JP5820109B2 - Sealing film for solar cell module and solar cell module using the same - Google Patents

Description

  The present invention relates to a sealing film for a solar cell module and a solar cell module using the same.

  Conventionally, solar energy has attracted attention as an alternative to fossil fuels. In particular, in recent years, so-called solar cell modules made for the purpose of using solar energy are rapidly spreading in various fields.

  In general, a solar cell module is formed by laminating a glass substrate, an upper surface sealing film, a photovoltaic element (for example, a silicon power generation element), a lower surface sealing film, and a back sheet in this order, and is bonded by heating and pressing. It is manufactured by making it.

  FIG. 6 is a cross-sectional view of a general solar cell module 5. As shown in FIG. 6, when a surface that receives sunlight (an arrow in FIG. 6) is the outermost surface, the general solar cell module 5 has a glass substrate 51, an upper surface sealing film 52, and light sequentially from the outermost surface. The electromotive force element 53, the lower surface sealing film 54, and a back sheet (sometimes referred to as a back sheet) 55 are configured.

  Each sealing film in such a solar cell module 5 (in the example of FIG. 6, the upper surface sealing film 52 and the lower surface sealing film 54) cover the photovoltaic element 53, and change the temperature of the element. It is necessary for securing adhesion to the glass substrate 51 and the back sheet 55 while protecting from a severe external environment such as humidity and impact. Accordingly, each sealing film of the solar cell module 5 is required to have transparency, weather resistance, heat resistance, adhesiveness, and the like. In order to satisfy these requirements, a crosslinking agent, a crosslinking aid, and a coupling agent are required. UV absorbers, light stabilizers, antioxidants and the like are blended.

  For example, as disclosed in Patent Document 1, in order to improve the weather resistance of the sealing film and the back sheet, the sealing film (in the example of FIG. The film 54) contains an ultraviolet absorber made of various organic compounds such as salicylic acid, benzophenone, benzotriazole, and cyanoacrylate.

JP 11-317475 A

  By the way, in recent years, in order to improve the power generation efficiency of the photovoltaic element in the solar cell module, it is possible to improve the power generation efficiency of the photovoltaic element by also receiving light in the ultraviolet region (approximately 300 nm to 400 nm). Such knowledge has been obtained. Therefore, the sealing film close to the outermost surface, more specifically, in the example of FIG. 6, the sealing film to which the ultraviolet absorber conventionally added to the upper surface sealing film 52 and the lower surface sealing film 54 is not added. There is a request.

  However, in the case of the sealing film, more specifically in the example of FIG. 6, when the ultraviolet absorber is not added to the top sealing film 52 and the bottom sealing film 54, the back sheet 55 is deteriorated (yellowed) by ultraviolet rays. There is a risk. The back sheet 55 is provided in the solar cell module 5 to protect the solar cell module 5 from impacts and the like. When the back sheet 55 deteriorates, the solar cell module 5 Impact resistance, water resistance, etc. will be impaired.

  On the other hand, in the example of the solar cell module 5 shown in FIG. 6, for example, it is conceivable to add an ultraviolet absorber only to the lower surface sealing film 54. However, even if an ultraviolet absorber is added only to the lower surface sealing film 54, depending on the actual use environment of the solar cell module 5, the ultraviolet absorber added to the lower surface sealing film 54 may be, for example, photovoltaic. It gradually moves to the upper surface sealing film 52 through the gap between the elements 53.

  In other words, in order to improve the power generation efficiency of the photovoltaic element 53 in the solar cell module 5, the ultraviolet absorber is not added to the sealing film closest to the outermost surface (upper surface sealing film 52). The upper surface sealing film 52 is in a state where an ultraviolet absorber is added. As a result, the photovoltaic element 53 cannot receive light in the ultraviolet region (approximately 300 nm to 400 nm), and the power generation efficiency decreases with time.

  The present invention has been made in view of the above circumstances, and the purpose thereof is that even if an ultraviolet absorber is added to one of a pair of films sealing a photovoltaic element, under actual use conditions, It is an object of the present invention to provide a solar cell module sealing film in which an ultraviolet absorber is difficult to move to the other film, and a solar cell module using the same.

