Composite film, method for preparing the same, and photovoltaic module

Abstract

This application relates to a composite film, its preparation method, and a photovoltaic module, falling within the field of photovoltaic technology. The composite film includes a barrier layer, a black high-reflectivity layer, and a white high-reflectivity layer. The water vapor transmission rate of the barrier layer is less than 0.1 g / m³. 2 The composite film with a multi-layered functional structure provided in this application sets a barrier layer with excellent barrier effect on the black high-reflection layer and the white high-reflection layer. On the one hand, it can prevent the colorant molecules in the black high-reflection layer from migrating under the influence of external factors, that is, prevent itself from fading, thereby reflecting sunlight to the upper solar cell layer and ensuring that the photovoltaic module as a whole has good output power. On the other hand, it can prevent water vapor from negatively affecting the lower structure, protect the use environment of the black high-reflection layer and the white high-reflection layer, thereby improving the stability of the black high-reflection layer and the white high-reflection layer, and achieving the effect of extending the service life of the film material and maintaining its high reflectivity.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular to a composite film, its preparation method, and a photovoltaic module. Background Technology

[0002] With the development of the photovoltaic industry, various photovoltaic module products, while meeting the requirement of high output power, are also facing increasingly higher demands for aesthetics. In recent years, black photovoltaic modules, as a type of aesthetically pleasing photovoltaic module, have been widely used as encapsulation materials, mainly including black high-reflective adhesive films and black solar backsheets. They are produced through processing using titanium black and other organic dyes. Typically, black photovoltaic modules can absorb light above 400nm. During the power generation process in conjunction with the overall photovoltaic module, the temperature of the black photovoltaic module will increase, resulting in a 3-5% decrease in output power.

[0003] Under normal temperature and pressure conditions, the backsheet and encapsulant film of existing black photovoltaic modules can maintain a relatively stable state when produced separately. However, after being laminated into photovoltaic modules, and subjected to PCT aging, boiling aging, or high temperature and humidity and ultraviolet aging, the colorant molecules in the high-reflectivity black encapsulant film migrate under the influence of external factors (high heat, high humidity, etc.), macroscopically manifesting as color difference and fading. When colorant molecules migrate to the surface of the cell or other components, it not only affects the normal operation of other functional structures, but also significantly reduces the overall power generation of the photovoltaic module. Furthermore, the black high-reflectivity encapsulant film in black photovoltaic modules, as an encapsulation material, is prone to adhesive overflow during the lamination process. Summary of the Invention

[0004] To address the problem that colorant molecules within the adhesive film can migrate under the influence of external factors, negatively impacting photovoltaic modules, this application provides a composite film, its preparation method, and a photovoltaic module thereof.

[0005] This application provides a composite film and its preparation method, which, along with a photovoltaic module, adopts the following technical solution: A composite membrane includes a barrier layer, a black high-reflectivity layer, and a white high-reflectivity layer, wherein the water vapor transmission rate of the barrier layer is less than 0.1 g / m³. 2 ·day; The barrier layer includes a protective layer and a functional layer. The functional layer is attached to the protective layer. The functional layer, by weight, includes 130-150 parts of a first resin, 35-45 parts of a first nanomaterial, and 10-20 parts of a curing agent.

[0006] By adopting the above technical solution, the composite film with a multi-layered functional structure provided in this application, through the setting of a barrier layer with excellent barrier effect on the black high-reflection layer and the white high-reflection layer, on the one hand, prevents the colorant molecules in the black high-reflection layer from migrating under the influence of external factors, that is, prevents itself from fading, thereby reflecting sunlight to the upper battery cell layer, so as to ensure that the photovoltaic module as a whole has good output power; on the other hand, the barrier layer can prevent water vapor from having a negative impact on the lower structure, that is, indirectly protect the use environment of the black high-reflection layer and the white high-reflection layer, thereby improving the stability of the black high-reflection layer and the white high-reflection layer, achieving the effect of extending the service life of the film material and maintaining its high reflectivity.

[0007] In one specific implementation scheme, the first nanomaterial comprises organic nanomaterials and inorganic nanomaterials, wherein the organic nanomaterials comprise modified polystyrene microspheres; the inorganic nanomaterials comprise one or more of nano-titanium dioxide, nano-calcium carbonate, nano-silica, nano-boron nitride, nano-chromium oxide, and nano-graphene; the mass ratio of the organic nanomaterials to the inorganic nanomaterials is 1:(1.5-2.3); and / or the particle size of the first nanomaterials is 50-150 nm; The first resin includes one or more of fluorocarbon resin, polyester resin, acrylic resin and epoxy resin; The curing agent includes one or more of polyurethane curing agents, isocyanate curing agents, and epoxy curing agents.

[0008] By adopting the above technical solutions and selecting different types of resins, such as fluorocarbon resin, polyester resin, acrylic resin and epoxy resin, as well as the combination of organic and inorganic nanomaterials, a variety of properties can be comprehensively improved in the composite film. Among them, fluorocarbon resin can improve chemical corrosion resistance, polyester resin can improve wear resistance, and epoxy resin can improve mechanical strength. The combined use of organic and inorganic nanomaterials leverages the unique properties of each, allowing them to complement each other's strengths. Organic nanomaterials, such as modified polystyrene microspheres, may exhibit good flexibility and toughness, absorbing energy when subjected to external impact or deformation, thus improving the flexibility and tensile strength of composite materials. Inorganic nanomaterials, such as nano-titanium dioxide, possess excellent weather resistance, resisting erosion from natural environmental factors like ultraviolet radiation, oxidation, and deliquescence, thereby extending the service life of composite materials. The combined use of organic and inorganic nanomaterials can construct complex interfacial structures, enhancing the barrier properties of composite materials. Inorganic materials like nano-titanium dioxide can form dense barriers on material surfaces, preventing gas or liquid penetration and further improving the barrier properties of composite materials. By rationally adjusting the mass ratio of organic and inorganic nanomaterials, an optimal balance between flexibility, weather resistance, and barrier properties can be achieved. Furthermore, by controlling the particle size of the first nanomaterial to be between 50-150 nm, its relatively large surface area allows for better interaction with the matrix resin. Due to the small particle size of the nanomaterial, it has a high specific surface area and high surface activity, which is conducive to full contact and interaction with the resin matrix, thereby achieving better dispersibility. This good dispersibility helps prevent the nanomaterial from agglomerating or accumulating, ensuring its uniform distribution in the composite material. In addition, within the particle size range of 50-150 nm, the nanomaterial has high surface activity, which means that there are a large number of active functional groups or defect sites on the surface of the nanomaterial, which can undergo physical or chemical adsorption with the resin matrix, thereby promoting good bonding between the two. This good interfacial activity helps to improve the interfacial strength and durability of the composite material, and reduce the possibility of interfacial shear stress and interfacial separation.

