Photovoltaic backboard and preparation method thereof, and photovoltaic module

Abstract

The invention provides a photovoltaic backboard, a preparation method thereof and a photovoltaic module. The photovoltaic backboard comprises a bonding layer, a permeable layer, a foaming base layer and a weather-proof layer which are sequentially stacked, wherein the bonding layer comprises a first coating; the permeable layer comprises a first foaming material and a second coating; the first coating and the second coating are respectively and independently prepared from the following components in parts by weight: 20 to 50 parts of matrix resin, 0.5 to 10 parts of epoxy resin, 0.5 to 5 parts of high-blackness pigment and 13.1 to 65 parts of auxiliaries; the thickness of the permeable layer is 0.05-1 [mu] m; and the reflectivity of the foaming base layer under the wavelength of 400-1100 nm is 90%-95%. According to the photovoltaic backboard, the low-permeability and high-integrating-degree black coating is used, light loss is reduced, the reflectivity of the backboard is greatly improved, and the problem that in the prior art, the reflectivity of a black backboard is low is solved.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and more specifically, to a photovoltaic backsheet and its preparation method, and a photovoltaic module. Background Technology

[0002] With the booming development of distributed photovoltaics, the requirements for modules are also gradually changing. Nowadays, black modules are receiving rave reviews. Among them, black backsheets with ultra-high infrared reflectivity not only demonstrate the ultimate pursuit of aesthetics in the photovoltaic module market, but can also bring about a significant increase in power.

[0003] The fine, uneven surface structure of foamed materials causes light to be reflected in multiple directions, a phenomenon known as diffuse reflection, which is the primary reflection mechanism of foamed reflective materials. For this type of thin film, the reflectivity is mainly enhanced by utilizing the difference in refractive index within the system. In addition to surface scattering, some light is refracted into the film medium. Inside the film, due to the large number of fillers and / or microbubbles, light encounters these foreign objects and undergoes further reflection, refraction, and re-reflection. Especially since the refractive index of the medium within the microbubbles is 1.0, light is reflected at the inner surface of the microbubbles and refracted at a relatively large angle. All these complex internal structures effectively prevent light from passing smoothly through the film medium, thus altering the light path and reflecting it back to the film surface. Therefore, foaming technology is applied to backsheets to improve the reflectivity of coatings / backsheets.

[0004] Foamed substrates utilize foamed materials to reduce material density and increase surface reflectivity by introducing tiny air bubbles or pores. This structure reduces the weight of the backsheet and improves light reflection, thereby increasing the light utilization efficiency of the photovoltaic module. Furthermore, foamed substrates also possess good insulation properties and mechanical strength, along with low density and high light reflectivity, which helps improve the light absorption efficiency of photovoltaic modules, meeting the requirements of the photovoltaic industry. The synergistic use of a high-reflectivity black coating with foamed substrates can further enhance the reflectivity of the high-reflectivity black backsheet, further increasing the power output of the module.

[0005] Existing high-reflectivity black backsheets are made by adding organic pigments to conventional photovoltaic PET (i.e., polyethylene terephthalate). Their reflectivity has reached a current bottleneck, and conventional modifications are unlikely to further improve it, necessitating alternative solutions. Currently, foamed PET with higher reflectivity is gradually appearing on the market. This is achieved by adding special reflective fillers to PET to enhance reflectivity, and this material can be used in photovoltaic backsheets to improve reflectivity. However, current foamed PET still faces the problem of high foaming rates. Combined with the low viscosity of current high-reflectivity black coatings, the combination results in excessively high permeability of the coating through the foam cells, thus affecting the reflectivity of the high-reflectivity black backsheet.

[0006] In summary, it is particularly important to develop a black coating with low permeability and high compatibility when combined with high-reflectivity foamed PET. Summary of the Invention

[0007] The main objective of this invention is to provide a photovoltaic backsheet and its preparation method, as well as a photovoltaic module, to solve the problem that the reflectivity of black backsheets in the prior art needs to be improved.

[0008] To achieve the above objectives, according to one aspect of the present invention, a photovoltaic backsheet is provided, comprising an adhesive layer, a permeation layer, a foamed substrate, and a weather-resistant layer stacked sequentially; wherein the adhesive layer comprises a first coating; the permeation layer comprises a first foaming material and a second coating; by weight, the first coating and the second coating each independently comprise 20-50 parts of a matrix resin, 0.5-10 parts of an epoxy resin, 0.5-5 parts of a high-reflectivity black pigment, and 13.1-65 parts of additives; the thickness of the permeation layer is 0.05-1 μm; and the reflectivity of the foamed substrate at wavelengths of 400-1100 nm is 90%-95%.

