KR20150037716A - Backsheet - Google Patents

Abstract

Provided are a back sheet, a manufacturing method thereof, and a photoelectric cell module. The present invention can provide a back sheet which can implement demanded black in a case that a black layer is formed thinly, blocks light of an infrared ray region which can increase the temperature of the module, prevents energy loss according to increase of the temperature, and can utilize infrared ray usable in the module to use in an element; a manufacturing method thereof; and a photoelectric cell module using the same.

Description

Backsheet {Backsheet}

The present application relates to a back sheet, a manufacturing method thereof, and a photovoltaic module.

The photovoltaic module is an eco - friendly energy source that does not emit carbon dioxide and has recently become popular in various fields.

The photovoltaic module has a structure in which elements are sandwiched between a light-receiving substrate on the side where solar light is incident and a back sheet disposed on the side opposite to the side on which sunlight is incident (back side). In the photovoltaic module, a resin such as EVA (ethylene vinyl acetate) resin is usually sealed between the light receiving substrate and the element and between the element and the back sheet.

The back sheet has a function of preventing moisture from intruding from the back surface of the photovoltaic module. Recently, a back sheet having various functions as well as a simple protection function has been developed.

For example, Patent Document 1 discloses a back sheet in which carbon black is introduced into a back sheet and the overall color feeling is changed to a black color sequence to improve the aesthetics. Carbon black absorbs light to give a black color, but the reflectance is lowered and the power generation efficiency is lowered. In addition, carbon black absorbs light in the infrared region, raises the temperature of the entire module, and also has a problem of lowering the power generation efficiency.

Patent Document 1: JP-A-2008-004839

The present application aims at providing a back sheet, a manufacturing method thereof, and a photovoltaic module. In this application, it is possible to prevent the energy loss due to the temperature increase of the module by reflecting the light of the infrared ray region which has an excellent effect on the aesthetics side by increasing the temperature of the module and can utilize the infrared rays that can be utilized in the module And a photovoltaic module using the same can be provided.

The back sheet of the present application may include a substrate layer, a black layer formed on one surface of the substrate layer, and a white layer formed on the other surface of the substrate layer. FIG. 1 is a view showing an exemplary back sheet, and shows a form in which a black layer 102, a base layer 102, and a white layer 103 are sequentially laminated.

The specific type of the substrate layer included in the backsheet is not particularly limited, and various materials known in this field can be used.

In one example, various metal sheets or polymer sheets can be used as the base layer. As the polymer sheet described above, a polyester sheet, a polyamide sheet, a polyimide sheet, or the like can be exemplified, and a polyester sheet is generally used, but the present invention is not limited thereto. As the polyester sheet, a single sheet such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC) or polybutylene terephthalate (PBT), a laminated sheet, But is not limited thereto.

The thickness of the base layer may be set in an appropriate range in consideration of the desired supporting force and the like, and may be set within a range of about 10 [mu] m to 500 [mu] m in one example. By adjusting the thickness of the base layer as described above, it is possible to maintain excellent electrical insulation, moisture barrier properties, mechanical properties and handling properties of the back sheet. However, the thickness described in the present application is not limited to the above-mentioned range, and it can be appropriately adjusted as required.

In the present application, the substrate layer is subjected to high frequency spark discharge treatment such as corona treatment or plasma treatment; Flame treatment; Coupling agent treatment; An anchoring treatment or a chemical activation treatment using a gaseous Lewis acid (ex. BF ₃ ), sulfuric acid or high temperature sodium hydroxide, or the like may be performed. Through such treatment, adhesion to other layers such as a black layer or a white layer can be enhanced.

An inorganic oxide such as silicon oxide or aluminum oxide may be deposited on the base layer from the viewpoint of further improvement of moisture barrier properties and the like. In this case, the spark discharge treatment, the flame treatment, the coupling agent treatment, the anchor treatment treatment, or the chemical activation treatment described above may be performed on the deposition treatment layer. The base sheet layer of the back sheet may also have an easy-to-adhere treatment layer such as a primer layer having an oxazoline group or the like for the purpose of improving adhesion with the above-mentioned black layer or white layer.

