JP2009212122A - Rear surface protecting sheet for solar cell and solar cell using this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rear surface protecting sheet for a solar cell which exhibits excellent whiteness degree, long term durability and weatherability and a very little environmental load while reducing the cost, and to provide a solar cell module using this. <P>SOLUTION: A rear surface protecting sheet 1 for a solar cell is constituted by sequentially laminating a first weatherability base 3 consisting of white resin, a weatherability barrier base 2 including a barrier layer 5 consisting of resin and a deposition layer 6 consisting of an inorganic compound deposited on one surface of the barrier layer 5, and a second weatherability base 4 including a white layer 4a obtained by coloring resin white and a transparent layer 4b consisting of resin which is not colored, wherein a transparent layer 4b is arranged on the side of the weatherability barrier base 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a solar cell back surface protective sheet (solar cell back surface sealing sheet), and more specifically, poor appearance and gas barrier performance due to poor adhesion even in a severe storage environment under high temperature and high humidity required for solar cells. It is related with the solar cell using the back surface protection sheet for solar cells which is not accompanied by the fall of this, and is excellent in wet-heat-resistant adhesiveness, and this back surface protection sheet for solar cells.

  In recent years, various efforts have been made to suppress carbon dioxide emissions while interest from various countries both inside and outside Japan has increased. Increasing fossil fuel consumption leads to an increase in atmospheric carbon dioxide, and the greenhouse effect raises the Earth's temperature, significantly affecting the global environment. Various studies have been carried out to solve this global problem, and in particular, solar power generation is highly expected in terms of cleanliness and non-pollution.

  A solar cell constitutes the heart of a photovoltaic power generation system that directly converts sunlight energy into electricity, and is made of a single crystal, polycrystalline, or amorphous silicon semiconductor. As the structure of the solar cell, a single solar cell element (cell) is not used as it is, and generally several to several tens of solar cell elements are wired in series and in parallel for a long time (about In order to protect the cell over 20 years, various packaging has been performed and unitized. The unit incorporated in this package is called a “solar cell module”.

  In general, a solar cell module covers the surface exposed to sunlight with a glass surface, fills the gap with a filler made of a thermoplastic (particularly ethylene-vinyl acetate copolymer (EVA)), and the back surface has heat and weather resistance. The structure is protected by a white back surface protection sheet made of a conductive plastic material. The reason for using the white back surface protection sheet is to reflect light and increase the power generation effect.

  By the way, since a solar cell module is used outdoors, sufficient durability and weather resistance are required in materials used and its configuration. In particular, the back surface protection sheet is required to be white and have a weather resistance and a low water vapor transmission rate. This is because if the filler in the unit is peeled off or discolored due to moisture permeation or the wiring is corroded, the module output itself is adversely affected.

  Conventionally, such a back surface protection sheet for a solar cell generally has a configuration in which a barrier layer 102 made of PET is sandwiched between fluororesin layers 101 and 103 as shown in FIG. The fluororesin layers 101 and 103 are used as the outer layer base material regardless of the presence or absence of the water vapor barrier. As a fluorine resin generally used for solar cells, there is polyvinyl fluoride (PVF) (such as PVF Tedlar manufactured by DuPont) (for example, see Patent Document 1). The fluororesin is extremely strong in intermolecular hydrogen bonds and is therefore difficult to decompose, and has an ideal weather resistance as a back surface protection sheet for solar cells that is used for a long time. On the other hand, fluororesin tends to remain in the environment, and when it burns, harmful hydrogen fluoride is generated, and the influence on the global environment is not small. In addition, the fluororesin is very expensive and may be about 20 to 30 times as much as a general polyethylene terephthalate (PET) having the same thickness. It has become a major obstacle.

  On the other hand, the back surface protection sheet for solar cells using polyester films, such as a weather-resistant polyethylene terephthalate (PET), instead of the fluororesin mentioned above is also proposed (for example, refer patent document 2, 3 etc.) .) However, in the solar cell back surface protection sheet using conventional PET, as shown in FIG. 3 (b), the barrier layer 202 sandwiched between the weather resistant PETs 201 and 203 is made of ordinary PET resin. Since the barrier layer 202 is manufactured as a base, the barrier layer 202 may deteriorate with time to lose the barrier property or cause delamination of the sheet.

