Composite photovoltaic adhesive film, preparation method thereof and photovoltaic module

Abstract

The invention provides a composite photovoltaic adhesive film as well as a preparation method and application thereof. The composite photovoltaic adhesive film comprises a supporting layer and a bonding layer which are superposed, the supporting layer comprises graft copolymer resin obtained by carrying out graft-copolymerization reaction on first matrix resin, an acidic graft monomer and an olefin comonomer; the bonding layer comprises the following components in parts by weight: 80-100 parts of second matrix resin, 1-3 parts of a cross-linking agent, 0.3-1 part of a silane coupling agent and 5-10 parts of a tackifier; the first matrix resin and the second matrix resin are respectively and independently selected from one or more of ethylene-alpha olefin copolymer resin, ethylene-vinyl acetate copolymer resin and polyethylene resin. According to the composite photovoltaic adhesive film, the special supporting layer and the special bonding layer are designed and matched, and the obtained composite photovoltaic adhesive film can achieve good bonding and packaging effects at high temperature and high pressure.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic devices, and more specifically, to a composite photovoltaic encapsulant film, its preparation method, and a photovoltaic module. Background Technology

[0002] In high-tech fields, particularly in the photovoltaic industry and electronic device packaging, encapsulant films serve as a crucial material, not only for bonding and encapsulation but also directly impacting the photoelectric performance, mechanical strength, and environmental adaptability of components. With the continuous advancement of photovoltaic technology and the increasing complexity of electronic packaging requirements, single-function encapsulant films can no longer meet the demands of high-performance packaged components. For example, in photovoltaic packaged components, the encapsulant film needs to maintain good structural stability during high-temperature, high-pressure lamination to avoid poor solder joint bonding or film overflow due to excessive fluidity, which would affect the photoelectric conversion efficiency and aesthetics of the photovoltaic module. Simultaneously, the encapsulant film must form strong and stable bonds with components of different materials, such as glass, metal backsheets, and solar cells, to ensure the long-term performance and reliability of the packaged component in complex environments.

[0003] However, traditional encapsulant materials, such as EVA (ethylene-vinyl acetate copolymer) films, while exhibiting excellent adhesion, suffer from insufficient flow control under high temperature and pressure, easily leading to adhesive overflow during the encapsulation process and affecting encapsulation quality and module structural stability. To address this issue, the industry has attempted to increase the melting point and reduce the flowability of encapsulants through copolymerization technology to adapt to high-temperature and high-pressure lamination processes. While copolymerization technology has solved the flowability problem to some extent, the adhesion strength of these films to materials such as metal backsheets and glass still needs improvement. Especially in photovoltaic module encapsulation, high adhesion strength is crucial to ensuring the durability of modules under extreme climatic conditions. Traditional high-viscosity EVA films, although possessing strong adhesion, are prone to structural changes in the module during lamination due to their high flowability, affecting the overall efficiency and lifespan of the photovoltaic module.

[0004] Therefore, the industry urgently needs a new type of encapsulant material that can not only maintain low flowability in high-temperature, high-pressure encapsulation environments, avoiding structural deformation and adhesive overflow, but also exhibit extremely high adhesion performance when in contact with various materials, especially with rigid materials such as glass and metals, to meet the stringent requirements of high-performance photovoltaic modules and electronic packaging. This necessitates that the encapsulant material possess complex and sophisticated structural characteristics in its design, ensuring both stability and mechanical strength at high temperatures, while also considering compatibility and adhesion with various encapsulation materials, providing a solid foundation for the further development of the photovoltaic industry and electronic packaging technology.

[0005] Therefore, how to provide a new composite photovoltaic film that can balance low fluidity and high adhesion under high temperature and high pressure is one of the important technical problems that need to be solved in this field. Summary of the Invention

[0006] The main objective of this invention is to provide a composite photovoltaic encapsulant film, its preparation method, and its application, in order to solve the problem that existing photovoltaic encapsulant films are difficult to simultaneously possess low fluidity under high temperature and high pressure, as well as high adhesion to glass and metal materials.

[0007] To achieve the above objectives, a first aspect of the present invention provides a composite photovoltaic film comprising a stacked support layer and an adhesive layer; the support layer comprises a graft copolymer resin obtained by a graft-copolymerization reaction of a first matrix resin, an acidic graft monomer, and an olefinic comonomer; the adhesive layer comprises, by weight, 80-100 parts of a second matrix resin, 1-3 parts of a crosslinking agent, 0.3-1 parts of a silane coupling agent, and 5-10 parts of a tackifier; the first matrix resin and the second matrix resin are each independently selected from one or more of ethylene-α-olefin copolymer resin, ethylene-vinyl acetate copolymer resin, and polyethylene resin.

