KR20160026107A - Back sheet - Google Patents

Abstract

The present application relates to a back sheet and a photovoltaic battery module including the same. According to the present application, the back sheet transmits light, having a wavelength range capable of transmitting a photovoltaic battery cell, among light entering the photovoltaic battery module to be able to minimize accumulated thermal energy in the back sheet. At the same time, the photovoltaic batter module reflects light, excepting an area wherein the light is transmitted and allows the photovoltaic battery cell to receive the reflected re-incident light to improve photoelectric conversion efficiency of the photovoltaic battery module. The back sheet comprises: a multi-layered body wherein a substrate body is formed on one surface thereof; and a reflective layer only formed on a portion of the multi-layered body.

Description

BACK SHEET {BACK SHEET}

Embodiments of the present application relate 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.

Generally, the photovoltaic module uses a back sheet having excellent weather resistance and durability so that the photovoltaic cell can be stably protected even when exposed to the external environment for a long period of time. Such a backsheet generally includes a backsheet on which a resin layer containing a fluorine-based polymer such as PVF (polyvinyl fluoride) is laminated.

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

The present application provides a backsheet. The back sheet according to the embodiments of the present application can minimize the energy stored in the back sheet by transmitting the light having the wavelength of the area band penetrating the photovoltaic cell among the light introduced into the photovoltaic module, And the reflected light is re-incident on the photovoltaic cell, thereby improving the photoelectric conversion efficiency of the photovoltaic module. 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 invention 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 exemplarily showing a cross section of a back sheet according to an embodiment of 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 reflective layer 120 formed only on a part of the surface of the laminate 110. As used herein, the term " laminate " means a sheet or film-like structure having a structure in which two or more layers are laminated. In the present specification, the term " multilayer film " For example, the laminate 110 includes a structure in which a base layer 111 and a surface layer 112 are laminated. In one example, the laminate 110 includes a base layer 111, And a surface layer 112 formed on at least one surface of the substrate 111. For example, the laminate 110 may be a laminate 110 having a two-layer structure in which a base layer 111 and a surface layer 112 are laminated on one surface of the base layer 111, (110) having a three-layer structure in which the surface layer (112) is laminated on both surfaces of the substrate (111).

The specific type of the base layer 111 included in the laminate 110 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.

In one example of the present invention, the base layer 111 may be a polymer film. Examples of the polymer film include 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 films, or a pneumatic article. For example, it is common to use a polyester film, but the present invention is not limited thereto. Examples of the polyester film include at least one film 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.

The polyester film may be one having excellent water-decomposing properties, or may be produced by using a film having excellent water-decomposing properties or may be a commercially available product. 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.

In order to further improve the adhesion of the surface layer 112 described above, a spark discharge treatment of high frequency, such as corona treatment or plasma treatment, is applied to one side or both sides of the base layer 111; Heat treatment; Flame treatment; Anchor treatment; Coupling agent treatment; Surface treatment such as primer treatment or chemical activation treatment using gaseous Lewis acid (ex. BF ₃ ), sulfuric acid or high temperature sodium hydroxide can be performed. The surface treatment method may be performed by any known means generally used in this field.

In addition, the substrate according to the embodiments of the present invention may be provided with an inorganic oxide deposited layer on one side or both sides of the substrate, from the viewpoint of further improvement of 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 deposition layer on one side or both sides of the base layer 111 is not particularly limited and may be a deposition method generally used in this field. As described above, in one embodiment of the present invention, when an inorganic oxide deposit layer is formed on one surface or both surfaces of the substrate layer 111, an inorganic oxide deposit layer is formed on the surface of the substrate layer 111, Surface treatment may be performed. That is, in one embodiment of the present invention, the spark discharge treatment, the flame treatment, the coupling agent treatment, the anchorage treatment or the chemical activation treatment described above are performed to further improve the adhesive force on the vapor deposition layer formed on the base layer 111 .

The thickness of the base layer 111 is not particularly limited and may be, for example, in the range of about 30 탆 to 500 탆 or about 50 탆 to 300 탆. By adjusting the thickness of the base layer 111 to the same range as described above, it is possible to improve the electrical insulating property, moisture barrier property, mechanical properties, handling property, and the like of the multilayer film. However, the thickness of the substrate according to the embodiments of the present invention is not limited to the above-mentioned range, and it can be suitably adjusted as required.