In addition, in order to enhance whiteness, a back protection sheet for solar cells equipped with a weather-resistant substrate colored with a white pigment has been developed. By mixing the white pigment, the cohesive strength of the resin itself is reduced. Will do. When this is used for a long time, even if the adhesion with the adhesive is ensured, there is a possibility that the surface of the resin is destroyed and peeling occurs.
JP 2000-164907 A JP 2002-26354 A JP 2005-11923 A

  The present invention has been made in view of the above circumstances, and has excellent whiteness, long-term durability, and weather resistance, and has a very low environmental load and can also reduce the cost. It aims at providing the solar cell using this.

The gist of the present invention aimed at solving the above problems is as follows.
[1] a first weather-resistant substrate made of a white resin;
A weather resistant barrier substrate comprising a barrier layer made of a resin and a deposited layer made of an inorganic compound deposited on one surface of the barrier layer;
A second layer comprising a white layer formed by coloring the resin in white and a transparent layer formed from a non-colored resin, and sequentially laminated;
A back protective sheet for solar cells, wherein the transparent layer is disposed on the weather-resistant barrier substrate side.
[2] In the above [1], the second weather-resistant substrate includes a quasi-white layer having a lower coloring degree than the white layer between the white layer and the transparent layer. The back surface protection sheet for solar cells as described.
[3] The back protective sheet for solar cells according to [1] or [2], wherein the white layer is formed by mixing a white pigment with solid phase polymerized polyethylene terephthalate (PET).
[4] The back protective sheet for a solar cell according to [2], wherein the quasi-white layer is formed by mixing a white pigment with polyethylene terephthalate (PET) subjected to solid phase polymerization.
[5] Any one of [1] to [4], wherein the second weather-resistant substrate is made of a resin mainly composed of polyethylene terephthalate (PET) or polyethylene naphthalate (PEN). The back surface protection sheet for solar cells as described in any one of.
[6] In any one of the above [1] to [5], the first weather-resistant substrate is made white by foaming a resin mainly composed of polyethylene terephthalate (PET). The back surface protection sheet for solar cells as described.
[7] The above [1] to [6], wherein the first weather-resistant base material is made white by foaming a mixed resin composed of polyethylene terephthalate (PET) and methylpentene resin (TPX). ] The back surface protection sheet for solar cells as described in any one of.
[8] The first weather-resistant substrate is formed by laminating polyethylene terephthalate (PET) on both sides of a whitened substrate obtained by foaming a mixed resin composed of polyethylene terephthalate (PET) and methylpentene resin (TPX). The back surface protection sheet for solar cells according to any one of [1] to [7], wherein the back surface protection sheet is for solar cells.
[9] The backside protection for solar cells according to any one of [1] to [8], wherein the weather-resistant barrier substrate is made of a resin mainly composed of polyethylene naphthalate (PEN). Sheet.
[10] The weather-resistant barrier substrate includes an easy-adhesion coat layer laminated on both surfaces of the barrier layer, and the vapor deposition layer is deposited on the one surface of the barrier layer via the easy-adhesion coat layer. The back surface protection sheet for solar cells according to the above [1] to [9], wherein
[11] The inorganic compound according to any one of [1] to [10], wherein the inorganic compound includes at least one inorganic oxide selected from silicon oxide, aluminum oxide, and magnesium oxide. The back surface protection sheet for solar cells as described.
[12] comprising a glass plate, a back surface protection sheet disposed to face the glass plate, and a solar cell module disposed between the glass plate and the back surface protection sheet,
The back surface protection sheet for solar cells according to any one of [1] to [11] is used for the back surface protection sheet, and the back surface protection sheet has the glass plate on the first weather-resistant substrate side. A solar cell characterized by being arranged so as to oppose.

