JP2014192341A - Rear surface protective sheet for solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rear surface protective sheet for a solar cell module, having favorable long term durability.SOLUTION: A rear surface protective sheet for a solar cell module comprises at least a polyester film and an ultraviolet protective layer. The ultraviolet protective layer includes a main agent and a hardener. The main agent contains 20-40 wt.% of titanium oxide, 15-35 wt.% of an acryl-based resin and 0.1-5 wt.% of a fluorine-based resin. The hardener contains polyisocyanate as a main component. The adhesion of the ultraviolet protective layer is class 0, a color difference ΔE after having being immersed in a 5% NaOH aqueous solution for 48 hours is 3.0 or less, and the adhesion of the ultraviolet protective layer after having being immersed in a 5% NaOH aqueous solution for 48 hours is class 0 or 1.

Description

  The present invention relates to a back surface protection sheet for a solar cell module.

  Solar power generation is being put into practical use as an inexhaustible and non-polluting new energy source, and as a solar cell module for this purpose, a surface protection sheet, an adhesive resin layer, a solar cell, an adhesive resin layer, and a back surface protection sheet are used. Laminated and integrated products are widely known.

  Although the back surface protection sheet is not directly exposed to sunlight, depending on the installation method, the back surface protection sheet is exposed to sunlight due to wraparound or reflection. Therefore, it is important to impart light resistance to the back surface protection sheet.

  As a back surface protection sheet conventionally used, a white polyvinyl fluoride film (DuPont Co., Ltd. “Tedlar” (registered trademark)) can be exemplified, and a back surface protection sheet having a laminated structure in which a polyester film is sandwiched between the films is Widely used in this general application. The polyvinyl fluoride film is excellent in light resistance, but is expensive and becomes an obstacle in terms of reducing the cost of the solar cell module. Moreover, since it contains fluorine, it has a problem of high disposal costs.

  In recent years, a back surface protective sheet in which an ultraviolet protective layer is laminated on a base film such as polyester has been proposed. Since the ultraviolet protective layer blocks the intrusion of light from the back surface, the base material is versatile and the cost can be reduced (Patent Document 1).

  By the way, in the case of a configuration in which an ultraviolet protective layer is provided, durability of the ultraviolet protective layer itself and long-term durability of the base film are important. Recently, long-term quality assurance of 20 to 30 years after installation has been demanded, and the demand for long-term durability has been increasing year by year.

International Publication No. 2010/067780

  The problem to be solved by the present invention is to provide a back surface protection sheet for a solar cell module with good long-term durability.

  In order to solve the above-mentioned problems, a back surface protection sheet for a solar cell module according to the present invention is a back surface protection sheet for a solar cell module comprising at least a polyester film and a UV protection layer, and the UV protection layer is cured with the main agent. The main agent contains 20 to 40% by weight of titanium oxide, 15 to 35% by weight of acrylic resin and 0.1 to 5% by weight of fluorine resin, and the curing agent is mainly composed of polyisocyanate. The UV protective layer has adhesion of class 0, the color difference ΔE after being immersed in 5% NaOH aqueous solution for 48 hours is 3.0 or less, and the ultraviolet protective layer after being immersed in 5% NaOH aqueous solution for 48 hours. The adhesiveness is class 0 to 1.

  ADVANTAGE OF THE INVENTION According to this invention, the back surface protection sheet for solar cell modules which is excellent in long-term durability and can endure use for a long time can be provided.

  The back surface protective sheet for a solar cell module according to one embodiment of the present invention is a back surface protective sheet for a solar cell module comprising at least a polyester film and an ultraviolet protective layer, and the ultraviolet protective layer has a main agent and a curing agent. The main component is 20 to 40% by weight of titanium oxide, 15 to 35% by weight of acrylic resin, and 0.1 to 5% by weight of fluorine resin, the curing agent is mainly composed of polyisocyanate, and adheres to the UV protective layer. The color difference ΔE after immersion in NaOH (5% aqueous solution) for 48 hours is 3.0 or less, and the adhesion of the UV protective layer after 48 hours immersion in NaOH (5% aqueous solution) is class 0 to 1 It is. Each configuration will be described below.

