KR101719873B1 - Back sheet - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a back sheet and a photovoltaic module including the same, wherein a back sheet according to the present application is formed by adhering a base layer and a fluorine polymer film with a pressure- , It is possible to prevent deterioration of the substrate layer due to its excellent ultraviolet shielding ability as compared with the conventional urethane adhesives and to provide ultraviolet shielding as well as light transmission efficiency and weather resistance even after high temperature / Can be maintained.

Description

BACK SHEET {BACK SHEET}

The present application relates to a backsheet and a photovoltaic module comprising the same.

Recently, interest in renewable energy and clean energy has increased 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. .

Photovoltaic (PV) solar photovoltaic (PV) technology is a device that converts sunlight into electric energy. Since it is required to be exposed to the external environment for a long time in order to easily absorb sunlight, various packaging for protecting the cell is performed, ), And these units are referred to as photovoltaic modules.

The photovoltaic module is required to include a back sheet having excellent properties such as weather resistance and durability so as to stably protect the photovoltaic cell even when exposed to the external environment for a long period of time. When the light is absorbed and converted into electric energy, shall.

On the other hand, Patent Document 1 proposes a technique of using a urethane-based adhesive for attaching a base film and a fluorine film to the back sheet.

However, since the urethane-based adhesive has a large amount of urethane bonds, not only the reliability is low but also the initial adhesive force is strong, the reworkability is lost and reusability is impossible, and the adhesive strength is deteriorated over time.

Patent Document 1: Korean Patent Publication No. 2011-0034665

The present application provides a backsheet and a photovoltaic module comprising the same.

The present application relates to backsheets.

The exemplary backsheet may be a backsheet for a photovoltaic module applicable to a photovoltaic module, where the " backsheet for a photovoltaic module " may be referred to as a " backsheet ".

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram schematically showing a cross section of a back sheet according to the present application. Fig.

In one example, as shown in Figure 1, the backsheet of the present application comprises a substrate layer 20; A fluoropolymer film (40) formed on at least one side of the substrate layer; And the fluororesin film 40 may be adhered to the base layer 20 and the fluororesin film 40 by the adhesive layer 30.

The substrate layer is not particularly limited, and various materials known in the art can be used, and can be appropriately selected depending on the required functions and applications.

As the base layer, a single sheet such as an acrylic film, a polyether film, a polyester film, a polyolefin film, a polyamide film, a polyurethane film, a polycarbonate film and a polyimide film, A laminated sheet of polymer films, or a pneumatic article, and a polyester film can be usually used, but the present invention is not limited thereto. Examples of the polyester film include at least one selected from the group consisting of a polyethylene terephthalate (PET) film, a polyethylene naphthalate (PEN) film, and a polycarbonate (PC) film , But is not limited thereto.

The thickness of the base layer is not particularly limited, but may be within a range of, for example, 10 탆 to 500 탆, 25 탆 to 400 탆, or 50 탆 to 300 탆. By controlling the thickness of the base layer within the above-mentioned 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 order to improve the adhesion of the surface layer described above, a spark discharge treatment at a high frequency such as corona treatment or plasma treatment is applied to one surface or both surfaces of the base layer. Heat treatment; Flame treatment; Anchor treatment; Coupling agent treatment; Primer treatment or a gas phase Lewis acid (ex. BF _3), can be done by a surface treatment such as a chemical activation treatment with sulfuric acid or hot sodium hydroxide. The surface treatment method may be carried out by any well-known means generally used in this field.

In addition, the substrate layer may be provided with an inorganic oxide deposited layer on one side or both sides from the viewpoint of improving 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. 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 fluoropolymer film may include a fluororesin. The back sheet includes a fluoropolymer film containing a fluororesin, so that the present application can have improved weather resistance and durability.

As the fluororesin, various resins containing fluorine atoms known in the art can be used. Examples of the fluororesin include vinylidene fluoride (VDF), vinyl fluoride (VF), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and the like. Perfluoroethyl vinyl ether (PMVE, perfluoro (methylvinylether)), perfluoroethyl vinyl ether (PMVE), perfluoroethyl vinyl ether Perfluoro (ethyl vinyl ether), perfluoropropyl vinyl ether (PPVE), perfluorohexyl vinyl ether (PHVE), perfluoro-2,2-dimethyl-1,3-dioxole (PDD) Copolymers or mixtures thereof comprising at least one monomer selected from the group consisting of methylene-4-methyl-4-methyl-1,3-dioxolane (PMD) in polymerized form, Quot; The fluororesin is a homopolymer or copolymer comprising vinylidene fluoride (VDF) in polymerized form; Or a mixture comprising the same.

