KR20160025244A - Back sheet - Google Patents

Abstract

The present application relates to a back sheet and a photovoltaic cell module comprising the same. According to the present application, the back sheet can transmit light, having an infrared wavelength range, among light entering the photovoltaic cell module to minimize heat energy stored in the back sheet. Simultaneously, on an area wherein the light is not transmitted, light, having wavelength ranges of visible light and a near infrared ray, is reflected, and the photovoltaic cell module receives the reflected re-incident light to improve photoelectric conversion efficiency thereof. The back sheet comprises: a multi-layered body including a substrate layer and a surface layer; and a patter layer including a reflective area.

Description

BACK SHEET {BACK SHEET}

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

There is a growing interest in renewable energy and clean energy due to global environmental problems and depletion of fossil fuels. Among them, photovoltaic energy is attracting attention as a representative pollution-free energy source that can solve environmental pollution problem and fossil fuel depletion problem have.

Photovoltaic (PV) solar photovoltaic (PV) technology is a device that converts solar energy into electrical energy. Since it is exposed to the external environment for a long time, various packaging for protecting the cell is carried out to manufacture the unit. 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.

Patent Documents 1 to 3 propose a back sheet for satisfying the above properties.

Patent Document 1: Korean Patent Publication No. 2013-0047696 Patent Document 2: Korean Patent Publication No. 2014-0074232 Patent Document 3: Korean Patent Publication No. 2014-0060531

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

The present application relates to backsheets.

Hereinafter, embodiments of the present application will be described in more detail with reference to the accompanying drawings. In the following description of the embodiments of the present application, a detailed description of known general functions or configurations will be 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.

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 FIG. 1, the back sheet 100 of the present application includes a laminate 110 and a pattern layer 120 present on the surface of the laminate 110.

The laminate may include a base layer and a surface layer formed on at least one surface of the base layer. For example, the laminate may be a laminate having a base layer and a two-layer structure having a surface layer formed on one surface of the base layer, and may be a three-layer laminate having a surface layer formed on both surfaces of the base layer have.

The base 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 or 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, for example, in the range of 1 탆 to 500 탆, 10 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 present application is not limited to the above-mentioned range, and can be suitably adjusted as necessary.

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.

In one example, the surface layer may comprise a fluororesin and an ultraviolet screening agent. Since the surface layer contains a fluororesin, it is possible to provide a back sheet excellent in physical properties such as weather resistance and durability.

As the fluororesin, various resins containing fluorine atoms known in the art can be used, and there is no particular limitation. For example, the fluororesin may be at least one 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-1,3-dioxolane (PMD) in the form of a polymer, in the form of a polymer, a copolymer or a mixture thereof, , remind Small resin homopolymer or a copolymer comprising vinylidene fluoride (VDF) in a polymerized form; Or a mixture comprising the same.

The type of the comonomer that can be included in the copolymer in the polymerized form together with vinylidene fluoride is not particularly limited and includes, for example, tetrafluoroethylene (TFE), hexafluoropropylene (HFP) Perfluoro (methylvinylether), perfluoro (methyl vinyl ether), perfluoro (methyl vinyl ether), perfluoro (methyl vinyl ether), perfluoro Perfluoro (ethyl vinyl ether), perfluoropropyl vinyl ether (PPVE), perfluorohexyl vinyl ether (PHVE), perfluoro-2,2-dimethyl-1,3-dioxole (PDD) And perfluoro-2-methylene-4-methyl-1,3-dioxolane (PMD), and examples thereof include hexafluoropropylene and chlorotrifluoroethylene May be more than one kind , Without being limited thereto.

In one example, the fluororesin is a polyvinylidene fluoride homopolymer; Copolymers of hexafluoropropylene and polyvinylidene fluoride; And a mixture of two or more selected from chlorotrifluoroethylene and polyvinylidene fluoride copolymers, or may be a homopolymer containing vinylidene fluoride in a polymerized form as the fluororesin and a copolymer of vinylidene fluoride and hexafluoro Propylene copolymer or a mixture of vinylidene fluoride and chlorotrifluoroethylene and a copolymer of vinylidene fluoride and hexafluoropropylene may be used, but the present invention is not limited thereto.

