KR101607014B1 - Multi-layered film - Google Patents

Abstract

Embodiments of the present application include a substrate layer; And a resin layer formed on one side or both sides of the substrate layer and including a polymer having polymerized units of a fluorine-based polymer and an ultraviolet absorber-containing reactive monomer. The present application can provide a multilayered film excellent in weatherability and durability reliability because of excellent compatibility with components contained in the resin layer, excellent in ultraviolet ray shielding effect, excellent in adhesion even under heat / humidity conditions, have.

Description

Multi-layered film < RTI ID = 0.0 >

Embodiments of the present application include multilayer films, backsheets for photovoltaic modules, methods of making the same, and photovoltaic modules comprising the same.

In recent years, interest in renewable energy and clean energy has been rising due to global environmental problems and depletion of fossil fuels. Among them, photovoltaic energy attracts attention as a representative pollution-free energy source that can solve environmental pollution problem and fossil fuel depletion problem. .

The photovoltaic cells to which the photovoltaic power principle is applied is a device that converts sunlight into electric energy. Since the photovoltaic cells must be exposed to the external environment for a long time in order to easily absorb the sunlight, various packaging for protecting the cells are performed, , And these units are referred to as photovoltaic modules.

The backsheet included in the photovoltaic module may be formed by laminating a film made of a fluoropolymer such as polyvinyl fluoride (PVF) having durability and weather resistance on one side of a substrate layer. Conventionally, a fluorine-based resin is film-processed and adhered to a substrate layer, or a fluorine-based resin is dissolved by using an organic solvent such as dimethylformamide (DMF), dimethylacetamide (DMAC), or N-methylpyrrolidone Then, this was coated on one side of the substrate layer, and the organic solvent was volatilized to form a fluorine resin layer.

However, since the fluorine-based film has poor adhesion to a PET (polyethylene terephthalate) film typically used as a base layer of a back sheet, the fluorine-based film is extruded or cast and then laminated on a substrate layer using a urethane-based adhesive or the like . However, this method requires an expensive film manufacturing facility, requires use of an adhesive, and further requires an adhesive coating process and a lamination process. In addition, there is a problem that a film which is thicker than the film thickness required for handling the film in the production process of the film should be used, the use of various additives, fillers, etc. is limited and a high process temperature is required.

On the other hand, an ultraviolet absorber may be added to the back sheet for a photovoltaic module in order to prevent deterioration of physical properties due to ultraviolet rays. However, in such a case, the compatibility of the ultraviolet absorber added to the film with the fluorinated polymer may be poor, so that the ultraviolet absorber can not be sufficiently added and the content thereof must be limited. In addition, the efficiency of the ultraviolet ray shielding effect by heat dissolving out of the ultraviolet absorber under high temperature and high humidity conditions such as PCT (Pressur Cooker Test) was not excellent.

Embodiments of the present application include a multilayer film, a method of making the same, a back sheet for a photovoltaic module, and a photovoltaic module comprising the same.

One embodiment of the present application includes a substrate layer; And a resin layer formed on the base layer, wherein the resin layer comprises a polymer having polymerized units of a reactive monomer containing an ultraviolet absorber. The resin layer may include a fluorine-based polymer as an additional component.

Another embodiment of the present application provides a method for producing a multilayer film comprising a step of forming a resin layer comprising a polymer having polymerized units of a reactive monomer containing an ultraviolet absorber on one side or both sides of a substrate layer in a process of producing a substrate layer do.

Another embodiment of the present application provides a backsheet for a photovoltaic module comprising a multilayer film according to embodiments of the present application.

Another embodiment of the present application provides a photovoltaic module comprising a back sheet for a photovoltaic module in accordance with embodiments of the present application.

The multilayer film according to embodiments of the present application includes a resin layer containing a polymer having polymerized units of a reactive monomer containing an ultraviolet absorber on the base layer. In particular, it is excellent in ultraviolet ray shielding effect, and is excellent in compatibility with a fluorine-based polymer, exhibits excellent adhesion even under heat / humidity conditions, and does not dissolve the ultraviolet absorber, resulting in excellent weather resistance and durability.

Fig. 1 shows the transmission spectra according to Example 3, Comparative Example 1 and Comparative Example 2 of the present application.
2 shows the transmission spectrum at the initial stage of PCT and the elapsed time of 75 hours in Example 4 of the present application.
3 shows the transmission spectrum at the initial stage of PCT and the elapsed time of 75 hours of Comparative Example 3 of the present application.
4 is a cross-sectional view of a multilayer film according to one embodiment of the present application.
5 is a cross-sectional view of a photovoltaic module according to one embodiment of the present application.
6 is a cross-sectional view of a photovoltaic module according to another embodiment of the present application.

Hereinafter, embodiments of the present application will be described in more detail with reference to the accompanying drawings. In the description of the present application, a detailed description of general functions and configurations well known in the art is omitted. It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. And the scope of the present application is not limited by the thickness, size, ratio or the like shown in the drawings.

One embodiment of the present application includes a substrate layer; And a resin layer formed on one side or both sides of the base layer and including a polymer having polymerized units of reactive ultraviolet absorber-containing monomer.

The term "ultraviolet absorber-containing reactive monomer" as used herein may mean a monomer which simultaneously contains at least one ultraviolet absorptive moiety and a polymerization reactive moiety. Accordingly, the monomer may be polymerized to form a polymer including an ultraviolet absorbing moiety.

4 is a cross-sectional view of a multilayer film according to one embodiment of the present application. As shown in Fig. 4, the multilayer film 10 comprises a base layer 12; And a resin layer (11) formed on the base layer (12), wherein the resin layer (11) comprises a polymer having polymerized units of a reactive monomer containing an ultraviolet absorber. The resin layer 11 may further include a fluorine-based polymer.

The specific type of the substrate layer included in the multilayer film is not particularly limited, and various materials known in this field can be used, and can be appropriately selected depending on the required function or use.

In one example of the present application, the base layer may be various metal films or polymer films. Examples of the metal film include those composed of common metal components depending on the application. Examples of the polymer film include a single sheet such as an acrylic film, a polyolefin film, a polyamide film, a polyurethane film, or a polyester film , And a laminated sheet in which two or more of the above-mentioned films are laminated. The laminated sheet can be produced, for example, by separately preparing two or more films and then laminating them, or by coextrusion.