The type of the comonomer that can be contained in the form of the polymer in the copolymer is not particularly limited and includes, for example, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), chlorotrifluoro But are not limited to, ethylene (CTFE), trifluoroethylene, hexafluoroisobutylene, perfluorobutyl ethylene, perfluoro (methylvinylether), and perfluoroethyl vinyl ether perfluorohexyl vinyl ether (PHVE), perfluoro-2,2-dimethyl-1,3-dioxole (PDD), and perfluoro-2 Methylene-4-methyl-1,3-dioxolane (PMD), and the like, and examples thereof include at least one of hexafluoropropylene and chlorotrifluoroethylene. However, But is not limited thereto.

In one example, the fluororesin may be a mixture of a homopolymer comprising vinylidene fluoride in polymerized form and a copolymer of vinylidene fluoride and hexafluoropropylene, or a mixture of vinylidene fluoride and chlorotrifluoro , A copolymer of ethylene and a copolymer of vinylidene fluoride and hexafluoropropylene.

The content of the comonomer contained in the copolymer is not particularly limited and may be, for example, about 0.5 to 50 wt%, 1 to 40 wt%, and 7 wt% based on the total weight of the copolymer % To 40 wt%, 10 wt% to 30 wt%, or 10 wt% to 20 wt%. By controlling the content of the comonomer in the above range, it is possible to further improve the adhesive force while ensuring the durability and weather resistance of the multilayer film.

The weight average molecular weight of the fluororesin contained in the fluoropolymer film may be from 50,000 to 100, and may be from 100,000 to 700,000, or from 300,000 to 50,000, but is not limited thereto. As used herein, the term " weight average molecular weight " is a conversion value of standard polystyrene measured by GPC (Gel Permeation Chromatograph). In the embodiments of the present application, by controlling the weight average molecular weight of the fluorine polymer within the above range, excellent solubility and other physical properties can be secured.

The fluoropolymer film may further include a (meth) acrylic polymer in addition to the fluororesin.

The acrylic polymer may be any polymer that can be used in the adhesive field without limitation, for example, polymethyl methacrylate (PMMA); A copolymer of methyl methacrylate and glycidyl methacrylate (MMA-GMA); A terpolymer of methyl methacrylate, glycidyl methacrylate and hydroxyethyl methacrylate (MMA-GMA-HEMA); Or copolymers of methyl methacrylate and cyclohexyl maleimide (MMA-CHMI), but are not limited thereto.

The content of the (meth) acrylic polymer is preferably 1 to 50% by weight, more preferably 5 to 30% by weight. If the content of the (meth) acryl-based polymer is less than 1% by weight, it may be difficult to ensure sufficient adhesion. If the content is more than 50% by weight, the fluoropolymer film may have poor weather resistance.

The weight ratio of the vinylidene fluoride polymer to the (meth) acrylic copolymer is preferably 9 to 7: 1 to 3, but is not limited thereto. For example, when the fluorine-based polymer film contains a vinylidene fluoride copolymer and polymethyl methacrylate, the weight ratio thereof is preferably 9 to 7: 1 to 3. When the fluorine-based polymer film contains a vinylidene fluoride copolymer and a copolymer of methyl methacrylate and glycidyl methacrylate, the weight ratio thereof is preferably 9 to 7: 1 to 3. When the fluorine-based polymer film contains a vinylidene fluoride copolymer and a ternary copolymer of methyl methacrylate, glycidyl methacrylate and hydroxyethyl methacrylate, the weight ratio thereof is 9 to 6: 0.5 To 2: 0.5 to 2. When the fluorine-based polymer film contains a copolymer of a vinylidene fluoride copolymer, methyl methacrylate and cyclohexylmaleimide, the weight ratio thereof is preferably 9 to 7: 1 to 3.

The glycidyl methacrylate and cyclohexyl maleimide are not included alone but are included in the form of a copolymer of methyl methacrylate and glycidyl methacrylate, a copolymer of methyl methacrylate and cyclohexyl maleimide In addition to these, methyl methacrylate and hydroxyethyl methacrylate copolymers, methyl methacrylate and acrylic acid copolymers, copolymers of methyl methacrylate and methacrylic acid, and the like may be further used.

In addition to the (meth) acrylic polymer, hydroxyethyl methacrylate, methacrylic acid, acrylic acid, and the like may be further used.

The fluorine-based polymer film may further include a pigment and / or a filler for improving the power generation efficiency of the solar cell and improving the physical properties of the back sheet for a photovoltaic module. Examples of the pigment and / or filler include titanium dioxide, Silica, alumina, calcium carbonate, barium sulfate, carbon black, metal oxide, and the like, and pigments for imparting black pigments and other colors such as carbon black can also be used.

The thickness of the fluorine-based polymer film may be in the range of 1 占 퐉 to 50 占 퐉, 2.5 占 퐉 to 45 占 퐉, or 5 占 퐉 to 40 占 퐉. By adjusting the thickness of the fluoropolymer film within the above-described range, it is possible to increase the light diffusing property and reduce the manufacturing cost.

In the back sheet of the present application, the above-described base layer and the fluorine-based polymer film may be adhered by a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer may comprise, for example, a crosslinked pressure-sensitive adhesive polymer.