The content of the comonomer to be contained together with vinylidene fluoride in the copolymer is not particularly limited, but may be, for example, about 0.5 to 50% by weight, 1 to 5% by weight, 40 wt%, 7 wt% 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 surface layer may be in the range of 50,000 to 100, and may be in the range of 100,000 to 700,000, or in the range of 300,000 to 50, but is not limited thereto. In the present specification, the weight average molecular weight is a conversion value of standard polystyrene measured by GPC (Gel Permeation Chromatograph). By controlling the weight average molecular weight of the fluororesin within the above range, excellent solubility and other physical properties can be secured.

If the ultraviolet ray blocking agent is a substance having a transmittance of 1% or less with respect to light having a wavelength of 400 nm or less, various ultraviolet ray blocking agents well known in the art can be used. Examples thereof include benzophenone based compounds, benzotriazole based compounds, Compounds or oxalic acid aniline compounds may be used, but are not limited thereto.

The content of the ultraviolet screening agent is not particularly limited and may be, for example, 10 parts by weight to 30 parts by weight, 12 parts by weight to 30 parts by weight, 14 parts by weight to 30 parts by weight, 15 parts by weight To 30 parts by weight. By controlling the content of the ultraviolet screening agent within the above-described range, it is possible to provide a back sheet having desired physical properties including ultraviolet shielding ability.

In one example, the surface layer may also comprise a fluororesin and an infrared-transparent colored pigment.

The content of the fluororesin is as described above, and the infrared-transparent colored pigment is a pigment having a property capable of transmitting infrared rays, and is not particularly limited as long as it is an infrared-transparent colored pigment. For example, Black pigments can be used.

The infrared-transmitting black pigment is not particularly limited as long as it is an organic pigment having a transmittance of 30% or more to light having a wavelength of 800 nm or more, and various black pigments known in the art can be used. For example, the infrared black organic pigment may be at least one compound selected from the group consisting of an azomethine compound and a perylene compound, but is not limited thereto.

The azomethine compound may include, for example, a compound represented by the following formula (1).

[Chemical Formula 1]

In the formula (1), R ₁ to R ₅ each independently represent an alkyl group or an alkoxy group having 1 to 16 carbon atoms, and each of X ₁ to X ₄ independently represents hydrogen or halogen.

The above-mentioned perylene-based compound may include compounds represented by the following formulas (2) to (4).

(2)

In the general formula (2), R ₆ and R ₇ each independently represent an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms, an alkoxyalkyl group having 1 to 40 carbon atoms, an aryl group having 1 to 40 carbon atoms, Lt; / RTI >

(3)

[Chemical Formula 4]

In the above Formulas 3 and 4, R ₈ To R ₁₁ each independently represent an alkyl group having 1 to 24 carbon atoms or an alkoxy group having 1 to 24 carbon atoms, an aryl group having 1 to 40 carbon atoms, an arylalkyl group having 1 to 40 carbon atoms, a phenylene group having 1 to 20 carbon atoms, or -AR ₁₂ , wherein A represents an arylene group having 1 to 20 carbon atoms, and R ₁₂ represents hydrogen, a hydroxyl group, a halogen, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group.

In one example, R ₈ To R ₁₁ each independently represent a phenylene group, a 3-methoxyphenylene group, a 4-methoxyphenylene group, a 4-ethoxyphenylene group, an alkylphenylene group having 1 to 3 carbon atoms, a hydroxyphenylene group, -Dimethylphenylene group, 3-chlorophenylene group, 4-chlorophenylene group, 5-chlorophenylene group, 3-bromophenylene group, 4-bromophenylene group, 5- And examples thereof include a methoxy group, an ethoxy group, an ethoxy group, an ethoxy group, an ethoxy group, an ethoxy group, an ethoxy group, Methyl-2,3-pyridinediyl group, 5-methyl-2,3-pyridinediyl group, 4-methyl-2,3-pyridinediyl group, -Methoxy-2,3-pyridinediyl group or a 4-chloro-2,3-pyridinediyl group, but is not limited thereto.