  The sealing film for solar cell modules of this invention is a pair of sealing film which consists of the 1st film and 2nd film for sealing a photovoltaic element, and a 1st film is the surface of a photovoltaic element. The second film is provided on the back surface of the photovoltaic element, and the transmittance of light having a wavelength of 350 nm in the first film is 80% or more. Further, the transmittance attenuation rate of the first film when tested by the following method is 10% or less. Hereinafter, a test method, that is, a method for calculating the transmittance attenuation ratio will be described.

  As the glass plate, white plate glass (high transmission glass) with less iron content is preferable from the viewpoint of light transmittance. Moreover, the template glass which gave the surface unevenness | corrugation is preferable. First, a first film having a thickness of 0.5 mm, a length of 100 mm, and a width of 50 mm and a second film having a thickness of 0.5 mm, a length of 100 mm, and a width of 50 mm are contacted in the width direction, and the thickness is 3.9 mm. A test plate was obtained in which the first film and the second film were sandwiched between two glass plates having a length of 100 mm and a width of 50 mm. And the transmittance | permeability of the light of wavelength 350nm was measured in the location (measurement area width 10mm x length 5mm square) 5mm in the 1st film direction from the joint of the 1st film and 2nd film in a test plate (measurement 1). . Thereafter, the test plate was heated at 85 ° C. for 14 days, and the transmittance of the test plate was measured in the same manner as in the above measurement 1 (measurement 2). Then, for the data obtained in the above measurement 1 and the above measurement 2, the transmittance in the above measurement 2 when the transmittance in the above measurement 1 is 100 is defined as the transmittance attenuation ratio.

  Moreover, this invention is a solar cell module by which a photovoltaic element is sealed with the said sealing film for solar cell modules.

  According to the present invention, even when an ultraviolet absorber is added to one of a pair of films sealing a photovoltaic element, the ultraviolet absorber is difficult to move to the other film under actual use conditions. A module sealing film and a solar cell module using the same can be provided.

The figure which showed the cross section of the solar cell module using the sealing film for solar cell modules which concerns on one Embodiment of this invention. Diagram showing test plate 3 The figure which showed the measurement area | region of the transmittance | permeability of the light of the ultraviolet region in the test plate 3 Example showing light transmittance in test plate (Example) Diagram showing light transmittance in test plate (comparative example) Diagram for explaining a general solar cell module

  Hereinafter, a sealing film for a solar cell module according to an embodiment of the present invention and a solar cell module using the same will be described with reference to the drawings.

  First, the structure of the solar cell module using the solar cell module sealing film according to an embodiment of the present invention will be described. In the following description, a solar cell module using the solar cell module sealing film according to an embodiment of the present invention may be simply referred to as a solar cell module 1.

  FIG. 1 is a view showing a cross section of the solar cell module 1.

  Specifically, FIG. 1 is a cross-sectional view of the solar cell module 1. In FIG. 1, the solar cell module 1 has a glass substrate 11, a first film 12, and a light in order from the outermost surface when the surface receiving sunlight (the arrow in FIG. 1) is the outermost surface, as shown in FIG. 1. The electromotive force element 13, the second film 14, and a back sheet (sometimes referred to as a back sheet) 15 are configured. The thicknesses of the glass substrate 11 are about 3 to 4 mm, the first film 12 is about 0.5 mm, the photovoltaic element 13 is about 0.2 mm, and the second film 14 is about 0.5 mm. The back sheet 15 is about 0.3 mm.

  The above is the configuration of the solar cell module 1.

  As a result of intensive studies, the present applicant has assumed an actual use environment of the solar cell module 1 even if an ultraviolet absorber is added to the second film 14 in the relationship between the first film 12 and the second film 14. Under the conditions, the ultraviolet absorber added to the second film 14 hardly moves to the first film 12, and the solar cell module 1 was produced.