In one example, a polyester film may be used as the substrate layer, but is not limited thereto. Specifically, the polyester film may be at least one selected from the group consisting of a polyethylene terephthalate (PET) film, a polyethylene naphthalate (PEN) film, and a polybutylene terephthalate (PBT) film But is not limited thereto.

As the polyester film, one having excellent water-decomposing properties may be used, and a film having excellent water-decomposing properties may be prepared and used, or a commercially available product may be used. For example, the polyester film having excellent hydrolysis resistance may be one having a small content of oligomers generated during the condensation polymerization. Further, it is also possible to further improve the moisture-decomposing property by reducing the water content and the shrinkage ratio of the polyester by additionally applying heat treatment to the polyester film to improve the water-decomposing property known in the art.

The base layer may comprise, for example, at least one selected from ultraviolet absorbers or ultraviolet stabilizers. The ultraviolet ray absorbing agent can be used without particular limitation as long as it does not inhibit the physical properties of the base layer. Examples of the ultraviolet absorber include 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (3 ', 5'-di- 2- (5'-tert-butyl-2'-hydroxyphenyl) benzotriazole, 2- (2-hydroxy-5- (1,1,3,3, tetramethylbutyl) Butyl-2'-hydroxyphenyl) -5-benzotriazole, 2- (3'-tert-butyl-2'- 2'-hydroxyphenyl) benzotriazole, 2- (2'-hydroxy-4'-methylphenyl) -5-benzotriazole, 2- (2'-hydroxyphenyl) -5-benzotriazole such as 2- (3 ', 5'-di-tert- butyl-2'-hydroxyphenyl) benzotriazole, Benzotriazole compounds such as benzotriazole based compounds; 4-methoxy, 4-octyloxy, 4-decyloxy, 4-dodecyloxy, 4-benzyloxy, 4,2 ', 4'-trihydroxy or 2'- Benzophenone compounds such as 2-hydroxybenzophenone-based compounds having a 4,4'-dimethoxy functional group; 4-tert-butylphenyl salicylate, phenyl salicylate, octylphenyl salicylate, dibenzoyl resorcinol, bis (4-tert-butyl-benzoyl) resorcinol, benzoyl resorcinol, 2,4 Di-tert-butylphenyl-3,5'-di-tert-butyl-4-hydroxybenzoate, hexadecyl 3,5-di- tert -butyl-4-4hydroxybenzoate, octadecyl 3, Di-tert-butyl-4-hydroxybenzoate or 2-methyl-4,6-di-tert-butylphenyl 3,5-di- A benzoic acid ester compound such as a compound having an ester structure; Or a triazine compound, but the present invention is not limited thereto. The specific kind of the ultraviolet stabilizer is not particularly limited, and those conventionally used in this field can be used without limitation.

The substrate layer may include at least one functional group selected from the group consisting of a carboxyl group, an aromatic thiol group, and a phenolic hydroxyl group on the surface on which the resin layer is formed. The functional group formed on the surface of the base layer can further improve the adhesion between the base layer and the resin layer containing the polymer having the polymerization unit of the ultraviolet absorber-containing reactive monomer.

The functional group formed on the surface of the base layer may be a spark discharge treatment of high frequency such as corona treatment or plasma treatment on one surface or both surfaces of the base layer; Heat treatment; Flame treatment; Anchor treatment; Coupling agent treatment; By performing the surface treatment such as primer treatment or a gas phase Lewis acid (ex. BF _3), chemical activation treatment with sulfuric acid or sodium hydroxide it can be introduced into the high temperature. The surface treatment method may be performed by any known means generally used in this field in addition to the above-described methods.

In embodiments according to the present application, an inorganic oxide deposited layer may be further formed on one side or both sides of the substrate layer to further improve moisture barrier properties and the like. The kind of the inorganic oxide is not particularly limited, and any inorganic oxide may be employed as long as it has moisture barrier properties. For example, silicon oxide or aluminum oxide can be used. The method of forming the inorganic oxide vapor deposition layer on one side or both sides of the substrate layer is not particularly limited and may be a vapor deposition method generally used in this field. In one example, when the inorganic oxide deposit layer is formed on one surface or both surfaces of the substrate layer, the above-described surface treatment may be performed on the deposition layer after the inorganic oxide deposit layer is formed on the surface of the substrate layer.

The thickness of the base layer is not particularly limited and can be, for example, in the range of about 10 탆 to 500 탆 or about 100 탆 to 300 탆. By adjusting the thickness of the base layer to the above range, it is possible to improve the electrical insulating property, moisture barrier property, mechanical property, handling property, and the like of the multilayer film. However, the thickness of the base layer according to the embodiments of the present application is not limited to the above-mentioned range, and it can be suitably adjusted as required.

In another example of the present application, the fluorinated polymer is a polymer of a single fluorinated monomer; And copolymers of a mixture containing at least two kinds of fluorine-based monomers.

The fluorine-based monomer may be, for example, vinylidene fluoride (VDF), vinyl fluoride (VF), tetrafluoroethylene (TFE), hexafluoropropylene (HFP) Perfluoroethyl vinyl ether (PEVE), perfluoroethyl vinyl ether (PMVE), perfluoroethyl vinyl ether (PEVE), perfluoroethyl vinyl ether perfluoro (ethylvinylether), perfluoropropyl vinyl ether (PPVE), perfluorohexyl vinyl ether (PHVE), perfluoro-2,2-dimethyl-1,3-dioxole Methylene-4-methyl-1,3-dioxolane (PMD).

The copolymer of the mixture containing the above two or more fluorine-containing monomers is, for example, a copolymer of tetrafluoroethylene (TFE), hexafluoropropylene (HFP), chlorotrifluoroethylene (CTFE) (Perfluoro (methylvinylether)), perfluoroethyl vinyl ether (PEVE, perfluoro (ethylvinylether)), perfluoroethyl vinyl ether (PMVE), perfluoro Vinyl ether (PPVE), perfluorohexyl vinyl ether (PHVE), perfluoro-2,2-dimethyl-1,3-dioxole (PDD) and perfluoro-2- One or more fluorine-based monomers selected from the group consisting of 3-dioxolane (PMD); And polyvinylidene fluoride (PVDF) or polyvinyl fluoride (PVF) in polymerized form.

