JP2018120883A - Back protective sheet for solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a back protective sheet for a solar cell module, excellent in a function for preventing the occurrence of poor appearance due to local pressure on the back protective sheet for a solar cell module during a solar cell module is manufactured, the pressure being caused due to a projection of wiring called as a bus bar.SOLUTION: A back protective sheet for a solar cell module includes an easily adhesive resin layer 1 with respect to a sealing material layer for holding and fixing a solar cell element, a polyethylene terephthalate film 2, an adhesive layer 3, and a light resistance polyethylene terephthalate film 4, which are laminated in the order. The back protective sheet for a solar cell module has a thickness of 360 μm or more, and a back sheet thickness in a DTI test is 300 μm or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a back surface protection sheet for solar cell modules, and more specifically, poor appearance due to local pressure on the back surface protection sheet for solar cell modules due to wiring protrusions called busbars when the solar cell module is produced. It is related with the back surface protection sheet for solar cell modules excellent in the generation | occurrence | production prevention function.

  In recent years, solar power generation as a clean energy source has attracted attention due to increasing awareness of environmental problems, and solar cell modules having various forms have been developed and proposed. Generally, a solar cell module uses a photovoltaic element such as a crystalline silicon solar cell element or an amorphous silicon solar cell element, a surface protection sheet, an encapsulant sheet such as ethylene / vinyl acetate copolymer resin, and a solar cell element. , A sealing material sheet, and a back surface protection sheet layer for solar cell modules are laminated in this order, and are manufactured by a method of vacuum suction, thermocompression bonding, and integration.

  As a back surface protection sheet for a solar cell module constituting a solar cell module, a plastic substrate that is light in weight and excellent in electrical characteristics and strength has been generally used, and is lightweight, moisture-proof, and high withstand voltage characteristics. Therefore, polyolefin resin films are used (Patent Documents 1 and 2).

  Moreover, the thickness of the back surface protection sheet for solar cell modules is generally 230 μm to 350 μm (Patent Document 3).

JP 2013-201155 A JP 2014-143259 A JP 2008-166338 A

  However, in the inventions disclosed in Patent Documents 1 and 2, if the bus bar is excessive or curved in the laminating process at the time of manufacturing the solar cell module, the bus bar after pressing may be bent or twisted. Part is generated. There has been a problem that the thickness of the polyolefin-based resin having low heat resistance becomes thin due to local pressure on the back surface protection sheet for the solar cell module due to the protruding portion of the bus bar, resulting in a decrease in insulation.

  Further, in order to cope with the above-mentioned problem, the solar cell module module safety certification standard IEC61730 standard, the thickness of the back surface protection sheet for the solar cell module, which contributes to the insulation, is measured after being pressed by the solder protrusion. (Distance through insulation) test has been introduced, and the thickness of the back surface protection sheet for solar cell modules having insulation properties corresponding to a solar cell module with a maximum system voltage of 1500 V is 300 μm or more after the DTI test. It has been sought.

  In the back surface protection sheet for solar cell module as shown in Patent Document 3, the appearance defect due to local pressure on the back surface protection sheet for solar cell module due to the bus bar protrusion of the back surface protection sheet for solar cell module is conspicuous. There is a problem.

  The object of the present invention is to protect the back surface for a solar cell module, which is excellent in the function of preventing the occurrence of defective appearance due to local pressure on the back surface protection sheet for the solar cell module caused by the protrusion of the wiring called a bus bar at the time of manufacturing the solar cell module Is to provide a sheet.

  In order to solve the above problems, the present invention has the following configuration.

  1st invention is the back surface protection sheet for solar cell modules laminated | stacked in order of the easily-adhesive resin layer with respect to the sealing material layer which hold | maintains and fixes a solar cell element, a polyethylene terephthalate film, and a light-resistant polyethylene terephthalate film, A back protective sheet for a solar cell module, having a thickness of 360 μm or more and a back sheet thickness of 300 μm or more by a DTI test.

  A second invention is characterized in that the light-resistant polyethylene terephthalate film is formed by laminating a polyethylene terephthalate resin layer and a light-resistant polyethylene terephthalate resin layer.