[0009] In some embodiments of this application, the mass percentage of the second coating in the permeation layer is 0.1% to 2%; and / or, the porosity of the permeation layer is 5% to 50%; and / or, the thickness of the permeation layer is 0.05 to 0.8 μm.

[0010] In some embodiments of this application, the foamed base layer includes a second foaming material, wherein the first foaming material and the second foaming material are each independently selected from any one or more of foamed PET, PP, PU, ​​PVC, PVB, PI, and PHA; and / or, the mass percentage of the second foaming material in the foamed base layer is 70% to 90%; and / or, the thickness of the foamed base layer is 50 to 300 μm; and / or, the pore size of the pores in the foamed base layer is 0.5 to 50 μm, and the porosity of the foamed base layer is 30% to 70%.

[0011] In some embodiments of this application, the weather-resistant layer is a combination of an adhesive layer and a weather-resistant film layer or a weather-resistant outer coating; and / or, the thickness of the weather-resistant layer is 10~50μm.

[0012] In some embodiments of this application, the thickness of the adhesive layer is 3~10μm.

[0013] In some embodiments of this application, the photovoltaic backsheet satisfies at least one of the following technical features (1) to (7): (1) the matrix resin is selected from any one or more of fluorocarbon resin, acrylic resin and polyester resin; (2) the epoxy resin is selected from any one or more of alicyclic epoxy resin, modified bisphenol A type epoxy resin, modified bisphenol F type epoxy resin, siloxane-containing modified epoxy resin, and photothermal dual-curing epoxy resin; (3) the high-reflectivity black pigment is selected from any one or more of organic pigment and inorganic pigment; the organic pigment is selected from any one or more of direct lightfast dye, direct diazo dye, direct cross-linked dye, azo dye containing complex metal, fused ring aromatic pigment, and heterocyclic aromatic pigment; the inorganic pigment is selected from any one of copper chromium black and manganese chromium black. (4) The additives include 2 to 15 parts of inorganic fillers, which are selected from any one or more of anti-scratch powder, transparent powder, silica powder, glass powder and matting powder; (5) The additives include 1 to 15 parts of curing agent, which are selected from any one or more of aromatic isocyanate curing agent, aliphatic isocyanate curing agent and blocked isocyanate curing agent; (6) The additives include 10 to 30 parts of organic solvent, which are selected from any one or more of ethanol, n-butanol, ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, xylene, methyl ethyl ketone; (7) The additives also include 0.1 to 5 parts of other additives, which are selected from any one or more of dispersants, antioxidants, leveling agents, catalysts and coupling agents.

[0014] In some embodiments of this application, the photovoltaic backsheet satisfies at least one of the following technical features (1) to (5): (1) the dispersant is an anionic dispersant and / or a polymeric dispersant; (2) the antioxidant is one or more of pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di-tert-butyl-4-methylphenol, 4,4'-diisopropylphenyl diphenylamine, and pentaerythritol β-dodecyl thiopropionate; (3) The leveling agent is one or more of the following: polyacrylate leveling agent, fluorocarbon modified polyacrylate leveling agent, fluorinated surfactant, polyether modified polysiloxane leveling agent, and reactive polysiloxane leveling agent; (4) the catalyst is an organotin catalyst; (5) the coupling agent is one or more of the following: vinyltrimethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropylmethyldimethoxysilane, isopropyltris(dioctylpyrophosphate)titanate, and bis(dioctyloxypyrophosphate)ethylenetitanate.

[0015] In some embodiments of this application, the viscosity of the first coating is 1000~10000 mPa·s, preferably 4000~8000 mPa·s; and / or, the viscosity of the second coating is 1000~10000 mPa·s, preferably 4000~8000 mPa·s.

[0016] According to another aspect of the present invention, a method for preparing the aforementioned photovoltaic backsheet is provided, comprising: coating a first coating on a first surface of a foamed substrate and then drying and curing it sequentially to form an adhesive layer and a penetration layer; and setting a weather-resistant layer on the surface of the foamed substrate opposite to the first surface to obtain a photovoltaic backsheet; preferably, the drying temperature is 170~180℃ and the drying time is 2~5min.

[0017] According to another aspect of the present invention, a photovoltaic module is provided, including a backsheet, wherein the backsheet is the aforementioned photovoltaic backsheet or a photovoltaic backsheet prepared by the aforementioned preparation method.

