JP5540825B2 - Shielding sheet, and back sheet and solar cell module for solar cell module using the same - Google Patents

Description

  The present invention relates to a light shielding sheet, and more particularly to a light shielding sheet used for constituting one layer of a back sheet for a solar cell module which is a laminate. Moreover, this invention relates to the solar cell module backsheet and solar cell module in which the said light shielding sheet was used.

  In recent years, solar cells as a clean energy source have attracted attention due to the growing awareness of environmental issues. Generally, the solar cell module which comprises a solar cell is a transparent front substrate, a surface side filler sheet, a solar cell, a back surface side filler sheet, and a back sheet (also called a back surface protection sheet) from the light receiving surface side. Each member has a structure in which the members are sequentially stacked, and has a function of generating electric power when sunlight enters the solar battery cell.

  Such a solar cell module is used outdoors. Therefore, each member constituting the solar cell module is required to have a characteristic that can withstand a harsh environment outdoors for a long period of time. Particularly, since the back sheet is used outside the solar cell module among the above members, a high level of weather resistance, light resistance, and the like are required.

  As a member of such a back sheet, for example, in Patent Document 1, a polyvinyl fluoride solution is coated on one side or both sides of a base material in which an adhesive layer is provided on an adhesive surface by coating an adhesive coating agent in advance. A back surface protection sheet for a solar cell module in which a polyvinyl fluoride layer is formed by heating and drying is proposed. Such a back surface protection sheet (back sheet) is considered to have high weather resistance because a polyvinyl fluoride layer having high weather resistance is formed on the surface of the substrate.

  Further, for example, Patent Document 2 proposes a back sheet for a solar cell cover material comprising a three-layer laminate of a hydrolysis-resistant resin film, a metal oxide-coated resin film, and a white resin film. ing. This white resin film is obtained by kneading a white pigment into a resin, and is used to reflect the light incident on the back sheet and return it to the solar cell element to improve the power conversion efficiency. Therefore, this white resin film is disposed at a position closest to the light incident side in the back sheet.

JP 2009-10269 A Japanese Patent Laid-Open No. 2002-100788

  By the way, a back sheet for a solar cell module is not only required to have its own light resistance and weather resistance, but also a factor that deteriorates members constituting the solar cell module such as moisture, oxygen, ultraviolet rays, etc. It also plays a role to prevent intrusion into the inside of the. For this reason, the back sheet for the solar cell module is also required to have characteristics such as gas barrier properties and light shielding properties.

  Among these characteristics, in particular, if attention is focused on the light shielding property, for example, in the back sheet proposed in Patent Document 2, since a white resin film is used, a certain light shielding property can be expected. However, in the back sheet proposed in Patent Document 2, the white resin film having a light-shielding property is disposed in the back sheet closest to the light incident side (side close to the solar battery cell). Of these, the layer located on the outside (the layer on the back side of the solar cell module) cannot be protected by the light shielding property of the white resin film. For this reason, in the layer constituting the outer side of the back sheet, it is possible to use a material that is low in cost and excellent in workability but inferior in light resistance, such as polyethylene terephthalate (PET), polypropylene (PP), and polyethylene (PE). Can not. From such a viewpoint, it is desirable that the layer for imparting light shielding properties to the backsheet is provided in the outermost layer of the backsheet. In addition, the layer for imparting light-shielding properties to the backsheet is desirably provided by coating from the viewpoint of workability.

  When trying to satisfy these, the layer for imparting light-shielding properties is provided by coating and is exposed to the external environment for a long time on the outer side of the backsheet. Even if it exists, the characteristic which does not produce problems, such as peeling during a use period, is required. However, the present situation is that the back sheet material for solar cell modules in which such a layer is formed by coating does not yet exist.

  The present invention has been made in view of the above situation, and is used for constituting one layer of a back sheet for a solar cell module that is a laminate, and a light-shielding layer that exhibits good adhesion to a substrate. An object of the present invention is to provide a light shielding sheet formed by coating, a back sheet for a solar cell module using such a light shielding sheet, and the like.

  As a result of intensive studies to solve the above problems, the present inventors applied a coating liquid containing a white pigment, a resin compound having a plurality of crosslinkable substituents, and a polyisocyanate compound to the surface of the substrate. When the light shielding layer, which is a film formed from the coating solution, is formed on the surface of the substrate, the white pigment in the coating solution is 70 parts by mass or more with respect to 100 parts by mass of the resin compound and the polyisocyanate compound. As a result, it was found that the adhesion between the coating film as the light shielding layer and the substrate was remarkably improved, and the present invention was completed.