[0009] In one specific implementation, the method for preparing the modified polystyrene microspheres includes the following steps: (1) First, styrene is copolymerized with functional monomers to obtain modified polystyrene precursor; the functional monomers include monomers containing amino, sulfonic acid and carboxyl groups; (2) The modified polystyrene precursor from step (1) is then subjected to suspension polymerization to obtain the modified polystyrene microspheres.

[0010] By employing the above technical solution and adding functional monomers containing amino, sulfonic acid, and carboxyl groups for copolymerization, these active functional groups can be introduced onto the surface of modified polystyrene microspheres. These functional groups are chemically reactive, making the microsphere surface more susceptible to chemical reactions with other materials, thus enhancing the surface activity of the modified polystyrene microspheres. This allows the modified polystyrene microspheres to better interact chemically or physically with other materials or systems, enhancing their application performance in composite materials and other fields. Furthermore, the introduction of amino, sulfonic acid, and carboxyl groups allows these functional groups to interact with other functional groups in the matrix through hydrogen bonding, electrostatic interactions, and other means, thereby improving the bonding between the microspheres and the matrix. The improved compatibility enhances the relationship between modified polystyrene microspheres and other matrices (such as resin matrices), improving their dispersibility and binding properties in composite materials. This, in turn, helps improve the performance of composite materials, such as strength, toughness, and durability. Furthermore, by selecting different functional monomers, the surface functional groups of modified polystyrene microspheres can be controlled, thereby endowing them with different chemical properties and functions. For example, amino groups can be used to react with other materials containing acidic functional groups, sulfonic acid groups can make modified polystyrene microspheres hydrophilic, and carboxyl groups can be used to react with alkaline substances, thus giving modified polystyrene microspheres more application characteristics.

[0011] In one specific implementation, the barrier layer has a light transmittance of more than 90% in the wavelength range of 400-1100nm.

[0012] In one specific implementation, the black high-reflectivity layer comprises, by weight, 140-160 parts of a second resin, 10-20 parts of a colorant, 10-20 parts of a second nanomaterial, and 1-3 parts of a crosslinking agent.

[0013] In one specific implementation, the colorant comprises dye red, dye yellow and dye blue, and / or the mass percentage of said dye red, dye yellow and dye blue is (20-25%):(40-50%):(25-30%). The second resin includes one or more of ethylene copolymer resins, propylene copolymer resins, and vinyl acetate copolymer resins; The second nanomaterial includes one or more of nano-silica and nano-titanium dioxide; The crosslinking agent includes one or more of tert-butyl peroxide-2-ethylhexanoate, dipentaerythritol hexaacrylate, and propoxytrimethylolpropane triacrylate.

[0014] In one specific implementation, the black high-reflectivity layer further includes a surfactant, which includes one or more of sodium dodecylbenzenesulfonate, alkyl glucoside, fatty acid glycerides, fatty acid sorbitan, polysorbate, and sodium glycocholate; and / or the mass ratio of the surfactant to the second nanomaterial is (0.1-0.2):1.

[0015] By adopting the above technical solution and improving each component in the black high reflectivity layer, the second nanomaterial and the surfactant are combined to enable the second nanomaterial to be uniformly dispersed in the resin system mixed with colorant. This improves the adhesion and compatibility of the second nanomaterial and the colorant, and to a certain extent blocks the colorant molecules of different sizes that are decomposed during the use of the black high reflectivity layer, thereby further preventing the problem of color migration.

[0016] In one specific implementation, the black high-reflectivity layer has a light reflectivity of 10%-15% in the 280-1400nm wavelength range; the black high-reflectivity layer has a transmittance of less than 0.5% for ultraviolet light in the 280-400nm wavelength range; the black high-reflectivity layer has a transmittance of less than 0.5% for visible light in the 400-700nm wavelength range; and the black high-reflectivity layer has a transmittance of more than 75% for infrared light in the 760-1100nm wavelength range. The white high-reflectivity layer has a reflectivity of more than 95% for light in the wavelength range of 400-1200nm.

[0017] In one specific implementation, the degree of cross-linking between the black high-reflectivity layer and the white high-reflectivity layer is 20%-50%.

[0018] By adopting the above technical solution, and achieving a crosslinking degree of 20%-50% between the black and white high-reflectivity layers, abnormal adhesive overflow during the lamination process of the composite film can be reduced. Pre-crosslinking treatment of the black and white high-reflectivity layers increases the material's stability and solvent resistance. Pre-crosslinking also helps improve the material's thermal stability, ensuring structural stability and performance at high temperatures, thus reducing adhesive overflow caused by thermal pressure during lamination. By controlling the crosslinking degree between the black and white high-reflectivity layers to between 20% and 50%, a good balance can be achieved, maintaining sufficient flexibility while improving stability during lamination, thereby reducing the risk of adhesive overflow. Pre-crosslinking treatment also improves the mechanical strength and wear resistance of the black and white high-reflectivity layers, increasing the durability and service life of the composite film. Furthermore, pre-crosslinking treatment makes the surfaces of the black and white high-reflectivity layers smoother and more uniform, improving their bonding strength with the substrate, thereby optimizing the lamination process and reducing the scrap rate during production.