The back sheet of the present application includes a black layer formed on one surface of the substrate layer. In the present application, the black layer is a layer capable of adjusting the overall color tone of the back sheet to black. For example, when the L value in the CIE color coordinates of the back sheet is within the range of about 20 to 40, 2.5, and the b value is in the range of about -1 to 3.

It is important that the transmittance of the backsheet, the transmittance over a wavelength range of from about 450 nm to about 650 nm, and especially the transmittance to a wavelength of about 550 nm, is adjusted to make the overall color of the backsheet a proper black color system. The lower the transmittance for the light having the wavelength of 550 nm, the more appropriate black can be realized. In one example, in the case of the backsheet of the present application, the transmittance of the black layer may be about 0.5% or less, about 0.4% or less, about 0.3% or less, about 0.2% or less, or about 0.15% have. The lower the numerical value of the transmittance is, the more appropriate the black color is realized. The lower limit of the transmittance is not particularly limited.

The black layer may include a pigment in order to impart the black color to the back sheet and to block the infrared rays that cause the temperature rise of the module and to allow the infrared rays contributing to the power generation efficiency of the module to be recycled .

The black layer may simultaneously contain an infrared transmitting pigment and an infrared reflecting pigment as a pigment. As the infrared transmitting pigment in the present application, a pigment having a reflectance within a range of 30% to 90% with respect to light having a wavelength of 800 nm can be used. In the present application, a pigment having a maximum absorption wavelength in the range of 570 nm to 800 nm can be used as the above-mentioned pigment. The maximum absorption wavelength of the transmissive pigment may be in the range of about 660 nm to 800 nm in other examples. Such a pigment can be combined with an infrared reflective pigment to be described below to form a desired black layer. As the infrared ray transmitting pigments, various known pigments having the above characteristics can be used. In one example, a perylene compound may be used as the infrared transmitting pigment, for example, a pigment known under the trade name Paliogen 0084, Lumogen 4280, Paliogen 0086 or Lumogen 4280, etc. may be used.

The infrared reflective pigment may have a reflectance in the range of 30% to 90% for light of 800 nm wavelength. The range of the reflectance may be the same as or different from that of the infrared transmitting pigment. As the reflective pigment, a pigment having a maximum absorption wavelength in the range of 570 nm to 800 nm can be used. The range of the maximum absorption wavelength may be the same as or different from that of the transmission pigment. In another example, the maximum absorption wavelength of the reflective pigment may be in the range of about 570 nm to 650 nm. These pigments can be combined with the infrared transmitting pigments to form the desired black layer.

As the infrared reflective pigment, various known pigments having the above characteristics can be used. In one example, a phenylene compound may be used as the infrared reflective pigment, for example, a pigment known under the trade name Paliogen red K 3580 or Paliogen red L 3875 may be used and is known by the trade name Sicopal 0095 Metal oxide pigments such as those available may be used.

In the present application, it is possible to realize an appropriate black color by controlling the blending ratio of the infrared ray transmitting pigment and the reflective pigment, to prevent an increase in temperature due to the absorption of unnecessary infrared rays, and to have excellent power generation efficiency. That is, the black layer may include the infrared ray transmitting and reflecting pigments such that the infrared ray transmitting and reflecting pigments contain 5 to 50 parts by weight of the infrared ray reflecting pigment, relative to 100 parts by weight of the infrared ray transmitting pigment. It is possible to realize an appropriate black color within the range of the blending ratio as described above, and to achieve other required physical properties, for example, blocking of unnecessary infrared rays, utilization of useful infrared rays, and the like. Unless otherwise specified, the term " weight portion " in the present application may mean a ratio of the weight between each component.