  Hereinafter, the present invention will be described in detail, but these descriptions do not limit the present invention. Accordingly, it goes without saying that various improvements and modifications can be made without departing from the scope of the present invention.

  First, the glass substrate 11, the photovoltaic element 13, and the back sheet 15 of FIG. 1 will be described, and then the first film 12 and the second film 14 will be described.

  The glass substrate 11 in FIG. 1 is a flat substrate made of glass with added functionality for industrial use. The glass substrate 11 includes, for example, a soda lime glass type and a non-alkali glass type depending on the composition of the glass. A flat display (FPD) such as a liquid crystal television (LCD), a plasma television (PDP), or a notebook computer, an organic A general plate glass used in EL or the like may be used. The glass substrate 11 in the solar cell module 1 may be a transparent resin or the like in addition to the plate glass as described above. Moreover, as the glass substrate 11, from the point of light transmittance, the white plate glass (high transmission glass) with little iron content, and the template glass which gave the surface unevenness | corrugation are preferable.

The photovoltaic element 13 in FIG. 1 is a part that receives sunlight and performs photoelectric conversion. The photovoltaic element 13 in FIG. 1 may be selected from various known elements used in general solar cell modules. For example, as an example of the photovoltaic element 13, pn junction type polycrystalline silicon, Examples thereof include pin junction type amorphous silicon and compound semiconductors including CuInSe ₂ , CuInS ₂ , GaAs, CdS / Cu ₂ S, CdS / CdTe, CdS / InP, and CdTe / Cu ₂ Te.

  The back sheet 15 of FIG. 1 is made of, for example, an ethylene-vinyl acetate copolymer (EVA), an ethylene-methyl acrylate copolymer (EMA), an ethylene-ethyl acrylate copolymer (EEA), a polyester resin, or the like. In addition, in addition to polyolefin resins including polyethylene resins, silicon resins, fluorine resins, and the like can also be mentioned. Among these, polyester resins and fluorine resins are preferably used. Further, a laminated sheet in which a metal such as an aluminum foil or an inorganic metal compound such as silica, alumina or silicon nitride is laminated is preferable because the gas barrier property can be further enhanced. The back sheet 15 may be a plate glass or the like.

  Next, the sealing film for solar cell modules according to an embodiment of the present invention, that is, the first film 12 and the second film 14 will be described with reference to FIG.

  As shown in FIG. 1, the solar cell module 1 includes the glass substrate 11, the first film 12, the photovoltaic element 13, the second film 14, and the back sheet 15. The solar cell module 1 is formed by sequentially laminating, for example, a first film 12 formed into a sheet shape on a glass substrate 11, a photovoltaic element 13, a second film 14 formed into a sheet shape, and a back sheet 15, It is produced by thermocompression bonding (for example, vacuum thermocompression bonding method).

  Next, the first film 12 and the second film 14 described above will be described more specifically below. Since the photovoltaic element 13 has been described above, a description thereof will be omitted.

  The first film 12 is, for example, a polyolefin such as a low-density polyethylene resin, a linear low-density polyethylene resin, or an ethylene-vinyl acetate copolymer resin (so-called EVA resin, hereinafter sometimes referred to as EVA resin). It is formed into a sheet-like film having a thickness of about 0.5 mm by a T-die method using a system resin. As described above, the first film 12 is mainly made of a polyolefin resin (for example, polyvinyl butyral resin, ionomer resin, etc.). Among the polyolefin resins, the vinyl film content is particularly high. About 15% to 40% EVA resin is preferable. The first film 12 may be appropriately blended with additives such as a crosslinking agent, a plasticizer, a heat stabilizer, an antioxidant, an antistatic agent, a pigment, and a dye as necessary. It is preferable not to add the agent.

  Similar to the first film 12, the second film 14 is mainly made of a polyolefin resin such as a low density polyethylene resin, a linear low density polyethylene resin, an EVA resin, and the like by a T-die method. It is formed into a sheet-like film having a thickness of about 0.5 mm. Similarly, the second film 14 is also mainly made of a polyolefin resin. Among the polyolefin resins (for example, polyvinyl butyral resin, ionomer resin, etc.), the vinyl acetate content is particularly 15. % To 40% EVA resin is preferred.