In one example, the tacky polymer may include a (meth) acrylic acid ester-based monomer polymerization unit and a crosslinkable monomer polymerization unit. As used herein, the term " monomeric polymerization unit " may refer to a form in which the monomer undergoes a polymerization reaction to form a skeleton of the polymer, for example, a main chain or a side chain.

The kind of the (meth) acrylate monomer is not particularly limited. In the present application, for example, alkyl (meth) acrylate can be used, specifically, an alkyl (meth) acrylate having an alkyl group having 1 to 14 carbon atoms, preferably 1 to 8 carbon atoms in view of controlling the adhesive force of the pressure- Methacrylate may be used. Examples of such monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, (Meth) acrylate, sec-butyl (meth) acrylate, pentyl (meth) acrylate, 2- ethylhexyl , Isooctyl (meth) acrylate or isononyl (meth) acrylate, and one kind or a mixture of two or more kinds can be used.

The crosslinkable monomer means a compound which simultaneously contains both a copolymerizable functional group such as a carbon-carbon double bond in the molecule and a crosslinkable functional group. The crosslinkable monomer can impart a crosslinking functional group to an acrylic resin to provide a crosslinking point or control the reliability and adhesion of the pressure-sensitive adhesive layer under high temperature or high humidity conditions.

Examples of the crosslinkable monomer that can be used in the present application include a hydroxy group-containing monomer or a carboxyl group-containing monomer, which may be used alone or in combination. Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (Meth) acrylate, 2-hydroxyethyleneglycol (meth) acrylate or 2-hydroxypropyleneglycol (meth) acrylate; Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, 2- (meth) acryloyloxyacetic acid, 3- (meth) acryloyloxypropyl acid, 4- (meth) acryloyloxybutyric acid, Butyric acid, itaconic acid, maleic acid, and the like.

In the present application, the pressure-sensitive adhesive polymer may include 70 to 99 parts by weight of a polymerization unit of a (meth) acrylic acid ester monomer and 0.1 to 30 parts by weight of a polymerization unit of a crosslinkable monomer. In the present specification, the unit " weight part " may mean a ratio of the weight between the respective components. By adjusting the ratio of the monomers contained in the tacky polymer to the above range, a more desirable level of adhesion can be ensured.

The pressure-sensitive adhesive polymer may further include a copolymerizable monomer in addition to the (meth) acrylic acid ester-based monomer unit and the crosslinkable monomer unit.

The copolymerizable monomer is not particularly limited as long as it is a copolymerizable monomer. For example, the copolymerizable monomer may include a monomeric polymerization unit capable of forming a homopolymer having a glass transition temperature of 0 ° C or higher.

When the glass transition temperature of a monomer is defined in this specification, its glass transition temperature can refer to the glass transition temperature of the homopolymer when the monomer is polymerized to form a homopolymer. Thus, for example, the term "monomer capable of forming a homopolymer having a glass transition temperature of 0 ° C or higher" may mean that the glass transition temperature of a homopolymer formed by polymerizing only monomers is 0 ° C or higher.

The glass transition temperature of the monomer capable of forming a homopolymer having a glass transition temperature of 0 ° C or higher may be 0 ° C or higher or 5 ° C or higher in another example and the upper limit of the glass transition temperature of the monomer is not particularly limited, 250 ° C, 200 ° C, 150 ° C, or 120 ° C.

But may include various types of copolymerizable monomers without particular limitation as long as the glass transition temperature has the above-mentioned range. For example, methacrylate, tertiary butyl acrylate, tert-butyl methacrylate Butyl acrylate, tert-butyl methacrylate, isobutyl methacrylate, normal-butyl methacrylate, 1-hexadecyl (meth) acrylate, (Meth) acrylates having a straight-chain or branched-chain alkyl group such as methyl methacrylate, n-propyl methacrylate or sec-butyl methacrylate, ; N-alkenylformamide having 2 to 20 carbon atoms, 2 to 16 carbon atoms, 2 to 12 carbon atoms, 2 to 8 carbon atoms, or an alkenyl group having 2 to 4 carbon atoms, such as N-vinylformamide; Acrylamide, N, N-diphenyl (meth) acrylamide, N- (n-dodecyl) (meth) acrylamide, N- (meth) acrylamide such as N, N-dimethyl acrylamide or N-hydroxyethyl acrylamide, N-alkyl (meth) acrylamide (Meth) acrylamide, N, N-dialkyl (meth) acrylamide or N, N-diaryl (meth) acrylamide; Alkoxyalkyl (meth) acrylates such as 2-methoxyethyl (meth) acrylate and the like; Dihydrodicyclopentadienyl acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, cyclopropyl (meth) acrylate, acrylate, N-naphthyl acrylate, 2-phenoxyethyl (meth) acrylate, phenyl (meth) acrylate, Acrylate, 2-phenylethyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate or (Meth) acrylate having a saturated or unsaturated cyclic hydrocarbon group or an aromatic group such as cyclohexyl (meth) acrylate and the like; Or styrene may be exemplified.