[0018] Applying the technical solution of this invention, the base resin in the first and second coatings provides the basic film-forming substance for the coating, forming a strong adhesive layer. The introduction of epoxy resin compensates for the defects of low surface energy and weak adhesion of the resin, and epoxy resin can ensure the UV resistance and weather resistance of the coating. High-reflectivity black pigment ensures the high reflectivity of the coating, while the combined use of additives further optimizes the performance of the coating, enhances the coating effect and the long-term stability of the backing plate. At the same time, the first and second coatings of the above components have suitable permeability and low cost, and controlling the thickness of the permeation layer to 0.05~1μm ensures that the second coating can form a proper filling in the pores of the first foaming material. This prevents the second coating from over-permeating and filling the pore structure, affecting the reflectivity, while ensuring sufficient permeation effect, improving the bonding strength between the coating and the foaming material, and forming a black appearance coating with low permeability, high adhesion, uniformity, stability and good weather resistance, reducing light loss and greatly improving the reflectivity of the backing plate. Meanwhile, the reflectivity of the foamed substrate remains at a high level of 90% to 95% at wavelengths of 400 to 1100 nm. Applying it to high-reflectivity black backsheets can effectively improve the light utilization rate of photovoltaic backsheets, thereby improving the power generation efficiency of photovoltaic modules. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0020] Figure 1 A schematic diagram of the structure of the photovoltaic backsheet according to the present invention is shown.

[0021] The above figures include the following reference numerals:

[0022] 1. Adhesive layer; 2. Penetrating layer; 3. Foamed base layer; 4. Weather-resistant layer. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] As analyzed in the background section of this application, the reflectivity of black backsheets in the prior art needs to be improved. To address this issue, this application provides a photovoltaic backsheet, its fabrication method, and a photovoltaic module.

[0025] According to a typical embodiment of this application, a photovoltaic backsheet is provided, such as... Figure 1 As shown, the photovoltaic backsheet includes an adhesive layer 1, a permeation layer 2, a foamed substrate 3, and a weather-resistant layer 4 stacked sequentially. The adhesive layer includes a first coating; the permeation layer includes a first foaming material and a second coating. By weight, the first and second coatings each independently include 20-50 parts of matrix resin, 0.5-10 parts of epoxy resin, 0.5-5 parts of high-reflectivity black pigment, and 13.1-65 parts of additives. The thickness of the permeation layer is 0.05-1 μm. The reflectance of the foamed substrate at wavelengths of 400-1100 nm is 90%-95%.

[0026] In the first and second coatings mentioned above, the base resin provides the basic film-forming substance for the coating, forming a strong adhesive layer. The introduction of epoxy resin compensates for the shortcomings of low surface energy and weak adhesion of the resin, and epoxy resin can ensure the coating's UV resistance and weather resistance. High-reflectivity black pigment ensures the coating's high reflectivity, while the combined use of additives further optimizes the coating's performance, enhances the coating effect, and improves the long-term stability of the backing plate. At the same time, the first and second coatings of the above components have suitable permeability and low cost, and controlling the thickness of the permeation layer to 0.05~1μm ensures that the second coating can form a proper filling in the pores of the first foaming material. This prevents excessive permeation of the second coating from filling the pore structure and affecting reflectivity, while ensuring sufficient permeation effect, improving the bonding strength between the coating and the foaming material, and forming a black appearance coating with low permeability, high adhesion, uniformity, stability, and good weather resistance, reducing light loss and greatly improving the reflectivity of the backing plate. Meanwhile, the reflectivity of the foamed substrate remains at a high level of 90% to 95% at wavelengths of 400 to 1100 nm. Applying it to high-reflectivity black backsheets can effectively improve the light utilization rate of photovoltaic backsheets, thereby improving the power generation efficiency of photovoltaic modules.

[0027] In some preferred embodiments of this application, the mass percentage of the second coating in the permeation layer is 0.1% to 2%; and / or, the porosity of the permeation layer is 5% to 50%; and / or, the thickness of the permeation layer is 0.05 to 0.8 μm.

[0028] The optimal mass percentage of the second coating in the penetrating layer within the above range helps the second coating fill the pores of the foamed substrate, enhancing the adhesion between the adhesive layer and the foamed substrate, while reducing the damage to the foamed structure caused by overfilling, thereby improving reflectivity performance. The optimal porosity of the penetrating layer within the above range helps reduce surface energy, decreasing the likelihood of excessive coating penetration and ensuring reflectivity. The optimal thickness of the penetrating layer within the above range allows for appropriate penetration of the coating into the foamed substrate, thus improving both the adhesion between the coating and the foamed substrate and reducing increased light absorption due to excessive coating thickness.

