JP5939636B2 - SOLAR CELL MODULE BACK SHEET AND METHOD FOR PRODUCING SOLAR CELL MODULE BACK SHEET - Google Patents

Description

  The present invention relates to a back sheet for a solar cell module, which is a member constituting a solar cell module, and is formed by laminating a plurality of types of functional films via an adhesive layer. More specifically, the adhesive itself used for forming the adhesive layer has a high gas barrier property, is excellent in adhesiveness, has a low decrease in adhesive strength even in a high-temperature, high-humidity environment, and an acidic environment, and its production raw material. In addition, since a resin in which carbon dioxide is fixed in the structure can be used, the present invention relates to a technique useful for the carbon dioxide reduction effect which is a problem on a global scale.

  In recent years, with increasing interest in global warming issues, various efforts have been made to suppress carbon dioxide emissions. On the other hand, considering the degree of dependence on electric power in modern society, electric power is indispensable as an energy source in order to maintain the modern society, and the degree of dependence on electric power is increasing. Specifically, in order to enable the use of a wide variety of electrical products and information equipment at home and in the places of civic life, the operation of public and commercial facilities in cities, etc. Electric power is required as a power source in the field. Furthermore, in recent years, electric power has also been used for the operation of electronic devices for information transmission whose development has been remarkable. In transportation, it is also used as a power source for mass transportation means such as trains and freight trains. However, in recent years, the power source for automobiles for personal use has also been attempted from a plug-in hybrid system to a fully electric vehicle. It is also being implemented, the use of electricity is becoming increasingly diverse and its consumption is increasing. As described above, the dependence of energy sources on power in modern society has become even greater.

  Nuclear power generation that does not emit carbon dioxide has been promoted all over the world in response to such increasing electric energy consumption. However, the safety myth of nuclear power generation collapsed due to the accident at the Fukushima Daiichi nuclear power plant in Japan that occurred on March 11, 2011, and it is insufficient due to the nuclear power generation shutdown that took place. In order to secure electric energy, the thermal power generation that has been stopped is in full operation, which is in conflict with the reduction of carbon dioxide emissions.

  On the other hand, solar power generation has been conventionally expected from the viewpoint of cleanliness and non-polluting properties. Solar cells that already use single crystal silicon, polycrystalline silicon, amorphous silicon, or the like for solar cell elements (cells). Has been put to practical use as an outdoor power solar cell. In particular, due to the circumstances described above, recently, it has attracted attention as a power generation technology that can replace nuclear power generation.

  The structure of a solar cell used for photovoltaic power generation is a variety of sealing methods in which a large number of solar cell elements (cells) are wired in series and in parallel, and these cells are protected for a long period (about 20 years or more). Is done and unitized. This unit is called a solar cell module or a solar panel. Generally, as shown in FIG. 1, the surface that is exposed to sunlight is covered with a glass plate 1 and the back surface is a protective sheet for sealing (back sheet). ) 5 and a glass plate 1 on which a solar cell element (cell) 3 is arranged with a filler (sealing material) 2 made of a thermoplastic such as ethylene-vinyl acetate copolymer (EVA). The gap with the back sheet 5 is filled.

  Since the above-described solar cell module is mainly used outdoors, its material and structure are required to have sufficient durability and weather resistance. In particular, the back sheet is required to have excellent weather resistance, gas barrier properties, and moisture barrier properties (water vapor barrier properties). This is because the penetration of moisture from the back sheet may cause the filler to peel off, discolor, and corrode the wiring, affecting the module output itself.

  As described above, the solar cell module backsheet (hereinafter, also simply referred to as “backsheet”) is required to have weather resistance, durability, gas barrier properties, and the like. The metal layer is a laminate in which the front and back surfaces are sandwiched between a pair of synthetic resin layers. Specifically, for example, a pair of "fluorine resin" films such as polyvinyl fluoride and polyvinylidene fluoride, one of a back sheet having a structure in which an aluminum foil (metal layer) is sandwiched, or a plastic film made of a polyester resin A back sheet having a structure in which an inorganic oxide thin film layer is laminated on this surface and a plurality of plastic films made of the same polyester resin are laminated on the outer surface of the thin film layer has been developed. Thus, the back sheet is a laminate composed of a plurality of types of films, and the plurality of films are laminated via an adhesive (Patent Documents 1 and 2).

  And, in the formation of the back sheet, polyurethane adhesive, acrylic adhesive, epoxy adhesive, etc. are actually used as adhesives, and these require the adhesiveness and durability, etc. It has been demonstrated that performance can be achieved. However, most of the films and adhesives used in the formation of these backsheets are derived from petroleum, and from the perspective of realizing cleanliness and pollution-free by promoting the use of solar cells, The required global environmental conservation is insufficient.

  In addition, global warming and ocean acidification, which are thought to be caused by the ever-increasing amount of carbon dioxide, have become a global problem, and reduction of carbon dioxide emissions is important worldwide. It is a difficult task. Furthermore, from the viewpoint of exhaustible petrochemical resources (petroleum), the conversion of materials to renewable resources such as biomass and methane has become a global trend.

  On the other hand, as can be seen in Non-Patent Documents 1 and 2, polyhydroxy polyurethane resin using carbon dioxide as a raw material has been known for a long time, but its application development has not progressed. The reason for this is that it is clearly inferior in terms of its characteristics as compared with the polyurethane-based resin that is compared as the same type of polymer compound.