When the tacky polymer is a copolymerizable monomer and contains a monomer capable of forming a homopolymer having a glass transition temperature of 0 ° C or higher, the tacky polymer is preferably a polymer comprising 30 to 90 parts by weight of a polymerization unit of a (meth) acrylic acid ester monomer; 1 to 20 parts by weight of a crosslinkable monomer; And 20 to 60 parts by weight of monomeric polymerized units capable of forming a homopolymer having a glass transition temperature of 0 ° C or higher. The pressure-sensitive adhesive polymer may further contain 40 to 70 parts by weight of a polymerization unit of a (meth) acrylic acid ester monomer so as to secure a desired level of adhesion. 5 parts by weight to 15 parts by weight of a crosslinkable monomer; And 30 to 50 parts by weight of monomeric polymerization units capable of forming a homopolymer having a glass transition temperature of 0 DEG C or higher.

In one example, the tacky polymer may comprise a UV blocking monomer as polymerized units.

Exemplary UV blocking monomers may be represented by the following formula (1).

[Chemical Formula 1]

In Formula 1, R < 1 _> To R ₅ are each independently hydrogen or an alkyl group having 1 to 16 carbon atoms, and R ₆ To R < ₈ > each represent a cyano group or an alkyl group having 1 to 16 carbon atoms in which a nitro group is substituted or unsubstituted; A halogen atom, a cyano group, or an aryl group having 6 to 20 carbon atoms in which a nitro group is substituted or unsubstituted; A halogen atom, a cyano group, or an alkoxy group having 1 to 16 carbon atoms in which a nitro group is substituted or unsubstituted; Or a halogen atom, a cyano group, or an aryloxy group having 6 to 20 carbon atoms in which a nitro group is substituted or unsubstituted, and R ₉ is hydrogen, an alkyl group having 1 to 16 carbon atoms, or a hydroxyl group.

The back sheet according to the present application is characterized in that the base layer and the fluorine polymer film are adhered by a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer includes a pressure-sensitive adhesive polymer containing the UV-blocking monomer. As a result, Not only deterioration of the base layer can be prevented, but also light transmittance efficiency and weather resistance as well as ultraviolet shielding ability can be maintained at the same time even after high temperature / high humidity.

The ultraviolet barrier monomer is not particularly limited as long as it is a polymerizable monomer having an ultraviolet shielding ability, and examples thereof include 2- (2'-hydroxy-5'-methacryloxyethylphenyl) -2H-benzotriazole, benzo Phenol, aryl ester, and oxanilide.

When the viscous polymer comprises an ultraviolet barrier monomer, the content ratio between the components may be appropriately adjusted as needed, for example, 30 parts by weight to 90 parts by weight of (meth) acrylic acid ester monomer polymerized units; 1 to 20 parts by weight of a crosslinkable monomer; And 1 to 10 parts by weight of an ultraviolet barrier monomer unit.

The method for producing the adhesive polymer is not particularly limited and may be a method in which the monomer is mixed at an appropriate ratio and solution polymerization, photo polymerization, bulk polymerization, suspension polymerization, Or by emulsion polymerization. [0033] The term " polymer " If necessary in this process, suitable polymerization initiators or molecular weight regulators, chain transfer agents and the like may be used together.

The pressure-sensitive adhesive layer may further comprise a crosslinking agent capable of crosslinking the pressure-sensitive adhesive polymer. The crosslinking agent may be a crosslinking agent having at least two or more functional groups capable of reacting with the crosslinkable functional group contained in the adhesive polymer, 2 to 10, 2 to 8, 2 to 6, or 2 to 4 Crosslinking agents may be used. As such a cross-linking agent, an appropriate type may be selected and used from among conventional cross-linking agents such as an isocyanate cross-linking agent, an epoxy cross-linking agent, an aziridine cross-linking agent or a metal chelate cross-linking agent considering the kind of the cross-linkable functional group of the adhesive polymer.

Examples of the isocyanate crosslinking agent include diisocyanate compounds such as tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoboron diisocyanate, tetramethylxylene diisocyanate, and naphthalene diisocyanate; And a reaction product of a polyol such as trimethylolpropane or an isocyanurate adduct of the above diisocyanate compound. Of these, xylene diisocyanate or hexamethylene diisocyanate can be preferably used. As the epoxy crosslinking agent Is preferably at least one selected from the group consisting of ethylene glycol diglycidyl ether, triglycidyl ether, trimethylolpropane triglycidyl ether, N, N, N ', N'- tetraglycidylethylenediamine and glycerin diglycidyl ether There is at least one selected from the group true can be exemplified.

As the aziridine crosslinking agent, N, N'-toluene-2,4-bis (1-aziridinecarboxamide), N, N'-diphenylmethane-4,4'- (2-methyl aziridine) or tri-1-aziridinyl phosphine oxide, and the like, but not limited thereto, and the metal chelate Examples of the crosslinking agent include compounds in which a polyvalent metal such as aluminum, iron, zinc, tin, titanium, antimony, magnesium, and / or vanadium is coordinated to acetylacetone or ethyl acetoacetate.