[Polyester film]
The polyester in this embodiment is a general term for polycondensation products of polyvalent carboxylic acids and polyalcohols, and is generally a resin having an ester bond in the main chain obtained by polycondensation of dicarboxylic acids and diols. For example, polyethylene terephthalate (PET) composed of terephthalic acid and diethylene glycol, polyethylene naphthalate (PEN) composed of 2,6-naphthalenedicarboxylic acid and diethylene glycol, and the like can be cited as representative examples. The polyester resin may be a copolymer. Examples of the copolymer component include diol components such as propylene glycol, diethylene glycol, neopentyl glycol, and cyclohexane dimethanol, isophthalic acid, adipic acid, azelaic acid, and sebacic acid. And the dicarboxylic acid component of the ester-forming derivative thereof.

  It is preferable that the polyester film of the back surface protection sheet for solar cell modules of this embodiment is a polyester film which is excellent in hydrolysis resistance from a viewpoint used for the outermost layer exposed directly to outside air. By the way, the polyester resin film contains 1.5 to 2% by weight of a low polymerization amount polymer called an oligomer. A typical polyester resin oligomer is a cyclic trimer. Films with a high content of these resins have reduced mechanical strength during long-term exposure, such as outdoors, and cracks and breakage due to the progress of hydrolysis due to rainwater. And so on. On the other hand, by forming a polyester resin film from a polyester resin having a cyclic trimer content of 1.0% by weight or less obtained by polymerization by a solid phase polymerization method as a raw material, Hydrolysis can be suppressed, and a film excellent in heat resistance and weather resistance can be obtained. The content of the cyclic trimer is obtained, for example, by a method of measuring the content (% by weight) relative to the resin weight by measuring by liquid chromatography using a solution obtained by dissolving 100 mg of a polymer in 2 ml of orthochlorophenol. It is done.

  In addition, the resin film may be added with additives such as an antistatic agent, an ultraviolet absorber, a stabilizer, an antioxidant, a plasticizer, a lubricant, a filler, and a coloring pigment, if necessary. A resin film or the like added within a range not damaged can also be used.

  The thickness of the resin film is not particularly limited, but is preferably in the range of 25 to 300 μm in view of the withstand voltage characteristics and cost of the back protective sheet.

[UV protective layer]
The UV protective layer in the back surface protective sheet for solar cell module of this embodiment has weather resistance, heat resistance, UV resistance, adhesion to the base polyester film, etc., in addition to UV absorption for fulfilling the original function. It is selected with consideration.

  The UV protection layer is a layer disposed on the outermost layer of the back surface protection sheet, and protects the back surface protection sheet laminated on the back surface side of the solar cell module from ultraviolet irradiation from the back surface side of the module. It has a function and is applied onto a polyester film and introduced into the back surface protection sheet.

  In addition to the structure for achieving the above functions, the ultraviolet protective layer may be added with a coloring agent according to the purpose in order to impart design properties.

  The ultraviolet protective layer contains, as main components, a colorant that absorbs or reflects ultraviolet rays and a binder resin for fixing it. The binder resin preferably has a crosslinked structure from the viewpoint of long-term weather resistance, and relatively inexpensive acrylic resins, urethane resins, styrene resins, and the like are preferably used. It is preferable to form a crosslinked structure by reacting a composition comprising a polyol-based binder resin having a hydroxyl group serving as a crosslinking base in the polymer structure and a polyisocyanate crosslinking agent in the coating process. Moreover, surface strength and durability can be improved by adding a fluororesin in addition to the above resin.

  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” (Mitsubishi Rayon Co., Ltd.), and the like. Examples of the polyurethane resin include “Samprene” (manufactured by Sanyo Chemical Industries), “Takelac” (manufactured by Mitsui Chemicals), “TA” (manufactured by Hitachi Chemical Polymer Co., Ltd.), “Seika Bond” ( Dainichi Seika Kogyo Co., Ltd.). These resins are desirably used in a mixture of two or more resins in the same resin system.

  Examples of the fluorine-based wax include “CERAFLOUR” (manufactured by Big Chemie Japan Co., Ltd.), “SST” (manufactured by Shamrock Co., Ltd.) and the like.

  The colorant used in this embodiment has a function of coloring the resin layer and maintaining the color tone for a long time. As for the back surface protection sheet for solar cell modules, white is mainly used from the viewpoint of light reflectivity and design. Since these pigments absorb or reflect light of a specific wavelength, the effect of protecting the binder resin of the ultraviolet protective layer from light can be obtained by coloring the resin layer using these pigments.