[0019] In one specific implementation, an adhesive layer is provided between the barrier layer and the black high-reflectivity layer or between the barrier layer and the white high-reflectivity layer, and the adhesive layer includes an ultraviolet absorber; The ultraviolet absorber includes one or more of the following: salicylic acid esters, benzophenones, benzotriazoles, substituted acrylonitriles, triazines, and hindered amines.

[0020] By adopting the above technical solution and setting an adhesive layer with excellent adhesion, displacement of materials on both sides of the adhesive bond can be reduced during lamination, thus mitigating the risk of adhesive overflow to some extent. Furthermore, since the protective layer of the barrier layer can be made of PET, the bond between the adhesive film and PET alone is easily detached after conventional damp heat aging. Therefore, the barrier layer and the adhesive film must be bonded together with an adhesive, and this adhesive layer meets its application requirements. Simultaneously, incorporating a certain amount of UV absorber into the adhesive layer meets the actual needs of composite films with different interlayer bonding structures. On the one hand, it improves the bonding effect between the upper and lower layers; on the other hand, it reduces the risk of UV aging of the lower film layer.

[0021] In one specific implementation, the ultraviolet cutoff layer has an absorption rate of >90% for ultraviolet light in the wavelength range of 280-380nm; The adhesive layer has a transmittance of less than 5% for ultraviolet light in the wavelength range of 280-380nm, and a transmittance of more than 90% for light in the wavelength range of 400-1100nm.

[0022] By adopting the above technical solution, the ultraviolet cutoff layer can effectively absorb ultraviolet rays while maintaining transparency. The ultraviolet cutoff layer can be applied in the production of photosensitive materials to prevent ultraviolet rays from damaging the photosensitive materials, thereby improving the quality and service life of the photosensitive materials.

[0023] A photovoltaic module includes photovoltaic glass, an encapsulating film, solar cells, and a photovoltaic backsheet. The photovoltaic module has a composite film as described above, which is disposed between the solar cells and the photovoltaic backsheet.

[0024] By adopting the above technical solution, the photovoltaic module of this application connects the solar cells and the photovoltaic backsheet through a composite film, which can improve the problem of color difference in the appearance of the photovoltaic module, meet the aesthetic appearance requirements of the photovoltaic module, and block substances such as oxygen and water vapor from "invading" the solar cells, thereby improving the overall output power of the photovoltaic module, increasing the overall reflectivity, improving the utilization rate of sunlight by the photovoltaic module, reducing the temperature of the photovoltaic module during power generation, and thus extending the service life of the photovoltaic module.

[0025] In summary, this application includes at least one of the following beneficial technical effects: 1. The composite film with a multi-layered functional structure provided in this application, by setting a barrier layer with excellent barrier effect on the black high-reflection layer and the white high-reflection layer, on the one hand, prevents the colorant molecules in the black high-reflection layer from migrating under the influence of external factors, that is, prevents itself from fading, thereby reflecting sunlight to the upper battery cell layer, so as to ensure that the photovoltaic module as a whole has good output power; on the other hand, the barrier layer can prevent moisture from negatively affecting the lower structure, that is, indirectly protect the use environment of the black high-reflection layer and the white high-reflection layer, thereby improving the stability of the black high-reflection layer and the white high-reflection layer, achieving the effect of extending the service life of the film material and maintaining its high reflectivity. 2. The composite film of this application can be used in photovoltaic modules. By connecting the solar cells and the photovoltaic backsheet through the composite film, the problem of color difference in the appearance of photovoltaic modules can be improved, meeting the aesthetic requirements of photovoltaic modules. It can also block oxygen, water vapor and other substances from "invading" the solar cells, improve the overall output power of photovoltaic modules, improve the overall reflectivity, improve the utilization rate of solar light by photovoltaic modules, and reduce the temperature of photovoltaic modules during power generation, thereby extending the service life of photovoltaic modules. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the composite membrane in Embodiment 1 of this application.

[0027] Explanation of reference numerals in the attached diagram: 1. Barrier layer; 11. Protective layer; 12. Functional layer; 2. Black high-reflectivity layer; 3. White high-reflectivity layer; 4. Ultraviolet cutoff layer; 5. Adhesive layer. Detailed Implementation

[0028] The following is in conjunction with the appendix Figure 1 This application will be described in further detail.

[0029] Reference Figure 1 This application discloses a composite film, which includes, but is not limited to, applications in photovoltaic module encapsulation. As an optional embodiment, the composite film includes, from top to bottom, a UV cutoff layer 4, a barrier layer 1, a black high-reflectivity layer 2, and a white high-reflectivity layer 3, arranged sequentially; the water vapor transmission rate of the barrier layer 1 is less than 0.1 g / m³. 2 ·day; The composite film with a multi-layered functional structure provided in this application has a barrier layer 1 with excellent barrier effect set on top of the black high-reflection layer 2 and the white high-reflection layer 3. On the one hand, it prevents the colorant molecules in the black high-reflection layer 2 from migrating under the influence of external factors, that is, it prevents the colorant from fading itself, and at the same time prevents it from negatively affecting the performance of other layers, that is, it prevents the colorant from fading itself, thereby preventing negative impact on photovoltaic modules, thus ensuring that the performance and quality of the entire composite film are effectively maintained and improving performance. On the other hand, the barrier layer 1 can prevent moisture from negatively affecting the underlying structure, that is, it indirectly protects the operating environment of the black high-reflection layer 2 and the white high-reflection layer 3, thereby improving the physical stability of the black high-reflection layer 2 and the white high-reflection layer 3, achieving the effect of extending the service life of the film material and maintaining its high reflectivity.