  Against the background as described above, the above-mentioned polyhydroxy polyurethane resin has been reviewed again. That is, carbon dioxide, which is the raw material for this resin, is an easily available and sustainable carbon resource. Plastics that use carbon dioxide as a raw material are also used for warming, acidification of the sea, depleted resources, etc. It can be an effective means to solve the problem.

Japanese Patent Laid-Open No. 6-177412 JP 2002-134771 A

N. Kihara, T. Endo, J. Org. Chem., 1993, 58, 6198 N. Kihara, T. Endo, J. Polymer Sci., Part A Polmer Chem., 1993, 31 (11), 2765

  Under the circumstances as described above, it is desired that each material constituting the solar cell module, which is expected to be used in the future, be reviewed. For this reason, high performance including the above viewpoint is also required for the adhesive used to form the back sheet of one member, and long-term adhesion and durability are maintained as basic performance. In addition to satisfying that the bonded materials have excellent weather resistance, high gas barrier properties and moisture barrier properties, development of environmentally friendly products with environmental conservation on a global scale is demanded. Yes.

  Therefore, when the objective of this invention is used as an adhesive agent of a solar cell module backsheet, the formed adhesive layer can not only maintain long-term adhesion and durability, but is also required for the backsheet. High-value-added solar cells that satisfy weather resistance and that are particularly satisfactory for high gas barrier properties and moisture barrier properties. It is to provide a module backsheet. That is, an object of the present invention is to provide a solar cell module that realizes high performance, and further contributes to global environmental conservation in terms of its raw materials, and has a multifaceted excellent feature. To provide a backsheet.

  The above object is achieved by the following invention. That is, the present invention provides (1) a solar cell module backsheet that is a member constituting a solar cell module, in which a plurality of types of films are laminated via an adhesive layer, and at least any of the adhesive layers described above. Is masked in its structure, which is derived from the reaction between a 5-membered cyclic carbonate compound and an amine compound, and is obtained by modifying a polyhydroxy polyurethane resin obtained by reacting carbon dioxide as a part of the raw material. Provided is a back sheet for a solar cell module, which is formed of a self-crosslinking polyhydroxy polyurethane resin-based adhesive having an isocyanate group.

The following are mentioned as a preferable form of the back sheet | seat for solar cell modules of the said invention.
(2) The masked isocyanate group in the structure of the self-crosslinking type polyhydroxy polyurethane resin is a reaction product of an organic polyisocyanate group and a masking agent, and the masked portion is dissociated by heat treatment. The back sheet for a solar cell module according to the above (1), which generates an isocyanate group and reacts with a hydroxyl group in the structure of the resin to self-crosslink.
(3) The 5-membered cyclic carbonate compound is a reaction product obtained by reacting an epoxy compound and carbon dioxide, and the self-crosslinking polyhydroxypolyurethane resin has a structure comprising carbon dioxide. The back sheet for a solar cell module according to (1) or (2), wherein the component (—COO) is contained in the range of 1 to 25% by mass.

  According to the present invention, by using a polyhydroxy polyurethane resin capable of self-crosslinking for the adhesive used for the backsheet, the resin can be self-crosslinked by, for example, heat treatment without using a crosslinking agent such as isocyanate. Thus, an adhesive layer can be formed. The adhesive layer not only satisfies the basic performance of durability and weather resistance, but also has a particularly high gas barrier property and moisture barrier property. Further, from the viewpoint of the global environment, the adhesive layer is used as a raw material for the resin used. Provided is a back sheet for a solar cell module that is useful as an environmentally-friendly product, because carbon is used and carbon dioxide is incorporated into a film formed by self-crosslinking made of the resin. .

The schematic cross section which shows the basic composition of an example of a solar cell module. The schematic cross section which shows an example of the back seat | sheet for solar cell modules. The schematic cross section which shows the test sheet | seat of the solar cell module backsheet produced in the Example.

  Next, the present invention will be described in more detail with reference to preferred embodiments. The back sheet for a solar cell module of the present invention is a member constituting the solar cell module, and a plurality of types of films are laminated via an adhesive layer. The adhesive layer is a five-membered cyclic carbonate. A self-crosslinking polyhydroxypolyurethane resin derived from a reaction between a compound and an amine compound and having an isocyanate group masked in its structure is used as an adhesive, and for example, the resin is self-crosslinked by heat treatment. It is a film.

  Hereinafter, the polyhydroxy polyurethane resin constituting the adhesive used for forming the adhesive layer characterizing the back sheet of the present invention will be described. Since the resin characterizing the present invention is a self-crosslinking polyhydroxypolyurethane resin having an isocyanate group masked in its structure, it can be rapidly self-crosslinked quickly by heat treatment or the like without using a crosslinking agent such as isocyanate. To do. For this reason, if the polyhydroxypolyurethane resin characterizing the present invention is used as an adhesive when producing a back sheet, for example, if the film is adhered by a method such as dry lamination after heat treatment, the adhesive layer becomes As a result, it becomes possible to provide a back sheet excellent in higher gas barrier properties and moisture barrier properties in addition to excellent durability and weather resistance. Hereinafter, the self-crosslinking type polyhydroxy polyurethane resin constituting the adhesive used to form the adhesive layer characterizing the back sheet of the present invention will be described.