The third invention has a breaking elongation retention of 70% or more after irradiating the light-resistant polyethylene terephthalate film with ultraviolet light having a strength of 180 W / m ² for 334 hours in an atmosphere of a temperature of 63 ° C. and a relative humidity of 50%. The color difference (ΔE ^* ) is 3 or less.

  The present invention has been made in view of the above-described problems of the prior art, and has poor appearance due to local pressure on the back surface protective sheet for solar cell module caused by wiring protrusions called a bus bar during solar cell module production. The back surface protection sheet for solar cell modules excellent in the generation | occurrence | production prevention function is provided.

It is the schematic sectional drawing which showed an example of the back surface protection sheet for solar cell modules of this invention. It is a sectional side view which illustrates the solar cell module using the back surface protection sheet for solar cell modules of this invention. It is a sectional side view which illustrates the DTI test using the back surface protection sheet for solar cell modules of this invention.

  Hereinafter, the present invention will be described in detail with reference to the drawings. In addition, what is shown to a figure is one Embodiment, It is not limited to this.

  FIG. 1 is a back protective sheet for a solar cell module in which an easy-adhesive resin layer 1, a polyethylene terephthalate film 2, and a light-resistant polyethylene terephthalate film 4 are laminated in this order with a sealing material sheet for holding and fixing a solar cell element. .

  FIG. 2 shows a surface protection sheet 5, a sealing material sheet (1) 7, a photovoltaic power generation element 6 provided with wiring, a sealing material sheet (2) 8, and a back surface protection sheet for a solar cell module of the present invention. 9 is a solar cell module in which 9 are stacked in this order.

  FIG. 3 shows a laminate when a DTI test sample is manufactured. In this laminated body, a back protective sheet 10 for a solar cell module, a sealing material sheet (1) 11, a solder wire 12, a release film 13, and a glass plate 14 are laminated in this order.

  The present invention is a back protective sheet for a solar cell module in which an easy-adhesive resin layer, a polyethylene terephthalate film, and a light-resistant polyethylene terephthalate film are stacked in this order on a sealing material layer for holding and fixing a solar cell element. Is a back surface protective sheet for a solar cell module, characterized in that the back sheet thickness by a DTI test is 300 μm or more.

(Easily adhesive resin layer)
First, the easily adhesive resin layer with respect to the sealing material layer in this invention is demonstrated.

  The easy-adhesion resin layer in the present invention is obtained by laminating a surface protective sheet, a sealing material sheet 1, a photovoltaic power generation element provided with wiring, a sealing material sheet 2, and a back surface protective sheet for a solar cell module in this order. In the manufacturing process of the solar cell module integrated by thermocompression molding, the adhesion between the solar cell module back surface protection sheet and the sealing material sheet is determined.

  The sealing material sheet in the present invention is a sheet made of an ethylene / vinyl acetate copolymer resin (EVA). In the present invention, it is preferable that the easy-adhesive resin layer surface, the sealing material sheet, and 180 ° peeling after thermocompression molding and the adhesion strength at 300 mm / min are 50 N / cm or more. If the adhesion strength after thermocompression molding is less than 50 N / cm, the initial specifications of the solar cell module design may not be satisfied. Moreover, it is necessary to maintain the adhesive strength for a long time even in an environment exposed outdoors, and the adhesive strength after thermocompression bonding with the sealing material sheet is 1000 hours after storage at 85 ° C. and 85% RH. And it is preferable that it is 40 N / cm or more.

  Furthermore, among the light rays incident from the front surface of the solar cell module, the light that passes through the cells and passes through the sealing material sheet layer and reaches the back surface protection sheet for the solar cell module is resistant to causing no photodegradation reaction. It is preferable to select the resin to be shown in order to stably maintain the adhesion performance over a long period of time. Accordingly, the resin that forms the easily adhesive resin layer is preferably a resin having light resistance, and it is preferable to use an acrylic resin, a polyurethane resin, or a fluorine resin having excellent light resistance.