The cross-linking agent may be contained in a proportion of, for example, 0.01 to 5 parts by weight, 0.015 to 4 parts by weight, 0.02 to 3 parts by weight or 0.025 to 1 part by weight based on 100 parts by weight of the adhesive polymer have. The adhesive force of the pressure-sensitive adhesive layer can be maintained at a desired level by controlling the cross-linking agent to be included in the pressure-sensitive adhesive polymer within the above-mentioned range.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, but may be within a range of, for example, 1 탆 to 100 탆, 2.5 탆 to 75 탆, or 5 탆 to 50 탆. The thickness of the pressure-sensitive adhesive layer can be controlled within the above-mentioned range to form a pressure-sensitive adhesive layer which secures more desired pressure-sensitive adhesive force.

The pressure-sensitive adhesive layer may further include at least one additive selected from the group consisting of a coupling agent, a tackifier, an antioxidant, a colorant, a reinforcing agent, a filler, a defoamer, a surfactant and a plasticizer, if necessary.

The backsheet of the present application may further include various functional layers known in the industry as needed in addition to the above-mentioned layers.

Examples of the functional layer include an adhesive layer or an insulating layer. The adhesive layer and the insulating layer may be sequentially formed on the other surface of the substrate layer when the reflective layer is formed on one surface of the substrate layer.

The adhesive layer or insulating layer may be formed in various ways known in the art. The insulating layer may be, for example, a layer composed of ethylene vinyl acetate (EVA) or low density linear polyethylene (LDPE). The layer composed of the ethylene vinyl acetate (EVA) or the low density linear polyethylene (LDPE) functions not only as an insulating layer but also an adhesive force of the encapsulant of the photovoltaic module to reduce the manufacturing cost, It is possible to simultaneously perform the function of maintaining excellent.

In one example, the backsheet of the present application can satisfy Equation 1 below.

[Equation 1]

X? 5%

Y? 20%

Z ≤ 30%

X, Y, and Z represent the ultraviolet transmittance for light in the 320 nm, 340 nm, and 360 nm wavelength regions measured after the back sheet for the photovoltaic module is left at 85 캜 and 85% for 3000 hours, respectively.

For example, the back sheet for a photovoltaic module is left at a temperature of 85 캜 and 85% for 3000 hours, and then the ultraviolet ray transmittance is measured at a wavelength of 320 nm The ultraviolet transmittance X to the light may be 4% or less, 3% or less, 2% or less, or 1% or less. The ultraviolet transmittance (Y) of the back sheet for the photovoltaic module is not more than 15%, not more than 10%, not more than 5%, or less than 1% of the light having a wavelength of 340 nm measured after being left at 85 ° C and 85% ≪ / RTI > The ultraviolet light transmittance (Z) for the light of 360 nm wavelength measured after the back sheet for the photovoltaic module is left for 3,000 hours under the conditions of 85 ° C and 85% is 20% or less, 15% Or less or 1% or less.

As described above, the back sheet of the present application comprises a base layer; A fluoropolymer film formed on at least one side of the substrate layer; And the fluorine-based polymer film are adhered to each other by a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is adjusted so as to include a pressure-sensitive adhesive polymer containing a UV blocking monomer as a polymerization unit, Not only deterioration of the base layer can be prevented, but also light transmittance efficiency and weather resistance as well as ultraviolet shielding ability can be maintained at the same time even after high temperature / high humidity.

The present application also relates to a method for producing a backsheet.

Exemplary methods for producing the backsheet include, but are not limited to, coating a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive polymer containing, as a polymerization unit, the above-described ultraviolet barrier monomer, on one surface or both surfaces of a substrate layer .

The method for producing the back sheet is not particularly limited as long as the pressure-sensitive adhesive layer is formed between the base layer and the above-mentioned fluoropolymer film in the back sheet. For example, in the case where the surface of the fluoropolymer film And coating the pressure-sensitive adhesive layer.

The coating method may be carried out by a conventional coating method. For example, a coating solution prepared by using the adhesive polymer is applied to a suitable processing substrate by a conventional means such as a bar coater and then cured to form a pressure- Can be manufactured. In the present application, it is preferable that the curing process is performed after sufficiently removing the bubble generating component such as volatile components or reaction residues contained in the adhesive polymer. The method for curing the coating liquid containing the tacky polymer is not particularly limited and may be selected from, for example, curing through appropriate heating, drying and / or aging, or irradiation with electromagnetic waves such as ultraviolet (UV) Can be employed.

In the present application, the pressure-sensitive adhesive layer may be prepared through the above-described processes, and the pressure-sensitive adhesive layer may be laminated to form the pressure-sensitive adhesive film. Alternatively, a pressure-sensitive adhesive layer may be directly formed on the pressure- May be produced in the form of the adhesive film.