[0030] The ultraviolet cutoff layer 4 has an absorption rate of >90% for ultraviolet light in the wavelength range of 280-380nm, a transmittance of <5% for ultraviolet light in the wavelength range of 280-380nm, and a transmittance of >90% for light in the wavelength range of 400-1100nm. The ultraviolet cutoff layer 4 is a film layer with high cutoff for ultraviolet light, and the thickness of the ultraviolet cutoff layer 4 is 200-400μm.

[0031] The material of the ultraviolet cutoff layer 4 includes, but is not limited to, using polymers as the base material. For example, polymers include polyimide, polyester, and polypropylene. Additives with ultraviolet cutoff function include, but are not limited to, being made from organic materials or silicon-based materials. Specifically, organic materials such as benzimidazole and dihydropyran have good ultraviolet absorption properties and can be used to prepare the ultraviolet cutoff layer 4; silicon-based materials such as nanocrystalline silicon and silicon dioxide have strong ultraviolet absorption capabilities and can be used to prepare the ultraviolet cutoff layer 4. The UV cutoff layer 4 effectively absorbs ultraviolet light while maintaining transparency. Its main function is to prevent harmful, high-energy ultraviolet light from entering the photosensitive material, thereby preventing rapid aging of the photosensitive material. The UV cutoff layer 4 can be applied in the production of photovoltaic modules to prevent ultraviolet light from damaging the modules made from the photosensitive material, thus improving the quality and lifespan of the photovoltaic modules.

[0032] The barrier layer 1 includes a protective layer 11 and a functional layer 12 attached to the protective layer 11. The light transmittance of the barrier layer 1 in the wavelength range of 400-1100nm is greater than 90%. The coating thickness of the functional layer 12 on the protective layer 11 is 5-30μm. The protective layer 11 includes, but is not limited to, a PET layer. The functional layer 12 includes 130-150 parts of a first resin, 35-45 parts of a first nanomaterial, and 10-20 parts of a curing agent. The thickness of the barrier layer 1 is 10-20μm. The first resin includes one or more of fluorocarbon resin, polyester resin, acrylic resin and epoxy resin; by selecting different types of resins, such as fluorocarbon resin, polyester resin, acrylic resin and epoxy resin, and the combination of organic and inorganic nanomaterials, a variety of properties can be comprehensively improved in the composite film. Among them, fluorocarbon resin can improve chemical corrosion resistance, polyester resin can improve wear resistance, and epoxy resin can improve mechanical strength. The first type of nanomaterials includes organic nanomaterials and inorganic nanomaterials; Organic nanomaterials include modified polystyrene microspheres. The main framework of polystyrene microspheres is composed of benzene rings, which have high chemical reactivity. Through appropriate reaction conditions, such as aromatization and alkylation, different functional groups can be introduced onto the benzene rings, thereby changing the properties and functions of polystyrene microspheres. The olefin double bonds in polystyrene microspheres are also active centers for chemical reactions. Through ring-opening reactions and addition reactions of olefin double bonds, various functional groups, such as carboxyl, amino, and hydroxyl groups, can be introduced, thereby changing the chemical properties and surface characteristics of polystyrene microspheres. The preparation method of modified polystyrene microspheres includes the following steps: (1) First, styrene is copolymerized with functional monomers to obtain modified polystyrene precursor; the functional monomers include monomers containing amino, sulfonic acid and carboxyl groups; (2) The modified polystyrene precursor from step (1) is then subjected to suspension polymerization to obtain modified polystyrene microspheres.

[0033] Adding functional monomers containing amino, sulfonic acid, and carboxyl groups for copolymerization can introduce these active functional groups onto the surface of modified polystyrene microspheres. These functional groups are chemically reactive, making the surface of the microspheres more likely to react chemically with other materials, thus enhancing the surface activity of the modified polystyrene microspheres. This allows the modified polystyrene microspheres to better interact chemically or physically with other materials or systems, thereby enhancing their application performance in composite materials and other fields. The introduction of functional groups such as amino, sulfonic acid, and carboxyl groups improves the bonding and compatibility between microspheres and the matrix by enabling these functional groups to interact with other functional groups in the matrix through hydrogen bonding, electrostatic interactions, and other means. This enhances the compatibility of modified polystyrene microspheres with other matrices (such as resin matrices), improves the dispersion and binding of modified polystyrene microspheres in composite materials, and thus helps improve the performance of composite materials, such as strength, toughness, and durability. Furthermore, by selecting different functional monomers, the functional groups on the surface of modified polystyrene microspheres can be controlled, thereby endowing modified polystyrene microspheres with different chemical properties and functions. For example, amino groups can be used to react with other materials containing acidic functional groups, sulfonic acid groups can make modified polystyrene microspheres hydrophilic, and carboxyl groups can be used to react with alkaline substances, thus giving modified polystyrene microspheres more application characteristics.

[0034] The inorganic nanomaterials include one or more of nano-titanium dioxide, nano-calcium carbonate, nano-silicon dioxide, nano-boron nitride, nano-chromium oxide, and nano-graphene. Preferably, the inorganic nanomaterial is nano-titanium dioxide. The mass ratio of organic nanomaterials to inorganic nanomaterials is 1:(1.5-2.3). And / or the particle size of the first nanomaterial is 50-150 nm. The combined use of organic and inorganic nanomaterials leverages the unique properties of each, allowing them to complement each other's strengths. Organic nanomaterials, such as modified polystyrene microspheres, may exhibit good flexibility and toughness, absorbing energy when subjected to external impact or deformation, thus improving the flexibility and tensile strength of composite materials. Inorganic nanomaterials, such as nano-titanium dioxide, possess excellent weather resistance, resisting erosion from natural environmental factors like ultraviolet radiation, oxidation, and deliquescence, thereby extending the service life of composite materials. The combined use of organic and inorganic nanomaterials can construct complex interfacial structures, enhancing the barrier properties of composite materials. Inorganic materials like nano-titanium dioxide can form dense barriers on material surfaces, preventing gas or liquid penetration and further improving the barrier properties of composite materials. By rationally adjusting the mass ratio of organic and inorganic nanomaterials, an optimal balance between flexibility, weather resistance, and barrier properties can be achieved. Furthermore, by controlling the particle size of the first nanomaterial to be between 50-150 nm, its relatively large surface area allows for better interaction with the matrix resin. Due to the small particle size of the nanomaterial, it has a high specific surface area and high surface activity, which is conducive to full contact and interaction with the resin matrix, thereby achieving better dispersibility. This good dispersibility helps prevent the nanomaterial from agglomerating or accumulating, ensuring its uniform distribution in the composite material. In addition, within the particle size range of 50-150 nm, the nanomaterial has high surface activity, which means that there are a large number of active functional groups or defect sites on the surface of the nanomaterial, which can undergo physical or chemical adsorption with the resin matrix, thereby promoting good bonding between the two. This good interfacial activity helps to improve the interfacial strength and durability of the composite material, and reduce the possibility of interfacial shear stress and interfacial separation.