[0029] In some embodiments of this application, the foamed base layer includes a second foaming material, wherein the first foaming material and the second foaming material are each independently selected from any one or more of foamed PET, PP, PU, ​​PVC, PVB, PI, and PHA; and / or, the mass percentage of the second foaming material in the foamed base layer is 70% to 90%; and / or, the thickness of the foamed base layer is 50 to 300 μm; and / or, the pore size of the pores in the foamed base layer is 0.5 to 50 μm, and the porosity of the foamed base layer is 30% to 70%.

[0030] The selection of a second foaming material in the foamed substrate expands its applicability and enhances the overall performance of the backsheet. Preferring the above-mentioned types of second foaming materials improves the backsheet's reflectivity and durability in complex environments. A preferred mass ratio of the second foaming material within the above-mentioned range helps balance the lightweight design of the backsheet with its reflectivity, mitigating the problems of reduced mechanical strength due to excessive foaming or poor reflectivity due to insufficient foaming. A preferred thickness of the foamed substrate within the above-mentioned range increases the reflective area of ​​the backsheet, improving its flexibility and ease of installation. Preferring pore size and porosity within the above-mentioned range improves the optical reflectivity of the foamed material, enhances the stability of its internal structure, and reduces the risk of pore collapse or blockage during long-term use, thus minimizing impacts on the backsheet's reflectivity and lifespan. In summary, by adjusting the composition, mass ratio, foam layer thickness, pore size, and porosity of the foaming material, not only is the reflectivity improved, but the reliability and long-term service capability of the back panel in harsh environments are also enhanced.

[0031] In some embodiments of this application, the weather-resistant layer is a combination of an adhesive layer and a weather-resistant film layer or a weather-resistant outer coating; and / or, the thickness of the weather-resistant layer is 10~50μm.

[0032] Optimizing the thickness of the weather-resistant layer within the above range helps enhance the backsheet's resistance to corrosion from ultraviolet radiation, moisture, and other environmental factors, while also improving the backsheet's mechanical properties and electrical insulation characteristics. Specifically, the weather-resistant outer coating or composite weather-resistant film layer provides additional protection, reducing direct damage from the external environment to the high-reflectivity foamed substrate, while the introduction of the adhesive layer strengthens the adhesion between coatings, enhancing the integrity of the entire photovoltaic backsheet structure.

[0033] In some embodiments of this application, the thickness of the adhesive layer is 3~10μm.

[0034] The optimal thickness of the adhesive layer within the above range helps enhance the coverage and adhesion of the coating, while reducing light absorption caused by excessive coating thickness, thereby improving the high reflectivity of the high-reflectivity backsheet. Furthermore, the adhesive layer thickness not only improves the bonding strength between the coating and the foamed substrate but also effectively controls the penetration depth of the second coating in the penetration layer, enhancing the connection stability between the adhesive layer and the foamed substrate without significantly affecting the microstructure and reflective properties of the foamed substrate.

[0035] In some embodiments of this application, the photovoltaic backsheet satisfies at least one of the following technical features (1) to (7): (1) the matrix resin is selected from any one or more of fluorocarbon resin, acrylic resin and polyester resin; (2) the epoxy resin is selected from any one or more of alicyclic epoxy resin, modified bisphenol A type epoxy resin, modified bisphenol F type epoxy resin, siloxane-containing modified epoxy resin, and photothermal dual-curing epoxy resin; (3) the high-reflectivity black pigment is selected from any one or more of organic pigment and inorganic pigment; the organic pigment is selected from any one or more of direct lightfast dye, direct diazo dye, direct cross-linked dye, azo dye containing complex metal, fused ring aromatic pigment, and heterocyclic aromatic pigment; the inorganic pigment is selected from any one of copper chromium black and manganese chromium black. (4) The additives include 2 to 15 parts of inorganic fillers, which are selected from any one or more of anti-scratch powder, transparent powder, silica powder, glass powder and matting powder; (5) The additives include 1 to 15 parts of curing agent, which are selected from any one or more of aromatic isocyanate curing agent, aliphatic isocyanate curing agent and blocked isocyanate curing agent; (6) The additives include 10 to 30 parts of organic solvent, which are selected from any one or more of ethanol, n-butanol, ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, xylene, methyl ethyl ketone; (7) The additives also include 0.1 to 5 parts of other additives, which are selected from any one or more of dispersants, antioxidants, leveling agents, catalysts and coupling agents.