The content of the infrared transparent black organic pigment may be in the range of 5 to 15 parts by weight, 7 to 13 parts by weight, 10 to 14 parts by weight or 9 to 12 parts by weight based on 100 parts by weight of the fluororesin, It is possible to provide a back sheet that satisfies physical properties including excellent infrared transmittance of the laminate by controlling the content of the black organic pigment.

The surface layer according to the present application may further comprise conventional components such as ultraviolet stabilizers, heat stabilizers or barrier particles.

In one example, the surface layer may be a coating layer. As used herein, the term " coating layer " means a layer formed by a coating method. More specifically, the term " coating layer " in this specification includes the layer formed by laminating the surface layer with a base material layer using an adhesive or the like, and the layer formed by the coating method, for example, May mean a layer formed by directly coating a coating liquid on a substrate layer.

The thickness of the surface layer may be in the range of 1 탆 to 30 탆, 5 탆 or less, or more preferably 5 탆 or less, by realizing a transmittance and / or a reflectance and a coloring effect of a proper visible light and / or infrared light through cooperation with an ultraviolet shielding agent or an infrared- Mu] m to 25 [mu] m, or 10 [mu] m to 20 [mu] m.

The laminate of the present application including the base layer and the surface layer described above has an excellent infrared ray transmittance and accordingly transmits light in the infrared region so that when heat is accumulated in the photovoltaic module by the light in the infrared region, The problem of the temperature rise of the semiconductor device can be solved.

The above-mentioned laminate can exhibit the above-described effects because of its excellent transmittance to light having a wavelength of 700 nm or more, 800 nm or more, or 900 nm or more. For example, the transmittance of the laminate may be 20% or more, 30% or more, 40% or more, 50% or less, Or more, 60% or more, or 80% or more.

The laminate of the present application can have a transmittance in the infrared region, for example, the light of the above-mentioned wavelength, in the above-described range, thereby preventing the heat storage phenomenon when applied to a photovoltaic module.

The backsheet of the present application may include the above-described laminate and a pattern layer including a reflection region existing on the surface of the laminate.

As used herein, the term " pattern layer present on the surface of the laminate " may refer to a layer formed only on a part of the surface of the laminate, and the " pattern layer including the reflection area " And the pattern layer may be referred to as a " reflective layer " or " white pattern layer " since it has the property of reflecting as described below and is white in appearance including a white pigment.

The pattern layer including the reflection region reflects light in the wavelength region, for example, visible light region and near-infrared region, when the wavelength region transmitted through the cell is regarded as a reflection region. The sheet may include the pattern layer so that the light reflected from the pattern layer can be incident on the photovoltaic cell again, thereby improving the photoelectric conversion efficiency of the photovoltaic module.

In one example, the reflection region has a reflectance of 40% or more with respect to light having a wavelength of 400 nm to 1300 nm, and an upper limit with respect to the reflectance is not particularly limited. However, for example, when the reflectance with respect to light having the above- , 60% or more, 70% or more, 80% or more, or 90% or more. The wavelength of 400 nm to 1300 nm corresponds to the light in the visible ray to the near-infrared ray region, and is a wavelength of light transmitted through a photovoltaic cell typically used in a photovoltaic module, in particular, an n-type photovoltaic cell. The back sheet of the present application has a structure capable of re-entering the photovoltaic cell by reflecting the light in the wavelength region transmitted through the cell by the pattern layer including the reflection region, thereby increasing the photoelectric conversion efficiency .

The pattern layer may include the above-described fluororesin in consideration of physical properties such as weather resistance of the back sheet, and may further include a white pigment in consideration of physical properties such as reflectance.

When the white pigment is a material having a reflectance of 40% or more with respect to light having a wavelength of 400 nm to 1300 nm, various white pigments known in the art can be selected and used. For example, titanium dioxide, barium sulfate, barium titanate _At least one selected from the group consisting of strontium titanate (SrTiO ₃ ), calcium titanate (CaTiO ₃ ), calcium carbonate, lead titanate (PbTiO ₃ ), zinc oxide, zinc sulfide, magnesium oxide, But are not limited thereto.