  As the colorant used in the present embodiment, various colored pigments such as inorganic pigments and organic pigments can be used. However, inorganic pigments having high photostability are preferably used because they are used outdoors for a long period of time. As the inorganic pigment, titanium oxide is preferably used from the viewpoint of availability and cost. The number average particle size of titanium oxide is particularly preferably 0.1 to 1.0 μm from the viewpoint of color development, and more preferably 0.2 to 0.5 μm from the viewpoint of dispersibility with respect to the binder resin and cost.

  The blending ratio of the binder resin and the colorant is 20 to 40% by weight of titanium oxide, 15 to 35% by weight of acrylic resin, and 0.1 to 5% by weight of fluorine resin.

  If the titanium oxide is less than 20% by weight, an appropriate ultraviolet blocking performance cannot be obtained, and if it exceeds 40%, the ultraviolet protective layer becomes brittle and it is difficult to obtain an appropriate strength. If the acrylic resin is less than 15%, poor dispersion of the colorant occurs and the ultraviolet blocking property tends to be lowered. On the other hand, if it exceeds 35%, the ultraviolet protective layer becomes hard and the adhesion to the substrate tends to decrease. If the fluororesin is less than 0.1%, the effect of improving the strength due to the addition cannot be obtained, and if it exceeds 5%, the ultraviolet protective layer becomes hard and the adhesion to the substrate tends to be lowered.

  As long as the characteristics are not impaired, a plasticizer, a heat stabilizer, an antioxidant, a reinforcing agent, a deterioration preventing agent, a weathering agent, a flame retardant, a release agent, etc. are added to the ultraviolet protective layer in this embodiment. Also good.

  The ultraviolet protective layer of this embodiment is blended with a curing agent having a functional group capable of reacting with a hydroxyl group in the acrylic resin for the purpose of improving the characteristics of the resin layer. By blending the curing agent, the effect of improving the adhesion between the polyester film and the ultraviolet protective layer or improving the durability of the ultraviolet protective layer accompanying the introduction of a crosslinked structure can be obtained. In particular, when the back protection sheet for a solar cell module is designed so that the ultraviolet protective layer in the present embodiment is located on the outermost layer, the manufacturing process of the solar cell module, specifically the glass laminating step (cell filling) In the step), since the resin layer is exposed to a heat treatment of about 30 minutes or longer at a high temperature of about 150 ° C. at the maximum, heat resistance is particularly required. In this embodiment, it is preferable to use a crosslinking agent capable of reacting with the hydroxyl group of the binder resin, and among them, a prescription using a polyisocyanate-based curing agent to promote the formation of a urethane bond (crosslinked structure) is preferable. Examples of the polyisocyanate-based crosslinking agent used as the crosslinking agent include aromatic polyisocyanates, araliphatic polyisocyanates, alicyclic polyisocyanates, and aliphatic polyisocyanates. These crosslinking agents are each made from the diisocyanate compounds shown below as raw materials.

  Examples of the diisocyanate used as a raw material for the aromatic polyisocyanate include m- or p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate (NDI), 4,4'-, 2,4. Examples include '-or 2,2'-diphenylmethane diisocyanate (MDI), 2,4- or 2,6-tolylene diisocyanate (TDI), and 4,4'-diphenyl ether diisocyanate.

  Examples of the diisocyanate used as a raw material for the aromatic aliphatic polyisocyanate include 1,3- or 1,4-xylylene diisocyanate (XDI) and 1,3- or 1,4-tetramethylxylylene diisocyanate (TMXDI). Etc. are exemplified.

  Examples of the diisocyanate used as a raw material for the alicyclic polyisocyanate include 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate; IPDI). 4,4'-, 2,4'- or 2,2'-dicyclohexylmethane diisocyanate (hydrogenated MDI), methyl-2,4-cyclohexanediisocyanate, methyl-2,6-cyclohexanediisocyanate, and 1,3- Examples thereof include 1,4-bis (isocyanatomethyl) cyclohexane (hydrogenated XDI).

  Examples of the diisocyanate used as a raw material for the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-, 2,3- Examples thereof include 1,3-butylene diisocyanate and 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate.