[0036] The preferred matrix resins exhibit superior weather resistance and stability, thereby enhancing the coating's durability in complex environments and effectively extending the lifespan of the photovoltaic backsheet. The preferred epoxy resins not only enhance the coating's adhesive strength but also improve its UV resistance, reducing yellowing caused by prolonged outdoor use. Simultaneously, they enhance diverse adhesive properties and curing speed, improving production efficiency, while also improving the coating's weather resistance and mechanical strength. Furthermore, the preferred epoxy resins, which do not contain benzene rings in their molecular structure, not only provide the formed coating with better adhesion but also exhibit good UV resistance and are less prone to yellowing. The preferred combination of organic and inorganic pigments helps improve the backsheet's reflectivity while also increasing pigment stability and enhancing the color consistency of the backsheet after prolonged use. The aforementioned inorganic fillers are chemically inert powders with high hardness, strengthening the backsheet's hardness and significantly improving its mechanical properties such as anti-sticking, scratch resistance, and embossing resistance. They also improve the backsheet's abrasion resistance, scratch resistance, and embossing resistance without affecting reflectivity. The selection of preferred curing agents within the above-mentioned range enhances the rapid curing of the coating at high temperatures, shortens the production cycle, and simultaneously strengthens the coating's tensile strength and hydrolysis resistance. The preferred organic solvents help regulate the coating's viscosity, promote uniform application of the coating to the foamed substrate, reduce pore filling, and minimize the risk of weakening the reflective properties of the foamed substrate. Depending on the specific application environment, other suitable additives can be added to achieve corresponding functions. For example, controlling the addition of dispersants, antioxidants, leveling agents, and other additives within the above-mentioned range helps enhance the surface quality and durability of the coating, and improves the compatibility and adhesion between the black coating layer and the foamed substrate.

[0037] In addition, the aforementioned high-reflectivity black pigments can also be black pigments formed by mixing different colored pigments, such as black pigments formed by mixing red, yellow and blue pigments, or black pigments formed by mixing green and purple pigments.

[0038] In some embodiments of this application, the photovoltaic backsheet satisfies at least one of the following technical features (1) to (5): (1) the dispersant is an anionic dispersant and / or a polymeric dispersant; (2) the antioxidant is one or more of pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di-tert-butyl-4-methylphenol, 4,4'-diisopropylphenyl diphenylamine, and pentaerythritol β-dodecyl thiopropionate; (3) The leveling agent is one or more of the following: polyacrylate leveling agent, fluorocarbon modified polyacrylate leveling agent, fluorinated surfactant, polyether modified polysiloxane leveling agent, and reactive polysiloxane leveling agent; (4) the catalyst is an organotin catalyst; (5) the coupling agent is one or more of the following: vinyltrimethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropylmethyldimethoxysilane, isopropyltris(dioctylpyrophosphate)titanate, and bis(dioctyloxypyrophosphate)ethylenetitanate.

[0039] The preferred dispersants help enhance the uniform dispersion of pigments and fillers in the coating, reduce agglomeration in the coating, and thus improve the uniformity and adhesion of the coating. The preferred antioxidants help reduce the risk of oxidative degradation of the coating due to ultraviolet radiation during long-term outdoor use, improving coating stability and maintaining a black appearance. The preferred leveling agents help the coating be evenly applied to the foamed substrate, reducing surface defects such as orange peel texture during the coating process, and improving the smoothness and aesthetics of the coating. The preferred catalysts help promote the curing reaction of the coating, increasing the curing speed and adhesion strength of the coating. The preferred coupling agents help enhance the interfacial adhesion between the coating and the foamed substrate, improving the overall structural stability and reliability of the backsheet. Through the rational selection and combination of the above additives, not only is the preparation and application process of the coating optimized, but the outdoor durability and power generation efficiency of the high-reflectivity black backsheet are also improved.

[0040] In some embodiments of this application, the viscosity of the first coating is 1000~10000 mPa·s, preferably 4000~8000 mPa·s.

[0041] The preferred viscosity of the first coating is within the above range, which enhances the adhesion between the coating and the foamed substrate and reduces the problem of excessive penetration filling the foam pores and affecting reflectivity. In addition, controlling the viscosity of the coating within the above range enhances the interfacial bonding between the coating and the high-reflectivity foamed substrate, while reducing the risk of damage to the reflectivity of the foamed substrate. Ultimately, this enhances the excellent environmental adaptability and mechanical strength of the photovoltaic backsheet while improving its light reflection capability.