In one example, the surface layer 112 comprises a fluororesin. By including the fluororesin in the surface layer 112, the present application can provide the back sheet 100 having improved 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 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 surface layer 112 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 50,000, 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). In the embodiments of the present invention, 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 thickness of the surface layer 112 containing the fluororesin is not particularly limited and may be, for example, 1 탆 to 50 탆, or 5 탆 to 30 탆. The ultraviolet transmittance of the laminate 110 can be improved by controlling the thickness of the surface layer 112 containing the fluororesin to the above range and the increase of the manufacturing cost can be prevented.

The laminate 110 including the base layer 111 and the surface layer 112 has an excellent infrared ray transmittance so that the light in the infrared ray region is transmitted, It is possible to solve the problem that the temperature of the module rises.

The laminate 110 may have a wavelength of 700 nm or more, for example, 710 nm or more, 750 nm or more, 800 nm or more, 900 nm or more, 1000 nm or more, 1100 nm or more, 1200 nm or more or 1300 nm or more The transmittance for light having a wavelength may be 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, or 80% or more. The laminate 110 according to the embodiment of the present application can have a transmittance in the infrared region, for example, light of the above-mentioned wavelength, in the above-described range, thereby preventing heat accumulation in the photovoltaic module .

In order to satisfy the above transmittance, the base layer 111 having transparency can be used as the base layer 111 of the laminate 110 of the present application. For example, the transmittance of the base layer 111 may be 80% or more, 90% or 95% or more with respect to light having a wavelength of 300 nm or more. For example, the polymer film described above may be used.

In addition, in one example, the surface layer 112 may comprise an infrared-transparent colored organic pigment or a UV-blocking agent.

For example, when the surface layer 112 includes an ultraviolet screening agent, the layered body 110 may transmit visible light and infrared light except for ultraviolet rays. If the ultraviolet screening agent is a substance having a transmittance of 1% or less with respect to light having a wavelength of 350 nm or less, various ultraviolet screening agents known in the art may be used. For example, benzophenone ultraviolet screening agents, benzotriazole ultraviolet screening agents , Triazine ultraviolet ray blocking agents or oxalic acid aniline ultraviolet ray blocking agents may be used, but are not limited thereto. When the surface layer 112 contains an ultraviolet screening agent, the content of the ultraviolet screening agent is 0.1 to 30 parts by weight, for example, 0.5 to 20 parts by weight, 1 to 18 parts by weight, 15 parts by weight. By controlling the content of the ultraviolet screening agent within the above-described range, transparency of the laminate 110 can be ensured, and thus the laminate 110 of the present application can exhibit excellent infrared ray transmittance. Unless otherwise specified, parts by weight in this specification means parts by weight.

On the other hand, the surface layer 112 may include an infrared-transparent colored organic pigment. The infrared-transparent colored organic pigment is an organic pigment having a property of transmitting infrared rays, and is not particularly limited as long as it is an infrared-transparent colored pigment. For example, an infrared-transparent black organic pigment can be used. The infrared transparent black organic pigment is not particularly limited as long as it is an organic pigment having a transmittance of 30% or more with respect to light having a wavelength of 800 nm or more, and various black pigments known in the art may be added to the back sheet 100 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 infrared transparent black organic pigment is contained in an amount of 1 to 20 parts by weight, for example, 5 to 15 parts by weight, 7 to 13 parts by weight, 10 to 14 parts by weight, and 9 to 12 parts by weight based on 100 parts by weight of the fluororesin By controlling the content of the black organic pigment within the above range, excellent infrared transmittance of the laminate 110 can be secured.

The surface layer 112 according to embodiments of the present application may further comprise conventional components such as ultraviolet stabilizers, thermal stabilizers, or barrier particles.

In one example, the surface layer 112 may be a coating layer. As used herein, the term " coating layer " means a resin layer formed by a coating method. More specifically, the " coating layer " is a layer in which the surface layer 112 containing the above-mentioned fluororesin is not laminated by using a casting method or a sheet produced by the extrusion method to the base layer 111 using an adhesive or the like , And a solvent, for example, a coating solution prepared by dissolving a component constituting the resin layer in a solvent having a low boiling point, is coated on the substrate.