[0008] Further, the graft copolymer resin is obtained by grafting-copolymerization reaction of the first matrix resin, acidic graft monomer and olefin comonomer in a weight ratio of (4~8):1:(1~3); preferably, the graft copolymer resin is obtained by grafting-copolymerization reaction of the first matrix resin, acidic graft monomer and olefin comonomer in a weight ratio of (5.0~6.0):1:(1.2~1.5).

[0009] Furthermore, the acidic graft monomer is selected from one or more of acrylic acid, maleic anhydride, methacrylic acid, methyl acrylate and butyl acrylate, preferably acrylic acid and / or maleic anhydride, more preferably acrylic acid; the olefinic comonomer is selected from one or more of C6-C10 straight-chain olefins, styrene and glycidyl methacrylate, preferably one or more of n-heptene, n-octene and n-nonene, more preferably n-octene.

[0010] Furthermore, the melting point of the support layer is 95℃~130℃, and the melt index is 2g / 10min~5g / 10min.

[0011] Further, in the adhesive layer, the second matrix resin is an ethylene-vinyl acetate copolymer resin, and the vinyl acetate segment accounts for 25%~30% by weight in the ethylene-vinyl acetate copolymer resin; and / or, the crosslinking agent is selected from tert-butyl peroxycarbonate isopropyl ester, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, tert-butyl peroxycarbonate-2-ethylhexyl ester, 2,5-dimethyl-2,5- One or more of the following: di(tert-butylperoxy)hexane, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-pentylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-pentylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, 2,2-bis(tert-butylperoxy)butane, tert-pentyl peroxyhexyl carbonate, 2,5-dimethyl-2,5-bis(benzoylperoxy)-hexane, tert-pentyl peroxy carbonate, and tert-butyl peroxyhexanoate; and / or, the silane coupling agent is selected from one or more of γ-methacryloyloxypropyltrimethoxysilane, vinyltrimethoxysilane, and γ-methacryloyloxypropyltriethoxysilane; and / or, the tackifier is selected from one or more of terpene resin, β-pinene resin, and terpene-styrene resin.

[0012] Furthermore, the thickness ratio of the support layer to the adhesive layer is (2~3.5):1.

[0013] A second aspect of the present invention provides a method for preparing the above-mentioned composite photovoltaic film, comprising: step S1, mixing a first matrix resin, an acidic graft monomer, and an olefinic comonomer, and obtaining a graft copolymer resin after a graft-copolymerization reaction; casting the graft copolymer resin to obtain a support layer film; step S2, mixing a second matrix resin, a crosslinking agent, a silane coupling agent, and a tackifier, and extruding the mixture to obtain an adhesive layer film; and step S3, subjecting the support layer film and the adhesive layer film to composite calendering treatment to form a support layer and an adhesive layer, respectively, thereby obtaining a composite photovoltaic film.

[0014] Further, in step S1, the reaction temperature of the graft-copolymerization reaction is 120℃~140℃, and the reaction time is 0.05h~0.14h; and / or, in step S2, the extrusion film formation is carried out at a temperature of 70℃~90℃; preferably, the graft-copolymerization reaction in step S1 is carried out in the presence of an initiator, and the amount of initiator is 0.1%~5%, more preferably 0.5%~1.8%, based on the total weight of the first matrix resin, acidic graft monomer and olefin comonomer as 100%; further preferably, the initiator is selected from one or more of dicumyl peroxide (DCP), di-tert-butyl peroxide (DTBP) and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (DBPH).

[0015] Furthermore, in step S3, the composite calendering process is carried out at a temperature of 70℃~90℃ and a pressure of 0.5MPa~1.5MPa.

[0016] A third aspect of the present invention provides a photovoltaic module comprising a glass sheet and a battery cell, wherein the surface of the glass sheet and / or the battery cell is provided with the aforementioned composite photovoltaic encapsulant film, and the adhesive layer in the composite photovoltaic encapsulant film is disposed in contact with the glass sheet and the battery cell.

[0017] By applying the technical solution of this invention, a special support layer and adhesive layer are designed and combined. The support layer exhibits high stability, especially with extremely low fluidity at high temperatures, effectively preventing structural deformation and adhesive overflow during lamination. The adhesive layer possesses extremely strong adhesion, particularly when in contact with rigid materials such as glass and metal backsheets, where the resulting bond strength far exceeds that of traditional adhesive films. Ultimately, the resulting composite photovoltaic film achieves excellent bonding and encapsulation effects under high temperature and pressure. Detailed Implementation

[0018] 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 embodiments.

