JPH10308521A - Protective sheet for solar cell module - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a protection sheet for a solar cell module that can exhibit performance stably for a long period of time even in an environment where temperature and humidity fluctuate greatly. SOLUTION: This sheet is used as a protective layer of a solar cell module and includes a fluororesin film layer having a silicon oxide thin film formed on its surface, and the sheet has an oxygen permeability of 5 cc / m ² · day · atm or less. water vapor transmission rate of 5g / m ² · day
Hereinafter, a protective sheet for a solar cell module, wherein the light transmittance is 80% or more, the thickness of the silicon oxide thin film is 150 to 500 °, and the adhesion strength of the film is 200 g / 15 mm or more. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a protective sheet for a solar cell module.

[0002]

2. Description of the Related Art Solar cells are particularly expected from new energy expected in the future because of their cleanliness, safety and ease of handling. Among these solar cells, a metal substrate such as stainless steel is often used as a base material because of excellent weather resistance, impact resistance, and flexibility. The photovoltaic element generally has a configuration in which a back electrode layer, a semiconductor layer as a photoelectric conversion layer, a transparent conductive layer, and a collecting electrode are formed on the metal substrate.

A solar cell module usually has a structure in which protective sheets are laminated on the front and back of a photovoltaic element formed on the above-mentioned metal substrate. Since it is necessary to be able to exhibit performance stably for a long time even in an environment with large fluctuations,
A protective sheet that is more excellent in transparency, light weight, moisture resistance, heat resistance, weather resistance, gas barrier properties, and the like than a general-purpose protective sheet is desired.

As this protective sheet for a solar cell module, a sheet containing a fluororesin film layer having a metal oxide thin film formed on the surface is particularly preferable (Japanese Patent Publication No. 4-33146, Japanese Patent Publication No. 4-76231, Japanese Patent Publication No. Fairness 4-
81869, JP-A-5-283727, JP-A-7-20
2236).

[0005]

However, according to the conventional proposals, the improvement is limited to a slight improvement in the position and layer structure of the protective sheet in the solar cell module or the specification of the metal oxide. In terms of point, it is not yet satisfactory.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have developed a film layer of a protective sheet for a solar cell module, a raw material of a metal oxide thin film, a production method, and a protective sheet to be obtained. As a result of earnestly conducting comprehensive analysis and study on physical properties, the present invention has been achieved. That is, the present invention relates to a sheet used as a protective layer of a solar cell module, the sheet including a fluororesin film layer having a silicon oxide thin film formed on the surface thereof, and having an oxygen permeability of 5 cc / m ² · day · atm or less, water vapor transmission rate 5g / m ²・ day
Hereinafter, a protective sheet for a solar cell module, wherein the light transmittance is 80% or more, the thickness of the silicon oxide thin film is 150 to 500 °, and the adhesion strength of the film is 200 g / 15 mm or more. Exists.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The basic structure of the protective sheet of the present invention includes a silicon oxide thin film and a fluororesin film layer. As the fluororesin used in the present invention, polyvinyl fluoride (PV
F), polyvinylidene fluoride (PVDF), ethylene tetrafluoride-ethylene copolymer (ETFE), ethylene tetrafluoride-propylene hexafluoride copolymer (FEP), ethylene tetrafluoride-pearlfluoroalkyl vinyl ether copolymer Coalesced (PFA), ethylene tetrafluoride polychlorinated ethylene trifluoride (PCTFE) and the like.
VF, PVDF and ETFE. Such a fluororesin film is used for the fluororesin film layer of the protective sheet of the present invention.

[0008] The fluororesin film is not limited because it is affected by various factors in the production method of the protective sheet, but preferably has a film thickness of 10-10.
0 μm, the thickness accuracy is ± 20% or less in the width direction and the flow direction of the film, the thermal shrinkage at 130 ° C. is 5% or less, and the tensile elongation at 50 g / 10 mm at 80 ° C. is 10% or less. It is particularly preferable that the film thickness is 20 to 70 μm, the thickness accuracy is ± 15% or less in the width direction and the flow direction of the film, the heat shrinkage at 130 ° C. is 3% or less, and 50 g / 10 mm at 80 ° C. Has a tensile elongation of 6% or less. The heat shrinkage is a value obtained by treating a film having a length of 100 mm at 130 ° C. for 5 minutes, and the tensile elongation is measured according to JIS K7.
127 is adopted. In order to obtain a desired film strength, the film thickness usually needs to be within the above range. In addition, it is necessary to pay special attention to thickness accuracy in order to express high gas barrier properties and high adhesion between layers when formed into a sheet, and a decrease in thickness accuracy means an increase in winding of the film,
The physical properties of the sheet are significantly reduced. Further, when the heat shrinkage and the tensile elongation are large, the protective sheet is likely to be wrinkled or cracked, and the physical properties of the sheet are reduced.