[0042] According to another aspect of the present invention, a method for preparing the aforementioned photovoltaic backsheet is provided, comprising: coating a first coating on a first surface of a foamed substrate and then drying and curing it sequentially to form an adhesive layer and a penetration layer; and setting a weather-resistant layer on the surface of the foamed substrate opposite to the first surface to obtain a photovoltaic backsheet; preferably, the drying temperature is 170~180℃ and the drying time is 2~5min.

[0043] The core of the above preparation method lies in controlling the application of a low-permeability black coating on the first surface of a high-reflectivity foamed substrate, followed by drying and curing steps to form an adhesive layer and a penetration layer, and setting a weather-resistant layer on the other side of the foamed substrate. The first coating applied to the surface of the foamed substrate, by adjusting its viscosity and component ratio, can moderately penetrate into the microporous structure of the foamed substrate during the bonding process without damaging its reflective properties. Photovoltaic backsheets prepared by this method not only improve the weather resistance and mechanical strength of the coating but also maintain the high-efficiency light reflection capability of the high-reflectivity black backsheet in the visible and near-infrared regions, thereby significantly enhancing the energy conversion efficiency of photovoltaic modules, especially achieving a dual improvement in aesthetics and performance in the design of black modules.

[0044] According to another aspect of the present invention, a photovoltaic module is provided, including a backsheet, wherein the backsheet is the aforementioned photovoltaic backsheet or a photovoltaic backsheet prepared by the aforementioned preparation method.

[0045] The photovoltaic backsheet of this application has stronger light absorption and conversion efficiency, which helps to improve the power generation efficiency of photovoltaic modules and make them fully meet the requirements for use.

[0046] The beneficial effects that this application can achieve will be further illustrated below with reference to embodiments and comparative examples.

[0047] Example 1

[0048] This embodiment provides a photovoltaic backsheet coating, the structure of which is as follows: Figure 1As shown, its main component is black. The photovoltaic backsheet coating includes, in sequence, an adhesive layer 1 (6 μm thick), a penetration layer 2 (a second coating (1.5% by mass in the penetration layer), 0.5 μm thick, with a porosity of 25%), a foamed base layer 3 (a second foaming material accounting for 80% by mass in the foamed base layer, with a pore size of 25 μm and a porosity of 50%), and a weather-resistant layer 4 (20 μm thick). The adhesive layer includes a high-reflectivity black coating (i.e., the first coating). Both the high-reflectivity black coating and the second coating are composed of the following raw materials in parts by weight: 36 parts hydroxyl acrylic resin; 8 parts epoxy-modified polyester polyol resin; 9 parts acrylate adhesion promoter resin; 13 parts high-reflectivity black pigment; 3 parts matting agent; 0.5 parts BYK carboxylic acid dispersant; 0.3 parts stannous catalyst; 0.04 parts polyacrylate leveling agent; 25 parts propylene glycol methyl ether acetate; and isocyanate curing agent selected from Asahi Kasei TPA 100. 3.5 parts of Mitsui aliphatic polyisocyanate adduct curing agent D120N and 3 parts of other ingredients. First, mix the above raw materials (except the isocyanate curing agent) thoroughly and sand-mill to obtain a coating. Then, mix the coating with the curing agent before use. Apply the mixed coating (viscosity 6000 mPa·s) to one side of a 280 μm thick PET sheet and cure it in a 175°C oven for 3 minutes to obtain a highly reflective black coating. Apply a weather-resistant coating to the other side, together forming a photovoltaic backsheet. The coating thickness on the encapsulating film bonding surface is 8 μm, and the coating thickness on the air side is 15 μm.

[0049] Example 2

[0050] The difference from Example 1 is that the mass ratio of the second foaming material in the foamed base layer is 90%, and the photovoltaic backsheet is finally obtained.

[0051] Example 3

[0052] The difference from Example 1 is that the mass ratio of the second foaming material in the foamed base layer is 50%, and a photovoltaic backsheet is finally obtained.

[0053] Example 4

[0054] The difference from Example 1 is that the pore size in the foamed substrate is 50 μm and the porosity is 70%, which ultimately yields a photovoltaic backsheet.

[0055] Example 5

[0056] The difference from Example 1 is that the pore size in the foamed substrate is 60μm and the porosity is 80%, which ultimately yields a photovoltaic backsheet.

[0057] Example 6

[0058] The difference from Example 1 is that the mass ratio of the second coating in the permeation layer is 1%, and a photovoltaic backsheet is finally obtained.

[0059] Example 7

[0060] The difference from Example 1 is that the mass ratio of the second coating in the permeation layer is 8%, and a photovoltaic backsheet is finally obtained.