The ratio of the above pigment in the black layer is not particularly limited and may be selected in consideration of the possibility of achieving the desired black color. For example, about 1 part by weight to 30 parts by weight The proportion of the pigment can be determined within a range of negative.

The black layer may include a resin, for example, a fluororesin together with the above components. As the resin, a known component can be used without any particular limitation. For example, a fluororesin having an amorphous region and a crystallinity of less than 60% can be used. The use of such a resin makes it possible to use a solvent having a low boiling point in the process of forming the black layer, thereby allowing the drying process to proceed at a low temperature, thereby improving the productivity of the product and securing a superior quality.

The fluororesin having an amorphous region in the present application may have a degree of crystallinity of less than 55%, 50% or 10% to 50%. The term crystallinity in the present application means the percentage (by weight) of the crystalline region contained in the total resin, which can be measured by a known method such as differential scanning calorimetry or the like.

The fluororesin having the above-described crystallinity can be obtained by copolymerizing a comonomer which is suitable at the time of production of the fluororesin and by releasing the regular element arrangement of the fluororesin or by polymerizing the polymer in the form of a branched polymer, Can be manufactured.

The specific kind of the fluororesin having the amorphous region is not particularly limited and includes, for example, vinyl fluoride (VF), vinylidene fluoride (VF2), tetrafluoroethylene (TFE) , Homopolymers containing polymerized units such as hexafluoropropylene (HFP), chlorotrifluoroethylene (CTFE) or perfluoro (ethylvinyl ether) (PEVE) Or a mixture thereof. In the above, the polymerization unit may mean a state in which the above-mentioned components are polymerized as monomers to form the skeleton of the resin.

In one example, a homopolymer or copolymer comprising vinyl fluoride polymerized units as the fluororesin; Or homopolymers or copolymers comprising vinylidene fluoride polymerized units; Or mixtures comprising two or more of the foregoing. In another example, as the fluororesin, a copolymer containing a vinylidene fluoride polymerization unit may be used. The type of the comonomer unit that can be included in the copolymer is not particularly limited and includes, for example, hexafluoropropylene polymerization unit, chlorotrifluoroethylene polymerization unit, tetrafluoroethylene polymerization unit, trifluoroethylene polymerization Unit, a hexafluoroisobutylene polymerization unit, a perfluorobutyl ethylene polymerization unit, a perfluoromethyl vinyl ether polymerization unit, a perfluoro-2,2-dimethyl-1,3-dioxole polymerization unit, and a perfluoro -2-methylene-4-methyl-1,3-dioxolane, and the like, but is not limited thereto. Also, the content of comonomer units in the copolymer may be, for example, from about 0.5% to 50%, from 1% to 40%, from 7% to 40% 10% by weight to 30% by weight or 10% by weight to 20% by weight. Within this range, the durability and weather resistance of the back sheet can be ensured.

In the present application, the fluororesin may have a weight average molecular weight of 50,000 to 1,000,000. In the present application, the weight average molecular weight is a conversion value of standard polystyrene measured by GPC (Gel Permeation Chromatograph). In the present application, by controlling the weight average molecular weight of the resin as described above, excellent solubility and other physical properties can be secured.

In the present application, the fluororesin may also have a melting point of from 80 캜 to 175 캜, preferably from 120 캜 to 165 캜. It is possible to control the melting point of the resin to 80 DEG C or higher to prevent the back sheet from being deformed during use and to control the melting point to 175 DEG C or lower to adjust the solubility in the solvent, Can be improved.

The black layer of the present application may further contain an amorphous resin together with the above-mentioned fluororesin, if necessary. Thus, by using a blend with an amorphous resin, the processability including solubility in a low boiling point solvent can be further improved. The term amorphous resin used in the present application includes not only the case where the entire structure of the resin is amorphous but also the case where the amorphous region exists predominantly even though a crystalline region exists in a part of the resin and the resin exhibits amorphousness as a whole .