The pattern layer may be formed, for example, spaced apart from a part of the surface of the laminate. Means that the pattern layer is formed so as not to cover the entire surface area, and the pattern layer is regularly or irregularly formed only on a part of the surface of the layer, And may be formed in a protruded shape.

2, the back sheet according to the present invention has a structure in which, when the area formed by the space between the photovoltaic cells 300 spaced apart from the photovoltaic module is projected onto the back sheet, The pattern layer 120 may be formed in a region where the photonic device 300 is formed, and a pattern layer may not be formed under the photovoltaic cell 300.

3 is a diagram schematically showing a plan view of a back sheet according to the present application. As shown in FIG. 3, the surface 120A of the pattern layer and the surface of the layered body without the pattern layer may have a sea island pattern. Refers to a shape in which any one of the surface of the pattern layer and the surface of the layered body in which the pattern layer is not present is surrounded by another surface forming the sea. In this case, the shape of the surface forming the image may include various shapes such as circular, elliptical, rectangular, triangular, and amorphous. 3 is a diagram exemplifying a state in which the surface on which the pattern layer is not formed is surrounded by the surface of the pattern layer in the sea while forming a rectangular figure. In the case where the surface of the pattern layer and the surface of the layer without the pattern layer have a sea-island shape as described above, the width of the surface of the pattern layer or the surface of the layer without the pattern layer, 3, the range of W, or the interval between phases, for example, the range of I in FIG. 3 is not particularly limited, and can be appropriately selected in consideration of, for example, the interval of the photovoltaic cells included in the photovoltaic module.

In one example, the spacing I between the reflective areas of the islands can be adjusted within a range of about 0.5 cm to about 10 cm, about 1 cm to about 7.5 cm, or about 1.5 cm to about 5 cm, W) can be adjusted in the range of about 3 cm to 25 cm. The shape, area, width, and spacing of the optical path are not necessarily regular, and may be appropriately adjusted in consideration of the interval of the photovoltaic cell when the photovoltaic module is applied.

The thickness of the pattern layer may be suitably formed in consideration of the reflectance for the light having a wavelength of 400 to 1300 nm, and is not particularly limited. For example, the thickness of the pattern layer may be 1 탆 to 20 탆, 2.5 탆 to 17.5 탆 Or in the range of 5 탆 to 15 탆.

The total area of the pattern layer may account for 10% to 95%, 25% to 90%, or 50% to 85% of the total area of the surface of the laminate. By controlling the total area of the surface of the pattern layer to fall within the above range, it is possible to reflect enough light to obtain the desired level of photoelectric conversion efficiency.

The backsheet of the present application may further comprise various functional layers known in the art as needed.

Examples of the functional layer include an adhesive layer or an insulating layer. In the backsheet according to one embodiment of the present invention, a surface layer containing the above-mentioned fluororesin may be formed on one surface of the substrate layer, and an adhesive layer and 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 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) serves not only to function as an insulating layer but also to increase the adhesive force between the encapsulant of the photovoltaic module and the manufacturing cost, re-workability can be performed at the same time.

The present application also relates to photovoltaic modules.

4 is a diagram schematically showing a cross section of a photovoltaic module including a back sheet according to the present application.

In one example, the photovoltaic module comprises a front substrate 400; The back sheet 100 includes the back sheet 100 and two or more photovoltaic cells 300 disposed between the front substrate 400 and the back sheet 100 and spaced apart from each other. The layer 120 may be spaced between the spaced photovoltaic cells 300.

The photovoltaic module of the present application includes the above-described backsheet. As shown in FIG. 4A, the photovoltaic module of the present application transmits light having a wavelength of an infrared region incident on a photovoltaic cell included in the back sheet, By reflecting light having a wavelength in the region of light and near infrared rays, it is possible to re-enter the reflected light photovoltaic cell to increase photoelectric conversion efficiency.

In one example, the width of the pattern layer may be wider than or equal to the spacing between the photovoltaic cells. It is possible to provide a photovoltaic module capable of increasing the photoelectric conversion efficiency by increasing the reflection efficiency for light having a wavelength in the visible light region and the near infrared region by adjusting the width of the pattern layer to the above-mentioned magnitude.