[0019] As described in the background section, existing photovoltaic encapsulating films suffer from the problem of simultaneously possessing low fluidity under high temperature and pressure and high adhesion to glass and metal materials. To address these technical problems, a first aspect of the present invention provides a composite photovoltaic film comprising a stacked support layer and an adhesive layer; the support layer includes a graft copolymer resin obtained by a graft-copolymerization reaction of a first matrix resin, an acidic graft monomer, and an olefinic comonomer; the adhesive layer comprises, by weight, 80-100 parts of a second matrix resin, 1-3 parts of a crosslinking agent, 0.3-1 parts of a silane coupling agent, and 5-10 parts of a tackifier; the first matrix resin and the second matrix resin are each independently selected from one or more of ethylene-α-olefin copolymer resin (POE), ethylene-vinyl acetate copolymer resin (EVA), and polyethylene resin (PE).

[0020] This invention designs a special support layer and an adhesive layer, and combines them to form a high-performance composite photovoltaic encapsulant film. The support layer exhibits high stability, especially with extremely low flowability at high temperatures, effectively preventing structural deformation and adhesive overflow during lamination. Specifically, the unique structure of the graft copolymer resin originates from its ternary components: a first matrix resin, an acidic graft monomer, and an olefinic comonomer. Through the grafting reaction, the acidic graft monomer forms side chains on the matrix resin molecular chain, increasing intermolecular forces, thereby raising the resin's melting point and lowering the melt flow index. This allows the support layer to exhibit excellent shape retention and low flowability during high-temperature, high-pressure lamination, preventing film flow that could lead to poor solder joint bonding or structural deformation, ensuring the encapsulation precision and reliability of the photovoltaic module. Simultaneously, further copolymerization forms a more complex and larger molecular chain structure, which not only reduces material flowability but also enhances mechanical strength, ensuring the encapsulant film does not easily break or lose its shape under external forces, thus providing effective physical support for the photovoltaic module.

[0021] The adhesive layer in the resulting composite photovoltaic film exhibits extremely strong adhesion while maintaining high light transmittance through meticulous formula adjustments. In particular, when in contact with rigid materials such as glass and metal backsheets, the adhesion strength formed far exceeds that of traditional films.

[0022] More importantly, based on the selection of the first and second matrix resins, the aforementioned support layer and adhesive layer are highly compatible and work together to achieve a comprehensive improvement in the performance of the encapsulant film. In particular, the low flowability of the support layer ensures precise control of the encapsulation process and avoids structural deformation problems; while the high-strength adhesive properties of the adhesive layer ensure stable adhesion between the encapsulant film and encapsulation materials such as glass and metal backsheets, making it less prone to peeling or failure even in extreme environments, greatly improving the structural stability and durability of photovoltaic modules.

[0023] In summary, the composite photovoltaic film obtained by this invention can achieve good bonding and encapsulation effects under high temperature and high pressure.

[0024] In several preferred embodiments, to achieve higher mechanical strength in the resulting support layer, the graft copolymer resin is preferably obtained by graft-copolymerization of a first matrix resin, an acidic graft monomer, and an olefinic comonomer in a weight ratio of (4-8):1:(1-3). In several more preferred embodiments, the graft copolymer resin is obtained by graft-copolymerization of a first matrix resin, an acidic graft monomer, and an olefinic comonomer in a weight ratio of (5.0-6.0):1:(1.2-1.5). Within this weight ratio range, grafting and copolymerization can be better achieved, forming a more stable graft copolymer network. The proportion of grafted side chains in the resulting graft copolymer resin is also more appropriate, thereby maintaining lower fluidity at high temperatures and exhibiting higher mechanical properties.

[0025] Furthermore, the acidic graft monomer is selected from one or more of acrylic acid (AA), maleic anhydride (MAH), methacrylic acid, methyl acrylate, and butyl acrylate, preferably acrylic acid and / or maleic anhydride. Acrylic acid, in particular, as a carboxyl-containing monomer, can significantly increase the polarity of the resulting graft copolymer resin through the grafting reaction, thereby better coordinating with the comonomer to form a stable network structure. The olefin comonomer is selected from one or more of C6-C10 straight-chain olefins, styrene, and glycidyl methacrylate, preferably one or more of n-heptene (specifically 1-heptene), n-octene (specifically 1-octene), and n-nonene (specifically 1-nonene). More preferably, the olefin comonomer is n-octene, which has a more suitable chain length, can significantly improve the resin's flowability through the copolymerization reaction, and can also effectively retain the structural stability and mechanical strength of the resulting support layer.