The surface layer 112 may be manufactured by a method of laminating a sheet prepared by a casting method or an extrusion method to a base layer 111 using an adhesive or the like.

The backsheet 100 according to embodiments of the present application may further include various functional layers as is known in the art, if desired. Examples of the functional layer include an adhesive layer or an insulating layer. In the back sheet 100 according to one embodiment of the present invention, the surface layer 112 including the above-described fluororesin is formed on one surface of the base layer 111, and the adhesive layer and the insulating layer are sequentially formed on the other surface As shown in FIG. 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 back sheet 100 of the present application also includes the above-described laminate 110 and a reflective layer 120 formed only on a part of the surface of the laminate 110, as shown in Fig. The reflective layer 120 is a layer that reflects light in a wavelength region transmitted through the cell, for example, an ultraviolet region and a near-infrared region. The back sheet 100 of the present application includes the reflective layer 120 Thus, the light reflected from the reflective layer 120 can be incident on the photovoltaic cell again, thereby improving the photoelectric conversion efficiency of the photovoltaic module.

In one example, the reflective layer 120 has a reflectance of 40% or more for light having a wavelength of 400 to 1300 nm. For example, the reflective layer 120 may reflect light having a wavelength of 400 to 1300 nm , 50% or more, 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 light region to the near-infrared region, and the wavelength of light transmitted through the photovoltaic cell 200, particularly the n-type photovoltaic cell 200, to be. The back sheet 100 of the present application can re-enter the photovoltaic cell 200 by reflecting the light of a wavelength transmitted through the cell by the reflective layer 120, thereby increasing the photoelectric conversion efficiency.

The reflective layer 120 includes a fluororesin in consideration of the weatherability of the back sheet 100 and may include a white pigment in order to satisfy the reflectance in the above-mentioned range.

If 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, zinc oxide, silver white, But are not limited to, zinc sulfide, antimony oxide, lithopone, calcined kaolins, calcium carbonate, white lead, or barium sulfate.

1, the reflective layer 120 may be formed only on a part of the surface of the layered body 110 described above. The reflective layer 120 is formed only on a part of the surface of the layer 110 so that the reflective layer 120 is formed on the surface of the layer 110 Or may be formed in a protruding shape on the surface of the substrate.

The surface of the reflection layer 120 existing only on the surface of the layered product 110 and the surface of the layered product 110 on which the reflection layer 120 is not present (hereinafter referred to as a non-reflective layer surface) sea island pattern). 2 is an exemplary plan view of the backsheet 100 of the present application. The sea-island shape in this case means a shape in which any one of the surface 120A and the non-reflecting layer surface 112A of the reflective layer is surrounded by another surface forming a sea. In this case, the shape of the surface forming the image may include various shapes such as a circle, an ellipse, a rectangle, a triangle, and an amorphous shape, and preferably a rectangular shape. 2 is a diagram exemplarily showing a state in which the non-reflecting layer surface 112A is surrounded by the reflecting layer surface 120A in the sea while being formed into a rectangular figure shape. In the case where the reflective layer surface 120A and the non-reflective layer surface 112A have a sea-island shape as described above, the width of the reflective layer surface 120A or the interval between the island- 2, the range of I in FIG. 2 is not particularly limited, and may be selected in consideration of, for example, the spacing of the photovoltaic cells 200 included in the photovoltaic module. In one example, the spacing between the marine reflective layer surfaces 120A or the width I of the non-reflective layer surface 112A may be adjusted within a range of about 5 to 20 cm, and the width of the reflective layer surface 120A W can be adjusted in the range of about 1 to 10 cm. In the above, the shape, area, width and interval of the image are not necessarily regular, but may be adjusted differently.

The thickness of the reflective layer 120 may be adjusted within a range of 0.5 to 20 占 퐉 in consideration of the range of reflectance of the reflective layer 120 with respect to light having a wavelength of 400 to 1300 nm, no.

The total area of the reflective layer surface 120A may occupy 1 to 50% of the total area of the surface of the laminate 110. The total area of the non-reflective layer surface 112A may range from ~ Lt; / RTI > By controlling the total area of the reflective layer surface 120A within the above range, it is possible to reflect enough light to obtain the desired photoelectric conversion efficiency.