Prior to forming a silicon oxide thin film, it is usually necessary to apply a surface treatment such as a corona discharge treatment, a flame treatment, a plasma treatment, a glow discharge treatment and a surface roughening treatment to the above-mentioned fluororesin film. is there. This is because the fluororesin film is generally considered to be difficult to wet the surface and to be difficult to laminate with another film with an adhesive. Also,
Although the silicon oxide thin film and the fluororesin film may be directly laminated, it is usually preferable that an anchor coat layer is interposed between the two layers. This is because adhesion between layers can be improved, and gas barrier properties as a protective sheet can be further improved. As a material of the anchor coat layer, a thermosetting resin such as a polyester resin, a urethane resin, an acrylic resin, a vinyl modified resin, an epoxy resin, a modified styrene resin, a modified silicon resin, or an alkyl titanate is used. These may be used alone or in combination of two or more. Further, additives such as a silane coupling agent and an ultraviolet absorber may be added. The thickness of the anchor coat layer is usually 0.0
It is in the range of 0.5-5 μm, preferably 0.01-1 μm. If the anchor coat layer is too thin, coating unevenness occurs and the gas barrier property is hardly improved. On the other hand, if the anchor coat layer is too thick, the adhesiveness is deteriorated and the gas barrier property is rather lowered, which is not preferable. As a method for forming the anchor coat layer, various resin coating methods such as a gravure coating method and a reverse coating method are exemplified.

In the protective sheet of the present invention, the silicon oxide thin film is formed directly on the surface of the fluororesin film or indirectly via an anchor coat layer. As the silicon oxide thin film, silicon oxide alone may be used, but a mixture with other metal oxides such as aluminum oxide, magnesium oxide, and tin oxide can also be used. Since the silicon oxide thin film is required to have a high gas barrier property for a solar cell module, the thickness of the silicon oxide thin film is 150 to 500.
Å, preferably in the range of 200 to 400Å. If the thickness is less than 150 mm, the gas barrier properties are generally insufficient,
On the other hand, when the thickness exceeds 500 °, not only the cost is increased, but also the silicon oxide thin film is slightly yellow, the light transmittance is reduced, and the weather resistance is further reduced, which is not preferable. The thickness of the thin film when other metal oxides are used in combination as the silicon oxide thin film means the thickness of the thin film as a metal oxide mixture.

The above-mentioned silicon oxide thin film can be formed by any known method such as a vacuum evaporation method, a sputtering method, and a CVD method. However, a high-performance film having excellent gas barrier properties and the like is stably formed. The vacuum deposition method is preferred in that the deposition is performed at a high productivity. In the case where a silicon oxide thin film is formed by vacuum deposition, the transparency of the resulting thin film can be improved by introducing oxygen gas or water vapor into the atmosphere. In this case, the pressure of the atmosphere is 1 × 10 ⁻⁵ to 1 ×.
It is preferable to introduce the gas so as to be in the range of 10 ^-3 Torr. When the pressure is 1 × 10 ⁻³ Torr or more, the gas barrier property of the formed thin film is reduced, and when the pressure is set to 1 × 10 ⁻⁵ Torr or less, productivity is reduced, which is not preferable.

[0012] The protective sheet of the present invention comprises the above-mentioned protective sheet of the present invention comprising the above-mentioned fluororesin film layer having a silicon oxide thin film formed on the surface thereof. Particularly preferred specific physical properties are as follows: the sheet has an oxygen permeability of 5 cc / m ² · day · atm or less, a water vapor permeability of 5 g / m ² · day or less, and a light transmittance of 8
0% or more, and the adhesion strength of the silicon oxide thin film is 2
It is characterized by being at least 00 g / 15 mm. Further, a particularly preferable range of the above-mentioned various physical properties is that the oxygen permeability is ² cc / m ^2.
Day · atm or less, water vapor transmission rate of 2 g / m ² · day or less, light transmittance of 85% or more, and adhesion strength of the silicon oxide thin film of 250 g / 15 mm or more. In order to obtain a sheet having such physical properties, it is necessary to appropriately select raw materials and manufacturing conditions.