In addition, if necessary, corona treatment may be appropriately performed in the process of forming the pressure-sensitive adhesive layer, and the corona treatment may be carried out by well-known means commonly used in this field.

The present application also relates to photovoltaic modules.

In one example, the photovoltaic module comprises a front substrate; The above-described back sheet, and two or more photovoltaic cells which are disposed between the front substrate and the back sheet and are spaced apart from each other.

The specific types of the front substrate and the photovoltaic cell that can be used in the above are not particularly limited. For example, the front substrate may be a conventional plate glass; Or a transparent composite sheet obtained by laminating a glass, a fluororesin sheet, a weather-resistant film and a barrier film. The photovoltaic cell may be, for example, an active layer of the silicon wafer type or a thin film active layer formed by chemical vapor deposition . In addition, the photovoltaic cell may be an n-type cell or a p-type cell, and may be an n-type cell, but is not limited thereto.

The back sheet according to the present application is characterized in that the base layer and the fluorine polymer film are adhered by a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer includes a pressure-sensitive adhesive polymer containing the UV-blocking monomer. As a result, Not only deterioration of the base layer can be prevented, but also light transmittance efficiency and weather resistance as well as ultraviolet shielding ability can be maintained at the same time even after high temperature / high humidity.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram schematically showing a cross section of a back sheet according to the present application. Fig.

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 examples.

The physical properties in Examples and Comparative Examples were evaluated in the following manner.

One. Electric power  Measurement of transmittance

The pressure-sensitive adhesive compositions prepared in Example 1 and Comparative Examples 1 and 2 were prepared in the form of a pressure-sensitive adhesive sheet, and were made into specimens having a width of 5 cm and a length of 7 cm. Each specimen was subjected to high temperature / high humidity conditions of 85 ° C. and 85% The sheet was allowed to stand for 1,000 hours, 2000 hours, and 3000 hours immediately after being produced in the form of a sheet, and the transmittance of light was measured and shown in Table 2 below.

2. Hayes  Measure

The pressure-sensitive adhesive compositions prepared in Example 1 and Comparative Examples 1 and 2 were prepared in the form of a pressure-sensitive adhesive sheet, and were then made into specimens of 5 cm in width × 7 cm in width. The specimens were subjected to UV-Vis spectrophotometer (UV-3600, Shimadzu) , 2000 hours, and 3000 hours, respectively, and the haze was measured. The results are shown in Table 2 below.

3. Yellow  Measurement of occurrence

The pressure-sensitive adhesive compositions prepared in Example 1 and Comparative Examples 1 and 2 were prepared in the form of a pressure sensitive adhesive sheet, and then prepared as specimens of 5 cm in width and 7 cm in length, placed in a metal halide ultraviolet lamp, Hours, 2000 hours, and 3000 hours, the discoloration of the specimen was measured using a haze meter (COH-400, manufactured by Nippon Denshoku) and the degree of occurrence of yellowing was shown in Table 2 below.

4. Ultraviolet transmittance measurement

Using a metal halide ultraviolet lamp, the wavelengths of the entire spectrum of the ultraviolet spectrum and the intensities of the UV-A, UV-B and UV-C regions were measured. Thereafter, the pressure-sensitive adhesive composition prepared in Example 1 and Comparative Examples 1 and 2 was formed in the form of a pressure-sensitive adhesive sheet on the bottom of an ultraviolet lamp, and the specimen was prepared as a 5 cm × 7 cm wide specimen. Ultrasonic intensity meter And the ultraviolet ray intensity was measured. The ultraviolet ray transmittance was calculated using the ultraviolet ray intensity change by the adhesive sheet sample, and it is shown in Table 3 below.

≪ Preparation of sticky polymer >

Manufacturing example  1. Preparation of adhesive polymer (A1)

50 parts by weight of 2-ethylhexyl acrylate (EHA), 40 parts by weight of methacrylate (MA), 2 parts by weight of 2-hydroxyethyl acrylate (HEA) and 5 parts by weight of "RUVA-93" (Otsuka Co.) as an ultraviolet barrier monomer. Subsequently, 100 parts by weight of ethyl acetate (EAc) was poured into a solvent, and nitrogen gas was purged for 60 minutes to remove oxygen. Then, while keeping the temperature at 60 ° C, 2,2'-azo And 0.04 parts by weight of bis (2,4-dimethylvaleronitrile) (V-65) were added to initiate the reaction. Thereafter, the reaction product which had been reacted for about 5 hours was diluted with ethyl acetate (EAc) to prepare a sticky polymer (A1).