Another embodiment of the present application provides a photovoltaic module. 3 is a cross-sectional view of an exemplary photovoltaic module of the present application, and Fig. 4 is an exemplary top view of the photovoltaic module.

In one example, as shown in FIG. 3, the photovoltaic module includes a front substrate 400; The back sheet 100 described above and two or more photovoltaic cells 200 disposed between the front substrate 400 and the back sheet 100 and spaced from each other are shown in FIGS. 3 and 4 As described above, the reflection layer 120 of the back sheet 100 may exist in the interval between the photovoltaic cells 200 that are spaced apart from each other. Quot; exists in the space between the photovoltaic cells 200 spaced apart " in the above description means that when the area formed by the spacing between the photovoltaic cells 200 spaced apart from each other is projected onto the back sheet 100, A region formed on the surface of the back sheet 100 is included in a region where the reflective layer 120 is present. As shown in FIG. 4, when the photovoltaic module is viewed from above, The reflective layer 120 is formed such that only the surface 120A is observed.

In one example, the width of the reflective layer 120 may be greater than or equal to the spacing between the photovoltaic cells 200, and preferably the width of the reflective layer 120 is greater than the width of the photovoltaic cells 200 May be 100 to 150% wider than the spacing.

The photovoltaic module of the present application may appear white due to the presence of the reflective layer 120 in the space between the photovoltaic cells 200 spaced apart from each other. "Appearance of white color in appearance" means that when the photovoltaic module is observed from above, the portion where the back sheet 100 is visible, that is, the space between the cell and the cell is observed as white.

In one example, the back sheet 100 included in the photovoltaic module has a lightness L ₁ * of 1 to 50 in a region where the reflective layer 120 is not present on the surface of the layer 110, ) May have a brightness L ₂ * of 50 to 99 in a region where the reflective layer 120 is present on the surface. For example, the back sheet 100 has a region where the reflective layer 120 does not exist, that is, a surface layer 112 in the region where the area occupied by the photovoltaic cell 200 is projected onto the back sheet 100 The lightness L ₁ * of the portion exposed to the outside may be 1 to 50, for example, 10 to 40 or 20 to 30, and the brightness L of the region where the reflective layer 120 exists in the surface of the layered body 110 ₂ * may be from 50 to 99, for example from 60 to 98, from 70 to 95 or from 90 to 95.

According to the photovoltaic module of the present application, it is possible to minimize the energy stored in the back sheet 100 by transmitting the infrared region, that is, the wavelength of 700 nm or more, transmitted through the cell, and at the same time, The remaining part reflects light of a visible light and near-infrared light (L _R ), for example, a light having a wavelength of 400 nm to 1300 nm, and re-enters the reflected light into the photovoltaic cell 200, Can be increased.

3, when light is irradiated onto the photovoltaic module of the present application, the light (L _T ) in the infrared region of the irradiated light passes directly through the photovoltaic cell 200 or passes through the backsheet 100 And the light transmitted through the cell is transmitted through the back sheet 100 through the region where the reflective layer 120 does not exist and thus emitted to the outside of the photovoltaic module without accumulating heat inside the photovoltaic module . Also, some of the infrared rays may be reflected by the reflection layer 120, passed through the front substrate 400 and then emitted to the outside, or re-incident to the photovoltaic cell 200. On the other hand, the light L _{R in} the visible light and near-infrared light reaches the back sheet 100 directly, without passing through the cells or transmitting through the cells, And the light in the near-infrared region can be reflected by the reflection layer 120, reflected by the front substrate 400, and re-incident on the photovoltaic cell 200.

The specific types of the front substrate 400 and the photovoltaic cell 200 that can be used in the above are not particularly limited. For example, the front substrate 400 may be a conventional plate glass; The photovoltaic cell 200 may be a silicon wafer-type active layer or a thin film active layer formed by chemical vapor deposition (CVD) or the like, for example. The photovoltaic cell 200 may be a transparent composite sheet obtained by laminating a glass, a fluororesin- Lt; / RTI > In addition, the photovoltaic cell 200 may be an n-type cell or a p-type cell, and may be an n-type cell, but is not limited thereto.