The kind of the amorphous resin is not particularly limited and includes, for example, acrylic resin, polycarbonate, polyvinyl chloride, styrene- (meth) acrylonitrile copolymer, styrene-maleic anhydride copolymer, cycloolefin polymer, Nitrile, polystyrene, polysulfone, polyethersulfone or polyarylate, or a mixture of two or more kinds of them.

When the black layer contains an amorphous resin, the black layer contains 50 parts by weight or more of a fluororesin and 50 parts by weight or less of an amorphous resin. More specifically, the black layer contains 70 to 97 parts by weight of a fluororesin, And 3 parts by weight to 30 parts by weight of the amorphous resin. The weight ratio between the resins is controlled as described above so that the components constituting the black layer have appropriate degrees of crystallinity and the backsheet exhibits excellent durability and properties such as weather resistance.

The black layer of the present application may further comprise conventional components such as UV stabilizers, thermal stabilizers or barrier particles.

The black layer may have a thickness of about 30 microns or less, about 25 microns or less, about 20 microns or less, or about 15 microns or less. The thickness of the black layer may be changed, for example, in the range of about 2 占 퐉 or more or 3 占 퐉 or more.

In the present application, the black layer may be a coating layer. The term coating layer in the present application means a layer formed by a coating method. More specifically, when a black layer or a white layer to be described later is defined as a coating layer, a sheet produced by a film forming method such as an extrusion method is not laminated to a substrate layer or an intermediate layer using an adhesive or the like , A solvent, for example, a coating solution prepared by dissolving a component constituting a layer in a low boiling point solvent is coated on the surface of a substrate layer or the like.

On the back sheet, a white layer is formed on the other surface of the substrate layer. The term white layer in the present application may mean a layer exhibiting an appropriate reflectivity to infrared rays and may be, for example, a reflectance for light of a wavelength within a range of 650 nm to 1200 nm or an average reflectance , More than 40%, at least 45%, at least 50%, or at least 55%.

The white layer may include a resin, for example, a fluororesin and a pigment as described above. In consideration of scratch resistance, interface adhesion, reflectance, durability and shielding property, it is possible to use an accicular pigment as the pigment so as to ensure the physical properties even when the white layer is formed to have a small thickness, Can be controlled.

As the needle-shaped pigment, any needle-shaped pigment capable of forming a white layer can be used without any particular limitation. In the present application, the ratio (L / D) of the aspect ratio (L / D) as the needle-shaped pigment, that is, the length (L) to the average particle diameter (D) of the pigment may be in the range of 1.1 to 50. The aspect ratio may be about 5 or more or 7 or more in another example. The aspect ratio may also be less than or equal to about 45, less than or equal to about 40, less than or equal to about 35, less than or equal to about 30, or less than or equal to about 25 in other examples.

As such a pigment, for example, titanium dioxide, zinc oxide, silver white or the like having an acicular shape as described above can be used.

The proportion of the pigment can be adjusted for securing the desired physical properties. For example, the white layer may comprise 10 to 55 parts by weight or 15 to 50 parts by weight of the pigment relative to 100 parts by weight of the resin. The desired scratch resistance, interface adhesion, reflectance, durability, shielding property, and the like can appropriately be ensured within the above-mentioned ratio range. In the present application, a unit weight portion may mean a weight ratio of each component.

The thickness of the white layer is not particularly limited as long as the above-mentioned reflectance can be secured, and may be, for example, about 30 占 퐉 or less, about 25 占 퐉 or less, about 20 占 퐉 or less or about 15 占 퐉 or less. The thickness of the white layer may be changed, for example, in the range of about 2 占 퐉 or more or 3 占 퐉 or more. In the case of the present application, the intended effect can be ensured even when the white layer has a very thin thickness by including the specific pigment in the specific ratio.