Manufacturing example  2 to Manufacturing example  3. Adhesive polymers (B1 and < C1 )

Adhesive polymers (A2 and A3) were prepared in the same manner as in Preparation Example 1, except that raw materials and additives used in polymerization of the adhesive polymer (A1) were controlled as shown in Table 1 in Production Example 1 .

division Raw material EA V-65 EHA MA HEA RUVA-93 SS Stickiness
polymer A1 50 40 10 5 - 100 0.04 B1 50 40 10 - 5 100 0.04 C1 50 40 10 - - 100 0.04 Content Unit: g
EHA: 2-ethylhexyl acrylate
MA: (meth) acrylate
HEA: 2-hydroxyethyl acrylate
RUVA-93: 2- (2-hydroxy-5'-methacryloxyethylphenyl) -2H-benzotriazole (Otsuka)
SS: 2- (2'-hydroxy-5'-methylphenyl) -benzotriazole (Songsorb 1000, Songwon Industrial Co., Ltd.)
EA: ethyl acetate
V-65: 2,2'-azobis (2,4-dimethyl valeronitrile)

≪ Preparation of coating composition >

Manufacturing example  4, Preparation of Coating Composition (A2)

0.25 parts by weight of xylene diisocyanate (Takenate D110N, Mitsui Chemicals, Inc.) as a cross-linking agent was uniformly mixed with 100 parts by weight of the adhesive polymer (A1) prepared in Preparation Example 1 to prepare a coating composition (A2).

Manufacturing example  5. Preparation of coating composition (B2)

0.25 parts by weight of xylene diisocyanate (Takenate D110N, Mitsui Chemicals) as a crosslinking agent was uniformly mixed with 100 parts by weight of the adhesive polymer (B1) prepared in Preparation Example 2 to prepare a coating composition (B2).

Manufacturing example  6. Coating composition ( C2 )

0.25 parts by weight of xylene diisocyanate (Takenate D110N, Mitsui Chemicals, Inc.) as a cross-linking agent was uniformly mixed with 100 parts by weight of the adhesive polymer (C1) prepared in Production Example 3 to prepare a coating composition (C2).

< Back sheet  And photovoltaic module &

Example  One.

The coated coating composition (A2) was coated on both sides of a PET (poly (ethylene terephthalate)) film (thickness: 200 μm) and dried, and then a fluorinated polymer film (transparent PVDF) Respectively.

Further, a plate glass (thickness: about 3 mm), an encapsulating material with a thickness of 500 mu m, a crystal silicon wafer photovoltaic cell, a sealing material with a thickness of 500 mu m and a back sheet manufactured in this way were laminated in this order. Min for 30 seconds to fabricate a photovoltaic module.

Comparative Example  One.

A backsheet and a photovoltaic module were prepared in the same manner as in Example 1, except that the coating composition (B2) prepared in Preparation Example 5 was used in place of the coating composition (A2) used in Example 1.

Comparative Example  2.

A backsheet and a photovoltaic module were prepared in the same manner as in Example 1, except that the coating composition (C2) prepared in Preparation Example 6 was used in place of the coating composition (A2) used in Example 1.

The results of physical properties measured for the above Examples and Comparative Examples are shown in Tables 2 and 3 below.

division Example Comparative Example One One 2 Electrophotographic transmittance 0h 90.85 90.76 91.11 1000h 88.64 90.49 89.37 2000h 87.45 89.45 88.57 3000h 87.52 87.54 87.64 Hayes 0h 13.98 14.10 13.89 1000h 16.55 16.45 15.22 2000h 16.89 16.78 15.78 3000h 17.01 17.05 16.02 Degree of yellowing 0h 0.55 0.67 0.46 1000h 0.71 0.96 0.73 2000h 0.75 0.98 0.78 3000h 0.74 0.99 0.81 H: hour, hour
unit: %

division Example Comparative Example One One 2 320nm
Transmittance at wavelength 0h 0 3.2 17.8 1000h 0 8.2 15.2 2000h 0 8.3 15.3 3000h 0 8.5 15.1 340 nm
Transmittance at wavelength 0h 0 14.7 60.8 1000h 0 21.8 53.8 2000h 0 22.9 54.3 3000h 0 23.1 54.1 360nm
Transmittance at wavelength 0h 0.2 24.5 71.2 1000h 0.3 33.2 68.6 2000h 0.3 33.7 66.9 3000h 0.4 34.3 66.3 h: hour, hour
unit: %

As shown in Tables 2 and 3, the backsheet (Example 1) including the pressure sensitive adhesive layer containing the ultraviolet barrier monomer of the present application (Comparative Example 1) including the additive type ultraviolet screening agent and the ultraviolet screening agent (Comparative Example 2), it was confirmed that not only the optical characteristics and the weather resistance were good even under severe conditions of high temperature / high humidity, but also the excellent blocking ability against the wavelength of light in the ultraviolet ray region.