According to the back sheet of the present application, light having a wavelength of a region that is transmitted through a photovoltaic cell can be transmitted among the light entering the photovoltaic module, thereby minimizing the energy stored in the back sheet. At the same time, The photovoltaic module according to the present invention can provide a photovoltaic module capable of increasing the photoelectric conversion efficiency of the photovoltaic module by reflecting the light in the remaining portions and re-entering the reflected light into the photovoltaic cell.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram exemplarily showing a cross section of a back sheet according to an embodiment of the present application. Fig.
Figure 2 is an exemplary top view of the backsheet of the present application.
3 is a cross-sectional view of an exemplary photovoltaic module of the present application.
4 is an exemplary top view of the photovoltaic module.
5 is a graph showing transmittance of a back sheet according to Examples and Comparative Examples of the present application.
6 is a graph showing the reflectance of the back sheet according to 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 not complying with the present application, but the scope of the present application is not limited by the following embodiments.

The transmittance and the reflectance of the back sheet prepared in Examples and Comparative Examples were measured under the following conditions.

<Measurement of transmittance>

The coated samples were cut to a size of about 5 cm x 5 cm and the transmittance was measured using a UV-Vis-NIR spectrometer equipped with an integrator-type detector. After the light measurement in the air state except for the sample was set to 100% transmittance, the cut sample was placed in the sample measurement part and the transmittance was measured by comparing the light transmission with the air state.

&Lt; Measurement of reflectance &

The coated samples were cut to about 5 cm × 5 cm and the reflectance was measured using a UV-Vis-NIR spectrometer equipped with an integrator-type detector. After setting the barium sulfate pellet to a reflectance of 100%, the cut sample was placed in the sample measuring section and the reflectance was measured by comparing the light reflection with the barium sulfate pellet.

In addition, the brightness of the back sheet prepared in the following examples and comparative examples was measured by the following method.

<Measurement of brightness>

The coated sample was cut into a piece of about 5 cm × 5 cm and the lightness was measured in a reflection mode using a spectroscopic colorimeter (CM-5, Konica Minolta) equipped with an integrator-shaped detector.

&Lt; Preparation of coating liquid composition >

Production Example 1

(Vinylidene fluoride (VDF) and chlorotrifluoro ethylene (CTFE) in a ratio of 85:15 (VDF: CTFE) to 800 g of N, N-diemtyl formamide (Copolymer containing VDF and hexafluoropropylene (HFP) in the form of a polymer in a weight ratio of 88:12 (VDF: HFP)) was added in an amount of 60 g Was previously dissolved to prepare a first coating solution.

2 parts by weight of an ultraviolet screening agent was added to the first coating liquid and stirred to prepare a transparent coating liquid composition (A).

Production Example 2

140 g of a polymer (copolymer containing VDF and CTFE in a polymerized form at a weight ratio of 85:15 (VDF: CTFE)) to 800 g of N, N-diemtyl formamide (DMF) In the form of a polymer in a weight ratio of 88:12 (VDF: HFP)) was previously dissolved to prepare a first coating solution.

Separately from the above, 3 g of BYK161 (BYK Co., Ltd.) as a pigment dispersant and 30 g of Azo methyne compound (Chromofine black A1103, Dainichiseika color & Chemicals MFD) as an infrared transparent organic pigment were dissolved in 200 g of dimethylformamide, Then, 100 g of zirconia beads having a diameter of 0.3 mm was added thereto, followed by stirring at 1,000 rpm for 1 hour. Then, the beads were completely removed to prepare 155.3 g of mill base dispersion.

155.3 g of the prepared mill base dispersion (containing 20 g of Azo methyne pigment) was added to the first coating liquid prepared beforehand and stirred for another hour to prepare a black coating liquid composition (B).

Production Example 3

140 g of a polymer (copolymer containing VDF and CTFE in a polymerized form at a weight ratio of 85:15 (VDF: CTFE)) to 800 g of N, N-diemtyl formamide (DMF) In the form of a polymer in a weight ratio of 88:12 (VDF: HFP)) was previously dissolved to prepare a first coating solution.