According to the back surface protection sheet for a solar cell of the present invention, the second weather-resistant substrate includes a white layer formed by coloring the resin in white and a transparent layer formed from an uncolored resin, thereby providing a barrier layer. And using a transparent layer on the adhesive surface of the second weather-resistant substrate to ensure the cohesive strength of the resin and using a white layer on the outer surface of the second weather-resistant substrate to prevent yellowing from being seen. Two requirements can be satisfied at the same time.
Therefore, it produces high-whiteness, long-term durability, and because it does not use fluorine, it produces a back protection sheet for solar cells that has very low environmental impact, low cost, and excellent weather resistance. be able to.

  Hereinafter, a solar cell back surface protection sheet (solar cell back surface sealing sheet) to which the present invention is applied and a solar cell using the same will be described in detail with reference to the drawings. In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for convenience, and the dimensional ratios of the respective components are the same as the actual ones. Not exclusively.

<Back side protection sheet for solar cells>
First, the back surface protection sheet for solar cells (henceforth a back surface protection sheet) 1 to which this invention shown in FIG. 1 is applied is demonstrated.
As shown in FIG. 1 (a), the back surface protection sheet 1 is laminated in a state where a weather resistant barrier substrate 2 is sandwiched between a first weather resistant substrate 3 and a second weather resistant substrate 4. It has an integrated structure.

(Weather-resistant barrier substrate)
The weather-resistant barrier substrate 2 is made of a laminate in which a barrier layer 5 made of a resin and a vapor deposition layer 6 made of an inorganic compound vapor-deposited on one surface of the barrier layer 5 are laminated.
The barrier layer 5 is preferably a polyethylene naphthalate (PEN) film, and PEN is superior in weather resistance compared to PET, and is less susceptible to deterioration over time. Problems when used can be greatly suppressed. In addition, it is preferable that the thickness of the barrier layer 5 is about 12-50 micrometers.

  It is preferable that an easy-adhesion coat layer 7 for improving the adhesion of PEN is provided on both surfaces of the barrier layer 5. The easy adhesion coat layer 7 is preferably made of an acrylic resin, an epoxy resin, a urethane resin, or the like.

  The vapor deposition layer 6 is vapor-deposited on one surface of the barrier layer 5 on which the easy adhesion coat layer 7 is laminated. The vapor deposition layer 6 is preferably made of at least one inorganic oxide selected from silicon oxide, aluminum oxide, and magnesium oxide.

(First weather-resistant substrate)
The first weather-resistant substrate 3 is not particularly limited as long as it is made of a white resin. For example, the resin may be made white by foaming, or a white pigment may be mixed to make a resin having whiteness by coloring, such as a film made by foaming a resin mainly composed of polyethylene terephthalate (PET). It is preferable to use it. Since the density of the first weather-resistant substrate 3 is reduced by foaming, it is possible to reduce the weight and reduce the unit price of the material. In addition, it is preferable that the thickness of the 1st weather resistant base material 3 is about 50-200 micrometers.

In addition, it is preferable to use a material obtained by foaming a mixed resin composed of polyethylene terephthalate (PET) and methylpentene resin (TPX) as the first weather-resistant substrate 3. By blending TPX, the whiteness of the first weather-resistant substrate 3 can be increased and the insulation can be improved.
Further, the PEN of the barrier layer 5 may be browned instead of being hardly deteriorated with time. Therefore, if the whiteness of the first weather-resistant substrate 3 is increased by TPX, the PEN with time elapses. It is possible to prevent problems such as the transparent color of the solar cell itself appearing brown.

  Further, the first weather-resistant substrate 3 is laminated with weather-resistant polyethylene terephthalate (PET) on both surfaces of a substrate obtained by foaming a mixed resin composed of polyethylene terephthalate (PET) and methylpentene resin (TPX). What was done can be used suitably. In addition, the PET laminated on both surfaces of the mixed resin only needs to have a minimum thickness required for manufacturing. Specifically, the thickness of the mixed resin of PET and TPX is preferably about 50 to 120 μm, and the thickness of the weather-resistant PET on both sides is preferably about 5 to 10 μm.