  The second film 14 may be appropriately blended with additives such as a crosslinking agent, a plasticizer, a heat stabilizer, an antioxidant, an antistatic agent, a pigment, and a dye as necessary. Unlike the first film 12, an ultraviolet absorber is added to the second film 14 as an essential additive in the second film 14.

  Here, a preferable ultraviolet absorber to be added to the second film 14 will be described. The ultraviolet absorber added to the second film 14 is a polymer ultraviolet absorber having a polystyrene-equivalent weight average molecular weight of 1000 or more by gel permeation chromatography (GPC). Preferably it is 5000 or more, More preferably, it is 10,000 or more.

  As a polymer type ultraviolet absorber added to the second film 14, for example, trade names ULS-935LH, ULS-700, ULS-635L, ULS-1935LH, ULS-1700, ULS manufactured by Otsuka Co., Ltd. are available. -1635, etc., trade name RUVA-93 manufactured by Otsuka Chemical Co., Ltd. is preferable.

  In addition to the above organic compounds, examples of the ultraviolet absorber added to the second film 14 include salicylic acid ester-based, benzophenone-based, benzotriazole-based, benzoate-based, and cyanoacrylate-based organic compounds. Among others, 2,2′-dihydroxy-4-4′-dimethoxybenzophenone, 2,4-dihydroxybenzophenone, 2 (2′-hydroxy-5′-methylphenyl) benzotriazole, 2 (2′-hydroxy-3 ′) 5'-di-tert-butylphenyl) benzotriazole, 2 (2-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2 (2-hydroxy-3 ', 5 Metal complexes such as' -di-tert-butylphenyl) -5-chlorobenzotriazole (eg, [2 2′-thiobis (4-tert-octylphenolate)]-n-butylamine nickel, nickel bis [O-ethyl (3,5-di-tert-butyl-4-hydroxybenzyl)] phosphonate, etc.), super Inorganic ultraviolet absorbers such as fine-particle titanium oxide and ultrafine-particle zinc oxide can also be used only in such an amount that the transfer to the first film can be ignored.

  In addition, the ultraviolet absorber added to the second film 14 is, for example, 0.01 to 2% by mass with respect to the EVA resin when the second film 14 is a film made of an EVA resin, preferably It is 0.1-1.4 mass%.

  Hereinafter, the present invention will be described in more detail on the basis of examples and comparative examples. However, the present invention is not limited to only the examples of the present invention, and each component contained in a quantitative and qualitative range that does not impair the effects of the present invention. You may change the combination and compounding quantity of these.

  As described above, the present invention, for example, in the relationship between the first film 12 and the second film 14 of the solar cell module 1 as shown in FIG. 1, even if an ultraviolet absorber is added to the second film 14, It is the 1st film 12 and the 2nd film 14 which the ultraviolet absorber added to the 2nd film 14 on the conditions supposing the actual use environment of the solar cell module 1 cannot move to the 1st film 12 easily.

  Therefore, the present applicant, in the relationship between the first film 12 and the second film 14, as an example, the second produced according to the conditions described below under the conditions assuming the actual use environment of the solar cell module 1. It was confirmed by the following test that the ultraviolet absorber added to the film 14 did not easily move to the first film 12.

  Moreover, although mentioned later for details, the applicant added the ultraviolet absorber different from the ultraviolet absorber added to the 2nd film 14 to the said 2nd film 14 as a comparative example, and performed the same experiment.

(Example)
[About test plate]
First, a test plate 3 as shown in FIG. 2 was produced. Specifically, as shown in FIG. 2A, the test plate 3 is formed in order from X2 to X1, in the same manner as the glass plate 21 (specifically, the glass substrate 11 in FIG. 1A). Or a test film 22 and a glass plate 21 (specifically, it may be the same as the glass substrate 11 in FIG. 1A). In other words, the test film 22 is sandwiched between two transparent glass plates 21. Then, after sandwiching the test film 22 between the glass plates 21, the hot plate temperature is set to 150 ° C. in a vacuum heating apparatus, left in a vacuum state for 5 minutes, and then pressed for 10 minutes to test plate 3 (see FIG. 2B). ) Was produced.