  As the acrylic resin, an acrylic resin, an acrylic polyol copolymer, an acrylic / urethane copolymer, or the like is used. For example, “Acrynal” (manufactured by Toei Kasei Co., Ltd.), “Akrit” (manufactured by Taisei Fine Chemical Co., Ltd.), “Hitaroid” (manufactured by Hitachi Chemical Co., Ltd.), “Acridic” (manufactured by DIC Corporation), “Udouble” (manufactured by Nippon Shokubai Co., Ltd.), “Dianar” (manufactured by Mitsubishi Rayon Co., Ltd.), and the like. Examples of polyurethane resins include “Samprene” (manufactured by Sanyo Chemical Industries), “Takelac” (manufactured by Mitsui Chemicals), TA (manufactured by Hitachi Chemical Co., Ltd.), and “Seika Bond” (Ohnissei). Chemical Industry Co., Ltd.).

  Examples of the fluorine-based resin include perfluoroolefin-based resins mainly composed of perfluoroolefin units from the viewpoint of structural units. Specific examples include a tetrafluoroethylene homopolymer (PTFE), a copolymer of tetrafluoroethylene with hexafluoropropylene, perfluoro (alkyl vinyl ether) or the like, and other monomers copolymerizable therewith. And a copolymer with the body. Of these, a fluororesin mainly composed of tetrafluoroethylene is preferable in terms of excellent pigment dispersibility, weather resistance, copolymerization, and chemical resistance. For example, “Zeffle” GK manufactured by Daikin Industries, Ltd. Examples include series. Since these fluororesins are also excellent in flame retardancy, they also have an effect of improving the flame retardancy of the film for the back surface protection sheet for solar cell modules.

  Moreover, in order to improve adhesiveness with a base film, or the back surface protection sheet for solar cell modules of this invention improves the heat resistance of a coating film from being exposed to a high temperature process in a solar cell module manufacturing process. For this purpose, it is preferable to form a crosslinked structure in these weather resistant resins.

  The thickness of the easily adhesive resin layer in the present invention is preferably 0.2 to 10 μm, more preferably 1 to 5 μm. When this easy-adhesive resin layer is formed by a coating method, if the thickness of the easy-adhesive resin layer is less than 0.2 μm, a phenomenon such as repellency or film breakage tends to occur during coating, and a uniform coating film is formed. Therefore, the adhesion strength to the polyethylene terephthalate film and the sealing material sheet may not be sufficiently developed. On the other hand, when the thickness of the easy-adhesive resin layer exceeds 10 μm, the adhesion strength is sufficiently developed, but the coating method is restricted, the production cost becomes high, the coating film adhesion to the transport roll and the coating film accompanying it There is a concern that the film will be easily peeled off.

  Examples of the solvent for the coating liquid for forming the easy-adhesion resin layer in the present invention by a coating method include, for example, toluene, xylene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dimethylformamide, dimethylacetamide, and methanol. Ethanol, water and the like can be exemplified, and the properties of the coating liquid may be either an emulsion type or a dissolution type.

  The method for forming the easily adhesive resin layer on the polyethylene terephthalate film is not particularly limited, and a known coating method can be used. As a coating method, various methods can be applied. For example, a roll coating method, a dip coating method, a bar coating method, a die coating method, a gravure roll coating method, or a combination of these methods can be used. it can. Among these, the gravure roll coating method is generally preferable because it can stably form an easily adhesive resin layer.

  It is preferable to add an inorganic color pigment to the easily adhesive resin layer of the present invention for the purpose of imparting light resistance. Currently, white and black are mainly used for the back surface protection sheet for solar cell modules, but for the purposes of the present invention, adding an inorganic white pigment imparts light resistance to the easily adhesive resin layer. Preferred for the purpose. In addition, there is an effect that a design pattern such as an electric wiring pattern in the solar cell module can be hidden.

  As the white pigment, titanium oxide having excellent light resistance is preferable. From the viewpoint of color development, the average particle diameter by particle diameter measurement using a dynamic light scattering method is preferably from 0.1 to 1.0 μm, more preferably from the viewpoint of dispersibility with respect to the easily adhesive resin layer and cost. ˜0.5 μm.