[0061] Example 8

[0062] The difference from Example 1 is that the porosity of the permeation layer is 50% and the thickness is 0.8 μm, which ultimately yields a photovoltaic backsheet.

[0063] Example 9

[0064] The difference from Example 1 is that the porosity of the permeation layer is 60% and the thickness is 1.5 μm, which ultimately yields a photovoltaic backsheet.

[0065] Example 10

[0066] The difference from Example 1 is that the thickness of the adhesive layer is 10 μm, and a photovoltaic backsheet is finally obtained.

[0067] Example 11

[0068] The difference from Example 1 is that the thickness of the adhesive layer is 2μm, resulting in a photovoltaic backsheet.

[0069] Comparative Example 1

[0070] The difference from Example 7 is that no epoxy resin is added to the coating, resulting in a photovoltaic backsheet.

[0071] Comparative Example 2

[0072] The difference from Example 7 is that the thickness of the permeation layer is 0.01 μm, and a photovoltaic backsheet is finally obtained.

[0073] Comparative Example 3

[0074] The difference from Example 7 is that the thickness of the permeation layer is 1.5 μm, and a photovoltaic backsheet is finally obtained.

[0075] Comparative Example 4

[0076] The difference from Example 7 is that the mass ratio of the second foaming material in the foamed base layer is 50%, the pore size is 55μm and the porosity is 75%, and the high reflectivity of the foamed base layer is 80% at wavelengths of 400~1100nm, thus obtaining a photovoltaic backsheet.

[0077] Performance testing:

[0078] The photovoltaic backsheet, back layer encapsulating film, battery cells, front layer encapsulating film and front glass obtained from the above embodiments and comparative examples were stacked and assembled into a photovoltaic module. The photoelectric conversion efficiency, peel strength between photovoltaic backsheet and EVA and reflectivity of the photovoltaic module were tested, and the test results are listed in Table 1.

[0079] Test method:

[0080] Photovoltaic conversion power: tested according to IEC61215-2:2016:4.2;

[0081] Peel strength between photovoltaic backsheet and EVA: Refer to standard GB / T2790 "Test method for peel strength of adhesives at 180°, flexible materials to rigid materials";

[0082] Reflectance: The reflectance of the sample in the wavelength range of 700~1200nm was measured at room temperature using a UV-Vis spectrophotometer with a D65 / 10 light source.

[0083] Table 1

[0084]

[0085] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0086] In the first and second coatings mentioned above, the base resin provides the basic film-forming substance for the coating, forming a strong adhesive layer. The introduction of epoxy resin compensates for the shortcomings of low surface energy and weak adhesion of the resin, and epoxy resin can ensure the coating's UV resistance and weather resistance. High-reflectivity black pigment ensures the coating's high reflectivity, while the combined use of additives further optimizes the coating's performance, enhances the coating effect, and improves the long-term stability of the backing plate. Simultaneously, the first and second coatings, composed of the above components, have suitable permeability and low cost. Controlling the thickness of the permeation layer to 0.05~1μm ensures that the second coating can form a proper filling in the pores of the first foaming material. This prevents excessive permeation of the second coating from filling the pore structure and affecting reflectivity, while ensuring sufficient permeation, improving the bonding strength between the coating and the foaming material. This results in a black coating with low permeability, high adhesion, uniformity, stability, and good weather resistance, reducing light loss and significantly improving the backing plate's reflectivity. Meanwhile, the reflectivity of the foamed substrate remains at a high level of 90% to 95% at wavelengths of 400 to 1100 nm. Applying it to high-reflectivity black backsheets can effectively improve the light utilization rate of photovoltaic backsheets, thereby improving the power generation efficiency of photovoltaic modules.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A photovoltaic backsheet, characterized in that, The photovoltaic backsheet comprises an adhesive layer, a permeable layer, a foamed base layer, and a weather-resistant layer stacked sequentially; wherein, the adhesive layer comprises a first coating. The permeation layer comprises a first foaming material and a second coating. By weight, the first coating and the second coating each independently comprise: 20-50 parts of matrix resin; 0.5 to 10 parts of epoxy resin; 0.5 to 5 parts of high-reflection black pigment; 13.1 to 65 parts of adjuvants; The thickness of the permeable layer is 0.05~1μm; the reflectivity of the foamed base layer is 90%~95% at a wavelength of 400~1100nm.

2. The photovoltaic backsheet according to claim 1, characterized in that, The second coating in the permeation layer accounts for 0.1% to 2% of the total mass; and / or, the porosity of the permeation layer is 5% to 50%; and / or, the thickness of the permeation layer is 0.05 to 0.8 μm.