[Self-crosslinking type polyhydroxy polyurethane resin]
The self-crosslinking polyhydroxypolyurethane resin used in the present invention uses, for example, a modifier having at least one free isocyanate group and a masked isocyanate group. It can be easily obtained by reacting with a hydroxyl group in a polyhydroxypolyurethane resin derived from a reaction between a cyclic carbonate compound and an amine-modified polysiloxane compound. As a modifier used at this time, a reaction product of an organic polyisocyanate compound and a masking agent may be used. Below, each component is demonstrated.

(Modifier)
<Organic polyisocyanate compound>
The components of the modifier used in the method for producing the self-crosslinking polyhydroxypolyurethane resin used in the present invention will be described. As the modifier, as described above, a reaction product of an organic polyisocyanate compound and a masking agent is used. The organic polyisocyanate compound is an organic compound having at least two isocyanate groups in an aliphatic or aromatic compound, and has been widely used as a raw material for synthesizing polyurethane resins. Any of these known organic polyisocyanate compounds are useful in the present invention. Particularly preferable organic polyisocyanate compounds are as follows.

  1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate), 4,4'-dicyclohexylmethane Diisocyanate, tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate, tolidine diisocyanate, xylylene diisocyanate, and adducts of these organic polyisocyanate compounds with other compounds, for example, Although the thing of the following structural formula is mentioned, it is not limited to these.

<Masking agent>
The modifier used in the production method of the present invention is a reaction product of the organic polyisocyanate compound and the masking agent described above, and the following can be used as the masking agent. There are alcohol-based, phenol-based, active methylene-based, acid amide-based, imidazole-based, urea-based, oxime-based and pyridine-based compounds, and these may be used alone or in combination. Specific masking agents are as follows.

  Examples of alcohols include methanol, ethanol, propanol, butanol, 2-ethylhexanol, methyl cellosolve, and cyclohexanol. Examples of the phenol type include phenol, cresol, ethylphenol, nonylphenol and the like. Examples of the active methylene type include dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, and acetylacetone. Examples of acid amides include acetanilide, acetic acid amide, caprolactam, and γ-butyrolactam. Examples of the imidazole series include imidazole and 2-methylimidazole. Examples of the urea system include urea, thiourea, and ethylene urea. Examples of the oxime type include formamide oxime, acetoxime, methyl ethyl ketoxime, and cyclohexanone oxime. Examples of the pyridine series include 2-hydroxypyridine and 2-hydroxyquinoline.

<Method of synthesizing denaturant>
A modifier having at least one free isocyanate group and the other having a masked isocyanate group is used in the present invention by reacting the organic polyisocyanate compound listed above with the masking agent listed above. Can be synthesized. The synthesis method is not particularly limited. For example, the masking agent as described above and an organic polyisocyanate compound are added in a functional group ratio in which one or more isocyanate groups are excessive in one molecule, in the presence or absence of an organic solvent and a catalyst. In the presence, it can be easily obtained by reacting at a temperature of 0 to 150 ° C., preferably 20 to 80 ° C. for 30 minutes to 3 hours.

<Polyhydroxy polyurethane resin>
The polyhydroxy polyurethane resin to be modified with the specific modifier as described above is obtained by a reaction between a 5-membered cyclic carbonate compound and an amine compound. Below, each component used in this case is demonstrated.

(5-membered cyclic carbonate compound)
The 5-membered cyclic carbonate compound used in the present invention can be produced, for example, by reacting an epoxy compound and carbon dioxide, as shown by the following [Formula-A]. More particularly, the epoxy compound is reacted with carbon dioxide in the presence or absence of an organic solvent and in the presence of a catalyst at a temperature of 40 ° C. to 150 ° C. under normal pressure or slightly elevated pressure for 10-20 hours. It is obtained by reacting. Since the self-crosslinking polyhydroxypolyurethane resin characterizing the present invention is obtained as described above, carbon dioxide containing a component (—COO) composed of carbon dioxide in the range of 1 to 25 mass% in its structure. It will have a reduction effect.

Examples of the epoxy compound used in the present invention include the following compounds.

  The epoxy compounds listed above are preferable compounds used in the present invention, and the present invention is not limited to these exemplified compounds. Accordingly, not only the compounds exemplified above, but also any other compounds that are currently commercially available and can be easily obtained from the market can be used in the present invention.

Examples of the catalyst that can be used in the reaction of the above epoxy compound and carbon dioxide include a base catalyst and a Lewis acid catalyst.
Base catalysts include tertiary amines such as triethylamine and tributylamine, cyclic amines such as diazabicycloundecene, diazabicyclooctane and pyridine, alkali metals such as lithium chloride, lithium bromide, lithium fluoride and sodium chloride Salts, alkaline earth metal salts such as calcium chloride, quaternary ammonium salts such as tetrabutylammonium chloride, tetraethylammonium bromide, benzyltrimethylammonium chloride, carbonates such as potassium carbonate and sodium carbonate, zinc acetate, lead acetate, acetic acid Examples thereof include metal acetates such as copper and iron acetate, metal oxides such as calcium oxide, magnesium oxide and zinc oxide, and phosphonium salts such as tetrabutylphosphonium chloride.

  Examples of the Lewis acid catalyst include tin compounds such as tetrabutyltin, dibutyltin dilaurate, dibutyltin diacetate, and dibutyltin octoate.