(Second weather-resistant substrate)
The second weather-resistant substrate 4 includes a white layer 4a formed by coloring the resin in white and a transparent layer 4b formed of an uncolored resin, and the transparent layer 4b is disposed on the weather-resistant barrier substrate 2 side. Has been.
Although the manufacturing method of the 2nd weather resistant base material 4 is not specifically limited, For example, it comprises the white layer 4a and the transparent layer 4b by coextruding resin from which the mixing ratio of resin and a pigment differs. In addition, the second weather resistant substrate 4 can be manufactured.

  Moreover, as shown in FIG.1 (b), the 2nd weather resistant base material 4 is equipped with the quasi-white layer 4c whose coloring degree is lower than the white layer 4a between the white layer 4a and the transparent layer 4b. May be. Also in this case, for example, the second weather-resistant substrate 4 composed of the white layer 4a, the quasi-white layer 4c, and the transparent layer 4b is manufactured by co-extruding resins having different mixing ratios of the resin and the pigment. Can do.

  The second weather-resistant substrate 4 is preferably made of a resin mainly composed of polyethylene terephthalate (PET) or polyethylene naphthalate (PEN). The white layer 4a and / or the quasi-white layer 4c are preferably made of a film colored white by mixing these resins with a white pigment such as titanium oxide or rutile type titanium oxide. Solid-phase-polymerized polyethylene terephthalate (PET More preferably, a white pigment is mixed with the white pigment.

The mixing amount of the white pigment in the white layer 4a is preferably 10 to 20% by mass, and the mixing amount of the white pigment in the quasi-white layer 4c is preferably less than 10% by mass.
By mixing the white pigment, the cohesive strength of the resin itself is lowered, and when the back surface protective sheet 1 is used for a long time, the adhesive strength with the adhesive is affected. Further, since the cohesive force of the second weather-resistant substrate is lowered, even if the adhesive force with the adhesive is ensured, there is a possibility that the surface of the resin is destroyed and peeling occurs.
Therefore, by dividing the second weather-resistant substrate into a white layer 4a containing a white pigment and a transparent layer 4b not containing a white pigment, the barrier layer 5 and the second weather-resistant substrate have an adhesive surface. The transparent layer 4b can be used to ensure the cohesive strength of the resin, and the outer surface that is not bonded can simultaneously satisfy the two requirements of using the white layer 4a to prevent yellowing.
In addition, since there is a difference in cohesion between a layer containing a large amount of pigment and a layer not containing the pigment, there is a possibility of peeling between the layers. Therefore, in order to alleviate this difference in cohesive force, it is preferable to provide the quasi-white layer 4c in the middle.

Moreover, this 2nd weather-resistant base material 4 increases the molecular weight of PET molecule | numerator dramatically by solid-phase-polymerizing PET (8000-20000 increases to about 80000-100000), and it is between molecules. The bond strength is very strong. Since the solid-phase polymerized PET molecules have a very large molecular weight, the crystal structure becomes dense and is hardly affected by hydrolysis or heat. Therefore, it is desirable to use such a resin for the outermost layer.
Thereby, especially weather resistance increases and deterioration with time can be remarkably suppressed as compared with ordinary PET. Further, if a white pigment is put in the second weather-resistant substrate 4, as in the case of the above-mentioned first weather-resistant substrate 3, the color of PEN will be transparent with time and the solar cell itself will be It is possible to prevent problems such as the appearance of brown.
In addition, it is preferable that the thickness of the 2nd weather resistant base material 4 is about 50-200 micrometers.

  The back surface protective sheet 1 is formed by sequentially laminating the above-described first weatherable substrate 3, weatherable barrier substrate 2 and second weatherable substrate 4, for example, a polyester-based adhesive, a polyurethane-based adhesive, Using an adhesive (not shown) such as a polyacrylic adhesive or a polycarbonate adhesive, the three layers are integrated by bonding them together.