[0026] In the graft copolymer resin, the grafting rate of the acidic graft monomer is preferably 8% to 25% (more preferably 10% to 20%), so as to further optimize the polymer network structure obtained by graft-copolymerization and provide more suitable support for the resulting composite photovoltaic film.

[0027] In particular, when the melting point of the support layer is 95℃~130℃ and the melt index is 2g / 10min~5g / 10min, it can reduce structural changes caused by excessive softening during high-temperature lamination; at the same time, it can more significantly reduce the fluidity of the adhesive film at high temperatures, more effectively prevent adhesive overflow, and extend its service life.

[0028] For the adhesive layer in the composite photovoltaic film structure, preferably, the second matrix resin is an ethylene-vinyl acetate copolymer resin, and the weight percentage of vinyl acetate segments in the ethylene-vinyl acetate copolymer resin is 25%~30%; and / or, the crosslinking agent is selected from tert-butyl peroxycarbonate isopropyl, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, tert-butyl peroxycarbonate-2-ethylhexyl, 2,5-dimethyl... 2,5-Di(tert-butylperoxy)hexane, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-pentylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-pentylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, 2,2-bis(tert-butylperoxy)butane, 2-ethylhexyl carbonate tert-amyl peroxide, 2,5-dimethyl-2,5-bis(benzoylperoxy)-hexane, tert-amyl carbonate peroxide, 3,3,5-trimethylcyclohexane peroxide One or more of tert-butyl trimethylhexanoate; and / or, the silane coupling agent is selected from one or more of γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and γ-methacryloxypropyltriethoxysilane; and / or, the tackifier is selected from one or more of terpene resin, β-pinene resin, and terpene-styrene resin. Among these, an ethylene-vinyl acetate copolymer resin with a vinyl acetate segment weight ratio of 25%~30% is selected as the second matrix resin. Combined with the use of crosslinking agents and silane coupling agents, a dense three-dimensional network structure can be formed, which not only enhances the cohesion of the adhesive layer but also significantly improves the bonding strength between the resulting composite photovoltaic film and encapsulation materials such as glass and metal. Furthermore, the addition of the tackifier further enhances the adhesion of the adhesive layer, allowing the film to maintain close contact with the encapsulation material even in extreme environments, thereby more effectively preventing moisture penetration, protecting the module from external factors, and extending the service life of the photovoltaic module.

[0029] In addition, in order to reduce the absorption and scattering of light inside the photovoltaic module and improve its energy conversion efficiency, the transmittance of the adhesive layer in the composite photovoltaic film obtained by the present invention is preferably 90%~93%.

[0030] In several preferred embodiments, the thickness ratio of the support layer to the adhesive layer is (2~3.5):1. A higher support layer thickness can more effectively resist deformation under high temperature and pressure, reducing misalignment between encapsulation materials; while a lower adhesive layer thickness provides excellent adhesion while minimizing the loss of mechanical properties. This results in a composite photovoltaic film that provides sufficient mechanical support and exhibits excellent adhesion during the encapsulation process.

[0031] A second aspect of the present invention provides a method for preparing the above-mentioned composite photovoltaic film, comprising: step S1, mixing a first matrix resin, an acidic graft monomer, and an olefinic comonomer, and obtaining a graft copolymer resin after a graft-copolymerization reaction; casting the graft copolymer resin to obtain a support layer film; step S2, mixing a second matrix resin, a crosslinking agent, a silane coupling agent, and a tackifier, and extruding the mixture to obtain an adhesive layer film; and step S3, subjecting the support layer film and the adhesive layer film to composite calendering treatment to form a support layer and an adhesive layer, respectively, thereby obtaining a composite photovoltaic film.

[0032] To address the aforementioned composite photovoltaic film, this invention provides a corresponding preparation method. First, a graft copolymer resin is prepared under graft-copolymerization reaction conditions. Then, the support layer film is cast and the adhesive layer film is extruded. Finally, the final composite photovoltaic film is obtained through composite calendering. The support layer and adhesive layer prepared by the casting and extrusion processes respectively possess low flowability and high adhesion. When these two layers are composited under suitable temperature and pressure, a structurally stable composite photovoltaic film with excellent adhesion performance is formed.

[0033] In step S1, the preferred reaction temperature for the graft-copolymerization reaction is 120℃~140℃ (more preferably 130±5℃), and the reaction time is 0.05h~0.1h, so as to more effectively optimize the grafting rate to between 10% and 20%, thereby optimizing the polymer network structure obtained by graft-copolymerization and providing higher support for the obtained composite photovoltaic film.