[0035] The thickness of the black high-reflectivity layer 2 is 20-100 μm. The black high-reflectivity layer 2 comprises, by weight, 140-160 parts of a second resin, 10-20 parts of a colorant, 10-20 parts of modified nanomaterials, and 1-3 parts of a crosslinking agent. The second resin includes, but is not limited to, ethylene-vinyl acetate copolymer, ethylene-α-olefin copolymer, ethylene-methyl methacrylate copolymer, ethylene-methacrylic acid ion-crosslinked polymer, low-density polyethylene, polypropylene, polybutene, polyvinyl butyral, and organosilicon materials. The colorants include red dye, yellow dye, and blue dye, with the mass ratio of red dye:yellow dye:blue dye being (20-25%):(40-50%):(25-30%). Black is achieved by adjusting the color using the principle of three primary colors. The second nanomaterial includes nano-silicon dioxide and nano-titanium dioxide; Crosslinking agents include one or more of tert-butyl peroxide-2-ethylhexanoate, pentaerythritol hexaacrylate, and propoxylated trimethylolpropane triacrylate; The black high-reflectivity layer 2 also includes a surfactant, which includes one or more of sodium dodecylbenzenesulfonate, alkyl glucoside, fatty acid glycerides, fatty acid sorbitan, polysorbate, and sodium glycocholate; the mass ratio of the surfactant to the second nanomaterial is (0.1-0.2):1. By improving the components of the black high-reflectivity layer 2, the second nanomaterial and the surfactant are combined to enable the second nanomaterial to be uniformly dispersed in the resin system mixed with the colorant. This improves the adhesion and compatibility between the second nanomaterial and the colorant, and to a certain extent blocks the colorant molecules of different sizes that are decomposed during the use of the black high-reflectivity layer 2, thereby further preventing the problem of color migration.

[0036] The black high-reflectivity layer 2 has a light reflectance of 10%-15% in the 280-1400nm wavelength range; its transmittance for ultraviolet light in the 280-400nm wavelength range is less than 0.5%; its transmittance for visible light in the 400-700nm wavelength range is less than 0.5%; and its transmittance for infrared light in the 760-1100nm wavelength range is greater than 75%. To improve the weather resistance and mechanical properties of the black high-reflectivity layer 2, plasticizers or antioxidants may be added, including but not limited to plasticizers. Plasticizers can improve the flexibility and toughness of the copolymer, while antioxidants can prevent material aging and degradation, thus extending the service life of the black high-reflectivity layer 2.

[0037] The white high-reflectivity layer 3 has a reflectivity greater than 95% in the wavelength range of 400-1200 nm. The thickness of the white high-reflectivity layer 3 is 50-250 μm. The white high-reflectivity layer 3 is made by dispersing inorganic filler titanium dioxide in ethylene-vinyl acetate copolymer. In order to ensure the reflectivity of the white high-reflectivity layer 3, the filler content of inorganic filler titanium dioxide is included but not limited to 10%-30%, which can improve the reflectivity of the white high-reflectivity layer 3 and ensure that the light transmittance of the film is still high enough. With the white high-reflectivity layer 3 made of the above materials, the light passing through the black high-reflectivity layer 2 has a high reflectivity after passing through the white high-reflectivity layer 3, further improving the reflectivity of the entire composite film.

[0038] The overall cross-linking degree of the black high-reflectivity layer 2 and the white high-reflectivity layer 3 is 20%-50%. Maintaining this cross-linking degree reduces abnormal adhesive overflow during the lamination process. Pre-cross-linking of the black high-reflectivity layer 2 and the white high-reflectivity layer 3 increases the material's stability and solvent resistance. Pre-cross-linking also improves the material's thermal stability, ensuring structural stability and performance at high temperatures, and reducing adhesive overflow caused by thermal pressure during lamination. This is achieved by controlling the cross-linking degree of the black high-reflectivity layer 2 and the white high-reflectivity layer 3. The crosslinking degree of the high-reflectivity layer 3 is between 20% and 50%, which achieves a good balance, maintaining sufficient flexibility while improving stability during the lamination process, thereby reducing the risk of adhesive overflow. The pre-crosslinking treatment can also improve the mechanical strength and wear resistance of the black high-reflectivity layer 2 and the white high-reflectivity layer 3, thereby increasing the durability and service life of the composite film. Furthermore, the pre-crosslinking treatment can make the surfaces of the black high-reflectivity layer 2 and the white high-reflectivity layer 3 smoother and more uniform, improving their bonding strength with the substrate, thereby optimizing the lamination process and reducing the scrap rate during production.

[0039] An adhesive layer 5 is provided on the side of the barrier layer 1 near the ultraviolet cut-off layer 4 and the black high reflectivity layer 2. The adhesive layer 5 includes an ultraviolet absorber. The adhesive resin used in the adhesive layer 5 can be selected as one or a mixture of two of polyolefin resins and polyester resins. Ultraviolet absorbers include one or more of the following: salicylic acid esters, benzophenones, benzotriazoles, substituted acrylonitriles, triazines, and hindered amines; The adhesive layer 5 eliminates the need for solvent removal in the drying tunnel, is energy-saving and environmentally friendly, has high production efficiency, and allows for simultaneous lamination of both sides. It also exhibits good adhesion, reducing displacement of materials on both sides during lamination and mitigating the risk of adhesive overflow. Furthermore, since the protective layer 11 of the barrier layer 1 can be made of PET, the bond between the simple film and PET is easily detached after conventional humid heat aging. Therefore, the barrier layer 1 and the film must be bonded together with an adhesive, and this adhesive layer 5 meets these requirements.