  The amount of the catalyst may be about 0.1 to 100 parts by mass, preferably 0.3 to 20 parts by mass, per 50 parts by mass of the epoxy compound. If the amount used is less than 0.1 parts by mass, the effect as a catalyst is small, and if it exceeds 100 parts by mass, various performances of the final resin may be deteriorated. However, in the case where the residual catalyst causes a serious performance deterioration, it may be configured to be removed by washing with pure water.

  Examples of the organic solvent that can be used in the reaction between the epoxy compound and carbon dioxide include dimethylformamide, dimethylsulfoxide, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, and tetrahydrofuran. These organic solvents and other poor solvents such as methyl ethyl ketone, xylene, toluene, tetrahydrofuran, diethyl ether, and cyclohexanone may be used in a mixed system. These organic solvents can also be used as a diluting solvent when the polyhydroxypolyurethane resin used in the present invention is produced or used as an adhesive.

  As shown in the following [Formula-B], the polyhydroxy polyurethane resin used in the present invention is obtained by, for example, combining a 5-membered cyclic carbonate compound and an amine compound obtained by the above reaction in the presence of an organic solvent at 20 ° C. It can be obtained by reacting at a temperature of ˜150 ° C.

  The amine compound that can be used in the above reaction is preferably a diamine, but any of those conventionally used in the production of polyurethane resins can be used and is not particularly limited. For example, aliphatic diamines such as methylenediamine, ethylenediamine, trimethylenediamine, 1,3-diaminopropane, hexamethylenediamine, octamethylenediamine; phenylenediamine, 3,3′-dichloro-4,4′-diaminodiphenylmethane, 4 , 4′-methylenebis (phenylamine), 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylsulfone, metaxylylenediamine, paraxylylenediamine, and the like; 1,4-cyclohexanediamine, 4 , 4'-diaminocyclohexylmethane, 1,4'-diaminomethylcyclohexane, isophoronediamine and other alicyclic diamines; monoethanoldiamine, ethylaminoethanolamine, hydroxyethylaminopropylamine Like alkanol diamine is.

  The amine compounds listed above are preferable compounds used in the present invention, and the present invention is not limited to these exemplified compounds. Accordingly, not only the compounds exemplified above, but also any other compounds that are currently commercially available and can be easily obtained from the market can be used in the present invention.

(Self-crosslinking type polyhydroxy polyurethane resin)
The self-crosslinking polyhydroxypolyurethane resin characterizing the present invention is obtained by reacting a modifier and a polyhydroxypolyurethane resin obtained as described above to modify the polyhydroxypolyurethane resin. More specifically, it can be obtained by reacting the hydroxyl group in the polyhydroxy polyurethane resin with at least one free isocyanate group in the modifier.

The modification rate of the self-crosslinking polyhydroxypolyurethane resin used in the present invention with the modifier is preferably 2 to 60%. When the modification rate is less than 2%, the film formed by self-crosslinking does not have a sufficient cross-linking structure when used as an adhesive layer of a back sheet, and the durability thereof may be inferior. On the other hand, if the modification rate exceeds 60%, there is a possibility that the dissociated isocyanate group may remain without reacting, which is not preferable. The modification rate is calculated as follows.
Modification rate (%) = {1− (hydroxyl group of resin after modification ÷ hydroxyl group of resin before modification)} × 100

  The reaction between the modifier and the polyhydroxypolyurethane resin is carried out in the presence or absence of an organic solvent and a catalyst, for example, at a temperature of 0 to 150 ° C., preferably 20 to 80 ° C. for 30 minutes to 3 hours. As a result, the self-crosslinking polyhydroxy polyurethane resin used in the present invention can be easily obtained. However, attention should be paid to the fact that the reaction is carried out at a temperature lower than the dissociation temperature of the masking agent during the reaction, and the resin after the reaction needs to have a masked isocyanate group in its structure.

  In addition, the self-crosslinking polyhydroxypolyurethane resin suitably used for forming the adhesive layer characterizing the present invention has a number average molecular weight (measured by GPC, standard polystyrene equivalent value; the same applies hereinafter) of 2,000. It is preferable that it is about -100,000, More preferably, it is about 5,000-70,000.

  The self-crosslinking polyhydroxypolyurethane resin used in the present invention is modified by a modifier, but is derived from a reaction between a 5-membered cyclic carbonate compound and an amine compound. The reaction produces hydroxyl groups in the structure that were impossible with conventional polyurethane resins. According to the study by the present inventors, the use of a resin having such a structure for the formation of the adhesive layer of the backsheet can further improve the performance of the backsheet. More specifically, since the hydroxyl group has hydrophilicity, it can improve the adhesion to the substrate, and at the same time, has a high gas barrier property that could not be achieved with conventional polyurethane resins. Can be obtained. Further, the durability can be further improved by crosslinking the hydroxyl group with the masked isocyanate group in the resin structure.

  In the present invention, the hydroxyl group content in the self-crosslinking polyhydroxypolyurethane resin used for the adhesive is preferably about 3 to 30% by mass (hydroxyl value 25 to 300 mgKOH / g). If the hydroxyl group content is less than the above range, the gas barrier property and carbon dioxide reduction effect of the formed adhesive layer may not be sufficiently obtained. This is not preferable because physical properties may not be realized.

  The adhesive (self-crosslinking polyhydroxypolyurethane resin-based adhesive) containing the above-mentioned self-crosslinking polyhydroxypolyurethane resin used for forming the adhesive layer of the backsheet of the present invention is the above-mentioned self-crosslinking polyhydroxypolyurethane. In addition to the polyurethane resin, a solvent, an additive, or the like may be included.