Separately from the above, 1.2 g of BYK161 (BYK Co., Ltd.) as a pigment dispersant and 120 g of titanium dioxide (Tipure TS6200, DuPont) were dissolved in 120 g of dimethylformamide, and then 0.3 g of zirconia 100 g of zirconia bead was added and stirred at 1,000 rpm for 1 hour. Then, the beads were completely removed to obtain 241.2 g of a mill base dispersion.

241.2 g (containing 120 g of titanium dioxide) of the mill base dispersion thus prepared was put into a first coating liquid prepared beforehand and stirred for another hour to prepare a coating liquid composition (C).

&Lt; Preparation of back sheet and photovoltaic module >

Example 1.

The transparent coating liquid composition (A) prepared in Preparation Example 1 was coated on one surface of a PET (poly (ethylene terephthalate)) film (thickness: 250 μm) and dried to form a uniform surface layer having a thickness of 10 μm, To prepare a laminate having a coating layer / PET thickness of 260 mu m. Thereafter, a coating solution composition (C) was applied to the other surface of the laminate, and a reflective layer having a pattern of the shape shown in Figs. 1 and 2 and having a thickness of 5 탆 and a width of 5 cm was formed by a gravure coating method To prepare a back sheet. The transmittance and reflectance of the prepared back sheet were measured and shown in Tables 1 and 2 below. The transmittance and the reflectance of the region (W / PET / T) where the reflection layer was present and the region (PET / T) The graphs are shown in Figures 5 and 6, respectively. In FIGS. 5 and 6, T / PET / K and W / PET / T indicate the cell side / PET / Air side, T denotes a transparent coating layer, K denotes a black coating layer and W denotes a white coating layer.

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.

Example 2.

A surface layer was formed on one surface of the PET film using the transparent coating liquid composition (A), and a surface layer was formed on the other surface using the black coating liquid composition (B) to prepare a laminate having a transparent coating layer / PET / black coating layer structure, A backsheet and a photovoltaic module were prepared in the same manner as in Example 1, except that a reflective layer was formed on the above-mentioned transparent coating layer using the coating liquid composition (C). The transmittance and the reflectance of the prepared back sheet were measured and shown in Tables 1 and 2 below. The transmittance and the transmittance of the region (W / T / PET / K) and the region (T / PET / K) The graphs of reflectance measurements are shown in Figs. 5 and 6, respectively. In addition, the brightness of the prepared back sheet was measured and shown in Table 4 below.

Example 3.

A surface layer was formed on one surface of a PET film using the black coating liquid composition (B) to prepare a laminate of a black coating layer / PET structure, and a reflective layer was formed on the other surface of the PET film using the coating liquid composition (C) , A back sheet and a photovoltaic module were produced in the same manner as in Example 1. [ The transmittance and reflectance of the prepared back sheet were measured and shown in Tables 1 and 2 below. The transmittance and the reflectance of the region (W / PET / K) where the reflection layer was present and the region (PET / K) The graphs are shown in Figures 5 and 6, respectively. In addition, the brightness of the prepared back sheet was measured and shown in Table 4 below.

Example 4.

A surface layer was formed on both sides of the PET film using the black coating liquid composition (B) to prepare a laminate having a first black coating layer / PET / second black coating layer structure, and a coating liquid composition (C) A backsheet and a photovoltaic module were produced in the same manner as in Example 1, except that a laminate was produced. The transmittance and the reflectance of the prepared back sheet were measured and shown in Tables 1 and 2 below. The transmittance and the transmittance of the region (W / K / PET / K) and the region (K / PET / K) The graphs of reflectance measurements are shown in Figs. 5 and 6, respectively. In addition, the brightness of the prepared back sheet was measured and shown in Table 4 below.

Comparative Example 1

The white coating liquid composition (C) prepared in Preparation Example 3 was coated on one surface of a PET film (thickness: 250 μm) and dried to form a uniform surface layer having a thickness of 10 μm, whereby the thickness of the white coating layer / A back sheet having a thickness of 260 mu m was produced. The transmittance and reflectance of the prepared backsheet were measured and shown in the following Table 3, and the graphs of transmittance and reflectance were shown in FIGS. 5 and 6, respectively. In addition, the brightness of the prepared back sheet was measured and shown in Table 4 below.

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.