The manner of forming the white layer is not particularly limited. For example, as in the case of the above-mentioned black layer, the white layer can be realized by using a coating liquid in which a resin component such as a fluororesin or the like is blended with a white pigment. In this case, Except that, it is similar to the case of black layer.

The backsheet may further include various functional layers known in the art as needed in addition to the above configuration. Examples of the functional layer include an adhesive layer or an insulating layer. The adhesive layer or insulating layer may be formed in a variety of ways known in the art. For example, the insulating layer may be a layer of ethylene vinyl acetate (EVA) or low density linear polyethylene (LDPE). The layer of the ethylene vinyl acetate (EVA) or the low density linear polyethylene (LDPE) improves the adhesion with the encapsulant as well as the insulating layer, reduces the manufacturing cost, and has the re-workability It is possible to simultaneously perform the function of maintaining excellent.

The present application also relates to a process for the production of a back sheet comprising a step of coating a base layer with a coating liquid comprising an infrared ray transmitting pigment and an infrared ray reflecting pigment in an amount of 5 to 50 parts by weight relative to 100 parts by weight of said infrared ray transmitting pigment, And a manufacturing method thereof. The method may include the step of forming the white layer before or after the black layer is formed, and the method of forming the white layer is the same as that of the black layer.

The coating solution may be prepared by dissolving the resin component, for example, an additive such as a fluororesin and a pigment in a solvent, for example, a solvent having a boiling point of 200 ° C or lower. For example, when a fluororesin having the above-described crystallinity is used as the resin component, it can exhibit excellent solubility even for a low-boiling solvent as described above. Accordingly, the present application does not require a high-temperature drying step in the manufacturing process, thereby reducing the manufacturing cost, preventing thermal deformation and thermal shock of the substrate which may be caused during high-temperature drying, and improving the quality of the product . Examples of the solvent that can be used in the present application include a solvent such as acetone, methyl ethyl ketone (MEK), dimethylformamide (DMF), dimethylacetamide (BMAC) It is not.

In addition to the fluororesin and the pigment, the coating liquid to be applied to the formation of the black layer in the present application may further contain various additives such as a filler, a UV stabilizer or a heat stabilizer. Each of the above additives may be dissolved in a solvent together with a fluororesin or the like, or may be prepared in a mill base form separately from the above components, and then mixed with a solvent containing the fluororesin or amorphous resin.

The coating liquid may be applied as described above, and if necessary, a black layer or a white layer may be formed by an appropriate drying process. In this case, the coating method is not particularly limited, and any method can be applied as long as it can form a uniform coating layer including offset, gravure, roll coat or knife edge coat, for example. In this application, various methods known in the art may be applied in addition to the above-described methods, and the coating solution may further include various other additives as necessary.

The specific types of substrate layers that can be used in the above step of the present application are as described above, and the substrate layer may be subjected to appropriate vapor deposition, plasma treatment, corona treatment, or the like.

The coating step may be followed by a step of drying the coated coating solution. The conditions at the time of drying are not particularly limited, and can be performed, for example, at a temperature of 200 DEG C or lower or at a temperature of about 100 DEG C to 180 DEG C for about 30 seconds to 30 minutes or about 1 minute to 10 minutes. By controlling the drying conditions as described above, it is possible to prevent an increase in manufacturing cost and to prevent the deterioration of product quality due to thermal deformation or thermal shock.

The present application also relates to a photovoltaic module comprising said backsheet. The photovoltaic module of the present application is not particularly limited as long as it includes the backsheet, and may have various structures known in the art.

Typically, the photovoltaic module may comprise a transparent front substrate, a backsheet, and a photovoltaic cell or photovoltaic array encapsulated by an encapsulant between the front substrate and the backsheet.

Examples of the active layer constituting the photovoltaic cell or the photovoltaic array include a crystalline or amorphous silicon wafer, a compound semiconductor such as CIGS or CTS, and the like.