  That is, the present invention is (1) a light shielding sheet that has a light shielding layer on one side of a substrate and is used to constitute one layer of a back sheet for a solar cell module that is a laminate, wherein the light shielding layer comprises: A light-shielding sheet comprising 70 parts by mass or more of a white pigment dispersed with respect to 100 parts by mass of a resin.

  Moreover, this invention is (2) The said resin is the fluororesin which has a some crosslinkable substituent, or the fluororesin which has a some crosslinkable substituent, and the (meth) acryl resin which has a some crosslinkable substituent. The light shielding sheet according to item (1), wherein the mixture is crosslinked with a polyisocyanate compound.

  Moreover, this invention is (3) The light shielding sheet | seat of the (1) term or (2) term whose said white pigment is a rutile type titanium oxide.

  Moreover, this invention is a solar cell module backsheet by which the light shielding layer of the light shielding sheet of any one of (4) (1) term-(3) term is arrange | positioned in the outermost layer.

  Moreover, this invention is a solar cell module in which the back sheet for solar cell modules as described in (5) and (4) term was used.

  According to the present invention, a light shielding sheet that is used to constitute one layer of a back sheet for a solar cell module that is a laminate, and that has a light shielding layer that exhibits good adhesion to a substrate formed by coating, and its A solar cell module backsheet or the like using such a light shielding sheet is provided.

  A specific embodiment of the present invention will be described. The present embodiment has a light shielding layer on one side of a base material, and is used for constituting one layer of a back sheet for a solar cell module that is a laminate, and for a solar cell module in which the light shielding sheet is used. A solar cell module in which the back sheet and the back sheet for the solar cell module are used.

[Shading sheet]
The light shielding sheet which is this embodiment is demonstrated. The light shielding sheet of this embodiment has a light shielding layer on the surface on one side of the substrate. This light shielding layer contains at least a resin and a white pigment, and 70 parts by mass or more of the white pigment is dispersed in 100 parts by mass of the resin in the light shielding layer. For such a light shielding layer, a coating liquid in which 70 parts by mass or more of a white pigment is dispersed with respect to 100 parts by mass of a resin compound having a plurality of crosslinkable substituents and a polyisocyanate compound is applied to the surface of the substrate. It is produced by forming a film from the applied coating solution. The resin constituting this film, that is, the resin contained in the light shielding layer is formed by crosslinking a resin compound having a plurality of crosslinkable substituents contained in the coating liquid with a polyisocyanate compound. That is, the resin contained in the light shielding layer is a reaction product of a resin compound having a plurality of crosslinkable substituents and a polyisocyanate compound. In the following description of the present specification, a resin compound having a plurality of crosslinkable substituents, that is, a resin compound before being cured by crosslinking with a polyisocyanate compound is referred to as “main resin” and is included in the light shielding layer. It is distinguished from the resin to be cured, that is, the resin cured to form the light shielding layer.

  The coating liquid for forming the light shielding layer on the surface of the substrate will be described. The coating liquid contains a main resin having a plurality of crosslinkable substituents, a polyisocyanate compound, a white pigment, and a solvent, and various additives as necessary. The white pigment is dispersed in the coating liquid. Here, the main resin is cross-linked and polymerized by reacting with the polyisocyanate compound. For this reason, this coating liquid is preferably composed of a main component containing a main component resin and a white pigment and a curing agent containing a polyisocyanate compound, and is a two-component type in which these are mixed immediately before use. The polyisocyanate compound is a compound containing a plurality of isocyanate groups in one molecule. Hereinafter, each constituent material will be described.

  The main resin has a plurality of crosslinkable substituents for reacting with the polyisocyanate compound, and is cured by reacting with the polyisocyanate compound to form a firm film. Here, examples of the crosslinkable substituent include a hydroxyl group, an amino group, and a carboxyl group. The main resin is selected from a solvent-soluble resin or a resin dispersible in a solvent.

  The coating liquid contains an organic solvent for dissolving or dispersing the main resin. And after drying a solvent from the apply | coated coating liquid, the main ingredient resin contained in a coating liquid is bridge | crosslinked with a polyisocyanate compound, and the film which is a light shielding layer is formed. The applied coating liquid is heated to 60 to 200 ° C., for example, for 1 to 5 minutes in order to volatilize the solvent. Thereafter, as an aging period for sufficiently carrying out the crosslinking reaction, it is left at, for example, 40 to 50 ° C. for 3 to 4 days. The temperature and time for drying the solvent, and the temperature and time for aging are appropriately adjusted according to the type of the solvent used, the main resin, and the polyisocyanate compound.