20: substrate layer
30: pressure-sensitive adhesive layer
40: Fluorine-based polymer film

Claims (18)

A base layer; And
Based polymer film formed on at least one surface of the substrate layer,
Wherein the base layer and the fluorine-based polymer film are attached by a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer comprises a pressure-sensitive adhesive polymer containing a UV blocking monomer as a polymerization unit, and the pressure- Back sheet:
[Equation 1]
X? 5%
Y? 20%
Z ≤ 30%
X, Y, and Z in the formula (1) were prepared by forming the pressure sensitive adhesive layer as a specimen having a width of 5 cm and a width of 7 cm, fixing the specimen, placing the UV intensity meter at the bottom of the specimen, And UV transmittance for light in the 320 nm, 340 nm and 360 nm wavelength regions measured after being left for 3,000 hours under the conditions of 85 캜 and 85%. [2] The method according to claim 1, wherein the substrate layer is a layer selected from the group consisting of an acrylic film, a polyether film, a polyester film, a polyolefin film, a polyamide film, a polyurethane film, a polycarbonate film and a polyimide film Back sheet for photovoltaic modules of more than two types. The back sheet according to claim 1, wherein the base layer has a thickness of 1 to 500 탆. The fluorine-based polymer film according to claim 1, wherein the fluorine-based polymer film is at least one selected from the group consisting of polyvinylidene fluoride (PVDF), hexafluoropropylene (HFP), chlorotrifluoroethylene (CTFE), tetrafluoroethylene (TFE) Perfluoroethyl vinyl ether (PPVE), perfluoroethyl vinyl ether (PEVE), perfluoromethyl vinyl ether (PMVE), perfluoro-2,2- Dimethyl-1,3-dioxole (PDD), and perfluoro-2-methylene-4-methyl-1,3-dioxolane (PMD). The back sheet for a photovoltaic module according to claim 1, wherein the fluoropolymer film further comprises a (meth) acrylic polymer. 6. The method of claim 5, wherein the (meth) acrylic polymer is selected from the group consisting of polymethyl methacrylate (PMMA), a copolymer of methyl methacrylate and glycidyl methacrylate (MMA-GMA), methyl methacrylate, glycidyl methacrylate (MMA-GMA-HEMA), a copolymer of methyl methacrylate and cyclohexylmaleimide (MMA-CHMI), and a ternary copolymer of acrylate and methacrylate Sheet. The back sheet for a photovoltaic module according to claim 1, wherein the thickness of the fluorine-based polymer film is in the range of 1 탆 to 50 탆. The back sheet for a photovoltaic module according to claim 1, wherein the ultraviolet barrier monomer is represented by the following formula (1)
[Chemical Formula 1]

In Formula 1, R &lt; 1 _&gt; To R ₅ are each independently hydrogen or an alkyl group having 1 to 16 carbon atoms, and R ₆ To R &lt; ₈ &gt; each represent a cyano group or an alkyl group having 1 to 16 carbon atoms in which a nitro group is substituted or unsubstituted; A halogen atom, a cyano group, or an aryl group having 6 to 20 carbon atoms in which a nitro group is substituted or unsubstituted; A halogen atom, a cyano group, or an alkoxy group having 1 to 16 carbon atoms in which a nitro group is substituted or unsubstituted; Or a halogen atom, a cyano group, or an aryloxy group having 6 to 20 carbon atoms in which a nitro group is substituted or unsubstituted, and R ₉ is hydrogen, an alkyl group having 1 to 16 carbon atoms, or a hydroxyl group. 9. The composition of claim 8, wherein the ultraviolet barrier monomer represented by Formula 1 is 2- (2'-hydroxy-5'-methacryloxyethylphenyl) -2H-benzotriazole, benzophenone, aryl ester, Rides, and the like. The back sheet for a photovoltaic module according to claim 1, wherein the tacky polymer is a polymer of a monomer mixture comprising a (meth) acrylic acid ester monomer and a crosslinkable monomer as polymerized units. The adhesive polymer of claim 1, wherein the adhesive polymer comprises 80 to 99 parts by weight of (meth) acrylic acid ester monomer units; 1 to 10 parts by weight of a crosslinkable monomer; And 1 to 10 parts by weight of an ultraviolet light blocking monomer unit, wherein the polymer is a polymer of a monomer mixture. The back sheet for a photovoltaic module according to claim 1, wherein the pressure-sensitive adhesive layer further comprises a crosslinking agent for crosslinking the pressure-sensitive adhesive polymer. The back sheet according to claim 12, wherein the crosslinking agent is at least one selected from the group consisting of an isocyanate compound, an epoxy compound, an aziridine compound and a metal chelate compound. The backsheet for a photovoltaic module according to claim 12, wherein the pressure-sensitive adhesive layer comprises 0.01 to 5 parts by weight of a crosslinking agent relative to 100 parts by weight of the pressure-sensitive adhesive polymer. The back sheet for a photovoltaic module according to claim 1, wherein the thickness of the pressure-sensitive adhesive layer is in the range of 1 탆 to 100 탆. delete A process for producing a back sheet for a photovoltaic module according to claim 1, comprising coating a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive polymer containing a UV-blocking monomer as a polymerization unit on one surface or both surfaces of the substrate layer. A front substrate; A photovoltaic module comprising: a back sheet for a photovoltaic module according to claim 1; and at least two photovoltaic cells disposed between the front substrate and the back sheet and spaced apart from each other.

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