  As the solvent, the same organic solvent as used when synthesizing the self-crosslinking type polyhydroxy polyurethane resin can be used. Moreover, as an additive, the additive etc. which are generally used when forming a film and a coating film can be used suitably. Specific examples of additives include inorganic fine particles such as leveling agents, colloidal silica, and alumina sol, polymethylmethacrylate and polyurethane organic fine particles, antifoaming agents, anti-sagging agents, silane coupling agents, titanium white , Carbon black, organic pigments, pigment dispersants, phosphorus antioxidants, phenolic antioxidants and other antioxidants, UV stabilizers, flame retardants, plasticizers, rust inhibitors, organic and inorganic UV absorbers An agent, an inorganic heat-absorbing agent, a flameproofing agent, an antistatic agent, a dehydrating agent and the like can be mentioned, but the present invention is not limited to such examples.

  The backsheet of the present invention is characterized by laminating a plurality of types of films (base materials) through an adhesive layer formed of the above-mentioned self-crosslinking type polyhydroxy polyurethane resin-based adhesive. Any adhesive layer may be formed of at least one of the above-mentioned self-crosslinking polyhydroxypolyurethane resin adhesives. In the present invention, it is more preferable to form all the adhesive layers with the above-mentioned self-crosslinking polyhydroxy polyurethane resin-based adhesive. The above-mentioned self-crosslinking polyhydroxypolyurethane resin-based adhesive is used, for example, for the purpose of improving the adhesiveness to the filler used in solar cells, and other adhesive resin components to the above-mentioned self-crosslinking polyhydroxypolyurethane resin. What mixed and adjusted the performance balance may be used. Examples of other resin components used in this case include polyester resins, modified polyolefin resins, ethylene-vinyl acetate copolymer resins, polyvinyl butyral resins, polyurethane resins, vinyl chloride resins, and the like. it can.

  Next, a plurality of types of films are laminated via an adhesive layer, and the adhesive layer is formed of the above-described polyhydroxy polyurethane resin-based adhesive. The material and structure will be described.

  FIG. 2 is a schematic cross-sectional view showing a sheet structure according to an embodiment of the back sheet of the present invention. The back sheet 5 shown in FIG. 2 has different functionality in the order of the base film 6, the adhesive layer 7, the gas barrier film 8, the adhesive layer 7, and the base film 10 made of the same or different material as described above. A plurality of films are laminated via an adhesive layer 7 formed of the specific adhesive described above. Note that the gas barrier film 8 shown in FIG. 2 is formed by forming a vapor deposition layer on the base film 6, and details of this point will be described later. Hereinafter, the film material etc. which can comprise the back sheet of this invention are demonstrated in detail using the back sheet of this invention of embodiment shown in FIG. 2 as an example.

  The synthetic resin used for the base film 6 constituting the back sheet of the present invention having the structure shown in FIG. 2 is not particularly limited, and a film made of the following resin is appropriately used according to the purpose. be able to. For example, polyethylene resin, polypropylene resin, cyclic polyolefin resin, polystyrene resin, acrylonitrile-styrene resin, polyvinyl chloride resin, fluorine resin, poly (meth) acrylic resin, polycarbonate resin, polyester resin, polyamide resin, polyimide resin, polyamideimide resin , Silicone resin, polysulfone resin, polyethersulfone resin, acetal resin, cellulose resin and the like. Among the above resins, polyester resins, fluororesins and cyclic polyolefin resins having high heat resistance, strength, weather resistance, durability, gas barrier properties, etc. and excellent adhesion to the aluminum vapor deposition layer are preferable.

  The base film 6 made of the resin material as described above may be subjected to surface treatment for improving adhesiveness such as corona treatment, flame treatment, plasma treatment, and the like, if necessary.

  Moreover, it is preferable that the thickness of the base film 6 is 10 micrometers-300 micrometers. When the thickness is less than 10 μm, for example, when the surface is subjected to a vapor deposition process such as aluminum vapor deposition in order to impart a function, curling tends to occur, which is not preferable. On the other hand, when the thickness exceeds 300 μm, it is not preferable because it is contrary to the reduction in thickness and weight of the solar cell module.

  Various additives and the like can be mixed in the forming material of the base film 6 for the purpose of improving processability, heat resistance, weather resistance, mechanical strength, dimensional stability, and the like. Examples of the additive include a lubricant, a crosslinking agent, an antioxidant, an ultraviolet absorber, a light stabilizer, a reinforcing fiber, a reinforcing agent, an antistatic agent, a flame retardant, an antifungal agent, a pigment, and a flame retardant. .

  As described above, the back sheet of the present invention may be one in which at least one of the adhesive layers 7 in the structure is formed of a specific self-crosslinking polyhydroxy polyurethane resin-based adhesive. However, it can be formed by the following methods. Specifically, an adhesive characterizing the present invention is applied on any of the base films by a method such as gravure coating, roll coating, bar coating, reverse coating, and the coated surface is coated with a dry laminate or the like. It can form by bonding another film by a method. The adhesive layer thus formed is a film that is self-crosslinked by reacting with a hydroxyl group in the structure of the resin by generating an isocyanate group by dissociating the masked portion in the resin during heat treatment or the like. It becomes. The thickness after drying of the adhesive layer formed as described above is preferably about 0.1 μm to 50 μm, more preferably in the range of 0.5 μm to 30 μm from the viewpoint of adhesion and weather resistance. . If the thickness of the adhesive layer after drying is smaller than this range, the adhesive strength and the defect sealing function of the gas barrier vapor deposition layer may not be obtained. On the other hand, if the thickness of the adhesive layer after drying is larger than this range, it is not preferable because sufficient adhesive strength and durability may not be obtained.