The content of polyvinylidene fluoride (PVDF) or polyvinyl fluoride (PVF) contained in the copolymer is not particularly limited and may be, for example, from 50% by weight to 99.5% by weight based on the total weight of the fluorine- 70 wt.% To 95 wt.%, 80 wt.% To 90 wt.% Or 50 wt.% To 80 wt.%, 50 wt.% To 70 wt.%. When the content of the comonomer is controlled within the above range, more excellent durability and weather resistance can be ensured.

The weight average molecular weight of the fluorine-based polymer may be from 50,000 to 1,000,000, from 100,000 to 700,000, or from 300,000 to 50,000, but is not limited thereto. The weight average molecular weight is a conversion value of standard polystyrene measured by GPC (Gel Permeation Chromatograph). When the weight average molecular weight of the fluorine-containing polymer is controlled within the above range, excellent water dispersibility and other physical properties can be secured.

The fluorine-based polymer may include i) a first fluorinated polymer having a melting point of 155 ° C or less and a softening point of 100 ° C or less. Such a first fluorinated polymer is excellent in compatibility and compatibility with a reactive polymer containing an ultraviolet absorber, and thus the adhesion can be further improved.

In addition to the first fluorinated polymer, the fluorinated polymer may further include a second fluorinated polymer having a melting point of 155 ° C or higher and a softening point of 100 ° C or higher, but the second fluorinated polymer may optionally be used as needed.

The first fluoropolymer and the second fluoropolymer correspond to the fluoropolymer described above and are classified according to the melting point and the softening point which are inherent characteristics of the polymer depending on the polymerization type and the blending ratio of the monomer forming the fluoropolymer . The first fluoropolymer having a melting point of 155 ° C or lower or a softening point of 100 ° C or lower may account for 20% by weight or more based on the weight of the total fluoropolymer contained in the resin layer, and if it is 50% or more, have.

The method for producing the fluorine-based polymer is not particularly limited, and means commonly used in the art may be employed without limitation. For example, the fluorine-based polymer may be produced by an emulsion (emulsion polymerization) method. When the fluoropolymer is produced by the emulsion polymerization method, the fluoropolymer can be produced in a uniform size while controlling the average particle diameter of the fluoropolymer to 10 탆 or less.

The polymer having a polymerization unit of the ultraviolet absorber-containing reactive monomer contained in the resin layer may be, for example, a homopolymer of a reactive monomer containing an ultraviolet absorber; And a copolymer of a mixture containing the ultraviolet absorber-containing reactive monomer and at least one comonomer.

In one example, the polymer having a polymerization unit of the ultraviolet absorber-containing reactive monomer may be formed by, for example, polymerizing a compound represented by the following formula (1).

[Chemical Formula 1]

In the formula (1), U is a residue of a benzotriazole-based, benzophenone-based, triazine-based, arylester-based or oxanilide-based ultraviolet absorbing compound, A and B are each independently an alkylene group, an alkenylene group, An arylene group or a single bond, and R is hydrogen or an alkyl group.

The alkylene group in formula (1) may be a straight, branched or cyclic alkylene group having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms or 1 to 4 carbon atoms, And may be substituted by one or more substituents.

The alkyl group in formula (1) may be a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms or 1 to 4 carbon atoms, . ≪ / RTI >

In the general formula (1), the alkenylene group and the alkynylene group are straight chain, branched or cyclic alkenylene groups having 2 to 20 carbon atoms, 2 to 16 carbon atoms, 2 to 12 carbon atoms, 2 to 8 carbon atoms or 2 to 4 carbon atoms, alkynylene groups And these alkenylene groups, alkynylene groups may optionally be substituted by one or more substituents.

In formula (1), the arylene group may be an arylene group having 6 to 30 carbon atoms, 6 to 24 carbon atoms, 6 to 18 carbon atoms, or 6 to 12 carbon atoms, which may be substituted with a substituent such as a hydroxyl group.

The term " single bond " in formula (1) may mean the case where no additional atom exists in the corresponding site.

As the monomer, for example, a monomer of the following formula (2) may be used.

(2)

In formula (2), U is a residue of a benzotriazole-based, benzophenone-based, triazine-based, aryl ester-based or oxanilide-based ultraviolet absorbing compound, R ₁ and R ₂ are each independently a hydrogen atom, an alkyl group, a halogen or an aryl group And R ₃ is an acyclic hydrocarbon group having an unsaturated bond.

In the formulas (1) and (2), the residue of the ultraviolet absorptive compound may mean a monovalent residue derived from an ultraviolet absorptive compound such as benzotriazole, benzophenone, triazine, aryl ester or oxanilide compound.

In the formula (2), the aryl group may be, for example, a substituted or unsubstituted phenyl group other than the acrylooxy group and the UVA group shown in the formula (2). Specifically, the substituted phenyl group may be, for example, a phenyl group substituted by at least one member selected from the group consisting of an amino group, a methyl group, a chloromethyl group and a chloro group, but is not limited thereto.

Examples of the acyclic hydrocarbon group having an unsaturated bond include, but are not limited to, an alkenyl group or an alkynyl group capable of radical polymerization.