[0040] The composite film with a multi-layered functional structure provided in this application, by setting a barrier layer 1 with excellent barrier effect on the black high-reflection layer 2 and the white high-reflection layer 3, on the one hand, prevents the colorant molecules in the black high-reflection layer 2 from migrating under the influence of external factors, that is, prevents itself from fading, thereby reflecting sunlight to the upper battery cell layer, so as to ensure that the photovoltaic module as a whole has good output power; on the other hand, the barrier layer 1 can prevent water vapor from having a negative impact on the lower structure, that is, indirectly protect the use environment of the black high-reflection layer 2 and the white high-reflection layer 3, thereby improving the stability of the black high-reflection layer 2 and the white high-reflection layer 3, and achieving the effect of extending the service life of the film material and maintaining its high reflectivity.

[0041] This application provides a method for preparing a composite membrane, using the following technical solution: S1: S10. The raw materials required for preparing the black high-reflectivity layer 2 are melt-co-extruded into a film to obtain the black high-reflectivity layer 2; the raw materials required for preparing the white high-reflectivity layer 3 are melt-co-extruded into a film to obtain the white high-reflectivity layer 3; the obtained black high-reflectivity layer 2 and the obtained white high-reflectivity layer 3 are then bonded together and subjected to irradiation crosslinking treatment; specifically, this includes, but is not limited to, adding fillers in the co-extrusion process. For the black high-reflectivity layer 2, an organic dye is added and dispersed in the ethylene-vinyl acetate copolymer in the extruder; for the white high-reflectivity layer 3, an inorganic filler, titanium dioxide, is added and dispersed in the ethylene-vinyl acetate copolymer in the extruder; the extruder melts the aforementioned multiple materials. By creating a black high-reflection layer 2 and a white high-reflection layer 3 on the same thin film, and controlling the material combination and thickness of different layers in the co-extrusion process, specifically controlling the thickness of the black high-reflection layer 2 to be 20-100 μm and the thickness of the white high-reflection layer 3 to be 50-250 μm, the desired black and white reflective properties can be achieved.

[0042] S20. Irradiation crosslinking treatment of the integrally formed black high reflectivity layer 2 and white high reflectivity layer 3 can improve their thermal stability, mechanical properties and chemical stability, so that the overall crosslinking degree of the black high reflectivity layer 2 and white high reflectivity layer 3 is between 20-50%. The irradiation crosslinking work of the black high reflectivity layer 2 and white high reflectivity layer 3 includes, but is not limited to, the use of electron beam irradiation or gamma ray irradiation equipment. The radiation dose applied during the irradiation of the black high reflectivity layer 2 and white high reflectivity layer 3 includes, but is not limited to, 10-50 kGy. In actual operation, experiments can be conducted to determine the appropriate irradiation dose and treatment conditions.

[0043] S2. Prepare the coating liquid for the functional layer 12, and then coat or vapor deposit the coating liquid onto the surface of the protective layer 11 to obtain the barrier layer 1. The specific steps of the coating method include: a. Preparing 130-150 parts of the first resin, 35-45 parts of the first nanomaterial, and 10-20 parts of the curing agent as raw materials for preparing the coating liquid, mixing and stirring to ensure that all components are fully and uniformly mixed together to prepare the functional layer 12 coating liquid; b. Coating: placing the PET protective layer 11 on a flat surface, and using a coating process to uniformly coat the functional layer 12 coating liquid onto the surface of the PET protective layer 11, including but not limited to using dip coating, scraping coating, or spraying methods; c. Drying and curing: drying the coated PET protective layer 11 to allow the barrier material to form a dense film structure, including but not limited to using natural drying, oven drying, or heat treatment methods for curing to form the barrier layer 1.

[0044] The specific steps of the vapor deposition method include: a. preparing 130-150 parts of the first resin, 35-45 parts of the first nanomaterial and 10-20 parts of the curing agent as raw materials for preparing the coating liquid, mixing and stirring to ensure that each component is fully and uniformly mixed together to prepare the vapor deposition liquid for the functional layer 12; b. vapor deposition: placing the PET protective layer 11 in a vacuum vapor deposition equipment, heating it to a certain temperature and generating sufficient vacuum, and then heating the vapor deposition liquid for the functional layer 12 to the evaporation temperature to evaporate and deposit it on the surface of the PET protective layer 11 to form the barrier layer 1, thus producing the barrier layer 1.

[0045] S3. Prepare adhesive solution for adhesive layer 5. In a solvent-free composite production line, use adhesive layer 5 to bond the UV cutoff layer 4 and the integrally formed black high reflective layer 2 and the black surface of the white high reflective layer 3 to both sides of the barrier layer 1, and press them together to form a composite. The specific steps include: a. Cleaning: Clean the surfaces of the UV-blocking layer 4 and the integrated black high-reflectivity layer 2 and white high-reflectivity layer 3 to be bonded, ensuring they are free of dust, oil, and other impurities; b. Adhesive application: Apply adhesive layer 5 to both sides of the barrier layer 1, including but not limited to spraying, rolling, or brushing; c. Bond the black sides of the UV-blocking layer 4 and the integrated black high-reflectivity layer 2 and white high-reflectivity layer 3 to both sides of the adhesive-coated barrier layer 1, ensuring accurate positioning during bonding to avoid air bubbles or misalignment; d. Pressing and molding: Place the bonded materials in a pressing device and press them together, setting appropriate parameters such as temperature, pressure, and time according to specific requirements and material characteristics.