The back sheet of the present application can be applied to various photovoltaic modules known in the art including the module having the active layer as described above. In this case, It is not limited.

In this application, for example, even when the black layer is formed thin, the required black can be realized, and the light in the infrared region, which can raise the temperature of the module, is blocked, The back sheet which can be utilized in the device can be utilized as an infrared ray, a manufacturing method thereof, and a photovoltaic module using the back sheet.

1 is a sectional view showing a back sheet according to one example.

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.

In the Examples and Comparative Examples, the physical properties of the sheet were measured in the following manner.

One. Color-coded  How to measure

The color coordinates of the back sheet were measured using a colorimeter (CM-5, Konica Minolta) equipped with an integrating sphere detector.

2. Transmittance ( transmittance ) And reflectance ( reflectance ) How to measure

The transmittance and reflectance of the backsheet were measured using a UV-Vis-NIR spectrometer (UV-3600, shimadzu).

Manufacturing example  1. Preparation of coating liquid (A)

VF2 (vinylidene fluoride) and chlorotrifluoroethylene (CTFE) were polymerized in a weight ratio of 85:15 (VF2: CTFE) to a solvent, N, N-dimethyl formamide And 30 g of a copolymer containing 70 g of a copolymer containing VF2 and hexafluoropropylene (HFP) in a weight ratio of 88:12 (VF2: HFP) were mixed, and the entire copolymer About 9 parts by weight of a first pigment (Paliogen 0084, maximum absorption wavelength: about 700 nm, reflectance (800 nm): about 80%, BASF) and about 1 part by weight 2 pigment (Paliogen red K3580, maximum absorption wavelength: about 600 nm, reflectance (800 nm): about 80%, BASF) were blended to prepare a coating solution (A).

Manufacturing example  2. Preparation of coating liquid (B)

Except that about 8 parts by weight of a first pigment (Paliogen 0084, BASF) relative to 100 parts by weight of the total weight of the copolymer and about 2 parts by weight of a second pigment (Paliogen red K3580, BASF) relative to 100 parts by weight of the total weight (B) was prepared in the same manner as in Preparation Example 1.

Manufacturing example  3. Preparation of coating liquid (C)

Except that about 7 parts by weight of a first pigment (Paliogen 0084, BASF) relative to 100 parts by weight of the total weight of the copolymer and about 3 parts by weight of a second pigment (Paliogen red K3580, BASF) relative to 100 parts by weight of the total weight (C) was prepared in the same manner as in Preparation Example 1.

Manufacturing example  4. Preparation of coating liquid (D)

(D) was prepared in the same manner as in Preparation Example 1, except that only about 10 parts by weight of the first pigment (Paliogen 0084, BASF) was added to 100 parts by weight of the total weight of the copolymer.

Manufacturing example  5. Preparation of coating liquid (E)

VF2 (vinylidene fluoride) and chlorotrifluoroethylene (CTFE) were polymerized in a weight ratio of 85:15 (VF2: CTFE) to a solvent, N, N-dimethyl formamide And 30 g of a copolymer containing 70 g of a copolymer containing VF2 and hexafluoropropylene (HFP) in a weight ratio of 88:12 (VF2: HFP) were mixed, and the entire copolymer About 40 parts by weight of acicular type TiO ₂ was added to 100 parts by weight of the coating liquid to prepare a coating liquid (E).

Example  One

On one side of the PET (poly (ethylene terephthalate)) film subjected to the corona treatment, first, the coating liquid (A) was applied in a comma reverse manner. Specifically, the thickness of the final coating layer was adjusted to be about 10 占 퐉, and then the coated PET film was coated with a PET film having a length of 2 m and a temperature of 80 占 폚, 170 占 폚 and 170 占 폚 Were sequentially passed through the oven at a speed of 1 m / min to form a black coating layer. Thereafter, the coating liquid (E) was coated on the opposite surface in the same manner so as to have a final thickness of about 13 mu m to form a white coating layer to prepare a back sheet.