  The light shielding layer is located on the outermost surface on the side opposite to the light receiving surface side (that is, the back surface side) in the solar cell module. That is, since the light shielding layer is exposed to a severe natural environment such as ultraviolet rays and wind and rain during a long period of use of the solar cell module, high light resistance and weather resistance are required. From such a viewpoint, the main resin used for forming the light-shielding layer has a fluororesin having a plurality of crosslinkable substituents, or a fluororesin having a plurality of crosslinkable substituents and a plurality of crosslinkable substituents ( A mixture with a (meth) acrylic resin is preferably used. Among them, from the viewpoint of availability and crosslinking reactivity, a fluororesin having a plurality of hydroxyl groups, or a fluororesin having a plurality of hydroxyl groups and a (meth) acrylic resin having a plurality of hydroxyl groups, Are more preferably used.

  First, a fluororesin having a plurality of crosslinkable substituents will be described. The fluororesin having a plurality of crosslinkable substituents is a so-called modified fluororesin, for example, a copolymer of a fluoroolefin and a monomer containing a crosslinkable substituent. As a monomer constituting this copolymer, another monomer having an ethylenically unsaturated bond may be used in combination. Such a fluororesin contains a fluorine atom that imparts light resistance and weather resistance, and imparts light resistance, weather resistance, and the like to the light shielding layer. The fluororesin having a plurality of crosslinkable substituents preferably has a fluorine atom content of 10 to 80% by mass, more preferably 30 to 70% by mass. When the amount of fluorine atoms in the resin is 10% by mass or more, good light resistance, weather resistance and the like can be imparted to the light shielding layer. Moreover, if the amount of fluorine atoms in the resin is 80% by mass or less, functional groups for imparting solubility or reactivity to the resin can be sufficiently introduced.

  Examples of such a fluororesin include a copolymer of tetrafluoroethylene and a hydroxyl group-containing vinyl ether, a copolymer of chlorotrifluoroethylene and a hydroxyl group-containing vinyl ether, and the like. Among these, a copolymer of chlorotrifluoroethylene and a hydroxyl group-containing vinyl ether is preferably used. An example of such a resin is a copolymer of chlorotrifluoroethylene, diethylene glycol monoallyl ether, and vinyl butyrate having a mass average molecular weight of 1000 to 30000 and a hydroxyl value of 5 to 200 mg / g.

  Next, a mixture of a fluororesin having a plurality of crosslinkable substituents and a (meth) acrylic resin having a plurality of crosslinkable substituents will be described. This is a mixture of a fluororesin having a plurality of crosslinkable substituents and a (meth) acrylic resin having a plurality of crosslinkable substituents. Adhesiveness to the substrate by the resin can be imparted to the light shielding layer. As the fluororesin having a plurality of crosslinkable substituents, those described above can be used. As a (meth) acrylic resin having a plurality of crosslinkable substituents, one or two or more (meth) acrylic acid compounds and monomers having a crosslinkable substituent are copolymerized, or one or two or more kinds The thing which copolymerized the monomer which has a (meth) acrylic acid compound and a crosslinkable substituent, and 1 type, or 2 or more types of ethylenic monomers is used. Here, in addition to the above monomer, a monomer having a substituent for imparting light resistance to the (meth) acrylic acid resin may be used as a monomer used to obtain the (meth) acrylic acid resin. . In the present invention, the term “(meth) acryl” is used to mean “acryl and / or methacryl”.

  Such (meth) acrylic resins include hydroxyl such as (meth) acrylic acid-2-hydroxyethyl, (meth) acrylic acid-2-hydroxypropyl, (meth) acrylic acid-2-hydroxy-3-phenoxypropyl, and the like. (Meth) acrylic compound having a group, and (meth) acrylic acid or alkyl group as methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, Examples include those obtained by copolymerizing an alkyl (meth) acrylate monomer having a 2-ethylhexyl group, a cyclohexyl group or the like. Moreover, as a monomer used for copolymerization, (meth) acrylamide, N-alkyl (meth) acrylamide, N, N-dialkyl (meth) acrylamide (the alkyl group includes a methyl group, an ethyl group, n -Propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group and the like), N-alkoxy (meth) acrylamide, N, N-di Alkoxy (meth) acrylamide (alkoxy groups include methoxy group, ethoxy group, butoxy group, isobutoxy group, etc.), amide group-containing monomers such as N-methylol (meth) acrylamide, N-phenyl (meth) acrylamide, Glycidides such as glycidyl (meth) acrylate and allyl glycidyl ether Group-containing monomer, styrene, α-methylstyrene, vinyl methyl ether, vinyl ethyl ether, maleic acid, alkyl maleic acid monoester, fumaric acid, alkyl fumaric acid monoester, itaconic acid, alkyl itaconic acid monoester, (meth) acrylonitrile Various compounds having an ethylenically unsaturated bond such as vinylidene chloride, ethylene, propylene, vinyl chloride, vinyl acetate, and butadiene may be used. Among these, a copolymer of methyl (meth) acrylate and 2-ethylhexyl acrylate and a copolymer of methyl (meth) acrylate, 2-ethylhexyl acrylate and hydroxyethyl acrylate are preferably used. Moreover, 1000-300,000 is mentioned as a preferable mass mean molecular weight of such resin.