  As a raw material of polyisocyanate, these diisocyanates can be used in combination, or used as a modified body such as a burette modified body (aliphatic) or a nurate modified body (alicyclic). Among them, as a raw material for polyisocyanate, 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, alicyclic polyisocyanate or aliphatic polyisocyanate It is preferable to use a curing agent containing as a main component. Furthermore, ethanol is often used to wipe off resin and dirt adhering to the outermost layer of the solar cell module back surface protection sheet in the finishing step of the solar cell module, and ethanol resistance is required for the outermost layer. Since the curing of the resin layer proceeds from the aliphatic polyisocyanate and the ethanol resistance is improved by using a curing agent mainly composed of an aliphatic polyisocyanate, it is preferable to use an alicyclic polyisocyanate. Moreover, it is preferable to use the hexamethylene diisocyanate modified nurate from the viewpoint of easy progress of the crosslinking reaction with the polyol-based binder resin, the degree of crosslinking, heat resistance, ultraviolet resistance and the like.

  Examples of the solvent for the coating liquid for forming the ultraviolet protective layer in this embodiment by a coating method include toluene, xylene, ethyl acetate, propyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, and water. Etc. can be illustrated. The properties of the coating liquid may be either an emulsion type or a dissolution type.

  The method for forming the ultraviolet protective layer on the substrate film is not particularly limited, and a known coating technique can be used. As the 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.

  The thickness of the ultraviolet protective layer in this embodiment is preferably 0.5 to 10 μm, more preferably 1 to 8 μm, and particularly preferably 1 to 6 μm. When this UV protective layer is formed by a coating method, if the thickness is less than 0.5 μm, a phenomenon such as repellency or film breakage tends to occur during coating, and it is difficult to form a uniform coating film. In some cases, adhesion to the film, UV-cutting property, peeling resistance, and scratch resistance are not sufficiently exhibited. On the other hand, when the thickness of the UV protective layer exceeds 10 μm, UV blocking performance is fully expressed, but there are restrictions on the coating method (specific processes that can be applied to thick films, restrictions on equipment), and the production cost increases. There is a concern that the coating film sticks to the transport roll and the coating film peels off easily.

[Back protection sheet]
In this embodiment, if necessary, a white film, a film having a metal oxide vapor-deposited layer on the surface opposite to the ultraviolet protective layer of the film, and an ethylene / vinyl acetate copolymer resin (EVA) that is a sealing material for solar cell elements By laminating one or more films different from the substrate film among the films having thermal adhesive properties, a solar cell back surface protective sheet satisfying various required characteristics can be obtained.

  Examples of white films include Toray's “Lumirror” E20F, which is a polyethylene terephthalate film, DuPont's “Tedlar” PV2001, which is a polyvinyl fluoride film, and Arkema's “Kyner” 302-PGM-TR, which is a polyvinylidene fluoride film. It can be illustrated. Examples of the film having an inorganic oxide vapor deposition layer include “Barrier Rocks” 1011HG manufactured by Toray Film Processing Co., Ltd., in which a metal oxide vapor deposition layer made of aluminum oxide is formed on a polyethylene terephthalate film substrate. Examples of the film having thermal adhesiveness with EVA include polyolefin films such as ZK93K, 4801, 4806, and B011W manufactured by Toray Film Processing Co., Ltd. When a white film is laminated, light reflectivity is imparted, when a film having a metal oxide vapor deposition layer is laminated, water vapor barrier property is imparted, and when an olefin film layer is laminated on the side facing the EVA Becomes excellent in thermal adhesiveness with EVA. Moreover, the film laminated | stacked on the back surface protection sheet for solar cell modules of this embodiment does not necessarily need to be 1 sheet, According to the characteristic to provide, each member film is combined suitably and the back surface protection sheet for solar cell modules is designed. Just do it.

  In addition, in the configuration of the back surface protection sheet for solar cell modules, a vapor deposition layer, a sputter layer, a wet coating layer, or the like for the purpose of imparting functionality is formed on any layer as long as it is not on the ultraviolet protective layer. May be.

  A known dry laminating method can be used as a method of laminating films and processing into sheets. 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.

  As a material for the adhesive layer, a known dry laminating adhesive can be used. In general, adhesives for dry laminating are prepared by diluting two components of the main agent and cross-linking agent with a diluting solvent. The cross-linking agent is highly reactive with active hydroxyl groups, its reaction rate and initial adhesion. A prescription using an isocyanate group-containing oligomer with a fast onset is preferred. In addition to these advantages, it is possible to form an adhesive resin layer that has high adhesive strength with the base film, and also has excellent constant temperature stability and long-term durability. Examples of the main resin used in combination with the isocyanate group-containing oligomer include polyether resins, polyester resins, polyol resins, and other urethane resins and epoxy resins, depending on detailed requirements and suitability for processing conditions. Can be appropriately selected and used. Moreover, depending on the structure of the back surface protection sheet for solar cell modules, it is also conceivable that UV light reaches the adhesive layer and induces photodegradation of the resin. From such a viewpoint, the resin used for forming the adhesive layer is preferably an aliphatic resin or an alicyclic resin that does not contain an aromatic ring or has a low content.