  The blending amount of the color pigment may be appropriately adjusted according to the design of the color tone to be developed. However, if the amount of pigment is too small, a color appearance with excellent design properties cannot be obtained, light resistance is insufficient, and conversely, if the amount is too large, the cost is high, resin There are concerns that the hardness of the layer is greatly increased, that the adhesion to the sealing material sheet is likely to be insufficient or reduced, and that the pigment bleeds out to the surface of the coating film.

  For the above reason, the blending amount of the color pigment is preferably 20 to 80 parts by mass, more preferably 30 to 70 parts by mass with respect to 100 parts by mass of the easily adhesive resin. If the color pigment is less than 20 parts by mass, appropriate light resistance cannot be obtained, and if it is more than 80 parts by mass, the resin layer becomes brittle and it is difficult to obtain appropriate strength, or the dispersion of the easily adhesive resin and the colorant is poor. Will occur and the light resistance tends to decrease.

  In addition, for the purpose of improving the heat resistance and mechanical properties of the easily adhesive resin layer of the present invention, it is preferable to have a crosslinked structure as described above, and it has a functional group capable of reacting with a hydroxyl group introduced into the easily adhesive resin layer. You may mix | blend a crosslinking agent. When a cross-linking agent is used in combination, the effect of improving the adhesion between the polyethylene terephthalate film and the easy-adhesive resin layer, or improving the heat resistance of the easy-adhesive resin layer accompanying the introduction of a cross-linked structure is obtained. In the solar cell module manufacturing process, in the glass laminating process, the easy-adhesive resin layer is exposed to a heat treatment of 30 minutes or more at a high temperature of about 150 ° C. at the maximum. In particular, heat resistance is required so that the coating film does not exhibit melting, flow, or the like. In this invention, the prescription which uses a polyisocyanate resin as a hardening | curing agent as a crosslinking agent which can react with a hydroxyl group as a hardening | curing agent, and promotes the production | generation of a urethane bond (crosslinked structure) is preferable. Examples of the polyisocyanate resin used as a crosslinking agent include aromatic polyisocyanates, araliphatic polyisocyanates, alicyclic polyisocyanates, and aliphatic polyisocyanates. Among them, as a polyisocyanate raw material, a resin containing an aromatic ring having a light absorption band in the ultraviolet region in the resin skeleton easily yellows upon irradiation with ultraviolet rays. Therefore, an alicyclic polyisocyanate and an aliphatic polyisocyanate. It is preferable to use a curing agent containing as a main component, and a nurate-modified product of hexamethylene diisocyanate is preferable from the viewpoint of easy progress of crosslinking reaction, degree of crosslinking, heat resistance, ultraviolet resistance and the like.

  Furthermore, the easy-adhesive resin layer of the present invention includes a heat stabilizer, an antioxidant, a reinforcing agent, a deterioration preventing agent, a weathering agent, a flame retardant, a plasticizer, a release agent, and a lubricant, as long as the characteristics are not impaired. Crosslinking aids, pigment dispersants, antifoaming agents, leveling agents, UV absorbers, light stabilizers, thickeners, adhesion improvers, matting agents, and the like may be added.

(Polyethylene terephthalate film)
Next, the polyethylene terephthalate film will be described.

  In the present invention, the polyethylene terephthalate film is responsible for imparting mechanical strength, heat resistance, and long-term property maintaining functions required as properties of the back surface protection sheet for solar cell modules. Moreover, it is preferably used also from the point of economical efficiency. The method for forming a polyethylene terephthalate film is not particularly limited, and a known method for forming a film can be used. Specifically, “Lumirror (registered trademark)” S10 manufactured by Toray Industries, Inc. can be preferably used as the polyethylene terephthalate film of the present invention. Moreover, since the total thickness of the back surface protection sheet for solar cell modules needs to be 360 micrometers or more, the thickness of a polyethylene terephthalate film has preferable 50 micrometers-360 micrometers. When the thickness is within this range, the processing suitability with the following light-resistant polyethylene terephthalate film is good, and the function of preventing the appearance defect due to the bus bar protrusion can be obtained.