  A fluororesin having a plurality of crosslinkable substituents (hereinafter also simply referred to as “fluororesin”) and a (meth) acrylic resin having a plurality of crosslinkable substituents (hereinafter also simply referred to as “(meth) acrylic resin”). The mixing ratio is preferably a ratio in which the (meth) acrylic resin is 20 to 90% by mass with respect to the total mass of the fluororesin and the (meth) acrylic resin, and a ratio in which it is 50 to 80% by mass. More preferably. When the (meth) acrylic resin is 20% by mass or more based on the total mass of the fluororesin and the (meth) acrylic resin, the adhesion between the light shielding layer and the substrate can be improved. In addition, when the (meth) acrylic resin is 90% by mass or less with respect to the total mass of the fluororesin and the (meth) acrylic resin, the light-shielding layer is imparted with characteristics such as good light resistance and weather resistance. Can do.

  The content of the main resin in the coating liquid is preferably 10 to 60% by mass, and more preferably 20 to 30% by mass. When the content of the resin in the coating liquid is 10% by mass or more, the white pigment contained in the coating liquid can be favorably dispersed. Moreover, the applicability | paintability of a coating liquid becomes favorable because content of resin in a coating liquid is 60 mass% or less.

  Next, the polyisocyanate compound will be described. A polyisocyanate compound is a compound having two or more isocyanate groups in one molecule. As described above, the polyisocyanate compound crosslinks the main resin and cures (high molecular weight) to form a resin contained in the light shielding layer. At this time, a polyisocyanate compound becomes a part of resin contained in a light shielding layer with main ingredient resin. Examples of the polyisocyanate compound include aliphatic, alicyclic, aromatic, and aromatic-aliphatic compounds, but the light shielding layer is exposed to the external environment for a long period of time. From the viewpoint of suppressing coloring, an aliphatic or alicyclic polyisocyanate compound is preferably used.

  Specific examples of the polyisocyanate compound include aliphatic isocyanates having 3 to 12 carbon atoms such as hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexane diisocyanate, and lysine diisocyanate; 1,4-cyclohexane diisocyanate, isophorone diisocyanate ( Alicyclic diisocyanates having 5 to 18 carbon atoms such as IPDI); modified products of these diisocyanates (burettes, isocyanurate modified products, etc.). These can be used alone or in combination of two or more.

  The amount of the polyisocyanate compound used is preferably such that the NCO / OH ratio (NCO number of the curing agent / OH ratio of the main resin) is 0.1 to 2.0, and is 0.2 to 1.0. More preferred is the amount. If the NCO / OH ratio is in the above range, it is preferable because good adhesion can be obtained. Moreover, it is preferable that it is 0.5-20 mass parts with respect to 100 mass parts of main ingredient resin, and, as for the usage-amount of a polyisocyanate compound, it is more preferable that it is 3-10 mass parts. When the amount of the polyisocyanate compound used is 0.5 parts by mass or more with respect to 100 parts by mass of the main resin, good curability can be imparted to the coating film formed from the coating liquid. A softness | flexibility can be provided to a coating film by being 20 mass parts or less with respect to a mass part. In addition, when using the solution containing a polyisocyanate compound as a hardening | curing agent and making it a 2 liquid type coating liquid, a well-known organic solvent is suitably selected and used for a hardening | curing agent. Such a solvent will be described later.

  Next, the white pigment will be described. The white pigment is added to impart light shielding properties to the light shielding layer prepared by applying and curing the coating liquid. Further, as will be described later, the white pigment also has an effect that the adhesion between the light shielding layer and the substrate is sufficient.

  Examples of white pigments include titanium oxide, talc, silica, barium sulfate, and calcium hydroxide. Among these, titanium oxide is preferably used as the white pigment. There are two types of titanium oxide, rutile type and anatase type. However, some anatase type titanium oxides exhibit oxidation catalytic action. It is preferable to use it.

  The addition amount of the white pigment in the coating liquid is 70 parts by mass or more with respect to 100 parts by mass of the main resin and the polyisocyanate compound. And the white pigment added to the coating liquid exists in the coating liquid in a dispersed state. Moreover, as already explained, the main resin and the polyisocyanate compound react and cure to become a resin contained in the light shielding layer. For these reasons, the light-shielding layer formed by applying and curing the coating liquid is obtained by dispersing 70 parts by mass or more of a white pigment with respect to 100 parts by mass of the resin.