Example  2

A back sheet was prepared in the same manner as in Example 1, except that a black coating layer having a thickness of about 12 占 퐉 was formed using the coating liquid (B) instead of the coating layer (A).

Example  3

A backsheet was prepared in the same manner as in Example 1, except that a black coating layer having a thickness of about 11 mu m was formed using the coating liquid (C) instead of the coating layer (A).

Comparative Example  One.

A back sheet was prepared in the same manner as in Example 1, except that a black coating layer was formed using the coating liquid (D) instead of the coating layer (A).

The results of measurement of the color coordinates, transmittance and reflectance of the examples and comparative examples are summarized in Table 1 below.

Example 1 Example 2 Example 3 Comparative Example 1 Black coating layer thickness (占 퐉) 10 12 11 12 White Coating Layer Thickness (占 퐉) 13 13 13 13 color
Left
table L 24.33 24.67 25.4 24.96 a 2.11 2.67 3.13 1.16 b 1.8 2.19 2.73 1.13 form
and
rate 450 nm 0.04 0.04 0.03 0.21 550 nm 0.11 0.11 0.1 0.83 650 nm 0.04 0.08 0.18 0.13 half
four
rate 450 nm 3.83 3.87 3.97 4.16 550 nm 4.03 4.06 4.23 4.34 650 nm 5.3 5.5 5.68 5.44

As can be seen from Table 1, the back sheet of the embodiment according to the present application absorbs light of 450 nm to 650 nm to exhibit appropriate color, while effectively reflecting infrared rays in the range of 650 nm to 800 nm in terms of characteristics, And the heat accumulated in the module could also be effectively released. However, in the case of the back sheet of the comparative example, in particular, the transmittance of light with a wavelength of 550 nm is excessively high, so that it is confirmed that the back sheet does not exhibit the desired color.

101: substrate layer
102: black layer
103: white layer

Claims (13)

A base layer; A black layer formed on the substrate layer and including an infrared ray transmitting pigment and an infrared ray reflecting pigment in a ratio of 5 parts by weight to 50 parts by weight to 100 parts by weight of the infrared ray transmitting pigment; And
And a white layer formed under the base layer,
A backsheet having a transmittance of 0.5% or less with respect to light having a wavelength of 550 nm. The backsheet according to claim 1, wherein the transmittance to light having a wavelength of 550 nm is 0.3% or less. The backsheet of claim 1, wherein the infrared transmitting pigment has a maximum absorption wavelength in the range of 570 nm to 1,000 nm. 2. The backsheet of claim 1, wherein the infrared transmitting pigment has a reflectivity for light of 800 nm wavelength in the range of 30% to 80%. The back sheet according to claim 1, wherein the infrared transmitting pigment is a perylene compound. The back sheet according to claim 1, wherein the infrared reflective pigment has a maximum absorption wavelength in the range of 570 nm to 1,000 nm. The backsheet of claim 1, wherein the infrared reflective pigment is in the range of 30% to 80% reflectance for light of 800 nm wavelength. The back sheet according to claim 1, wherein the black layer comprises a resin and an infrared ray transmitting pigment and an infrared ray reflective pigment in a range of 1 to 30 parts by weight relative to 100 parts by weight of the resin. The backsheet according to claim 8, wherein the resin is a fluororesin. The back sheet according to claim 1, wherein the black layer has a thickness of 20 탆 or less. A process for producing a back sheet as claimed in claim 1, comprising the step of coating a base layer with a coating liquid containing an infrared ray transmitting pigment and an infrared ray reflecting pigment in an amount of 5 to 50 parts by weight based on 100 parts by weight of the infrared ray transmitting pigment to form a black layer. The method according to claim 11, further comprising the step of forming a white layer on the substrate layer after forming the black layer, or simultaneously with formation of the black layer, before forming the black layer. A photovoltaic module comprising the back sheet of claim 1.

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