(Light resistant polyethylene terephthalate film)
Next, the light resistant polyethylene terephthalate film in the present invention will be described.

  In the present invention, the light-resistant polyethylene terephthalate film has a function of preventing deterioration of ultraviolet rays such as color change of the entire back surface protection sheet of the solar cell and deterioration of elongation at break due to reflection from the ground or roof even in long-term outdoor exposure. An ultraviolet reflection function is required. Therefore, specifically, the light-resistant polyethylene terephthalate film is preferably a polyester film having at least one polyethylene terephthalate resin layer to which a whitening agent is added, and is light-resistant to which a polyethylene terephthalate resin layer and a whitening agent are added. A layer in which a functional polyethylene terephthalate resin layer is laminated by co-extrusion is more preferable for efficient use of a whitening agent. In this case, it is an industrially important method to add the recovered raw material to the polyethylene terephthalate resin layer side up to the upper limit of 50% by weight. In this case, the whitening agent is somewhat present on the polyethylene terephthalate resin layer side. Will be added. As the whitening agent for imparting light resistance, inorganic fine particles such as calcium carbonate, silica, alumina, magnesium hydroxide, zinc oxide, talc, kaolin clay, titanium oxide, and barium sulfate can be used.

It is important that the light transmittance of the light-resistant polyethylene terephthalate film at a wavelength of 360 nm is less than 5%, more preferably less than 1%, so that the color tone change and elongation at break of the entire back surface protective sheet for solar cell module are achieved. Deterioration can be reduced. Specifically, under an atmosphere of a temperature of 63 ° C. and a relative humidity of 50%, UV light having an intensity of 180 W / m ² is irradiated to the light-resistant polyethylene terephthalate film side of the back protective sheet for 334 hours (UV irradiation integrated amount 60 kWh / m ² , solar The color difference (ΔE ^* ) of the back surface protection sheet before and after the battery module safety certification standard GB / T9535 grade 1) can be 3 or less, and the elongation at break can be 70% or more.

  As such a light-resistant polyethylene terephthalate film, a hydrolysis-resistant white polyethylene terephthalate film film obtained by co-extrusion of a hydrolysis-resistant polyethylene terephthalate resin layer and a hydrolysis-resistant polyethylene terephthalate resin layer to which a whitening agent is added. “Lumirror (registered trademark)” MX11 manufactured by Toray Industries, Inc. can be preferably used.

  Since the total thickness of the back surface protection sheet for solar cell modules needs to be 360 μm or more, the thickness of the light-resistant polyethylene terephthalate film is preferably 50 μm to 360 μm. When the thickness is within this range, the processability with the polyethylene terephthalate film is good, and the function of preventing the appearance defect due to the bus bar protrusion can be obtained.

(Back protection sheet)
The back surface protective sheet for a solar cell module of the present invention is a member in which an easy-adhesive resin layer having adhesion to a sealing material sheet is applied to one side of a polyethylene terephthalate film, and the easy-adhesive resin layer of the member is prepared. Is obtained by bonding the surface opposite to the light-resistant polyethylene terephthalate film with an adhesive. When the light-resistant polyethylene terephthalate film is laminated with a polyethylene terephthalate resin layer and a light-resistant polyethylene terephthalate resin layer to which a whitening agent is added by coextrusion molding, the side opposite to the easily adhesive resin layer is used. The surface is bonded to the polyethylene terephthalate resin layer surface of the light-resistant polyethylene terephthalate film with an adhesive.

  The back surface protection sheet for solar cell modules having insulation properties corresponding to the solar cell module having the maximum system voltage of 1500 V needs to have a thickness of 300 μm or more after the DTI test. In the present invention, the thickness of the back surface protection sheet for the solar cell module is to prevent the appearance defect due to the protrusion of the bus bar on the back surface protection sheet surface of the solar cell module while ensuring the thickness after the DTI test. It is necessary to set it as 360 micrometers or more, More preferably, it is 400 micrometers or more. By setting the thickness to 360 μm or more, it is possible to obtain an appearance defect preventing function by the bus bar protrusion. In order to achieve this, it is necessary to appropriately combine the thicknesses of the polyethylene terephthalate film and the light-resistant polyethylene terephthalate film within the above range.