As a protective sheet for a solar cell module, a high degree of gas barrier properties is required. For example, an increase in water vapor transmission rate means a decrease in moisture resistance, which significantly reduces the output characteristics of the solar cell. Not preferred.
Also, a decrease in the light transmittance reduces the energy efficiency of the solar cell, which is not preferable. Further, poor adhesion of the silicon oxide thin film is not preferable because the gas barrier property tends to be reduced when the solar cell is used for a long period of time, or the sheet tends to peel or crack.

In an actual solar cell module, an adhesive layer covers the periphery of a photovoltaic element formed on a metal substrate, and a protective layer covering the light irradiation side surface and the back surface exists as its outer surface. The sheet can be used on either the front side or the back side. Here, as the adhesive layer, although not particularly limited, an adhesive mainly composed of an immediate resin such as vinyl acetate-ethylene copolymer, polyvinyl butyral, silicone resin, acrylic resin, and epoxy resin is used. Is preferred.

In the protective sheet of the present invention, it is usually preferable to laminate a silicon oxide thin film with silicon oxide, and a multilayer protective sheet may be used. Further, when the fluororesin film layer (A) and the silicon oxide thin film (B) have a basic structure, in addition to the layer structure of A / B / adhesive layer / photovoltaic element, A / B / adhesive layer / A / Layer configurations such as B / adhesive layer / photovoltaic element are also possible.

In some cases, a synthetic resin other than A and B may be further laminated on the protective sheet of the present invention to the extent that the characteristics of the protective sheet of the present invention are not impaired.
Examples of the plastic film as a base material of such a film include polyolefin resins such as polyethylene, polypropylene and polybutene; polyester resins such as polyethylene terephthalate and polyethylene-2,6-naphthalate; polyamide resins such as nylon 6 and nylon 12; Vinyl alcohol-based resins such as polyvinyl alcohol and ethylene-vinyl alcohol copolymer, furthermore, polyimide, polyetherimide, polysulfone,
Polyether sulfone, polyether ether ketone,
Examples thereof include polycarbonate, polyvinyl butyral, polyarylate, and cyclic polyolefin.

[0017]

The present invention will be described more specifically with reference to the following examples and comparative examples, but the present invention is not limited to these examples. In addition, the measuring method in the following examples is shown below. (1) Thickness of Silicon Oxide Thin Film The thickness was measured by an electron microscope (H-600, manufactured by Hitachi, Ltd.). (2) Oxygen Permeability In accordance with ASTM D3985, the oxygen permeability was measured under the conditions of a temperature of 25 ° C. and a relative humidity of 75% using an oxygen permeability measuring device (OX-TRAN100 manufactured by Modern Control).

(3) Water Vapor Permeability According to ASTM F1249, a water vapor permeability measuring device (Permatran-, manufactured by Modern Control Co., Ltd.)
The measurement was carried out using W1) under the conditions of a temperature of 40 ° C. and a relative humidity of 90%. (4) Total light transmittance Measured using a spectrophotometer according to JIS K7105.

(5) Evaluation of adhesion strength of silicon oxide thin film A urethane-based adhesive (AD-900: AD-900) manufactured by Toyo Morton Co., Ltd.
RT5 = 10: 1.5 mixture) and a thickness of 50
Dry-laminated low-density polyethylene film (TUX-TC, manufactured by Tokyo Cellophane Paper Co., Ltd.)
Aged for 3 days. Next, the laminated film was cut into a strip having a width of 15 mm and a length of 100 mm to obtain a test piece.

One end of the interface between the vapor-deposited film of the test piece and the low-density polyethylene film was previously peeled off by 50 mm, and both peeled surfaces were respectively autographed (test apparatus according to JIS K7127, DSS-10 manufactured by Shimadzu Corporation).
0) Attach the fixed gripper and the movable gripper at a distance of 100 mm between the grippers, and pull the movable gripper at a pulling speed of 3 mm.
The specimen was moved by 60 mm at a rate of 00 mm / min. During this time, the value of the center line of the wavy curve of the tensile load recorded on the strain gauge was determined, and the average value of three test pieces was defined as the adhesion strength (unit: g / 15 mm). The judgment was made. (Judgment) ○:> 200 g, Δ: 100 to 200 g, ×:
<100g