In one example, UVA is a benzotriazole-based, benzophenone- or benzoate-based ultraviolet absorber, and R ₁ and R ₂ are each independently a hydrogen atom, an alkyl group, a halogen or a phenyl group And R ₃ may be an alkenyl group having 2 to 8 carbon atoms. Specifically, for example, UVA is a benzotriazole ultraviolet absorber, R ₁ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R ₂ is a phenyl group, and R ₃ is an alkenyl group having 2 to 8 carbon atoms, But is not limited to. More specifically, the compound represented by Formula 2 may be selected from the group consisting of 2- [2'-hydroxy-3'-acryloyloxymethyl) phenyl] benzotriazole, 2- [2'- Phenyl] benzotriazole, 2- [2'-hydroxy-3'-acryloyloxymethyl-5'-tert- 3'-acryloyloxymethyl-5'-sec-butyl) phenyl] benzo [b] thiophene Triazole, 2- [2'-hydroxy-3'-sec-butyl-5'-acryloyloxymethyl) phenyl] benzotriazole, 2- [2'-hydroxy-3'-acryloyloxy Ethyl] phenyl] benzotriazole, 2- [2'-hydroxy-5'-acryloyloxyethyl) phenyl] benzotriazole, 2- [2'- Phenyl] benzotriazole, 2- [2'-hydroxy-3'-tert-butyl-5'-acryloyloxyethyl) phenyl] benzotriazole, 2- [ Hydroxy-3'-acryloyloxyethyl-5'-sec-butyl) phenol ] Benzotriazole, 2- [2'-hydroxy -3'-sec- butyl-5'-acryloyloxyethyl) phenyl] but can be one or more selected from the group consisting of benzo triazolo, but is not limited thereto.

The copolymer of the ultraviolet absorber-containing reactive monomer and the mixture containing at least one comonomer may contain at least 1 wt%, at least 5 wt% to 95 wt%, and at most 35 wt% of polymerized units derived from the compound represented by Formula 1 or 2, To 75 wt%, 55 wt% to 65 wt%, 75 wt% to 95 wt%, or 80 wt% to 90 wt%. When the content of the polymerization unit is controlled within the above range, the adhesive strength between the resin layer containing the copolymer of the reactive ultraviolet absorber-containing monomer and the mixture containing at least one comonomer and the base layer can be further improved.

The type of the comonomer forming the copolymer is not particularly limited and is not limited as long as it can be copolymerized with the compound represented by the above formula (1) or (2) without reacting with the reactive ultraviolet absorber.

The comonomer may be, for example, an alkyl (meth) acrylate, an amide group containing monomer, an unsaturated nitrile monomer, a vinyl ester monomer, a vinyl ether monomer, a halogen-containing alpha, beta -unsaturated monomer and an alpha, But are not limited to, at least one selected from the group consisting of monomers.

The alkyl (meth) acrylate may have an alkyl group having 1 to 14 carbon atoms, for example, methyl (meth) acrylate, ethyl (meth) acrylate and the like in order to give a balance of compatibility with the fluorine- (Meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, isobutyl (meth) acrylate, (Meth) acrylate, n-octyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (Meth) acrylate, isodecyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate and n-tetradecyl .

Examples of the amide group-containing monomer include (meth) acrylamide, diethylacrylamide, N-vinylpyrrolidone, N, N-dimethyl (meth) acrylamide, N, Amide, N, N'-methylenebisacrylamide, N, N-dimethylaminopropylacrylamide, N, N-dimethylaminopropylmethacrylamide, diacetone (meth) acrylamide or methylol Examples of the unsaturated nitrile monomer include (meth) acrylonitrile, ethacrylonitrile, phenyl acrylonitrile, and? -Chloroacrylonitrile. Examples of the vinyl ester monomer include vinyl acetate or vinyl propionate Examples of the vinyl ether monomer include methyl vinyl ether and ethyl vinyl ether. Examples of the halogen-containing alpha, beta -unsaturated monomers include vinyl chloride, vinyl chloride And vinyl fluoride. Examples of the?,? - unsaturated aromatic monomers include, but are not limited to, styrene and? -Methylstyrene.

The copolymer may include an acrylic monomer containing a radical scavenging compound in a polymerized form. When the acrylic monomer containing the radical scavenging compound is incorporated in the polymerized form in the copolymer as described above, it is possible to prevent deformation or discoloration of the resin layer due to ultraviolet rays while maintaining compatibility with the fluorinated polymer, and improve the weatherability . The radical scavenging compound may be at least one selected from, for example, a peroxide decomposer, a radical scavenger and a hindered amine compound.

The weight average molecular weight of the polymer having the polymerization unit of the ultraviolet absorber-containing reactive monomer is not particularly limited, but may be, for example, 5,000 to 50, and may be 10,000 to 250,000, or 20,000 to 15,000. By controlling the weight average molecular weight of the polymer having the polymerization unit of the ultraviolet absorber-containing reactive monomer within the above-mentioned range, it is possible to secure an appropriate compatibility and / or fluidity with the fluoropolymer contained in the resin layer have.

The polymerization method of the polymer having the polymerization unit of the ultraviolet absorber-containing reactive monomer is not particularly limited and may be polymerized by a known method such as solution polymerization, emulsion polymerization, bulk polymerization or suspension polymerization. The resulting copolymer may be a random copolymer, a block copolymer, an alternating copolymer or a graft copolymer. A variety of methods are known in the art for producing polymers having polymerized units of UV absorber-containing reactive monomers, and all of these methods can be applied.

The resin layer may further comprise a pigment or filler together with a polymer having polymerized units of a fluorine-based polymer and a reactive monomer containing an ultraviolet absorber for the purpose of controlling color or opacity or for other purposes. Examples of pigments or fillers which may be used at this time, the metal oxides such as titanium dioxide (TiO _2), silica or alumina; Black pigments such as calcium carbonate, barium sulfate or carbon black; Or a pigment component showing a different color, but the present invention is not limited thereto. Such pigments or fillers can control the hue and opacity of the resin layer and provide appropriate reflection characteristics to increase the efficiency of the module.

The multilayer film according to the embodiments of the present application may further include various functional layers known in the art as needed. Examples of the functional layer include an adhesive layer or an insulating layer. For example, a resin layer containing a polymer having a polymerized unit of the fluorine-based polymer and the ultraviolet absorber-containing reactive monomer may be formed on one surface of the substrate layer, and an adhesive layer or an insulating layer may be sequentially formed on the other surface . The adhesive layer or insulating layer may be formed in various ways known in the art. The insulating layer can be, for example, a layer comprising ethylene vinyl acetate (EVA) or low density linear polyethylene (LDPE). The layer containing the ethylene vinyl acetate (EVA) or the low density linear polyethylene (LDPE) functions not only as an insulating layer but also with an encapsulant of a photovoltaic module to be described later, It is possible to simultaneously perform the function of maintaining excellent re-workability.

Another embodiment according to the present application can provide a method for producing a multilayered film comprising forming a resin layer containing a polymer having polymerized units of a reactive monomer containing an ultraviolet absorber on a substrate layer.