  The glass plate 21 was 3.9 mm thick, 100 mm long, and 50 mm wide.

[About test film]
Here, the test film 22 will be described. As shown in FIG. 2B, the test film 22 is sandwiched between two glass plates 21 in a state where the first film 12 and the second film 14 are in contact with each other in the width direction. The first film 12 and the second film 14 are specifically as follows.
First film: ethylene-vinyl acetate copolymer (vinyl acetate content 28%, MFR 20 g / 10 min, melting point 71 ° C.) 100 parts by mass, cross-linking agent (t-butylperoxy 2-ethylhexyl monocarbonate) 0 parts by mass were dry blended with a ribbon blender, melt-kneaded with an extruder (uniaxial, caliber 90 mm), and a film with a thickness of 0.5 mm was obtained by extrusion using a T die. The temperature of the T die was 90 ° C., and the screw rotation speed was 20 rpm. The film was cut into a length of 50 mm and a width of 50 mm.
Second film: UV absorber (commercial name ULS-635L, manufactured by Yushi Kogyo Co., Ltd .; acrylic copolymer having a UV-absorbing skeleton (benzophenone)) in the side chain, gel perm It was obtained in the same manner as in the first film except that 0.4 parts by mass of polystyrene-converted weight average molecular weight of about 20000) by addition chromatography (GPC) was added.

[Moving ratio of UV absorber]
The test plate 3 shown in FIG. 2 was heated at 85 ° C. for 14 days, and it was examined how much the ultraviolet absorber contained in the second film 14 moved to the first film 12 in the test film 22. Specifically, as shown in FIG. 3A, first, in the test plate 3 (before heating) 3 before heating at 85 ° C. for 14 days, the first film 12 and the second film 14 are joined from the joint. The transmittance of light in the ultraviolet region at a location of 5 mm in one film 12 direction (measurement area width 10 mm × length 5 mm square, location indicated by A in FIG. 3A) was measured.

Then, in the test plate 4 after heating at 85 ° C. for 14 days (after heating), the transmittance of light in the ultraviolet region at the position A shown in FIG.
Measuring instrument: UV-visible spectrophotometer manufactured by JASCO Corporation (product number: V-570)

  The measurement results are shown in FIG. In FIG. 4, the solid line indicates the light transmittance of the test plate 3 before heating, and the broken line indicates the light transmittance of the test plate 4 after heating.

  First, as described above, since the ultraviolet absorber is not blended in the first film 12 of the test film 22, the solid line in FIG. 4 is considered as a reference for the moving ratio of the ultraviolet absorber. That is, if the ultraviolet absorber added to the second film 14 moves to the first film 12, the transmittance is attenuated as compared with the solid line in FIG. On the contrary, if the ultraviolet absorber added to the second film 14 does not move to the first film 12, it is considered that a curve substantially the same as the solid line in FIG. 4 is obtained.

  Here, the first film 12 and the second film 14 are incorporated into an actual product (incorporated into a solar cell module), and the transmittance of light having a wavelength of 350 nm on the solid line in FIG. In this case, the transmittance after heating at 85 ° C. for 14 days is set to 91.5 or more. That is, even if the ultraviolet absorber added to the second film 14 moves to the first film 12, it is set to what extent it can be tolerated.

  As a result, as shown by the broken line in FIG. 4, it was found that the test film 22 according to the present example was 97, which satisfies the above criteria.

(Comparative example)
Next, the 2nd film which added the ultraviolet absorber different from the said Example to the said 2nd film 14 was produced, and the same measurement was performed. In addition, since it is the same as that of the said Example except the ultraviolet absorber added to the 2nd film 14 differing, the description is abbreviate | omitted.
Second film: 0.4 parts by mass of UV absorber (SEESORB151; 1,4-bis (4-benzoyl-3-hydroxyphenoxy) -butane, molecular weight 482.5) manufactured by Sipro Kasei Co., Ltd., in the composition of the first film The film was obtained in the same manner as the first film except that it was added.