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 . Also, the photovoltaic cell may be an n-type cell or a p-type cell, but is not limited thereto.

The back sheet according to the present invention can minimize the energy stored in the back sheet by transmitting the light having the wavelength in the infrared region through the photovoltaic cell among the light entering the photovoltaic module and at the same time, It is possible to provide a photovoltaic module capable of increasing the photoelectric conversion efficiency of the photovoltaic module by reflecting the light having a wavelength in the visible region and the near infrared region as the region and then re-entering the reflected light into the photovoltaic cell.

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.
2 is a diagram specifically showing a structure of a back sheet according to the present application including a photovoltaic cell.
3 is a diagram schematically showing a plan view of a back sheet according to the present application.
4 is a diagram schematically showing a cross section of a photovoltaic module including a back sheet according to the present application.
5 is a graph showing the transmittance of the back sheet or photovoltaic module measured in Examples and Comparative Examples of the present application.
6 is a graph showing the reflectance of the back sheet or photovoltaic module measured in Examples and Comparative Examples of the present application.

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

The transmittance and the reflectance of the manufactured photovoltaic module of the present application were measured under the following conditions

1. Measurement of transmittance

The coated sample was made into a sample of about 5 cm x 5 cm and the transmittance was measured using a UV-Vis-NIR spectrometer (UV-3600, manufactured by Shimadzu) equipped with an integrating sphere type detector. , The transmittance was measured after comparing the transmittance of the prepared sample with that of the sample measured in a vacuum state.

2. Measurement of reflectance

The coated samples were made into specimens of about 5 cm x 5 cm and the reflectance was measured using a UV-Vis-NIR spectrometer (UV-3600, Shimadzu) equipped with an integrating sphere type detector. The reflectance of the barium sulfate pellets Was set at a reflectance of 100%. Then, the prepared specimen was placed in a sample measuring section, and light reflection with the barium sulfate pellet was compared to measure the reflectance.

≪ Preparation of coating liquid &

Manufacturing example  One

(Vinylidene fluoride (VDF) and chlorotrifluoroethylene (CTFE) in a weight ratio of 85:15 (VDF: CTFE) to 800 g of N, N-dimethyl formamide (DMF) , And a copolymer comprising a polymer (vinylidene fluoride and hexafluoropropylene) polymerized in a weight ratio of 88:12 (VDF: HFP) ) Was dissolved to prepare a first coating solution. 2 parts by weight of 'Tinuvin 531' as an ultraviolet screening agent was added to the first coating solution and stirred to prepare a coating solution (A).

Manufacturing example  2

(Vinylidene fluoride (VDF) and chlorotrifluoroethylene (CTFE) in a weight ratio of 85:15 (VDF: CTFE) to 800 g of N, N-dimethyl formamide (DMF) , And a copolymer comprising a polymer (vinylidene fluoride and hexafluoropropylene) polymerized in a weight ratio of 88:12 (VDF: HFP) ) Was dissolved to prepare a first coating solution. Separately from the above, 3 g of BYK 161 (manufactured by BYK) as a pigment dispersant and 30 g of an azomethine compound (chromofine black A1103, dainichiseika color & chemicals MFD) as an infrared transparent black pigment were dissolved in 200 g of DMF, 100 g of zirconia bead was added and stirred at 1,000 rpm for 1 hour. Then, the beads were completely removed to prepare 155.3 g of a mill base dispersion. 155.3 g of the obtained mill base dispersion (containing 20 g of azomethine pigment) was added to the previously prepared first coating solution and stirred for about 1 hour to prepare a coating solution (B).