  The gas barrier film 8 may be, for example, a metal foil such as an aluminum foil, but the vapor deposition layer 9 is formed on the surface of the base film 6 such as a metal vapor deposition film or an oxide vapor deposition film as shown in FIG. A formed vapor deposition substrate can be used.

  As said metal vapor deposition film, the aluminum vapor deposition film etc. which vapor-deposited aluminum on the polyester film and the polyolefin-type stretched film are mentioned, for example.

  As said oxide vapor deposition film, the film which vapor-deposited complex oxides, such as aluminum oxide, silicon dioxide, a tin oxide, an indium oxide, etc., for example is mentioned, It uses preferably. In these oxide-deposited films, the thickness of the oxide deposition layer such as a composite oxide varies depending on the type and composition of the oxide, but in general, from the viewpoint of forming a uniform oxide deposition layer, the thickness is 5 nm to A range of 300 nm is preferred. From the viewpoint of imparting flexibility and preventing the occurrence of cracks and the like due to external stress, the thickness of the oxide deposition layer is preferably in the range of 10 nm to 150 nm. Examples of the method for forming an oxide deposition layer include a vacuum deposition method, a sputtering method which is a thin film formation method, an ion plating method, a plasma vapor deposition method (CVD), and the like. It is not limited to.

  The base film 10 constituting the back sheet having the structure shown in FIG. 2 is positioned on the side to be bonded to the filler (sealing agent) 2 when the solar cell module is manufactured. For this reason, it is preferable that it is a film of the form which has adhesiveness with respect to sheets and fillers, such as ethylene-vinyl acetate copolymer (EVA), among the base material mentioned above.

  The present invention is characterized in that at least any one or all of the adhesive layers constituting the backsheet are formed of a specific self-crosslinking polyhydroxy polyurethane resin-based adhesive, The masked portion of the resin constituting the adhesive is dissociated to generate isocyanate groups, which react with the hydroxyl groups in the resin structure to form a self-crosslinked film. By setting it as such a structure, it becomes a solar cell module backsheet excellent in durability, a weather resistance, especially gas barrier property. The reason is that the hydroxyl group of the polyhydroxypolyurethane resin forming the adhesive layer interacts strongly at the interface with the substrate sheet, thereby having excellent adhesion and flexibility to the substrate. it is conceivable that. In addition, as described above, the isocyanate group and the hydroxyl group in the structure are self-crosslinked to form an adhesive layer, whereby a back sheet having further excellent heat resistance and durability is obtained. Furthermore, the polyhydroxypolyurethane resin used in the present invention is derived from the reaction between a 5-membered cyclic carbonate compound and an amine compound, and the 5-membered cyclic carbonate compound contains carbon dioxide as a part of its raw material. For example, since it is obtained by reacting an epoxy compound and carbon dioxide, carbon dioxide can be incorporated and fixed in the resin. This means that the present invention makes it possible to provide a backsheet as an environmental protection product that was useful from the viewpoint of reducing greenhouse gases and that could not be achieved with conventional products.

  Next, the present invention will be described in more detail with reference to specific production examples, examples and comparative examples, but the present invention is not limited to these examples. In the following examples, “part” and “%” are based on mass unless otherwise specified.

<Production Example 1> (Production of modifier)
Trimethylolpropane and hexamethylene diisocyanate trimer adduct [Coronate HL (trade name), manufactured by Nippon Polyurethane, NCO = 12.9%, solid content 75%] 100 parts, ethyl acetate 24.5 parts, While stirring well at 100 ° C., 25.5 parts of ε-caprolactam was added and allowed to react for 5 hours. According to the infrared absorption spectrum of the obtained modifier (measured with FT-720 manufactured by Horiba, the same applies hereinafter), absorption due to free isocyanate groups remained at 2,270 cm ⁻¹ . When this free isocyanate group was quantified, the theoretical value was 2.1% at a solid content of 50%, whereas the measured value was 1.8%. Therefore, the main structure of the above modifier is presumed to be the following formula.

<Production Example 2> (Production of modifier)
Hexamethylene diisocyanate and water adduct [Duranate 24A-100 (trade name), Asahi Kasei Co., Ltd., NCO = 23.0%] 100 parts, while stirring ethyl acetate at 80 ° C, 32 parts of methyl ethyl ketoxime was added. The reaction was performed for 5 hours. According to the infrared absorption spectrum of the resulting modifier, absorption due to free isocyanate groups remains at 2,270 cm ⁻¹ , and when this free isocyanate group is quantified, the theoretical value is 2. at a solid content of 50%. The actual measured value was 2.6%, compared with 9%. Therefore, the main structure of the above modifier is estimated as the following formula.

<Production Example 3> (Production of 5-membered cyclic carbonate compound)
In a reaction vessel equipped with a stirrer, a thermometer, a gas introduction tube and a reflux condenser, a divalent epoxy compound represented by the following formula A [Epicoat 828 (trade name), manufactured by Japan Epoxy Resins Co., Ltd .; epoxy equivalent 187 g / mol] 100 parts, 100 parts of N-methylpyrrolidone and 1.5 parts of sodium iodide were added and dissolved uniformly.