[0046] S4. Place the multi-layer adhesive film layer that has been pressed in S3 into a curing room at 20-35℃ and cure for 20-30 hours to ensure that the adhesive reacts completely. After curing, the composite film is obtained. The specific steps include: a. Preparing a curing chamber, ensuring the temperature inside is controlled within the range of 20-35℃. A constant temperature chamber or other temperature control equipment can be used to maintain the required temperature; b. Placing the adhesive film layer: Place the pressed adhesive film layer into the curing chamber, taking care not to stack or compress the adhesive film layer to avoid affecting the curing effect; c. Setting the curing time to 20-30 hours based on experience and actual conditions, and regularly checking the temperature and humidity inside the curing chamber during the curing process to ensure the stability of the curing conditions; d. After the curing time is completed, remove the adhesive film layer from the curing chamber. At this point, the adhesive has fully reacted, forming a composite film.

[0047] In the above preparation process, the order of S1, S2, S3, and S4 can be interchanged.

[0048] This application also provides a photovoltaic module having the aforementioned composite film; the photovoltaic module includes photovoltaic glass, encapsulating film, solar cells, and a photovoltaic backsheet, with the composite film disposed between the solar cells and the photovoltaic backsheet; The photovoltaic module of this application connects the solar cells and the photovoltaic backsheet through a composite film, which can improve the problem of color difference in the appearance of the photovoltaic module, meet the aesthetic requirements of the photovoltaic module, and block substances such as oxygen and water vapor from "invading" the solar cells, thereby improving the overall output power of the photovoltaic module, increasing the overall reflectivity, improving the utilization rate of sunlight by the photovoltaic module, reducing the temperature of the photovoltaic module during power generation, and thus extending the service life of the photovoltaic module.

[0049] Example This application provides a composite membrane, such as Figure 1 As shown, from top to bottom, there are an ultraviolet cutoff layer 4, an (upper) adhesive layer 2, a protective layer 11, a functional layer 12, a (lower) adhesive layer 2, a black high reflectivity layer 2, and a white high reflectivity layer 3. The raw materials for each layer are shown in Table 1 below.

[0050] The components used in Examples 1-10 are described in detail below: Functional layer: (A) First resin (A1) Polyester resin (Nan Ya Plastics Industrial Co., Ltd., NPSN resin), (A2) Acrylic resin (Zhejiang Lihuo New Material Technology Co., Ltd., LHC1011 resin).

[0051] (B) First Nanomaterial (B1) Organic nanomaterials: modified polystyrene microspheres.

[0052] (B2) Inorganic nanomaterials: (B21) Nano titanium dioxide (Zhejiang Zhitai Nanomaterials Co., Ltd., ZT-T60), (B22) Nano calcium carbonate (Zhejiang Changshan Jinxiong Co., Ltd., CCR nano calcium carbonate), (B23) Nano silicon dioxide (Zhejiang Zhitai Nanomaterials Co., Ltd., ZT-SP30T).

[0053] (C) Curing agent (C1) Polyurethane curing agent (Asahi Kasei, TPA-90SB curing agent), (C2) Isocyanate curing agent (Covestro Polymer Co., Ltd., N3400 curing agent), (C3) Epoxy curing agent (Wanhua Chemical, WH-602).

[0054] Black high-reflectivity layer: (D) Second resin (D1) Ethylene copolymer resin (Total 282PV photovoltaic EVA resin from South Korea), (D2) Vinyl acetate copolymer resin (Lianhong UL00428 from Shandong).

[0055] (E) Coloring agent (E1) Dye Red (Clariant D3G70), (E2) Dye Yellow (Clariant H3G), (E3) Dye Blue (Clariant A2R).

[0056] (F) Second nanomaterial (F1) Nano silica (Zhejiang Zhitai Nano Micro New Materials Co., Ltd., ZT-SP30T), (F2) Nano titanium dioxide (Zhejiang Zhitai Nano Micro New Materials, ZT-T60).

[0057] (G) Crosslinking agent (G1) tert-butyl peroxide-2-ethylhexanoate, (G2) dipentaerythritol hexaacrylate.

[0058] (H) Surfactant (H1) Sodium dodecylbenzenesulfonate, (H2) Fatty acid glycerides.

[0059] Table 1 Comparative Example Comparative Example 1 This comparative example provides a composite film that differs from Example 1 in that no organic nanomaterials are added to the first nanomaterial of the functional layer. Comparative Example 2 This comparative example provides a composite film, which differs from Example 1 in that the mass ratio of organic nanomaterials to inorganic nanomaterials in the first nanomaterial of the functional layer is 3:1. Comparative Example 3 This comparative example provides a composite film that differs from Example 1 in that the mass ratio of surfactant to second nanomaterial in the black high-reflectivity layer is 1:1. Comparative Example 4 This comparative example provides a composite film that differs from Example 1 in that, in the preparation method, step S1 does not involve radiation crosslinking between the black high-reflectivity layer and the white high-reflectivity layer.

[0060] Performance testing The composite membranes prepared in Examples 1-10 and Comparative Examples 1-4 were subjected to the following performance tests, and the test results are shown in Table 2 below.

[0061] Test method: 1. Water vapor transmission rate: The barrier layers in each embodiment and comparative example were tested according to ASTM-F1249, "Standard Test Method for Water Vapor Transmission Rate of Plastic Films and Sheets". 2. Reflectivity test: Tests were conducted according to ASTM-17, "Test Methods for Solar Transmission and Reflection in Sheet Materials". 3. Photovoltaic module appearance test: Tests were conducted in accordance with IEC 61215 "Ground-mounted crystalline silicon photovoltaic modules - identification and type approval". The test conditions were 85°C, 85% humidity, and 2000 hours. The appearance of the photovoltaic modules before and after the damp heat aging test was monitored. Visual inspection revealed pigment agglomeration and precipitation in the composite film layer. 4. Peel strength test between conventional backsheet and the composite film of this application: The rigid material was tested according to the GB / T2790 test method for 180° peel strength of adhesives; After testing the peel strength between the back panel and the composite film of this application at 85℃, 85% humidity, and 2000h, visual inspection was conducted to check whether the black high-reflection layer of the composite film layer showed fading or color migration.