Manufacturing example  3

(Vinylidene fluoride (VDF) and chlorotrifluoroethylene (CTFE) in a weight ratio of 85:15 (VDF: CTFE) to 800 g of N, N-dimethyl formamide (DMF) , And a copolymer comprising a polymer (vinylidene fluoride and hexafluoropropylene) polymerized in a weight ratio of 88:12 (VDF: HFP) ) Was dissolved to prepare a first coating solution. Separately, 1.2 g of BYK 111 (manufactured by BYK) and 120 g of titanium dioxide (TiPure TS6200, produced by DuPont) were dissolved in 120 g of DMF, and 100 g of zirconia bead having a diameter of 0.3 mm was further added thereto The mixture was stirred at 1,000 rpm for 1 hour, and then the beads were completely removed to obtain 241.2 g of a mill base dispersion. 241.2 g of the mill base dispersion liquid (containing 120 g of titanium dioxide) was added to the previously prepared first coating liquid and stirred for another 1 hour to prepare a coating liquid (C).

< Back sheet  And photovoltaic module &

Example  One.

The coating liquid composition (A) prepared in Preparation Example 1 was coated on one surface of a PET (poly (ethylene terephthalate)) film (thickness: 250 탆) and dried to form a uniform surface layer having a thickness of 10 탆, Mu] m. Thereafter, a pattern layer having a thickness of 5 탆 and a width of 5 cm was formed on one surface of the laminate by a gravure coating method using the coating liquid composition (C) to prepare a back sheet. The transmittance and the reflectance of a portion of the back sheet which does not have a pattern layer including a reflection region were measured and shown in Table 1 below. The reflectance of a portion of the back sheet including the reflection region was measured, Table 2 shows the results. 5 and 6 are graphs showing transmittance and reflectance of a portion of the back sheet without a pattern layer including a reflection region, respectively.

A silicon wafer photovoltaic cell, a sealing material having a thickness of 500 mu m, and a back sheet prepared above were laminated in this order and laminated in a vacuum laminator at 150 DEG C for 15 minutes and 30 minutes, Lt; / RTI &gt; for 2 seconds to fabricate a photovoltaic module.

Example  2.

A back sheet and a photovoltaic cell were produced in the same manner as in Example 1, except that a surface layer was formed on one side of the PET film using the coating liquid composition (A) and a surface layer was formed using the coating liquid composition (B) Module. The transmittance and the reflectance of a portion of the back sheet which does not have a pattern layer including a reflection region were measured and shown in Table 1 below. The reflectance of a portion of the back sheet including the reflection region was measured, Table 2 shows the results. 5 and 6 are graphs showing transmittance and reflectance of a portion of the back sheet without a pattern layer including a reflection region, respectively.

Example  3.

A back sheet and a photovoltaic module were produced in the same manner as in Example 1, except that a surface layer was formed on one side of the PET film using the coating liquid composition (B). The transmittance and the reflectance of a portion of the back sheet which does not have a pattern layer including a reflection region were measured and shown in Table 1 below. The reflectance of a portion of the back sheet including the reflection region was measured, Table 2 shows the results. 5 and 6 are graphs showing transmittance and reflectance of a portion of the back sheet without a pattern layer including a reflection region, respectively.

Example  4.

A back sheet and a photovoltaic module were produced in the same manner as in Example 1, except that the surface layer was formed on both surfaces of the PET film using the coating liquid composition (B). The transmittance and the reflectance of a portion of the back sheet which does not have a pattern layer including a reflection region were measured and shown in Table 1 below. The reflectance of a portion of the back sheet including the reflection region was measured, Table 2 shows the results. 5 and 6 are graphs showing transmittance and reflectance of a portion of the back sheet without a pattern layer including a reflection region, respectively.

Comparative Example  One.

The coating liquid composition (C) prepared in Preparation Example 3 was coated on one surface of a PET film (thickness: 250 탆) and dried to form a uniform surface layer having a thickness of 10 탆 to prepare a back sheet having a thickness of 260 탆 Respectively. The transmittance and the reflectance of a portion of the back sheet which does not have a pattern layer including a reflection region were measured and shown in Table 1 below. The reflectance of a portion of the back sheet including the reflection region was measured, Table 2 shows the results. 5 and 6 are graphs showing transmittance and reflectance of a portion of the back sheet without a pattern layer including a reflection region, respectively.