[Adhesion]
Regarding the substrate adhesion of the ultraviolet protective layer, in accordance with ISO 2409, the ultraviolet protective layer is cut on a lattice, and a tape is applied and peeled off at an angle of 60 ° to confirm the state of peeling. In ISO 2409, the peeling time is defined as 0.5 to 1 second, but as the strength test of the ultraviolet protective layer for solar cells, the peeling time was set to 0.1 to 0.2 seconds.

  The UV protective layer of this embodiment needs to have a base material adhesion of class 0. Classes are classified as follows. If it is Class 1 or higher, adhesion during production and use cannot be guaranteed.

Class 0: The edges of the cut are completely smooth and there is no peeling on the eyes of any lattice.
Class 1: Small peeling of the coating film at the intersection of cuts (degree of peeling: 5% or less).
Class 2: The coating film is peeled along the edge of the cut and / or at the intersection (degree of peeling: 5% to 15%).
Class 3: The paint film is partially or completely peeled along the edge of the cut, or various parts of the eye are partially or completely peeled off (degree of peeling: 15% ~ 35%).
Class 4: The coating film is partially or completely peeled along the edge of the cut, or some eyes are partially peeled completely (degree of peeling: 35% to 65 %).
Class 5: Large peeling that cannot be classified into any of classes 0 to 4 occurs.

[NaOH resistance]
Regarding the NaOH resistance of the ultraviolet protective layer, it is necessary that the ultraviolet protective layer has a color difference ΔE of 3 or less after being immersed in a 5 wt% NaOH aqueous solution at 23 ° C. for 48 hours, washed with water and taken out. In outdoor use, since there are places where the use environment becomes alkaline (such as farmland), NaOH resistance is important. When the color difference ΔE is 3 or more, the color change due to long-term use becomes large even in actual use, and appearance defects, reduction in power generation efficiency, and the like may occur. Further, the adhesion of the ultraviolet protective layer after washing and taking out is measured by the above-mentioned method, and it is necessary to be class 0 to 1. If it is class 2 or higher, the adhesion force may be reduced during long-term use in actual use, resulting in poor appearance and deterioration of the substrate.

  Next, an Example is given and the back surface protection sheet for solar cell modules of this invention is demonstrated concretely.

<Evaluation method of characteristics>
The characteristic evaluation method used in this embodiment is as follows.

(1) Adhesiveness of ultraviolet protective layer According to ISO 2409, the ultraviolet protective layer is cut on a lattice, and a tape is applied and peeled off at an angle of 60 ° to confirm the state of peeling. In ISO 2409, the peeling time is defined as 0.5 to 1 second, but as the strength test of the ultraviolet protective layer for solar cells, the peeling time was set to 0.1 to 0.2 seconds. The results were classified from class 0 to class 5 described above.

(2) NaOH resistance 50 g of sodium hydroxide (99% purity) manufactured by Wako Pure Chemical Industries, Ltd. was dissolved in pure water in a glass container to make 1000 g, and a 5 wt% aqueous sodium hydroxide solution was prepared. Since heat was generated with dissolution, the mixture was left at room temperature in a 23 ° C. environment for 3 hours. A sample provided with an ultraviolet protective layer on a substrate was cut into a 20 cm square, placed so as to be completely immersed in the prepared aqueous sodium hydroxide solution, and left in a dark place for 48 hours. The sample was washed with pure water and dried.

  The adhesion test of (2) was similarly performed on the treated sample.

  Moreover, about the sample before and behind a process, color difference was measured using X-RITE spectrophotometer SP68, and (DELTA) E was computed.

(3) Durability test Using a pressure cooker TPS-211 manufactured by Espec, heat treatment for 48 hours was performed on a sample provided with an ultraviolet protective layer in an environment of 120 ° C. and 100% RH. Thereafter, the adhesion test (2) and the adhesion evaluation with the junction box resin described below were carried out.