The method of forming the resin layer on the substrate layer is not particularly limited as long as it is carried out by a coating method. For example, the fluorinated polymer and the polymerization unit of the ultraviolet absorber-containing reactive monomer May be coated on the substrate layer to coat the resin layer.

The coating method may be a method in which one or more surface treatments selected from the group consisting of plasma treatment, corona treatment, primer treatment, anchor treatment, coupling agent treatment, vapor deposition treatment and heat treatment are performed on one surface or both surfaces of the substrate layer before forming the resin layer May be further included.

The step of forming the resin layer may be performed by applying a resin layer coating liquid containing a fluorine-based polymer and a solvent having a boiling point of 200 DEG C or lower on the substrate layer.

The coating solution can dissolve the components of the polymer having the polymerization unit of the ultraviolet absorber-containing reactive monomer well by evaporating the solvent at a relatively low temperature of 200 ° C or lower, Can be lowered. In one example, the boiling point of the solvent is from 45 to 200, from 60 to 200, from 75 to 200, from 90 to 200, from 100 to 200, from 110 to 200, from 120 to 200, from 130 to 200, from 130 to 190, 130-170 or 140-170.

The solvent having a boiling point of 200 ° C or lower may be, for example, one or more selected from the group consisting of distilled water, acetone, methyl ethyl ketone, dimethyl formamide and dimethylacetamide. The solvent having a low boiling point is easy to evaporate and can be easily dried at a relatively low temperature after being coated on the resin layer.

The coating method of the coating solution is not particularly limited, and any method can be applied as long as it can form a uniform resin layer including well-known printing methods such as offset printing or gravure printing. The coating liquid for forming a resin layer may further include various additives as required.

The resin layer coating solution may further contain various additives such as a pigment or a filler in addition to the fluorine-based polymer and the solvent having a boiling point of 200 캜 or lower.

Further, a step of applying the resin layer coating solution and then drying may be further performed. The conditions at the time of drying are not particularly limited, and can be performed, for example, at a temperature of 50 to 200 DEG C for 30 seconds to 30 minutes or for 1 minute to 10 minutes. By performing the drying process in the temperature range as described above, it is possible to prevent an increase in manufacturing cost and to prevent a deterioration in product quality due to thermal deformation or thermal shock.

Another embodiment of the present application relates to a backsheet for a photovoltaic module comprising a multilayer film according to the above embodiments.

The back sheet for a photovoltaic module includes a resin layer containing a polymer having polymerized units of a fluorine-based polymer and a UV absorber-containing reactive monomer formed on a base layer. The ultraviolet absorber of the resin layer forms a chemical covalent bond with various functional groups on the surface of the base layer, so that it is possible to provide excellent adhesion between the base layer and the resin layer. Further, it is possible to provide a multilayered film excellent in weatherability and durability while maximizing the bonding force between the substrate layer and the resin layer and having excellent reliability and adhesion under heat / humidity conditions.

In addition, the back sheet for a photovoltaic module according to the embodiments of the present application has characteristics such as insulation and moisture blocking as well as durability and weather resistance so as to stably protect the photovoltaic cell even when exposed to an external environment for a long period of time.

Another embodiment of the present application relates to a photovoltaic module comprising a back sheet for a photovoltaic module as described above.

The structure of the photovoltaic module is not particularly limited as long as it includes the back sheet for the photovoltaic module, and various structures generally known in this field can be employed without limitation. For example, the structure of a photovoltaic module includes a back sheet; A photovoltaic cell or photovoltaic array formed on the backsheet; A light-receiving sheet formed on the photovoltaic cell or the photovoltaic array; And an encapsulant layer sealing the photovoltaic cell or the photovoltaic array between the back sheet and the light receiving sheet.

The thickness of the backsheet is not particularly limited and may be, for example, 30 μm to 2,000 μm, 50 μm to 1,000 μm, or 100 μm to 600 μm. By controlling the thickness of the back sheet within the range of 30 占 퐉 to 2,000 占 퐉, properties of the photovoltaic module such as durability and weather resistance can be maintained while making the photovoltaic module thinner.

The specific type of the photovoltaic cell formed on the back sheet is not particularly limited as long as it can generate photovoltaic power, and a photovoltaic device generally used in this field can be used. (Amorphous silicon photovoltaic cells, such as single crystal silicon carbide, gallium arsenide (GaAs), indium-phosphorus (InP), etc.) III-V compound semiconductor photovoltaic cells such as cadmium-tellurium (CdTe) and copper-indium-selenide (CuInSe ₂ ), and the like. In addition, a thin film polycrystalline silicon photovoltaic cell , A thin film purity silicon photovoltaic cell, and a hybrid photocell of thin film crystalline silicon and amorphous silicon.

The photovoltaic cell can form a photovoltaic array (photovoltaic assembly) by wiring connecting the photovoltaic cell and the photovoltaic cell. When sunlight is irradiated on a photovoltaic module, electrons (-) and holes (+) are generated inside the photovoltaic cell, and current flows through the wiring connecting the photovoltaic cell and the photovoltaic cell.

The light-receiving sheet formed on the photovoltaic cell or the photovoltaic array can function to protect the inside of the photovoltaic module from rainfall, external impact, fire or the like and ensure long-term reliability when the photovoltaic module is exposed to the outside. Specific examples of the light-receiving sheet include, but not particularly limited to, glass, fluorine resin, cyclic polyolefin, , A poly (meth) acrylic resin sheet, a polyamide resin sheet, or a polyester resin sheet. In one embodiment, a glass plate having excellent heat resistance can be used as the light receiving sheet, but the present invention is not limited thereto.

The thickness of the light-receiving sheet is not particularly limited, and may be, for example, 0.5 mm to 10 mm, 1 mm to 8 mm, or 2 mm to 5 mm. By controlling the thickness of the light-receiving sheet within the range of 0.5 mm to 10 mm, the physical properties such as long-term reliability of the photovoltaic module can be maintained excellent while the photovoltaic module is made thinner.

In addition, an encapsulant layer for encapsulating the photovoltaic cell or the photovoltaic array in the inside of the photovoltaic module, that is, between the back sheet and the light receiving sheet, may employ any encapsulant generally known in this field.