  As already described, the light-shielding sheet of the present invention contains 70 parts by weight or more of white pigment in 100 parts by weight of the resin in the light-shielding layer (coating) produced by applying the coating liquid to the substrate and curing it. Characterized by points. Although depending on the thickness of the coating film to be formed, if the light shielding property by the white pigment is simply imparted to the formed coating film, about 10 to 40 parts by weight of the white pigment is added to 100 parts by weight of the resin. This is sufficient, and it is not necessary to use the white pigment at a high concentration as described above. On the other hand, as a result of intensive investigations, the present inventors surprisingly formed a white pigment on the substrate by using 70 parts by mass or more of white pigment with respect to 100 parts by mass of the resin contained in the coating. It was found that the adhesion between the coated film and the substrate was improved. Since this invention is completed based on such knowledge, a white pigment is used in a high density | concentration of 70 mass parts or more with respect to 100 mass parts of resin in a light shielding layer. In the light shielding layer, the white pigment is preferably 110 parts by mass or more, and more preferably 130 parts by mass or more with respect to 100 parts by mass of the resin.

  Thus, the reason why the adhesion between the light-shielding layer formed on the surface of the substrate and the substrate is improved by the presence of a large amount of white pigment in the light-shielding layer is not always clear. However, when the pigment is present at a high concentration in the resin, it is considered that the pigment is present between the resin molecule chains and the resin molecule chains are firmly entangled with each other, It is assumed that even if a part of the light shielding layer is peeled off by some external stimulus, it is possible to prevent the entire light shielding layer from being peeled off as a film.

  From this point of view, for example, even if the resin sheet used as the base material of the light shielding sheet is deteriorated by light, moisture, or the like, thereby reducing the adhesion between the base material and the light shielding layer, the light shielding layer is the base material. It is also expected that the portion peeled off from the substrate can be minimized to prevent further light degradation of the substrate from proceeding as much as possible. That is, the aspect of the present invention can minimize damage even if partial destruction of the light shielding layer occurs by using a large amount of white pigment in the light shielding layer as described above. Have.

  The amount of the white pigment to be used is not particularly limited. However, from the viewpoint of favorably dispersing the white pigment in the coating liquid and ensuring good coating properties, the white pigment is used as the main resin and the coating liquid. The amount is preferably less than 300 parts by weight, preferably 250 parts by weight or less, and most preferably 200 parts by weight or less based on 100 parts by weight of the polyisocyanate compound.

  As described above, in the light shielding sheet of the present invention, from the viewpoint of obtaining sufficient adhesion between the light shielding layer (coating film) formed on the surface of the substrate and the substrate, the resin in the light shielding layer 70 parts by mass or more of white pigment is contained with respect to 100 parts by mass. Here, the adhesion between the light shielding layer and the substrate is not only given by the white pigment, but is also greatly influenced by the type of the resin component contained in the light shielding layer. For example, when the resin component contained in the light-shielding layer is obtained by curing a mixture of a fluororesin and a (meth) acrylic resin, the acrylic resin greatly contributes to the adhesion to the base material. The contribution to adhesion to the substrate is increased. On the other hand, in the case where the resin component contained in the light shielding layer is obtained by curing only the fluororesin, the contribution of adhesiveness to the substrate by the resin component is reduced. In addition, "only the fluororesin was cured" means that only the fluororesin was used as the main resin and was crosslinked and cured with a polyisocyanate compound.

  Therefore, when the resin component contained in the light shielding layer is obtained by curing only a fluororesin, it is preferable to use 110 parts by mass or more of a white pigment in 100 parts by mass of the resin in the light shielding layer. From such a viewpoint, when the resin component is obtained by curing only the fluororesin, the white pigment is contained in the coating solution in an amount of 110 parts by mass or more with respect to 100 parts by mass of the main resin and the polyisocyanate compound. It is more preferable that 125 parts by mass or more is included, and 140 parts by mass or more is most preferable.

  Next, the solvent used for the coating liquid will be described. The solvent is added to impart applicability to the substrate to the coating liquid and to disperse the white pigment in the coating liquid. After the coating solution is applied to the substrate, the solvent contained in the applied coating solution is volatilized, and a light-shielding layer is formed on the surface of the substrate by the subsequent curing reaction. Therefore, the ratio between the resin component and the white pigment in the light shielding layer is the same as the ratio between the resin component and the white pigment in the coating liquid.