  Thereafter, the mixture was heated and stirred at 80 ° C. for 30 hours while bubbling carbon dioxide at a rate of 0.5 liter / min. After completion of the reaction, the resulting solution was gradually added to 300 parts of n-hexane with high-speed stirring at 300 rpm, and the resulting powdery product was filtered through a filter, further washed with methanol, and N-methylpyrrolidone. And sodium iodide was removed. The obtained powder was dried in a drier to obtain 118 parts (yield 95%) of a white powder 5-membered cyclic carbonate compound (1-A).

The infrared absorption spectrum of the product obtained above shows that the peak derived from the epoxy group near 910 cm ⁻¹ almost disappears in the product, and the carbonyl group of the cyclic carbonate group that does not exist in the raw material near 1,800 cm ^−1. Absorption was confirmed. Moreover, the number average molecular weight of the product was 414 (polystyrene conversion, Tosoh; GPC-8220). In the obtained 5-membered cyclic carbonate compound (1-A), 19% of carbon dioxide is immobilized.

<Production Example 4> (Production of 5-membered cyclic carbonate compound)
Similar to Production Example 3 using the following formula B [YDF-170 (trade name), manufactured by Tohto Kasei Co., Ltd .; epoxy equivalent 172 g / mol] instead of the divalent epoxy compound (A) used in Production Example 3. To obtain 121 parts (yield 96%) of white powder 5-membered cyclic carbonate compound (1-B). The obtained product was confirmed by an infrared absorption spectrum and GPC as in the case of Production Example 3. In the obtained 5-membered cyclic carbonate compound (1-B), 20.3% of carbon dioxide is immobilized.

<Polymerization Example 1> (Production of self-crosslinking type polyhydroxy polyurethane resin)
A reaction vessel equipped with a stirrer, a thermometer, a gas introduction pipe and a reflux condenser was replaced with nitrogen, and 100 parts of the 5-membered cyclic carbonate compound obtained in Production Example 3 was added thereto so that the solid content became 35%. Propylene glycol monoether acetate (PGM) was added to and uniformly dissolved. Next, 27.1 parts of hexamethylene diamine was added, and the mixture was stirred at a temperature of 90 ° C. for 10 hours and reacted until no hexamethylene diamine could be confirmed to synthesize a polyhydroxy polyurethane resin. Next, 20 parts of the modifier of Production Example 1 (solid content 50%) was added and reacted at 90 ° C. for 3 hours. After confirming that the absorption of the isocyanate group by the infrared absorption spectrum disappeared, a self-crosslinking polyhydroxy polyurethane resin solution was obtained.

<Polymerization Examples 2 to 4> (Production of self-crosslinking type polyhydroxy polyurethane resin)
Hereinafter, in the same manner as in Polymerization Example 1, a 5-membered cyclic carbonate compound, a polyamine compound, and the modifier obtained in Production Example 1 or 2 were combined and reacted in the same manner as in Polymerization Example 1, and listed in Table 1. The self-crosslinking type polyhydroxy polyurethane resin solutions of Polymerization Examples 2 to 4 were obtained.

<Comparative polymerization example 1> (polyester urethane resin)
The polyester urethane resin used in the comparative example was synthesized as follows. A reaction vessel equipped with a stirrer, thermometer, gas introduction pipe and reflux condenser was replaced with nitrogen, and 150 parts of polybutylene adipate having an average molecular weight of about 2,000 and 15 parts of 1,4-butanediol were 250 parts. In dimethylformamide. Then, with good stirring at 60 ° C., 62 parts of water-added MDI (methylenebis (1,4-cyclohexylene) -diisocyanate) dissolved in 171 parts of dimethylformamide was gradually added dropwise. For 6 hours.

<Comparative Polymerization Example 2> (Polycarbonate polyurethane resin)
In the same manner as in Comparative Polymerization Example 1, a polycarbonate polyurethane resin used in the Comparative Example was synthesized. In a reaction vessel similar to Comparative Polymerization Example 1, 150 parts of polycarbonate diol having an average molecular weight of about 2,000 (manufactured by Ube Industries, Ltd.) and 15 parts of 1,4-butanediol were mixed with 200 parts of methyl ethyl ketone and 50 parts. In a mixed organic solvent composed of dimethylformamide. Then, a solution obtained by dissolving 62 parts of water-added MDI in 171 parts of dimethylformamide was gradually added dropwise with stirring at 60 ° C., and reacted at 80 ° C. for 6 hours after the completion of the addition.

  Table 1 shows the compositions and properties of the resins obtained in Polymerization Examples 1 to 4 and Comparative Polymerization Examples 1 and 2.

<Examples 1-4, Comparative Examples 1 and 2>
Using the resin solutions obtained in Polymerization Examples 1 to 4 and Comparative Polymerization Examples 1 and 2, respectively, a coating solution for an adhesive layer was prepared according to the formulation shown in Table 2. Using this, a test sheet for a back sheet for a solar cell module having the structure shown in FIG. 3 was produced. Specifically, as shown in Table 2, in Polymerization Examples 1 to 4, the adhesive coating solution prepared above was used, and in Comparative Polymerization Examples 1 and 2, the resin solution prepared above was used as a crosslinking agent. A further addition of isocyanate was used. The obtained test sheets were evaluated by the following methods.