Figures 5 and 6 are cross-sectional views of photovoltaic modules in accordance with various embodiments of the present application.

5 is a diagram illustrating an example of a wafer based photovoltaic module 20 including a back sheet for a photovoltaic module in accordance with embodiments of the present application. 5, the photovoltaic module according to one embodiment of the present application typically includes a light-receiving sheet 21, which may be composed of a ferroelectric (e.g., glass); A back sheet (23) for a photovoltaic module; A photovoltaic device 24 such as the silicon wafer; And an encapsulant layer 22 that encapsulates the photovoltaic device 24. The encapsulant layer 22 encapsulates the photovoltaic device 24 and encapsulates the first layer 22a and the photovoltaic device 24 attached to the light-receiving sheet 21, And a second layer 22b attached to the second layer 22b. The first layer and the second layer constituting the encapsulant layer 22 may be composed of a material generally known in this field as described above.

6 is a sectional view of a thin-film photovoltaic module 30 according to another embodiment of the present application. As shown in Fig. 6, in the case of the thin-film photovoltaic module 30, the photovoltaic device 34 can be formed on the light-receiving sheet 31, which can typically be constituted by a ferroelectric. Such a thin film photovoltaic device 34 may be deposited by a method such as chemical vapor deposition (CVD). The photovoltaic module 30 of FIG. 6 includes a back sheet 33, an encapsulant layer 32, a photovoltaic device 34, and a light receiving sheet 31, similar to the photovoltaic module 20 of FIG. The encapsulant layer 32 may be composed of a single layer. The sealing material layer 32 and the back sheet 33 are described in detail above.

The method for manufacturing the above-described photovoltaic module is not particularly limited, and various methods known to those skilled in the art can be employed without limitation.

The photovoltaic modules shown in FIGS. 5 and 6 are only one example of various implementations of photovoltaic modules according to embodiments of the present application, and if they include a backsheet for a photovoltaic module according to embodiments of the present application, The structure of the module, the kind and size of the material constituting the module, and the like are not particularly limited, and any of generally known in this field can be employed without limitation.

Hereinafter, the present application will be described in more detail by way of examples according to the present application and comparative examples not complying with the present application, but the scope of the present application is not limited by the following embodiments.

< Manufacturing example >

Preparation of Polymer Having Polymerized Unit of Reactive Monomer Containing Ultraviolet Absorber

After maintaining the temperature of the 1 L reactor under a nitrogen atmosphere at 60 占 폚, 360 g of toluene, 60 g of RUVA-93 (manufactured by Ottsuka) and 336 g of methyl methacrylate (MMA) as a monomer containing a benzotriazole ultraviolet absorber were placed, , 4 g of an azo-based initiator, V-65, was dissolved to prepare an initiator solution. The initiator solution was slowly added dropwise over 2 hours. The reaction was terminated after a total of 5 hours based on the initiator dropping time to prepare a polymer having polymerized units of the UV absorber-containing reactive monomer.

< Example  1>

Preparation of Coating Solution for Resin Layer Formation

70 g of a copolymer containing 400 g of dimethylformamide (DMF) in a weight ratio of vinylidene fluoride (VDF) and chlorotrifluoroethylene (CTFE) 85:15; 30 g of a copolymer containing vinylidene fluoride (VDF) and hexafluoropropylene (HFP) in the form of a polymer in a weight ratio of 85:15 and a polymer having a polymerization unit of the UV absorber-containing reactive monomer prepared in the above Preparation Example (Solid content: 50%) were previously dissolved to prepare a coating solution.

Coating and drying the resin layer

The coating solution prepared in the above example was coated on a 250 탆 PET of acrylic primer treated colloid using a coating bar and dried in a drying oven at 180 캜 for 2 minutes to obtain a polymerized unit of a fluoropolymer and a reactive monomer containing an ultraviolet absorber The thickness of the resin layer including the polymer having a thickness of 10 mu m was prepared.

< Example  2 to 4>

A specimen was prepared in the same manner as in Example 1, except that the content of the polymer having the polymerization unit of the ultraviolet absorber-containing reactive monomer was changed as shown in Table 1 below.

< Comparative Example  1>

A specimen was prepared in the same manner as in Example 1, except that a polymer having a polymerization unit of a UV absorber-containing reactive monomer was not added.

< Comparative Example  2 to 3>

Specimens were prepared in the same manner as in Example 1, except that 1 and 2 g of SONGSORB 1000 (manufactured by Songwon Co., Ltd.), a benzotriazole-based ultraviolet absorber, was added in place of the polymer having polymerized units of the UV absorber-containing reactive monomer.

The content of the components contained in the coating solution (resin composition) Fluoropolymer Containing ultraviolet absorber
The reactive polymer (g) Content of added ultraviolet absorber (g) Furtherance Content (g) Ultraviolet absorber (g) - room
city
Yes One Fluoropolymer 1
Fluoropolymer 2 70
30 1.3 - 0.1 2 Fluoropolymer 1
Fluoropolymer 2 70
30 6.7 - 0.5 3 Fluoropolymer 1
Fluoropolymer 2 70
30 13.3 - One 4 Fluoropolymer 1
Fluoropolymer 2 70
30 26.7 - 2 ratio
School
Yes One Fluoropolymer 1
Fluoropolymer 2 70
30 - - 2 Fluoropolymer 1
Fluoropolymer 2 70
30 - One 3 Fluoropolymer 1
Fluoropolymer 2 70
30 - 2 In Table 1, the ultraviolet absorber means an ultraviolet absorber-containing acrylic monomer used when preparing a reactive polymer containing an ultraviolet absorber.

< Test Example  1>

With respect to the specimens prepared in Examples 1 to 4 and Comparative Examples 1 to 3, physical properties were measured by the following evaluation methods. Specifically, each of the specimens was allowed to stand for 25 hours, 50 hours, and 75 hours at 2 atmospheres, 121 ° C, and 100% RH, and then the ultraviolet light blocking properties And the results are shown in Tables 2 and 3 and FIGS. 1, 2 and 3, respectively.