  The solvent is not particularly limited as long as it can dissolve or disperse components such as the main resin and the polyisocyanate compound and does not react with the polyisocyanate compound contained in the coating liquid. Examples of such solvents include water-insoluble solvents such as toluene, xylene, butyl acetate, and ethyl acetate, and water-soluble solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone. A solvent is suitably selected according to the resin component used for a coating liquid, and is used individually or in combination of 2 or more types. Further, a high boiling point solvent such as tripropylene glycol dimethyl ether may be added to adjust the drying rate during coating.

  Next, the additive used for a coating liquid is demonstrated. Additives are added as necessary to impart weather resistance, light resistance, heat resistance, moisture resistance, flame resistance, and the like to the light shielding layer. In addition, the additive is added as necessary to improve the stability, coating property, drying property, blocking property and the like of the coating solution.

  Examples of the additive include a dispersant, an antifoaming agent, a light stabilizer, an ultraviolet absorber, a heat stabilizer, and an antioxidant. Any known one can be used without particular limitation, and is appropriately selected according to the performance required for the coating liquid and the light shielding layer.

  The coating liquid is prepared by mixing a main resin, a white pigment, a solvent, and, if necessary, an additive and dispersing the white pigment. As a method for dispersing the white pigment in the coating liquid, a known method can be used without particular limitation. For example, a method of preparing a mixed solution by mixing a main resin, a white pigment, a solvent, and, if necessary, an additive, and then stirring the mixed solution using a stirrer. Of the components contained in the coating liquid, for the polyisocyanate compound, as described above, in order to avoid reacting with the main resin component during storage, a solution different from the main agent containing the main resin and white pigment is used. It is preferable to keep it as a curing agent. In this case, the main agent and the curing agent are mixed immediately before use to form a coating liquid.

  What is necessary is just to set the viscosity of a coating liquid suitably according to the coating method of a coating liquid. An example of the viscosity of the coating solution is preferably 10 to 100 cPs, more preferably 50 to 80 cPs. The viscosity of the coating solution may be adjusted by adjusting the amount of solvent added to the coating solution.

  Next, the base material which comprises a light shielding sheet is demonstrated. A base material becomes a light shielding sheet by forming the above-mentioned light shielding layer on the surface.

  As the substrate, a resin sheet obtained by molding a resin into a sheet shape is used. Examples of such resin sheets include polyethylene resins, polypropylene resins, cyclic polyolefin resins, polystyrene resins, acrylonitrile-styrene copolymers, acrylonitrile-butadiene-styrene copolymers, polyvinyl chloride resins, fluorine Resins, poly (meth) acrylic resins, polycarbonate resins, polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate, polyamide resins such as various nylons, polyimide resins, polyamideimide resins, polyaryls Various resin sheets such as phthalate resin, silicone resin, polysulfone resin, polyphenylene sulfide resin, polyethersulfone resin, polyurethane resin, acetal resin, cellulose resin, etc. It is possible to use. Among these resin sheets, polyethylene resin, polypropylene resin, polyethylene terephthalate resin, polycarbonate resin, and polyethylene naphthalate are particularly preferably used. Among them, for example, a biaxially stretched polyethylene terephthalate film or sheet as described in JP 2008-31680 A is particularly preferable. In this specification, the term “resin sheet” is used as the name of a product obtained by processing these resins into a sheet shape, but this term is used as a concept including a resin film.

  As already described, the light shielding layer is provided on the outer surface of the solar cell module among the surfaces of the base material. Therefore, from the viewpoint of cost, it is possible to use a resin sheet having a somewhat low light resistance as the base material. Examples of such a resin sheet include, but are not limited to, polyethylene terephthalate resin, polypropylene resin, polyethylene resin, and the like.

  What is necessary is just to determine the thickness of a base material suitably in consideration of the thickness requested | required of the back sheet | seat for solar cell modules in which a light shielding sheet is used. As an example, the thickness of the substrate may be 10 to 300 μm, but is not particularly limited.

  Next, a method for forming the light shielding layer by applying the coating liquid on the surface of the substrate will be described. The light-shielding layer forms the coating film by applying the coating liquid on the surface of the substrate, evaporates the solvent contained in the coating film, and then crosslinks the main resin and polyisocyanate compound contained in the coating film. It is formed by reacting and curing.

  As a method for applying the coating liquid to the surface of the substrate, a conventionally known method can be used without particular limitation. Examples of such a coating method include a printing method, a coating method using a gravure coater, a roll coating method, a spray coating method, a dip coating method, a solid coating method, and a brush coating method.