[Manufacture of test sheet for back sheet for solar cell module]
An aluminum vapor deposition layer 9 having a thickness of 50 nm was laminated on one surface of a PET resin film (base material) 6 having a thickness of 100 μm by a vacuum vapor deposition method to produce a barrier film sheet (vapor deposition substrate) 8. Then, using the two produced barrier film sheets 8, as shown in FIG. 3, the aluminum vapor deposition layer 9 of one sheet and the back surface of the other PET resin film (base material) 6 overlap each other (aluminum vapor deposition layer). Are laminated to each other using the coating solution for adhesive layer prepared in Polymerization Examples 1 to 4 and Comparative Polymerization Examples 1 and 2, to obtain a solar cell module backsheet test sheet. Specifically, each adhesive layer coating solution is applied to one of the two barrier film sheets 8 so that the thickness after drying is 10 μm, heat-treated at 140 ° C. for 5 minutes, and then dry laminated. Two barrier film sheets 8 were laminated and bonded via the adhesive layer 7.

[Evaluation]
Each test sheet obtained above was used for evaluation according to the following methods and criteria. The results are summarized in Table 3.

(Oxygen gas permeability)
The oxygen gas permeability of each test sheet of Examples and Comparative Examples was measured according to JIS-K-7126 with MOCON (USA) · OX-TRAN. The results are shown in Table 3.

(Water vapor permeability)
The water vapor permeability of each test sheet of Examples and Comparative Examples was measured by MOCON (USA) Permantran-W under the conditions of a temperature of 40 ° C. and a relative humidity of 90% based on the JIS-Z-0208B method. The results are shown in Table 3.

(Lamination strength)
Each test sheet of the example and the comparative example was cut into A4 size, and the peel strength at 180 ° was measured for the test piece after being left in a constant temperature bath at 85 ° C. and 85% RH for 1,000 hours. The results are shown in Table 3.

(Environmental compatibility)
It evaluated by (circle) * by the presence or absence of the fixation of the carbon dioxide in resin used for the adhesive bond layer of each test sheet of an Example and a comparative example. The results are shown in Table 3.

  As is apparent from the results in Table 3, durability, weather resistance, particularly gas barrier properties and moisture barriers can be obtained by using an adhesive containing a self-crosslinking polyhydroxypolyurethane resin for the adhesive layer of the solar cell module backsheet. A solar cell module back sheet having excellent properties can be obtained. Since the hydroxyl group of the self-crosslinking polyhydroxypolyurethane resin interacts strongly with the base material sheet at the interface, excellent adhesion to the base material and flexibility are imparted. Further, the masked isocyanate group present in the structure of the resin is heated to dissociate the masking agent to form an isocyanate group, which crosslinks with the hydroxyl group in the structure. It becomes a back sheet with excellent durability. Furthermore, the self-crosslinking polyhydroxypolyurethane resin used in the present invention is a useful material that contributes to solving problems such as global warming and resource depletion by incorporating and fixing carbon dioxide in the resin. The solar cell module backsheet obtained is also a product for environmental conservation that cannot be achieved with conventional products.

1: Glass plate 2: Filler (EVA)
3: Solar cell element (cell)
4: Cover material 5: Back sheet 6: Base film 7: Adhesive layer 8: Gas barrier film 9: Deposition layer 10: Base film (EVA)

Claims (4)

In the back sheet for a solar cell module, which is a member constituting a solar cell module, in which a plurality of types of films are laminated via an adhesive layer,
At least one of the adhesive layers for laminating a gas barrier film in which a metal foil or a vapor deposition layer is formed on a base film having a thickness of 10 μm to 300 μm is composed of a 5-membered cyclic carbonate compound and an amine compound. derived from the reaction, carbon dioxide a port polyhydroxy polyurethane resins which as part of the raw materials, self-crosslinking of the polyhydroxy polyurethane resins self cross-linking skin layer having a b isocyanate group derived from the modifying agent A back sheet for a solar cell module, which is formed.   2. The gas barrier film is formed by forming a metal vapor deposition layer or an oxide vapor deposition layer in a range of 5 nm to 300 nm on a base film selected from the group consisting of a polyester resin, a fluororesin, and a cyclic polyolefin resin. The back sheet for solar cell modules as described in 2. A method for producing a back sheet for a solar cell module, which is a member constituting a solar cell module, wherein a plurality of types of films are laminated via an adhesive layer,
When laminating a gas barrier film in which a metal foil or a vapor deposition layer is formed on a base film having a thickness of 10 μm to 300 μm, carbon dioxide derived from the reaction between a 5- membered cyclic carbonate compound and an amine compound Self-crosslinking by heat treatment using a self-crosslinking polyhydroxypolyurethane resin adhesive having a masked isocyanate group in its structure, which is obtained by modifying a polyhydroxypolyurethane resin obtained by reacting as part of the raw material The manufacturing method of the solar cell module backsheet characterized by forming the adhesive bond layer which consists of a membrane | film | coat . The masked isocyanate group in the structure of the self-crosslinking type polyhydroxypolyurethane resin is a reaction product of an organic polyisocyanate group and a masking agent, and the masked portion is dissociated by heat treatment to remove the isocyanate group. The method for producing a back sheet for a solar cell module according to claim 3 , wherein the method produces and self-crosslinks by reacting with a hydroxyl group in the resin structure.

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