Transmittance (%) of the portion without the reflective layer Reflectivity (%) of the portion without the reflective layer Wavelength (nm) 500 700 900 1100 1300 500 700 900 1100 1300 Example 1 86.18 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 8.83 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

Reflectivity (%) of the portion having the reflective layer 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

Transmittance (%) reflectivity(%) Wavelength (nm) 500 700 900 1100 1300 500 700 900 1100 1300 Comparative Example 1 4.46 6.30 8.10 9.07 10.79 81.13 73.24 65.29 59.16 54.34

The L L of the portion where the reflective layer exists Example 2 30.59 90.22 Example 3 24.32 90.65 Example 4 21.03 91.06 Comparative Example 1 - 89.86

As shown in FIG. 5, the light in the infrared region transmitted through the cell is transmitted through the region where the reflection layer does not exist, that is, the region of the black coating layer (PET / K, T / PET / K, PET W / PET / K, W / K / PET / K, and W / PET / K) ) White coating layer shows a low transmittance.

Further, as shown in FIG. 6, it can be confirmed that the reflectance in the white coating layer is excellent in the region other than the cell, that is, the region where the reflection layer exists.

As shown in Table 3 and FIGS. 5 and 6, the back sheet having the white coating layer / PET structure in which no pattern is formed as in the comparative example exhibits a transmittance of less than 20% in all wavelength regions and a reflectance of more than 50% .

100: back sheet
110:
111: substrate layer
112: Surface layer
112A: non-reflective layer surface
120: reflective layer
120A: Reflective layer surface
200: photovoltaic cell
300: encapsulant film
400: front substrate
L _T : Light in the infrared region
L _R : visible light and near-infrared light

Claims (17)

A base layer and a laminate formed on at least one surface of the base layer, the laminate having a surface layer including a fluororesin and having a transmittance of 20% or more with respect to light having a wavelength of 700 nm or more; And
And a reflective layer formed only on a part of the surface of the laminate and having a reflectance of 40% or more with respect to light having a wavelength of 400 nm to 1300 nm. The back sheet according to claim 1, wherein the reflective layer comprises a white pigment and a fluororesin. The white pigment according to claim 2, wherein the white pigment comprises at least one selected from the group consisting of titanium dioxide, zinc oxide, silver white, zinc sulfide, antimony oxide, lithopone, calcined kaolin, calcium carbonate, . The backsheet of claim 1, wherein the surface layer comprises an infrared-transparent colored organic pigment or an ultraviolet screening agent. The backsheet according to claim 4, wherein the surface layer comprises 0.1 to 30 parts by weight of the ultraviolet blocking agent per 100 parts by weight of the fluororesin. The back sheet according to claim 4, wherein the infrared-transparent colored organic pigment is an infrared-transparent black organic pigment. The back sheet according to claim 6, wherein the infrared transparent black organic pigment comprises at least one selected from the group consisting of an azomethine compound and a perylene compound. 5. The backsheet according to claim 4, wherein the surface layer comprises 1 to 20 parts by weight of an infrared transparent black organic pigment based on 100 parts by weight of the fluororesin. [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 A back sheet which is a polymer film or a metal film of a kind or more. The back sheet according to claim 1, wherein the base layer has a thickness of 30 to 500 탆. The back sheet according to claim 1, wherein the surface layer has a thickness of 1 to 50 탆. The back sheet according to claim 1, wherein the total area of the surface of the reflective layer is 1 to 50% of the total area of the surface of the laminate. The back sheet according to claim 1, wherein the spacing between the reflective layers is 5 to 20 cm. The backsheet of claim 1, wherein the thickness of the reflective layer is 0.5 to 20 占 퐉. A front substrate; A back sheet according to any one of claims 1 to 3, further comprising two or more photovoltaic cells disposed between the front substrate and the back sheet and spaced apart from each other, wherein the reflective layer of the back sheet exists in the space between the photovoltaic cells Photovoltaic modules. 16. The photovoltaic module according to claim 15, wherein a width of the reflective layer is wider than or equal to an interval between the photovoltaic cells. The photovoltaic module according to claim 15, wherein the back sheet has a lightness L ₁ * in a region where the reflective layer is absent is 1 to 50, and a lightness L ₂ * in the region where the reflective layer is 50 to 99.

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