  In the back surface protective sheet 1 having the above-described structure, the adhesion between the barrier layer 5 and the second weather resistant substrate 4 is enhanced, the long-term durability is good, and the outer surface of the second weather resistant substrate 4 It is possible to prevent yellowing. Moreover, it is possible to obtain very excellent weather resistance without using a fluororesin for the exterior base material. In addition, since the above-described fluororesin is not used, the environmental load is very small and the cost can be kept low.

<Solar cell>
Next, the solar cell module 10 to which the present invention shown in FIG. 2 is applied will be described.
As shown in FIG. 2, the solar cell 10 is schematically configured by a glass plate 11, a solar cell module 13 as a photovoltaic element provided with wiring, the back surface protection sheet 1, and a filler 14. ing.

  Moreover, the said back surface protection sheet 1 is arrange | positioned so that the 1st weathering base material 3 side may oppose the glass plate 11. FIG. Thereby, the 2nd weather resistant base material 4 excellent in the weather resistance is arrange | positioned in the outermost layer.

  In the solar cell 10 having the above structure, by using the above-described back surface protective sheet 1 of the present invention, it is possible to ensure long-term durability and insulation at a low cost with high whiteness.

  Hereinafter, the effects of the present invention will be made clearer by examples. In addition, this invention is not limited to a following example, In the range which does not change the summary, it can change suitably and can implement.

Example 1
In Example 1, a 125 μm-thick foamed polyethylene terephthalate (PET) film (trade name / model number “Lumirror KT-01” manufactured by Toray Industries, Inc.) was used as the first weather-resistant substrate.
As a weather-resistant barrier substrate, a 12 μm thick polyethylene naphthalate (PEN) film (trade name / model number “Teonex Q-51” manufactured by Teijin Ltd.) is provided with an easy-adhesion coat layer made of acrylic resin. A laminate film in which a barrier layer obtained by depositing silicon oxide on one surface provided with an adhesive coat layer was used.
As a second weather-resistant substrate, a 50 μm thick polyethylene terephthalate (PET) film (trade name / model number “Lumirror QG-01” manufactured by Toray Industries, Inc.) mixed with 20% by mass of a white pigment (rutile-type titanium oxide) is used. A film was used.
A transparent layer is arranged on the weather-resistant barrier substrate side, these substrates are sequentially laminated, and a polyester adhesive (trade name / model number “AD-76-P1” manufactured by Toyo Morton Co., Ltd.) is used between the layers. The back surface protection sheet for solar cells was produced by bonding together by dry lamination.

(Comparative Example 1)
In Comparative Example 1, a foamed polyethylene terephthalate (PET) film (trade name / model number “Lumirror KT-01” manufactured by Toray Industries, Inc.) having a thickness of 125 μm was used as the foamed weather resistant substrate, and the thickness was used as the weather resistant barrier substrate. A laminate film provided with a barrier layer obtained by depositing silicon oxide on one surface of a 12 μm polyethylene terephthalate (PET) film, and a white pigment (titanium oxide) mixed polyethylene terephthalate (PET) film having a thickness of 50 μm as a colored weather resistant substrate (Product name and model number “Lumirror QG-01” manufactured by Toray Industries, Inc.) are sequentially laminated, and each layer is dried with a polyester-based adhesive (product name and model number “AD-76-P1” manufactured by Toyo Morton Co., Ltd.). The back surface protection sheet for solar cells was produced by bonding together by lamination.

And about the back surface protection sheet for solar cells of Example 1 and Comparative Example 1, an accelerated test of 500, 1000, 1500, 2000, 2500 hours was performed in an 85 ° C.-85% RH environment immediately after the production (initial stage). The decrease in adhesive strength was measured. Measurement is performed between the first weather-resistant substrate and the weather-resistant barrier substrate (1 layer / 2 layers) and between the weather-resistant barrier substrate and the second weather-resistant substrate (2 layers / 3 layers). It was done in. The results are shown in Table 1.
In addition, about adhesive strength, the strip of width 15mm was cut out from each back surface protection sheet to make a test piece, and this test piece was measured by the T-shaped peeling test at a speed of 300 mm / min.