  The measurement result of the transmittance is shown in FIG. In FIG. 5, the solid line is before heating, and the broken line is after heating. As indicated by the broken line in FIG. 5, when the transmittance of light having a wavelength of 350 nm in the solid line in FIG. 5 is set to 100, it is attenuated to 65 after heating and does not satisfy the above criteria.

  From the above, it was found that the ultraviolet absorber added to the second film 14 may be a polymer type having a weight average molecular weight of 1000 or more. That is, referring to (a) of FIG. 1 described above again, if an ultraviolet absorber having a melting point of 70 ° C. or higher, more preferably 120 ° C. or higher is added to the second film 14, the actual solar cell module 1 will be described. Even in the use environment, there is no possibility that the ultraviolet absorbent added to the second film 14 gradually moves to the first film 12 through the gaps between the photovoltaic elements 13, for example. Furthermore, there is no possibility that the back sheet 15 is deteriorated (yellowed) by ultraviolet rays.

  As a result, the photovoltaic element 13 can receive light in the ultraviolet region (approximately 300 nm to 400 nm), and the power generation efficiency can be improved.

  The sealing film for solar cell module according to the present invention and the solar cell module using the same can be usefully applied to, for example, power sources of various electronic devices that require electric power, solar panels used in solar power generation, and the like. .

DESCRIPTION OF SYMBOLS 1, 5 ... Solar cell module 11, 51 ... Glass substrate 12 ... 1st film 13, 53 ... Photovoltaic element 14 ... 2nd film 15, 55 ... Back surface sheet 21 ... Glass plate 22 ... Test film 3, 4 ... Test Plate 52 ... Upper surface sealing film 54 ... Lower surface sealing film

Claims (5)

A sealing film for a solar cell module,
The solar cell module sealing film is a pair of sealing films composed of a first film and a second film for sealing a photovoltaic element,
The first film is provided on a surface of the photovoltaic element;
The second film is provided on the back surface of the photovoltaic element,
The first film and the second film include an ethylene-vinyl acetate copolymer,
The transmittance of light having a wavelength of 350 nm in the first film is 80% or more,
The second film contains a benzophenone-based ultraviolet absorber having a molecular weight of 1000 or more,
A sealing film for a solar cell module, wherein the transmittance attenuation ratio of the first film when tested by the following method is 10% or less.
<Test method>
(1) The first film having a thickness of 0.5 mm, a length of 50 mm, and a width of 50 mm, and the second film having a thickness of 0.5 mm, a length of 50 mm, and a width of 50 mm are contacted in the width direction, and the thickness is 0. A test plate was obtained in which the first film and the second film were sandwiched between two glass plates having a length of 0.5 mm, a length of 50 mm, and a width of 50 mm.
(2) The transmittance of light having a wavelength of 350 nm is measured at a location 5 mm (measurement area width 10 mm × length 5 mm square) from the joint between the first film and the second film in the test plate in the first film direction. did.
(3) The test plate was heated at 85 ° C. for 14 days.
(4) The transmittance in this test plate was measured by the same method as in (2) above.
(5) When the transmittance in (2) is 100, the transmittance in (4) is defined as the transmittance attenuation ratio.   The sealing film for a solar cell module according to claim 1, wherein the ultraviolet absorber is contained only in the second film.   The sealing film for a solar cell module according to claim 1, wherein the ultraviolet absorbent has a molecular weight of 5000 or more. Before Stories second film of the ethylene - wherein the ultraviolet absorber of 0.01 to 2 wt% with respect to vinyl acetate copolymer resin is contained, the solar cell module according to claim 1 Sealing film.   The solar cell module by which a photovoltaic element is sealed with the sealing film for solar cell modules of any one of Claims 1 thru | or 4.

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