3. The photovoltaic backsheet according to claim 1 or 2, characterized in that, The foamed base layer includes a second foamed material, wherein the first foamed material and the second foamed material are each independently selected from any one or more of foamed PET, PP, PU, ​​PVC, PVB, PI, and PHA; And / or, the mass percentage of the second foaming material in the foamed base layer is 70% to 90%; And / or, the thickness of the foamed base layer is 50~300μm; And / or, the pore size of the foamed base layer is 0.5~50μm, and the porosity of the foamed base layer is 30%~70%.

4. The photovoltaic backsheet according to any one of claims 1 to 3, characterized in that, The weather-resistant layer is a combination of an adhesive layer and a weather-resistant film layer or a weather-resistant outer coating; and / or, the thickness of the weather-resistant layer is 10~50μm.

5. The photovoltaic backsheet according to any one of claims 1 to 4, characterized in that, The thickness of the adhesive layer is 3~10μm.

6. The photovoltaic backsheet according to any one of claims 1 to 5, characterized in that, The photovoltaic backsheet satisfies at least one of the following technical features (1) to (7): (1) The matrix resin is selected from any one or more of fluorocarbon resin, acrylic resin and polyester resin; (2) The epoxy resin is selected from any one or more of alicyclic epoxy resin, modified bisphenol A type epoxy resin, modified bisphenol F type epoxy resin, siloxane-containing modified epoxy resin, and photothermal dual-curing epoxy resin; (3) The high-reflectivity black pigment is selected from any one or more of organic pigments and inorganic pigments; the organic pigment is selected from any one or more of direct lightfast dyes, direct diazo dyes, direct cross-linked dyes, azo dyes containing complex metals, fused ring aromatic pigments, and heterocyclic aromatic pigments; the inorganic pigment is selected from any one or more of copper chromium black and manganese chromium black. (4) The additives include 2 to 15 parts of inorganic filler, wherein the inorganic filler is selected from any one or more of anti-scratch powder, transparent powder, silica powder, glass powder and matting powder; (5) The additives include 1 to 15 parts of curing agent, wherein the curing agent is selected from any one or more of aromatic isocyanate curing agents, aliphatic isocyanate curing agents and blocked isocyanate curing agents; (6) The additive includes 10 to 30 parts of an organic solvent, wherein the organic solvent is selected from any one or more of ethanol, n-butanol, ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, xylene, and methyl ethyl ketone; (7) The additives also include 0.1 to 5 parts of other additives, which are selected from any one or more of dispersants, antioxidants, leveling agents, catalysts, and coupling agents.

7. The photovoltaic backsheet according to claim 6, characterized in that, The photovoltaic backsheet satisfies at least one of the following technical features (1) to (5): (1) The dispersant is an anionic dispersant and / or a polymeric dispersant; (2) The antioxidant is one or more of the following: pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di-tert-butyl-4-methylphenol, 4,4'-diisopropylphenyl diphenylamine, and pentaerythritol β-dodecyl thiopropionate; (3) The leveling agent is one or more of the following: polyacrylate leveling agent, fluorocarbon modified polyacrylate leveling agent, fluorinated surfactant, polyether modified polysiloxane leveling agent, and reactive polysiloxane leveling agent; (4) The catalyst is an organotin catalyst; (5) The coupling agent is one or more of vinyltrimethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropylmethyldimethoxysilane, isopropyltris(dioctylpyrophosphate)titanate, and bis(dioctyloxypyrophosphate)ethylenetitanate.

8. The photovoltaic backsheet according to any one of claims 1 to 7, characterized in that, The viscosity of the first coating is 1000~10000 mPa·s, preferably 4000~8000 mPa·s; and / or the viscosity of the second coating is 1000~10000 mPa·s, preferably 4000~8000 mPa·s.

9. A method for preparing a photovoltaic backsheet according to any one of claims 1 to 8, characterized in that, The preparation method includes: After applying a first coating to the first surface of the foamed substrate, the substrate is dried and cured sequentially to form an adhesive layer and a penetration layer. A weather-resistant layer is then applied to the surface of the foamed substrate opposite to the first surface to obtain the photovoltaic backsheet. Preferably, the drying temperature is 170~180℃ and the drying time is 2~5 minutes.

10. A photovoltaic module, comprising a backsheet, characterized in that, The backsheet is the photovoltaic backsheet according to any one of claims 1 to 8 or the photovoltaic backsheet prepared by the preparation method according to claim 9.

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