  From the measurement results shown in Table 1, the solar cell back surface protective sheet of Example 1 has a small decrease in adhesive strength against deterioration with time and excellent weather resistance compared to the solar cell back surface protective sheet of Comparative Example 1. You can see that

It is sectional drawing which shows one structural example of the back surface protection sheet for solar cells to which this invention is applied. It is sectional drawing which shows one structural example of the solar cell module to which this invention is applied. It is sectional drawing which shows an example of the back surface protection sheet for conventional solar cells.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Back surface protection sheet for solar cells, 2 ... Weather resistance barrier base material, 3 ... 1st weather resistance base material, 4 ... 2nd weather resistance base material, 4a ... White layer, 4b ... Transparent layer, 4c ... Semi White layer, 5 ... barrier layer, 6 ... vapor deposition layer, 7 ... easy adhesion coat layer, 10 ... solar cell, 11 ... glass plate, 13 ... solar cell module, 14 ... filler.

Claims (12)

A first weather-resistant substrate made of a white resin;
A weather resistant barrier substrate comprising a barrier layer made of a resin and a deposited layer made of an inorganic compound deposited on one surface of the barrier layer;
A second layer comprising a white layer formed by coloring the resin in white and a transparent layer formed from a non-colored resin, and sequentially laminated;
A back protective sheet for solar cells, wherein the transparent layer is disposed on the weather-resistant barrier substrate side.   2. The solar cell according to claim 1, wherein the second weather-resistant substrate includes a quasi-white layer having a lower coloring degree than the white layer between the white layer and the transparent layer. Back surface protection sheet.   The back protective sheet for a solar cell according to claim 1 or 2, wherein the white layer is formed by mixing a white pigment with polyethylene terephthalate (PET) subjected to solid phase polymerization.   The back protective sheet for a solar cell according to claim 2, wherein the quasi-white layer is formed by mixing a white pigment with polyethylene terephthalate (PET) subjected to solid phase polymerization.   5. The solar cell according to claim 1, wherein the second weather-resistant substrate is made of a resin mainly composed of polyethylene terephthalate (PET) or polyethylene naphthalate (PEN). Back protection sheet.   The back surface for a solar cell according to any one of claims 1 to 5, wherein the first weather-resistant substrate is made white by foaming a resin mainly composed of polyethylene terephthalate (PET). Protective sheet.   The said 1st weather-resistant base material was made into the whiteness which foamed the mixed resin which consists of a polyethylene terephthalate (PET) and methylpentene resin (TPX), The any one of Claims 1-6 characterized by the above-mentioned. The back surface protection sheet for solar cells as described in any one of.   The first weather-resistant substrate is formed by laminating polyethylene terephthalate (PET) on both sides of a white substrate obtained by foaming a mixed resin composed of polyethylene terephthalate (PET) and methylpentene resin (TPX). The back surface protection sheet for solar cells as described in any one of Claims 1-7 characterized by the above-mentioned.   The said weatherproof barrier base material consists of resin which has a polyethylene naphthalate (PEN) as a main body, The back surface protection sheet for solar cells as described in any one of Claims 1-8 characterized by the above-mentioned.   The weather-resistant barrier substrate includes an easy adhesion coat layer laminated on both surfaces of the barrier layer, and the vapor deposition layer is deposited on the one surface of the barrier layer via the easy adhesion coat layer. The back surface protection sheet for solar cells of Claims 1-9 characterized by these.   The said inorganic compound consists of an at least 1 sort (s) or more inorganic oxide chosen from silicon oxide, aluminum oxide, and magnesium oxide, The back surface for solar cells as described in any one of Claims 1-10 characterized by the above-mentioned. Protective sheet. A glass plate, a back surface protection sheet disposed opposite to the glass plate, and a solar cell module disposed between the glass plate and the back surface protection sheet,
The solar cell back surface protection sheet according to any one of claims 1 to 11 is used as the back surface protection sheet, and the first weather-resistant substrate side of the back surface protection sheet faces the glass plate. A solar cell that is arranged as described above.

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