-resistant plastic films 1 and 4 were 38 μm thick.
m, and a 25 μm-thick aluminum foil was laminated in place of the inorganic oxide thin film layer 2 except for using a white polyvinyl fluoride film having a thickness of 25 m and a back protective sheet 10 for solar cells in the same manner. A solar cell module 60 was created.

Comparative Example 2 In Example 1, the heat and weather resistant plastic films 1 and 4 had an intrinsic viscosity of less than 0.6 (dl / g) and a cyclic trimer content of 0.5. Thickness of polyester resin exceeding 5% by weight
Except for using a 0 μm white polyester film,
Similarly, a back surface protection sheet 10 for a solar cell was produced, and a solar cell module 60 using the sheet was produced.

<Evaluation> The moisture permeability of the back protective sheets for solar cells prepared in Examples 1 and 2 and Comparative Examples 1 and 2 was measured, and a solar cell module prepared using these back protective sheets was used. Then, battery characteristics such as short-circuit current, open-circuit voltage, maximum output, and the like, and a high-temperature and high-humidity (85 ° C., 95% RH) exposure test based on JIS-C8913 were implemented and evaluated. Table 1 shows the results.

[0032]

[Table 1]

From Table 1, the moisture permeability of the back protective sheets for solar cells of Examples 1 and 2 and Comparative Examples 1 and 2 are all very small and excellent. In addition, as a result of exposing each of the prototyped solar cell modules in a state of high temperature and high humidity (85 ° C., 95%) for 2000 hours, the battery characteristics are shown in Examples 1 and 2 and Comparative Example 1.
Although there was no particular abnormality, in the appearance inspection, the polyester resin film used for the back surface protection sheet of Comparative Example 2 was cracked and the battery characteristics were deteriorated. Further, Comparative Example 1 has good battery characteristics and no co-deterioration even after the exposure test, but has a disadvantage that the cost is very high. When comprehensively evaluated based on the results as described above, Examples 1 and 2 were used as backsheets for solar cells.
It turns out that it is excellent both in terms of function and cost.

[0034]

The solar cell back protective sheet of the present invention is
An inorganic oxide thin film is formed on one surface of a heat-resistant and weather-resistant plastic film made of a polyester resin having an intrinsic viscosity of 0.6 (dl / g) or more and a cyclic trimer content of 0.5% by weight or less. The layer has a laminated structure in which another heat-resistant, weather-resistant plastic film made of the same resin is laminated on the surface of the thin film layer, so that it is excellent in heat resistance, weather resistance, and moisture resistance. There is no adverse effect on battery performance due to a short circuit caused by damage to the protective sheet, there is no deterioration in various functions in outdoor use for a long time (about 20 years), and the price is lower than that of the conventional back protective sheet. Any advantages that can stabilize the quality of the battery module and reduce the cost can be obtained, and have great value in the industrial field related to photovoltaic power generation.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a backsheet for a solar cell of the present invention.

FIG. 2 is a schematic side sectional view of a solar cell module using the solar cell back surface protection sheet of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heat-resistant and weather-resistant plastic film 2 ... Inorganic oxide thin film layer 3 ... Adhesive layer 4 ... Heat-resistant and weather-resistant plastic film 10 ... Solar cell back protective sheet 20 ... Solar cell element 21 ... Wiring 30 ... Filler 40 ... Upper transparent material 50 ... Frame

 ──────────────────────────────────────────────────の Continuing on the front page F term (reference) 4F071 AA43 AA88 AF45 AF57 AH12 BC01 BC12 4F100 AA17B AA19B AA20B AK41A AK41C AK51G BA03 BA06 BA10A BA10C EH46 EH462 EH66 EH662 EJ86 EJ862 J90 J06A09 5F051 BA18 JA03 JA04 JA05

Claims (2)

[Claims] 1. A heat-resistant and weather-resistant plastic film made of a polyester resin having an intrinsic viscosity of 0.6 (dl / g) or more and a cyclic trimer content of 0.5% by weight or less. A backside protective sheet for a solar cell, comprising a laminate in which an inorganic oxide thin film layer is provided and another heat-resistant and weather-resistant plastic film made of the same resin is laminated on the thin film layer surface. 2. The backsheet according to claim 1, wherein the inorganic oxide thin film layer is formed of one of silicon oxide and aluminum oxide.