  As a method for evaporating the solvent contained in the coating film, a conventionally known method can be used without particular limitation. Examples of such an evaporation method include a heating method, a reduced pressure drying method, a hot air drying method, and a natural drying method, but are not particularly limited. The conditions for evaporating the solvent contained in the coating film may be appropriately set according to the solvent to be used, and examples include heating to 60 to 200 ° C. for 1 to 5 minutes. The coating film obtained by evaporating the solvent is subjected to aging for sufficiently carrying out the crosslinking reaction. The aging conditions may be appropriately set according to the types of the main resin and polyisocyanate compound used. For example, the aging condition may be left at 40 to 50 ° C. for 3 to 4 days.

  When the solvent is removed from the coating film by evaporation, the base resin, white pigment, polyisocyanate compound and additives added to the coating solution remain on the surface of the substrate to form a film. This film is cured to become a light shielding layer. The thickness of the light shielding layer is not particularly limited, and may be determined as appropriate according to the conditions to which the light shielding sheet is applied. As thickness of a light shielding layer, 1-30 micrometers is preferable and 3-15 micrometers is mentioned more preferably. If the thickness of the light shielding layer is 1 μm or more, sufficient light shielding properties can be imparted. If the thickness of the light shielding layer is 30 μm or less, it is possible to impart processability with good drying property and it is possible to suppress the cost.

[Back sheet for solar cell module]
Next, the solar cell module backsheet using the light shielding sheet will be described. The solar cell module backsheet is a laminate, and the light shielding sheet is present in the outermost layer. And in this solar cell module backsheet, the said light shielding sheet has the light shielding layer arrange | positioned in the outermost layer. Thereby, when the solar cell module backsheet is applied to the solar cell module, the light shielding layer of the light shielding sheet becomes the surface on the back surface side of the solar cell module.

  The method for laminating the light shielding sheet on the outermost layer of the solar cell module backsheet is not particularly limited. As an example, a dry laminating process in which, for example, a urethane-based adhesive is applied to the surface of the base material side of the light shielding sheet to form an adhesive surface, and this adhesive surface is bonded to a back sheet for a solar cell module.

[Solar cell module]
Next, a solar cell module in which the solar cell module backsheet is used will be described.

  The solar cell module is configured by laminating a solar cell module back sheet, a first filler, a solar cell element, a second filler, and a transparent front substrate in this order from the back side of the solar cell module. The back sheet for the solar cell module has the surface opposite to the light shielding layer bonded to the first filler. Therefore, the back surface of the solar cell module coincides with the surface of the solar cell module backsheet on the light shielding layer side.

  For example, the solar cell module is formed by sequentially laminating the members forming the respective layers and then integrating them by vacuum suction or the like, and then thermocompression-bonding the respective layers as an integrally formed body by a molding method such as a lamination method. Can be manufactured.

  Further, the solar cell module has a first filler and a second filler on each of the front side and the back side of the solar cell element by a molding method usually used in ordinary thermoplastic resins, for example, T-die extrusion molding. The solar cell element is sanded with the first filler and the second filler, then the transparent front substrate and the back sheet for the solar cell module are sequentially laminated, and then these are integrated by vacuum suction or the like. It may be manufactured by a method of thermocompression bonding.

  As already described, in the light shielding sheet, even if the adhesion between the base material and the light shielding layer of the light shielding sheet is lowered, the portion where the light shielding layer is peeled off from the base material can be minimized. For this reason, even if it is a case where partial destruction of the light shielding layer of the light shielding sheet used for the back sheet for solar cell modules occurs by using the back sheet for solar cell modules in the solar cell module, the influence thereof. It is possible to suppress the entire light shielding layer. Therefore, the power generation performance of the solar cell module can be maintained over a long period of time by using the solar cell module backsheet for the solar cell module. A method of maintaining the power generation performance of such a solar cell module over a long period is also one aspect of the present invention.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

<Preparation of back sheet for solar cell module>
Product name Zeffle GK-570 (hydroxyl value 90-100 mg / g) manufactured by Daikin Industries, Ltd. as a fluororesin having a plurality of crosslinkable substituents, Shin-Nakamura Chemical Co., Ltd. as an acrylic resin having a plurality of crosslinkable substituents Product name: Vanaresin UVA-5080 (OHV20) (mass average molecular weight 50,000, Tg 80 ° C., hydroxyl value 20 mg / g) as a white pigment, titanium oxide (manufactured by Sakai Chemical Industry Co., Ltd., product name R-5N: average As a solvent, a mixed solution of toluene: methyl ethyl ketone = 1: 1 was used as a solvent. The main agent of each coating liquid was prepared with the formulation described in Tables 1-3. The solid content concentration of the main agent was 60% by mass. In the preparation of each main agent, a mixture was prepared by combining the components and solvents described in Tables 1 to 3, and then the mixture was stirred for 60 minutes using a paint shaker. Next, a 1: 1 solution of toluene: methyl ethyl ketone containing a modified isocyanurate of hexamethylene diisocyanate (HDI) (Desmodule N3300 manufactured by Sumiyo Bayer Urethane Co., Ltd.) at a concentration of 50% by mass is prepared. As a common curing agent. These main agent and curing agent are mixed so that the blending amount of the polyisocyanate compound becomes the amount described in Tables 1 to 3 immediately before use (coating) to become a coating liquid. Thereafter, a polyethylene terephthalate (PET) sheet is used as a base material, and the coating liquid prepared as described above is applied to the surface of the base material with a bar coater. After drying for 4 minutes, the film was aged at 40 ° C. for 3 days to form a light shielding layer (thickness 5 μm), and the light shielding sheets of Examples 1 to 18, Comparative Examples 1 and 2, and Reference Example 1 were produced. In addition, about the light shielding sheet of the reference example 1, since the coating liquid was not able to be prepared, the following evaluation was not performed.