A silicon wafer photovoltaic cell, a sealing material having a thickness of 500 mu m, and a back sheet prepared in this order were laminated in this order and laminated in a vacuum laminator at 150 DEG C for 15 minutes And pressed for 30 seconds to fabricate a photovoltaic module.

division Transmittance (%) of a portion without a pattern layer including a reflection region The reflectance (%) of the portion without the pattern layer including the reflection region Wavelength (nm) 500 700 900 1100 1300 500 700 900 1100 1300 Example 1 86.16 88.20 89.16 89.47 90.21 8.52 8.14 8.05 7.94 7.81 Example 2 2.10 9.44 50.70 61.56 68.17 5.95 8.86 20.23 15.45 13.03 Example 3 2.09 9.50 49.71 60.29 66.83 4.08 7.96 21.22 16.69 14.27 Example 4 0.06 1.12 30.79 43.24 52.32 4.01 7.72 31.10 23.79 19.58 Comparative Example 1 4.46 6.30 8.10 9.07 10.79 81.13 73.24 65.29 59.16 54.34

division The reflectance (%) of the portion having the pattern layer including the reflection region Wavelength (nm) 500 700 900 1100 1300 Example 1 84.44 77.72 69.64 62.86 57.49 Example 2 80.26 71.73 67.28 60.66 55.51 Example 3 80.65 71.85 67.35 60.61 55.45 Example 4 80.22 78.43 74.20 67.60 62.18 Comparative Example 1 81.13 73.24 65.29 59.16 54.34

100: back sheet
110:
111: substrate layer
120: pattern layer
120A: pattern layer surface portion
300: photovoltaic cell
400: front substrate

Claims (19)

A base layer and a surface layer formed on at least one side of the base layer, wherein the laminate has a transmittance of 20% or more with respect to light having a wavelength of 700 nm or more; And a reflective layer which is present on the surface of the laminate and has a reflectance of 40% or more with respect to light within a wavelength range of 400 nm to 1300 nm. [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 Over sheet of paper. The back sheet according to claim 1, wherein the thickness of the base layer is in the range of 1 탆 to 500 탆. The backsheet according to claim 1, wherein the surface layer comprises a fluororesin and an ultraviolet screening agent. The backsheet according to claim 4, wherein the surface layer comprises 10 to 30 parts by weight of the ultraviolet blocking agent per 100 parts by weight of the fluororesin. The backsheet according to claim 1, wherein the surface layer comprises a fluororesin and an infrared-transparent colored pigment. The back sheet according to claim 6, wherein the infrared transmitting color pigment is an infrared transmitting black pigment. 8. The backsheet of claim 7, wherein the infrared transmitting black pigment comprises at least one member selected from the group consisting of an azomethine compound and a perylene compound. The backsheet according to claim 7, wherein the surface layer comprises 5 to 15 parts by weight of an infrared ray-transparent black pigment based on 100 parts by weight of the fluororesin. The back sheet according to claim 1, wherein the surface layer has a thickness of 1 to 30 占 퐉. The back sheet according to claim 1, wherein the pattern layer comprises a fluororesin and a white pigment. The method of claim 11, wherein the white pigment is titanium dioxide, barium sulfate, barium titanate (BaTiO _3), strontium titanate (SrTiO _3), calcium titanate (CaTiO _3), calcium carbonate, lead titanate (PbTiO _3), Zinc oxide, zinc oxide, zinc oxide, magnesium oxide, or aluminum oxide. 12. The backsheet according to claim 11, wherein the pattern layer comprises 5 to 100 parts by weight of a white pigment based on 100 parts by weight of the fluororesin. The back sheet according to claim 1, wherein the total area of the pattern layer is 10% to 95% of the total area of the surface of the laminate. The back sheet according to claim 1, wherein the interval between the reflection areas is 0.5 cm to 10 cm. The back sheet according to claim 1, wherein the thickness of the pattern layer is from 1 m to 20 m. A front substrate; A photovoltaic module comprising: the back sheet of claim 1; and at least two photovoltaic cells located between the front substrate and the back sheet and spaced apart. 18. The photovoltaic module according to claim 17, wherein a reflection region of the back sheet exists in a space between the photovoltaic cells that are spaced apart from each other. 18. The photovoltaic module of claim 17, wherein the width of the white pattern layer is greater than or equal to the distance between the photovoltaic cells.

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