Evaluation method of physical property

1. Cloudiness ( Haze )

Using a haze meter (HM-150 manufactured by Murakmi color research laboratory), the total light transmittance (Tt) and haze (Haze) of the specimen coated with the resin layer were measured at 380 to 780 nm. (JIS K7361)

2. Transmittance and Yellowing index

The transmittance of the back sheet for solar cell manufactured in Examples and Comparative Examples was measured at 800 nm at 200 nm, 320 nm, 340 nm and 360 nm wavelength using a Shimadzu UV Vis spectrometer (UV 03000) according to ASTM D1925, YI (Yellowness Index) was calculated according to the following general formula (1).

[Formula 1]

YI = [100 (1.28X _CIE -1.62Z _CIE )] / Y _CIE

YI is a value calculated by using a color difference analysis program in the UV / VIS / NIR spectrometer (ASTM, D1925), and X _CIE , Z _CIE and Y _CIE are relative values indicated by red, green and blue coordinates, respectively.

3. PCT ( pressure cooker test )

The multilayer film prepared in Examples and Comparative Examples (the cross section of the base layer was coated with a resin layer containing a polymer having polymerized units of a fluorine-based polymer and an ultraviolet ray absorber-containing reactive monomer) was irradiated under conditions of 2 atm, 121 ° C and 100% RH After standing for 25 hours, 50 hours, and 75 hours in the oven maintained, the change in adhesion was observed.

Total light transmittance (Tr) Haze Yellowing index (YI) Early 25hrs 50hrs 75hrs Early 25hrs 50hrs 75hrs Early 25hrs 50hrs 75hrs Example One 90.8 91.7 90.3 89.4 13.0 15.2 18.2 15.5 2.99 2.98 2.99 3.00 2 89.6 90.8 89.5 88.6 15.8 16.3 17.0 16.6 3.12 3.21 3.22 3.22 3 89.1 90.3 88.5 87.3 20.3 18.7 20.7 26.8 3.02 3.04 3.05 3.06 4 88.2 88.9 88.4 86.7 27.0 25.6 25.6 30.8 3.10 3.09 3.11 3.11 Comparative Example One 91.9 92.0 90.6 89.1 12.8 14.7 16.2 20.3 2.24 2.27 2.45 2.53 2 91.9 91.8 91.3 89.8 12.2 14.6 18.2 15.5 2.56 2.63 2.64 2.61 3 91.4 91.9 90.6 88.8 10.6 12.5 22.0 24.2 2.46 2.56 2.60 2.61

As shown in Table 2, in the case of a multilayer film comprising a resin layer containing a polymer having polymerized units of a fluorine-based polymer and an ultraviolet absorber-containing reactive monomer according to the present invention, Comparative Example 1 (without using an ultraviolet absorber) and It was confirmed that the total light transmittance and the fog were not lowered at wavelengths of 380 to 780 nm even under high temperature and high humidity conditions such as PCT as in Comparative Examples 2 to 3 (using a non-reactive benzotriazole based ultraviolet absorber).

Transmittance (%) 320 nm 340 nm 360 nm Early 25hrs 50hrs 75hrs Early 25hrs 50hrs 75hrs Early 25hrs 50hrs 75hrs Example One 16.5 13.3 13.2 12.9 41.2 35.9 36.7 35.6 54.7 50.7 52.3 51.0 2 4.5 3.1 3.3 3.4 8.6 6.3 7.3 7.5 20.1 17.5 19.9 20.0 3 0.9 0.4 0.4 0.3 1.2 0.6 0.6 0.6 5.0 4.6 4.5 4.4 4 0.4 0.0 0.0 0.3 0.4 0.0 0.0 0.3 0.5 0.2 0.3 0.4 Comparative Example One 19.1 19.4 19.2 18.6 55.4 56.2 55.5 53.3 64.2 65.8 66.0 64.8 2 13.0 17.5 17.7 18.0 29.9 49.1 50.0 51.6 43.8 59.4 61.1 63.2 3 10.7 16.5 16.3 16.1 22.3 45.9 46.0 46.6 33.5 56.2 56.2 57.6

Table 3 shows the transmittance measured values of Examples 1 to 4 and Comparative Examples 1 to 3. Also, the graphs of Figs. 1 to 3 were prepared on the basis of the values in Table 3 above.

 FIG. 1 shows a comparison between Example 3 in which 1% of ultraviolet absorber in the form of a reactive polymer was added in the form of a reactive polymer, Comparative Example 1 in which no ultraviolet absorber was added, and Comparative Example 1 in which 1% The transmission spectrum of Example 2 is shown. 1, when the same amount of ultraviolet absorber as that of the fluorine-based polymer was used, the case of using the reactive ultraviolet absorber of Example 3 of this Example exhibited more excellent ultraviolet screening characteristics than that of the case of using the benzotriazole-based ultraviolet absorber of Comparative Example 2 .

FIG. 2 shows the transmission spectrum at the initial stage of PCT and the elapsed time of 75 hours in Example 4 in which the ultraviolet absorber was added in the form of a reactive polymer. FIG. 3 shows the transmittance spectrum of Comparative Example 3 in which the ultraviolet absorber was added in the form of a non- The transmission spectrum at the initial stage of PCT and the elapsed time of 75 hours is shown. As shown in Fig. 2, in the case of the multilayer film comprising the fluoropolymer and the ultraviolet absorber of the present invention, the ultraviolet shielding effect does not deteriorate even after the PCT. However, as in Comparative Example 3 of Fig. 3, the benzotriazole- , It was confirmed that the ultraviolet blocking effect after PCT was greatly lowered.

Therefore, in the case of the multilayer film including the resin layer including the fluorine-based polymer and the reactive ultraviolet absorbent-containing polymer as in the above-described Examples 1 to 4, even when a small amount of the ultraviolet absorbent is used, It exhibits an excellent ultraviolet shielding effect and at the same time does not deteriorate the ultraviolet shielding effect even after the PCT, it can exhibit more excellent weather resistance and effectively shield ultraviolet rays and protect the substrate layer from ultraviolet rays.