  About each of the produced light shielding sheet | seat of Examples 1-18 and Comparative Examples 1-2, it is a bar coater (# 10) about the surface of the PET base material on the side where the light shielding layer is not provided. And dried at 80 ° C. for 1 minute. Then, the surface which applied the adhesive agent of the light shielding sheet was bonded together with the polyethylene sheet, and the solar cell module backsheet was produced.

<Evaluation of adhesion>
About each of the back sheet | seat for solar cell modules in which the light shielding sheet of Examples 1-18 and Comparative Examples 1-2 was used, the coating | coated of a light shielding sheet and a base material are 100 squares with a cutter. 10 mm × 10 mm) was scratched, and a 12 mm wide cellophane tape (CT405AP-12 manufactured by Nichiban Co., Ltd.) was rubbed and pulled away at an angle of 60 degrees, and then the area of the remaining part was evaluated.
[Evaluation criteria]
◎: Not peeled ○: Remaining portion is 90% or more and less than 100% △: Remaining portion is 80% or more and less than 90% ×: Remaining portion is less than 80%

<Evaluation of yellowing (YI)>
In order to evaluate the degree of yellowing of the light shielding layer, the yellow index (YI) was measured for each of the back sheets for solar cell modules after the wet heat or light resistance test. YI measurement uses SM color computer (model SM-7 Ver3.11L, measurement conditions: C light source, viewing angle 2 degrees, reflection, d-8 (excluding specular reflection light)) manufactured by Suga Test Instruments Co., Ltd. I went. This YI was measured before and after the following wet heat or light resistance test, and the amount of change ΔYI = YI (after test) −YI (before test) was calculated.
[Evaluation criteria]
◎: ΔYI is less than 0.5 ○: ΔYI is 0.5 or more and less than 1.0 Δ: ΔYI is 1.0 or more and less than 2.0 ×: ΔYI is 2.0 or more

<Moist heat test>
About each of the back sheet | seat for solar cell modules in which the light shielding sheet | seat of Examples 1-18 and Comparative Examples 1-2 was used, 120 degreeC, 85% RH in HASTEST (MODEL PC-R8D) by Hirayama Manufacturing Co., Ltd. It was stored for 96 hours in an environment of 1.65 atm. Thereafter, adhesion and YI were evaluated.

<Light resistance test>
About each of the back sheet | seat for solar cell modules in which the light shielding sheet of Examples 1-18 and Comparative Examples 1-2 was used, Iwasaki Electric Co., Ltd. EYESUPERUVTESTER (MODEL SUV-W151) WHEREIN: Illuminance 100mW, temperature 63 degree | times, A light irradiation test for 168 hours was performed in an environment with a humidity of 50% RH. Thereafter, adhesion and YI were evaluated.

  As shown in Tables 1 to 3, it is understood that good initial adhesion can be obtained when the content of titanium oxide is 70 parts by mass or more with respect to 100 parts by mass of the resin.

Claims (3)

A back sheet for a solar cell module having a light shielding layer of 5 μm or more and 15 μm or less on one side of the substrate, and being arranged in the outermost layer so that the light shielding layer is a surface on the back side of the solar cell module,
The light shielding layer state, and are not a white pigment with respect to 100 parts by weight of the resin was dispersed 130 parts by mass or more 250 parts by weight,
The resin is a mixture of a fluororesin having a plurality of crosslinkable substituents and a (meth) acrylic resin having a plurality of crosslinkable substituents, crosslinked with a polyisocyanate compound,
The back sheet for a solar cell module, wherein the (meth) acrylic resin is 50 to 80% by mass with respect to the total mass of the fluororesin and the (meth) acrylic resin. The back sheet for a solar cell module of the white pigment according to claim 1, which is a rutile type titanium oxide. A solar cell module in which the back sheet for a solar cell module according to claim 1 or 2 is used.