  As a method of laminating a polyethylene terephthalate film coated with an easy-adhesive resin layer and a light-resistant polyethylene terephthalate film and processing it into a sheet shape, a known dry laminating method can be used. Bonding of the resin film using the dry laminating method includes a main component such as a polyether polyurethane resin, a polyester polyurethane resin, a polyester resin, a polyepoxy resin, and a polyisocyanate curing agent. A known dry laminating adhesive can be used. However, the adhesive layer formed using these adhesives does not cause peeling due to deterioration of the adhesive strength due to long-term outdoor use, which leads to deterioration in appearance and light reflectance. It is necessary not to cause yellowing. Moreover, as thickness of an adhesive bond layer, Preferably it is the range of 1-5 micrometers. If it is less than 1 μm, it may be difficult to obtain sufficient adhesive strength. On the other hand, if it exceeds 5 μm, the coating speed of the adhesive does not increase, and the amount of adhesive used increases, leading to an increase in production cost.

  Hereinafter, the present invention will be described in detail by way of examples. Each characteristic was measured and evaluated by the following methods.

(1) Backsheet thickness by DTI test In the direction in which the easy-adhesive resin layer of the back surface protective sheet for solar cell modules faces the encapsulant sheet, the back surface protective sheet for solar cell modules / encapsulant sheet (manufactured by FirstEVA, F806 Thickness 450μm) / Solder Wire (SD-62, Taiyo Denki Sangyo Co., Ltd., Leaded Type, Diameter 0.8mm) / Release Film (Toray Film Processing Co., Ltd., “Celapeel®” MD ) / Glass plates are laminated in this order and installed in a solar cell module laminator (LM-50X50-S) manufactured by NPC Corporation, followed by a vacuum time of 5.5 minutes, a control time of 1 minute, and a press time of 11 The thermocompression bonding was performed at a temperature of 148 ° C. for 5 minutes. After the pressure bonding, it was cooled to room temperature to prepare a back surface protection sheet for DTI test solar cell module. The thickness of the back surface protection sheet for solar cell modules at the portion where the solder wire and (back surface protection sheet for solar cell module / sealing material sheet) overlap is measured using an optical microscope (UDMECLIPSELV100D-U manufactured by Nikon Corporation). It was measured. The thing whose thickness of the back surface protection sheet for solar cell modules is 300 micrometers or more was set as the pass determination.

(2) Breaking elongation retention after UV treatment Solar cell module with a UV intensity of 180 W / m ² at a temperature of 63 ° C. and 50% RH using a Super Xenon Weather Meter SX2-75 manufactured by Suga Test Instruments Co., Ltd. The back surface protective sheet for the light-resistant polyethylene terephthalate film was irradiated with ultraviolet rays (ultraviolet irradiation accumulated amount 60 kWh / m ² ). The elongation before and after that was measured by using Tensilon PTM-50 manufactured by Orientec Co., Ltd., at a pulling speed of 300 mm / min. A judgment of 70% or more as a determination of the breaking elongation retention was regarded as acceptable.

(3) Color difference after UV treatment Using a Super Xenon Weather Meter SX2-75 manufactured by Suga Test Instruments Co., Ltd., at a temperature of 63 ° C. and a 50% RH atmosphere with an ultraviolet intensity of 180 W / m ² and a back surface protection sheet for a solar cell module The light resistant polyethylene terephthalate film surface was irradiated with ultraviolet rays (ultraviolet irradiation cumulative amount 60 kWh / m ² ). The color system L ^* , a ^* , and b ^* values before and after that were measured. A measured value calculated by the following formula (color difference ΔE ^* ) of less than 3 was determined to be acceptable.
Initial value: L ^* , a ^* , b ^*
Value after UV treatment: L ^* ', a ^* ', b ^* '
ΔE = ((L ^* ′ − L ^* ) ² + (a ^* ′ − a ^* ) ² + (b ^* ′ − b ^* ) ² ) ^0.5 .