[0034] In practical applications, the graft copolymerization reaction in step S1 is carried out in the presence of an initiator. The initiator dosage is 0.1% to 5% based on the total weight of the first matrix resin, acidic graft monomer, and olefinic comonomer (100%). An appropriate amount of initiator can decompose to generate free radicals. These free radicals react with the first matrix resin to generate macromolecular free radicals. Subsequently, under the action of these macromolecular free radicals, the acidic graft monomer and olefinic comonomer can undergo grafting and copolymerization reactions more efficiently, forming a complex molecular network structure, thereby significantly reducing the fluidity of the resulting support layer under high temperature and pressure. More preferably, the initiator dosage is 0.5% to 1.8% to more effectively promote the graft copolymerization reaction, increase the reaction rate and grafting rate, and thus obtain a more stable, low-fluidity support layer. In several typical embodiments, the initiator is selected from one or more of dicumyl peroxide (DCP), di-tert-butyl peroxide (DTBP), and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (DBPH).

[0035] In step S2, the extrusion film is preferably carried out at a temperature of 70°C to 90°C in order to improve the compatibility of the components in the adhesive layer and enable it to exhibit higher adhesion in subsequent composite processes and during use.

[0036] Furthermore, in step S3, the composite calendering process is preferably carried out at a temperature of 70℃~90℃ and a pressure of 0.5MPa~1.5MPa, and more preferably at a temperature of 80±5℃ and a pressure of 0.6±0.05MPa. These preferred and more preferred composite calendering conditions can more effectively form a good bonding interface between the two film layers, while reducing excessive flow of the material components at high temperatures, thereby better maintaining the overall low fluidity and mechanical strength of the resulting composite photovoltaic film.

[0037] In several typical embodiments, the thickness of the support layer film is 0.2 mm to 0.6 mm, more preferably 0.25 mm to 0.35 mm, so as to more effectively ensure that the resulting composite photovoltaic film has sufficient support strength under high temperature and high pressure, and reduce structural deformation; the thickness of the adhesive layer film is 0.05 mm to 0.5 mm, more preferably 0.10 mm to 0.18 mm, thereby providing high adhesive strength while effectively reducing the cost increase and material waste in the encapsulation process caused by the increase in thickness. Combining the two intermediate films with the above-mentioned thickness characteristics can more effectively balance the mechanical properties and adhesive properties of the resulting composite photovoltaic film.

[0038] A third aspect of this invention provides a photovoltaic module comprising a glass sheet and solar cells. The surface of the glass sheet and / or solar cells is coated with the aforementioned composite photovoltaic encapsulant film, and the adhesive layer in the composite photovoltaic encapsulant film is disposed in contact with the glass sheet and solar cells. The composite photovoltaic encapsulant film obtained by this invention not only effectively prevents structural deformation during the encapsulation process but also maintains good adhesion performance under high temperature and pressure, ensuring the stability of the photovoltaic module during long-term operation and extending its service life. By directly contacting the adhesive layer of the composite photovoltaic encapsulant film with the glass sheet or solar cells, a strong adhesive interface is formed, significantly improving the durability and photoelectric conversion efficiency of the photovoltaic module in extreme environments. Simultaneously, the high light transmittance of the adhesive layer ensures the light absorption efficiency of the photovoltaic module, further enhancing its overall performance.

[0039] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0040] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0041] Example 1

[0042] A method for preparing a composite photovoltaic encapsulant film:

[0043] (1) Take 60g of PE as the first matrix resin, 10g of AA as the acidic graft monomer, 15g of n-octene as the olefin comonomer, and 0.5g of BPO as the initiator (i.e., the weight ratio of the first matrix resin, acidic graft monomer and olefin comonomer is 6:1:1.5; based on the total weight of the first matrix resin, acidic graft monomer and olefin comonomer as 100%, the amount of initiator is 0.59%). After a graft-copolymerization reaction at 130℃ for 0.05h, the mixture is granulated and cast into a support layer film with a thickness of 0.30mm.

[0044] (2) Take 90g of EVA (VA=28%) as the second matrix resin, 1.5g of crosslinking agent DCP, 0.8g of silane coupling agent γ-methacryloxypropyltrimethoxysilane, and 8g of terpene resin as tackifier, and extrude them at 70°C to form an adhesive layer film with a thickness of 0.15mm.

[0045] (3) The obtained support layer film and adhesive layer film are combined online and calendered at a calendering temperature of 80℃ and a pressure of 0.6MPa to form a support layer and an adhesive layer respectively, thereby obtaining a composite photovoltaic film with a thickness of 0.45mm.