[0062] Table 2 Based on the analysis in Tables 1 and 2 above, the composite films of Examples 1-10 all exhibit good water-blocking properties. Furthermore, the color of the black high-reflectivity layer remained unchanged after aging tests at 85°C, 85% humidity, and 2000 hours. This indicates that the addition of the aforementioned nanomaterials and a certain degree of cross-linking in the composite film effectively prevents pigment migration, meeting the requirements for photovoltaic module use. Comparative Examples 1-3 show slightly poorer water-blocking properties, leading to pigment migration. In Comparative Example 4, the non-pre-cross-linked composite film exhibits mutual interference between the black and white high-reflectivity layers during lamination, resulting in abnormal appearance. After 2000 hours at 85°C and 85% humidity, pigment migration significantly impacts the peel strength between the conventional backsheet and the composite film.

[0063] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A composite membrane, characterized in that: It includes a barrier layer (1), a black high-reflectivity layer (2), and a white high-reflectivity layer (3), wherein the water vapor transmission rate of the barrier layer (1) is less than 0.1 g / m. 2 ·day; The barrier layer (1) includes a protective layer (11) and a functional layer (12). The functional layer (12) is attached to the protective layer (11). The functional layer (12) includes, by weight, 130-150 parts of a first resin, 35-45 parts of a first nanomaterial and 10-20 parts of a curing agent. The first nanomaterial comprises organic nanomaterials and inorganic nanomaterials. The organic nanomaterials include modified polystyrene microspheres. The inorganic nanomaterials include one or more of nano-titanium dioxide, nano-calcium carbonate, nano-silica, nano-boron nitride, nano-chromium oxide, and nano-graphene. The mass ratio of the organic nanomaterials to the inorganic nanomaterials is 1:(1.5-2.3). The particle size of the first nanomaterial is 50-150 nm. The degree of cross-linking between the black high-reflectivity layer (2) and the white high-reflectivity layer (3) is 20%-50%; the protective layer (11) is a PET layer; The first resin includes one or more of fluorocarbon resin, polyester resin, acrylic resin and epoxy resin; The black high-reflectivity layer (2) comprises, by weight, 140-160 parts of the second resin, 10-20 parts of the colorant, 10-20 parts of the second nanomaterial and 1-3 parts of the crosslinking agent; The second resin includes one or more of ethylene copolymer resins, propylene copolymer resins, and vinyl acetate copolymer resins; The second nanomaterial includes one or more of nano-silica and nano-titanium dioxide; The method for preparing the modified polystyrene microspheres includes the following steps: Step 1: First, copolymerize styrene with functional monomers to obtain modified polystyrene precursor; the functional monomers include monomers containing amino, sulfonic acid, and carboxyl groups; Step 2: The modified polystyrene precursor from Step 1 is then subjected to suspension polymerization to obtain the modified polystyrene microspheres.

2. The composite membrane according to claim 1, characterized in that: The curing agent includes one or more of polyurethane curing agents, isocyanate curing agents, and epoxy curing agents.

3. The composite membrane according to claim 1, characterized in that: The barrier layer (1) has a light transmittance of more than 90% in the wavelength range of 400-1100nm.

4. The composite membrane according to claim 1, characterized in that: The colorant includes dye red, dye yellow and dye blue, and the mass percentage of dye red, dye yellow and dye blue is (20-25%):(40-50%):(25-30%). The crosslinking agent includes one or more of tert-butyl peroxide-2-ethylhexanoate, dipentaerythritol hexaacrylate, and propoxylated trimethylolpropane triacrylate.

5. The composite membrane according to claim 1, characterized in that: The black high-reflectivity layer (2) also includes a surfactant, which includes one or more of sodium dodecylbenzenesulfonate, alkyl glucoside, fatty acid glycerides, fatty acid sorbitan, polysorbate, and sodium glycocholate; the mass ratio of the surfactant to the second nanomaterial is (0.1-0.2):

1.

6. The composite membrane according to claim 1, characterized in that: The black high reflectivity layer (2) has a light reflectivity of 10%-15% in the wavelength range of 280-1400nm; the black high reflectivity layer (2) has a transmittance of less than 0.5% for ultraviolet light in the wavelength range of 280-400nm; the black high reflectivity layer (2) has a transmittance of less than 0.5% for visible light in the wavelength range of 400-700nm; and the black high reflectivity layer (2) has a transmittance of more than 75% for infrared light in the wavelength range of 760-1100nm. The white high reflectivity layer (3) has a reflectivity of more than 95% for light in the wavelength range of 400-1200nm.

7. The composite membrane according to claim 1, characterized in that: An adhesive layer (5) is provided between the barrier layer (1) and the black high reflective layer (2). The adhesive layer (5) includes an ultraviolet absorber; The ultraviolet absorber includes one or more of the following: salicylic acid esters, benzophenones, benzotriazoles, substituted acrylonitriles, triazines, and hindered amines; The transmittance of the adhesive layer (5) to ultraviolet light in the wavelength range of 280-380nm is less than 5%, and the transmittance of the adhesive layer (5) to light in the wavelength range of 400-1100nm is greater than 90%.

8. The composite membrane according to claim 1, characterized in that: It also includes an ultraviolet cutoff layer (4), which is located on the light-facing side of the composite film; The ultraviolet cutoff layer (4) has an absorption rate of >90% for ultraviolet light in the wavelength range of 280-380nm.

9. A photovoltaic module, comprising photovoltaic glass, encapsulating film, solar cells, and photovoltaic backsheet, characterized in that: The photovoltaic module has a composite film as described in any one of claims 1-8, wherein the composite film is disposed between the solar cell and the photovoltaic backsheet.

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