(4) Appearance of bus bar protrusions In the direction in which the easy-adhesive resin layer of the back surface protective sheet for solar cell modules faces the encapsulant sheet, the back surface protective sheet / encapsulant sheet 1 for solar cell modules (manufactured by FirstEVA, F806) Thickness 450 μm) / Lead solder plating ribbon wire 1 (Marumasa Co., Ltd. 200 μm thickness × 6.0 mm width) / Lead solder plating ribbon wire 2 (Marumasa Co., Ltd. 200 μm thickness × 6.0 mm width) / Encapsulant Sheet 2 (manufactured by FirstEVA, F806, 450 μm thick) / glass plate is laminated in this order, and after installation on a solar cell module laminator (LM-50X50-S) manufactured by NPC Corporation, a vacuum time of 5. Thermocompression bonding was performed under the conditions of 5 minutes, a control time of 1 minute, a press time of 11.5 minutes, and a temperature of 148 ° C. After crimping, the solar cell module for cooling the room temperature was confirmed by cooling the room temperature. However, the lead solder plating ribbon wire 2 was arranged so as to be orthogonal to the lead solder plating ribbon wire 1.

  Ten sheets of each level were prepared by the above method, and visually observed from the side of the solar cell module back surface protection sheet under a fluorescent lamp and reflected. As a judgment of the external appearance of the bus bar protrusion, a grade 2 or higher was accepted according to the following criteria.

  Third grade: All 10 sheets have no appearance defect due to the protrusion on the surface of the bus bar protrusion.

  Second grade: A slight appearance defect due to a protrusion on the surface of the bus bar protrusion on any of the ten sheets.

  First grade: Clear protrusions on the surface of the bus bar protrusions can be seen on any of the 10 sheets.

(Preparation of paint for forming an easily adhesive resin layer)
100 parts by weight of a coating agent PRC-004 (solid content concentration: 30% by mass) manufactured by Toyo Ink SC Holdings Co., Ltd. containing an acrylic copolymer and a blocked isocyanate compound, and 20 parts by weight of n-butyl acetate as a diluent By stirring for 15 minutes, an easy-adhesive resin layer-forming coating material (solid content concentration: 25% by mass) was obtained.

Example 1
As a polyethylene terephthalate film, “Lumirror” S10 250 μm manufactured by Toray Industries, Inc. was prepared. On one surface of this base film, the above-mentioned paint for forming an easily adhesive resin layer was applied using a dry laminator (Dry Laminator OG / DL-130TA-AF with one-color printing manufactured by Okazaki Machinery Co., Ltd.), 150 It dried for 30 seconds at 0 degreeC, and provided the easily-adhesive resin layer so that it might become 2 micrometers of solid content application | coating thickness.

  Next, to the polyethylene terephthalate resin layer side of the light-resistant polyethylene terephthalate film (“Lumirror” MX11 125 μm manufactured by Toray Industries, Inc.) in which the polyethylene terephthalate resin layer and the light-resistant polyethylene terephthalate resin layer are coextruded by the dry laminator. A urethane-based adhesive layer (a mixture of 10 parts by weight of AD503 manufactured by Toyo Morton Co., Ltd. and 1 part by weight of isocyanate-based curing agent CAT-10 manufactured by Toyo Morton Co., Ltd.) was applied and dried so that the coating thickness was 4 μm. Lamination was carried out with an uncoated side of “Lumirror” S10 and a nip pressure of 60 N / cm.

  The laminated film was aged at a temperature of 40 ° C. for 72 hours to accelerate the curing reaction of the adhesive layer, thereby obtaining the back surface protective sheet for solar cell module of the present invention. The evaluation results are shown in Table 1.

  The judgment of the thickness after the DTI test, the breaking elongation retention after the UV treatment, the color difference after the UV treatment, and the appearance of the bus bar protrusion was acceptable.