[0046] Example 2

[0047] A method for preparing a composite photovoltaic encapsulant film:

[0048] (1) Take 60g of PE as the first matrix resin, 10g of AA as the acidic graft monomer, 15g of n-octene as the olefin comonomer, and 0.5g of BPO as the initiator (i.e., the weight ratio of the first matrix resin, acidic graft monomer and olefin comonomer is 6:1:1.5; based on the total weight of the first matrix resin, acidic graft monomer and olefin comonomer as 100%, the amount of initiator is 0.59%). After a graft-copolymerization reaction at 130℃ for 0.05h, the mixture is granulated and cast into a support layer film with a thickness of 0.35mm.

[0049] (2) Take 90g of EVA (where VA=28%) as the second matrix resin, 1.5g of crosslinking agent DCP, 0.8g of silane coupling agent vinyltrimethoxysilane, and 8g of terpene resin as tackifier, and extrude them at 80°C to form an adhesive layer film with a thickness of 0.10mm.

[0050] (3) The obtained support layer film and adhesive layer film are combined online and calendered at a calendering temperature of 80℃ and a pressure of 0.6MPa to form a support layer and an adhesive layer respectively, thereby obtaining a composite photovoltaic film with a thickness of 0.045mm.

[0051] Example 3

[0052] A method for preparing a composite photovoltaic encapsulant film:

[0053] (1) Take 60g of EVA (where VA=28%) as the first matrix resin, 10g of AA as the acidic graft monomer, 15g of n-octene as the olefin comonomer, and 1.5g of DCP as the initiator (i.e., the weight ratio of the first matrix resin, acidic graft monomer and olefin comonomer is 6:1:1.5; based on the total weight of the first matrix resin, acidic graft monomer and olefin comonomer as 100%, the amount of initiator is 1.76%), and after a graft-copolymerization reaction at 130℃ for 0.05h, granulate and cast into a support layer film with a thickness of 0.30mm.

[0054] (2) Take 90g of EVA (where VA=28%) as the second matrix resin, 1.5g of crosslinking agent DCP, 0.8g of silane coupling agent vinyltrimethoxysilane, and 8g of terpene resin as tackifier, and extrude them at 85°C to form an adhesive layer film with a thickness of 0.15mm.

[0055] (3) The obtained support layer film and adhesive layer film are combined online and calendered at a calendering temperature of 80℃ and a pressure of 0.6MPa to form a support layer and an adhesive layer respectively, thereby obtaining a composite photovoltaic film with a thickness of 0.45mm.

[0056] Example 4

[0057] A method for preparing a composite photovoltaic encapsulant film:

[0058] (1) Take 60g of POE as the first matrix resin, 10g of AA as the acidic graft monomer, 15g of n-octene as the olefin comonomer, and 1.5g of DCP as the initiator (i.e., the weight ratio of the first matrix resin, acidic graft monomer and olefin comonomer is 6:1:1.5; based on the total weight of the first matrix resin, acidic graft monomer and olefin comonomer as 100%, the amount of initiator is 1.76%), and after a graft-copolymerization reaction at 130℃ for 0.05h, granulate and cast into a support layer film with a thickness of 0.30mm.

[0059] (2) Take 90g of EVA (where VA=28%) as the second matrix resin, 1.5g of crosslinking agent DCP, 0.8g of silane coupling agent vinyltrimethoxysilane, and 8g of terpene resin as tackifier, and extrude them at 90°C to form an adhesive layer film with a thickness of 0.15mm.

[0060] (3) The obtained support layer film and adhesive layer film are combined online and calendered at a calendering temperature of 80℃ and a pressure of 0.6MPa to form a support layer and an adhesive layer respectively, thereby obtaining a composite photovoltaic film with a thickness of 0.45mm.

[0061] Example 5

[0062] A method for preparing a composite photovoltaic encapsulant film:

[0063] The only difference between this embodiment and Embodiment 1 is that the weight ratio of the first matrix resin, acidic graft monomer and olefin comonomer is changed to 4:1:1 in step (1).

[0064] Example 6

[0065] A method for preparing a composite photovoltaic encapsulant film:

[0066] The only difference between this embodiment and Embodiment 1 is that the weight ratio of the first matrix resin, acidic graft monomer and olefin comonomer is changed to 8:1:3 in step (1).