(6) Evaluation of moisture permeability Using a device specified in JIS C0022-2, temperature 8
It was left for 1000 hours under the conditions of 5 ± 2 ° C. and 85 ± 5% of relative humidity, and the electrical performance before and after being left was measured, and the following judgment was made. (Judgment) ：: Retention ratio of electric output characteristics> 90% Δ: Retention ratio of electric output characteristics = 70 to 90% X: Retention ratio of electric output characteristics <70%

Examples 1 and 2 and Comparative Examples 1 to 3 A surface-treated PVF film having a thickness of 25 μm as a fluororesin film (thickness accuracy is about 10% each in the width direction and the flow direction of the film, and the heat at 130 ° C.) The shrinkage was 2%, and the tensile elongation at 50 g / 10 mm at 80 ° C. was 5%). In Table 1, when the PVF film has an anchor coat layer, the isocyanate compound (trade name: Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.)
Saturated polyester (manufactured by Toyobo, trade name; Byron 30)
0) was applied to a PVF film with a coater and dried to form an anchor coat layer having a thickness of about 0.1 μm.

Using a roll-up type vacuum evaporation apparatus, silicon oxide (SiO, Sumitomo Sitix Co., Ltd.) was applied to the above-mentioned fluororesin film (anchor coat surface if an anchor coat layer is provided) under a vacuum of 8 × 10 ⁻⁵ Torr. Is deposited at a film forming rate of 2000 ° / sec by a high frequency induction heating method.
A sheet on which a silicon oxide film having a thickness shown in Table 1 was formed was manufactured. Table 1 shows the physical property evaluation results of the sheet.

COMPARATIVE EXAMPLE 4 A plasma CVD method (film forming speed 40
Example 1 except that a silicon oxide film was formed at 0 ° / sec).
A sheet was produced in the same manner as described above. Table 1 shows the physical property evaluation results of the sheet.

[0025]

[Table 1] Note) In Table 1 above, the unit of oxygen permeability is (cc / m ² · day · atm) and the unit of water vapor permeability is (g / m ² · day).

Examples 3 to 4 and Comparative Examples 5 to 6
ETFE film having a thickness shown in FIG. 2 (thickness accuracy is about 10% in each of the width direction and the flow direction of the film, 130 ° C.
Each sheet was manufactured under the same conditions, except that the heat shrinkage in the above was 2% and the tensile elongation at 50 g / 10 mm at 80 ° C. was 5%). Table 2 shows the physical property evaluation results of the sheet.

[0027]

[Table 2] Note) In Table 2 above, the unit of oxygen permeability is (cc / m ² · day · atm) and the unit of water vapor permeability is (g / m ² · day).

[0028]

The protective sheet of the present invention is transparent, lightweight,
Excellent in various physical properties such as moisture resistance, heat resistance, weather resistance, gas barrier properties, etc., so that a solar cell module using this protective sheet can perform stably for a long time even in an environment where temperature and humidity fluctuate greatly. Can be demonstrated.

Claims (6)

[Claims] 1. A sheet for use as a protective layer of a solar cell module, comprising a fluororesin film layer having a silicon oxide thin film formed on its surface, wherein the sheet has an oxygen permeability of 5 cc / m ² · day · atm. Below, the water vapor transmission rate is 5 g / m ² · day
Hereinafter, a protective sheet for a solar cell module, wherein the light transmittance is 80% or more, the thickness of the silicon oxide thin film is 150 to 500 °, and the adhesion strength of the film is 200 g / 15 mm or more. . 2. The thickness is 10 to 100 μm, the thickness accuracy is ± 20% or less in the width direction and the flow direction of the film, the heat shrinkage at 130 ° C. is 5% or less, and 50 g at 80 ° C.
The protective sheet for a solar cell module according to claim 1, wherein a fluororesin film having a tensile elongation at / 10 mm of 10% or less is used. 3. The protection for a solar cell module according to claim 1, wherein an anchor coat layer having a thickness of 0.005 to 5 μm is interposed between the silicon oxide thin film and the fluororesin film. Sheet. 4. The protective sheet for a solar cell module according to claim 1, wherein the silicon oxide thin film is formed by a vacuum deposition method. 5. A solar cell module, wherein the protective sheet for a solar cell module according to claim 1 is used as a protective layer covering a light irradiation side surface of a photovoltaic element. 6. A solar cell module, wherein the protective sheet for a solar cell module according to claim 1 is used as a protective layer for covering the back surface of the photovoltaic element on the light irradiation side.