(Example 2)
The same as Example 1 except that the thickness of the light-resistant polyethylene terephthalate film “Lumirror” MX11 described in Example 1 was changed from 125 μm to 75 μm, and the thickness of the polyethylene terephthalate film “Lumirror” S10 was changed from 250 μm to 350 μm. The back surface protection sheet for solar cell modules was produced by the method. The evaluation results are shown in Table 1.

  The judgment of the thickness after the DTI test, the breaking elongation retention after the UV treatment, the color difference after the UV treatment, and the appearance of the bus bar protrusion was acceptable.

(Comparative Example 1)
A back protective sheet for a solar cell module was produced in the same manner as in Example 1 except that the thickness of the light-resistant polyethylene terephthalate film “Lumirror” MX11 described in Example 1 was changed from 125 μm to 75 μm. The evaluation results are shown in Table 1.

  The thickness of the back surface protection sheet for solar cell modules was 331 μm, and the determination of the appearance of the bus bar protrusion was unacceptable.

(Comparative Example 2)
“Lumirror” MX11 150 μm manufactured by Toray Industries, Inc. as a light-resistant polyethylene terephthalate film and “Trephan” (registered trademark) manufactured by Toray Film Co., Ltd. as a polypropylene film instead of a paint for forming an easily adhesive resin layer as an easily adhesive resin layer “B013W 160 μm was prepared. Next, with a dry laminator, a urethane adhesive layer (10 parts by weight of AD503 manufactured by Toyo Morton Co., Ltd., 1 part by weight of isocyanate-based curing agent CAT-10 manufactured by Toyo Morton Co., Ltd.) was applied to the light-resistant polyethylene terephthalate resin layer side ) Was applied to a solid content thickness of 4 μm, dried, and laminated with the above “Trefan” B013W at a nip pressure of 60 N / cm.

  The laminated film was aged at a temperature of 40 ° C. for 72 hours to accelerate the curing reaction of the adhesive layer, and used as the back surface protective sheet for the solar cell module of the present invention. The evaluation results are shown in Table 1.

  The thickness of the back surface protection sheet for solar cell modules was 314 μm, and the thickness after the DTI test and the judgment of the appearance of the bus bar protrusion were unacceptable.

(Comparative Example 3)
A back protective sheet for a solar cell module in the same manner as in Example 1 except that the light-resistant polyethylene terephthalate film described in Example 1 was changed to a polyethylene terephthalate film without light resistance ("Lumirror" S10 125 µm). Was made. The evaluation results are shown in Table 1.

  The determination of the elongation at break after UV treatment and the color difference after UV treatment was unacceptable.

1: Easy-adhesive resin layer 2: Polyethylene terephthalate film 3: Adhesive layer 4: Light-resistant polyethylene terephthalate film 41: Polyethylene terephthalate resin layer 42: Light-resistant polyethylene terephthalate resin layer 5: Surface protective sheet 6: Wiring is provided Solar power generation element 7: encapsulant sheet layer 1
8: Sealant sheet layer 2
9: Back surface protection sheet for solar cell module 10: Back surface protection sheet for solar cell module 11: Sealing material sheet layer 1
12: Solder wire 13: Release film 14: Glass plate

Claims (3)

  A back protective sheet for a solar cell module laminated in the order of an easy-adhesive resin layer, a polyethylene terephthalate film, and a light-resistant polyethylene terephthalate film for a sealing material layer for holding and fixing a solar cell element, and having a thickness of 360 μm or more A back protective sheet for a solar cell module, wherein the back sheet thickness by a DTI test is 300 μm or more.   The back protective sheet for a solar cell module according to claim 1, wherein the light-resistant polyethylene terephthalate film is formed by laminating a polyethylene terephthalate resin layer and a light-resistant polyethylene terephthalate resin layer. In an atmosphere at a temperature of 63 ° C. and a relative humidity of 50%, the light-resistant polyethylene terephthalate film was irradiated with UV light having an intensity of 180 W / m ² for 334 hours, and the elongation at break was 70% or more, and the color difference (ΔE ^* ) Is 3 or less, The back surface protection sheet for solar cell modules according to claim 1,