10: multilayer film
11: Resin layer
12: substrate layer
20: Wafer-based photovoltaic module
30: Thin-film photovoltaic module
21, 31: Light receiving sheet
22, 32:
22a: First layer
22b: second layer
23, 33: back sheet
24, 34: photovoltaic device

Claims (18)

A base layer; And a resin layer formed on the base layer and including a polymer having polymerized units of an ultraviolet absorbing group-containing reactive monomer represented by the following formula (1):
[Chemical Formula 1]

In the formula (1), U is a residue of a benzotriazole-based, benzophenone-based, triazine-based, arylester-based or oxanilide-based ultraviolet absorbing compound, A and B are each independently an alkylene group, an alkenylene group, An arylene group or a single bond, and R is hydrogen or an alkyl group. The multilayer film according to claim 1, wherein the resin layer further comprises a fluorine-based polymer. The multilayer film according to claim 1, wherein the base layer comprises at least one functional group selected from the group consisting of a carboxyl group, an aromatic thiol group, and a phenolic hydroxyl group on the surface. The fluorine-based polymer according to claim 2, wherein the fluorine-based polymer is a polymer of a single fluorine-based monomer; And copolymers of a mixture containing at least two kinds of fluorine-based monomers. The method of claim 4, wherein the fluorine-based monomer is selected from the group consisting of vinylidene fluoride (VDF), vinyl fluoride (VF), tetrafluoroethylene (TFE), hexafluoropropylene (HFP) Perfluoroethyl vinyl ether (PMVE, perfluoro (methylvinylether), perfluoroethyl vinyl ether (PMVE), perfluoroethyl vinyl ether Perfluoro (ethylvinylether), perfluoropropyl vinyl ether (PPVE), perfluorohexyl vinyl ether (PHVE), perfluoro-2,2-dimethyl-1,3-dioxole (PDD) Methyl-4-methyl-1,3-dioxolane (PMD). The method of claim 4, wherein the copolymer is selected from the group consisting of tetrafluoroethylene (TFE), hexafluoropropylene (HFP), chlorotrifluoroethylene (CTFE), trifluoroethylene, hexafluoroethylene Butylene, perfluorobutyl ethylene, perfluoro (methylvinylether), perfluoro (ethylvinylether), perfluoro (vinyl) vinyl ether (PPVE), purple Perfluoro-2,2-dimethyl-1,3-dioxolane (PDD) and perfluoro-2-methylene-4-methyl-1,3-dioxolane (PMD) At least one fluorine-based monomer selected from the group consisting of: And polyvinylidene fluoride (PVDF) or polyvinyl fluoride (PVF) in polymerized form. The polymer having a polymerization unit of the ultraviolet absorber-containing reactive monomer according to claim 1, wherein the polymer comprises a homopolymer of a reactive monomer containing an ultraviolet absorber; And a copolymer of a mixture comprising an ultraviolet absorber-containing reactive monomer and at least one comonomer. delete The organic electroluminescent device according to claim 1, wherein U is a residue of a benzotriazole-based, benzophenone- or benzoate-based ultraviolet absorbing compound, A is an arylene group having 6 to 12 carbon atoms, B is an alkyl group having 1 to 8 carbon atoms And R is hydrogen or an alkyl group having 1 to 4 carbon atoms. The ultraviolet absorber-containing reactive monomer according to claim 1, wherein the UV absorber-containing reactive monomer is 2- [2'-hydroxy-3'-acryloyloxymethyl) phenyl] benzotriazole, 2- [2'- Phenyl] benzotriazole, 2- [2'-hydroxy-3'-acryloyloxymethyl-5'-tert- 3'-acryloyloxymethyl-5'-sec-butyl) phenyl] benzo [b] thiophene Triazole, 2- [2'-hydroxy-3'-sec-butyl-5'-acryloyloxymethyl) phenyl] benzotriazole, 2- [2'-hydroxy-3'-acryloyloxy Ethyl] phenyl] benzotriazole, 2- [2'-hydroxy-5'-acryloyloxyethyl) phenyl] benzotriazole, 2- [2'- Phenyl] benzotriazole, 2- [2'-hydroxy-3'-tert-butyl-5'-acryloyloxyethyl) phenyl] benzotriazole, 2- [ Hydroxy-3'-acryloyloxyethyl-5'-sec-butyl) phenol ] Benzotriazole, 2- [2'-hydroxy -3'-sec- butyl-5'-acryloyloxyethyl) phenyl] multi-layer film at least one selected from the group consisting of benzo triazolo. The copolymer according to claim 7, wherein the comonomer contained in the copolymer is at least one selected from the group consisting of alkyl (meth) acrylates, amide group-containing monomers, unsaturated nitrile monomers, vinyl ester monomers, vinyl ether monomers, And?,? - unsaturated aromatic monomers. 8. The multi-layer film of claim 7, wherein the copolymer comprises an acrylic monomer comprising a radical scavenging compound in a polymerized form. 13. The multilayer film according to claim 12, wherein the radical scavenging compound is at least one selected from peroxide dissociation, radical scavenger and hindered amine compounds. Forming a resin layer comprising a polymer having polymerized units of an ultraviolet absorber-containing reactive monomer represented by the following formula (1) on a base layer:
[Chemical Formula 1]

In the formula (1), U is a residue of a benzotriazole-based, benzophenone-based, triazine-based, arylester-based or oxanilide-based ultraviolet absorbing compound, A and B are each independently an alkylene group, an alkenylene group, An arylene group or a single bond, and R is hydrogen or an alkyl group. 15. The method according to claim 14, wherein one or more surfaces selected from the group consisting of a plasma treatment, a corona treatment, a primer treatment, an anchor treatment, a coupling agent treatment, a vapor deposition treatment and a heat treatment are applied to one surface or both surfaces of the substrate layer before forming the resin layer &Lt; / RTI &gt; further comprising the step of: 15. The method according to claim 14, wherein the step of forming the resin layer is performed by applying a resin layer coating solution containing a fluoropolymer, a polymer having a polymerization unit of an ultraviolet absorber-containing reactive monomer, and a solvent having a boiling point of 200 DEG C or lower on a substrate layer A method for producing a multilayer film. A backsheet for a photovoltaic module, comprising the multilayer film of claim 1. 17. A photovoltaic module comprising a back sheet for a photovoltaic module according to claim 17.

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