[0067] Example 7

[0068] A method for preparing a composite photovoltaic encapsulant film:

[0069] The only difference between this embodiment and embodiment 1 is that the casting or extrusion conditions in steps (1) and (2) are changed to obtain a support layer film with a thickness of 0.40 mm and an adhesive layer film with a thickness of 0.10 mm. At this time, the thickness ratio of the support layer to the adhesive layer is changed to 4:1.

[0070] Example 8

[0071] A method for preparing a composite photovoltaic encapsulant film:

[0072] The only difference between this embodiment and embodiment 1 is that the casting or extrusion conditions in steps (1) and (2) are changed to obtain a support layer film with a thickness of 0.20 mm and an adhesive layer film with a thickness of 0.20 mm. At this time, the thickness ratio of the support layer to the adhesive layer is changed to 1:1.

[0073] Example 9

[0074] A method for preparing a composite photovoltaic encapsulant film:

[0075] The only difference between this embodiment and Embodiment 1 is that in step (1), the reaction temperature of the graft-copolymerization reaction is changed to 120°C and the time is changed to 0.14h.

[0076] Example 10

[0077] A method for preparing a composite photovoltaic encapsulant film:

[0078] The only difference between this embodiment and Embodiment 1 is that in step (1), the reaction temperature of the graft-copolymerization reaction is changed to 140°C and the time is changed to 0.05h.

[0079] Comparative Example 1

[0080] A method for preparing a composite photovoltaic encapsulant film:

[0081] The only difference between this comparative example and Example 1 is that acrylic acid (AA), an acidic graft monomer, was not added in step (1).

[0082] Comparative Example 2

[0083] A method for preparing a composite photovoltaic encapsulant film:

[0084] The only difference between this comparative example and Example 1 is that n-octene, an olefinic comonomer, was not added in step (1).

[0085] Although the composite photovoltaic films obtained in Comparative Examples 1 and 2 have acceptable adhesion, the supporting layer has a low melting point. During high-temperature lamination, it is prone to excessive softening, which can lead to structural changes. In practical applications, it is difficult to achieve effective encapsulation, and the encapsulated devices are also prone to short service life due to structural instability.

[0086] Test methods

[0087] The grafting rate of acidic grafted monomers in the support layer was calculated based on Fourier transform infrared spectroscopy (FT-IR).

[0088] Melting point of the support layer: measured according to GB / T 28724-2012.

[0089] Melt flow index of the support layer: measured according to GB / T 3682.1-2018.

[0090] Light transmittance of the adhesive layer: measured according to IEC 61215.

[0091] Glass / film peel strength test and sample preparation: measured according to GB / T29848-2018.

[0092] The composite photovoltaic films obtained in each embodiment and comparative example were subjected to the above tests, and the results are shown in Table 1. The thickness ratio of the support layer to the adhesive layer in each composite photovoltaic film sample is also shown in Table 1.

[0093] Table 1

[0094]

[0095] As can be seen from the above description, the embodiments of the present invention have achieved the preparation of a composite photovoltaic encapsulant film with excellent comprehensive performance. The obtained composite photovoltaic encapsulant film not only has lower fluidity under high temperature and high pressure, but also can better adhere to glass / metal, thereby significantly improving the durability and photoelectric conversion efficiency of the photovoltaic module under extreme environments.

[0096] Specifically, in each embodiment:

[0097] Comparing Examples 5 and 6 with Example 1, it can be seen that by optimizing the weight ratio of the first matrix resin, acidic graft monomer, and olefinic comonomer, grafting and copolymerization can be better achieved, forming a more stable graft copolymer network. The proportion of grafted side chains in the resulting graft copolymer resin is also more appropriate, thus maintaining lower fluidity at high temperatures and having higher mechanical properties.

[0098] Comparing Examples 7 and 8 with Example 1, it can be seen that by optimizing the thickness ratio of the support layer to the adhesive layer, the resulting composite photovoltaic film can provide sufficient mechanical support and exhibit excellent adhesion performance during the encapsulation process.

[0099] Comparing Examples 9 and 10 with Example 1, it can be seen that by optimizing the reaction conditions of the graft-copolymerization reaction, the grafting rate can be optimized more effectively, thereby optimizing the polymer network structure obtained by graft-copolymerization and providing higher support for the obtained composite photovoltaic film.

[0100] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0101] 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 composite photovoltaic encapsulant, characterized by, The composite photovoltaic film includes a stacked support layer and an adhesive layer; The support layer includes a graft copolymer resin obtained by graft-copolymerization reaction of a first matrix resin, an acidic graft monomer, and an olefinic comonomer. By weight, the adhesive layer comprises 80-100 parts of a second matrix resin, 0.1-3 parts of a crosslinking agent, 0.3-1 parts of a silane coupling agent, and 0.1-10 parts of a tackifier; The first matrix resin and the second matrix resin are each independently selected from one or more of ethylene-α-olefin copolymer resin, ethylene-vinyl acetate copolymer resin, and polyethylene resin.