(4) Evaluation of Adhesiveness with Silicone Resin for Junction Box Adhesion The adhesion strength between the ultraviolet protective layer and the dedicated silicone resin used for adhering the junction box was evaluated by the following method. Applying “Solar PV” 804 manufactured by Dow Corning to a thickness of 0.2 mm using a spacer on the UV protective layer of the back surface protection sheet for the solar cell module, and for another solar cell module The back surface protection sheet was laminated so that the ultraviolet protection layers faced each other, and pressed and adhered with a rubber roller so as to remove air. A sample prepared by allowing the adhesion sample to stand at room temperature for 1 week and drying was used as a test piece. Three test pieces for measurement were cut out from this test piece in a strip shape with a width of 15 mm, and based on JIS K6854, the sample was peeled off at an upper and lower peeling angle of 90 °, and the adhesive strength was measured with a so-called T-type peel. The measurement was performed once for each of the three strip-shaped test pieces, and the average value of the obtained strengths was taken as the value of the silicone resin adhesive strength. It was determined that the adhesive strength was 8N / 15mm or more was good (◯), 6-8N / 15mm was usable (Δ), and less than 8N / 15mm was unusable (x).

Example 1
(Preparation of UV protective layer coating)
A titanium oxide dispersion was prepared by dispersing using a paint shaker (using glass beads having a diameter of 2 mm) in accordance with Table 1.

  Using the dispersion liquid, as shown in Table 2, UV protective layer paints of Examples 1 and 2 and Comparative Examples 1 and 2 were prepared.

(Preparation of back protection sheet)
The above-mentioned paint was applied on a polyethylene terephthalate film “Lumirror” X10S (thickness 125 μm) manufactured by Toray Industries, Inc., which had been subjected to corona treatment, so that the thickness became 3 to 5 μm after drying with a bar coater # 12. Dry at 10 ° C. for 10 seconds. The base material with the ultraviolet protective layer of Example 1 was produced by carrying out aging at 50 ° C. for 72 hours. The adhesion of the ultraviolet protective layer of Example 1 is class 0, ΔE after NaOH treatment is 2.0, and adhesion is class 0. As a result of the durability evaluation, adhesion and adhesion with the junction box resin were good. The test results are shown in Table 3.

(Example 2)
A back protective sheet of Example 2 was produced in the same manner as in Example 1 except that the acrylic resin was changed to “Acrynal” TZ # 7501 manufactured by Toei Kasei Co., Ltd. The adhesion of the ultraviolet protective layer of Example 2 is class 2, ΔE after NaOH treatment is 1.8, and adhesion is class 4. As a result of the durability evaluation, adhesion and adhesion with the junction box resin were good.

(Comparative Example 1)
A back protective sheet of Comparative Example 1 was produced in the same manner as in Example 1 except that the blending amount of the acrylic resin was 5 parts by weight. The adhesion of the ultraviolet protective layer of Comparative Example 1 is class 0, ΔE after NaOH treatment is 2.0, and adhesion is class 0. As a result of the durability evaluation, both adhesion and adhesion to the junction box resin were poor.

(Comparative Example 2)
A back protective sheet of Comparative Example 2 was produced in the same manner as Example 1 except that no fluororesin was added. The adhesion of the ultraviolet protective layer of Comparative Example 2 is class 3, ΔE after NaOH treatment is 4.5, and adhesion is class 5. As a result of the durability evaluation, both adhesion and adhesion to the junction box resin were poor.

  As is clear from the results of the above examples and comparative examples, according to the method of the present invention, the long-term durability is excellent, and the adhesion with the terminal box adhesive silicone resin required for use in the outermost layer is also achieved. A film for solar cell back surface sealing material having an excellent ultraviolet protective layer is obtained.

  The solar cell back surface sealing sheet of the present invention is excellent in long-term durability and excellent in adhesion to a terminal box adhesive silicone resin required for use in the outermost layer, and is suitably used in a solar cell module.

Claims (1)

  A back protective sheet for a solar cell module comprising at least a polyester film and an ultraviolet protective layer, wherein the ultraviolet protective layer has a main agent and a curing agent, the main agent being 20 to 40% by weight of titanium oxide, and an acrylic resin 15 to 35. The curing agent is mainly composed of polyisocyanate, the adhesion of the UV protective layer is class 0, and it is added to a 5% NaOH aqueous solution for 48 hours. Back surface protection for solar cell modules, characterized in that the color difference ΔE after immersion is 3.0 or less, and the adhesion of the ultraviolet protective layer after immersion in a 5% NaOH aqueous solution for 48 hours is class 0 to 1 Sheet.