2. The composite photovoltaic glue film according to claim 1, characterized in that, The graft copolymer resin is obtained by grafting-copolymerization reaction of the first matrix resin, the acidic graft monomer and the olefin comonomer in a weight ratio of (4~8):1:(1~3); Preferably, the graft copolymer resin is obtained by graft-copolymerization of the first matrix resin, the acidic graft monomer, and the olefinic comonomer in a weight ratio of (5.0~6.0):1:(1.2~1.5).

3. The composite photovoltaic film according to claim 1 or 2, characterized in that, The acidic grafting monomer is selected from one or more of acrylic acid, maleic anhydride, methacrylic acid, methyl acrylate and butyl acrylate, preferably acrylic acid and / or maleic anhydride, and more preferably acrylic acid; The olefin comonomer is selected from one or more of C6-C10 straight-chain olefins, styrene, and glycidyl methacrylate, preferably one or more of n-heptene, n-octene, and n-nonene, and more preferably n-octene.

4. The composite photovoltaic glue film according to any one of claims 1 to 3, characterized in that, The supporting layer has a melting point of 95℃~130℃ and a melt index of 2g / 10min~5g / 10min.

5. The composite photovoltaic glue film according to any one of claims 1 to 4, characterized in that, In the adhesive layer, The second matrix resin is the ethylene-vinyl acetate copolymer resin, and the vinyl acetate segment in the ethylene-vinyl acetate copolymer resin accounts for 25% to 30% by weight; and / or, The crosslinking agent is selected from tert-butyl peroxycarbonate isopropyl ester, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, tert-butyl peroxycarbonate-2-ethylhexyl ester, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-pentylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-pentylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, 2,2-bis(tert-butylperoxy)butane, tert-pentyl peroxycarbonate, 2,5-dimethyl-2,5-bis(benzoylperoxy)-hexane, tert-pentyl peroxycarbonate, and 3,3,5-diethylhexyl peroxycarbonate. One or more of tert-butyl trimethylhexanoate; and / or The silane coupling agent is selected from one or more of γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and γ-methacryloxypropyltriethoxysilane; and / or The tackifier is selected from one or more of terpene resins, β-pinene resins, and terpene-styrene resins.

6. The composite photovoltaic glue film according to any one of claims 1 to 5, characterized in that, The thickness ratio of the support layer to the adhesive layer is (2~3.5):

1.

7. A method of producing the composite photovoltaic adhesive film according to any one of claims 1 to 6, characterized by, include: Step S1: The first matrix resin, the acidic graft monomer, and the olefin comonomer are mixed and subjected to the graft-copolymerization reaction to obtain the graft copolymer resin. The grafted copolymer resin is cast into a film to obtain a support layer film; Step S2: The second matrix resin, the crosslinking agent, the silane coupling agent and the tackifier are mixed and extruded to form a film, thereby obtaining an adhesive layer film. In step S3, the support layer film and the adhesive layer film are subjected to composite calendering to form the support layer and the adhesive layer respectively, thereby obtaining the composite photovoltaic film.

8. The method for preparing the composite photovoltaic film according to claim 7, characterized in that, In step S1, the graft-copolymerization reaction is carried out at a temperature of 120°C to 140°C for a reaction time of 0.05 h to 0.14 h; and / or, In step S2, the extrusion film formation is carried out at a temperature of 70°C to 90°C. Preferably, the graft copolymerization reaction in step S1 is carried out in the presence of an initiator, and the amount of the initiator is 0.1% to 5%, more preferably 0.5% to 1.8%, based on the total weight of the first matrix resin, the acidic graft monomer, and the olefin comonomer as 100%. More preferably, the initiator is selected from one or more of dicumyl peroxide (DCP), di-tert-butyl peroxide (DTBP), and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (DBPH).

9. The method for preparing the composite photovoltaic film according to claim 7 or 8, characterized in that, In step S3, the composite calendering process is carried out at a temperature of 70℃~90℃ and a pressure of 0.5MPa~1.5MPa.

10. A photovoltaic module, comprising a glass sheet and solar cells, characterized in that, The surface of the glass sheet and / or the battery cell is provided with the composite photovoltaic film as described in claims 1 to 6, and the adhesive layer in the composite photovoltaic film is disposed in contact with the glass sheet and the battery cell.

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